Abstract: The structure and catalytic property of the supported Ni/γ-Al2O3catalysts prepared with different nickel salt precursors for hydrogenation of α-pinene have been studied usingX-raydiffraction, UV-VIS diffuse reflectance spectroscopy, temperature-programmed reduction, CO chemisorption, and microreactor tests. It has been shown that the catalytic hydrogenation activity of the Ni/γ-Al2O3catalyst increases with increasing Ni loading, and the catalytic activity of the nickel acetate-derived Ni/γ-Al2O3catalyst is much higher than that of the nickel nitrate-derived catalyst. The catalyst characterization results indicate that the catalytic hydrogenation activity of Ni/γ-Al2O3catalysts prepared with different nickel salt precursors is correlated to the different ratios of Ni2+ions in the tetrahedral and octahedral vacancies ofγ-Al2O3and the different reduction degrees of the NiO/γ-Al2O3precursors. When the nickel ion loading is far below the dispersion capacity, the supported nickel ions preferentially incorporate into the tetrahedral vacancies ofγ-Al2O3. With increasing nickel loading, the ratio of Ni2+ions that incorporate into the octahedral vacancies ofγ-Al2O3increases. The dispersion capacity of nickel ions onγ-Al2O3derived from nickel acetate is lower than that of the sample derived from nickel nitrate due to the greater shielding effect of acetate anions than nitrate anions. Moreover, the ratio of octahedral Ni2+to tetrahedral Ni2+on the nickel acetate-derived sample is higher than that on the nickel nitrate-derived sample because of the lower density of octahedral vacancies onγ-Al2O3. As octahedral Ni2+ions are easier to be reduced to the metallic state than tetrahedral Ni2+ions, the catalytic activity of the Ni/γ-Al2O3catalyst prepared with the nickel acetate precursor is much higher than that of the catalyst of the same nickel loading prepared with the nickel nitrate precursor.

Key words: nickel, alumina, supported catalyst, precursor, α-pinene, catalytic hydrogenation