Abstract: TiO₂-SiO₂ aerogel with different TiO₂ content was prepared by the sol-gel method. Ni/TiO₂-SiO₂ catalyst samples were then prepared via impregnation, and were applied to the selective hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL). The catalyst samples were characterized by infrared spectroscopy, N₂ adsorption-desorption, temperature-programmed reduction, X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, and H₂ temperature-programmed adsorption-mass spectroscopy techniques. The characterization results indicated that smaller Ni⁰ species favored the formation of GBL. Meanwhile, TiO_x (x < 2) species, produced by the partial reduction of TiO₂, was generated during the reduction process. The formation of TiO_x (x < 2) species effectively promoted the hydrogenation of C=O group. Therefore, the hydrogenation of carbonyl was affected by both the size of Ni⁰ and TiO_x species. When the synergistic effect of small Ni⁰ and TiO_x species existed, the catalyst showed higher hydrogenation activity for C=O group.

Key words: nickel, titania, silica, supported catalyst, maleic anhydride, selective hydrogenation, butyrolactone