Influence mechanism of the compositions in coal-fired flue gas on Hg0 oxidation over commercial SCR catalyst

Abstract

Optimizing the performance of commercial SCR catalyst (i.e., V2O5–WO3/TiO2) for Hg0 oxidation remained stagnant as the influence mechanism of the compositions of flue gas on Hg0 oxidation was unclear. In this work, the mechanism of Hg0 oxidation and the influence mechanism of the compositions of flue gas on Hg0 oxidation over V2O5–WO3/TiO2 were investigated. The reaction orders of Hg0 oxidation over V2O5–WO3/TiO2 in regard to both the concentrations of Hg0 and HCl in gas phase were approximately 0. Hence, Hg0 oxidation over V2O5–WO3/TiO2 primarily followed the Langmuir–Hinshelwood mechanism, and the elementary reactions of Hg0 oxidation primarily involved the physical adsorption of Hg0, the formation of Cl* radial, and the reaction of physically adsorbed Hg0 and Cl* radial. SO2, NO, H2O, and NH3 not only restrained the Cl* radial formation but also disturbed the reaction of physically adsorbed Hg0 and Cl* radial. Meanwhile, the physical adsorption of Hg0 was restrained by both H2O and NH3. Hence, Hg0 oxidation over V2O5–WO3/TiO2 was obviously restrained when SO2, NO, H2O, and NH3 were present in flue gas.