Preparation of Ni/mSiO2 with the existence of hydrogelator: Insight into hydrogelator self-assembly on metal dispersion and catalytic performance in quinoline hydrogenation

Abstract

With the aim of testing whether a low molecular weight gelator could be used as metal dispersion agent for supported nickel based catalysts. A series of Ni/mSiO2-DMBSx (x represents the concentration of hydrogelator during preparation, g mL−1) catalysts were prepared by aqueous wet impregnation of nickel nitrate with the existence of a hydrogelator, [2,4-(3,4-dimethylbenzylidene)-D-sorbitol, DMBS] and used in quinoline hydrogenation to produce 1,2,3,4-tetrahydroquinoline, which is an important synthetic intermediate. The impact of DMBS aggregates on the structure of resulted catalysts was carefully studied by using a series of characterization methods. It was found that the addition of DMBS leading to an increase in Ni dispersion as well as to an enhanced metal-support interaction, which is of benefit for maintaining activity during reactions. Hence, Ni/mSiO2-DMBSx catalysts exhibited better activity in quinoline hydrogenation compared to Ni/mSiO2. Ni/mSiO2-DMBS0.005 showed the best activity and stability due to the better metal dispersion and stronger metal-support interaction among the prepared Ni/mSiO2-DMBSx catalysts.