Fabrication of surface passivated two-dimensional MFI zeolite for alkylation between toluene with methanol

The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired. Here, the two-dimensional pillared MFI zeolite was modified by silicalite-1, and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process. The MFI zeolites were characterized by X-ray diffraction, transmission electron microscopy, pyridine-infrared and N₂ adsorption-desorption isotherms. The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded. Interestingly, the P-MFI-23 showed long lifetime and high selectivity of para-xylene (about 35%) based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer. It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites, resulting in the deactivation of catalyst. Furthermore, the highest selectivity of para-xylene (about 48%) can be achieved for P-MFI-30 under harsh reaction condition, which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol. The strategy described in present research may open a window for the design of other advanced materials.