Crude Oil and Hydrocarbons

Definitions:

Hydrocarbon: Is a compound or a molecule made up of carbon and hydrogen ONLY

Saturated: Contains only C-C bonds

Unsaturated: Contains a C=C bond

Crude Oil: A mixture of hydrocarbons

1. Crude oil can be separated into fractions because the fractions have different boiling points.
2. Small size hydrocarbon molecules have less surface contact and so less van-der-Waals forces between the molecules, so less energy is needed to break them.
3. Branched chain hydrocarbons have lower boiling points than straight chain hydrocarbons.
4. Branched chains have less surface contact, less Van-der-Waals forces between molecules, less energy needed to overcome them.

Fractional Distillation Process

• Fractions are separated because of their differences in boiling point.
• Crude oil vapour is fed into the fractionating tower.
• The tower has a temperature gradient.
• The upper part has lower temperatures and the temperature in the tower increases as you go down.
• Small size hydrocarbon fractions condense from the top.
• Larger sized hydrocarbon fractions condense from the bottom.

 

• Petrol is of highest demand.
• The amount of petrol produced from fractional distillation is not enough to meet the demand..
• Petrol has to be refined to increase the quality/octane number.

Here are the three ways to increase the octane number: