Pd添加ラネー銅触媒の組織におよぼす凝固条件とPd量の影響

Abstract

Cu-70 at%Al alloys with various amount of Pd were solidified at different cooling rates and structures of the as-solidified alloys and catalysts made by leaching Al from them were examined by SEM, DSC and X-ray diffraction as a basic study for improvement of the catalytic activity of Raney copper catalysts for the hydration reaction of acrylonitrile which is important for production acrylamide. The specific surface area of the catalysts were measured by the BET Ar-absorption technique. The activity of the catalysts was evaluated by the conversion ratio from acrylonitrile to acrylamide by the hydration reaction. The results are as follows.(1)In the conventional slowly solidified alloys, most of the added Pd was distributed in primary ε phase and its solubility in the θ phase was quite few. On the other hand, in the rapidly solidified alloys, the formation of the primary ε phase was almost suppressed and Pd was supersaturated in the θ phase.(2)Raney copper with soluted Pd was newly obtained by leaching the θ phase with Pd. This suggests that the rapid solidification process is an effective process to get new catalysts.(3)Specific surface area of Raney copper produced by leaching rapidly solidified alloys increased with Pd content. It was about 3 times higher in the 1.5 at%Pd alloy than that in the Pd-free alloy.(4)The catalytic activity of 1.5 at%Pd catalysts showed a maximum, but its value per unit specific surface area decreased with Pd content.