Potassium Poisoning Effects on Sol-gel Mn/TiO₂ Catalyst for Selective Catalytic Reduction (SCR) of NOx with NH₃ at Low Temperature

Mn/TiO2 catalysts exhibited more excellent activity and higher selectivity in low-temperature SCR of NOx with NH3. Alkali metal, particularly potassium presented in the ash, could severely deactivate SCR catalyst and then reduce its lifetime. In this study, sol-gel Mn/TiO2 catalyst was employed to evaluate its SCR activity with and without the presence of KNO3 at 100-300 degrees C. The influence of various parameters such as KNO3 loading amount, calcination time, temperature and catalyst deactivation was investigated. The characterization results indicated that the doping of potassium on Mn/TiO2 surface obviously resulted in a great decrease of reducibility, surface acidity and NH3 adsorption capacity. XPS spectra revealed the decrease of Mn4+ atomic concentration and chemisorbed oxygen species caused by potassium doping. In addition, obvious variation of potassium states (K1.04Ti8O16) was detected for K-Mn/TiO2 catalyst after calcining treatment, which may lead to a poorer performance of SCR catalyst.