WO2025205990A1 - Method for producing sustainable aviation fuel and biodiesel fuel - Google Patents

Abstract

The present invention relates to a method for producing a sustainable aviation fuel and a biodiesel fuel.

Description

Sustainable Aviation Fuel and Biodiesel Production Methods

The present invention relates to a method for producing sustainable aviation fuel (SAF) and biodiesel fuel (BDF (registered trademark)).

SAF is a jet fuel made from renewable or waste materials that meets sustainability standards. In recent years, there has been an international movement to introduce SAF from the perspective of preventing global warming and recycling resources. Furthermore, from an environmental perspective, attempts are being made to use biomass resources as aviation fuel.

Biomass resources are used as raw materials for SAF, such as waste wood, waste cooking oil, vegetable oil, etc. Known methods for producing SAF using biomass resources as raw materials include the Fischer-Tropsch method, which synthesizes SAF from CO and _H2 using a catalytic reaction of Co, Fe, etc., and a method for producing SAF using hydrocracking (Non-Patent Document 1).

However, both methods consume a large amount of energy during fuel production, making them ineffective measures to mitigate climate change. Furthermore, there are other problems, such as high costs due to the rising price of waste cooking oil, the raw material, and the low yield of SAF from biomass feedstock, at less than 10% with the Fischer-Tropsch process and 2-30% with methods using hydrocracking (Non-Patent Document 2).

NG, Kok Siew; FAROOQ, Danial; YANG, Aidong. Global biorenewable development strategies for sustainable aviation fuel production. Renewable and Sustainable Energy Reviews, 2021, 150: 111502. VERMA, Vikas, et al. Catalytic hydroprocessing of waste cooking oil for the production of drop-in aviation fuel and optimization for improving jet biofuel quality in a fixed bed reactor. Fuel, 2023, 333: 126348.

The problem that the present invention aims to solve is to provide a new method for producing sustainable aviation fuel (SAF) and biodiesel fuel (BDF), and the SAF and BDF obtained by said method.

After extensive research, the inventors discovered that SAF and BDF can be obtained using a new method using coconut oil as a raw material, and thus completed the present invention.

That is, the present invention includes the following embodiments.
[1]
A method for producing sustainable aviation fuel, comprising: using coconut oil as a raw material, producing a mixture of fatty acid alkyl esters by reacting fatty acid triglycerides and/or fatty acids that are degradation products thereof with a lower alcohol; and vacuum distilling the mixture of fatty acid alkyl esters to separate a C8 fatty acid alkyl ester fraction and/or a C10 fatty acid alkyl ester fraction.
[2]
The production method according to [1], further comprising distilling the mixture obtained after separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction under reduced pressure to separate the C12 fatty acid alkyl ester fraction.
[3]
The method according to [1], wherein the mixture of fatty acid alkyl esters is produced by a transesterification reaction using coconut oil-derived fatty acid triglycerides and a lower alkyl alcohol.
[4]
The method of producing the mixture of fatty acid alkyl esters is to produce the mixture of fatty acid alkyl esters by an ester production reaction using a fatty acid that is a decomposition product of fatty acid triglycerides derived from coconut oil and a lower alkyl alcohol.
[5]
Using coconut oil as a raw material, a mixture of fatty acid alkyl esters is produced by reacting fatty acid triglycerides and/or fatty acids that are decomposition products thereof with a lower alcohol;
A method for producing a biodiesel fuel, comprising: distilling a mixture of fatty acid alkyl esters under reduced pressure to remove a C8 fatty acid alkyl ester fraction and/or a C10 fatty acid alkyl ester fraction; and obtaining a mixture obtained after removing the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction.
[6]
Producing the mixture of fatty acid alkyl esters comprises:
The method according to [5], wherein a mixture of fatty acid alkyl esters is produced by transesterification using fatty acid triglycerides derived from coconut oil and lower alkyl alcohols.
[7]
The method according to [5], wherein the mixture of fatty acid alkyl esters is produced by an ester production reaction using a fatty acid that is a decomposition product of fatty acid triglycerides derived from coconut oil and a lower alkyl alcohol.
[8]
The method according to any one of [1] to [7], wherein the mixture to which water has been added is distilled under reduced pressure.
[9]
The method according to any one of [1] to [7], wherein the lower alkyl alcohol is methanol, ethanol, propanol, isopropanol, or butanol.
[10]
The method according to any one of [1] to [7], wherein in separating or distilling off the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction, the reduced pressure distillation is carried out at a temperature of 110°C or higher and 130°C or lower.
[11]
The method according to any one of [1] to [7], wherein a transesterification reaction is carried out in the presence of coconut oil, a lower alkyl alcohol, a catalyst, and an organic solvent.
[12]
The method according to any one of [1] to [7], wherein the organic solvent is acetone.
[13]
A sustainable aviation fuel produced by the method according to any one of [1] to [4].
[14]
A biodiesel fuel produced by the method according to any one of [5] to [7].
[15]
The sustainable aviation fuel according to [13], wherein the energy consumption in terms of oil equivalent during production is 0.5 L/LSAF or less.
[16]
The biodiesel fuel according to [14], wherein the energy consumption during production, calculated in terms of petroleum, is 0.5 L/LSAF or less.

The present invention provides a novel method for producing SAF and BDF, as well as SAF and BDF obtained by this method.

1 is a diagram showing an overview of the present invention; FIG. 1 shows a GC/FID chromatogram of fatty acid esters made from virgin coconut oil in Example 1. FIG. 1 shows a GC/FID chromatogram of fatty acid esters made from waste edible coconut oil in Example 1. FIG. 1 shows GC/FID chromatograms of C8 and C10 fatty acid methyl esters in Example 1. FIG. 1 shows GC/FID chromatograms of C8 and C10 fatty acid ethyl esters in Example 1. FIG. 1 shows GC/FID chromatograms of C8 and C10 fatty acid isopropyl esters in Example 3. FIG. 1 shows the results of HPLC analysis of C8 and C10 fatty acid methyl esters in Example 1. FIG. 1 shows the results of HPLC analysis of C8 and C10 fatty acid ethyl esters in Example 1. FIG. 1 shows the results of HPLC analysis of C8 and C10 fatty acid isopropyl esters in Example 3.

The following describes an embodiment of the present invention (hereinafter referred to as the "present embodiment"), but the present invention is not limited to the following examples.

(coconut oil)
In this specification, the term "coconut oil" is not particularly limited as long as it is coconut oil extracted from the endosperm of coconut fruit.
Known types of coconut oil include coconut oil extracted by pressing the solid endosperm of coconut without heating (so-called virgin coconut oil), and coconut oil extracted by adding water to the solid endosperm of coconut and heating it (so-called refined coconut oil).
As the coconut oil, commercially available coconut oil may be used, or extracted coconut oil may be used.

Coconut oil may contain, but is not limited to, C6, C8, C10, C12, C14, C16, and/or C18 fatty acid triglycerides. An example of the fatty acid composition of triglycerides contained in coconut oil is shown in Table 1.

Coconut oil may be virgin coconut oil or used, waste coconut oil. Examples of the fatty acid composition of virgin coconut oil and waste coconut oil are shown in Table 2.

(Method for manufacturing SAF)
In a first aspect, a method for producing an SAF is provided.

Producing a Mixture of Fatty Acid Alkyl Esters The method of the present embodiment includes producing a mixture of fatty acid alkyl esters using coconut oil as a feedstock.
The fatty acid composition in the mixture of fatty acid alkyl esters has a composition derived from the coconut oil used as a raw material.
The mixture of fatty acid alkyl esters can be produced, for example, by the following method.
In producing the mixture of fatty acid alkyl esters, coconut oil is used as a raw material. In the production reaction, coconut oil itself may be used as a raw material, or fatty acid triglycerides extracted from coconut oil may be used as a raw material.
In either case, fatty acid triglycerides derived from fatty acid alkyl esters are the starting material in the production reaction.
Examples of the production reaction include a transesterification reaction using a fatty acid triglyceride derived from coconut oil and a lower alkyl alcohol, or an ester formation reaction using a fatty acid obtained by hydrolyzing a fatty acid triglyceride derived from coconut oil and a lower alkyl alcohol.

The mixing may be carried out to the extent that the reaction system becomes a homogeneous phase system, which means that the fatty acid triglyceride or fatty acid, catalyst, organic solvent, and lower alkyl alcohol form a single phase.
The catalyst may be a catalyst commonly used in transesterification reactions. Examples include alkali catalysts such as sodium hydroxide and potassium hydroxide, acid catalysts such as hydrochloric acid, sulfuric acid, and hydrofluoric acid, enzymes such as lipase, inorganic substances such as calcium oxide, and solid catalysts such as ion exchange resins such as cation exchange resins and anion exchange resins. Preferably, an alkali catalyst or an acid catalyst is used. Furthermore, a single catalyst may be used, or multiple catalysts may be used in combination. The alkali catalyst or acid catalyst may be used in the form of an aqueous solution or the like according to a known method.

The organic solvent may be at least one selected from the group consisting of acetone, isopropanol, and acetonitrile. The organic solvent may be added in an amount of 10% by weight or more relative to the coconut oil. Preferably, the organic solvent may be added in an amount of 10% to 50% by weight relative to the coconut oil.

Isopropanol reacts with the fatty acids produced by the hydrolysis of fatty acid triglycerides, so when using isopropanol, it is preferable to use fatty acids produced by the hydrolysis of fatty acid triglycerides as the raw material.

The lower alkyl alcohol may be at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol, and butanol. It is suitable to use a stoichiometric ratio of 1 to 1.6 times, preferably 1 to 1.2 times, and more preferably 1 to 1.17 times, the fatty acid. The stoichiometric ratio for transesterification of the fatty acid and alcohol is 3 moles of alcohol per mole of fatty acid.

The amount of catalyst may be adjusted as appropriate depending on the type of catalyst used, the amount of fatty acids in the raw materials, the scale of the reaction system, etc. Specifically, an amount that allows the transesterification reaction to proceed satisfactorily without slowing down the rate of transesterification, and that allows the catalyst to be separated during refining, may be determined as appropriate. For example, when using an alkaline catalyst, the amount of alkaline catalyst used is 0.03 to 1.0% by weight of coconut oil, preferably 0.3 to 0.8% by weight.

The transesterification reaction after mixing may be carried out at room temperature, preferably between 5°C and 35°C, more preferably between 10°C and 30°C, and even more preferably between 15°C and 25°C. The reaction time is adjusted appropriately depending on the reaction, so is not particularly limited, but is set to 1 minute to 3 hours, preferably 5 minutes to 2 hours, and more preferably 10 minutes to 1 hour.

The transesterification reaction involves mixing fatty acid triglycerides derived from coconut oil or fatty acids produced by decomposing fatty acid triglycerides derived from coconut oil, a catalyst, an organic solvent, and a lower alkyl alcohol.

Mixing may be carried out in a container equipped with a stirring means. The fatty acid triglyceride or fatty acid, catalyst, organic solvent, and lower alkyl alcohol are placed in the container and mixed. The stirring may be done manually or by using a device, and any known stirring means may be used.

Recovery of Acetone, Alcohol, and Glycerin The method of this embodiment further includes recovering acetone, alcohol, and glycerin. The recovery of acetone and alcohol may be carried out by distilling or vacuum distilling the reaction solution containing the fatty acid alkyl ester obtained by the above reaction. The distillation or vacuum distillation may be carried out according to a known method. For example, the distillation or vacuum distillation may be carried out at a temperature of 100°C or less, preferably 60°C to 80°C, and more preferably 65°C to 75°C. The distillation or vacuum distillation may also be carried out at a pressure of 1 atmosphere or less, preferably 0.9 atmospheres or less, and more preferably 0.8 atmospheres or less. The reaction time is adjusted appropriately depending on the reaction, so is not particularly limited, but is set to a reaction time of 1 minute to 3 hours, preferably 5 minutes to 2 hours, and more preferably 10 minutes to 1 hour.

Glycerin may be recovered by allowing the reaction solution to stand and separate into a fatty acid alkyl ester layer (upper layer) and a glycerin layer (lower layer), and then recovering the lower glycerin layer.

The method of this embodiment may include washing the reaction solution after glycerin recovery. This washing may be carried out by adding water to the reaction solution after glycerin recovery, leaving it to stand to separate into an alkyl ester layer and a water layer, and then recovering the water in the lower layer. This washing may be carried out multiple times until the pH of the washed water becomes neutral.

Separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction The method of this embodiment further includes separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction. Separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction may be carried out by adding water to the fatty acid alkyl esters after the washing and distilling under reduced pressure. The reduced pressure distillation may be carried out according to a known method. For example, distillation or reduced pressure distillation may be carried out at a temperature of 150°C or less, preferably 110°C to 130°C, more preferably 115°C to 120°C. Alternatively, distillation or reduced pressure distillation may be carried out at a pressure of 1 atmosphere or less, preferably 0.9 atmospheres or less, more preferably 0.8 atmospheres or less. The reaction time is adjusted appropriately depending on the reaction and is not particularly limited, but is set to 1 minute to 3 hours, preferably 5 minutes to 2 hours, and more preferably 10 minutes to 1 hour.
When the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction are separated, they may be separated under conditions for separating both fractions simultaneously, or separately, or a portion may be separated simultaneously and the remainder separately. As the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction, fractions containing C8 fatty acid alkyl esters and/or C10 fatty acid alkyl esters may be mixed.

The C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction obtained by the above-mentioned vacuum distillation may be heated under reduced pressure to remove moisture. For example, moisture may be removed at a pressure of 1 atmosphere or less, preferably 0.9 atmospheres or less, more preferably 0.8 atmospheres or less, and at a temperature of 100°C or less, preferably 90°C or less, more preferably 80°C or less. The C8 fatty acid alkyl ester and/or the C10 fatty acid alkyl ester obtained in this manner can be used as SAF.

Separating the C12 fatty acid alkyl ester fraction The method of this embodiment further includes separating the C12 fatty acid alkyl ester fraction. Separating the C12 fatty acid alkyl ester fraction may be carried out by adding water to the fatty acid alkyl ester remaining after separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction, followed by vacuum distillation. The vacuum distillation may be carried out according to a known method. For example, distillation or vacuum distillation may be carried out at a temperature of 170°C or lower, preferably 130°C to 150°C, more preferably 135°C to 145°C. Alternatively, distillation or vacuum distillation may be carried out at a pressure of 1 atmosphere or lower, preferably 0.9 atmospheres or lower, more preferably 0.8 atmospheres or lower. The reaction time is adjusted appropriately depending on the reaction and is not particularly limited, but is set to 1 minute to 3 hours, preferably 5 minutes to 2 hours, and more preferably 10 minutes to 1 hour.

The C12 fatty acid alkyl ester fraction separated by the above-mentioned vacuum distillation may be subjected to a known hydrodecarboxylation reaction to produce C12 isoparaffins. For example, the C12 fatty acid alkyl esters may be subjected to a sulfide treatment using a known method, and after the sulfide treatment, hydrogen may be added and the reaction may be carried out at 200°C to 300°C, preferably 230°C to 270°C, and more preferably 240°C to 260°C, for 30 minutes to 4 hours, preferably 1 hour to 3 hours. The C12 isoparaffins obtained in this manner can be used as SAF.

The method of the present embodiment includes producing isopropyl esters by an esterification reaction, which may be carried out by reacting a C8 fatty acid and/or a C10 fatty acid with a catalyst, an organic solvent, and isopropanol.

The catalyst used in the ester production reaction may be an acid catalyst, preferably sulfuric acid. In the present invention, the amount of catalyst used in the ester production reaction may be adjusted appropriately depending on the amount of fatty acid in the raw material, the scale of the reaction system, etc. Specifically, an amount may be determined appropriately so that the rate of the ester production reaction does not decrease, the reaction can proceed sufficiently, and the catalyst can be separated during purification.

The organic solvent used in the ester production reaction may be isopropanol, acetone, or acetonitrile. The organic solvent may be added in an amount of 10% by weight or more relative to the fatty acid. Preferably, the organic solvent may be added in an amount of 10% to 50% by weight relative to the fatty acid.

The ester production reaction involves heating a solution containing a mixture of C8 fatty acids and/or C10 fatty acids, a catalyst, an organic solvent, and isopropanol. The heating is carried out at a temperature of 30°C to 90°C, preferably 40°C to 80°C, more preferably 50°C to 70°C, and even more preferably 55°C to 65°C. The reaction time is adjusted appropriately depending on the reaction, so is not particularly limited, but is typically set to 1 to 12 hours, preferably 2 to 8 hours, and more preferably 4 to 6 hours.

After the ester production reaction, the reaction solution may be allowed to stand to separate into a fatty acid alkyl ester layer (upper layer) and a water layer (lower layer), and the lower water layer may then be collected to recover water containing the catalyst.

The method of this embodiment may also include washing the reaction solution after catalyst recovery. This washing may be carried out by adding water to the reaction solution after catalyst recovery, leaving it to stand to separate into an alkyl ester layer and a water layer, and then recovering the water from the lower layer. This washing may be repeated multiple times until the pH of the washed water becomes neutral.

The method of this embodiment may also include drying the reaction solution after washing. This drying may be carried out according to a known method. For example, drying may be carried out at a temperature of 100°C or less, preferably 60°C to 90°C, and more preferably 75°C to 85°C. Drying may also be carried out at a pressure of 1 atmosphere or less, preferably 0.9 atmospheres or less, and more preferably 0.8 atmospheres or less. The C8 fatty acid isopropyl ester and/or C10 fatty acid isopropyl ester obtained in this manner can be used as an SAF.

(Method for producing BDF)
In a second aspect, a method for producing BDF is provided.

The method of this embodiment includes producing a mixture of fatty acid alkyl esters, recovering acetone, alcohol, and glycerin, and distilling off the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction, but these may be similar to the producing a mixture of fatty acid alkyl esters, recovering acetone, alcohol, and glycerin, and separating off the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction described in the above-mentioned method for producing SAF, and therefore further explanation will be omitted. The method of this embodiment may also include obtaining the reaction solution after the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction has been distilled off as BDF.

The method of this embodiment may further include distilling off the C12 fatty acid alkyl ester fraction, and this distillation may be similar to the separation of the C12 fatty acid alkyl ester fraction described in the above-mentioned method for producing SAF. The method of this embodiment may also include obtaining the reaction solution after distilling off the C12 fatty acid alkyl ester fraction as BDF.

The properties of the fatty acid esters produced by the above method are shown in Table 3.

In this embodiment, C6, C8, and C10 methyl esters, C6, C8, C10, and C12 ethyl esters, C6, C8, C10, and C12 propyl esters, C6, C8, C10, and C12 isopropyl esters, and C6, C8, and C10 butyl esters may be used as SAFs. C12, C14, C16, and C18 methyl esters, C14, C16, and C18 ethyl esters, C14, C16, and C18 propyl esters, C14, C16, and C18 isopropyl esters, and C12, C14, C16, and C18 butyl esters may be used as BDFs.

(Use of SAF)
The SAF produced by the above-described method may be mixed with conventional aviation fuel for use as aviation fuel. The conventional aviation fuel may be kerosene. Kerosene is a C10 to C15 hydrocarbon that is a fractional distillation component of petroleum.

The SAF produced by the above-mentioned method may be added to kerosene in an amount of 10% or more, preferably 30% or more, and more preferably 50% or more. When the SAF is C8, C10, and C12 fatty acid ethyl esters, fatty acid propyl esters, and isopropyl esters, the SAF may be added to kerosene in an amount of 30% or more. When the SAF is C8 and C10 fatty acid methyl esters, the SAF may be added to kerosene in an amount of 10% or more. When the SAF is C8 and C10 fatty acid ethyl esters and fatty acid propyl esters, the SAF may be added to kerosene in an amount of up to 50%.

(Energy consumption in oil equivalent)
"L/LSAF" refers to a numerical unit that converts the amount of energy consumed for heating a solution, etc., when producing 1 L of SAF into the amount of petroleum. The numerical value expressed in this unit serves as an evaluation index of the energy consumption during SAF production. The energy consumption during production, converted into petroleum equivalent, is preferably 1 L/LSAF or less, more preferably 0.7 L/LSAF or less, more preferably 0.5 L/LSAF or less, and even more preferably 0.2 L/LSAF.

The present invention will be explained in more detail below using specific examples, but the present invention is not limited to the following examples. Note that in the description of these examples, "%" means "% by mass."

Example 1
(1-1) Preparation of reaction solution 1000 mL of coconut oil (LUNAS coconut oil (virgin coconut oil) or Philippine waste edible coconut oil; analytical results by GC/FID (Agilent Technologies, GC systems HP 6890 series) are shown in Figures 2 and 3), 100 mL of acetone (Wako Pure Chemical Industries, 10% based on oil), and 8.9 g of potassium hydroxide (KOH, Wako Pure Chemical Industries, 1.0% based on coconut oil) were dissolved in methanol (Wako Pure Chemical Industries) or ethanol (Wako Pure Chemical Industries) in a reaction vessel (Yashiro Scientific Instruments). The amount of alcohol was 4 to 5 times the molar ratio of the triglyceride.

(1-2) Transesterification reaction and recovery of acetone, alcohol, and glycerin The reaction solution prepared in (1-1) above was subjected to a transesterification reaction at room temperature for 30 minutes. After the reaction, the reaction solution was heated to 70°C under reduced pressure (approximately 0.8 atmospheres), and the co-solvent acetone and the remaining unreacted alcohol were recovered. The recovery time was 30 minutes, and approximately 80% of the acetone and approximately 90% of the alcohol were recovered. After allowing to stand for 10 minutes, the mixture was separated into an alkyl ester layer and a by-product glycerin layer, and the glycerin was recovered from the bottom of the reactor.

(1-3) Washing of Alkyl Esters and Recovery of C8 and C10 Alkyl Esters After glycerin recovery, the crude alkyl esters produced were mixed with water at a volume ratio of 30% to the alkyl ester. After separation into the alkyl ester and water layers, water was recovered from the bottom of the reactor. This washing process was repeated three times. Approximately 30% water, by volume, was added to the washed alkyl esters and heated to 115-120°C under vacuum. This operation removed the C8 (alkyl caprylate) and C10 (alkyl caprate) components from the coconut oil, along with the water vapor present in this temperature range, from the system and liquefied and recovered using a chiller (heat exchanger). This yielded pure C8 and C10 alkyl esters containing water. Water was removed from the mixture of water and C8 and C10 alkyl esters at 80°C under reduced pressure. The resulting C8 and C10 alkyl esters were used as SAF.

When C8 and C10 alkyl esters were converted into SAF using process (1-3), 15-20% of the raw material weight could be used as SAF and 80-85% as BDF.

Example 2
The same steps as in the processes (1-1) to (1-3) of Example 1 were carried out, except that the dried C12 to C18 fatty acid alkyl component remaining in the reactor was not recovered.

(2-1) Recovery of C12 alkyl esters After recovering C8 and C10 alkyl esters with steam in the process (1-3) of Example 1, about 30% water was added to the reactor again, and the mixture was heated to 140° C. under reduced pressure. As a result, C12 alkyl esters were recovered together with steam.

A high-pressure reactor (manufactured by Yashiro Scientific Instruments) was used for the hydrodecarboxylation reaction. A Ni-Mo catalyst (manufactured by Ketjen Corporation) and methyl sulfide (manufactured by Wako Pure Chemical Industries) were added and sulfide treatment was performed. Hydrogen (2 atmospheres) and a C12 alkyl ester were added, and the reaction was carried out at 250°C for 2 hours. The dodecane yield obtained was approximately 65-70%, and the isoparaffin ratio was approximately 15-20%. Adding Co and Fe as promoters to the Ni-Mo catalyst increased the isoparaffin ratio by approximately 5%.

When C8 and C10 alkyl esters were converted to SAF using process (1-3) in Example 1, 15-20% of the raw material weight could be used as SAF and 80-85% as BDF. When process (2-1) was carried out in Example 2 above, 60-65% of the coconut oil could be used as SAF and 35-40% as BDF.

Example 3
The same steps as in (1-1) to (1-3) of Example 1 were carried out to obtain C8 and C10 alkyl esters.

(3-1) Production of isopropyl ester by ester formation reaction 200 mL of acetonitrile as a co-solvent, 2.0 moles of isopropanol (total amount = 23 moles) in a molar ratio to the alkyl ester, and 20 mL of concentrated sulfuric acid as an acid catalyst were added to 1000 mL of C8 caprylic acid and 1000 mL of C10 capric acid (total amount = 2000 mL = caprylic acid = 6.3 moles, capric acid = 5.18 moles, total amount = 11.5 moles), and the ester formation reaction was carried out at 60°C for approximately 5 hours. The by-product of the ester formation reaction was water. After the reaction, the mixture was separated into an alkyl ester layer and a water layer, and then the water mixed with the sulfuric acid catalyst was recovered from the bottom of the reactor.

Water was added at a volume ratio of 30% to the alkyl ester. After separation into an alkyl ester layer and a water layer, the water was recovered from the bottom of the reactor. This washing process was carried out three times in total. The washed alkyl ester was then washed three times in the same manner as above, and then dried at 80°C under reduced pressure.

The results of GC/FID (Agilent Technologies, GC systems HP 6890 series) analysis of the C8 and C10 fatty acid methyl esters and ethyl esters produced in Example 1 (1-3) and the isopropyl ester produced in (3-1) above are shown in Figures 3 to 5.

The HPLC analysis results of the C8 and C10 fatty acid methyl esters and ethyl esters produced in Example 1 (1-3) and the isopropyl esters produced in (3-1) above are shown in Figures 6 to 8.

Figures 2 to 9 show that the yields of SAF and BDF in the examples were all within the range of 97% to 99%. The yield of BDF in this example exceeded the 96.5% fatty acid ester content standard specified in JIS K2390.

Claims (16)

A method for producing sustainable aviation fuel, comprising: using coconut oil as a raw material, producing a mixture of fatty acid alkyl esters by reacting fatty acid triglycerides and/or fatty acids that are degradation products thereof with a lower alcohol; and vacuum distilling the mixture of fatty acid alkyl esters to separate a C8 fatty acid alkyl ester fraction and/or a C10 fatty acid alkyl ester fraction. The production method of claim 1 further comprises subjecting the mixture obtained after separating the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction to vacuum distillation to separate the C12 fatty acid alkyl ester fraction. The manufacturing method described in claim 1, wherein producing the mixture of fatty acid alkyl esters is a transesterification reaction using coconut oil-derived fatty acid triglycerides and a lower alkyl alcohol to produce the mixture of fatty acid alkyl esters. The method according to claim 1, wherein the production of the mixture of fatty acid alkyl esters is carried out by an ester production reaction using a fatty acid that is a decomposition product of fatty acid triglycerides derived from coconut oil and a lower alkyl alcohol. Using coconut oil as a raw material, a mixture of fatty acid alkyl esters is produced by reacting fatty acid triglycerides and/or fatty acids that are decomposition products thereof with a lower alcohol;
A method for producing a biodiesel fuel, comprising: distilling a mixture of fatty acid alkyl esters under reduced pressure to remove a C8 fatty acid alkyl ester fraction and/or a C10 fatty acid alkyl ester fraction; and obtaining a mixture obtained after removing the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction. Producing the mixture of fatty acid alkyl esters comprises:
The method according to claim 5, wherein a mixture of fatty acid alkyl esters is produced by transesterification using fatty acid triglycerides derived from coconut oil and lower alkyl alcohols. The manufacturing method described in claim 5, wherein producing the mixture of fatty acid alkyl esters is performed by an ester production reaction using fatty acids that are decomposition products of fatty acid triglycerides derived from coconut oil and lower alkyl alcohols. The method according to any one of claims 1 to 7, wherein the mixture to which water has been added is distilled under reduced pressure. The method according to any one of claims 1 to 7, wherein the lower alkyl alcohol is methanol, ethanol, propanol, isopropanol, or butanol. The method according to any one of claims 1 to 7, wherein, in separating or distilling off the C8 fatty acid alkyl ester fraction and/or the C10 fatty acid alkyl ester fraction, vacuum distillation is carried out at a temperature of 110°C or higher and 130°C or lower. The method according to any one of claims 1 to 7, wherein the transesterification reaction is carried out in the presence of coconut oil, a lower alkyl alcohol, a catalyst, and an organic solvent. The method according to any one of claims 1 to 7, wherein the organic solvent is acetone. A sustainable aviation fuel produced by the method of any one of claims 1 to 4. Biodiesel fuel produced by the method of any one of claims 5 to 7. The sustainable aviation fuel described in claim 13, wherein the energy consumption during production, in terms of oil equivalent, is 0.5 L/LSAF or less. The biodiesel fuel according to claim 14, wherein the energy consumption during production, calculated in terms of petroleum, is 0.5 L/LSAF or less.