Catalytic Hydrogenation Of P-Phenylenediamine To Prepare Diaminocyclohexane Over Raney-Ni

1,4-diaminocyclohaxane(DACH) is an important intermediate in the polyurethane industry. In th research, the important point in the thesis is to develop a process route how to prepare DACH hydrogenated from PDA, including quantitative analysis of the PDA hydrogenation products, thermodynamic and kinetics analysis of the hydrogenation reaction, catalyst preparation and optimization of operating conditions for PDA hydrogenation.The optimum reaction conditions for conversion of PDA hydrogenation were determined by experiments as follows:PDA mass was 5g, and the mole ratio to H2SO4 was 1:1.16, and DI water was 50ml, the temperature was 80℃, the pressure was 3MPa, the reaction time was 8h, and catalyst was 3ml, and the selectivity was 30.781%. In the paper, thermodynamic analysis of the PDA hydrogenation system was done by the group contribution approach; While dynamic model was established on the basis of the dynamic analysis, and in the exclusion of mass transfer resistance influence inside and outside, the model of dynamic parameters of the main reaction and reaction activation energy was determined under the condition of the eigenvalue through dynamics experiments:-dC对苯二胺/dt=1.0289×106exp(-41294/RT)C对苯二胺PH20.12.Then we used orthogonal experiments to study reaction conversion of PDA hydrogenation, hoping to get a high selectivity of DACH based on high conversion. So on basis of rising selectivity, decreasing temperature was needed. The better selectivity was 55.003% of PDA when at 70℃,5MPa,36h.Considering by-products caused by the hydrolysis reaction, some change was needed to adjust the system, under the condition of 5g PDA, and the mole ratio to H2SO4 was 1:1.16, the optimum condition of reaction conversion with ethanol as solvent was studied through the orthogonal experiments:the temperature was 80℃, the pressure was 4MPa, the reaction time was 8h,3ml catalyst. Also the conversion could reach 99%, and selectivity was 43.736%. The life of Raney-nickel catalyst used in PDA hydrogenation was also studied, analysised the reason of catalyst deactivation from literaries, and the catalyst activity got certain recovery through regeneration.