Transesterification
The fatty acid triglycerides themselves are esters of fatty
acids and the chemical splitting up of the heavy molecules,
giving rise to simpler esters, is known as Transesterification.
The triglycerides are reacted with a suitable alcohol (Methyl,
Ethyl, or others) in the presence of a catalyst under a controlled
temperature for a given length of time. The final products are
Alkyl esters and Glycerin. The Alkyl esters, having favorable
properties as fuels for use in CI engines, are the main product
and the Glycerin, is a by-product.The chemical reaction of the
Tri-glyceride with Methyl alcohol is shown below. With higher
alcohols the chemical equation would change correspondingly.
It can be seen from the above reaction that one mole of
the heavy tri-glyceride and three moles of methyl alcohol yields
one mole of Glycerol and three moles of lighter fatty methyl
esters. Without the use of a catalyst the reactions would be very
slow and also incomplete. A temperature of 60°C to 70°C would
be needed for the reactions to become effective. Also a vigorous
agitation of the reactants would be needed and so a mechanized
stirrer in the reaction vessel becomes necessary. Various catalysts
can be used. The most common are the acid catalysts, like
H2SO4
and the Alkalies, like NaOH or KOH. For transesterification any alcohol can be used. The most popular is
Methyl Alcohol. Most of investigators and those who produce
vegetable oil esters in bulk use only Methyl Alcohol.
Transesterification The fatty acid triglycerides themselves are esters of fatty acids and the chemical splitting up of the heavy molecules, giving rise to simpler esters, is known as Transesterification. The triglycerides are reacted with a suitable alcohol (Methyl, Ethyl, or others) in the presence of a catalyst under a controlled temperature for a given length of time. The final products are Alkyl esters and Glycerin. The Alkyl esters, having favorable properties as fuels for use in CI engines, are the main product and the Glycerin, is a by-product.The chemical reaction of the Tri-glyceride with Methyl alcohol is shown below. With higher alcohols the chemical equation would change correspondingly.It can be seen from the above reaction that one mole of the heavy tri-glyceride and three moles of methyl alcohol yields one mole of Glycerol and three moles of lighter fatty methyl esters. Without the use of a catalyst the reactions would be very slow and also incomplete. A temperature of 60°C to 70°C would be needed for the reactions to become effective. Also a vigorous agitation of the reactants would be needed and so a mechanized stirrer in the reaction vessel becomes necessary. Various catalysts can be used. The most common are the acid catalysts, like H2SO4and the Alkalies, like NaOH or KOH. For transesterification any alcohol can be used. The most popular is Methyl Alcohol. Most of investigators and those who produce vegetable oil esters in bulk use only Methyl Alcohol.
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