Acetophenone preparation via continuous bubbling of ozone for catalyst-free ethylbenzene oxidation

Acetophenone is essential to chemical synthesis. Hence, completely using coal tar resources via liquid-phase oxidization to obtain acetophenone is crucial. This study demonstrates a novel, efficient, and environment-friendly technique for converting ethylbenzene to acetophenone based on ozone oxidation and continuous bubbling. Analysis of the mass transfer characteristics of the continuously bubbling ozone in various polar organic solvents showed that alcohol solvents had a higher equilibrium concentration than ethyl acetate and acetone. Equilibrium ozone concentrations were identical in solvents such as chlorinated methane. The solubility of ozone in different solvents may be affected by hydrogen bonding or dipole–dipole interactions between ozone and the solvent molecules. Ethyl acetate was found to be the best solvent after the ozone oxidation conditions of ethylbenzene were refined. The highest amount of acetophenone produced was 74%, and the reaction duration was 120 min; and the corresponding molar ratio of ozone to ethylbenzene was 1.6. Finally, the oxidation of ethylbenzene using ozone was proposed. Hydrogen peroxide accelerated this process, while ethanol slowed it down. The hydroxyl, alkyl, and superoxide free radicals in the reaction system were confirmed via electron paramagnetic resonance studies. Results showed that the key chemical process is indirect ozone oxidation.