Synergy of NaCl and Hg⁰ on V₂O₅-WO₃/TiO₂ SCR catalysts

The nano V₂O₅-WO₃/TiO₂ catalysts were prepared. NaCl was loaded on the catalysts by impregnation and Hg⁰ was loaded by adsorption. The samples were characterized by XRD, SEM, BET, NH₃-TPD and FT-IR measurements to investigate the effect of NaCl and Hg⁰ on the performance of V₂O₅-WO₃/TiO₂ SCR catalysts. Besides, the functional mechanism was proposed combining with previous conclusions. The results indicate that NaCl causes the agglomeration of catalysts, leading to the decrease of BET surface area. For NaCl poisoning catalysts, the deactivation is observed obviously with the increase of NaCl loadings. Brφnsted acid sites (-V-OH) are neutralized by Na to ultimately form-V-O-Na and Cl-V-O-Na, resulting in the decline of catalytic activity. Hg⁰ shows no influence on the microstructure and phase composition of the catalysts. However, it can be adsorbed on the V active sites to weaken the De-NO_x activities slightly. When NaCl and Hg⁰ exist simultaneously, Hg⁰ will combine with Cl that is introduced from NaCl to form HgCl or HgCl₂ and partly replace Na, and -V-O…Hg or-V-O-Hg-Cl is produced finally.