Chemical deactivation of V₂O₅-WiO₃/TiO₂ SCR catalyst by combined effect of potassium and chloride

Abstract

V₂O₅-WO₃/TiO₂ catalyst was poisoned by impregnation with NH₄Cl, KOH and KCl solution, respectively. The catalysts were characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), N₂ physisorption, Raman, UV-vis, NH₃ adsorption, temperature-programmed reduction of hydrogen (H₂-TPR), temperature-programmed oxidation of ammonia (NH₃-TPO) and selective catalytic reduction of NO_x with ammonia (NH₃-SCR). The deactivation effects of poisoning agents follow the sequence of KCl>KOH>>NH₄Cl. The addition of ammonia chloride enlarges the pore size of the titania support, and promotes the formation of highly dispersed V=O vanadyl which improves the oxidation of ammonia and the high-temperature SCR activity. K⁺ ions are suggested to interact with vanadium and tungsten species chemically, resulting in a poor redox property of catalyst. More importantly, potassium can reduce the Brønsted acidity of catalysts and decrease the stability of Brønsted acid sites significantly. The more severe deactivation of the KCl-treated catalyst can be mainly ascribed to the higher amount of potassium resided on catalyst.

Keywords

V₂O₅-WO₃/TiO₂ / potassium chloride / poisoning / reducibility / acid sites

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