CO ₂ hydrogenation to methanol over CuO–ZnO–TiO₂–ZrO₂: a comparison of catalysts prepared by sol–gel, solid-state reaction and solution-combustion

Three CuO–ZnO–TiO₂–ZrO₂ catalysts with the same composition were prepared through sol–gel, solid-state reaction, and solution-combustion methods and characterized by X-ray diffraction (XRD), N₂ adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction with H₂ (H₂-TPR), reactive N₂O adsorption, and adsorption of H₂ and CO₂ followed by temperature-programmed desorption (H₂-TPD, CO₂-TPD) techniques. Their catalytic performances for CO₂ hydrogenation to methanol were tested in a fixed-bed reactor under the conditions of 200–280 °C, 3 MPa, and SV = 2400 mL g_cat⁻¹ h⁻¹. The results indicated that the texture, structure, reducibility, and adsorption capacity for reactants of the CuO–ZnO–TiO₂–ZrO₂ catalyst were affected noticeably by preparation methods and the catalyst prepared by sol–gel method exhibited the highest CO₂ conversion and methanol selectivity, which reached to 17.0% and 44.0%, respectively. The highest activity of the CuO–ZnO–TiO₂–ZrO₂ catalyst prepared by sol–gel method was attributed to the largest metallic Cu surface area and adsorption capacity for H₂.