Abstract: In the electrolytic process of out-cell indirect electrosynthesis of benzaldehyde, electrolytic yield of electrooxidating Ce³⁺ to Ce⁴⁺ in an undivided electrolytic cell was lower, while in diaphragm electrolytic cell would cause a high energy consumption. Based on this, a research with a combination of indirect electrosynthesis benzaldehyde and direct electroreduction maleic acid to succinic acid was carried out, and a new paired electrosynthesis system was constructed, that was, ion membrane paired electrolysis for preparations of Ce⁴⁺ on PbO₂/Pb anode coupling with succinic acid on Pb cathode using sulfuric acid solution as medium under ultrasonic radiation, then oxidizing toluene to benzaldehyde with the Ce⁴⁺ solution prepared in the first step. Experimental results showed that the synthesis of benzaldehyde and succinic acid by paired electrosynthesis with on-line ultrasound was feasible, and a high current efficiency could be obtained in both cathode and anode, which was 92.71% and 87.81% in average, respectively. Thus the total current efficiency was up to 180.52%. The percent conversion of maleic acid reached 92.09%, and the bath potential decreased 0.25 V. Besides, a good result was also obtained in oxidating toluene to benzaldehyde using the Ce⁴⁺ solution with on-line ultrasound, the yield of benzaldehyde was 95.78% in average.

Key words: Sonoelectrosynthesis, Paired electrosynthesis, Benzaldehyde, Succinic acid