AQA A Level Chemistry

Revision Notes

7.3.3 Biodiesel

Biodiesel

Biodiesel

  • Biodiesel is made from renewable vegetable oils rather than non sustainable petrochemicals
  • Natural triglyceride oils are converted to esters of methanol, which makes them less viscous
  • Biodiesel made from rapeseed oil for example is produced by transesterification
    • The triglyceride is converted, or transesterified, into the less viscous fatty acid methyl ester (FAME) using methanol
    • Acids and alkalis can both be used to catalyse the reaction
      • An acid works by protonating the carbonyl group
      • An alkali works by deprotonating the alcohol / methanol
      • However, it is more common to use an alkaline catalyst such as NaOH / KOH
    • The transesterification is reversible, so an excess of methanol is used to drive the equilibrium to the right
    • Under optimum conditions this process can produce a very successful yield of 98%

Transesterification, downloadable AS & A Level Chemistry revision notes

Transesterification forming methyl esters

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