The catalytic effect of Red Mud on the degradation of poly (vinyl chloride) containing polymer mixture into fuel oil

Thermal and catalytic degradation of poly (vinyl chloride) (PVC) containing polymer mixtures, PVC/PE, PVC/PP and PVC/PS, into fuel oil was investigate d. In the catalytic degradations, Red Mud (a waste from alumina production) was tested as both cracking and dechlorination catalyst. For comparison, g amma -Fe2O3 as a chlorine sorbent and SA-1 (silica alumina) as a solid acid catalyst were also used. The effect of degradation conditions, such as nit rogen gas flow, stepwise pyrolysis, catalyst contact mode, on the dechlorin ation was also investigated. The use of N-2 gas how suppressed partially th e reaction between HCl gas from the degradation of PVC and polymer degradat ion products. By stepwise pyrolysis, over 90% chlorine in the feed plastic was recovered as HCl gas. SA1 catalyst accelerated the rate of polymer degr adation and lowered the boiling point of liquid products, but the chlorine content of oil over SA1 was also the highest. Red Mud (RM) and iron oxides sorbents showed good effect on the fixation of evolved HCl. However, they h ad no effect on the cracking of polymers. The oils derived from PVC contain ing pure polymer mixtures by thermal degradation contained a lower amount o f chlorine than the oils obtained using RM and other catalysts. From this r esult we conclude that the formation of some organic chlorine compounds may be promoted by the interaction of the HCl and the catalysts. (C) 2001 Else vier Science Ltd. All rights reserved.