Synthesis of m-phenylenediamine from m-dinitrobenzene over silica-supported nickel catalyst

The liquid-phase hydrogenation of m-dinitrobenzene to m-phenylenediamine was studied over silica-supported nickel catalyst. The effects of Ni loading, calcination temperature, and reduction temperature on the physicochemical characteristics and activity of the catalyst were investigated by XRD, TEM, TPR, and activity tests. The results show that the silica-supported nickel catalysts exhibited high catalytic property, which depended on the particle size of Ni and the reduction degree of NiO. The optimal Ni loading, calcination temperature and reduction temperature of the catalyst for m-dinitrobenzene hydrogenation were found to be 20 wtc/b, 773 K in air and 723 K, respectively. Under this condition, 97.2% conversion of m-dinitrobenzene and 88.9% yield of m-phenylenediamine were obtained at 373 K and 2.6 MPa hydrogen pressure. The particle size of nickel species increased with the increase in Ni loading or calcination temperature. In addition, it was found that the catalyst could not be completely reduced at low reduction temperature, whereas high reduction temperature led to the sintering of Ni.