INVESTIG/~TIONS UNDER

NONISOTHERMAL R.

I. Soloukhin

OF

CHEMICAL

KINETICS

OF

REACTIONS

CONDITIONS UDC 541.124

This and the next i s s u e of F i z i k a G o r e n i y a i V z r y v a e o n t a i n g e n e r a l i z i n g a n d o r i g i n a l a r t i c l e s which c o n s t i t u t e the m a i n content of the w o r k of the A l l - U n i o n w o r k s h i p " C h e m i c a l k i n e t i c s of r e a c t i o n s under n o n i s o t h e r m a l c o n d i t i o n s " held on June 20-29, 1972 in N o v o s i b i r s k . The c h r o n i c l e of the r e s u l t s of the w o r k s h o p w a s p u b l i s h e d in F i z i k a G o r e n i y a i V z r y v a , Noo 3, 1972. The s u c c e s s f u l e x p e r i e n c e of this w o r k shop c o n f i r m e d the c o r r e c t n e s s of the s e l e c t i o n of the s u b j e c t and u r g e n c y of the topic, which a l s o c l e a r l y i n d i c a t e s the b r o a d front of t h e o r e t i c a l and e x p e r i m e n t a l i n v e s t i g a t i o n s in the a r e a of the k i n e t i c c h a r a c t e r i s t i c s of n o n i s o t h e r m a l s y s t e m s being c a r r i e d out in v a r i o u s s c i e n t i f i c o r g a n i z a t i o n s of the c o u n t r y . S p e c i a l i s t s in the a r e a s of o r g a n i c , i n o r g a n i c , and p h y s i c a l c h e m i s t r y , c a t a l y s i s , c h e m i c a l p h y s i c s , t h e r m a l p h y s i c s , p h y s i c a l gas d y n a m i c s , and applied m a t h e m a t i c s a r e p a r t i c i p a t i n g in the i n v e s t i g a t i o n s . R e a c t i o n s in g a s e o u s , condensed, and h e t e r o g e n e o u s s y s t e m s a r e being i n v e s t i g a t e d f r o m the g e n e r a l t h e o r e t i c a l and p r a c t i c a l standpoints in a wide range of t h e r m a l and p h y s i c o c h e m i c a l conditions. All t h i s a l s o d e t e r m i n e s the acute mutual i n t e r e s t of s p e c i a l i s t s f r o m d i f f e r e n t f i e l d s , t h e i r e n d e a v o r to w o r k out a unif o r m t e r m i n o l o g y , to s e l e c t the m o s t effective e x p e r i m e n t a l m e t h o d s , a n d t o develop e f f e c t i v e m e t h o d s of t h e o r e t i c a l a n a l y s i s and n u m e r i c a l c a l c u l a t i o n s . N o n i s o t h e r m i c i t y of the r e a c t i o n conditions is a l w a y s c h a r a c t e r i s t i c f o r s t r o n g l y e x o t h e r m i c or e n d o t h e r m i c s y s t e m s , and t h e r e f o r e when d e s c r i b i n g , for e x a m p l e , the c h a r a c t e r i s t i c s of ignition, spontaneous combustion, or an e x p l o s i o n it is n e c e s s a r y to deal with a c o m p l e x set of i n t e r r e l a t e d t h e r m o p h y s i c a l and c h e m i c a l p r o c e s s e s : on one hand, the r a t e of r e l e a s e (absorption} of heat of the r e a c t i o n and conditions of heat a b s t r a c t i o n and diffusion c o n t r o l the c o u r s e of the d e v e l o p m e n t and o c c u r r e n c e of the c h e m i c a l t r a n s f o r m a t i o n , a n d o n the other the r a t e and extent of o c c u r r e n c e of the r e a c t i o n d e t e r m i n e the t h e r m a l c o n d i tions within the r e a c t i n g m e d i u m . In t h i s connection we can t e n t a t i v e l y single out two p r o b l e m s of the inv e s t i g a t i o n of n o n i s o t h e r m a l s y s t e m s : a) a c l o s e d c o m p l e x d e s c r i P t i o n of the d y n a m i c s of the o c c u r r e n c e of the r e a c t i o n under n o n i s o t h e r m a l conditions with the use of g e n e r a l c h e m i c a l - k i n e t i c r e g u l a r i t i e s , which a r e u s u a l l y obtained u n d e r s i m p l e r t h e r m a l c o n d i t i t i o n s , and b) the o b t a i n m e n t of b a s i c data on the k i n e t i c m e c h a n i s m and c o n s t a n t s of the e n t i r e p r o c e s s or its e l e m e n t a r y s t a g e s f r o m the c h a r a c t e r i s t i c s of the o c c u r r e n c e of the r e a c t i o n s u n d e r n o n i s o t h e r m a l c o n d i t i o n s . Unfortunately, so n a t u r a l , in our opinion, a d i v i s i o n of the p r o b l e m into d i r e c t and i n v e r s e cannot always be r e a l i z e d , since the k i n e t i c m e c h a n i s m of the r e a c t i o n - sequence of s t a g e s , c o u r s e of " r e c o m b i n a t i o n " and b a c k r e a c t i o n s , e t c . - can v a r y d e pending on the d e g r e e of d e v i a t i o n f r o m i s o t h e r m i c i t y . In o t h e r w o r d s , in the g e n e r a l c a s e the s u p e r p o s i tion of c h e m i c a l and t h e r m o p h y s i c a l p r o c e s s e s is not r e a l i z e d . N e v e r t h e l e s s , the data obtained in e x p e r i m e n t s with n o n i s o t h e r m a l s y s t e m s can be a s o u r c e (and in many c a s e s the only one) f o r d e t e r m i n i n g k i n e t i c r e g u l a r i t i e s . The p o s s i b i l i t y o f obtaining such i n f o r m a t i o n and the d e g r e e of its r e l i a b i l i t y a r e d e t e r m i n e d m a i n l y by the d e g r e e of c o r r e s p o n d e n c e of the s e l e c t e d model of the n o n i s o t h e r m a l r e a c t o r to the r e a l s y s t e m and to t h e l e v e l of " s e n s i t i v i t y " of the model s y s t e m (usually this is a n u m e r i c s y s t e m on a computer} to p o s s i b l e v a r i a t i o n s of the k i n e t i c m e c h a n i s m of the r e a c t i o n and to the q u a n t i t a t i v e data on r a t e s of e l e m e n t a r y s t a g e s . The d e g r e e of s e n s i t i v i t y and u n i v e r s a l i t y of the e x p e r i m e n t a l m e t h o d s used a l s o play a substantial role. The a r t i c l e s being p u b l i s h e d can be a s s i g n e d to the following t h r e e d i r e c t i o n s : c h a r a c t e r i s t i c s of the c o u r s e of r e a c t i o n s in n o n i s o t h e r m a l s y s t e m s ; m o d e l s and e x p e r i m e n t a l m e t h o d s f o r obtaining k i n e t i c data; some new n o n e q u i l i b r i u m p r o c e s s e s o c c u r r i n g u n d e r n o n i s o t h e r m a l conditions. T r a n s l a t e d f r o m F i z i k a G o r e n i y a i V z r y v a , Vol. 9, No. 1, pp. 3-4, J a n u a r y - F e b r u a r y , 1973.

9 1975 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from the publisher for $15.00.

The investigations c o v e r s a wide range of reaction s y s t e m s - ignition and burning of gases, thermal decomposition and burning of condensed s y s t e m s , reactions in heterogeneous s y s t e m s , catalysis, etc. Serious attention is given to the development of new experimental methods and to the c r e a t i o n of effective m a t h e m a t i c a l models. The c l a r i t y of the selection of the main scientific direction of the workshop and the practical and constructive c h a r a c t e r of the work of each of its participants were due largely to the participation of Prof. A. G. Merzhanov in its p r e p a r a t i o n and conduction.