Abstract
Deactivation and regeneration of arsenic are studied on novel CeO2–WO3/TiO2 for selective catalytic reduction (SCR) of NOx with NH3. It is found that the activity and N2 selectivity of poisoned catalyst are inhibited immensely at the entire temperature range. The fresh, poisoned and regenerated catalysts are characterized using XRD, BET, XPS, H2-TPR, NH3-TPD, NO+O2-TPD, in situ Raman and in situ DRIFTS. The characterization results indicate that the poisoning of arsenic decrease BET surface area, surface Ce3+ concentration and the amount of Lewis acid sites and adsorbed NOx species but increase the reducibility and number of chemisorbed oxygen species. According to the in situ DRIFTS investigations, the adsorption of surface-adsorbed NH3 and NOx species is suppressed at low temperature, while the reactivity between surface-adsorbed NH3 and NO is prohibited at high temperature. A novel H2 reduction regeneration not only effectively removes arsenic from the poisoned catalysts, but promotes surface Ce3+/Ce4+ ratio and form new NOx adsorptive sites. However, it also affects the chemical properties of catalyst such as crystalline Ce2(WO4)3 forming, surface active oxygen species raise and loss of Brønsted acid sites.
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