Petrochemicals

Petrochemical, in the strictest sense, any of a large group of chemicals (as distinct from fuels) derived from petroleum and natural gas and used for a variety of commercial purposes. The definition, however, has been broadened to include the whole range of aliphatic, aromatic, and naphthenic organic chemicals, as well as carbon black and such inorganic materials as sulfur and ammonia. In many instances, a specific chemical included among the petrochemicals may also be obtained from other sources, such as coal, coke, or vegetable products. For example, materials such as benzene and naphthalene can be made from either petroleum or coal, while ethyl alcohol may be of petrochemical or vegetable origin. This makes it difficult to categorize a specific substance as, strictly speaking, petrochemical or nonpetrochemical.
Products made from petrochemicals include such items as plastics, soaps and detergents, solvents, drugs, fertilizers, pesticides, explosives, synthetic fibres and rubbers, paints, epoxy resins, and flooring and insulating materials. Petrochemicals are found in products as diverse as aspirin, luggage, boats, automobiles, aircraft, polyester clothes, and recording discs and tapes.
Like crude oil and natural gas, petrochemicals are composed primarily of carbon and hydrogen and are called hydrocarbons. If, in the molecules, the carbon atoms are linked by single bonds, the molecules are said to be saturated. If they are linked by one or more double bonds, the molecules are said to be unsaturated. Unsaturated chemicals are preferred as petrochemical feedstocks because they are more chemically reactive and can more easily be changed into other petrochemicals.
The various components of petroleum used as raw materials in the production of other chemicals are known as feedstocks. Petrochemical feedstocks can be classified into three general groups