Kinetics and mechanism of catalytic ozonation of acetone in air over MnOx/Al2O3 catalyst

The catalytic ozonation of acetone using MnOx/Al2O3 catalysts prepared by polyol and impregnation methods was investigated. The synthesized catalysts exhibited excellent catalytic activity at room temperature with conversions of around 95%. Although many studies focus on catalytic processes to oxidize VOCs more efficiently, the mechanism behind this reaction is still unknown. The In-situ DRIFTS and activity results show that alumina not only acts as a support for MnOx, but it also involves in the reaction with acetone and creates surface carboxylate intermediates. MnOx sites are required for further oxidation of the generated intermediates to the final products. Therefore, Langmuir-Hinshelwood dual-site (LHd) mechanism was evaluated to demonstrate the reaction pathway. The kinetic data were expressed well by LHd model, indicating that both MnOx and Al2O3 sites are essential and involved in the reaction. The cooperation of these sites on the surface of the catalyst provides the adjacent attack and migration of intermediates and enables the dual-site mechanism. The reaction order, activation energy, and kinetic parameters were determined for both catalysts and confirmed that the model is physically meaningful. Other than LHd, common Langmuir-Hinshelwood single-site (LHs) and power law (PL) kinetic models were tested to describe the acetone ozonation process and kinetic mechanism. Although the models can describe the reaction kinetic adequately, the LHs did not properly fit the experimental data suggesting that more than a single site is involved in the reaction and PL model in unable to provide the mechanistic view for the reaction.

Automated summary

The catalytic ozonation of acetone using MnOx/Al2O3 catalysts prepared by polyol and impregnation methods has been studied, showing excellent catalytic activity at room temperature. Results suggest that alumina not only acts as a support for MnOx, but also participates in the reaction with acetone, forming surface carboxylate intermediates. The Langmuir-Hinshelwood dual-site (LHd) mechanism was evaluated to demonstrate the reaction pathway, indicating the essential involvement of both MnOx and Al2O3 sites in the reaction.