Catalytic Oxidation of Elemental Mercury in Coal-Combustion Flue Gas over the CuAIO_2 Catalyst

摘要

Elemental mercury (Hg-0) emission is a well-known environmental issue in traditional coal-combustion power plants. Now, enhancing Hg-0 oxidation in the selective catalytic reduction of the NOx unit is a promising strategy to reduce mercury pollution. In this study, CuAlO2 catalyst was engaged in Hg-0 oxidation for the first time. The CuAlO2 catalyst exhibited more remarkable Hg-0 catalytic oxidation ability than commercial SCR catalysts and self-made V2O5-WO3/TiO2. The Hg-0 oxidation efficiencies over the CuAlO2 catalyst were above 89.6 and 97.9% in SCR and SFG atmospheres at 300 degrees C, respectively. The effects of flue gas components over the CuAlO2 catalyst were studied systematically for Hg-0 oxidation. The co-presence of NO and O-2 could generate active nitrogen oxide species over the CuAlO2 catalyst to promote the Hg-0 oxidation. HCl played a crucial role in high-efficiency He oxidation due to the activation of chlorine on the CuAlO2 surface. NH3, SO2, and H2O inhibited Hg-0 conversion by occupying the active sites or consuming active chlorine species. However, the suppression effect of NH3, SO2, and H2O would be eclipsed by appropriately decreasing reaction GHSV (gas hourly space velocity), adding NO, and increasing HCl concentration, respectively. Furthermore, the mechanism of Hg-0 oxidation over CuAlO2 followed the Deacon reaction and partial Deacon reaction mechanism according to Y-tube experiment and XPS (X-ray photoelectron spectroscopy) analysis. This work provided the basic data regarding industrial applications of novel CuAlO2 catalysts and was significant for further improving its Hg-0 oxidation activity.