Method for producing biofuel and method for improving methyl esterification efficiency of tamanu oil

Abstract

The present invention provides a method for producing a biofuel, the method including: (a) a tamanu oil purification step which comprises a deoxidization step for deoxidizing a crude oil of a tamanu oil, wherein the absorbance of the refined tamanu oil at the wavelength of 330 nm is 0.08 or less; and (b) a methyl esterification step in which methanol is added to the refined tamanu oil so as to produce a fatty acid methyl ester (FAME) by a transesterification reaction. The present invention also provides a method for improving the methyl esterification efficiency of a tamanu oil.

Description

Method for producing biofuel and method for improving methyl esterification efficiency of Calophyllum indicum oil

[0001] The present invention relates to a method for producing biofuel and a method for improving the efficiency of methyl esterification of Calophyllum indicum oil.

[0002] In recent years, the world has been facing an energy crisis due to the depletion of fossil fuels and worsening environmental problems. Under these circumstances, biofuels derived from sustainable biomass resources have attracted attention as a means of diversifying energy sources and reducing carbon emissions, and research and development efforts are being actively conducted toward their widespread adoption. Non-edible oil resources grow in many parts of the world, especially in wastelands unsuitable for the cultivation of food crops. The use of non-edible oil resources for biofuel production reduces the use of food crops and leads to reduced competition in the food market. Calophyllum indicum is widely cultivated in tropical and subtropical regions around the world and is abundantly available. Calophyllum indicum oil, obtained from its seeds, is used as an ingredient in traditional medicines and cosmetics and is also known for its high calorific value and large oil yield. Patent Document 1 describes a method for producing biodiesel using calophyllum indicum oil as a raw material. The document describes pretreatment of calophyllum indicum oil with toluene followed by methyl esterification.

[0003] Australian Patent Application Publication No. 2011200655

[0004] It is desirable to provide a method for efficiently producing biofuel using non-edible oil resources while reducing the environmental impact.

[0005] The present invention encompasses the following aspects and embodiments. [1] A method for producing a biofuel, comprising: (a) a refining step of caltrop oil, including a deacidification step of deacidifying a crude caltrop oil, wherein the refined caltrop oil has an absorbance at a wavelength of 330 nm of 0.08 or less; and (b) a methyl esterification step of adding methanol to the refined caltrop oil to produce fatty acid methyl esters (FAME) by a transesterification reaction. [2] The biofuel production method according to [1], wherein the deacidification step includes a deacidification treatment using an alkaline aqueous solution by an alkaline deacidification method, and wherein the addition ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the crude caltrop oil is 0.6 to 1.2. [3] The biofuel production method according to [1] or [2], wherein the methyl esterification step produces fatty acid methyl esters by a transesterification reaction in the presence of an alkali metal catalyst. [4] The method for producing a biofuel according to any one of [1] to [3], wherein the content of pyranocoumarins in the Calophyllum indicum oil refined in the refining step is 18 mass% or less based on the mass of the refined Calophyllum indicum oil. [5] The method for producing a biofuel according to any one of [1] to [4], wherein the biofuel is a biodiesel fuel. [6] The method for producing a biofuel according to [5], wherein the content of fatty acid methyl esters in the biodiesel fuel is 96.5 mass% or more. [7] A method for improving the methyl esterification efficiency of caltrop oil, comprising: (a) a refining step of caltrop oil, including a deacidification step of deacidifying crude caltrop oil, wherein the refined caltrop oil has an absorbance of 0.08 or less at a wavelength of 330 nm; and (b) a methyl esterification step of adding methanol to the refined caltrop oil to produce fatty acid methyl esters (FAME) by a transesterification reaction.[8] The method for improving the methyl esterification efficiency of caltropic oil according to [7], wherein the deacidification step includes deacidification treatment by an alkaline deacidification method using an alkaline aqueous solution, and the addition ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the crude caltropic oil is 0.6 to 1.2. [9] The method for improving the methyl esterification efficiency of caltropic oil according to [7] or [8], wherein the methyl esterification step produces fatty acid methyl esters by a transesterification reaction in the presence of an alkali metal catalyst.

[10] The method for improving the methyl esterification efficiency of caltropic oil according to any one of [7] to [9], wherein the content of pyranocoumarins in the caltropic oil refined in the refining step is 18% by mass or less based on the mass of the refined caltropic oil.

[0006] According to the present invention, biofuel can be efficiently produced from crude Calophyllum indicum oil while reducing the environmental impact. Since the present invention uses non-edible oil resources, it is possible to provide sustainable biofuel without competing with the food market.

[0007] 1 is a graph showing a calibration curve used for quantitative analysis of pyranocoumarins in Calophyllum indicum oil obtained in an example.

[0008] The present invention will be specifically described below.

[0009] The present inventors attempted to remove impurities and the like contained in crude calcite oil by subjecting crude calcite oil to a refining process used for edible oil resources, which has a smaller environmental impact than conventional techniques. After various investigations, the present inventors discovered that deacidification can effectively remove components contained in crude calcite oil that inhibit the methyl esterification reaction of calcite oil, thereby allowing the subsequent methyl esterification reaction to proceed efficiently, thereby completing the present invention. Specifically, the present invention provides a method for producing biofuel, which includes: (a) a refining process for calcite oil, including a deacidification process for deacidifying crude calcite oil, wherein the refined calcite oil has an absorbance at a wavelength of 330 nm of 0.08 or less; and (b) a methyl esterification process for adding methanol to the refined calcite oil and producing fatty acid methyl esters (FAME) by transesterification.

[0010] Calophyllum inophyllum oil, the raw material fat for the biofuel used in the present invention, is a non-edible oil derived from the seeds of Calophyllum inophyllum. Calophyllum inophyllum (scientific name: Calophyllum inophyllum L.) is an evergreen tree of the Calophyllum family. It is native to tropical coastal regions from the Indian Ocean to the Pacific Ocean (from Madagascar to India, the Marquesas Islands in Polynesia), the Northern Mariana Islands, the Okinawa Islands, and other areas, and is widely cultivated in tropical and subtropical regions. Calophyllum inophyllum produces approximately 20 to 100 kg of fruit per tree per year, and the seeds contain 50 to 70% oil by mass. It is said that 1 to 10 kg of oil can be extracted from a mature tree per year (see "Tamanu Oil (Callophyllum inophyllum Seed Oil)" by BFPRO (Forest Business Database for Developing Countries) https: / / jifpro.or.jp / bfpro / product / 1334 / ).

[0011] The crude oil of Calophyllum indicum used in the present invention is not limited, and may be a pressed oil obtained by pressing Calophyllum indicum seeds, or an extracted oil obtained by extracting Calophyllum indicum seeds. Alternatively, a mixture of pressed oil and extracted oil may be used as the crude oil. The pressing method is not limited, and may be, for example, an expeller-type press comprising a cylindrical casing and a rotatable screw mounted therein. The extraction method is not limited, and may be, for example, by contacting a solvent with the residue obtained after pressing or pressing Calophyllum indicum seeds, and then distilling off the solvent from the resulting solution to obtain an oil.

[0012] Each step will be described below.

[0013] (a) Refining Step The refining step is a step of removing impurities and the like contained in crude calendula oil. The refining step of the present invention includes at least a deacidification step of deacidifying crude calendula oil. By performing the deacidification step, phospholipids, free fatty acids, trace metals, and the like contained in crude calendula oil can be removed. Furthermore, by performing the deacidification step, components that inhibit the methyl esterification reaction contained in the crude calendula oil can be effectively removed. When the absorbance at a wavelength of 330 nm of the refined calendula oil is 0.08 or less, components that inhibit the methyl esterification reaction can be sufficiently removed. The refining step may consist solely of a deacidification step. Although the crude calendula oil can be sufficiently refined with the deacidification step alone, other refining steps may be combined within a range that does not impair the object of the present invention.

[0014] [Deacidification Step] The deacidification step is not limited, but is preferably performed by an alkaline deacidification method using an alkaline aqueous solution. For example, the deacidification step can be performed by treating the crude oil with an aqueous solution of an alkaline substance dissolved in water. Examples of alkaline substances include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and sodium bicarbonate. Among these, sodium hydroxide and potassium hydroxide are preferred. A single alkaline substance may be used, or two or more may be used in combination. The amount of alkaline substance added is preferably 0.6 to 1.2, more preferably 0.6 to 1.1, and even more preferably 0.6 to 1.0, relative to the neutralization equivalent of the acidic substance contained in the crude Calophyllum indicum oil. If the alkaline substance addition ratio is too low, impurities may not be sufficiently removed. Furthermore, if it exceeds 1.2, the yield may be easily reduced due to the saponification reaction. The water used in the alkaline aqueous solution is not limited, but purified water is preferred.

[0015] In one embodiment, the deacidification step can be carried out by stirring a mixture containing a crude caltrop oil and an aqueous alkali solution, followed by separating and removing the aqueous layer. The deacidification step can be carried out either batchwise or continuously. The stirring method can be appropriately selected depending on the reaction treatment method, the type of reactor, etc., and known stirring methods can be applied. Stirring is preferably carried out under heating, for example, at a temperature of 60°C or higher and 100°C or lower, preferably 70°C or higher and 90°C or lower. The stirring time may be within a range that sufficiently removes impurities contained in the crude caltrop oil, and those skilled in the art can appropriately select the stirring time depending on the reaction treatment method, the type of reactor, etc. For example, in a batch-type deacidification step, the stirring time can be appropriately selected, approximately 30 to 60 minutes as a guide. After stirring, centrifugation or the like is performed as needed to separate and remove the aqueous layer. Water is added to the oil layer as needed, and the mixture is stirred and washed with water, and the aqueous layer is then removed. The water washing is preferably carried out under heating, for example, by heating the oil layer to 70°C or higher and 110°C or lower, preferably 80°C or higher and 100°C or lower, and then adding water. If necessary, the water washing may be repeated several times. Thereafter, the oil layer is dried under reduced pressure or the like to remove moisture, if necessary.

[0016] In the deacidification step, as necessary, a pretreatment may be performed by adding an aqueous solution of an acid selected from organic acids such as oxalic acid, citric acid, and phosphoric acid, and inorganic acids, to the crude oil and stirring the mixture. This allows the gums contained in the crude oil to be removed together during the deacidification step. It is not necessary to remove the aqueous acid solution; deacidification can be performed by directly adding an aqueous alkali solution. Regarding the amount of acid added, for example, the ratio of the acid to the phosphorus content (phospholipids) contained in the crude caltrop oil is preferably 1.0 to 2.0, more preferably 1.0 to 1.7, and even more preferably 1.0 to 1.5. A ratio less than 1.0 may result in insufficient removal of phosphorus. Furthermore, a ratio exceeding 2.0 may increase the amount of alkali required for neutralization, thereby increasing the refining load. Alternatively, the amount of acid added is preferably 0.03 to 0.15% by mass, more preferably 0.03 to 0.12% by mass, and even more preferably 0.03 to 0.10% by mass, relative to the mass of the crude caltrop oil. If the concentration is less than 0.03% by mass, phosphorus removal may be insufficient. If the concentration is more than 0.15% by mass, the amount of alkali required for neutralization may increase, which may increase the purification load. The water used for the aqueous acid solution is not limited, but purified water is preferred.

[0017] The free fatty acids contained in the crude oil are converted into soap by the alkaline aqueous solution. By removing the soap, the free fatty acids can be removed from the crude oil. Furthermore, the deacidification step can remove phospholipids, trace metals, etc., and can also effectively remove components that inhibit the methyl esterification reaction contained in the crude oil of Calophyllum indicum oil. This can also improve the efficiency of the subsequent hydrogenation reaction.

[0018] The refining step of the present invention may be combined with other refining steps as needed in addition to the deacidification step. Specifically, it may include one or more other refining treatments used for edible oil resources, such as a degumming step, a bleaching step, and a deodorizing step.

[0019] [Bleaching Step] The bleaching step is a step of removing pigments contained in crude oil. The bleaching step is not limited, but can be carried out by, for example, adsorbing the pigments onto activated clay, activated carbon, silica (silicon dioxide), etc. The activated clay or the like to which the pigments are attached is removed, for example, by vacuum filtration, etc.

[0020] [Degumming Process] The degumming process is a process for hydrating and removing gums, mainly composed of phospholipids, contained in crude oil. The degumming process is not limited, but can be carried out, for example, by adding steam or water to the crude oil, stirring, and removing the aqueous layer. The degumming process may also be carried out by adding a degumming agent. The degumming agent may be, for example, an aqueous solution of an organic acid such as oxalic acid, citric acid, or phosphoric acid.

[0021] [Deodorization Step] The deodorization step is a step of removing odorous components contained in the crude oil. The deodorization step is not limited, but can be carried out, for example, by steam distillation under reduced pressure.

[0022] The degumming step, bleaching step, and deodorizing step may be any step generally used in the refining process of edible oil resources. When the degumming step, bleaching step, and deodorizing step are performed in addition to the deacidification step, it is preferable to perform the steps in the following order, as in the refining process of edible oil resources. In this case, any one of the degumming step, bleaching step, and deodorizing step may be omitted, and it is preferable to omit the degumming step.

[0023] The acid value of the Calophyllum indicum oil refined in the refining step is, for example, 40 or less, preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0024] Crude Calophyllum oil contains various impurities, such as phenols, flavonoids, and pyranocoumarins. Among these, pyranocoumarins are likely to inhibit the methyl esterification reaction and the subsequent hydrogenation reaction, and it is therefore preferable to remove as many pyranocoumarins as possible during the refining process. Here, "pyranocoumarins" refers to a group of compounds including inocalophilin A, inocalophilin B, inophyllum C, inophyllum E, inophyllum P, inophyllum D, calophyllolide, calanolide GUT70, calanolide A, calanolide B, epicalanolide C, 12-oxocalanolide A, calanolide D, (-)-tamanolide D, (-)-tamanolide P, and tamanolide. In the present invention, the pyranocoumarins in the calico oil refined in the refining step are preferably 18% by mass or less, more preferably 16% by mass or less, even more preferably 10% by mass or less, even more preferably less than 9% by mass, still more preferably 8% by mass or less, particularly preferably 7% by mass or less, and especially preferably 6% by mass or less, based on the mass of the refined calico oil. The lower limit is not particularly limited, but some pyranocoumarins may remain, for example, 0.1% by mass or more. The content of pyranocoumarins in the refined calico oil can be measured by the method described in the Examples.

[0025] As described above, in the present invention, the purification step includes at least a deacidification step as part of the purification treatment, thereby making it possible to remove impurities and to efficiently proceed with the subsequent methyl esterification step.

[0026] In the present invention, by setting the amount or addition ratio of the alkaline substance in the deacidification step within an appropriate range, the purification step can be carried out so that the purified caltrop oil has an absorbance of 0.08 or less at a wavelength of 330 nm. When the purified caltrop oil has an absorbance of 0.08 or less at a wavelength of 330 nm, the subsequent methyl esterification reaction proceeds efficiently. The purified caltrop oil has an absorbance of preferably 0.075 or less at a wavelength of 330 nm, more preferably 0.070 or less, and even more preferably 0.065 or less. When the absorbance at a wavelength of 330 nm is within the above range, the methyl esterification efficiency in the methyl esterification step can be improved.

[0027] (b) Methyl Esterification Step In the methyl esterification step, methanol is added to the Calophyllum indicum oil refined in the refining step, and fatty acid methyl esters (FAME) are produced by a transesterification reaction (methanolysis). The transesterification reaction of fats and oils with alcohol is a known reaction, and a commonly known method can be used in the present invention.

[0028] In the present invention, the methyl esterification step is preferably carried out in the presence of a basic catalyst. Examples of the basic catalyst that can be used include alkali metal catalysts, alkaline earth metal catalysts, and amine-based ion exchange resins. Among these, alkali metal catalysts are preferred due to their high catalytic activity. Examples of alkali metal catalysts include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates; alkali metals; and alkali metal oxides. These catalysts may be used alone or in combination of two or more. Among these, sodium hydroxide and potassium hydroxide are preferred, with potassium hydroxide being particularly preferred. The amount of the basic catalyst used is preferably 0.5% by mass or more and 3.0% by mass or less, more preferably 1.0% by mass or more and 2.5% by mass or less, and even more preferably 1.0% by mass or more and 2.0% by mass or less, relative to the mass of the substrate.

[0029] In one embodiment of the present invention, an acid catalyst may be used together with a basic catalyst. By adding methanol and an acid catalyst to the purified caltrop oil and allowing the reaction to proceed, protons coordinate to the carbonyl groups of the caltrop oil, thereby increasing the electrophilicity of the carbonyl groups. Subsequently, by adding methanol and a basic catalyst and allowing the reaction to proceed, the transesterification reaction can be carried out more efficiently. Examples of acid catalysts that can be selected include inorganic acids such as sulfuric acid and phosphoric acid; inorganic oxides such as tin oxide and zinc oxide; alcoholates such as titanium tetrapropoxide; and cation exchange resins. The amount of acid catalyst used is preferably 0.05% by mass to 3.0% by mass, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.1% by mass to 1.5% by mass, based on the mass of the substrate.

[0030] The methyl esterification step is preferably carried out in the presence of a solvent. The solvent that can be used may be methanol alone or a mixed solvent of methanol and another solvent. For example, by using not only methanol as the solvent but also tetrahydrofuran as a co-solvent, the purified Calophyllum chinense oil, which is the substrate, can be uniformly dissolved in the reaction system, and the reactivity may be further enhanced.

[0031] The methyl esterification step can be carried out either batchwise or continuously. The stirring method can be appropriately selected depending on the reaction treatment method, the type of reactor, etc., and known stirring methods can be used. Stirring is preferably carried out under heating, for example, at a temperature of 25°C or higher and 80°C or lower, preferably 30°C or higher and 70°C or lower, and more preferably 40°C or higher and 65°C or lower. Stirring may also be carried out under pressure. Those skilled in the art can also select preferred temperatures and pressures depending on the desired reaction time, etc. The stirring time may be within a range that allows the transesterification reaction to proceed sufficiently, and those skilled in the art can select the stirring time appropriately depending on the reaction treatment method, the type of reactor, etc. For example, when carried out in a batchwise manner, the stirring time can be appropriately selected, with approximately 30 to 60 minutes as a guideline.

[0032] The methyl esterification step is generally carried out in a stirred tank in a batchwise manner. However, because the transesterification reaction carried out in the presence of a basic catalyst proceeds relatively easily, the reaction can also be carried out continuously in a flow-through manner, such as a fixed-bed method in which the purified Calophyllum indicum oil and methanol are circulated countercurrently or cocurrently through a catalyst bed, or a fluidized-bed method in which a solid catalyst is fluidized. After completion of the reaction, unreacted methanol is separated from the reaction solution discharged from the reactor by vacuum distillation or the like, and the by-product glycerin, water, and catalyst residue that have phase-separated from the fatty acid methyl esters (FAME) are separated by decantation, centrifugation, solvent, or the like, to recover the fatty acid methyl esters. Water washing may be carried out by adding water to the oil layer and stirring, as needed. The water washing is preferably carried out under heated conditions, for example, by heating the oil layer to 40°C or higher and 80°C or lower, preferably 50°C or higher and 70°C or lower, and then adding water. Water washing may be repeated several times as needed. Subsequently, water may be removed by vacuum drying or the like, as needed, to obtain the fatty acid methyl esters (FAME).

[0033] The resulting fatty acid methyl esters (FAMEs) can be used as biodiesel fuels as they are, or, if necessary, can be subjected to hydrotreating or other processes to produce biofuels such as hydrogenated vegetable oil (HVO) or sustainable aviation fuel (SAF).

[0034] (c) Hydrogenation Step In the hydrogenation step, it is preferable to carry out hydrogenation treatment by adding hydrogen in an amount that saturates the unsaturated moieties in the methyl ester.

[0035] The hydrogenation step is preferably carried out in the presence of a catalyst.

[0036] The catalyst preferably contains one or more metals selected from Groups 7 to 10 of the periodic table, and more preferably contains one or more metals selected from the group consisting of iridium, palladium, platinum, rhenium, rhodium, ruthenium, and nickel. The metal may be supported on a catalyst support. The amount of the metal supported is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and even more preferably 3% by mass or more and 5% by mass or less, based on the mass of the catalyst support.

[0037] The catalyst support is not particularly limited as long as it is a solid inert material capable of supporting the catalyst metal. Examples include metal oxides (e.g., silica, alumina, zeolite, titania, etc.) and activated carbon. The catalyst support can be used in the form of powder, granules, pellets, etc.

[0038] The catalyst can be prepared by impregnation. For example, a hydrochloric acid solution of a metal chloride is added to a catalyst carrier in advance so that a predetermined amount is supported, and after stirring, the mixture is dried at about 60°C to 80°C for about 1 to 3 hours, further dried at about 90°C to 110°C for about 5 to 24 hours, and after drying, calcined at about 400°C to 600°C for about 3 to 4 hours. The metal chloride is not limited as long as it contains the above metal. For example, ruthenium chloride (RuCl ３ ・3H ２ O), rhodium chloride (RhCl ３ ・3H ２ O), palladium chloride (PdCl ２ ), chloroiridic acid (H ２ IrCl ６ ), chloroplatinic acid (H ２ PtCl ６ ) etc.

[0039] The amount of catalyst (including the metal and catalyst support) used is preferably 3% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 20% by mass or less, based on the mass of the substrate.

[0040] The catalyst may optionally contain one or more promoters. It is more preferable that the promoter contains one or more metals selected from Groups 6 to 10 of the periodic table. The promoter can be provided in the form of a salt or an acid, for example, as an oxyanion such as perrhenic acid, molybdic acid, or tungstic acid. The promoter may be supported on a catalyst support, or may be further supported on a support on which the catalytic metal is supported. The amount of the supported metal, expressed as a molar ratio to the catalytic metal, is preferably 0.25 to 10, more preferably 0.5 to 6, and even more preferably 1 to 4. The promoter can be supported on the catalyst support by impregnation, similar to the catalytic metal. For example, the catalyst can be prepared by adding an aqueous solution of the co-catalyst to the catalyst support in advance so that the predetermined loading amount is achieved, stirring, followed by drying at about 60° C. or higher and 80° C. or lower for about 1 to 3 hours, further drying at about 90° C. or higher and 110° C. or lower for about 5 to 24 hours, and, after drying, calcining at about 400° C. or higher and 600° C. or lower for about 3 to 4 hours. Alternatively, when a co-catalyst is further supported on the support on which the catalytic metal is supported, the catalyst can be prepared by adding an aqueous solution of the co-catalyst to the support on which the catalyst is supported in advance so that the predetermined loading amount is achieved, stirring, followed by drying at about 60° C. or higher and 80° C. or lower for about 1 to 3 hours, further drying at about 90° C. or higher and 110° C. or lower for about 5 to 24 hours, and, after drying, calcining at about 400° C. or higher and 600° C. or lower for about 3 to 4 hours.

[0041] The above description is merely an example, and a person skilled in the art can appropriately select the types, combinations, amounts of the catalyst, co-catalyst and catalyst support, preparation methods, etc. in order to optimize the hydrogenation reaction.

[0042] The hydrogenation step can be carried out in the presence or absence of a solvent. When a solvent is used, any solvent commonly used in hydrogenation reactions can be used. For example, C ５ ~C １２ Hydrocarbon solvents, such as hexane, cyclohexane, dodecane; ４ ~C ８ Ethers, such as tetrahydrofuran, methyl t-butyl ether; ４ ~C １０Esters, for example, ethyl acetate; chlorinated C １ ~C ２ Hydrocarbons, for example, dichloromethane; ２ ~C ６ Examples of suitable solvents include primary or secondary alcohols, such as isopropanol and ethanol, and other polar solvents, such as dimethylformamide, acetonitrile, dimethyl sulfoxide, and acetone, or mixtures thereof. Those skilled in the art can select an appropriate solvent to optimize the hydrogenation reaction in each case depending on the type of catalyst, etc.

[0043] In the hydrogenation step of the present invention, the hydrogenation treatment is carried out at a pressure of 0.1 MPa to 30 MPa. ２ It is preferred to carry out the reaction at a pressure of 0.5 MPa to 3 MPa, more preferably 0.5 MPa to 2.5 MPa, particularly preferably 1 MPa to 2.5 MPa, or if necessary even higher pressures, which are preferred. Those skilled in the art can also adjust the pressure depending on the catalyst loaded and on the dilution of the substrate in the solvent.

[0044] The temperature at which the hydrogenation treatment is carried out is preferably 50° C. to 300° C., more preferably 100° C. to 200° C., and even more preferably 150° C. to 200° C. Those skilled in the art can select a preferred temperature depending on the desired reaction time, etc.

[0045] The hydrogenation step is preferably carried out in an atmosphere consisting of only hydrogen gas, but may also be carried out in a mixed gas containing an inert gas such as nitrogen or argon, as long as it does not affect the hydrogenation reaction.

[0046] The reaction vessel is preferably a fixed bed type. The reaction is preferably carried out as a continuous reaction. The reaction is preferably carried out with stirring. The stirring method can be appropriately selected depending on the purpose, and known stirring methods can be used.

[0047] After the hydrogenation reaction is completed, the reaction mixture is recovered using a solvent, which may be the same as that used in the hydrogenation step.

[0048] The resulting linear hydrocarbons can be used as biofuels such as hydrogenated vegetable oil (HVO) and sustainable aviation fuel (SAF). Although these linear hydrocarbons have a high cetane number, they have poor low-temperature fluidity. Therefore, when they are used as sustainable aviation fuel (SAF), they are processed through isomerization / hydrocracking to meet the SAF specifications.

[0049] (d) Isomerization / hydrocracking step The isomerization / hydrocracking step is a step in which the hydrocarbons obtained in the hydrogenation step are isomerized or hydrocrackered. In this step, the linear hydrocarbons obtained in the hydrogenation step are converted by isomerization and hydrocracking into desired hydrocarbons, i.e., isoparaffins containing one or more methyl groups in the molecule or paraffins with a lower carbon number, so as to have a high flash point and good flow properties in cold temperatures.

[0050] Isomerization and hydrocracking are well-known techniques, and those skilled in the art can appropriately select catalysts and reaction conditions to meet the specifications of various fuels. In this process, the isomerization and hydrocracking reactions may be carried out simultaneously or successively.

[0051] Isomerization can convert linear hydrocarbons into isoparaffins, thereby lowering the freezing point. Isomerization can be carried out in the presence of an acidic catalyst. As the isomerization catalyst, a bifunctional catalyst having metal sites for hydrogenation / dehydrogenation and acid sites for skeletal isomerization via carbocation is preferably used. For example, Pt / SAPO-11 / Al ２ O ３ , Pt / ZSM-22 / Al ２ O ３ , Pt / ZSM-23 / Al ２ O ３ , and Pt / SAPO-11 / SiO ２ etc.

[0052] Typically, linear hydrocarbons are dehydrogenated on the metal sites of the catalyst and react on the acid sites to form alkyl carbocations, producing protonated olefins. The alkyl carbocations rearrange to mono-, di-, and tri-branched alkyl carbocations on the acid sites. The branched alkyl carbocations are deprotonated and hydrogenated to produce the corresponding paraffins.

[0053] Hydrocracking is an exothermic reaction that produces liquid or gaseous shorter carbon number paraffins. Because the reaction is relatively slow, most of the hydrocracking occurs in the final section of the reactor. Hydrocracking primarily involves the cracking and saturation of paraffins. Excessive cracking can result in the formation of lower paraffins (C １ ~C ４ ) and naphtha (C ５ ~C ８ ) is produced, which is undesirable.

[0054] After the isomerization / hydrocracking step, the mixture was treated with paraffinic kerosene (C ９ ~C １６ ), paraffinic diesel (C １６ ~C １８ ), naphtha and light gases. ７ ~C １６ ) can then be distilled and used as the SAF.

[0055] According to the present invention, by subjecting crude caltrop oil to deacidification treatment, components contained in the crude caltrop oil that inhibit the methyl esterification reaction of caltrop oil can be effectively removed. That is, one aspect of the present invention also includes a method for improving the methyl esterification efficiency in a methyl esterification treatment of caltrop oil, the method including a deacidification step of deacidifying crude caltrop oil. The method preferably includes: (a) a caltrop oil refining step, the deacidification step being a deacidification step of deacidifying crude caltrop oil, wherein the refined caltrop oil has an absorbance at a wavelength of 330 nm of 0.08 or less; and (b) a methyl esterification reaction in which methanol is added to the refined caltrop oil to produce fatty acid methyl esters (FAME) by transesterification. The deacidification step of deacidifying crude Calophyllum kohlraum oil, steps (a) and (b), has been described above, and therefore will not be described again here.

[0056] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0057] [Refining Step] Pressed oil of Calophyllum indicum grown in Miyakojima, Okinawa Prefecture (a mixture with an acid value (AV) of about 20 to 30: AV = 21.9 mg / g) was used as a raw material and subjected to one of the following refining steps.

[0058] <Deoxidation step> 250 g of caltrop pressed oil was placed in a 500 ml beaker and heated to 80 ° C., and then 75% by weight of aqueous phosphoric acid solution was added at 0.06% by weight relative to the weight of caltrop pressed oil, and stirred for 10 minutes. Then, 16% by weight of aqueous sodium hydroxide solution or 16% by weight of aqueous potassium hydroxide solution was added so that the alkali addition ratio was 0.4 to 1.2, and the mixture was stirred at 80 ° C. for 20 minutes using a stirring blade, and centrifuged at 3,000 rpm for 3 minutes to remove the aqueous layer. After centrifugation, the oil layer was heated to 90 ° C., and 10% by weight of distilled water was added and stirred for 10 minutes, followed by centrifugation at 3,000 rpm for 3 minutes to remove the aqueous layer. Again, the mixture was washed under the same conditions, and the resulting oil layer was dried under reduced pressure at 60 ° C. and 20 hPa for 30 minutes to obtain a deoxidized oil. The alkali addition ratio indicates the ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the oil or fat (i.e., Calophyllum rubrum compressed oil) to be subjected to the deacidification step. For example, an addition ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the oil or fat of "1.2" means that the amount (molar amount) is 1.2 times the amount of the alkaline substance required to neutralize the acidic substance contained in the oil or fat.

[0059] <Degumming Step> 250 g of Calophyllum indicum compressed oil was placed in a 500 ml beaker and heated to 80°C. 0.06% by mass of a 75% by mass aqueous phosphoric acid solution was added to the Calophyllum indicum compressed oil, and the mixture was stirred for 10 minutes. 3% by mass of distilled water was then added to the Calophyllum indicum compressed oil. The mixture was stirred for 20 minutes at a stirring speed of 300 rpm using a stirring blade, and then centrifuged at 3,000 rpm for 3 minutes. The resulting upper layer was used as degummed oil.

[0060] <Decolorization Step> 340 g of Calophyllum indicum compressed oil was placed in a 1000 ml three-neck flask and heated to 80° C., and then 2% by mass of silica gel ("Sorbsil R92" manufactured by PQ Corporation) was added to the Calophyllum indicum compressed oil. The mixture was then stirred at 300 rpm using a stirring blade under 10 hPa for 30 minutes, and then subjected to static filtration using a filter paper for qualitative analysis (No. 2 filter paper manufactured by Advantec Toyo Kaisha, Ltd.) to obtain a decolorized oil.

[0061] [Methyl esterification process (alkali method)] Approximately 2 to 300 ml of the raw material was placed in an Erlenmeyer flask and heated to 60°C. Then, 18% by mass and 1.5% by mass of methanol and potassium hydroxide were added to the raw material, and the mixture was stirred for 30 minutes. The reaction mixture was then transferred to a 500 ml separatory funnel and allowed to stand at room temperature for 40 minutes for separation, and the lower layer was removed. The upper layer was placed in a 300 ml Erlenmeyer flask and heated to 60°C. Then, 20% by mass of distilled water relative to the raw material was added, and the mixture was washed with water by stirring for 20 minutes. After washing with water, the reaction mixture was transferred to a 500 ml separatory funnel and allowed to stand at room temperature for 40 minutes for separation, and the lower layer was removed. The upper layer was again placed in a 300 ml Erlenmeyer flask and washed with water under the same conditions. After the lower layer was separated and removed, the resulting upper layer was dried under reduced pressure at 60°C and 20 hPa for 30 minutes to obtain biodiesel fuel. Special grade methanol and potassium hydroxide were used.

[0062] [Methyl esterification step (acid-alkali method)] The raw material was charged into a 300 ml Erlenmeyer flask and heated to 60 ° C., and then 3.6% by mass and 0.4% by mass of methanol and concentrated sulfuric acid were added to the raw material, respectively, and stirred for 60 minutes. Then, 16% by mass and 3% by mass of methanol and potassium hydroxide were added to the reaction solution, and the mixture was stirred at 60 ° C. for 30 minutes. The reaction solution was then transferred to a 500 ml separatory funnel, allowed to stand at room temperature for 40 minutes for separation, and the lower layer was removed. The upper layer was charged into a 300 ml Erlenmeyer flask and heated to 60 ° C., and then 20% by mass of distilled water relative to the raw material was added, and the mixture was washed with water by stirring for 20 minutes. After washing with water, the reaction solution was transferred to a 500 ml separatory funnel, allowed to stand at room temperature for 40 minutes for separation, and the lower layer was removed. The upper layer was again placed in a 300 ml Erlenmeyer flask and washed with water under the same conditions. The lower layer was then separated and removed, and the resulting upper layer was dried under reduced pressure at 105°C and atmospheric pressure for 60 minutes to obtain a biodiesel fuel. Note that special grade methanol, concentrated sulfuric acid, and potassium hydroxide were used.

[0063] <Yield and yield of biodiesel fuel> The yield (g) of biodiesel fuel obtained in the methyl esterification step, the biodiesel reaction yield (mass%), and the biodiesel yield (mass%) were determined. The biodiesel reaction yield (mass%) and the biodiesel yield (mass%) were calculated using the following formulas: Biodiesel reaction yield (mass%) = Biodiesel yield (g) / Amount of raw material charged (g) × 100 Biodiesel yield (mass%) = Purification yield (mass%) × Biodiesel reaction yield (mass%) / 100

[0064] <Quantitative Analysis of FAME> The FAME content was measured by gas chromatography analysis with reference to the Standard Method for Analysis of Fats, Oils and Related Compounds 2.4.2.3-2013. Approximately 30 mg of the biodiesel fuel obtained by the preparation was precisely weighed out, and 1 ml of a methyl heptadecanoate-hexane solution was added as a standard substance to be used as an analytical sample. The FAME content (mass%) was calculated using the following formula: FAME content (mass%) = (each peak area × amount of standard substance added / peak area of ​​standard substance / amount of sample collected) × 100

[0065] <Quantitative Analysis of Pyranocoumarins> The pyranocoumarin content of unrefined Calophyllum indicum crude oil (AV26, AV80) and Calophyllum indicum oil after the refinement process (hereinafter referred to as Calophyllum indicum oil) was measured using the following procedure. (1) Preparation of a Calibration Curve Coumarin (stock solution 118 μg / ml, molecular weight 146.14) was serially diluted with hexane to specific concentrations, and the concentration was measured at a wavelength of 330 nm using a spectrophotometer. The analytical conditions were as follows: Instrument: UV2600-i spectrophotometer (Shimadzu Corporation); Analysis: LabSolutions UV-vis analytical data system (Shimadzu Corporation); Wavelength: 330 nm. The results are shown in Table 1. A calibration curve was prepared based on the results in Table 1. As shown in Figure 1, a highly linear calibration curve was prepared.

[0066]

[0067] (2) Measurement of 330 nm absorbance (inocalophyllins) in Calophyllin oil. 2 mg of purified Calophyllin oil was weighed into a 15 ml Falcon tube, and 10 ml of hexane was added using a volumetric pipette. A fixed amount of this solution was measured in a disposable PMMA (polymethyl methacrylate) cuvette, and the absorbance at a wavelength of 330 nm was measured. The concentration in coumarin equivalent was calculated, and assuming the extinction coefficients were equivalent, the mg / g equivalent of pyranocoumarins was calculated using the average molecular weight of inocalophyllin A and B, 548.22, and the mass % was measured.

[0068] Table 2 shows the relationship between the type of refining process for Calophyllum indicum oil and the yield and volume of biodiesel fuel. As shown in Table 2, the yield and reaction yield of biodiesel fuel were improved by performing deacidification treatment in the refining process.

[0069]

[0070] The relationship between deoxidation conditions and the quality of biodiesel fuel is shown in Table 3. The quality of fatty acid methyl esters (FAME) was evaluated based on JIS K2390, with a FAME content of 96.5% or higher considered to be acceptable, and anything below that level considered to be unacceptable.

[0071]

[0072] As shown in Table 3, by carrying out the deacidification step in the refining step, the absorbance of the refined Calophyllum indicum oil at a wavelength of 330 nm was reduced to 0.08 or less, and components that inhibit the methyl esterification reaction, such as pyranocoumarins contained in the crude Calophyllum indicum oil, were effectively removed.

[0073] By carrying out the deacidification step in the refining step, the methyl esterification step proceeded efficiently. Furthermore, by appropriately setting the alkali addition ratio, the yields of biodiesel fuel and fatty acid methyl esters (FAME) were further improved, and high-quality fatty acid methyl esters (FAME) were obtained. It is believed that the deacidification step in the refining step effectively removed components that inhibit the methyl esterification reaction contained in the crude oil of Calophyllum indicum oil, which allowed the subsequent methyl esterification step to proceed efficiently.

[0074] As described above, according to the method of the present invention, by using non-edible oil resources and employing the refining process used for edible oil resources, it is possible to efficiently produce biofuels while reducing the environmental burden.

Claims

1. A method for producing biofuel, comprising: (a) a refining process for Calophyllum indicum oil, the refining process including a deacidification process for deacidifying crude Calophyllum indicum oil, the refined Calophyllum indicum oil having an absorbance of 0.08 or less at a wavelength of 330 nm; and (b) a methyl esterification process for adding methanol to the refined Calophyllum indicum oil and producing fatty acid methyl esters (FAME) by a transesterification reaction.

2. A method for producing biofuel as described in claim 1, wherein the deacidification step includes a deacidification treatment by an alkaline deacidification method using an alkaline aqueous solution, and the addition ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the crude oil of Calophyllum persulphate is 0.6 or more and 1.2 or less.

3. The method for producing biofuel according to claim 1, wherein the methyl esterification step produces fatty acid methyl esters by transesterification in the presence of an alkali metal catalyst.

4. A method for producing biofuel as described in claim 1, wherein the content of pyranocoumarins in the Calophyllum persulphate oil refined in the refining step is 18 mass% or less based on the mass of the refined Calophyllum persulphate oil.

5. The method for producing a biofuel according to claim 1, wherein the biofuel is a biodiesel fuel.

6. The method for producing biofuel described in claim 5, wherein the content of fatty acid methyl esters in the biodiesel fuel is 96.5 mass% or more.

7. A method for improving the efficiency of methyl esterification of calendula oil, comprising: (a) a refining process for calendula oil, the refining process including a deacidification process for deacidifying a crude calendula oil, the refined calendula oil having an absorbance of 0.08 or less at a wavelength of 330 nm; and (b) a methyl esterification process for adding methanol to the refined calendula oil and producing fatty acid methyl esters (FAMEs) by a transesterification reaction.

8. A method for improving the methyl esterification efficiency of Calophyllum oil as described in claim 7, wherein the deacidification step includes a deacidification treatment by an alkaline deacidification method using an alkaline aqueous solution, and the addition ratio of the alkaline substance to the neutralization equivalent of the acidic substance contained in the crude Calophyllum oil is 0.6 or more and 1.2 or less.

9. The method for improving the efficiency of methyl esterification of Calophyllum indicum oil according to claim 7, wherein the methyl esterification step produces fatty acid methyl esters by transesterification in the presence of an alkali metal catalyst.

10. A method for improving the methyl esterification efficiency of Calophyllum indicum oil described in claim 7, wherein the content of pyranocoumarins in the Calophyllum indicum oil refined in the refining process is 18 mass% or less based on the mass of the refined Calophyllum indicum oil.

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