Catalytic dehydration of methanol to dimethyl ether over micro–mesoporous ZSM-5/MCM-41 composite molecular sieves

A series of micro–mesoporous ZSM-5/MCM-41 composite molecular sieves were prepared by combining a microporous zeolite silica source with nano self-assembly methods, and characterized by SEM, TEM, XRD, N2 adsorption and desorption, TPD of ammonia, and their catalytic performance for the dehydration of methanol to dimethyl ether (DME) in a fixed bed microreactor at atmospheric pressure. Among these catalysts, the ZSM-5/MCM-41 sample alkali-treated with 1.5 mol/L NaOH solution, in which the relative crystallinity of ZSM-5 and MCM-41 are 54.5% and 30.5%, respectively, gave the best activity (XMeOH > 80%) with 100% selectivity and a long lifetime in a wide range of temperature from 190 °C to 300 °C. From the characterization and activity data, the formation mechanism of the micro–mesoporous composite molecular sieves was proposed to be a liquid-crystal templating mechanism.

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► The ZSM-5/MCM-41 were synthesized in nano self-assembly method under an alkaline hydrothermal condition.
► Special acid distribution and micro–mesoporous structure of the ZSM-5/MCM-41 contribute to excellent catalytic performance.
► The combination of ZSM-5/MCM-41 and Cu/ZnO/Al2O3 was a promising catalyst for DME directly synthesis.