In this work, a series of cesium (Cs) modified metal oxide (Co3O4, CuO, Mn2O3, and NiO) catalysts were synthesized and investigated for N2O catalytic decomposition. More than 95% N2O conversion was obtained with the Cs-supported Co3O4 (Cs/Co) catalyst at 300 °C, but only a slight increase or even suppression was obtained with the other catalysts. The activation energy (E a) varied significantly for Cs modified catalysts. It was found that both of N2O adsorption–dissociation (from N2O-TPD) and O2 desorption capacities (from O2-TPD) were highly correlated with the N2O decomposition activity. Highly optimized N2O activation and O2 desorption capacities contributed to the boosting performance of the Cs/Co catalyst. Moreover, the improved electron transfer property inferred from H2-temperature-programmed reduction and X-ray photoelectron spectroscopy was likely to facilitate the reaction processes and promote N2O catalytic decomposition performance.

Selective catalytic reduction of NO x by ammonia (NH 3 -SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MO x -WO 3 /TiO 2 (MW/Ti, M = Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NO x conversion over MnW/Ti and CeW/Ti catalysts, respectively. While the SCR activity over VW/Ti catalyst was hardly affected by HCl. Over MnW/Ti catalyst, the rupture of the MnÀ O bond by the strong MnÀ Cl binding induced the formation of amorphous MnCl 2 species. This Cl-containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in lowtemperature SCR activity. However, instead of directly affecting the CeO x and VO x sites, gaseous HCl reacted with NH 3 to form NH 4 Cl species on the surface of CeW/Ti and VW/Ti catalysts. As a result, the SCR activity of VW/Ti catalyst was scarcely influenced by HCl, taking the unchanged redox ability and NH 3 adsorption. With a further accumulation of NH 4 Cl on CeW/Ti catalyst, the NO x conversion at low temperature was evidently enhanced due to the promotion in NO-to-NO 2 conversion (Fast-SCR).

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Selective catalytic reduction of nitrogen oxides (NO x ) with C 3 H 6 (C 3 H 6 -SCR) was investigated over NiO catalysts supported on different metal-oxides. A NiAlO x mixed oxide phase was formed over NiO/γ-Al 2 O 3 catalyst, inducing an immediate interaction between NiO x and AlO x species. Such interaction resulted in a charge transfer from Ni to Al site and the formation of Ni species in high oxidation state. In comparison to other NiO-loaded catalysts, NiO/γ-Al 2 O 3 catalyst exhibited the highest NO x conversion at temperature higher than 450 °C, but a poor C 3 H 6 oxidation activity due to the decreased nucleophilicity for surface oxygen species. By temperature-programed NO oxidation, it is indicated that nitrate species were rapidly formed and stably maintained at high temperature over NiO/γ-Al 2 O 3 catalyst. In situ transient reactions further verified the Langmuir-Hinshelwood mechanism for C 3 H 6 -SCR, where both gaseous NO and C 3 H 6 were adsorbed and activated on catalyst surface and reacted to generate N 2 . Due to the strong metal-support interaction over NiO/γ-Al 2 O 3 catalyst, both nitrate and C x H y O z intermediates were well preserved to attain high C 3 H 6 -SCR activity.

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