Synthesis Of 3,3'-dichlorobenzidine By Pd/C Catalytic-hydrogenation

2,2'-dichlorohydrazobenzene was prepared from o-nitrochlorobenzene, using 0.8% Pd/C as catalytst in the base media .Some parameters including the rate of the hydrogen consumed, the mass fraction of the sodium hydroxide, reaction temperature and co-catalytic etal., was investigated in our experiments. Optimum reaction conditions were determined by orthogonal experiments e as follow: o-nitrochlorobenzene 30g; reaction temperature 75 ℃, mass fraction of sodium hydroxide 25%, Pd/C catalystl .2g, the dosage.of NQ 0.08g, The high active of Pd/C catalyst can be held after used repeatedly for 5 times under optimum conditions, and the yields of DHB were all more than 94.5%. Moreover, the function of the co-catalytic was discussed. The reason that the active of catalytic was descend was studied, which reveals that the catalytic was not poisoned by Cl~-, aniline or o-chloroaniline. However, active of catalyst depended on the size of active carbon, when the size of active carbon was in the range of 100-150 mesh,the used-life and selective of the catalytic was fine. The catalyst owned high active after used at least for 14 times, and the yield of DHB was always above 90.0%.Some parameters including reaction temperature, mass concentration and dosage of the sulfur acid reaction time etc., was discussed through different rearranged -methods. For each experiment under optimum reaction conditions, the yields of DCB from DHB was up to 90.0% .Moreover, gross yield was up to 80.0-85.0%, the ammonia group value was 95.0%, and the purity of chromatogram was above 97.5%.