Role of the external surface Brønsted acid of ZSM-5 in the suppressed side reaction of olefin hydrogenation during syngas conversion

Abstract

Recent studies have demonstrated that metal-free zeolite could catalyze olefin hydrogenation. This significantly influences the product selectivity during CO_x hydrogenation reaction. However, there lacks of knowledge about the active sites and their distribution, which is essential for further optimization of the catalysts. Herein, we demonstrated experimentally for the first time, the role of the external surface Brønsted acid sites of ZSM-5 on the olefin hydrogenation. By selectively shielding the acid site on the external surface of zeolite, the side reaction of olefin hydrogenation is effectively inhibited. This inhibition leads to the formation of fewer paraffin byproducts during syngas conversion. This promotes polymerization of olefins to the aliphatic hydrocarbons as well as aromatics formation. These results not only shed light on the selectivity control mechanism in syngas conversion but also inspire further optimization of zeolite-based catalysts for hydrogen-involving reactions.