Product distribution from catalytic degradation of polyethylene over H-gallosilicate

Abstract

For developing a novel technology to reuse plastic waste chemically, the degradation of low-density polyethylene into aromatic hydrocarbons was investigated with H-gallosilicate as a catalyst at 375–550°C. The gallosilicate produced valuable aromatic hydrocarbons, mainly benzene, toluene and xylenes (BTX). The BTX yield increased with reaction temperature and went up to over 58 wt.% at 500°C. The liquid products obtained at temperatures above 500°C consisted of aromatics only. For this simplified liquid composition and the high BTX yield, the catalytic degradation of polyethylene using H-gallosilicate is highly promising as a new technology for chemical recycling of polyolefins. The polyethylene degradation occurring at temperatures below 450°C involved aromatization by direct cyclization of the decomposed fragments that correspond to the liquid products with six or more carbon atoms. In addition to this, above that temperature, the aromatization also proceeded through the oligomerization of the C 4 and C 5 fractions formed in the degradation steps and subsequent cyclization. The latter mechanism contributed more to the formation of aromatics with increasing reaction temperature.