Catalytic ozonation of p-xylene over Mn/Ce oxide nanorods treated by vacuum deoxidation

Xylene with high photochemical activity is commonly used as a raw material and organic solvent. The treatment of waste gases containing xylene is a necessary measure to ensure the air quality. Mn/Ce oxide nanorods were prepared using SBA-15 as a template and subjected to vacuum deoxidation for catalytic ozonation of p-xylene. Hydrothermal demolding conduced to detach the nanorods to improve the surface area and porosity, providing massive active sites for catalytic ozonation. The results indicated that numerous Mn-O-Ce solid solution structures formed in Mn/Ce composite oxides, especially Mn0.5Ce0.5Ox, to enhance weak- and medium-acid sites and oxygen vacancies (OVs) on the catalysts. Vacuum deoxidation effectively and facilely raised OVs for the catalysts. Vacuum-deoxidated Mn0.5Ce0.5Ox with the most Mn-O-Ce structures achieved the highest removal rate of pxylene and CO2 selectivity since the most OVs and weak- and medium-acid sites appeared in it compared with the other catalysts. The mechanism of catalytic ozonation may be that p-xylene adsorbed on the acid site of vacuumdeoxidized Mn0.5Ce0.5Ox is attacked by the reactive oxygen species (ROS) generated by the dissociation of O3 on OVs. The degraded p-xylene and its intermediate are finally oxidized by ROS to CO2 and H2O.