Chemical Reaction Engineering Reviews - ACS Publications

8 Oxidation Reaction Engineering

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

A.

CAPPELLI

Montedison Fibre R&D, Milan, and Istituto di Chimica Industriale, Politecnico di Milano, Italy

This review

presents

of oxidation

a selection

reactions.

The

of work on various

papers

reviewed

into four sections: (a) vapor phase oxidation air, (b) liquid oxidation

phase oxidation

with

hydroperoxides,

of homogeneous (and

with oxygen,

catalytic

most important)

and

section

tion When

is paid

to

the data

chemical

automotive

munication

exhaust

engineering,

between

researchers

from

or

phase

heterogeneization

are examined

are evaluated

reaction

with oxygen

The papers of the first

process type and certain basic aspects. about the state of the art of oxidation

divided

(c) liquid

(d)

processes.

aspects

are

according

Information

reactors.

Special

treatment the

is

point

it is concluded

to given atten-

processes. of view that

and process engineers

of

comneeds

improvement.

' " p h e f o l l o w i n g r e v i e w is a r e p r e s e n t a t i v e selection of w o r k o n v a r i o u s aspects

of o x i d a t i o n reactions p u b l i s h e d i n 1972, 1973, a n d 1974.

T h r e e g e n e r a l sections a r e discussed w h i c h c o r r e s p o n d to a n a t u r a l d i v i s i o n o f t h e subject matter. T h e s e a r e : ( a ) v a p o r phase o x i d a t i o n w i t h o x y g e n o r a i r , ( b ) l i q u i d phase o x i d a t i o n w i t h o x y g e n , a n d ( c ) l i q u i d phase oxidation w i t h hydroperoxides.

A f o u r t h section, o n t h e hetero-

g e n e i z a t i o n of h o m o g e n e o u s processes, i n w h i c h t h e p r e p a r a t i o n of s u p p o r t e d h o m o g e n e o u s catalysts is treated, is discussed separately.

Special

emphasis is g i v e n to a u t o m o t i v e exhaust. Vapor Phase Oxidation

with Oxygen or Air

T h e d i s c u s s i o n focuses o n heterogeneous c a t a l y t i c processes, w h i c h are b y f a r t h e most i m p o r t a n t ones. P a p e r s a r e r e v i e w e d a c c o r d i n g to different aspects w h i c h are o f p a r t i c u l a r interest i n this area. F i r s t c o n s i d e r e d are t h e types of processes, w h i c h i n c l u d e t h e o x i d a t i o n of o r g a n i c 212

In Chemical Reaction Engineering Reviews; Hulburt, H.; Advances in Chemistry; American Chemical Society: Washington, DC, 1975.

8.

and

Oxidation

CAPPELLI

Reaction

some inorganic molecules.

and/or active

p h y s i c a l aspects centers,

Engineering Secondly,

213

some of the b a s i c

chemical

of o x i d a t i o n , s u c h as m e c h a n i s m s , n a t u r e

r e a c t i o n patterns, effects of

operating

conditions

catalyst m o d i f i c a t i o n s , a n d role of d i f f u s i o n are c o n s i d e r e d .

of and

F i n a l l y , some

i n f o r m a t i o n a b o u t the present state of the art i n the field of o x i d a t i o n reactors, b o t h o n a l a b o r a t o r y a n d i n d u s t r i a l scale, is g i v e n . I n the papers e x a m i n e d the o x i d a t i o n of olefins,

Types of Processes.

aromatics, N H , S 0 , a n d C O have been studied.


3

2

W i t h r e g a r d to

the

o x i d a t i o n of olefins, the reactions s t u d i e d are l i s t e d i n T a b l e I , a p p r o x i m a t e l y a c c o r d i n g to t h e i r degree of o x i d a t i o n . DEHYDRODIMERIZATION.

T r i m m et al. ( 1 ) a t t e m p t to i d e n t i f y a c a t a -

lyst for t h e p o l y m e r i z a t i o n a n d s u b s e q u e n t c y c l i z a t i o n of olefins u n d e r o x i d a t i v e c o n d i t i o n s , u s i n g the o x i d a t i o n of p r o p e n e

to b e n z e n e as a n

i l l u s t r a t i o n . A s u r v e y of possible c o m p o u n d s s h o w e d t h a t i n d i u m o x i d e c o u l d b e a s u i t a b l e catalyst.

T h e o x i d e w a s tested e x p e r i m e n t a l l y a n d

f o u n d to b e a selective catalyst for t h e o x i d a t i o n of p r o p e n e to b e n z e n e . 1,5-Hexadiene and

acrolein were produced

i n the e a r l y stages of

r e a c t i o n , a n d the d i e n e o x i d i z e d f u r t h e r to p r o d u c e benzene.

the

T h e kinetics

of the r e a c t i o n w e r e e x a m i n e d i n some d e t a i l , a n d a tentative m e c h a n i s m was advanced. T h e note b y P a r e r a et al.

( 2 ) reports the analogous

o x i d a t i o n of

i s o b u t e n e to 2 , 5 - d i m e t h y l - l , 5 - h e x a d i e n e a n d p - x y l e n e over i n d i u m oxide. T h e kinetics were examined, and a mechanism was proposed. OXIDATIVE DEHYDROGENATION.

Sterrett et al. ( 3 )

s t u d y of the o x i d a t i v e d e h y d r o g e n a t i o n z i n c c h r o m i u m — i r o n catalyst.

present a k i n e t i c

of b u t e n e to b u t a d i e n e over

a

T h e d a t a o n w h i c h t h e k i n e t i c m o d e l is

b a s e d w e r e o b t a i n e d u s i n g a set of s t a t i s t i c a l l y d e s i g n e d

experiments.

S e l e c t i v i t y to b u t a d i e n e r e m a i n e d h i g h t h r o u g h o u t the r u n s . T h e f o r m a t i o n of b u t a d i e n e w a s fit to a s e m i e m p i r i c a l rate expression b y a n o n - l i n e a r , least-square, c u r v e - f i t t i n g t e c h n i q u e . In

the

study reported

phosphorus-tin

oxide

by

Pitzer

catalyst, a c t i v e

methods

(48)

a n d selective

of for

activating a the

d e h y d r o g e n a t i o n of butènes to b u t a d i e n e , w e r e i n v e s t i g a t e d .

oxidative Objectives

of a c t i v a t i o n i n c l u d e d s e v e r a l properties of the catalyst, a n d the a u t h o r a t t e m p t e d to a c c o m p l i s h these objectives b y h e a t i n g the finished catalyst i n steam, a i r , a n d n i t r o g e n . C a t a l y t i c a c t i v i t y w a s i m p r o v e d b y s t e a m i n g at e l e v a t e d

temperatures w h i l e h e a t i n g i n a i r a n d n i t r o g e n gave

improvement.

no

O n l y m a c r o p o r o s i t y s e e m e d to a c c o u n t for the increase i n

catalytic activity, and steaming

appeared

to

affect

the

bulk

of

the

catalyst i n s t e a d of a l t e r i n g o n l y the surface of t h e catalyst p a r t i c l e s . A L L Y L I C OXIDATION.

F i v e papers describe experiments c a r r i e d out

over m o l y b d a t e catalysts. I n the s t u d y b y W r a g g et al. (5)

the ammooxi-

d a t i o n of p r o p e n e a n d of a c r o l e i n w a s s t u d i e d over t w o

catalysts—one


214

CHEMICAL

REACTION ENGINEERING REVIEWS

T a b l e I.

V a p o r Phase

Catalyst

Process

i n d i u m oxide


z i n c - c h r o m i u m oxide p h o s p h o r u s - t i n oxide molybdate tungstate u r a n i u m - a n t i m o n i u m oxide m e r c u r i c chloride

i A l l y l i c oxidation

silver molybdate ( P d doped) v a n a d i u m pentoxide molybden-alumina O x i d a t i v e C - C cleavage

supported i r i d i u m

Complete combustion

p l a t i n u m - a l u m i n a spinels chromite

s i m i l a r to c o m m e r c i a l b i s m u t h m o l y b d a t e

catalysts a n d the other

con-

s i s t i n g of the k o e c h l i n i t e phase B i 0 - M o 0 . T h e rates, r e a c t i o n orders, 2

3

3

A r r h e n i u s parameters, a n d selectivities of the a m m o x i d a t i o n s w e r e s t u d i e d at a fixed t e m p e r a t u r e , a n d t e n t a t i v e m e c h a n i s m s h a v e b e e n M a n n a n d K o (6)

advanced.

r e p o r t the effect of several v a r i a b l e s o n c o n v e r s i o n a n d

y i e l d of the o x i d a t i o n of 2 - m e t h y l p r o p e n e to m e t h a c r o l e i n over a b i s m u t h molybdate mechanism.

catalyst.

A rate e q u a t i o n has b e e n e v a l u a t e d b a s e d

P a s q u o n et al.

on

a

investigated the catalytic behavior

of

some m o l y b d a t e catalysts i n the o x i d a t i o n of 1-butene to b u t a d i e n e

or

to m a l e i c a n h y d r i d e .

is

The

(7)

c a t a l y t i c a c t i o n of b i s m u t h m o l y b d a t e s

discussed b y S c h u i t ( 8 ) i n its c o n n e c t i o n w i t h the s o l i d s t r u c t u r e , m e t h o d of

p r e p a r a t i o n , kinetics of

reactants a n d p r o d u c t s .

the reaction catalyzed, and adsorption

the a m m o x i d a t i o n of p r o p e n e a n d a m m o n i a are p r o p o s e d . Keulks (9)

of

M e c h a n i s m s for the o x i d a t i o n of olefins a n d for Daniel and

r e p o r t p r e l i m i n a r y results of a n i n v e s t i g a t i o n o n a catalyst

containing B i , M o , and Fe.

T h e authors h a v e f o u n d that the a c t i v i t y

a n d s e l e c t i v i t y of this catalyst are c o m p a r a b l e w i t h b i s m u t h for the o x i d a t i o n of p r o p e n e to a c r o l e i n . V i l l a et al. (10)

molybdate

report the results

of a n i n v e s t i g a t i o n o n t h e c a t a l y t i c b e h a v i o r of B i tungstates for o x i d a t i o n a n d a m m o x i d a t i o n of olefins ( p r o p e n e a n d 1-butene ). i n g to this s t u d y B i W 0 2

6

is the o n l y active a n d selective c o m p o u n d .

l a b o r a t o r y s t u d y b y G r a s s e l l i a n d S u r e s h (4)

the

AccordIn a

a u r a n i u m - a n t i m o n y oxide

catalyst, k n o w n to be p a r t i c u l a r l y efficient for s y n t h e s i z i n g a c r y l o n i t r i l e , w a s s t u d i e d to d e v e l o p a n u n d e r s t a n d i n g of s t r u c t u r a l features r e l a t e d to


8.

Oxidation

CAPPELLi

Reaction

Engineering

215

O x i d a t i o n of Olefins Examples propene —> benzene


3 48

butene —> butadiene

5, 6, 7,8, 9 10 4 16

propene —» a c r o l e i n

11,29, 30, 31 7,12,13 15

ethylene —» ethylene oxide butene —» m a l e i c a n h y d r i d e ethylene - » acetaldehyde propene -> acetone

25

propene - »

17,18 19

hydrocarbons and C O - » C 0

butene - » butadiene propene —» a c r y l o n i t r i l e , a c r y l i c a c i d

acetaldehyde 2

c a t a l y t i c a c t i v i t y . A m e c h a n i s m for the o x i d a t i o n a n d a m m o x i d a t i o n of p r o p e n e is p r o p o s e d i n v o l v i n g a l l y l i c i n t e r m e d i a t e s .

A r a i et

presents a k i n e t i c s t u d y of the o x i d a t i o n of isobutene to

ah

(16)

methacrolein

over m e r c u r i c c h l o r i d e s u p p o r t e d o n a c t i v e c h a r c o a l . T h e k i n e t i c s of the o x i d a t i o n w e r e d e t e r m i n e d , a n d r e a c t i o n rates of other olefins w e r e also measured. O X Y G E N I N S E R T I O N . M e t c a l f et al. (11) c a t a l y z e d ethylene o x i d a t i o n .

s t u d i e d the k i n e t i c s of s i l v e r -

T h e behavior

i n v e s t i g a t e d , a n d the k i n e t i c d a t a w e r e

fitted

of v a r i o u s i n h i b i t o r s w a s to L a n g m u i r - H i n s e l w o o d

rate expressions, a l t h o u g h some inconsistencies w e r e n o t e d . s k y et al. ( 2 9 ) , C a r b e r r y et al. (30)

a n d F o r z a t t i et al. (31)

Marcinkowalso r e p o r t

studies o n ethylene o x i d a t i o n o v e r A g s u p p o r t e d catalysts. T r i f i r o et al. (12)

present a s t u d y of the o x i d a t i o n of 1-butene to

m a l e i c a n h y d r i d e over a M n - M o 0

6

b a s e d catalyst. A m o n o c e n t e r o x i d a -

t i o n m e c h a n i s m , a c c o u n t i n g for t h e f o r m a t i o n of C O , C 0 , a n d m a l e i c 2

a n h y d r i d e , is p r o p o s e d . (7)

I n the a b o v e m e n t i o n e d p a p e r b y P a s q u o n et al.

o n the c a t a l y t i c b e h a v i o r of some m o l y b d a t e

catalysts a tentative

m e c h a n i s m of f o r m a t i o n of m a l e i c a n h y d r i d e f r o m 1-butene o v e r F e M 0 O 4 is a d v a n c e d .

A k i m o t o et al. (13)

r e p o r t t h e results of a n i n v e s t i -

g a t i o n o n s u p p o r t e d m o l y b d e n a catalysts for t h e o x i d a t i o n of b u t a d i e n e . E v n i n et al. (14)

d e s c r i b e w o r k o n the d e v e l o p m e n t of a heterogeneous

c a t a l y t i c system, consisting of p a l l a d i u m - d o p e d v a n a d i u m p e n t o x i d e a n d a t h i r d c o m p o n e n t , w h i c h is c a p a b l e of o x i d i z i n g ethylene d i r e c t l y to acetaldehyde

w i t h h i g h specificity, a c t i v i t y , a n d s t a b i l i t y .

T h e results


216

CHEMICAL


of a n i n v e s t i g a t i o n o n the c a t a l y t i c a c t i v i t y of a M0O3 · A 1 0 2

system for

3

the o x i d a t i o n of p r o p e n e are r e p o r t e d b y G i o r d a n o et al. (15),

and a

tentative m e c h a n i s m is a d v a n c e d . O X I D A T I V E C - C C L E A V A G E . C a n t a n d H a l l ( 2 5 ) c o m p a r e d the o x i d a t i o n reactions of

ethylene, p r o p y l e n e ,

1-butene, cis-2-butene,

trans-2-

b u t e n e , isobutene, a n d t h e t w o 2-pentenes over s u p p o r t e d I r catalysts. T h e most i m p o r t a n t o x i d a t i o n p r o d u c t s w e r e acetic a c i d f r o m ethylene, Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

propene,

the 2-butenes,

a n d the 2-pentenes,

and propionic acid and

acetone f r o m 1-butene a n d isobutene, r e s p e c t i v e l y . P o s s i b l e m e c h a n i s m s are discussed. COMPLETE COMBUSTION. of

carbon

monoxide

catalyst w e r e d e t e r m i n e d . and

I n a s t u d y b y V o l t z et al. (17)

and propene

oxidation on

the k i n e t i c s

a platinum-alumina

C o m p l e x k i n e t i c equations w e r e f o r m u l a t e d ,

some rate constants a n d a c t i v a t i o n energies w e r e c a l c u l a t e d .

o x i d a t i o n k i n e t i c s w e r e u s e d to d e s c r i b e the p e r f o r m a n c e c a t a l y t i c converters i n a u t o m o t i v e emission c o n t r o l systems.

The

of p l a t i n u m The oxida-

t i o n of p r o p e n e over C r ( I I I ) a n d F e ( I I I ) spinels has b e e n i n v e s t i g a t e d b y Z a n d e r i g h i et al.

A non-selective o x i d a t i o n to C 0

(18).

s e r v e d , a n d a tentative m e c h a n i s m was a d v a n c e d . (19)

f o u r types of « - C r 0 2

3

2

was

ob-

I n a study b y Yao

m i c r o c r y s t a l s w e r e p r e p a r e d a n d u s e d as

catalysts for the o x i d a t i o n of C H , C H , C H , C H , a n d C O . R e a c t i o n 2

4

3

6

2

6

3

8

rates w e r e m e a s u r e d , a n d some m e c h a n i s m s w e r e a d v a n c e d . Chemical Kinetic and Physical Aspects. Some of the r e v i e w e d papers are discussed a c c o r d i n g to the f o l l o w i n g aspects: proposed mechanisms nature of active sites r e a c t i o n patterns effects of o p e r a t i n g c o n d i t i o n s effect of catalyst modifications a n d a d d i t i o n of p r o m o t e r s or i n h i b i t o r s role of diffusion PROPOSED M E C H A N I S M S .

K i n e t i c s a n d m e c h a n i s m of g a s - s o l i d c a t a -

l y t i c oxidations are g e n e r a l l y e x p l a i n e d o n the basis of r e d o x or L a n g m u i r - H i n s h e l w o o d m e c h a n i s m s or e v e n t u a l l y of a t h i r d m e c h a n i s m , w h i c h can

b e c o n s i d e r e d as c o m b i n a t i o n of the other t w o .

The mechanism

a c c o r d i n g to w h i c h the substance to b e o x i d i z e d reduces t h e catalyst, w h i c h is r e o x i d i z e d b y o x y g e n f r o m the f e e d , is k n o w n as r e d o x m e c h a n i s m . T h i s c a n be a s s u m e d to take p l a c e i n t w o stages: C - o x + molecule —» C - r e d + o x i d i z e d molecule C-red + 0

2

-> C - o x

(2)

T h i s m e c h a n i s m has b e e n tested either d i r e c t l y o n the basis of o b t a i n e d b y p u l s e m i c r o r e a c t o r s (4, 12, 20, 24),

(1)

data

i n w h i c h stage 1 a n d


8.

CAppELLi

Oxidation

Reaction

stage 2 w e r e separated, or b y

217

Engineering

fitting

the e x p e r i m e n t a l d a t a f r o m f l o w

reactors to k i n e t i c equations d e r i v e d f r o m the m e c h a n i s m (1, 21, 22,

23).

A c c o r d i n g to L a n g m u i r - H i n s h e l w o o d m e c h a n i s m the substance to

be

o x i d i z e d a n d o x y g e n r e a c t together i n t h e a d s o r b e d state. I n this case also, either o x i d a t i o n runs d o n e i n p u l s e m i c r o r e a c t o r s w e r e u s e d to test t h e p r o p o s e d m e c h a n i s m (12,

18, 26),

or the constants of the k i n e t i c

equations b a s e d o n this m e c h a n i s m w e r e e s t i m a t e d b y the least-squares Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

method

(1,6,11).

F i n a l l y the t h i r d m e c h a n i s m , w h i c h has b e e n tested i n t h e o x i d a t i o n of butènes to m a l e i c a n h y d r i d e ( 3, 12, 26 ) c a n b e a s s u m e d to take p l a c e i n three stages, w h i c h m a y b e w r i t t e n as: C - o x - f butènes C-red + 0 C-red — 0

2

C - r e d - j - butadiene + H 0

(1)

2

2

-> C - r e d -

0

2

-> C - o x

(2)

+ butadiene -> m a l e i c a n h y d r i d e - f C O , C 0

(3)

2

T a b l e s I I , I I I , a n d I V s h o w some reactions for w h i c h the v a r i o u s m e c h a nisms w e r e tested.

Table II.

Redox Mechanism

Process

Reference

O x i d a t i o n of butene to butadiene over v a r i o u s oxide c a t a l y s t s O x i d a t i o n of propene to a c r o l e i n over B i - M o oxide c a t a l y s t s O x i d a t i o n of propene to a c r y l o n i t r i l e over U - S b oxide c a t a l y s t s O x i d a t i o n of anthracene to a n t h r a q u i n o n e over C o - M o oxide catalyst O x i d a t i o n of anthracene to a n t h r a q u i n o n e over V oxide c a t a l y s t O x i d a t i o n of m e t h a n o l to f o r m a l d e h y d e o v e r M o 0 — F e ( M o 0 ) catalyst O x i d a t i o n of propene to benzene over I n oxide c a t a l y s t O x i d a t i o n of butènes to m a l e i c a n h y d r i d e over M n M o 0 catalyst 3

4

20 21 4 22 23

2

24 1

3

4

Table III.

12

Langmuir-Hinshelwood Mechanism

Process O x i d a t i o n of 2 - m e t h y l p r o p e n e to m e t h a c r o l e i n over B i - m o l y b date c a t a l y s t O x i d a t i o n of ethylene to ethylene oxide over A g c a t a l y s t O x i d a t i o n of propene to C 0 over C r ( I I I ) a n d F e ( I I I ) spinels O x i d a t i o n of propene to benzene over I n oxide c a t a l y s t O x i d a t i o n of butènes to m a l e i c a n h y d r i d e over M n M o 0 catalyst

Reference

2

6 11 18 1

4


12,26

218

CHEMICAL

Table IV.


Mixed Mechanism Reference

Process O x i d a t i o n of butènes to m a l e i c a n h y d r i d e over M n M o 0 - b a s e d catalyst O x i d a t i o n of butene to b u t a d i e n e over ferrite c a t a l y s t 4

N A T U R E O F A C T I V E SITES.

26 3

H y p o t h e s e s r e l a t i v e to the c h e m i c a l n a t u r e


of a c t i v e sites h a v e b e e n a d v a n c e d . I n the case of ethylene o x i d a t i o n over A g catalyst, m a n y authors agree that a d s o r b e d forms of p e r o x i d i c m o l e c u lar o x y g e n are r e s p o n s i b l e for t h e f o r m a t i o n of e t h y l e n e o x i d e (27, C0

2

f o r m a t i o n has b e e n a t t r i b u t e d to a t o m i c forms of a d s o r b e d

28).

oxygen

( 2 7 , 2 8 ) . F o r the a l l y l i c o x i d a t i o n of olefins a n d f o r t h e selective o x i d a t i o n of m e t h a n o l to f o r m a l d e h y d e , l a t t i c e o x y g e n ( M e = 0 t y p e ) is p r o p o s e d as the a c t i v e o x i d i z i n g site (4, 7, 10, 12). e r e d are U - S b oxides (4), (10).

T h e c a t a l y t i c systems c o n s i d -

m o l y b d a t e s ( 7 , 12),

a n d b i s m u t h tungstates

I n t h e o x i d a t i o n of butènes a n d b u t a d i e n e to m a l e i c a n h y d r i d e

o v e r m o l y b d e n a catalysts, the active sites are a s s u m e d to b e f o r m s of o x y g e n o n M o ( V ) o r M o ( I V ) (12,13).

adsorbed

F i n a l l y , for t h e c o m p l e t e

c o m b u s t i o n of olefins over v a r i o u s catalysts, a d s o r b e d forms of a t o m i c a n d m o l e c u l a r o x y g e n h a v e b e e n suggested

(12,

In Table V

17, 18).

the

a b o v e m e n t i o n e d hypotheses are s u m m a r i z e d . REACTION PATTERNS.

E x c e p t for t o t a l o x i d a t i o n reactions, i n a l l other

cases t h e i n t e r e s t i n g p r o d u c t s are i n t e r m e d i a t e s .

It c a n b e

expected,

therefore, t h a t p a r t i a l o x i d a t i o n p r o d u c t s are t h e r e s u l t of successive or p a r a l l e l reactions, a n d f r o m the d a t a i n l i t e r a t u r e there is e n o u g h e v i d e n c e t h a t b o t h m e c h a n i s m s c a n b e assumed. A n e x a m p l e , c o n c e r n i n g t h e o x i d a t i o n of butènes, is g i v e n i n F i g u r e 1. A p a r t i c u l a r case is the f o r m a t i o n of a c r y l o n i t r i l e a n d m a l e i c a n h y d r i d e since these p r o d u c t s seem to be successive to other stable i n t e r m e d i a t e s — a c r o l e i n a n d b u t a d i e n e , r e s p e c t i v e l y . T h i s s h o u l d b e t r u e at least i n t h e f o r m a t i o n of m a l e i c a n h y d r i d e , w h e r e t h e c o n c l u s i o n is that Table V .

Nature

Catalyst

Reaction O x i d a t i o n of ethylene to ethylene oxide

Ag

O x i d a t i o n of propene to a c r y l o n i t r i l e O x i d a t i o n of 1-butene to b u t a d i e n e O x i d a t i o n a n d a m m o x i d a t i o n of olefins O x i d a t i o n of butènes to m a l e i c a n h y d r i d e O x i d a t i o n of b u t a d i e n e to m a l e i c a n h y d r i d e C o m p l e t e o x i d a t i o n of propene

U - S b oxide Fe 0 -Mo0 Bi W0 MnMo0 Mo0 Pt C r ( I I I ) and F e ( I I I ) spinels

C o m p l e t e o x i d a t i o n of propene

2

3

2

3

6

4

3


8.

Oxidation

CAPPELLi

Reaction

b u t a d i e n e is the i n t e r m e d i a t e (47);

219

Engineering

h o w e v e r , some controversy s t i l l exists

for t h e f o r m a t i o n of a c r y l o n i t r i l e . F i g u r e 2 gives a r e a c t i o n scheme, a n d s o m e values of c a l c u l a t e d k i n e t i c constants are g i v e n i n T a b l e V I . EFFECTS O F O P E R A T I N G CONDITIONS.

F r o m some p a p e r s e x a m i n e d i n

this r e v i e w i t is possible to d e r i v e i n f o r m a t i o n a b o u t the r o l e of o p e r a t i n g c o n d i t i o n s s u c h as contact t i m e , t e m p e r a t u r e , p a r t i a l pressure of o x y g e n , o n y i e l d s , selectivities, types of p r o d u c t s , etc. T h e p a p e r b y Trifîrô et al. Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

(12)

o n t h e o x i d a t i o n of butènes gives a t a b l e s h o w i n g the influence of

p e r c e n t oxygen, t e m p e r a t u r e , a n d contact t i m e o n t h e types of reactions o c c u r r i n g . W h e n t h e a m o u n t of o x y g e n is i n c r e a s e d f r o m 0 to 2 0 % , t h e t e m p e r a t u r e is i n c r e a s e d f r o m 350° to 480 ° C , a n d t h e contact t i m e is i n c r e a s e d f r o m 0.27 to 2 sec, the f o l l o w i n g s e q u e n c e of c a t a l y t i c a c t i o n c a n be obtained: i s o m e r i z a t i o n - » o x i d a t i v e d e h y d r o g e n a t i o n -> o x i d a t i o n w i t h i n s e r t i o n of 0 -> cleavage of C - C bonds a n d complete o x i dation 2

In

a n other p a p e r b y Trifîrô et al.

influence of 0

2

o n the same subject the

(26)

p a r t i a l pressure o n y i e l d s a n d selectivities is r e p o r t e d .

I n a p a p e r b y T r i m m a n d D o e r r ( 1 ) o n the o x i d a t i o n of p r o p e n e to b e n z e n e over i n d i u m oxides the y i e l d of m a j o r p r o d u c t s w a s e x a m i n e d as a f u n c t i o n of contact t i m e a n d of o x y g e n a n d f u e l concentrations.

They

showed that: T h e y i e l d of b e n z e n e passes t h r o u g h a w e l l - d e f i n e d m a x i m u m at a c e r t a i n v a l u e of the contact t i m e . T h e m a j o r products—i.e., h e x a d i e n e a n d b e n z e n e — i n c r e a s e a n d pass t h r o u g h a m a x i m u m as the c o n c e n t r a t i o n of o x y g e n is i n c r e a s e d . T h e y i e l d of C 0

2

increases l i n e a r l y w i t h o x y g e n c o n c e n t r a t i o n .

T h e y i e l d of h e x a d i e n e increases w i t h p r o p e n e c o n c e n t r a t i o n w h i l e the y i e l d of b e n z e n e passes t h r o u g h a m a x i m u m a n d the y i e l d of C 0 passes t h r o u g h a m i n i m u m . 2

T h e effect of t e m p e r a t u r e o n t h e r e a c t i o n was m o r e

complex—the

amounts of h e x a d i e n e a n d b e n z e n e p r o d u c e d a p p e a r e d to be i n v e r s e l y of A c t i v e Sites Reference

Active

Sites

4 7 10 12 13 17

peroxide m o l e c u l a r o x y g e n ( f o r m a t i o n of ethylene oxide) a t o m i c o x y g e n ( f o r m a t i o n of C 0 ) lattice oxygen lattice oxygen lattice oxygen lattice oxygen oxygen [ o n M o ( V ) or M o ( I V ) ] atomic and molecular oxygen

18

atomic and molecular oxygen

27,28

2


220

CHEMICAL


CO

But-l-ene

C0

2

Furan


Acrolein n-Butyraldehyde Buta-l,3-diene

cïs-But-2-ene

Figure 1.

Acetaldehyde

Oxidation of butènes

Acrylonitrile ' Acrolein M e t h y l Cyanide

CO

Ethylene

co

2

Acetaldehyde " Figure 2.

Ammoxidation

of propene and acrolein

r e l a t e d . F r o m t h e a b o v e m e n t i o n e d papers it is possible to d e d u c e that the r a t e of t o t a l o x i d a t i o n increases as the p a r t i a l pressure of o x y g e n is increased. A different effect of the p a r t i a l pressure of o x y g e n w a s d e s c r i b e d i n a s t u d y b y M e t c a l f et al. (11)

on silver-catalyzed ethylene oxidation.

T h e rates of b o t h e t h y l e n e o x i d e a n d c a r b o n d i o x i d e f o r m a t i o n passed t h r o u g h m a x i m a w i t h i n c r e a s i n g o x y g e n pressure a n d t h e n

decreased.

T h i s b e h a v i o r was b y means of i n h i b i t i n g effects of the r e a c t i o n p r o d u c t s . EFFECTS

OF CATALYST

OR INHIBITORS.

MODIFICATIONS

A N D ADDITION

OF PROMOTERS

F o r ethylene o x i d a t i o n over silver catalysts some authors

( 27, 28 ) r e p o r t that the effect of c h l o r i n e is to i n h i b i t dissociative a d s o r p t i o n of o x y g e n a n d thus to increase t h e s e l e c t i v i t y of e t h y l e n e e p o x i d a t i o n since d i a t o m i c o x y g e n

o n s i l v e r is r e s p o n s i b l e for

the


selective

8.

CAPPELLi

Oxidation

Reaction

221

Engineering

o x i d a t i o n of e t h y l e n e to ethylene oxide.

T h e r o l e of C a a n d B a i n the

same r e a c t i o n is c o n t r o v e r s i a l ; some authors (32)

c o n t e n d t h a t the p r e s -

ence of C a increases s e l e c t i v i t y w h i l e others ( 33, 34 ) b e l i e v e the a d d i t i o n of B a a n d C a influences o n l y a c t i v i t y . In the o x i d a t i o n of 1-butene over F e 0 - M o 0 , P a s q u o n et al. 2

3

(7)

3

s t u d i e d the effect of gaseous o x y g e n a n d T e o n selectivity. T h e y f o u n d that at the lowest o x y g e n concentrations b u t a d i e n e a n d 2-butenes are the Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

m a i n p r o d u c t s ; w h e n the c o n c e n t r a t i o n of o x y g e n is i n c r e a s e d , b u t a d i e n e and

butènes decrease, a n d m a l e i c a n h y d r i d e f o r m a t i o n reaches a m a x i -

mum.

I t was also o b s e r v e d t h a t a d d i t i o n of T e increases t h e s e l e c t i v i t y

in butadiene. ROLE O F DIFFUSION.

T h r e e papers (14, 42, 43)

d e a l w i t h effects of

diffusion o n c a t a l y z e d o x i d a t i o n reactions. F o r the o x i d a t i o n of ethylene to a c e t a l d e h y d e over P d s u p p o r t e d catalysts, E v n i n et al. (14)

report

that the l o w values d e t e r m i n e d for the a p p a r e n t a c t i v a t i o n energies for e t h y l e n e c o n v e r s i o n a n d a c e t a l d e h y d e f o r m a t i o n are a n i n d i c a t i o n of diffusional

rather than kinetic control.

The

presence

of

diffusional

l i m i t a t i o n s is c o n f i r m e d b y experiments i n w h i c h the r a t e w a s s h o w n to d e p e n d o n the p a r t i a l pressure of the n i t r o g e n c a r r i e r gas. In and

a s t u d y o n a m m o n i a o x i d a t i o n over p l a t i n u m , r e p o r t e d b y P i g n e t

S c h m i d t (42),

a strong influence of mass transfer was observed.

Near

the s t o i c h i o m e t r i c c o m p o s i t i o n ( 2 1 % N H i n a i r ) a n d a b o v e , s e l e c t i v i t y 3

for N O d r o p p e d to z e r o , i n contrast to the r e a c t i o n i n the k i n e t i c r e g i m e w h e r e significant N O p r o d u c t i o n was o b s e r v e d i n excess N H

3

a n d at

temperatures a b o v e 1200 ° C F i n a l l y , i n a s t u d y r e p o r t e d b y K a d l e c et al. (43) fusivities of air a n d S 0

2

the effective d i f -

i n four i n d u s t r i a l v a n a d i u m p e n t o x i d e catalysts

for s u l f u r d i o x i d e o x i d a t i o n w e r e m e a s u r e d at the steady state.

With

models for the effective d i f f u s i v i t y a n d the k i n e t i c s of the c a t a l y t i c o x i d a t i o n of S 0 , a n o p t i m u m a p p a r e n t d e n s i t y of the catalyst m a y b e deter2

m i n e d w h i c h gives the m a x i m u m r a t e of r e a c t i o n p e r u n i t v o l u m e

of

catalyst. Types of Reactors.

LABORATORY

SCALE.

O n the l a b o r a t o r y scale

p u l s e m i c r o r e a c t o r s h a v e b e e n u s e d l a r g e l y to d i s t i n g u i s h b e t w e e n r e d o x and

L a n g m u i r - H i n s h e l w o o d m e c h a n i s m s . I n these studies o x i d a t i o n runs

of o r g a n i c molecules w e r e d o n e w i t h a n d w i t h o u t o x y g e n i n the gas p h a s e (4, 7, 12, 18, 20, 24). (7, 12)

I n the o x i d a t i o n of butènes to m a l e i c a n h y d r i d e

a C a r b e r r y s s t i r r e d - t a n k flow reactor was chosen since heat a n d

mass gradients c a u s e d b y transfer p h e n o m e n a are absent i n this t y p e of reactor. C o n v e n t i o n a l t y p e flow reactors w e r e u s e d i n most other cases. I N D U S T R I A L S C A L E . L i t e r a t u r e reports of e x p e r i m e n t a l w o r k i n o x i d a d a t i o n reactors are scarce, thus m a k i n g i t difficult to v e r i f y the m a t h e m a t i c a l m o d e l s a v a i l a b l e . T h e reactors w h i c h d o m i n a t e i n this area are


222

CHEMICAL

REACTION ENGINEERING

Table V I .

Κ


Reaction Propene a m moxidation Propene oxidation Acrolein a m moxidation Acrolein oxidation

κ,

REVIEWS

Kinetic

κ

Κ'

Κ" 2

Κ

2

2

3

5.2

4.8

0.16

0.16

—

0

0.1

8.0

—

5.85

—

0

0.06

2.0

—

—

—

0

—

—

170.0 97.0

t h e c o n v e n t i o n a l types—i.e., t u b u l a r reactors, m u t i p l e t u b e

reactors,

m u l t i l a y e r reactors, a n d fluidized b e d reactors. A n e w t y p e of reactor for gas phase c a t a l y t i c r e c y c l e reactions w a s r e c e n t l y p a t e n t e d b y et al. (49).

Collina

T h i s r e a c t o r is s k e t c h e d i n F i g u r e 3 a n d consists essentially

of a n injector, f o l l o w e d b y a single r a d i a l - f l u x l a y e r of catalyst, a n d s u r r o u n d e d b y a n a n n u l a r e m p t y space t h r o u g h w h i c h the r e a c t e d gases flow

b a c k f r o m t h e catalyst l a y e r to the injector, e x c h a n g i n g h e a t w i t h

f e e d gas i n a heat exchanger.

T h e c o n v e r s i o n p e r pass is k e p t v e r y l o w ,

a n d i t is therefore easy to c o n t r o l t e m p e r a t u r e increases.

T h e pressure

d r o p is l o w e r t h a n i n c o n v e n t i o n a l reactors, a n d i t is possible to r e a c h h i g h capacities. T h e reactor is s u i t a b l e for o x i d a t i o n reactions s u c h as t h e o x i d a t i o n of m e t h a n o l to f o r m a l d e h y d e , e t h y l e n e to ethylene o x i d e , p r o p e n e to a c r o l e i n a n d a c r y l i c a c i d , a n d butènes to m a l e i c a n h y d r i d e . B o t h p l a n t a n d o p e r a t i n g costs for these processes seem c o m p e t i t i v e w i t h conventional plants. Papers Presented in This Section. F o u r of the papers d i s c u s s e d i n t h e last session of the T h i r d

International Symposium on C h e m i c a l

Reaction Engineering ( A D V A N C E S I N C H E M I S T R Y SERIES N O . 1 3 3 ) belong

to this section o n gas phase c a t a l y t i c o x i d a t i o n . T w o papers c o n c e r n the o x i d a t i o n of o-xylene to p h t h a l i c a n h y d r i d e over v a n a d i u m catalysts. T h e other t w o r e p o r t studies o n t h e - o x i d a t i o n of c a r b o n m o n o x i d e i n a u t o m o t i v e exhausts. OXIDATION

OF O-XYLENE

OVER

VANADIUM

CATALYSTS.

Calderbank

( 5 0 ) s t u d i e d the k i n e t i c s of p h t h a l i c a n h y d r i d e f o r m a t i o n i n the o x i d a t i o n of o-xylene over a c o m m e r c i a l v a n a d i u m catalyst. T h e e x p e r i m e n t a l runs w e r e c a r r i e d out i n a s p i n n i n g catalyst-basket reactor, a n d the k i n e t i c s w e r e d e t e r m i n e d for the d i s a p p e a r a n c e of o-xylene a n d of the p a r t i a l oxidation products o-tolualdehyde and phthalide. T h e kinetics predict o b s e r v e d t e m p e r a t u r e profiles i n large t u b u l a r reactors. W a i n w r i g h t a n d H o f f m a n ( 51 ) also s t u d i e d the k i n e t i c s of o-xylene o x i d a t i o n over a v a n a d i u m - o n - s i l i c a catalyst o n the basis of e x p e r i m e n t a l d a t a o b t a i n e d i n a l a b o r a t o r y - s c a l e fixed b e d reactor a n d i n a p i l o t - s c a l e t r a n s p o r t e d b e d reactor. T h e k i n e t i c rate expression, w h i c h is l i m i t e d to


8.

Oxidation

CAPPELLi

Reaction

Engineering

223


Constants K±

K±

K4"

K±"

K

K

7

Kg

Kq

25.8

—

—

0

0.9

0

1.77

—

—

165.0

1

3

0

28

22

—

—

—

—

—

7

42

—

48

—

0

390

Kg

5

o-xylene d i s a p p e a r a n c e , is b a s e d o n a r e d o x m e c h a n i s m . T h e o p e r a t i o n of the t r a n s p o r t e d b e d reactor has b e e n p r e d i c t e d w i t h g o o d a c c u r a c y , a n d some considerations a b o u t selectivities, m e c h a n i s m s , a n d p h y s i c a l p h e n o m e n a , together w i t h suggestions for f u r t h e r r e s e a r c h , are i n c l u d e d . A g r e e m e n t b e t w e e n t h e results r e p o r t e d i n these t w o papers seems to b e f a i r l y g o o d . F o r e x a m p l e the rate expression suggested b y W a i n w r i g h t a n d H o f f m a n n contains a p a r a m e t e r Θ, w h i c h becomes e q u a l to 1 w i t h a f u l l y o x i d i z e d catalyst, i n agreement w i t h t h e d i s a p p e a r a n c e k i n e t i c s of o-xylene p r o p o s e d b y C a l d e r b a n k , w h i c h are first o r d e r u p to n e a r l y 1 m o l e % of x y l e n e c o n c e n t r a t i o n . T h e observations r e g a r d i n g t h e a c t i v a t i o n e n e r g y are also s i m i l a r i n b o t h papers.

T h e a c t i v a t i o n energy

de

creased as the r e a c t i o n t e m p e r a t u r e i n c r e a s e d , b e c o m i n g a b o u t a t h i r d of that at l o w e r temperatures. T h e o p e r a t i o n t e m p e r a t u r e r a n g e , h o w e v e r , is c o n s i d e r a b l y

lower

i n W a i n w r i g h t and Hoffman's

study,

possibly

b e c a u s e of the different catalysts used. OXIDATION

OF CARBON

MONOXIDE

IN AUTOMOTIVE

EXHAUSTS.

The

c a t a l y t i c o x i d a t i o n of c a r b o n m o n o x i d e has b e e n s t u d i e d extensively w i t h m a n y catalysts.

N o b l e catalysts h a v e r e c e i v e d

considerable attention

d u r i n g the last s e v e r a l years f o r use i n a u t o m o t i v e emission c o n t r o l sys tems. A k i n e t i c m o d e l of C O a n d C H 3

6

oxidation on a pelleted p l a t i n u m -

a l u m i n a catalyst was p r e p a r e d a n d i n c o r p o r a t e d into a p r e v i o u s l y d e v e l o p e d converter m o d e l , w h i c h has b e e n u s e d to p r e d i c t a n d o p t i m i z e the p e r f o r m a n c e of v a r i o u s types of p l a t i n u m catalysts ( i n c l u d i n g m o n o l i t h i c t y p e s ) ; this m a t h e m a t i c a l converter m o d e l was d e s c r i b e d b y K u o et al. (52,53). T h e o x i d a t i o n of C O over p l a t i n u m catalysts has b e e n s t u d i e d f o r m a n y years, b u t t h e conclusions

r e g a r d i n g the m e c h a n i s m s a n d rate

equations are s o m e w h a t c o n f l i c t i n g (54, 55, 56, 5 7 ) . S h i s h u ( 5 8 ) m a d e a c o m p r e h e n s i v e i n v e s t i g a t i o n of C O o x i d a t i o n o n a m o n o l i t h i c p l a t i n u m catalyst i n a d i f f e r e n t i a l flow reactor a n d d e v e l o p e d Harned

(59)

r a t e equations.

p r e p a r e d a m a t h e m a t i c a l m o d e l for c a t a l y t i c converters

u s e d for the o x i d a t i o n of C O a n d h y d r o c a r b o n s , a n d T a y l o r ( 6 0 )

ob

t a i n e d a m o d e l of the o x i d a t i o n k i n e t i c s for p l a t i n u m catalysts. C O o x i d a -


224

CHEMICAL

REACTION

t i o n has b e e n s t u d i e d w i t h other catalysts also.

ENGINEERING REVIEWS

L a i d l e r (61)

reported

some studies d o n e w i t h catalysts s u c h as q u a r t z glass, r o c k c r y s t a l , p l a t i n u m , a n d c o p p e r oxide. S c h w a b a n d G o s s n e r (62) a n d s i l v e r - p a l l a d i u m alloys. P a r r a v a n o (63)

u s e d silver, p a l l a d i u m ,

r e p o r t e d t h e use of n i c k e l

o x i d e , to w h i c h f o r e i g n ions h a d b e e n a d d e d . α - A l u m i n a pellets w i t h 0.5 wt %

p a l l a d i u m a n d x - r a y i r r a d i a t e d a l u m i n a h a v e also b e e n

as catalysts (64,

proposed

65).


A t present, exhaust t r e a t m e n t devices, s u c h as c a t a l y t i c converters s h o w p r o m i s e i n r e d u c i n g C O emissions to the l o w levels r e q u i r e d b y the restrictions i m p o s e d i n m a n y countries. T h e catalysts to be u s e d b y auto m a n u f a c t u r e r s i n the next years g e n e r a l l y c o n t a i n p l a t i n u m , w h i c h is, h o w e v e r , expensive a n d e a s i l y p o i s o n e d . T h u s , there is a n e e d for c h e a p e r catalysts w i t h g o o d p e r f o r m a n c e a n d of r e l i a b l e c a t a l y t i c converter m o d e l s . T h e p a p e r s d i c u s s e d b e l o w d e a l w i t h these t w o p r o b l e m s . K a l m a n et al. (66)

e v a l u a t e d t h e p e r f o r m a n c e of c r y s t a l l i n e c o p p e r -

s u b s t i t u t e d z i r c o n i u m p h o s p h a t e i n the c a t a l y t i c o x i d a t i o n of C O .

A

r e a c t i o n rate expression was o b t a i n e d b y a p p l y i n g the i n t e g r a l m e t h o d of analysis to t h e e x p e r i m e n t a l d a t a . E v e n t h o u g h a d i r e c t c o m p a r i s o n of t h e p e r f o r m a n c e of this catalyst w i t h other catalysts is difficult o w i n g to the l a c k of l i t e r a t u r e d a t a o b t a i n e d u n d e r s i m i l a r c o n d i t i o n s , i t seems that copper-substituted

α-zirconium phosphate

is

at least

comparable

in

a c t i v i t y w i t h other catalysts a n d merits f u r t h e r i n v e s t i g a t i o n . Y o u n g a n d F i n l a y s o n (67)

p r o p o s e t w o m a t h e m a t i c a l m o d e l s for a

p a r t i c u l a r t y p e of c a t a l y t i c c o n v e r t e r — t h e m o n o l i t h converter. T w o types of c a t a l y t i c c o n v e r t e r s — p a c k e d beds a n d m o n o l i t h s — h a v e b e e n p r o p o s e d f o r the o x i d a t i o n of C O a n d h y d r o c a r b o n s i n a u t o m o b i l e exhausts.

As

m e n t i o n e d above, K u o has d e v e l o p e d a m o d e l for the m o n o l i t h converter, a n d m a t h e m a t i c a l m o d e l s h a v e b e e n p r o p o s e d a n d s o l v e d also for p a c k e d b e d converters (52,

59, 68, 69).

T h e m o n o l i t h c o n v e r t e r consists of a n

a r r a y of ducts o r cells t h r o u g h w h i c h the exhaust gas flows

axially.

B e c a u s e of a s m a l l e r v o l u m e t r i c heat c a p a c i t y , m o n o l i t h i c converters w a r m u p m o r e q u i c k l y t h a n p a c k e d b e d devices, b u t h a v e

problems

caused b y t h e r m a l expansion. T h e mathematical models developed illus trate i m p o r t a n t features of t h e t h e r m a l b e h a v i o r of t h e m o n o l i t h c o n verter.

T h e r e a c t i o n rate expression u s e d was f o u n d i n the l i t e r a t u r e ,

a n d some assumptions w e r e m a d e to o b t a i n s u i t a b l e m o d e l s , t a k i n g i n t o a c c o u n t h e a t a n d mass transfer across the c e l l cross-section.

T h e two

p r o p o s e d m o d e l s differ b e c a u s e i n one of t h e m heat a n d mass transfer coefficients d e f i n e d i n the u s u a l w a y are u s e d . S u i t a b l e s o l u t i o n m e t h o d s h a v e b e e n u s e d for b o t h m o d e l s , a n d b o t h t r a n s i e n t a n d steady-state c a l c u l a t i o n s f o r t y p i c a l cases are i l l u s t r a t e d i n some

figures.

T h e study

seems to be v e r y a c c u r a t e a n d gives u s e f u l a d v i c e for d e s i g n i n g this t y p e of converter.



8.

CAPPELLi

Oxidation

Figure 3.

Liquid

Phase Oxidation

I n this g r o u p

Reaction

Engineering

225

Reactor for catalytic gas phase reactions

with

Oxygen

of processes b o t h h o m o g e n e o u s a n d heterogeneous

c a t a l y z e d reactions are presented.

T h e l i q u i d - p h a s e o x i d a t i o n of o r g a n i c

c o m p o u n d s w i t h a i r or o x y g e n is c o m p l e x , a n d the m e c h a n i s m s are f u r t h e r c o m p l i c a t e d b y mass transfer processes. W h e n o x y g e n transfer b e c o m e s the r a t e - l i m i t i n g step, the rate of the o v e r a l l process is n o longer c o n t r o l l e d b y the c h e m i c a l m e c h a n i s m s . A p a p e r b y H o b b s et al. o n mass transfer r a t e - l i m i t a t i o n effects i n l i q u i d phase o x i d a t i o n (45)

indicates that p h y s i c a l a n d c h e m i c a l effects

are t h e o r e t i c a l l y separable, a n d t h e i r r e l a t i v e c o n t r i b u t i o n s c a n b e e s t i m a t e d . A s a n e x a m p l e , the l i q u i d phase o x i d a t i o n of m e t h y l e t h y l ketone i n acetic a c i d solvent is c o n s i d e r e d . I n the s t u d y r e p o r t e d b y G u r u m u r t h y a n d G o v i n d a r a o (46) e q u a t i o n is d e v e l o p e d for the l i q u i d p h a s e o x i d a t i o n of

a rate

propionaldehyde


226

CHEMICAL


w i t h o x y g e n i n t h e presence of manganese p r o p i o n a t e catalyst, de W i l t a n d V a n d e r B a a n (44)

present a k i n e t i c m o d e l for the p l a t i n u m c a t a l y z e d

o x i d a t i o n of glucose to k - g l u c o n a t e w i t h o x y g e n i n aqueous a l k a l i n e s o l u tions. T h e experiments w e r e d o n e b a t c h w i s e i n a reactor e q u i p p e d w i t h a h i g h - s p e e d stirrer to m i n i m i z e the i n f l u e n c e of o x y g e n transport f r o m the gaseous to t h e l i q u i d phase. T h e reactions s t u d i e d are l i s t e d i n T a b l e V I I .


Table VII.

L i q u i d Phase Oxidation with Oxygen

Process

Catalyst

O x i d a t i o n of p r o p i o n a l d e h y d e O x i d a t i o n of glucose O x i d a t i o n of m e t h y l e t h y l ketone A l a g y et al. (70)

Reference

Mn-propionate platinum cobaltous acetate

Jfi 44 4$

d e s c r i b e a s t u d y o n the l i q u i d phase o x i d a t i o n of

c y c l o h e x a n e w i t h oxygen. A m a t h e m a t i c a l m o d e l has b e e n d e v e l o p e d o n the basis of k i n e t i c d a t a c o n c e r n i n g c y c l o h e x a n e

o x i d a t i o n a n d mass-

transfer i n f o r m a t i o n d e r i v e d f r o m experiments o n c y c l o d o d e c a n e

oxida

t i o n . T h e e x p e r i m e n t a l runs w e r e d o n e i n s e m i c o n t i n u o u s , m e c h a n i c a l l y stirred equipment.

O n the p i l o t scale a 150-liter c y l i n d r i c a l r e a c t o r w a s

u s e d , i n w h i c h s t i r r i n g was a c h i e v e d b y i n j e c t i n g gas at the b o t t o m of the c o l u m n a n d b y i n t r o d u c i n g t a n g e n t i a l l y at the top a l i q u i d stream d e r i v e d f r o m t h e b o t t o m of the c o l u m n . T h e k i n e t i c m o d e l has seven p a r a m e t e r s w h i c h h a v e b e e n d e t e r m i n e d b y a n o n - l i n e a r regression m e t h o d .

The

agreement b e t w e e n c a l c u l a t e d a n d e x p e r i m e n t a l d a t a seems g o o d , t a k i n g i n t o a c c o u n t t h a t the r e a c t i o n is c o m p l e x a n d b o t h c h e m i c a l a n d p h y s i c a l p h e n o m e n a a r e i m p o r t a n t . A s i m p l i f i e d m o d e l has also b e e n p r e p a r e d b y i n c o r p o r a t i n g c e r t a i n assumptions i n the o r i g i n a l m o d e l . Liquid Phase Epoxidation

of Olefins with

F o u r papers (35, 86, 37, 38)

r e p o r t studies o n l i q u i d p h a s e e p o x i d a -

t i o n of olefins w i t h h y d r o p e r o x i d e s .

N

N

C = C ^

/

+

Hydroperoxides

T h e reaction is:

R O O H

+

R

0

H

a n d is c a t a l y z e d b y m a n y t r a n s i t i o n a l m e t a l catalysts. T h e k i n e t i c e q u a t i o n , w h i c h has b e e n o b t a i n e d f o r different m o l y b d e n u m catalysts is of the type: V ^= Κ

^olefin

^hydroperoxide

Ccatalysts

a n d is c a t a l y z e d b y m a n y t r a n s i t i o n m e t a l catalysts. T h e k i n e t i c e q u a -


8.

Oxidation

CAPPELLi

Reaction

227

Engineering

e q u i l i b r i u m f o r m a t i o n of a c a t a l y s t - h y d r o p e r o x i d e c o m p l e x ; the

second

step is the r a t e - d e t e r m i n i n g r e a c t i o n of the c o m p l e x w i t h the olefin to f o r m the epoxide, c o p r o d u c t a l c o h o l , a n d the m o l y b d e n u m catalyst. B a k e r et al. (35)

present k i n e t i c d a t a o n the e p o x i d a t i o n of 1-octene

b y c u m e n e a n d tert-butyl

h y d r o p e r o x i d e i n the presence of m o l y b d e n u m

h e x a c a r b o n y l as catalyst. T h e o b s e r v e d k i n e t i c b e h a v i o r is c o m p a t i b l e w i t h the p r e v i o u s l y p r o p o s e d

g e n e r a l m e c h a n i s m for the

epoxidation


reaction. I n the s t u d y r e p o r t e d b y S h e l d o n a n d V a n D o o m (36)

cyclohexene

a n d 1-octene, u s e d as m o d e l olefins of different r e a c t i v i t y , w e r e e p o x i d i z e d i n the l i q u i d p h a s e w i t h tert-butyl

h y d r o p e r o x i d e i n t h e presence of v a r i -

ous t r a n s i t i o n m e t a l catalysts. I t is c o n c l u d e d that a n active e p o x i d a t i o n catalyst s h o u l d be b o t h a w e a k o x i d a n t a n d a f a i r l y strong L e w i s a c i d . T h e s e r e q u i r e m e n t s are best m e t b y c o m p o u n d s of c e r t a i n metals i n h i g h o x i d a t i o n states [ M o ( V I ) , W ( V I ) , T i ( I V ) ] . I n the p a p e r b y S u et al. (37)

o n v a n a d i u m a n d m o l y b d e n u m chelates

as catalysts i n the e p o x i d a t i o n of c y c l o a l k e n e s , rate l a w s for t h e v a n a d i u m c a t a l y z e d systems are consistent w i t h r e a c t i o n via r a t e - d e t e r m i n i n g attack of olefin o n a v a n a d i u m ( V ) - h y d r o p e r o x i d e

complex.

Arguments

are

p r e s e n t e d to s u p p o r t the v i e w that the m o l y b d e n u m - c a t a l y z e d e p o x i d a t i o n , l i k e those i n v o l v i n g v a n a d i u m , p r o c e e d s b y r e a c t i o n of olefins w i t h a metal-hydroperoxide complex. I n a s t u d y b y Trifîrô et al. (38) c y c l o h e x e n e b y tert-butyl

o n the l i q u i d phase e p o x i d a t i o n of

h y d r o p e r o x i d e o n a M o - b a s e d catalyst, a rate

l a w is g i v e n , a n d the presence

of a c a t a l y s t - h y d r o p e r o x i d e r e v e r s i b l e

c o m p l e x as the a c t i v e species i n t h e e p o x i d a t i o n is a d v a n c e d o n the basis of a s p e c t r o s c o p i c s t u d y . T h e reactions i n v e s t i g a t e d are l i s t e d i n T a b l e VIII. Heterogeneization

of Homogenous Catalytic

Processes

S o m e studies h a v e b e e n r e p o r t e d o n t h e t r a n s f o r m a t i o n of

homo-

geneous processes i n t o heterogeneous

ones b y s u p p o r t i n g the catalysts.

T h i s is the case of a heterogeneous

catalyst system w h i c h has

been

d e v e l o p e d for the v a p o r p h a s e o x i d a t i o n of e t h y l e n e to a c e t a l d e h y d e

(14).

T h e catalyst consists of p a l l a d i u m - d o p e d v a n a d i u m p e n t o x i d e a n d u s u a l l y a third component

s u c h as T i , R u , P t , or Ir. A catalyst consisting of

m e r c u r i c c h l o r i d e s u p p o r t e d o n active c h a r c o a l w a s u s e d b y A r a i et al. (16)

for the a l l y l i c o x i d a t i o n of olefins. T h e o x i d a t i o n over m e r c u r i c i o n

catalyst occurs at a t e m p e r a t u r e w h i c h is l o w e r t h a n t h a t necessary over b i s m u t h m o l y b d a t e catalyst. F i n a l l y , catalysts p r e p a r e d b y s u p p o r t i n g M o ( V I ) o n S i 0 h a v e b e e n p r o p o s e d b y F o r z a t t i et al. (40) 2

f o r the e p o x i -

d a t i o n of olefins w i t h h y d r o p e r o x i d e s .


228

CHEMICAL

Evaluation

of the Literature


Data

T h i s section focuses o n those aspects of interest to c h e m i c a l r e a c t i o n engineers i n m o d e l i n g reactions a n d i n d e s i g n i n g i n d u s t r i a l reactors.

The

f o r e g o i n g w i l l h a v e g i v e n the reader a n a p p r e c i a t i o n not o n l y of w h a t has b e e n d o n e b u t of the c r i t e r i a w h i c h are g e n e r a l l y f o l l o w e d b y the authors active i n this area. T h e points e x a m i n e d u n d e r c h e m i c a l k i n e t i c a n d p h y s i c a l aspects, for e x a m p l e , are t y p i c a l of these k i n d s of papers a n d Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

a c c o u n t for t h e f a c t t h a t t h e interests of the authors are f u n d a m e n t a l l y chemical.

M o s t papers d e a l w i t h m i c r o s c o p i c m e c h a n i s m s , a n d several

specific c h e m i c a l systems are u s e d to i l l u s t r a t e these m e c h a n i s m s ,

but

g e n e r a l i z e d r e a c t i o n m o d e l s are s e l d o m g i v e n . O f t e n , d e t a i l e d a n d elegant studies c o n c e r n i n g the c a t a l y t i c c h e m i s t r y of the reactions are c a r r i e d o u t b u t u s e f u l m o d e l s for reactor d e s i g n are not a t t e m p t e d . T h e r a n g e of catalysts c o n s i d e r e d is extensive, b u t some differ i n i r r e l e v a n t details. D i s c u s s i o n of the details of surface b o n d s c a n b e f o u n d i n m a n y papers, a n d p a r a m e t r i c effects of o p e r a t i n g c o n d i t i o n s o n a c t i v i t y a n d s e l e c t i v i t y are often discussed, b u t m o s t l y o n the l a b o r a t o r y scale. the other h a n d , i t is n o t easy to find k i n e t i c studies d o n e to

On

provide

r e l i a b l e d a t a to p r e d i c t reactor p e r f o r m a n c e , a n d systematic t e c h n i q u e s i n c h e m i c a l k i n e t i c s i n v e s t i g a t i o n are not often

applied.

T h e use

of

statistically d e s i g n e d experiments, f o r e x a m p l e , is m e n t i o n e d i n o n l y a

Table VIII.

L i q u i d Phase Epoxidation with Hydroperoxides Catalyst

Process E p o x i d a t i o n of 1-octene b y cumene a n d i e r i - b u t y l hydroperoxide E p o x i d a t i o n of 1-octene a n d cyclohexene b y tert-butyl hydroperoxide E p o x i d a t i o n of c y c l o a l k e n e s b y tertbutyl h y d r o p e r o x i d e E p o x i d a t i o n of cyclohexene b y tertbutyl h y d r o p e r o x i d e

Reference

Mo-hexacarbonile

35

t r a n s i t i o n metals

36

V a n d M o chelates

37

M o based

38

f e w papers, a n d i t does not seem that a d v a n c e d p a r a m e t e r e s t i m a t i o n t e c h n i q u e s are often u s e d also i f a c e r t a i n i m p r o v e m e n t f r o m t h i s p o i n t of v i e w c a n b e n o t i c e d . T h e r e is l a c k of i n f o r m a t i o n c o n c e r n i n g studies c a r r i e d out s e q u e n t i a l l y o n the l a b o r a t o r y , p i l o t , a n d c o m m e r c i a l scale. I n this c o n n e c t i o n most of the papers c o m e f r o m universities r a t h e r t h a n f r o m i n d u s t r i e s , a n d t h e p o s s i b i l i t y of o b t a i n i n g v a l u a b l e i n f o r m a t i o n o n process k i n e t i c s f r o m c o m m e r c i a l scale reactors is g e n e r a l l y d i s r e g a r d e d , at least f o r p u b l i c a t i o n purposes.

Nevertheless, s o m e authors seem to b e

m o r e a n d m o r e conscious of t h e necessity of p r o v i d i n g u s e f u l d a t a for


8.

CAPPELLi

Oxidation

Reaction

229

Engineering

d e s i g n purposes; i n those fields w h i c h are m o r e s t r o n g l y c o n n e c t e d solving practical problems

(as, for example,

i n automative

with

emission

control), reliable models are available. Conclusions T h e s i t u a t i o n i n this area has some p o s i t i v e aspects b u t is n o t e n t i r e l y satisfactory f r o m t h e p o i n t o f v i e w o f a c h e m i c a l engineer. T h e q u a l i t y o f Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0148.ch008

papers f o u n d i n l i t e r a t u r e is g e n e r a l l y g o o d , b u t most studies are b a s e d o n l a b o r a t o r y scale experiments, a n d scale-up rules are s e l d o m g i v e n . I n this area s o m e authors still " p l a y w i t h m e c h a n i s m s " a n d c a r r y o u t e x p e r i ments w i t h different catalysts a n d u n d e r different o p e r a t i n g c o n d i t i o n s w i t h o u t a r r i v i n g at conclusions of a n y sort. H o w e v e r , a definite i m p r o v e m e n t has b e e n e v i d e n c e d i n t h e last f e w years; i n most cases n o w a t least k i n e t i c m o d e l s , u s e f u l f r o m a n e n g i n e e r i n g p o i n t o f v i e w , are p r o p o s e d as a result o f a r e s e a r c h s t u d y . N e v e r t h e l e s s , t h e c o m m u n i c a t i o n b e t w e e n those w h o p r o p o s e m o d e l s a n d those w h o s h o u l d use t h e m does n o t seem e n t i r e l y satisfactory. T h e b r i d g e b e t w e e n researchers a n d those i n v o l v e d i n d e s i g n a n d o p e r a t i o n of reactors, that Professor F r o m e n t m e n t i o n e d at the e n d o f a r e v i e w d u r i n g t h e first I n t e r n a t i o n a l S y m p o s i u m o n C h e m i c a l R e a c t i o n E n g i n e e r i n g , is s t i l l a w e a k b r i d g e o f boats, a n d n o t e v e n t h e o b s e r v a t i o n t h a t t h e R o m a n s w e r e a b l e to u n i f y t h e w e s t e r n w o r l d u s i n g this t y p e o f b r i d g e c a n reassure us e n t i r e l y i n t h e 1970's.

Literature Cited 1. Trimm, D. L., Doerr, L. Α., J. Catalysis (1972) 26, 1. 2. Parera, N. S., Trimm, D. L., J. Catalysis (1973) 30, 485. 3. Sterrett, J. S., Hollvried, H. G., Ind. Eng. Chem., Process Design Develop. (1974) 13, 54. 4. Grasselli, R. K., Suresh, D. D., J. Catalysis (1972) 25, 273. 5. Wragg, R. D., Ashmore, P. G., Hockey, J. Α., J. Catalysis (1973) 31, 293. 6. Mann, R. S., Ko, D. W., J. Catalysis (1973) 30, 276. 7. Pasquon, I., Trifirò, F., Caputo, G., Chim. Ind. (1973) 55, 168. 8. Schuit, G. C. Α., paper presented at the Conference on The Chemistry and Uses of Molybdenum, University of Reading, England, Sept. 1973. 9. Daniel, C., Keulks, G. W., J. Catalysis (1973) 29, 475. 10. Villa, P. L., Caputo, G., Sala, F., Trifirò, F., J. Catalysis (1973) 31, 200. 11. Metcalf, P. L., Harriot, P., Ind. Eng. Chem., Process Design Develop. (1972) 11, 478. 12. Trifirò, F., Banfi, C., Caputo, G., Forzatti, P., Pasquon, I.,J.Catalysis (1973) 30, 393. 13. Akimoto, M., Echigoya, E., J. Catalysis (1973) 29, 191. 14. Evnin, A. B., Rabo, J. Α., Kasai, P. H., J. Catalysis (1973) 30, 109. 15. Giordano, N., Vaghi, Α., Bart, J. C. J., Castellani, Α., Symposium on the Mechanisms of Hydrocarbon Reactions, Siojok, June 1973. 16. Arai, H., Uehara, K., Kinoshita, S., Kunugi, T., Ind. Eng. Chem., Prod. Res. Develop. (1972) 11, 308. 17. Voltz, S. E., Morgan, C. R., Liederman, D., Jacob, S. M., Ind. Eng. Chem., Prod. Res. Develop. (1973) 12, 294.


230 18. 19. 20. 21.


22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49.

CHEMICAL REACTION ENGINEERING REVIEWS

Zanderighi, L., Faedda, M. P., Carrá, S., J. Catalysis, in press. Yao, Y. Y., J. Catalysis (1973) 28, 39. Niwa, M., Murakami, Y., J. Catalysis (1972) 27, 26. Gernan, K., Grzybowska, B., Haber, J., Bull. Acad. Polonaise Sci. (1973) 21, 5. Subramanian, P., Murthy, M. S., Chem. Eng. Sci. (1974) 29, 25. Subramanian, P., Murthy, M. S., Ind. Eng. Chem., Process Design Develop. (1972) 11, 242. Liberti, L., Pernicone, N., Soattini, S., J. Catalysis (1972) 27, 52. Cant, N. W., Hall, W. K., J. Catalysis (1972) 27 ,70. Trifirò, F., Caputo, G., Villa, P. L., J. Less Common Metals (1974) 36, 305. Kilty, P. Α., Rol, N. C., Sachtler, W. M. H., Proc. Intern. Congr. Catalysis, 5th, Miami Beach, V. S. D. Elsevier (1972) 64, 929. Spath, H. T., Proc. Congr. Catalysis, 5th, Miami Beach, V. S. D. Elsevier (1972) 65, 945. Marcinkowsky, A. E., Berty, J. M., J. Catalysis (1973) 29, 494. Carberry, J. J., Kuczynski, G. C., Martinez, E., J. Catalysis (1972) 26, 246. Forzatti, P., Martinez, E., Kuczynski, G. C., Carberry, J.J.,J.Catalysis (1973) 28, 455. Forzatti, P., Klimasara, Α., Kuczynski, G. G., Carberry, J. J., J. Catalysis (1973) 19, 169. Spath, H. T., Tomazic, G. S., Würm, H., Torkar, K., J. Catalysis (1972) 26, 18. Spath, H. T., Torkar, K., J. Catalysis (1972) 26, 163. Baker, T. N., Mains, G. J., Sheng, M. N., Zatacek, J. G., J. Org. Chem. (1973) 38, 1145. Sheldon, R. Α., Van Doorn, J. Α., J. Catalysis (1973) 31, 427. Su, C. C., Reed, J. W., Gould, E. S., Inorg. Chem. (1973) 12, 337. Trifirò, F., Forzatti, P., Preite, S., Pasquon, I., J. Less Common Metals (1974) 36, 319. Fujimoto, K., Negami, Y., Takahashi, T., Kunugi, T., Ind. Eng. Chem., Prod. Res. Develop. (1972) 11, 303. Forzatti, P., Trifirò, F., Pasquon, I., Chim. Ind. (1974) 56, 259. Walsh, M. Α., Katzer, J. R., Ind. Eng. Chem., Process Design Develop. (1973) 12, 477. Pignet, T., Schmidt, L. D., Chem. Eng. Sci. (1974) 29, 1123. Kadler, B., Hudgins, R. R., Silveston, P. L., Chem. Eng. Sci. (1973) 28, 935. De Wilt, H . G. J., Van Der Baan, H . S., Ind. Eng. Chem., Prod. Res. Develop. (1972) 11, 374. Hobbs, C. C., Drew, Ε. Η., Van't Hoff, Η. Α., Mesich, F. G., Onorem, J., Ind. Eng. Chem., Prod. Res. Develop. (1972) 11, 220. Gurumurthy, C. C., Govindarao, V. M. H., Ind. Eng. Chem., Fundamentals (1974) 13, 9. Dente, M., Ranzi, E., Quiroga, S. P., Biardi, G., Chim. Ind. (1973) 55, 563. Pitzer, E. W., Ind. Eng. Chem., Prod. Res. Develop. (1972) 11, 299. Collina, Α., Malfatti, E., Cappelli, Α., Italian Patent 955,507 corresponding to German Patent Application 2,324,164.

50. Calderbank, P. H., ADVAN. C H E M . SER. (1974) 133, 646.

51. Wainwright, M. S., Hoffmann, T. W., ADVAN. CHEM. SER. (1974) 133, 669. 52. Kuo, J. C. W., Horgan, C. R., Lassen, H. G., SAE Automotive Eng. Congr., Detroit, Jan. 1972, paper 710289. 53. Kuo, J. C. W., Prater, C. D., Osterhout, D. P., Snyder, P. W., Wej, J., Int. Automobile Tech. Congr. FISITA, 14th, London, June 1972, paper 2/14. 54. Langmuir,.I., Trans. Faraday Soc. (1922) 17, 621. 55. Sklyarov, Α. V., Tretyakov, I. I., Shad, B. R., Roginski, S. Z., Dokl. Phys. Chem. (1969) 189, 829.


CAPPELLi

56. 57. 58. 59.

Su, E. C., Shishu, R. C., private communication, 1972. Soloveva, L. S., RussianJ.Phys. Chem. (1960) 34, 586. Shishu, R. C., Ph.D. Dissertation, University of Detroit (1972). Harned, J . L., SAE Nat. Automotive Eng. Congr., Detroit, May 1972, paper 720520. Taylor, K. C., unpublished results (1971). Laidler, J. K., Catalysis (1954) 1, 16. Schwab, G. M., Gossner, I. Α., Phys. Chem.,N.F.(1958) 16, 39. Parravano, G., J. Am. Chem. Soc. (1953) 75, 1448. Taibl, D. B., Simons, J. B., Carberry, J. J., Ind. Eng. Chem., Fundamentals (1966) 5, 171. Coekelbergs, R., Collin, R., Cruez, Α., Decot, J., Degols, L.,Timmerman, L., J. Catalysis (1967) 7, 85. Kalman, T. J., Duovkovic, M., Clearfield, Α., ADVAN. CHEM. SER. (1974) 133, 654. Young, L. C., Finlayson, Β. Α., ADVAN. CHEM. SER. (1974) 133, 629. Ferguson, Ν. B., Finlayson, D. Α., AIChE Meetg., Philadelphia, Nov. 1973. Wei, J., Chem. Eng. Progr., Monograph Ser. (1969) 6, 65. Alagy, J., Trambouze, P., Van Landeghem, H., ADVAN. CHEM. SER. (1974) 133, 644.


60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70.

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