Study On The Supported Nickel-based Catalyst For Dinitrotoluene Liquid Phase Hydrogenation

Toluenediamine(TDA),the alternate name of which is diaminotoluene,is an important chemical raw materials and chemical intermediate.In industry,TDA is synthesized by dinitrotoluene(DNT)liquid phase hydrogenation in the condition of organic solvent and catalyst.At present,the noble metal and Raney-Ni catalyst are the main industrial catalysts used in liquid phase DNT hydrogenation.The noble metal catalyst of Pd/C and Pt/C et al has the advantage of low pressure and high activity,but the price of which is expensive,and the catalyst is easy deactivation by coke and poisoning.The price of the Raney-Ni catalyst is low,but it is easy to spontaneous combustion in the air.Therefore,the development of low cost,high activity in the condition of low pressure and independent intellectual property rights for DNT hydrogenation catalyst is of great signification.Supported Ni-based catalysts possessing the advantage of low cost and activity,is widely used in a variety of hydrogenation reactions.In this paper,a series of supported Ni-based catalysts was prepared by impregnation method,and firstly applied in the hydrogenation of dinitrotoluene to diaminotoluene.The effects of carrier types,Ni loading,calcination temperature,reduction temperature and additives on microstructure and catalytic properties were investigated.And the catalysts were characterized by XRD,XPS,and TPR,BET and H2-TPD.The catalytic performance of Ni-La/Si02 catalyst was the further improved by optimizing the reaction conditions of reaction temperature,reaction pressure and the amount of catalyst and solvent.The main conclusions as follows:(1)A series of supported Ni-based catalysts were prepared by impregnation method,and the effect of carriers on microstructure and the catalytic performance was studied.The characterization of XRD,BET,H2-TPR H2-TPD and XPS showed that Ni/Si02 catalyst exhibited higher active surface area and appropriate strength of hydrogen adsorption compared with the catalyst supported on others carriers.Therefore,Ni/Si02 catalyst revealed best catalytic preformance in the reaction of dinitrotoluene hydrogenation.The conversion of the DNT and the selectivity for TDA reach 45.51%and 76.38%,respectively.(2)The effect of nickel loading on microstructure of the Ni/Si02 catalyst and catalytic hydrogenation performance of were investigated.The results showed that the conversion of the DNT and the selectivity for TDA reach 93.68%and 97.73%,respectively,when Ni loading was 28wt%.(3)The effects of calcination temperature and reduction temperature on microstructure of the Ni/SiO2 catalyst and catalytic hydrogenation performance were studied.The results showed that the hydrogenation performance Ni/SiO2 catalyst calcined and reducted at 500? is the highest,and the conversion of DNT and the selectivity for TDA reach 94.03%and 98.01%,respectively.(4)The effect of the additives of La,Fe,Zr,Ce and Co on the microstructure and the hydrogenation performance of DNT were investigated.The results showed that the introduction of the La additives improved the dispersion of Ni grains on the carrier surface and the catalytic performance of Ni/SiO2-The conversion of DNT and the selectivity of TDA were 98.13%and 99.06%,respectively.(5)The influence of La content on the microstructure and catalytic hydrogenation performance of Ni/SiO2 catalyst were studied.The results showed that the introduction of La additive improved the dispersion properties of Ni and lowered the reduction temperature,but also weaken the strength of Ni-H bond,leading to the easy folwing of H2 species more and participate into the reaction.When La addition is 7 wt%,the performance of the supported Ni-La/SiO2 catalytic was best,The conversion of the DNT and the selectivity for TDA reach 99.51%and 99.18%,respectively.(6)The reaction conditions were optimized by the Ni-La/SiO2-7wt%catalyst.The results showed that The optimal reaction conditions were as follows:reaction temperature 110 ?,reaction time 90 min,the reaction pressure of 2 MPa,the amount of catalyst 0.5 g,solvent methanol.Under the optimal reaction conditions,the Ni-La/SiO2-7wt%catalyst exhibited the best catalytic performance,and the conversion of DNT and the selectivity for TDA are 99.53%and 99.65%,respectively.