Process And Kinetic Study On The Catalytic Hydrogenation Of 2,4- Dinitrotoluene To 2,4-tolylenediamine Over Ni/HY Catalysts

The hydrogenated product 2,4-toluenediamine(2,4-TDI) finds a variety of applications, of which the most important one is the production of toluenediisocynate(TDA), used in the manufacture of polyurethanes. The supported nickel catalyst has been used for some hydrogenation technologies, due to its lower cost, easy availability, high catalytic activity and environmental benefit. In this thesis, the supported nickel catalyst has been attempted to use for the hydrogenation of dinitrobenzene in order to find an effective catalyst with high activity, good selectivity and long life span.In this paper, HY zeolite was used as the carrier, the Ni/HY catalyst was prepared by impregnation precipitation method, and the microstructure of the catalyst was studied by IR, AAS, XRD, BET, H2-TPR and TEM technology. The results showed that the nickel content of the catalyst was 39.1%, and the specific surface area was 345m2/g.Catalytic hydrogenation of 2,4-DNT over Ni/HY catalysts indifferent solvents was studied, which demonstrated that the reaction exhibits the best performance in protic solvents. The reason is the strong hydrogen-bond interaction between the protic solvents with the reactant, intermediates and product due to their excellent hydrogen-bond donating capability, which favors the desorption of the adsorbed intermediates and product from the catalysts and helps to polarize the N=O bonds of the reactant and intermediates. Subsequently, the hydrogenation in the mixed solvents of water and ethanol was investigated, which showed that the reaction can be significantly accelerated by adding water into ethanol and the optimum volume percentage of water is verified to be 40%.And the catalytic activities, selectivies of the catalysts have been evaluated. The results show that under optimal experimental condition with such a mixing speed as 600r/min, When the catalyst particle size less than 150?m, and the reaction into the intrinsic region; the effect of agitation speed, catalyst particle size, 2,4-DNT concentration(0.0549-0.1281mol/L), catalyst loading, H2 pressure(1.8-2.2MPa), and on concentration-time was studied in a temperature range of 343-363 K. Catalyst loading, temperature, pressure and reactant initial concentration had little effect on 2,4-DNT conversion rate, but a key influence on the intermediates conversion rate.An excellent agreement between the model predictions and the experimental data was observed. The reactions activation energies are 26~32kJ/mol, and the heat of the intermediates adsorption are-9~-30 kJ/mol.