For three-way and dual-bed catalytic converters, which statement is true?

• A. They perform both oxidizing and reducing reactions.
• B. They perform only oxidizing reactions.
• C. They perform only reducing reactions.
• D. They are not catalytic converters.

Answer: (B)

These converters are designed to handle two kinds of pollutant transformations in the exhaust: oxidation and reduction. A three-way catalyst uses metals like platinum and palladium to oxidize carbon monoxide and unburned hydrocarbons into carbon dioxide and water, while rhodium promotes the reduction of nitrogen oxides to nitrogen. This setup means it performs both oxidizing and reducing reactions, but only under the right engine fueling around the stoichiometric air–fuel ratio. A dual-bed system achieves the same overall goal in two stages: one bed reduces NOx, and the other bed oxidizes remaining CO and hydrocarbons. So the true statement is that they perform both oxidizing and reducing reactions, not only oxidizing.