JP5282951B2 - Method for producing fatty acid alkyl ester - Google Patents

Description

  The present invention relates to a method for producing a fatty acid alkyl ester that obtains a fatty acid alkyl ester by transesterifying an oil and fat with an aliphatic alcohol.

Conventionally, fossil liquid fuels such as kerosene, light oil, and heavy oil have been used as fuels for internal combustion engines and the like, but in recent years, depletion of these fossil liquid fuel resources has become a problem. In addition, products such as SO _X , NO _X , and CO ₂ generated from these fossil liquid fuels cause air pollution.

  Therefore, in recent years, fuels using reproducible raw materials (biomass) such as vegetable oils and animal oils have been developed. For example, biodiesel fuel, which is a representative fuel using biomass, does not contain sulfur and aromatics, and can be used for the same internal combustion engine as conventional internal combustion engines using petroleum liquid fuel. Since it is carbon neutral, greenhouse gases can be greatly reduced.

  As such biodiesel fuel, fatty acid alkyl ester synthesized from triglyceride contained in synthetic oil, vegetable oil, animal oil and the like is usually used. As a method for producing such a fatty acid alkyl ester, for example, there is a method of transesterifying triglyceride and methanol in the presence of an alkali catalyst (see Patent Documents 1 to 3).

  In this method, triglyceride and methanol are first reacted in the presence of, for example, sodium hydroxide to obtain a reaction mixture mainly of fatty acid alkyl ester and glycerin. Next, in order to purify the fatty acid alkyl ester from the reaction mixture, first, the fatty acid alkyl ester and glycerin are phase-separated to separate a light liquid containing the fatty acid alkyl ester. Next, after methanol contained in the separated light liquid is distilled off to obtain a crude fatty acid alkyl ester, the first washing is performed by adding an acid aqueous solution such as hydrochloric acid to the crude fatty acid alkyl ester. A second wash is performed by adding water, and finally water is removed by heating to obtain a fatty acid alkyl ester.

In recent years, as a catalyst for the transesterification reaction between triglyceride and methanol, in addition to a sodium-based catalyst such as sodium hydroxide or sodium methoxide, or a potassium-based catalyst such as potassium hydroxide or potassium methoxide, the catalyst can be separated. In order to facilitate, it has been proposed to use a highly active solid alkali catalyst such as highly active calcium oxide or activated calcium oxide.
Japanese Patent Laid-Open No. 7-31090 WO2006 / 134845 pamphlet WO2007 / 088702 pamphlet

  However, when the phase separation is performed as described above, there is a problem that the purification process requires many steps and a long time because two washing steps and a heating step are required thereafter.

  In addition, when a calcium-based catalyst is used as an alkali catalyst, a large amount of calcium compound remains in a floating state in a light liquid, and it takes a very long time to separate by sedimentation. In the light liquid containing the alkyl ester, the calcium-based catalyst remains in the form of fatty acid calcium (calcium soap), and in order to remove this, a large amount of adsorbent such as activated carbon is required. The present inventors have clarified that there is a problem that the cost increases.

  Therefore, the present invention provides a method for producing a fatty acid alkyl ester that is inexpensive and can purify a fatty acid alkyl ester without requiring many steps and a long time even when a calcium-based catalyst is used. For the purpose.

  In order to achieve the above object, the present inventors have conducted intensive studies, and as a result, added a chelating agent to the reaction mixture after the transesterification of fats and fatty alcohols in the presence of a calcium-based catalyst. Thus, it has been found that even when a calcium-based catalyst is used, the fatty acid alkyl ester can be purified at low cost and without requiring many steps and a long time. That is, the present invention is a method for producing a fatty acid alkyl ester that obtains a fatty acid alkyl ester by transesterification of fats and oils and an aliphatic alcohol in the presence of a calcium-based catalyst, wherein the reaction mixture after the transesterification reaction, A step of adding a chelating agent before the reaction mixture is phase-separated into a light liquid and a heavy liquid and the both are separated is provided.

  As described above, according to the present invention, even when a calcium-based catalyst is used, the fatty acid alkyl ester can be purified at low cost and without requiring many steps and a long time. A manufacturing method can be provided.

  In the method for producing a fatty acid alkyl ester according to the present invention, an oil and fat and an aliphatic alcohol are subjected to a transesterification reaction in the presence of a calcium catalyst to obtain a reaction mixture containing a fatty acid alkyl ester, glycerin and a calcium compound. In addition to the remaining calcium-based catalyst, the calcium compound includes substances derived from calcium-based catalysts such as fatty acid calcium. This transesterification reaction can be carried out in various reaction modes. For example, it may be performed batchwise or continuously. In the transesterification reaction, the reaction mixture may be uniformly mixed during the reaction, or may be separated into two layers as long as the reaction is possible. In the case of separation into two layers, for example, the reaction can be promoted more efficiently by increasing the contact area of the two layers by carrying out the reaction under stirring.

  After completion of the transesterification reaction, a chelating agent is added to the obtained reaction mixture before phase separation of the reaction mixture into a light liquid and a heavy liquid to separate them. Separation of the light liquid and the heavy liquid may be performed by removing the heavy liquid from the reaction mixture or extracting the light liquid. The chelating agent may be added before the phase separation of the light liquid and the heavy liquid immediately after the transesterification reaction as long as it is before the separation of the light liquid and the heavy liquid. After the transesterification reaction, the reaction mixture may be after phase separation into a light liquid and a heavy liquid. When the chelating agent is added, the reaction mixture may be extracted from the reaction vessel into another vessel, and the chelating agent may be added to the reaction mixture. In addition, it is preferable to stir the reaction mixture at the time of adding the chelating agent, and it is not necessary to cool the reaction mixture. The temperature is, for example, 50 to 70 ° C. when the aliphatic alcohol is methanol. It is preferable that After the chelating agent is added, it is preferable to stir the reaction mixture within this temperature range for about 5 to 30 minutes. The reaction mixture is phase-separated into a light liquid (upper phase) mainly containing fatty acid alkyl ester and a heavy liquid (lower phase) mainly containing glycerin by standing or centrifuging. Thus, the calcium compound contained in the fatty acid alkyl ester can be transferred to the heavy liquid containing glycerin in a short time. According to the method for producing a fatty acid alkyl ester according to the present invention, the calcium content of the light liquid is 5 ppm or less (within EU standards).

  In the method for producing a fatty acid alkyl ester according to the present invention, the chelating agent is preferably in the form of an aqueous solution, and may be preheated to the temperature of the reaction mixture to be added even at room temperature. Examples of chelating agents include polyvalent carboxylic acids and oxyacids, phytic acid, and EDTA that act as chelating agents such as oxalic acid, citric acid, tartaric acid, gluconic acid, malic acid, and lactic acid. The addition amount of the chelating agent is 1 to 2 times equivalent, preferably 1 to 1.5 times equivalent, more preferably 1 to 1.2 times equivalent to calcium, and the chelating agent concentration in the aqueous solution is 30 mass. % Or less, more preferably 20% by mass or less, and particularly preferably 20% by mass or less and 5% by mass or more. The amount of water in the aqueous solution is in the range of 25 to 200 g, more preferably 25 to 150 g, with respect to 1 kg of fat and oil. It is preferable. If the amount of water used is small, the Ca compound cannot be removed efficiently, and if the amount of water used is large, the treatment of heavy liquid after phase separation becomes complicated.

  It is preferable to distill off the fatty acid alcohol contained in the obtained light liquid by effectively utilizing heat without cooling. In distilling off the fatty acid alcohol contained therein, for example, methanol may be heated to about 70 ° C. under reduced pressure. When a precipitate further precipitates by this operation, it can be removed by filtration or the like. Further, following the distillation of the fatty acid alcohol contained, water in the light liquid can also be distilled off in the same manner. In this case, the precipitated precipitate can be removed after the distillation of the fatty acid alcohol and water contained therein. preferable. In addition, it is preferable that water is also distilled off under reduced pressure. As described above, fatty acid methyl ester (BDF) conforming to EU standards having a metal content of 5 ppm or less can be obtained.

  In the method for producing a fatty acid alkyl ester according to the present invention, fats and oils and aliphatic alcohols are preferably reacted at a ratio of 4 to 150 times moles of the fatty alcohol to the fats and oils and reacted at a ratio of 5 to 50 times moles. More preferably. Moreover, it is preferable that the usage-amount of a catalyst is the calcium amount corresponded to 0.5-30g as CaO amount with respect to 1 kg of fats and oils.

  The reaction temperature at the time of reacting oil and fat and aliphatic alcohol should just be 30 degreeC or more. For example, it may be in the range of 30 ° C. to near the boiling point of the alcohol under normal pressure, preferably 50 ° C. to the reflux temperature of the reaction solution. If the alcohol is methanol, it is in the range of 30 to 70 ° C., preferably 50 to 70 ° C. It can be. The reaction pressure when reacting fats and oils with the aliphatic alcohol is preferably 0.1 to 8 MPa, and the reaction time is preferably 30 minutes or more, and more preferably 30 minutes to 3 hours. Each reaction condition such as reaction temperature, reaction pressure, reaction time, and catalyst addition amount can be appropriately selected according to the above range as necessary.

  In the method for producing a fatty acid alkyl ester according to the present invention, the fat / oil is a substance mainly containing a triglyceride represented by Chemical Formula 1, and is contained in a natural fat / oil such as vegetable fat / animal fat / oil or chemically synthesized. Various things, such as a thing, can be used. Examples of vegetable oils include rice oil, rapeseed oil, sesame oil, soybean oil, palm oil, palm oil, cottonseed oil, peanut oil, coconut oil, linseed oil, olive oil, safflower oil, and Jatropha oil. Animal oils include beef fat, horse There are fat, sheep fat, pork fat, fish oil, whale oil, shark liver oil and so on. Moreover, what mixed these oils and fats, the fats and oils containing a diglyceride and a monoglyceride, and the fats and oils which carried out modification | denaturation, such as oxidation and a reduction | restoration, may be sufficient. In addition, unrefined oils and fats that contain a small amount of free fatty acids and moisture may be used, and waste cooking oils discarded from restaurants, food factories, general households, etc. may be used, but appropriate pretreatment is performed as necessary. It is preferable.

Triglycerides represented by Formula ^1, as long as R 1, ^{R 2} and ^{R 3} contains from 6 to 24 carbon ^atoms, R 1, ^{R 2} and ^{R 3} is a saturated aliphatic It may be mono, di, or triunsaturated aliphatic. Furthermore, R ¹ , R ² and R ³ may contain a hydroxy group.

  In the method for producing a fatty acid alkyl ester according to the present invention, the aliphatic alcohol is an aliphatic lower alcohol having 1 to 6 carbon atoms, particularly 1 to 4 carbon atoms, preferably methanol or ethanol, and particularly preferably methanol.

In the method for producing a fatty acid alkyl ester according to the present invention, the calcium-based catalyst may be any calcium-based catalyst as long as it can be used as a catalyst for transesterification of fats and fatty alcohols, such as calcium oxide, calcium hydroxide, calcium methoxide, and the like. Calcium alkoxides, and calcium alkoxide hydrates such as Ca (OH) (OCH ₃ ). As calcium oxide, calcium oxide having high base strength described in Patent Documents 2 and 3 and calcium oxide activated in methanol can be used.

  Examples of the fatty acid alkyl ester obtained in the method for producing a fatty acid alkyl ester according to the present invention include valeric acid, caproic acid, enatonic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecylic acid, myristic acid, pentadecyl. Acid, palmitic acid, heptedecyl acid, stearic acid, nonadecanoic acid, arachidic acid, pepenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccelic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid , Elaidic acid, celetic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearolic acid, nervonic acid, ricinoleic acid, (+)-hydronocarbic acid, (+)-chaulum -Glynic acid etc. There is an ester, an alcohol residue of the ester is determined by the alcohol used. For example, when methyl alcohol is used as alcohol, methyl ester is obtained, and when ethyl alcohol is used, ethyl ester is obtained.

  The method for producing a fatty acid alkyl ester according to the present invention does not require a two-stage washing process or a heating process, can greatly reduce the amount of water used and the amount of wastewater generated, and can also effectively use heat to consume energy. Can be reduced. Moreover, in the manufacturing method of the fatty acid alkyl ester which concerns on this invention, the stationary time in the case of phase separation can be shortened significantly, and Ca density | concentration in fatty acid methyl ester can be reduced.

[Example 1]
(1) Preparation of catalyst The catalyst calcium oxide was prepared according to Example 1 described in the pamphlet of International Publication WO2008 / 090987.
(2) Manufacture of fatty acid methyl ester In a 1 L separable flask equipped with a stirrer, a reflux condenser, and a warm water jacket, 750 g of rapeseed oil (manufactured by Riken Agricultural Chemicals), 163.6 g of methanol, and calcium oxide prepared in (1) 2.625 g (0.0469 mol) was added, and a transesterification reaction was performed at 64 to 70 ° C. for 3 hours with stirring.
When a part of the obtained reaction mixture was collected and analyzed by gas chromatography, the ratio of fatty acid methyl ester to the total of fatty acid methyl ester, monoglyceride, diglyceride and triglyceride was 99%.
(3) Purification of fatty acid methyl ester To the reaction mixture (about 70 ° C.) obtained in (2), 60 g of an aqueous 10.0% by mass citric acid solution (0.0312 mol citric acid; 0.67 citric acid relative to 1 mol of Ca) Mol) was added under stirring and stirring was continued at that temperature for 5 minutes. Thereafter, the reaction mixture was allowed to stand for 90 minutes and phase-separated into a light liquid and a heavy liquid. Methanol was distilled off from the obtained light liquid under reduced pressure, and the light liquid was cooled to room temperature to obtain a fatty acid methyl ester. . It was 2 mass ppm when the Ca density | concentration (metal conversion value) in the obtained fatty acid methyl ester was measured by the ICP emission analysis.

[Comparative Example 1]
The fatty acid methyl ester was purified in the same manner as in Example 1 except that the citric acid aqueous solution was not added. As a result, the Ca concentration in the obtained fatty acid methyl ester was 1032 mass ppm.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the purification of the fatty acid methyl ester was changed as follows. The reaction mixture obtained in Example 1 was allowed to stand for 90 minutes and phase-separated into a light liquid and a heavy liquid, and 60 g of a 10% by mass citric acid aqueous solution was stirred into the resulting light liquid (Ca concentration: 1051 mass ppm). And continued stirring and mixing for 5 minutes. Thereafter, the reaction mixture was allowed to stand for 90 minutes and phase-separated into a light liquid and an aqueous phase, and methanol was distilled off from the light liquid and then cooled in the same manner. As a result, the Ca concentration in the obtained fatty acid methyl ester was 105 mass ppm.

[Example 2]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the amount of 10.0% by mass citric acid aqueous solution added was changed to 80 g (citric acid 0.0417 mol; citric acid 0.89 mol with respect to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained fatty acid methyl ester was 2 ppm by mass.

[Example 3]
The fatty acid methyl ester was purified in the same manner as in Example 1 except that the addition amount of the 10.0 mass% citric acid aqueous solution was changed to 120 g (citric acid 0.0625 mol; citric acid 1.33 mol with respect to 1 mol of Ca). did. As a result, the Ca concentration in the obtained fatty acid methyl ester was less than 1 mass ppm.

[Example 4]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 30 g of a 20.0 mass% citric acid aqueous solution (citric acid 0.0312 mol; 0.61 mol of citric acid relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained fatty acid methyl ester was 4 mass ppm.

[Example 5]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 80 g of a 7.5% by mass citric acid aqueous solution (citric acid 0.0312 mol; citric acid 0.67 mol relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained purified fatty acid methyl ester was 1 ppm by mass.

[Example 6]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 120 g of a 5.0% by mass citric acid aqueous solution (citric acid 0.0312 mol; citric acid 0.67 mol relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained purified fatty acid methyl ester was 1 ppm by mass. The results of Examples 1 to 6 and Comparative Examples 1 and 2 are summarized in Table 1.

[Examples 7 to 10]
After adding 60 g of 10.0 mass% citric acid aqueous solution to the reaction mixture (about 70 ° C.) and stirring and mixing at that temperature for 5 minutes, the standing time was changed to 60 minutes, 30 minutes, 10 minutes and 5 minutes. The fatty acid methyl ester was purified in the same manner as in Example 1 except that each phase was separated. As a result, the Ca concentration in the fatty acid methyl ester obtained was 2 ppm by mass for 60 minutes, 2 ppm by mass for 30 minutes, 3 ppm by mass for 10 minutes, and 5 minutes for static time. It was 4 mass ppm. In the present invention, the standing time during phase separation can be greatly shortened in this way, and the Ca concentration in the fatty acid methyl ester can be reduced. The results are summarized in Table 2.

[Example 11]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the aqueous citric acid solution was changed to 60 g of an aqueous 7.24% by mass oxalic acid solution (0.0483 mol of oxalic acid; 1.03 mol of oxalic acid relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained fatty acid methyl ester was 2 ppm by mass.

[Example 12]
The fatty acid methyl ester was purified in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 60 g of 15.6% by weight tartaric acid aqueous solution (0.0624 mol of tartaric acid; 1.33 mol of tartaric acid with respect to 1 mol of Ca). . As a result, the Ca concentration in the obtained fatty acid methyl ester was 2 ppm by mass.

[Example 13]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 60 g of an 11.5 mass% phytic acid aqueous solution (0.0105 mol of phytic acid; 0.22 mol of phytic acid relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained fatty acid methyl ester was 3 ppm by mass.

[Example 14]
Purification of fatty acid methyl ester in the same manner as in Example 1 except that the citric acid aqueous solution was changed to 80 g of a 30.6% by mass gluconic acid aqueous solution (0.1248 mol of gluconic acid; 2.67 mol of gluconic acid relative to 1 mol of Ca). Was done. As a result, the Ca concentration in the obtained fatty acid methyl ester was 1 ppm by mass. The results of Examples 11 to 14 are summarized in Table 3.

Claims (3)

A method for producing a fatty acid alkyl ester, wherein a fatty acid alkyl ester is obtained by transesterification of fats and oils and an aliphatic alcohol in the presence of a calcium-based catalyst,
Production of fatty acid alkyl ester comprising a step of adding a chelating agent to the reaction mixture after the transesterification reaction before phase-separating the reaction mixture into a light liquid and a heavy liquid and isolating both of them. Method.   The method for producing a fatty acid alkyl ester according to claim 1, wherein the reaction mixture is not cooled during the addition of the chelating agent.   After adding the chelating agent, the reaction mixture is phase-separated into a light liquid and a heavy liquid, and then the light liquid is isolated and the aliphatic alcohol contained therein is distilled off without cooling the light liquid, The method for producing a fatty acid alkyl ester according to claim 1, further comprising a step of purifying the fatty acid alkyl ester.