The Study Of Carbon Dioxide Hydrogenation To Methanol Over In₂O₃-ZrO₂ Catalysts

Methanol synthesis with high selectivity by CO₂ hydrogenation is one of the most valuable ways for the utilization of carbon dioxide.Significant efforts have been made towards In₂O₃-based catalysts due to their high methanol selectivity.Cost reduction and further improvement of catalytic performance are still necessary.Introducing zirconium oxide is one of the effective methods that would reduce cost and improve catalytic activity meanwhile.Here we design a novel gold catalyst supported by In₂O₃-ZrO₂ with a solid solution structure,which shows a methanol selectivity of 70.1%and a methanol space-time yield of 0.59 g_MeOH h^-1 g_cat^-1 for CO₂ hydrogenation to methanol at 573 K and 5 MPa.The presence of Zr mainly exhibits four effects:（1）reducing the apparent activation energy,（2）stabilizing the structure of In₂O₃,（3）increasing the amount of oxygen vacancies,and（4）enhancing the CO₂ adsorption.The strong metal-support interaction effect between Au and In₂O₃-ZrO₂ solid solution facilitates H₂ dissociation,leading to the increased oxygen vacancies.The effects of zirconia crystal phases on the catalytic hydrogenation performance over In₂O₃/ZrO₂ catalysts were investigated as well.We used a dielectric barrier discharge plasma technology to prepare amorphous ZrO₂ with excellent thermal stability and a high specific surface area.In₂O₃ supported amorphous ZrO₂catalyst shows the highest methane selectivity comparing to other In₂O₃ based catalysts supported on tetragonal or monoclinic ZrO₂,while monoclinic ZrO₂ is the most optimum support for methanol synthesis.Further characterization results exhibit that the OH groups on the surface of amorphous ZrO₂ play a crucial role in the reaction.The bicarbonate formed through OH groups could stabilize above 548 K,producing methane via hydrogenation over the In₂O₃/a-ZrO₂ catalyst with the main methanol yield.