JPH0116820B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fatty acid lower alkyl esters using fats and oils containing water as raw materials, and more specifically, the present invention relates to a method for producing fatty acid lower alkyl esters using fats and oils containing water as raw materials. This invention relates to an improved method for producing lower alkyl esters. Lower alkyl esters of higher fatty acids are useful as raw materials for surfactants and as starting materials for producing soaps, higher alcohols, and the like. This fatty acid lower alkyl ester is produced on an industrial scale by transesterifying a fatty acid glyceride and a lower alcohol in the presence of an alkali catalyst. However, since these industrially produced fatty acid lower alkyl esters usually use crude oils and fats as raw materials, many of them contain relatively large amounts of free fatty acids as well as various impurities, such as palm kernel oil and coconut oil. However, if the harvest time is delayed, the free fatty acids in the oil will increase and the acid value (AV) will reach 10 to 30.
When such fats and oils with a high acid value are used as a raw material for transesterification, the alkali used as a catalyst is consumed for neutralization, producing a large amount of soap, and the recovery rate of the target product, lower alkyl ester, decreases. Therefore, such oils and fats with a high acid value are heated to, for example, 60 to 80°C in a column filled with a cation exchange resin to which about 10 to 20% by weight of lower alcohols such as methanol or ethanol are added. Pretreatment is carried out to esterify free fatty acids under conditions and at a slow rate with a residence time of about 60 to 90 minutes. Through this treatment, free fatty acids are esterified and essentially converted into fatty acid lower alkyl esters, but water generated during the esterification reaction is mixed in the fats and oils. In some cases, the treated fats and oils contain about 0.3 to 1% by weight of water. In addition, when fats and oils with a high water content are subjected to normal transesterification reactions, the activity of the alkali catalyst decreases,
As a result, the reaction rate also decreases, making it impossible to obtain the target product with high efficiency. Even when a pretreated water-containing fat or oil is used as described above, the catalytic activity is significantly reduced, and such fats and oils usually have to be subjected to troublesome dehydration or drying treatments. The present inventors have conducted research on a method for transesterifying water-containing oils and fats, such as oils and fats that have been treated to reduce the amount of free fatty acids as much as possible as described above, at an excellent reaction rate without water removal treatment. As a result of repeated efforts, the inventors have found that the objective can be achieved very effectively when a fatty acid alkali metal salt is added to the transesterification reaction system, leading to the present invention. That is, the present invention uses a fatty acid glyceride containing water as a raw material and performs a transesterification reaction with a lower alcohol in the presence of an alkali catalyst to produce a fatty acid lower alkyl ester. The present invention provides a method characterized in that parts by weight of a fatty acid alkali metal salt are added, sufficiently dispersed, and then an alkali catalyst is added and reacted. The fatty acid glycerides used in the transesterification reaction in the method of the present invention include natural fats and oils, such as vegetable fatty acid glycerides such as coconut oil, palm oil, palm kernel oil, cottonseed oil, and soybean oil, and beef tallow, lard, and fish fat. Including animal fatty acid glycerides, etc.
The present invention is directed to glycerides containing 0.05 to 1% by weight of water, which is unfavorable for transesterification reactions, especially those made from hydrous fatty acid glycerides that have been subjected to the esterification treatment of free fatty acids as described above. be. Further, the lower alcohol used in the transesterification reaction of fatty acid glyceride is usually a lower aliphatic alcohol whose alkyl group has 1 to 3 carbon atoms, and such alcohols include methanol, ethanol, propanol, and - Examples include propanol. In addition, as a catalyst for the transesterification reaction, an alkali catalyst that is commonly used for the transesterification reaction is used, and specific examples thereof include sodium,
Potassium hydroxide or their methylates can be mentioned. The transesterification reaction in the method of the present invention is carried out in accordance with a conventional method by adding a lower alcohol in an amount of 2 to 10 times equivalent to the fatty acid glyceride and an alkali catalyst of 0.1 to 1 part by weight to 100 parts by weight of the fatty acid glyceride. The transesterification is carried out by reacting for 0.5 to 2 hours at a temperature near the boiling point of the lower alcohol, but in the present invention, a fatty acid alkali metal salt, preferably a _C12-18 Alkali metal salts of higher fatty acids are added. Examples of such alkali metal salts include sodium and potassium salts of lauric acid, myristic acid, oleic acid and stearic acid. These soaps may be used alone or in combination of two or more, and the amount added is 0.5 to 3 parts by weight per 100 parts by weight of fats and oils. The amount added or used can be increased or decreased as appropriate depending on the water content of the fatty acid glyceride, but if it is less than 0.5 parts by weight,
This is not preferable because the catalyst activity decreases, and 3
If it exceeds 1 part by weight, the target ester will be eluted into the lower layer of glycerin during stationary separation after transesterification, resulting in a decrease in recovery rate, which is not preferable. In the present invention, it is important to add an alkali metal to the fatty acid glyceride and the lower alcohol, and then add an alkali catalyst to the composition, which is sufficiently dispersed by stirring or the like, to cause a reaction. If the dispersion is insufficient, a high reaction rate cannot be obtained due to the decreased activity of the catalyst due to the water contained. It is desirable to stir for at least a minute. In the method of the present invention, an alkali metal compound is actively added to the system before adding the catalyst, but the reaction product containing the compound after transesterification may be used as it is or it may be left to stand for liquid separation. It is also possible to recycle a portion of the upper layer, for example 30 to 50%, to effectively utilize the alkali metal compounds contained therein. When transesterification is carried out in a system in which an alkali metal compound is present, the activity of the catalyst is substantially reduced even when fatty acid glyceride containing about 1% by weight of water introduced in the pretreatment is used as a starting material. The process of the present invention is industrially desirable since high esterification and recovery rates of, for example, 95% or more are obtained without any deterioration. The product liquid subjected to the transesterification reaction by the method of the present invention is allowed to stand still and separated into an upper layer of higher fatty acid lower alcohol ester and a lower layer of glycerin, and then separated to obtain the desired ester, as in the conventional method. be able to. In addition, the ester thus obtained is subjected to another esterification reaction using a lower alcohol in the presence of an alkali catalyst, and a small amount of water is added to the resulting esterification mixture with a high reaction rate and stirred. The ester can also be purified by transferring impurities to the aqueous lower alcohol layer. Next, the present invention will be explained in more detail with reference to Examples. In addition, in the examples, the esterification rate (%) is
It is determined from the weight of glycerin produced by transesterification with respect to the theoretical weight of glycerin of glyceride. Examples 1 to 2 and Comparative Examples 1 to 4 A solution of palm kernel oil with an acid value of 12.7 and a water content of 0.1% and 20% by weight of methyl alcohol was added to a cation exchange resin (manufactured by Mitsubishi Kasei Corporation: DIAION SK).
104H) Introduce the solution into a packed column, maintain the solution temperature in the column at 60°C, and set the residence time to about 1 hour.
By methyl esterifying free fatty acids, the acid value is 1,
Oil and fat with a moisture content of 0.4% were obtained. Using this pretreated oil and fat as a raw material for fatty acid glyceride, a transesterification reaction was carried out using a solution prepared by adding 22 parts by weight of methyl alcohol to 100 parts by weight under various conditions shown in Table 1 below. In addition, sodium stearate was used as the fatty acid alkali metal mixture, and sodium hydroxide was used as the catalyst per 100 parts by weight of glyceride.
0.31 parts by weight was used. In addition, the temperature of the reaction system is 60~
The mixture was kept at 70°C and stirred for 1 hour to carry out the transesterification reaction. After the reaction is complete, leave the solution to cool for about 30 minutes.
After a few minutes, when the liquid temperature reached approximately 40°C, the upper ester layer, which was separated into two layers, was collected. The results of each experiment are summarized in a table together with various parts by weight added to 100 parts by weight of Setsuken glyceride and conditions for changing the stirring time (minutes) before adding the catalyst. For comparison, the conditions and results for oils and fats that were not pretreated are also listed (Comparative Example 4).

[Table] Examples 3 to 4 and Comparative Example 5 The esterified fats and oils used above (AV1,
22 parts by weight of methyl alcohol was similarly added to this (moisture content: 0.4%), and instead of adding Setsuken, a part of the product after the transesterification reaction performed in Comparative Example 1 was recycled and used for the next ester. A similar experiment was conducted using Setsuken in the circulating fluid by subjecting it to an exchange reaction. Table 2 shows the recycling conditions and results.

【table】

[Table] Example 5 A solution prepared by adding 20 parts by weight of methyl alcohol to 100 parts by weight of coconut oil with an acid value of 20 and a moisture content of 0.05% by weight was passed through a cation exchange resin column and deacidified, resulting in a solution with an acid value of 2 and a water content of 0.05% by weight. A fat and oil concentration of 0.5% by weight was obtained. Add 24 parts by weight of methyl alcohol to this, stir well,
0.52 parts by weight of sodium methylate (0.22 parts by weight as Na) was added as a catalyst, and the transesterification reaction was carried out at a temperature of about 70° C. for 1 hour. Esterification rate
The recovery rate was 91% and 98%. This was separated by standing and the upper layer was recycled to make up 30% of the total fats and oils. The amount of setsuken incorporated in this case is 0.5 parts by weight. After 5 minutes of stirring, add sodium methylate (0.14 parts by weight as Na) and methyl alcohol.
Transesterification was carried out by adding 24 parts by weight. The results were an esterification rate of 96.0% and a recovery rate of 98%.

Claims (1)

[Scope of Claims] 1 In producing a fatty acid lower alkyl ester by transesterifying a fatty acid glyceride containing water with a lower alcohol in the presence of an alkali catalyst, the fatty acid glyceride 100
1. A method for producing a fatty acid lower alkyl ester, which comprises adding 0.5 to 3 parts by weight of a fatty acid alkyl metal salt, sufficiently dispersing the salt, and then adding an alkali catalyst for reaction. 2. The method of claim 1, wherein the fatty acid alkali metal salt is selected from sodium laurate, potassium myristate, sodium oleate, and sodium stearate.