In situ DRIFTS investigation for the oxidation of toluene by ozone over Mn/HZSM-5, Ag/HZSM-5 and Mn–Ag/HZSM-5 catalysts

•Toluene oxidation by ozone is investigated by in situ DRIFTS.•The key factor for toluene ozonation over Mn–Ag/HZSM-5 catalyst is discussed.•The reaction pathways for toluene oxidation with or without ozone are proposed. The mechanism of toluene oxidation at room temperature over Mn/HZSM-5, Ag/HZSM-5 and Mn–Ag/HZSM-5 catalysts was investigated by in situ DRIFTS. The results show that only a little toluene can be partially oxidized into benzyl alcohol in the absence of O3, while it can be further oxidized into benzaldehyde, benzoic acid, maleic anhydride, and ultimately mineralized to CO2 in the presence of O3. The lattice oxygen is the oxygen species of oxidizing toluene into benzyl alcohol, and the active oxygen species generated from ozone decomposition on the oxygen vacancy over the catalysts are responsible for its complete oxidation. Compared with Mn/HZSM-5 and Ag/HZSM-5 catalysts, the Mn–Ag/HZSM-5 catalyst shows higher catalytic activity for toluene oxidation by ozone, which is attributed to more oxygen vacancy in this catalyst, based on the XPS characterization results.