Insight into the homogenous and heterogeneous transformation behavior of arsenic on commercial V2O5-WO3-TiO2 and novel γ-Fe2O3 catalysts during selective catalytic reduction of NOx

Abstract Effect of arsenic on the activity of V2O5-WO3-TiO2 and γ-Fe2O3 catalysts for selective catalytic reduction of NOx with ammonia were studied in this work, and the more important objective was to reveal the heterogeneous and homogeneous reactions about arsenic on V2O5-WO3-TiO2 and γ-Fe2O3 catalysts during arsenic poisoning process. It was discovered that oxygen enhanced the deactivation of V2O5-WO3-TiO2 caused by arsenic. However, the increased oxygen exhibited a contrast impact on arsenic poisoning process of γ-Fe2O3 catalyst. On the other hand, temperature suppressed deactivation effect of arsenic both on V2O5-WO3-TiO2 and γ-Fe2O3. Further concluded from the results of arsenic content in poisoned catalysts, it was found that promotion effect of oxygen on the oxidation of trivalent arsenic in gas side intensified the combination between vanadium and arsenic while inhibited reactions between iron and arsenic. Besides, the aggravation effect of temperature rising on the decomposition of gaseous pentavalent arsenic weakened the combination between gaseous arsenic and vanadium on V2O5-WO3-TiO2 catalyst, while facilitated the combination between gaseous arsenic and non-active iron sites on γ-Fe2O3. Moreover, after trivalent arsenic combined on the surface of catalyst, adsorbed oxygen and pentavalent vanadium competed for providing vacant electron sites to proceed the oxidation of combined trivalent arsenic.