Kinetics of the reduction of NO by C3H6 and C3H8 over Pt based catalysts under lean-burn conditions

The effect of temperature, contact time and reactant concentration on the kinetics of NO reduction by C3H6 and by C3H8 over Pt/Al2O3 under lean-burn conditions have been investigated and kinetic models which satisfactorily fit the data have been developed. The results suggest that with C3H6 the Pt surface is dominated by carbonaceous species, while with C3H8 adsorbed atomic oxygen is the main species on the Pt surface. This difference in the state of the Pt surface results in different mechanisms for NOx reduction. Thus, with C3H6, NOx reduction seems to occur; via the dissociation of adsorbed NO on the Pt surface, while with C3H8, NOx reduction appears to occur via spill-over of NO2 from the Pt metal onto the Al2O3 support where it reacts with C3H8-derived species to form N-2 and N2O.