Boosting CO2 hydrogenation performance for light olefin synthesis over GaZrOx combined with SAPO-34

Abstract

A highly active and selective GaZrOx/SAPO-34 bifunctional catalyst was developed for CO2 hydrogenation into C2=–C4=. A high C2=–C4= selectivity of 88.8% at CO2 conversion of 26.7% was achieved, and the olefin yield reached 11.3%, outperforming the previous reports. As Ga:Zr atomic ratio increases, the surface oxygen vacancy content (OV), responsible for CO2 activation, firstly increases from 22.5% to 32.6% and then decreases to 15.4%, while the H2 dissociation ability produced by Ga site increases gradually. Activated CO2 at Zr–OV–Zr site could either react with Ga–Hδ– to form HCOO* , then successive hydrogenation to CH3O* intermediate, or combine with O–Hδ+ to form COOH* , followed by dissociation to form CO. The formation of CH3O* or CO is competitive, which highly depends on the H2 dissociation ability, only the moderate H2 dissociation ability benefits CO2 hydrogenation to CH3O* at high temperature, leading to a high C2=–C4= yield.