Chlorobenzene (CB) inhibits SCR activity of V-based catalysts at low temperature, though the adsorption amount is small. NH3 adsorption increases due to the break in the C-Cl bond during CB oxidation. The dissociated Cl- ions provide extra Brønsted acid sites, leading to the formation of inactive NH4Cl. Ce and Mn improve dechlorination, forming more NH4Cl on the catalyst surface.