JPWO2018212049A1 - Method of removing monoglyceride in biodiesel - Google Patents

Abstract

Provided is a method of removing monoglycerides which are impurities in fatty acid alkyl ester compositions such as biodiesel. Impurity monoglycerides are crystallized out and removed by stirring the fatty acid alkyl ester composition containing monoglycerides under specific conditions.

Description

  The present invention relates to a method of removing monoglycerides in fatty acid alkyl ester compositions such as biodiesel.

  Biodiesel is a diesel fuel mainly composed of fatty acid alkyl ester, and is produced by transesterification of fats and oils such as vegetable fats and oils with alcohols such as methanol. Biodiesel generally contains impurities such as monoglycerides. Monoglycerides, when used in biodiesel, lead to obstacles such as filter clogging due to precipitation. Therefore, a technology for removing monoglyceride from biodiesel is required.

  As a method for removing monoglyceride in biodiesel, for example, water washing, distillation, extraction, membrane separation, adsorption removal with an adsorbent is known.

  Also, as a method for removing monoglycerides in biodiesel, a method is disclosed in which unsaturated fatty acid monoglycerides are selectively converted into easily precipitated saturated fatty acid monoglycerides by hydrogenation of biodiesel, and the precipitated fatty acid monoglycerides are removed. (Patent Document 1). The document states that precipitation (crystallization) of monoglyceride can be carried out under standing conditions, and the standing time is preferably 24 hours or more.

WO2015 / 056767

  An object of the present invention is to provide a method for removing monoglyceride in a fatty acid alkyl ester composition such as biodiesel.

  The present inventors considered that the method described in Patent Document 1 had room for improvement in terms of the time required for precipitation (crystallization) of monoglyceride. Furthermore, the present inventors are able to precipitate the monoglyceride efficiently by stirring the fatty acid alkyl ester composition containing the monoglyceride under specific conditions, so that the monoglyceride can be easily removed. The present invention has been completed.

That is, the present invention can be exemplified as follows.
[1]
A method for producing a fatty acid alkyl ester, comprising
Method comprising the following steps (A) and (B):
(A) stirring the mixture containing fatty acid alkyl ester and monoglyceride to precipitate the monoglyceride;
(B) removing the precipitated monoglyceride from the mixture.
[2]
Stirring power during agitation in the step (A) is a ^{5W / m 3 ~1000W / m 3} , said process.
[3]
The method, wherein the tip speed of the stirring blade at the time of stirring in the step (A) is 0.2 m / s to 3.0 m / s.
[4]
The method wherein the temperature of step (A) is 14 ° C to 20 ° C.
[5]
The method wherein the time of step (A) is 0.5 hours to 20 hours.
[6]
The method according to the above, wherein a period during which the stirring in the step (A) is performed is 0.5 hour to 10 hours.
[7]
The method according to the above, wherein the period during which the stirring in the step (A) is stopped is 0 hour to 10 hours.
[8]
The method wherein the fatty acid alkyl ester is a fatty acid methyl ester.
[9]
The method, further comprising the step of hydrogenating the mixture prior to performing step (A).
[10]
The method, further comprising the step of adding monoglyceride seed crystals to the mixture before or during the step (A).
[11]
The method, further comprising the step of adding light oil to the mixture before or during the step (A).
[12]
The method further comprising the step of removing the monoglyceride remaining in the mixture using an adsorbent after performing the step (B).
[13]
Stirring power during agitation in the step (A) ^is a ^{14W / m 3 ~391W / m 3} , said process.
[14]
The method, wherein the tip speed of the stirring blade at the time of stirring in the step (A) is 0.4 m / s to 1.4 m / s.

The figure which shows the correlation with the crystallization temperature, the monoglyceride removal rate, and the fatty-acid alkyl ester yield. The figure which shows the correlation with stirring power, a monoglyceride removal rate, and fatty acid alkyl ester yield. The figure which shows the correlation with the crystallization time, the monoglyceride removal rate, and the fatty-acid alkyl ester yield. The figure which shows the correlation with stirring power, fatty acid alkyl ester yield, and a filtration rate. The figure which shows the correlation with crystallization time, fatty acid alkyl ester yield, and a filtration rate.

  Hereinafter, the present invention will be described in detail.

The method of the present invention is a method of removing monoglyceride, comprising the following steps (A) and (B):
(A) stirring the mixture containing fatty acid alkyl ester and monoglyceride to precipitate the monoglyceride;
(B) removing the precipitated monoglyceride from the mixture.

  In addition, fatty acid alkyl esters are obtained by the method of the present invention. That is, the method of the present invention may be read as a method for producing a fatty acid alkyl ester comprising the above steps (A) and (B).

  The above step (A) is also referred to as a “stirring step”. The above step (B) is also referred to as “removal step”. The mixture for carrying out the above step (A) is also referred to as "crude mixture". The fatty acid alkyl ester obtained by the process of the present invention is also referred to as "product". The fatty acid alkyl ester itself or a mixture (composition) containing the same is also referred to as "fatty acid alkyl ester composition". In addition, "precipitation" is also referred to as "crystallization".

  The crude mixture is a mixture containing fatty acid alkyl ester and monoglyceride. The crude mixture is, in other words, a fatty acid alkyl ester composition containing monoglycerides. The crude mixture may consist of fatty acid alkyl ester and monoglyceride, and may further contain other components. Other ingredients include diglycerides, triglycerides, glycerin, alcohols, water, salts.

  The content (concentration) of each component in the crude mixture is not particularly limited as long as the effects of the present invention are not impaired.

  The total content of fatty acid alkyl ester and monoglyceride in the crude mixture is, for example, 90% (w / w) or more, 95% (w / w) or more, 97% (w / w) or more based on the total amount of the crude mixture It may be 98% (w / w) or more, or 99% (w / w) or more.

  The content of the fatty acid alkyl ester in the crude mixture is, for example, 80% (w / w) or more, 85% (w / w) or more, 90% (w / w) or more, 95% (w / w) based on the total amount of the crude mixture w / w), 97% (w / w), 98% (w / w), or 99% (w / w) or more, and less than 100% (w / w).

  The content of monoglycerides in the crude mixture is, for example, 0.2% (w / w) or more, 0.25% (w / w) or more, 0.3% (w / w) or more based on the total amount of the crude mixture , 0.35% (w / w) or more, 0.4% (w / w) or more, 0.45% (w / w) or more, 0.5% (w / w) or more, 0.7% (w / w) w / w) or more, 1% (w / w) or more, 2% (w / w) or more, 3% (w / w) or more, or 5% (w / w) or more, 10% (W / w) or less, 7% (w / w) or less, 5% (w / w) or less, 3% (w / w) or less, 2% (w / w) or less, 1% (w / w) Hereinafter, it may be 0.7% (w / w) or less, or 0.5% (w / w) or less, or may be a consistent combination thereof.

  The content of monoglyceride in the crude mixture is, for example, 0.2% (w / w) or more, 0.25% (w / w) or more, 0.3% or more relative to the content of fatty acid alkyl ester in the crude mixture (W / w) or more, 0.35% (w / w) or more, 0.4% (w / w) or more, 0.45% (w / w) or more, 0.5% (w / w) or more 0.7% (w / w) or more, 1% (w / w) or more, 2% (w / w) or more, 3% (w / w) or more, or 5% (w / w) or more 10% (w / w) or less, 7% (w / w) or less, 5% (w / w) or less, 3% (w / w) or less, 2% (w / w) or less, 1 % (W / w) or less, 0.7% (w / w) or less, or 0.5% (w / w) or less, or a compatible combination thereof.

  In the case where the content of each component in the crude mixture (for example, the range of the content exemplified above) is added to the crude mixture such as light oil etc., unless otherwise specified, the content prior to the addition of the external component The content in the crude mixture is shown. In that case, the content of each component in the crude mixture after the addition of the external component may be, for example, a range calculated based on the range of the exemplified content and the addition amount ratio of the external component.

  Examples of the fatty acid and alkyl group constituting the fatty acid alkyl ester include those described later. That is, as fatty acid alkyl ester, ester comprised with the combination of the constituent fatty acid mentioned later and the alkyl group mentioned later is mentioned. That is, as fatty acid alkyl ester, saturated fatty acid alkyl ester and unsaturated fatty acid alkyl ester are mentioned. As unsaturated fatty acid alkyl ester, monounsaturated fatty acid alkyl ester and polyunsaturated fatty acid alkyl ester are mentioned. As unsaturated fatty acid alkyl ester, trans fatty acid alkyl ester and cis fatty acid alkyl ester are mentioned. In addition, fatty acid alkyl esters include fatty acid methyl esters. The crude mixture may contain one fatty acid alkyl ester, and may contain two or more fatty acid alkyl esters.

  As a fatty acid which comprises monoglyceride, what is mentioned later is mentioned. That is, monoglycerides include monoglycerides of constituent fatty acids described later. That is, as monoglycerides, saturated fatty acid monoglycerides and unsaturated fatty acid monoglycerides can be mentioned. Examples of unsaturated fatty acid monoglycerides include monounsaturated fatty acid monoglycerides and polyunsaturated fatty acid monoglycerides. The position of the constituent fatty acid in monoglyceride is not particularly limited. The monoglyceride may have the constituent fatty acid at the 1-position (the same as the 3-position), or may have the 2-position. The crude mixture may contain one monoglyceride or may contain two or more monoglycerides.

  As constituent fatty acids, fatty acids having 6 to 26 carbon atoms, particularly 8 to 24 carbon atoms, and more particularly 12 to 18 carbon atoms can be mentioned. The fatty acids include saturated fatty acids and unsaturated fatty acids. The unsaturated fatty acids include monounsaturated fatty acids and polyunsaturated fatty acids. Examples of unsaturated fatty acids include trans fatty acids and cis fatty acids. Trans fatty acids are produced, for example, by hydrogenation. As fatty acids, specifically, caprylic acid (C8: 0), capric acid (C10: 0), lauric acid (C12: 0), myristic acid (C14: 0), palmitic acid (C16: 0), stearic acid Saturated fatty acids such as (C18: 0), arachidic acid (C20: 0), behenic acid (C22: 0), lignoceric acid (C24: 0), palmitoleic acid (C16: 1), oleic acid (C18: 1), Monounsaturated fatty acids such as eicosenoic acid (C20: 1) and erucic acid (C22: 1), divalent unsaturated fatty acids such as linoleic acid (C18: 2), trivalent nonbasic acids such as linolenic acid (C18: 3) Saturated fatty acids, tetravalent unsaturated fatty acids such as stearidonic acid (C18: 4), pentavalent unsaturated fatty acids such as eicosapentaenoic acid (C20: 5) or docosapentaenoic acid (C22: 5), docosahexaenoic acid (C22: 6) Etc.) and the like.

  As an alkyl group, a C1-C6 alkyl group is mentioned. Examples of the alkyl group include linear alkyl groups and branched alkyl groups. As the alkyl group, specifically, methyl group, ethyl group, propyl group, isopropyl group, 1-butyl group, 2-butyl group, isobutyl group, tert-butyl group, 1-pentyl group, 3-pentyl group, 3 -Methyl-1-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 2-methyl-1-pentyl and 3,3-dimethyl-1-butyl Be As alkyl group, mention may in particular be made of methyl.

  The composition of the fatty acid alkyl ester and the monoglyceride (for example, the kind and presence ratio of the constituent fatty acid and the alkyl group) is not particularly limited as long as the effect of the present invention is not impaired. The composition of these components can be suitably set according to various conditions, such as a use of a product, and a use aspect, for example. For example, the compositions exemplified below may be suitable when using the product as a diesel fuel.

  The content of the monounsaturated fatty acid alkyl ester in the crude mixture is, for example, 5% (w / w) or more, 10% (w / w) or more, 20% (w) with respect to the total amount of fatty acid alkyl ester in the crude mixture. / W) 30% (w / w) or more, 40% (w / w) or more, 50% (w / w) or more, 60% (w / w) or more, or 70% (w / w) or more 95% (w / w) or less, 90% (w / w) or less, 80% (w / w) or less, 70% (w / w) or less, 60% (w / w) or less 50% (w / w) or less, 40% (w / w) or less, or 30% (w / w) or less, or a compatible combination thereof.

  The content of polyunsaturated fatty acid alkyl ester in the crude mixture is, for example, 10% (w / w) or less, 7% (w / w) or less, 5% (w) with respect to the total amount of fatty acid alkyl ester in the crude mixture / W) or less, 3% (w / w) or less, 2% (w / w) or less, 1% (w / w) or less, or zero.

  The content of the trans-fatty acid alkyl ester in the crude mixture is, for example, 28% (w / w) or less, 17% (w / w) or less, 10% (w / w) based on the total amount of fatty acid alkyl ester in the crude mixture 7% (w / w) or less, 5% (w / w) or less, 3% (w / w) or less, 2% (w / w) or less, 1% (w / w) or less, or zero It may be.

  The content of unsaturated monoglycerides in the crude mixture is, for example, 10% (w / w) or less, 7% (w / w) or less, 5% (w / w) or less, based on the total amount of monoglycerides in the crude mixture % (W / w) or less, 2% (w / w) or less, 1% (w / w) or less, or zero.

  The crude mixture can be produced, for example, by transesterification of triglycerides with alcohol. That is, the method of the present invention may include the step of transesterifying triglyceride and alcohol to produce a crude mixture. The same process is also referred to as "ester exchange process".

  The triglyceride is not particularly limited as long as it gives the desired constituent fatty acid. As such triglyceride, those having the constituent fatty acids exemplified above and those having constituent fatty acids which can be converted to the constituent fatty acids exemplified above can be mentioned. As triglyceride, fats and oils can be used, for example. As fats and oils, natural fats and oils, the waste fats and oils derived from them, those processed goods are mentioned. Natural fats and oils include vegetable derived fats and oils (vegetable fats and oils) and animal derived fats and oils (animal fats and oils). Examples of vegetable fats and oils include rapeseed oil, sesame oil, jatropha oil, soybean oil, corn oil, sunflower oil, palm oil, palm kernel oil, cotton seed oil, rice oil, coconut oil and safflower oil. Examples of animal fats and oils include beef tallow, pork fat, chicken fat and fish oil. Examples of the processed products include hardened oils (oils and fats whose degree of unsaturation has been reduced by hydrogenation). As fats and oils, 1 type of fats and oils may be used and 2 or more types of fats and oils may be combined and used.

  The alcohol is not particularly limited as long as it gives the desired alkyl group. As such alcohol, those having the alkyl group exemplified above and those having the alkyl group convertible to the alkyl group exemplified above can be mentioned. As alcohol, a C1-C6 linear or branched alkyl alcohol is mentioned. Specific examples of the alcohol include methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, 3-pentanol, 3-methyl-1-butanol, Examples include 2,2-dimethyl-1-propanol, 1-hexanol, 2-hexanol, 2-methyl-1-pentanol, and 3,3-dimethyl-1-butanol. Alcohols include, in particular, methanol. As the alcohol, one alcohol may be used, or two or more alcohols may be used in combination.

  The transesterification reaction can be carried out, for example, by contacting triglyceride and alcohol in the presence of a catalyst. The catalyst includes an alkali catalyst, an acid catalyst, a biocatalyst (lipase etc.) and a solid catalyst. The reaction conditions can be appropriately set according to various conditions such as the type of raw material and the type of catalyst. The molar ratio of triglyceride to alcohol (triglyceride: alcohol) may be, for example, 1: 3 to 1: 100, 1: 3 to 1:20, or 1: 3 to 1:12. The reaction temperature may be, for example, 40 to 120 ° C. The reaction time may be, for example, 0.1 to 6 hours. The reaction may be carried out batchwise or continuously.

  By carrying out transesterification in this way, a reactant containing a fatty acid alkyl ester is obtained. The obtained reaction product can be used as a crude mixture as it is or after being subjected to a treatment such as purification. Examples of the purification treatment include fractionation, washing with water and dehydration. The purification treatment can be carried out, for example, so as to obtain the composition of the crude mixture exemplified above.

  Fatty acid alkyl esters produced from biological fats and oils are generally referred to as "biodiesel". That is, the crude mixture may specifically be, for example, biodiesel containing monoglycerides.

  The crude mixture may be hydrogenated. That is, the method of the present invention may include the step of hydrogenating the crude mixture. The same process is also called "hydrogenation process". The hydrogenation step may, in other words, be a step of hydrogenating the crude mixture to obtain a hydrogenated crude mixture. The term "crude mixture" may be used either before or after hydrogenation unless otherwise stated. The hydrogenation can be carried out specifically on fatty acid alkyl esters and / or monoglycerides or other components with unsaturated bonds. By hydrogenation, the degree of unsaturation of the constituent fatty acids of these components can be reduced. The hydrogenation can be carried out, for example, to obtain the composition of the crude mixture exemplified above. However, the crude mixture may have the above exemplified composition without the hydrogenation step. By reducing the degree of unsaturation of the constituent fatty acids of the fatty acid alkyl ester, the oxidation stability of the fatty acid alkyl ester can be enhanced. On the other hand, saturated fatty acid alkyl esters have higher melting points than unsaturated fatty acid alkyl esters, and may not be suitable for diesel fuel. Thus, the hydrogenation may, for example, be carried out such that the polyunsaturated fatty acid alkyl ester is converted to a monounsaturated fatty acid alkyl ester. Also, saturated fatty acid monoglycerides are easy to crystallize as compared to unsaturated fatty acid monoglycerides. Thus, hydrogenation may be performed, for example, such that unsaturated fatty acid monoglycerides are converted to saturated fatty acid monoglycerides. Specifically, hydrogenation may be carried out, for example, so that polyunsaturated fatty acid alkyl ester is converted to monounsaturated fatty acid alkyl ester, and unsaturated fatty acid monoglyceride is converted to saturated fatty acid monoglyceride. Good.

  Examples of the hydrogenation method include the methods described in WO 2011/105291 and WO 2015/133487. That is, the crude mixture is specifically brought into contact with a hydrogen atmosphere at a low hydrogen pressure, for example, in the coexistence of a hydrogenation catalyst containing a noble metal selected from Periodic Table Group 8-10 noble metals, It can be hydrogenated (WO2011 / 105291). Such noble metals include palladium (Pd), platinum (Pt), rhodium (Rh), iridium (Ir), rhenium (Re) and ruthenium (Ru). The hydrogen pressure may be, for example, 0.2 MPa or more, 1 MPa or less, 0.7 MPa or less, or 0.5 MPa or less in absolute pressure, or a combination thereof. The hydrogen pressure may be absolute pressure, specifically, for example, 0.2 to 0.7 MPa. The reaction temperature may be, for example, 80 to 130 ° C. In the above method, the presence of oxygen in the reaction system enables efficient and stable utilization of the hydrogenation catalyst (WO 2015/133487). The amount of oxygen to be present in the reaction system is, for example, 150 to 3500 ppm (mol / mol) with respect to the amount of crude mixture (for example, converted to the number of moles based on the average molecular weight of palm oil-derived biodiesel) It may be 300-2000 ppm (mol / mol), or 400-1500 ppm (mol / mol).

  The crude mixture may be added with light oil (ie, containing light oil). That is, the method of the present invention may include the step of adding light oil to the crude mixture. The term "crude mixture" may be used either before or after the addition of light oil, unless otherwise stated. Gas oil can be added to the crude mixture before or during the execution of step (A). "During implementation of step (A)" refers to a period from the start to the end of step (A). The amount of light oil added is, for example, 0.5 parts by volume or more, 0.7 parts by volume or more, 1 part by volume or more, 1.5 parts by volume, based on 1 part by volume of the crude mixture (before adding the light oil) Or more, or 2 parts or more, 33 parts or less, 20 parts or less, 15 parts or less, 10 parts or less, 5 parts or less, 2 parts or less, 1.5 parts or less, Alternatively, it may be 1 part by volume or less or a combination thereof. The addition amount of light oil is not particularly limited as long as the effects of the present invention are not impaired. The amount of light oil added is, for example, 0.5 to 33 parts by volume, 0.5 to 2 parts by volume, 1.5 parts by volume relative to 1 part by volume of the crude mixture (before adding the light oil). There may be ~ 33 parts by volume, 1.5 to 15 parts by volume, 1.5 to 5 parts by volume, 2 to 33 parts by volume, 2 to 15 parts by volume, or 2 to 5 parts by volume. Examples of light oil include general light oil that can be used for diesel engines. Specific examples of such a light oil include the No. 1 light oil, the No. 1 light oil, the No. 2 light oil, the No. 3 light oil, and the No. 3 light oil standardized by JIS K2204. By adding light oil, for example, it may be possible to lower the crystallization temperature while maintaining the crystallization efficiency of monoglycerides.

  The crude mixture may be seeded with monoglyceride seeds (ie, containing monoglyceride seeds). That is, the method of the present invention may include the step of adding monoglyceride seed crystals to the crude mixture. The term "crude mixture" may be used either before or after monoglyceride seeding, unless otherwise stated. Seed crystals of monoglyceride can be added to the crude mixture before or during the execution of step (A). Seed crystals of monoglyceride may, for example, be added to the crude mixture before crystallization of monoglyceride begins. The addition amount of monoglyceride seed crystals is not particularly limited as long as the effects of the present invention are not impaired. The amount of monoglyceride seed crystals added may be, for example, 1 to 10 mg based on 100 g of the crude mixture (prior to addition of monoglyceride seed crystals). Examples of monoglycerides constituting seed crystals include the monoglycerides exemplified above. The monoglyceride contained in the crude mixture and the monoglyceride constituting the seed crystals may or may not be the same.

  The method of the present invention comprises a stirring step (step (A)). Step (A) is carried out so as to precipitate monoglyceride. Step (A) can, in particular, be carried out in such a way that monoglycerides precipitate selectively. "Monoglyceride selectively precipitates" means that monoglycerides selectively precipitate as compared to fatty acid alkyl ester. The phrase "monoglyceride selectively precipitates" specifically refers to the precipitation of monoglyceride relative to the precipitation of fatty acid alkyl ester as compared to the ratio of the content of monoglyceride to the content of fatty acid alkyl ester in the crude mixture. It says that the ratio is high. The conditions (for example, the number of stirring, the crystallization temperature, the crystallization time) of step (A) are not particularly limited as long as the effects of the present invention are not impaired.

  Step (A) can be performed, for example, using a stirring device. Thus, for example, the crude mixture can be introduced into a stirring device and the crude mixture can be stirred. The stirring apparatus should just be comprised so that process (A) can be implemented on desired conditions. The stirring device may, for example, comprise a vessel (stirred tank) in which the stirring of the introduced crude mixture is carried out. The stirring device may also comprise means for stirring the crude mixture introduced. Such means include stirring blades. That is, the crude mixture can be agitated by giving motions such as rotation and movement to a stirring blade in contact with the crude mixture. The stirring device may also comprise means for controlling the temperature of the introduced crude mixture. Moreover, the stirring apparatus may be equipped with the means to scrape off the component which deposited on the wall surface of the stirring tank. Such means include scrapers. As a stirring apparatus, the crystallization apparatus provided with stirring means etc. is mentioned. As such a crystallizer, specifically, a scraper-type crystallizer (Tsukishima Kikai Co., Ltd.) can be mentioned.

  The degree of agitation in step (A) is not particularly limited, and a sufficient effect can be obtained if a flow occurs in the agitation tank (ie, if a flow occurs in the crude mixture).

Stirring speed in the step (A) (stirring speed), as a stirring power, for example, 5W / ^{m 3} or more, 7W / ^{m 3} or more, 10 W / ^{m 3} or more, 14W / ^{m 3} or more, 20W / ^{m 3} or more, 30 W / ^{m 3} or more, 50 W / ^{m 3} or more, 70 W / ^{m 3} or more, 100W / ^{m 3} or more, 150 W / ^{m 3} or more, 161W / ^{m 3} or more, 200 W / ^{m 3} or more, 250 W / ^{m 3} or more, or 300 W / It may also be m ³ or more, 1000W / ^{m 3} or less, 700 W / ^{m 3} or less, 500 W / ^{m 3} or less, 400W / ^{m 3} or less, 391W / ^{m 3} or less, 300 W / ^{m 3} or less, 250 W / ^{m 3} or less , 200 W / ^{m 3} or less, 150 W / ^{m 3} or less, 100W / ^{m 3} or less, 70 W / ^{m 3} or less, or 50 W / ^{m 3} may be less, or may be a combination of those not inconsistent. Stirring speed (stirring speed), as a stirring power, specifically, for ^example, at ^{5W / m 3 ~1000W / m 3} , 14W / m 3 ~391W / m 3 or ^{161W / m 3 ~391W / m 3} , It may be. In other words, the stirring power at the time of stirring in step (A) may be in the above range.

  The stirring number (stirring speed) in the step (A) is, for example, 0.2 m / s or more, 0.3 m / s or more, 0.4 m / s or more, 0.5 m / s or more, as the tip speed of the stirring blade. It may be 0.6 m / s or more, 0.7 m / s or more, 0.8 m / s or more, 0.9 m / s or more, 1 m / s or more, or 1.2 m / s or more, 3 m / s or less , 2.5 m / s or less, 2 m / s or less, 1.7 m / s or less, 1.4 m / s or less, 1.2 m / s or less, 1 m / s or less, 0.9 m / s or less, 0.8 m / s It may be s or less, or 0.7 m / s or less, or may be a consistent combination thereof. The stirring number (stirring speed) is, for example, 0.2 m / s to 3 m / s, 0.4 m / s to 1.4 m / s, or 0.9 m / s as the tip speed of the stirring blade. It may be -1.4 m / s. In other words, the tip speed of the stirring blade at the time of stirring in step (A) may be in the above range. In addition, the tip speed of a stirring blade means the speed of the largest diameter location around a circle at the time of assuming that the stirring blade was extended to the inner wall of a stirring tank. Further, the tip speed of the stirring blade may be read as the tip speed of the scraper in the case of using a stirring device provided with the scraper.

  The temperature of the step (A) (the temperature of the crude mixture at the time of performing the step (A); also referred to as "crystallization temperature") is, for example, 2 ° C or more, 3 ° C or more, 4 ° C or more, 5 ° C or more, 6 ° C Or more, 7 ° C or more, 8 ° C or more, 9 ° C or more, 10 ° C or more, 11 ° C or more, 12 ° C or more, 13 ° C or more, 14 ° C or more, 15 ° C or more, or 16 ° C or more, 20 ° C Below, 19 ° C. or less, 18 ° C. or less, 17 ° C. or less, 16 ° C. or less, 15 ° C. or less, 14 ° C. or less, 13 ° C. or less, 12 ° C. or less, 11 ° C. or less, 10 ° C. or less, 9 ° C. or less, 8 ° C. or less, It may be 7 ° C. or less, or 6 ° C. or less, or a combination thereof. The crystallization temperature can be set in consideration of, for example, the presence or absence of addition of light oil and the addition amount of light oil. That is, the crystallization temperature may be set low, for example, when light oil is added, or may be set lower as the amount of light oil added is larger. Specifically, the crystallization temperature may be, for example, 14 ° C. to 20 ° C., 14 ° C. to 19 ° C., 14 ° C. to 18 ° C., or 15 ° C. to 17 ° C. In particular, no light oil is added In this case, it may be in the relevant range. Moreover, specifically, the crystallization temperature is, for example, 5 ° C. to 15 ° C., 5 ° C. to 10 ° C., 5 ° C. to 9 ° C., 5 ° C. to 8 ° C., 5 ° C. to 7 ° C., 3 ° C. to 9 ° C. It may be 3 ° C. to 8 ° C., 3 ° C. to 7 ° C., or 3 ° C. to 6 ° C., and in particular, it may be in the above range when light oil is added. When the crystallization temperature is too low, fatty acid alkyl ester may precipitate, and when the crystallization temperature is too high, precipitation of monoglyceride may be insufficient. That is, for example, the crystallization temperature may be set low as long as the fatty acid alkyl ester does not precipitate.

  The time of the step (A) (the time from the start to the end of the step (A); also referred to as "crystallization time") is, for example, 0.5 hours or more, 1 hour or more, 1.5 hours or more, 2 hours or more , 2.5 hours or more, 3 hours or more, 3.5 hours or more, 4 hours or more, 4.5 hours or more, 5 hours or more, 5.5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, or 10 hours or more, 20 hours or less, 15 hours or less, 12 hours or less, 10 hours or less, 8 hours or less, 7 hours or less, 6 hours or less, 5.5 hours or less, 5 hours or less, or 4. It may be 5 hours or less, or may be a consistent combination thereof. The crystallization time may specifically be, for example, 0.5 hour to 20 hours, 0.5 hour to 10 hours, or 3 hours to 6 hours. If the crystallization time is too long, fatty acid alkyl ester may precipitate, and if the crystallization time is too short, precipitation of monoglyceride may be insufficient.

  The stirring may be performed continuously or intermittently. In other words, the stirring may be performed only once, or may be performed twice or more. In addition, after stirring starts until it stops, it is "one time." The conditions such as the number of stirring and the crystallization temperature may or may not be constant while the stirring is performed once. When stirring is performed intermittently (performed twice or more), conditions such as the number of stirring, crystallization temperature, stirring duration, etc. may or may not be the same each time . The number of stirring may be in the above range in the entire period of step (A), but may be in the above range only in a part of period of step (A) (that is, it may temporarily deviate from the above range Good). For example, the stirring may be temporarily performed with a stirring number outside the above range, or may be temporarily stopped. “The number of stirring (stirring speed) in step (A) is within a certain range (for example, the stirring power during stirring in step (A) or the tip speed of the stirring blade is within a certain range)” The stirring number is not limited to the case where the number of stirring is within the range in the entire period of A), and the number of stirring is within the range only during a part of the step (A) (ie, the number of stirring is temporarily outside the range Be included). Similarly, the crystallization temperature may be in the above range for the entire period of step (A), but may be in the above range for only a part of step (A) (ie, temporarily the above range You may lose it). For example, the step (A) may be started at a crystallization temperature outside the above range (for example, a crystallization temperature higher than the above range), and the crystallization temperature may reach the above range during the execution of the step (A). In addition, the crystallization temperature may be, for example, at least in the above range at the end of step (A). The crystallization temperature may be, for example, in the above-mentioned range at least from the start of crystallization of monoglyceride to the end of the step (A). “The temperature in the step (A) is in a certain range” is not limited to the case where the crystallization temperature is within the range in the entire period of the step (A), but only in a part of the step (A). Also included is the case where the crystallization temperature is within the range (ie, the crystallization temperature temporarily falls outside the range). The length and timing of the "partial period" or "temporary" mentioned here are not particularly limited as long as the effects of the present invention are not impaired. The “partial period” means, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 97% or more of the entire period of the step (A). Or the period may be 99% or more. The “partial period” means, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more of the period during which the stirring in step (A) is performed. , 97% or more, or 99% or more.

  As described above, the step (A) may include a period during which the stirring is stopped (also referred to as a "residence time") in addition to a period during which the stirring is carried out (also referred to as "stirring time") . Crystallization time = stirring time + residence time. In addition, when stirring is carried out intermittently (carried out twice or more), unless otherwise specified, "period in which stirring is carried out (stirring time)" is the total of periods in which stirring is carried out. The term "period in which stirring is stopped (residence time)" refers to the total of periods in which stirring is stopped. The stirring time is, for example, 0.5 hours or more, 1 hour or more, 1.5 hours or more, 2 hours or more, 2.5 hours or more, 3 hours or more, 3.5 hours or more, 4 hours or more, or 4.5 10 hours or less, 8 hours or less, 7 hours or less, 6 hours or less, 5.5 hours or less, 5 hours or less, or 4.5 hours or less, which do not contradict each other It may be a combination. The stirring time may specifically be, for example, 0.5 hour to 10 hours, or 3 hours to 6 hours. The residence time is, for example, 0 hours or more, 0.5 hours or more, 1 hour or more, 1.5 hours or more, 2 hours or more, 2.5 hours or more, 3 hours or more, 3.5 hours or more, 4 hours or more, Alternatively, it may be 4.5 hours or more, 10 hours or less, 8 hours or less, 7 hours or less, 6 hours or less, 5.5 hours or less, 5 hours or less, or 4.5 hours or less. There may be a consistent combination of them. Specifically, the residence time may be, for example, 0 to 10 hours.

  The method of the present invention comprises a removal step (step (B)). Step (B) can be carried out by means of solid-liquid separation. Such means include spontaneous sedimentation, centrifugation, filtration. For filtration, a suitable filter such as filter paper or filter membrane can be used. Alternatively, the removed monoglyceride may be washed and the resulting washing solution may be used. The washing solution contains a fatty acid alkyl ester. The cleaning solution can be used, for example, as a mixture with the product. After mixing, the medium used for washing can optionally be separated from the product. The medium used for washing is preferably one having a low monoglyceride solubility. Such media include methanol. In addition, monoglycerides such as monoglycerides after washing may be used. Monoglycerides can be used, for example, as fatty acid alkyl ester sources back to the raw materials of the transesterification step.

  Part or all of the process of the present invention can be carried out batchwise, semi-batchwise, continuously. For example, the crude mixture may be fed continuously to the stirring apparatus to carry out step (A), and the stirring material may be withdrawn continuously to be subjected to step (B).

  The method of the present invention may include the step of removing remaining monoglycerides from the crude mixture from which monoglycerides have been removed (the crude mixture after the implementation of step (B)). Residual monoglycerides can be removed, for example, using an adsorbent. Examples of the adsorbent include silica gel, clay minerals (such as activated clay and montmorillonite), zeolite, diatomaceous earth, magnesium silicate and alumina.

  By carrying out the method of the present invention in this manner, monoglycerides can be removed and a product (fatty acid alkyl ester) is obtained.

  The monoglyceride removal rate in the method of the present invention is, for example, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% The above may be 97% or more, or 99% or more.

The monoglyceride removal rate is calculated by the following formula:
Monoglyceride removal rate (%) = (concentration of monoglyceride in crude mixture-concentration of monoglyceride in product) / concentration of monoglyceride in crude mixture x 100

  The fatty acid alkyl ester yield in the method of the present invention may be, for example, 90% or more, 95% or more, 97% or more, or 99% or more.

The fatty acid alkyl ester yield is calculated by the following formula:
Fatty acid alkyl ester yield (%) = product weight after removal of monoglyceride (product weight) / weight of suspended crude mixture before removal of monoglyceride × 100

For example, when the step (B) is carried out by filtration, the fatty acid alkyl ester yield is calculated by the following formula:
Fatty acid alkyl ester yield (%) = filtrate weight after filtration (product weight) / suspended crude mixture weight before filtration × 100

  The product is, in other words, a fatty acid alkyl ester composition. The product may specifically be a fatty acid alkyl ester composition from which monoglycerides have been removed, and may be a fatty acid alkyl ester composition from which monoglyceride concentration has been reduced. The product may consist of fatty acid alkyl ester, and may further contain other components. Other ingredients include monoglycerides, diglycerides, triglycerides, glycerin, alcohols, water, salts.

  The content of monoglyceride in the product is, for example, 0.3% (w / w) or less, 0.25% (w / w) or less, 0.2% (w / w) or less based on the total amount of the product , 0.15% (w / w) or less, 0.1% (w / w) or less, 0.5% (w / w) or less, or zero. The content of monoglycerides in the product is, for example, 0.3% (w / w) or less, 0.25% (w / w) or less, 0.2% or less based on the content of fatty acid alkyl ester in the product (W / w) or less, 0.15% (w / w) or less, 0.1% (w / w) or less, 0.5% (w / w) or less, or zero. For the content of fatty acid alkyl ester in the product and the composition of fatty acid alkyl ester and monoglyceride (for example, types and abundance ratios of constituent fatty acids and alkyl groups), for example, the description of those in the crude mixture can be applied correspondingly.

  In addition, the content of each component in the product (for example, the range of the content described above or applied mutatis mutandis) is an external component such as light oil, in the case where it is added to the crude mixture or product, unless otherwise specified. The range converted into the content in the product when assuming that the component is not added is shown. That is, for example, when the method of the present invention is practiced by adding 2 parts by volume of light oil to 1 part by volume of the crude mixture, three times the actual content of each component in the product containing the light oil It may be within the range of the content.

  The monoglyceride removal rate and the fatty acid alkyl ester yield may be calculated by correcting the content (concentration) of each component according to the addition mode of the external component.

  The application of the product is not particularly limited. The product can be used, for example, as a diesel fuel. Specifically, the product can be used as a diesel fuel, for example, alone or in combination with a light oil.

  Hereinafter, the present invention will be more specifically described by way of examples.

<1>
In this example, crystallization is carried out while stirring partially hydrogenated (partially hydrogenated) biodiesel as a raw material under various conditions, residual concentration of monoglyceride (MG) and fatty acid methyl ester (partially hydrogenated) Yields of H-FAME) were compared. The crystallization was performed by indirect cooling using a separable flask. The partially hydrogenated biodiesel is obtained by partially hydrogenating palm oil-derived biodiesel (obtained from PTT and Bangchak Petroleum) according to the method described in Japanese Patent No. 5756972. Specifically, hydrogenation was carried out using a 0.5 wt% Pd alumina support catalyst under a pressure of 1.0 MPaG, a temperature of 100 ° C., a WHSV of 24 hr ⁻¹ , and an H ₂ / diene ratio of 2.2 mol / mol. Partially hydrogenated biodiesel contains fatty acid methyl ester, C14: 0: 1.2 wt%, C16: 0: 43.2 wt%, C18: 2: 1.7 wt%, C18: 1: 43.4 wt%, C18: 0: 9.4 wt%, others (including C12: 0, C20: 0, C20: 1, C22: 0, C24: 0): 1 wt% or less. The partially hydrogenated biodiesel contained 0.49 wt% of monoglyceride, 0.13 wt% of diglyceride, 0.06 wt% of triglyceride, and 0.05 wt% of glycerin.

(Test Example 1)
Crystallization is performed by adding several mg of monoglyceride as seed crystals to 100 g of partially hydrogenated biodiesel at normal temperature with a crystallization temperature of 15 ° C., stirring power of 161 W / m ³ , and a crystallization time of 6 hours. Thereafter, the mother liquor was subjected to suction filtration using a membrane filter with a pore size of 3 μm and a diameter of 90 mm. As a result, the monoglyceride concentration of the filtrate was 0.20 wt%, and the fatty acid methyl ester yield was 97%. Stirring was continued for a crystallization time with a predetermined stirring power (the same applies to the following test examples). In addition, the stirring was started at 40 ° C., and the temperature reached a predetermined crystallization temperature during the stirring (the same applies to the following test examples).

(Test Example 2)
Crystallization is carried out by adding several mg of monoglycerides as seed crystals to 100 g of partially hydrogenated Biodiesel at normal pressure with a crystallization temperature of 17 ° C., stirring power of 161 W / m ³ , and a crystallization time of 3 hours, As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.18 wt%, and the yield of fatty acid methyl ester was 98%.

(Test Example 3)
Crystallization is performed by adding several mg of monoglyceride as seed crystals to 100 g of partially hydrogenated biodiesel at normal pressure with a crystallization temperature of 17 ° C., stirring power of 14 W / m ³ , and a crystallization time of 6 hours, As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.20 wt%, and the yield of fatty acid methyl ester was 98%.

(Test Example 4)
Crystallization is performed by adding several mg of monoglyceride as seed crystals to 100 g of partially hydrogenated Biodiesel at normal pressure with a crystallization temperature of 17 ° C., stirring power of 391 W / m ³ , and a crystallization time of 6 hours, As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.18 wt%, and the fatty acid methyl ester yield was 97%.

Test Example 5
Crystallization is performed by adding several mg of monoglyceride as seed crystals to 100 g of partially hydrogenated biodiesel at normal pressure with a crystallization temperature of 17 ° C., stirring power of 161 W / m ³ , and a crystallization time of 6 hours, As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.18 wt%, and the yield of fatty acid methyl ester was 98%.

(Test Example 6)
Crystallization is performed by adding several mg of monoglycerides as seed crystals to 100 g of partially hydrogenated biodiesel at normal pressure with a crystallization temperature of 17 ° C., a stirring power of 161 W / m ³ , and a crystallization time of 9 hours. As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.18 wt%, and the fatty acid methyl ester yield was 97%.

Test Example 7
Crystallization is performed by adding several mg of monoglycerides as seed crystals to 100 g of partially hydrogenated biodiesel at normal pressure with a crystallization temperature of 13 ° C., stirring power of 161 W / m ³ , and a crystallization time of 6 hours. As a result of suction filtration of the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.18 wt%, and the fatty acid methyl ester yield was 43%.

Test Example 8
Crystallization is performed by adding several mg of monoglycerides as seed crystals to 100 g of partially hydrogenated biodiesel at normal pressure with a crystallization temperature of 17 ° C., a stirring power of 161 W / m ³ , and a crystallization time of 1 hour. As a result of suction-filtering the mother liquor using a membrane filter with a pore size of 3 μm and a diameter of 90 mm, the monoglyceride concentration of the filtrate was 0.33 wt%, and the fatty acid methyl ester yield was 99%.

(Test Example 9)
Crystallization temperature 17 ° C, no stirring, crystallization time 6 hours, under normal pressure, 100 mg of partially hydrogenated biodiesel is crystallized by adding several mg of monoglyceride as a seed crystal in advance, and then pore diameter 3 μm, diameter The mother liquor is suction filtered using a 90 mm membrane filter.

  The results are shown in Table 1 and FIGS. In any case of Test Examples 1 to 8, monoglyceride could be crystallized and removed. In particular, in the test examples 1 to 6, the monoglyceride concentration could be reduced to 0.18 to 0.20 wt%, and the yield of fatty acid methyl ester could be maintained as high as 97 to 98%. On the other hand, in Test Example 7, although the monoglyceride concentration could be sufficiently reduced, the yield of fatty acid methyl ester was lower than in the other Test Examples. It is considered that this is because fatty acid methyl ester is also crystallized because of low temperature. In addition, in Test Example 8, the yield of fatty acid methyl ester was sufficiently high, but the monoglyceride concentration was higher than in the other test examples. It is considered that this is because the crystallization time of monoglyceride was insufficient because the crystallization time was short.

<2>
In this example, light oil is added to partially hydrogenated (partially hydrogenated) biodiesel and crystallization is carried out with stirring under various conditions, and residual concentration of monoglyceride (MG) and fatty acid methyl ester (partial The yields of hydrogenated; H-FAME) were compared. The crystallization was performed by indirect cooling using a separable flask. The partially hydrogenated biodiesel is obtained by partially hydrogenating the palm oil-derived biodiesel in the same manner as in Example <1> except that the temperature of hydrogenation is set to 80 ° C. The partially hydrogenated biodiesel contained 0.45 wt% of monoglyceride.

Test Example 10
70 parts by volume of No. 1 light oil was mixed with 30 parts by volume of partially hydrogenated biodiesel to prepare a light oil-containing biodiesel. Crystallization is performed by adding several mg of monoglyceride to be seed crystals beforehand to 100 g of light oil-containing biodiesel at normal temperature with a crystallization temperature of 5 ° C., stirring power of 161 W / m ³ , and a crystallization time of 6 hours. As a result of suction filtration of the mother liquor using a membrane filter of 3 μm and diameter 90 mm, the monoglyceride concentration of the filtrate is 0.08 wt% (0.27 wt% in terms of concentration in biodiesel before light oil mixing), fatty acid methyl ester yield is 98.9 It was wt%. Stirring was continued for a crystallization time with a predetermined stirring power (the same applies to the following test examples). In addition, the stirring was started at 40 ° C., and the temperature reached a predetermined crystallization temperature during the stirring (the same applies to the following test examples).

(Test Example 11)
A light oil-containing biodiesel was prepared by mixing 50 parts by volume of No. 1 light oil with 50 parts by volume of partially hydrogenated biodiesel. Crystallization is performed by adding several mg of monoglyceride to be a seed crystal to 100 g of light oil-containing biodiesel in a crystallization temperature of 10 ° C., stirring power of 161 W / m ³ and crystallization time of 6 hours under normal pressure. As a result of suction filtration of the mother liquor using a membrane filter of 3 μm and diameter 90 mm, the monoglyceride concentration of the filtrate is 0.21 wt% (0.42 wt% converted to the concentration in biodiesel before light oil mixing), fatty acid methyl ester yield is 98.7 It was wt%.

  The results are shown in Table 2. In the table, "raw material" refers to biodiesel before mixing with light oil. In addition, in the table, the data of Test Example 8 is a repeat of the data obtained in Example <1>. In Test Example 10, the yield of fatty acid methyl ester was sufficiently high, and the monoglyceride concentration was sufficiently reduced. On the other hand, in Test Example 11, although the yield of fatty acid methyl ester was sufficiently high, the monoglyceride concentration was high. It is considered that this is because monoglyceride dissolved and remained in light oil due to the high crystallization temperature.

  According to the present invention, monoglycerides in fatty acid alkyl ester compositions such as biodiesel can be removed.

Claims (14)

A method for producing a fatty acid alkyl ester, comprising
Method comprising the following steps (A) and (B):
(A) stirring the mixture containing fatty acid alkyl ester and monoglyceride to precipitate the monoglyceride;
(B) removing the precipitated monoglyceride from the mixture. Stirring power during agitation in the step (A) is a ^{5W / m 3 ~1000W / m 3} , The method of claim 1.   The method according to claim 1 or 2, wherein the tip speed of the stirring blade at the time of stirring in the step (A) is 0.2 m / s to 3.0 m / s.   The method according to any one of claims 1 to 3, wherein the temperature of the step (A) is 14 ° C to 20 ° C.   The method according to any one of claims 1 to 4, wherein the time of the step (A) is 0.5 hours to 20 hours.   The method according to any one of claims 1 to 5, wherein a period during which the stirring in the step (A) is carried out is 0.5 hours to 10 hours.   The method according to any one of claims 1 to 6, wherein the period during which the stirring in the step (A) is stopped is 0 hour to 10 hours.   The method according to any one of claims 1 to 7, wherein the fatty acid alkyl ester is a fatty acid methyl ester.   The method according to any one of the preceding claims, further comprising the step of hydrogenating the mixture prior to performing step (A).   The method according to any one of claims 1 to 9, further comprising the step of adding monoglyceride seed crystals to the mixture before or during the step (A).   The method according to any one of claims 1 to 10, further comprising the step of adding light oil to the mixture before or during the step (A).   The method according to any one of claims 1 to 11, further comprising the step of removing the monoglyceride remaining in the mixture using an adsorbent after carrying out the step (B). The stirring power during the stirring in the step (A) ^is a ^{14W / m 3 ~391W / m 3} , The method according to any one of claims 1 to 12.   The method according to any one of claims 1 to 13, wherein the tip speed of the stirring blade at the time of stirring in the step (A) is 0.4 m / s to 1.4 m / s.