Coupled conversion of polyethylene and carbon dioxide catalyzed by a zeolite–metal oxide system

Abstract

Zeolite-catalyzed polyethylene (PE) aromatization achieves reduction of the aromatic yield via hydrogenation and hydrogenolysis reactions. The hydrogen required for CO 2 hydrogenation can be provided by H radicals formed during aromatization. In this study, we efficiently convert PE and CO 2 into aromatics and CO using a zeolite–metal oxide catalyst (HZSM-5 + CuZnZrO x ) at 380°C and under hydrogen- and solvent-free reaction conditions. Hydrogen, derived from the aromatization of PE over HZSM-5, diffuses through the Brønsted acidic sites of the zeolite to the adjacent CuZnZrO x , where it is captured in situ by CO 2 to produce bicarbonate and further hydrogenated to CO. This favors aromatization while inhibiting hydrogenation and secondary hydrogenolysis reactions. An aromatic yield of 62.5 wt % is achieved, of which 60% consisted of benzene, toluene, and xylene (BTX). The conversion of CO 2 reaches values as high as 0.55 mmol g PE −1 . This aromatization–hydrogen capture pathway provides a feasible scheme for the comprehensive utilization of waste plastics and CO 2 .