Effects of Ni‐Loading on the Performance of Ni/SiO2 Catalysts for the Highly Selective Hydrogenation of Biphenyl to Cyclohexylbenzene

Abstract This article investigated the effects of Ni loading on the performance of Ni/SiO 2 catalysts for the selective hydrogenation of biphenyl (BP) to cyclohexylbenzene (CHB). The catalysts were characterized by the techniques of thermogravimetric analysis, X‐ray powder diffraction, N 2 ‐physisorption, scanning electron microscope, inductively coupled plasma‐atomic emission spectroscopy, transmission electron microscope, H 2 temperature‐programmed reduction. It was found that under the given reaction conditions, BP conversion showed an increased trend with the increasing Ni loading. However, 25 % Ni/SiO 2 catalyst exhibited the lower CHB yield than 20 % Ni/SiO 2 catalyst, which was attributed to the overhydrogenation of BP on the former with the excessive metal active sites. Besides, over 25 % Ni/SiO 2 catalyst, BP conversion gradually increased with the extended reaction time, the enhanced hydrogen pressure or the improved temperature, but CHB selectivity and yield increased first and then decreased. Additionally, isopropanol was considered to be the best one among the representative solvents in BP hydrogenation reaction. Moreover, the conversion of BP and the selectivity/yield of CHB could keep above 99 % and 96 %, respectively, after eight consecutive cycles.