Enhancement of stability and activity of Cu/ZnO/Al2O3 catalysts by microwave irradiation for liquid phase methanol synthesis

► Microwave irradiation is used in preparation of Cu/ZnO/Al2O3 catalysts. ► The stability of the Cu/ZnO/Al2O3 catalyst is significantly improved by microwave irradiation. ► Microwave irradiation promote the substitution of Zn2+ in Zn5(CO3)2(OH)6 by Cu2+. ► The calcined CuO/ZnO/Al2O3 show strong interaction between CuO and ZnO and well dispersed CuO. The stability and activity of Cu/ZnO/Al2O3 catalysts in liquid phase methanol synthesis have been enhanced by using microwave irradiation in precipitation and aging processes. The phase composition of precursors and the microstructure of calcined CuO/ZnO/Al2O3 catalysts were characterized by XRD, FT-IR, DTG, HR-TEM, H2-TPR and XPS, and the catalytic performances were tested in liquid phase reactor for methanol synthesis from syngas (CO+H2). The results showed that the microwave irradiation during precipitation process leaded to a slight improvement of activity of Cu/ZnO/Al2O3 catalysts. In the aging process, microwave irradiation promoted the substitution of Zn2+ in Zn5(CO3)2(OH)6 compound by Cu2+, leading to enhancement of the content of (Cu, Zn)5(CO3)2(OH)6 phase in precursors and the stability and activity of Cu/ZnO/Al2O3 catalysts. When microwave irradiation was used in both precipitation and aging processes, the stability and activity of Cu/ZnO/Al2O3 catalysts were further enhanced. The optimum preparation conditions for the Cu/ZnO/Al2O3 catalyst were precipitated at 60°C and aged at 80°C under microwave irradiation, the average methanol space time yield (STY) and deactivation rate (R) of the optimum catalyst were 312mg/(gh) and 0.05%/d, respectively.