Chemical Properties
Melting point | -95.4--90.5 °C |
Boiling point | 32-210 °C |
Density | 0.70-0.80 g/cm3 |
form | Liquid gasoline is a complex mixture of at least 150 hydrocarbons with about 60–70% alkanes, 25–30% aromatics, and 6–9% alkenes. The small-chain, low-carbonnumbered components are more volatile and thus in higher percentages in the vapor phase than the larger and heavier molecules. The concentrations of aromatics, the more toxic of the components, are depleted to about 2% in the vapor phase. The light alkanes, the less toxic components, are enriched to about 90%. Benzene is also present and represents a component of major concern. |
Dielectric constant | 2.0(Ambient) |
EPA Substance Registry System | Natural gasoline (8006-61-9) |
Safety Information
Hazardous Substances Data | 8006-61-9(Hazardous Substances Data) |
Usage And Synthesis
Known as petrol to the British and benzin to the Germans, is a mixture of C4 to Cl2 hydrocarbons. Natural gasoline obtained by fractional distillation of petroleum contains mostly saturated hydrocarbons. The ordinary commercial grades of motor gasoline contain paraffins, olefins, naphthenes, and aromatics, all in substantial concentrations. Motor gasolines are made chiefly by cracking processes in which heavier petroleum factions are converted into more volatile fractions by thermal or catalytic decomposition. Where petroleum is scarce, as in Germany, gasoline also has been made commercially by catalytic high-pressure hydrocarbons from carbon monoxide and hydrogen. Some gasolines sold in the USA contain a minor proportion of tetraethyllead, which is added in concentrations not exceeding 3 mil per gallon of motor gasoline to prevent "knock" in engines in which the gasoline is used as fuel. Commercial grades of tetraethyllead or Ethyl fluid typically contain about 63% tetraethyllead and about 35% ethylene dichloride or dibromide which aids in evacuating the products of the lead from engines. In addition, the fluid contains a red or a blue dye. All leaded gasolines are dyed for recognition and should be used only as motor fuel. Other materials occasionally blended in gasoline, particularly in Europe, to decrease knock are benzene and ethanol.
Gasoline is a highly flammable, mobile liquid with characteristic odor. Evaporates quickly and is insoluble in water, freely soluble in alcohol, ether, chloroform, and benzene; and dissolves fats, oils, and natural resins. Used as fuel in internal combustion engines ofthe spark-ignitedreciprocating type.
There are several methods used for the production of gasoline. Among these, distillation or fractionation yields a straight run product of relatively low octane number, which is used primarily for blending, thermal and catalytic cracking, reforming, polymerization, isomerization and dehydrocyclodimerization. The various means of converting hydrocarbon gases into motor fuels by modification of chemical structure usually makes use of catalysts. The present source of gasoline is petroleum; gasoline may also be produced from shale oil and tar sands as well as by gasification of coal.
While gasoline can be synthesized from carbon monoxide and hydrogen, almost all gasoline is made by refining, cracking and alkylation. The fractions are blended to produce the required fuels. Motor gasoline boils between 30°C and 200°C. If the fuel is too volatile, the vapor bubbles are formed which hinder the flow of fuel (vapor lock).
Different kinds of gasoline are:
(a) Cracked gasoline: Gasolines are produced by catalytic decomposition of high-boiling components of petroleum. Such gasolines have higher octane ratings than that produced by fractional distillation. The difference is due to a higher content of unsaturated, aromatic and branched-chain hydrocarbons. The actual properties vary widely depending on the source, temperature, pressure and the catalyst used in cracking.
(b) High-octane gasoline: It is a gasoline with an octane value of 90to 100.
(c) Lead-free gasoline: It is a gasoline containing no more than 0.05 g of lead per 4.5 1 designed for use in engines equipped with a catalytic converter.
(d) Natural gasoline: It is the gasoline based on butane, pentane and hexane hydrocarbons. It is used in blending to produce finished gasoline with adjusted volatility but having a low octane number.
(e) Polymer gasoline: A gasoline produced by polymerization of low molecular weight hydrocarbons such as ethylene, propene and butene is called polymer gasoline. It is used in small amounts for blending with other gasolines to improve their octane number.
(f) Pyrolysis gasoline: Gasolinep roduced by thermal cracking as a by-product of ethylene manufacture is pyrolysis gasoline. It is used as a source of benzene.
(8) Reformed gasoline: It is a high octane gasoline obtained from low octane gasoline by heating the vapors to high temperatures or passing the vapors over a catalyst.
(h) Straight-run gasoline: Gasoline produced by distillation, without the use of cracking or other chemical conversion processes, is called straight-run gasoline.
(i) White gasoline: It is an unleaded gasoline especially designed for use in motor boats. It is uncracked and strongly inhibited against oxidation to avoid gum formation, and is usually not colored to distinguish it from other grades. It also serves as a fuel for camp lanterns and portable stoves.
Aviation fuel contains a less of low and high boiling components. The octane number or maximum power is carefully controlled by the structure of gasoline components. The gasoline may further be improved by an antiknocking additive. Other additives include lead scavengers (ethylene bromide), antioxidants, metal deactivators, anti-icing agents and detergents. The host of properties exhibited by gasolines results from the use of additives. These gasolines are used as a source of hydrogen in ammonia manufacture and as a source of energy for tractors and jeeps.
In addition, these components can leach through the soil and contaminate groundwater where they may remain for long periods of time. Under aerobic conditions, biodegradation of gasoline components can occur in soil and surface water.
Preparation Products And Raw materials
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