Catalytic Oxidation of Volatile Organic Compounds over Porous Manganese Oxides Prepared via Sol-Gel Method

Abstract

A set of transition metal oxides was prepared via a sol-gel synthesis using different metal (Mn, Cu, and Fe) nitrates to ensure a proper manganese to metal ratio in the final product. Specifically, three pure metal oxides (Mn2O3, CuO, and Fe2O3) and mixed oxides (MnCu15, MnFe15, and MnCu7.5Fe7.5) were synthesized and characterized by means of XRD, N2-physisorption at −196 °C, H2-TPR, FESEM, and XPS techniques. The catalysts were tested for the catalytic oxidation of volatile organic compounds (VOCs) using two probe molecules, namely ethylene and propylene. As a result, the best reaction rates were observed for the MnCu7.5Fe7.5 powder sample and were attributed to the synergistic interactions occurring between the Mn, Cu, and Fe species in the crystalline structure. Similarly, Mn2O3 showed a good catalytic performance. The excellent catalytic activity of the oxides was correlated with the high amount of reactive chemisorbed oxygen species located on the surface, since these species are useful for the oxidation of VOCs. As well, the improvement of the catalytic activity corresponded to the enhanced reducibility of the catalysts at lower temperatures (i.e., better lattice-oxygen mobility) observed during the temperature-programmed reduction studies.