Natural aluminosilicates for catalytic depolymerization of polyethylene to produce liquid fuel-grade hydrocarbons and low olefins

摘要

Different chemical modifications were performed to the natural aluminosilicate Montanit300 (R) in order to improve its catalytic activity in PE depolymerization. Performance of such prepared catalysts was compared to established solid acid catalysts, such as HZSM-5, sulfonated and fluorinated gamma-Al2O3 and amorphous silica-alumina. Pyridine TG and DRIFTS characterization revealed mild acid treatment and aluminum grafting as successful in increasing acid site density through impurity removal and specific surface area increase. Mesoporous catalyst structure that allows facile diffusion through its pore network, together with high-density Bronsted acid sites, was found to be crucial to obtain high catalytic activity. The T-50 value for PE depolymerization was lowered by 162 degrees C with sulfonated gamma-Al2O3 solid, compared to non-catalyzed reaction, whereas with aluminum-grafted Montanit300 (R) catalyst this value was lowered by 65 degrees C. PE depolymerization products present in the condensed liquid phase using aluminum-grafted Montanit300 (R) catalyst were exclusively alkanes with chain length up to 21 carbon atoms. Liquid, coke and gas yields were found to be 53, 0.4 and 46.6%, respectively, the latter consisting of linear and branched C-2-C-4 alkenes and alkanes. (C) 2015 Elsevier B.V. All rights reserved.