How do catalytic converters reduce vehicle emissions, and which pollutants do they primarily target?

• A. Catalytic converters promote redox reactions to convert CO to CO2, hydrocarbons to CO2 and H2O, and NOx to N2 and O2.
• B. They remove all pollutants entirely.
• C. They only reduce CO2 emission.
• D. They speed up formation of NOx.

Answer: (A)

Catalytic converters use a surface of precious metals to speed up oxidation and reduction reactions that would occur slowly on their own. In the exhaust, this means carbon monoxide is oxidized to carbon dioxide, unburned hydrocarbons are oxidized to carbon dioxide and water, and nitrogen oxides are reduced to nitrogen and oxygen. These reactions dramatically cut the amount of toxic pollutants released, even though CO2 is produced as a byproduct of oxidation. They work best at the right high temperature and with a near-stoichiometric air-fuel mixture, and they don’t remove all pollutants entirely or speed up NOx formation.