Hg⁰ Conversion over Sulfureted HPMo/γ-Fe₂O₃ with HCl at Low Temperatures: Mechanism, Kinetics, and Application in Hg⁰ Removal from Coal-Fired Flue Gas

Abstract

Recently, sulfureted metal oxides have been developed for the catalytic oxidation of Hg 0 to HgCl 2 using HCl as an oxidant at low temperatures, and they exhibit excellent Hg 0 removal performance. Owing to the lack of reaction mechanisms and kinetics, further improvement in their performance for Hg 0 conversion is extremely restricted. In this study, the reaction mechanism of Hg 0 conversion over sulfureted HPMo/γ-Fe 2 O 3 with HCl at low temperatures was investigated using Hg balance analysis and transient reaction. The chemical adsorption of Hg 0 as HgS and the catalytic oxidation of Hg 0 to HgCl 2 both contributed to Hg 0 conversion over sulfureted HPMo/γ-Fe 2 O 3 . Meanwhile, the formed HgCl 2 can adsorb onto sulfureted HPMo/γ-Fe 2 O 3 . Then, the kinetics of Hg 0 conversion, Hg t adsorption, and HgCl 2 desorption were developed, and the kinetic parameters were gained by fitting the Hg balance curves. Subsequently, the inhibition mechanism of H 2 O and SO 2 on Hg 0 conversion over sulfureted HPMo/γ-Fe 2 O 3 was determined by comparing the kinetic parameters. The kinetic model suggested that both HgCl 2 resulting from Hg 0 oxidation and unoxidized Hg 0 can be completely adsorbed on sulfureted HPMo/γ-Fe 2 O 3 with a moderate mass hourly space velocity. Therefore, sulfureted HPMo/γ-Fe 2 O 3 can be developed as a reproducible sorbent for recovering Hg 0 emitted from coal-fired power plants.