Effective conversion of CO2 into lower olefins over GaCrZrOx/SAPO-34 tandem catalysts

Promoting the efficient formation of methanol intermediates during CO 2 hydrogenation to lower olefins plays a decisive role in improving the catalytic performance of a tandem catalyst. In this study, a series of chromium (Cr)-modified gallium–zirconium oxides with the formula GaCrZrO x (y%) were prepared via the sol–gel method. The characterization and experimental results show that the addition of moderate amounts of Cr not only facilitates the formation of more oxygen vacancies on the surface of GaZrO x but also strengthens the adsorption and activation ability of CO 2 and H 2 , thereby promoting the generation of formate and methoxy intermediates. After coupling with SAPO-34 zeolite, the methanol intermediate produced on GaCrZrO x (y%) is rapidly converted into lower olefins. This integration manner oxide and zeolite catalysts is particularly important for catalytic performance because an appropriate affinity between components can induce the formation of methanol intermediates via the kinetic effect, which limits the reverse water–gas shift reaction at high temperature. The GaCrZrO x (3.0 %)/SAPO-34 tandem catalyst synthesized via grinding and mixing at 390 °C and 3 MPa exhibits remarkable stability and catalytic performance, achieving a CO 2 conversion close to 30 %, a lower olefin selectivity of 85.8 %, and a lower olefin yield of 11.7 %.