Crude glycerine is a viscous liquid with naturally sweet taste and light yellow to dark brown in color. It is the impure form of glycerine. Crude glycerine is derived from both natural and chemical feedstocks. Crude glycerine is obtained as a byproduct form biodiesel manufacturing plant and oleochemical industries.
1. Crude glycerine form biodiesel root: Biodiesel is fatty acid methyl ester (FAME), which is produced by transesterification of fats and oils obtained from vegetable oils such as palm oil, rapeseed oil, soyabean oil, sunflower oil, etc. Sodium hydroxide and methanol are mixed in a tank separately. Feed oil is heated up to 120oC and mixed with the catalytic mixture of sodium hydroxide and methanol. Final mixture of sodium hydroxide, methanol and feed oil is fed to a reactor at 120oC and normal pressure.
Triglyceride of fats or oils reacts with methanol in the presence of sodium hydroxide and produces fatty acid methyl ester and glycerol, this reaction is called transesterification reaction. The presence of sodium hydroxide as catalyst speeds up the replacement of glycerol with three methanol creating three molecules of fatty acid methyl ester which is a biodiesel. Now the oil is allowed to settle down and since glycerol is much denser than biodiesel, so it settle at the bottom of the separator and the glycerol is easily drawn off from bottom of the separator
2. Crude glycerine from oleochemcial root: During the manufacturing of soap noodles, fats or oils react with sodium hydroxide resulting in glycerol and soap base, which is a sodium salt of fatty acid. In this reaction glycerine is produced as a by-product which is more pure than that of from biodiesel process.