Crude oil, a vital fossil fuel, is a complex mixture of hydrocarbons used in fuel production, heating, and manufacturing plastics. Its formation involved ancient marine organisms subjected to heat and pressure, while refining processes like fractional distillation and catalytic cracking make its compounds useful. Despite its benefits, crude oil poses environmental risks, including pollution and wildlife damage, and its future availability is uncertain.

1. Crude Oil Refining

2. What do these have in Common

3. Crude Oil

4. What is crude oil?
Crude oil is a fossil fuel and one of the most important substances in
the world. It is a mixture of hundreds of different compounds.
Crude oil is used to
• Make fuels for transport
• Heating
• Generating electricity.
• Making Plastics
• Different Chemicals
Every day, the world uses over 70 million barrels of oil.

5. Crude oil: a brief history
The modern oil industry began in the
mid-19th century when kerosene was
distilled from crude oil and used as
cheap and clean-burning fuel for
lamps.
It wasn’t until the development of the internal combustion engine
and gasoline-powered cars in the late 19th century that gasoline
became highly valuable.
Gasoline was a by-product in
kerosene production, and was initially used as a solvent.
This led to a great increase in the demand for crude oil, which has
continued to this day.

6. How was crude oil made?
Crude oil is thought to have been made
from the remains of marine plants and
animals that died millions of years ago.
These remains sank to the
bottom of the sea, where they
were buried in layers of sand and
mud, preventing them from rotting. These layers
gradually became sedimentary rock.
Over millions of years the layers of rock built up, increasing the heat
and pressure. This caused the remains to be broken down into the
molecules that form crude oil and natural gas.

7. Hydrocarbons in crude oil
Many compounds in crude oil only contain the elements carbon and
hydrogen. They are called hydrocarbons.
Most hydrocarbons in crude oil are compounds called alkanes.
Alkanes contain a single chain of carbon atoms with hydrogen atoms
bonded along the side.

8. What are alkanes?
Alkanes are a family of hydrocarbon compounds with the general
formula CnH2n+2.
 The simplest alkane is methane. It
has the formula CH4.
 The second simplest alkane is
ethane. It has the formula C2H6.
 The third simplest alkane is propane.
It has the formula C3H8.

9. Where in the world is crude oil?

10. Finding crude oil at sea
Crude oil is often found trapped in rocks of the sea bed.
Oil rigs or drilling platforms
are used to drill through the
sea bed to obtain the oil.
Once the oil has been
removed from the sea bed, it
is pumped in long pipelines to
an oil tanker terminal or an oil
refinery on land.

11. Crude oil itself has no uses – it must first be processed or refined.
This is done in an oil refinery.
The first step is to
separate compounds
in the oil into groups
called fractions.
Each fraction
contains a mix of
compounds with a
similar number of
carbon atoms.
How can crude oil be made useful?

12. Molecule size and boiling point
The more carbon atoms in a hydrocarbon molecule, the larger the
molecule. How does this affect its boiling point?
Generally, the larger a hydrocarbon, the
higher its boiling point.
This is because the intermolecular forces between large molecules
are stronger than the intermolecular forces between small
molecules.
More energy is needed to break the forces between large molecules,
and so the boiling point is higher.
Molecules in crude oil can contain anything from just 1 carbon atom
to well over 50.

13. Boiling point of alkanes

14. What is fractional distillation?
Fractional distillation is a process used to separate a mixture of
liquids that have different boiling points.
Fractional distillation is used to separate
crude oil into fractions with different
boiling points.
When the mixture is heated, liquids with a low boiling point
evaporate and turn to vapour.
Liquids with a higher boiling point remain as
liquid. The vapour can then be separated from
the liquid.

15. Fractional distillation of crude oil
Crude oil is separated into fractions by fractional distillation.
1. Oil is heated to about 450 °C and pumped into the
bottom of a tall tower called a fractionating
column, where it vaporizes.
2. The column is very hot at the bottom but much
cooler at the top. As the vaporized oil rises, it
cools and condenses.
3. Heavy fractions (containing large molecules)
have a high boiling point and condense near the
bottom of the column.
4. Lighter fractions (containing small molecules)
have a lower boiling point and condense further
up the column.

16. How does fractional distillation work?

17. Supply and demand
The amount of each type of fraction obtained by fractional distillation
does not usually match the amount of each fraction that is needed.
Crude oil often contains more
heavier fractions than lighter
fractions, which are more useful
and therefore more desirable.
The large hydrocarbon molecules
in the heavier fractions can be
broken down into smaller, more useful,
molecules to meet demand
for raw materials for fuels and plastics.

18. Catalytic cracking
Large hydrocarbon molecules can be broken down into smaller
molecules using a catalyst. This is called catalytic cracking.
The smaller molecules produced by catalytic cracking are a mixture
of alkanes and alkenes.
The hydrocarbon molecules are heated until they turn into vapour,
and then mixed with a catalyst. The type of reaction in catalytic
cracking is called thermal decomposition.
Alkenes are reactive molecules that are used to make plastics and
other chemicals.

19. What are alkenes?
Alkenes are a family of hydrocarbon compounds with the general
formula CnH2n.
Alkenes are very similar to alkanes, but they have one important
difference: they contain at least one double covalent bond between
carbon atoms.
 The simplest alkene is ethene. It
has the formula C2H4.
 The second simplest alkene is
propene. It has the formula C3H6.

20. Cracking decane
Decane from the naphtha fraction can be cracked to form pentane
(for use in petrol), propene and ethene.
decane
(C10H22)
pentane
(C5H12)
propene
(C3H6)
ethene
(C2H4)
+

+

21. Saturated vs. unsaturated
Alkanes are examples of saturated compounds.
Alkenes are examples of unsaturated compounds.
A saturated compound only contains single
covalent bonds between carbon atoms.
An unsaturated compound contains at least one double
covalent bond between carbon atoms.
A test to distinguish between saturated and unsaturated
compounds is to add red bromine water. In the presence of
unsaturated compounds, the red colour disappears.

22. How does catalytic cracking work?

23. Removing impurities
An important step in refining is removing impurities from fractions.
These can damage equipment that uses the fraction, and cause
pollution.
One of the most important
impurities to remove is
Sulphur.
When burnt, this forms the
gas Sulphur dioxide, which
causes acid rain.
Other impurities that need to be removed include nitrogen, oxygen,
water and dissolved metals.

24.  alkanes – A family of hydrocarbon molecules with the
general formula CnH2n+2.
 alkenes – A family of hydrocarbon molecules with the
general formula CnH2n.
 catalytic cracking – A reaction where a large
molecule is broken down into smaller molecules in the
presence of a catalyst.
 crude oil – A naturally-occurring mixture of different-
sized hydrocarbon molecules.
 fraction – A mixture of hydrocarbon molecules of a
similar size.
Glossary (1/2)

25.  fractional distillation – The process used to
separate crude oil into different fractions.
 hydrocarbon – A molecule containing only
hydrogen and carbon.
 saturated – A compound that only contains single
covalent bonds between carbon atoms.
 unsaturated – A compound that has at least one
double covalent bond between carbon atoms.
Glossary (2/2)

26. Problems with crude oil
Crude oil is extremely useful but it has several drawbacks:
 Burning the products of crude oil as fuel produces gases and
particles that contribute to global warming and air pollution.
 Removing oil from the ground,
as well as oil spillages and
slicks, can be very damaging to
wildlife and the environment.
 The high value of oil means it is sometimes the cause of military
conflict, especially because a large amount of oil comes from
countries that are politically unstable.

27. When will crude oil run out?
It is difficult to say when crude oil will run
out because no-one knows exactly how
much oil there is left in the world.
Some scientists believe there is a lot more oil still to find, but
others think that most oil has already been discovered.
There are over 1 trillion (1 million million)
barrels of crude oil in proven oil reserves
At current rates, this will last about 44 years, but the amount of oil
used in the world increases each year.

28. Thank You