Deactivation performance and mechanism of alkali (earth) metals on V 2O 5–WO 3/TiO 2 catalyst for oxidation of gaseous elemental mercury in simulated coal-fired flue gas

Abstract

Catalysis deactivation caused by alkali (earth) metals (Na, K, Mg and Ca) over V 2O 5–WO 3/TiO 2 catalyst for oxidation of Hg 0 by hydrogen chloride was investigated in the presence of O 2. Deactivation effects caused by alkali (earth) metals were well associated with alkalinity value and shown in sequence as: K > Na ∼ Ca > Mg. Results also indicated that the deactivation increased proportionately with alkali (earth) metal doping amounts. Further investigations on BET surface area, XRD, Hg-TPD, XPS and H 2-TPR demonstrated that surface characteristics were not the dominant factor for the deactivation. However, surface coverage by alkali (earth) metals might cause decrease in the surface area and total pore volume. Hg-TPD results indicated that the doping of alkali (earth) metals would decrease surface Hg 0 adsorption amount associated with alkalinity value. More decrease of surface adsorption and redox ability (Oα) in doped catalysts than the fresh one could lead to less active performance according to the H 2-TPR and XPS of O 1s results. Consequently, the decrease of Hg 0 adsorption and surface redox ability (Oα), and the formation of inactive metavanadate species such as KVO 3 could be responsible for the deactivation performance caused by alkali (earth) metals over vanadium-based catalyst for oxidation of gaseous elemental mercury.