Crude Oil
- Created by: saffa713
- Created on: 04-03-18 13:07
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- Crude Oil
- Fractional distillation
- Crude oil is vapourised and lightest hydrocarbons rise to the top.
- The largest hydrocarbons aren't vapourised so thy run to the bottom.
- Fractionating column separates hydrocarbons of different lengths
- Different length alkanes have different boiling points so each fraction condenses at a different temperature. The different fractions are drawn off at different temperatures.
- Order of alkanes: LPG, Petrol, Naphtha, Kerosene, Diesel, Mineral oil, Fuel oil, Bitumen
- Different length alkanes have different boiling points so each fraction condenses at a different temperature. The different fractions are drawn off at different temperatures.
- The largest hydrocarbons aren't vapourised so thy run to the bottom.
- Crude oil is vapourised and lightest hydrocarbons rise to the top.
- Cracking
- Heavy fractions can be 'cracked' to make smaller, more useful molecules
- Cracking is breaking long chain alkanes into shorter hydrocarbons by breaking the carbon-carbon bonds. Where the chain breaks is random so there will be different products each time.
- Lighter fractions such as petrol and naphtha are more in demand than heavier fractions such as bitumen, so heavy fractions are cracked to meet the demand.
- Example: Octane can be cracked to give hexane and ethene.
- Types of cracking:
- Thermal cracking: This happens at a high temperature (1000 Degrees Celsius) and high pressure (70 atm). It produces alkenes which are used to make plastics.
- Catalytic cracking: This happens at a high temperature (450 Degrees Celsius) and a slight pressure with a zeolite catalyst. It produces aromatic hydrocarbons (contain benzene rings) and motor fuels.
- Catalysts lower cost by lowering the temperature and pressure that the reaction is carried out at. Catalysts also speed up the reaction time.
- Heavy fractions can be 'cracked' to make smaller, more useful molecules
- Reforming
- Knocking happens when alkanes explode when the fuel mixture in the engine is compressed.
- Alkanes can be reformed into branched alkanes, aromatic hydrocarbons and cycloalkanes.
- Adding branched chain alkanes and cycloalkanes makes knocking less likely so fuel combustion is more efficient.
- Knocking happens when alkanes explode when the fuel mixture in the engine is compressed.
- Example: octane can be reformed into 2,5-dimethyl hexane
- Adding branched chain alkanes and cycloalkanes makes knocking less likely so fuel combustion is more efficient.
- Process to get Petrol from crude oil: 1) crude oil 2) Fractional distillation 3) cracking 4) Reforming 5) Petrol
- Fractional distillation
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