Liquefied petroleum gas
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Description
Liquefied petroleum gases (LPGs), namely propane and butane, are alkane gases of fossil fuel origin which can be maintained in liquid form in low-pressure vessels. They are used mainly as fuel, [[aerosol (cans}|aerosol can propellants]] and refrigerants. They are produced as impurities from natural gas and from petroleum distillation after reduction of propylene and butylene derived from cracking.
Detailed description
Propane
Propane is the third member of the alkane series with the general formula CH3(CH2)nCH3, where n=1, after methane CH4 and ethane with n=0. It has a boiling point of -44.5 °C.
Butane
Butane has two isomers. The more common one, n-butane, is the fourth member of the alkane series with the general formula CH3(CH2)nCH3, where n=2. It It has a boiling point of -0.3 °C. The other one, iso-butane or 2-methylpropane, CH3CH(CH3)CH3 has a boiling point of -10.3 °C.
Refrigerants
Pure gases are used as refrigerants. Iso-butane is used in domestic refrigerators and some freezers, especially in Europe, whereas propane can be used in some commercial applications, such as the primary refrigerant in the production of liquid natural gas.
Fuel
Although the gases are obtainable in a more or less pure state, the quality used as "bottled gas" or "camping gas" is a mixture of butane and propane isomers with some other impurities, of indeterminate proportions, but mostly n-butane. It has a higher calorific value than natural gas. If completely combusted, 1 kg of 80% butane, 20% propane, will produce 3.02 kg of carbon dioxide, compared with 2.74 kg from methane (natural gas).
