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 cat alytic reduction of NO with ammonia was studied by low-temperature arg on sorption and XPS. Active material reacted with oxidation products o f SO2 to form appropriate sulphates. The reaction rate, expressed as s urface 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.