The poisoning effect of Na+ and Ca2+ ions doped on the V2O5/TiO2 catalysts for selective catalytic reduction of NO by NH3

Abstract: Deactivation of the supported V2O5/TiO2 catalysts due to deposition of alkali and alkaline earth metal salts in fly ashes is one of the most important problems in the selective catalytic reduction (SCR) of NO x by NH3. In this work, the poisoning effect of Na+ and Ca2+ ions doped on the V2O5/TiO2 catalysts for selective catalytic reduction of NO by NH3 has been studied. It has been shown that the Na+ and Ca2+ ions doped can poison the V2O5/TiO2 catalyst and the Na+ ions exhibit greater poisoning effect than Ca2+ ions. The NO rate constant k on the Na+-V2O5/TiO2 catalyst decreased very sharply from 97.1 to 35.0cm3 g−1 s−1 with increasing Na/V molar ratio from 0.00 to 0.20. In comparison, k on the Ca2+-V2O5/TiO2 catalyst remained almost unchanged when Ca/V molar ratio was below 0.05. Further increasing Ca/V molar ratio to 0.20 resulted in an obvious decrease of k from 101.8 to 46.3cm3 g−1 s−1. It was suggested that Na+ ions combined strongly with dispersed vanadia species, neutralized the Brønsted acid sites and reduced their reducibility. In comparison, Ca2+ ions slightly affected the Brønsted acid sites of catalyst. Besides, the dispersed vanadia species on the Ca2+-V2O5/TiO2 catalyst had higher reducibility than Na+-V2O5/TiO2 catalyst. The different poisoning effects of Na+ and Ca2+ ions doped on the V2O5/TiO2 catalyst were correlated not only to the surface acidity but also to the reducibility of catalyst. [Copyright &y& Elsevier]