WO2007060993A1

WO2007060993A1 - Process for producing fatty acid alkyl ester

Info

Publication number: WO2007060993A1
Application number: PCT/JP2006/323325
Authority: WO
Inventors: Keiichi Tsuto; Yuuichiro Azuma; Tetsuya Koshikawa
Original assignee: Revo International Inc.
Priority date: 2005-11-28
Filing date: 2006-11-22
Publication date: 2007-05-31
Also published as: JP2007145759A

Abstract

A process for producing a fatty acid alkyl ester by transesterification of a fat-and-oil with an alcohol in the presence of an alkaline catalyst. The process is characterized in that such a fat-and-oil is subjected to the transesterification that is obtained in a pretreatment step comprising mixing an alkali-containing glycerine produced in the transesterification as a by-product with a raw fat-and-oil to neutralize a free fatty acid contained in the raw fat-and-oil with an alkaline catalysts contained in the alkali-containing glycerine. The fatty acid alkyl ester can be suitably used as a biomass-derived diesel fuel or the like which is now receiving attention as a new alternative energy to petroleum.

Description

Specification

Method for producing fatty acid alkyl ester

Technical field

The present invention relates to a method for producing a fatty acid alkyl ester. More specifically, fatty acid alkyl esters are produced by a transesterification reaction with alcohol using oils and fats derived from plants, or waste edible oils discarded from restaurants, food factories, general households, etc. as a suitable raw material fats and oils. Regarding the method. Background art

[0002] Fatty acid alkyl esters are important as raw materials for oil and fat products, for example, various surfactants, in the oil and fat chemical industry. Therefore, the manufacturing process is one of the most important processes in the oil and chemical industry as a J11 process.

[0003] Furthermore, fatty acid alkyl esters are attracting attention as a new energy alternative to petroleum because they can be used as diesel fuel derived from biomass.

[0004] Cooking oil (waste cooking oil) that is used and discarded in restaurants, food factories, general households, etc. is treated with a coagulant and buried in the soil, or discarded as household waste and incinerated. In recent years, as the idea of cleansing the global environment has increased, the movement of effective reuse of these edible oils has become active. . As one of them, an attempt to produce an oil suitable for diesel fuel by obtaining fatty acid methyl ester by transesterification with methanol has begun for a while.

[0005] That is, fatty acid methyl esters obtained from vegetable oils used for edible oils are similar to light oil in physical properties such as viscosity and specific gravity, and combustibility, and can be used without engine modification. Although it has been pointed out for a long time, it has recently been highlighted as a recyclable biofuel and is widely used especially in the United States and Europe. However, fatty acid methyl esters derived from edible oils are mainly used in mixed systems with light oil because of the higher cost compared to light oil.

[0006] Currently, it has been put into practical use in the oil and fat chemical industry and biodiesel fuel production! In the process of transesterification of fats and oils (triglycerides) and alcohol, sodium hydroxide is used. Alcohol-soluble alkali catalysts such as sulfur and potassium hydroxide are used.

[0007] On the other hand, fats and oils used as raw materials for edible oils contain about 3% by weight or less of free fatty acids, and the free fatty acids neutralize the alkali catalyst used in the transesterification reaction. As a result, the amount of alkali catalyst required for the transesterification reaction increases, and subsequent catalyst removal costs high. Therefore, expensive fats and oils from which free fatty acids have been removed are required for the transesterification reaction. Even when waste cooking oil is used, the content of free fatty acid in the cooking oil before use is 0.1% by weight or less, but the cooking oil after use is usually deteriorated to 0.5%. Since it contains about 1% by weight of free fatty acids, it is necessary to remove the free fatty acids. Therefore, in order to use inexpensive fats and oils, it is necessary to solve this problem of free fatty acids.

[0008] In the prior art, a method of removing free fatty acids by removing an aqueous layer containing fatty acid sarcophagus produced by treating fats and oils with alkaline water, and reducing the fats and oils under a temperature condition of about 200 ° C (2-5mmHg ) Methods for removing free fatty acids by steaming have been proposed, and fats and oils treated by these methods are supplied as edible oils and raw oils and fats used in transesterification (see Non-Patent Document 1). ).

[0009] Further, as another method for removing free fatty acids, there is a method in which free fatty acids in fats and oils are esterified under a large excess of alcohol under a solid acid catalyst to reduce free fatty acids (non-free). (See Patent Document 2).

Non-Patent Document 1: Edited by Akio Kato, “Use of palm oil and palm kernel oil”, Sachibo, 1990, P. 35

Non-Patent Document 2: “Biomass Handbook”, Japan Institute of Energy, 2002, P. 138

Disclosure of the invention

Problems to be solved by the invention

[0010] The method of treating with alkaline water while damaging the phospholipid, protein (gum)

Although there is a merit that pigments are adsorbed or included in fatty acid sarcophagus and removed at the same time, since water is used, oil and fat are included between the oil layer and the water layer due to the presence of sarcophagus when standing and separating Wastewater treatment has the disadvantage that an intermediate layer is formed and the yield is likely to decrease immediately. Is also very expensive. In addition, the vacuum steaming method requires a high reaction temperature of about 200 ° C, and requires a large vacuum facility for exhausting high-temperature heat sources and steam, limiting the usable reaction facilities. Is not economical. On the other hand, in Esterig under a large excess of alcohol, an expensive solid acid catalyst or a complicated process such as a molecular sieve method may be required to remove the produced water. Therefore, the development of a method that can produce fatty acid alkyl esters more economically is desired as a method for producing a new diesel fuel that is economically burdensome for both methods.

An object of the present invention is to provide an efficient method for producing a fatty acid alkyl ester, which can be carried out at a low operating cost, using an inexpensive raw material fat and oil in view of the above-described conventional technology. .

Means for solving the problem

[0012] As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found a method capable of removing free fatty acids contained in raw oils and fats in a simple pretreatment step, and to complete the present invention. It came.

[0013] The present invention is a method for producing a fatty acid alkyl ester by carrying out a transesterification reaction of fats and oils in the presence of an alkali catalyst, wherein the alkali-containing glycerin by-produced by the transesterification reaction is produced. It is mixed with raw material fats and oils and fats obtained in a pretreatment step including a step of neutralizing free fatty acids in the raw material fats and oils with an alkali catalyst in an alkali-containing glycerin, and subjected to the transesterification, The present invention relates to a method for producing a fatty acid alkyl ester.

The invention's effect

[0014] According to the present invention, a fatty acid alkyl ester can be efficiently produced at a low operating cost by using an inexpensive raw material fat.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The present invention provides a method for producing a fatty acid alkyl ester by performing a transesterification reaction between an oil and a fat and an alcohol in the presence of an alkali catalyst, and treating the raw oil and fat with an alkali-containing glycerin by-produced in the transesterification reaction. Obtained in the pretreatment step It has a great feature in that fats and oils are subjected to a transesterification reaction. The pretreatment step includes a step of mixing the alkali-containing glycerin by-produced in the ester exchange reaction with the raw material fat and oil, and neutralizing the free fatty acid in the raw material fat with an alkali catalyst in the alkali-containing glycerin. In the present invention, a fatty acid alkyl ester can be efficiently produced by using the alkali-containing glycerin by-produced in the transesterification reaction by this pretreatment step.

[0016] In the pretreatment step, the step of neutralizing the free fatty acid in the raw oil and fat is, for example, mixing alkali-containing glycerin and the raw oil and fat, and optionally heating appropriately to proceed with the neutralization reaction. Can be implemented.

[0017] In consideration of the amount of free fatty acid contained in the raw material fat to be mixed, the amount of alkali-containing glycerin used is such that the amount of the alkali catalyst contained is commensurate with the amount required for neutralization of the free fatty acid. It is preferable to adjust. The content of the alkali catalyst in the alkali-containing glycerin used in the pretreatment step is not particularly limited, but is preferably about 2 to 10% by weight from the viewpoint of operability. The usage form of alkali-containing glycerin produced as a by-product in the transesterification reaction should be selected as appropriate in consideration of the production scale and other factors, whether batch or continuous, in combination with the transesterification reaction. Can do.

[0018] After neutralization, the fats and oils can be separated by separating them into a fat layer and a glycerin layer containing an alkali metal salt of a fatty acid by a method such as stationary separation. In the method of the present invention using an alkali-containing glycerin, an intermediate layer is hardly generated even in the case of stationary separation, so that the fat and oil layer can be separated with a high yield. Therefore, it is a method having excellent viewpoint power for removing gums only by free fatty acid treatment, and the pretreatment step in the present invention can be said to be a high yield defree fatty acid step and degumming step.

[0019] Since the fat and oil obtained in the pretreatment step has a reduced amount of free fatty acid, deactivation due to neutralization of the alkali catalyst used in the ester exchange reaction can be suppressed. The fats and oils subjected to the ester exchange reaction are preferably reduced to 0.06 wt% or less, more preferably 0.03 wt% or less, by a method such as dehydration under reduced pressure. On the other hand, glycerin containing an alkali metal salt of a fatty acid can be widely reused as a chemical product by removing the alkali metal salt and purifying it, or as a fuel as a heat source. [0020] Specific examples of raw oils and fats used in the pretreatment process include rapeseed oil, sesame oil, soybean oil, corn oil, sunflower oil, palm oil, palm kernel oil, palm oil, safflower oil, and papaya seed oil. And one or a mixture of two or more selected from the group consisting of vegetable oils. In these vegetable oils, when fatty acid alkyl esters are produced in large quantities, palm oil is preferred because of its high productivity (cultivation efficiency) and easy availability. Moreover, papaya seed oil is preferable for the viewpoint of the amount of free fatty acid. Papaya seed oil has a free fatty acid content of about 0.9 to 1.1% by weight, which is relatively toxic to vegetable oils. In addition to its low load, it is toxic to animals and humans. It is not available as an edible oil (JOUNAL OF FOOD SCIENCE, Vol. 43 (1978), P225, Food Chemistry, 22 (1986), P259). Therefore, it can be used rationally by using it as a raw material for fatty acid alkyl esters used in diesel fuel and the like.

[0021] In addition, the raw oil and fat used in the present invention is not limited to unused clean oil, and waste edible oil is preferable from the viewpoint of economic and social demands that may be waste edible oil. The waste edible oil in the present invention refers to edible oil that is used and discarded in restaurants, food factories, general households, etc., and is a rational raw material. Free fatty acids contained in waste edible oil increase due to deterioration compared to unused edible oil, but 0.5 to 1 weight compared to fat and oil used as a raw material for edible oil before removal of free fatty acid Like papaya seed oil, which is a small percentage, it is also suitably used as a raw material fat in the present invention from the viewpoint of the amount of free fatty acid.

[0022] Therefore, in the present invention, waste edible oil and Z or papaya seed oil can be suitably used as the raw oil and fat from the viewpoint that the amount of free fatty acid can be rationally utilized.

[0023] The alcohol used in the present invention is selected from the group consisting of alkyl alcohol having 1 to 10 carbon atoms such as methyl alcohol (methanol), ethyl alcohol (ethanol), isobutyl alcohol, etc. 1 Species or a mixture of two or more. The purity of the alcohol is not particularly limited, but a lower water content is preferred. Of the alkyl alcohols having 1 to 10 carbon atoms, methyl alcohol and ethyl alcohol are preferred in consideration of the use of fatty acid alkyl esters as diesel fuel oil. That's right.

[0024] Since the transesterification reaction is an equilibrium reaction, it is preferable to use as much alcohol as possible. However, from the viewpoint of obtaining a reaction rate improvement effect commensurate with the amount of use, 100 parts by weight of fats and oils used for the transesterification reaction On the other hand, 12 to 50 parts by weight is preferred, and 15 to 35 parts by weight is more preferred.

[0025] Examples of the alkali catalyst that promotes the transesterification reaction between fat and alcohol include sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium alcoholate, and potassium alcoholate. Among the alkali catalysts, at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium alcoholate and potassium alcoholate is preferred, which is preferably highly alkaline hydroxide sodium and Z or hydroxide. Potassium halide is more preferred.

[0026] In the present invention, fats and oils whose free fatty acid amount has been reduced by the pretreatment step are used, so that the amount of alkali catalyst consumed for neutralization of free fatty acids contained in the fats and oils is extremely small, and the ester exchange reaction itself. Is promoted by an Al force catalyst having a catalyst amount of 0.2 to 0.5 parts by weight per 100 parts by weight of fats and oils. However, in the present invention, after the reaction is completed, the by-produced alkali-containing glycerin is continuously used in the pretreatment step and mixed with the raw material fats and oils to neutralize the free fatty acids contained in the raw material fats and oils. It is preferable to use an alkali catalyst in an amount capable of neutralizing the free fatty acid contained in the raw material oil to be mixed for the transesterification reaction. For this reason, an alkali catalyst in an amount more than that required for the transesterification reaction may be used. In the present invention, however, the alkali catalyst is not only used as a catalyst. Can be used twice as an agent. As a result, it is possible to reduce the amount of alkaline compound required to use the raw fat and oil containing free fatty acids, and to remove the used alkali catalyst after the transesterification reaction. Powerful load will be reduced.

[0027] The amount of alkali catalyst used varies depending on the type of alkali catalyst and the type of raw material oil and fat, and cannot be determined unconditionally. However, by using sodium hydroxide or potassium hydroxide as an alkali catalyst, In the method for continuously producing a fatty acid alkyl ester while subjecting the alkali-containing glycerin to a pretreatment step as needed, 0.5 to 3.0 weight of free fatty acid is obtained. When using raw material fats and oils containing 0.1%, sodium hydroxide or potassium hydroxide is preferably used in an amount of 0.2 to 1.5 parts by weight with respect to 100 parts by weight of fats and oils used in the transesterification reaction. 2 to 1.0 part by weight is more preferable. For example, when using waste edible oil or papaya seed oil containing 0.5 to 1% by weight of free fatty acid as the raw oil or fat, the amount of sodium hydroxide or potassium hydroxide used is the transesterification reaction. 0.2 to 0.6 parts by weight is preferable with respect to 100 parts by weight of the fats and oils to be supplied to the oil. In addition, when using palm oil containing 2 to 3% by weight of free fatty acid, the amount of sodium hydroxide or potassium hydroxide used is 100 parts by weight of fats and oils used in the transesterification reaction. 0.5 to 1.5 parts by weight are preferred 0.5 to 1.0 parts by weight are more preferred.

[0028] In the transesterification reaction, the influence of the reaction temperature on the reaction rate is small, but from the viewpoint of preventing side reactions such as reaction speed and oxidation reaction of fats and oils, the reaction temperature is 50 to 90 ° C. preferable.

[0029] A mixture containing the desired fatty acid alkyl ester, by-produced glycerin, an alkali catalyst, and the like is obtained by the transesterification of the above fat and alcohol. The progress of the reaction can be confirmed by, for example, collecting the sample solution and allowing it to stand, and then analyzing the ester content of the upper ester layer by gas chromatography. After completion of the reaction, for example, the residual alcohol is evaporated and removed as necessary, and the reaction mixture is phase-separated by using the difference in specific gravity by standing or centrifuging, so that the oil layer has a strong fatty acid alkyl ester strength. And the alkali-containing glycerin layer can be easily separated. Almost all of the alkali catalyst used as a catalyst remains in the alkali-containing glycerin, and in the present invention, this alkali-containing glycerin is used in the pretreatment step in which it is mixed with newly used raw material fats and oils.

[0030] It is preferable that the content of fatty acid methyl ester is at least 96% as a nanofuel. Therefore, when the content of the fatty acid methyl ester obtained by the transesterification reaction is less than 96%, an alcohol and an alkali catalyst are mixed with the oil layer made of the fatty acid alkyl ester carbonate obtained by the transesterification reaction. It is preferable to increase the content of fatty acid methyl ester to such an extent that it can be suitably used as diesel fuel by subjecting it to an ester exchange reaction again. [0031] Furthermore, when the fatty acid alkyl ester contains a trace amount of an alkali component or the like, it can be removed by a purification operation such as washing with water.

[0032] According to the present invention, the fatty acid alkyl ester can be produced economically and efficiently, so that the fatty acid alkyl ester as a biofuel expected as an alternative to light oil can be further spread.

Example

[0033] Hereinafter, the present invention will be described in more detail based on examples. The present invention is not limited to such examples.

[0034] Reference Example 1

Almost free fatty acids are included! /, Commercially available tempura oil (Nisshin Oilio Co., Ltd., Salada Ace, [measured during testing] acid value: 0.15 mg KOH / g, free fatty acids: 0.07% by weight ) Was directly subjected to a transesterification reaction as a raw oil and fat, and fatty acid alkyl ester was prepared by the following method using sodium hydroxide as an alkali catalyst. The acid value was measured by neutralization titration, and the free fatty acid content was measured by gas chromatography (the same applies hereinafter).

[0035] [First stage reaction]

In a 500 mL glass container equipped with a stirrer, commercially available tempura oil (acid value: 0.15 mg KOH / g, free fatty acid: 0.07 wt%) 100 parts by weight (300 g), methanol 30 parts by weight ( 90g) and 0.3 parts by weight of sodium hydroxide (0.9g) were mixed, and the ester exchange reaction was carried out under the usual reaction conditions (reaction temperature 60 ° C, stirrer rotation speed 500rZmin, reaction time 2 hours). went . After evaporating and removing methanol from the reaction product, a 500-mL separatory funnel was used, and the alkali-containing glycerin layer was removed by stationary separation, and an oil layer having fatty acid methyl ester strength was separated.

[0036] [Second stage reaction]

100 parts by weight of the oil layer obtained by the first stage reaction, 20 parts by weight of methanol and 0.05 part by weight of sodium hydroxide were mixed, and a transesterification reaction was carried out under the same reaction conditions as in the first stage reaction. Then, after removing the methanol by evaporation, a 500 mL separatory funnel was used, and the glycerin layer was removed by stationary separation to obtain an oil layer made of fatty acid methyl ester. [0037] The content of fatty acid methyl ester contained in each oil layer obtained in the first-stage reaction and the second-stage reaction was analyzed by gas chromatography. As a result, it was found that 90.0% (after the first-stage reaction), 97. It was 3% (after the second stage reaction), and it was possible to obtain a fatty acid methyl ester satisfying quality as a diesel fuel.

[0038] Example 1

Using waste edible oil (acid value: 1.8 mgKOHZg, free fatty acid content: 0.9 wt%) as raw oil and fat, alkali-containing glycerin obtained in the first stage reaction of Reference Example 1 was pretreated as follows. Used in the process. In Reference Example 1, unused edible oil was used, the amount of free fatty acid was as small as 0.07% by weight, and when the amount of free fatty acid was less than 0.2% by weight, free fatty acid was used. The amount of alkali catalyst consumed for neutralization is negligible. Therefore, the alkali-containing glycerin obtained in the first stage reaction of Reference Example 1 contains almost 0.3 part (0.9 g) of the alkali catalyst (sodium hydroxide) used in the transesterification reaction. Remained.

[0039] [Pretreatment step]

The first stage alkali-containing glycerin 39g and cooking oil obtained by reaction of Reference Example 1 (acid value: 1. 8mgKOHZg, free fatty acid content: 0.9 wt ^_0/0) and 300 g, reactor in 500mL volume And the mixture was neutralized at 60 ° C for 3 hours. Thereafter, the reaction solution was transferred to a separatory funnel and allowed to stand and separate to remove the glycerin layer to obtain a pretreated waste cooking oil (acid value: 0.34 mg KOHZg, free fatty acid: 0.17). weight%). Since the obtained edible oil contained 0.22% by weight of moisture, it was dehydrated under reduced pressure at 90 ° C to reduce the moisture to 0.02% by weight. The water content was measured by the Karl Fischer method (the same applies hereinafter).

[0040] Thereafter, the first-stage reaction and the second-stage reaction were carried out in the same manner as in Reference Example 1 except that the waste edible oil obtained in the pretreatment step was used instead of the tempura oil, and the fatty acid methyl ester Got.

[0041] In the same manner as in Reference Example 1, the content of fatty acid methyl ester contained in each oil layer obtained in the first-stage reaction and second-stage reaction was analyzed. After) 97.1% (after the second stage reaction), a fatty acid methyl ester satisfying quality as a diesel fuel could be obtained. [0042] Example 2

A fatty acid methyl ester was obtained in the same manner as in Example 1, except that the pretreatment step was performed using the alkali-containing glycerin obtained in the first-stage reaction of Example 1. In Example 1, since the waste edible oil whose free fatty acid content was reduced to 0.17% by weight in the pretreatment step was subjected to the ester exchange reaction, the alkali-containing product obtained in the first stage reaction of Example 1 was used. Most of 0.3 part by weight (0.9 g) of the alkali catalyst (sodium hydroxide) used in the transesterification reaction remained in dalyserin.

[0043] In the same manner as in Reference Example 1, when the content of fatty acid methyl ester contained in each oil layer obtained in the first-stage reaction and second-stage reaction was analyzed, 89.5% each (first-stage reaction) After), 97.2% (after the second stage reaction), it was possible to obtain a fatty acid methyl ester satisfying quality as a diesel fuel.

[0044] Comparative Example 1

Reference Example 1 except that 100 parts by weight of waste edible oil similar to that used in Example 1 (acid value: 1.8 mgKO HZg, free fatty acid content: 0.9% by weight) was used instead of tempura oil. In the same manner, fatty acid methyl ester was obtained. However, since waste edible oil contained 0.2% by weight of water, we used oil whose water content was reduced to 0.02% by weight at 90 ° C by dehydration under reduced pressure.

[0045] The content of fatty acid methyl ester contained in each oil layer obtained in the first-stage reaction and second-stage reaction was analyzed in the same manner as in Reference Example 1. After), it was 72.1% (after the second stage reaction), and did not satisfy the quality as diesel fuel. This is presumably because most of the alkali catalyst (sodium hydroxide) was consumed to neutralize free fatty acids contained in the waste cooking oil. That is, sodium hydroxide required for neutralization of free fatty acid contained in 100 parts by weight of used cooking oil is about 0.25 part by weight when calculated based on molecular weight based on oleic acid. . Therefore, out of 0.3 parts by weight of sodium hydroxide used in the ester exchange reaction, the amount used as a catalyst is about 0.3—0.25. .

[0046] From the above results, according to the method of the example, by using 0.3 part by weight of sodium hydroxide, sufficient catalytic action was exhibited, and in the first stage reaction, 85% or more Fatty acid content by content A chill ester is obtained. On the other hand, in the method of the comparative example, since the amount of sodium hydroxide used as an alkali catalyst is small, the content of fatty acid methyl ester obtained is low. In the comparative example, sodium hydroxide requires a large amount of sodium hydroxide of about 0.3 + 0.25 = 0.55 parts by weight in order for the sodium hydroxide hydroxide to function as an alkali catalyst in the same way as the examples. The use of a large amount of alkali catalyst is not only costly, but also increases the cost burden of purification and treatment of glycerin after the transesterification reaction. Therefore, it can be seen that the fatty acid alkyl ester satisfying the quality as a diesel fuel oil can be easily produced at a low operating cost by the method of the example.

Industrial applicability

The fatty acid alkyl ester obtained by the present invention can be suitably used as a biomass-derived diesel fuel that is attracting attention as a new energy alternative to petroleum.

Claims

The scope of the claims

[1] A method for producing a fatty acid alkyl ester by performing a transesterification reaction between an oil and a fat in the presence of an alkali catalyst, wherein the alkali-containing glycerin produced as a by-product through the transesterification reaction is mixed with the raw oil and fat. And the fatty acid obtained in the pretreatment step including the step of neutralizing the free fatty acid in the raw material fat with an alkali catalyst in the alkali-containing glycerin is subjected to the transesterification reaction. Manufacturing method.

[2] The method according to claim 1, wherein the catalyst is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium alcoholate and potassium alcoholate.

[3] The production method according to claim 1 or 2, wherein the raw material fat is waste cooking oil.

[4] The production method according to any one of claims 1 to 3, wherein a fatty acid alkyl ester for diesel fuel is produced.