Synthesis Of DHB By Catalytic Hydrogenation

2,2'-dichlorohydroazoxybenzene(DHB) is an important commercial interme -diate of 3,3'-dichlorobenzidine(DCB). Synthesis of DHB by hydrogenation of ortho-nitrochlorobenzene is studied in this paper. SEM, nitrogen adsorption and ICP are used to analyze the activated carbon. Platinum catalysts supported on the activated carbon with high purity, large surface area, large pore volume and appropriate pore structure usually exhibit higher activities for hydrogenation of ortho-nitrochlorobenzene to 2,2'-dichlorohydrazobenzene, the content of metal affects less. The process to prepare catalyst is optimized in this paper..The catalyst prepared from 0.05625g/ml H2PtCl6 with pH3 added in 90 minutes shows greater catalytic performance than those prepared under other conditions. The selectivity of the catalyst is 88%, the activity of the recycled catalyst and selectivity to DOB remained constant after 10 runs of recycle.Rideal-Eley course expresses the process better at the temperature from 313-343K and pressure from 0.3~0.6MPa. The intrinsic kinetic is evaluated by simulation of the experimental data, kinetic equations of principal and secondary reactions are as follows:principal reactionsecondary reactionActivation energy is 24.0 kJ/mol and 19.7kJ/mol respectively. Therefore, the temperature of reaction and pressure should be higher.