A method for producing a hydrodeoxygenatable intermediate using conjugated fatty acids and uses thereof

Abstract

The application discloses a method for preparing a hydrogenation deoxidation intermediate by using conjugated fatty acids and application thereof, and belongs to the technical field of oil production biofuel. The method comprises the following steps: (1) subjecting conjugated fatty acids and a dienophilic monomer to a Diels-Alder addition reaction to obtain an addition product; and (2) removing unreacted raw materials from the addition product, so that the hydrogenation deoxidation intermediate is obtained. The method breaks the traditional idea of deoxidation first and isomerization later, and instead adopts the idea of "structure modification first and hydrogenation deoxidation later" to prepare the hydrogenation deoxidation intermediate, so that the hydrogenation isomerization process can be omitted, the generation of cracking products is reduced, the content of isomerization products in the biodiesel is significantly improved, and higher-quality biofuel is obtained.

Description

Technical Field

[0001] This application relates to a method for preparing hydrodeoxygenable intermediates using conjugated fatty acids and its application, belonging to the field of oil and fat biofuel technology. Background Technology

[0002] With the scarcity of fossil fuels and increasingly stringent environmental requirements, the production of renewable biofuels from waste oils has become an important development direction in the biomass energy sector. After pretreatment to remove impurities, moisture, and free fatty acids, waste oils typically undergo catalytic hydrodeoxygenation to remove oxygen atoms, converting them into long-chain n-alkanes. Further hydroisomerization converts straight-chain alkanes into branched-chain alkanes, effectively improving the fuel's low-temperature fluidity. After fractionation, compliant hydrocarbon-based biodiesel, biojet fuel, and other green fuels can be obtained. This route, using renewable waste as raw material, has become a key technological path for replacing fossil fuels.

[0003] However, existing hydroisomerization routes for oils and fats suffer from poor reaction selectivity, easy coking, numerous side reactions, and wide carbon chain distribution of products. The main production path involves first hydrodeoxygenating and then hydroisomerizing. The applicant has discovered that cracking reactions are highly likely to occur during the hydroisomerization of oils and fats, which is a major reason affecting the yield of target biofuels. To reduce the content of cracking products during hydroisomerization, current methods mainly focus on controlling the reaction parameters of hydroisomerization or designing catalysts with high isomerization selectivity.

[0004] For example, patent 202610199622.4 utilizes a novel hierarchical porous composite molecular sieve catalyst to achieve a uniform transition of pores, thereby regulating the hydroisomerization catalytic effect on oils and fats to reduce cracking products and increase the content of isomerization products in biofuels. While such modulating catalysts can improve the pour point or freezing point of biofuels to some extent by modifying the product composition, the numerous oil and fat catalytic hydrogenation processes still present problems such as highly complex reaction mechanisms and difficulty in controlling the reaction process, which are not conducive to further improving the quality of biofuels. Summary of the Invention

[0005] To address the aforementioned issues, a method for preparing hydrodeoxygenable intermediates using conjugated fatty acids is provided. This method breaks away from the traditional approach of first deoxygenating and then isomerizing, instead employing a "first modify the structure, then hydrodeoxygenate" approach to prepare hydrodeoxygenable intermediates. This eliminates the need for the hydroisomerization process, thereby reducing the generation of cracking products and significantly increasing the content of isomerization products in biodiesel, resulting in higher-quality biofuels.

[0006] According to a first aspect of this application, a method for preparing a hydrodeoxygenable intermediate using conjugated fatty acids is provided, comprising the following steps: (1) Conjugated fatty acids and dienophilic monomers are subjected to Diels-Alder addition reaction to obtain addition products; (2) Remove the unreacted raw material from the addition product to obtain the hydrodeoxygenable intermediate.

[0007] This application utilizes conjugated fatty acids to undergo a Diels-Alder addition reaction to obtain an addition product with a cyclic structure. By modifying the structure of the conjugated fatty acids, the structural disorder of the hydrodeoxygenable intermediate is increased. This hydrodeoxygenable intermediate can be directly hydrodeoxygenated without further isomerization to obtain biofuels, fundamentally reducing the formation of cracking products during isomerization and significantly improving the quality of biofuels.

[0008] Optionally, the conjugated fatty acid includes at least one of conjugated linolenic acid, conjugated linoleic acid, and sorbic acid.

[0009] Specifically, due to the cis-trans isomerism of the double-bonded molecules, the above-mentioned conjugable fatty acids have multiple CAS numbers. Substances with different CAS numbers can all be used to prepare the hydrodeoxygenable intermediate of this application. For example, the CAS numbers of conjugated linolenic acid can be: 544-72-9, 28872-28-8, 506-23-0, 4337-71-7, 544-73-0; the CAS numbers of conjugated linoleic acid can be: 121250-47-3, 2420-56-6; and the CAS numbers of sorbic acid can be: 22500-92-1, 110-44-1.

[0010] Optionally, the conjugated fatty acid is obtained by a conjugation reaction of a conjugable fatty acid, wherein the conjugable fatty acid contains at least one adjacent double bond and a -CH2- group is present between the adjacent double bonds.

[0011] The adjacent double bonds in the conjugable fatty acids of this application refer to the -CH=CH-CH2-CH=CH- structure, where an adjacent double bond contains a -CH2- group between two double bonds. Only fatty acids of this type can undergo conjugation reactions and, through Diels-Alder addition reactions, yield hydrodeoxygenable intermediates with cyclic structures. Compared to the starting material (conjugable fatty acids), these hydrodeoxygenable intermediates exhibit a higher degree of molecular chain disorder, resulting in a higher degree of disorder in the alkane produced by hydrodeoxygenation. This improves the low-temperature cooling performance of biofuels and lowers their freezing point.

[0012] The conjugable fatty acids of this application may contain one "-CH=CH-CH2-CH=CH-" structure or two "-CH=CH-CH2-CH=CH-" structures. In addition, the "-CH=CH-CH2-CH=CH-CH2-CH=CH-" structure represents the presence of two adjacent double bonds, and so on.

[0013] Optionally, the conjugable fatty acids include at least one of α-linolenic acid, linoleic acid, eicosadienoic acid, eicosatrienoic acid, eicosatraenoic acid, eicosapentaenoic acid, and docosahexaenoic acid.

[0014] Specifically, the CAS number for alpha-linolenic acid is 463-40-1, and the CAS number for linoleic acid is 60-33-3.

[0015] Among them, eicosaadienoic acid, eicosatrienoic acid, eicosatraenoic acid, eicosapentaenoic acid, and docosahexaenoic acid have multiple CAS numbers due to the position of their functional groups and cis-trans isomerism. Substances with different CAS numbers can all be used to prepare the hydrogenodeoxygenable intermediates of this application. For example, the CAS numbers for eicosaadienoic acid can be: 2091-39-6, 122458-81-5, and 82073-91-4; the CAS numbers for eicosatrienoic acid can be: 20590-32-3, 1783-84-2, 17046-59-2, and 2091-27-2; the CAS numbers for eicosatraenoic acid can be: 506-32-1 and 24880-40-8; the CAS number for eicosapentaenoic acid is: 10417-94-4; and the CAS number for docosahexaenoic acid is: 6217-54-5.

[0016] Optionally, the conjugable fatty acids undergo a conjugation reaction as follows: The conjugable fatty acids were reacted at 160-260℃ for 2-10 hours under the action of a catalyst; Preferably, the catalyst comprises an alkaline substance or elemental iodine, and the amount of the catalyst added accounts for 0.3wt%-1.2wt% of the mass of the conjugable fatty acid.

[0017] Under the above reaction conditions and with the addition of a catalyst, the yield of conjugated fatty acids can be improved, impurities can be avoided, and production costs can be saved.

[0018] Specifically, the alkaline substance includes at least one of potassium hydroxide, sodium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, and cesium hydroxide.

[0019] Optionally, the dienophile monomer includes at least one of maleic acid dienophile monomers, fumaric acid dienophile monomers, itaconic acid dienophile monomers, and C8-C16 olefins.

[0020] Preferably, the maleic acid-based diephilic monomer is selected from compounds of formula I or maleic anhydride, the fumaric acid-based diephilic monomer is selected from compounds of formula II, and the itaconic acid-based diephilic monomer is selected from compounds of formula III.

[0021] Formula I;

[0022] Formula II;

[0023] Formula III; R1, R3, R4, R6, R7, and R8 are independently selected from alkyl groups containing 1 to 8 carbon atoms, and R2 and R5 are independently selected from H or alkyl groups containing 1 to 4 carbon atoms.

[0024] The aforementioned dienophilic monomers can undergo Diels-Alder addition reactions with conjugated fatty acids, which improves reaction efficiency, shortens reaction time, reduces production costs, and is easy to remove in subsequent washing, reducing post-processing difficulty and improving the production operability of this method.

[0025] Optionally, the compound of Formula I includes at least one of dimethyl maleate, 2-methyl dimethyl maleate, diisooctyl maleate, and dibutyl maleate.

[0026] Specifically, the CAS number for dimethyl maleate is 624-48-6, the CAS number for 2-methyl dimethyl maleate is 617-54-9, the CAS number for dibutyl maleate is 105-76-0, and the CAS number for diisooctyl maleate is 1330-76-3.

[0027] Optionally, the fumarate diacetic monomer includes at least one of dimethyl fumarate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, and diisobutyl fumarate.

[0028] Specifically, the CAS number for dimethyl fumarate is 624-49-7, the CAS number for 2-methyl fumarate is 617-53-8, the CAS number for diethyl fumarate is 623-91-6, the CAS number for dibutyl fumarate is 105-75-9, the CAS number for dioctyl fumarate is 2997-85-5, and the CAS number for diisobutyl fumarate is 7283-69-4.

[0029] Optionally, the itaconic acid-based diephilic monomer includes at least one of dimethyl itaconic acid, diethyl itaconic acid, and dibutyl itaconic acid.

[0030] Specifically, the CAS number for dimethyl itaconic acid is 617-52-7, the CAS number for diethyl itaconic acid is 2409-52-1, and the CAS number for dibutyl itaconic acid is 2155-60-4.

[0031] Optionally, in step (1), the molar ratio of conjugated fatty acid to dienophilic monomer is 1:(1-1.5), the reaction temperature is 160-260℃, and the reaction time is 2-10h.

[0032] The molar ratio of the two substances in step (1) can ensure that the conjugated fatty acid is completely converted into the hydrodeoxygenable intermediate, improve the reaction rate of the conjugated fatty acid, and thus improve the yield of the hydrodeoxygenable intermediate, which can be stabilized at over 80%.

[0033] The reaction temperature of step (1) is not higher than the temperature of normal oil hydroisomerization. Therefore, compared with the conventional production method of first deoxygenating and then isomerizing, the production method of first modifying the structure to obtain a hydrodeoxygenable intermediate can reduce production costs and operation difficulty, and is more conducive to industrial promotion and use.

[0034] Specifically, the molar ratio of conjugated fatty acid to dienophilic monomer can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or any ratio in between.

[0035] Optionally, after removing unreacted raw materials in step (2), the process may also include washing with a non-polar organic solvent; Preferably, the nonpolar organic solvent includes n-hexane and water.

[0036] The addition product of this application contains both a hydrodeoxygenation intermediate and unreacted feedstock. The reactants can be removed by vacuum distillation in step (2). If the unreacted feedstock is not removed, it will remain in the hydrodeoxygenation intermediate, reducing the hydrodeoxygenation efficiency in subsequent processes and thus decreasing the biofuel yield. Furthermore, the presence of impurities will raise the freezing point of the biofuel, lowering its quality. To remove the hydrodeoxygenation intermediate from the unreacted feedstock, further washing with a non-polar solvent can achieve further removal of the unreacted feedstock, thereby further improving the quality of the biofuel.

[0037] According to a second aspect of this application, the application of the method described in any of the preceding claims in the production of biofuels, including biodiesel and biojet fuel.

[0038] The beneficial effects of this application include, but are not limited to: 1. The method for preparing hydrodeoxygenable intermediates using conjugated fatty acids according to this application achieves molecular structure modification under mild conditions, providing suitable intermediates for subsequent hydrodeoxygenation, and developing a biofuel production route of "modifying structure first and then hydrodeoxygenating", filling the technological gap in biofuels.

[0039] 2. The method for preparing hydrodeoxygenable intermediates using conjugated fatty acids according to this application increases the disorder among long-chain alkanes after hydrodeoxygenation by modifying the process, thereby improving the low-temperature cold flow performance of biodiesel and resulting in better quality biofuel.

[0040] 3. The method for preparing hydrodeoxygenable intermediates using conjugated fatty acids according to this application, compared with the catalyst-modified method, fundamentally reduces the generation of cracking products during isomerization, significantly increases the content of isomerization products, and broadens the application prospects of oil and fat production for biofuels.

[0041] 4. The method for preparing hydrodeoxygenable intermediates using conjugated fatty acids according to this application has mild reaction conditions, which can reduce coking and side reactions to a certain extent, reduce the cost of biofuel production, and facilitate industrial-scale promotion and use. Attached Figure Description

[0042] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is the 1H NMR spectrum of the hydrogen deoxygenable intermediate involved in Example 1 of this application.

[0043] Figure 2 This is a liquid chromatography-mass spectrometry (LC-MS) chromatogram of the hydrodeoxygenable intermediate involved in Example 1 of this application.

[0044] Figure 3 The image shows the infrared spectra of the raw materials and products involved in Example 1 of this application.

[0045] Figure 4 This is a thermogravimetric curve of the raw material linolenic acid and its product involved in Example 1 of this application.

[0046] Figure 5 This is the infrared spectrum of the hydrogen deoxygenable intermediate involved in Embodiment 2 of this application after hydrogen deoxygenation. Detailed Implementation

[0047] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0048] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application were purchased commercially. The CAS numbers for α-linolenic acid, linoleic acid, docosahexaenoic acid, conjugated linoleic acid, and sorbic acid are as follows: 463-40-1, 60-33-3, 6217-54-5, 2420-56-6, and 6217-54-5. CAS numbers for the following products are listed: 110-44-1, dimethyl maleate (CAS number: 624-48-6), dibutyl maleate (CAS number: 105-76-0), diisooctyl maleate (CAS number: 1330-76-3), maleic anhydride (CAS number: 108-31-6), dimethyl fumarate (CAS number: 624-49-7), dibutyl fumarate (CAS number: 105-75-9), dioctyl fumarate (CAS number: 2997-85-5), dimethyl itaconic acid (CAS number: 617-52-7), and 1-octene (CAS number: [missing information]). 111-66- 0 , 1-Hexadecene The CAS number is: 629-73-2 .

[0049] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art.

[0050] Example 1 This embodiment relates to a method for preparing a hydrodeoxygenable intermediate using conjugated fatty acids, comprising the following steps: (1) Add 1.0 wt% of elemental iodine catalyst to α-linolenic acid and carry out a conjugation reaction at 260 °C for 2 h to obtain conjugated fatty acids; add the conjugated fatty acids and dibutyl maleate in a molar ratio of 1:1 to a high-pressure reactor and carry out a Diels-Alder addition reaction at 260 °C for 2 h to obtain the addition product; (2) The addition product is subjected to vacuum distillation to remove unreacted raw materials, yielding a hydrodeoxygenable intermediate with the following structural formula: .

[0051] The above-mentioned reactants and the final hydrodeoxygenable intermediate product were subjected to 1H NMR spectroscopy, and their 1H NMR spectra are shown below. Figure 1 As shown, 1¹H NMR (400 MHz, CDCl₃, 25 °C) results are as follows: δ 5.90 ppm (d, 1×CH, 1H), 5.59 ppm (dd, 1×CH, 1H), 5.49 ppm (dd, 1×CH, 1H), 5.35 ppm (dd, 1×CH, 1H), 4.06 ppm (m, 2×CH₂, 4H), 3.27 ppm (m, 1×CH, 1H), 3.14 ppm (m, 1×CH, 1H), 3.01 ppm (m, 1×CH, 1H), 2.49 ppm (m, 1×CH, 1H), 2.21 ppm (t, 1×CH₂, 2H), 1.94 ppm (m, 1×CH₂, 2H), 1.25–1.54 ppm (m, 12×CH2, 24H), 0.8–0.90 ppm (t, 3×CH3, 9H). By comparing the chemical shifts of the characteristic groups in the target compound structure, it can be determined that the obtained product is consistent with the target Diels-Alder addition product, yielding a hydrogenation-deoxygenation intermediate with high structural disorder.

[0052] Figure 2 The image shows the liquid chromatography-mass spectrometry (LC-MS) chromatogram of the hydrodeoxygenable intermediate in this embodiment. Since the Diels-Alder reaction is an atom-economical reaction, with no atoms disappearing or increasing after the reaction, the theoretical molecular weight of the product should be the sum of the molecular weights of linolenic acid and dimethyl maleate, approximately 506 Da. The results show an ion peak at m / z 507.3685 in the product, with a fitted molecular formula of C0. 30 H 51 O6, with an error of -1.2 ppm, can be attributed to the target Diels-Alder addition hydrodeoxygenation intermediate product C. 30 H 50 O6's [M+H] + Ion peaks. This result indicates that linolenic acid underwent a Diels-Alder addition reaction with dibutyl maleate, generating the target adduct containing a long-chain fatty acid structure and a dibutyl ester-substituted cyclohexene structure.

[0053] Infrared spectroscopy tests were performed on the raw materials and enhanced deoxidation intermediates of this embodiment. Figure 3 As can be seen from the data, linolenic acid (I) at a wavenumber of 3008.9 cm⁻¹ -1 The characteristic stretching absorption peak of the olefin =CH group is significantly reduced in the infrared spectrum of the hydrodeoxygenable intermediate (III); the peak of dibutyl maleate (II) is reduced at a wavenumber of 1634.4 cm⁻¹. -1The characteristic stretching absorption peak of the C=C olefin at the position basically disappears in the infrared spectrum of the hydrogenable deoxygenable intermediate (III), which indicates that a Diels-Alder addition reaction did indeed occur between dibutyl maleate and linolenic acid. Figure 4 Thermogravimetric curves of the reactant linolenic acid and the hydrodeoxygenable intermediate are shown. Figure 4 (a) and Figure 4 As shown in curve (b), both linolenic acid and the product mainly undergo a primary weight loss stage, but their thermal behaviors differ significantly. Compared to linolenic acid, the initial weight loss temperature of the hydrodeoxygenable intermediate is earlier, indicating that it begins thermal decomposition at a lower temperature; simultaneously, its DTG peak is wider and weaker, indicating a slower decomposition process over a wider temperature range. Linolenic acid, on the other hand, exhibits a more concentrated and more vigorous primary decomposition process. The hydrodeoxygenable intermediate still shows a certain degree of slow weight loss tailing in the high-temperature region, indicating that its thermal decomposition process is more complex than that of the raw material. These results indicate that the hydrodeoxygenable intermediate and linolenic acid are not the same substance; their molecular structures have changed, which also supports the conclusion that the addition reaction has occurred.

[0054] Example 2 This embodiment relates to a method for preparing a hydrodeoxygenable intermediate using conjugated fatty acids, comprising the following steps: (1) Add 1.2 wt% of elemental iodine catalyst to linoleic acid and carry out conjugation reaction at 160 °C for 10 h to obtain conjugated fatty acid; add conjugated fatty acid and maleic anhydride to a high-pressure reactor at a molar ratio of 1:1.5 and carry out Diels-Alder addition reaction at 160 °C for 10 h to obtain addition product; (2) The addition product is subjected to vacuum distillation to remove unreacted raw materials, then deionized water is added for washing, and then vacuum distillation is performed to remove deionized water and unreacted raw materials to obtain the hydrodeoxygenable intermediate.

[0055] Example 3 This embodiment relates to a method for preparing a hydrodeoxygenable intermediate using conjugated fatty acids, comprising the following steps: (1) Add 0.3 wt% NaOH to docosahexaenoic acid and carry out a conjugation reaction at 180 °C for 2 h to obtain conjugated fatty acids; add the conjugated fatty acids and dimethyl fumarate in a molar ratio of 1:1.2 into a high-pressure reactor and carry out a Diels-Alder addition reaction at 180 °C for 1 h to obtain the addition product; (2) Remove unreacted raw materials by vacuum distillation of the addition product to obtain the hydrodeoxygenable intermediate.

[0056] Example 4 The difference between this embodiment and Example 1 is that conjugated linoleic acid is used as the conjugated fatty acid, and dimethyl itaconic acid is used instead of dibutyl maleate. That is, in this embodiment, conjugated linoleic acid is directly used for the reaction, and the rest is the same as in Example 1.

[0057] Example 5 The difference between this embodiment and Embodiment 1 is that dimethyl maleate is used instead of dibutyl maleate, while the rest is the same as in Embodiment 1.

[0058] Example 6 The difference between this embodiment and Embodiment 1 is that diisooctyl maleate is used instead of dibutyl maleate, while the rest is the same as in Embodiment 1.

[0059] Example 7 The difference between this embodiment and Embodiment 1 is that dibutyl fumarate is used instead of dibutyl maleate, while the rest is the same as in Embodiment 1.

[0060] Example 8 The difference between this embodiment and Example 1 is that sorbic acid is used as the conjugated fatty acid, and dioctyl fumarate is used instead of dibutyl maleate. That is, sorbic acid is used directly for the reaction in this embodiment, and the rest is the same as in Example 1.

[0061] Example 9 The difference between this embodiment and Example 1 is that 1-octene is used instead of dibutyl maleate, while the rest is the same as in Example 1.

[0062] Example 10 The difference between this embodiment and Embodiment 1 is that it uses... 1-Hexadecene Replace dibutyl maleate, otherwise the same as in Example 1.

[0063] Comparative Example 1 The difference between this comparative example and Example 1 is that the α-linolenic acid conjugation in step (1) is not performed, and the α-linolenic acid and dimethyl maleate are directly used for the Diels-Alder addition reaction. The rest is the same as in Example 1.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 is that step (2) is omitted, while the rest is the same as Example 1.

[0065] Test Example 1 The products of Examples 2-8 and Comparative Examples 1-2 were subjected to infrared spectroscopy tests according to the test method of Example 1. The results showed that cyclic hydrodeoxygenable intermediate products were successfully prepared in Examples 2-8 and Comparative Example 2, while in Comparative Example 1, since α-linolenic acid was not conjugated, α-linolenic acid and dimethyl maleate did not react directly in step (1), and hydrodeoxygenable intermediate could not be obtained.

[0066] Test Example 2 The hydrodeoxygenable intermediates prepared in the above examples and Comparative Example 2 were subjected to hydrodeoxygenation to obtain hydrodeoxygenated products. The freezing point and yield of the hydrodeoxygenated products were calculated, and the test results are shown in Table 1.

[0067] All examples and Comparative Example 2 used the same catalyst, and the specific hydrodeoxygenation conditions were: temperature 300°C, pressure 6 MPa, and liquid hourly space velocity 1.5 h⁻¹. -1 The hydrogen-to-oil ratio is 1500:1.

[0068] Figure 5 The image shows the infrared spectrum of the hydrodeoxygenable intermediate involved in Example 2 of this application after hydrodeoxygenation. As can be seen from the image, compared with direct hydrodeoxygenation of linolenic acid, the absorption peaks of C=O and CO in the product after the Diels-Alder reaction of linolenic acid are significantly weakened or disappear, indicating more thorough deoxygenation. This may be because the Diels-Alder reaction consumes some unsaturated double bonds, reducing the possibility of side reactions such as polymerization and condensation during the reaction, thus helping to maintain catalyst activity. Furthermore, the cyclic structure and ortho-carbonyl / anhydride type oxygen-containing structure formed in the Diels-Alder product are more easily activated by catalysis, and are more likely to undergo decarboxylation, decarbonylation, and hydrocracking reaction pathways, making it easier for oxygen atoms to be removed in the form of CO, CO2, or H2O, ultimately generating low-oxygen or even oxygen-free products such as cycloalkanes or branched alkanes, achieving the goal of producing bio-jet fuel without the need for a hydroisomerization reaction step.

[0069] Table 1

[0070] As can be seen from the test results in Table 2, the hydrodeoxygenable intermediate prepared in this application embodiment can directly yield biofuel after hydrodeoxygenation without the need for a hydroisomerization step, and the resulting biofuel has a high yield and a low freezing point, thus broadening the application prospects of biofuel.

[0071] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a hydrodeoxygenable intermediate using conjugated fatty acids, characterized in that, Includes the following steps: (1) Conjugated fatty acids and dienophilic monomers are subjected to Diels-Alder addition reaction to obtain addition products; (2) Remove the unreacted raw material from the addition product to obtain the hydrodeoxygenable intermediate.

2. The method according to claim 1, characterized in that, The conjugated fatty acids include at least one of conjugated linolenic acid, conjugated linoleic acid, and sorbic acid.

3. The method according to claim 1, characterized in that, The conjugated fatty acid is obtained by conjugating a conjugable fatty acid, wherein the conjugable fatty acid contains at least one adjacent double bond and there is a -CH2- group between the adjacent double bonds; Preferably, the conjugable fatty acids include at least one of α-linolenic acid, linoleic acid, eicosadienoic acid, eicosatrienoic acid, eicosatraenoic acid, eicosapentaenoic acid, and docosahexaenoic acid.

4. The method according to claim 3, characterized in that, The specific process of conjugation reactions of conjugable fatty acids is as follows: The conjugable fatty acids were reacted at 160-260℃ for 2-10 hours under the action of a catalyst; Preferably, the catalyst comprises an alkaline substance or elemental iodine, and the amount of the catalyst added accounts for 0.3wt%-1.2wt% of the mass of the conjugable fatty acid.

5. The method according to claim 1, characterized in that, The dienophile monomers include at least one of maleic acid-based dienophile monomers, fumarate-based dienophile monomers, itaconic acid-based dienophile monomers, and C8-C16 olefins; Preferably, the maleic acid-based diephilic monomer is selected from compounds of formula I or maleic anhydride, the fumaric acid-based diephilic monomer is selected from compounds of formula II, and the itaconic acid-based diephilic monomer is selected from compounds of formula III. Formula I; Formula II; Formula III; R1, R3, R4, R6, R7, and R8 are independently selected from alkyl groups containing 1 to 8 carbon atoms, and R2 and R5 are independently selected from H or alkyl groups containing 1 to 4 carbon atoms.

6. The method according to claim 5, characterized in that, The compound of Formula I includes at least one of dimethyl maleate, dimethyl 2-methyl maleate, dibutyl maleate, and diisooctyl maleate.

7. The method according to claim 5, characterized in that, The fumarate dienephilic monomer includes at least one of dimethyl fumarate, 2-methyl dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, and diisobutyl fumarate; and / or The itaconic acid diacetic monomer includes at least one of dimethyl itaconic acid, diethyl itaconic acid, and dibutyl itaconic acid.

8. The method according to any one of claims 1-7, characterized in that, In step (1), the molar ratio of conjugated fatty acid to dienophilic monomer is 1:(1-1.5), the reaction temperature is 160-260℃, and the reaction time is 2-10h.

9. The method according to any one of claims 1-7, characterized in that, After removing unreacted raw materials in step (2), the process also includes washing with a non-polar organic solvent; Preferably, the nonpolar organic solvent includes n-hexane and water.

10. The application of the method according to any one of claims 1-9 in the production of biofuels, wherein the biofuels include biodiesel and biojet fuel.

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