Synergetic NO_x Removal and Hg⁰ Oxidation over V₂O₅–WO₃/TiO₂ Catalysts in a Simulated Fast SCR Atmosphere: Catalytic Performance and Hg⁰ Oxidation Mechanism

Abstract

Fast selective catalytic reduction (SCR) atmosphere can significantly improve the NO x removal activity of VWTi catalysts, while the catalytic performance and reaction pathway of Hg 0 oxidation in a fast SCR atmosphere are still unclear. In this paper, the catalytic activity of simultaneous NO x removal and Hg 0 oxidation over VWTi catalysts in a simulated fast SCR atmosphere was investigated for the first time. The results showed that VWTi catalysts possessed a wide NO x removal active temperature window and a high Hg 0 oxidation activity in a fast SCR atmosphere. The X-ray photoelectron spectroscopy (XPS) and Hg temperature-programmed desorption (Hg-TPD) methods were used to investigate the Hg 0 oxidation process over VWTi catalysts in a fast SCR atmosphere. Combined with the homogeneous Hg 0 oxidation experiment results, two domination reaction routes of Hg 0 oxidation over VWTi catalysts in a fast SCR atmosphere were proposed. One was that the adsorbed Hg 0 could react with the surface active species to form HgO. The other reaction route was a gaseous homogeneous route that the gaseous Hg 0 could be oxidized directly to Hg(NO 3 ) 2 by gaseous NO 2 . Particularly, the gaseous homogeneous Hg 0 oxidation process could notably weaken the inhibition effect of NH 3 on Hg 0 oxidation, thus improving the Hg 0 oxidation activity of VWTi catalysts in a fast SCR atmosphere.