Comparative investigation on catalytic ozonation of VOCs in different types over supported MnO_x catalysts

This paper conducted catalytic ozonation of CB (chlorobenzene) over a series of MnO_x based catalysts with different supports (Al₂O₃, TiO₂, SiO₂, CeO₂, and ZrO₂) at 120 °C. Mn/Al₂O₃ exhibited highest CB conversion efficiency, ca. 82.92 %, due to its excellent textual properties, O₂ desorption, redox ability, and desirable surface adsorbed oxygen species and acidity. O₃ conversion all approached nearly 100.0%, with residual <10 ppm. Mn/Al₂O₃ was further employed to investigate effect of temperature, O₃/CB, and space velocity on CB conversion. Hereafter, catalytic ozonation of single and binary VOCs in different types was performed, i.e., CB, DCE (dichloroethane), DCM (dichloromethane), and PhH (Benzene). Conversion results demonstrated aromatics degraded easier than alkanes and more carbon atoms decreased difficulty, as CB∼PhH > DCE∼DCM, and DCE > DCM; but chlorinated substitution increased difficulty, as PhH > CB. Catalytic co-ozonation of CB/DCE indicated that DCE significantly improved CB conversion to reach totally degradation at low O₃ input, but inhibited DCE conversion, especially at higher ratio of DCE/CB. Co-ozonation improved ozone utilization efficiency, and maintained the original property of catalyst. By contrast, CB/PhH co-ozonation displayed very mild effects. Finally, critical intermediates during catalytic CB ozonation, i.e., DCM, carboxyl and formic acid, were detected from mass spectrum results.