Kolmoiskatalyytit

Kolmoiskatalyytit, also known as three-way catalysts, are emission control devices used in internal combustion engines. Their primary function is to reduce harmful pollutants in exhaust gases by facilitating chemical reactions that convert them into less harmful substances. These pollutants include carbon monoxide (CO), unburnt hydrocarbons (HC), and nitrogen oxides (NOx).

The "three-way" designation refers to the three main chemical conversions that occur within the catalyst: the oxidation of carbon monoxide to carbon dioxide (CO2), the oxidation of unburnt hydrocarbons to carbon dioxide and water (H2O), and the reduction of nitrogen oxides to nitrogen gas (N2). This complex process relies on a ceramic honeycomb structure coated with precious metals, typically platinum (Pt), palladium (Pd), and rhodium (Rh). These metals act as catalysts, lowering the activation energy required for these reactions to occur efficiently.

For the three-way catalyst to function optimally, the air-fuel ratio in the engine must be precisely controlled, ideally at the stoichiometric point. This ensures a balanced supply of oxygen for oxidation reactions and a sufficient amount of reducing agents (hydrocarbons and CO) for NOx reduction. Engine control units (ECUs) monitor exhaust gas composition using oxygen sensors and adjust fuel injection accordingly to maintain this critical balance. The widespread adoption of three-way catalysts has significantly improved air quality by dramatically reducing vehicular emissions.