Effect of the nature of copper species on methanol synthesis from CO2 hydrogenation reaction over CuO/Ce0.4Zr0.6O2 catalyst

A series of x wt.% CuO/Ce0.4Zr0.6O2 (x = 2, 5, 15, 25, 35 and 40) catalysts obtained by oxalate co-precipitation method are characterized by XRD, BET, SEM, Raman, EPR, H-2-TPR, CO2/H-2-TPD and high pressure (3 MPa) in situ DRITFS techniques in order to elucidate the effect of CuO loading on the catalytic activity of CO2 hydrogenation to methanol. Catalytic activity results demonstrate that CO2 conversion and methanol selectivity enhance with an increase of the CuO loading until it reaches the maximum values at a CuO loading of 35 wt.%, while further addition of CuO inhibits the catalytic performance. The higher CO2 conversion of 7.0 % (13.2 %) and methanol selectivity of 96.4 % (71.8 %) are obtained over 35 wt.% CuO/Ce0.4Zr0.6O2 catalyst at 220 degrees C (280 degrees C) and 3 MPa. The excellent performance of 35 wt.% CuO/Ce0.4Zr0.6O2 is attributed to the presence of adequate copper species with higher copper surface area and larger number of Cu-Ce-Zr solid solution. These two features are benefit to provide larger number of activated hydrogen atom and promote CO2 adsorption, respectively, which are the key to the hydrogenation reaction related to the hydrogen dissociation and the activation of the carbon dioxide.