1. Crude oils and fuels
Crude oil and fuels
Click to continue

2. Overview — crude oil
Crude oil is derived from an ancient biomass found in rocks.
Many useful materials can be produced from crude oil.
Crude oil can be fractionally distilled. Some of the fractions can be used as fuels.
What useful materials can be made from crude oil?
Click to continue

3. Overview — biofuels Biofuels are produced from plant material.
There are advantages and disadvantages to their use as fuels.
Fuels can come from renewable or non-renewable resources.
What are the advantages and disadvantages of biofuels?
Click to continue

4. Crude oil Crude oil is a mixture of a large number of compounds.
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
It is possible to separate the substances in a mixture by physical methods, including distillation.
Why does crude oil have so many different compounds in it?
Click to continue

5. Hydrocarbons 1
Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons).
Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2.
What would a model of ethane (two carbons) look like?
A molecular model of methane and its structural formula
Click to continue

6. Hydrocarbons 2
The many hydrocarbons in crude oil may be separated into fractions by evaporating the oil and allowing it to condense at a number of different temperatures.
Each fraction contains molecules with a similar number of carbon atoms.
This process is called fractional distillation.
Click to continue

7. Fractional distillation
Explain how the fractionating column works.
Click to continue

8. Properties 1
Some properties of hydrocarbons depend on the size of their molecules. Look at the table below and on the next slide. What patterns do you notice?
Fraction
Carbon atoms in the molecule
Description
Boiling point (C)
Flammability
Uses
Petroleum gas
1–4
Colourless gas
Less than 40
Explodes if mixed with air and lit
Used as a fuel in the refinery
Bottled and sold as LPG
Naphtha
5–10
Yellowish liquid, flows easily
25–175
Evaporates easily, vapour mixed with air is explosive
Petrol
Used for making other chemicals
Kerosene
10–14
Yellowish liquid, flows like water
150–260
Burns when heated
Aircraft fuel
Click to continue

9. Properties 2 Fraction Carbon atoms in molecule Description
Boiling point (C)
Flammability
Uses
Light gas oil
14–20
Yellow liquid, thicker than water
235–360
Only burns when soaked onto a wick or other material
Diesel fuel
Heavy gas oil
20–50
Yellow brown liquid
330–380
Only burns when soaked onto a wick — very smoky
Used in the catalytic cracker
Lubricants (car engine oils)
50–60
Thick brown syrup-like liquid
340–575
Only burns when hot and soaked onto a wick
Grease for lubrication
Catalytic cracker
Fuel oil
60–80
Thick brown sticky liquid
Above 490
Fuel oil for power stations and ships
Bitumen
More than 80
Black semi-solid
Above 580
Only burns if very hot
Road and roof surfaces
Click to continue

10. Hydrocarbon fuels 1
Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.
The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, sulfur dioxide and oxides of nitrogen.
Solid particles (particulates) may also be released.
What problems do carbon dioxide, sulfur dioxide and particulates cause? (Answers on the next slide.)
Click to continue

11. Hydrocarbon fuels 2 The combustion of hydrocarbon fuels releases heat.
During combustion, the carbon and hydrogen in the fuels are oxidised.
Sulfur dioxide causes acid rain.
Carbon dioxide causes global warming.
Solid particles cause global dimming.
How can these effects be reduced? (Answers on the next slide.)
Click to continue

12. Hydrocarbon fuels 3
Sulfur can be removed from fuels before they are burned, for example in vehicles.
Sulfur dioxide can be removed from the waste gases after combustion, for example in power stations using scrubbers.
Catalytic converters in the exhausts of vehicles reduce the release of nitrogen oxides.
Click to continue

13. Biofuels
Biofuels, including biodiesel and ethanol, are produced from plant material, e.g palm oil. There are economic, ethical and environmental issues surrounding their use.
What are the issues with biofuels?
Shariff Che’Lah/Fotolia
Click to continue