Abstract: Five kinds of transition metal oxides supported on alumina and prepared by wetness impregnation were evaluated for the catalytic ozonation of toluene at room temperature and characterized by temperature-programmed reduction, temperature-programmed oxidation, N₂ adsorption-desorption, and X-ray photoelectron spectroscopy. The catalysts with a lower reduction temperature and less H₂ consumption showed a higher efficiency for ozone and toluene decomposition, such as NiO/Al₂O₃, CoO/Al₂O₃, and MnO₂/Al₂O₃, while lower efficiency were observed on Fe₂O₃/Al₂O₃ and CuO/Al₂O₃. Toluene decomposition efficiency was obviously dependent on ozone. Because of the low ozone to toluene concentration ratio, a CO₂ yield of less than 30% was obtained. At a toluene concentration of 666 mg/m³ and an ozone concentration between 193 and 965 mg/m³, toluene conversion was found to vary from 15.2% to 46.7%. Additionally, we observed an increase in oxidation products and lattice oxygen on the catalyst surface. A preliminary investigation into the reaction pathway was undertook by in situ diffuse reflectance Fourier transform infrared spectroscopy. With regards to the formation of COO^-, C=O, and C–O groups the high ozone concentration accelerated the transformation from COO^- to C=O and C–O. The substance containing COO^- remained unchanged at 573 K, while the substances containing C=O and C–O underwent oxidation at higher than 373 K. A possible reaction pathway is proposed based on these findings.

Key words: alumina, transition metal oxide, toluene, ozone, room temperature, in situ diffuse reflectance Fourier transform infrared spectroscopy