KR20070106236A - Method and apparatus for preparing fatty acid alkyl ester using fatty acid - Google Patents

Abstract

A method for preparing a fatty acid alkyl ester from a fatty acid is provided to obtain a fatty acid alkyl ester suitable for bio-diesel fuel, to avoid the use of a catalyst, and to allow the use of a cost-efficient starting material. A method for preparing a fatty acid alkyl ester for bio-diesel fuel comprises a step of carrying out esterification of a fatty acid starting material and an alcohol at a reaction temperature of 200-350 deg.C under ambient pressure to a pressure of 10 bar. The fatty acid starting material is a fatty acid distillate generated as a byproduct during the purification of vegetable oil that includes a step of heating crude. The fatty acid distillate comprises 65-95 wt% of fatty acids having an aliphatic moiety containing 14-24 carbon atoms.

Description

Method and apparatus for preparing fatty acid alkyl ester using fatty acid {Method and apparatus for preparing fatty acid alkyl ester using fatty acid}

1 is an overall configuration of the fatty acid alkyl ester production apparatus according to an embodiment of the present invention.

Figure 2 is a detailed block diagram of a fatty acid alkyl ester reaction unit shown in FIG.

3 and 4 respectively show the structure of a reactor used in the fatty acid alkyl ester production apparatus according to an embodiment of the present invention.

The present invention relates to a method and apparatus for preparing fatty acid alkyl esters using fatty acids, and more particularly, to a catalyst and glycerin by reacting a fatty acid, particularly fatty acid distillate and an alcohol, without introducing a catalyst. The present invention relates to a method and apparatus for producing fatty acid alkyl esters for biodiesel, in which not only the purification step is unnecessary but also excellent in the conversion of fatty acids.

Diesel oil has advantages such as good fuel economy, low price, and low amount of carbon dioxide generation, among various fuels obtained from crude oil, while many air pollutants are generated after combustion. In order to solve this problem, researches on alternative fuels having similar physical properties to diesel oil, excellent economical aspects and preventing air pollution have been conducted in various ways. Biodiesel is a natural circulation energy that has similar properties to diesel oil but can significantly reduce air pollution. Generally, vegetable oils and animal fats such as rapeseed oil, soybean oil, sunflower oil, palm oil, etc. Obtained by the transesterification reaction of alcohol, waste cooking oil and the like. In the production of such biodiesel, glycerin is produced as a by-product of about 10% by weight of biodiesel. Considering the fact that the plant construction of biodiesel is rapidly progressing in the world, the oversupply of glycerin It is expected.

On the other hand, fats and oils generally contain free fatty acids, and are present in a mixed form with fatty acid triglycerides. Free fatty acids are separated as by-products during the purification of fats and oils, and several methods are known for preparing fatty acid alkyl esters from these separated free fatty acids. Methods of esterifying free fatty acids are disclosed in EP 127104A, EP 184740A, and US Pat. No. 4,164,506, which involve fatty acids and fatty acid triglycerides at temperatures around 65 ° C. under sulfuric acid or sulfonic acid catalysts. The esterification reaction was carried out by heating the mixture of and methanol together. Further, as a method for increasing the yield of fatty acid alkyl esters from fats and oils, a method of separating free fatty acids on glycerin obtained as a result of a transesterification reaction and then esterifying the isolated free fatty acids is disclosed in European Patent Publication No. 708813A. . In this method, free fatty acids obtained from neutralization on glycerin were reacted for 2 hours at a temperature of about 85 ° C. under a concentrated sulfuric acid catalyst, thereby reducing the content of fatty acids from 50% to 12%. In addition, a method of increasing the esterification efficiency of fatty acids using a mechanical device or ultrasonic wave that causes dynamic turbulence in a reactor has been known (Korean Patent Publication No. 2004-0101446, International Application Publication No. WO 2003/087278). In the above, sulfuric acid or ion exchange resin was used as a catalyst, and fatty acid or fatty acid contained in fat or oil was reacted with alcohol under high pressure and high temperature. In addition, Korean Patent Publication No. 2004-87625 discloses a method for removing free fatty acids from waste cooking oil using a solid acid catalyst. The above methods commonly use catalysts such as sulfuric acid. Since such an acid catalyst degrades the quality of biodiesel if not completely removed after the reaction, it is not only necessary to perform a complicated process for neutralizing, filtration and washing, but also solids. In the case of acid, the catalyst has a short life and a high cost for regenerating the catalyst. In addition, the conventional methods, because the esterification reaction of fatty acids at low temperature, the water produced in the reaction step is not effectively removed to the outside of the reaction system, the conversion rate of fatty acids to fatty acid alkyl ester is low, biodiesel use There is a disadvantage of not having proper physical properties.

It is therefore an object of the present invention to provide a process for preparing fatty acid alkyl esters suitable for biodiesel fuels.

Another object of the present invention is that, unlike a conventional method for producing fatty acid alkyl esters and glycerin by transesterifying vegetable or animal fats and alcohols under a catalyst, fatty acids and alcohols in a high temperature region without the use of a catalyst It is to provide a method for producing a fatty acid alkyl ester by esterification.

Still another object of the present invention is to provide a method for producing fatty acid alkyl esters using fatty acid distillate, which is generated as a by-product in the process of purifying vegetable oils, as a raw material, which is simple and economical, without generating glycerin.

Still another object of the present invention is to provide an apparatus capable of effectively carrying out the preparation of the fatty acid alkyl ester.

In order to achieve the above object, the present invention is a method for producing a fatty acid alkyl ester for biodiesel fuel comprising the step of esterifying a fatty acid raw material and alcohol at a reaction temperature of 200 to 350 ℃ and a reaction pressure of normal pressure to 10 bar. To provide. The present invention also provides a primary reactor for esterifying a fatty acid raw material and an alcohol at a reaction temperature of 200 to 350 ° C. and a reaction pressure of normal pressure to 10 bar, while converting 80 to 90% of all fatty acids to fatty acid alkyl esters; And a secondary reactor for converting the remaining fatty acids not converted in the primary reactor into fatty acid alkyl esters. The present invention also includes one or more reactors, the reaction unit for obtaining a fatty acid alkyl ester by reacting a fatty acid raw material and an alcohol; Primary purification unit for distilling low boiling point impurities from the fatty acid alkyl ester; And a second purification unit for distilling the first purified fatty acid alkyl ester and removing residues. The upper part of the reaction unit is configured to recycle excess alcohol and to remove water generated in the reaction unit. Provided is an apparatus for producing a fatty acid alkyl ester for biodiesel fuel, in which an alcohol recovery unit is connected.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail.

1 is an overall configuration of the fatty acid alkyl ester production apparatus according to an embodiment of the present invention. As shown in FIG. 1, a fatty acid raw material 1 (hereinafter, simply referred to as fatty acid as necessary) and an alcohol 2 are added to the reaction unit 10, and an esterification reaction proceeds at a constant temperature and pressure conditions. do. Crude fatty acid alkyl ester (4) produced in the esterification reaction is transferred to the primary purification unit 20, the low boiling point impurities (5) by distillation through the top of the distillation column of the primary purification unit 20 Can be removed. The primary purified fatty acid alkyl ester (6) is transferred to the secondary purification unit (30), residual impurities (8) are left by distillation, and the purified fatty acid alkyl ester (7) is the secondary purification unit (30). Is discharged through the top of the distillation column. On the other hand, the reaction unit 10 is connected to the alcohol recovery unit 40, the excess alcohol (alcohol / water, 3) that does not participate in the reaction with water generated in the reactor of the reaction unit 10 is alcohol recovery It is sent to the unit 40, where the alcohol 2 is distilled off and recycled to the reaction unit 10, and the water 9 is sent to a wastewater treatment plant.

In the present invention, the fatty acid raw material (1) used in the production of the fatty acid alkyl ester (7) may be a pure fatty acid (RCOOH) having 14 to 24 carbon atoms of the aliphatic moiety (R). In the case of obtaining vegetable refined oils such as rapeseed oil, soybean oil, sunflower oil and palm oil by heating vegetable crude oils obtained from plants such as sunflower and palm with high pressure steam, etc. It is preferable to use fatty acid distillate which is generated, and a mixture of pure fatty acid and fatty acid distillate may be used if necessary. The fatty acid distillate comprises 65 to 95% by weight, preferably 80 to 85% by weight of fatty acids having 14 to 24 carbon atoms in the aliphatic moiety, β-carotene, less than 14 carbon atoms in the aliphatic moiety, Or more than 24 fatty acids and the like. In the production of fatty acid alkyl esters according to the invention, it is more economically advantageous to use the fatty acid distillates as raw materials. As the alcohol used in the present invention, a monohydric alcohol having 1 to 10 carbon atoms, preferably a lower monohydric alcohol having 1 to 4 carbon atoms such as methanol, ethanol or propanol can be used, and methanol is particularly preferable.

In the present invention, the esterification reaction may be performed in one step or two steps. In the case where the esterification reaction is performed in one step, the reaction part 10 is composed of one reactor and one distillation column, and in the case of two steps, the reaction part 10 is composed of two reactors and one distillation column. The distillation column may be used in common, or each stage may be composed of one reactor and one distillation column as shown in FIG. 2. In addition, the reactor and the distillation column may be integrally configured without being present separately, wherein the lower part serves as a reactor and the upper part is configured to serve as a distillation tower. In this case, a seal tray may be installed between the upper part serving as a distillation column and the lower part serving as a reactor so that water does not fall from the upper part to the lower part. The esterification reaction according to the present invention may be carried out in batch or continuous mode, and may be made in one step or divided into two steps as described above. In the case of the continuous reaction, if the residence time is sufficient, high conversion can be obtained by only one step reaction, but the reaction is preferably carried out in two steps. Even in the case of a batch type, if the conversion rate in the primary reaction is not sufficient, the conversion rate can be increased by performing the secondary reaction under different reaction conditions.

FIG. 2 is an example in which the reaction part 10 of FIG. 1 is embodied, and shows a reaction part including two reactors 11 and 12 and two distillation towers 13 and 14. Referring to FIG. 2, the product 4a having undergone a reaction in the primary reactor 11 is introduced into the secondary reactor 12 together with the alcohol 2 to participate in the secondary reaction, and the product undergoes the secondary reaction. (Crude fatty acid alkyl ester, 4) is transferred to the purification section 20, 30 of FIG. The mixture 3a of water produced in each reactor 11 and 12 and excess alcohol not participating in the reaction is discharged to the distillation towers 13 and 14, separated from the distillation towers 13 and 14, and the distillation tower 13 14) pure alcohol or alcohol / water azeotropy mixture 3b at the top, and water / alcohol mixture 3 having a high water concentration are discharged below the distillation columns 13 and 14. Here, the pure alcohol or alcohol / water azeotropic mixture 3b obtained at the top of the distillation column 13 and 14 may be reused as the alcohol introduced into the reaction section 10, and the water / alcohol mixture 3 having a high water concentration may be It is transferred to the alcohol recovery part 40 of FIG.

Hereinafter, the production conditions of the fatty acid alkyl ester according to the present invention will be described in detail. The esterification reaction according to the present invention does not introduce a catalyst, but is carried out in a high temperature region, so that a high reaction rate and a conversion rate of fatty acids can be obtained. The esterification temperature is 200 to 350 ° C, preferably 250 to 320 ° C, and the reaction pressure is from normal pressure to 10 bar, preferably from atmospheric pressure to 5 bar. The reaction may be batchwise or continuously. When the reaction is batch-wise, the reaction is carried out while maintaining a constant pressure of atmospheric pressure to 10 bar, or initially the reaction at a relatively high pressure of 3 bar to 10 bar to increase the reaction rate, at the end of normal pressure to 3 bar By lowering the pressure, the water produced is removed from the reaction liquid to increase the conversion of the reaction. When the reaction is carried out continuously, the reaction of the entire stage is carried out at a constant pressure of atmospheric pressure to 10 bar, or in the case of a two-stage reaction, 3 bar to 10 bar in the first reactor, normal pressure to 3 bar in the secondary reactor The reaction is carried out at. If the reaction temperature and pressure are out of the above range, the reaction rate and the conversion rate of fatty acids may decrease or there may be a side reaction.

The conventional esterification reaction of a fatty acid using a catalyst is usually carried out at a low temperature of less than 100 ° C., and since water produced during the reaction cannot be removed from the reaction system, the reaction cannot proceed beyond the reaction equilibrium. However, in the present invention, since the reaction is carried out at a high temperature of 200 to 350 ℃, the water produced in the reaction is continuously removed from the reaction system, with excess alcohol. Therefore, the esterification reaction according to the present invention has an advantage in that the reaction conversion rate is so high that the reaction reaction is over and close to the complete reaction. In particular, in the biodiesel which is the main use of fatty acid alkyl ester according to the present invention, the acid value (mg KOH / g) should be lowered below a predetermined value, but the unreacted fatty acid component (the aliphatic moiety has 13 to 18 carbon atoms) If it remains, the acid value (mg KOH / g) of the produced fatty acid alkyl ester becomes high, and there exists a possibility that it may not satisfy | fill biodiesel quality standards. Since the unreacted fatty acid component is similar in boiling point to fatty acid methyl ester and is not separated even by distillation, it must be removed by complete reaction in the reaction step. The fatty acid alkyl ester production method according to the present invention has a conversion rate of fatty acids of 99.7% or more, which can satisfy the value of the acid value on the biodiesel quality standard, whereas the fatty acid alkyl ester production method using a conventional catalyst is a conversion rate of fatty acids. Is difficult to improve to more than 99.7%.

In the case of continuous type, alcohol is added at a flow rate of 0.5 to 5 times, preferably 1 to 3 times, by weight relative to the fatty acid to be added, and the residence time of the entire reaction process is 1 to 10 hours, preferably 3 To 5 hours. Here, if the amount of alcohol is out of the above range, there is a fear that the reaction rate, reaction yield, etc. are lowered, and it is not economically preferable. In the case of the batch type, 0.1 to 3 times the weight of the fatty acid and the fatty acid is added to the reactor in the reactor and filled, and when the predetermined pressure and temperature is reached, the alcohol to participate in the main reaction is added. The flow rate is maintained so that the total amount of is 0.5 to 5 times, preferably 1 to 3 times by weight relative to the fatty acid, and the reaction is carried out for 1 to 10 hours, preferably 3 to 5 hours. In addition, by increasing the input amount of alcohol in the latter batch or continuous reaction, the reaction conversion may be further increased by adding 1 to 3 times the initial dose, preferably 1.5 to 3 times.

 As the esterification reactor used in the present invention, without limitation, a continuous stirred tank reactor (CSTR type) with a stirrer, a baffle is attached to the inside of the reactor to maintain a sufficient residence time. A plug flow reactor (PFR) or the like can be used, and preferably, a diaphragm is installed in the reactor to separate the reactor into a plurality of compartments, and the reactant overflows. It is preferred to use a reactor that can be given a sufficient residence time to the reactants by being sequentially transferred to the next compartment.

3 and 4 are views showing the structure of a reactor that can be particularly useful in the apparatus for producing a fatty acid alkyl ester according to an embodiment of the present invention. As shown in FIG. 3, the esterification reactor used in the present invention is the primary reactor 30 for converting 80 to 90% of the total fatty acids into fatty acid alkyl esters and the remaining unconverted in the primary reactor 30. And a secondary reactor 40 for converting fatty acids to fatty acid alkyl esters. Fatty acids (1) and alcohols (2), which are raw materials, are introduced into the primary reactor (30) and reacted firstly. The product (4a) of the primary reaction is discharged through the lower portion of the reactor (30), and the primary The mixture 3a of water produced in the reaction and excess alcohol not participating in the reaction is discharged to the top of the reactor 30 in a gaseous state. The secondary reactor 40 divides the reactor body 42 and the inside of the body 42 into two or more internal spaces 44a, 44b, and 44c, and is open at the top so that the reactant overflows to the top. Barrier ribs 46a and 46b. The inner spaces 44a, 44b, 44c of the secondary reactor 40 may be coplanar, and adjacent inner spaces 44a, 44b, 44c flow through the partition walls 46a, 46b. It is possibly connected. Thus, for example, the product 4a of the first reaction introduced into the first inner space 44a and the alcohol 2 are sufficiently reacted in the first inner space 44a, and then the product of the first reaction 44a. As the inflow amount of 4a increases, it flows into the second inner space 44b beyond the first partition wall 46a, reacts with the alcohol 2 in the second inner space 44b, and then the second partition wall It reacts in the 3rd internal space 44c beyond 46b, is converted to the crude fatty acid alkyl ester 4, and is discharged | emitted from the secondary reactor 40. FIG. At this time, the mixture 3a of water and alcohol generated during the reaction is discharged to the upper portion of the secondary reactor 40. In each of the inner spaces 44a, 44b, 44c of the primary reactor 30 and the secondary reactor 40, agitators 38 and 48 for stirring the reactants may be mounted.

The esterification reactor shown in FIG. 4 converts 80 to 90% of all fatty acids into fatty acid alkyl esters and the remaining fatty acids not converted in the primary reactor 30 to fatty acid alkyl esters. It includes a secondary reactor (50). The primary reactor 30 has the same structure as described in FIG. The secondary reactor 50 includes a reactor body 52 and partition walls 56a and 56b that divide the inside of the body 52 into two or more internal spaces 54a, 54b, and 54c. The inner spaces 54a, 54b and 54c of the secondary reactor 50 are arranged in a vertically stacked manner, and the partition walls 56a and 56b constitute lower surfaces of the inner spaces 54a and 54b. . That is, the first inner space 54a and the second inner space 54b are divided up and down by the first partition wall 56a. The liquid flow path 62 and the gas flow path 64 are provided in the first partition wall 56a. One end of the liquid flow path 62 is located at a height corresponding to the upper surface of the reaction liquid located in the first internal space 54a, and the other end penetrates through the first partition wall 56a and the second internal space 54b. ) It is located higher than the upper surface of the internal reaction solution. One end of the gas flow path 64 is located at a position higher than an upper surface of the reaction liquid located in the first internal space 54a, and the other end penetrates through the partition wall 56a and enters the second internal space 54b. It is located higher than the upper surface of the reaction solution. The liquid flow path 62 and the gas flow path 64 are installed in each of the partition walls 56a and 56b in the same manner as above. In this way, the adjacent inner spaces 54a, 54b, and 54c are connected through the liquid flow path 62 and the gas flow path 64 provided in the partition walls 56a and 56b. After the first reaction product 4a and the alcohol 2 introduced into the space 54a are sufficiently reacted in the first internal space 54a, as the inflow amount of the product 4a of the first reaction increases, The liquid flow path overflows through the liquid flow path 62, flows into the second internal space 54b, reacts with the alcohol 2 in the second internal space 45b, and is then installed in the second partition wall 56b. It overflows through (62) and reacts in the third internal space (54c), is converted into a crude fatty acid alkyl ester (4), and then flows out of the secondary reactor (50). At this time, in each of the interior spaces 54a and 54b, the mixture 3a of water and alcohol generated during the reaction is sequentially moved to the upper interior spaces 54b and 54a through the gas flow path 64, and the top interior Through the space 54a, it is discharged to the upper part of the secondary reactor 50.

As such, 80 to 90% of all fatty acids are converted to fatty acid alkyl esters in the primary reactor 30, and then the fatty acids are converted into fatty acid alkyl esters while sequentially passing through the inner spaces of the secondary reactors 40 and 50. By carrying out the remaining conversion reaction, the reaction residence time can be increased, and the conversion reaction efficiency (conversion rate) of fatty acids to fatty acid alkyl esters can be improved.

Crude fatty acid alkyl esters (4) obtained in the esterification reaction of the present invention mostly consist of fatty acid alkyl esters, but relatively low molecular weight and high molecular weight fatty acid alkyl esters for use as industrial or biodiesel fuels, remainder Residue, etc. must be removed. Particularly in the case of fatty acid methyl esters, in order to meet the quality standards of biodiesel, fatty acid alkyl esters having less than 14 or more than 24 carbon atoms in aliphatic parts and other low molecular weight impurities should be removed. Accordingly, the present invention performs purification through a two-step distillation process. Referring back to Figure 1, in the first purification unit 20 according to the present invention, the bottom temperature of the distillation column under a vacuum of 0.1 to 150 torr, preferably 0.1 to 40 torr 150 to 250 ℃, preferably 180 to Maintained at 220 ° C., 1-10% by weight, preferably 2-5% by weight, of the influent is removed from the top of the distillation column. If the amount removed to the top of the distillation column is less than 1% by weight relative to the feed (feed) there is a fear that the low boiling point impurities may not be sufficiently removed, if the amount exceeds 10% by weight relative to the inflow may be a yield lowered. Here, since most of the low boiling point impurities removed to the top of the distillation column are fatty acid alkyl esters of low molecular weight, they may be directly used as fuels such as boilers without undergoing an additional process. In the secondary refining unit 30 according to the present invention, the lower temperature of the distillation column is maintained at 200 to 300 ° C., especially 220 to 280 ° C. under a vacuum of 0.1 to 150 torr, preferably 0.1 torr to 40 torr, Depending on the composition of the fatty acid of the phosphorus, it may be removed by removing 1 to 25% by weight of impurities in the bottom of the distillation column in the bottom of the distillation column, purified fatty acid alkyl ester of purified high purity in the top of the distillation column. If the impurities remaining in the lower part of the distillation column is less than 1 wt% with respect to the influent, there is a fear that a high-purity fatty acid alkyl ester cannot be obtained, and if it exceeds 25 wt% with respect to the influent, the yield may be lowered. Since the residual impurities are fatty acid alkyl esters having more than 24 carbon atoms in most of their compositions, they can be used as fuels for boilers and the like. Fatty acid alkyl esters, particularly fatty acid methyl esters, purified by the above method satisfy all quality standards of major countries such as Korea, the United States, and Europe for biodiesel, and thus may be immediately used as biodiesel oil.

On the other hand, the water produced in the esterification reaction of the present invention is discharged from the reaction unit 10 with the excessively unreacted alcohol, this mixture is separated from the alcohol recovery unit 40, the water is wastewater treatment plant The alcohol is circulated back to the reaction unit 10 and reused. The alcohol recovery unit 40 is composed of a distillation column and an accompanying facility, and the lower temperature of the distillation column is adjusted according to the boiling point of the alcohol to distill the alcohol. The alcohol that is distilled and reused may contain 0 to 10% by weight, specifically 0.001 to 10% by weight of water. When the content of water contained in the alcohol is more than 10% by weight, there is a fear that the reaction rate in the reaction unit 10 lowers the reaction rate. In the case of using methanol, only one distillation column can be used to purify sufficiently pure methanol to circulate to the reaction section 10, and when using two or more carbon atoms such as ethanol, the methanol is discharged to the column. After the dehydration process is performed on the water / alcohol azeotrope, the water may be removed and the alcohol may be recycled to the reaction unit 10.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by these examples.

Example 1 Preparation of Fatty Acid Methyl Ester (Continuous Reaction)

The esterification reaction proceeded in a two step reaction, using a reactor as shown in FIG. 3. First, the primary reactor was adjusted to a temperature of 300 ° C. and a pressure of 3 bar, and 1 kg of fatty acid distillate obtained by distilling crude palm oil and 1 kg of methanol were added and reacted for 2 hours. Next, the temperature of the secondary reactor was maintained the same as the primary reactor, the pressure was lowered to atmospheric pressure and reacted for 2 hours, and 2 kg of methanol (two times the primary inflow) were divided into three equal parts of each internal space ( 44a, 44b, 44c). The reaction product was transferred to the first purification unit, and the lower temperature was maintained at 200 ° C. at 20 torr to distill off and remove 3% by weight of low-boiling impurities relative to the inflow to the top of the distillation column, and the purified product was transferred to the second purification unit. In the secondary purification unit, a pressure of 20 torr and a lower temperature were maintained at 250 ° C. to obtain 80% by weight of fatty acid methyl ester relative to the inflow amount. Meanwhile, methanol that did not participate in the reaction with water generated in the reactor was transferred to an alcohol recovery unit, and methanol was circulated in a manner of recovering methanol to the reactor through distillation. The conversion rate of the fatty acid methyl ester obtained in the above reaction was 99.7%.

Example 2 Preparation of Fatty Acid Methyl Ester (Batch Reaction)

The esterification reaction proceeded in a one step reaction, using a batch reactor. First, 1 kg of fatty acid distilate and 0.5 kg of methanol were added to the reactor, and then, the temperature was adjusted to 300 ° C. and a pressure of 3 bar, and then 1 kg of methanol was further added to react for 2 hours. Then, the pressure was lowered to atmospheric pressure, and further reacted for 1 hour. At this time, the methanol inflow was increased, and 2 kg of methanol (two times the primary inflow) was added. The reaction product was purified in the same manner and in the same manner as in Example 1, to obtain 90% by weight of fatty acid methyl ester relative to the inflow amount of the secondary purification process. On the other hand, excess methanol not participating in the reaction was recovered and reused in the same manner as in Example 1, and water was removed. The conversion rate of fatty acid methyl ester obtained in the above reaction was 99.8%.

As described above, the fatty acid alkyl ester production method according to the present invention reacts a fatty acid with an alcohol under constant high temperature and pressure conditions without introducing a catalyst. Therefore, neutralization, filtration and washing are not necessary to remove the used catalyst, and fatty acid alkyl ester of high purity and high conversion can be obtained by simple two-step distillation process. And operating cost can be reduced. In addition, the present invention is not only economical because it uses discarded fatty acid distilate or inexpensive fatty acids as raw materials, and does not generate by-products such as glycerin, which is free from the glycerine market environment that may cause oversupply and does not participate in esterification By recovering and reusing excess alcohol, there is an advantage of minimizing the amount of alcohol used. The production method of the fatty acid alkyl ester according to the present invention is not only an ideal production in an industrial scale device, but also economical production method in a small device, especially when producing a fatty acid methyl ester without additional process It can be immediately used as biodiesel.

Claims (12)

A method for producing a fatty acid alkyl ester for biodiesel fuel, comprising the step of esterifying a fatty acid raw material and an alcohol at a reaction temperature of 200 to 350 ° C. and a reaction pressure of normal pressure to 10 bar. The fatty acid raw material for biodiesel fuel according to claim 1, wherein the fatty acid raw material reacted with the alcohol is a fatty acid distillate generated as a by-product when the vegetable crude oil is heated to obtain a vegetable refined oil. Method for producing alkyl ester. The method of claim 2, wherein the fatty acid distillate comprises 65 to 95% by weight of fatty acids having 14 to 24 carbon atoms in the aliphatic moiety. The method of claim 1, wherein the crude fatty acid alkyl ester produced by the reaction of the fatty acid raw material and the alcohol is introduced into the distillation column, and the lower boiling point impurities are distilled off by maintaining the lower temperature of the distillation column at 150 to 250 ℃ under a vacuum of 0.1 to 150 torr. Primary purification step to remove; And distilling the primary purified fatty acid alkyl ester into a distillation column having a lower temperature of 200 to 300 ° C. under a vacuum of 0.1 to 150 torr, to obtain a fatty acid alkyl ester having 14 to 24 carbon atoms in the aliphatic portion, and a residue. Method for producing a fatty acid alkyl ester for biodiesel fuel further comprising a secondary purification step to remove the. According to claim 1, wherein the input ratio of the alcohol to the fatty acid raw material is 0.5 to 5 times by weight, the reaction temperature of the esterification reaction is 250 to 320 ℃, the reaction pressure is from normal pressure to 5 bar for biodiesel fuel Method for producing fatty acid alkyl ester. The biodiesel fuel according to claim 1, wherein the excess alcohol in the esterification reaction is discharged to the upper portion of the reactor together with the generated water, collected by an alcohol recovery unit attached to the reactor, and then distilled and recycled to the reactor. Method for producing fatty acid alkyl esters. At a reaction temperature of 200 to 350 ° C. and a reaction pressure of atmospheric pressure to 10 bar, a primary reactor for esterifying a fatty acid raw material and an alcohol, converting 80 to 90% of all fatty acids to fatty acid alkyl esters; And Apparatus for producing a fatty acid alkyl ester for biodiesel fuel comprising a secondary reactor for converting the remaining fatty acid not converted in the primary reactor to fatty acid alkyl ester. 8. The reactor of claim 7, wherein the secondary reactor comprises: a reactor body; And dividing the inside of the reactor body into two or more internal spaces, the top of which is open, and a partition wall of which the reactant overflows to the top. 8. The reactor of claim 7, wherein the secondary reactor comprises: a reactor body; And a partition wall dividing the inside of the reactor body into two or more spaces, wherein the divided internal spaces inside the secondary reactor are arranged in a vertically stacked manner, and the partition wall is provided with a liquid flow path and a gas flow path. Apparatus for producing a fatty acid alkyl ester for biodiesel fuel. The liquid crystal display of claim 9, wherein the inner space includes a first inner space and a second inner space disposed below the first inner space, and one end of the liquid flow path is formed on an upper surface of the reaction liquid located in the first inner space. Located at a corresponding height, the other end penetrates through the first partition wall, and is located higher than the upper surface of the reaction liquid inside the second internal space, and one end of the gas flow path is located on the upper surface of the reaction liquid located in the first internal space. It is located in a higher position, the other end penetrates the partition, the apparatus for producing a fatty acid alkyl ester for biodiesel fuel is located higher than the upper surface of the reaction liquid located in the second internal space. Reaction unit including at least one reactor, the fatty acid raw material and the alcohol to obtain a fatty acid alkyl ester; A primary refining unit for distilling and removing low boiling point impurities from the fatty acid alkyl esters; And It is obtained by distilling the primary purified fatty acid alkyl ester, and comprises a secondary purification unit for removing the residue, An apparatus for producing a fatty acid alkyl ester for biodiesel fuel, wherein an alcohol recovery unit for recycling excess alcohol and recycling water generated in the reaction unit is connected to an upper portion of the reaction unit. 12. The apparatus of claim 11, wherein the reactor is a continuous stirring tank reactor with a stirrer or a tubular reactor with a baffle.

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