Studies Of Ni-based Catalysts On Hydrogenation Of Isophthalonitrile To Meta-xylenediamine

Meta-xylenediamine(MXDA)is an aliphatic diamine containing benzene ring.MXDA is widely used as an curing agents of epoxy directly and is useful as a raw material in the production of surfactants,pesticides,rubber stabilizers,pharmaceuticals,disinfectants,painting.M-xylene is the raw material of producing MXDA in the industrial process.MXDA has been manufactured by ammoxidation of pure meta-xylene into isophthalonitrile,followed by hydrogenation of the isophthalonitrile.This production raised much concern owing to the advantages of mild reaction conditions,easy operation and the low cost.In this paper,we prepared a series of nickel catalysts for hydrogenation of IPN to MXDA.We investigated the mechanism of the reaction.The effects of supports,solvents and reaction conditions on the hydrogenation of isophthalonitrile were studied.Moreover,We optimized the synthesis conditions.Furthermore,Combined the characterizations methods,the properties of the catalysts and catalytic performance were studied.The main contents and results are as follows:1.The mechanism of the hydrogenation of isophthalonitrile to meta-xylenediamine was studied.Self-made solvent A can serve as solvent as well as can react with intermediate imine,which is beneficial to the hydrogenation reaction.2.The effects of supports and solvents on the hydrogenation of isophthalonitrile were discussed.Supported nickel catalysts Ni/Al2O3,Ni/SiO2,Ni/TiO2 were prepared.The hydrogenation of isophthalonitrile was carried out in fixed bed and autoclave to study the influence of supports.The results showed the yield of MXDA is highest on the Ni/TiO2 catalyst.Nickel had a better dispersion on TiO2 compared with Al2O3 and SiO2 according to XRD.The acidity may have an effect on the catalytic performance according to NH3-TPD.Besides,the stronger chemisorption to H2 induced by Ni/TiO2 is in favour of the reaction according to H2-TPD.Afterwards,Methanol,toluene,THF and Self-made solvent A were used as solvents to investigate the effects of on the hydrogenation of IPN.The results showed solvents had a great influence on the catalytic performance.The conversion of IPN was close to 100%and the selectivity of MXDA was 90.7%using self-made A as a solvent after reacting 4 h.3.We optimized many factors such as the synthesis conditions in preparation progress and reaction conditions to further improve the activity of Ni/TiO2 catalysts:the precursors of nickel are nickel acetate,the optimal loading of Ni was 20%,choosing appropriate capping agent,optimal pH of preparing catalysts was slightly alkaline.The optimized temperature and pressure was 413 K,2.5 MPa,respectively.