Studies Of Transition Metal Catalysts On Hydrogenation Of Isophthalonitrile To Meta-xylenediamine

Meta-xylenediamine(MXDA)is an aliphatic diamine with benzene ring.MXDA can be used as an epoxy resin hardener directly and raw material in producing polyurethane,photo-plastics,rubber chemicals and painting.At present,there are two ways to produce MXDA,one is that m-xylene first reacts with bromine,then ammonia reacts with the product after bromination.However,this reaction pathway is too complicated with a great cost and pollution.The other is hydrogenation of isophthalonitrile(IPN)which is produced from m-xylene after reacting with ammonia and air.This way raised much concern for the advantages of mild reaction conditions,simple process and low cost raw material.However,the present process has some disadvantages about the low selectivity of MXDA and the corrosion of instrument for the addition of strong acid or base,restricting the applying in industrial manufacture.In this paper,we prepared a series of catalysts for hydrogenation of IPN to MXDA.And we not only investigated the effect made of the active metal elements,carriers,second component introduction,catalysts preparation method,and reaction conditions to the catalysts performance,but the stability of catalysts under the optimized conditions.Furthermore,we discussed the relation between the catalytic properties and the catalysts structure with the application of characterization methods.1.We prepared Pd,Pt,Co and Ni based catalysts supported by Al2O3 through impregnation method to select the active metal of the catalysts with evaluating them in the hydrogenation of IPN.The results showed that the yield of MXDA is highest on the Ni based catalyst.Followed,we prepared Ni-based catalysts supported on SiO2,TiO2,Al2O3,the reaction showed that the yield of MXDA is highest on the Ni/Al2O3 catalyst.Besides,during the investigation of the catalysts pretreatment and reaction conditions which had much effect on the reaction activity and selectivity,we found that calcined with high temperature would increase the interaction between the metal and the supports which contributed to lower activrity of catalysts.The conversion rate of IPN raised up with increasing the reaction temperature and pressure.The conversion was higher then 99.9%,and the selectivity of MXDA achieved 96.5%after the catalyst was used for five times during the recycling experiments.2.The investigation of the effect of introducing of Pt to Ni/Al2O3 catalysts performance shows that the presence of Pt appears to promote the reduction of nickel oxides.Besides,Pt also raised catalytic activity and stability with increasing the dispersion of Ni.3.To further improve the activity of Ni/Al2O3 catalysts,we prepared the catalysts through deposition-precipitation method.After investigation,we finally determined the preparation and preltreatment conditions.The nickel particle size was about 3nm in the DP(deposition-precipitation)Ni/Al2O3 catalysts obtained finally.The evaluation results showed that in the conditions of 413K,pressure of 3.5MPa,m(catalyst)/m(IPN)=5%,IPN conversion was more than 99.9%,and the selectivity of MXDA achieved 97.5%.