Study On The Preparation Of Hydroquinone By Electrosynthesis

Hydroquinone is an important fine organic chemical raw material and is widely used.It can be used for medicine, pesticides, rubber production as an important intermediate.This paper studied that the process of the hydroquinone preparation by electrosynthesis with benzene and phenol as raw materials.In this paper,we used the C6H6 and C6H6O as electrolyte which were cheap,easy to get,in sulfuric acid and potassium sulfate,by ultrasonic shock treatment forming to emulsion. First, the reactant was oxidized to benzoquinone at the anode surface or other intermediate products, and thus at the graphite cathode surface was reduced to hydroquinone.In the experiment, we prepared three kinds of electrode as the anode of lead dioxide by electrodeposition, observed crystal morphology by scanning electron microscopy, analysed the structure of the electrode layer by X-ray diffraction, and investigated electrochemical properties of electrodes by cyclic voltammetry curves and polarization curves.Determined the Ti/SnO2+Sb2O3/PbO2 with the the better performance as the anode in the electrolysis experiments to prepare the hydroquinone.Studied the effect of the electrolysis time, electrolysis temperature,current density, initial concentration of reactants,electrolyte concentration and the phase transfer catalyst on the reaction with benzene or phenol as raw materials. Determined the best conditions with benzene as raw materials to prepare hydroquinone:electrolysis time was 60min, the reaction temperature was 30℃, current density was 40mA/cm2,pH value was 3.7,the initial concentration of benzene was 52%,anode and cathod area ratio was 1.5:1.The best conditions with phenol as raw materials to prepare hydroquinone:electrolysis time was 2h,reaction temperature was 50℃,current density was 50mA/cm2,pH value was 3.0,the electrolyte concentration of potassium sulfate as a supplement wasl.5g/L,the initial concentration of phenol was 25g/L,anode and cathod area ratio was 1.5:1.The results show that:it was due to oxidation of the product,by-products increasing gradually, the current efficiency reducing,the target yield reducing that time delaying,the current density overtop,the initial concentration of raw materials, high temperature and large.With the pH value increasing,the surface ofβ-PbO2 activity decreased and was unstable;the active site of the electrode was covered,so that the electrode took palce passivation,affecting the formation of hydroxyl radicals,so the yield of hydroquinone decreased with the increase of pH value. Increasing the area ratio of anode and cathode appropriatly could decrease transfer resistance to increase the reaction active sites,which can increase the yield.