MORPHOLOGICAL-CHANGES DURING OXIDATION OF A SINGLE CHAR PARTICLE

The e v o l u t i o n of pore s i z e d i s t r i b u t i o n d u r i n g t h e o x i d a t i o n of s i n g l e Spherocarb c h a r p a r t i c l e s has been measured u n d e r c h e m i c a l c o n t r o l l e d c o n d i t i o n s . E l e c t r o d y n a m i c a l l y l e v i t a t e d p a r t i c l e s were heated t o r e a c t i o n t e m p e r a t u r e u s i n g a l a s e r and t h e weight and s i z e changes m o n i t o r e d . The l a s e r h e a t i n g was i n t e r r u y p t e d a t s e l e c t e d c o n v e r s i o n s and t h e C 0 2 a d s o r p t i o n determined at ambient c o n d i t i o n s . A s r e a c t i o n p r o c e e d s , p a r t i c l e s a r e found t o s h r i n k , t h e macropore volume d e c r e a s e s i n p r o p o r t i o n t o t h e t o t a l p a r t i c l e volume, m a i n t a i n i n g a c o n s t a n t m a c r o p o r o s i t y . The micropore volume, however, d e c r e a s e s w i t h i n c r e a s i n g c o n v e r s i o n whereas t h e n o r m a l i z e d p o r e size d i s t r i b u t i o n remains unchanged, s u g g e s t i n g t h a t t h e d e n s i f i c a t i o n of t h e microporous volume which l e a d s to. p a r t i c l e s h r i n k a g e r e s u l t s from pore e l i m i n a t i o n . A t t h e same time t h e mesopore volume i n c r e a s e s with i n c r e a s i n g c o n v e r s i o n i n d i c a t i n g t h a t t h e mesopores play a dominant r o l e i n t h e c h a r r e a c t i o n