Abstract: The effects of the silica promoter on the properties of the Cu-ZnO/HZSM-5 catalyst were investigated by means of X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The addition of a small amount of silica (e.g. 1.0%) to Cu-ZnO/HZSM-5 could greatly improve the CO2 conversion and the selectivity for dimethyl ether, and decrease the selectivity for CO, and increase the catalytic stability of the catalyst. However, a large amount of silica caused a decrease in the catalytic activity. The presence of SiO2 led to the changes of phase structure in calcined samples, improved the dispersion of CuO and ZnO, and increased the reduction temperature of CuO. The silica added could suppress the crystallization of Cu0 and ZnO during the reaction, stabilize the active Cu0, and thus improve the activity and stability of the catalyst.

Key words: silica, copper-based catalyst, carbon dioxide, catalytic hydrogenation, dimethyl ether