JP2005060591A - Method for non-catalytic production of biological diesel fuel without generating by-product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a biological diesel fuel from an animal or vegetable oil-and-fat or its waste edible oil and methanol without using a catalyst and forming glycerol as a by-product. <P>SOLUTION: The biological diesel fuel is produced by mixing the animal or vegetable oil-and-fat or its waste edible oil with methanol and subjecting the mixture to methanolysis reaction at a reaction temperature of 370-500°C, a reaction pressure of 20-60 MPa and a reaction time of 4-12 min without using a catalyst. This invention further provides a biological diesel fuel composed mainly of a fatty acid methyl ester, a monoacyl glycerol and a diacyl glycerol. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing biodiesel fuel from animal and vegetable fats and oils or waste cooking oils thereof and methanol.

  In recent years, so-called biodiesel fuel produced from animal or vegetable fats or waste cooking oils has been used due to increasing awareness of environmental protection.

  In general, biodiesel fuel is a fuel mainly composed of fatty acid methyl ester obtained by transesterification (hereinafter referred to as methanolysis) of triacylglycerol, which is the main component of animal and vegetable oils and fats and waste cooking oil, with methanol. Point to.

  The methanolysis reaction of triacylglycerol and methanol can be divided into three stages. The first stage is a stage in which one molecule of fatty acid methyl ester and one molecule of diacylglycerol are produced from one molecule of triacylglycerol and one molecule of methanol. The second stage is a stage in which one molecule of fatty acid methyl ester and one molecule of monoacylglycerol are produced from one molecule of diacylglycerol and one molecule of methanol. The third stage is a stage in which one molecule of fatty acid methyl ester and one molecule of glycerin are generated from one molecule of monoacylglycerol and one molecule of methanol.

  In the conventional method for producing biodiesel fuel, the methanolysis reaction is completed up to the third stage. As a result, glycerin is produced as a by-product. Various attempts have been made to effectively use glycerin (see Patent Document 1). However, the domestic glycerin market is in an excessive supply state, and it is actually incinerated by a dedicated furnace. In addition, since the calorific value is low, it cannot be used as a heat source. Although there is a strong demand for producing biodiesel without producing glycerin, there is no such technology.

  In the production of biodiesel fuel, it is common to perform a methanolysis reaction using a catalyst such as an alkali catalyst or an acid catalyst. However, in the catalytic method, since a catalyst (for example, sodium hydroxide) is mixed in the reaction product, it is necessary to neutralize the product, wash it, and purify the washing water.

  As a method for producing biodiesel fuel without using a catalyst, there is a method using a supercritical fluid (see Non-Patent Document 1). However, the problem that glycerin is produced as a by-product remains.

Prior art document information related to the invention of this application includes the following.
Japanese Patent Laid-Open No. 2003-096473 Shiro Saka, “Application of Supercritical Fluids to Post-Petrochemistry”, Jasco Report Special Issue on Supercritical Technology No.3, Jusco Report, May 28, 1999, p. 28-31.

  An object of the present invention is to provide a method for producing biodiesel fuel from animal and vegetable oils or fats or waste cooking oil thereof and methanol, which does not use a catalyst and does not produce glycerin as a by-product.

That is, the present invention includes the following inventions.
(1) A method for producing biodiesel fuel, comprising mixing animal and vegetable oil or fat or its waste edible oil and methanol, and performing a methanolysis reaction without using a catalyst under reaction conditions in which glycerin is not generated.
(2) The above (1) is characterized in that the reaction conditions under which the glycerin is not generated are a reaction temperature of 370 to 500 ° C., a reaction pressure of 20 to 60 MPa, and a reaction time of 4 to 12 minutes. The method described.
(3) The method according to (1) or (2) above, wherein a decomposition reaction of a carbon chain of a fatty acid group is performed in parallel with the methanolysis reaction.
(4) The method according to any one of (1) to (3) above, wherein the animal or vegetable oil or fat or waste cooking oil thereof and methanol are mixed at a volume ratio of 1: 2 to 2: 1.
(5) The method according to any one of (1) to (4) above, wherein the methanolysis reaction is performed in a Hastelloy tubular reaction tube capable of maintaining an appropriate mixed state.
(6) Biodiesel fuel mainly composed of fatty acid methyl ester, monoacylglycerol and diacylglycerol.

  According to the present invention, biodiesel fuel can be produced without generating glycerin as a by-product. That is, according to the present invention, a more complete carbon circulation type energy system can be constructed. Moreover, since the by-product is not generated, the yield of biodiesel is improved. Furthermore, the non-catalyst can eliminate the need for raw material pretreatment, product neutralization, washing, and cleaning water purification, which are essential for conventional production methods.

  The present invention produces biodiesel fuel without producing glycerin by appropriately controlling various conditions in the methanolysis reaction, thereby completing the first stage reaction and suppressing the third stage reaction. Make it possible. The degree of reaction in the second stage may be any degree, but as the reaction in the second stage proceeds, the concentration of diacylglycerol in the biodiesel fuel obtained decreases and the concentration of monoacylglycerol increases and biodiesel increases. Since the viscosity of the fuel decreases, it is preferable to control the conditions of the methanolysis reaction so that the second-stage reaction is promoted.

  Non-catalytic formation can be achieved by conducting a methanolysis reaction under supercritical conditions.

  In addition, the yield of biodiesel fuel is improved because no by-products are produced. Preferably, the yield, which was conventionally about 80% of the feedstock, is almost 100%.

  The biodiesel fuel produced by the method of the present invention is mainly composed of fatty acid methyl ester, diacylglycerol and monoacylglycerol. On the other hand, the biodiesel fuel produced by the prior art is composed mainly of fatty acid methyl ester and substantially free of diacylglycerol or monoacylglycerol.

  Animal and vegetable oils and fats are rich in long-chain fatty acids having 16 or more carbon atoms. In general, diacylglycerol or monoacylglycerol having a long chain fatty acid group is often unsuitable for diesel fuel due to its higher viscosity than fatty acid methyl ester.

  Therefore, the present invention further performs a decomposition reaction of the carbon chain of the fatty acid group in parallel with the methanolysis reaction, and converts the long chain fatty acid group into a medium chain fatty acid group having about 6 to 12 carbon atoms, thereby converting the fatty acid methyl ester, diacyl ester. By reducing the viscosity of a mixture based on glycerol and monoacylglycerol, it is possible to provide a biodiesel fuel having a viscosity that can be used as a biodiesel fuel.

The invention further relates to a biodiesel fuel based on fatty acid methyl esters, monoacylglycerol and diacylglycerol. Here, “mainly comprising” means that fatty acid methyl ester is contained in an amount of 40% by weight or more, monoacylglycerol is contained in an amount of 10% by weight or more, and diacylglycerol is contained in a proportion of 5% by weight or more. Preferred biodiesel fuel of the present invention is 40-60% by weight of fatty acid methyl ester, 10-30% by weight of monoacylglycerol, 5-20% by weight of diacylglycerol, 5-20% by weight of other aliphatic compounds, It contains triacylglycerol in a proportion of less than 1% by weight and glycerin in a proportion of less than 1% by weight. For the “other aliphatic compounds”, see the following description. More preferably, it is a biodiesel fuel having a cetane number of 49 to 65, a flash point of 100 to 200 ° C., a kinematic viscosity at 30 ° C. of 3 to 20 mm ² / sec., And a pour point of −5 ° C. or less.

Hereinafter, the present invention will be described in more detail.
1. Starting material The methanolysis reaction in the present invention starts with a mixture of animal and vegetable oil or fat or its waste cooking oil and methanol. Examples of vegetable oils and fats in the present invention include, but are not limited to, rapeseed oil, canola oil, corn oil, soybean oil, sunflower oil, and safflower oil. Animal fats and oils in the present invention include but are not limited to pork fat (lard) or beef tallow. Waste cooking oil means animal and vegetable oils and fats that have been discarded due to deterioration after being used for cooking at home, restaurants, fast food stores, bento manufacturing factories, and the like. Examples of the waste edible oil of animal and vegetable oils and fats that can be used in the present invention include, but are not limited to, waste products of fried oil used for cooking such as tempura, tonkatsu, and fried chicken.

  The mixing ratio of animal and vegetable oil or fat or its waste cooking oil and methanol can be arbitrarily selected. Preferably, animal and vegetable fats or oils or waste cooking oil thereof and methanol are mixed at a volume ratio of 1: 2 to 2: 1.

2. Reaction conditions The methanolysis reaction in the present invention is carried out without using a catalyst under reaction conditions in which glycerin is not produced.

  The above “reaction conditions under which glycerin is not generated” can be arbitrarily selected as long as the requirement that “glycerin is not generated” is satisfied. In the present invention, “reaction conditions in which glycerin is not produced” includes not only conditions in which glycerin is not produced at all, but also reaction conditions in which glycerin is not substantially produced. “Reaction conditions under which glycerin is not substantially produced” means reaction conditions under which glycerin is produced but the produced glycerin is not separated from biodiesel fuel. Here, when “the produced glycerin is not separated from the biodiesel fuel”, the produced glycerin is so small that it is not separated from the biodiesel fuel, and the produced glycerin is further reacted. (For example, OH group is replaced with methyl group), and the case where it is no longer separated from biodiesel fuel as a result of enhanced lipophilicity. The reaction conditions are preferably a reaction temperature of 370-500 ° C, preferably 380-450 ° C, a reaction pressure of 20-60 MPa, preferably 30-50 MPa, most preferably 40 MPa, and a reaction time of 4-12. A condition that is minutes. Furthermore, it is more preferable that the temperature of the mixture when flowing into the reaction tube in which the reaction is performed is 250 ° C. or higher.

  In parallel with the methanolysis reaction, it is preferable to carry out a decomposition reaction of the carbon chain of the fatty acid group. Decomposition reaction of fatty acid group carbon chain refers to a reaction in which long chain fatty acid groups (14 or more carbon atoms) contained in a large amount of animal and vegetable fats or waste cooking oils are converted to medium chain fatty acid groups (6 to 12 carbon atoms). Point to. The reaction conditions are not particularly limited, but, for example, animal and vegetable oils or waste edible oils and methanol are mixed, the reaction temperature is 390 to 500 ° C., preferably 390 to 450 ° C., the reaction pressure is 20 to 60 MPa, preferably 30 to When the methanolysis reaction is performed under the conditions of 50 MPa, most preferably 40 MPa, and a reaction time of 4 to 12 minutes, the decomposition reaction of the carbon chain of the fatty acid group proceeds in parallel with the methanolysis reaction. Furthermore, it is more preferable that the temperature of the mixture when flowing into the reaction tube in which the reaction is performed is 250 ° C. or higher. Although the mechanism by which a long chain fatty acid group is converted to a medium chain fatty acid group is not always clear, it is considered that, for example, an unsaturated bond in the long chain fatty acid group is cleaved at high temperature and high pressure to become a medium chain fatty acid group. There are various “cut pieces” after the cutting, and examples thereof include hydrocarbons, fatty acids, and aliphatic alcohols having about 6 to 12 carbon atoms. These “snips” may be included in the final biodiesel fuel.

  After completion of the methanolysis reaction, unreacted methanol is removed from the reaction mixture by evaporation under reduced pressure and heating to obtain a final biodiesel fuel. Preferably, the removed methanol is recovered by cooling and used again as a raw material in the methanolysis reaction.

3. Reactor In the present invention, the methanolysis reaction can be carried out in any reaction vessel as long as the above reaction conditions can be realized. Preferably, the methanolysis reaction is carried out in a Hastelloy tubular reaction tube capable of maintaining an appropriate mixed state. More preferably, the methanolysis reaction is carried out in a Hastelloy tubular reaction tube that can be heated uniformly to the inside, has a sufficient length for the reaction, and can maintain an appropriate mixed state. Stainless steel, Hastelloy, and Inconel are listed as metals that are commonly used as materials for reaction vessels or reaction tubes in supercritical reactors. The method of the present invention is preferably made of Hastelloy. This is because stainless steel may not be able to withstand high temperatures and pressures, and inconel may accelerate the reaction and produce glycerin. There are various types of hastelloy such as hastelloy A, B, C, F, and any of them can be used in the present invention. Typically, Hastelloy C is used. Specific examples of Hastelloy C that can be used in the present invention include HC-22 or HC-276 manufactured by Mitsubishi Materials Corporation. The “tubular reaction tube that can be heated uniformly to the inside” means a tubular reaction tube that can maintain the internal temperature condition substantially uniformly so that the methanolysis reaction can proceed uniformly. “Tubular reaction tube having a sufficient length for the reaction” means a tubular reaction tube having a sufficient length to ensure the reaction time necessary to obtain a biodiesel fuel having an appropriate composition. To do. If the reaction tube is too short, sufficient reaction time is not secured and the methanolysis reaction does not proceed sufficiently, so that a biodiesel fuel having an appropriate composition cannot be obtained. “Tubular reaction tube capable of maintaining an appropriate mixed state” means a tubular reaction tube capable of maintaining a mixed state in which a methanolysis reaction proceeds uniformly without producing glycerin as a by-product. It refers to a tubular reaction tube that can maintain a mixed state by the flow of the supercritical fluid itself without using means (such as a static mixer). This is because when general stirring means is used, stirring tends to be too strong, and when stirring is strong, glycerin tends to be generated as a by-product. More preferably, the methanolysis reaction is carried out in a tubular reaction tube made of Hastelloy having an inner diameter of 1.8 mm to 7.0 mm, a length of 0.5 m to 15 m, and an internal volume of 14 ml to 600 ml. The tubular reaction tube can be used in an arbitrary state. For example, the tubular reaction tube may be linear, wound in a coil, or folded in a zigzag manner. Typically, the methanolysis reaction is carried out in a coiled tubular reaction tube made of hastelloy C with an inner diameter of 1.8 mm, a length of 8 m and an internal volume of 20 ml.

  The reaction apparatus including the reaction tube is schematically shown in FIG. 1, for example. According to the said apparatus, the stable continuous operation is possible by mixing a raw material appropriately before a heating with a mixer. The mixer is preferably a T-type mixer in which the ratio of the total channel area before mixing to the total channel area after mixing is 2: 1. According to this apparatus, unreacted methanol can be recovered by evaporation under reduced pressure and heating and reused as a raw material.

4). Products The biodiesel fuel produced by the process of the present invention preferably comprises 40-60 wt% fatty acid methyl ester, 10-30 wt% monoacylglycerol, 5-20 wt% diacylglycerol, and other aliphatics The compound is contained in a proportion of 5 to 20% by weight, triacylglycerol is less than 1% by weight, and glycerin is less than 1% by weight. Here, the “other aliphatic compound” means an aliphatic group derived from glycerin when the glycerin produced during the methanolysis reaction as described above is further reacted to replace the OH group with a methyl group, for example. Compounds, "snips" that occur when long chain fatty acid groups are converted to medium chain fatty acid groups as described above (eg, hydrocarbons, fatty acids, aliphatic alcohols with about 6-12 carbon atoms), and other It is a generic name for aliphatic compounds containing free fatty acids that are caused by the cause.

  Biodiesel fuel composition (each content of fatty acid methyl ester, monoacylglycerol, diacylglycerol, triacylglycerol, glycerin and other aliphatic compounds) was measured by gas chromatography mass spectrometry under the following conditions: . Gas chromatography 6890N manufactured by Agilent Technology and mass spectrometer GC-mate II manufactured by JEOL Datum were used, and HP-5TA (15 m × 0.32 m × 0.1 μm) manufactured by Agilent Technology was used as the column. Helium (flow rate 1.5 ml / min) was used as the carrier gas. The oven temperature was maintained at 50 ° C. for 1 minute at the start of measurement, then heated to 250 ° C. at 10 ° C./minute, then heated to 365 ° C. at 15 ° C./minute, and held at 365 ° C. for 8 minutes. The inlet temperature was 220 ° C., the split ratio was 45: 1, and the sample injection volume was 2 μl. The measurement sample was diluted with 1-butanol so as to be about 20 mg / ml. Components were identified from the obtained mass spectrum, and the content was calculated based on the peak area of the gas chromatogram. Tridecanoic acid methyl ester or ethylene glycol was used as an internal standard.

  Under the above measurement conditions, the composition of fatty acid groups cannot be analyzed. Therefore, the fatty acid composition of fatty acid methyl ester in biodiesel fuel was analyzed by gas chromatography mass spectrometry under the following conditions. The above equipment is equipped with Agilent Technology column HP-INNOWax (Cross-Linked PEG 30m x 320μm x 0.5μm), helium (flow rate 1.5ml / min) as carrier gas, and oven temperature is 150 ° C at the start of measurement At 1 ° C./minute, then raised to 200 ° C. at 15 ° C./minute, then raised to 250 ° C. at 2 ° C./minute and held at 250 ° C. for 5 minutes. The inlet temperature was 220 ° C., the split ratio was 45: 1, and the sample injection volume was 2 μl. The measurement sample was diluted with 1-butanol so as to be about 20 mg / ml. The type of fatty acid was identified from the obtained mass spectrum, and its content was calculated based on the peak area of the gas chromatogram. Tridecanoic acid methyl ester was used as an internal standard. In the biodiesel fuel produced by the method of the present invention, the fatty acid composition of the fatty acid methyl ester is considered to be almost the same as the composition of fatty acid groups contained in all molecular species constituting the biodiesel fuel. This is because the methanolysis reaction in the supercritical fluid proceeds without being affected by the chain length of the fatty acid.

The biodiesel fuel produced by the method of the present invention preferably has a cetane number of 49 to 65, a flash point of 100 to 200 ° C., a kinematic viscosity at 30 ° C. of 3 to 20 mm ² / sec., And a pour point of −5. It is below ℃.

  The cetane number was measured according to JIS K2280, the pour point was measured according to JIS K2269, the kinematic viscosity (30 ° C.) was measured according to JIS K2283, and the flash point (PMCC) was measured according to JIS K2265.

  Biodiesel fuel was produced from commercially available canola oil using the apparatus shown in FIG. 1 according to the following procedure. The reaction tube used was a coil made of HC-22 (Hastelloy C, Mitsubishi Materials Corporation) having an inner diameter of 1.8 mm, a length of 7.8 m, and an internal volume of about 20 ml.

Canola oil (Nisshin Oil Co., Ltd., Oilio (trademark)) is put into the raw material tank 1 and methanol (Wako Pure Chemical Industries, Ltd., special grade reagent) is put into the raw material tank 2, respectively. The feed pump was adjusted to mix at a ratio. The temperature in the reaction tube was 395 ° C., the pressure was 40 MPa, the reaction tube passage time was 4 minutes, and the temperature at the reaction tube inflow was 270 ° C. The composition of the produced biodiesel fuel is about 50% by weight of various fatty acid methyl esters, about 25% by weight of monoacylglycerol, about 20% by weight of diacylglycerol, about 5% by weight of other aliphatic compounds, and triacyl. Glycerol and glycerin were each less than 1% by weight. The fuel characteristics are cetane number 51.6, flash point (PMCC) 136 ° C, kinematic viscosity 15.10mm ² / sec., Pour point -5.0 ° C, almost the same as general rapeseed biodiesel fuel Met. The fatty acid composition of the fatty acid methyl ester in the biodiesel fuel is 55% by weight for oleic acid (C18: 1), 16% by weight for linoleic acid (C18: 2), and 5% for stearic acid (C18: 0). %, Palmitic acid (C16: 0 and C16: 1) 12%, eicosanoic acid (C20: 0, C20: 1 and C20: 2) 7%, medium chain fatty acids (C6-12) 5% %Met.

  Biodiesel fuel was produced from waste cooking oil discharged from ordinary households by the following procedure using the apparatus shown in FIG. The reaction tube used was a coil made of HC-22 having an inner diameter of 1.8 mm, a length of 7.8 m, and an internal volume of about 20 ml.

  First of all, only large impurities such as fried residue were removed from waste cooking oil discharged from ordinary households. Pretreatment such as water removal and free fatty acid removal was not performed. The liquid feed pump was adjusted so that the volume ratio of waste cooking oil to methanol was 2: 1.

  When the temperature in the reaction tube was 380 ° C., the pressure was 40 MPa, the reaction tube passage time was 4 minutes, and the temperature at the reaction tube inlet was 270 ° C., the viscosity of the manufactured product was 24.3 mPa · sec. This is a large value compared to a normal biodiesel fuel (8.6 mPa · sec.). Viscosity was measured at 23 ° C. using AND CVJ5000. The fatty acid composition of fatty acid methyl ester in the manufactured biodiesel fuel is 64% by weight of oleic acid (C18: 1), 1% by weight of linoleic acid (C18: 2), and 13% of stearic acid (C18: 0). %, Palmitic acid (C16: 0) was 14% by weight, eicosanoic acids (C20: 0, C20: 1 and C20: 2) were 3% by weight, and medium chain fatty acids (C6-12) were 5% by weight. .

  When the temperature in the reaction tube was 450 ° C., the pressure was 40 MPa, the reaction tube passage time was 4 minutes, and the temperature at the reaction tube inlet was 270 ° C., the kinematic viscosity of the manufactured product decreased to 9.16 mPa · sec. The fatty acid composition of fatty acid methyl ester in the produced biodiesel fuel is 60% by weight of oleic acid (C18: 1), 0.6% by weight of linoleic acid (C18: 2), and 11% of stearic acid (C18: 0). %, Palmitic acid (C16: 0) was 14% by weight, eicosanoic acids (C20: 0, C20: 1 and C20: 2) were 2% by weight, and medium chain fatty acids (C6-12) were 12% by weight. .

  A biodiesel fuel was produced from a commercially available lard by the following procedure using the apparatus shown in FIG. The reaction tube used was a coil made of HC-22 having an inner diameter of 1.8 mm, a length of 7.8 m, and an internal volume of about 20 ml.

  Lard (Miyoshi Oil & Fat Co., Ltd., high grade lard, 99.5% fat content) was put into the raw material tank 1 and heated to 60 ° C. to keep it warm to improve fluidity. Methanol (Wako Pure Chemical Industries, Ltd., special grade reagent) was placed in the raw material tank 2, and the liquid feed pump was adjusted so that lard: methanol was mixed at a volume ratio of 1: 2. The temperature in the reaction tube was 500 ° C., the pressure was 40 MPa, the reaction tube passage time was 8 minutes, and the temperature when the reaction tube was introduced was 300 ° C. The composition of the biodiesel fuel produced was 56% by weight of various fatty acid methyl esters, 20% by weight of monoacylglycerol, 10% by weight of diacylglycerol, 14% by weight of other aliphatic compounds, triacylglycerol and glycerin. Each was less than 1% by weight (not detectable). The fatty acid composition of fatty acid methyl ester in the biodiesel fuel is 10% by weight of oleic acid (C18: 1), 25% by weight of stearic acid (C18: 0), and 33% by weight of palmitic acid (C16: 0). %, Medium chain fatty acids (C6-12) 23%, myristic acid (C14: 0) 4%, heptadecanoic acid (C17: 0) 1.3%, other fatty acids (C13, C15, C20) Was 2.2% by weight.

  In the case of producing biodiesel fuel from lard by the conventional alkaline catalyst method, the fuel solidifies at about 10 ° C., but the biodiesel fuel produced by this example did not solidify even at 0 ° C.

1 is an example of the schematic diagram of a manufacturing apparatus for the present invention.

Explanation of symbols

1 Raw material tank 1 (animal and vegetable fats and oils)
2 Liquid feed pump for animal and vegetable oils 3 Raw material tank 2 (methanol)
4 Liquid feed pump for methanol 5 Preheating tube 6 Preheating tube heater 7 Reaction tube 8 Heater for reaction tube 9 Cooling tube 10 Exhaust pressure valve 11 Depressurization tank 12 Decompression pump 13 Excess methanol recovery line 14 Cooler (methanol recovery device)
15 Biodiesel fuel outlet

Claims (6)

  A method for producing biodiesel fuel, comprising mixing animal and vegetable oil or fat or its waste edible oil and methanol, and carrying out a methanolysis reaction without using a catalyst under reaction conditions in which glycerin is not produced.   The process according to claim 1, wherein the reaction conditions under which the glycerin is not generated are a reaction temperature of 370 to 500 ° C, a reaction pressure of 20 to 60 MPa, and a reaction time of 4 to 12 minutes.   The method according to claim 1, wherein a decomposition reaction of the carbon chain of the fatty acid group is performed in parallel with the methanolysis reaction.   The method according to any one of claims 1 to 3, wherein the animal and vegetable oil or fat or its waste cooking oil and methanol are mixed at a volume ratio of 1: 2 to 2: 1.   The method according to any one of claims 1 to 4, wherein the methanolysis reaction is performed in a Hastelloy tubular reaction tube capable of maintaining an appropriate mixed state.   Biodiesel fuel mainly composed of fatty acid methyl ester, monoacylglycerol and diacylglycerol.

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