Gasoline catalyst vehicles

Individual polycyclic aromatic hydrocarbons (PAH) were measured for 18 light-duty vehicles representing 1978 through 1981 model-year production cars for the European and US market. In detail, the test fleet included the following classes 1) gasoline non-catalyst vehicles, 2) gasoline catalyst vehicles, 3) diesel vehicles, 4) neat methanol vehicles with and without a catalyst, and 5) methanol-gasoline blend vehicles. 

Figure 55. Concentration of various types of hydrocarbons in the exhaust gas of different gasoline powered spark ignition engines without catalysts (vehicles A-F) and one diesel engine without catalyst (vehicle G) during the first bag of the US-FTP 75 vehicle test cycle. Reprinted with permission from ref. [39], 1993 Society of Automotive Engineers, Inc.

Exhaust gas catalysts has been widely used since the laimching of the 1970 Clean Air Act in the USA and especially after the introduction of stricter regulations in 1981. At present, one of the fastest growing areas of catalyst-based technology is automotive pollution control. All gasoline-fuelled vehicles sold in the USA, Japan and in the European Community must be equipped with exhaust aftertreatment in order to meet the emission standards. Oxidation catalysts for heavy-duty vehicles have only been used for a short period, but following the tightening emission standards there will be an increased demand for such systems. 

A three-way catalyst (TWC) is used for the conversion of exhaust emissions from gasoline-fuelled vehicles. The TWC converts toxic emissions (like CO, NOx, hydrocarbons) into their non-toxic components N2, 02, HzO, and C02. The TWC gives the best conversion at the stoichiometric air/fuel (A/F) ratio (=14.6/1), which is... 

The major use of monoliths is in catalytic converters for gasoline-fueled vehicles. All new cars need a converter to control emissions of carbon monoxide, hydrocarbons, and nitric oxide, and most use a monolith impregnated with Pt or Pd and Rh. Even though the catalysts have 0.1% or less of noble metal, the annual cost of these units exceeds that of all other catalysts sold for the petroleum and chemical industries. 

The second period is closely related to the development of the so-called three-way catalysts (TWC). As is known, TWCs constitute the current technology of election for the abatement of exhaust emissions (Unbumed hydrocarbons, CO, and NOx) from gasoline-fuelled vehicles [10,18,19,246,247]. More than 95% of the gasoline vehicles nowadays produced in the world are equipped with a TWC converter [247]. The economic importance is also extraordinary, the TWC sales representing about one fourth of global catalyst market [246]. 

Emissions from methanol vehicles are expected to produce lower HC and CO emissions than equivalent gasoline engines. However, methanol combustion produces significant amounts of formaldehyde (qv), a partial oxidation product of methanol. Eormaldehyde is classified as an air toxic and its emissions should be minimized. Eormaldehyde is also very reactive in the atmosphere and contributes to the formation of ozone. Emissions of NO may also pose a problem, especiaHy if the engine mns lean, a regime in which the standard three-way catalyst is not effective for NO reduction. 

SiHcone residue introduced to gasoline with toluene plugged catalysts on vehicles (83). Also a manganese-based octane improver known as MMT has been shown to clog catalyst surfaces (84). 

Engines are also designed to use either gasoline or methanol and any mixture thereof (132—136). Such a system utilizes the same fuel storage system, and is called a flexible fueled vehicle (EEV). The closed loop oxygen sensor and TWC catalyst system is perfect for the flexible fueled vehicle. Optimal emissions control requires a fuel sensor to detect the ratio of each fuel being metered at any time and to correct total fuel flow. 

J. J. Mooney, J. G. Hansel, and K. R. Bums, Three-Waj Conversion Catalysts on Vehicles Fueled with Ethanol-Gasoline Mexuture, SAE 790428, Society of Automotive Engineers, Warrendale, Pa., 1979. 

By 1999, General Motors, Daimler-Clirysler, Toyota, and Nissan all had demonstration fuel cell vehicles operating on niethanol, with plans to start introducing vehicles into the market by 2005. Auto makers have shown a preference for methanol over gasoline primarily because of the likelihood of the sulfur content in gasoline poisoning some of the catalysts used in the fuel cell. 

Catalytic treatment of motor vehicle exhaust has been applied in all passenger cars in the USA since the 1975 models. The first cars with electronic feedback systems and three-way catalysts were 1979 Volvos, sold in California. Today all new gasoline cars sold in the Western world are equipped with catalytic converters. It... 

Gobel, U., Hoehne, J., Lox, E.S. et al. (1999) Durability Aspects of NOx Storage Catalysts for Direct Injection Gasoline Vehicles, SAE Technical Paper 99FL-103. 

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