Bifunctional Oxidation of Ammonia with Metal Oxide–Pt/Al2O3 Mechanical Mixtures

Abstract Selectivity to N2 in the reaction of NH3 with metal oxides has been markedly increased by the addition of Pt/Al2O3 to the metal oxides, whereas the activity of the metal oxides has not been changed. The metal oxides on their own have oxidized NH3 to NO, NO2, and N2O as well as N2, and furthermore, the selectivities in the reaction with metal oxides have depended markedly on the reaction temperature and inlet concentration of NH3 in the pulse. In the oxidation of NH3 with metal oxide–Pt/Al2O3 mechanical mixtures, N2 has been selectively produced irrespective of the reaction temperature and the inlet concentration of NH3 in the pulse. The activity of the mixtures has been shown, on the other hand, to be the same as that of the metal oxides. All of the experimental data have been explained in terms of the following scheme: In the oxidation of NH3 with metal oxide–Pt/Al2O3 mixtures, NH3 is at first oxidized by metal oxides to form NOx(NO, NO2, and N2O) and N2, then the NOx components is transfered through the gas phase from the metal oxides to Pt particles on Al2O3, and finally the NOx. components react with NH3 on Pt particles to form N2 selectively.