Abstract: The effects of calcination and reduction temperature on the properties of the Ni/TiO2 catalyst were studied by means ofX-raydiffraction, temperature-programmed reduction, H2 chemisorption, and the performanceevaluationfor hydrogenation of p-nitrophenol. The results showed that nickel species existed in the form of NiO in the catalysts calcined at ≤923 K, and the interaction between NiO and TiO2 was enhanced with the increase in calcination temperature. However, nickel species existed in the form of NiTiO3 in the catalyst calcined at1023K. For the catalysts calcined at ≤923 K and reduced at 723 K, there was no remarkable difference in the nickel crystallite size, whereas the amount of H2 chemisorption decreased as the calcination temperature increased, which was due to the increase of the interaction between nickel and TiOx (x<2). The catalyst calcined at 923 K showed better catalytic performance for hydrogenation of p-nitrophenol than the ones calcined at lower temperatures, which was also closely related to the strong interaction between nickel and TiOx species. The reduction temperature also deeply affected the properties of Ni/TiO2. At low reduction temperature, the catalyst could not be reduced completely, while the high reduction temperature would cause nickel sintering and an excessively strong interaction between nickel and TiOx, leading to a decrease in H2 chemisorption amount, all of which were not beneficial to the catalytic performance. The suitable reduction temperature was 673 K. It was suggested that both the suitable interaction between nickel and TiOx species and the suitable H2 chemisorption amount favored the harmonious effect of nickel and TiOx on the activation of the -NO2 group.

Key words: nickel, titania, supported catalyst, catalytic hydrogenation, p-nitrophenol, p-animophenol