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 CO₂ hydrogenation can be provided by H radicals formed during aromatization. In this study, we efficiently convert PE and CO₂ into aromatics and CO using a zeolite-metal oxide catalyst (HZSM-5 + CuZnZrO<i>_x</i>) 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<i>_x</i>, where it is captured in situ by CO₂ 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 CO₂ 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 CO₂.