Highly dispersed nickel catalyst formation and its activity in benzene hydrogenation

Abstract The process of the formation of a supported nickel catalyst obtained by reduction in hydrogen of nickel chloride heterogenized on silica was studied by X-ray photoelectron spectroscopy, UV and Ferromagnetic resonance spectroscopy and the magnetic susceptibility method. No direct dependence between metal dispersion and metal content was found in the range 0.8–4.6 wt.% of nickel. An increase in the reduction temperature from 250 to 360°C resulted in growth of the average diameter of nickel particles from 4.0 to 8.0 nm. Reduction of heterogenized and impregnated nickel chloride catalysts was found to differ considerably. In the first instance, reduction starts at the lower temperature (250°C), but 15% of nickel remains unreduced at 450°C. In the latter, nickel chloride is completely reduced to Ni° in the range 300–450°C. A mechanism of metallic phase formation is suggested for heterogenized nickel chloride catalyst. A study of benzene hydrogenation over this catalyst revealed that the turnover number exeeds the value for impregnated samples by more than one order of magnitude. High stability and easy regeneration of the newly synthesized catalysts should be noted.