Hydro carbon
Any of a class of organic compounds composed only of carbon and hydrogen.
The carbon atoms form the framework, and the hydrogen atoms attach to them.
Hydrocarbons, the principal constituents of petroleum and natural gas, serve as fuels, lubricants, and raw materials for production of plastics, fibres, rubbers, solvents, explosives, and industrial chemicals.
All burn to carbon dioxide and water with enough oxygen or to carbon monoxide without it.
The two major categories are aliphatic, with the carbon atoms in straight or branched chains or in nonaromatic rings, and aromatic (see aromatic compound).
Aliphatic compounds may be saturated (paraffins) or, if any carbon atoms are joined by double or triple bonds, unsaturated (e.g., olefins, alkenes, alkynes). All but the simplest hydrocarbons have isomers (see isomerism). Ethylene, methane, acetylene, benzene, toluene, and naphthalene are hydrocarbons.
Petroleum
As a technical term, petroleum encompasses the liquid (crude oil), gaseous (natural gas), and viscous or solid (bitumen, asphalt) forms of hydrocarbons that occur in the Earth, but the meaning is often restricted to the liquid oil form.
Crude oil and natural gas are the most important primary fossil fuels. Asphalt has been used since ancient times to caulk ships and pave roads. In the mid 1800s petroleum began to replace whale oil in lamps, and the first well specifically to extract it was drilled in 1859.
The development of the automobile gave petroleum a new role as the source of gasoline.
Petroleum and its products have since been used as fuels for heating, for land, air, and sea transport, and for electric power generation and as petrochemical sources and lubricants.
Crude oil and natural gas, produced mostly in Saudi Arabia, the U.S., and Russia, now account for about 60% of world energy consumption; the U.S. is by far the largest consumer.
At present rates of consumption, the known supply will be exhausted by the mid 21st century. Petroleum is recovered from drilled wells, transported by pipeline or tanker ship to refineries, and there converted to fuels and petrochemicals.
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.
Natural Gas
Colourless, highly flammable gaseous hydrocarbon consisting primarily of methane and ethane.
It may also contain heavier hydrocarbons, carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, helium, and argon. I
t commonly occurs in association with crude oil (see petroleum). Natural gas is extracted from wells drilled into the Earth.
Some natural gas can be used as it comes from the well, without any refining, but most requires processing.
It is transported either in its natural gaseous state by pipeline or, after liquefaction by cooling, by tankers. Liquefied natural gas occupies only about 1/600 of the volume of the gas. It has grown steadily as a source of energy since the 1930s.
Petro Chemical
Strictly, any of a large class of chemicals (as distinct from fuels) derived from petroleum and natural gas.
The category has been broadened to include a much larger range of organic compounds and a few inorganic compounds (including carbon black, sulfur, and ammonia).
Some materials cannot be classifed unequivocally because they have alternative sources (benzene from coal, ethanol from fermentation). Like crude oil and natural gas, most petrochemicals consist mainly of carbon and hydrogen and are called hydrocarbons.
Petrochemicals used as raw materials (feedstocks) include ethylene, propylene, butadiene, benzene, toluene, xylene, and naphthalene. Among the myriad petrochemical products are plastics (e.g., polyethylene, polypropylene, polystyrene), soaps and detergents, solvents, drugs, fertilizers, pesticides, explosives, synthetic fibres and rubberss, paints, epoxies, flooring and insulating materials, luggage, and recording disks and tapes.
