Effects of calcination and support on supported manganese catalysts for the catalytic oxidation of toluene as a model of VOCs

The conventional impregnation method was used to prepare 15 wt% Mn-supported catalysts, which were applied to the catalytic oxidation of volatile organic compounds (VOCs; toluene, benzene, and o-xylene). The effects of calcination temperatures in the range of 500-900 A degrees C and supports (gamma-Al2O3, SiO2, and TiO2) on the property and performance of 15 wt% Mn-supported catalysts were investigated. Their physicochemical characteristics were analyzed by the BET, XRD, NH3-TPD, H-2-TPR, and XPS. The calcination temperature greatly affected the crystalline structure and O1s (D) (defect oxides)/O1s (L) (lattice oxides) area ratio of the 15 wt% Mn/gamma-Al2O3 (15 Mn/Al) catalyst. The order of the O1s (D)/O1s (L) area ratios of the 15 Mn/Al catalysts with respect to calcination temperature was 900 > 500 > 700 A degrees C, which was in good agreement with that observed for the catalytic activity. In addition, the activity order of the 15 wt% Mn-supported catalysts with respect to the type of support was gamma-Al2O3 > SiO2 > TiO2. The 15 wt% Mn/Al catalyst, which had a higher O1s (D)/O1s (L) area ratio, showed better activity than the 15 wt% Mn/SiO2 (15 Mn/Si) and 15 wt% Mn/TiO2 (15 Mn/Ti) catalysts. Defect oxides played a significant role in the catalytic oxidation of VOCs. The catalytic activity with respect to the type of VOC decreased in the order of benzene > toluene > o-xylene.