Effects of precursors and preparation methods on the potassium deactivation of MnOx/TiO2 catalysts for NO removal

To investigate the effects of precursors and preparation methods on the potassium (K) deactivation, fresh and potassium-deactivated MnOx/TiO2 catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR) in the temperature range between 353 K and 453 K were investigated. Potassium nitrate (KNO3), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), potassium sulfate (K2SO4) and potassium chloride (KCl) were used as K precursors. Meanwhile, K salts deposited MnOx/TiO2 catalysts were prepared with different methods, and the influence of different K doping amounts on NH3-SCR was investigated. According to the NH3-SCR experimental results, K salts had negative effects on the catalytic activities, and the preparation methods of the catalysts and the precursors of K salts also affected the catalytic activity. The precursor KNO3 had the greatest impact on the catalytic activity, while K2SO4 had the least effect. Meanwhile, physical and chemical properties of catalysts were characterized by XRD, H2-TPR, NH3-TPD, BET, FESEM and TG analyses. Characterization results indicated that significant changes in surface properties of K-deactivated MnOx/TiO2 catalysts were observed after K salts were doped on the catalysts. The K-deactivated MnOx/TiO2 showed smaller specific surface areas, larger particle sizes, lower manganese oxide reducibility and less acidic sites on the surface, which could be considered as the main reasons for the deactivation of K deposited MnOx/TiO2 catalysts. Furthermore, the large particles and fibrous materials were attributed to the new phases (K1.33Mn8O16 and K2Ti8O17) found in some catalysts, indicating the strong interactions between K and MnOx/TiO2 catalysts.