Effects of precursors for manganese-loaded γ-Al2O3 catalysts on plasma-catalytic removal of o-xylene

Abstract

The effects of precursors and Mn loading amounts on Mn/Al2O3 catalysts for plasma-catalytic removal of o-xylene were systematically investigated. Catalysts were characterized by XRD, XPS, and H2-TPR. Experimental results show that o-xylene conversion was greatly increased even at very low specific energy density with addition of Mn/Al2O3 catalysts. The Mn/Al2O3 catalyst prepared with a manganese acetate precursor had the highest catalytic activity for o-xylene removal. Among tested loading amounts, 6wt% Mn loading was the optimum condition for preparation of catalysts for o-xylene conversion. The presence of more Mn4+ species, higher proportion of lattice oxygen and microcrystalline MnO2 phase on the surface of catalysts was responsible for the high catalytic activity for o-xylene removal. To compare with Mn/Al2O3 catalysts prepared with manganese acetate precursor, α-MnO2/Al2O3 with more Mn4+ and lattice oxygen on the surface was also prepared. The o-xylene conversion, CO2 selectivity, and (CO+CO2) (i.e. COx) yield increased with introduction of α-MnO2/Al2O3 catalyst, which was due to the high oxidation ability of α-MnO2/Al2O3 induced by higher amounts of Mn4+ and lattice oxygen. The concentrations of O3 and NOx byproducts greatly decreased when catalysts were used. The FT-IR spectrum show that CH3CHO, O3, NOx and HNO3 products were formed without catalyst, while HCOOH/CH3COOH formation occurred with catalysts.