Refining Crude oil

• Fractional Distillation: Industrially

  1. Oil is pre-heated

  2. Then passed into column

  3. The fractions condense at different heights

  4. The temperature of column decreases upwards

  5. The separation depends on boiling point

  6. Boiling point depends on size of molecules

  7. The larger the molecule the larger the van der waals forces

  8. Similar molecules (size, bp, mass) condense together

  9. Small molecules condense at the top at lower temperatures

  10. Big molecules condense at the bottom at higher temperatures
• Fractional Distillation

  • This is a physical process involving the splitting of weak van der waals forces between molecules
• Vacuum Distillation Unit

  1. Heavy residues from the fractionating column are distilled again under a vacuum

  2. Lowering the pressure over a liquid will lower its boiling point
• Vacuum Distillation

  Allows heavier fractions to be further separated without high temperatures which could break them down
• Petroleum

  A mixture consisting mainly of alkane hydrocarbons
• Petroleum Fraction

  A mixture of hydrocarbons with a similar chain length and boiling point range
• Fractional Distillation: In the Laboratory

  1. Heat the flask

  2. Vapours pass up the fractionating column

  3. The vapour of the substance with the lower boiling point reaches the top first

  4. The thermometer should be at or below the boiling point of the most volatile substance

  5. The vapours with higher boiling points condense back into the flask

  6. Only the most volatile vapour passes into the condenser

  7. The condenser cools the vapours and condenses to a liquid and is collected
• Fractional Distillation

  Used to separate liquids with similar boiling points