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» Petroleum (Petra = rock, oleum = oil) is a fossil fuel with the mixture of hydrocarbons. It is a dark viscous liquid. It occurs at various depths under the crust of the Earth.

» It is believed that it was formed beneath the Earth strata by the decomposition of dead remains of organisms living in the sea. When these organisms died, their bodies settled at the bottom of the sea and got covered with many layers of sand and clay. Over the years, these dead organisms transformed into petroleum and natural gas due to the absence of air, high temperature, and pressure.

Refining of Petroleum

» Petroleum gas, light petrol, petrol, kerosene oil, fuel oil (diesel oil), lubricating oil, and paraffin wax are the various constituents of petroleum.

» The process of separating of various constituents/fractions of petroleum is known as refining. It is carried out in a petroleum refinery.

Various Fractions of Petroleum and their Uses

Fractions Composition Boiling Range (K) Uses
Gaseous hydrocarbons C2 - C2 More than 303°C As fuel gas after liquefaction, carbon black.
Crude naphtha (Petroleum ether, petrol, benzene) C3 - C10 303-423°C As a solvent in varnish and rubber industry for dry-cleaning, motor fuel.
Kerosene Oil C10 - C13 423-513°C As a fuel, manufacturing of oil gas
Fuel oil (gas oil, diesel, furnace oil) C13 - C18 513-623°C Fuel of diesel engines, cracking stock for gasoline
Lubricant oil (medicinal oil, motor oil and grease) C15 - C18 Above 543°C Paint oil, transformer oil, lubrication
Paraffin wax (Petroleum jelly, petroleum wax, petroleum coke) C18 - C30 More than 673°C Ointment, paints, water proofing, solid fuel, candles, etc
Heavy fuel oil and bitumen C18 - onwards Residue Paints, road surfacing.

Liquefied Petroleum Gas (LPG)

It is a mixture of n-butane, iso-butane, and some propane. It is easily compressed under pressure as liquid and stored in iron cylinders.

A strong foul smelling substance called ethyl mercaptan is added to LPG which detect the gas leakage.

Compressed Natural Gas

It consists mainly of methane (95%), which is a relatively unreactive hydrocarbon and makes its nearby complete combustion.

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