Synthesis of propylene oxide in a paired electrolytic system: Studies on the mechanism and operating factors

Epoxidation of propylene to propylene oxide (PO) by means of paired electrolysis was studied in a bubbling system. An electrolytic cell, divided by an anion exchange membrane, was designed for producing PO in both anode and cathode compartments simultaneously. In the anode compartment, AgNO₃ in the anolyte was used to form redox mediator, Ag⁺/AgO⁺, for indirect epoxidation of propylene. In the cathode compartment, oxygen was introduced into an acidic aqueous catholyte to form H₂O₂, hydrogen peroxide, which further epoxided propylene. The examined factors, which affected the amount of PO production per unit faraday, were the applied current, gas flow rate, electrolyte concentration and temperature. The optimum operating conditions of the anode and the cathode compartments were obtained. The overall amount of PO production per unit of energy consumption was evaluated, and a mechanism of paired electro-epoxidation of propylene is also proposed.