Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Patent
1996-02-27
1998-12-15
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
554161, 554163, C11C 310
Patent
active
058499393
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/AT94/00088 filed Jul. 8, 1994.
BACKGROUND OF THE INVENTION
The invention relates to a method for the preparation of fatty acid alkyl esters by transesterification, in particular catalytic transesterification, of triglycerides, wherein from a reaction mixture, in which the transesterification is carried out, an ester phase and a glycerol phase containing fatty acids, fatty acid salts and/or other fatty acid compounds are formed, which are separated from each other.
By transesterification the alcoholysis of triglycerides is to be understood, i.e. the reaction with alcohols, in particular methanol and ethanol, the monoesters of the fatty acids as well as glycerol forming via the intermediate products di- and monoglycerides.
DESCRIPTION OF CONVENTIONAL ART
Fatty acid esters, in particular the methyl esters, are important intermediate products in oleochemistry. In Europe alone, 200,000 tons of vegetable oil methyl ester are produced annually as raw materials primarily for surfactants. Beside this, the fatty acid methyl ester is of increasing importance as a substitute fuel for diesel fuel.
As the catalysts for the transesterification, basic catalysts (alkali hydroxides, alcoholates, oxides, carbonates, anion exchangers), acidic catalysts (mineral acids, p-toluene sulfonic acid, boron trifluoride, cation exchangers) and enzymes (lipases) may be used. Today catalysts which are soluble in the reaction mixture are preferably used. They form a homogenous mixture and guarantee fast reaction rates and mild reaction conditions. The homogenous catalysts most frequently used are sodium and potassium hydroxide as well as sodium methylate, which, dissolved in alcohol, are admixed to the vegetable oil. Such a method is known from AT-B 386 222. The acidic catalysis requires higher reaction temperatures and pressures and a more complex reaction procedure. An acidic transesterification is known from FR-A-85 02340.
Transesterification with basic catalysis is carried out without the use of a solvent. The reaction starts with a two-phase system of triglyceride and alcohol, yet during reaction progress and the formation of ester, a homogenous phase forms, which turns into two phases again by the formation and separation of glycerol.
In the alcoholysis of triglycerides for the preparation of esters of fatty acids with monohydric alcohols, a phase rich in glycerol is obtained as a by-product. This phase further contains fatty acids, fatty acid salts and fatty acid esters. In order to separate these fatty acid compounds from the glycerol phase, it is generally treated with acids. By this treatment, the fatty acids are set free from the fatty acid salts. The fatty acids as well as the fatty acid esters themselves are not mixable with glycerol and therefore settle as a separate phase from the glycerol phase.
So far, there has not been demonstrated any reasonable use of this fatty acid phase, this phase generally being accepted in the art as a loss from the transesterification process. This loss has a negative effect particularly when the process is carried out on a large scale, where an improvement in the order of 1-2% already increases decisively the economy of the process.
SUMMARY OF THE INVENTION
It is the object of the invention to provide an improved method for the preparation of fatty acid alkyl esters by transesterification, in particular catalytic transesterification, of triglycerides.
The method according to the invention is characterized in that the fatty acids, the fatty acid salts und/or other fatty acid compounds are separated from the glycerol phase, esterified with an alcohol and recycled to a different or further reaction mixture, in which a further transesterification is carried out.
The esterification may be carried out according to known methods, being particularly suitable an esterification with an acidic catalyst. As an example, an acidic catalysis with sulfuric acid, para-toluene sulfonic acid or with ion exchangers in the form of H.sup.+ is mentioned.
An esterification of
REFERENCES:
R.C.A. Lago et al., Extraction and transesterification . . . , Oleagineux, vol. 40, No. 3, Mar. 1985, pp. 147-151.
Koncar Michael
Mittelbach Martin
Carr Deborah D.
Geist Gary
Koncar Michael
Mittelbach Martin
Vogel & Noot Industrieanlagenbau Gesellschaft m.b.H.
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