Feature ArticleSO42−/TiO2 promotion on HZSM-5 for catalytic cracking of paraffin

•SO42−/TiO2/ZSM-5 catalysts were prepared by the sequential TiO2-CLD and sulfation of commercial HZSM-5 zeolite.•The surface SO42−/TiO2 phase promoted the paraffin saturation adsorption by 8%, and significantly enhanced the diffusion process in the ZSM-5 based catalysts.•The introduction of SO42−/TiO2 resulted in a significant promotion of catalytic activity in n-pentane cracking.•The SO42−/TiO2/ZSM-5 catalysts exhibited excellent catalytic stability and coke-resistance ability in normal-paraffin cracking.

A new kind of SO42−/TiO2/ZSM-5 catalysts were prepared by the sequential TiO2-CLD and sulfation of commercial HZSM-5 zeolite. Characterization results revealed that the external surface of ZSM-5 crystallite was wrapped by SO42−/TiO2 phase; at the same time, the unique MFI-structure and pore properties were well preserved, and the new L acid sites were generated on the external surface. The surface SO42−/TiO2 phase promoted the paraffin saturation adsorption by 8%, and significantly enhanced the diffusion process in the ZSM-5 based catalysts. Compared to the parent HZSM-5 zeolite, a significant promotion of catalytic activity in n-pentane cracking was observed over the SO42−/TiO2/ZSM-5 catalysts, which was probably due to the enhancement of sorption process for the gas-phase n-pentane molecules into HZSM-5 crystallite caused by the surface SO42−/TiO2 phase. Moreover, the SO42−/TiO2/ZSM-5 catalysts with a suitable TiO2-loading exhibited excellent catalytic stability and coke-resistance ability in normal-paraffin cracking. A possible role of the surface SO42−/TiO2 phase in coke formation was proposed that it effectively hindered the routes from olefins to aromatic hydrocarbons, and thus restrained the accumulation of coke deposit on the external surface.

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