High temperature chlorination of titanium bearing minerals: part IV
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e a r l i e r p a p e r s of this s e r i e s , 1-3 s o m e of the r e a c t i o n s i d e n t i f i e d as s i g n i f i c a n t c o n t r i b u t o r s to the high t e m p e r a t u r e attack of c h l o r i n e on t i t a n i a and i l m e n i t e l a t t i c e s w e r e p r e s e n t e d . The c a r b o n / c h l o r i n e r e a c t i o n with t i t a n i a was not included. D u r i n g the two decades that have e l a p s e d s i n c e the f i r s t p a p e r , m a n y s t u d i e s of the C/C12 r e a c t i o n have b e e n r e p o r t e d , a m o n g t h e s e p a p e r s of B e r g h o l m and of M o r r i s and J e n k i n s 4,s T h i s p a p e r d e s c r i b e s the n a t u r e of the c a r b o n / c h l o r ine r e a c t i o n with TiO2 to make t i t a n i u m t e t r a c h l o r i d e in a fluidized r e a c t o r , the m e c h a n i s m and the s i g n i f i cant r e a c t i o n v a r i a b l e s . Although n e a r l y e v e r y r e a c t i o n m e c h a n i s m has b e e n invoked f r o m s o l i d contact to a t o m i c r a d i c a l s , the autocatalytic reaction involving titanium tetrachloride attack upon the lattice f i r s t p r o p o s e d by the a u t h o r in 1961 has not b e e n noted. 6 The r e a c t i o n s p r o p o s e d have a l l v i s u a l i z e d the c h l o r i n e v a l u e s m o v i n g to the t i t a n i a s u r f a c e to a c c o m p l i s h the c h l o r i n a t i o n . T h i s p a p e r c o n s i d e r s the r e v e r s e , the c h l o r i n e a c t i n g at the c a r bon s u r f a c e . Although s o m e have held that the a c t i v i t y of t h e c a r bon was i m p o r t a n t , and it would be if r e d u c t i o n of c a r bon dioxide to c a r b o n monoxide were a s i g n i f i c a n t r e a c t i o n path, n e v e r t h e l e s s we find t i t a n i a c h l o r i n a t i o n is c a r r i e d on in s c o r e s of p l a n t s u s i n g a highly i n e r t f o r m of c a r b o n , p e t r o l e u m coke. Though m a n y p a p e r s have held that c h l o r i n e p a r t i a l p r e s s u r e i s a d r i v i n g f o r c e in the r e a c t i o n , r e a c t o r s a l l over the world have v e r y high c h l o r i n e c o n v e r s i o n l e a v i n g only t e n t h s of a pct of c h l o r i n e in the exit g a s e s . C l e a r l y this would r e q u i r e staged r e a c t o r s o r v e r y deep and efficient bed contact if c h l o r i n e p a r t i a l p r e s s u r e w e r e even a l i n e a r d r i v i n g f o r c e . Close c a r b o n - t i t a n i a contact has b e e n f r e q u e n t l y r e c o m m e n d e d and p e l l e t i n g was p r a c t i c e d in e a r l y tit a n i u m t e t r a c h l o r i d e g e n e r a t i o n p r o c e s s e s , but r e a c t o r s a r e now o p e r a t e d with fluidized beds with low t i t a n i u m content and with l a r g e gangue content without the s e r i o u s r e a c t i v i t y loss that might be e x p e c t e d as WENDELL E. DUNN, JR., formerly General Manager, Chlorine Technology Limited, Sydney, Australia, is now with Wen
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