CO2 reduction over Cu-ZnGaMO (M = Al, Zr) catalysts prepared by a sol-gel method: Unique performance for the RWGS reaction

Cu-ZnGaMO (M = Al, Zr) catalysts prepared by a surfactant-free sol-gel method were characterized and tested in the reverse water-gas shift (RWGS) reaction. Their catalytic behavior was analyzed under 0.1-3 MPa at 250-325 degrees C and using a reactant mixture of CO2/H-2 = 1/3. The catalytic results are analyzed in the light of the characteristics of the catalysts. The Cu-ZnGaZrO catalysts were highly selective for the RWGS reaction; a major role of surface copper and interface oxygen vacancies is proposed. CO2 conversion and CO selectivity increased on increasing the reaction temperature. CO2 conversion reaches 16.8% with 99.7% selectivity for CO under 0.1 MPa at 325 degrees C over the Cu-ZnGaZrO1 catalyst. It is suggested that CO and methanol production proceed via independent reaction pathways.