60% Ni/MgO (wt%) catalysts were prepared by the co-precipitation method and the influence of n-butanol treatment was investigated. The results showed that the treatment with n-butanol improved the dispersion and reducibility of supported nickel, resulted in an increase of H-2 uptake from 410 to 582 mu mol/g, corresponding to an increase of active Ni surface area from 32 to 46 m(2)/g (increased by 42%). Accordingly, the catalytic activity for the hydrogenation of toluene to methyl cyclohexane was significantly increased. Microcalorimetric adsorption of H-2 and CO indicated that the treatment with n-butanol increased the amount of active metal sites on the surface, without the change of electron densities of supported nickel surface. Microcalorimetric adsorption of CO2 and NH3 revealed the strong surface basicity and weak surface acidity for the Ni/MgO catalysts, especially for the reduced ones. The initial heat for the adsorption of acetonitrile was measured to be about 130 kJ/mol on the Ni/MgO catalysts, indicating the strong interaction between acetonitrile and the supported nickel, which might be an important factor determining the activity of nickel for the hydrogenation of aliphatic nitriles. The surface basicity of the Ni/MgO catalysts might play a role in inhibiting the formation of secondary and tertiary amines and therefore improved the selectivity to primary amine during the hydrogenation of lauronitrile to laurylamine. In addition, the Ni/MgO-B catalyst prepared with n-butanol treatment seemed more active for the hydrogenation of lauronitrile.