Process for the production of diesel fuel by non-catalytic transesterification using vegetable oils

Abstract

A method for preparing diesel fuel includes mixing a tetraalkoxyborate with a triglyceride composition to form a reaction mixture, wherein the triglyceride composition comprises one of a vegetable oil or an animal fat. The method further includes heating the reaction mixture to above 40°C to form a diesel fuel comprising alkyl esters of fatty acids.

Description

Cross-references to related applications

[0001] This application claims the benefit and priority of U.S. Provisional Patent Application Serial No. 63 / 607,280, filed December 7, 2023, and U.S. Provisional Patent Application Serial No. 63 / 563,614, filed March 11, 2024. The entire contents of the above applications are incorporated herein by reference. Background Technology

[0002] Diesel fuel is derived from dwindling non-renewable oil reserves, whose combustion is a major source of global warming gases. Crude oil obtained from these depleted reserves consists of a wide mixture of numerous hydrocarbon molecules. Through fractionation processes, various products such as gasoline, jet fuel, diesel fuel, and tar are obtained. Notably, each of these final products typically consists of a complex mixture of hundreds of different hydrocarbons. Gasoline is the first fraction of petroleum, typically composed of hydrocarbons in the C4-C12 range. Jet fuel is an intermediate distillation product between gasoline and diesel, with its boiling range significantly overlapping with gasoline and almost completely overlapping with diesel fuel. Jet fuel is typically a mixture of hydrocarbons in the C8-C16 range. Diesel fuel has the highest boiling point, with its mixture ranging from C8 to C23. Tar is a residue from the petroleum distillation process.

[0003] Biodiesel comprises fatty acid alkyl esters (FAAEs) derived from the transesterification of triglycerides (such as vegetable oils or animal fats), such as fatty acid methyl esters (FAMEs). These fatty acid methyl esters can be used in conventional diesel engines without any modifications. Biodiesel is a net-zero or near-net-zero carbon-emission fuel because the carbon produced by combustion originates from carbon absorbed by plants from the air. Furthermore, waste cooking oil can be used as feedstock chemicals in biodiesel production, thereby eliminating dependence on fresh vegetable oils (e.g., soybean oil, rapeseed oil, coconut oil, sesame oil, etc.) and significantly reducing the cost of biodiesel production. Currently, using virgin vegetable oils makes biodiesel cost 1.5 times that of petroleum-based diesel. This also alleviates the burden on restaurants and fast-food chains disposing of large quantities of waste cooking oil. Compared to conventional diesel, biodiesel also has lower nitrogen and sulfur content. These compounds respectively contribute to the generation of highly polluting compounds such as nitrogen oxides and sulfur oxides. In addition, unlike fossil fuel-derived diesel, biodiesel does not contain aromatics, which are a cause of increased diesel smoke / fumes.

[0004] Conventional biodiesel production methods using vegetable oils suffer from significant drawbacks, including undesirable soap formation, low yields, and / or purification difficulties. Currently, homogeneous base catalysts are receiving the most attention in biodiesel production due to their availability and low cost. Commonly used base catalysts utilize hydroxide ions in the form of sodium hydroxide (NaOH) or potassium hydroxide (KOH) for the transesterification reaction of vegetable oils in methanol (MeOH). The role of the hydroxyl group (-OH) is to deprotonate the weakly acidic proton of MeOH, forming […]. - OMe ions are used in transesterification reactions. Both NaOH and KOH exhibit excellent catalytic activity for biodiesel production, but have the major drawback of producing water. This reduces biodiesel yield and increases the complexity of purifying the desired biodiesel from alkali metal fatty acid carboxylate byproducts (called soaps). Sodium methoxide (NaOMe) and potassium methoxide (KOMe) have also been used in biodiesel production because they are […]. - [OMe] is a direct source of ions. However, these reagents also increase the complexity of separating biodiesel from byproducts and reduce the feasibility of the method. Most notably, FAME containing double bonds is unsuitable for use in diesel engines because the olefins react with hydroxyl radicals present during combustion. These radicals polymerize the diesel fuel during combustion and lead to premature engine aging. Therefore, a catalyst-free transesterification method for vegetable oils is desired to convert them into high-value biodiesel FAME. Summary of the Invention

[0005] This disclosure overcomes the limitations of currently known methods for producing biodiesel from vegetable oils. This is achieved by developing a reaction that is independent of hydroxide bases, solvent-free, and does not require any extreme conditions. Currently, the widely adopted approach is to produce biodiesel from vegetable oils using sodium hydroxide (NaOH) or potassium hydroxide (KOH) in the presence of methanol (MeOH) with a metal catalyst. This method has several highly undesirable effects. [The text then abruptly shifts to a seemingly unrelated topic:] ...to deprotonate MeOH to form methoxy groups for the transesterification process... - The hydroxide base of OMe also reacts with the ester group of biodiesel fatty acid methyl ester (FAME) to form a sodium salt of fatty acid carboxylate, called soap. This undesirable product leads to saponified biodiesel and thus results in lower biodiesel yields, requiring additional purification steps to obtain a product usable in unmodified diesel engines.

[0006] The method disclosed herein can be used to produce biodiesel FAME from commercial waste oil and / or virgin cooking oil. The method involves reacting sodium borohydride (NaBH4) with methanol (MeOH). NaBH4 is a source of hydride anions and reacts with MeOH to produce […]. -[OMe] ions are used in the transesterification reaction of vegetable oils to form FAME. The reaction of NaBH4 with MeOH can be carried out in a pure environment or in a solvent (e.g., toluene) and produces sodium tetramethoxyborate [NaB(OMe)4]. Hydrogen is also produced as a byproduct of the reaction and can be used to hydrogenate the fatty acid chains of newly formed biodiesel. In some embodiments, NaB(OMe)4 can also be produced in methanol using trimethoxyborate [B(OMe)3] and NaOMe to produce FAME.

[0007] As mentioned above, FAME containing double bonds is unsuitable for use in diesel engines because the olefins react with hydroxyl radicals present during combustion, causing these radicals to polymerize the diesel fuel during combustion and leading to premature engine aging. This problem is completely avoided if the alkyl chain of the FAME is completely reduced. Therefore, the method disclosed herein focuses on the transesterification aspect of producing biodiesel from vegetable oils using the transesterification reagent NaB(OMe)4, which is synthesized by reacting NaBH4 with MeOH or by combining B(OMe)3 with NaOMe in MeOH.

[0008] The method disclosed herein also avoids the use of hydroxide bases, thereby avoiding the production of saponified diesel and eliminating the need for dehydration from the reaction mixture. Furthermore, the byproduct glycerol-borate compound forms a solid that settles at the bottom of the reaction vessel, facilitating easy separation of biodiesel by simple decantation. The resulting methyl ester of the vegetable oil can be used as a renewable carbon-neutralized alternative to petroleum-based diesel for use in any diesel engine without modification. The transesterification reaction was successful when using waste cooking oil from large fast-food chains, as well as commercial soybean oil, sesame oil, olive oil, and animal fats. An average yield of approximately 85% was achieved at 80°C within a reaction time of approximately one hour. 1 H and 11 Characterization by Brønsted-NMR showed the effectiveness of the method and the quality of the resulting biodiesel. The method disclosed herein can be extended to the synthesis of other FAAEs, such as those including ethyl, propyl, and butyl. This is achieved by adding waste cooking oil... In situ The generated sodium tetraethoxyborate [NaB(OEt)4], sodium tetrapropoxyborate NaB(OPr)4, and sodium tetrabutoxyborate NaB(OBu)4 are achieved by reacting sodium tetraethoxyborate, sodium tetrapropoxyborate, and sodium tetrabutoxyborate, respectively, with ethanol (EtOH), propanol (PrOH), and butanol (BuOH).

[0009] Problems associated with undesirable soap production, low yields, and / or purification difficulties were eliminated by using the reaction between NaBH4 and MeOH to form NaB(OMe)4, a previously undeveloped method for delivering […]. - [OMe] is a molecular species used for transesterification reactions of vegetable oils. The method disclosed herein successfully produces biodiesel from waste cooking oil, a commercially viable feedstock chemical that both mitigates the environmental burden of waste cooking oil and is an inexpensive starting material. Both of these aspects are key components enabling biodiesel to compete with conventional fossil fuel diesel in price.

[0010] The method disclosed herein also allows for the easy synthesis and separation of biodiesel at temperatures as low as 40°C for approximately one hour. The resulting byproduct glycerol-boron compound does not form an emulsion with the product biodiesel, but rather forms an easily separable solid, for example, at the bottom of the reaction vessel, thus allowing the biodiesel to be readily decanted. 11 B NMR was used to confirm that the supernatant was free of any detectable levels of boron contamination. Additional purification steps, such as centrifugation, were performed to remove any solids transferred with the FAME during decantation, and the product was eluted with hexane to extract the biodiesel and remove excess MeOH from the reaction. Yields of all oils were demonstrated to be approximately 85%, using a scale of approximately 4 mmol of vegetable oil.

[0011] According to one embodiment of this disclosure, a method for transesterification of triglycerides is disclosed. The method includes mixing a tetraalkoxyborate with a triglyceride composition to form a reaction mixture. The method may include heating the reaction mixture to above 40°C to form a fatty acid alkyl ester.

[0012] According to another embodiment of this disclosure, a method for preparing diesel fuel is disclosed. The method includes mixing a tetraalkoxyborate with a triglyceride composition to form a reaction mixture, wherein the triglyceride composition comprises one of vegetable oil or animal fat. The method further includes heating the reaction mixture to above 40°C to form a diesel fuel that may comprise alkyl esters of fatty acids.

[0013] Implementations of any of the above embodiments may include one or more of the following features. According to one aspect of the above embodiments, the tetraalkoxyborate may be one of tetramethoxyborate, tetraethoxyborate, tetrapropoxyborate, or tetrabutoxyborate. The fatty acid alkyl ester may be one of fatty acid methyl ester, fatty acid ethyl ester, fatty acid methyl ester, fatty acid propyl ester, and fatty acid butyl ester. Heating may be carried out for about 1 hour to about 24 hours. The method may further include preparing the tetraalkoxyborate in a reaction vessel and adding a triglyceride composition to the reaction vessel. Preparing the tetraalkoxyborate may include mixing a borohydride with an alcohol. The alcohol and the tetraalkoxyborate may contain the same alkoxy group, which may be one of methoxy, ethoxy, epoxy, and butoxy. Preparing the tetraalkoxyborate may include mixing a trialkoxyborane with an alkoxide. The trialkoxyborane, the alkoxide, and the tetraalkoxyborate may contain the same alkoxy group, which may be one of methoxy, ethoxy, epoxy, and butoxy. The method may further include hydrogenating the fatty acid alkyl ester. Hydrogenation may be carried out using hydrogen gas collected during the preparation of the tetraalkoxyborate. Tetraalkoxyborate can be one of tetramethoxyborate, tetraethoxyborate, tetrapropoxyborate, or tetrabutoxyborate.

[0014] Brief description of the attached figures The following describes various embodiments of this disclosure with reference to the accompanying drawings: Figure 1A This is a biodiesel produced according to one embodiment of the present disclosure by reacting coconut oil with NaOMe at 80°C. 1 H NMR spectrum; Figure 1B According to one embodiment of this disclosure, the contamination with residual FAME results in the production of glycerol byproduct solids. 1 H NMR spectrum; Figure 2 This indicates the presence of tetracoordinated boron in NaB(OMe)4. 11 B NMR spectrum; Figure 3 It is pure coconut oil. 1 1H NMR spectrum, in which the protons of the glycerol backbone are labeled; Figure 4 The decantation product / toluene layer of a reaction mixture according to one embodiment of this disclosure. 1 HNMR spectrum, inset shows the same sample. 11 B NMR spectrum; Figure 5 This is an implementation of the content of this disclosure. - OMe: Fatty acids ）Pure biodiesel (FAME) obtained from coconut oil at a molar ratio of 2:1 for 1 hour at 80°C. 1 1H NMR spectrum, inset shows the same sample. 11 The B NMR spectrum showed no glycerol-boron byproducts. Figure 6 This is a solid byproduct obtained from methanol-d4 according to one embodiment of this disclosure. 11 BNMR spectrum; Figure 7 The following diagram illustrates the reaction product of NaB(OMe)4 and coconut oil in toluene according to one embodiment of this disclosure. 1 The 1H NMR spectra showed that no FAME was produced after 1 hour and 24 hours of reaction at 25°C. Figure 8 The following describes an embodiment of FAME synthesized from soybean oil (25°C) or coconut oil (40, 60, and 80°C) according to this disclosure. 1 1H NMR spectra show the effect of temperature on transesterification of soybean oil (25°C) or coconut oil (40, 60 and 80°C) over a 1-hour reaction period; Figure 9 This is a biodiesel synthesized from waste cooking oil according to one embodiment of this disclosure. 1 1H NMR spectrum, inset shows the same sample. 11 B NMR spectrum, free of boron byproduct contaminants; Figure 10 This is an embodiment of the present disclosure, comprising an initial reaction mixture produced by mixing B(OMe)3 and NaOMe in MeOH. 11 B NMR spectrum, with the inset showing a magnified view of the signal region; Figure 11A FAME is a product obtained by reacting coconut oil with NaB(OMe)4, which is produced by mixing B(OMe)3 and NaOMe in MeOH, according to one embodiment of this disclosure. 1 H NMR spectrum; Figure 11B This refers to the solid byproducts remaining after decantation of FAME according to one embodiment of this disclosure. 11 BNMR spectrum; Figure 12 The image shows a mixture of reaction products of NaBH4 with EtOH (top), PrOH (middle), and BuOH (bottom) according to an embodiment of this disclosure. 11 B NMR spectrum and integration; Figure 13AThis is a FAME produced from cooking oil according to one embodiment of this disclosure. 1 H NMR spectrum; Figure 13B This refers to the production of ethyl fatty acid esters using this method according to one embodiment of the present disclosure. 1 HNMR spectrum; Figure 13C This refers to the production of propyl fatty acid esters using this method according to one embodiment of the present disclosure. 1 HNMR spectrum; Figure 13D This refers to butyl fatty acid esters produced using this method according to one embodiment of the present disclosure. 1 HNMR spectrum; and Figure 14 A flowchart of a method for preparing fatty acid alkyl esters from triglycerides according to one embodiment of the present disclosure is shown. Detailed Implementation

[0015] This disclosure provides a method for preparing fatty acid alkyl esters (FAAEs), such as fatty acid methyl esters (FAMEs), which can be used as biodiesel. The method includes a transesterification reaction of triglycerides, which are major components of vegetable oils or animal fats. The transesterification reaction involves adding a transesterification reagent along with the oil to form FAME or any other desired FAAE.

[0016] Figure 14 A method 10 for preparing FAAE suitable for use as biodiesel is shown. Method 10 includes preparing a transesterification reagent in step 12. The transesterification reagent may be a salt of a tetraalkoxyborate, such as sodium tetramethoxyborate [NaB(OMe)4], sodium tetraethoxyborate [NaB(OEt)4], sodium tetrapropoxyborate [NaB(OPr)4], and sodium tetrabutoxyborate [NaB(OBu)4]. Any suitable salt of the compositions described in this disclosure may be used, and sodium is used herein as an exemplary cation.

[0017] The choice of alkoxy group corresponds to the fatty acid ester produced via transesterification. Sodium tetraalkoxyborate can be prepared by adding sodium borohydride (NaBH4) to an alcohol, which may include, but is not limited to, methanol (MeOH), ethanol (EtOH), propanol (PrOH), and butanol (BuOH). An exemplary reaction for the preparation of NaB(OMe)4 is shown in Equation I below, wherein sodium borohydride is mixed with an alcohol to form a tetraalkoxyborate.

[0018] NaBH4+ 4 MeOH NaB(OMe)4+ 8H2 The alkoxy and tetraalkoxyborate groups of the alcohol can be the same, and can be one of methoxy, ethoxy, epoxy, or butoxy groups. The product of any of the above reactions (I) is an alkoxyborate / alcohol slurry (e.g., NaB(OMe)4 / MeOH), which acts as a methoxy anion source for the formation of FAME from vegetable oils. During the reaction, the hydride anion of NaBH4 reacts with the acidic proton of MeOH to form […]. - [OMe] and hydrogen. The reaction can continue for about 30 minutes or longer, or until hydrogen production stops. In step 14, the hydrogen can be collected and stored for later use. In an embodiment, the hydrogen can be used for the hydrogenation of fatty acid chains. Reaction (I) can be carried out at room temperature in any suitable container equipped with a gas outlet for collecting hydrogen, and can be aided by stirring.

[0019] In this embodiment, the resulting slurry can be dried to remove trace amounts of alcohol. Drying can be carried out using any suitable technique, such as a vacuum oven that can operate at approximately 80°C and 20 Torr.

[0020] In another embodiment, sodium tetraalkoxyborate, such as NaB(OMe)4, can also be prepared using the reaction shown in Equation II below, wherein a trialkoxyborane is mixed with an alkoxide to form a tetraalkoxyborate.

[0021] B(OMe)3+ NaOMe NaB(OMe)4 The reaction in equation (II) can be carried out in an alcohol, such as methanol, having the same alkoxy group as that of trialkoxyboranes, alkoxides, and tetraalkoxyborates, which may be one of methoxy, ethoxy, epoxy, or butoxy. The resulting solution can be stirred and then mixed with a triglyceride composition as described below.

[0022] In step 16, the transesterification reagent is mixed with the triglyceride composition (e.g., vegetable oil and / or animal fat). Suitable vegetable oils (e.g., collected from a deep fryer) or unused oils can be used, including soybean oil, rapeseed oil, coconut oil, sesame oil, nut oil, olive oil, seed oil, and combinations thereof. The oil can be added to the container containing the transesterification reagent at a molar ratio of transesterification reagent to oil of approximately 2:1 or higher. The oil can be added with or without a solvent (e.g., toluene).

[0023] In step 18, the reaction vessel may be heated to above 40°C, in some embodiments from about 40°C to about 80°C. Heating may take place for about 1 hour to about 24 hours. In another embodiment, the reaction may continue for about 1 hour to about 3 hours. The reaction mixture may be stirred by stirring or any other suitable mechanism.

[0024] In step 20, the obtained FAAE product is separated. After the reaction is complete, the FAAE forms a liquid, and the solid byproduct settles to the bottom of the reaction vessel. The liquid can be separated by any suitable method, such as decantation, filtration, centrifugation, etc. In another embodiment, a solvent such as hexane can be used to extract the residual liquid FAAE from the solid byproduct by rinsing the reaction vessel with the solvent. The solvent can then be removed from the liquid product by evaporation after heating the product to the boiling point of the solvent (approximately 80°C).

[0025] In optional step 22, hydrogenation can be performed using hydrogen produced during the production of tetraalkoxyborate and / or hydrogen from any other suitable source. The extracted FAAE can be hydrogenated in a reaction vessel with introduced hydrogen in the presence of a catalyst, which can be a bifunctional catalyst containing both acidic and metallic sites. The hydrogenation reaction can be carried out at a temperature of about 300°C and a pressure of about 5 MPa. Hydrogen reacts with the double bonds present in the FAAE fatty acid chain. This reaction saturates the double bonds through the addition of hydrogen atoms, converting unsaturated FAAE into its saturated counterpart. Furthermore, during hydrogenation, the catalyst also promotes hydrocracking, which involves breaking down long fatty acid chains into smaller molecules similar in length to those found in conventional diesel fuels. The final product can be further processed to remove impurities and obtain high-quality biodiesel.

[0026] The following examples illustrate implementations of the present disclosure. These examples are intended to be illustrative only and are not intended to limit the scope of the present disclosure. Furthermore, unless otherwise stated, parts and percentages are by weight. As used herein, “room temperature” or “ambient temperature” means a temperature of about 20°C to about 25°C.

[0027] Example Example 1 This example describes the synthesis of FAME using sodium methoxide.

[0028] for( - Ome:fatty acid) 1:1 (mol / mol), A 50 mL round-bottom flask equipped with a stir bar was used, and molten coconut oil (2.75 g, 4.0 mmol, 12 mmol fatty acid equivalent) was added to MeOH (2.5 mL). Then, NaOMe (0.65 g, 12 mmol) was added to the mixture. The flask was fitted with a diaphragm and a venting needle, and the reaction mixture was heated to approximately 80°C for about one hour. The resulting white slurry was decanted into a conical centrifuge tube and centrifuged with hexane (2... Rinse the reaction flask twice with 5 mL of the eluent, adding the eluent to a centrifuge tube, and then centrifuge. Decant the supernatant into a 100 mL round-bottom flask and evaporate hexane under vacuum (approximately 20 Torr) at approximately 80°C. The residue is an oily solid, which is dissolved in chloroform-d(CDCl3) for use in...1 H NMR analysis.

[0029] NMR was performed using a Bruker 500MHz spectrometer at 300K with a composite pulse sequence. The signal was analyzed at 160 and 500MHz. 11 B and 1 H record. 11 B and 1 H NMR chemical shifts were measured relative to external standards BF3:Oet2 (δ = 0 ppm) and TMS (δ = 0 ppm), respectively.

[0030] For 80°C and ( - The reaction was carried out in a 1:1 ratio of OMe (fatty acid chain) to FAME, and after one hour, a white slurry was produced from the reaction mixture. This slurry was washed with hexane to extract biodiesel and decanted into centrifuge tubes. Even after multiple centrifugation attempts, the residual solid byproducts in the decantation could not be separated from the hexane / biodiesel product. The decantation was added to a round-bottom flask, and despite the presence of a small amount of solids, hexane was evaporated at 80°C under house vacuum. No obvious biodiesel collection was observed in the flask. Byproduct crystals were present in the flask, and the presence of FAME was only as an oily substance on the flask walls. Chloroform-d was added to the flask to dissolve the oily substance, which was then absorbed through... 1 H NMR confirmed it to be biodiesel, such as Figure 1A As shown. The solid byproduct containing glycerol oxide was dissolved in methanol-d4, and then... 1 Analyze using H NMR, such as Figure 1B As shown.

[0031] use( - Additional experiments were conducted at 25 and 80°C with a NaOMe (NaOme:fatty acid) ratio of 2:1. At both temperatures, NaOMe powder was added to round-bottom flasks containing only oil and stirred vigorously. Both reaction mixtures rapidly thickened into a brown paste, making it impossible to rotate the stir bar. These reaction mixtures were not further analyzed.

[0032] for( -NaOMe (2.75 g, 4.0 mmol, 12 mmol fatty acid equivalent) was added to MeOH (2.5 mL) in a 50 mL round-bottom flask equipped with a stir bar. Then, NaOMe (1.30 g, 24 mmol) was added to the mixture. The flask was fitted with a diaphragm and a venting needle, and the reaction mixture was heated to 80°C. Within minutes, the mixture thickened into a brown paste, making it impossible to turn the stir bar. No liquid was observed, and the mixture was discarded. The same experiment was performed at 25°C, with the same results as at 80°C. These reaction mixtures were not further analyzed.

[0033] Example 2 This example describes the synthesis of NaB(Ome)4 for the synthesis of FAME from vegetable oil.

[0034] Introduced in the form of NaB(OMe)4 [ - OMe] was used as a means of producing FAME from vegetable oil. The synthesis of NaB(OMe)4 was accomplished by mixing NaBH4 (0.228 g, 6.0 mmol) with MeOH (2.5 mL) in a 50 mL round-bottom flask equipped with a stir bar. The flask was fitted with a diaphragm and a venting needle, and stirred at room temperature for approximately 30 minutes or until no more hydrogen gas was observed being produced in the NaB(OMe)4 / MeOH slurry. In this reaction, the hydride anions of NaBH4 react with the acidic protons of MeOH to form [ - [OMe] and hydrogen. Hydrogen can be stored and used for the hydrogenation of FAME fatty acid chains, making it a fully viable alternative to conventional diesel. 1 mole of NaBH4 reacts with 4 moles of MeOH to produce NaB(OMe)4 as the sole product. In a separate container, liquid coconut oil (2.15 g, 3.0 mmol) was dissolved in toluene (5 mL). This solution was then added to the NaB(OMe)4 / MeOH slurry, heated to 80°C, and allowed to react for two hours with stirring. The liquid was then decanted into a separate container and, without further purification, was obtained by... 1 H and 11 B NMR was used for analysis.

[0035] To produce FAME from vegetable oil, use [ - [OMe]. In Example 1, this was obtained from NaOMe. However, this makes it difficult to separate the liquid FAME from the solid byproduct compound, even by filtration and centrifugation.

[0036] The transesterification of vegetable oil into biodiesel was achieved through the reaction between NaBH4 and MeOH, as shown in equation (I) above.

[0037] Upon addition of NaBH4 to MeOH, hydrogen gas is released from the solution as the hydride anions of NaBH4 react with the acidic protons of MeOH. Sufficient MeOH is used to allow the resulting viscous mixture to be freely stirred using a magnetic stirrer. After hydrogen production ceases, approximately 30 minutes after the reaction begins, the resulting thick slurry of NaB(OMe)4 in MeOH serves as a methoxy anion source for the formation of FAME from vegetable oils.

[0038] Initially, a transesterification reaction was carried out in toluene using solid NaB(OMe)4. NaB(OMe)4 was prepared as described in Example 2, and excess MeOH was removed using a vacuum oven (80°C, 20 Torr), leaving pure NaB(OMe)4 for the initial experimental group. The transesterification reaction was carried out by adding coconut oil (2.15 g oil, 3 mmol oil; 9 mmol fatty acid) from toluene (5 mL) to solid NaB(OMe)4. The reaction was carried out at 80°C with vigorous stirring, using NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4). - NaB(OMe)4 is produced by Ome.

[0039] All four hydride anions of NaBH4 react with MeOH, resulting in the formation of - OMe, which combines with boron to form NaB(OMe)4, such as Figure 2 shown 11 As shown by B NMR. NaB(OMe)4 is used to form FAME from vegetable oils. - The source of OMe. The reaction proceeded to completion because no NaBH4 quintet was observed at approximately -42 ppm. The NaBH4-related quintet is shown in... Figure 10 middle.

[0040] Example 3 This example describes the effect of the (NaBH4: fatty acid) ratio on the synthesis of FAME in Example 2.

[0041] Various reaction conditions were explored to understand the reaction between NaB(OMe)4 and triacylglycerols. The ratio of NaBH4 to vegetable oil was investigated first. Due to the properties of NaB(OMe)4... - OMe reacts with the ester group of coconut oil to form FAME, the reaction being relative to... - OMe and fatty acid chains, rather than relative to NaB(OMe)4 or NaBH4 and coconut oil. Therefore, each molecule of NaB(OMe)4 contains four molar equivalents. - OMe can be formed from vegetable oils to produce FAME. Furthermore, since each triacylglycerol contains three molar equivalents of ester groups, 1:1, 3:2, and 2:1 ratios were explored. -The molar ratio of OMe (NaBH4:coconut oil) was 3:4, 1:1, and 3:2, respectively. The reaction was carried out with coconut oil and stirred at 80°C for one hour.

[0042] use( - The reaction of OMe (ometabolite and fatty acid) in a 1:1 (mol / mol) ratio produces a homogeneous emulsion, making it difficult to separate biodiesel using laboratory-developed separation methods. This may be due to... - OMe forms surfactants from vegetable oils when not present in excess. These surfactants can be glyceryl monolaurate and / or dilaurate. Surfactants promote the emulsification of FAME with byproducts, making separation a difficult task.

[0043] When the score is 3:2 or 2:1 ( - OMe (fatty acids) ratio used in excess [ - In the case of OMe, biodiesel and byproducts can be more easily separated. FAME can be decanted from the byproducts, making it a highly desirable method for biodiesel production. Using hexane improves the yield by extracting FAME from the byproducts and residual MeOH. Evaporation of the solvent hexane yields substantially pure FAME, which... 1 The 1H NMR spectrum shows a methyl peak at approximately 3.6 ppm, and no distinguishable peaks attributable to the initial triglyceride or MeOH, such as... Figure 5 As shown. Due to 2:1 ( - The OMe:fatty acid molar ratio provides the optimal FAME yield, using a ratio close to this ( - The values ​​of the OMe:fatty acid molar ratio were used to screen different vegetable oils and to study the effect of temperature on biodiesel production.

[0044] Biodiesel products 1 The absence of a glycerol peak in an 1H NMR spectrum is a good qualitative tool for determining the reaction progress. As a means of... 1 A more quantitative method for determining the completion of the reaction is ¹H NMR, which compares the integral of the methyl ester peak of FAME with the integral of the terminal -CH3 group of the fatty acid side chain of FAME. Since both the methyl group and the terminal carbon have three protons, the two integrals must have the same value to indicate the purity of FAME. Figure 5 As shown. Essentially pure methyl laurate was obtained as the major product of this reaction, as... Figure 5 As shown. This molecule, along with its 1 The H NMR spectra are displayed together. (The same sample) 11 B NMR spectra showed that the generated FAME was pure, and no glycerol or boron byproducts were present after centrifugation.

[0045] The initial reaction mixture of coconut oil and NaB(OMe)4 was present as a homogeneous emulsion. As the reaction proceeded, the FAME layer separated from a denser, semi-solid gel-like byproduct. The byproduct consisted of excess initial NaB(OMe)4 (3.01 ppm) and three other glyceroborates, such as... Figure 6 As shown. The initial NaB(OMe)4 has four methoxy groups bonded to the B atom. When the methoxy groups react with the triacylglycerols of coconut oil, glycerol oxides are formed and remain in their deprotonated state due to excess... - The presence of OMe ions leads to the formation of new boron-oxygen bonds by the negatively charged oxygen atoms in the newly formed glycerol oxide, resulting in glycerol oxide borate byproducts.

[0046] Based on reported chemical shift values ​​for several five- and six-membered mono- and double-chelated polyols of boric acid ([B(OH)₂L]⁻ and [BL₂]⁻), the peak at approximately 10.47 ppm can be attributed to Figure 6 The pentagonal bis(glycerol)borate shown typically has a signal in the range of about 9.8 to about 14.0 ppm. 11 The peaks at approximately 6.83 and 1.68 ppm in the 2000 NMR spectrum cannot be definitively attributed and may be from multiple cyclic borate species.

[0047] The dense byproducts accumulate at the bottom of the flask, allowing the newly formed FAME to be separated by simple decantation. An additional advantage of this reaction is that the glycerol oxide byproducts and the product FAME do not form an emulsion, allowing for easy separation. The initially separated FAME layer has a slightly turbid appearance but becomes clear by centrifugation followed by decantation of the supernatant. The turbidity is attributed to a small amount of suspended glycerol-boron byproducts. This is achieved by obtaining a small amount of solids accumulated at the bottom of the centrifuge tube. 11 The B NMR spectrum confirmed this. The collected [data / data]... 11 The B spectrum is identical to that of the bulk byproducts.

[0048] The effect of the ratio of NaBH4 to vegetable oil on biodiesel production was studied. Due to the […] derived from NaB(OMe)4 - The OMe equivalent is the active component of the reaction, and the [OMe] equivalent was evaluated. - [OMe] equivalents and various ratios of fatty acid chains in vegetable oils. When 1 molar equivalent of NaBH4 reacts with excess MeOH, 4.0 molar equivalents of [OMe] are produced due to the formation of NaB(OMe)4. - [OMe]. On the other hand, 1 molar equivalent of vegetable oil contains 3 molar equivalents of fatty acids that can be used to produce FAME biodiesel. Each molar ratio explored had the same amount of NaBH4 added to the varying amounts of coconut oil. Therefore, for [ -The reaction of OMe:fatty acid] with a molar ratio of 1:1, 3:2 and 2:1 (mol / mol) involves NaBH4 (0.228g NaBH4, 6.0mmol NaBH4; 24mmol NaBH4). - Add 2.5 mL of MeOH to a 50 mL round-bottom flask equipped with a stir bar. Then attach a diaphragm and a needle for venting the generated hydrogen gas, while allowing a minimal amount of air into the reaction mixture. Stir the mixture at room temperature for about 30 minutes or until the bubbling of hydrogen gas noticeably stops, then remove the diaphragm and needle.

[0049] For the 1:1, 3:2, and 2:1 reactions, the following amounts of coconut oil and fatty acid equivalents were added to the flasks: 5.51 g oil (8.0 mmol oil; 24 mmol fatty acid); 3.65 g oil (5.3 mmol oil; 16 mmol fatty acid); and 2.18 g oil (3.2 mmol oil; 10 mmol fatty acid). The needle and diaphragm were returned to the flasks, and the mixture was stirred vigorously at 80°C for one hour.

[0050] For the 1:1 reaction, a viscous emulsion was observed, with no discernible biodiesel layer. Hexane (10 mL) was added to the mixture to extract the biodiesel, but the emulsion remained, and no phase separation was observed. No further action was taken on the reaction mixture.

[0051] For the 3:2 reaction mixture, FAME was clearly separated from the byproducts at the end of the one-hour reaction time. FAME was decanted from the solid byproducts adhering to the bottom of the round-bottom flask. The flask was then rinsed twice with hexane, and the decant was added to the mixture, followed by centrifugation to remove any transferred solids. The liquid layer was added to the round-bottom flask, and hexane was evaporated under vacuum (20 Torr) at 80°C. The resulting product was a clear, colorless liquid, collected for use in... 1 H and 11 B NMR analysis.

[0052] Example 4 This example describes the effect of temperature on the synthesis of FAME in Example 2.

[0053] Use 2:1 ( - The effect of different reaction temperatures on the OMe:fatty acid molar ratio was investigated. Reactions at 40°C and 60°C were run under pristine conditions, where liquid coconut oil was added directly to the NaB(OMe)4 / MeOH slurry. At 25°C, soybean oil was used because it is more liquid than coconut oil at room temperature. A reaction temperature of 80°C was excluded because most of the above results were obtained at 80°C.

[0054] Due to the relatively simple chemical properties of this vegetable oil, transesterification using coconut oil was explored. Starting with coconut oil... 1 H NMR and proton assignment of the glycerol skeleton are shown in Figure 3 In the middle, all signals to the right of 3 ppm are related to the protons of the fatty acid chain, and for all practical purposes, they are assumed to be entirely lauric acid, labeled "R". The small signal to the left of the leftmost "H" originates from the small amount of unsaturation in coconut oil.

[0055] Coconut oil contains a significantly higher saturated fat content than other common edible vegetable oils. Its main components are lauric acid (12:0), myristic acid (14:0), and palmitic acid (16:0), accounting for approximately 32% to approximately 51%, approximately 17% to approximately 21%, and approximately 6.9% to approximately 14%, respectively. Understanding the starting oil... 1 In the case of H NMR, the reaction process towards FAME can be monitored.

[0056] After NaB(OMe)4 reacts with coconut oil in toluene for one hour, the upper layer of the mixture is decanted and collected for use in [further processing]. 1 H and 11 B NMR analysis ( Figure 4 ). 1 1H NMR spectra show that coconut oil has been completely converted into biodiesel, such as glycerol. 1 This is evidenced by the disappearance of the H signal and the appearance of the methyl peak in the product FAME. The small peak at approximately 3.3 ppm... 1 The H singlet (occasionally two overlapping singlets) is attributed to residual methanol ( see below ). 11 B NMR such as Figure 4 As shown, no boron impurities are present in the toluene / biodiesel layer. The small boron signal in the inset is from the borosilicate glass of the NMR tube.

[0057] use( - The effect of various temperatures (25°C, 40°C, 60°C, and 80°C) on FAME synthesis was investigated using an OMe:fatty acid ratio of 2:1 (mol / mol). NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4) was added to a 50 mL round-bottom flask equipped with a stir bar. -OMe) was added to MeOH (2.5 mL). The flask was then fitted with a diaphragm and a venting needle for the generated hydrogen, and the mixture was stirred at 25°C for approximately 30 minutes or until bubbling clearly stopped. Liquid coconut oil (2.18 g oil, 3.2 mmol oil; 10 mmol fatty acid) was added to the resulting NaB(OMe)4 / MeOH slurry. The diaphragm and venting needle were returned to the flask, and the mixture was heated to 80°C and stirred for one hour. The resulting liquid layer was decanted into a Falcon tube, and the reaction mixture was washed with hexane (2 mL) to extract residual biodiesel. The wash was added to the decanter. The solution was then centrifuged to remove any small amount of solid byproducts transferred with the decanter. The resulting liquid layer was added to a round-bottom flask, and the hexane was evaporated under vacuum (20 Torr) at 80°C. The residue was collected for use in... 1 H and 11 B NMR analysis.

[0058] 1 ¹H NMR showed that the reaction at 25°C produced almost no FAME. This was indicated by the presence of a glycerol proton signal at approximately 4.2 ppm and the absence of a methyl ester peak for FAME at approximately 3.6 ppm. Figure 7 As shown. Even after 24 hours, the glycerol-related signal remained significant, indicating a substantial amount of initial soybean oil. The singlet at approximately 3.4 ppm is attributed to methanol, its presence being due to the product not being extracted with hexane. If the reaction were stirred for 24 hours, much more biodiesel would be produced, but the presence of unreacted glycerol indicates the presence of unreacted soybean oil in the FAME. The chromatogram of the 24-hour reaction also contained significantly less residual MeOH from the initial NaB(OMe)₄ / MeOH slurry, such as... Figure 7 As shown. This is likely due to the evaporation of MeOH during the long reaction process.

[0059] A one-hour reaction at 40°C and 60°C yielded a complete conversion of coconut oil to fAME, as shown in the figure. Figure 8 As shown, the reaction proceeded as described above, similar to the reaction carried out at 80°C. The singlet at approximately 3.46 ppm in the spectra at 25°C, 40°C, and 60°C is attributed to residual MeOH, as the final product was only decanted from the reaction mixture without extraction with hexane. Extraction of the product with hexane at 80°C was performed to confirm that the MeOH peak would originate from the reaction mixture. 1 Completely removed from the H spectrum. The distinguishing feature between the reaction run at 80°C and those run at 40°C and 60°C is that the former... 1 In the 1H NMR spectrum, the glycerol hydrogens completely disappear. Although they are in Figure 8The effect is not obvious, but a region around 4.20 ppm exposes a small glycerol signal in the original spectrum, just above the background noise. Its presence is so small that the integrals of the methyl and terminal fatty acid protons are unaffected, and the integral shows 100% reaction completion, although the signal is barely detectable. For a reaction run at 80°C... 1 Any amplification by ¹H NMR failed to reveal any signal associated with glycerol. To completely eliminate the presence of any detectable glycerol in the product diesel, chemical treatments were performed using waste cooking oil as a feedstock at 80°C and (…). - Experiments were conducted with an OMe:fatty acid ratio of 2:1.

[0060] Example 5 This embodiment describes the synthesis of FAME from waste cooking oil.

[0061] To a 50 mL round-bottom flask equipped with a stir bar, add NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4). - OMe) was added to MeOH (2.5 mL). The flask was fitted with a diaphragm and a needle for venting the generated hydrogen, and the reaction was stirred at room temperature for about 30 minutes or until bubbling subsided. Then, cooking oil (3.23 g oil, 3.5 mmol oil; 10 mmol fatty acid) was added, and the diaphragm and needle were reattached. The reaction mixture was heated to 80°C and stirred vigorously for one hour. The liquid was decanted from the solid byproducts and precipitated with hexane (2... Wash the flask twice with 2 mL of the eluent, combine with the decantate, and then centrifuge to remove any additional trace amounts of solid byproducts. Then evaporate hexane under vacuum (20 Torr) at 80°C. The product, FAME, is a yellow-orange, slightly viscous liquid, collected for use in... 1 H and 11 B NMR analysis.

[0062] Example 6 This example describes the synthesis of FAME using NaB(OMe)4, which is synthesized from the reaction of B(OMe)3 and NaOMe in MeOH.

[0063] Add MeOH (3 mL) to a 50 mL round-bottom flask equipped with a stir bar, followed by B(OMe)3 (0.67 mL, 6 mmol). Add NaOMe (0.324 g, 6 mmol) to the solution and stir briefly to dissolve all solids. Add molten coconut oil (3.23 g, 3.5 mmol oil, 10 mmol fatty acid) to the solution. Fit the flask with a diaphragm and a venting needle, and stir the reaction at 80°C for one hour. After one hour, remove the product from the heat source and allow it to cool slightly so that the product FAME can be easily decanted from the solid byproducts. Decant the liquid from the solid byproducts with hexane (2... Wash the flask twice with 2 mL of the eluent, combine with the decantate, and then centrifuge to remove any additional trace amounts of solid byproducts. Then evaporate hexane under vacuum (20 Torr) at 80°C. The product, FAME, is a clear, colorless, slightly viscous liquid, collected for use in... 1 H and 11 B NMR analysis.

[0064] The above experiments show that NaB(OMe)4 is - An efficient source of OMe allows for the simple synthesis and isolation of FAME without the generation of water or the need for a heterogeneous catalyst. Examples to date have synthesized NaB(OMe)4 via the reaction between NaBH4 and MeOH. However, this salt can also be synthesized using the highly inexpensive chemicals B(OMe)3 and NaOMe, as shown in equation (II) above.

[0065] This alternative chemical route for NaB(OMe)4 production, utilizing abundant and inexpensive reagents, makes the biodiesel production process truly industrially feasible. The method disclosed herein successfully produced pure FAME under the same conditions explored using NaBH4 and MeOH.

[0066] The process involves adding B(OMe)3 and NaOMe to MeOH to form a mixture containing NaB(OMe)4. 11 BNMR analysis showed that the mixture was not pure NaB(OMe)₄, but rather a combination of four different boron products, possibly originating from impurities in commercially purchased NaOMe, such as... Figure 10 As shown. The signal at approximately 3.3 ppm corresponds to NaB(OMe)4, as observed when producing this molecule using NaBH4 and MeOH. The presence of additional boron species does not affect the production of FAME from coconut oil, as... Figure 11A As shown. The solid byproducts remaining after decantation of FAME are chemically identical to the byproducts produced by transesterification using NaB(OMe)4 produced from NaBH4 and MeOH, such as... Figure 11B As shown.

[0067] Further experiments showed that the reaction could be run under pure, solvent-free conditions. It was also found that the excess MeOH used to prepare NaB(OMe)4 did not need to be evaporated before the addition of coconut oil. However, it was crucial that hydrogen evolution was completed before the coconut oil was added to the reaction flask. This would indicate that all NaBH4 had reacted with MeOH and that there were no hydride ions to reduce the ester groups of the coconut oil. For these reactions, MeOH was added directly to NaBH4 to obtain a NaB(OMe)4 / MeOH slurry. Coconut oil was then added directly to this slurry. This experimental protocol allowed the investigation of the following variables: 1) -The effects of the ratio of OMe (fatty acids) on: 2) reaction temperature; and 3) the type of vegetable oil that can be used to form FAME. Biodiesel was extracted from the crude reaction mixture in a near-quantitative yield using hexane, and MeOH was removed from the final product.

[0068] Example 7 This example describes the synthesis of fatty acid ethyl esters.

[0069] To further investigate the versatility of synthesizing FAAE from waste cooking oil using NaBH4 in the presence of alcohol, the synthesis of ethyl esters was tested. This was carried out by adding NaBH4 to ethanol (EtOH) and allowing the solution to react until no more visible hydrogen gas was produced. The reaction of NaBH4 with EtOH proceeds at room temperature, but is slower than the reaction of NaBH4 with MeOH. As observed in the reaction of NaBH4 with MeOH, the product of the reaction of NaBH4 with EtOH is NaB(OEt)4. However, unlike NaBH4 and MeOH, NaBH4 does not react completely with EtOH, as... Figure 12 of 11 The quintet is shown at -42 ppm in the B NMR. This is still the case even when the reaction is carried out in the presence of excess alcohol until no hydrogen evolution is observed.

[0070] The reaction was carried out in a 50 mL round-bottom flask equipped with a stir bar. NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4) was added. - OEt was added to EtOH (2.5 mL). The flask was fitted with a diaphragm and a needle for venting the generated hydrogen gas, and stirred at room temperature for about 10 minutes, during which slight bubbling was observed. The reaction was then heated to 80°C and reacted for another hour; no bubbling was observed thereafter. Not all of NaBH4 reacted. A sample of the mixture was collected for use... 11 B NMR. Waste cooking oil (3.23 g oil, 3.5 mmol oil; 10 mmol fatty acid) was added to the turbid reaction mixture, and the diaphragm with a needle was placed back onto the flask. The mixture was then heated to 80°C and stirred vigorously for two hours. The mixture at the end of the two-hour reaction time was a clear, yellow-orange putty-like substance. Hexane (4... Extract the ethyl fatty acid ester using 10 mL of the extract and centrifuge. Decant the liquid layer into a round-bottom flask and evaporate hexane under vacuum (20 Torr) at 80°C. Collect the product and residual byproducts for further processing. 1 H and 11 BNMR analysis, as described in Example 9.

[0071] Example 8 This example describes the synthesis of fatty acid propyl esters.

[0072] To further investigate the versatility of synthesizing FAAE from waste cooking oil using NaBH4 in the presence of alcohol, the synthesis of propyl ester was also tested. This was carried out by adding NaBH4 to propanol (PrOH) and allowing the solution to react until no more visible hydrogen gas was produced. The reaction between NaBH4 and PrOH did not proceed at a considerable rate at room temperature, so heating at 80°C was performed until no further hydrogen gas was observed to be produced. As seen in the reaction of NaBH4 with MeOH, the product of the reaction of NaBH4 with PrOH is NaB(OPr)4. However, unlike NaBH4 and MeOH, NaBH4 did not react completely with PrOH, as... Figure 12 of 11 The quintet is shown in the B NMR spectrum at -42 ppm. This is still the case even when the reaction is carried out in the presence of excess alcohol until no hydrogen evolution is observed.

[0073] The reaction was carried out in a 50 mL round-bottom flask equipped with a stir bar. NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4) was added. - OPr was added to PrOH (2.5 mL). The flask was fitted with a diaphragm and a needle for venting the generated hydrogen gas, and stirred at room temperature for about 10 minutes; no bubbling was observed during this time. The mixture was heated to 80°C and stirred vigorously for about one hour; no further bubbling was observed afterward. Not all of NaBH4 dissolved; aliquots of the viscous, turbid mixture were collected for… 11 B NMR analysis. Waste cooking oil (3.23 g oil, 3.5 mmol oil; 10 mmol fatty acid) was added to the reaction flask, and the diaphragm with a needle was placed back onto the flask. The mixture was then heated to 80°C and stirred vigorously for two hours. The unpurified mixture was a viscous, transparent, yellow-orange substance. Hexane (4... Extract propyl fatty acid alkyl esters (10 mL) and add them to a centrifuge tube. Then centrifuge the mixture and add the clear hexane layer to a round-bottom flask. Evaporate the hexane under vacuum (20 Torr) at 80°C, and collect the residue for further processing. 1 H and 11 B NMR analysis was also performed. Solid byproducts were also collected for further analysis. 1 H and 11 B NMR analysis, as described in Example 9.

[0074] Example 9 This example describes the synthesis of fatty acid butyl esters.

[0075] To further investigate the versatility of synthesizing FAAE from waste cooking oil using NaBH4 in the presence of alcohol, the synthesis of butyl ester was also tested. This was carried out by adding NaBH4 to butanol (BuOH) and allowing the solution to react until no more visible hydrogen gas was produced. The reaction between NaBH4 and BuOH did not proceed at a considerable rate at room temperature, so heating at 80°C was performed until no further hydrogen gas was observed to be produced. As seen in the reaction of NaBH4 with MeOH, the product of the reaction of NaBH4 with BuOH is NaB(OBu)4. However, unlike NaBH4 and MeOH, NaBH4 did not react completely with BuOH, as... Figure 12 of 11 The quintet is shown at -42 ppm in the B NMR. This remains true even when the reaction is carried out in the presence of excess alcohol until no hydrogen evolution is observed. The order of reactivity of NaBH4 with alcohols described in Examples 7, 8 and this example follows the trend MeOH > EtOH > PrOH > BuOH.

[0076] The reaction was carried out in a 50 mL round-bottom flask equipped with a stir bar. NaBH4 (0.228 g NaBH4, 6 mmol NaBH4; 24 mmol NaBH4) was added. - OBu) was added to BuOH (5.0 mL). The flask was fitted with a diaphragm and a needle for venting the generated hydrogen gas, and stirred at room temperature for about 10 minutes; no bubbling was observed during this time. The reaction mixture was heated to 80°C and stirred vigorously for about 20 minutes, after which additional BuOH (5 mL) was added. The mixture was reheated to 80°C and stirred vigorously for about three hours; no further bubbling was observed after this time. Not all NaBH4 dissolved; a sample of the viscous, turbid mixture was collected for further processing. 11 B NMR. Waste cooking oil (3.23 g oil, 3.5 mmol oil; 10 mmol fatty acid) was added to the reaction flask, and the diaphragm with a needle was placed back onto the flask. The mixture was then heated to 80°C and stirred vigorously for two hours. The unpurified mixture was a clear, viscous, yellow-orange mixture. Hexane (4... Extract 10 mL of butyl fatty acid alkyl ester and add it to a centrifuge tube. Then centrifuge the mixture; no obvious liquid separation was observed. Add additional hexane (3 mL) to the mixture. (10 mL), after centrifugation, a small amount of phase separation was discernible. The liquid layer was decanted into a round-bottom flask, and hexane was removed by vacuum evaporation (20 Torr) at 80°C. The final product was a yellow, highly viscous material. Samples of the product and byproducts were collected for use... 1 H and 11 BNMR analysis.

[0077] like Figure 12 As shown,11 B NMR spectra revealed the presence of unreacted NaBH4 in the initial borate-alkoxide / alcohol slurry. The presence of unreacted NaBH4 does not affect the transesterification reaction. Its presence was originally expected to cause problems because NaBH4 can react with EtOH, PrOH, and BuOH to form NaBH3(OEt), NaBH3(OPr), and NaBH3(OBu), respectively. These substances are intermediates of NaB(OEt)4, NaB(OPr)4, and NaB(OBu)4. The hydrides of these intermediate species are more reactive than the hydrides of NaBH4, reducing the ester groups of vegetable oils and preventing transesterification. However, 1 ¹H NMR showed that transesterification did indeed occur, producing ethyl, propyl, and butyl FAAE, such as Figures 13A-13D As shown. The success of the reaction is clearly demonstrated by the complete disappearance of the glycerol signal centered at approximately 4.20 ppm in the waste cooking oil, and the appearance of a new signal (quartet) for ethyl fatty acid alkyl esters at approximately 4.1 ppm, and new signals (triplet) for propyl and butyl FAAEs at approximately 4.0 ppm. Unlike the closely related FAME, ethyl, propyl, and butyl esters are quite difficult to separate from the glycerol oxide byproducts. This is because the emulsions present in EtOH, PrOH, and BuOH are more difficult to demulsify than the emulsions in MeOH.

[0078] Example 10 This embodiment describes the synthesis of FAME from cooking oil obtained from a commercial fast-food chain.

[0079] Using edible crude oil to produce biodiesel not only diverts a vital food resource from consumers but also results in an uncompetitive price compared to fossil fuel-derived diesel. Waste cooking oil is currently a large-scale waste product that can become an environmental pollutant. Using waste cooking oil as a feedstock for biodiesel eliminates the need for crude cooking oil and makes the biodiesel process potentially competitive with fossil fuel diesel. For these reasons, the possibility of producing biodiesel using NaBH4 in MeOH with waste cooking oil from a large fast-food chain was investigated. When the waste oil was added to a NaB(OMe)4 / MeOH slurry and stirred at 80°C for one hour, pure biodiesel was produced as the sole byproduct. Figure 9 As shown. An additional benefit is that the byproduct exists in solid form at the bottom of the flask, and the product biodiesel can be easily separated by simple decantation. 1 H and 11 B NMR showed that the collected biodiesel was free of boron impurities, such as Figure 9 As shown.

[0080] Example 11 This example describes the synthesis of FAME from different oils.

[0081] The method disclosed herein is applicable to industrially real feedstock oils, such as waste cooking oil from fast-food chains. Practical application would be far off if the method were limited to raw edible oils. For completeness, raw oils were also used to study the mechanism of this novel reaction, as they are readily available.

[0082] Although waste cooking oils are typically mixtures of vegetable oils, the synthesis of FAME using a variety of common edible oils was investigated to ensure that this biodiesel production method is applicable to a variety of pure oils. When NaB(OMe)4 / MeOH is mixed with any of corn oil, olive oil, sesame oil, soybean oil, or lard, biodiesel is produced as a separate liquid layer, with byproducts present as solids at the bottom of the flask. This allows for easy separation of the biodiesel from the glycerol-boron byproducts and excess starting NaB(OMe)4 material. A small amount of this undesirable solid contaminates the biodiesel, but the amount is so small as to be negligible. 11 BNMR spectroscopy detected the contaminant. However, due to this contaminant, the biodiesel exhibited a slightly cloudy appearance. To obtain the purest biodiesel, the initial decantation of FAME was extracted with hexane to remove any excess MeOH, and the entire mixture was centrifuged to remove any remaining solid byproducts. Hexane was then evaporated from the decantation, yielding a pure, clear biodiesel solution with a yellow-orange to colorless appearance. These solutions... 1 The H NMR results were identical to those of previously observed biodiesel samples. The yield of all oils was approximately 85%.

[0083] Alternative implementation schemes may be designed without departing from the spirit or scope of this technology. Furthermore, well-known elements of the implementation schemes of the systems, apparatus, and methods are not described in detail or are omitted to avoid obscuring the relevant details of the systems, apparatus, and methods.

[0084] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article of manufacture, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article of manufacture, or apparatus. Without further limitation, an element beginning with “comprising…a” does not exclude the presence of additional identical elements in the process, method, article of manufacture, or apparatus that includes that element. As used herein, the terms “comprising” and / or “having” are defined as inclusion (i.e., open-ended language). As used herein, the term “an” is defined as one or more. As used herein, the term “a plurality” is defined as two or more. As used herein, the term “another” is defined as at least a second or more. The description may use the terms “implementation” or “multiple embodiments,” each referring to one or more of the same or different embodiments.

[0085] For descriptive purposes, phrases of the form "A / B", "A and / or B", or "at least one of A and B" represent (A), (B), or (A and B), where A and B are variables indicating a particular object or attribute. When used, the phrase is intended and specifically defined as a choice of A or B, or both A and B, similar to the phrase "and / or". When more than two variables are present in such a phrase, the phrase is specifically defined as including only one variable, any single variable, any combination of any variables, and all variables; for example, a phrase of the form "at least one of A, B, and C" represents (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0086] Various operations can be described as a series of discrete operations in sequence, which may help in understanding the implementation scheme; however, the order of description should not be interpreted as implying that these operations are sequentially dependent.

[0087] As used herein, the terms “about” or “approximately” apply to all numerical values, whether explicitly stated or not. These terms generally refer to a range of numbers that a person skilled in the art would consider equivalent to the stated numerical value (i.e., having the same function or result). In many cases, these terms may include numbers rounded to the nearest significant figure.

[0088] As will be appreciated from the foregoing, specific embodiments of this disclosure have been described herein for illustrative purposes, but various modifications may be made without departing from the scope of this disclosure. Therefore, this disclosure is not limited except as defined by the appended claims.

Claims

1. A method for transesterification of triglycerides, the method comprising: Tetraalkoxyborate is mixed with a triglyceride composition to form a reaction mixture; as well as The reaction mixture is heated to above 40°C to form fatty acid alkyl esters.

2. The method according to claim 1, wherein the tetraalkoxyborate is selected from the group consisting of tetramethoxyborate, tetraethoxyborate, tetrapropoxyborate and tetrabutoxyborate.

3. The method according to claim 1, wherein the fatty acid alkyl ester is selected from the group consisting of fatty acid methyl ester, fatty acid ethyl ester, fatty acid methyl ester, fatty acid propyl ester and fatty acid butyl ester.

4. The method of claim 1, wherein heating is performed for about 1 hour to about 24 hours.

5. The method according to claim 1, further comprising: The tetraalkoxyborate was prepared in a reaction vessel; as well as The triglyceride composition is added to the reaction vessel.

6. The method according to claim 5, wherein the preparation of the tetraalkoxyborate comprises: The borohydride is mixed with the alcohol.

7. The method of claim 6, wherein the alcohol and the tetraalkoxyborate contain the same alkoxy group.

8. The method according to claim 7, wherein the alkoxy group is selected from the group consisting of methoxy, ethoxy, epoxy, and butoxy.

9. The method according to claim 5, wherein the preparation of the tetraalkoxyborate comprises: Mix the trialkoxyborane with the alkoxide.

10. The method of claim 9, wherein the trialkoxyborane, the alkoxide, and the tetraalkoxyborate contain the same alkoxy group.

11. The method of claim 10, wherein the alkoxy group is selected from the group consisting of methoxy, ethoxy, epoxy, and butoxy.

12. The method according to claim 1, further comprising: Hydrogenation of fatty acid alkyl esters.

13. The method of claim 12, wherein the hydrogenation is performed using hydrogen gas collected during the preparation of the tetraalkoxyborate.

14. A method for preparing biodiesel, the method comprising: Tetramethoxyborate is mixed with a triglyceride composition to form a reaction mixture, wherein the triglyceride composition comprises at least one of vegetable oil or animal fat; as well as The reaction mixture is heated to above 40°C to form a diesel fuel containing fatty acid methyl esters.

15. The method of claim 14, wherein heating is performed for about 1 hour to about 24 hours.

16. The method of claim 14, further comprising: The tetramethoxyborate was prepared in a reaction vessel; as well as The triglyceride composition is added to the reaction vessel.

17. The method of claim 16, wherein the preparation of the tetramethoxyborate comprises: The borohydride was mixed with methanol.

18. The method of claim 14, wherein the preparation of the tetramethoxyborate comprises: Trimethoxyborane was mixed with methanol salt.

19. The method of claim 14, further comprising: Hydrogenation of fatty acid methyl esters.

20. The method of claim 19, wherein the hydrogenation is performed using hydrogen gas collected during the preparation of the tetramethoxyborate.

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