Effects of alkaline-earth oxides on the performance of a CuO–ZrO2 catalyst for methanol synthesis via CO2 hydrogenation

Abstract

CuO–ZrO₂ catalysts doped with alkaline-earth oxides were prepared by a urea-nitrate combustion method. The catalysts were characterized with N₂ adsorption, N₂O titration, XRD, H₂-TPR, XPS and CO₂-TPD techniques and tested for methanol synthesis from CO₂ hydrogenation. With the incorporation of alkaline-earth oxides, the copper surface area increases remarkably, whereas the reducibility of CuO in the catalyst decreases. The doping of alkaline-earth oxides leads to an increase in the strength and contribution of the strong basic site on the catalyst surface. The results of catalytic tests indicate that the conversion of CO₂ depends not only on the copper surface area but also on the reducibility of CuO in the catalyst, and the latter is a predominant factor for CaO-, SrO- and BaO-doped CuO–ZrO₂ catalysts. The selectivity to methanol is related to the basicity of the catalyst. Moreover, the influence of the doping amount of MgO on the properties of CuO–ZrO₂ was investigated, and the optimum catalytic activity is obtained as the amount of MgO doping is 5 mol%.