Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

MnO<inf>x</inf>-based catalysts supported at different loadings on TiO<inf>2</inf> (2-10wt%) and H-ZM5 (2-20wt%) were tested for the NH<inf>3</inf>-SCR of NO in the temperature range 50-250°C. All catalysts showed enhanced activity at low temperature compared to conventional SCR catalyst. A detailed characterization of catalysts (BET, H<inf>2</inf>-TPR, NH<inf>3</inf>- and O<inf>2</inf>-TPD) revealed the predominance of MnO<inf>2</inf>, with an enhanced dispersion when supported on TiO<inf>2</inf>. SCR activity at low temperature correlated with lattice oxygen availability, which in turn increased for highly dispersed MnO<inf>x</inf>. The poisoning effects deriving from a hypothetical Sea Water Scrubber Desulphurization unit placed upstream of the SCR unit were investigated by ex-situ addition of KCl to the catalysts. KCl affected the acidic properties, and particularly the oxygen mobility of the catalysts, lowering, as a consequence, their SCR activity. The strong acidic character of ZSM5 enhanced the tolerance to such poisoning effect.