废塑料裂解催化剂研究进展

Progress in the catalysts for cracking of waste plastics

废塑料造成的环境污染日趋严重,处理回收废塑料已成为全球关注的问题。催化裂解作为一种新的塑料回收方法,具有高效、环保、无二次污染和产物油品质高等特点。综述了国内外废塑料裂解制油催化剂如分子筛、氧化物、黏土和过渡金属负载型双功能催化剂的研究进展。分子筛类、黏土类和无定形氧化铝-二氧化硅催化剂属酸性催化剂,其裂解废塑料机理为碳正离子机理;碱金属氧化物催化剂裂解废塑料机理为碳负离子机理;过渡金属负载型催化剂具有双功能,其中,金属活性位起加氢-脱氢作用,载体酸性位起异构化作用;而粉煤灰催化剂可同时实现废塑料与粉煤灰两种废弃物的综合回收利用。今后应注意在催化机理指导下,进一步提高催化剂性能,并研究对复杂废塑料混合物的催化裂解效果。

Because environmental pollution caused by waste plastics is getting worse, treatment and recovery of waste plastics has become a global concern. As a novel recovery method of plastics, catalytic cracking of waste plastics possessed the advantages of high efficiency, environment-friendliness and getting high quality fuel oil without secondary pollution. The progress in various catalysts for catalytic cracking of waste plastics such as molecular sieves, oxides, clay and transition metal supported bi-functional catalysts was reviewed in this paper. The catalytic degradation mechanisms of acidic catalysts such as molecular sieves, clay and amorphous Al2O3-SiO2 followed earbocation mechanism, whereas alkali metal oxides catalysts for degrading waste plastic followed carbanion mechanism. Transition metal supported catalysts possessed the dual function, in which metal catalytic active sites played a role in hydrogenation-dehydrogenation, while acidic sites of the supports performed an isomerization function. Fly ash catalysts could recycle waste plastics and fly ash at the same time. The research direction of waste plastics cracking in the future should focus on improving the performance of the catalysts under the guidance of catalysis mechanism and the catalytic cracking effect on the waste plastics mixture.