Promoter not inhibitor: The antidotal effects of arsenic on lead-poisoning V2O5−WO3/TiO2 catalyst for selective catalytic reduction of NOx with NH3

Abstract

Arsenic has been considered a strong inhibitor for a variety of catalysts for the selective catalytic reduction of NOx with NH3 (NH3−SCR). However, in this work, we found arsenic exhibits a remarkable detoxification effect on lead-poisoning V2O5−WO3/TiO2 catalysts. With only 0.9 wt% arsenic introduction, the NOx conversion over Pb–V2O5−WO3/TiO2 (lead: 2 wt%) could be raised from 35% to 81% at 250 °C under a GHSV of 100,000 h−1. More surprisingly, the negative effect of arsenic on N2 selectivity was greatly inhibited simultaneously. The catalyst characterizations and DFT simulation manifest that arsenic could not only extricate VOx sites and related Lewis acid sites from lead shackles but also promote the redox property through its stronger electronic interaction with the lead. On the basis of in situ DRIFTS and kinetic study, regenerated V=O sites were profitable to the adsorption and activation of NH3 species, thus greatly improving the SCR activity. We demonstrate that the antidotal effect of arsenic to lead poisoning V2O5−WO3/TiO2 catalyst is the increase of active site amount rather than the change of reaction pathway. It is believed that the novel findings above could open up an innovative pathway for toxic heavy metals reduction and catalyst designing with virtuous anti-poisoning performance.