Boosting Conversion of CO2 to Light Olefins over MgO-Promoted ZnZrO/SAPO-34 Bifunctional Catalyst

CO2 hydrogenation to produce light olefins is a hopeful route to the cyclic utilization of CO2. Although metal oxide/zeolite bifunctional catalysts show outstanding performance for CO2 hydrogenation to olefins, they still expect to further improve its performance. Here, a ternary metal oxide solid solution catalyst by incorporating MgO into ZnZrO to adjust the acid and redox active sites and coupled with SAPO-34 zeolite (noted as Mg-ZnZrO/SAPO-34) was developed. The Mg-ZnZrO/SAPO-34 catalyst exhibits light olefins yield of 5.7% that higher than those of ZnZrO/SAPO-34 catalyst (4.5%) at 390 °C. The results discovered that the introduction of MgO can neutralize the strong acid site of zeolite and generate more oxygen vacancies, and exhibit superior ability to adsorb and activate CO2 and H2. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrate that carbonate formation by CO2 adsorption of doped MgO and participation in the reaction to form more HCOO* and CH3O* species on the Mg-ZnZrO/SAPO-34 catalyst. The strategy via adjusting the acid intensity and the content of oxygen vacancies developed in this work supplies a guideline to design high-performance catalysts for CO2 utilization.