Tuning the interfacial sites between copper and metal oxides (Zn, Zr, In) for CO2 hydrogenation to methanol

The influence of different metal oxides (ZnO, ZrO2, In2O3) in CO2 hydrogenation to methanol over Cu-based catalysts was studied. The catalysts were characterized using x-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), N2-physisorption, N2O chemisorption, H2 temperature-programmed reduction (H2-TPR), and CO2 temperature-programmed desorption (CO2-TPD). It was found that impregnating ZrO2 onto Cu/ZnO enhances the methanol formation rate from 14.7 mmol∙gcat−1∙h−1 to 15.6 mmol∙gcat−1∙h−1 (230 °C, 30 bar, 38 000 cm3/(gcat h)), which is attributed to the formation of Cu-ZrO2 sites. The results also indicate that In-doping of the Cu-based catalysts generates CuxIny alloys, which seems to inhibit the active sites on the Cu surface. However, new sites for methanol synthesis are present when Cu/ZrO2/In2O3 is prepared by co-precipitation. This is attributed to In-Zr mixed oxide species that increases the methanol formation rate from 53.2 mmol∙gcat−1∙h−1 to 60.5 mmol∙gcat−1∙h−1 (270 °C, 30 bar, 140 000 cm3/(gcat h)).