Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone in airlift sonochemical reactor

Abstract

Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone was studied in a new type reactor – the airlift loop sonochemical reactor. The reactor plays a synergistic effect of sonochemsity and higher oxygen transfer rate. The influences of ultrasound intensity, reaction temperature, the molar ratio of benzaldehyde to cyclohexanone and oxygen gas flow rate on the conversion and selectivity of cyclohexanone were investigated and discussed. Under ultrasound, the amount of benzaldehyde can be reduced from 75% to 67%. Ultrasound not only intensified the rates of reactions but also increased the yield of product. The optimized operation conditions are listed as follows: the reaction temperature is 30 °C, the molar ratio of cyclohexanone to benzaldehyde is 1:2, the oxygen gas flow rate is 1.15 cm s −1, and ultrasonic irradiations 2 h at 40 kHz, 2.25 W cm −2. Under the optimum operation conditions, the average molar yield of ε-caprolactone comes up to 87.7%.