KR101297495B1 - Process for the preparation of fatty acid alkylester - Google Patents

Abstract

The present invention (i) esterification reaction of fatty acids, oils or mixtures thereof containing free fatty acids with an acid value of 2 to 200 at 150-250 ° C. and 5-100 atm under a non-catalyst with a low alcohol of C ₁ -C ₅ . And a first step of obtaining a trans fatty acid alkyl ester by a transesterification reaction; And (ii) recovering the crude fatty acid alkyl ester of the first step to obtain C ₁ -C ₅ low alcohol and at least one catalyst of MgO and Mg (OH) ₂ under 150-250 ° C. and 5-100 atmospheres. It provides a method for producing a fatty acid alkyl ester, comprising a second step of esterification and transesterification reaction.

Description

Process for the preparation of fatty acid alkylester

The present invention relates to a process for effectively preparing fatty acid alkyl esters from oils, fats, or mixtures thereof containing free fatty acids in the presence of a base catalyst.

Fatty acid alkyl esters are generally prepared by homogeneous liquid phase reaction using oil, fat, or mixtures thereof and methanol having an acid value of 2 or less free of fatty acids, and methanol as a raw material.The catalysts include sodium hydroxide (NaOH) and potassium hydroxide ( KOH), potassium methylate (KOCH ₃ ), sodium methylate (NaOCH ₃ ), and the like. These reaction conditions are gentle conditions of 40-80 degreeC.

Examples of such homogeneous liquid phase reaction forms are as follows.

EP 1308498 A1 proposes a process for preparing fatty acid alkylesters from fats and oils comprising free fatty acids via a multistage homogeneous liquid phase process using Lewis acid catalysts. However, the method has a high catalyst usage and is difficult to apply to high acid value raw materials.

EP 1092703 A1 discloses a process for producing fatty acid methyl ester by reacting a glyceride raw material having an acid value of 5 to 20 in the presence of a transition metal salt, but it is also difficult to use the high acid raw material.

U.S. Patent 5,434,279 describes a process for producing fatty acid esters by two step reaction at low temperatures of up to 60 ° C using excess catalyst. In this method, the amount of catalyst used is high and the yield of fatty acid alkyl ester is low, and the method is difficult to apply to a high acid value raw material.

U.S. Patent 4,668,439 describes a process for producing fatty acid alkyl esters by reacting excess alkali metal salts or heavy metal salts with excess methanol, liquid glycerides under high temperature and low pressure and then layering the reactants. The catalyst used in this process forms an emulsion, making it difficult to separate glycerin. This process is not particularly desirable for high acid value raw materials.

In addition, Korean Patent Publication No. 10-2008-0036107 discloses a method for preparing a carboxylic acid ester in the presence of a liquid metal catalyst using an alkaline earth metal salt of carboxylic acid, but this method requires a separate process for preparing a catalyst and a fatty acid salt. The loss of yield is high by using a large amount of catalyst in the form.

As seen above, the prior art uses an excess of catalyst and methanol, where fatty acid salts are formed by the reaction of the catalyst with free fatty acids when oil, fat, or mixtures thereof are present in large amounts. These fatty acid salts form an emulsion with glycerin, which makes it difficult to separate by-product glycerin after the reaction.

In the case of using a homogeneous catalyst, an additional process of washing with water or distillation is required to remove the catalyst, and in order to solve this problem, development of a non-uniform solid catalyst has been carried out. U.S. Patent 5,908,946 discloses a process for producing fatty acid alkyl esters using at least one of zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), zinc aluminate (ZnAl ₂ O ₃ ) as a catalyst, U.S. Patent 6,818,026, the second is under critical conditions to a catalyst using calcium hydroxide, calcium carbonate, calcium oxide, magnesium oxide, the Republic of Korea Patent Application 644 246 discloses a magnesium oxide-zinc oxide-zinc aluminate _{(xMgO · yZnO · ZnAl 2 O} 4) The method using the catalyst system of the Republic of Korea, Korean Patent Publication No. 2007-0104041 is a solid phase for producing biodiesel comprising at least one of the transition metal oxide group including zinc oxide, nickel oxide, cobalt oxide, molybdenum oxide and titanium dioxide as an active ingredient Catalytic process is disclosed. However, in these non-uniform solid catalyst processes, when raw materials containing 1% or more free fatty acids are used, the metal components, which act as catalytic active materials, combine with free fatty acids to form salts and melt into the reaction solution, thereby causing the catalyst to react. The service life is shortened, and especially high-value raw materials containing more than 5% of free fatty acids can cause more serious problems.

It is an object of the present invention to provide a method for producing fatty acid alkyl esters in high yield with high reaction activity while using oils, fats, or mixtures thereof having a high free fatty acid content as raw materials.

The present inventors have studied a method for producing fatty acid esters using oils, fats, or mixtures of high acid values, and as a result, esterification is preferred to transition esterification under high temperature and high pressure without catalyst. Under homogeneous base catalyst conditions at high temperature and high pressure, the esterification reaction and the transesterification reaction proceed simultaneously. Particularly, when the reaction is performed using MgO or Mg (OH) ₂ as the homogeneous base catalyst, the conventional alkali metal catalyst is used. The present invention has been found to show high catalytic activity even with a small amount of catalyst and easy separation of layers in the separation of by-product glycerin after the reaction.

The present invention

(i) esterification and transesterification of fats, oils or mixtures thereof containing free fatty acids with an acid value of 2 to 200 at 150-250 ° C. and 5-100 atm under a non-catalyst with C ₁ -C ₅ low alcohol; A first step of obtaining a crude fatty acid alkyl ester by subjecting to a polymerization reaction; And

(ii) recovering the crude fatty acid alkyl ester of the first step to obtain the C ₁ -C ₅ low-alcohol and the ester at 150-250 ° C. and 5-100 atm under one or more catalysts of MgO and Mg (OH) ₂ . It provides a method for producing a fatty acid alkyl ester, comprising a second step of the reaction and the transesterification reaction.

<First Step>

1. oils, fats, or mixtures thereof

Oils or fats of the present invention are fatty acid glycerol esters, which are esters of glycerol and saturated or unsaturated fatty acids, meaning fats or oils of animal or vegetable origin, and include free fatty acids. Fats or oils of the invention include, but are not limited to, lower oils, fats, or mixtures thereof containing large amounts of free fatty acids, such as, but not limited to, waste cooking oil, waste fat, yellow grease, and the like. Vegetable origin includes soybean oil, palm oil, castor oil, rapeseed oil, and the like, and animal origin include tallow, lard, poultry fat and the like.

The oils, fats, or mixtures thereof of the invention have an acid value of 2 to 200, preferably 5 to 100, more preferably 10 to 60.

The oils, fats, or mixtures thereof of the present invention can be prepared into fatty acid alkylesters by reaction with alcohols and through esterification and transesterification reactions.

2. Alcohol

The alcohol used in the esterification or transesterification reaction with the oil, fat, or mixtures thereof of the present invention may be selected from one or more linear or branched alcohols having 1 to 5 carbon atoms, preferably Methanol or ethanol is used.

3. Reaction of the first step

In the present invention, the first process is performed without a catalyst. The reaction temperature is 150 ~ 250 ℃ and the reaction pressure is 5 ~ 100 atm. Preferably reaction temperature is 180-230 degreeC, More preferably, 190-220 degreeC, Reaction pressure becomes like this. Preferably it is 10-70 atmospheres, More preferably, it is 20-50 atmospheres. The ratio of oils, fats, or mixtures thereof (oil, fats, or mixtures / alcohols) to alcohols may be 100/80 to 100/10 by weight, preferably 100/70 to 100/15 More preferably, it may be 100 / 60-100 / 20. When considering the recovery cost of alcohol, the ratio is preferably 100/80 or more, and the ratio is preferably 100/10 or less for a smooth conversion reaction. The process can be carried out in a continuous or batch process. The reaction time of the batch process and the raw material residence time of the continuous process are preferably 30 minutes to 6 hours. As the reactor, for example, a reactor such as a stirred reactor type (CSTR) in the case of a batch process, a line or a static mixer form in the case of a continuous process may be used. Some of the water produced during the reaction can be removed continuously out of the reactor by adjusting the reaction pressure, thereby promoting the esterification reaction to lower the acid value of the reactants more efficiently.

The reaction product of the first step is a crude fatty acid alkyl ester including fatty acid ester, monoglyceride, diglyceride, triglyceride, methanol, water and the like. It is injected into the second process.

After evaporating methanol and water in the first step, the glycerin produced by layer separation may be removed. The first step can greatly reduce the acid value of oils, fats, or mixtures thereof, and the triglycerides in the oils, fats, or mixtures thereof are converted to fatty acid alkyl esters at high conversion rates by transesterification with alcohols. Is switched. If the pressure is lowered continuously to remove a portion of the water generated, the pretreatment process of water removal can be omitted. The pretreatment process of the present invention may be particularly effective when the acid value of the oil or fat is 10 or more, specifically 20 or more.

&Lt; Second Step &

The second step is performed by continuous addition or discontinuous addition of alcohol and base catalyst newly added to the fatty acid ester layer which has separated the glycerin layer by reaction product or layer separation in the first step under similar reaction conditions as the first step. The reaction proceeds. As the alcohol, the same alcohol as that used in the first step can be used.

The ratio of the crude fatty acid alkyl ester to the alcohol may be 100/80 to 100/10 by weight, preferably 100/70 to 100/15, more preferably 100/60 to 100/20 days Can be. When considering the recovery cost of alcohol, the ratio is preferably 100/80 or more, and the ratio is preferably 100/10 or less for a smooth conversion reaction.

As the catalyst, magnesium oxide (MgO) or magnesium hydroxide (Mg (OH) ₂ ) may be used alone or in combination. Base catalysts such as sodium hydroxide (NaOH) and potassium hydroxide (KOH) react with free fatty acids contained in oils or fats to form soaps, and thus esterification is impossible. While it is possible to use a high acid value raw material including free fatty acids, it is possible to simultaneously esterify the free fatty acids, thereby increasing the conversion to fatty acid alkyl esters and lowering the yield loss.

The content of the catalyst may be 0.001 to 0.5% by weight based on the weight of the crude fatty acid alkyl ester, preferably 0.005 to 0.3% by weight, more preferably 0.01 to 0.1% by weight. In the present invention, a small amount of the catalyst can be used. When a small amount of the catalyst is used, the yield loss can be minimized by suppressing the generation of the emulsion upon separation of the layer after completion of the reaction.

The catalyst may be diluted and used in a slurry state by mixing with the alcohol or the end of the first process reaction, and the slurry raw material and the catalyst mixture are continuously or intermittently introduced into the second process. Most of the catalysts added to the reaction participate in the reaction in the form of a homogeneous system, and they may participate in the reaction in the form of oxides, hydroxides, fatty acid salts, and the like. This catalyst promotes both transesterification and esterification. In the high acid value raw material, the esterification to reduce the acid value proceeds more slowly. Therefore, in a high acid value raw material, ester reaction can be advanced effectively by the 1st process which is a catalyst-free process.

The reaction temperature of the 2nd process is 150-250 degreeC, Preferably it is 180-230 degreeC, More preferably, it is 190-220 degreeC. If the reaction temperature is less than 150 ℃, the conversion rate to fatty acid alkyl ester is reduced because the activity of the metal base catalyst does not appear, and if it exceeds 250 ℃ energy cost increases to increase the process cost and the raw material oil, fat, or Carbonization of these mixtures may occur.

The reaction pressure is 5 to 100 atm, preferably 10 to 70 atm, more preferably 20 to 50 atm. If the reaction pressure is less than 5 atm, the alcohol is present in the gas phase to make a uniform reaction system, excess alcohol is required. In addition, if it exceeds 100 atm, the process equipment becomes complicated and the process cost increases, making it difficult to apply to commercial production.

The second process can be carried out continuously or batchwise. Both the reaction time of the batch process and the reaction time of the continuous process may be 30 minutes to 6 hours, preferably 1 hour to 4 hours. In order to sufficiently proceed to the fatty acid alkyl ester, the reaction time is preferably 30 minutes or more, and when considering the generation of carbides and the progress of the reverse reaction due to long-term stagnation at high temperature, the reaction time is preferably 6 hours or less.

As the reactor, for example, a continuous stirred reactor (CSTR) in the case of a continuous process, a reactor in the form of a line or a static mixer in the case of a batch, or the like can be used. Some of the water produced during the reaction can be removed continuously out of the reactor by adjusting the reaction pressure, thereby promoting the esterification reaction to lower the acid value of the product more efficiently.

After removing the unreacted methanol and water from the reaction finished product produced in the second step by a known method such as evaporation and extraction, and separating the layers, fatty acid esters, monoglycerides, diglycerides, catalysts, etc. Glycerin, catalysts, other unconverted glycerides, and the like. The fatty acid alkyl ester with the acid value greatly reduced by the 2nd process can be obtained. The fatty acid ester may be separated from the upper layer or introduced into the third process, and the lower glycerin may be sent to the purification process. The catalyst used after the end of the second process can be removed from the fatty acid alkylester by distillation or acid washing. Distillation residues during distillation contain large amounts of catalyst and can be reused as catalysts for esterification and transesterification reactions.

<Third Step>

The fatty acid ester layer, which is the upper portion, may be added to the third process as it is. In the second step, 80% or more of the catalytically active material is present in the upper layer, and in the third step, they are added as they are so that the reaction can proceed without additional catalyst. However, if desired, additional catalysts can be added, which are catalysts used in the second process, ie MgO and Mg (OH) ₂ , or other applicable catalysts, for example base catalysts, in particular metals. Base catalysts may be added alone or in mixtures. Other applicable catalysts include base catalysts such as NaOH, KOH, KOCH ₃ , NaOCH ₃ and the like.

The amount of the catalyst used in the case of further addition of the catalyst may be preferably 0.001 to 0.5% by weight, more preferably 0.005 to 0.3% by weight, most preferably based on the weight of the raw material of the third step except for alcohol 0.01 to 0.1% by weight.

The reaction pressure of the third process may be a condition of high pressure or low pressure. In the case of high pressure, it may be 5 to 100 atm, preferably 10 to 70 atm, more preferably 20 to 50 atm, and in the case of low pressure, it may be at normal to 10 atm, preferably at atmospheric pressure to 5 atm. In addition, the reaction temperature may be a condition of high temperature or low temperature. In the case of high temperature, it may be 150 to 250 ° C, preferably 180 to 230 ° C, more preferably 190 to 220 ° C, and in the case of low temperature, 40 to 100 ° C, preferably 50 to 80 ° C.

When the catalyst used in the third step is MgO or Mg (OH) ₂ can be reacted at the high temperature and high pressure, NaOH, KOH, KOCH ₃ , NaOCH ₃ And the like can be reacted at low temperature and low pressure.

The manner of other third processes, such as the content of alcohols, is basically the same as in the previous esterification and transesterification reactions.

After the third step, methanol and water are first removed from the reaction product by evaporation. Fatty acid alkylesters can be recovered from known reaction products from which alcohol and water have been removed. For example, the reaction product is distilled to obtain fatty acid alkyl esters and glycerin from the top of the distillation column, and then the layers are separated to obtain fatty acid alkyl esters. The fatty acid alkyl esters are separated from the reaction product by separating the fatty acid alkyl esters and glycerin. How to get. The recovered fatty acid alkyl ester can be purified by additional known methods such as washing with water and dehydration.

Through the third step, it is possible to obtain a fatty acid alkyl ester having greatly reduced acid value. In addition, the fatty acid alkyl ester having a low content of unconverted glyceride, which has a low content of monoglyceride, diglyceride and triglyceride, can be secured in high yield.

If the quality of the fatty acid ester obtained through the second step is appropriate, the third step may not be selectively performed.

The catalyst used after the end of the third process may be removed by distillation or pickling. The distillation residue during distillation contains a large amount of catalyst and can be used as a catalyst in esterification and transition esterification processes.

According to the present invention, fatty acid alkyl esters can be produced in high yield with high reaction activity while using oils, fats, or mixtures thereof having a high free fatty acid content of 2 to 200 as a raw material.

Hereinafter, the present invention will be described in more detail with reference to Examples, and the present invention is not limited to the following Examples.

Example  1-1

166 g of crude palm oil (acid value 60 mgKOH / g) and 78 g of methanol were added to a 500 ml high-pressure reactor, and the reaction was performed at 200 ° C. and 30 atm for 2 hours. After removing the unreacted methanol and the water produced by a distillation evaporator, the fatty acid alkyl ester layer and the glycerin layer were separated, and a crude fatty acid alkyl ester layer was recovered. The acid value and organic matter content of the recovered crude fatty acid alkyl ester layer were analyzed according to the following KS standard. In addition, the yield loss was calculated by comparing the content of crude fatty acid alkyl ester recovered after layer separation with the theoretical content of fatty acid alkyl ester that can be produced. This yield loss refers to the loss of fatty acid alkylesters upon layer separation due to emulsion formation.

Acid value measurement method (KS M ISO 6618: 2003)

(1) Depending on the acid value, take a sample in the range of 0.1 to 2.0 g, dissolve in 100 ml of toluene (50%), isopropyl alcohol (49.5%), and water (0.5%) mixed solution, and add 0.5 ml of p-naphtolbenzein solution. .

(2) Titrate with 0.1N KOH solution until the red solution turns blue.

(3) Perform the background test without inserting the sample.

Here, the acid value can be obtained by the following equation.

Acid value = [volume of KOH solution used for sample titration (ml)-volume of KOH solution used in background test (ml)] * concentration of KOH solution (mol / L) * 56.1 / mass of sample (g)

Fatty acid alkyl ester content (conversion) measurement method (KS M 2413: 2004)

0.25 g of the sample is dissolved in 5 ml of 10 mg / ml Methylheptadecanoate Heptane solution and analyzed using gas chromatography (Agilent, 6790A) equipped with FID.

Method for determining the content of free glycerol (glycerine) and bound glycerol (mono-, di-, triglycerides ) (KS M 2412: 2004)

(1) 100 μl of N-methyl-N-trimethylsilyltrifluoracetamide, 100 μl of Tricaprin, in 0.1 g of sample,

After mixing 100 μl of Butantriol, it is allowed to stand for at least 30 minutes.

(2) 8 ml of Heptane is added to the still solution.

(3) Analyze with FID-equipped gas chromatography (Agilent, 6790A).

Example  1-2

65 g of crude fatty acid ester obtained in Example 1-1, 28 g of methanol, and 0.021 g of magnesium oxide were added to a 160 ml high-pressure reactor, and the reaction was carried out at a reaction temperature of 200 ° C. and 30 atm for 2 hours. After removing unreacted methanol and water, the fatty acid ester layer and the glycerin layer were separated by layer separation. The acid value, organic matter content, and yield loss of the fatty acid ester layer were analyzed in the same manner as in Example 1-1.

Example  1-3

In a 160 ml high pressure reactor, 43 g of fatty acid ester obtained in Example 1-2 and 18 g of methanol were reacted at 200 ° C. and 30 atm for 1 hour, and then proceeded in the same manner as in Example 1-2. The yield loss was analyzed.

Comparative example  One

55 g of crude palm oil (acid value 9 mgKOH / g) and methanol 23.5 g were added to a 160 ml high-pressure reactor, and reacted at 200 ° C. for 1 hour using 0.054 g of NaOH as a catalyst. After removing the unreacted methanol and the water produced, the fatty acid ester layer and the glycerin layer were separated by layer separation, and then the fatty acid ester was recovered, and then the fatty acid ester layer recovered in the same manner as in Examples 1-1 to 1-3. Acid value, organic content and yield loss were analyzed.

Comparative example  2

A fatty acid ester was produced and recovered in the same manner as in Comparative Example 1 except that KOH 0.052 g was used as a catalyst, and then the acid value, organic matter content, and yield loss of the recovered fatty acid ester layer were analyzed.

Comparative example  3

Fatty acid ester was prepared and recovered in the same manner as in Comparative Example 1 except that 0.3 g of sodium hydroxide (NaOH) was used as a catalyst and reacted at 80 ° C., and then the acid value, organic matter content, and yield loss of the recovered fatty acid ester layer were lost. Was analyzed.

Comparative example  4

A fatty acid ester was prepared and recovered in the same manner as in Comparative Example 1 except that 0.6 g of sodium hydroxide (NaOH) was used as a catalyst, and then the acid value, organic matter content, and yield loss of the recovered fatty acid ester layer were analyzed.

The analysis results are shown in Table 1 below.

Recovery layer analysis Acid value (mg KOH / g) MG (% by weight) DG (% by weight) TG (% by weight) Conversion Rate (%) Example 1-1 15 5 11 19 57 Examples 1-2 1.3 2 0.3 0 97 Example 1-3 0.4 0.4 0.1 0 99 Comparative Example 1 1.5 4 3 1.5 90 Comparative Example 2 2.5 4 7.5 9 78 Comparative Example 3 2.4 0.5 5 86 8 Comparative Example 4 0.3 0.5 0.5 0.5 98

(MG: monoglyceride, DG: diglyceride, TG: triglyceride)

As shown in the above table, in the case of Example 1, which was subjected to three steps using MgO catalyst, fatty acid ester having a lower acid value was prepared at a higher conversion rate than Comparative Examples 1 to 3, which were subjected to only one step using NaOH or KOH catalyst. . In particular, in the case of Comparative Example 3 in which a large amount of the existing base catalyst at a low temperature it can be seen that the conversion rate to the fatty acid alkyl ester is very low. In Comparative Example 4, which used more catalyst than Comparative Example 3, the reaction proceeded rapidly and the conversion to fatty acid alkyl ester was also high. However, when the layer was separated after completion of the reaction, the glycerin layer was equivalent to 40% by weight. Since it is included in a large amount by weight level, it can be confirmed that the yield loss of fatty acid ester is large.

Example  2

180 g of palm oil mixture (acid value 60 mgKOH / g) and 80 g of methanol were added to a 500 ml high-pressure reactor, and the first process was performed at 200 ° C. and 30 atm for 2 hours. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure, and the layers were separated for 1 hour to separate fatty acid alkyl esters, unreacted fatty acids, glycerides, and glycerin from lower layers. The upper fatty acid alkyl ester, unreacted fatty acid, 180 g of glyceride, and 80 g of methanol were added to a 500 ml high pressure reactor, and a second process was performed at 200 ° C. and 30 atm for 2 hours using a MgO catalyst. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure, and the layers were separated for 1 hour to separate fatty acid alkyl esters, unreacted fatty acids, glycerides, and glycerin from lower layers. The upper fatty acid alkyl ester, unreacted fatty acid, glyceride 180g and methanol 80g were put into a 500ml high pressure reactor, and MgO was further added, and the third process was performed at 200 ° C. and 30 atm for 2 hours. After the unreacted methanol and the produced water are removed by evaporation, the fatty acid alkyl ester layer and the glycerin layer are separated by layer separation to recover the fatty acid alkyl ester layer, and the acid value, organic content and yield loss of the recovered fatty acid alkyl ester layer are performed. The analysis was conducted in the same manner as in Example 1.

Table 2 shows the analysis results of acid value, organic matter content, and yield loss of the fatty acid alkyl ester layer in Example 2.

division Catalytic
Kinds usage
(g) Reaction temperature
(℃) Recovery layer analysis Yield loss after layer separation
(weight%) Acid
(mgKOH / g) MG (% by weight) DG
(weight%) TG
(weight%) Conversion rate (% by weight) First step - - 200 15.97 5.74 14.52 11.04 68.70 none Second Step MgO 0.05 200 1.3 1.13 0.17 0.00 98.70 none Third step MgO 0.084 200 0.5 0.54 0.08 0.00 99.38 none

Example  3

180 g of waste cooking oil (acid value 43 mgKOH / g) and 80 g of methanol were added to a 500 ml high-pressure reactor, and the first step was performed at 200 ° C. and 30 atm for 2 hours. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure and the layers were separated for 1 hour to separate crude fatty acid alkyl ester, unreacted fatty acid and glyceride from upper layer, and glycerin from lower layer. 180 g of fatty acid alkyl ester, unreacted fatty acid, glyceride, and 80 g of methanol were added to a 500 ml high pressure reactor, and a secondary process was performed at 200 ° C. and 30 atm for 2 hours using a MgO catalyst. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure, and the layers were separated for 1 hour to separate fatty acid alkyl esters, unreacted fatty acids, glycerides, and glycerin from lower layers. 180 g of fatty acid alkyl ester, unreacted fatty acid, glyceride, and 80 g of methanol were added to a 500 ml high pressure reactor, and a third step was performed at 200 ° C. and 30 atm using MgO catalyst. The unreacted methanol and the produced water were removed by evaporation, and the fatty acid alkylester layer and the glycerin layer were separated by layer separation to recover the fatty acid alkylester layer. The acid value, organic matter content, and yield loss of the recovered fatty acid alkyl ester layer were analyzed in the same manner as in Example 1.

The analysis results of the acid value, organic matter content, and yield loss of the fatty acid alkyl ester layer in Example 3 are shown in Table 3 below.

division Catalytic
Kinds usage
(g) Recovery layer analysis After layer separation
Yield loss
(weight%) Acid
(mgKOH / g) MG
(weight%) DG
(weight%) TG
(weight%) Conversion rate
(weight%) First step - - 13.91 9.21 22.02 14.54 52.70 none Second Step MgO 0.054 2.24 3.71 0.63 0.30 94.42 none Third step MgO 0.054 0.43 0.8 0.00 0.16 98.0 none

As a result of the first step, the second step, and the third step in a continuous process using high or medium acid low-value raw materials through Examples 2 and 3, fatty acid alkyl esters can be produced at high conversion rates without loss of yield while lowering the acid value. It can be seen that. Conventional base catalyst process is difficult to separate the layer because the emulsion is formed when using a high acid value raw material and a gel-like mixture is formed, the yield loss of fatty acid alkyl ester is large, but the problem can be solved by the method of the present invention.

Example  4

180 g of waste cooking oil (acid value 80 mgKOH / g) and 80 g of methanol were added to a 500 ml high-pressure reactor, and the first step was performed at 200 ° C. and 30 atm for 2 hours. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure, and the layers were separated for 1 hour to separate fatty acid alkyl esters, unreacted fatty acids, glycerides, and glycerin from lower layers. The upper fatty acid alkyl ester, unreacted fatty acid, 180 g of glyceride, and 80 g of methanol were added to a 500 ml high-pressure reactor, and the second process was performed at 200 ° C. and 30 atm for 2 hours using 0.054 g of MgO catalyst. After completion of the reaction, unreacted methanol and generated water were removed under reduced pressure, and the layers were separated for 1 hour to separate fatty acid alkyl esters, unreacted fatty acids, glycerides, and glycerin from lower layers. 180 g of fatty acid alkyl ester, unreacted fatty acid, glyceride, and 40 g of methanol were added to a 500 ml high pressure reactor, and 1.13 g of NaOCH ₃ (30% solution in Methanol) was performed at 70 ° C. and atmospheric pressure for 2 hours. The unreacted methanol and the produced water were removed by evaporation, the fatty acid alkylester layer and the glycerin layer were separated by layer separation to recover the fatty acid alkylester layer, and the acid value and organic content of the recovered fatty acid alkylester layer were analyzed. Are listed in Table 4.

division Catalytic
Kinds usage
(g) Recovery layer analysis Acid
(mgKOH / g) MG
(weight%) DG
(weight%) TG
(weight%) Conversion rate
(weight%) First step - - 12.9 6.8 10.9 5.5 70.3 Second Step MgO 0.054 1.3 2.5 0.4 0.1 96 Third step NaOCH ₃ 1.13 0.1 0.6 0 0 99

Through the analysis results, after the first process using a high acid low-grade raw material, and then proceeding to the second process using the MgO catalyst, the existing base catalyst process is carried out in a continuous process to proceed to the third process When lowering the acid value it can be seen that the fatty acid alkyl ester can be produced with a high conversion rate.

Claims (8)

(i) esterification and transesterification of fats, oils or mixtures thereof containing free fatty acids with an acid value of 2 to 200 at 150-250 ° C. and 5-100 atm under a non-catalyst with C ₁ -C ₅ low alcohol; A first step of obtaining a crude fatty acid alkyl ester by subjecting to a polymerization reaction; And
(ii) recovering the crude fatty acid alkyl ester of the first step to obtain the C ₁ -C ₅ low-alcohol and the ester at 150-250 ° C. and 5-100 atm under one or more catalysts of MgO and Mg (OH) ₂ . A method for producing a fatty acid alkyl ester, comprising a second step of subjecting a polymerization and a transesterification reaction. The method of claim 1,
The ratio of the oil, fat, or mixtures thereof to the alcohol in the first step is a method for producing a fatty acid alkyl ester, characterized in that 100/80 ~ 100/10 by weight. The method of claim 1,
The method of producing a fatty acid alkyl ester, characterized in that in the second step the catalyst is used 0.001 to 0.5% by weight based on the total weight of the crude fatty acid alkyl ester. The method of claim 1,
The ratio of the crude fatty acid alkyl ester to the alcohol in the second step is 100/80 ~ 100/10 by weight based on the method for producing a fatty acid alkyl ester. The method of claim 1,
(iii) a third step of recovering the fatty acid alkyl ester obtained in the second step to obtain a fatty acid alkyl ester by esterifying and transesterifying the C ₁ -C ₅ low-cost alcohol with a base catalyst or no catalyst. Method for producing a fatty acid alkyl ester, characterized in that. The method of claim 5,
Wherein the base catalyst is at least one catalyst selected from the group consisting of MgO, Mg (OH) ₂ , NaOH, KOH, and NaOCH ₃ . The method of claim 5,
The base catalyst is a fatty acid alkyl ester production method characterized in that it is used in 0.001 to 0.5% by weight based on the weight of the fatty acid alkyl ester obtained in the second step. The method of claim 5,
The third step is a method for producing a fatty acid alkyl ester, characterized in that carried out at 150 ~ 250 ℃ and 5 ~ 100 atm or 40 ~ 100 ℃ and atmospheric pressure-10 atm.