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

MnOx-based catalysts supported at different loadings on TiO2 (2-10wt%) and H-ZM5 (2-20wt%) were tested for the NH3-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, H2-TPR, NH3- and O2-TPD) revealed the predominance of MnO2, with an enhanced dispersion when supported on TiO2. SCR activity at low temperature correlated with lattice oxygen availability, which in turn increased for highly dispersed MnOx. 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.