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