ALKANES

• Fractional Distillation


  Process of separating crude oil into different hydrocarbons based on their boiling points
• Fractional Distillation


  1. Mixture is vapourised and fed into fractionating column

  2. Vapours rise, cool and condense

  3. Products are siphoned off for different uses
• Fractional Distillation


  • Products with short carbon chains have lower boiling points and are collected at the top
  • Products with long carbon chains have higher boiling points and are collected at the bottom
• Cracking


  Process of breaking down longer carbon chains into smaller, more useful molecules
• Thermal Cracking


  1. High temperatures around 1200 K and pressures around 7000 kPa used

  2. Produces a high proportion of alkanes and alkenes
• Catalytic Cracking


  1. Lower temperatures around 720 K used with normal pressure

  2. Zeolite catalyst used

  3. Produces aromatic compounds with carbon rings
• Combustion of Alkanes


  Alkanes undergo complete combustion with sufficient oxygen to produce carbon dioxide and water
• Insufficient oxygen


  Incomplete combustion produces carbon monoxide and water
• Catalytic Converters


  • Use rhodium catalyst to convert harmful products like carbon monoxide and oxides of nitrogen into more stable products like CO2 and H2O
• Carbon particulates from incomplete combustion can cause serious respiratory problems
• Flue Gas Desulfurisation


  Process of removing sulfur impurities from waste products to prevent acidification of water
• Pollutants from alkane combustion can contribute to global warming, acid rain and health issues
• Chlorination of Alkanes


  Alkanes react with halogens in the presence of UV light to produce halogenoalkanes
• Chlorination of Alkanes


  1. Initiation - halogen is broken down to form free radicals

  2. Propagation - hydrogen is replaced and Cl• radical reformed as a catalyst

  3. Termination - two radicals join to end the chain reaction
• Reaction conditions can be altered to favour the termination step and limit the number of substitutions