MO-ZRO2 CATALYSTS FOR NITROGEN-OXIDES REDUCTION BY HYDROCARBONS IN OXYGEN EXCESS - PREPARATION AND PROPERTIES

The physico-chemical and catalytic properties of MO-ZrO2 systems (wher e M is Ca, Sr, Ba) have been studied as a function of the synthesis pa rameters. Finely powdered heterogeneous mixtures of solid solutions wi th cubic+monoclinic or tetragonal+monoclinic phase composition were fo und to be formed. These systems possess quite good high-temperature ac tivity in the reaction of NOx selective reduction by propane under oxy gen excess. For a given system, the rate constant depends linearly upo n the M-O bond dissociation energy in the surface layer, the slope bei ng positive for Ca and Sr and negative for Ba.