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Mechanistic Aspects of deNOx Processing over TiO2 Supported Co–Mn Oxide Catalysts: Structure–Activity Relationships and In Situ DRIFTs Analysis

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journal contribution
posted on 17.12.2015, 09:55 by Hang Hu, Sixiang Cai, Hongrui Li, Lei Huang, Liyi Shi, Dengsong Zhang
Anatase TiO2-supported manganese and cobalt oxide catalysts with different Co/Mn molar ratios were synthesized by a conventional impregnation method and used for selective catalytic reduction (SCR) of NOx with NH3. The catalysts were characterized by N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption with NH3 and NOx. Characterization of the catalyst confirmed that by using Co3O4 over Mn/TiO2, we enhanced NO oxidation ability. From in situ diffuse reflectance infrared transform spectroscopy (DRIFTs) analysis of desorption and the transient reaction, we concluded that the addition of Co could remarkably lower the activation energy of NOx chemisorption on the catalyst surface. In addition, low-temperature SCR activity mainly results from a “fast SCR” reaction. We observed four NOx species (bidentate nitrates, gaseous NO2, linear nitrites, and monodentate nitrites) on the surface of Mn/TiO2 and Co–Mn/TiO2 catalysts that all participated in the SCR reaction in the high temperature range. Doping of cobalt greatly improved the reactivity of gaseous NO2, linear nitrites, and monodentate nitrites, which makes Co–Mn/TiO2 a highly effective NH3–SCR catalyst.