 | Gasoline: Encyclopedia II - Gasoline - Additives
Gasoline - Additives
Gasoline - Lead
The mixture known as gasoline when used in high compression internal combustion engines, has a tendency to explode early ( pre-ignition pre-detonation) causing a damaging "engine knocking" (also called "pinging") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo in England and Thomas Midgley and Thomas Boyd in the United States. The discovery that lead additives modified this behavior led to the widespread adoption of the practice in the 1920s and hence more powerful higher compression engines. The most popular additive was tetra-ethyl lead. However, with the recognition of the environmental damage caused by the lead, and the incompatibility of lead with catalytic converters found on virtually all automobiles since 1975, this practice began to wane in the 1980s. Most countries are phasing out leaded fuel; different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).
In the U.S., where lead has been blended with gasoline, primarily to boost octane levels, since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total gasoline sales and less than 2,000 tons of lead per year. Effective January 1, 1996, the Clean Air Act banned the sale of the small amount of leaded fuel that was still available in some parts of the country for use in on-road vehicles. Possession and use of leaded petrol in a regular on-road vehicle now carries a maximum $10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines. The ban on leaded gasoline was presumed to lower levels of lead in people's bloodstream and led to thousands of tons of lead being removed from the air.
A side effect of the lead additives was protection of the valve seats from erosion. Many classic car's engines have needed modification to use lead-free fuels since leaded fuels became unavailable.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates.
Gasoline - MMT
Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used for many years in Canada and recently in Australia to boost octane. It also helps old cars designed for leaded fuel run on unleaded fuel without need for additives to prevent valve problems.
There are currently ongoing debates as to whether or not MMT is harmful to the environment and toxic to humans. However, US Federal sources state that MMT is suspected to be a powerful neurotoxin and respiratory toxin. Other substances listed as having toxic neurological effects and toxic effects on the respiratory system include homobatrachotoxin (from Latin American kokoa or arrow-poison frogs), curare (from Latin American plants, also known as strychnine), and tetrodotoxin (from the puffer fish.) Tetrodotoxin has caused a number of deaths (around 20 per year), mostly in Japan, through puffer-fish (fugu) consumption.
Gasoline - Oxygenate blending
Oxygenate blending adds oxygen to the fuel in oxygen-bearing compounds such as MTBE, ethanol and ETBE, and so reduces the amount of carbon monoxide and unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending is mandatory. For example, in Southern California, fuel must contain 2% oxygen by weight. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline.
MTBE use is being phased out due to issues with contamination of ground water. In some places it is already banned. Ethanol and to a lesser extent the ethanol derived ETBE are a common replacements. Especially ethanol derived from biomatter such as corn, sugar cane or grain is frequent, this will often be referred to as bio-ethanol. An ethanol-gasoline mix of 10% ethanol mixed with gasoline is called gasohol. An ethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85. The most extensive use of ethanol takes place in Brazil, where the ethanol is derived from sugarcane. Over 3,400 million US gallons (13,000,000 m³) of ethanol mostly produced from corn was produced in the United States in 2004 for fuel use, and E85 is fast becoming available in many of the United States. The use of bioethanol, either directly or indirectly by conversion of such ethanol to bio-ETBE, is encouraged by the European Union Biofuels Directive.
Other related archives1920s, 1973, 1980s, 1995, 1996, 2, 2, 4-trimethylpentane, Australia, BP, Benzine, Bertha Benz, Brazil, Canada, Clean Air Act, Diesel, Diesel engine, Drāno, E85, EPA, Ethanol, Filling station, Germany, Harry Ricardo, Hurricane Katrina, Indigenous Australians, Internal combustion engine, January 1, List of automotive fuel brands, MTBE, Mannheim, Methylcyclopentadienyl manganese tricarbonyl, Oil refinery, Old French, Opal, Pforzheim, Romania, Russell Marker, Stephen L. Johnson, Thomas Midgley, US, United States, WWII, Wankel engine, additives, alcohol, alkanes, alkenes, alkylation, aromatic hydrocarbons, aromatics, atoms, benzene, billion, bloodstream, butane, carbon, carbon dioxide, carbon monoxide, carcinogenic, catalyst, catalytic converters, catalytic cracker, catalytic reformer, classic car, combustion, compounds, compression, compression ratio, crude oil, crystal, cycloalkanes, density, dermatitis, diesel, distillation, disulfides, drinking water, engine, engine knocking, ethanol, ethers, evaporates, exhaust, fuel, fuel taxes, gallons, gas, gasohol, heptane, hydrocarbons, hydrogen, hydrogen sulfide, inhalant, internal combustion engines, isomer, kerosene, knock resistance, knocking, lead, lice, liquid, litres, megajoules, mercaptans, methanol, molecule, nitrogen oxides, nitrous oxide, octane, octane rating, oil refineries, oil refinery, olefins, organic compounds, organic ethers, oxygen, ozone, paraffin, petroleum, public's health, sacrificial anodes, sodium hydroxide, spontaneous combustion, sugarcane, sulfur, superchargers, tetra-ethyl lead, thiophenes, trade name, tuned, valve, volatile, volatility
 Adapted from the Wikipedia article "Additives", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki |
