Final answer:
Modern three-way catalytic converters effectively reduce emissions in gasoline engines by catalyzing pollutants such as nitric oxide into less harmful substances. However, in diesel engines, these converters are less efficient at removing nitrogen oxides due to differences in combustion and exhaust composition.
Step-by-step explanation:
Oxides of nitrogen, such as nitrogen dioxide (NO₂), are concerning pollutants produced by diesel engines. Modern three-way catalytic converters, which are common in gasoline engines, utilize a platinum-rhodium catalyst surface to facilitate the conversion of nitric oxide into less harmful substances, such as dinitrogen (N₂) and oxygen (O₂). The process also addresses carbon monoxide (CO) and hydrocarbons, converting them into carbon dioxide (CO₂) and water vapor (H₂O), leading to a significant reduction in toxic emissions.
However, in a diesel engine, the conditions for the catalytic converter to remove nitrogen oxides are not optimal. Diesel fuel burns at different temperatures and has a different exhaust gas composition compared to gasoline, which can affect the effectiveness of the converter. As a result, while converters can still treat other emissions, they might be less efficient at converting nitrogen oxides in diesel engines. Therefore, alternative methods like selective catalytic reduction (SCR) or exhaust gas recirculation (EGR) are often used in diesel vehicles to reduce these emissions.