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

Recently, sulfureted metal oxides have been developed for the catalytic oxidation of Hg-0 to HgCl2 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/gamma-Fe2O3 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 HgCl2 both contributed to Hg-0 conversion over sulfureted HPMo/gamma-Fe2O3. Meanwhile, the formed HgCl2 can adsorb onto sulfureted HPMo/gamma-Fe2O3. Then, the kinetics of Hg-0 conversion, Hgt adsorption, and HgCl2 desorption were developed, and the kinetic parameters were gained by fitting the Hg balance curves. Subsequently, the inhibition mechanism of H2O and SO2 on Hg-0 conversion over sulfureted HPMo/gamma-Fe2O3 was determined by comparing the kinetic parameters. The kinetic model suggested that both HgCl2 resulting from Hg-0 oxidation and unoxidized Hg-0 can be completely adsorbed on sulfureted HPMo/gamma-Fe2O3 with a moderate mass hourly space velocity. Therefore, sulfureted HPMo/gamma-Fe2O3 can be developed as a reproducible sorbent for recovering Hg-0 emitted from coal-fired power plants.

Automated summary

Recently, sulfureted metal oxides have shown excellent performance in the catalytic oxidation of Hg-0 to HgCl2 using HCl as an oxidant at low temperatures. However, the lack of reaction mechanisms and kinetics has limited further improvement in Hg-0 conversion. This study investigated the reaction mechanism of Hg-0 conversion over sulfureted HPMo/gamma-Fe2O3 with HCl at low temperatures. The results showed that both chemical adsorption as HgS and catalytic oxidation to HgCl2 contribute to Hg-0 conversion.