engleski

Combining hierarchization and Mg2+ ions insertion in ZSM-5: acidity-modulation effect on MTO reaction

Acid catalysis is recognised as the most reliable industrial ì way to convert hydrocarbons into various products (methanol to olefins and aromatics, glycerol to olefins, methane dehydroaromatization, isomerization, etc.). In this concern, ZSM-5 is extensively used, also because of peculiar type of active sites of such zeolite. In this paper, a fine tuning of the acidity content and strength of ZSM-5 was investigated through a combination of post- synthesis treatments: desilication via alkaline solution and wet impregnation with Mg2+ions followed by calcination. Results show that the insertion of Mg2+has a large influence on the distribution and strength of Brønsted and Lewis acid sites of the hierarchical ZSM-5, as well as an improved crystallinity with respect to the desilicated-one. The hierarchical ZSM-5 zeolite incorporating Mg-species was tested in Methanol- to-olefins reaction and the reduction of acid strength of catalyst increased the selectivity toward light olefins (mainly propylene) as well as it suppressed oligomerisation reactions delaying the coke formation.

Hierarchical zeolites ; Mg insertion in zeolites ; Acidity tuning ; MTO reaction

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