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Selective catalytic reduction of NOx by ammonia (NH3‐SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MOx‐WO3/TiO2 (MW/Ti, M=Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NOx 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 Mn−O bond by the strong Mn−Cl binding induced the formation of amorphous MnCl2 species. This Cl‐containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in low‐temperature SCR activity. However, instead of directly affecting the CeOx and VOx sites, gaseous HCl reacted with NH3 to form NH4Cl 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 NH3 adsorption. With a further accumulation of NH4Cl on CeW/Ti catalyst, the NOx conversion at low temperature was evidently enhanced due to the promotion in NO‐to‐NO2 conversion (Fast‐SCR). [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of NOx by ammonia (NH3‐SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MOx‐WO3/TiO2 (MW/Ti, M=Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NOx 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 Mn−O bond by the strong Mn−Cl binding induced the formation of amorphous MnCl2 species. This Cl‐containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in low‐temperature SCR activity. However, instead of directly affecting the CeOx and VOx sites, gaseous HCl reacted with NH3 to form NH4Cl 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 NH3 adsorption. With a further accumulation of NH4Cl on CeW/Ti catalyst, the NOx conversion at low temperature was evidently enhanced due to the promotion in NO‐to‐NO2 conversion (Fast‐SCR). [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of nitrogen oxides (NOx) with C3H6 (C3H6‐SCR) was investigated over NiO catalysts supported on different metal‐oxides. A NiAlOx mixed oxide phase was formed over NiO/γ‐Al2O3 catalyst, inducing an immediate interaction between NiOx and AlOx 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‐Al2O3 catalyst exhibited the highest NOx conversion at temperature higher than 450 °C, but a poor C3H6 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‐Al2O3 catalyst. In situ transient reactions further verified the Langmuir–Hinshelwood mechanism for C3H6‐SCR, where both gaseous NO and C3H6 were adsorbed and activated on catalyst surface and reacted to generate N2. Due to the strong metal‐support interaction over NiO/γ‐Al2O3 catalyst, both nitrate and CxHyOz intermediates were well preserved to attain high C3H6‐SCR activity. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of nitrogen oxides (NOx) with C3H6 (C3H6‐SCR) was investigated over NiO catalysts supported on different metal‐oxides. A NiAlOx mixed oxide phase was formed over NiO/γ‐Al2O3 catalyst, inducing an immediate interaction between NiOx and AlOx 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‐Al2O3 catalyst exhibited the highest NOx conversion at temperature higher than 450 °C, but a poor C3H6 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‐Al2O3 catalyst. In situ transient reactions further verified the Langmuir–Hinshelwood mechanism for C3H6‐SCR, where both gaseous NO and C3H6 were adsorbed and activated on catalyst surface and reacted to generate N2. Due to the strong metal‐support interaction over NiO/γ‐Al2O3 catalyst, both nitrate and CxHyOz intermediates were well preserved to attain high C3H6‐SCR activity. [ABSTRACT FROM AUTHOR]

Considering the radius similarity of Al3+ (0.50 Å) and Ga3+ (0.62 Å), Al−Co and Ga−Co layered double hydroxides (LDH) was prepared as precursor to improve the synergetic interaction of the transition metals. The Al−Co and Ga−Co spinel catalysts were obtained by the following calcination for the toluene oxidation. The Ga−Co (Ea=79.5 kJ mol−1) showed higher activity than the Al−Co (Ea=95.4 kJ mol−1), and it exhibited excellent stability and resistance to carbon deposition during a 50 h reaction period at 300 °C. Characterization results indicated that the improved activity of Ga−Co spinel could be attributed to the higher reducibility (H2‐TPR), more surface Co3+ and adsorbed oxygen in quantity (XPS) and adsorbed toluene (Toluene‐TPD) than Al−Co spinel. Compared with traditional Ga−Co binary catalyst, the spinel structure possessed more B‐sites cations outermost of the surface and surface oxygen vacancies for the toluene adsorption and ring‐open reaction. It′s all about how big you are: Considering the radius similarity of Al3+ (0.50 Å) and Ga3+ (0.62 Å), Al−Co and Ga−Co LDH were prepared as precursor to improve the synergetic interaction of the transition metals. The Al−Co and Ga−Co spinel were obtained by the following calcination for the toluene oxidation. Characterization results indicated that the improved activity of Ga−Co spinel could be attributed to the higher reducibility, more surface Co3+ and adsorbed oxygen in quantity and adsorbed toluene than Al−Co spinel." [ABSTRACT FROM AUTHOR]

Abstract: Copper‐exchanged H‐SAPO‐47 zeolites were synthesized by an aqueous solution ion exchange method and applied in the selective catalytic reduction of NO with NH3 (SCR). The microporous chabazite (CHA) structure of the catalysts was characterized and confirmed using synchrotron X‐ray diffraction and nitrogen adsorption–desorption experiments. The synthesized Cux‐SAPO‐47 catalysts exhibited excellent SCR activity and nearly 100 % N2 selectivity in a wide temperature range. The Cu0.1‐SAPO‐47 sample exhibited higher activity than the other samples below 250 °C. The weak Lewis acid sites originating from the introduction of Cu2+ were more active than the Brønsted acid sites of the zeolites framework at low temperature. Two types of isolated Cu2+ species with different coordination surroundings were found, namely, Cu2+ cations bonded with the six‐membered rings and those bonded in the CHA cages. The former species exhibited good stability and activity at high temperature, whereas the latter ones were more active at low temperature. The Cu0.1‐SAPO‐47 catalyst provided a considerable amount of isolated Cu2+ bonded in the CHA cages. These results indicated that active Lewis acid sites and isolated Cu2+ species are responsible for their excellent SCR activity. [ABSTRACT FROM AUTHOR]