The effects of calcination temperature and reduction temperature on the silica supported nickel catalyst

which were prepared by impregnation of silica with nickel nitrate solution

were investigated in the liquid-phase hydrogenation of m-dinitrobenzene to m-phenylenediamine. The nature of the catalysts was discussed based on the characterization results of nitrogen adsorption-desorption (BET)

X-ray diffraction (XRD)

transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). With increasing calcination temperature

the surface area of the catalyst decreased progressively

but the interaction between NiO and SiO2 became stronger. At the same time

the crystallite of nickel increased with the increase of calcination temperature. The optimal calcination temperature was 773 K

at which highly dispersed nickel species could be present. The reduction temperature also affected the properties of the catalyst. At a lower temperature

the catalyst could not be reduced completely

while an improperly high temperature would cause sintering of the catalyst. The catalyst reduced at 723 K showed higher catalytic activity and selectivity.