Selasa, 14 Februari 2012
Petrochemicals are chemical products derived from petroleum. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as corn or sugar cane.
Two petrochemical classes are olefins including ethylene and propylene, and aromatics including benzene, toluene, and xylene isomers. Oil refineries produce olefins and aromatics by fluid catalytic cracking of petroleum fractions. Chemical plants produce olefins by steam cracking of natural gas liquids like ethane and propane. Aromatics are produced by catalytic reforming of naphtha. Olefins and aromatics are the building-blocks for a wide range of materials such as solvents, detergents, and adhesives. Olefins are the basis for polymers and oligomers used in plastics, resins, fibers, elastomers, lubricants, and gels.
Global ethylene and propylene production are ~110 million tonnes and ~65 million tonnes per annum, respectively. Aromatics production is ~70 million tonnes. The largest petrochemical industries are located in the USA and Western Europe; however, major growth in new production capacity is in the Middle East and Asia. There is substantial inter-regional petrochemical trade.
Primary petrochemicals are divided into three groups depending on their chemical structure:
* Olefins includes ethylene, propylene, and butadiene. Ethylene and propylene are important sources of industrial chemicals and plastics products. Butadiene is used in making synthetic rubber.
* Aromatics includes benzene, toluene, and xylenes. Benzene is a raw material for dyes and synthetic detergents, and benzene and toluene for isocyanates MDI and TDI used in making polyurethanes. Manufacturers use xylenes to produce plastics and synthetic fibers.
* Synthesis gas is a mixture of carbon monoxide and hydrogen used to make ammonia and methanol. Ammonia is used to make the fertilizer urea and methanol is used as a solvent and chemical intermediate.
The prefix "petro-" is an arbitrary abbreviation of the word "petroleum"; since "petro-" is Ancient Greek for "rock" and "oleum" means "oil". Therefore, the etymologically correct term would be "oleochemicals". However, the term oleochemical is used to describe chemicals derived from plant and animal fats.
Oil to Petrochemicals
Petrochemicals are chemicals made from petroleum (crude oil) and natural gas. Petroleum and natural gas are made up of hydrocarbon molecules, which are comprised of one or more carbon atoms, to which hydrogen atoms are attached.
Currently, oil and gas are the main sources of the raw materials because they are the least expensive, most readily available, and can be processed most easily into the primary petrochemicals listed on the left.
Only about five percent of the oil and gas consumed each year is needed to make all the petrochemical products.
Petrochemicals have had a dramatic impact on our food, clothing, shelter and leisure. Some synthetics, tailored for particular uses, actually perform better than products made by nature because of their unique properties.
"Primary Petrochemicals" include: olefins (ethylene, propylene and butadiene) aromatics (benzene, toluene, and xylenes); and methanol.
Olefins are unsaturated molecules of carbon (C) and hydrogen (H) that appear as short chains, of two, three or four carbons in length.
Aromatics contain a six carbon ring structure. The oxygen/hydrogen (OH) group in methanol denotes that it is an alcohol.
Intermediates and Derivatives:
Petrochemical intermediates are generally produced by chemical conversion of primary petrochemicals to form more complicated derivative products (see graphic on the left).
Petrochemical derivative products can be made in a variety of ways: directly from primary petrochemicals; through intermediate products which still contain only carbon and hydrogen; and, through intermediates which incorporate chlorine, nitrogen or oxygen in the finished derivative. In some cases, they are finished products; in others, more steps are needed to arrive at the desired composition.
Of all the processes used, one of the most important is polymerization. It is used in the production of plastics, fibers and synthetic rubber, the main finished petrochemical derivatives.
Some typical petrochemical intermediates are:
vinyl acetate for paint, paper and textile coatings
vinyl chloride for polyvinyl chloride (PVC)
ethylene glycol for polyester textile fibers
styrene which is important in rubber and plastic manufacturing.
Major End Use Products:
Some typical petrochemical intermediates are:
- vinyl acetate for paint, paper and textile coatings vinyl chloride for
- polyvinyl chloride PVC)
- resin manufacture
- ethylene glycol for polyester - textile fibers
- styrene which is important in rubber and plastic manufacturing.