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

Abstract

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 °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, H₂-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 In₁₀₀ at 300 °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 °C.