It has now been over 25 years since the introduction of the catalytic converter to reduce emissions from the internal combustion engine. It is considered one of the greatest environmental successes of the 20th century, however, new emission control technologies are still being developed to meet ever more stringent mobile source (gasoline and diesel) emissions. This short review will discuss the basis for improvements and highlight technology area, which will require further improvements in emissions and fuel economy. Some of the issues related to fuel cells which some believe may replace the internal combustion engines for automobile applications is also be briefly discussed.

Automobile exhaust catalysts

Fundamental Studies of Diesel Particulate Filters: Transient Loading, Regeneration and Aging

An exhaust gas purification system for an internal combustion engine includes a dual passage portion having a first passage and a second passage which are connected in parallel to each other. In the first passage, a first catalyst constructed of lean NOx catalyst is located and further a second catalyst constructed of oxidizing catalyst or three-way catalyst is located downstream of the first catalyst. In the second passage, a third catalyst constructed of oxidizing or three-way catalyst is located. A flow switching valve is provided so as to switch the flow of exhaust gas between the first passage and the second passage. The flow switching valve is switched so that exhaust gas flows through the third catalyst when the engine is being warmed-up and flows through the first catalyst and the second catalyst after the engine has been warmed-up.

Exhaust gas purification system for an internal combustion engine

Catalytic automotive exhaust aftertreatment

Monolith structures, materials, properties and uses

An engine exhaust system and method of controlling hydrocarbon emissions are provided. The system and method are based on the use of two catalytic converter chambers, a first chamber containing a catalytic material and a second chamber containing catalyst as well as molecular sieves capable of adsorbing hydrocarbons during engine start-up and of having hydrocarbons desorbed therefrom when the catalysts reach an effective converting temperature. According to the invention, engine exhaust is selectively conveyed to each of the two converters in a manner such that initially produced hydrocarbon is withheld in the system by the molecular sieves in order to be recycled through the converters and brought into contact with the catalyst after an effective converting temperature has been attained.

Dual converter engine exhaust system for reducing hydrocarbon emissions

An engine exhaust system disclosed which is designed to reduce hydrocarbon emissions caused by the evaporation of fuel from the fuel tank and by the inefficiency of combustion and catalytic conversion during cold engine start-up. This system utilizes molecular sieves, such as high-silica zeolites, which adsorb hydrocarbons evaporating from the fuel tank or emitted during engine start-up, before the catalytic converter has attained an effective operating temperature. This system is designed so that hydrocarbons that would otherwise be emitted to the atmosphere from the fuel tank or by passing through the converter unconverted are held within the system either for combustion in the engine or passage through the converter once it is operating efficiently.

Engine exhaust system for reduction of hydrocarbon emissions

A catalyst system for the oxidation of hydrocarbons, carbon monoxide, and the reduction of nitrogen oxides is provided. The unique synergy of the catalyst system, a combination of molecular sieves and noble metals, provides a system that partially or entirely replaces the need for rhodium as a catalyst in three way catalyst systems.

Louis S. Socha

Papers

Dual converter engine exhaust system for reducing hydrocarbon emissions

Engine exhaust system for reduction of hydrocarbon emissions

Molecular sieve-palladium-platinum catalyst on a substrate

Development of a Diesel Particulate Filter Composition and Its Effect on Thermal Durability and Filtration Performance

Electrically heated extruded metal converters for low emission vehicles