Selective aromatization of 1-hexene to BTX over core-shell structured Silicalite-1@ZSM-5 catalyst

Abstract

The strong acidity on the external surface of ZSM-5 is a primary factor resulting in the low BTX selectivity and catalyst deactivation during the olefin aromatization. In this study, a membrane-restricted Silicalite-1@ZSM-5 core–shell structured catalytic catalyst was designed and constructed for 1-hexene aromatization using a hydrothermal coating method. TEM and NMR results confirmed the complete coverage of Silicalite-1 on the surface of ZSM-5, with a shell thickness of 50 nm. The further reaction of the TIPB (1,3,5-triisopropylbenzene) molecular probe reactions demonstrated the passivation of the acid sites on ZSM-5 external surface. The inert shell layer passivated the acid sites on the external surface, thereby suppressing the isomerization of PX and the side-chain alkylation reaction of light aromatics. Compared to ZSM-5, the Silicalite-1@ZSM-5 catalyst exhibited a 37.15 % increase in BTX selectivity, a 58.65 % increase in PX selectivity, significantly reduced coke deposition, and demonstrated better stability. This strategy of in-situ epitaxial growth of inert shell layers holds significant promise for enhancing the selectivity of shape-selective catalysts and extending catalyst lifetime.