From Catalytic Converter
The centerpiece of the motor vehicle emission control program is the catalytic converter. Since the mid-1970s, catalysts equipped on passenger cars, from the first two-way oxidation catalysts to today's advanced three-way catalysts, have cut pollution by more than 1.5 billion tons in the U.S. Catalyst technology frequently has been hailed as one of the great automotive engineering achievements. Catalytic converters have also been developed for use on trucks, buses, and motorcycles, as well as on construction equipment, lawn and garden equipment, and other non-road engines.
- When strict vehicle emission standards were first set in the Clean Air Act Amendments of 1970, automakers did not possess the technology to significantly lower vehicle emissions.
- Catalytic converters for automobiles were developed to meet the standards set by the U.S. Congress.
- Catalytic converters, or “catalysts,” were first installed on cars in the mid-1970s.
- Over the past 25 years, catalyst technology has continued to advance to meet increasingly tighteremissions standards and greater durability requirements.
The term covers the stainless steel box mounted in the exhaust system. Inside is the auto catalyst, a ceramic or metallic substrate with an active coating incorporating alumina, ceria and other oxides and combinations of the precious metals - platinum, palladium and rhodium. For ceramic substate, the substrate can be protected from vibration and shock by a resilient ceramic or metallic 'mat'.
Autocatalysts can be oxidation or three-way types. Oxidation catalysts convert carbon monoxide (CO) and hydrocarbons (HC) to carbon dioxide (CO2) and water and decrease the mass of diesel particulate emissions, but have little effect on nitrogen oxides (NOx) and particulate number. Three-way catalysts operate in a closed-loop system including a lambda, or oxygen, sensor to regulate the air:fuel ratio on petrol engines. The catalyst can then simultaneously oxidise CO and HC to CO2 and water while reducing NOx to nitrogen.
Catalytic converter & automobiles