Anti-carbon deposition performance of twinned HZSM-5 encapsulated Ru in the toluene alkylation with methanol

Abstract

Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied. However, the methanol-to-hydrocarbons (MTH) side reaction in this reaction is difficult to be inhibited, which will cause a mass of carbon deposition and cover the catalyst surface, resulting in catalyst deactivation. Here, a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5. According to catalytic performance studies, the Ru@HZSM-5 catalyst produced xylene selectivity of 98% and para-xylene selectivity of 96%. Meanwhile, we find that carbon precursors (e.g. ethylene) were very little when Ru catalyst was used, but the results of HZSM-5 catalyst were completely opposite. Ru@HZSM-5 catalyst achieves a lower carbon deposition rate of only 6% of HZSM-5. The main possible reason for this is that the initial C–C bond between methanol and the olefin is difficult to form.