Boosting Conversion of CO<sub>2</sub> to Light Olefins over MgO-Promoted ZnZrO/SAPO-34 Bifunctional Catalyst
Lizhi Zhang, Zhihua Cao, Ziliang Gao, Wenming Liu, Yiru Mao, Miao Li, Honggen Peng
Abstract
CO 2 hydrogenation to produce light olefins is a hopeful route to the cyclic utilization of CO 2 . Although metal oxide/zeolite bifunctional catalysts show outstanding performance for CO 2 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 CO 2 and H 2 . In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrate that carbonate formation by CO 2 adsorption of doped MgO and participation in the reaction to form more HCOO* and CH 3 O* 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 CO 2 utilization.