Formaldehyde intermediate participating in the conversion of methanol to aromatics over zinc modified H-ZSM-5

Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics (MTA) reaction, which is often attributed to the metal promoting the aromatization of intermediate olefins. However, the effect of methanol dehydrogenation on aromatics formation over these catalysts is rarely studied. Here, we report that HCHO, which is formed by methanol dehydrogenation over Zn/H-ZSM-5 prepared by Zn impregnation, can participate in the synthesis of aromatics. Methanol conversion can produce more aromatics than olefins (propylene or ethylene) conversion over Zn/H-ZSM-5, indicating the conventional MTA pathway including methanol-to-olefins and olefins-to-aromatics is not complete. Moreover, an MTA mechanism including the conventional pathway and the methanol and HCHO coupling pathway is systematically proposed. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.