Gas Aftertreatment Systems

The internal combustion engine serves a vast array of transportation needs, but pollutants produced during combustion can harm the environment and human health. Primary gaseous pollutants include carbon monoxide (CO), oxides of nitrogen (NO [[inf]]x[[/inf]] ), and hydrocarbons (HC). These pollutants have the potential to harm human health directly or through the formation of ground-level ozone by atmospheric reactions with sunlight. Regulations exist to insure that pollution from vehicles is limited, and vehicles are carefully designed and engineered to meet these regulations. Catalyst technologies are the primary means of reducing pollutants from engine exhaust. Various types of catalysts are used based on the engine combustion technique and other factors. The three-way catalyst is the predominant catalyst used in spark-ignited gasoline engine vehicles. Other catalyst technologies such as selective catalytic reduction and lean NO [[inf]]x[[/inf]] traps help to reduce NO [[inf]]x[[/inf]] from lean engine vehicles such as diesel vehicles. By the combination of nanoscale engineering of catalytically reactive surfaces and the coupling of catalyst to engine controls, the modern catalyst dramatically reduces pollutants from automobiles and enables cost-effective transportation with minimal impact on the environment and human health.