Preparation of highly dispersed CuO-ZnO-ZrO2 catalysts and their improved catalytic performance for hydrogenation of CO2

Highly dispersed CuO-ZnO-ZrO2 (CZZ) catalysts were prepared by the citrate gel method. The structures of catalysts and precursors were characterized by XPS, BET, XRD, H-2-TPR, H-2-TPD, CO2-TPD, and TG-DTA. The effects of wet gel drying time and citric acid dosage on the catalyst structure were studied and compared with the catalysts prepared by the combustion method to investigate the performance of different catalysts for CO2 hydrogenation to methanol. Studies have shown that prolonging the drying time of wet gel can effectively prevent the splashing of the catalyst during calcination. The BET surface area of the catalyst dried at 120 degrees C for 48 h is 44.8 m(2)/g, which is higher than that of the combustion method. When the amount of citric acid is equal to the stoichiometric ratio, the catalyst has the best performance. Under the conditions of 240 degrees C, 2.6 MPa, space velocity of 3600 h(-1), and H-2/CO2 volume ratio of 3, the space-time yield of methanol reaches 110.3 g/(kg h). Excessive citric acid will affect the dispersion of catalyst components and result in decomposition residue covering catalyst surface active sites, which is not conducive to CO2 hydrogenation reaction.