Experimental and theoretical (ReaxFF) study of manganese-based catalysts for low-temperature toluene oxidation

This study presents detailed experimental and theoretical investigation of manganese-based metal oxides, MnMO_x (M: Fe, Ni, Cu) as potential catalysts for the low-temperature toluene oxidation. The first part of the paper deals with the detailed characterization of the prepared catalysts and testing of their catalytic activity and stability in the fixed-bed reactor. The MnFeO_x exhibited superior and stable catalytic activity for toluene oxidation (T₉₀ = 419–446 K), comparable with the activity of the commercial Pt–Al₂O₃ catalyst (T₉₀ = 393–423 K). Among the studied catalysts the following order of catalytic activity was determined: MnFeO_x > MnNiO_x ≈ MnCuO_x > MnO_x. The one-dimensional (1D) pseudo-homogeneous model was applied to describe behavior of the fixed bed reactor for the low temperature toluene oxidation over prepared MnFeO_x catalysts. The second part of the paper is focused on theoretical investigation of toluene interaction on the surface of the single metal oxides (Mn₂O₃, MnO₂, Fe₂O₃, NiO and CuO) in the oxygen atmosphere using the ReaxFF method, since they were individual dominant phases in the prepared catalysts. A good correlation between the predicted binding energy of toluene adsorption on the surface of studied metal oxide phases and experimentally determined catalytic activities was observed.