A novel, shape-selective H-MCM-22/MCM-41 composite catalyst: Synthesis, characterization and catalytic performance

A novel, shape-selective H-MCM-22/MCM-41 composite catalyst is synthesized for the first time by overgrowing MCM-41 over the external surface of H-MCM-22. Results of FT-IR characterization with 2,4-dimethylquinoline adsorption indicate that the Brønsted acidic sites of H-MCM-22 located on the external surface can virtually be completely covered by the generated layer of MCM-41. When applied to the synthesis of p-xylene by the alkylation of toluene with dimethyl carbonate, the H-MCM-22/MCM-41 composite exhibits significant enhancement in p-xylene selectivity, which can be ascribed to the decrease in the number of external Brønsted acid sites of the composite.

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► MCM-41 layer overgrows on the external surface of H-MCM-22.
► The external Brønsted acid sites of H-MCM-22 are covered by MCM-41.
► High selectivity for para-xylene is obtained over the H-MCM-22/MCM-41composite.