Electrochemical Synthesis Of 2,2'-Dichlorohydrazobenzene From O-Chlornetrobenzene

2,2'-dichlorohydrazobenzene (DHB) is an important intermediates of organic and material of fine chemistry, which widely used in pharmacy and dyes industry,such as for synthesis of benzidine yellow and permanent yellow HR, etc. A series of paints based on these account for 25% of total output in the world. so more attention were paid on the study about the production technology and method of DHB, especially at the end of last century there were many kinds of synthesis methods occurred. Metal-acid reduction, hydration hydrazine reduction, catalytic hydrogenation reduction and electro-chemical reduction successively were carried out for preparation of DHB from o-chlornetrobenzene (o-CNB). Due to its pollution of the environment and long reaction time, Metal-acid reduction and hydration hydrazine reduction have been phased out and no longer recommended in many countries. Compared with catalytic hydrogenation reduction now widely used and accepted by many plants mainly in developing countries such as China and India, but conducted at hard reaction condition, with complicated facilities and expensive,precious metal catalysts (Pt/C), electro-chemical reduction has many merits:environmental friendliness, low cost and mild reaction condition, using electron as reducing agent and been called "green chemosynthesis method", and been regard as the most attractive method.In this paper, The electrochemical synthesis method was introduced for the synthesis of DHB by using steel plate electrode as anode and porous Ni-Fe electrode as cathode. Some different electrodes was prepared to study theirs performance of electrochemical synthesis, for example, steel palate electrode, nickel palate electrode and porous Ni electrode, and the preparation methods of theirs were also included. Especially a novel synthesis method of DHB from o-chlornetrobenzene (o-CNB) in a membrane-separated cell was developed based on the porous nickel electrode, on which PbO particles dispersed finely over its surface and in it which indicated by SEM and XRD analysis. The electrochemical synthesis in an aqueous-organic solution containing o-CNB, sodium hydroxide, toluene and SDBS were investigated. The effects of cathodic surface morphology, electrolyte temperature, initial concentration of o-CNB, modes of dispersion and toluene on electrolytic reduction are discussed. It was found that the optimum reaction temperature is 70℃, moderate current density (e.g.,3-6A/dm2), and flow rate were beneficial to improve the hydrogenation reduction and yield can reach 91%. A pilot test on the synthesis of DHB from was employed under the cooperation with tai'an dry Co. Ltd in Shandong province, and higher yield of DHB was achieved compared with the synthesis in lab by using the alike Ni electrode.