How is Crude oil refined?

Crude oil that comes out of an oil well is a thick, dark liquid containing a mixture of many organic compounds. It cannot be put to use without refining. The different constituents of crude oil boil at different temperatures. Refining processes may be classified as fractional distillation, conversion and chemical treatment. Fractional distillation separates crude oil into some of its fractions depending on their boiling points. Some components are separated by solvent extraction in which an organic solvent is used to extract the substances especially solids which are then recovered by crystallization or evaporation of the solvent. Cracking is also a process used in refineries to produce useful petrochemicals. Here heat and catalysts are used to break down some of the heavier hydrocarbons to lighter, more useful fractions.