48 Designing a Cyclohexane Oxidation Reactor J. ALAGY, P. TRAMBOUZE, and H. VAN LANDEGHEM
Downloaded by UNIV OF IOWA on August 24, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1974-0133.ch048
Institut Francais du Pétrole, Centre d'études et de développement industriels Solaize, B.P. 3, 69390 Vernaison, France
As part of the development of a liquid-phase cyclohexane oxidation process, various aspects of the reactor design were studied: (1) Fundamental research on the influence of mass transfer on reaction selectivity (2) Laboratory and development research on boric acid as coreagent (3) Hydrodynamic research to determine the optimum reactor configuration.
Purge
Recycle liquidy
Cyclohexane feed'
Tangential Q ,(0)e T
Injection
2
Products
Figure 1.
Pilot plant continuous reactor 644
Hulburt; Chemical Reaction Engineering—II Advances in Chemistry; American Chemical Society: Washington, DC, 1974.
48.
ALAGY E T A L .
Cyclohexene
Oxidation
645
Reactor
A s i m p l i f i e d reaction scheme was established w h i c h l e d to a m a t h e m a t i c a l m o d e l w h i c h was not too complex. T h i s m o d e l was not available w h e n the p i l o t p l a n t b e g a n o p e r a t i n g . T h e r e f o r e , a s i m p l i f i e d m o d e l w a s a d o p t e d , so t h a t t h e r e s u l t s o f a o n e - r e a c t o r stage p i l o t p l a n t a l l o w e d d e s i g n o f a m u l t i s t a g e i n d u s trial unit. These t w o approaches agreed w e l l , a n d the industrial reactor con firmed predictions. T h e conclusions f r o m this study are: (1) T h e reactor operates u n d e r k i n e t i c conditions a l t h o u g h mass transfer influences the transformation rate. (2)
A s a r e s u l t , s t i r r i n g h a s n o d i r e c t effect o n s e l e c t i v i t y .
Downloaded by UNIV OF IOWA on August 24, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1974-0133.ch048
(3) F o r the operating conditions b y the fresh-air m a k e u p i n the reactor.
chosen,
conversion
can be
controlled
( 4 ) T h e f a v o r a b l e i n f l u e n c e o f a h i g h gas flow r a t e c a n b e e x p l a i n e d b y t h e e l i m i n a t i o n o f r e a c t i o n w a t e r . T h i s t h u s r e q u i r e s a sufficient g a s - l i q u i d t r a n s f e r coefficient. ( 5 ) T h e selectivity of the t r a n s f o r m a t i o n c a n b e a p p r e c i a b l y i n c r e a s e d b y u s i n g p e r f e c t l y - s t i r r e d r e a c t o r s i n series. F o r the i n d u s t r i a l construction of s u c h a u n i t , w e chose reactors of the t y p e i l l u s t r a t e d i n F i g u r e 1. T h i s c h o i c e w a s m o t i v a t e d b y t h e t e n d e n c y , observed i n the p i l o t p l a n t , for h e a v y a n d sticky b y p r o d u c t to a c c u m u l a t e o n the r e a c t o r w a l l at t h e s u r f a c e o f t h e l i q u i d . T a n g e n t i a l i n j e c t i o n s w e r e p e r f o r m e d to w a s h t h e w a l l at t h o s e p o i n t s , b u t a p o o r d e s i g n c o u l d r e s u l t i n t h e f o r m a t i o n o f a v o r t e x i n s i d e t h e r e a c t o r ; i n t h i s case t h e g a s - l i q u i d c o n t a c t a r e a w o u l d b e c o m e v e r y s m a l l ; a f t e r gas is i n j e c t e d i n t o t h e l i q u i d , i t is q u i c k l y s u c k e d t o w a r d this axial c h a n n e l created b y the vortex. T o prevent this, turbulence a n d n o n - s y s t e m a t i c c i r c u l a t i o n s c a u s e d b y t h e gas flow m u s t b e r e l i e d u p o n . T h i s p h e n o m e n o n w a s a n a l y z e d i n t w o scale m o d e l s , 3 0 a n d 6 0 c m i n d i a m e t e r , and a design criterion was w o r k e d out. T h e m a t h e m a t i c a l models a n d this h y d r o d y n a m i c criterion a l l o w e d the t w o i n d u s t r i a l projects to be c a r r i e d out w i t h f u l l success. R E C E I V E D January 2, 1974.
Hulburt; Chemical Reaction Engineering—II Advances in Chemistry; American Chemical Society: Washington, DC, 1974.
