Gasoline (redirected from unleaded gasoline)

gasoline or petrol, light, volatile mixture of hydrocarbons for use in the internal-combustion engine and as an organic solvent, obtained primarily by fractional distillation and "cracking" of petroleum, but also obtained from natural gas, by destructive distillation of oil shales and coal, and by a process that converts methanol to gasoline using zeolite as a catalyst. Gasoline intended for use in engines is rated by octane number, an index of quality that reflects the ability of the fuel to resist detonation and burn evenly when subjected to high pressures and temperatures inside an engine. Premature detonation produces "knocking" and "pinging"; it wastes fuel and may cause engine damage. The addition of tetramethyl lead and tetraethyl lead to raise the octane number is no longer permitted in the United States because it leads to dangerous emissions containing lead. New formulations of gasoline designed to raise the octane number contain increasing amounts of aromatics and oxygen-containing compounds (oxygenates), such as alcohols, methyl tertiary butyl ether (MTBE), and methylcyclopentadienyl manganese tricarbonyl (MMT). Automobiles are now equipped with catalytic converters that oxidize unreacted gasoline; the cars are designed to run on newly formulated gasolines as well as on gasohol, which contains 10% ethanol or 3% methanol. In addition, since 1998 a number of American automobiles have been equipped to enable them to run on either gasoline or E85, a mixture of 85% ethanol and 15% gasoline. Some racing cars use pure methanol as fuel.

There are five blends of gasoline marketed in the United States. Conventional gasoline, the most widely available, is sold where air quality is satisfactory; since 1992, it has been formulated to evaporate more slowly in hot weather so as to reduce smog, and it now contains detergent additives to reduce engine deposits. Winter oxygenated gasoline, introduced in 1992, is formulated as conventional gasoline with oxygen-rich chemicals added, such as MTBE or ethanol. The oxygen promotes cleaner burning, reducing carbon monoxide, and is generally sold from November to March because cold engines operate less efficiently and produce more carbon monoxide. Reformulated gasoline (RFG), introduced in Jan., 1995, is mandated in areas where toxins in the air are a constant problem; it contains oxygen-rich chemicals in lesser concentrations than the winter oxygenated gasoline and is formulated to reduce certain toxic chemicals found in conventional and winter oxygenated fuels. Oxygenated reformulated gasoline is a wintertime fuel exclusive to the New York City area, where heavy carbon monoxide pollution occurs. California reformulated gasoline, introduced in 1996, has a different formulation and burns cleaner than regular reformulated gasoline. Because MTBE has been implicated as a pollutant, particularly of groundwater, its use is being curtailed. In 1999, California ruled that the MTBE in California reformulated gas must be phased out by Dec. 31, 2002.

Bibliography

See Society of Automotive Engineers Incorporated, ed., Gasoline and Diesel Fuel: Performance and Additives (1997).

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gasoline

 British petrol

Mixture of volatile, flammable hydrocarbons derived from petroleum, used as fuel for internal-combustion engines and as a solvent for oils and fats. Gasoline became the preferred automobile fuel because it releases a great deal of energy when burned, it mixed readily with air in a carburetor, and it initially was cheap due to a large supply. Costs have now increased greatly except where subsidized. Gasoline was first produced by distillation. Later processes increased the yield from crude oil by splitting large molecules into smaller ones. Still other methods, such as conversion of straight-chain hydrocarbons into their branched-chain isomers, followed. The resulting gasoline is a complex mixture of hundreds of hydrocarbons. A gasoline's octane number indicates its ability to resist knocking (premature combustion) and can be altered by changing the proportions of certain components. The compound tetraethyl lead, once used to reduce knocking, has been banned as toxic. Other additives include detergents, antifreezes, and antioxidants. Since the mid-20th century gasoline fumes have been recognized as a major component of urban air pollution. Efforts to reduce dependence on gasoline, which is a nonrenewable resource, include use of gasohol, a 9:1 mix of gasoline and ethanol, and the development of electric automobiles.

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gasoline, gasolene

US and Canadian any one of various volatile flammable liquid mixtures of hydrocarbons, mainly hexane, heptane, and octane, obtained from petroleum and used as a solvent and a fuel for internal-combustion engines. Usually petrol also contains additives such as antiknock compounds and corrosion inhibitors

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gasoline [′gas·ə‚lēn]

(materials)

A fuel for internal combustion engines consisting essentially of volatile flammable liquid hydrocarbons; derived from crude petroleum by processes such as distillation reforming, polymerization, catalytic cracking, and alkylation; the common name is gas. Also known as petrol.

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Gasoline 

a mixture of hydrocarbons of various structures; a colorless liquid that boils in the range from 30° to 205° C. Its freezing temperature is below -60° C, its flash point is below 0°C, and its density is 700–780 kg/m³(0.70–0.78 g/cm³). Explosive mixtures are formed at concentrations of 74–123 g of gasoline vapors per cu m of air.

The primary sources of gasoline are distillation and catalytic refining of oil; small amounts are obtained by the conversion of mineral coal and bituminous shales, as well as from natural and by-product gases. Gasoline is used primarily as fuel for internal-combustion engines with spark ignition (with carburetors or with direct injection); approximately 10 percent of gasoline is used as solvents or cleaning fluids and for other purposes. The gasolines that are used as fuel are divided into automotive and aviation types (see Tables 1 and 2).

Automotive gasolines are divided into summer types (for use from April through September in all regions except the northern and northeastern) and winter types (for the northern and northeastern regions; in the remaining regions from October through March). Winter gasolines contain a larger quantity of low-boiling hydrocarbons than do summer gasolines. Gasolines are characterized by the following indexes: a tendency toward the formation of deposits (existent resin content), corrosional aggressiveness (acidity and sulfur content), and stability in storage (induction period and period of stability).

The major performance characteristic of gasolines is their antiknock rating—that is, the ability to burn normally in a motor under various conditions. The antiknock properties of gasolines are rated by the octane rating and, for aviation gasolines, by the performance rating as well. The higher the octane or performance rating of a gasoline, the better its antiknock properties. The division of gasolines into grades is based on these properties: for automotive gasolines, the value of the octane rating is given (A-66, A-72, AI-93); aviation

Table 1. Grades and quality of automotive gasolines manufactured in the USSR
		Grade
Index		A-66	A-72	A-76	AI-93	AI-98
1 For AI–98 gasoline there is no division Into summer and winter types; for the other gasolines, the numerator gives the summer value and the denominator gives the winter value.
Minimum octane rating by the motor method		66	72	76	85	89
Maximum tetraethyl lead content (g/kg)		0.6	—	0.41	0.82	0.82
Minimum temperature of start of distillation (°C)		35	35	35	35	35
Maximum end point of boiling (°C)		205/185	195/185	195/185	195/185	1951
Maximum pressure of saturated vapors
	(kilonewtons per sq m)	670/930	670/930	670/930	670/930	670
	(mm of mercury)	500/700	500/700	500/700	500/700	500
Minimum induction period (min)		450	600	900	900	900
Maximum acidity, KOH (mg/l)		30	30	30	30	30
Maximum (existent) resin content (mg/l)		150	100	100	70	70
Maximum sulfur content (%)		0.15	0.12	0.10	0.10	0.10

Table 2. Grades and quality of aviation gasolines manufactured in the USSR
		Grade
Index		B-100/130	B-95/130	B-91/115	B-70
Antiknock rating
	minimum octane rating by the motor method	98.6	95	91	70
	minimum performance rating for a rich mixture	130	130	115	—
Maximum tetraethyl lead content (g/kg)		2.7	3.3	2.5	—
Minimum temperature of start of distillation (°C)		40	40	40	40
Maximum end point of boiling (°C)		180	180	180	180
Maximum acidity, KOH (mg/l)		10	10	10	10
Maximum (existent) resin content (mg/l)		20	20	20	20
Maximum sulfur content (%)		0.05	0.05	0.05	0.05
Period of stability (hr)		8	8	8

gasolines (except B-70) are graded by a fraction (B-100/130, B-91/115), where the numerator is the octane rating and the denominator is the performance rating. An antiknock agent, tetraethyl lead, is added to gasolines to increase their antiknock rating. Such ethylated gasolines are toxic, and precautionary measures are necessary when working with them; they must be dyed to distinguish them from nonethylated gasolines.

Effect on the organism Gasoline passes into the organism mainly through the lungs. The danger of gasoline poisoning exists at all stages of its production and transportation and particularly in its use. The maximum permissible concentration of gasoline vapors in air is 100–300 mg/m³; for solvent gasoline it is 300 mg/m³. In acute poisoning by gasoline vapors, headache, unpleasant sensations in the throat, coughing, and irritation of the mucous membranes of the eye and nose develop; in serious cases dizziness, unsteady walk, psychic excitation, slowing of pulse, and sometimes loss of consciousness result. For chronic poisoning the usual complaints include headaches, dizziness, sleep disorders, irritability, increased fatigability, loss of weight, and pains in the region of the heart.

First aid and medical treatment Treatment of acute poisoning includes fresh air, oxygen, and cardiac and tranquilizing agents; in cases of stoppage of breathing, artificial respiration is used. In case of entry of gasoline into the stomach, 30–50 g of vegetable oil are given internally. In cases of chronic poisoning, general restorative treatment, physiotherapy, and temporary removal from work with gasoline are required. Persons suffering from functional illnesses of the nervous system and endocrine organs are not allowed to work with gasoline.

REFERENCES

Nefteprodukty: Svoistva, kachestvo, primenenie: Spravochnik. Moscow, 1966.
Vrednye veshchestva v promyshlennosti, 4th ed., part 1. Editor in chief, N. V. Lazareva. Leningrad, 1963.
Professional’nye bolezni, 2nd ed. Moscow, 1964.

A. A. GUREEV

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Gasoline 

a mixture of light liquid hydrocarbons obtained during the distillation of petroleum or the separation of industrial gases. Gasoline is a readily combustible and dangerously explosive liquid that is used as a fuel for carburetor internal-combustion engines (natural gasoline with a boiling range of 30° C to 200° C), as a solvent for the extraction of oils and resinated substances (fraction 70° C to 100° C), for laboratory analysis (petroleum ether with a boiling range of 30° C to 80° C), and for other purposes. Gasoline as a single commercial product with precisely standardized properties is not produced industrially.