Gas phase hydrogenation of maleic anhydride to γ-butyrolactone by Cu–Zn–Ti catalysts

Cu–Zn–Ti catalysts were prepared by coprecipitation method. The calcined and reduced Cu–Zn–Ti catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and N2 adsorption. The calcined Cu–Zn–Ti catalysts were composed of CuO, ZnO, and amorphous TiO2. There were two kinds of CuO species present in the calcined Cu–Zn–Ti catalyst. At a lower copper content, CuO species interacted with ZnO and TiO2; at a higher copper content, both the surface-anchored and bulk CuO species were present. After reduction, metallic copper (Cuo) appeared in all Cu–Zn–Ti catalysts. Cuo produced by reduction of the surface-anchored CuO favored the deep hydrogenation of maleic anhydride. ZnO and TiO2 had synergistic effect on the catalytic activity of Cu–Zn–Ti catalysts in hydrogenation of maleic anhydride.