Composition of hydrocarbon
(i) Alkanes: found 30 to 70% consist of upto 40 carbon molecule. Alkanes are mainly linear chain but some are branched chain isomers.
(ii) Cycloalkanes : Found 16 to 64% cycloalkanes exist in petroleum are; methyl cyclopentane, cyclohexane etc. cycloalkanes rich oil is known as asphaltic oil.
(iii) Aromatic hydrocarbon: found 8 to 15% compound exist in petroleum are; Benzene, Toluene, Xylene, Naphthalene etc.
(iv) Sulphur, nitrogen and oxygen compound: Sulphur compound present to the extent of 6% that contain mercaptans [R-SH] and sulphides [R-S-R]. The not likable smell of petroleum is due to sulphur elements. Nitrogenous substances are pyrroles, pyridines and quinolines. Oxygen elements exist in petroleum are Phenols, resins and Alcohols. Compounds such as haemin, chlorophyll are also found in it.
(v) Natural gas: It is a mixture of Methane of 80%, Ethane of 13%, Propane of 3%, Butane of 1%, Vapours of low boiling pentanes and hexanes of 0.5% and Nitrogen of 1.3%. L.P.G. consists of butanes and pentanes and used as cooking gas. It is extremely inflammable. It has methane, ethane and nitrogen.
(vi) C.N.G.: When natural gas compressed at extremely high pressure is known as compressed natural gas (CNG). Natural gas has octane number of 130 it has, partly of methane and can consist of, small volume of propane and ethane.