XPS STUDIES OF NO SELECTIVE REDUCTION CATALYSTS AFTER SO2 POISONING

The effect of an SO2-water vapour-air mixture on the structure of Fe3+-, CU2+-, CO2+- or Ni2+-active carbon catalysts used for selective catalytic reduction of NO with ammonia was studied by low-temperature argon sorption and XPS. Active material reacted with oxidation products of SO2 to form appropriate sulphates. The reaction rate, expressed as surface sulphur-to-cation ratio, depended on the distribution of active material on the starting samples. The distribution of Fe3+, Cu2+, Ni2+ and Co2+ changed during the reaction as a result of movement of the cations into the porous system and was accompanied by some decrease in specific surface area and partial blocking of micropores.