Co- and Ni-promoted indium oxide for CO2 hydrogenation to methanol

CO2 emission and its conversion to valuable carbon-containing products have attracted increasing attention. In2O3-based catalysts have high selectivity but limited activity for CO2 hydrogenation to methanol. To improve the methanol production of In2O3 and compare the influence of added cobalt or nickel, two series of In2O3-based catalysts with different Co or Ni mole fractions were synthesized by a co-precipitation method and tested at 240-300 degrees C, 3 MPa, and GHSV = 7200 mL (g(cat)(-1) h(-1)) to compare their activity and stability. The catalysts were further investigated by XRD, Ar physical adsorption, ICP, XPS, H-2-TPR, CO2-TPD, HR-TEM and HAADF-STEM. The results show that adding Co can enhance the reducibility of In2O3 but the effect of Ni is in contrast. Abundance of surface oxygen vacancies was not a determining factor for methanol production, and the metal-oxide interface was significant for In2O3 catalytic behavior. Adding Ni can significantly improve the CO2 conversion (17.63% for Ni10In90 and 5.32% for In-100 at 300 degrees C and 3 MPa) but lower the methanol selectivity. Ni-In bimetallic species, which have a negative effect on methanol production, can easily form under a reducing and reaction atmosphere. The Co-promoted samples have higher methanol productivity and stability than Ni-promoted samples, with Co20In80 having the highest Y-MeOH, calculated as 5.36% at 280 degrees C.