PETROLEUM is a dark coloured, viscous, and foul smelling crude oil. The name of petroleum means rock oil (petra=rock ; oleum=oil). It is found under the crust of earth trapped in rocks .The crude oil petroleum is a complex mixture of several solid, liquid and gaseous hydrocarbons mixed with water, salt and earth particles. Thus, the crude petroleum oil is not a single chemical compound, it is a mixture of compounds. Petroleum is lighter than water and insoluble in it. Petroleum is a natural product obtained from oil wells.
Petroleum oil was formed by the decomposition of the remains of extremely small plants and animals (micro-organisms) buried under the sea millions of years ago. It is believed that millions of years ago, the microscopic plants and animals (or micro-organism) which lived in seas, died. Their bodies sank to bottom of sea and were soon covered with mud and sand. The chemical effects of pressure, heat and bacteria, converted the remains of microscopic plants and animals onto petroleum oil just as they converted forest trees into coal. This conversion took place in absence of oxygen or air. The petroleum thus formed got trapped between two layers of impervious rocks (non-porous rocks) forming an oil trap. Natural gas is above this petroleum oil.
Petroleum occurs deep down under the earth between two layers of impervious rocks (non-porous rocks). Oil deposites are usually found mixed with water, salt and sand (earth-particles).Natural gas occurs above the petroleum oil trapped under the rocks.
PETROLEUM is obtained by drilling holes (oil wells) into earth’s crust where the presence of oil has been predicted by survey. When a well is drilled through the rocks, natural gas comes out first with a great pressure and for a time, the crude oil comes out by itself due to gas pressure. After the pressure has subsided, the crude oil is pumped out of the oil wells. It should be noted that many wells yield only natural gas but no oil. So, hundreds of wells may have to be drilled into the rocks and tested before getting an oil well from which oil can be produced profitably.
Some of the places in our country where petroleum oil is being produced from the oil wells are
1.Ankeleshwar and Kalol in Gujrat
2 Rudra Sagar and Lakwa in Assam
3. Mumbai high (off store area)
There are two government for exploration of production and petroleum oil in India . These are :
1.Oil and Natural Gas Commission (ONGC)
2. Oil India Limited (OIL)
Oil and Natural Gas Commission (ONGC) is a major government organization engaged in the exploration and production of the oil in India. It was established in 1956 . ONGC is exploring and production oil from land (on-shore) and sea-side (off-shore) areas of country . A recent achievement of ONGC is the production of oil from Mumbai High seas. The other organization, Oil India Limited, was established in 1981 . It is working in the Eastern region, Mahandi Basin and Rajasthan.
The crude petroleum oil is a complex mixture of alkene hydrocarbons with water, salt and earth particles. So, before it can be used for specific purposes, it has to be purified or refined. The process of separating crude petroleum oil into more useful fractions is called refining. The refining of petroleum is done by the process of fractional distillation. In other words, petroleum is separated into its constituents by the process of fractional distillation. The refining of petroleum or separation of petroleum into different components is based on the fact that the different components of crude oil have different ‘boiling point’ ranges. The fractional distillation of petroleum is done by using a tall fractionating tower .
The crude petroleum oil is heated to a temperature of about 400oC in a furnance and the vapours thus formed are passed into a tall fractionating column from near its bottom. As the mixture of hot vapors rises in the column, it starts getting cooled gradually. Due to this, the vaporous of higher boiling fractions of petroleum condense first in the lower part of the tower, but the vapours of the low boiling fractions rise up into the tower and condense later. In this way the fraction of petroleum having highest boiling point range is collected in the lowest part of the fractionating tower, whereas the fraction having lowest boiling point range is collected in the topmost part of the tower.
The various fractions or products obtained by the fractional distillation of petroleum, their moleculer compositions, boiling ranges and uses are given below.
1.PETROLEUM GAS :- The moleculer composition of petroleum gas is from C1 to C4 hydrocarbons i.e., it contains hydrocarbons having 1 to 4 carbon atoms per molecule its boiling range is below 40o C. Petroleum gas is used as fuel as such or in form of liquefied petroleum gas (LPG). Petroleum gas is also used in the production of carbon black (needed in tyre industry) and of hydrogen industry). It is also used in the manufacture of gasoline (petrol) by the process of polymerization.
2.GASOLINE OR PETROL:- The moleculer composition of gasoline is from C5 to C10 hydrocarbons and its boiling range is 40o C to 170o C. Gasoline or petroleum is used as in fuel in motor cars, scooters, motor-cycles and other light vehicles. Petrol is also used as a solvent; for dry cleaning clothes, and for making petrol gas. Petrol is more volatile than Kerosene oil.
3. KEROSENE OIL:- The moleculer composition of Kerosene oil is from C10 to C12 hydrocarbons and its boiling range is from 1700 C to 2500 C. Kerosene oil is used as a household fuel. For examples Kerosene is used in wick stoves or pressure stoves to cook food. Kerosene is also used as an illuminant (for lighting purposes) in hurricane or petromax lamps. Kerosene is also used for making oil gas. A special grade of Karosene oil is used as ‘activation oil’ in jet airplanes.
4. DIESEL OIL:- The moleculer composition of diesel oil is from C13 to C15 hydrocarbons and its boiling. Diesel oil is used as a fuel for heavier vehicles like buses, trucks, railway engines and ships. Diesel is also used to run water pumps required for irrigation in fields and diesel generators to produce electricity on small scale.
5.FUEL OIL:- The moleculer composition of fuel oil is from C15 to C18 hydrocarbons and range is 350o C to 400o C. Fuel oil is used in industries to heat boilers and in furnances. Fuel oil is better oil than than coal because fuel oil is completely and does not need any residue. On other hand , When coal is burned , it leaves behind a lot of ash which has to be removed from the coal furnance.
6.LUBRICATING OIL:- The moleculer composition of lubricant oil is C17 to C20 hydrocarbons, and its boiling range is beyond 400o C. Lubricant oil is obtained during the fractionation of residual oils. It is used for lubricant machinery.
7.PARAFFIN WAX:- The moleculer composition of paraffin wax is from C20 to C30 hydrocarbons and its boiling range is above 400o C. Paraffin wax is also obtained during the further fractionation of residual oils. Paraffin wax is used for making candles, Vaseline, ointments, wax papers and grease.
8.ASPHALT:- Asphalt is a black, sticky substance having moleculer composition of C30 to C50 hydrocarbons. Asphalt is a non-volatile substance, so it does not vaporize. It is left behind as a residue in the fractionation of residue oils. Asphalt is used for making road surfaces.