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

Abstract

Arsenic has been found as a serious toxicant for the catalysts in the selective catalytic reduction of NOx with NH3 (NH3-SCR). However, the detoxification effect of arsenic on the cadmium-poisoned V2O5/TiO2 catalyst was found in this work. With an arsenic loading of 1.8 wt %, the NOx conversion over cadmium-poisoned V2O5/TiO2 increased from 45.1 to 88.3% at 350 °C under a GHSV of 300,000 h–1. Meantime, the adverse effect on N2 selectivity caused by arsenic was reduced. The catalyst characterization manifests that the surface VOx-active 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 VOx sites. In situ experiments proved that the released surface VOx species could not only provide the Lewis sites for the NH3 adsorption but also dominate the redox cycle (V5+ ↔ V4+) during the NH3-SCR process. We believe that this study can inspire directions for the design of NH3-SCR catalysts with superior resistance to different poisons.