Electrochemical Synthesis Of2,2′-Dichlorohydrazobenzene From Ochlornetrobenzene

2,2’-dichlorohydrazobenzene (DHB) is an important intermediates of3,3’-dichlorobenzidine (DCB), which widely used in pharmacy and dyesindustry, such as for synthesis of benzidine yellow and permanent yellow HR,etc. For having so large a market share, much more attention has been paid onthe study about the production technology and method of synthesis DHB. Thetraditional synthesis methods of DHB, such as metal-acid reduction, sodiumhydrosulfide reduction, catalytic hydrogenation reduction, have not enjoyedtheir increasingly wide application to industrial area due to the expensivenessof the catalyst, high cost of equipment and environmental pollution.Electro-chemical reduction with ion-exchange membrane has thus come to beregarded as the most attractive synthesis method, with merits includingenvironmental friendliness, low cost, and mild reaction conditions. DHB was synthesized by the electrochemical reduction ofo-chloronitrobenzene using the ion-exchange membrane method. The effectsof different ion-exchange membrane, current densities and catalysts on thesynthesis were investigated. The electrochemical properties and productchanging of membrane-separated cell are investigated by Electrochemicalworkstation and Liquid chromatography. The results show that the yield ofDHB could reach to95.4%with a moderate current density (e.g.,3.125A/dm~2)and catalysts (PbO) in5hours. The properties of ion exchange membrane inelectrolytic cell have important effect for the synthesis yield of DHB, whenthe ion exchange membrane has high water content and ion exchange capacity,synthesis reaction is beneficial to improve the yield of DHB and decrease thereaction time. Catalyst activity of PbO is better than that of SnO2and Sb2O3inthe electrochemical synthesis reaction.A serious of experiments was designed to observe the cycle technologyand investigate the circling of the anolyte and catholyte. With the increase ofcycle number of cathode liquid, the reaction time is shortened and the yield ofDHB stability in high content.