A Study of the Vapor Phase Nitration of Butane with Emphasis on the Effect of Adding Oxygen

Citation preview

PUKDUE UNIVERSITY

TH IS IS TO CERTIFY THAT THE TH ESIS PREPA R ED U N D E R MY SU PE R V ISIO N

BY______________ I ie s lie Mande v i l l e Addison

ENTITLED

_________

A Study o f The Vapor Phase N itr a tio n o f Butane w ith

Emphasis on The E f f e c t o f Adding Oxygen_______________________

COMPLIES WITH THE UNIVERSITY REG ULATIO NS O N GRADUATION T H E SE S

AND IS APPROVED BY ME A S FULFILLING THIS PART O F THE REQUIREM ENTS

F O R TH E DEG REE OF

Doctor o f P hilosop hy

P R O F K S SO B IN C H A RG E OF T H E S IS

H

ead o p

S

ohooe or

D

epartm ent

.19. 4 ^

TO THE LIBRARIAN:---IS TH IS T H ESIS m NOT TO B E REGARDED A S CONFIDENTIAL.

PSOFS6SOB m CHABGB GBA1>. SCHOOLFOKM9— 3-49--XM

A STUDY OF THE VAPOE PHASE NITRATION OF BUTANE WITH EMPHASIS ON THE EFFECT OF ADDING OZYGEN A T h e s is S u h m itte d t o th e F a c u lty of Purdue U n iv e rs ity hy

Le s l i e Mand e v i l l e A ddison In P a r t i a l F u lf illm e n t o f th e Eeq.uirem ents f o r th e D egree of D o cto r o f P hilosophy November^ 19^9

ProQuest N um ber: 27712202

All rights reserved INFORMATION TO ALL USERS The q u a lity of this re p ro d u c tio n is d e p e n d e n t u p o n the q u a lity of the co p y su b m itte d . In the unlikely e v e n t that the a u th o r did not send a c o m p le te m a n u scrip t and there are missing p a g e s, these will be n o te d . Also, if m a te ria l had to be re m o v e d , a n o te will in d ic a te the d e le tio n .

uest P roQ uest 27712202 Published by ProQuest LLO (2019). C o p y rig h t of the Dissertation is held by the A uthor. All rights reserved. This work is p ro te cte d a g a in s t u n a u th o rize d co p yin g under Title 17, United States C o d e M icroform Edition © ProQuest LLO. ProQuest LLO. 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346

ACKNOWLEDGMENT

C r e d it f o r th e c o D cep tio r and i n i t i a l d i r e c t i o n o f t h i s r e s e a r c h goes to D r. H. B. H ass.

F o llo w in g th e te r m in a tio n o f h i s

a s s o c i a ti o n w ith th e problem^ D r. G. B. Bachman provided, much c o u n s e l and w ise g u id a n c e .

In p a r t i c u l a r ^ h i s s u g g e s tio n s r e l a t i n g

t o th e t h e o r e t i c a l a s p e c ts o f th e problem have been m ost v a lu a b l e . T h is r e s e a r c h was supported, in p a r t by fu n d s provided, by Commercial S o lv e n ts C o r p o r a tio n .

EFFECT OF OZYG^ ON THE VAPOE PEASE NITRATION OF BUTANE AND TEE MECHANISM OF THE NITRATION REACTION AN ABSTRACT SUMMARY The optimum c o n v e rsio n in th e vapor phase n i t r a t i o n o f h u te n e may he in c re a s e d s u b s t a n t i a l l y hy th e a d d itio n o f orygen to th e r e a c ­ t io n m ix tu re .

Under o rd in a ry c o n d itio n s , t h i s a d d itio n o f oxygen

d e c re a s e s g r e a t ly th e u ltim a te y ie ld based on h y d ro ca rb o n .

However,

in c r e a s in g th e r a t i o o f s u r f a c e to volume in th e r e a c t o r ms.kes p o s s ib le s l i g h t l y h ig h e r c o n v e rsio n s based on n i t r i c a c id and p ro d u ces s t r i k i n g improvem ents in th e y ie ld based on b u tan e consumed.

The use o f steam

a s a d i lu e n t in th e p re se n c e o f oxygen a ls o m it ig a t e s th e h a rm fu l e f f e c t o f th e oxygen and a id s in r a i s i n g th e c o n v e rsio n s t i l l f u r t h e r . A more com plete mechanism f o r vapor phase n i t r a t i o n i s p r e s e n te d .

T h is

p o s tu l a te s th e p ro d u c tio n o f f r e e a l k y l r a d i c a l s by an o x id a tiv e a t t a c k on th e hydrocarbon by deco m p o sitio n p ro d u c ts o f th e n i t r i c acid.; combina­ t io n o f th e s e r a d i c a l s w ith NOp to produce n i t r o p©,rs.ffins and a l k y l n i t r i t e s ; d ecom position o f th e n i t r i t e s to produce a ld e h y d e s and low er a l k y l r a d i c a l s which a ls o undergo n i t r a t i o n .

The p ro d u c tio n o f o l e f i n s

i s accounted, f o r by th e decom position o f a p a r t o f th e f r e e a l k y l ra d ic a ls . INTRODUCTION In an i n v e s t ig a l io n o f th e e f f e c t s o f v a rio u s g a se s on th e vapor phase n i t r a t i o n o f propane. Hass and A lex an d er ( 4 ) , d isc o v e re d

2. t h a t th e a d d itio n o f oxygen to th e r e a c ti o n m ix tu re caused, an i n c r e a s e in th e c o n v e rsio n o f n i t r i c acid, to n i t r o p a r a f f i n s .

The p ro d u c tio n

o f oxygenated, b y -p ro d u c ts was noted, b u t no d e te rm in a tio n was ma.de o f th e ty p e compounds produced o r o f th e am ounts o f each form ed.

In f a c t ,

in a l l p re v io u s s tu d ie s o f vapor phase n i t r a t i o n , a t t e n t i o n has been d ir e c te d a lm o st e x c lu s iv e ly to an i n v e s t ! g a l lo n o f th e ty p e and q u a n tity o f n i t r o p a r a f f i n s pro d u ced .

The la c k o f d a ta on th e n a tu r e and y i e l d s

o f b y -p ro d u c ts has ma.de an e lu c id a tio n o f th e d e t a i l e d mechanism o f th e r e a c ti o n im p o s s ib le .

S in c e oxygen in c r e a s e s th e p ro d u c tio n o f th e s e

b y - p ro d u c ts , a stu d y o f them becomes im p o rta n t from an economic s ta n d ­ p o in t a s w e ll a s d e s ir a b le from th e t h e o r e t i c a l v ie w p o in t. B utane was chosen f o r t h i s in v e s t ig a t io n s in c e i t has n o t been given th e same amount o f a t t e n t i o n accorded th e low er h y d ro carb o n s. I t i s i n t e r e s t i n g to n o te t h a t d a ta by Hass and Hodge ( 5 ) show t h a t a s th e homologous s e r i e s o f norm al p a r a f f i n s i s ascended from m ethane to b u ta n e , n i t r a t i o n becomes e a s i e r . APPARATUS The a p p a ra tu s c o n s is te d o f a m e te rin g sy ste m f o r th e r e a c t a n t s , a gas p r e h e a te r , a r e a c t o r , and a c o n d en sin g sy stem .

The flow c o n tr o l

f o r th e buta.ne and oxygen was p ro v id e d by o r i f i c e ty p e flow m e te rs o p e ra te d w ith th e r a t i o o f upstream to dow nstream p r e s s u r e above th e c r i t i c a l p ressu re r a t i o .

Thus th e flow was in d ep e n d e n t o f sm a ll p r e s ­

s u re f l u c t u a t i o n s in th e r e a c t o r .

N i t r i c a c id was fo rc e d from a l i q u i d

r e s e r v o i r th ro u g h a c a lib r a te d , j e t in to th e p r e h e a te r by a c o n tr o lle d p ressu re o f n itro g e n .

3. The p r e h e a te r c o n s is te d o f a c o i l o f 10 mm. I .D . p y rex g la s s tu b in g 250 cm. lo n g w ith an opening 60 cm. from th e o u t l e t f o r th e i n j e c t i o n o f th e n i t r i c a c id ..

T his was immersed in a s a l t b a th ms.in-

ta in e d a t a te m p e ra tu re o f 26^*0 . by s t a i n l e s s s t e e l s t r i p h e a t e r s . Two r e a c t o r s were u se d .

The f i r s t c o n s is te d o f a c o i l o f 10

mm. pyrex g la s s tu b in g , 880 cm. lo n g , and h a v in g a d ia m e te r o f 20 cm. The second was ms.de so t h a t i t could be packed f o r s tu d i e s on th e e f f e c t o f th e s u rf a c e to volume r a t i o under c o n d itio n s o f c o n sta.n t h e a t t r a n s ­ fer.

I t c o n s is te d o f th r e e 90 cm. le n g th s o f 20 mm. I .D . p y rex g la s s

tu b in g .

Each was b e n t i n to th e form o f a U and th e t h r e e were connected

in s e r i e s by tu b e s sealed, n e a r th e to p o f each l e g .

P a c k in g was i n t r o ­

duced th ro u g h th e ends o f th e tu b e s which w ere s e a le d o f f b e fo re o p e ra ­ t io n .

The t h r e e p a rk in g s u sed were 3/1 6 and I /8 in ch p y rex g la s s

h a l i c e s and pyrex gla.ss w ool.

The h e a tin g o f b o th r e a c t o r s was

accom plished, by use o f a s a l t b o th provided, w ith im m ersion h e a te r s o p e ra te d by an a u to m a tic te m p e ra tu re c o n t r o l l e r . The e x i t g a se s were cooled by pa.ssa.ge th ro u g h a w a te r con­ d e n s e r to remove th e m a jo r ity o f th e l iq u i d p ro d u c ts end th en th ro u g h a dry i c e - t r i c h l o r o e t h y l e n e t r a p to remove gaseous p ro d u c ts and e x c e ss b u ta n e .

Any g a se s re m a in in g uncondensed were p assed th ro u g h a w et t e s t

gas m eter to E ra su re t h e i r volume and were th en c o lle c te d , o v er w a te r o r vented a s d e s ir e d . PRODUCT ANALYSIS The t o t a l l i q u i d p ro d u c t was e x tr a c te d w ith e th e r to s e p a r a te th e aqueous and non-aqueous m s b e r ia l s .

The a ld e h y d e s p r e s e n t in each

4. l a y e r were determ ined by th e hydroxy lam ine h y d ro c h lo rid e m ethod.

The

e th e r l a y e r was e x tr a c te d w ith s o d iu m -b ic a rb o n a te to remove a c i d i c m a te ria ls .

The n i t r o p a r a f f i n s re m s tn in g in th e e th e r l a y e r were

d eterm ined by a n itr o g e n a n a ly s i s on an a l i q u o t p o r tio n . Propene and b u te n e , e th y le n e , carbon monoxide and carbon d io x id e were determ ined, by an O rs a t a n a ly s i s on a sam ple o f th e e x i t g ases. C onversions were based on th e f r a c t i o n o f th e n i t r i c a c id charged, which ap p e are d a s n i t r o p a r a f f i n s .

Y ie ld s a r e based on th e

b u ta n e which r e a c t e d . NITRATION OF BUTANE 'MITHOCT OXYGEN E a r l i e r work on th e n i t r a t i o n o f b u tan e was o f an e x p lo r a to r y n a tu r e .

Hence a stu d y o f th e e f f e c t o f oxygen, d i f f e r e n t s u r f a c e to

volume r a t i o s , and d i l u e n ts r e q u ir e d f i r s t an i n v e s t ig a t io n o f th e r e s u l t s o b ta in a b le w ith n i t r i c a c id a lo n e .

S in c e th e c o n ta c t tim e ,

mole r a t i o o f hydrocarbon to n i t r i c a c id and p r e s s u r e had. been a r b i t r a r i l y chosen to conform t o e a r l i e r s t u d i e s , th e one re m a in in g v a r ia b le was te m p e ra tu re . E xperim ents c a r r ie d o u t a t 405*C. , 425®C., and 439*C. s e rv e d to d e te rm in e th e optimum te m p e ra tu re . a r e given in T able I .

The data, from th e s e e x p e rim e n ts

A p l o t o f co n v e rsio n a g a in s t te m p e ra tu re

(F ig u re l ) shows t h a t th e b e s t r e s u l t s a r e o b ta in e d a t a te m p e ra tu re o f 425®C. From th e a c t u a l q u a n t i t i e s o f m a te r ia ls produced a s l i s t e d , in T able I , i t can be seen t h a t te m p e ra tu re has a marked e f f e c t on th e

F ig u re s r e f e r r e d to in th e a b s t r a c t a r e i d e n t i c a l w ith th o se h a v in g th e same number in th e t h e s i s p r o p e r.

p ro d u c tio n o f n i t r o p a r a f f i n s . d e c re a s e s w ith te m p e ra tu re .

T h is r e a c h e s a mximum and s u b s e q u e n tly

No s u b s t a n t i a l v a r i a t i o n s a r e n o ted in th e

p ro d u c tio n s o f th e v a rio u s b y -p ro d u c ts . The optimum te m p e ra tu re e f f e c t observed in th e p ro d u c tio n o f n i t r o p a r a f f i n s has p re v io u s ly been e x p la in e d in two w ays.

One i s t h a t

a s th e te m p e ra tu re i s in c r e a s e d , deco m p o sitio n o f n i t r o p a r a f f i n s b eg in s to tak e p la c e , th u s re d u c in g th e amount found, in th e p ro d u c t.

However,

T a y lo r ( l4 ) found t h a t th e h a l f - l i f e of n ltro m e th a n e a t 420*0. i s 4 m in u te s.

Even assum ing a much g r e a t e r deg ree o f i n s t a b i l i t y f o r th e

h ig h e r members o f th e s e r i e s , p y r o ly s is should be n e g l i g i b l e a t a con­ t a c t tim e o f 1 .6 se co n d s.

Hence t h i s e x p la n a tio n seems in a d e q u a te to

a c co u n t f o r th e f a c t s . A l t e r n a ti v e ly i t has been su g g e ste d th a ,t com peting s id e r e a c ­ tio n s w ith h ig h e r a c tiv a .tlo n e n e rg ie s and in v o lv in g o rg a n ic m a te r ia ls become more prom inent a t th e h ig h e r te m p e ra tu re s .

Such r e a c ti o n s would

be expected, to produce in c r e a s in g amounts o f b y -p ro d u c ts a s th e tem pera­ tu r e in c r e a s e s .

T h is i s n o t th e case how ever.

I t may be c a lc u la te d

from T able I t h a t th e change w ith te m p e ra tu re in th e amounts o f o l e f i n s , c a rb o n y l compounds and carbon o x id e s p ro d u ced , when c a lc u la te d on th e b a s is o f grams o f carbon in v o lv e d , does n o t compare w ith th e change in b u tan e consumed.

A c tu a lly th e d e c re a se in m oles o f n i t r o p a r a f f i n s pro­

duced i s a p p ro x im ate ly e q u a l to th e d e c re a s e in m oles o f b u tan e r e a r t i n g . I t may be concluded t h a t a d e c re a s e in c o n v e rsio n by com peting s id e r e a c tio n s in v o lv in g o rg a n ic m a t e r i a ls , which become pronounced a t th e h ig h e r te m p e ra tu re s , i s n o t su p p o rte d by e x p e rim e n ta l e v id e n c e . NITRATION QE BUTANE NITH OXYGEN The i n i t i a l e x p e rim e n ts w ith oxygen were perform ed a t th re e d i f f e r e n t te m p e ra tu re s to d e te rm in e th e v a r i a ti o n in optimum te m p e ra tu re

T able I N i t r a t i o n o f B utane W ithout Oxygen E f f e c t o f T em perature (C o n ta c t Time = 1 .6 Seconds; 10 mm. I.D . C o il R e a c to r)

Bun No.

42

10

41

Hodge*

(^4%o/BNOg

1 5 .0

1 2 .3

1 5 .0

1 4 .0

T em p eratu re, *C.

405

42^

435

420

% C onversion**

15

36

22

37

BNOg

0 .1 0

0 .2 9

0 .1 4

> c=o

0 .0 6

0 .0 6

0 .1 0

C3H5 +

0 .1 0

0 .1 1

0 .1 4

CpHt

0 .1 0

0.18

0 .1 2

CO

0 .1 3

0 .0 7

0 .1 3

COg

0 .1 0

0 .2 6

0 .0 7

0 .3 1

0 .5 5

0 .4 1

Moles Formed***

Butane Consumed. Moles****

*

A pproxim ately 3seconds c o n ta c t tim e .

**

Based on n i t r i c a c id c h a rg e d .

***

C o rre c te d to m oles p e r 10 m oles o f b u ta n e

**** C a lc u la te d from

ch arg ed .

th e carbon c o n te n t o f th e p ro d u c ts .

7. a s oxygen was added.

The r e s u l t s given in T able I I show a maximum

c o n v e rsio n o f 43 p e r c e n t which r e p r e s e n t s a s i g n i f i c a n t in c r e a s e over th e c o n v e rsio n o b ta in e d under com parable c o n d itio n s w ith o u t oxygen. When th e s e c o n v e rsio n s a r e p l o tt e d a g a in s t te n p e r a tu r e (F ig u re l ) i t i s seen t h a t th e optimum te m p e ra tu re i s s t i l l in th e neigh b o rh o o d o f 425®C . S ince i t was dem onstrated t h a t th e optimum te m p e ra tu re does n o t vary a p p re c ia b ly w ith th e a d d itio n o f oxygen, th e rem a in in g e x p e r i- . ment8 were perform ed a t a te m p e ra tu re o f 42$*C.

The d a ta given in

T able I I I show th e e f f e c t s on y i e l d s and c o n v e rsio n s o f v a ry in g th e amount o f oxygen added to th e n i t r a t i o n m ix tu re . F ig u re 2, which shows th e r e l a t i o n betw een c o n v e rsio n and th e amount o f oxygen added

r e v e a ls t h a t th e h ig h e s t c o n v e rsio n o b ta in a b le

in t h i s r e a c t o r i s 44 p e r c e n t a t a te m p e ra tu re o f 42$*C. w ith a mole r a t i o o f b u ta n e /o x y g e n /n itr ic a c id o f I 5 / I . 6 / I . The y i e l d , based, on th e amount o f b u ta r e consumed, i s F ig u re

shown in

3 to d e c re a s e n e a rly l i n e a r l y w ith th e amount o f oxygen em ployed.

Thus i t i s obvious t h a t th e in c r e a s e in c o n v e rsio n observed upon a d d in g oxygen i s a t t a i n e d only a t th e s a c r i f i c e o f a c o n s id e r a b le amount o f -h y d ro c a rb o n th rough s id e r e a c t i o n s .

The s e r io u s n a tu r e o f t h i s a s p e c t

i s e v id e n t when i t i s noted, t h a t a t th e oxygen vs.lue f o r ma.ximum con­ v e r s io n , only 26 p e r c e n t o f th e b u tan e r e a c t i n g i s c o n v e rte d to n i t r o p a ra ffin s . The a c t u a l amounts o f p ro d u c ts from each r e a c ti o n a r e T able I I I .

The fo rm atio n o f c a rb o n y l compounds i s p r o p o r tio n a l

amount o f oxygen added.

given in to th e

The o l e f i n s and th e carbon monoxide a.ppear to

T able I I N i t r a t i o n o f B utane W ith Oxygen E f f e c t o f Tem perature (C o n ta c t Time = 1 .6 Seconds; 10 mm. I.D . C o il R e a c to r)

Run No.

12

11

13

CkHio/MO^

1 2 .7

1$.$

1 6 .0

Og/ENO^

2

2

2

T e m p era tu re , ®C.

411

42$

4$0

% C onversion*

33

43

27

i Yield.

1 7 .4

24

1 $ .6

RNOg

0.26

0 .2 7

0 .1 7

t>C=0

0 .7 3

0 .6 8

0 .4 9

C3E6 + C4E8

0 .73

0 .3 7

0 .6 1

CpHi}.

0 .3 1

0 .2 $

0 .1 1

CO

0 .1 0

0.4$

0 .2 6

CO2

0 .3 1

0 .1 7

0 .2 1

1 . 3S

1 .06

1 .0 1

Moles Formed.

B utane Consumed, Moles

*

Based on n i t r i c a c id c h a rg e d .

9. in c r e a s e slow ly a t f i r s t , b u t f i n a l l y show an a b ru p t r i s e .

I t is

i n t e r e s t i n g to n o te t h a t th e amounts o f carbon d io x id e ps.ss th ro u g h a minimum a t th e same p o in t where th e n i t r o p a r a f f i n s show a mximum. T h is mximum in th e p ro d u c tio n curve o f n i t r o compounds in th e p re se n c e o f in c r e a s in g amounts o f oxygen i s somewhat p u z z lin g u n le s s i t i s assumed t h a t vapor phase n i t r a t i o n i s a f r e e r a d i c a l p r o ­ cess.

A p o r tio n o f th e a l k y l r a d i c a l s r e a c t w ith th e n i t r a t i n g a g e n t

to produce n i t r o p a r a f f i n s .

However, th e r e a c ti o n o f a l k y l r a d i c a l s

w ith oxygen a ls o o ccu rs w ith extrem e e a s e .

Thus when th e oxygen con­

t e n t o f th e r e a c ti o n m ix tu re i s in c r e a s e d , a p o r tio n o f th e f r e e r a d i c a l s p r e v io u s ly a v a il a b l e f o r n i t r a t i o n a r e removed, by r e a c ti o n w ith oxygen and a r e c o n v e rted to b y - p r o d u c ts . The p re se n c e o f o l e f i n s in th e e x i t g a ses r e g a r d le s s o f th e oxygen c o n te n t o f th e r e a c ti o n m ix tu re i s ev id e n c e o f th e p re se n c e o f fre e a lk y l r a d ic a ls .

The fo rm a tio n o f o l e f i n s from s a tu r a te d hydro­

carbons by^ a f r e e r a d i c a l p ro c e ss i s a w e ll known phenomenon and in t h i s case in d ic a te s t h a t a c e r t a i n number o f th e f r e e r a d i c a l s und.ergo o l e f i n fo rm a tio n b e fo re an e f f e c t i v e c o l l i s i o n w ith a n i t r a t i n g a g e n t can ta k e p la c e .

I t i s r e a d i l y seen t h a t i f th e number o f f r e e r a d i c a l s

i s in c re a s e d w h ile m a in ta in in g th e same c o n c e n tra tio n o f n i t r a t i n g a g e n t, th e fo rm a tio n o f o l e f i n s should become g r e a t e r .

The e f f e c t o f

oxygen i s p o s tu la te d , a s a f r e e r a d ic a l- f o r m in g p r o c e s s , s.nd i t ms.y be n o ted t h a t th e p r e d ic te d r i s e in o l e f i n p ro d u c tio n does o ccu r upon in c r e a s in g th e amount o f oxygen added. The t o t a l amount o f b u tan e consumed, in th e e x p erim en ts con­ d u c te d a t v a rio u s te m p e ra tu re s w h ile u s in g a r e a c tio n m ix tu re h a v in g a b u ta n e /o x y g e n /n itr ic a c id r a t i o o f I 5/ 2/ I a r e given in T able I I .

An

10,

T ab le I I I N i t r a t i o n o f Butane E f f e c t o f Oxygen a t C o n sta n t Tem perature (C o n ta c t Time = 1 .6 Seconds; 10 mm. I.D . C o il R e a c to r)

Run No,

10

16

11

14

CI1H10/SNO3

1 2 .3

13.5

1 5.5

1 3 .2

O2/BNO3

0

1

2

3

T em p eratu re, *C.

425

42$

42$

42$

^ C onversion

36

42

43

26

io Y ield

48

32

24

10

RNOg

0 .2 9

0 .3 2

0 .2 7

0 .2 0

>C =0

0 .0 6

0 .3 7

0 .6 8

0 .9 6

C3 ÏÏ5 + Cij.ES

0 .1 1

0 .3 3

0 .3 7

1 .1 6

CpEij.

0 .1 8

0 .1 6

0 .2 $

0 .3 1

CO

0 .0 7

0 .$ 1

0 .4 $

0 .7 8

CO2

0 .2 6

0 .0 $

0 .1 7

0 .3 8

0.55

0 .9 3

1 .0 6

1 .9 3

Moles Formed

Butane Consumed, Moles

11. e x am in atio n o f th e s e f ig u r e s shows t h a t th e t o t a l amount o f r e a c ti o n a g a in d e c re a s e s w ith in c r e a s in g te m p e ra tu re a s was observed p r e v io u s ly in th e c o rre sp o n d in g e x p erim en ts w ith o u t oxygen.

In t h i s c a se no ma.jcl-

mum i s o b se rv e d , a lth o u g h one m ust ap p ear a t low er te m p e ra tu re s th an th o se s tu d ie d s in c e o b v io u sly i f a s u f f i c i e n t l y low te m p e ra tu re were ch o sen , th e amount o f m a t e r i a l r e a c ti n g could be ma,de a s sma.ll as d e s ir e d .

The d e c re a s e in b u tan e consumed i s p ro b ab ly a tt r ib u t a .b l e

h e re to a g r e a t e r e x te n t o f ch ain te rm in a tio n in th e oxygen r e a c ti o n a t h ig h e r te m p e ra tu re s . EFFECT OF O T f W ON THE NITRO PARAFFINS PRODUCED The n i t r o p a r a f f i n s formed in Runs 11 and 12 were d r ie d and f r a c ti o n a te d in a f o u r f o o t colim n packed w ith a. n i chrome w ire s p i r a l . As can be seen in T able IV, when th e Og/HNO^ r s .tio i s changed from zero to two, th e amounts o f th e n itr o b u ta n e s formed a r e d e c re a sed s i g n i f i ­ c a n tly , w h ile th e amounts o f th e n itro m e th a n e and n itr o e th a n e a re in c re a s e d by a f a c t o r o f two.

The data, from Runs 11 and 12 show t h a t

te m p e ra tu re has l i t t l e , i f an y , e f f e c t on p ro d u ct d i s t r i b u t i o n . These r e s u l t s show very c l e a r l y t h a t carbon to carbon bond f i s s i o n i s in c re a s e d in th e p re se n c e o f oxygen.

I t w i l l be shown in a

fo llo w in g s e c tio n on mechanism t h a t t h i s r e s u l t i s to be e x p e c te d . EFFECT OF SURFACE ON NITRATION S h e c h te r (6) f i r s t m entioned th e p o s s ib le in flu e n c e on th e n itr a .tio n r e a c ti o n o f th e s u rf a c e to volume r a t i o in th e r e a c t o r . ever

h is s o le concern was a p p a re n tly w ith h e a t t r a n s f e r .

How­

I f one views

th e n i t r a t i o n r e a c ti o n a s a f r e e r a d i c a l p ro c e s s which in th e p re se n c e

12.

T able IV N i t r a t i o n o f Butane E f f e c t o f Oxygen on Type o f N itr o P a r a f f in s

Run No.

Eodge*

11

12

C2j.Hio/HN03

14

1 5.6

1 2 .7

Og/SNOg

0

2

2

T em p eratu re, ®C.

420

42$

411

CE^N02

10

22

19

C2H^ 0 2

13

30

32

1-C3HYNO2

8

5

11

2-Cij.H9N02

45

27

21

1-C jj^H^N02

24

16

17

Mole P e r Cent

* D ata tak en from Hodge ( l l )

13. o f oxygen in v o lv e s c e r t a i n c h ain m echanism s, then i t becomes obvious t h a t extended s u rf a c e could be im p o rta n t f o r s t i l l o th e r re a s o n s . The packed r e a c t o r d e s c rib e d above was used to i n v e s t ig a t e th e s e e f f e c t s u s in g v a ry in g amounts o f oxygen and s u rf a c e to volume r a t i o s o f 20, 28, and 300.

W hile th e h e a t t r a n s f e r a r e a was c o n s ta n t

in t h i s s e r i e s o f e x p e rim e n ts, i t was c o n s id e ra b ly low er than t h a t a .v a ila b le in th e e a r l i e r e x p erim en ts in th e 10 mm, I .D . c o i l r e a c t o r . C o n seq u en tly , no d i r e c t com parison may be ms.de betw een th e two s e t s o f d a ta . The r e s u l t s from t h i s ex p erim en ts a r e given in T able 7 .

A

com parison o f th e c o n v e rsio n s o b ta in e d w ith o u t oxygen w ith S/V r a .tio s o f 2 0 , 2 8 , and 300 shows t h a t co n v e rsio n a c tu a ll y d e c re a s e s a s th e amount o f s u rf a c e i n c r e a s e s .

T hat t h i s i s n o t due to th e fa v o r in g o f

some o th e r r e a c tio n over n i t r a t i o n i s dem onstrated by com paring th e t o t a l amount o f b u tan e consumed in each c a s e .

T his v a lu e d e c re a s e s

from 0 .5 1 m oles to O.32 m oles w h ile th e c o n v e rsio n d e c re a s e s from 27 p e r c e n t to 20 p e r c e n t .

I t w i l l be noted t h a t th e v a lu e o f 27 p e r

c e n t obts.ined w ith an s / v r a t i o o f 20 in th e packed r e a c t o r i s much low er th an th e 36 p e r c e n t c o n v e rsio n re p o r te d f o r th e 10 mm. I.D . c o il re a c to r.

S in c e , in th e l a t t e r c a se th e s /V r a t i o i s 4 / l , a p o r­

t io n o f t h i s d e c re a s e must be due to th e s u rfa c e e f f e c t .

However, i t

i s f e l t th a.t to some e x te n t th e p o o re r h e a t t r a n s f e r in th e packed, r e a c to r i s r e s p o n s ib le . In each c a s e , a s oxygen was added, th e c o n v e rsio n r o s e to a maximum va.lue th en f e l l o f f . F ig u re 4.

These r e s u l t s a r e given g r a p h ic a lly in

The maximum v a lu e s were 42.$ p e r c e n t a t s / v r a t i o s o f 20

and 28, and 44 p e r c e n t w ith S/V r a t i o s o f 3OO.

Hence no s i g n i f i c a n t

in c r e a s e s in ms.ximum c o n v e rsio n in th e p re se n c e o f oxygen a re noted w ith a change in s u r f a c e .

On th e o t h e r han d , a marked change in th e q u a n tity

14. o f oxygen r e q u ir e d to g iv e th e optimum co n v e rsio n i s n o te d . I t would be ex p ected t h a t a d e c re a s e in th e amount o f oxygen would, in c r e a s e th e y ield , based on h y d ro c a rb o n .

F ig u re $ shows a com­

p a ris o n o f th e y ie ld s o b tain e d by v a ry in g th e r a t i o o f oxygen w ith th e th r e e p a c k in g s.

C o n sid e ra b le d if f e r e n c e s a r e noted betw een th e y i e l d s

a t s / v r a t i o s o f 20, 28, and 300. r a t i o i s 3OO i s q u ite u n u s u a l.

The peak y ie ld o b ta in e d when th e s / v

I t i s th e f i r s t c a se in which an a c t u a l

in c r e a s e in y ield , o f n i t r o p a r a f f i n s was o b ta in e d upon ad d in g oxygen and a ls o th e f i r s t case in which mxims. in b o th th e y ie ld s and con­ v e rs io n s occu rred w ith e q u a l amounts o f oxygen.

In th e pe.st th e c h ie f

o b je c tio n to th e use o f oxygen has been t h a t th e maximum y ie ld s were o b tain e d a..t d i f f e r e n t oxy-gen/hydrocarbon r a t i o s th an were th e maximum c o n v e rs io n .

E v id e n tly a la r g e S/V r a t i o b rin g s th e s e two maxima,

to g e th e r a t th e same oxygen c o n te n t o f feed g a s . "While th e e x a c t mechanism by which s u r f a c e e x e r c is e s i t s e f f e c t i s somewhat o b s c u re , c e r t a i n c o n c lu s io n s ms.y be drawn from an exam ination o f th e q u a n t i t i e s o f p ro d u cts o b ta in e d in th e above e x p e r i­ ments (s e e T able V) .

A r a t h e r la r g e p o r tio n o f th e b u ta n e i s c o n v erted

to b u ten e s and propene th u s mahing t h i s one o f th e g r e a t e s t s o u rc e s o f lo s s .

F ig u re 6 shows how t h i s lo s s v a r ie s w ith oxygen f o r each packing.

In each c a se th e r e i s a g ra d u a l in c r e a s e in l o s s u n t i l th e Og/ENOg r a t i o re a c h e s approxim s.tely one.

A t t h i s p o in t th e r a t e of in c r e a s e in t h i s

l o s s becomes much le .r g e r.

T his same e f f e c t was n o tic e d , when u sin g th e

10 mm. c o i l r e a c t o r .

I t p ro b ab ly i n d ic a te s th e a b i l i t y o f ihe n i t r a t i n g

a g e n t to u t i l i z e a r e l a t i v e l y h ig h p o r tio n o f th e f r e e a lk y l r a d i c a l s formed by o x id a tiv e a t t a c k u n t i l a c e r t a i n c o n c e n tra tio n of th e s e r a d i c a l s i s re a c h e d .

A f te r t h a t p o in t, a much l a r g e r p e rc e n ta g e o f

th e s e r a d i c a l s sim ply undergo decom position to form o l e f i n s . se en t h a t s. h ig h e r

s/v

I t can be

r a t i o ce n se s a g e n e r a l d e c re a s e in l o s s e s es

15

'ï ^

%

I CQ .s

cm

§Ü

W VO

0)

I H

3 m

f

&

*H

Ü

§

«H

O m

ê

8 0

OJ

I

Ü

% O

€ O

o Ü

OJ

o

Ü

Ü ©

§ -p ffl

16. o le fin s .

R e f e r r in g now to F ig u re 7, i t i s seen t h a t th e t o t a l amount

o f b u tan e r e a c t i n g in c r e a s e s w ith oxygen, h u t t h a t th e in c r e a s e i s l e s s th e g r e a t e r th e s /V r a t i o .

I t has p re v io u s ly been proposed t h a t such a

d e c re a s e in th e amount o f b u tan e r e a c ti n g i s due to c h a in s to p p in g w ith l e s s t o t a l p ro d u c tio n o f f r e e r a d i c a l s .

Hence th e d e c re a se in o l e f i n

fo rm atio n observed upon I n c r e a s in g th e s u rf a c e i s sim ply a r e f l e c t i o n o f a low er r a t e o f f r e e r a d i c a l fo rm a tio n . The d a ta given in T able V show t h a t p ro d u c tio n o f n i t r o p a r a f f i n s goes th ro u g h a maximum w ith in c r e a s in g oxygen.

These maxiroa,

a r e th e same h e ig h t r e g a r d le s s o f th e s/V r a t i o b u t o ccur w ith l e s s oxygen a s th e s / v r a t i o in c r e a s e s .

S in ce th e t o t a l number o f f r e e

r a d i c a l s p r e s e n t i s d ecreased by more su rfa .c e , th e f a c t t h a t th e same number o f f r e e r a d i c a l s a r e c o n v e rted to n i t r o p a r a f f i n s must mea.n t h a t t h e i r re a .c tio n to form oxygenated, m a te r ia ls i s a c h a in r e a c ti o n which i s hin d ered by s u r f a c e .

Such a r e a c ti o n would presum ably in v o lv e

■OH o r -OpH r a d i c a l s as chain c a r r i e r s which would be stopped on th e w a lls .

A l a t e r s e c tio n w i l l p r e s e n t a, mechanism based on th e s e con­

c lu s io n s . THE USB OF STEAM AS A DILUENT In th e fo re g o in g s e c tio n i t was p o in te d o u t t h a t an e x c ess o f f r e e ra d ie s .I s i s formed when oxygen i s added to th e n i t r a t i o n m ix tu re to th e e x te n t o f two m oles f o r each mole o f n i t r i c a c i d . The f a c t t h a t co n v e rsio n does n o t in c r e a s e g r'e a tly under th e s e c irc u m sta n c e s in d ic a te s than a.n i n s u f f i c i e n t amount o f th e n i t r a t i n g a g e n t i s p r e s e n t a.t th e tim e th e e x tr a f r e e r a .d ic a ls a re a v a .lia b le .

T his could stem from, e i t h e r o f two f a c t o r s : ( l ) decom posi­

tio n o f n i t r i c a c id in o th e r w ays, or (2) p ro d u c tio n o f f r e e ra.dica.ls

17. o v e r such a s h o r t period, o f tim e t h a t th e a c t u a l n i t r a t i n g a g e n t ( p r e ­ sumably NOp) i s n o t form ed f a s t enough to u t i l i z e them b e fo re th ey undergo o th e r change.

The obvious s o lu tio n to th e d i f f i c u l t y in th e

l a t t e r c a se would, be to add. an i n e r t d i lu e n t to th e m ix tu re s in c e t h i s would e f f e c t i v e l y d e c re a s e th e r a t e a t which th e f r e e r a d i c a l s a r e form ed.

I t would, n o t , how ever, in flu e n c e m s .te ria lly th e t o t a l q u a n tity

o f them fornfâd b e fo re th e end o f th e n i t r a t i o n tu b e i s re a c h e d . m ost l i k e l y c h o ic e o f d i lu e n t would seem to be steam .

The

I t is in e rt,

cheap, has a h ig h h e a t c a p a c ity and i s a lr e a d y b e in g in tro d u c e d a s w a te r in th e 70 p e r c e n t n i t r i c a c id . Work by E ib sh m n ( 7) on th e n i t r a t i o n o f e th a n e w ith o u t added oxygen shows t h a t in c r e a s in g th e d i l u t i o n o f th e n i t r i c a c id has an a d v e rse e f f e c t on c o n v e rs io n .

Under th e s e c o n d itio n s , how ever, th e

r a t i o o f f r e e r a d i c a l s to n i t r a t i n g a g e n t does n o t re a c h an optimum vs.lue.

Hence, a d i lu e n t which d e c re a s e s th e r a t e o f f r e e r a d i c a l forma.-

t io n would n o t be ex p e cte d to in c r e a s e b u t r a t h e r to d e c re a s e th e con­ v e rs io n .

W ith e x c ess oxygen p r e s e n t, how ever, th e r a t i o o f f r e e r a d i c a l s

to n i t r a t i n g a g e n t ms,y exceed th e optimum v s .lu e .

A d i lu e n t p r e s e n t in

s u it a b le amounts would, d e c re a s e t h i s r a t i o to th e optimum va.lue and th e re b y le a d to in c re a s e d c o n v e rs io n s . To t e s t t h i s re a s o n in g , two e x p erim en ts were c a r r ie d o u t u s in g eq u im o lar amounts o f hydrocarbon and. steam . b u tS D e /o x y g e n /n itric a c id r a t i o was I 5/ 2/ 1 . 10 mm. c o i l which has an s/V r s ,tio o f 20.

In each case th e

One was p erform ed in th e O ther p e r t i n e n t in fo rm a tio n

a lo n g w ith th e r e s u l t s a r e given in T ab le V I.

A lso in c lu d e d f o r com­

p a ris o n a r e Runs 11 and. 2$ which a r e e q u iv e .le n t in a l l r e s p e c ts e x c e p t th e y were perform ed w ith o u t added steam .

A s t r i k i n g improvement in

b o th co n v e rsio n and y ie ld was o b ta in e d a s a r e s u l t o f th e a d d it io n of

18. s te a m .

I n c r e a s in g th e s/V r a ,tio caused a f u r t h e r improvement in y ie ld

a lth o u g h th e c o n v e rsio n was n o t a p p re c ia b ly a f f e c t e d . An ex am in atio n o f th e p ro d u c ts shows t h a t th e steam in c r e a s e s th e amount o f a ld e h y d e s produced b u t t h a t th e t o t a l amount o f o l e f i n s formed, d e c re a s e s .

T his d e c re a s e , w h ile s m a ll in th e S/V = 4 r e a c t o r ,

becomes c o n s id e ra b le when th e s/V r a t i o i s r a i s e d to 20.

In e i t h e r case

th e a c t u a l number o f m oles o f n i t r o p a r a f f i n s produced shows a subs t a .n t i a l r i s e which i s g r e a t e r than th e in c r e a s e b ro u g h t ab out by any 0t h e r s in g le v a r ia b le . MECHANISM E vidence t h a t vapor phase n i t r a t i o n p ro ceed s by a f r e e r a d i c a l mechanism i s fu rn is h e d by th e fo llo w in g f a c t s : (1)

B arton (2) n i t r a t e d o p t i c a l l y a c ti v e 3 -^6 th y Ih ex an e and,

o b ta in e d racem ic 2 - n it r o b u t a n e .

T his in d ic a te d t h a t th e secondary b u ty l

group p a s se s th ro u g h a c o n f ig u r a tio n a lly u n s ta b le form in th e n i t r a t i o n p ro ce ss.

The m ost l i k e l y assum ption i s t h a t t h i s in te r m e d ia te i s th e

c o rre sp o n d in g f r e e r a d i c a l . (2)

B l i c k e n s ta f f ( l ) s u c c e s s f u lly n i t r a t e d th e b rid g e h e ad carbon

in b ic y c lo ( 2 ,2 ,1 ) h e p ta n e .

T h is would r u l e o u t th e re p la c e m e n t o f

hydrogen by a rea rw a rd a t ta n k and would i n d ic a te in s te a d a forw ard a t t a c k w ith th e p ro b a b le fo rm a tio n o f a f r e e r a d i c a l i n te r m e d ia t e . ( 3)

Hass and S h e c h te r (6 ) found n i t r a t i o n to le a d to th o se n i t r o

p a r a f f i n s c o rre sp o n d in g to a l l p o s s ib le a l k y l r a d i c a l s which can be formed by b re a k in g only one carbon to carbon bond, in th e o r i g i n a l hydro­ carb o n .

MeC le a ry (lO ) a.lso showed th e fo rm a tio n o f o l e f i n s c o rre sp o n d in g

to a l l of th e a l k y l r a d i c a l s p r e s e n t in n i t r o p a r a f f i n s .

T h is in d ic a te s

t h a t a l k y l f r e e r a d i c a l s me,y be p r e s e n t , s in c e th e y a r e known to decom­ po se r e a d i l y and r a p i d l y to o l e f i n s ,

19

T a b le VI

N i t r a t i o n o f Butane in th e P re se n c e o f Oxygen Use o f Steam a s D ilu e n t (C o n ta c t Time = 1 .6 Seconds)

Run No.

11

25

17

20

s / v R a tio

4

20

4

20

c 4810/ 32*03

1 5 .6

1 3 .3

1 4 .6

1 4 .0

O2/BNO3

2

2

2

2

O4810/ 82O

9 .6

9 .6

1

1

^ C onversion

36

42

55

54

i Yield.

24

22

30

35

RNOg

0 .2 6

0 .28

0 .3 6

0 .3 9

>C=0

0 .6 8

0 .$ 8

0 .8 2

0 .8 8

0 .3 7

0 .$ 9

0 .4 1

0 .2 $

C2H4

0.2$

0 .2 0

0 .1 0

0 .0 8

CO

0 .4 $

0 .3 9

0 .4 7

0 .4 1

CO2

0 .1 7

0 .1 0

0 .1 0

0.0$

1 .0 6

1.18

1 .1 2

1 .0 2

Moles Formed.

^3^6

0483

Butane Consumed, Moles

20. (4)

McCleary was a ls o a b le to form n i t r o p a .ra ffin s by th e r e a c ­

tio n betw een t e t r a e t h y l lee.d and n i t r i c a c id in th e vapor p h a se .

T etrs.-

e th y l le a d has been shown by P aneth ( l l ) to form e th y l r a d i c a l s when h e a te d under dim in ish ed p r e s s u r e .

I f th e sajne b e h a v io r ms.y be assumed

a t a tm o sp h eric p r e s s u r e , th e n i t r o p a .ra ffin s probably came from th e union o f an e t h y l r a d i c a l w ith th e n i t r a t i n g a g e n t. T his p r e s e n t work d is c lo s e s two o th e r f a c t s o f s ig n i f ic a n c e : (5)

The p re se n c e o f in c re a s e d s u rfa c e c a u se s a d e c re a se in th e

t o t a l amount o f hydrocarbon r e a c t i n g .

T his may be a s c r ib e d to d e s tr u c ­

t io n o f f r e e r a d i c a l in te r m e d ia te s by s u rfa c e r e a c ti o n s ( 9 )• (6)

The in c re a s e d p ro d u c tio n o f o l e f i n s a s w e ll a s n i t r o :para.ffins

when oxygen i s added to th e n i t r a t i o n m ix tu re s u g g e sts f r e e a lk y l radica.1 in te r m e d ia te s s in c e th e s e a r e known to be formed in o x id a tio n s under com­ p a ra b le c o n d itio n s ( 19) . Much has been s a id a b o u t th e s o - c a lle d a g e n t of n i t r a t i o n . T his i s d e fin e d a s th e m a te r ia l which r e a c t s w ith th e a l k y l f r e e r a d i ­ c a ls to produce n i t r o p a r a f f i n s .

I t i s w e ll known t h a t n i t r i c a c id i s

u n s ta b le a t 425*C. and t h a t th e p ro d u c ts o f th e decom position a r e n itr o g e n d io x id e , n i t r i c o x id e , oxygen, and w a te r (3)*

U n fo rtu n a te ly ,

no d e ta i le d no d e ta ile d , mechanism has been worked o u t f o r t h i s r e a c ti o n . These p ro d u c ts (e x c e p t f o r th e w ater) may, how ever, be accounted f o r by th e fo llo w in g r e a c t i o n s : (1)

HOUÛ2 — >

HO- + -EOg

( 2)

2 ■WO2

2N0 • + O2

9

Of th e f r e e r a d i c a l s shown, th e HO- r a d i c a l i s th e l e a s t s ta b l e and th e most r e a c t i v e .

Hence i t would be expected, to I n i t i a t e th e fo rm a tio n o f

f r e e r a d i c a l s from hydrocarbons in th e n itr a .tio n p r o c e s s . ( 3)

HO * + E H

E - -f HOH

21. The f r e e a l k y l r a d i c a l s so produced co u ld th e n u n ite w ith -ilOg r a d i c a l s ( ^)

*E + -W02 —-4^

RHOg

p ro d u cin g n i t r o p a r a f f i n s .

N i t r a t io n th e r e f o r e i s a f r e e r a d i c a l p r o ­

c e ss h u t i s n o t a c h ain r e a c t i o n .

I t should he n o ted t h a t any o th e r

c o n c u rre n t p ro c e ss le a d in g to th e fo rm a tio n o f r e a c ti v e f r e e r a d i c a l s would he expected to c o n tr ib u te t o th e n i t r a t i o n p ro c e ss by in c r e a s in g th e c o n c e n tra tio n o f a l k y l f r e e r a d i c a l s and hence th e p e r pa.ss con­ v e rs io n s to n i t r o p a r a f f i n s . w ith oxygen.

I t has been shown t h a t t h i s can be done

E v idence t h a t n i t r a t i o n i s n o t a ch ain r e a c tio n i s found

in th e f a c t t h a t increa.sed s u rf a c e in th e r e a c t o r tu b e does n o t a l t e r th e y ie ld s o f p ro d u c ts s u f f i c i e n t l y to be in agreem ent w ith th e r e s u l t s expected o f a c h a in r e a c ti o n o f any c o n s id e ra b le le n g th ( 9 ) • On th e b a s is o f th e proposed mechanism th e n i t r a t i n g a g e n t i s a c tu a ll y -NOg.

However, -NOp n i t r a t e s n o t hydrocarbon m olecules

d i r e c t l y b u t a l k y l r a d i c a l s d e riv e d from them , and th e l a t t e r a r e g e n e ra te d more e f f e c t i v e l y by HO- r a d i c a l s th an by -NOg r a d i c a l s .

T his

e x p la in s th e f a c t t h a t -HOg a lo n e i s l e s s e f f e c t i v e th a n n i t r i c a c id a s a n i t r a t i n g a g e n t in th e vapor ph ase. A n o th er ad vantage to th e assum ption t h a t e q u a tio n (^ ) r e p r e ­ s e n ts th e c h ie f vapor phase n i t r a t i o n p ro c e ss i s th e ease w ith which i t may be adapted, to an e x p la n a tio n o f th e f o r m t i o n o f o th e r p ro d u c ts o f th e r e a c t i o n .

The -NOg r a d i c a l i s a re so n a n c e h y b rid whose c h ie f

c o n tr ib u tin g form s p ro b ab ly in c lu d e :

(-)(+) :0 : N ::0 : - - ^ I

:0 ::N :0 : II

22. I f an a l k y l r a d i c a l r e a c t s w ith -NOg in Form I th e p ro d u c t i s a n i t r o p a r a f f i n , h u t i f in Form H th e p ro d u c t i s an a l k y l n i t r i t e .

The

heha.vior o f a l k y l n i t r i t e s under th e c o n d itio n s o f vapor phase n i t r a ­ tio n i s th e r e f o r e im p o rta n t to a more com plete u n d e rs ta n d in g o f th e n itr a tio n p ro cess. A lk y l n i t r i t e s a p p e ar to he ex tre m e ly u n s ta b le a t e le v a te d te m p e ra tu re s .

B ice (12) decomposed e th y l n i t r i t e a t k2^**C, in th e p r e ­

sence o f b u tan e a s a d i l u e n t .

Ik d e r such c o n d itio n s th e r e i s s l i g h t

chance t h a t th e decom position p ro d u c ts w i l l c o l l i d e w ith u n rea c te d n i t r i t e m o le c u le s, and th e decom position pro ceed s a s fo llo w s : ( 5)

CH3CH2ONO - —>

(6 )

CE^CEgO - —

CE^CEgO. + NO ECHO + CE3

The m ethyl r a d i c a l s were I d e n t i f i e d a s t e l l u r i d e s .

I f n o t removed from

th e r e a c ti o n m ix tu re th ey re a c te d , w ith n i t r i t e m o lecu les as fo llo w s : ( 7) (8 )

CE3* + CE3CH2ONO —

CEb + CH3ÇHONO

CE3ÇHONO — ». CE3CHO + -NO

Kornblum and O liv e to (8) have shown t h a t i f a h ig h e r c o n c e n tra tio n o f n i t r i t e i s p r e s e n t, th e a lk o x id e r a d i c a l s f i r s t produced r e a c t as fo llo w s : (9 ) (1 0 )

CH3CHgO- + CÏÏ3CH2ONO — -V

CE3CH2OH + CH3CHONO

CH3ÇHONO — - > CH3CHO + -NO

I t i s e v id e n t from th e s e e q u a tio n s t h a t any n i t r i t e s produced in th e n i t r a t i o n p ro c e ss would decompose to low er h y d ro ca rb o n s, a ld e ­ hydes and n i t r i c o x id e , a l l o f which a r e observed p ro d u c ts o f n i t r a t i o n . The low er a lk y l r a d i c a l s a ls o produced ac co u n t in p a r t a t l e a s t f o r th e lower n i t r o p a r a f f i n s obtained, in th e n i t r a t i o n p r o c e s s . ra d ic a ls

a r e a ls o formed from th e d i r e c t d eco m position

r a d i c a l s ( I 3) •

T h is a c c o u n ts f o r

p a r a f f i n s p ro d u ced .

th e rem ain d er

Lower a lk y l

of h ig h e r

o f th e low er n i t r o

a lk y l

23. The above e x p la n a tio n o f th e o r ig in o f th e low er n i t r o p a r a f f i n s and b y -p ro d u c ts o f th e n i t r a t i o n r e a c tio n i s more s a t i s ­ f a c to r y th an th e assum ption o f sim ple th e rm a l c ra c k in g as a s o u rc e o f th e s m a lle r a l k y l r a d i c a l s .

As a m a.tter o f f a c t th e p ro d u c tio n o f

m eth y l, e t h y l , and p ro p y l r a d i c a l s from b u tan e i s n e g li g ib l e a t th e optimum te m p e ra tu re and c o n ta c t tim e f o r th e n i t r a t i o n o f b u ta n e . F u rth e rm o re , s u b sta n c e s such a s iro n s a l t s , which c a ta ly z e th e c ra c k ­ in g o f C-C bonds in h y d ro ca rb o n s, d e c re a se m arkedly r a t h e r th an in c re a s e th e y i e l d s o f n i t r o p a r a f f i n s o b ta in e d .

I f th e rm a l c ra c k in g were c h ie f ly

r e s p o n s ib le f o r th e fo rm a tio n o f low er n i t r o p a r a f f in s i t would be expected, t h a t cyclohexane would y ie ld c o n s id e ra b le amounts o f 1 ,6 d in itro h e x a .n e on n i t r a t i o n . CHp I 2

I

CHp /C H p

I

CHp

I

CHg /C E p

'^CEg

CHp

I

I

CHp / C H p

^C H pCEg

CHp

^GHgEOg

2 -N02 .............

CHg

I

CEgNOg

I

CHg ^ C H g

^CEg

S h e c h te r '8 work on cyclohexane showed t h a t t h i s was n o t th e c a s e .

He

o b ta in e d o nly n itro c y c lo h e x a n e and a n o th e r p ro d u c t which c o n ta in e d n itr o g e n b u t decomposed, r e a d i l y on w arm irg to form a t a r .

T h is r e s u l t

would, be expected,, i f i t i s assiumed, t h a t f i s s i o n o c c u rs th ro u g h th e n itrite .

Such a r e a c tio n m ight le a d to a n i t r o aldehyde which would be

q u ite r e a c t i v e .

24, CHg

I

CEg

CHOWO

1

> I

CEO-

I

+ -NO

CEp /C E p

C E p /C E p

/.C E p CEp ^CEO-

/-C E pCEp CEO

I

I

> I

CEp /C E p

1

CEp /C E p

/C E p CEp CEO I 1 CEp /C E p ^ CHp

/.CEpNOp CEp CEO I I CHp / C E p \ CHp

F o llo w in g th e above re a s o n in g , th e vapor phase n i t r a t i o n o f b u tan e should p ro ceed a s fo llo w s : D ecom position o f n i t r i c a c id : (11)

HÏÏO3 — ^

HO - + *NOp

Forms.tion o f a lk y 'l r a d i c a l s : (12)

r — y CEgCEpCEpCEp - + EpO CHoCHpCHpCHo + H0 - ( '• — ?> CH3CH2ÇECH3 + EpO

D ecom position o f a l k y l f r e e r a d i c a l s : >

CS3CEpCH=CEp + -H

>

CE3CH2’ + CEp=CEp

( 13) CEoCEpCEpCEp'C

r —^

CH3CH=CHCH3 + H--

(14) CE3CEpCBCH3( >

CE3 - + CEp=CECE3

R e a c tio n of a l k y l r a d i c a l s w ith NOp: CE3CH2CE2CH2NO2 ( 15)

CEjCEpCSpCEp" + -N O / >

CEgCEpCEpCEpONO

25. (16)

/--> CH3CH2CHCH3 + -NOp^ ^

(IT )

CE3CE2' + -NOp —

(iB )

CE3' + -NOp —->

CH0CÏÏ2CÏÏCÏÏ3 NOp CH3CEpCECE3 ÔNO

CEÿEpNOp + CH3CE2OEO CH3NO2 + CH3ONO

D ecom position o f n i t r i t e s : (19)

C3E.JCH2ONO —

-NO + C3EYCSPO.

(20)

CPH5ÇHCE3 — >

>

C3HY' + ECHO

y - —> CpEr ' + CEoCEO -NO + CpE^ÇBCEo

6nO

"0

> CE3* + CpE^CEO

Now i t w i l l be observed t h a t th e m eth y l, e th y l , and. p ro p y l f r e e r a d i c a l s produced in ( 13) , ( l 4 ) , ( 19) , and (20) ma,y r e a c t w ith j u s t a s th e o r i g i n a l f r e e r a d i c a l s did in ( 15) and ( 16) .

-NOp

T his would

ac co u n t a t l e a s t q u a l i t a t i v e l y f o r th e low er n i t r o p a r a f f in s o b tain ed e x p e rim e n ta lly and would, a ls o r e s u l t in th e form a.tion o f a d d it io n a l f r e e r a d i c a l s w ith one l e s s carbon atom .

The o l e f i n s ob serv ed in th e

p ro d u c ts a p p a re n tly come from d.ecom position o f th e f r e e r a d i c a l s by ( 13 ) and ( l4 ) and. a ls o from : (21)

2CE3 '

>

CEp=CEp + 2E-

R e a c tio n s (19) and (20) account f o r th e a ld e h y d e s .

The la r g e

amount o f carbon monoxide a p p a re n tly r e s u l t s from th e w e ll known p y r o ly s is o f a ld e h y d e s ( l 5 ) • (22)

ECHO

400^*0. >

RE + CO

In s u p p o rt o f t h i s i s th e f a c t t h a t b o th hydrogen and methane a re found in th e e x i t g a ses a s would be ex p ected from th e decom position o f form aldéhyde and a c e ta ld e h y d e , o r p ro p an e.

No t e s t s were c a r r i e d o u t f o r ethane

The o rg a n ic a c id s o b ta in e d r e s u l t from th e f u r t h e r o x id a tio n

26. o f th e a ld e h y d e s . S in ce only s m l l amounts o f a lc o h o ls a r e form ed, th ey can w ell he acco u n ted f o r hy th e fo llo w in g decom position o f a t y p i c a l a lk o x y l r a d i c a l a s i l l u s t r a t e d hy e q u a tio n (9 )•

In a d d itio n , a w a ll r e a c tio n of

th e fo llo w in g ty p e may a ls o occu r: (2 3 )

s u rfa c e E ' + -OH ---------- -> EOH The mechanisms p resen ted , above may e a s i l y be extended to cover

th e e f f e c t o f oxygen on th e n i t r a t i o n p ro c e s s .

A ccording to "Walsh ( I 5 );

th e low te m p e ra tu re (below 500®C.) o x id a tio n o f b u tan e w ith oxygen p ro ­ ceeds a s fo llo w s : (2 5 )

CH3CH2CE2CH3 + ‘OE — ->• CE3CH2CHCE3 + EpO

(2 5 )

CE3CH2ÇHCH3 + Op —

CE3CH2ÇECH3

Ô ( 26 )

CH3CH2ÇBCH3 + CbEpo

>

CH3CH2ÇHCH3 + CbH^-

6' (2 7 )

ÔE

CÏÏ3CH2CHCE3 - —>- CH3CH2ÇECH3 + -OS

Ô

Ô•

Os (2 8 )

CH3CH2ÇBCH3 - —V- CpE^- + CEOCEO

The same ty p e s o f r e a c tio n s would be expected to r e s u l t from an i n i t i a l a t t a c k on a prim ary hydrogen e x cep t the.t forms,Idehyde would s p l i t o f f in s te a d o f a h ig h e r a ld e h y d e .

In e i t h e r c a s e , th e a l k y l f r e e r a d i c a l s

so produced would, be a v a ila b le f o r f u r t h e r r e a c tio n w ith oxygen or w ith •NOp.

I t w i l l be noted t h a t th e above o x id a tio n p ro ce ss in v o lv e s a

ch ain r e a c tio n which would be h in d ere d by in c re a s e d s u rfa c e due to d ecom nosition o r r e a c tio n o f b o th -OE and. -R r a d i c a l s on i t (9) ■

27. s u rfa c e ------ ——

( 29)

'E + *E

( 30)

-OH + -OH

EE

s u rfa c e ---------- ^

EgOp

A lc o h o l f or ma.t Ion could a ls o occur by r e a c tio n ( 23) . I f th e o x id a tiv e s e r i e s o f r e a c tio n s le a d in g to th e f o r m t i o n o f f r e e a l k y l r a d i c a l s ru n s c o n c u rre n tly w ith th e n i t r a t i o n , then th e p ro d u c tio n o f n i t r o p a r a f f i n s should in c re a s e due to th e e x is te n c e o f a h ig h e r c o n c e n tra tio n o f a lk y l r a d i c a l s .

In a d d it io n , th e r a t i o o f

low er to h ig h e r m o le c u la r w eight n i t r o p a r a f f in s should a ls o in c r e a s e due to a g r e a t ly in c re a s e d c o n c e n tra tio n o f th e low er m o le c u la r w eight a lk y l r a d i c a l s to g e th e r w ith t h e i r g r e a t e r s t a b i l i t y .

I t has been p r e ­

v io u s ly shown t h a t th e s e p r e d ic tio n s a r e borne o u t by ex p erim en t.

23. KSFSRMCSS 1 . B l i c k e n s t a f f , E . T. , and Hs,ss, H. B ., J . Am. Chem. S o c . 6Q, 14-31 (1 9 4 6 ). 2. B u rto n , T, M., P r iv a te Communication. 3 ' F o rs y th e , W. E . , and G ia rg u e , W. F . , J . Am. Chem. Soc. $0, 3216-21 (1 9 2 8 ). 4 . H ass, ÏÏ. B ., and A le x a n d er, L. B ., In d . Eng. Chem.

2266-70

(1 9 4 9 ). 5 ' H ass, H. B ., Hodge, S . B .. and V a n d e rb ilt, V. M., In d . Eng. Chem. 2 8 . 339-44 ( 1936) . 6 . B aas, H. B . , and S h e c h te r, H ., In d . Eng. Chem. 39; 817 (1947). 7 . Bibshman, H. J . , P ie rs o n , E. H ., and B ass, B. B ., In d . Eng. Chem. 32, 427-9 (1 9 4 0 ). 8 . Kornblum, N ., and O liv e to , E . P ., J . Am. Chem. Soc. 71 226-8 (1949) 9 . L ew is, B ., and von E lb e , G .. "Com bustion, Flames and E x p lo sio n s o f G a se s", Cambridge U n iv e rs ity P r e s s , Cambridge (1 9 3 8 ). 10. McCleary , E . F . , and D egering, Ed.. F . , In d . Eng. Chem.

64-7

( I 93B). 11. P a n e th , F. A ., and H o fe d ity , ¥ . . B er. 62E, 1335 (1929); 64, 2702 ( 1931) . 12. E ic e , F . 0 . , and Eodowskas, E. L ., J . Am. Chem. Soc. 57, 350-2 ( 1935) . 1 3 . E ic e , F. 0 . , "The A lip h a tic F ree R a d ic a ls " - Johns Hopkins P r e s s , B a ltim o re (1935)• 14. T a y lo r, H- A ., and V easelo v sk y , V. V ., J . P h y s. Chem. 39, 1095-1 ( 1935) . 1 5 . W alsh, A. D ., T ra n s. Faraday Soc.

297 (1947) -

A. STUDY OF THE YAPOE PHASE NITRATION

OF BTJTAflE WITH EMPHASIS ON THE EFFECT OF ADDING OZYŒN A T h e s is S u b m itted to th e F a c u lty of Purdue U n iv e rs ity

L e s li e Man d e v i l l e Addison In P a r t i a l F u lf illm e n t o f th e R equirem ents f o r th e D egree of D o c to r o f P h ilo so p h y November „ 194-9

TABLE OF CONTENTS Page I n tr o d u c tio n ........................................................................................................................

1

D is c u ss io n o f R e s u l t s ........................................................................................................... 7 N i t r a t i o n o f M ethane.................................................................................................. 9 N i t r a t i o n o f Butane in th e 10 mm. C o il R e a c to r .......................................11 W ithout Oxygen ............................................................................................. 11 W ith Oxygen.........................................................................................................13 E f f e c t o f Oxygen on P ro d u c t D i s t r i b u t i o n ....................................................17 E f f e c t o f S u rfa c e on N i t r a t i o n ..........................................................................l3 Use o f Steam a s a D i l u e n t ...................................................................................22 N i t r a t i o n o f P ro p a n e ................................................................................................24N itro g e n B alance - Forma.tion o f N itro g e n G as..............................................27 M e c h a n ism ......................................................................................................................30 E x p e r i m e n t a l .......................................................................................

4-2

A p p aratu s and T e c h n iq u e s.......................................................................................4-2 P ro d u c t A n a ly s is ........................................................................................................ 4-7 N itr o P a r a f f i n s .

.

47

A c id s ......................................................................................................................49 A ld e h y d e s.............................................................................................................$0 G a s e s ......................................................................................................................50 Chemica,ls U sed.........................................................

54-

T ab les o f Da,ta .............................................................................................................. 55 Sumirery B ib lio g rap h y

56 ....................................................................................................................... 53

LIST OF TABLES T ab le I

Pa.ge V a r ia tio n o f Maximum C onversion on N itra .tio n o f an Homologous S e r i e s .........................................................

4s

II

N i t r a t i o n o f M ethane........................................................................................ 9&

III

N i t r a t io n o f Butane W ithout Oxygen - E f f e c t o f T em p eratu re.

IV

N i t r a t i o n o f Butane W ith Oxygen - E f f e c t o f T em perature .

V

N i t r a t i o n of Butane - E f f e c t o f Oxygen a t C o n sta n t

. 12a . . l4 a

T e m p e r a tu r e ............................................................................................................. l4 b VI

N i t r a t io n o f Butane

- E f f e c t o f Oxygen on Type o f N itro

P a r a f f i n s ................................................................................................................. 17a V II

N i t r a t io n of Butane

- E f f e c t o f Oxygen a t a Surface/V olum e

o f 2 0 .......................................................................................................................... 19a V III N i t r a t io n o f B utane - E f f e c t o f Oxygen a t a Surface/V olum e o f 2 8 ..........................................................................................................................19b IX

N i t r a t io n o f B utane

- E f f e c t o f Oxygen a t a Surface/V olum e

of 3 0 0 ....................................................................................................................... 19c X

N i t r a t io n o f

Butane U sing Oxygen and Steam a s a D ilu e n t . , . 23a

XI

N itra tio n of

Propane in th e Packed R e a c to r ........................................25a

X II

L oss o f N i t r i c Acid to N itro g e n G a s .......................................................27a

X III A nalyses f o r

N itro g e n G a s .......................................................................

26a

E x p e rim e n ta l D ata ........................................................................................ 5 5 a ,b ,c

LIST OF FIGURES F ig u re

Page o f B u ta n e ............................. 12b

1

E f f e c t o f T em perature on th e N i t r a t io n

2

V a r ia tio n o f C onversion w ith Oxygen..... .................................................... l4 c

3

V a r ia tio n o f Y ie ld w ith Oxygen.

4

V a r ia tio n o f C onversion w ith Oxy^gen U sing

..............................................................l4d D iffe re n t

Surface/V olum e R a t i o s .......................................................................................19d 5

V a r ia tio n o f Y ield w ith Oxygen U sing D if f e r e n t Surface/V olum e R a tio s ..................................................................................... 19e

6

E f f e c t o f Oxygen on th e P ro d u c tio n o f O le fin s U sing D i f f e r e n t Surface/V olum e R a tio s ............................................................... 20a

7

E f f e c t o f Oxygen on th e T o ta l Amount o f Butane R e a c tin g . . . 21a

INTRODUCTION The p urpose o f t h i s i n v e s t ig a t io n was to d e te rm in e th e in flu e n c e o f oxygen gas upon th e vapor phase n i t r a t i o n o f b u tan e w ith n i t r i c s-cid. In view o f th e la r g e amount o f e x p e rim e n ta l work t h a t has been done on vapor phase n i t r a t i o n , a b r i e f rev iew o f th e r e l e v a n t p o r tio n s w i l l se rv e to c l a r i f y th e s t a t u s o f th e problem and p la c e th e p r e s e n t work in i t s p ro p e r p e r s p e c tiv e . The vapor pha.se n i t r a t i o n o f b u tan e w ith n i t r i c a c id was f ir s tperform ed by Hod.ge ( l l ) in 1936.

T h is work, conducted a t appro x in n .tely

th r e e seconds c o n ta c t tim e and a t a te m p e ra tu re o f 420®, gave a c o n v e r­ s io n to n i tr o p a ,r a f f i n s o f 37 p e r c e n t based on th e n i t r i c a c id charg ed . McCleary ( 1 5 ), in 1938, performed, th e same n i t r a t i o n a t v a rio u s tem pera­ t u r e s b u t a t u n d isc lo s e d c o n ta c t tim e s .

U n fo rtu n a te ly he used a r a t h e r

low mole r a t i o o f hydrocarbon to n i t r i c a c id and obtained, somewhate rra tic r e s u lts .

His d a ta a r e u s e f u l , c h ie f ly in t-hs.t he i s o l a t e d and

i d e n t i f i e d th e dibromo d e r i v a ti v e s o f th e o l e f i n s p r e s e n t in th e e x it gases.

In t h i s wa.y he was a b le to show t h a t th e o l e f i n s formed c o r r e ­

sponded. to each o f th e rad ic e ,Is (e x c e p t m ethyl) a p p e a rin g e,s n i t r o p a re ffin s . O ther i n v e s t i g a t o r s , w orking la r g e ly w ith m ethane, determ ined th e e ffe c t- o f p r e s s u r e , mole r a t i o , c o n c e n tra tio n o f n i t r i c a c i d . con­ t a c t tim e , and te m p e ra tu re .

S h e c h te r (22) found tha.t In c re a se d p re s s u re

had no n o tic e a .b le e f f e c t on c o n v e rsio n b u t sh o rte n e d th e optimum c o n ta c t tim e f o r a given te m p e ra .tu re .

Hedge ( l l ) n i t r a t e d Iso b u te n e a t mole

r a t i o s o f from two to tw en ty , and showed t h a t c o n v e rsio n in c r e a s e s w ith mole ra .tlo b u t ap p roaches a s y m p to t-ic slly a maximum v a lu e which i s mu.ch

l e s s than 100 p er c e n t.

Hlbshmsn (9) used n i t r i c a c id o f s tr e n g th

v a ry in g from 40 to JO p e r c e n t and. found t h a t c o n v e rsio n d e c re a sed as th e c o n c e n tra tio n o f a c id was lo w e re d ,

Boyd (3 ) ; who in v e s tig a .te d th e

optimum c o n d itio n s f o r th e n i t r a t i o n o f m ethane, found t h a t th e r e i s an optimum c o n ta c t tim e f o r each te m p e ra tu re and t h a t th e r e i s a s l i g h t v a r i a ti o n o f co n v e rsio n betw een d i f f e r e n t te m p e ra .tu re s .

Thus th e p ro ­

p e r m atching o f c o n ta c t tim e w ith te m p e ra tu re w i l l g iv e a good, c o n v e r­ s io n , b u t th e r e i s an optimum co n v e rsio n which may be o b ta in e d a t one p a r t i c u l a r te m p e ra tu re and c o n ta c t t im e . A lexander ( l ) , w h ile i n v e s t i g a t i n g i n t e r n a l h e a tin g o f th e n i t r a t i o n r e a c ti o n by th e i n tr o d u c tio n o f a lim ite d , amount o f a i r to burn p e r t o f th e h ydrocarbon, d isco v ered , a s u r p r i s i n g in crea.se in con­ v e rs io n to n i t r o compounds.

T h is was tra c e d to th e oxy:gen c o n te n t o f

th e a i r , and su bsequent e x p erim en ts on th e n i t r a t i o n of m ethane and propane w ith oxy'gen added gave an in c r e a s e in co n v e rsio n from 23 to "jG p e r c e n t w ith p ro p an e.

The r o l e o f oxygen was p o stu la .ted to in v o lv e

th e form a,tion o f f r e e r a d i c a l s th ro u g h o x id a tiv e a t t a c k on th e hydro­ carbons p r e s e n t, a lth o u g h no d i r e c t e v id e n c e was o ffe re d to s u p p o rt t h i s c o n c lu s io n .

I t was pointed, o u t t h a t an e a r l i e r s u g g e s tio n by Hass (7)

t h a t oxygen m ight aid, th e r e a c ti o n by o x id iz in g th e n i t r i c o x ide produced to n itro g e n d io x id e which could, a c t a s a n i t r a t i n g a g e n t was u n lik e ly b o th from a k i n e t i c and thermodyna.mic s ta n d p o in t.

At any te m p e ra tu re

t h i s re a .c tio n i s slow compared to th e exposure tim e o f 1 .6 seconds used, in th e s e n i t r a t i o n s , and th e e q u ilib r iu m m ix tu re a t 400®C. in a system c o n s is tin g o f 15 m oles i n e r t ga,s, 2 m oles w a te r , one mole oxygen, and, one mole o f NO + NOy would conta,in 50 p e r c e n t n i t r i c o x id e . In a l l th e work m entioned above w ith th e e x c e p tio n o f t h a t of M cCleary, th e only dependent v a r i a b le s studieg^ were c o n v e rsio n o f n i t r i c

3a c id

to n it r o

and th e r a t i o o b ta in e d o le f in s

p a r a ff in s , a c id it y

o f th e a queous p o r t i o n o f th e p ro d u c t

o f gas o u t to r e a c t a n t s f e d .

u n d e r u n s ta te d

M c C le a r y ' s d a ta , a lth o u g h

do g iv e an i d e n t i f i c a t i o n

c o n d it io n s ,

fo rm e d and a j ^ a r t i a l d e te r m in a tio n

no case was e c o m p le te d e te r m in a tio n

o f th e am ounts p r e s e n t.

o f th e b y - p r o d u c ts m ade.

q u e n tly no data, a re a v a i l a b le r e l a t i v e

o f th e

t o th e y i e l d

based on th e am ount o f h y d ro c a rb o n consumed, i n

o f n it r o

th e r e a c t i o n .

In

C onse­ p a r a ff in s T h is

omi.Gsion ste m s fr o m th e lo w c o s t o f gaseous h y d ro c a rb o n s w h ic h p r e v a ile d a t th e tim e when vapor phase n i t r a t i o n is

o b v io u s t h a t a tte m p ts t o f o l l o w

s t u d ie s o r ig in a t e d , .

H ow e ver, i t

th e c o u rs e o f th e r e a c t io n more

c lo s e ly 8.8 w e l l a s p r e s e n t day c o s t c o n s id e r a t io n s make a s tu d y o f b y ­ p r o d u c ts m a .n d a to ry.

T h is becomes o f p rim e im p o rta ,n c e i n

th o s e p ro c e s s e s

i n v o l v i n g oxygen b ecau se o f th e la r g e am ounts o f o xyge na te d, m a .te ri8 .l8 fo rm e d . The p r e s e n t s tu d y o f th e n i t r a t i o n

o f b u ta n e w i t h n i t r i c

a c id

and oxyge n i s a d i r e c t s e q u e l t o A le x a n d e r ’ s w o rk on znethane end pro pa ne . A lth o u g h b u ta n e has s e v e r a l d is a d v a n ta g e s as a raw ra s .te ria .l fr o m a com­ m e r c ia l s t a n d p o in t in t h a t i t d e s ir a b le lo w e r n i t r o

i s more e x p e n s iv e , y i e l d s le s s o f th e

p a r a f f i n s , and i s

somewhat le s s a v a i l a b l e ,

a re s e v e r a l fan t o r s w h ic h le n d i n t e r e s t t o n it r a tio n s to

such

a. s tu d y .

u s in g only th e h y d ro c a rb o n and n i t r i c

g iv e a h ig h e r c o n v e rs io n th a n propane w h ic h in

c o n v e r s io n s t o

e th a n e .

M ethane i s

so d i f f i c u l t

In

th e r e

o r d in a r y

a c id , b u tan e a p p e a rs tu rn

g iv e s s u p e r io r

to n it r a t e

t h a t i t was

th o u g h t im p o s s ib le f o r a. number o f y e a rs u n t i l la n d on ( I 3) i n 1939 ; d is ­ c lo s e d a w o rk a b le p ro c e s s .

T h is d i f f i c u l t y

is

illu s t r a t e d

data, fr o m H odge’ s t h e s i s w h ic h a re i n t e r e s t i n g in r e s u lt s

i n p a r t by

t h a t th e y show th e

o f n i t r a t i n g th r e e d i f f e r e n t h y d ro c a .rb o n s u n d e r th e same c o n d it io n s

4. (420®C., mole r a t i o o f 3 -5 , end c o n ta c t tim e o f a p p ro x lim te ly 3 seconds). H ydrocarbon

C o n v e rsio n , 5

Methane

0

E thane

9

Propane

21

Butane

29

Of p erhaps g r e a t e r s ig n if ic a n c e a re th e optimum c o n v e rsio n s f o r th e fo u r

low er norms.l p a r a f f i n s a s l i s t e d in T able

th a .t

th e maximum c o n v e rsio n s in c r e a s e w ith

hy d rocarbon.

I.

I t w ill

be noted

th e m o le c u la r w eight

o f th e

S in c e a d d in g oxygen in th e n i t r a t i o n o f propane gs.ve such

marked improvements in th e c o n v e rsio n s to n i t r o p a r a f f i n s , b u tan e would be expected, to show even more fa v o r a b le r e s u l t s . The use o f g a se s such a s b u tan e f o r th e p ro d u c tio n o f oxygenated chem icals by d i r e c t o x id a tio n in th e C elan ese C o rp o ra tio n p la n t a t B ishop, T exas, s u g g e s ts t h a t th e b y -p ro d u c ts from n i t r a t i o n in th e p rese n c e o f oxygen mi.ght be im p o rta n t from an economic v iew p o in t. A side from such c h a r a c t e r i s t i c s which mi.ght be p e c u lia r to b u ta n e , th e la c k o f p re v io u s d a ta would make such a. stu d y v a.lu ab le, S h e c h te r noted th e im portance o f r e a c t o r d e s ig n s on con­ v e rs io n s and c ite d t h i s a s s re a so n f o r th e d iv e rg e n c e betw een h is r e s u l t s and th o se o f Boyd f o r th e n i t r a t i o n o f rnethsne.

Boyd used a.

r e a c t o r ma.de o f 25 mm. O.D. pyrex tu b in g and obtained, a maximum con­ v e rs io n o f 12.2 p e r c e n t a.t 46l®C. end a, c o n ta c t tim e o f 0 .42 seco n d s. S c h e c h te r ’s r e a c t o r , made o f 5 mm. O.D. tu b in g , allow ed a co n v e rsio n o f l 9 .7 p e r c e n t a t 435®C. and a c o n ta c t tim e of 1 .4 9 seco n d s.

He s t a t e s

t h a t th e e f f e c t i s due to th e la r g e r a t i o o f s u rf a c e to volume which g iv e s e x c e lle n t h e a t t r a n s f e r end te m p e ra tu re c o n tr o l .

A lexander p o in te d

o u t t h a t h is p o s it i v e r e s u l t s in th e use o f oxy gen as a. n i t r a t i o n a i d ,

4a.

T a b le I

V a r ia tio n o f Maximum C onversion Upon A scending an Homologous S e r ie s

Hydrocarbon

CHb

I n v e s tig a to r *

S h e c h te r

C o n ta c t Time, S ec.

C3S8

n-CqHj_o

Hibshms.n

A lexander

Addison

1 .4 7

0 .2 1

1 .6

1 .6

Mole Ee.tio

1 2.5

12.5

1 1.0

12.3

T em p eratu re, ®C.

435

470

410

425

Maximum C o n v ersio n ,

19

25

28

36

* A ll r e s u l t s tak en from th e Purdue Ph.D . th e s e s by th e inve s tig a .to r s named

In

c o n tra s t to

w e re due to

s i m i l a r u n s u c c e s s fu l e x p e rim e n ts p e rfo rm e d by H odge,

im p ro v e d h e a t t r a n s f e r o b ta in e d

in

th e s m l l e i ' d ia m e te r'

t u b in g . On th e o th e r hand.. Pease ( l ? )

fo u n d t h a t e x te n d e d g la s s s u r ­

fa c e s s u p p re s s th e hom ogeneous, n o n - e x p lo s iv e r e a c t io n betw e en p ro p a n e and oxygen w h ic h i s

n o r m a lly

c o m p le te a t 375 * 0 .

U nder th e s e c o n d it io n s

does n o t b eg in u n t i l th e te m p e ra tu re re a c h e s 500®C. and

th e r e a c t i o n th e p r o d u c ts ,

in s te a d o f b e in g m o s tly carbon m o n o x id e , c o n s is t o f

la r g e a.mounts o f o l e f i n s , a ld e h y d e s , m ethane and h y d ro g e n . fo u n d t h a t a t h i n

He a ls o

c o a t in g o f p o ta s s iu m c h lo r id e r a i s e s th e re q u ire d

te m p e r a tu r e an a d d i t i o n a l h u n d re d d e g re e s . th e o b s e rv B .tio n o f Hodge ( lO )

T h is c o r r e la t e s w e l l w it h

t h a t p o tassiu m n i t r a t e

re d u c e s th e e f f e c t

o f oxygen on n i t r a t i o n . S i m i l a r e x p e rim e n ts by Pease end M unro (iS ) d is c lo s e f o r u m t io n o f s i g n i f i c a n t c u a n t i t i e s h y d r o p e r o x id e s .

These r e s u l t s

o f h y d ro g e n p ero x id e end a l k y l

f e l l lo g ic a lly

s.cce p te d m echanism f o r th e o x id a t io n

th e

in to

th e p r e s e n t ly

o f h y d ro c a rb o n s in

th e absence

o f fla m e , w h ic h p o s tu l a te s f r e e r a d i c a l s as i n t e r m e d ia t e s . ¥hen th e above e f f e c t s r e c a ll e d

t h a t extended s u r fa c e s s to p f r e e r a d i c a l s

r e a c tio n s , e ffe c ts

of s u r fa c e a re n o te d and when i t

it

is

tr a n s fe r e ffic ie n c y .

hand a re i n s u f f i c i e n t t o a llo w

w o u ld be m ost i n t e r e s t i n g t o have r e s u l t s s u r fa. ce to

th u s e n d in g c h a in

c le a r t h a t th e s u r fa c e t o volum e r a t i o may have

o th e r th a n th o s e due to h o s t

th e d a ta i n

is

volum e r a t i o

C e r t a in ly

c o n c lu s io n s to be d ra w n .

It

fr o m e x p e rim e n ts w here th e

hs.d been \a .r ie d u n d er c o n d it io n s o f c o n s ta n t

hee.t t r a n s f e r .

T h is i n v e s t lg e t io n hes shown t h a t c m oderate in c r e a s e in con­ v e rs io n i s o b teln ed in th e n i t r a t i o n o f b u tan e in th e p rese n c e o f oxygen

U nder th e s e c o n d it io n s , hydes.

th e m a jo r b y -p ro d u c ts a r e o l e f i n s

The h e a t t r a n s f e r a re a pi e se n t in

q u it e an im p o r te n t e f f e c t It

end a ld e ­

th e r e a c t o r ap p e a rs t o have

on th e maximum c o n v e r s io n ,

has been fo u n d

th e t th e s u r fa c e to volum e r a t i o he.s en

e f f e c t a p e r t fr o m b e e t t r s n s f e r .

T h is he s been a s c r ib e d

s to p p in g m e c h a n is m ‘whi.ch causes e more even r a t e f r e e r a d i c a l s th ro u g h o u t th e r e a c t o r .

to a, c h a in

o f p ro d u c tio n o f alley 1

Steam as a. d i l u e n t hs.s been fo u n d

to e x e r t a s im ila r in f lu e n c e . I n a d d itio n , a. m echanism has been w orked o u t w h ic h a c c o u n ts

f o r a l l o f th e known f a c t s c o n cern in g n i t r a t i o n . fo r m a tio n o f allQ -l f r e e r a d i c a l s , t o p ro d u c e n i t r o p o s itio n

t h e i r r e a c t i o n w it h n it r o g e n d io x id e

p a r a f f i n s end a .lk y 'l n i t r i t e s ,

o f th e n i t r i t e s

T h is p o s t u la t e s ib e

end th e s u b s e q u e n t decom­

to a ld e h y d e s and lo w e r alky 1 i & d i c a l s .

F is s io n

p r o d u c ts a re a c c o u n te d f o r by a s i m i l a r s e r ie s o f r e a c ti o n s w i t h th e s e a lk y l r a d ic a ls -

7. DISCUSSION OF RESTITS The s e le c t io n u n d e r w h ic h i t th e d e s ir e

o f th e

ty p e o f a p o e .ra iu s and th e c o n d it io n s

was t o he o p e ra te d w ere g overned hy tw o f a c t o r s :

to e lim i.n a te e x tra n e o u s " v a r ia h le s

and s e c o n d ,

f o r c o r r e l a t i n g r e s u l t s w i t h th o s e o f po.st i n v e s t i g a t o r s .

fir s t,

th e n e c e s s ity S in c e Hodge

has shown t h a t c o n v e rs io n a p p ro a c h e s a zmximimi v a lu e as th e mole r a t i o is

in c r e a s e d , w it h n e g l i g i b l e e f f e c t s sh ove h y d r o c s r h o n / n i t r i c a c id

r a tio s

o f l 4 , a r a tio

o f Ip was chosen f o r t h i s

work.

A le x a n d e r , who

p e rfo rm e d th e p r e v io u s w o rk w i t h o x y g e n , o p e ra ted a t a c o n ta c t tim e o f 1 .6 se con ds end a t te m p e r a tu r e s betw een 350 *C . and. t 35 ®C. a c o n ta c t tim e o f 1 .6 seconds was used u n ifo rm ly m ents and w hatever iem pere.ture The i n i t i a l w o rk was done i n

r e q u ir e d

Hence

in a l l th e s e e x p e r i ­

to g iv e ms.xlinum c o n v e r s io n .

an a p p a ra tu s p a tte r n e d a f t e r A le x a n d e r ’ s ,

u s in g a r e a c t o r c o n s i s t i n g o f 7 nm. O .D . p y re x t u b in g . m ethane c o u ld he ma.de s e t i s f e . c t o r i l y

in

C heck r u n s on

t h i s sp p -e .ra tu s, b u t i t

p ro v e d

u n s u it a b le f o r b u ta n e w h ic h has a much h ig h e r v i s c o s i t y , th u s g iv i n g e xtre m e ly - h ig h p re s s u r e d ro p s and r e q u i r i n g v e ry H o d g e 's work on b u ta n e was done i n

la r g e i n l e t p re s s u r e s .

a r e a c t o r c o n s tr u c te d

o f 1 C mm. I . D .

tu b in g , hence a d u p lic a te o f t h i s r e s e t o r was made f o r th e work on L a t e r work on th e e f f e c t o f th e s u r fa c e t o vo lu m e r a t i o

b u ta n e . r a tio ) it

was done i n

a r e a c t o r m d e o f 22 mm. O .D . t u b in g so d e v is e d t h a t

c o u ld be ps.cked w i t h v a r io u s s iz e s o f p y re x h e lic e s

o rd e r to

v a ry

r e la t iv e ly s ta n t,

(s/V

th e am ount o f s u r f a c e .

A re a c to r o f t h is

o r g la s s w o o l in ty p e has

p o o r h e a t t r a n s f e r c h a r a c t e r is t ic s , , a lt h o u g h th e s e e re c o n ­

th u s e l i m i n a t i n g h e a t t r a n s f e r es a v a r i a b l e . The m e te r in g o f th e r e a c t a n t m a t e r ia ls by a. new , improved

m ethod a llo w e d

e x c e l l e n t c o n t r o l o f fe e d

c o m p o s itio n and r a t e .

T h is

is

d e s c r ib e d more c o m p le te ly u n d e r Api^arn t u s .

The m ethod o f a n e ly s is

f o r p r o d u c ts o f e x p e rim e n ts 1 -1 2 was th e same as t h a t used by A le x a n d e r . F o r th e re m s .in d e r o f th e w o rk , n i t r o

a n a ly s e s w ere p e rfo rm e d by e

m o d if ie d K j e ld e h l m ethod w h ic h e l i m in â te s u n c e r t a in a s s u m p tio n s f o r m e r ly me,d e .

A ls o a s y s te m o f a n a ly s is f o r th e p r i n c i p a l b y - p r o d u c ts

( n a m e ly , o l e f i n s , a ld e h y d e s , a c id s , n it r o g e n was a d o p te d .

T h is added g re e .tly

end made p o s s ib le a c a lc u l a t i o n sumed.

o x id e s and carbon o x id e s )

to th e u t i l i i y o f y ie ld

o f th e d a ta o b ta in e d

based on th e hydrocarbon c o n ­

D e t a i l s o f th e a n a l j t i c e l p ro c e s s e s a re g iv e n u n d e r F x p e i'im e n ta l

P ro c e d u re .

I.

N itr a tio n

o f M ethane

A c c u r a te , c u a n t i t e t i v e

s t u d ie s on ve.por phase n i t r a t i o n

of

h y d ro c a rb o n s a re a b ra n c h o f e x p e r im e n ta l o r g a n ic c h e m is try r e q u i r i n g e s p e c i a l te c h n iq u e .

T h is

i s am ply

S h e c h te r, end A le x a n d e r on th e n i t r a t i o n e t a tm o s p h e ric p re s s u r e o r s l i g h t l y c o n t a c t tim e s , and m ole r a t i o s . o b ta in e d w ere 1 2 . P p e r c e n t , tiv e ly .

by th e work o f B oyd,

illu s t r a t e d

o f m e th a n e .

A l l th r e e w orked

above u s in g c o m p a ra b le te m p e r a tu r e s ,

N e v e r t h e le s s , th e ms.ximum c o n v e rs io n s

l B . 7 p e r c e n t, end 1 7 -1 p e r c e n t , r e s p e c ­

W h ile much o f th e T 's r ia t io n me.y be tr a c e d t o th e d ia m e te r o f

th e r e a c t o r used (1 0 mm., 5 mm., and 7 mm., r e s p e c t i v e l y ) , v a r ia b le s

o th e r

su ch as th e m e te r in g s y s te m end m ethod o f p r o d u c t a n a ly s is

a re in v o lv e d .

The im p o rta n c e o f t h i s

c o m p a ris o n s o f th e r e s u l t s S h e c h te r a t 100 p s i .

la t t e r fa c to r is

o f H at c h e r ( 6 ) w it h

apT^arent fr o m

th o s e o f A le x a n d e r and

The fo r m e r i n v e s t i g a t o r o b ta in e d a c o n v e rs io n o f

2 7 .1 p er c e n t a t e, te m p e ra tu re o f The l a t t e r w o r k e r s , u s in g en

. end 0 .7 5 se con ds c o n ta c t tim e .

i d e n t i c a l a p p a ra tu s and

th e same c o n d it io n s ,

g o t a, c o n v e rs io n o f 2 1 .1 p e r c e n t. In s tra te

v ie w o f th e above data., i t

a b ilit y

to

was th o u g h t e s s e n t i a l t o demon­

ch e ck p r e v io u s r e s u l t s .

C o n s e q u e n tly , e x p e rim e n ts 1-6

w ere p e rfo rm e d u s in g m ethane as th e h y d r o c a rb o n . in

T a b le I I

A le x a n d e r .

The r e s u l t s

a re l i s t e d

a lo n g w i t h c o rr e s p o n d in g e x p e rim e n ts fr o m th e w o rk o f E x p e rim e n ts 1 and 4 have been o m i.tte d

d u c t a n a ly s e s f o r th e s e w ere th e c o n v e rs io n s

ina sm u ch as th e p r o ­

extrem ely d o u b t f u l . I t w i l l be n o te d

In Runs 2 end 3 do n o t

c h e c k very c lo s e ly

w ith

th e

c o r r e s p o n d in g c o n v e rs io n s o b ta in e d by A .le x a n d e r ( 1 1 -A and y -A ) . if

th e r e s u l t s

fr o m Runs 2 and 3 e re c o r r e c te d

to

th a t

H ow e ver,

uhe seme c o n d itio n s as

T able I I N itra .tio n o f Methane

Run No.

2

3

5

6*

5 -A **

11 - A * *

C o n ta c t Tim e, S ec.

1 .2 3

1 .4 7

1 .0

1 .6

1 ,6

1 .7

CEp/mOg

12 .3

1 1 .0

1 5 .0

1 5 .0

1 5 .3

1 6.0

O g/m o^

1 .5 6

0

0

1 .5 6

0

1 .3

1 8.0

1 4 .1

1 7 .2

1 7 .6

2 3 .4

iü C o rre c te d C onversion****

2 1 .0

1 7 .0

1 7 .2

--

1 7 .6

22 .0

Rea.ctor D ia m e ter, mm.

7

7

10

10

7

7

°!q

C onversion***

*

R e s u lte d in an e x p lo sio n

**

A le x a n d e r's d a ta .

***

P er c e n t o f n i t r i c a c id charge which i s co n v erted to n i t r o p a ra ffin s .

**** C orrected, to a c o n ta c t tim e o f 1 .6 seconds and a mole r a t i o o f 15.

10. 1 1 -A and 5 -A a c c o r d in g to c o r r e l a t i o n s f o r m ole r a t i o and c o n t a c t tim e d e te rm in e d by A le x a n d e r th e a g re e m e n t i s w ere made i n

s e tls fs c to r y .

Runs p snd 6

th e 10 mm. I . D . r e a c t o r p re p a re d f o r b u ta n e .

a g re e m e n t was o b ta in e d between 5 and p - A , b u t i t

E x c e l le n t

wss fo u n d th a .t

e x p e rim e n t 6 i n w h ic h oxygen was added c o u ld n o t be c o n t r o l l e d . d if f ic u lt y

was e p p e r 'e n tly due t o in a d e q u a te h e a t t r a n s f e r w i t h

The its

s tte n d e .n t p o o r te m p e r a tu r e c o n t r o l . As a r e s u l t o f th e s e e x p e rim e n ts , m ethod fo llo w e d

fo r n it r a tio n

it

was d e c id e d t h a t th e

was s a t i s f a c t o r y and t h a t s u f f i c i e n t

te c h n ic u e had been m a s te re d t o e .llo w i n v e s t i g a t i o n

o f b u ta n e .

11. I I . N i t r a t i o n o f Butane In th e Ten M illim e te r R e a c to r N i t r a t i o n W ithout Oxygen P re lim in a ry a tte m p ts to n i t r a t e b u tan e in th e 7 inm. r e a c t o r ■were u n s u c c e s s fu l because th e la r g e p r e s s u r e drop th ro u g h th e r e a c t o r under h ig h r a t e s o f flow m d e th e vapor p r e s s u r e o f b u tan e I n s u f f i c i e n t to im, in t a i n th e p ro p e r c o n ta c t tim e .

W hile work could have been p e r ­

formed w ith th e c o n ta c t tim e o b ta in a b le ^ i t was th o u g h t t h a t th e 1 .6 second m lu e used by A lexander would be ad'vantageous to m a in ta in in t h a t com parisons could be ms.de more r e a d ily .

I t would have been

p o s s ib le to a tts .in t h i s r e s u l t e i t h e r by s h o rte n in g th e 7 mm. r e a c t o r o r by u s in g a. c o i l o f l a r g e r d ia m e te r.

The l a t e r d e v ic e was adopted

s in c e th e form er would have meant u s in g a low er th ro u g h p u t w ith a lo n g e r p e rio d o f o p e ra tio n and would have in g e n e ra l a ffo rd e d a l e s s f l e x i b l e a p p s .ra tu s .

The o n ly f o re s e e a b le d e f e c ts in th e 10 mm. r e a c to r

were i t s p o o rer h e a t t r a n s f e r c h a r a c t e r i s t i c s .

However^ D r. Hodge o f

Commercial S o lv e n ts was o f th e o p in io n t h a t t h i s r e a c t o r would be s a t i s f a c t o r y f o r b u tan e s in c e t h i s hydrocarbon has a l a r g e r h e a t c a p a c ity than m ethane.

D r. Hass p o in te d o u t t h a t th e r e s u l t s w ith

methane o b ta in e d in t h i s r e a c t o r in Run No. 5 gs,ve ev id en ce o f s u it a b le o p e r a tin g c h a r a c t e r i s t i c s in a s much as th e n i t r a t i o n o f methane has p re v io u s ly been shown to r e q u ir e e x c e lle n t h e a t t r a n s f e r . A. r e a c t o r c o n s is t in g o f 25 f e e t o f 10 mm. O.D. pyrex tu b in g b e n t in to a 18 cm. O.D. c o i l was i n s t a l l e d .

A t th e same tim e i t was

found p o s s ib le to use a j e t ty p e o f gas flow m eter which g r e a tly improved th e e a se o f o p e ra tio n and a c c u ra c y o f th e n i t r a t o r .

I t was n e c e s s a ry to

r e p la c e th e dry ic e t r a p s and w a te r s c ru b b e r used by A lex an d er w ith a r e f l u x condenser capa.ble o f c o n d en sin g a l l th e u n rea c te d b u tan e in o rd e r to g e t s a t i s f a c t o r y remo-va.l o f a l l n itr o p a .r a f f in s from th e ga.s stre a m .

12. T able I I I g iv e s th e r e s u l t s from th e n i t r a t i o n o f b u ta n e a t th r e e d i f f e r e n t te m p e ra tu re s b u t a t a c o n s ta n t c o n ta c t tim e o f 1 .6 s e c o n d s.

A r e s u l t o b ta in e d by Hodge ( l l )

i s a ls o in c lu d e d f o r com­

p a r is o n .

U n fo rtu n a te ly , on ly an e s tim a te d c o n ta c t tim e i s a v a il a b l e

f o r h is work b u t i t can be seen t h a t th e r e s u l t s a re s u b s t a n t i a l l y d u p lic a te d by th e p r e s e n t work.

A graph o f th e s e c o n v e rsio n s ag a ,in st

te m p e ra tu re (F ig u re l ) shows t h a t optimum r e s u l t s a re a tt a i n e d a t a, te m p e ra tu re o f ^25*C. A t t h i s p o in t i t was decided t h a t th e n i t r a t i o n d a ta would be more u s e f u l i f th e y in clu d e d q u a n tita b iv e d e te rm in a tio n s o f m s.te ria ls o th e r th an n i t r o p a r a f f i n s produced. e th y le n e , ald e h y d e s

T h is would in c lu d e propene, b u te n e ,

carbon monoxide and carbon d io x id e .

O ther o x id a ­

tio n p ro d u c ts a r e produced, b u t th e q u a n t i t i e s a r e sm a.ll, an d , due to th e d i f f i c u l t y o f a n a l y s i s , th e y a r e n o t c o n s id e re d .

T h is new in fo rm a­

tio n perm i.ts th e c a lc u la tio n o f y i e l d s of each p ro d u ct based on th e p e r c e n t o f th e b u ta n e r e a c t i n g . Such d a ta from th e fo re g o in g e x p erim en ts a t ^05®C., 4 2 5 ^ 0 ., and

. a re a ls o given in T able H I .

I t can be seen t h a t in th e

m o d erately narrow te m p e ra tu re ran g e re p o r te d h e r e , te m p e ra tu re has a marked e f f e c t on th e q u a n tity o f n i t r o p a r a f f i n s produced..

T h e ir p ro ­

d u c tio n re a c h e s a maximum and s u b se q u e n tly d e c re a s e s w ith in c r e a s in g te m p e ra tu re . The optimum te m p e ra tu re e f f e c t observed in th e p ro d u ctio n o f n i t r o p a r a f f i n s has p r e v io u s ly been e x p la in e d in two ways.

One i s t h a t

a s th e te m p e ra tu re i s in c r e a s e d , d ecom position o f n i t r o p a r a f f i n s begins to ta k e p la c e th u s re d u c in g th e amount found in th e p ro d u c t.

However,

T a y lo r (2k) found tha.t th e h a l f - l i f e o f n i t r o methane a t 420*0. i s fo u r m in u te s .

Even assum ing a much g r e a t e r d egree o f i n s t a b i l i t y f o r th e

12s,

T able I I I N i t r a t i o n o f Butane W ithout Oxygen E f f e c t o f T em perature ; 10 mm. I.D . C o il R e a c to r) Run No.

42

10

41

Hodge*

Ci,Hio/HH 03

15.0

12.3

15.0

1 4 .0

T em p eratu re, ®C.

405

425

435

420

$ C onversion**

15

36

22

37

RNOg

0 ,1 0

0.29

0 .1 4

J> 0 = 0

0 .0 6

0 .06

0 .10

C^Hg+CgHg

0.1 0

0 .1 1

0 .14

0.10

0.18

0.12

CO

0.13

0 .0 7

0.13

COg

0 .1 0

0 .26

0 .0 7

0 .3 1

0.55

0.41

c h a rg e d .

M oles Formed***

Butane Consumed., Moles****

*

A pproxim ately 3 seconds c o n ta c t tim e .

**

Based on n i t r i c a c id ch arg ed ,

***

C o rre c te d to m oles p e r 10 moles o f b u tan e

**** C a lc u la te d , from th e carbon c o n te n t o f

th e p ro d u c ts .

yz b

FIGURE

I

EFFECT OF TEMPERATURE ON THE NITRATION OF BUTANE AT ( . 6 CECONOC CONTACT TIME (RATIO C)4H,q/HN0-,. = O

I5 ;

10 MM.

I.D .

2 MOLES Og/MOLE HNOg

□ - NO OXYGEN

4o

>20

10

0 400

%^0 TEMPERATURE,

440

REACTOR)

13. h ig h e r iDembers o f th e s e r i e s , t a c t tinie o f 1 .6 se co n d s.

l y s i s should he n e g li g ib l e a t a con­

Hence t h i s e x p la n a tio n seems in a d e q u a te to

a c c o u n t f o r th e f a c t s . A l t e r n a t i v e l y i t has been s u g g e ste d t h a t com peting s id e r e a c ­ t io n s •with h ig h e r a c tiv s -tio n e n e rg ie s becomes more prom inent a t th e h ig h e r te m p e ra tu re s .

Such r e a c ti o n s -would be expected to produce

in c r e a s in g siaounts o f b y -p ro d u c ts a s th e te m p e ra tu re in c r e a s e s . i s n o t th e case ho-wever.

T his

I f th e to-ts.l number o f m oles o f b u tan e which

r e a c t a re c a l c u l a t e d , i t can be seen t h a t th ey in c r e a s e up to a c e r t a i n te m p e ra tu re and then d e c re a s e .

Hence th e d e c re a se in y i e l d s o f n i t r o

p a r a f f i n s observed above th e optimum te m p e ra tu re cannot be th e r e s u l t o f com peting s id e r e a c t i o n s .

A c tu a lly th e d e c re a se in m oles o f n i t r o

p a r a f f i n s produced i s a p p ro x im a te ly e q u a l to th e d e c re a se in m oles o f b u tan e r e a c t i n g .

Hence i t may be concluded t h a t th e assum ption o f

com peting s id e r e a c ti o n s which occur a t th e h ig h e r te m p e ra tu re s i s n o t su p p o rted by e x p e rim e n ta l e v id e n c e . The d e c re a s e in y i e l d s o f n i t r o p a r a f f i n s can be e x p la in e d more sim ply and in b e t t e r acco rd w ith th e d a ta assem bled in th e fo llo w ­ in g way.

The n i t r a t i o n would a p p e a r to be a f r e e r a d i c a l r e a c t i o n .

such i t should be s e n s i t i v e to f r e e r a d i c a l s to p p in g m echanism s.

As

If

th e s e mechanisms a r e assumed to become more and more prom inent a s th e te m p e ra tu re r i s e s , i t fo llo w s th a.t th e y ie ld s o f n i t r o p a r a f f i n s should d e c re a s e c o rre s p o n d in g ly .

T h is i s b e lie v e d to c o n s t i t u t e e-vldence f o r

th e f r e e r a d i c a l mechanism o f n i t r a t i o n which i s proposed in a l a t e r s e c tio n . N i t r a t i o n o f Butane W ith N i t r i c Acid and Oxygen I t was concluded from an exam in atio n o f A le x a n d e r 's d a ta t h a t th e a d d itio n o f oxygen would n e c e s s i t a t e th e use o f a low er te m p e ra tu re

14. to a tts .in optimum r e s u l t s .

A r e a c ti o n m ix tu re c o n s is tin g o f b u ta n e ,

oxygen, and n i t r i c a c id in a r a t i o of 15: 2 :1 was used a t th r e e d i f f e r e n t te m p e ra tu re s . o f 43 p e r c e n t.

The r e s u l t s , given in Table IV, show a maximum c o n v e rsio n However, when th e s e co n v e rsio n s a r e p lo tte d a g a in s t

te m p e ra tu re (F ig u re l ) , i t i s seen t h a t th e optimum te m p e ra tu re i s s t i l l in th e neighborhood o f 425*C. S in c e th e in c r e a s e in co n v ersio n w ith t h i s amount o f oxygen was n o t very g r e a t , f u r t h e r ex perim ents were c a r r ie d o u t to determ in e th e e f f e c t o f v a ry in g th e amount o f oxygen added (T able V ).

In itia lly ,

i t was th o u g h t t h a t a te m p e ra tu re o f 425®C. would be s a t i s f a c t o r y s in c e th e r e was no change in th e optimum tem p e ra tu re when th e oxygen r a t i o was changed from zero to two.

Ifh ile i t was su sp ected t h a t th e d e c re a se

no ted w ith an oxygen r a t i o of th r e e m ight have been caused by u n d e s ir ­ a b le e f f e c t s r e s u l t i n g from too hig h a t e n p e r a t u r e . Run No. 15, p e r ­ formed a t 8 te m p e ra tu re o f 405*C. a ls o showed a d e c re a se in c o n v ersio n to 21 p e r c e n t.

Hence th e h ig h e r tem p e ra tu re can n o t have been th e

dom inant f a c t o r in re d u c in g th e y i e l d , F ig u re 2, which shows th e r e l a t i o n betw een con v ersio n and th e amount o f oxygen added, r e v e a ls t h a t th e h ig h e s t con v ersio n o b ta in a b le in t h i s r e a c t o r i s 44 p e r c e n t a t a te m p e ra tu re o f 425*0. w ith a mole r s .t i o o f b u ta n e :o x y g e n :n itr ie a c id o f 15/ I . 6/ I . The y i e l d , based on th e amount o f b u tan e consumed, i s shown in F ig u re 3 to d e c re a se n e a rly l i n e a r i l y w ith th e amount o f oxygen employed.

Thus i t i s obvious t h a t th e in c r e a s e in co n v ersio n upon

ad d in g oxygen i s a tt a in e d only w ith th e s a c r i f i c e o f c o n s id e ra b le amounts o f th e h y d ro ca rb o n .

The s e rio u s n a tu re o f t h i s a s p e c t i s

e v id e n t when i t i s noted t h a t a t th e oxygen v alu e f o r ms.ximum conversion .

l4 a

T able IV N i t r a t io n o f B utane With Oxygen E f f e c t o f T em perature (C o n ta c t Time = 1 .6 Seconds; 10 mm. I.D . C o il R e a c to r) Eun No.

12

11

13

C4H10/BNO3

1 2 .7

15.5

1 6 .0

O2/ÏÏNO3

2

T em p eratu re, ®C.

4 ll

4-25

450

io

C onversion*

33

43

27

io

Y ield

1 7 .4

24

I5 .6

ENOg

0 .2 6

0 .2 7

0 .1 7

> C =0

0 .7 3

0 .6 8

0 .4 9

C^HG+C^^

0-^3

0 .3 7

0 .6 1

C2H4

0 .3 1

0 .2 5

0 .1 1

CO

0 ,1 0

0 .4 5

0 .2 6

COg

0 ,3 1

0 .1 7

0 .2 1

I.3 S

1 . 06

1 .0 1

Moles Formed

Bu ta n e Con s umed, Mol e s

*

Ba.sed on n i t r i c a c id c h a rg e d .

141,

T able V E f f e c t o f Oxygen a t C o n sta n t T em perature (C o n tac t Time = 1 .6 Seconds; 10 ram. I.D . C o il R e a c to r) Run No.

10

16

11

14

Ci^Eio/mOq

12.3

13.5

15.5

13.2

Og/SNOg

0

1

2

3

T e m p era tu re , *C.

425

425

425

425

^ C onversion

36

42

43

26

i Y ie ld

48

32

24

10

ENOg

0 .2 9

0 .3 2

0 .2 7

0 .20

> c=o

0 .0 6

0 .3 7

0.68

0 .9 6

CqB^+CAHg

0 .1 1

0 .3 3

0 .3 7

1.16

CgEi),

0 .1 8

0 .1 6

0.25

0 .3 1

CO

0 .0 7

0 .5 1

0.45

0.78

COg

0 .2 6

0.05

0 .17

0.38

0.55

0.93

1.06

1.93

M oles Formed

Butane Consumed, Moles

/4

FIGURE 2 NITRATION OF BUTANE VARIATION OF CONVERSION WITH OXYGEN AT k 2 y c . (RATIO C^Hjo/HNOq OF I 5 , CONTACT TIME

1.6 SECONDS;

10 MM.

I.D .

REACTOR)

40

X fe z o

W y

i

2

MOLES OXYGEN PER MOLE NITRIC ACID

3

FIGURE 3 NITRATION OF BUTANE VARIATION OF YIELD WITH OXYGEN AT (RATIO Ci.Hjq/HNO^ OF I 5 , CONTACT TIME = I . 6 S E C O N D S 10 MM.

I.D .

REACTOR)

ÜJ

w 20

LÜ

2 MOLES OXYGEN PER MOLE OF NITRIC ACID

3

15. o n ly 26 p e r c e n t o f th e b u ten e r e a c ti n g i s con v erted to n i t r o p a r a f f i n s . The a c t u a l amounts o f p ro d u c ts from each r e a c tio n a r e given in T able V.

The form a.tion o f c a rb o n y l compounds i s a s t r a i g h t l i n e fu n c tio n

o f th e oxygen added.

The b u te n e s p lu s propene and th e carbon monoxide

a p p e a r to in c r e a s e s lo v ly a t f i r s t , b u t f i n a l l y show an a b ru p t r i s e .

It

i s i n t e r e s t i n g to n o te t h a t th e amounts o f e th y le n e and carbon d io x id e seem to pa,ss th ro u g h a minimum a t th e same p o in t where th e n i t r o p a r a f f i n s show a raa.ximum. T h is ma.ximum p ro d u c tio n o f n i t r o compounds i s somewhat p u z z lin g u n le s s i t

i s a.ssumed t h a t vapor phase n i t r a t i o n i s a f r e e r a d i c a l p ro c e s s .

A p o r tio n

o f th e alk j^l r a d i c a l s r e a c t w ith th e n i t r a t i n g a g e n t to produce

n itr o p a ra ffin s .

However, th e r e a c tio n o f a lk ^ 1 r a d i c a l s w ith oxygen a ls o

p ro ce e d s w ith extrem e ea.se.

Thus when th e oxygen c o n te n t o f th e r e a c tio n

m ix tu re i s in c r e a s e d , a. p o r tio n o f th e f r e e r a d i c a l s p re v io u s ly a v a ila .b le f o r n i t r a t i o n a re removed by r e a c tio n w ith oxygen. The p re se n c e o f o l e f i n s in th e e x i t gases r e g a r d le s s

o f th e

oxygen c o n te n t o f th e r e a c ti o n m ix tu re i s ev id en ce o f th e p rese n c e of f r e e alky^l r a d i c a l s .

The fo rm a tio n o f o l e f i n s from s a tu r a te d hydro­

carbons by a f r e e r a d i c a l p ro c e ss i s a w e ll known phenomenon end in t h i s case i n d ic a te s t h a t a c e r t a i n number o f th e f r e e r a d i c a l s undergo o l e f i n fo rm a tio n b e fo re an e f f e c t i v e c o l l i s i o n w ith a n i t r a t i n g a g e n t can ta k e p la c e .

I t i s r e a d i l y seen t h a t i f th e number o f f r e e r a d i c a l s

i s in c re a s e d w h ile ma. in ta. in in g th e same c o n c e n tra tio n o f n i t r a t i n g a g e n t, th e f o r m t i o n o f o l e f i n s should become g r e a t e r .

The e f f e c t o f oxygen is

p o s tu la te d s,s a f r e e r a d ic a l- f o r m in g p ro c e s s , and i t may be no ted t h a t th e p r e d ic te d r i s e in o l e f i n p ro d u c tio n does occur upon in c r e a s in g th e amount o f oxygen a d d e d .

16. The t o t a l amount o f b u tan e consumed in th e e x p erim en ts con­ ducted a t v a rio u s te m p e ra tu re s w h ile u sin g a r e a c tio n m ix tu re h aving a buta,n e /o x y g e n /n itr ic a c id r a t i o o f I 5/ 2/ I a re given in Table I I I .

An

ex am ination o f th e s e f ig u r e s shows t h a t th e t o t a l amount of r e a c tio n aga.in d e c re a s e s w ith in c r e a s in g te m p e ra tu re a s was observed p re v io u s ly in th e c o rre sp o n d in g ex p erim en ts w ith o u t oxygen. mum i s o b s e rv e d .

In t h i s case no ma.xi-

I t i s obvious t h a t i f a s u f f i c i e n t l y low tem p e ra tu re

were chosen, th e amount o f m t e r i a l . r e a c tin g could be ma,de as sm a ll a s d e s ir e d .

The te m p e ra tu re r e q u ir e d f o r the d e c re a se would l o g i c a l l y be

ex p ected to be low er in th e p re se n c e o f oxygen.

The d e c re a se in b utane

consumed i s a ttr lb u t a .b l e h e re t o th e same e f f e c t as b e fo re : nam ely, a g r e a t e r e x te n t of ch ain te rm in a tio n a t h ig h e r te m p e ra tu re s .

17. III.

E f f e c t o f Oxygen on th e H itro P a r a f f in s Produced The n i t r o p a r a f f i n s formed in Puns 11 and 12 were d rie d and

f r a c t i o n a t e d in a f o u r f o o t column parked w ith a w ire s p i r a l .

A lthough

g r e a t a c c u ra c y was prohahly n o t o b ta in e d , th e r e s u l t s a re q u ite in te re s tin g . As can be seen in T able VI, when th e Og/ENOg r a t i o i s changed from zero to two, th e amounts o f th e n i t r o b u ta n e s formed a r e d e c re a sed s i g n i f i c a n t l y , w h ile th e n i t r o methane and n i t r o ethane a re In c re a se d bj" a f a c t o r o f tw o .

The r e s u l t s from Buns 11 and 12 show t h a t tem p e ra tu re

has l i t t l e , i f any, e f f e c t on p ro d u c t d i s t r i b u t i o n . These r e s u l t s show very c le a r l y t h a t carbon to carbon bond f i s s i o n i s in c re a s e d by th e p re s e n c e o f oxygen.

I t w i l l be shown in a

fo llo w in g s e c tio n on mechanism t h a t t h i s r e s u l t i s to be e x p e cte d .

l? a

T able VI N i t r a t io n o f Butane E f f e c t o f Oxygen on Type o f N itro P a r a f f in s Bun No,

Hod ge*

11

12

14

15.6

1 2 .7

O2/MO3

0

2

2

T em p era tu re , *C

420

425

411

CÏÏ3NO2

10

22

19

CgE^NOg

13

30

32

1-CgEyNOg

8

5

11

2-CkEÿîOg

45

37

21

l-Ci^EgNOg

24

16

17

Mole P er Cent

* Data, tak en from Hodge ( l l )

IS . IV,

E f f e c t o f S u rfa c e on N itr a tio n

The p o s s ib le in flu e n c e of th e r a t i o o f s u rfa c e to volume in th e r e a c t o r on th e n i t r a t i o n r e a c tio n was f i r s t m entioned by S h e c h te r (2 2 ).

W hile he p o in te d o u t th e d e s i r a b i l i t y of h av in g a la r g e

s/V

r a t i o , h is s o le concern was a p p a re n tly h e a l t r a n s f e r . . However, i f one view s th e n i t r a t i o n r e a c tio n a s a f r e e r a d i c a l p ro ce ss in v o lv in g c h a in s, then i t becomes e v id e n t t h a t extended s u rfa c e could r e a d i ly be im p o rta n t f o r s t i l l o th e r r e a s o n s .

An i l l u s t r a t i o n of t h i s i s a ffo rd e d by th e

work o f Pease (iT ) on th e n o n -e x p lo siv e r e a c tio n between oxygen and pro­ pane.

Here In c re a se d s u rfa c e cau ses th e minimum r e a e tio n tem p e ra tu re

to be r a i s e d from 375*C. to pOO®C. and changes th e p r in c i p a l p ro d u cts from carbon monoxide to o l e f i n s , a ld e h y d e s, hydrogen and m ethane. In o rd e r to i n v e s t ig a t e th e s e s u rfa c e e f f e c t s more c a r e f u ll y , a r e a c t o r was c o n s tr u c te d from 22 mm. O.D. pyrex tu b in g which could r e a d i ly be packed to give v a ry in g amounts o f s u rfa c e w h ile m i n t a i n i n g th e same w a ll a r e a and n e a rly th e same volume.

I t was reco g n ized t h a t a

r e a c t o r made o f tu b in g w ith t h i s la r g e a d iam e te r would have r e l a t i v e l y poor h e a t t r a n s f e r c h a r a c t e r i s t i c s .

N e v e r th e le s s , i f th e s / v r a t i o was

to be i n v e s t i ga.ted as an in d ep en d en t v a r i a b le , th e h e a t t r a n s f e r had to be k e p t c o n s ta n t r e g a r d le s s o f i t s a c tu a l v a lu e .

Hence th e optimum

r e s u l t s should be b e t t e r than th o se h e re in o b tain ed b u t th e e f f e c t of changing th e s/V r a t i o should be th e same in e i t h e r c a se . The th r e e p a c k in g s used to vary th e s / v r a t i o were 3 /l6 inch p yrex h e l i c e s , l / S in ch pyrex h e l i c e s , and g la s s w ool. o b ta in e d were 2 0 / l , 2 S / l , and 3OO/I, r e s p e c t i v e l y .

The s / v r a t i o s

I t m ight be p o in te d

out t h a t in th e c a se of th e g la s s wool th e e f f e c t i v e s / v r a t i o was proba.bly somewhat l e s s than t h a t c a lc u la te d because o f cha.nneling.

With

19. each p a rk in g , a. s e r i e s o f ex p erim en ts were perform ed u sin g Og/SNOg r a t i o s o f from zero to t h r e e .

In a l l c a se s i t was obvious t h a t f u r t h e r

a d d itio n s o f oxygen would have no b e n e f i c i a l e f f e c t .

R e s u lts o b tain e d

under th e th r e e c o n d itio n s o f p a rk in g a re given in T ables V II, V I I I, and IX. A com parison o f th e c o n v e rsio n s o b tain ed w ith o u t oxygen w ith s / v r a t i o s o f 20 , 28 , and 300 shows t h a t th e con v ersio n a c tu a ll y d e c re a s e s a s th e amount o f s u rf a c e in c r e a s e s .

T hat t h i s i s n o t due to th e fa v o rin g

o f some o th e r r e a c tio n over n i t r a t i o n i s dem onstrated by com paring th e t o t a l amount o f b u ta n e consumed in each c a se .

This v a lu e d e c re a s e s from

0 .5 1 mole to 0 .3 2 mole w h ile co n v ersio n changes from 27 per c e n t to 20 p e r c e n t.

I t w i l l be noted t h a t th e v alu e o f 27 p er c e n t o b tain e d w ith

an s / v r a t i o o f 20 in th e packed r e a r t o r i s much low er than th e 36 per c e n t c o n v ersio n r e p o r te d f o r th e 10 mm. I.D . c o i l r e a c t o r .

S ince in the

l a t e r c a se th e s/V r a t i o i s 4 / l , a p o rtio n o f t h i s d e c re a se must be due to th e s u rf a c e e f f e c t .

However, i t i s f e l t t h a t to some e x te n t th e pocr

h e a t t r a n s f e r in th e packed r e a c t o r i s r e s p o n s ib le .

C e r ta in ly t h i s i s

to be expected from th e work on methane u s in g v a rio u s ty p e s o f a p p a ra tu s a s d isc u s s e d on pa.ge 9In each c a se a s oxygen was added, th e c o n v e rsio n ro s e to a maximum v a lu e th en f e l l o f f . F ig u re k.

These r e s u l t s a re given g ra p h ic a lly in

The ms.ximum v a lu e s were 42.5 p er c e n t a t s/V r a t i o s o f 20 and

28 , and 44 p e r c e n t w ith S/V r a t i o s o f 3OO.

Hence no s i g n i f i c a n t

in c r e a s e s in maximum co n v e rsio n in th e p rese n c e o f oxygen a re noted with a change in s u r f a c e .

On th e o th e r hand, a marked change in th e q u a n tity

o f oxygen re q u ir e d to g iv e th e optimum co n v ersio n i s n o te d . I t would be expected t h a t a d e c re a s e in th e amount o f oxygen would a f f e c t th e y ie ld based on h y d ro carb o n .

F ig u re 5 shows a comparison

19a

T able VII N i t r a t io n o f Butane E f f e c t o f Oxygen a t an

s/v

R a tio of 20

(T em perature = 425®c,. ; C o n tact Time = 1 .6 Seconds) Run No.

13

21

25

22

C4H10/ENO3

1 2.0

16.0

14.3

15.9

O2/BNO3

0

1

2

3

C o nversion,

27

33

42

39

Y ie ld ,

33

30

22

13

RNOg

0 .2 1

0.21

O .2S

0.25

> c=o

0 .1 4

0.32

0.58

0 .9 0

^ 3^ 6+Fi(-H8

0.15

0.2 1

0.59

0.93

0 .03

0.13

0 .20

0.5 1

CO

0 .3 3

0 .30

0 .39

0 .6 7

COg

0.03

0 .0 6

0.10

0 .0 7

0 .5 1

0 .6 4

1.13

1.76

M oles P roducts***

Butane Consumed , Ploles

*

Based on th e amount o f n i t r i c a c id charged.

**

Ba,sed on b u tan e consumed.

*** C o rre c te d to a t o t a l bu tan e flow o f 10 m o les,

19b,

T able V III N i t r a t io n o f Butane E f f e c t o f Oxygen a t an s/V R a tio o f 28 (T em perature = 425*0.; C ontact Time = 1 . 6 Seconds) Run No.

31

30

28

29

C4H10/BNO2

16.2

1 5.6

13.8

1 4.1

Og/SNOg

0

1

2

3

C o n v ersio n ,

25

39

39

30

Y ie ld ,

44

36

23

12

0.16

0.25

0.28

0 .21

0.09

0 .3 0

0 .58

0 .8 1

C3H6+Ci|.H8

0.09

0 .2 1

0.48

0.82

C2%

0 .06

0.12

0.28

0.59

CO

0 .1 4

0 .2 9

0.43

0.63

COg

0 .0 6

0 .0 4

0.1 1

0.07

0 .3 4

0.68

1.13

1 .67

Moles P roducts*** RNOg C=0

B utane Consumed, Moles

*

Ba.sed on th e amount o f n i t r i c a c id c h a rg e d .

**

Based, on th e bu tan e consumed.

*** C o rre c te d to a t o t a l . b utane flow of 10 m o les-

19c

T ab le IX N i t r a t i o n o f Butane E f f e c t o f Oxygen a t an S/V R a tio o f 3OO (T em perature = 4 2 5*0.j C o n ta c t Time = 1 .6 Seconds) Run No.

34

35

32

36

33

C4B10/BNO3

1 5.6

15.5

15 .7

14.8

14.6

O2/HNO3

0

0 .5

1

1.25

2

C o n v ersio n ,

20

33

44

41

34

Y ie ld ,

37

46

45

38

20

RNOg

0.13

0 .2 1

0.28

0.2 8

0 .2 4

>C=0

0.05

0.18

0 .3 2

0 .4 1

0.63

C3ÏÏ5+Cij.BB

0.10

0.09

0 .1 4

0.18

0 .4 4

C2H4

0 .0 7

0.05

0 .0 3

0 .1 2

0 .2 9

CO

0 .2 4

0.18

0 .2 3

0.28

0 .4 9

COg

0 .0 4

0 .0 9

0 .1 2

0 .0 6

0 .0 7

0 .3 2

0.42

0 .58

0.68

1 .07

Moles Formed***

Butane Consumed, Moles

*

Baaed on th e amount o f n i t r i c a c id c h a rg e d .

**

Baaed on th e b u tan e consumed..

*** C o rre c te d to a t o t a l . b utane flow o f 10 moles

FIG U RE 4 EFFECT OF OXYGEN ON CONVERSION W IT H D IF F E R E N T SU RFACE/VO LU IC

R A TIO S

(TEMPERATURE = 4 Z 5 ° C . , CONTACT TIM E =

0-

s /v

“ 20}

s /v

=

28; D -

on

9 i

30

U!

MOLES 0 - PER MOLE HNO

C /V

I .6

=

SECONDS) 3OO

FIGURE 5 NITRATION OF BUTANE EFFECT OF OXYGEN ON YIELD WITH DIFFERENT SURFACE/VOLUME RATIOS {TEMPERATURE = 4 2 ^ * 0 , , CONTACT TIME = ( .< SECONDS)

O-

0

s /v

=

20;

6-

s /v

=

28;

D-

S /V

=

gOO

2 MOLES OXYGEN PER MOLE OF N IT R IC AC I

3

20. o f th e y ie ld s o b ta in e d by V8.rying th e r a t i o o f oxygen w ith th e th r e e p a c k in g s .

I f th e curve f o r th e 2 0 / l s/V r a t i o i s compared w ith th s.t

given in F ig u re 3 f o r th e 10 mm. c o i l , i t w i l l be seen t h a t th ey a re s u b s t a n t i a l l y e q u iv a le n t.

T h is proba.bly r e s u l t s fr*om, com pensation f o r

th e d e c re a s e in h e a t t r a n s f e r a r e a by th e in c r e a s e in s u r f a c e .

On th e

o th e r hand, c o n s id e r a b le d i f f e r e n c e s a r e noted between th e y i e l d s a t s / v r a t i o s o f 20, 28, and 300300 i s q u ite u n u su a l.

The peak o b ta in e d when th e s / v r a t i o i s

I t i s th e f i r s t experim ent in which an a c t u a l

in c r e a s e has been o b ta in e d upon a d d in g oxygen.

In a d d itio n

t h i s v a lu e

i s e q u iv a le n t to th e b e s t y ie ld p re v io u s ly o b tain e d w ith b u ta n e , w hich, i t w i l l be r e c a l l e d , was g o tte n in th e 10 mm. c o i l w ith o u t oxygen.

In as­

much a s a p p ro x im a te ly th e same amount o f oxygen i s r e q u ir e d under th e s e c o n d itio n s f o r rte.ximum y ie ld and c o n v e rs io n , th e use o f oxygen a s a. n i t r a t i o n a id would be f e a s i b l e from an economi.c s ta n d p o in t.

S in c e th e

d e c re a s e in y ie ld caused by oxygen was th e c h ie f com m ercial draw back to t h i s p ro c e s s in th e p a s t , i t i s f e l t t h a t th e b e n e f i c i a l e f f e c t o f th e p ro p e r amount o f s u rf a c e c o n s t i t u t e s a m ajor c o n tr i b u ti o n .

I t should be

a g a in p o in te d o u t t h a t th e s e r e s u l t s pro b ab ly do n o t r e p r e s e n t th e b e s t o b ta in a b le .

A more s u it a b ly designed r e a c t o r , based on th e d a ta h e re in

p r e s e n te d , should g iv e c o n v e rsio n s t h a t a re s u b s t a n t i a l l y h ig h e r w ith no d e c re a s e in y i e l d .

I t w i l l be shown in a fo llo w in g s e c tio n t h a t

th e s e same c o n c lu s io n s a re a p p lic a b le to propane. W hile th e e x a c t mechanism by which s u rfa c e e x e r c is e s i t s e f f e c t in somewhat o b sc u re , c e r t a i n c o n c lu s io n s me.y be drawn fi'om an exa.m ination o f th e q u a n t i t i e s o f p ro d u c ts o b ta in e d in th e above e x p e r i­ m ents.

A r a t h e r la r g e p o r tio n o f th e b u tan e i s c o n v e rted to b u te n e s and

propene th u s making t h i s one o f th e g r e a t e s t s o u rc e s o f l o s s .

F ig u re 6

FIGURE 6 EFFECT OF OXYGEN ON FORMATION OF PROPENE ANO BUTENES WITH VARIOUS

s u r f a c e / vo lu m e

RATIOS

(CONTACT TIME = 1 .6 SECOriF;S; C};H;r)/HNOg = l|))

O-

s /v

=

20;

s /v

=

28;

O-

S /V

=

.0

CO w z L-J Hg a! w z w CL O

cc

CL

o CO ÜJ

2 MOLES OXYGEN PER MOLE N ITR IC ACID

300

21. shows how t h i s quaxitity v a r ie s w ith oxygen f o r each p a c k in g .

In each

c a se th e r e i s a, g ra d u a l in c r e a s e u n t i l th e Og/ENO^ r a t i o re a c h e s a p p ro x ima.tely one.

At t h i s p o in t th e r a t e o f in c r e a s e becomes much l a r g e r .

T h is same e f f e c t was n o tic e d when u s in g th e 10 mm. c o i l r e a c t o r .

It

p ro h ah ly i n d ic a te s th e a b i l i t y o f th e r e a c tio n m ix tu re to u t i l i z e a r e l a t i v e l y h igh p o r tio n o f th e f r e e a lk y l r a d i c a l s formed by o x id a tiv e a t t a c k u n t i l a c e r t a i n c o n c e n tra tio n i s re a c h e d .

A f te r t h a t p o in t, a

much l a r g e r p e rc e n ta g e o f th e s e r a d i c a l s undergo decom position to form o le fin s .

I t can be seen t h a t a h ig h e r s / v r a t i o ca u se s a g e n e ra l low er­

in g o f th e curve w ith o u t a l t e r i n g i t s b a s ic sh a p e.

R e f e r r in g now to

F ig u re 7 , i t i s seen t h a t th e t o t a l amount o f b u tan e r e a c ti n g in c r e a s e s w ith oxygen, b u t t h a t in c re a s e d s u rf a c e d e c re a s e s th e amount o f t h i s in c r e a s e a t any given oxygen r a t i o .

I t has p r e v io u s ly been assumed t h a t

such a d e c re a s e in th e amount o f b u tan e r e a c ti n g i s due to ch ain s to p p in g w ith l e s s t o t a l p ro d u c tio n o f f r e e r a d i c a l s .

Hence th e d e c re a s e in o l e f i n

fo rm a tio n observed upon in c r e a s in g th e s u rfa c e i s sim ply a r e f l e c t i o n of a low er r a t e o f f r e e r a d i c a l fo rm a tio n . The d a ta given in T a b le s V II, V TII, and IZ show t h a t pro d u c­ t io n o f n i t r o p a r a f f i n s goes th ro u g h a ma.ximum w ith in c r e a s in g oxygen. These maxima, a r e th e sa,me h e ig h t r e g a r d le s s o f th e w ith l e s s oxygen a.s th e r a t i o i n c r e a s e s .

s/v r a t i o b u t occur

S in c e th e t o t a l number o f fre e

r a d i c a l s has been d e c re a se d by s u r f a c e , th e f a c t t h a t th e same number a re c o n v e rted i n to n i t r o p a ra .ffin s must mean t h a t t h e i r r e a c ti o n to form oxygéna,te d m a t e r i a ls i s a c h a in r e a c ti o n which i s h in d e re d by s u r f a c e . Such a r e a c ti o n would presuma,bly in v o lv e HO o r HOp r a d i c a l s a s chain c a r r i e r s and would be stopped on th e w a lls . s e n t a mechanism based on th e s e c o n c lu s io n s .

A l a t e r s e c tio n w i l l p r e ­

EFFECT OF OXYGEN ON AMOUNT OF BUTANE REACTING USING VAR IOUS'SURFACE/VOLUME RATIOS (CONTACT TIME

1.6 SECONDS,

Ci^H,o/HN03 = 1 5 , TEMPERATURE = 4 2 $ T . )

O - s / v = 20; A - s / v - 28; O - S /v = 300

X u

E3 y

o w 0_

i y

2 MOLES OXYGEN PER MOLE OF NITRIC AC in

3

22. V.

The Use o f Steam a s a D ilu e n t

In the fo reg o in g s e c tio n i t was p oin ted out th a t an e x c e s s o f f r e e r a d ic a ls are formed when oxygen i s added to the n itr a t io n m ixture to th e e x te n t o f two moles fo r each mole o f n i t r i c a c id . The f a c t th a t conversion does not in c re a se g r e a tly under these circum stances in d ic a te s th a t an in s u f f i c i e n t amount o f th e n it r a t in g agent i s p resen t a t the time the ex tra f r e e r a d ic a ls are a v a ila b le .

This

could stem from e it h e r o f two fa c to r s : ( l ) decom position o f n i t r i c a c id in oth er ways, or (2) production o f fr e e r a d ic a ls over such a sh ort p erio d o f tim e th a t the a c tu a l n it r a t in g agent (presumably NO2) i s n ot formed f a s t enough to u t i l i z e them b efore they undergo oth er change. The obvious s o lu tio n to the d i f f i c u l t y in the l a t t e r case would be to add an in e r t d ilu e n t to the m ixture sin c e t h is would e f f e c t i v e l y d ecrease the r a te a t which the fr e e r a d ic a ls are formed.

I t would n o t,

however, in flu e n c e m a te r ia lly the t o t a l q u an tity o f them formed b efo re the end o f the n itr a t io n tube i s reached. d ilu e n t would seem to be steam.

The mast l i k e l y ch oice o f

I t i s in e r t , cheap, has a high heat

c a p a c ity and i s alrea d y bein g introduced to some e x te n t a s water in the 70 per cen t n i t r i c a c id . Dr. Bass p o in ted out th a t work by Hibshman (9 ) on the n it r a ­ tio n o f ethane w ithout added oxygen show th a t in c r e a sin g th e d ilu tio n o f th e n i t r i c a c id has an adverse e f f e c t on co n v ersio n .

Ifeder th e se

c o n d itio n s , however, th e r a t io o f fr e e r a d ic a ls to n it r a t in g agent does n o t reach an optimum v a lu e .

Hence, a d ilu e n t which d ecrea ses the r a te

o f fr e e r a d ic a l form ation would not be expected to in c re a se but r a th er to decrease the con version .

With ex c ess oxygen p r e se n t, however, the

r a t io o f fr e e r a d ic a ls to n it r a t in g agen t exceeds the optimum v a lu e .

A

23. d ilu e n t p resen t in s u ita b le amounts would, decrease t h is r a t io to the optimum value and thereby le a d to in crea sed co n v ersio n s. To t e s t t h i s rea so n in g two experim ents were c a r r ie d out u sin g equim olar amounts o f hydrocarbon and steam. b u ta n e /o x y g e n /n itr lc a c id r a t io was I 5/ 2/ I .

In each case the

One was performed in the

10 mm. c o i l which has an S/V r a t io o f h and the other in the packed r e a c to r w ith an s /T r a t io o f 20.

Other p e r tin e n t in fo r n a tio n alon g

w ith the r e s u lt s are given in Table X.

A lso included fo r comparison

are Buns 11 and 25 which are e q u im le n t in a l l r e sp e c ts excep t they were performed, w ithout added steam.

A s tr ik in g improvement in both

conversion and y i e l d was obtained, a s a r e s u lt o f the a d d itio n o f steam. In c r ea sin g the s / v r a t io caused, a fu rth er improvement in y ie ld , alth ou gh the conversion was not ap p reciab ly a f f e c t e d . An exam ination o f the prod.ucts shows th a t the steam in c r e a se s the amount o f aldehydes produced but th a t the t o t a l amount o f o le f in s formed d e c r ea se s.

This d ecrease

w h ile sm all in the 8/7= 4 r e a c to r ,

becomes c o n sid era b le when the s / 7 r a tio i s r a is e d to 20.

In e ith e r

ca se the a c tu a l number of moles o f n itr o p a r a ffin s produced shows a s u b s t a n t ia l r i s e which i s g r e a te r than the in crea se brought about by any other s in g le v a r ia b le . I t i s f e l t th a t the g r e a te s t p o s s i b i l i t y o f e f f e c t in g improve­ ments in the vapor phase n itr a t io n process l i e s in the use o f steam as a d ilu e n t in a p rocess u sin g oxygen and a la r g e amount o f su r fa c e .

From

the r e s u lt s given here i t i s obvious th a t s t r ik in g improvements can be made p a r t ic u la r ly in view o f the f a c t th a t no attem pt was made to d eter­ mine optimum c o n d itio n s .

23 a

T able X N i t r a t i o n o f B utane in th e P re se n c e o f Oxygen Use o f Steam a s D ilu e n t (C o n ta c t Time = 1 .6 Seconds)

Bun N o.

11

25

17

20

s /v

k

20

4

20

Ci^Eio/ENOq

1 5 .6

13.3

1 4 .6

14.0

Og/SNOg

2

2

2

2

9 .6

9 .6

1

1

C o n v ersio n , ^

36

42

55

54

Y ie ld , i

2k

22

30

35

0 .2 6

0.28

0 .3 6

0 .39

0 .6 8

O.5B

0 .8 2

0.88

0 .3 7

0 .59

0 .4 1

0.25

CgBh

0 .25

0.20

0 .1 0

0.08

CO

0 .4 5

0.39

0 .4 7

0 .4 1

COg

0 .1 7

0 .1 0

0 ,1 0

0.05

1 .0 6

1.18

1 .1 2

1.02

Moles Formed: RNOg >0=0

B utane Consumed, Moles

2k.

VI.

N itr a tio n o f Propane

The e f f e c t o f oxygen on conversion obtain ed in t h is in v e s tig a ­ tio n was s m l l e r than th a t rep orted by Alexander fo r propane.

A s e r ie s

o f con version s ob tain ed in the in v e s tig a tio n s w ith propane u sing various O2/HNO3 r a t io s a t two d iff e r e n t tem peratures are given below: O2/M O 3

0

0 .9

1 .9

3-5

io Conversion

at

395‘*C. 20

38

53

76

^ Conversion

at

4lO®C. 28

49

53

62

These experim ents were conducted in a 7 mm. 0, D. c o i l r e a cto r w h ile the experim ents w ith butane were performed e ith e r in a 10 mm. I . D. c o i l r e a c to r or in a 22 mm. O.D. packed r e a c to r .

One d iffe r e n c e between the

two c o i l r e a c to r s i s th e S/V r a t io which i s 8 in the case o f the former and 4 w ith the l a t t e r .

However, i t has been shown th a t v a r ia tio n s in

t h is r a t io do not cause s ig n if ic a n t v a r ia tio n s in the maximum conversion o b ta in a b le w ith butane.

The only other fa c to r s which could be r e sp o n sib le

fo r the d iffe r e n c e are: ( l ) a d iffe r e n c e in the heat tra n sfe r area pre­ se n t in the two c o i l s , or (2) a d iffe r e n c e in the chem ical behavior o f the two hydrocarbons In view o f the in t e r e s t in g e f f e c t o f the su rface to volume r a t io on y ie ld (based, on hydrocarbon) in the case o f butane, i t was deemed im portant to d isco v e r whether th ese e f f e c t s could be observed w ith propane.

S in ce a complete d u p lica tio n o f the work already done

was im p o ssib le , i t was decid ed to check on ly a few d iff e r e n t experim ents. I f a c lo s e correspondence between butane and. propane was obtained in th e se

then I t would be assumed, th a t d u p lic a tio n could, probably be

obtained, under oth er c o n d itio n s .

I t would a ls o fo llo w th a t butane

would g iv e s im ila r r e s u lt s to those obtain ed w ith propane by Alexander i f a d u p lic a te apparatus were used.

The e x p erim en ts l i s t e d in T ab le XI

were perform ed w ith p r o ­

pane in th e pa,cked. r e a c t o r u sin g s / v r a t i o s o f 3OO and 28.

I t w i l l be

noted. th a ,t th e c o n v e rsio n s and y ie ld s given in Runs 38 , 3 9 , and 40 a r e th e same o rd e r o f m agnitude a s th o se o b tain e d w ith b u tan e in Runs 33; 32, and 28, r e s p e c ti v e ly .

W ith b u tan e in th e s/v= 300 r e a c t o r , th e

c o n v e rsio n and y ie ld b o th d e c re a sed a s th e O2/HNO3 r a t i o was changed from one t o two.

T h at th e co n v e rsio n did n o t d e c re a s e w ith propane

under th e same c o n d itio n s shows t h a t propane r e q u ir e s s l i g h t l y more oxygen f o r maximum c o n v e rsio n under th e s e c o n d itio n s .

The d a ta would

i n d ic a te a co n v ersio n w ith propane a t an O2/M O 3 r a t i o o f 1 .5 t h a t would be compa,rable to th e v alu e o f 44 p e r c e n t o b ta in e d in Run 33 w ith b u ta n e . S in c e A lex an d er worked a t a c o n s id e ra b ly low er te m p e ra tu re . Run 40 was conducted a t 400*C.

I t was found t h a t w ith th e parked

r e a c t o r , t h i s m erely caused a d e c re a se in c o n v e rsio n .

Hence i t i s n o t

p o s s ib le to a s c r ib e th e d if f e r e n c e s in co n v ersio n to te m p e ra tu re .

It

becomes obvious t h a t d i f f e r e n t optimum te m p e ra tu re s a s w e ll a s co n v er­ s io n s a r e shown by d i f f e r e n t r e a c t o r s . A f i n a l check was provided by Run 43 which was ma,de w ith an s / v r a t i o o f 28 and on O2/HNO3 r a t i o o f tw o .

The c o n v ersio n o b tain e d

was s l i g h t l y b e t t e r th a n t h a t o b ta in e d w ith b u ta n e .

The y ie ld o f 33

p e r c e n t for th e n i t r a t i o n o f propane was s i g n i f i c a n t l y h ig h e r than th e 23 p e r c e n t v a lu e f o r b u ta n e .

I t ms.y be concluded then t h a t propane

w i l l show th e same e f f e c t w ith in c re a s e d s u rfa c e in th e p re se n c e of oxygen that b u tan e d o e s.

From th e d a ta f o r Run 43, i t would ap p ear

p o s s ib le to a c h ie v e even more s t r i k i n g e f f e c t s .

T h is r e s u l t i s n o t

p a r t i c u l a r l y s t a r t l i n g in t h a t propane i s more r e s i s t a n t to o x id a tio n

25a

T able XI N i t r a t i o n of Propane in th e Packed R e a c to r (C o n ta c t Time = 1 . 6 Seconds)

Run N o.

33

39

40

43

CgEg/mOg

1 5 .0

15.8

14.6

1 3.0

O2/HNO3

1

2

2

2

Tem pera,ture, ®C .

425

425

400

425

s / v R a tio

300

300

300

26

C o n v ersio n , ^

33

39

16

44

Y ie ld , i

37

24

31

33

RNO2

0 .2 6

0 .2 4

C.13

0 .3 4

t> C=0

0 .3 4

0.6 2

0 .0 3

0 .6 4

C3B6

0 .1 6

0 .2 0

0 .1 0

0.18

C2%

0 .0 6

0.07

0.05

0.08

CO

0 .2 8

0 .3 4

0 .2 9

0.35

C02

0 .0 8

0.10

0 .08

0.1 5

0 .6 5

0 .9 6

0 .3 9

0.93

Moles o f P ro d u c ts :

Propane R e a c tin g , Moles

26.. t h a t b u tan e and p ro p y l r a d i c a l s sh o u ld show l e s s tendency to decompose in to o le f in s .

Hence i t i s th e o p in io n o f t h i s a u th o r t h a t w ith th e

p ro p e r S/V r a t i o , th e n i t r a t i o n o f propane w ith oxygen could be ma.de to g iv e c o n v e rsio n s ap p ro a c h in g th o se o b ta in e d by A lexander b u t w ith y i e l d s o f th e same o rd e r a s th o se o b ta in e d w ith no oxygen. steam a s a d i lu e n t would be s tr o n g ly a d v is e d .

The use o f

27. V II. N itro g e n B alance D ata re p o rte d by Hodge ( l l ) and H atcher (8) i n d ic a te t h a t 5 p e r c e n t o r l e s s of th e n i t r i c a c id charged i s co n v erted to m o lecu lar n itr o g e n .

However, th e s e f ig u r e s a r e a t v a ria n c e w ith th e 20 p e r c e n t

l o s s o b ta in e d in com m ercial n i t r a t i o n a c c o rd in g to v e rb a l in fo rm a tio n from a Commercial S o lv e n ts r e p r e s e n t a t i v e .

T h is f ig u r e i s q u ite

im p o rta n t com m ercially s in c e i t r e p r e s e n ts u n rec o v e rab le n itro g e n w hereas th e n i t r i c oxide and n itro g e n d io x id e may be rec o v e red as n itr ic a c id . U n fo rtu n a te ly , t h i s d isc re p a n c y was n o t n o ted u n t i l n e a r th e end o f t h i s i n v e s t i g a t i o n .

S in ce a n a ly s e s had been ms,de r e g u l a r l y f o r

n i t r i c o x id e , n itr o g e n d io x id e and n i t r o p a r a f f i n s , i t should, have been p o s s ib le to e stim s.te n itr o g e n l o s s by d i f f e r e n c e .

However, a s e rio u s

e r r o r was p r e s e n t in a l l d e te rm in a tio n s o f n i t r i c oxide p r io r to Run 26. T h is had r e s u l te d from a la c k o f a p p r e c ia tio n o f th e s o l u b i l i t y o f b u tan e in th e f e r r o u s s u l f a t e re a g e n t used f o r a b s o rb in g th e n i t r i c oxide A lso th e n itr o g e n d io x id e v a lu e was p ro b ab ly somewhat low in most ca se s becau se o f l o s s e s due to i t s s o l u b i l i t y in th e r e t a i n i n g s o lu tio n used in sam p lin g .

However. th e p e rc e n ta g e n itr o g e n l o s t a s c a lc u la te d in

t h i s m n n e r i s s e m i- q u a n tita tiv e ly a c c u r a te .

Such v a lu e s a s could be

o b ta in e d a r e given in T able X II. The la r g e a p p a re n t in c r e a s e in n itro g e n l o s s on going from th e c o i l r e a c t o r to th e peeked r e a c t o r w ith an s/V r a t i o o f 28 could be due e i t h e r to a d e c re a s e in h e a t t r a n s f e r o r to an in c r e a s e in s u rfa c e S in c e a f u r t h e r in c r e a s e in th e s/V r a t i o to 3OO caused a sm a ll f u r t h e r d e c re a s e in l o s s , i t i s f e l t t h a t poor h e a t c o n tr o l m ust be r e s p o n s ib le f o r th e d i f f e r e n c e .

T h is p o in t i s , o f c o u rs e , s u b je c t fco q u e s tio n and

i t would be d e s ir a b le to o b ta in more p o s it i v e e x p e rim e n ta l evidence to

27 a,

T able X U L oss o f N i t r i c A cid to N itro g e n Gas ( A ll E xperim ents a t 425®C., 1 .6 Seconds C o n tact Time and Ci^Hio/HNO, R a tio o f I 5 )

s / v R a tio 4* Og/SNOg

*

23

300

P e r Cent Loss to Ng**

0

20

30

33

1

--

27

24

2

0

24

7

3

—

11

E xperim ents in th e 10 mm. I.D . c o i l .

** C a lc u la te d by d if f e r e n c e betw een n i t r i c a c id charged and recovered. NO, NOg, and RNOg.

23. c o n firm i t .

N e v e rth e le s s

th e i n d ic a tio n t h a t s u rfa c e has no d e t r i ­

m en ta l e f f e c t i s e n c o u ra g in g in l i g h t o f th e a d v an tag es shown hy t h i s f a c t o r in im proving hydrocarbon co n v ersio n to n i t r o p a r a f f i n s . The e f f e c t o f oxygen a p p e a rs to be q u ite d e f i n i t e and f a v o r ­ a b le .

No mechanism i s o f fe r e d f o r th e n itr o g e n l o s s so t h a t i t i s

im p o s s ib le to e x p la in j u s t why th e a d d itio n o f oxygen should p re v e n t it.

However, i t should, be recognized, t h a t th e c o n v e rsio n o f n i t r i c

a c id to n itr o g e n i s a r e d u c tio n , and t h a t th e a d d itio n o f oxygen would be expected, to m inim ize such a p ro c e s s . In o rd e r to o b ta in a check on th e v a l i d i t y o f th e above m easurem ents, a method, o f a n a ly s is was worked out and a p p lie d to s e v e r a l e x p e rim e n ts.

S in c e even a r e l a t i v e l y la r g e n itr o g e n l o s s would r e p r e ­

s e n t only a sm s.ll p o r tio n o f th e ga.seous p ro d u c ts , i t was found n e c e ssa ry t o remove a l a r g e p o r tio n o f th e condensable m s.te ria ls in a dry ic e t r a p , An a l i q u o t p o r tio n o f th e rem ainder was s u b je c te d to th e r e g u la r ga,s a n a ly s i s p ro ce d u re to remove carbon d io x id e axd n i t r i c o x id e .

carbon monoxide, o l e f i n s

The rem s-inder o f th e b u tan e was absorbed, in kero sen e.

Oxygen was added and th e m ix tu re was burned over h o t copper o x id e .

From

th e d e c re a s e in volume upon com bustion a lo n g w ith a m easure o f th e carbon d io x id e produced . i t was determ ined th a.t hydrogen and methane were p r e ­ s e n t.

The o r i g i n a l r e s id u e l e s s th e q u a n ti ti e s o f th e s e m a te r ia ls gs.ve

th e amiount o f m o le c u la r n itr o g e n .

A q u a l i t a t i v e t e s t was perform ed on

t h i s m s b e ria l by a llo w in g i t to r e a c t w ith h o t ms.gnesium to form th e n itrid e .

S ubsequent h y d r o ly s is gave th e odor o f ammonia. The r e s u l t s o f t h r e e such a n a ly s i s a r e given in T able X H I.

I t w i l l be observed, t h a t rough checks a r e o b ta in e d between th e measured

28a

T able X III A n aly ses f o r N itro g e n Gas

Bun N o.

36

38

4l

H ydrocarbon

Butane

Propane

Butane

s / v R a tio

300

300

4

O2/M O 3

1 .2 5

1

0

T em p eratu re, ®C .

425

425

425

M easured N itro g e n * L o s s , ^

19

23

24

E stim a te d N itro g en * * L o s s , ^^

13

28

31

Moles Hp

0 .0 2

0 .0 1

0 .01

Moles CHi|_

0 .0 3

0.02

0.02

*

Measured, by gs.s a n a ly s is and. re p o r te d a s mole fb o f th e n i t r i c a c id c h a rg e d .

** E stim a te d by method used in T able X.

29. v a lu e and t h a t c a lc u la t e d hy d if f e r e n c e .

As would he expected from th e

low v a lu e s f o r NOg, th e m easured n itro g e n l o s s i s g e n e ra lly low er th an th e c a lc u la t e d v alu e and i s p ro b ab ly more a c c u r a te . T able X I I I a ls o l i s t s th e a c t u a l q u a n ti ti e s o f hydrogen and m ethane formed

W hile s m a ll, th e s e v a lu e s do giv e a d d it io n a l ev id en ce

o f th e p re se n c e o f a f r e e r a d i c a l p ro c e ss inasm uch a s th e methane m ust have been formed, by th e a t t a c k o f a m ethyl r a d i c a l on a n o th e r h y d ro ­ carbon m o le c u le . In g e n e ra l, th e n , i t would ap p ear t h a t l o s s o f n i t r i c a c id to m o le c u la r n itr o g e n i s a s e r io u s problem in vapor phase n i t r a t i o n . F u rth e rm o re , i t i s aggrava.ted by poor h e a t c o n tr o l.

On th e o th e r hand,

th e p re s e n c e o f oxygen in th e n i t r a t i o n m ix tu re and perhaps a la r g e s/V r a t i o a p p e a r to red u c e th e lo s s c o p s id e r a b ly .

30. MECHMISM S p e c u la tio n s c o n c ern in g th e mechanism o f vs,por phase n i t r a ­ t io n have been r i f e . D egering ( I 5 ) .

I t was in v e s tig a te d , d i r e c t l y by McCleary and.

Hass e t a l ( 6 ) s ta te d , c o n c lu sio n s drawn from examina­

tio n o f t h e i r e x p e rim e n ta l data,.

The c o n c lu sio n s reach ed ms,y be sta b e d

a s fo llo w s : (1)

N i t r a t i o n p ro ce e d s th ro u g h a f r e e r a d i c a l p ro c e s s .

( 2)

A lk y l f r e e r a d i c a l s a r e formed, by an o x id a tiv e a t t a c k on

th e hydrocarbon by n i t r i c a c i d . ( 3)

These f r e e r a d i c a l s a t t a c k a n i t r i c a c id m olecule w ith th e

fo rm a tio n o f a n i t r o p a r a f f i n m olecule and an -OH r a d i c a l . (4 )

Lower m o le c u la r w eight n i t r o p a r a f f i n s r e s u l t from a lk y l

r a d i c a l s produced d i r e c t l y from th e hydrocarbon. (5 )

The form s,tion o f o x id iz e d ro a,terial i s th e r e s u l t o f r e a c tio n

betw een th e hydrocarbon and n i t r i c a c i d . (6 )

Some d ecom position of n i t r o p a r a f f in s o ccu rs by r e a c tio n w ith

n itr ic a c id . W hile such a view o f th e sechanism ms,y n o t be in h e r e n tly w rong, i t does l i t t l e more than s u g g e st th e n a tu r e s o f th e r e a c tio n s ta k in g p la c e .

I t is

how ever, p o s s ib le , w ith th e a id o f o ld e r data,

and th e newer d a ta assem bled in t h i s t h e s i s to propose a s e r i e s o f e q u a tio n s which a c c o u n t f o r m ost o f th e observed p ro d u c ts and f o r th e v a r i a t i o n s in th e s e p ro d u c ts which r e s u l t from c e r t a i n changes in condi­ t io n s and in th e mole r a t i o s o f th e r e a c t a n t s .

The p roposed mechanisms

in v o lv e r e a c t i o n s , which f o r th e most p a ,rt, have been o b serv ed to occur p re v io u s ly under s i m i l a r c o n d itio n s .

31. E vidence t h a t n i t r a t i o n pro ceed s by a f r e e r a d i c a l mechanism i s fu rn is h e d by th e fo llo w in g f a c t s : (1)

B urton (4) n i t r a t e d o p t i c a l l y a c ti v e 3-m ethylhexane and

o b ta in e d racem ic 2 - n it r o b u t a n e .

T his in d ic a te s t h a t th e secondary

b u t y l group p a s se s th rough a c o n f1g u r a tio n a lly u n s ta b le form in th e n i t r a t i o n p ro c e s s .

The most l i k e l y assum ption i s t h a t t h i s i n t e r ­

m ed iate i s th e c o rre sp o n d in g f r e e r a d i c a l . (2)

B l i c k e n s ta f f (2) s u c c e s s f u lly n i t r a t e d th e b rid g eh ead carbon

in b ic y c lo (2 2 .1 ) h e p ta n e .

T h is would r u l e out th e rep la ce m e n t o f

hydrogen by a rea rw a rd a t t a c k and would in d ic a te in s te a d a forw ard a t t a c k w ith th e p ro b a b le form a,tion o f a f r e e r a d i c a l in te r m e d ia te . ( 3)

S h e c h te r (22) found n i t r a t i o n to lead to th o se n i t r o p a r a f f in s

c o rre sp o n d in g to a l l p o s s ib le a lk y l r a d i c a l s which can be formed, by b re a k in g only one carbon to carbon bond in th e o r i g i n a l h y d ro ca rb o n . M cCleary (15) a l s o showed th e fo rm atio n o f o l e f i n s c o rre sp o n d in g to a l l o f th e a l k y l r a d i c a l s p r e s e n t in n i t r o p a r a f f i n s .

T his in d ic a te s

t h a t a l k y l f r e e r a d i c a l s may be p r e s e n t s in c e they a re known to decom­ pose r e a d i l y and r a p i d l y to o l e f i n s . (4)

M cCleary was a ls o a b le to form n i t r o pa.rs,ffin s by th e r e a c ­

t io n betw een t e t r a e t h y l le a d and n i t r i c a c id in th e vapor p h a s e . T e t r a e th y l le a d has been shown by P aneth ( I 6 ) t o form e th y l r a d i c a l s when h e a te d under d im in ish ed p r e s s u r e .

I f th e same b e h a v io r ms.y be

assumed a t a tm o sp h eric p r e s s u r e , th e n i t r o p a .ra ffin s probably came from th e union o f an e th y l r a d i c a l w ith th e n i t r a t i n g a g e n t. T h is p r e s e n t work d is c lo s e s two o th e r f a c t s o f s ig n if ic a n c e : (5 )

The p re s e n c e o f in c re a s e d s u rf a c e cau ses a d e c re a se in th e

t o t a l amount o f hydrocarbon r e a c ti n g .

T his ms,y be a s c r ib e d to d e s tr u c ­

t io n o f f r e e ra ,d ic a l in te r m e d ia te s by s u rfa c e r e a c tio n s (1 4 ).

32. ( 6)

The in c r e a s e d p ro d u c tio n o f o l e f i n s a s w e ll a s n i t r o p a r a f f in s

when oxygen i s added to th e n i t r a t i o n m ix tu re s u g g e sts f r e e a l k y l r a d i c a l in te r m e d ia te s s in c e th e s e a r e known to he formed in o x id a tio n s under c o m p a ralle c o n d itio n s ( 25) . Much has been said, s h o u t th e s o - c a lle d a g e n t of n i t r a t i o n . T h is i s d e fin e d a s th e n e .te r ia l which r e a c t s w ith th e a l k y l f r e e r a d i c a l s t o produce n i t r o p a r a f f i n s

I t i s w e ll known t h a t n i t r i c a c id i s

u n s ta b le a t 425*C . and t h a t th e p ro d u c ts o f th e decom position a re n itr o g e n d io x id e , n i t r i c o x id e , oxygen

and w ater ( 5 )•

U n fo rtu n a te ly ,

no d e ta i le d mechanism has been worked out f o r t h i s r e a c t i o n .

These pro­

d u c ts (e x c e p t f o r th e w a te r) may. how ever, be accounted f o r by th e fo llo w in g r e a c ti o n s : (1 )

HONOg ——— ^

HO* + 'NO2

(2)

2 "NO2

2N0 • + Og

Of th e f r e e r a d i c a l s shown, th e HO- r a d i c a l i s th e l e a s t s ta b l e and th e m ost r e a c t i v e .

Hence i t would be ex p ected to i n i t i a t e th e form a­

tio n o f f r e e r a d i c a l s from hydrocarbons in th e n i t r a t i o n p ro c e s s . (3 )

HO" + EH — >

E- + HOH

The f r e e a lk y l r a d i c a l s s o produced could th en u n ite w ith -NOg r a d i c a l s (4)

"E + *NOg — ^

ENOg

p ro d u cin g n i t r o p a r a f f i n s .

N i t r a t io n t h e r e f o r e i s a f r e e r a d i c a l p ro ­

c e s s b u t i s n o t a c h a in r e a c t i o n .

I t should be n o te d t h a t any o th e r

c o n c u rre n t p ro c e s s le a d in g to th e fo rm a tio n o f r e a c ti v e f r e e r a d i c a l s would, be expected to c o n tr ib u te to th e n i t r a t i o n p ro c e ss by in c r e a s in g th e c o n c e n tra tio n o f a l k y l f r e e r a d i c a l s and hence th e p e r pass con­ v e rs io n s to n i t r o p a r a f f i n s . w ith oxygen.

I t has been shown t h a t t h i s can be done

E vidence t h a t n i t r a t i o n i s n o t a chain r e a c tio n i s found

in th e f a c t t h a t in c re a s e d s u rf a c e in th e r e a c t o r tu b e does n o t a l t e r

33. th e y i e l d s o f p ro d u c ts s u f f i c i e n t l y to he in agreem ent w ith th e r e s u l t s ex p ected o f a c h ain r e a c ti o n o f any c o n s id e ra b le le n g th ( l 4 ) . On th e b a s is o f th e proposed mechanism, th e n i t r a t i n g agœ t i s a c t u a ll y

-NOg.

However, -NOg n i t r a t e s n o t hydrocarbon m olecules

d i r e c t l y b u t a lk y l r a d i c a l s derived, from them

end. th e l a t t e r a re

g e n e ra te d more e f f e c t i v e l y by HO- r a d i c a l s than by -NOg r a d i c a l s .

T his

e x p la in s th e f a c t t h a t -NOg a lo n e i s l e s s e f f e c t i v e than n i t r i c a c id as a n i t r a t i n g a g e n t in th e vapor ph ase. A nother ad v an tag e to th e assum ption t h a t e q u a tio n (4) r e p r e ­ s e n ts th e c h ie f vapor phase n i tr a .tio n p ro c e ss i s th e e a se w ith which i t may b e a d a p te d to an e x p la n a tio n o f th e f o r m t i o n o f o th e r p ro d u c ts o f th e r e a c t i o n .

The -NOg r a d i c a l i s a reso n an ce h y b rid whose c h ie f con­

t r i b u t i n g form s probably^ in c lu d e : (-)(+) :0: N : : 0 :

:0::N:0:

I

II

I f an a lk y l r a d i c a l r e a c t s w ith -NOg in Form I th e p ro d u c t i s a n i t r o p a r a f f i n , b u t i f in Form I I th e p ro d u c t i s an a lk y l n i t r i t e .

The

b e h a v io r o f a l k y l n i t r i t e s under th e c o n d itio n s o f vapor phase n i t r a t i o n i s th e r e f o r e im p o rta n t to a more com plete u n d e rsta n d in g o f th e n i t r a t i o n p ro ce ss. A lk y l n i t r i t e s a p p e a r to be extrem ely u n s ta b le a t elevabed te m p e ra tu re s .

E ic e (20) decomposed e th y l n i t r i t e a t 425®C. in th e p r e ­

sence o f buta.ne a s a d i l u e n t .

Under such c o n d itio n s th e r e i s s l i g h t

chance t h a t th e d ecom position p ro d u c ts w i l l c o ll id e w ith unr e a c te d n i t r i t e m o le c u le s . and th e d eco m position p ro ceed s a s fo llo w s : (5)

CH3CH2ONO

>

(6)

CHgCHgO - —->

CE3CH2O ' + NO ECHO + CE3 -

34, The m ethyl r a d i c a l s were i d e n t i f i e d a s

t e l l u r I d e s . I f n o t removed

th e r e a c ti o n m ix tu re th ey re a c te d w ith

n i t r i t e m o lecu les a s f o llo w s ;

( 7)

CH^- + CH3CH2ONO — ->

(S)

CH3CHONO — ^

CSij, +

from

CH3ÇHONO

CH3CHO + -NO

Kornhlum and. O ilv e to (12) have shown t h a t i f a h ig h e r c o n c e n tra tio n o f n i t r i t e i s p r e s e n t, th e a lk o x id e r a d i c a l s f i r s t produced r e a c t as fo llo w s : (9) ( 10)

CÏÏ3CH20- + CH3CH2ONO — CE3ÇHONO — ^

CH3CE2OH + CE3ÇÏÏONO

CH3CHO + -NO

I t i s e v id e n t from th e s e e q u a tio n s t h a t any n i t r i t e s produced in th e n i t r a t i o n p ro c e s s would decompose to low er h y d ro carb o n s, ald eh y d es and n i t r i c o x id e , a l l o f which a r e observed p ro d u c ts o f n i t r a t i o n .

The

low er a l k y l r a d i c a l s a ls o produced account in p a r t a t l e a s t f o r th e low er n i t r o p a r a f f i n s o b ta in e d in th e n i t r a t i o n p r o c e s s .

Lower a lk y l

r a d i c a l s a r e a ls o formed from th e d i r e c t decom position o f h ig h e r a lk y l r a d i c a l s (19) •

T h is a c co u n ts f o r th e rem ain d er o f th e low er n i t r o

p a r a f f i n s produced. The r e l a t i v e amounts o f NOg r a d i c a l s which r e a c t in Forms I and I I , r e s p e c t i v e l y , a r e n o t knov/n b u t th e r a t i o m ust be a t l e a s t 3 /1 to a c c o u n t f o r th e r e l a t i v e q u a n t i t i e s o f low er n i t r o p a r a f f i n s produced. From T able VI i t may be seen t h a t th e p e rc e n ta g e y ie ld s o f n i t r o butanes b e a r a r a t i o o f 3 /1 to th e p e rc e n ta g e y i e l d s o f low er n i t r o p a r a f f i n s . The a c t u a l r a t i o i s undoubtedly low er th an 3/ I s in c e a l l of th e n i t r i t e formed, i s n o t c o n v e rted to low er a l k y l r a d i c a l s b u t i s co n v erted in pa.rt to a ld e h y d e s , o l e f i n s , and s a tu r a te d hydrocarbons and i s th u s l o s t to f u r t h e r form s.tion o f n i t r o p a r a f f i n s .

35. The above e x p la n a tio n o f th e o r ig in o f th e low er n i t r o p a r a f f i n s and b y -p ro d u c ts o f th e n i t r a t i o n r e a c tio n i s more s a .tis f a c t o r y th an th e assum ption o f sim ple therm s.! c ra c k in g a s a so u rc e o f t h e s m a lle r a l k y l r a d i c a l s .

As a m a tte r o f f a c t th e p ro d u c tio n o f

m e th y l, e t h y l , and p ro p y l r a d i c a l s from b u tan e i s n e g li g ib l e a t th e optimum te m p e ra tu re and c o n ta c t tim e f o r th e n i t r a t i o n o f b u ta n e . F u rth e rm o re , su b s ta n c e s such a s iro n s a l t s , which c a ta ly z e th e c ra c k ­ in g o f C-C bonds in h y d ro carb o n s, d e c re a se ma.rkedly r a t h e r than in c re a s e th e y i e l d s o f n i t r o p a r a f f i n s o b ta in e d .

I f th erm al c ra c k in g were c h ie f ly

r e s p o n s ib le f o r th e fo rn e .tio n o f low er n i t r o p a r a f f i n s i t would be expected, t h a t cyclohexane would y ie ld c o n s id e ra b le amounts o f 1 ,6 - d in i tr o hexane on n itr e ,tio n . ^C H p CHp '^CHp 1 I

CHp CHp — > 1 ^ 1

CHg ^ CHp

CHg

/C E g .

NCHg

^ CHp

CEo

CEg t " 1 ^ 2 CHp / C S g

-HOj ^

CHp CHpNOp I t CEg /C H p

CHp

^CEp

S h e c h te r* s work on cyclohexane showed t h a t t h i s was n o t th e ca,se.

Ee

o b ta in e d only n itro c y c lo h e x a n e and a n o th e r p ro d u ct which c o n ta in e d n itr o g e n b u t decomposed r e a d i l y on warming to form a t a r .

T his r e s u l t

would be e x p e c te d , i f i t i s assumed, t h a t f i s s i o n occurs th rough th e n itrite .

Such a r e a c ti o n m ight lea d to a n i t r o aldehyde which would be

q u ite r e a c t i v e . CHg

CHONO

I

1

CHp ^ CEo

'-CHg

—->

CHp

XEO-

)

)

CHp .CHp < c E2

+ -NO

36 ^CHp CEp ^CEONO I I -----> C ^^^C H g

^CHo CH., '^CHOI I CHg^CHg

^^ C“Eîp p

+

•NO

"^CH' p

y.#»CHp

CEg '

CHp '^CEO-

1

I

—

CHp / C H .

-

CHp

CEO

1

I

CHp /C H p

< c4

CHg

y / CHg

/ . CEgNOg

CHp

CEO

I

I

-NO.

->

CHg^^CHg

CHp

CEO

I

1

° ^ c -3

F o llo w in g th e above re a s o n in g , th e ■vs.por phase n i t r a t i o n o f b u tan e should, proceed, a s fo llo w s : D ecom position o f n i t r i c a c id : (11)

HNOp —

HO- + -NOp

F o r m tio n o f a l k y l r a d i c a l s : (12)

y—

CEqCHpCHpCHp ' + HpO

CH.CEpCHpCHo + HO- ( CHgCHpCHCEq + HpO

D ecom position o f a l k y l f r e e r a d i c a l s : ( 13 )

CE3CHpCE=CEp + -H

CHpCHpCHpCHp ' ( CHgCHp ' + CEp=CHp

(14)

CHpCH=CHCH3 + H* CHoCHpCHCHn CEo- + CHp=CBCEq

37. R e a c tio n o f a l k y l r a d i c a l s w ith NOg: ( 15 )

y - -> CH3CE2CÏÏ2CH2 • +

CH.CHpCHpCHpNC p

-NOp

CEpCEpCHpCEpONO ( 16 )

CEgCEpCECEp NOp

CÏÏ3CH2CECH3 + 'EOp-^

CE3CE2CHCH3 ONO (17)

CS3CEP - + 'NOg —- >

( 18)

CE3 " + -NOp

CH3CE2NO2 + CE3CEgOWO

CE3NO2 + CE3ONO

D ecom position o f n i t r i t e s : ( 19 )

C3EYCEgONO

>

( 20)

'NO + CpE^CEgO- - - - >

y --> > -NO + CpSsCECS^( "0

C2H5CHCH3 ^ONO

C3EY - + ECHO CpEz" + CH3CH0 CE,- + CgScCSO

Now i t w i l l he observed t h a t th e m ethyl, e th y l , and p ro p y l f re e r a d ic a ls produced In ( I 3) , ( 1 4 ), (1 9 ), end (20) may r e a c t w ith -NOp j u s t as th e o r i g i n a l f r e e r a d i c a l s did in ( I 5 ) and ( 16) .

T his would account a t

l e a s t q u a l i t a t i v e l y f o r th e low er n i t r o p a r a f f in s o b tain e d e x p e r i­ m e n ta lly and would a ls o r e s u l t in th e fo rm ation o f a d d it io n a l f r e e r a d i c a l s w ith one l e s s carbon atom .

The o le f in s observed in th e p ro ­

d u c ts a p p a r e n tly come from decom position of th e f r e e r a d i c a l s by ( 13) and ( l4 ) and a ls o from : ( 21)

2CE3 '

CEp=CEg + 2E-

R e a c tio n s (19) end (20) acco u n t f o r th e a ld e h y d e s.

The

la r g e amount o f carbon monoxide a p p a re n tly r e s u l t s from th e w e ll known p y r o ly s is o f a ld e h y d e s ( 25) : , , 400® C . (22) RCEO RE + CO

33. I n s u p p o r t o f t h i s i s t h e f a c t t h a t b o th hydrogen and m ethane a r e found in t h e e x i t g a s e s a s would be e x p e c te d fro m th e d e c o m p o s itio n o f form a.ldehyde and a c e t a l d e h y d e . c a r r i e d o u t f o r etha.ne o r p r o p a n e .

No t e s t s w ere

The o rg a n ic a c id s o b ta in e d r e s u l t

fro m th e f u r t h e r o x id a tio n o f th e a ld e h y d e s . S in c e o n ly s m a ll am ounts o f a lc o h o l s a r e fo rm ed , th e y can w e l l be a c c o u n te d f o r by t h e f o llo w in g d e c o m p o sitio n o f a t y p i c a l a l k o x y l r a d i c a l a s i l l u s t r a t e d by e q u a tio n ( 9 ) •

In a d d i t i o n , a w a ll

r e a c t i o n o f th e f o llo w in g ty p e ms.y a l s o o c c u r: (2 3 )

R- + -OH

ROE

The m echa.nlsms p r e s e n te d above may e a s i l y b e e x te n d e d t o c o v e r t h e e f f e c t o f oxygen on th e n i t r a t i o n p r o c e s s .

A c c o rd in g to

W alsh ( 2 5 ) , th e low te m p e r a tu re (below 500 ®C.) o x id a tio n o f b u ta n e w ith oxygen p ro c e e d s a s fo llo w s : ( 24 )

CEgCEgCEpCEg + -OH —

(2 5 )

CH3CE2ÇBDH3 + Op

4^

CH3CH2ÇHCE3 + EpO CH3CH2ÇHCH3

Ô(2 6 )

CH3CH2ÇHCÏÏ3 +

^

Ô(2 7 )

CH3CH2CHCE3 + OE

CH3CE2CHCE3 - —■> CH3CH2ÇHCE3 + -OH ÔH

( 28 )

CH3CH2CÏÏCH3 — 0

CgH^* + CH3CHO

•

The same ty p e s o f r e a c t i o n s would be e x p e c te d lo r e s u l t fro m an l n i t l a .1 a t t a c k on a prim a.ry h y drogen e x c e p t th a .t form ald eh y d e would s p l i t o f f i n s t e a d o f a h ig h e r a ld e h y d e .

In e i t h e r c a s e , th e slk y 1 f c e e r a d i c a l s

s o p roduced would b e a .v a lia b le f o r f u r t h e r r e a c t i o n w ith oxygen o r w ith 'NOg.

I t w i l l be n o te d t h a t th e above o x id a tio n p ro c e s s in v o lv e s a

c h a in r e a c t i o n w hich would be h in d e re d by in c re a s e d s u r f a c e due to

39decom positdon o r r e a c tio n o f b o th -OH and -R r a d i c a l s on i t ( l 4 ) . (29)

-R + .R

§ B # 8 .ç e ^ pp

(30)

"OE + "OS

EgOp

A lc o h o l fo rm a tio n could a ls o occur by r e a c tio n ( 23) . I f th e o x id a tiv e s e r i e s o f r e a c tio n s le a d in g to th e form a,tion o f f r e e a l k y l r a d i c a l s ru n s c o n c u rre n tly w ith th e n i t r a t i o n , then th e p ro d u c tio n o f n i t r o p a r a f f i n s should in c r e a s e due to th e e x is te n c e o f a h ig h e r c o n c e n tra tio n o f a lk y l r a d i c a l s .

In a d d it io n , th e r a t i o o f

low er to h ig h e r m o le c u la r w eight n i t r o p a .ra ffin s should a ls o in c re a s e due to a g r e a t ly in c re a s e d c o n c e n tra tio n o f th e low er m o le c u la r w eight a l k y l r a d i c a l s to g e th e r w ith t h e i r g r e a te r s t a b i l i t y .

I t has been p r e ­

v io u s ly shown t h a t th e s e p r e d ic tio n s a re borne o u t by experim ent (se e T able Vl) . An e x c e l le n t t e s t o f t h i s th e o ry i s a ffo rd e d by Robinson *s ( 21) work on th e n i t r a t i o n o f 1 ,1 ,1 - tr if l u o r o p r o p a n e .

He found t h a t

th e o n ly n i t r o compounds formed were l - n i t r o - 3 , 3, 3- tr if lu o r o p r o p a n e and l - n i t r o - 2 , 2 , 2 - t r i f l u o r o e t h a n e .

F a ilu r e to produce 2 - n i t r o - 3 , 3, 3-

tr if lu o r o p r o p a n e r e s u lte d from th e h ig h ly n e g a tiv e c h a r a c te r o f th e tr if lu o r o m e th y l group which prev en ted an a tta .c k in g group from ap p ro ach ­ in g th e 2- p o s i t i o n .

C o n seq u en tly , th e o n ly n i t r i t e which could be

formed would be th e l , l , l - t r i f l u o r o - 3 - p r o p y l n i t r i t e .

Decom position o f

t h i s could le a d o n ly to th e form atio n o f a 1 , 1 ,1- t r i f l u o r o e t h y l r a d i c a l a lo n g w ith fo rm ald eh y d e.

As was p r e d ic te d , no n itro m e th an e was form ed.

The above o v e r - a l l mechanism f o r th e vapor phase n i t r a t i o n p r o c e s s , w h ile i t i s n o t com plete nor e n t i r e l y proven, o f f e r s many a d v a n ta g e s over p r e v io u s ly proposed mechanisms.

Among th e s e a r e i t s

im p lic a tio n s a s to p ro ce d u re s f o r inq)rovlng the y ie ld s o f n i t r o p a r a f f i n s

40.

o b ta in a b le and f o r a l t e r i n g th e r a t i o s o f th e n i t r o p a r a f f i n s p ro d u ce d . Some o f th e s e im p lic a tio n s a r e l i s t e d below . (1 )

Any a g e n t which in c r e a s e s th e c o n c e n tra tio n o f

a lk y l

fre e

r a d i c a l s p r e s e n t in th e n i t r a t i o n m ix tu re w i l l in crea.se th e p e r pass c o n v e rs io n .

T his a g e n t may be a. s u b sta n c e l i k e oxygen which produces

a l k y l r a d i c a l s by an o x id a tiv e a t t a c k o r i t could be a compound s im ila r to azom ethane o r d im e th y l m ercury which have been shown to low er th e p y r o ly s is te m p e ra tu re o f h y d ro carb o n s. (2)

Both th e p e r pass co n v e rsio n and th e y ie ld based on h ydro­

carbon ma.y be improved i f th e p ro d u ctio n o f f r e e a lk y l r a d i c a l s i s ma.de t o ta k e p la c e a t a u niform optimum r a t e which c o rr e ls .te s v/ith th e r a t e o f p ro d u c tio n o f "NOg r a d i c a l s .

T his ma.y be accom plished by adding

oxygen to in c r e a s e th e r a t e o f form a.tion o f a lk y l r a d i c a l s , o r i f e x c e ss oxygen i s p r e s e n t, by in c r e a s in g th e amount o f s u rfa c e in th e r e a c t o r t o d e c re a s e th e r a t e o f form a.tion o f a lk y l r a d i c a l s .

A d ilu e n t,

such a s steam , w i l l a ls o se rv e to d e c re a se th e r a t e o f a lk y l r a d i c a l form a.tion .

P ro p e r ad ju stm e n t o f th e s e v a rio u s f a c t o r s should le a d to

th e h ig h e s t p o s s ib le p ro d u ctio n o f n i t r o p a .ra ffin s . ( 3)

C a re fu l h e a t c o n tr o l i s e s s e n t i a l to ms. in t a in th e v a rio u s

r e a c ti o n s in p ro p e r b a la n c e .

W ithout q u a n ti ta t iv e inform a.tion on r a t e

c o n s ta n ts i t i s im p o ssib le to c a lc u la te th e optimum te m p e ra tu re f o r a given s e t o f c o n d itio n s , b u t i t i s p o s s ib le to p r e d ic t t h a t th e r e w i l l be an optimum te m p e ra tu re and a ls o how c e r ta in f a c t o r s w i l l in flu e n c e t h i s te m p e ra tu re . (4)

The use o f a h ig h r a t i o o f hydrocarbon to n i t r i c a c id should

n o t be n e c e s s a ry i f a n o th e r d ilu e n t i s u s e d .

The s u b s t i t u t i o n o f a

41. d i l u e n t which may e a s i l y he condensed, such a s steam , m ight s im p lif y th e r e c y c li n g o p e ra tio n and im prove hydrocarbon u t i l i z a t i o n a s w e ll. (5 )

The y ie ld based on hydrocarbon i s lim ite d b o th by th e decom­

p o s it i o n o f a l k y l r a d i c a l s to o l e f i n s and by th e f i s s i o n p ro c e ss which i s r e s p o n s ib le f o r th e p ro d u c tio n o f low er n i t r o p8,rs.ffins and v a rio u s b y - p ro d u c ts .

Hence any a tte m p t to in c r e a s e th e p ro d u c tio n o f th e low er

n i t r o p a r a f f i n s a t th e expense o f th e h ig h e r ones w i l l le a d t o a g r e a te r d e s tr u c ti o n o f hydrocarbon.

T h is s u g g e sts t h a t , o th e r f a c t o r s b e in g

e q u a l, th e more e f f i c i e n t p ro c e ss f o r th e p ro d u ctio n o f low er n i t r o p a r a f f i n s would be to n i t r a t e low er hydrocarbons r a t h e r than h ig h e r h y d ro c a rb o n s , (6)

The f i s s i o n p ro c e ss may be fav o red by any means which w i l l

cause a l a r g e r r e l a t i v e p ro d u c tio n o f a lk y l n i t r i t e s or o f a lk y l hydro­ p e ro x id e s .

Oxygen has t h i s e f f e c t as i s shown by T able V I.

A p ro ce ss

which u se s a h ig h e r c o n c e n tra tio n o f th e n i t r a t i n g a g e n t r e l a t i v e to the hydrocarbon b u t in th e p rese n c e o f a d ilu e n t to avoid e x p lo s iv e c o n d i­ tio n s sh o u ld have t h i s same e f f e c t . ( 7)

W ith regard to a l t e r i n g th e r a t i o s o f n i t r o p a r a f f in s p ro ­

duced, i t should be noted t h a t o x id a tiv e a t t a c k fa v o rs secondary hydrogens o v er prim ary h y d ro g e n s.

Hence b u tan e would be expected to

produce more n i t r o e th a n e th an n i t r o propane s in c e i t has a h ig h e r r a t i o o f secondary to prim ary hydrogens ( s e e e q u a tio n s (19) sad ( 2 0 ) ) , An in c r e a s e in th e o x id a tiv e a t t a c k by added oxygen should cause a, g r e a t e r in c r e a s e in n i t r o e th a n e p ro d u c tio n w ith b u tan e than w ith p ro ­ pane,

On th e o th e r h and, n i t r a t i o n a t h ig h e r te m p e ra tu re s should, cause

an even l a r g e r amount o f p rim ary a t t a c k s in c e a,s th e te m p e ra tu re i s r a i s e d th e r a t e s o f a t t a c k on prim ary and secondary hydrogens become more n e a rly th e same ( 25) .

W ith propane t h i s would be expected to lead

t o a h ig h e r p e rc e n ta g e o f n i t r o e th a n e in th e n r o d u c t.

42.

EXPERIMENTAL I.

A p p aratu s and Technique

The a p p a ra tu s used, in t h i s in v e s tig a tio n i s very s im i la r to t h a t used, hy A lex an d er ( l ) . in v o lv ed would be re d u n d a n t.

A com plete d e s c r ip tio n o f many o f th e item s However, sone improvements have been

e ffe c te d , in th e equipm ent and th e o p e ra tin g pro ced u re has been imde e a s ie r.

A d is c u s s io n o f such p e r t i n e n t f a c t o r s w i l l be g iv e n .

Gas Flow The a c c u r a te m e te rin g o f th e hydrocarbon and oxygen stream s employed in n i t r a t i o n s tu d ie s i s d e s ir a b le .

O r ig in a lly th e s e flow s

were c o n tr o lle d by a n e e d le v a lv e a.nd th e r a t e measured by th e sim ple manometer ty p e flow m eter d e s c rib e d by A lex an d er.

T his was n o t v ery

s a t i s f a c t o r y inasmuch a s c lo s e c o n tr o l by such v a lv e s a s were a v a ila b le was d i f f i c u l t .

A lso th e r a t e o f flow was in flu e n c e d to a marked degree

by f l u c t u a t i o n s in downstream p r e s s u r e .

T his proved p a r t i c u l a r l y

troublesom e in e x p e rim e n ts in v o lv in g oxygen and in one case (Run 6) caused an e x p lo s io n .

A s o lu tio n to th e problem was found in th e use

o f j e t s o f such a s i z e t h a t th e u p stream p re s s u re re q u ire d to m ain tain th e d e sire d , gas r a t e was a t l e a s t 2 .5 tim es th e downstream p r e s s u r e . I t should b e n o ted t h a t under th e s e c o n d itio n s , th e mass r a t e o f flow is c o m p le te ly in d ep en d en t o f th e downstream p r e s s u r e .

The c o n tr o l o f th e

p r e s s u r e in f r o n t o f th e j e t was c o n v e n ie n tly accom plished, w ith diaphragm r e d u c tio n v a lv e s .

A s ta n d a rd Hoke re d u c in g v a lv e was used on th e oxygen

c y lin d e r and an a c e ty le n e re d u c in g ga.uge f o r th e b u tan e o r propane c y lin d e r. The j e t s th em selv es c o n s is te d o f a p ie c e o f 8 mm. pyrex tu b in g which was drawn down t o a c a p i l l a r y a t one e n d .

Sm oother

43. o p e ra tio n •was o t ta in e d when th e c a p i l l a r y p o r tio n was a t l e a s t one in ch in le n g t h .

A s e c tio n o f 10 mm. tu h in g was s lip p e d ov er th e c a p i l l a r y

end. o f th e j e t and r i n g s e a le d to th e c e n te r o f th e 8 mm. tu h in g .

In

o p e ra tio n ^ th e 8 ram. tu h in g was connected to th e diaphragm gauge w ith a heavy w a lle d , ru h h e r tu h in g which was cap ab le o f w ith s ta n d in g 100 pounds o f p r e s s u r e .

Such a tu h e w i l l o p e ra te s a t i s f a c t o r i l y a t p re s s u r e s

up to 80 pounds over lo n g p e rio d s o f tim e .

The 10 mm. end o f th e j e t

assem bly was connected to th e i n l e t o f th e r e a c t o r hy Tygon tu h in g o f an a p p r o p r ia te s i z e . The j e t may he c o n v e n ie n tly c a li h r a t e d e i t h e r s e p a r a te ly or in p la c e in th e a p p a ra tu s .

W ith th e p re s s u re in f r o n t o f i t a d ju s te d

to a, s u i t a b l e v a lu e and a l l o th e r flow s c u t o f f , th e gas is s u in g i s passed, th ro u g h a wet t e s t m eter f o r a m easured p erio d o f tim e .

Flow

r a t e s a r e o b ta in e d in t h i s way f o r s e v e r a l p re s s u r e s and a c a li b r a t io n curve i s drawn.

T here i s a l i m i t to th e v a r ia tio n in r a t e which may he

g o tte n w ith any one j e t w ith o u t u sin g e x c e s s iv e ly h ig h p r e s s u r e s .

Hence

th e s iz e o f th e c a p il la r y i s somewhat c r i t i c a l , h u t th e p ro p e r diam eter i s e a s i l y determ ined, a f t e r some e x p e rim e n ta tio n . H i t r i c A cid Feed The n i t r i c a c id i n je c ti o n system used was e x a r tly th e same as t h a t d escrib ed , in d e t a i l hy A le x a n d er.

In g e n e ra l, i t c o n s is te d o f a

one l i t e r round bo tto m f l a s k as th e n i t r i c r e s e r v o i r which was f i t t e d w ith an i n l e t f o r n itr o g e n ga.s above th e s u rfa c e and. an e x i t tuhe d ip p in g below th e l iq u i d l e v e l .

T his d ip tu h e connected to a c a p il la r y

j e t which was f i t t e d , i n to th e p r e h e a te r .

A d i f f e r e n t i a l m n o m eter was

connected, betw een th e n itr o g e n i n l e t and th e p o in t where th e j e t en te red

44.

th e p r e h e a te r , so t h a t th e p re s s u re a c ro s s th e j e t could be m easured. A by-pa,ss was provided, a c ro s s th e manometer f o r e a se in s t a r t i n g the a p p a r a tu s ,

The p r e s s u r e to th e a c id r e s e r v o i r was c o n tro lle d , by a

diaphragm gauge, and. a b le e d v a lv e was provided, to r e l e a s e p r e s s u re in o rd e r t o s to p th e a c id flo w .

The amount o f n i t r i c a c id used, was

m easured by w eighing th e f l a s k b e fo re and. a f t e r each ru n . C a lib r a tio n o f th e j e t ha.d to be ma,d.e in s i t u under a c tu a l o p e r a tin g c o n d itio n s a s th e flow r a t e under a given p r e s s u re was in flu e n c e d by th e te m p e ra tu re o f th e j e t .

I t was found t h a t f lu c t u a ­

t io n s were d e c re a se d c o n s id e ra b ly by p la c in g a fo u r l i t e r su rg e v e s s e l in th e n itr o g e n l i n e j u s t b e fo re th e a c id f l a s k . Preheat, e r A p r e h e a te r was pro v id ed to b r in g th e g ases c lo s e to r e a c tio n te m p e ra tu re b e fo re e n te r in g th e r e a c t o r and to f u r n is h th e means o f v a p o riz in g th e n i t r i c a c id .

T his c o n s is te d o f l8 0 cm. o f 10 mm. pyrex

tu b in g made i n t o a c o l l 15 cm. in d ia m e te r and. jo in e d by a T to a n o th e r c o i l 60 cm. lo n g and. 20 cm. in d ia m e te r.

The open end o f th e T was

p la c e d v e r t i c a l l y , and th e o u te r s e c tio n o f a b a l l j o i n t s e a le d to i t , so t h a t th e j o i n t pi*ojected. above th e c o i l . s e a t f o r th e n i t r i c a c id i n j e c t i o n j e t .

T his b a l l j o i n t provided, a

The lo n g e r c o l l was connected

to th e oxygen and. hydrocarbon fe e d system s and th e s h o r te r c o i l led. to th e r e a c t o r .

The whole assem bly was placed, in a s a l t b a th m in ta in e d

a t a te m p e ra tu re o f 265*0. R e a c to rs Three r e a c t o r s were used in t h i s i n v e s t i g a t i o n . R e a c to r 1 .

T h is c o n s is te d o f a c o i l o f 7

would i n to two c o n c e n tric s p i r a l s , 15 and

pyrex tu b in g

20 cm. in d ia m e te r, r e s p e c ti v e ly ,

45.

and had a volume o f 600 m l.

The c o i l was an e x a c t d u p lic a te of t h a t

used, hy A lexander and was used only f o r p re lim in a ry experim ents on m eth a n e .

I t was found to g iv e such la r g e p re s s u re drops w ith "butane

t h a t i t could n o t "be used . R e a c to r 2 .

T h is r e a c to r was a ls o o f th e c o i l ty p e and con­

t a i n e d a p p ro x im a te ly 25 f e e t o f 10 ram. I.D . pyrex tu b in g . was 600 m l. in

ex p erim en ts 5 -1 2 .

At

I t s volume

t h i s p o in t i t was r e p a ire d and

th e volume was in c re a s e d to 7OO m l. R e a c to r 3•

T his r e a c to r was d esig n ed f o r a stu d y o f th e

e f f e c t o f th e su rfa c e/v o lu m e r a ,tio . le n g th s o f 22 ram. O.D. pyrex tu b in g .

I t c o n sisted , o f th re e 90 cm. Each was b e n t i n to th e form o f

a U and th e th r e e were connected in s e r i e s .

The c o n n e ctin g tu b es were

s e a le d in th e s id e s o f th e la r g e IT-shaped p ie c e s n e a r th e to p . was in tro d u c e d th ro u g h th e open to p s which were th en s e a l e d .

Packing The

a.ssembly was p lac e d v e r t i c a l l y in a s a l t b a th and held th e r e by w eig h ts a.ttach ed to th e bottom o f th e r e a c t o r . P ro d u c t Recovery^ The e x i t ga.ses from th e r e a c to r were passed th rough a v e r t i c a l l y p la c e d , s p i r a l , w a te r condenser i n to a 5OO m l. f l a s k w ith a s id e arm. Most o f th e liq u i d p ro d u c ts were condensed h e re , b u t some s t i l l rem ained in th e ga.s s tre a m . by p a s s in g th e

Complete rem o m l o f th e liq u i d p ro d u cts

was o b ta in e d

g ases which issu e d from th e f l a s k in to a dry ic e condenser

s e t above a one l i t e r f la e k p laced in a dry ic e - e th y le n e t r i c h l o r i d e b a th . T h is condensed most o f th e butane and a l l o f th e rem ain in g liq u id p r o ­ d u c ts .

The i s o l a t i o n o f th e liq u id p ro d u c ts was e f f e c te d by slow evs.pora-

t io n o f th e b u ta n e .

The uncondensed ga.ses

p a s sin g th rough th e dry ic e

c o n d e n se r, were measured by" s wet t e s t m eter and vented to th e hood .

46. O p e ra tio n The p ro ce d u re fo llo w ed in p e rfo rm in g a n i t r a t i o n ws.s as fo llo w s : (1)

The n i t r i c a c id fla ,sk was w eighed, connected to th e d e liv e ry

j e t and n itr o g e n c y li n d e r .

The h y -p a ss a c ro s s th e d i f f e r e n t i a l manometer

was o p e n e d . (2 )

The r e g u l a t i n g v a lv e on th e hydrocarbon fe e d system was

a d ju s te d to th e p r e s s u r e r e q u ir e d to g iv e th e d e s ire d flow . (3) p ressu re (4 ) p r e s s u re (5) were

The r e g u l a ti n g v alv e on th e oxygen system

was a d ju s te d to th e

r e q u ir e d to g iv e th e d e s ire d flow . The by-ps.ss was closed, and th e d e s ire d amount

o f n itro g e n

was adm i.tted to th e n i t r i c a c id fla .sk . The g a ses from th e r e a c t o r which had been v e n tin g to th e hood

d ir e c te d th ro u g h th e condensing

system and,th e tim j.ng c lo c k was

s ta rte d . D uring th e c o u rse o f th e ru n , a sam ple o f th e e x i t g8.ses was taken f o r a n a ly s is .

A f t e r s u f f i c i e n t m a t e r i a l had been c o ll e c t e d , th e run was

term i.nated in (1)

The

th e fo llo w in g manner: v e n t vs.lve on th e n itr o g e n system was opened to s to p

n i t r i c a c id flo w .

th e

The c lo c k was stopped and th e gs,s s tre a m was d iv e rte d

to th e hood.. ( 2)

The oxygen flow was s to p p e d .

( 3)

A f t e r p u rg in g th e r e a c t o r f o r one m inute th e hydrocarbon flow

was sto p p e d . The n i t r i c acid, f l a s k was now re-w eig h ed to determ in e th e amount used . The p ro d u c ts c o ll e c t e d by th e w a te r con d en ser and th e dry ic e condenser were weighed and th e wet t e s t m eter r e a d in g was re c o rd e d .

47. II.

P ro d u c t A n a ly s is

The fo llo w in g methods o f p ro d u ct a n a ly s e s were worked o u t in c o n ju n c tio n w ith Mr. J . V. H ew ett. E l t r o P a r a f f in s The method used, by pa.st i n v e s t i gs,tors f o r th e d e te rm in a tio n of n i t r o p a r a f f i n s was a s fo llo w s .

The t o t a l r e a c tio n p ro d u ct was su b je c te d

to a z e o tro p ic d i s t i l l a t i o n w ith w a te r, r e c y c lin g th e aqueous la y e r u n t i l o n ly one phase appeared in th e d i s t i l l a t e .

T his non-aqueous m a te r ia l

was d r ie d and s trip p e d , o f a l l m a te r ia ls b o i li n g below 80*C. rem s.inder was assumed, to be n i t r o p a r a f f i n s .

The

The number o f moles p re s e n t

was estim a.ted from th e av erag e m o lecu lar w eight a s o b ta in e d by a crude f ra c tio n a tio n .

T h is method was used in experim ents 1-12.

I t was rec o g n ize d t h a t th e above method o f a n a ly s is perm itted, many p o s s i b i l i t i e s f o r e r r o r .

Such e r r o r s would in c lu d e incom plete

remova.l o f th e n i t r o p a r a f f i n s from th e r e a c tio n m ix tu re , in c lu s io n o f oxygenated hydrocarbons in th e is o l a te d non-aqueous m a te r ia l, and th e in a c c u ra c y o f d e te rm in in g avera.ge m o lecu lar w eights by f r a c ti o n a ti o n in th e columns a v a i l a b l e .

A method was evolved which e lim in a te d th e s e

e r r o r s and ma,d.e th e a n a ly s i s q u ic k e r and e a s i e r . The t o t a l l i q u i d p ro d u ct was e x tr a c te d r e p e a te d ly w ith e th e r to remove a l l n i t r o p a r a f f i n s .

T his e th e r la y e r was tr e a te d w ith s o lid

sodium b ic a r b o n a te to remove a c id ic m a .te ria ls Inasmuch as some o f th e s e m ight have been n itr o g e n a c id s .

A s tr o n g e r base could, n o t be used a s i t

would have caused r e a c ti o n betw een th e n i t r o compounds and any aldehydes p r e s e n t.

An a l i q u o t p o r tio n o f t h i s e th e r s o lu tio n was an aly zed f o r

n itr o g e n by one o f th e methods p re se n te d below .

S ince a l l o f th e

n itr o g e n p r e s e n t was due to n i t r o p a r a f f i n s , t h i s gave d i r e c tl y th e number o f m oles produced..

48. No s im p le , q u ick y e t a c c u r a te method o f a n a ly s i s f o r n i t r o p a r a f f i n was found, in th e l i t e r a t u r e .

A K je ld a h l proceudre given hy

Somers ( 23) looked, p ro m isin g h u t had p r e v io u s ly been found in th e s e l a b o r a t o r i e s n o t to give re p ro d u c ib le r e s u l t s .

However, w ith s u it a b le

m o d if ic a tio n s i t was ms.de to g iv e very a c c u r a te a n a ly s e s on known com­ pounds and was found, to be s u i t a b l e . Improved. K je ld a h l A n a ly s is f o r N itr o Compounds A sam ple o f th e compound to be a n a ly z e d , o f s u f f i c i e n t s iz e to c o n ta in ftom 3 t o 5 1% . o f n itr o g e n , i s introduced, in to a 100 m l. K J e ld a h l f l a s k c o n ta in in g 2 ml. o f e th a n o l and 1 ml. o f TiClg re a g e n t (20 p e r c e n t s o lu tio n c o n c e n tra te d h y d ro c h lo ric a c i d ) . i s added and th e s o lu tio n i s b o ile d f o r 2 m in u te s .

One gla.ss bead

I f th e p u rp le c o lo r

o f th e T iC lg r e a g e n t i s c o m p letely d e s tro y e d , th e re d u c tio n should be re p e a te d w ith a sm a,ller sam ple.

A f te r c o o lin g , O.5 g- KgSOi^, 5O mg.

CuSOk, 50 log. HgO, and 5 lol. c o n c e n tra te d EpSO^ a re added, and th e m ix tu re i s d ig e s te d u n t i l th e l iq u i d rem a.ining i s c o lo r l e s s .

The

cooled c o n te n ts a r e d i lu t e d w ith 20 m l. o f w ater and th e f l a s k i s a tta c h e d to an a e r a tio n a p p a r a tu s .

An e x c e lle n t d e s c r ip tio n of t h i s

a p p a ra tu s i s given by Somers ( 23) .

The a s p i r a t o r i s s t a r t e d and th e

f l a s k i s h e a te d f o r 2 m in u tes to remove a c id ic g a s e s .

The r e c e iv e r i s

now f i l l e d w ith 50 m l. o f 2 p e r c e n t b o r ic a c id s o lu tio n to absorb th e ammonia.

The fla ,s k i s then cooled in ic e and '^0 p er c e n t aqueous NaOH

c o n ta in in g 2 .5 g. NapS p e r l i t e r i s added u n t i l th e s o lu tio n tu rn s a d i r t y brown c o l o r .

The ic e b a th i s removed and. b e a t i s a p p lie d to the

d ig e s tio n fla .s k f o r 15 m in u te s .

The b o r ic a c i d - f i l l e d r e c e iv e r i s then

removed, and th e ab so rb ed ammonia t i t r a t e d d i r e c t l y u sin g 0 .0 1 N. a c id and. a mixed brown c r e s o l gr-een-m ethyl re d I n d ic a to r .

49. A s e a rc h f o r an a n a l y t i c a l method which would n o t in v o lv e a K je ld a h l d ig e s tio n has r e s u l te d in a new p ro c e d u re .

Inasmuch a s th e

v o l a t i l i t y o f th e am ines c o rre sp o n d in g to th e low er n i t r o p a r a f f in s i s f a i r l y h ig h and t h e i r b a s i c i t y i s g r e a t e r than t h a t o f ammonia, i t has been found p o s s ib le to red u c e th e n i t r o p a r a f f in s w ith T iC l^ in hydro­ c h lo r i c a c id , n e u t r a l i z e , d i s t i l l th e am ines in to b o ric a c id and t i t r a t e them d i r e c t l y w ith a c id .

The a d v a n ta g e s claim ed f o r th e method a re

g r e a t e r a c c u ra c y , s im p lic ity and in c re a s e d speed. S im p lifie d P ro ced u re f o r th e Lower N itro P a r a f f in s A sample o f th e n i t r o p a r a f f i n o f such a s iz e a s to c o n ta in 2 to 5 iHg- o f n itr o g e n i s weighed in to a 100 m l. K je ld a h l f l a s k c o n ta in ­ in g 1 m l. o f 20 p e r c e n t TiClg in h y d ro c h lo ric a c id and 2 m l. o f e th a n o l. T h is i s b o ile d f o r 2 m inutes then d ilu te d to 30 m l. w ith d i s t i l l e d w ater and p la c e d on a E je ld a h l a e r a tio n a p p a ra tu s and 10 ml. o f 50 per c e n t aqueous NaOH added.

The f l a s k i s h e a te d s tro n g ly f o r 15 m inutes and

th e am ines cau g h t in 50 m l. o f 2

p e r cen t b o r ic acid s o lu tio n .

They

a re then t i t r a t e d w ith 0 .0 1 N a c id u sin g brom c r e s o l green-m ethyl red mixed i n d i c a t o r . A c id ic M a te r ia ls The above p ro c e d u re f o r h a n d lin g th e liq u i d r e a c tio n p ro d u cts gave an aqueous p o r tio n and an e th e r e x t r a n t .

An a li q u o t p o rtio n o f

each (b e fo re tre a tm e n t w ith sodium b ic a rb o n a te in th e c a se o f th e e th e r e x tra ,c t) was t i t r a t e d w ith s ta n d a rd b a se to b o th th e m ethyl orange and p h e n o lp h th a le in e n d p o in ts .

The t o t a l number o f m oles o f a c id th u s found

were c a lc u la .te d and, r e p o r te d as su ch .

S ince th e q u a n ti ti e s involved

were ex trem ely sm a,ll, no a tte m p t was made to determ in e th e in d iv id u a l a c id s p r e s e n t .

From th e r e la .tiv e amounts o b ta in e d w ith th e two

50. i n d i c a t o r s , i t can be seen t h a t a c o n s id e ra b le p o rtio n o f th e a c i d i t y was due t o o rg a n ic a c id s . C arb onyl Compounds An a l i q u o t p o r tio n o f b o th th e w ater and th e e th e r la y e r was b ro u g h t t o th e m ethyl orange en d p o in t w ith O.5 N b a s e .

A few m i l l i l i t e r s

o f a s a tu r a te d s o lu tio n o f hydroxy lam ine h y d ro c h lo rid e was then added to th e sam ple b e in g a n a ly z e d , which was then a.Howed to stan d f o r 10 m inutes. Any a ld e h y d e s and k e to n e s p r e s e n t r e a c t w ith th e hydroxy lam ine and l i b e r a t e h y d ro c h lo ric a c id .

The amount o f a c id th u s formed i s a

m easure o f th e c a rb o n y l compounds and m y be determ ined by b rin g in g th e s o lu tio n back to th e m ethyl orange e n d p o in t w ith s ta n d a rd b a se .

The pH

o f th e hydroxylam ine h y d ro c h lo rid e s o lu tio n should be a d ju s te d to a v a lu e o f 3-4 b e fo re i t i s u sed . Gas A n a ly s is An O rs a t ty p e a n a ly s is was used to determ ine th e amounts of carbon d io x id e , carbon monoxide, n itro g e n d io x id e , n i t r i c o x id e, butenes p lu s p ro p en e, e th y le n e , b u ta n e , m ethane, hydrogen , and. n i tr o g e n .

Because

o f th e tim e consuming n a tu r e o f th e p ro c e s s , th e l a s t fo u r m a te ria ls were only determ ined in a few c a s e s .

The a p p a ra tu s c o n s is te d o f a 100 ml. ga.s

b u r e t t e w ith a t h r e e way sto p c o c k jo in e d to a m anifold to which were connected s e v e r a l gas a b s o rp tio n p i p e t t e s .

Samples f o r th e analy^sis

were ta.ken in g a llo n ju g s by d is p la c e n e n t o f a, s a tu r a te d sodium s u l f a t e s o lu tio n .

The m a te r ia ls removed a.re l i s t e d below in th e o rd e r o f t h e i r

rem oval a lo n g w ith th e a b s o rb e n t used in each c a s e . ( 1)

N itro g e n d io x id e .

Absorbed in 5O p er c e n t s u l f u r i c a c id ,

u s in g a f r e s h 1 m l. p o r tio n o f th e a b s o rb e n t f o r each p a s s .

A s p e c ia .l

51.

p i p e t t e was used f o r t h i s a b s o rp tio n .

A 125 m l. b u lb , parked w ith

g la s s ro d s was s e a le d to th e m anifold th ro u g h a th re e way sto p c o c k .

A

l e v e l i n g b u lb was a tta c h e d to th e low er end, and th e assem bly was f i l l e d w ith m ercury.

The o th e r arm o f th e sto p c o c k was s e a le d to a n o th e r th re e

way s to p c o c k .

One arm o f t h i s was s e a le d to th e bottom o f a c a lib r a te d

c e n tr if u g e tu b e and th e o th e r was b e n t to d isc h a rg e in to a w aste a c id fla s k .

The c e n tr if u g e tube serv ed as an a c id r e s e r v o i r .

In o p e ra tio n ,

1-2 m l. o f acid, was l e t in on to p o f th e mercury and. th e stopcock turned, to co n n ect t h i s b u lb to th e m an ifo ld .

The ga.s was adm itted, by low ering

th e m ercury b u lb and e x p e lle d by r a i s i n g i t .

The acid, was then d i s ­

charged by a p ro p e r m an ip u la tio n o f th e sto p co ck s and a f r e s h sample introduced-. ( 2)

Carbon d io x id e .

T his was absorbed in 30 per c e n t aqueous KOH

s o lu t i o n , making th r e e ps.sses b e fo re each r e a d in g , u n t i l a c o n sta n t r e a d in g wan o b ta in e d . ( 3)

N i t r i c o x id e .

T h is was absorbed in a s a tu r a te d s o lu tio n of

f e r r o u s s u l f a t e in 15 p e r c e n t s u l f u r i c a c id u n t i l a c o n s ta n t re a d in g was o b ta in e d . (4)

Propene p lu s b u te n e s .

E ig h ty -o n e and 38 p er c e n t s u lf u r ic

a c id was used a s an a b s o rb e n t in th e p i p e t t e d e sc rib e d under n itro g e n d io x id e .

A f r e s h 1 m l. p o r tio n was used f o r each pa,ss.

The 31 p e r cent

acid, was used u n t i l th e a b s o rp tio n p e r pe.ss was l e s s than O.5 m l. 88 p e r c e n t was u sed u n t i l th e lo s s p e r p a ss became c o n s ta n t.

The

The sum

o f th e s e c o n s ta n t lo s s e s in th e 83 p e r c e n t a c id , s u b tra c bed from th e to ta .1 amount ab so rb ed in th e 8l and, 38 p e r c e n t a c id ga,ve th e q u a n tity o f th e s e o l e f i n s p r e s e n t. (5 )

E th y le n e .

T his was ab so rb ed in 96 p e r c e n t s u l f u r i c a c id

which c o n ta in e d one p e r c e n t s i l v e r s u l f a t e .

The a n a ly s i s i s c a r r ie d

o u t in th e sa.me manner a s f o r th e 38 p e r c e n t a c id .

52. (6)

Carbon m onoxide.

Ammonleal cuprous c h lo r id e was used a s

th e a b s o rb e n t and th e a n a ly s is c o n tin u ed u n t i l a c o n s ta n t r e a d in g was a tta in e d . (7 )

B utane.

K erosene was used as th e a b s o rb e n t.

I t wa.s found,

n e c e s s a ry to renew th e a b s o rb e n t once to com plete th e a n a ly s i s , s in c e th e va.por p re s s u re above a m o derately c o n c e n tra te d s o lu tio n o f butane in kero sen e i s c o n s id e ra b le . (8)

Hydrogen and m ethane.

The r e s i d u a l gas from th e above

a n a ly s e s was mixed w ith a m easured volume o f a i r and burned, over th e h o t copper o x id e.

The i n i t i a l volume l o s s to g e th e r w ith th e lo s s

o b ta in e d by a b s o rp tio n o f th e r e s id u e in aqueous KOH allow ed th e c a l ­ c u la tio n o f hydrogen and m ethane. (9 )

N itro g e n .

O btained by d iff e re n c e between the re s id u e b e fo re

com bustion and th e sum of th e hydrogen and m ethane. I t i s a b s o lu te ly n e c e ssa ry tha.t th e p o tassiu m hy d ro x id e, f e r r o u s s u l f a t e , and cuprous c h lo rid e s o lu tio n s be s a tu r a te d w ith b u tan e b e fo re th e s t a r t o f th e a n a ly s i s .

F a ilu r e to observe t h i s p r e ­

c a u tio n w i l l r e s u l t in high v a lu e s f o r carbon d io x id e , n i t r i c o x id e, and carbon monoxide.

III.

C a lc u la tio n s

C o n ta c t Time T h is was c a lc u la te d from th e number o f moles o f m a te ria ls charged on th e b a s is of no change in th e number o f moles d u rin g th e re a c tio n .

O bviously t h i s assum ption i s in c o r r e c t b u t in tro d u c e s no

g r e a t e r r o r in t h a t th e m a jo r ity o f th e m a te r ia l charged i s butane ■which comes th ro u g h unchanged .

The mean p re s s u re pre■ vailing in th e

r e a c t o r i s used where th e r e i s a c o n s id e ra b le p r e s s u re d ro p .

In a l l b u t

th e e x p erim en ts perform ed in th e 7 mm. r e a c t o r , th e p r e s s u re drop was n e g li g ib l e and th e p r e s s u r e used was t h a t measured a t th e o u t l e t . C onversion T his was c a lc u la te d a s th e mole p e rc e n ta g e o f th e n i t r i c a c id charged which appeared a s n i t r o p a r a f f i n s . M oles o f P ro d u c ts The a c t u a l m olar amounts o f th e v a rio u s p ro d u cts o b tain ed a re r e p o r te d a s su ch .

No e s tim a tio n o f th e w ater produced was ma,de in ■view

o f th e in ac c u ra c y o f such a d e te rm in a tio n .

These q u a n ti ti e s were

a d ju s te d

f o r th e D isc u ssio n S e c tio n to th e v alu es which would have been

o b ta in e d

i f e x a c tly 10 m oles o f bu tan e had been used.

Y ie ld s By a c o n s id e r a tio n o f th e p r o d u c t,

number o f moles of carbon in each

an e s tim a tio n o f th e t o t a l amount o f b utane r e a c tin g wa.s ob tain ed

The number o f m oles o f bu tan e co n v erted to n i t r o p a r a f f i n s , a s computed on t h i s b a s i s , d.i'vlded, by th e t o t a l moles r e a c ti n g gave th e y ie ld based on h y d ro carb o n .

54. IV. ChemicalB Used. Met ha,ne S in ce pure methane in c y lin d e rs i s q u ite expensive and because i t was to be used only f o r checking th e a p p a ra tu s , i t was prepared from n a t u r a l g a s.

The method o f Boyd ( 3) wan used in which th e gs.s i s scrubbed

w ith c o n c e n tra te d s u l f u r i c a c id , pa.ssed over s o lid c a u s t i c , and then p assed a t 100 pounds p re s s u re ov er a c tiv a te d c h a rc o a l which a b so rb s th e h ig h e r homologs o f m ethane. Propane T his was o b tain e d from P h i l l i p s P etro leu m Company a s t h e i r T e c h n ic a l Gra.de and was 95 p e r c e n t p u re. B utane T h is was s u p p lie d by P h i l l i p s P etro leu m Company a s t h e i r P ure Grade and was g u aranteed to be 99 p e r c e n t p u re . N i t r i c Acid, B a k e r's C .P . n i t r i c a c id was used a s o b ta in e d .

T itr a .tio n s

were made t o check th e s ta te d a ssa y in every ca.se.

Oxygen Pure oxyrgen, as su p p lie d by th e L inde A ir P ro d u c ts Company in c y li n d e r s , was u sed .

55

V.

E x p e rim e n ta l Da,t a

The fo llo w in g ta b u la r d a ta (T able Xrv) give th e c o n d itio n s f o r and r e s u l t s from e x p erim en ts 1-43 on which t h i s t h e s i s i s b a sed . C a lc u la te d v a lu e s ,s u c h a s c o n ta c t tim e , c o n v e rsio n , and y i e l d , a r e n o t in c lu d e d inasm uch a s th e y a p p e ar in th e t h e s i s i t s e l f and may be derived, from th e d a ta p re s e n te d h e r e . The r e a c t o r used in each case i s designated, by a number to th e fo llo w in g schem e.

s/v

Volume (m l.)

I.D .

1

625

5

None

8

2

600

10

None

4

2a

TOO

10

None

4

3a

623

20

3/ 16" h e li c e s

20

3b

TOO

20

1/ 8” h e li c e s

28

3c

800

20

G lass wool

R e a c to r No.

P acking

R a tio

300

55a. CO C'~

VO

o

vq P

CO o

p o

in .y

o o

_y

r-i

d

OJ

d

p

P

o

p

d

o q

oo c-

o o

q CJ

VO o\

o\ p

P fO

p 00

o\ CO

r4

o

OJ

o

o

p

o

o

O

OJ

-yoo

jno

cp

o in

OJ VO

p p

VO OJ

p (VJ

o

P

d

d

d

o

o

o

OJ

tn

o in

-yH

g

%

S '

O

.y-

rri

£D

OJ

o S '

1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1

1 1 i

8

o w

a

-y-

o

8

a1

1 1

8

a

ir\ s

o

cvj

3

t— 1 o m

-y-

-y

VO

M

p

OJ

o

I—1

P

d

H

OJ OJ

VO m

OJ in

CA CM

o tp

s

p

OJ

o

P

d

CVJ VO

q

P

d

d

O-v

o\ rH

t— H

OJ

p

>-

OD

1

CO

d

OJ

VO ro

0p

P

o

d

o

1 1 I 1

o o

8

f 1 1 1 1 1 1 1

CO

o

o

p

1 1

!

O OJ

o

o

O

CO OJ

8

VO p

VO n

d

o

d

o

1

d

c

VO m 1

1

o

-y

-p

p 1

1

1

1 1

VO

VO

GO

p OJ

CO 1

1

vH

d

M -p

1 1 y-

CO

I

d

T*

I

_y in !

1

1 1

1 1

o o 0

o

in

VO

cv

o o

1 1

o

1 I

1 1

1 1

1 1

8,

1 1

1

1 1 1

m

1

ir \

s d

g d

1 1

1 1

1 1

1 1

1 1

1 1

1 1

I 1

1 1

I 1

1

1

I 1

1

1

1

1

1 1

-P

1

1

OJ

1

*

1 1

VO

I 1 1 1 1

1 1 1 1

ITS

I 1

-y-

cn

1 IT\ oo dj1 1

» 1 1

O

1 1 1 1 1 1

1 1

H

1 1

1 1 1 1

O m

o VO

uo r-

o

VO

1

1 1 1 1

-yW o 1

p LTV -=r

1 1 1 1

I 1

1 I

1 1 1 1 1 1 1 1

1

1

1 1 1 1 1 1 1 1

1

1

OJ

1 1 1

1 I 1

1 1 1 1

1 i 1 1 1 1

1

I

1

1 1

1

1

1 1

1

1

1

I

1

1

1

1

1 1

1 1

K OJ

1

t

«gI

«N -P OJ VO p

CO

-y o

p

1—1

o

o

p

-yro

ICO cu

P

8

OJ

on

d

1 1

1

1

1 I

< 1

1 I

I

1

1 1

°

o

tr -

in

CO 0-

P

OJ

d

1 I

1

1

I

1

1 1

1 1

1 1

® s

1

§ t>