Page 62 - Science Class 08

Origin 20°C Petroleum

It is believed that petroleum has been formed Gas
15°C
from the organisms living in the sea over
Gasoline
millions of years. As these organisms died, (Petrol)
200°C
their bodies se led on the sea bed and got
Kerosene
covered with sand and clay. Due to high 300°C
temperature and pressure, they got converted Crude Oil Diesel
into petroleum.
370°C
Occurrence Industrial
Petroleum is found deposited deep inside the Fuel Oil
earth’s crust. It is obtained by drilling through 400°C
Lubricating
the earth and impervious (non-porous) rock Oil, Paraffin
Furnace
above it. Petroleum is obtained in the form of Wax and
black liquid. Due to its great importance it is, Asphalt
therefore, also called black gold.
Refining of Petroleum
The world’s first oil well to obtain petroleum
Crude oil is separated by frac onal dis lla on.
was dug in Pennsylvania, USA, in 1859. The
The process of frac onal dis lla on is fairly
petroleum produc on in India is not enough to
simple, but is powerful in the way that it
fulfil its demand. Therefore, our country import
separates all the different, complex compo-
crude oil from Arabian countries and some
nents of crude oil. First, the crude oil is heated
other countries to fulfil its own demand.
to vapourize it and is fed into the bo om of a
However, there are oil wells in Assam, Gujarat,
dis lla on tower. The resul ng vapour, then
Bombay and in the delta of the rivers Godavari
rises through the ver cal column. As the gases
and Kaveri.
rise through the tower, the temperature
Refining of Petroleum decreases.
Crude oil is a mixture of various hydrocarbons As the temperature decreases, certain hydro-
which needs extensive refining. These different carbons begin to condense and run off at
hydrocarbons have different boiling points. As different levels. Each frac on that condenses

the number of carbon atoms in a hydrocarbon off at a certain level contains hydrocarbon
increases, its boiling point also increases. This molecules with a similar number of carbon
property can be used to separate the different atoms. These boiling point ‘cuts’ allow several
components of petroleum by frac onal hydrocarbons to be separated, but in a single
dis lla on. The components with different process. It is, thus, cooling with the height of
boiling points are called frac ons and the the tower that allows for the separa on.
process of separa ng the frac ons by frac onal
A er this rough refinement, individual fuels
dis lla on is known as refining.
may undergo more refinement to remove any
Refining of petroleum is carried out in contaminants or undesirable substances or to
petroleum refineries. improve the quality of the fuel through
cracking.

62 Science-8