(617gc) Study of Reactivity of CO+NO Reaction on Supported Pd Catalyst

Palladium (Pd) is the primary component in most automotive three-way catalysts (TWCs). Under slightly lean conditions, CO in the exhaust emissions can be oxidized to CO₂. The light-off of CO oxidation by O₂ follows an S-shaped curve. Under stoichiometric conditions, where there is a lack of molecular O₂ in the exhaust emissions, the conversion of CO to CO₂ can be accomplished by the CO+NO reaction, where NO is reduced by CO to N₂, to achieve the simultaneous removal of CO and NO. However, we found that when CO is oxidized by NO, instead of O₂, the CO light-off curve has a concave shape. This phenomenon has been further investigated by comparing Al₂O₃ and Ce-Zr-O supported Pd catalysts with focus on the effects of different catalyst pre-treatment methods, catalyst aging, reactant feed (CO/NO) ratio, as well as the operating conditions such as heating and cooling on the reactivity of CO+NO reaction. DRIFTs experiments were carried out to study the CO+NO conversion to CO₂+N₂O, instead of the target products CO₂+N₂.