アモルファス合金超微粒子の液相合成 第２報 液相還元法合成Ｎｉ金属，Ｎｉ‐Ｚｎ合金超微粒子の表面反応特性

Abstract

Since metallic ultrafine particles are known to have characters different from bulk-phase, such particles are expected to be applied to various materials, in particular, catalysts. The surface reaction characteristics of metallic ultrafine particles produced by the liquid-phase reduction method were investigated. The possibility of such particles as a catalyst for benzene hydrogenation which was sensitive to the surface character, was also studied, giving the following results.(1) Metallic Ni ultrafine particles synthesized by the liquid-phase reduction method were found more active for benzene hydrogenation to cyclohexane than the conventional Ni catalyst. The catalytic activity reached a maximum at a quantity of reducer, LiAlH4, enough for the reduction of Ni cation into metal.(2) The addition of Zn to Ni ultrafine particles resulted in the great enhancement of catalytic activity. This Zn effect could be accounted not only by the change in a surface area, but also by the ensemble and ligand effect.(3) Metallic Co ultrafine particles were found to have high catalytic activity which was much higher than on Ni particles.(4) The promotional effect of the addition of Zn to Co ultrafine particles were found negligible. Since no Co-Zn alloy phase in the X-ray diffraction analysis was obaerved for Co-Zn bimetallic ultrafine particles, the ensemble effect and/or the ligand effect of Zn to Co could not be induced.