Poisoning effects of KCl and As2O3 on selective catalytic reduction of NO with NH3 over Mn-Ce/AC catalysts at low temperature

The poisoning effects of KCl and As2O3 on selective catalytic reduction (SCR) of NH3 with NO over Mn-Ce/AC catalysts were investigated with the reaction temperature range of 100–250 °C. KCl and As2O3 poisoned catalysts were synthesized by impregnation method and catalytic activity test was performed under the condition of simulated flue gas. The changes of crystal structure, microstructure, surface atomic state, surface acidity and functional groups were characterized by XRD, SEM, BET, XPS, NH3-TPD and FT-IR. Deactivation for single KCl or As2O3 doping catalyst was observed and severe synergistic inactivation occurred with the common effect of KCl and As2O3 on the catalyst. KCl destroyed the porosity of active carbon (AC) and could react with OH and CO on the surface of AC to ultimately form -O-K and Cl-C-O-K, resulting in the decrease of NH3 and NO adsorption. Besides, KCl caused the reduction of oxygen vacancies and chemisorbed oxygen on the Mn-Ce/AC catalyst. Lattice oxygen of MnOx may be transformed to surface chemisorbed oxygen to oxidize As2O3. As2O3 was oxidized to As2O5 and some layer was formed on the surface of catalyst preventing NH3 and NO adsorption. In addition, As2O3 could increase the number of oxygen vacancies and decrease the surface acidity of Mn-Ce/AC catalyst. According to the experimental results and theoretical analysis, the synergy poisoning model of KCl and As2O3 on Mn-Ce/AC catalysts was schematically established.