Ag-Mo modified SCR catalyst for a co-beneficial oxidation of elemental mercury at wide temperature range

摘要

V2O5-MoO3-TiO2 (V-Mo-Ti) is often used as a selective catalytic reduction catalyst for NOx from coal-fired flue gas. The performance of a V-Mo-Ti catalyst for the oxidation of elemental mercury (Hg-0) was investigated. It was found that Mo was resistant toward sulfur dioxide and can enhance the Hg-0 adsorption capacity. Ag was employed to enhance the Hg-0 oxidation reaction and can enlarge reaction temperature window. Doping with Ag can significantly enhance the oxidation of Hg-0, and adding only 0.5% Ag can keep Hg-0 oxidation efficiency to approximately 90% with 5 ppm HCl, with an increase of 20-40% compared to that of V-Mo-Ti catalyst. Besides, the reaction temperature window of catalyst was enlarged from 150 to 400 degrees C. TEM and XPS characterization data indicated that Ag nanoparticles were loaded on the Mo/V-Ti carrier, maintaining Ag-Mo/V-Ti at a higher oxidation state. Furthermore, the TPR and Deacon reaction tests suggested that the Ag dopant might enhance the redox behavior, which facilitates the Deacon or semi-Deacon reactions for HCl activation. In addition, Hg-0 desorption and breakthrough experiments and mercury valence state change experiments were carried out to investigate the Hg catalytic oxidation mechanisms at various temperature ranges. (C) 2017 Elsevier Ltd. All rights reserved.