Efficiently Paired Electrosynthesis of Hydroquinone from Phenol by Refreshing the Passivated Pb Anode

In this work, a novel paired electrosynthesis was adopted to prepare hydroquinone from phenol at Pb electrodes. The electrolysis results showed that the anode was passivated during the phenol oxidation, leading to a decrease in anode activity. Characterizations of the passivated anode revealed that the by-products were absorbed on the anode surface, such as polymers (produced from the electrochemical polymerization of phenol), and poorly conductive PbSO4 appeared. Therefore, the exchange of anode and cathode in the reaction intervals was done to refresh the passivated anode. No sticking organics were basically found on the refreshed anode surface and the Pb oxides were reduced to Pb. The yield of hydroquinone reached to 77.4 % by refreshing the passivated anode at the optimized conditions of 20 mA/cm2, 4.8 A & sdot; h, and 30 degrees C. Furthermore, the 71.1 % yield of hydroquinone was maintained when the catholyte was recycled after four extraction cycles. This study presents a promising technique for hydroquinone preparation. The yield of hydroquinone can reach 77.4 % from phenol via paired electrosynthesis by refreshing (exchange of anode and cathode in the reaction intervals) the passivated anode (Pb) and the 71.1 % yield of hydroquinone maintains after four recycling of the catholyte.+image