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Biodiesel production

There are three basic methods to biodiesel production:
  • Base catalyzed transesterification of the oil
  • Acid catalyzed transesterification of the oil
  • Conversion of the oil to its fatty acids and then to biodiesel.
biodieselMost of the biodiesel produced today is done with the base catalyzed reaction. This catalyst splits the oil into glycerine and biodiesel.

The catalyst is typically sodium hydroxide or potassium hydroxide, which is dissolved in methyl alcohol. The reaction mix of oil and catalyst is kept just above the boiling point of the alcohol to speed up the reaction. Recommended reaction time varies between 1 to 8 hours. Excess alcohol is normally used to ensure total conversion of the fat or oil to its esters. After separation of the glycerol and biodiesel phases, the excess alcohol is removed with a evaporation process or by distillation.

Degussa catalyst for biodiesel production

Degussa has developed a special catalyst: sodium methylate. During the production process a 30 percent sodium methylate solution in methanol controls the reaction of the oil to biodiesel and glycerol.
One tonne of raw material requires only about 17 to 18 kilograms of this catalyst. At the end of the process, the methyl ester and glycerol are separated. The glycerol can be sold to the chemical or pharmaceutical industry, after purification.
Degussa markets these catalyst solutions in a ready-to-use form. The catalyst can be added directly from the storage tank to the production process and are mainly used in large facilities with an annual capacity of 50,000 to 100,000 tonnes.
One advantage of the Degussa catalyst is that it produces a high glycerol yield of high quality. Around two thirds of the large biodiesel facilities are designed around this catalyst.
Another related catalyst, potassium methylate, is used to make biodiesel from old cooking fat. Biodiesel production with the alkoxide catalysts offer significant commercial advantages over the alternatives sodium and potassium hydroxide.

[Source: Degussa]


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