Dehydrogenation activity of nickel-tin-silica catalyst

Abstract The effect of nickel-to-tin ratio on the following dehydrogenation reactions is studied, namely, cyclohexanone to phenol, cyclohexylamine to aniline, cyclohexane to benzene and 2-propanol to acetone. The optimum ratio catalyst for each reaction was Ni Sn = 2.5 (atomic ratio), 8, 10 and 8, respectively. The rate of each reaction was zero order with respect to the partial pressure of reactant for cyclohexanone and 2-propanol, and first order for others. Metallic nickel and β-tin were observed on the catalysts by means of X-ray diffractometry. The presence of the alloy phases, such as Ni3Sn4, Ni3Sn2 and NiSn, on the catalysts was also inferred on the basis of X-ray diffraction study on nickel-tin sintered metal. The presence of molten tin on the catalyst above about 230 °C was proved by differential thermal analysis. Intimate contact of nickel and molten tin probably results in the formation of alloy phases without difficulty. The effect of the addition of tin seems to moderate the strong adsorption of polar substances on nickel-silica catalyst.