Thermal and catalytic degradation of high density polyethylene and commingled post-consumer plastic waste

Abstract

High density polyethylene (HDPE) and commingled post-consumer plastic waste (CP#2) were thermally and catalytically depolymerized in both a 27-cm 3 tubing reactor and a 150-cm 3 autoclave reactor at 400–435°C, 60 min. under N 2 or H 2, with or without TiCl 3 or HZSM-5 as catalyst. For both HDPE and CP#2, no significant non-catalytic reactions occurred until the reaction temperature reached 430°C. For depolymerization reactions of HDPE and CP#2 in the autoclave reactor at 435°C, the optimum oil yields (88.7% for HDPE and 86.6% for CP#2) were obtained over TiCl 3 catalyst, while the maximum gas yields (21.2% for HDPE and 17.6% for CP#2) were produced over HZSM-5 catalyst. HZSM-5 catalyzed cyclization and aromatization reactions while TiCl 3 catalyzed recombination and disproportionation reactions. Detailed product analyses and characterization lead to a reasonable explanation of reaction pathways and mechanisms.