Investigations of increase of the efficiency of an afterburning catalyst

Starting from an alkali-containing copper oxide/manganese oxide catalyst on a silica support, the influence of n- and p-doping on the activity of afterburning catalysts for the purification of engine exhaust gases was investigated. By applying a measurement method that captures the time dependence of the reaction setting, the exact correlation between conversion and catalyst temperature was achieved even in exothermic reactions. The catalyst activity is impaired by p-doping with alkali, while n-doping with tetravalent ions enhances it. In particular, thorium proves to be an extremely effective promoter. In addition to the temperature dependence of the conversion, reaction kinetic parameters can also be determined. The results are consistent with the concepts regarding the relationship between semiconductor and catalyst properties of metal oxides.