Nanonickel particles supported on silica. Morphology effects on their surface and hydrogenating properties

We have studied a whisker-like nickel phase supported on silica and obtained by the reduction of nickel acetate in aqueous hydrazine media. Under H-2/300degreesC flow, the obtained phase remains stable when the reduction is carried out at 70 degreesC for 2 h whereas it totally tranforms to spherical-like particles when the reduction is performed at 80 degreesC for 30 min after a gradual heating from room temperature. It is shown that the whisker-like nickel phase adsorbs and stores more hydrogen than the spherical-like nickel particles. It also exhibits a higher activity in the gas phase hydrogenation of benzene ( 3 - 4 times greater). In acetylene hydrogenation, it strongly favors the cylotrimerization process to benzene at the expense of the processes to linear C-2 - C-4 hydrocarbons. This work is a direct demonstration of the influence of the metal phase morphology of nickel supported catalysts on their surface and catalytic properties.