Mo-modified MCM-48 Encapsulated ZSM-5 Core-shell Catalyst for Methane Dehydro-aromatization with Enhanced Activity and Stability

Abstract

Methane dehydro-aromatization (MDA) is an attractive and effective avenue to converting methane into valuable aromatics, but it faces challenges due to the rapid deactivation of popular zeolite-based catalysts. Herein, we successfully constructed the Mo-modified MCM-48 encapsulated ZSM-5 (Mo/Z@M-x) catalysts with a core-shell structure into MDA reaction. Benefitting from the great efficiency in regulating the outer surface Brønsted acid sites (BAS) and suppressing the loss of Mo active species, the MCM-48 encapsulation shell with specific 3D network structured mesopores could significantly improve the deposition of coke and enhance the catalytic stability and activity. Impressively, the methane converted quantity over Mo/Z@M-2 at 700 °C reached up to 87.4 mmol/gcat in the 10 h MDA reaction, while the coke selectivity dramatically decreased to 4.2% compared with that of 26.3% for bare Mo-modified ZSM-5 (Mo/Z). Further mechanistic studies through in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) validated a radical-initiated reaction mechanism of MDA reaction, which was beneficial to the enhancement of benzene selectivity. This work not only opens up an appealing approach for the design of highly active and stable zeolite-based catalysts, but also advances the mechanistic understanding of MDA from free-radical insight.