Laboratory experiments were conducted to evaluate a commercial Pd/Rh three-way catalyst as regards its effectiveness in the catalytic oxidation of hydrocarbons (HC) under conditions encountered in spark ignition engine exhaust (air/fuel ratio = 14.7). These tests aimed to determine light-off temperatures (50 % conversion temperatures) for HC, CO and NO in mixtures containing CO2, H2O, H2, CO, NO, O2, N2 and one hydrocarbon.
First, the effect of the concentration of different compounds (H2O, H2, CO, NO) on the catalytic oxidation of propane was studied.
The oxidation of the most important HC species, i.e. alkanes (C1 to C7), alkenes (C2 to C6), alkenes (C2 to C6) and aromatics (C6 to C9), was then investigated. The results were compared to those obtained with a Pt/Rh catalyst.
The inhibiting effect of hydrocarbons as concerns CO oxidation and NO reduction was finally examined.