Study On Catalytic Hydrogenation Of M-Dinitrobenzene Over Nickel-Based Catalyst

The catalytic hydrogenation technology of m-dinitrobenzene in liquid phase is an attractive and elegant routine for the production of m-phenylenediamine, owing to the advantages such as high product yield, good product quality and much less pollution to environment. Thus, it is practically significant to develop a new catalyst with high catalytic property for m-dinitrobenzene hydrogenation. The supported nickel catalyst has been long-term used for some hydrogenation technologies, due to its lower cost, easy availability, ideal catalytic activity and environmental benefit. Up to now, however, few works about hydrogenation of m-dinitrobenzene over supported nickel catalyst has been reported. In this thesis, the supported nickel catalyst has been attempted to use for the hydrogenation of m-dinitrobenzene in order to find an effective catalyst with high activity, selectivity and long service life.A series of supported nickel-based catalysts for the liquid-phase catalytic hydrogenation of m-dinitrobenzene to m-phenylenediamine have been designed and prepared by the incipient impregnation methods. The effects of different types and contents of promoters on the physico-chemical properties of catalysts have been characterized, using the technologies of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and the catalytic activities, selectivies and stabilities of the catalysts have been evaluated. It has been found that among the catalysts prepared by impregnation method, the nickel-based catalyst supported on SiO2 with the nickel content of 20wt% which is calcinated at 773K and reduced at 723K in hydrogen respectively, has showed the better activity and selectivity. Before impregnating nickel, the addition of La2O3 promoter and K2O promoter into Ni/SiO2 could enhance the activity, selectivity and stability of catalyst apparently.Under the reaction conditions: alcohol is used as solvent, the reaction temperature is 365 K, the pressure is 2.9 MPa, the weight ratio of m-dinitrobenzene to catalyst is 10:1, it is found that the activity of the nickel-based catalyst supported on SiO2 with 20wt% Ni, 3wt% La and 3wt% K2O is the best one among all the catalysts we researched in this work. After 1 hour, conversion of m-dinitrobenzene, selectivity and yield of m-phenylenediamine are 99.3％,99.5％和98.8％, respectively. The catalyst K-La-Ni/SiO2-1 could be utilized over 8 times without apparent decrease of catalytic performances.