Chemical Reaction EngineeringâBoston - ACS Publications

1 Catalytic Air Oxidation of Propylene to Acrolein: Modeling Based on Data from an Industrial Fixed-Bed Reactor Downloaded by UNIV OF WATERLOO on December 15, 2014 | http://pubs.acs.org Publication Date: September 16, 1982 | doi: 10.1021/bk-1982-0196.ch001

D. ARNTZ, Κ. ΚΝΑΡΡ, and G. PRESCHER Degussa AG, Hanau, Federal Republic of Germany G. EMIG and H . H O F M A N N Inst. f. Techn. Chemie I, Universität Erlangen-Nürnberg, Federal Republic of Germany

From a few w e l l chosen experiments in an i n t e g r a l r e a c t o r o f t e c h n i c a l dimensions with side-stream a n a l y s i s both r e a c t i o n schemes and the e f f e c t i v e heat t r a n s f e r and k i n e t i c parameters o f a r e a c t i o n model f o r propylene o x i d a t i o n could be deduced, from which v a l u a b l e information f o r both c a t a l y s t development and o p t i m i z a t i o n o f the r e a c t i o n c o n d i t i o n s could be obtained. The economic s i g n i f i c a n c e (1,2,3) o f the c a t a l y t i c p r o p y l e ne o x i d a t i o n n e c e s s i t a t e s a c o n t i n u i n g refinement o f the c a t a l y s t . This i n t u r n r e q u i r e s c o n t i n u i n g o p t i m i z a t i o n o f the r e a c t i o n c o n d i t i o n s , as these depend upon the c a t a l y s t . The goal o f t h i s i n v e s t i g a t i o n was the development o f a s u i t a b l e r e a c t o r model f o r propylene o x i d a t i o n i n an i n d u s t r i a l s i z e packed-bed r e a c t o r operated under i n d u s t r i a l l y r e l e v a n t conditions (4). From the l i t e r a t u r e i t i s not p o s s i b l e t o deduce a k i n e t i c scheme s u i t a b l e f o r modeling the r e a c t i o n , s i n c e the majority of p u b l i c a t i o n s (10-39) do not present an unequivocal p i c t u r e . Also the fundamental d i f f i c u l t i e s o f e s t i m a t i n g from independent measurements heat t r a n s f e r parameters f o r a packed-bed r e a c t o r are w e l l known (5,6,7). Therefore, an attempt was made t o determine the k i n e t i c r e a c t i o n scheme and e f f e c t i v e heat t r a n s f e r as w e l l as k i n e t i c parameters from a l i m i t e d number o f experimental r e s u l t s i n a s i n g l e - t u b e r e a c t o r o f i n d u s t r i a l dimensions with side-stream a n a l y s i s . The data e v a l u a t i o n was performed with a pseudohomogeneous two-dimensional continuum model without a x i a l d i s p e r s i o n . The model was t e s t e d f o r i t s s u i t a b i l i t y f o r p r e d i c t i o n .

0097-6156/82/0196-0003$06.00/0 © 1982 American Chemical Society

In Chemical Reaction Engineering—Boston; Wei, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

4

CHEMICAL REACTION ENGINEERING

Downloaded by UNIV OF WATERLOO on December 15, 2014 | http://pubs.acs.org Publication Date: September 16, 1982 | doi: 10.1021/bk-1982-0196.ch001

E x p e r i m e n t a l Set-Up

and R e s u l t s

The r e s u l t s w e r e o b t a i n e d i n a c o n t i n u o u s l y o p e r a t e d p o l y t r o p i c p i l o t p l a n t r e a c t o r w i t h a f e e d o f a p p r o x i m a t e l y 2-5 m o l e s p r o p y l e n e p e r h o u r . The r e a c t o r was a s i n g l e t u b e h a v i n g a c a t a l y t i c b e d l e n g t h o f 2.70 m a n d a n i n n e r d i a m e t e r o f 0 . 0 2 0 5 m. T e m p e r a t u r e was c o n t r o l l e d b y a c i r c u l a t i n g m o l t e n s a l t b a t h . T h e t e m p e r a t u r e p r o f i l e w i t h i n t h e r e a c t o r was m o n i t o r e d w i t h s i d e - e n t r y t h e r m o c o u p l e s : e l e v e n i n t h e c e n t e r o f t h e t u b e , t w o i n a n 1/2 r a d i u s p o s i t i o n , and t h r e e a t t h e w a l l . F e e d s o f p r o p y l e n e , a i r , i n e r t g a s a n d w a t e r w e r e m o n i t o red by r o t a m e t e r s and preheated t o s a l t bath temperature. O v e r a l l a c r o l e i n y i e l d s a v e r a g e d o v e r 48 h o u r s p e r i o d s , were e v a l u a t e d by i s o l a t i n g c r u d e a c r o l e i n by a b s o r p t i o n with water and subsequent d e s o r p t i o n . Unreacted p r o p y l e n e , c a r b o n o x i d e s a n d o x y g e n w e r e m e a s u r e d i n t h e e f f l u e n t g a s ( G . C . ) a n d a c r y l i c a c i d was a n a l y s e d (G.C.) i n t h e a c r o l e i n - f r e e bottoms. To measure t h e a x i a l c o n c e n t r a t i o n p r o f i l e o f t h e r e a c t o r gaseous samples ( 5 p r o b e s a l o n g t h e r e a c t o r ) were a n a l y s e d (water scrubber and e f f l u e n t gas a n a l y s i s ) . Minor s i d e products as acetaldehyde and f o r m a l d e h y d e ( G . C , a n a l y s e d i n c r u d e i s o l a t e d a c r o l e i n ) , a c e t i c a c i d ( G . C , analysed b e s i d e s a c r y l i c a c i d ) and p o l y a c r o l e i n ( r e s i d u e o f e v a p o r a t i o n ) always t o t a l e d l e s s t h a n 4 %, b a s e d o n t h e p r o p y l e n e f e d i n ; t h e c o r r e s p o n d i n g s i d e - r e a c t i o n s were n e g l e c t e d f o r m o d e l i n g . The s p h e r i c a l c a t a l y s t , b a s e d o n a m u l t i c o m p o n e n t b i s m u t h m o l y b d a t e was p r e p a r e d a c c o r d i n g t o ( 8 ) w i t h d = 5.3 . 1 0 " m , λ = 0.8 . 1 0 - K J / m . s . ° K a n d P = 1145 kg/m f o r t h e c a t a l y t i c b e d . The range o f v a r i a b l e s s t u d i e d i n t h e packed-bed experiments i s given i n Table I . T y p i c a l d e t a i l e d r e s u l t s f o r an ex perimental run are given i n Table I I . 3

p

3

ρ

3

g

Modeling R e a c t o r Model. The d e s i g n o f an i n d u s t r i a l packed-bed r e a c t o r r e q u i r e s a r e a c t o r m o d e l a s w e l l a s t h e c h e m i c a l a n d t h e h e a t a n d mass t r a n s f e r p a r a m e t e r s of the c a t a l y s t bed - gas stream system. Since these parameters are model-speci f i c , i t seemed a d v i s a b l e t o employ a continuum model f o r t h e r e a c t o r c a l c u l a t i o n . T h i s i s t h e o n l y model t o date f o r which t h e l i t e r a t u r e c o n t a i n s c o n s i s t e n t d a t a f o r c a l c u l a t i n g h e a t a n d mass t r a n s f e r p a r a m e t e r s ( 5 , 6 , 7 ) . T h i s m o d e l i n i t s

Table I

Experiments Run No.

Τ

1 2 3 4 5

296 320 311 334 377

- Range o f V a r i a b l e s

Τ

w

max C o m p o s i t i o n o f R e a c t o r F e e d ( M o l e F r a c t i o n ) O v e r a l l propene propene propane N 0 H 0 c o n v e r s i o n {%) 301 0.047i 0.0022 0.595 0.158 0.198 45 335 0.047 0 . 0 0 2 4 0 . 5 9 9 0.159 0.192 72 325 0.088 0.0041 0 . 5 7 0 0.151 0.187 42 358 0.089! 67 0 . 0 0 3 8 0.569 0.151 0.187 415 0.089 0 . 0 0 4 3 0.567 0.150 0.190 85 2

2

2

6

2

5

T =T(salt bath); G - 1.16 ± 0.02 ( k g / m * . s ) ; ρ = 1.63 ± 0.01 ( b a r ) a t r e a c t o r i n l e t ; p r e s s u r e d r o p : A P = 0 . 0 4 9 g - 0 . 0 0 2 , * = remains unreacted under a l l o p e r a t i n g c o n d i t i o n s . (bar/m) w


1.

ARNTZ ET A L .

Table I I

Run No. 5 - D e t a i l e d I n f o r m a t i o n

bed l e n g t h


Catalytic Propylene Oxidation

(•) 0 0.15 0.30 0.45 0.60 0.80 1.00 1.20 1.40 1.70 2.00 2.30 2.60 2.70

m o l e f r a c t i o n x\ p r o p e n e I C 0 , CO a c r o l e i n a c r y l i c

temperatureQ)

] acid;

2

°C 377 415 413 387® 407 406 385© 397 391 390 388 387 386

0.089

5

0.071

6

0.003J

0.056

3

0.005

0

4

0

0

.

0.0162

0.00054

:

0.030

0.0010

8

]

0.00218

1 1

2

; 0.035

0.008g

2

0.049

0

?

0.021

4

0.013

0

0.059

8

0.013

6

0.016

2

0.065

3

0.0036

i

6

j t (

0.0050 J 15 i n c e n t e r o f t u b e , (^ 2 iΓ n 1/2 r p o s i t i o n G = 1.178 ( k g / m * . s ) Δ ρ = 0.051 ( b a r / m ) ρ = 1.633 ( ° ) 0

a r

two-dimensional form, i n which t h e a x i a l heat c o n d u c t i o n and a x i a l d i s p e r s i o n a r e n e g l e c t e d , y i e l d s f o r t h e mass b a l a n c e o f t h e c o m p o n e n t s :

3 y

3z

j

1 3 , 3j r~ 3Γ" r (Γ 1

»'

M ] Γ : i=l

r

V

a

2

i

e

f

;

j=l

Ν

(1)

with t h e boundary

and f o r t h e e n e r g y b a l a n c e : 3Θ S-^f

f

conditions:

z=0:yj=yj ; 9=0 (r), 0

k

Σ 1=1

(-

Û H

0*r*l

0

r

i

) i,eff 3 y

3 y

^

i

3Θ

i =

3Θ 3 T »

0 ;

O^z^l

B

i

(

e

- V

0^z="l

The t r a n s p o r t p a r a m e t e r s i n a j , b j a n d B i a r e e f f e c t i v e p a r a m e t e r s w i t h w h i c h , j u s t a s w i t h t h e e f f e c t i v e r a t e r f f , s e v e r a l d i f f e r e n t p h y s i c a l phenomena a r e lumped. The t w o - d i m e n s i o n a l p s e u d o h o m o g e n o u s r e a c t o r m o d e l ( E q . l ) i s t h e b a s i s f o r t h e s t a n d a r d i z e d c o m p u t e r p r o g r a m F I B S A S ( 9 ) , w h i c h was u s e d f o r t h e e v a l u a t i o n and s i m u l a t i o n r e p o r t e d h e r e . e

Reaction Schemes and Networks. Within the l a s t few years a s e r i e s o f review a r t i c l e s have appeared concerning the o x i d a t i o n o f propylene t o a c r o l e i n (10-16). I t i s g e n e r a l l y assumed that the f i r s t r e a c t i o n step, the formation o f an adsorbed a l l y l i c s p e c i e s , i s rate-determining f o r the formation o f aero-



6


l e i n . Side r e a c t i o n s o f t h i s intermediate s p e c i e s as w e l l as d i r e c t p a r a l l e l r e a c t i o n s are p o s s i b l e . However, previous mechanistic i n v e s t i g a t i o n s l e a d n e i t h e r to unequivocal c o n c l u s i o n s over the r e a c t i o n scheme nor over the r e a c t i o n k i n e t i c s . A l a r g e number o f i n v e s t i g a t i o n s do not even consider the formation o f the i n d u s t r i a l l y important a c r y l i c a c i d (Models I I I I ) . The most d e t a i l e d Model V, on the other hand, i s too complex f o r a p r a c t i c a l a p p l i c a t i o n . I n v e s t i g a t i o n s o f model s i m p l i f i c a t i o n s f o r i n d u s t r i a l l y r e l e v a n t c a t a l y s t s are e i t h e r nonexistent or lead to d i f f e r i n g r e s u l t s (Models I-IV). A p o i n t common to a l l the models i s that they are based upon a redox-type mechanism, i n which the r e o x i d a t i o n o f the c a t a l y s t i s not a l i m i t i n g f a c t o r . Corresponding, none o f them employ the model expression o f Mars and van Krevelen (37). On c o n t r a s t newer works by Keulks (38,39) assume, a t lower r e a c t i o n temperatures, a l i m i t i n g e f f e c t from the r e o x i d a t i o n which leads to a dependence on oxygen p a r t i a l pressure f o r the a c r o l e i n formation and to a two to t h r e e - f o l d higher a c t i v a t i o n energy compared with the r e a c t i o n at higher temperatures. Thus a c o n s i d e r a t i o n o f the l i t e r a t u r e data n e c e s s i t a t e s e s t a b l i s h i n g a network before determining the e f f e c t i v e k i n e t i c parameters. D e r i v a t i o n o f Reaction Schemes Based on Experimental R e s u l t s . Although numerous methods f o r e v a l u a t i n g r e a c t i o n s schemes have been developed (40-44), most o f them (40-42) s t a r t with a hypothet i c a l mechanism which i s , by means o f experiments, e i t h e r c o n f i r med or r e j e c t e d . A newly developed method f o r the systematic e l u c i d a t i o n o f r e a c t i o n schemes o f complex systems r e q u i r e s no chemic a l c o n s i d e r a t i o n s , but concentration-time measurements and sys t e m - a n a l y t i c a l c o n s i d e r a t i o n s (45). The method i s based on the i n i t i a l slope o f the concentration-time p r o f i l e s and when necessary the higher d e r i v a t i v e s o f these curves a t t = 0. Reaction steps i n which products are formed d i r e c t l y from r e a c t a n t s can be i d e n t i f i e d i n a concentration-time p l o t by a p o s i t i v e g r a d i e n t dc- a t t = 0 (zero order d e l a y ) . dt I t can be seen from a t y p i c a l , p r a c t i c a l l y isothermal conc e n t r a t i o n p r o f i l e (Figure 1) t h a t a t t = 0 a l l products e x h i b i t a non-zero s l o p e . This i m p l i e s that a l l o f them must be formed d i r e c t l y from the r e a c t a n t s propylene and oxygen, which e l i m i n a tes the r e a c t i o n schemes I and IV (Table I I I ). Therefore the f o l l o w i n g s t o i c h i o m e t r i c equations were used i n the a n a l y s i s ; f o r equation (4) the approximately constant r a t i o o f CO and CO^ which was a c t u a l l y measured was a p p l i e d . J

k

Pe

+

0

Pe

+

1.5 0

Pe

+

4 1/6

2

i * > Ac + H 0

(2)

^> As + H 0

(3)

2

2

2

0

2

*3

y

2/3

CO + 2 1/3

C0 + 3 H 0 2

2


(4)

1.

ARNTZ ET A L .


Table III

7

R e a c t i o n Models

I

(17-20)

P e — » Ac —> C 0 , C 0 ;

III

(26-30)

Pe

2

vC0,C0 ;

I I (21-25)

I V (31) Pe — >

o

co,co

2

Fo,Ad


V

(32-36)

Pe - M s \

C0,C0 y

2

9

Fo.Ad

acrolein acetaldehyde acrylic acid formaldehyde propylene

Ac Ad As Fo Pe

Further systematic a p p l i c a t i o n o f the new method l e d t o the con c l u s i o n that the r e a c t i o n scheme was s t i l l incomplete but that such r i g o r o u s model b u i l d i n g demands independent v a r i a t i o n s o f a l l r e a c t a n t c o n c e n t r a t i o n s , which was beyond the scope o f t h i s investigation.

(5) The r e a c t i o n scheme was t h e r e f o r e completed using a d d i t i o n a l i n formation from the concentration-time-diagram. In experiments with a high degree o f conversion (Table I I ) the y i e l d o f a c r o l e i n i s obviously l i m i t e d with i n c r e a s i n g residence time. At the same time the a c r y l i c a c i d c o n c e n t r a t i o n i s s t i l l i n c r e a s i n g a t the end o f the r e a c t o r , suggesting a concecutive o x i d a t i o n o f a c r o l e i n to a c r y l i c a c i d as an a d d i t i o n a l r e a c t i o n . Heat T r a n s f e r Parameters. Attempts i n t h i s i n v e s t i g a t i o n t o use heat t r a n s f e r parameters ( λ ^ h ) c a l c u l a t e d from c o r r e l a t i o n s based on data without r e a c t i o n Τβ,7) l e d t o the r e s u l t t h a t the energy balance o f the r e a c t o r a t the measured temperatures was not s a t i s f i e d . On the other hand, the simultaneous e s t i m a t i o n o f heat t r a n s f e r and k i n e t i c parameters by r e g r e s s i o n a n a l y s i s o f p o l y t r o p i c measurements allows these parameters t o i n f l u e n c e each other. I t was observed that the parameters c a l c u l a t e d by these two methods were q u i t e d i f f e r e n t (5,46). Therefore i n t h i s r e p o r t the heat t r a n s f e r parameters were determined from experimental r e s u l t s by a t h i r d method with a minimum o f a d d i t i o n a l assumptions: The e n e r g y b a l a n c e e q u a t i o n was s o l v e d f o r t h e m o s t e x o t h e r m i c c a s e ( R u n 5 ) , ( T a b l e s I and I I ) t o g e t h e r w i t h t h e mass b a l a n c e e q u a t i o n ( 1 ) . T h u s , t h e r ^ were d e d u c e d f r o m a w e l l - f i t t e d b u t w i t h r e s p e c t t o t h e k i n e t i c e x p r e s s i o n ' s t i l l a r b i t r a r y d e s c r i p t i o n of the experimental c o n c e n t r a t i o n p r o f i l e along the r e a c t o r . S i n c e t h e Δ Η ^ a r e known, i t r e m a i n s t o c h o o s e h and X f f s o t h a t t h e e x p e r i m e n t a l l y measured temperature g r a d i e n t § | i s c o r r e c t l y d e s c r i b e d . For t h i s , w

e




8

mole nj 100 mole Pe

Figure 1.

Experimental results from Run 3, Table 1.


1.

9


ARNTZ ET A L .

two a s s u m p t i o n s w e r e made: 1. t h e m o d e l e x p r e s s i o n g i v e n i n ( 7 ) ( w i t h o u t t h e l o n g i t u d i n a l c o r r e c t i o n ( 9 ) i s c o r r e c t ) ; 2 . B i o t i s c o n s t a n t ( t h e same c o r r e c t i o n f a c t o r f o r h and * f f ) · These heat t r a n s f e r parameters were used f o r a l l experiments (Table IV); they are d i s t i n c t l y higher than those which can be c a l c u l a t e d from ( 7 ) f o r the case without r e a c t i o n . T h i s agrees with i n v e s t i g a t i o n s o f the o x i d a t i o n o f CO ( 5 ) . w

e

Table IV


λ „ (KJ/m.s.K) err, r h (KJ/m w

i

2

R e f e r e n c e (2) 0.82 χ 10-

experimentally determined 1.25 χ 1 ( H

.s . K)

0.27

0.412

E f f e c t i v e K i n e t i c Parameters. t h r e a c t i o n the p o t e n t i a l law

r. = A. exp(-Ei/RT)T

0

Pj

F o r the r a t e

e

f

f

o f the

'

(6)

ij

was chosen. An i n i t i a l s e t o f parameters ( Α χ , E n j ) was de termined f o r each t r i a l s e p a r a t e l y (Runs 1 - 5 ) , (Table I ) by simultaneous f i t t i n g o f measured c o n c e n t r a t i o n and temperature p r o f i l e s along the r e a c t o r . I n i t i a l gross f i t t i n g was accompli shed by o p t i c a l o p t i m i z a t i o n ( 4 7 ) t h r o u g h v a r i a t i o n o f A E i , n i j . I t p r o v e d e f f e c t u a l t o s e t s m a l l v a l u e s f o r i{ ( 4 0 - 7 0 x l 0 J / k m o l e ) and n i j ( 0 . 3 - 0 . 5 ) a n d a c h i e v e t h e f i r s t f i t b y v a r y i n g A j . A b e t t e r f i t was a c h i e v e d b y v a r i a t i o n o f E j a n d n j : , w h e r e b y A j was r e c a l c u l a t e d f o r e a c h s u b s e q u e n t com putation according to ( 7 ) . l f

x

l f

6

The k i n e t i c parameters obtained from t h i s o p t i c a l o p t i m i z a t i o n are used as s t a r t i n g values f o r the FIBSAS o p t i m i z a t i o n sub r o u t i n e SIMPLEX. The procedure d e s c r i b e d above was a p p l i e d t o a l l t r i a l s (Runs 1 - 5 ) , whereby some o f the parameters obtained f o r the d i f f e r e n t t r i a l runs s t i l l showed s i g n i f i c a n t v a r i a t i o n . A set o f parameters v a l i d f o r a l l runs was obtained from the l i n e a r regression ( 8 ) : I n r . = I n A. - ( E . / R T ) Σ η . . I n p . ι ι ι j 1J j

( 8 )

Τ and p. i n ( 8 ) a r e experimental values; the other parameters a r i s e from the former f i t t i n g s f o r Runs 1 - 5 . In each step o f approximation the best f i t i s f i r s t achieved f o r i = l and then, one a f t e r another, f o r i = 2 - 4 . The r e s u l t o f t h i s e s t i m a t i o n o f k i n e t i c parameters i s shown i n Table V and F i g u r e s 2 - 4 .


10

CHEMICAL RE ACTION

Table V

Results for Effective Kinetic

/ r- / χ i , e f f " i * *P · P e

A.

E.

1

1

RT

[Z n..) K m o l e / n r . s . P a s c a l J i j J/Kmole

i


A

1 2 3 4

16.7 χ 1.3 χ 1.28x 77.1 χ

ΙΟ-* 10~ 10" 10~

5

47.4 42.8 52.8 93.2

6

3

3

χ χ χ χ

106 10 10 10 6

6

6

Parameters

π., η. _ η. _ i l ι2 ι3 · \ ·P c

Λ Τ

r

ENGINEERING

P e

A

"il

n

i2

η. i3

0.44 0.54 0.66 0

0.93 0.54 0 0

0 0 0 1

0

Discussion The model d e s c r i b e s , w i t h i n the l i m i t s o f measuring e r r o r , the experimental temperature and c o n c e n t r a t i o n p r o f i l e s q u i t e w e l l over a wide temperature range (more than 100 C) and propy lene conversion range (Table I ) , (Figures 2 - 4 ) . But the r e a c t i o n orders f o r propylene and oxygen have only a l i m i t e d r e l i a b i l i t y s i n c e e s p e c i a l l y the oxygen c o n c e n t r a t i o n along the r e a c t o r v a r i e d only w i t h i n narrow l i m i t s . A d d i t i o n a l l y , pressure and flow r a t e were, f o r the most p a r t , h e l d constant (Table I ) . The model was then used to p r e d i c t measured r e s u l t s f o r a wide range o f experimental c o n d i t i o n s (T = 343-360 , ( x ) = 0.07-0.09, ( x ) = 0.13-0.15 , ( x ) = 0 . I 8 5 " 0-003, p

β

W

Q

5

H 2 0

1

G = 1.17 - 1.70 kg.m^s" ) as w e l l as f o r a c a t a l y s t d i f f e r e n t from t h a t used i n Runs 1-5 . The new c a t a l y s t was based upon the same chemical system but contained more a c t i v e m a t e r i a l ( 8 ) . It was s u r p r i s i n g t h a t only the pre-exponential f a c t o r s A^ had to be newly estimated (Table VI) whereby the conversion f a c t o r s f o r A f o r the three p a r a l l e l r e a c t i o n s s t a r t i n g from propylene ( i = l - 3 , Table VI) proved to be about the same. From these r e l a t i o n s h i p s u s e f u l i n f o r m a t i o n f o r f u t u r e c a t a l y s t p r e p a r a t i o n may be drawn ("learning model"). x

Table

VI

A . f o r new r u n s

1

A.

1

1 j 2 3! 4 ·

3

(Kmole/m s . P a s c a l 30.4 2.26 2.03 272.5

χ χ χ χ

ΙΟ" 10~ 10" 10"

6

J

(different

catalyst)

i n . . A. (5 new r u n s ) ) A* ( r u n 1 - 5 ) 1 J

1

1.8 1.7 1.5g 3.5 2

6

4

3

3

3

The agreement o f the p r e d i c t i v e c a l c u l a t i o n s with the measu red r e s u l t s i s q u i t e good f o r those new runs ( " p r e d i c t i v e model")



1.

ARNTZ ET AL.

11


Figure 2. Experimental results from Run 2, Table L Key: X , temperature mea sured; •> propylene; · , acrolein; A * acrylic acid; and ψ , CO and C0 . Z

Figure 3. Experimental results from Run 4, Table I. Symbols are the same as in Figure 2.



1 2


Figure 4.

Experimental results from Run 5, Table I. Symbols are the same as in Figure 2.

Figure 5.

Data plotted of a predicted run. Symbols are the same as in Figure 2.


1.

ARNTZ ET A L .

13


as i l l u s t r a t e d i n Figure 5 ( d i f f e r e n t c a t a l y s t ; reduced bed length; (XQ ) = 0.127; ( X H O ) = °·004; G = 1.67 k g . m ^ s " ) . The p r e d i c t i o n o f the new runs succeeded, even though, be s i d e s the c a t a l y s t , the r e a c t o r feed and flow r a t e were s i g n i f i c a n t l y d i f f e r e n t from those o f the experimental r e s u l t s (Tables I and II) from which the model was d e r i v e d . C l e a r l y , the s i m p l i f i c a t i o n o f the r e a c t i o n scheme t o the four r e a c t i o n s found i n network (5) i s only v a l i d f o r the tempe r a t u r e and c o n c e n t r a t i o n range which was i n v e s t i g a t e d . E s p e c i a l l y at higher temperatures, a d d i t i o n a l secondary r e a c t i o n s , p a r t i c u l a r l y the o x i d a t i o n o f a c r o l e i n t o CO and CO2, must be e x p l i c i t l y considered. 1

2


2

0

Legend of Symbols 4.(q /P ).(L/d ).(d /d ).(Pe )Pascal Pj,P= p a r t i a l p r e s s u r e ; p r e s s . L · M /G P*m = u . d p / D f f , P e e l e t No. ( m a s s , r a d i a l ) P e - G . C p . d p A f f , P e c l e t No.(heat,radial) preexponential factor 4.(L/d ).(d /d ).(Pe )r 2r'/d^, reduced r a d i a l coordinate L/(G.c .T ) b r' = radial coordinate m Bi df h /2V,eff B i ° t number r i f f = e f f . rate of i th reaction Cp = mass s p e c i f i c h e a t a t c o n s t a n t time s pressure K J k g " Κ"* temperature CJ = molar c o n c e n t r a t i o n kmole linear velocity ms dp,d|.= d i a m e t e r ( p a r t i c l e , t u b e ) mole f r a c t i o n ^r,eff effective radial dispersion pseudo-mole f r a c t i o n y j = n j / 5 n j coefficient mV z'/L reduced a x i a l coordinate E = a c t i v a t i o n energy J mole""* ζ· = a x i a l c o o r d i n a t e m G = mass s p e c i f i c f l o w r a t e k g n r ^ s " * V , e f f e f f e c t i v e r a d i a l t h e r m a l c o n d u c t i = reaction enthalpy J mole"* ΔΗ v i t y o f t h e c a t a l . b e d K J . n r V .K" = wall heat t r a n s f e r stoichiometric coefficient w coefficient KJ.nrV ^| v o l u m e t r i c mass kg m • reaction rate constant o f i th θ : reduced temperature T / T ki reaction superscript: L = lenght of reactor b

0

t

p

t

m

0

0

r? e

h

r f e

1

t

p

2

p

t

h

0

w

f e

1

- 1

0

1

1

h

1

Y i j

- 3

0

M

= mean m o l a r mass = amount o f s u b s t a n c e = reaction order

subscripts: g = gasphase i = f o r t h e it h r e a c t i o n j = f o r t h e jt h s p e c i e s ρ = particle

kg k m o l e - 1 mole

i , (i+1) step o f i t e r a t i o n

s t w 0

= s o l i d phase = tube = wall = conditions at reactor inlet

Literature Cited

1. 2.

Kirk-Othmer "Encyclopedia of Chemical Technology"; Wiley, J., New York, 1978; Vol. 1, p. 288. Weigert,W. "Ullmanns Encyklopädie d. technischen Chemie"; Verlag Chemie, Weinheim, 1974; Vol. 7, p. 74.



14


3. Weigert, W.M; Maschke, H. Chew. Zeitung, 1974, 98 ( 2 ) , 61 4. Shinnar, R. "ACS-Symposium Series 72", American Chemical Society, Washington D.C., 1978; p. 1-36 5. Hofmann, H. Chem. Ing. Techn., 1979, 51, 257 6. Schlünder, E.U., "ACS-Symposium Series 72", Chem. React. Eng. Rev.-Houston, 1978, p. 110 - 161 7. "VDI-Wärmeatlas"; VDI-Verlag, Düsseldorf, 1977; p. Gg 8. Degussa, DE-PS 20 49 583, 1970, Degussa, DOS 31 25 061, 1981 9. Hofmann, U., Fortschr.-Ber., VDI-Zeitung. 1977, 3, 49 10. Haber. J., Kin. K a t a l . , 1980. 21, 123 - 135 11. Hucknall, D.J., " S e l e c t i v e Oxidation o f Hydrocarbons", Academic Press, London 1974 12. V.D.Wiele. K., v.d.Berg, P.J., "Comprehensive Chemical K i n e t i c s " , E l s e v i e r , Amsterdam, 1978, V o l . 20, p. 123 13. Krenzke, L.D., Keulks, G.W., Sklyarov, A.V., Firsova,A.A., Kutirev,M., Margolis,L.Y., Krylov,O.V,J.Catal.,1978,52, 418 14. Burlington, J.D., G r a s s e l l i , R.K., J. Catal., 1979, 59, 79 15. G r a s s e l l i , R.K., Burrington, J.D.,Bradzi1, J.D. Faraday Discussion, 1981, 72-72/12 16. Aso, J., Furukawa, S., Yamazone, N., Seiyama, T. J. Catal., 1980, 64, 29 17. Serban, S. Revue Chim. (Bucharest) 1967, 18, 65 18. C a r t l i d g e , J . , Mc Grath, L., Wilson, S.H., Trans. Inst. Chem. Eng., 1975, 53, 117 19. Köppner, D i s s e r t a t i o n U n i v e r s i t ä t Erlangen-Nürnberg, 1975 20. Varadarajan, T.K., Visvanathan, Β., S a s t r i , M.V.C., Indian J. Chem., 1977, 15, 452 21. Adams, C.R., Voge, J . J . C a t a l . 1961, 3, 379 22. Peacock, J.M., Parker, A.J., Ashmore,P.G., Hockey, J.A. J. C a t a l . , 1968, 15, 308 23. Wragg, R.P., Ashmore, P.G., Hockey, J.A., J. C a t a l . , 1973, 31, 293 24. S h i p a i l o , V.Y., Fedevich, E.V., Krivko, V.R., Zhurnal F i z i c h e s k o i Khimii, 1977, 51, 538 25. Lemberanskij, R.A., Azerb. Khim. Zh., 1968, 6, 19 26. Lapidus, V.L., Neftek., 1968, 9, 400 27. Gorshkov, A.P.,Gargarin. S.G., Kolchin, K., Neftek.,1970, 10, 59 28. Crozat, M., Germain, J.E., B u l l . Soc. Chim. F., 1973, 2498 29. Daniel, Ch., Keulks, G., J. Catal., 1973, 29, 475 30. Seinalow, R.J., Rustamow, M.I., Aliew, W.S., Model Khim. Reactorov T r . Vsos. Konf. Khim. Reactoram, 1968, 3, 41 31. Berty, J.M., Vortrag, U n i v e r s i t ä t Erlangen-Nürnberg, 1978 32. Moro-Oka, Y., Tan. S., Ozaki, Α., J. Catal., 1968, 12, 291 33. T j u r i n , J.N. Andruskewitsch, TW., Neftek., 1977, 17, 744 34. Bednorova, S., Habersberger, K., Chem. Prum., 1978, 28, 182 35. Vinogradova, O.M., Vytnov, G.F., Luiksaar, I.V., K i n . K a t a l . , 1975, 16, 576 36. Sheplew. W.S., Andruskewitsch, T.W., K a t a l l z . i. K a t a l i t . Processy, 1977, 171 37. Mars, P., v.Krevelen, D.W., Spec. Supp. Chem. Eng. S c i . , 1954, 3, 41 38. Krenzke, L.D., Keulks, G.W., J . C a t a l . , 1980, 64, 295 39. Monnier, J.R., Keulks, G.W., J . C a t a l . , 1981, 68, 51 40. Frost, Α.Α., Pearson, R.G., " K i n e t i c s and Mechanism.", John Wiley and Sons, New York, 1961 41. Petersen, E.E., "Chemical Reaction A n a l y s i s " , P r e n t i c e - H a l l , Inc. Engelwood Cliffs, 1964 42. Wei, J . , Prater, C.D., Adv. Cat., 1962, 13, 203 43. Lee, H.H., AIChE Journal, 1977, 23, 116 44. Akella, L.M., Lee, H.H., Chem. Eng. Jl., 1981, 22, 25 - 41 45. Probst, K., D i s s e r t a t i o n . U n i v e r s i t ä t Erlangen-Nürnberg, 1981 46. Emig, G., Hofmann. H., F r i e d r i c h , H., Proc. 5 th Europ. 2nd Int. Symp. Chem. React. Eng., 1972. Β 5 - 23 47. Gans, P. Comp. Chem., 1977, 1, 291

RECEIVED April 27, 1982.


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