Sunday, July 9, 2017

4.17: Describe How Long-Chain Alkanes are Converted to Alkenes and Shorter-Chain Alkanes by Catalytic Cracking (Using Silica or Alumina as the Catalyst and a Temperature in the Range of 600-700°C)



LONG - CHAIN HYDROCARBONS: Hydrocarbons with large number of hydrocarbon molecules


SHORT - CHAIN HYDROCARBONS: Hydrocarbons with small number of hydrocarbon molecules
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CONVERSION OF ALKANES TO ALKENES:
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CATALYTIC CRACKING
Picture showing Industrial Catalytic Cracking
EXPLANATION:

  • Cracking breaks down large hydrocarbon molecules into smaller hydrocarbon molecules that are more useful, hence breaking down long-chain hydrocarbons into short-chain hydrocarbons
  • Fractions containing large hydrocarbon molecules (long-chain hydrocarbons) are heated and vaporised at 600 - 700°C
  • Vapours will then pass over a hot catalyst of Silica or Alumina, breaking down covalent bonds in molecules which causes thermal decomposition to occur
  • As a result, cracking produces smaller Alkanes and Alkenes

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