AQA A Level Chemistry复习笔记7.3.3 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