http://www.primeonlinetutor.com/cd2 Fossil fuels such as coal, petroleum and natural gas are important sources of energy for industrialised countries. These fuels, which are mixtures of hydrocarbons, are burned in air or oxygen to release energy. However fossil fuels, particularly petroleum (crude oil) and natural gas, have another important use. They are an invaluable source of raw materials for the petrochemical industry. About 95% of all synthetic carbon compounds, including plastics, resins and solvents, are derived from compounds produced from petroleum and natural gas. Petroleum (crude oil) is a complex mixture of hydrocarbons consisting mainly of alkanes and cycloalkanes with smaller quantities of unsaturated hydrocarbons including alkenes. Regardless of whether the petroleum is used for fuels or as raw material (feedstock) for the petrochemical industry, it must first be refined. Crude oil can be separated into various fractions by the process called fractional distillation. Separation into fractions is based on differences in boiling points of the hydrocarbon components. The crude oil is vaporised and the vapour mixture rises up the fractionating column. The short-chain hydrocarbons have lower boiling points and rise higher in the column before condensing. The long-chain hydrocarbons condense in the lower parts of the column. The liquid fractions are removed at various levels. The residue consists of long-chained bituminous solids that are periodically removed from the base. The nature and composition of the fractions varies somewhat between refineries. CD2111 http://youtu.be/In3Slgka8gc

• published: 20 Sep 2013
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