液相還元法によるNi金属超微粒子の合成と水素化反応触媒への応用

抄録

Amorphous metallic Ni ultrafine particles were synthesized in aqueous or nonaqueous media with a reducing agent, NaBH₄, by the liquid-phase reduction method. Their size was affected by the synthesis temperature and drop rate of the reducing agent addition. Because the reduction rate of Ni cation into metal was very high, under the condition that the supply of a reducing agent was a rate-determining step a particles size was considerably promoted. With increasing in temperature the size was decreased, because the reduction rate was increased and nuclei numbers were enlarged. As in aqueous media at high temperature the decomposition rate of a reducing agent exceeded that of the reduction into metal, no metallic Ni ultrafine particles were obtained. The size of Ni particles synthesized in 2-propanol as a solvent at 82°C, the boiling point, was 50nm in volume average. The particles were found as a catalyst highly active for 1-octene hydrogenation.It is to be noted that cyclohexene was predominantly obtained in the benzene hydrogenation with using the particles. However, they didn't play a role of a hydrogenation catalyst but provided hydrogen derived from a reducing agent in preparation to benzene; the reaction continued until the complete consumption of hydrogen in a particle.