JP2006001893A - Method for producing alkyl ester of fatty acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an alkyl ester of a fatty acid by which a monoglyceride can be efficiently removed from a fatty acid ester mixture containing the monoglyceride. <P>SOLUTION: The method for producing the alkyl ester of the fatty acid involves carrying out the distillation by adding an acid or an alkali to a fatty acid ester mixture containing the monoglyceride. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a high purity fatty acid alkyl ester. Specifically, the present invention relates to a method for producing a fatty acid alkyl ester having a reduced monoglyceride content.

  The fatty acid alkyl ester obtained by transesterification of fatty acid glyceride and lower alcohol in the presence of an alkali catalyst contains water-soluble impurities such as glycerin, free alkali and soap, as well as monoglyceride and diglyceride which are reaction intermediates, As well as unreacted triglyceride. Water-soluble impurities can be removed by washing the fatty acid alkyl ester with water. However, since glycerides are oil-soluble, contrivance is required for their separation.

  The separation of glycerides is known to be concentrated and removed to a distillation residue by distillation, for example (Patent Document 1).

  In the distillation method, triglycerides and diglycerides have a boiling point that is significantly different from that of fatty acid alkyl esters, so they can be removed to the residue.Monoglycerides, especially short-chain fatty acid monoglycerides, have a boiling point that is close to that of long-chain fatty acid alkyl esters, so that a certain amount is retained. It is difficult to mix and remove completely.

Further, by repeating the transesterification step a plurality of times, the conversion rate can be improved and the monoglyceride content in the fatty acid ester can be reduced. However, this method does not essentially improve the monoglyceride removal efficiency in the distillation separation, and has a disadvantage that the process is complicated and the time required is long.
US Pat. No. 2,383,580

  The subject of this invention is providing the manufacturing method of the fatty-acid alkylester which can remove a monoglyceride efficiently from the fatty-acid ester mixture containing a monoglyceride.

  The present invention provides a method for producing a fatty acid alkyl ester, in which an acid or an alkali is added to a fatty acid ester mixture containing monoglyceride to perform distillation.

  By the production method of the present invention, it is possible to efficiently produce a high-purity fatty acid alkyl ester with a small content of impurities, particularly monoglyceride.

  The fatty acid alkyl ester in the present invention is preferably an ester of a saturated or unsaturated fatty acid having 6 to 24 carbon atoms and a lower alcohol. The preparation method includes a method of transesterifying a fatty acid glyceride such as fat and oil and a lower alcohol in the presence of a transesterification catalyst.

  Examples of the oils and fats include vegetable oils such as palm oil, palm kernel oil, coconut oil, soybean oil, rapeseed oil, olive oil, and sesame oil, animal oils such as fish oil, beef tallow, lard, and whale oil, or mixtures thereof.

  As a lower alcohol, C1-C5 alcohol is preferable, For example, methanol, ethanol, a propanol, a butanol, a pentanol etc. are mentioned, Methanol is especially preferable.

  As the transesterification catalyst, an alkali catalyst or an acid catalyst can be used. Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, sodium methylate, potassium methylate and the like. Examples of the acid catalyst include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, benzenesulfonic acid, and toluenesulfonic acid.

  The transesterification reaction is not particularly limited, and can be suitably performed under the conditions usually used as follows. That is, 1.2 to 5.0 moles of lower alcohol and an appropriate amount of catalyst, for example, 0.01 to 1.0% by weight of alkali catalyst, are mixed with fatty acid glyceride, reaction temperature 40 to 70 ° C., reaction time 5 It can be done in ~ 120 minutes. The reaction pressure may be reduced pressure, normal pressure, or increased pressure.

  The reaction product obtained after the reaction contains glycerin, lower alcohol, soap, catalyst and the like in addition to the fatty acid alkyl ester, and the fatty acid ester layer is obtained by separating the glycerin and lower alcohol layers. There is no particular limitation on the separation method, but stationary separation, centrifugation, and the like are preferable.

The fatty acid ester layer contains glycerin, lower alcohol, soap, catalyst and the like corresponding to the solubility, and these are appropriately removed by washing with water.
Similar transesterification and water washing operations can be repeated.

In the present invention, acid or alkali is added to the fatty acid ester mixture containing monoglyceride obtained by the method as described above and distilled. The _{acid, H 2 SO 4, HNO 3} , H 3 PO 4, HPO 3, H 4 P 2 O 7, H 3 BO 3 and the like. Examples of the alkali include CaO, Ca (OH) ₂ , MgO, Mg (OH) _{2 and the} like. These can be used alone or in combination of two or more, but from the viewpoint of liquid properties during distillation, H ₂ SO ₄ , H ₃ PO ₄ , H ₃ BO ₃ , CaO, Ca (OH) ₂ , MgO, Mg ( OH) ₂ is preferable, and H ₃ PO ₄ , H ₃ BO ₃ , CaO, Ca (OH) ₂ , MgO, and Mg (OH) ₂ are more preferable.

  The addition amount of the acid or alkali is preferably 0.1 to 10 mol times, preferably 0.1 to 3 mol times with respect to the monoglyceride from the viewpoint of efficiently removing the monoglyceride and suppressing the decomposition of the fatty acid alkyl ester. More preferred.

  The distillation conditions can be appropriately selected according to the fatty acid alkyl ester to be obtained and the boiling point of the monoglyceride contained, but it is desirable to carry out the distillation under reduced pressure. From the viewpoint of the burden of equipment on the degree of vacuum, the pressure at the distillation bottom is preferably 0.1 kPa or more, and more preferably 1 kPa or more. Moreover, it is effective not to raise the bottom temperature excessively from the viewpoint of inhibiting decomposition of the fatty acid alkyl ester, and the pressure of the distillation bottom is preferably 100 kPa or less, and more preferably 10 kPa or less.

  The distillation column used in the distillation process is a column packed with a regular packed plate of metal plate or wire mesh for contact with gas and liquid, or an irregular packing such as Raschig ring or pole ring, or perforated plate tray, foam Either a rectifying column provided with a shelf such as a bell-type tray or a flash column not provided with a gas-liquid contact portion in the column may be used. The distillation operation of the present invention can be carried out continuously, batchwise, or semi-batch.

  In the following examples, a mixed methyl ester containing a monoglyceride having a boiling point lower than that of a methyl ester having 18 carbon atoms in the fatty acid group and having 10 carbon atoms in the fatty acid group (hereinafter referred to as C10 monoglyceride) is used as a raw material. The effect of the present invention is shown by the C10 monoglyceride content in the distillation fraction in the distillation purification.

  The raw fatty acid ester used was a monoglyceride-containing fatty acid ester obtained by transesterifying palm kernel oil with methanol. As the transesterification catalyst, a methanol solution of sodium hydroxide was used. The composition of the raw material fatty acid ester was as shown in Table 1. The Cn fatty acid methyl ester means a methyl ester of a fatty acid having n carbon atoms.

Example 1
The raw material fatty acid ester 300g was supplied into the distillation flask. The content of C10 monoglyceride contained was 3.0 g (molecular weight: 246, 12.2 mmol). To this, 85% phosphoric acid was added in an amount of 3.39 g in terms of phosphoric acid (molecular weight: 98, 34.6 mmol, 2.84 mol times monoglyceride), heated to 2.7 kPa up to 220 ° C. and distilled, % By weight was distilled off. When the fraction was analyzed by gas chromatography, the C10 monoglyceride content was reduced to 0.02% by weight.

Example 2
The same treatment as in Example 1 was performed except that the amount of 85% phosphoric acid added was 0.34 g in terms of phosphoric acid (molecular weight: 98, 3.5 mmol, 0.28 mol times monoglyceride).

Example 3
The same treatment as in Example 1 was carried out except that 0.18 g of boric acid (molecular weight: 61.8, 2.9 mmol, 0.24 mol times of monoglyceride) was added instead of 85% phosphoric acid.

Example 4
The same treatment as in Example 1 was performed except that 0.17 g of calcium oxide (molecular weight: 56, 3.0 mmol, 0.25 mol times monoglyceride) was added instead of 85% phosphoric acid.

Comparative Example 1
The same treatment as in Example 1 was performed, except that 3.00 g of sodium stearate (molecular weight: 306, 9.8 mmol, 0.82 mol times of monoglyceride) was added instead of 85% phosphoric acid. The content of C10 monoglyceride in the fraction was not changed, and the monoglyceride removal effect was not obtained.

  The analysis results of the fractions obtained in Examples 1 to 4 and Comparative Example 1 are summarized in Table 2.

Claims (5)

  A method for producing a fatty acid alkyl ester, wherein an acid or an alkali is added to a fatty acid ester mixture containing monoglyceride to perform distillation. The acid to be added is at least one selected from the group consisting of H ₂ SO ₄ , HNO ₃ , H ₃ PO ₄ , HPO ₃ , H ₄ P ₂ O ₇ , and H ₃ BO ₃ . A method for producing a fatty acid alkyl ester. Alkali to be _{added, CaO, Ca (OH) 2} , MgO, and a Mg (OH) of at least one selected from the group consisting of _2, method for producing a fatty acid alkyl ester of claim 1, wherein.   The manufacturing method of the fatty-acid alkylester in any one of Claims 1-3 whose addition amount of an acid or an alkali is the range of 0.1-10 mol times with respect to monoglyceride. The method for producing a fatty acid alkyl ester according to any one of claims 1 to 4, wherein the fatty acid ester mixture containing monoglyceride is obtained by transesterification of fatty acid glyceride and a lower alcohol having 1 to 5 carbon atoms.