Investigation of the reduction of nitric oxides by CO and H2 on Pt-Mo catalysts under oxidizing conditions

The currently used three-way catalyst in passenger cars reduces CO, H2, and NOx in the exhaust if O2 is stoichiometrically introduced to the motor. However, the new lean-burn engines work with an excess of O2 thus, requiring less fuel and producing less CO2. The currently used catalyst is not able to reduce NOx under oxidizing conditions. The results of NOx reduction by H2 and CO under oxidizing conditions are presented and discussed.The reduction of NOx by H2 and CO was studied at 100-250 °C in oxidizing atmospheres present in the exhaust of diesel or lean-burn cars. The reduction of NOx by H2 occurred in Pt-MO catalysts at a high excess of O2. At the highest stoichiometric ratio of excess oxygen at 14-20, the CO showed inhibiting effects. The addition of Co as a third catalyst component increases the NOx conversion significantly in the presence of 0.3-0.6% CO which corresponded to the concentrations in the exhaust of lean-burn cars.