Extraordinary Detoxification Effect of Arsenic on the Cadmium-Poisoned V₂O₅/TiO₂ Catalyst for Selective Catalytic Reduction of NO_x by NH₃

Abstract

Arsenic has been found as a serious toxicant for the catalysts in the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR). However, the detoxification effect of arsenic on the cadmium-poisoned V 2 O 5 /TiO 2 catalyst was found in this work. With an arsenic loading of 1.8 wt %, the NO x conversion over cadmium-poisoned V 2 O 5 /TiO 2 increased from 45.1 to 88.3% at 350 °C under a GHSV of 300,000 h −1 . Meantime, the adverse effect on N 2 selectivity caused by arsenic was reduced. The catalyst characterization manifests that the surface VO xactive sites were liberated from the restriction of cadmium due to the interaction between cadmium and arsenic. More importantly, it was found that the SCR performance of the catalysts was highly dependent on the surface VO x sites. In situ experiments proved that the released surface VO x species could not only provide the Lewis sites for the NH 3 adsorption but also dominate the redox cycle (V 5+ ↔ V 4+ ) during the NH 3 -SCR process. We believe that this study can inspire directions for the design of NH 3 -SCR catalysts with superior resistance to different poisons. KEYWORDS: NH 3 -SCR, V 2 O 5 /TiO 2 , cadmium and arsenic, VO x sites, redox cycle