Biodiesel (AQA A Level Chemistry)

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 forming methyl esters