Crude oil

Crude oil

1. Crude oil

   • Crude oil needs to be separated to make useful fuels
     • Contains different compounds that boil at different temperatures
       • These compounds burn under different conditions
       • Compounds: hydrocarbons (molecules only contain hydrogen and carbon)
     • Separate a mixture of liquids by distillation
       • Distillation of crude oil produces different liquids that boil at different temp ranges- these liquids are called fractions

2. Fractional distillation

   • How crude oil is separated
     • The larger the size of the molecule, the higher the boiling point of the hydrocarbon
   • Crude oil is vaporised and fed into a fractionating column (hot at the bottom and cooler at the top)
     • The vapours move up the column; getting cooler as they go up.
       • The hydrocarbons condense to liquids when they reach the level/tray that is at their boiling point
         • Hydrocarbons with the smallest molecules have the lowest boiling points (collected at the top of the column)
           • Low viscosity, very flammable, burn with clean flames- produce little smoke (useful fuels)
           • Short-chain hydrocarbons
         • Hydrocarbons with the largest molecules have a higher boiling point (collected at the bottom of the column)
           • High viscosity, not very flammable (useful when making roads etc)
           • Long-chain hydrocarbons