Characterization of MnO-doped lanthanum hexaluminate (LaMnAl11O19) in terms of selective catalytic reduction of NOx by addition of hydrocarbon reductant (HC-SCR)

Abstract

Environmental pollution by vehicles, turbines and aircrafts has enormously increased in the last decade. New generation lean-burn combustion engines which are more effective and require less fuel consumption will raise the emission of nitrogen oxides (NOX) even more. Thus, especially in urban areas, more stringed environmental regulations are to release which can only be met by development of new catalytic materials and concepts. Rare earth oxide catalysts are reported to offer highly effective conversion of NOX by methane (CH4) in the terms of selective catalytic reduction (HC-SCR). Especially La2Oa is reported to have a high NO reduction by CH4 to N2, although its technical realization as catalyst material has not yet reported and can be challenging due to the hydroscopic property of La2O3. Complex oxide compounds containing La2Oa however can be suitable alternatives and promising candidates for technical application as catalysts. In this study, LaMnAlnOi9 is characterized in terms of HC-SCR with methane. Phase and morphological characterization of the powder synthesized by sol-gel route and coatings by electron-beam physical vapor deposition (EB-PVD) deposition was presented. LaMnAlnOi9 crystallizes to the magnetoplumbite phase at about 1000°C and is then thermally stabile up to 1400°C. FTIR spectra of pressed sol-gel powder showed that NO is adsorbed superficially and oxidized by the surface. The addition of oxygen led to changes of the spectrum in the nitritenitrate region and the formation of NO+ and N2O4 species. The EB-PVD coated LaMnAlnOi9 layer was catalytically characterized at 200°, 400° and 600 °C and showed catalytic activity towards NO depending on temperature.