Degradation And Dechlorination Of PVC-Containing Polyolefin Mixtures

Thermal degradation of polyolefins such as poly(ethylene)(PE), poly(propylene) (PP) and poly(styrene)(PS), and their mixtures with poly(vinyl chloride)(PVC) at different temperatures(420℃ for PE/PVC, 380℃ for PP/PVC and 360℃ for PS/PVC ) was carried out in a glass reactor under atmospheric pressure in order to investigate the effect of PVC on the degradation of polyolefins. Compared to the degradation of polyolefins containing no PVC, the liquid product yield lowered, and the rate of degradation decreased; the weight fraction of lighter hydrocarbons increased for PP/PVC or PS/PVC degradation system, but decreased for PE/PVC. Organic and inorganic chlorine compounds existed in the cracking products from polyolefins containing PVC.The degradation of the polyolefin mixtures was also carried out in the presence of ZSM-5 catalyst and iron oxides as chlorine sorbents in order to investigate the catalytic effect of ZSM-5 and dechlorination effect of iron oxides. Compared to thermal degradation, the ZSM-5 catalyst accelerated the rate of the degradation and lowered the boiling point (bp) of the liquid products; iron oxides a -FeOOH and Fe3O4 significantly decreased the chlorine content in the oil.In order to search out new composite catalysts that can simultaneously have catalytic and dechlorination effect on degradation of PVC mixed polyolefins, some new composite catalysts were prepared using Al2O3 as a carrier. Among the composite catalysts, Al-Zn and Al-Mg catalysts could effectively reduced the chlorine content in the oil derived from PVC mixed polyolefins. At the same time they effectively accelerated the degradation rate of polyolefin mixtures and lowered the bp of the liquid products. However, other catalysts had no obvious dechlorination effect. In addition, both Al-Co and Al-Cu catalysts had a good catalytic effect on the degradation of PP/PVC system.