In our other videos, we learnt how fractional distillation is used to separate hydrocarbons
into
fractions with a similar boiling point.
In this video, you will learn the names of some important
fractions and their uses.
As you are now aware, large hydrocarbons have high boiling points and so are removed at
the
bottom of the fractionating column.
Smaller molecules condense higher up the column.
We will now take a look at some of the common fractions as we move down from the top of
the
fractionating column.
Some of the smallest molecules are between 1 and 4 carbons in length.
This fraction has such a low
boiling point that it is still as a gas when it is removed from the very top of the fractionating
column.
This fraction is known as refinery gas or bottled gas.
Bottled gas because it can be stored in bottles
under high pressure.
You could well have seen bottles of propane or butane running barbeques or
heaters in your home and these are examples of the Refinary gas fraction.
Petrol is between 5-7 carbons in length.
It is still a fraction of small chain hydrocarbons and
therefore these vaporise at a low temperature and are easily ignited.
This makes it useful as a fuel in
the internal combustion engine of a car.
Naphtha is not such a useful fuel but is a valuble source of organic molecules which
can be cracked
to make more fuels or form alkenes.
Alkenes can be turned into polymers and polymers can make
plastics which are used in our everyday lives.
Kerosene has an important use as a fuel for jet engines in aircraft and even in some rockets.
Kerosine is also called Paraffin in some parts of the world and is a common fuel burnt in
Paraffin or
Kerosene lamps used for lighting.
Diesel is the next fraction.
It is a common fuel in cars, vans and lorries.
It is not as volatile as petrol
and instead of spark ignition like petrol, it ignites under compression.
Below Diesel is the residue fractions:
fuel oil used as a fuel in power stations and ships, lubricating oil which sticks to
surfaces and reduces
friction and protects from rust.
And finally waxes which along with the oils can be used for polishing
surfaces.
The very bottom fraction is Bitumen.
This is the thick black adhesive used on roads either as the
surface finish or combined with stone chippings to create a solid resistant material.
It can also be
used to cover roofs due to its waterproofing properties.
All these fractions are separated from the crude oil mixture.
To try explain the importance of
crude oil consider this - there is estimated to be over 1 billion cars in the world of
which many will
use petroleum as fuel.
There are many million flights per year, each burning Kerosene fuel.
Not
forgetting the mass of plastic that is made each day for products and their packaging
and even the
Bitumen used to surface and resurface roads around the world.
As you can see, crude oil containts
many useful products that just need to be separated from the mixture!
Now at the end of this lesson you should have a better understanding of why crude oil is
such a
valuable resource and use of each of the main fractions.