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

摘要

Thermal and catalytic degradation of poly (vinyl chloride) (PVC) containing polymer mixtures, PVC/PE, PVC/PP and PVC/PS, into fuel oil was investigated. In the catalytic degradations, Red Mud (a waste from alumina production) was tested as both cracking and dechlorination catalyst. For comparison, γ-Fe_2O_3 as a chlorine sorbent and SA-1 (silica alumina) as a solid acid cat- alyst were also used. The effect of degradation conditions, such as nitrogen gas flow, stepwise pyrolysis, catalyst contact mode, on the dechlorination was also investigated. The use of N2 gas flow suppressed partially the reaction between HCI gas from the degradation of PVC and polymer degradation products. By stepwise pyrolysis, over 90/100 chlorine in the feed plastic was recovered as HCl gas. SA1 catalyst accelerated the rate of polymer degradation 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 had no effect on the cracking of polymers. The oils derived from PVC containing pure polymer mixtures by thermal degradation contained a lower amount of chlorine than the oils obtained using RM and other catalysts. From this result we conclude that the formation of some organic chlorine compounds may be promoted by the interaction of the HCl and the catalysts.