Method for preparing biological hydrocarbon compound through organic photocatalysis higher fatty acid decarboxylation

Abstract

The invention discloses a method for preparing a biological hydrocarbon compound by organic photocatalysis higher fatty acid decarboxylation, which comprises the following steps: adding higher fatty acid, a hydrogen atom transfer catalyst and an acridine photocatalyst / solid-phase acridine photocatalyst into a reaction solvent, stirring and reacting for 12-24 hours under the conditions of blue light irradiation and room temperature to obtain a reaction solution, filtering, washing and drying to obtain the biological hydrocarbon compound. And removing the reaction solvent of the obtained reaction solution under reduced pressure, and purifying by thin layer chromatography / column chromatography to obtain the long-chain alkane compound after decarboxylation of the higher fatty acid. The method is simple in step, mild in reaction condition and high in product yield, does not use any metal compound, and has the characteristics of high atom economy and environmental protection. And for unsaturated carboxylic acid, olefin configuration before and after decarboxylation is not influenced. When solid-phase acridine is used as a photocatalyst for reaction, the catalyst can be recycled through simple washing, filtering and recycling, excellent catalytic activity can still be kept after the catalyst is recycled for more than 10 times, and the reaction cost is further reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy chemistry, and specifically relates to a method for preparing biohydrocarbon compounds by the organic photocatalytic decarboxylation of higher fatty acids. Background Art

[0002] The exploitation and use of fossil fuels have caused great negative impacts on the environment, including greenhouse gas emissions, climate change, air pollution and other problems. Moreover, fossil fuels are non-renewable resources, and with their increasing depletion, the development of their substitutes has become particularly important. As a kind of energy that can replace petroleum resources, the development of new processes for second-generation biodiesel is particularly important.

[0003] The first-generation biodiesel is mainly fatty acid methyl ester (FAME) prepared by the transesterification reaction of animal and vegetable oils and fats (such as soybean oil, rapeseed oil, palm oil, etc.) with alcohols (such as methanol or ethanol) under the action of a catalyst. This kind of biodiesel has good renewability and environmental friendliness, but has great limitations, such as poor combustion performance, high freezing point, insufficient compatibility with traditional diesel, etc. Moreover, the raw materials used to produce this kind of biodiesel are in competition with human food resources, so its industrial application is greatly limited and faces great controversy. In view of the above disadvantages, the industrial use of the deep hydrodeoxygenation process for oil treatment, that is, the oil is catalytically hydrogenated to produce straight-chain alkanes under high temperature and high pressure conditions by heavy metals (Pd, Ni, Ir, etc.), which is the second-generation biodiesel. The second-generation biodiesel can be produced using various waste oils, agricultural by-products and other raw materials, and the raw material sources are wide and the cost is low. It is called green diesel internationally, and is similar to traditional diesel in structure and performance, has good combustion calorific value and low density and condensation point, can be directly mixed with diesel for use, and at the same time its production process reduces greenhouse gas emissions and has low sulfur content, with less impact on the environment. However, it also has the disadvantage of a relatively high freezing point and cannot be incorporated into petrochemical diesel at a very high ratio. If an isomerization treatment device is added to solve this problem, special equipment and technical support are required, and the production cost will further increase. In addition, although the second-generation biodiesel has less environmental impact, wastewater and waste gas will still be generated during the production process, which will inevitably have a negative impact on the environment. Therefore, it is of great significance to develop a more efficient, mild and green production process for the second-generation biodiesel.

[0004] Photoredox catalysis is a transformation method that has emerged in the field of organic synthesis in recent years. Due to its mild and green characteristics, it has been widely used in the decarboxylation modification of carboxylic acid compounds. Summary of the Invention

[0005] In view of the problems of the current second-generation diesel, the present invention provides a method for preparing biohydrocarbon compounds by the organic photocatalytic decarboxylation of higher fatty acids. The present invention uses saturated / unsaturated higher fatty acids or their corresponding fatty acid esters (used after alkaline hydrolysis treatment) with a wide range of sources as starting materials, and under mild and efficient conditions, the desired decarboxylated hydrogenation products, namely various second-generation biodiesels, can be obtained in high yield in an environmentally friendly manner. This solution is expected to be further developed and utilized in the fields of petrochemical industry and aviation fuel.

[0006] Technical solution: A method for preparing biohydrocarbon compounds by the organic photocatalytic decarboxylation of higher fatty acids, comprising the following steps:

[0007] S1. Under an inert gas atmosphere, add higher fatty acid compounds, hydrogen atom transfer catalysts, and photocatalysts to a reaction solvent, and stir and react for 12-24 h under blue light irradiation and at room temperature to obtain a reaction solution;

[0008] S2. After monitoring the completion of the reaction by TLC, filter the reaction solution obtained in S1 to obtain a filtrate. After removing the reaction solvent and purifying the filtrate, long-chain alkane (alkene) compounds after the decarboxylation of higher fatty acids are obtained.

[0009] Further, in S1, the molar volume ratio of the higher fatty acid compounds, hydrogen atom transfer catalysts, photocatalysts, and reaction solvents is: (0.2-1.0) mmol: (0.01-0.05) mmol: (0.02-0.1 mmol): (1-5) mL.

[0010] Further, the stirring time is 24 h under blue light irradiation and at room temperature (25 °C - 30 °C); when irradiating with blue light, a blue LED lamp is used, and the power of the LED lamp is 18 W and the wavelength is 460 nm.

[0011] Further, in S2, the method for removing the reaction solvent is to use a vacuum rotary evaporator to remove the reaction solvent; the purification method is to purify by thin layer chromatography or column chromatography, and the developing agent system is pure petroleum ether.

[0012] Further, the photocatalyst includes a non-solid-phase photocatalyst and a solid-phase photocatalyst;

[0013] The non-solid-phase photocatalyst is any one of 3,6-di-tert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 2,7-di-tert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2-chloro-4-vinylphenyl)acridine, 9-(2-methyl-4-vinylphenyl)acridine, 3,6-di-tert-butyl-9-mesityl acridine, 2,7-di-tert-butyl-9-mesityl acridine, 9-(2-chlorophenyl)acridine, 9-mesityl acridine, 9-(o-tolyl)acridine, 9-phenylacridine, 9-(2,6-dimethylphenyl)acridine, 9-(4-methoxy-2,6-dimethylphenyl)acridine, 9-(4-fluoro-2,6-dimethylphenyl)acridine, 9-([1,1'-biphenyl]-4-yl)-2,7-dimethylacridine, 9-(2,4,6-triisopropylphenyl)acridine;

[0014] The solid-phase photocatalyst is any one of 3,6-di-tert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 2,7-di-tert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 3,6-di-tert-butyl-9-(4-vinylphenyl)acridine, 9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2-chloro-4-vinylphenyl)acridine, 9-(2-methyl-4-vinylphenyl)acridine loaded on polystyrene.

[0015] Furthermore, the higher fatty acid compound is any one or several of valeric acid, caproic acid, enanthic acid, octanoic acid, nonanoic acid, decanoic acid, 2-heptyldecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, heneicosanoic acid, behenic acid, tricosanoic acid, lignoceric acid, pentacosanoic acid, cerotic acid, melissic acid, lignoceric acid, oleic acid, linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

[0016] Furthermore, the reaction solvent is any one of dichloromethane, 1,2-dichloroethane, acetonitrile, ethanol, n-hexane, tetrahydrofuran, toluene, dimethyl sulfoxide, and N,N-dimethylformamide.

[0017] Furthermore, the hydrogen atom transfer catalyst is any one of p-methylbenzenethiol, p-chlorobenzenethiol, p-methoxybenzenethiol, diphenyl disulfide, 4,4'-dichlorodiphenyl disulfide, 4,4'-dimethoxydiphenyl disulfide, N-tert-butoxycarbonyl-L-cysteine methyl ester, and N-acetyl-L-cysteine ethyl ester.

[0018] Further, the solid-phase photocatalyst is 3,6-di-tert-butyl-9-homomesitylene acridine or acridine supported by polystyrene, the hydrogen atom transfer catalyst is p-chlorothiophenol, and the reaction solvent is dichloromethane.

[0019] Further, when the photocatalyst is a solid-phase photocatalyst, the solid obtained by filtering the reaction solution obtained in S1 is the solid-phase photocatalyst, which is washed with petroleum ether and then recycled.

[0020] Further, when the solid-phase photocatalyst is 3,6-di-tert-butyl-9-(4-vinylphenyl) acridine supported by polystyrene, the preparation steps are as follows:

[0021] Step 1: Add 4-vinylbenzoic acid, potassium carbonate, and N,N-dimethylformamide to a round-bottom flask, and then add methyl iodide. React at room temperature for 24 h to obtain Compound 2. The reaction equation is as follows;

[0022]

[0023] Step 2: Add 1-bromo-3-(tert-butyl) benzene, 3-(tert-butyl) phenol, cesium carbonate, copper(I) iodide, 2,2,6,6-tetramethylheptane-3,5-dione, and N,N-dimethylformamide to the round-bottom flask. Stir and react at 110 °C for 24 h to obtain Compound 5. The reaction equation is as follows:

[0024]

[0025] Step 3: Under an argon atmosphere, add Compound 5, anhydrous n-hexane, and N,N,N',N'-tetramethylethylenediamine to the flask. Then, dropwise add a n-hexane solution of sec-butyllithium under an ice bath condition, and raise the temperature to room temperature and stir for 4 h. Then, cool the flask to -78 °C. Under an argon atmosphere, add an anhydrous n-hexane solution of Compound 2, and raise the temperature to room temperature and stir for 18 h to obtain a reaction solution;

[0026] In the organic layer extracted from the reaction solution, add concentrated HCl to obtain a brown suspension, then stir for 30 minutes, dilute with water, wash the organic layer with water, add sodium tetrafluoroborate to the obtained washing solution, and then add dichloromethane for extraction; for the organic layer obtained after extraction, first remove part of the solvent under reduced pressure, then add diethyl ether complex of tetrafluoroboric acid, stir the solution until homogeneous, then wash with water and aqueous sodium tetrafluoroborate solution respectively. After that, extract the organic layer with dichloromethane until colorless, and then dry the organic layer with solid sodium tetrafluoroborate, filter and remove the solvent under reduced pressure to obtain Compound 6.

[0027] The reaction equation is as follows:

[0028]

[0029] Step 4: First, compound 6 was added to ethanol, and then concentrated aqueous ammonia solution was added. The reaction mixture was stirred at room temperature for 6 h to obtain compound 7. The reaction equation is as follows:

[0030]

[0031] Step 5: Compound 7 was dissolved in tetrahydrofuran. After adding azobisisobutyronitrile, it was placed in an autoclave. Under an argon atmosphere, it was heated to 100 °C and reacted continuously for 24 hours to obtain compound 8, which is the POL-acridine photocatalyst. The reaction equation is as follows:

[0032]

[0033] Beneficial effects:

[0034] 1) In the present invention, hydrocarbon compounds are prepared from higher fatty acids. The preparation steps are simple, the reaction conditions are mild, the product yield is high, and no metal compounds (no heavy metals are involved) are used. It has the characteristics of high atom economy, environmental friendliness, and the catalyst can be recycled.

[0035] In the present invention, the reaction is carried out under blue light irradiation at room temperature. Thiophenol compounds or disulfides are directly used as hydrogen atom transfer catalysts. Saturated higher fatty acids or unsaturated higher fatty acids and (solid-phase) photocatalysts are selected to introduce radical fragments through proton-coupled electron transfer process (PCET) by decarboxylation, and then through hydrogen atom transfer process (HAT) with the hydrogen atom transfer catalyst to obtain the final product.

[0036] 2) When using solid-phase acridine (POL-Acridine) as the photocatalyst in the present invention, the catalyst can be recycled by simple filtration recovery. It can still maintain excellent catalytic activity after being recycled more than 10 times, further reducing the reaction cost.

[0037] 3) The higher fatty acids used in the method of the present invention are commercially available and inexpensive compounds, including various saturated / unsaturated higher fatty acids (C5-C26), and have a wide range of applications.

[0038] 4) The method for preparing bio-hydrocarbon compounds by photocatalytic decarboxylation of higher fatty acids in the present invention successfully realizes the decarboxylation and hydrogenation of higher fatty acids to obtain long-chain alkanes through photocatalytic decarboxylation and hydrogen atom transfer processes, providing a green route for the fuel sources of various engines and aviation machinery in the later stage, and is expected to be further developed and utilized in the fields of petrochemical industry and aviation fuel. Description of the drawings

[0039] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of compound 9 in Example 1 of the present invention;

[0040] Figure 2 It is the carbon nuclear magnetic resonance spectrum of Compound 9 in Example 1 of the present invention;

[0041] Figure 3 It is the hydrogen nuclear magnetic resonance spectrum of Compound 11 in Example 2 of the present invention;

[0042] Figure 4 It is the carbon nuclear magnetic resonance spectrum of Compound 11 in Example 2 of the present invention;

[0043] Figure 5 It is the hydrogen nuclear magnetic resonance spectrum of Compound 13 in Example 3 of the present invention;

[0044] Figure 6 It is the carbon nuclear magnetic resonance spectrum of Compound 13 in Example 3 of the present invention;

[0045] Figure 7 It is the hydrogen nuclear magnetic resonance spectrum of Compound 15 in Example 4 of the present invention;

[0046] Figure 8 It is the carbon nuclear magnetic resonance spectrum of Compound 15 in Example 4 of the present invention;

[0047] Figure 9 It is the hydrogen nuclear magnetic resonance spectrum of Compound 17 in Example 5 of the present invention;

[0048] Figure 10 It is the carbon nuclear magnetic resonance spectrum of Compound 17 in Example 5 of the present invention;

[0049] Figure 11 The relationship diagram between the number of catalyst cycles and the product yield in Example 1 of the present invention;

[0050] Figure 12 The relationship diagram between the number of catalyst cycles and the product yield in Example 2 of the present invention;

[0051] Figure 13 The relationship diagram between the number of catalyst cycles and the product yield in Example 3 of the present invention;

[0052] Figure 14 The relationship diagram between the number of catalyst cycles and the product yield in Example 4 of the present invention;

[0053] Figure 15 The relationship diagram between the number of catalyst cycles and the product yield in Example 5 of the present invention. Detailed implementation manners

[0054] The technical solution of the present invention will be described in detail below through examples, but the protection scope of the present invention is not limited to the described examples.

[0055] Example 1

[0056] The synthesis steps of the photocatalyst polystyrene-supported acridine (POL-Acridine) used in this example are as follows:

[0057] (1) Under room temperature conditions, 4-vinylbenzoic acid (2.96 g, 20.0 mmol, 1 equiv. of compound 1), potassium carbonate (4.15 g, 30.0 mmol, 1.5 equiv.), and 25 mL of N,N-dimethylformamide were added to a 100 mL round-bottom flask equipped with a magnetic stir bar. Then, methyl iodide (1.5 mL, 24.0 mmol, 1.2 equiv.) was slowly added, and the resulting suspension was vigorously stirred at room temperature for 24 h to obtain a reaction mixture. The reaction equation is as follows:

[0058]

[0059] (2) The reaction mixture was transferred to a separatory funnel with 50 mL of ethyl acetate. The organic layer was washed with water (330 mL) and saturated sodium chloride solution (230 mL) respectively, and then the organic layer was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the crude product was separated by column silica gel chromatography. The eluent was a petroleum ether / ethyl acetate system (5 / 1), and the product was a white solid (compound 2) with a yield of 86% (2.8 g).

[0060] (3) 1-Bromo-3-(tert-butyl)benzene (5.0 g, 26.5 mmol, 1.0 equiv. of compound 4), 3-(tert-butyl)phenol (5.3 g, 35.2 mmol, 1.5 equiv. of compound 3), cesium carbonate (15.3 g, 46.9 mmol, 2 equiv.), copper(I) iodide (447 mg, 2.35 mmol, 10 mol%), 2,2,6,6-tetramethylheptane-3,5-dione (490 μL, 2.35 mmol, 10 mol%), and 6 mL of N,N-dimethylformamide were added to a 100 mL round-bottom flask equipped with a magnetic stir bar. Then, the reaction was stirred at 110 °C for 24 h to obtain a reaction solution. The reaction equation is as follows:

[0061]

[0062] (4) The reaction solution was cooled to room temperature, filtered through diatomaceous earth, and the filter cake was washed with ether until the washing solution was colorless. The filtrate was washed with water (3 × 30 mL) and saturated sodium chloride solution (2 × 30 mL) respectively. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The crude product was separated and purified by column silica gel chromatography. The eluent was a petroleum ether / ethyl acetate system (100 / 1), and the product was a colorless oil (compound 5) with a yield of 88% (5.8 g).

[0063] (5) In an argon atmosphere, add the above compound 5 (1.5 g, 5.3 mmol, 1 equiv.), 5.3 mL of anhydrous n-hexane, and N,N,N',N'-tetramethylethylenediamine (1.6 mL, 10.9 mmol, 2.06 equiv.) to a dry 100 mL round-bottom flask. Then, slowly add sec-butyllithium (1.3 M n-hexane solution, 8.5 mL, 10.9 mmol, 2.06 equiv.) dropwise under an ice bath condition. Slowly raise the reaction temperature to room temperature and stir for 4 hours. Then, cool the reaction flask to -78 °C through a low-temperature reactor. Under an argon atmosphere, slowly add a 5.3 mL anhydrous n-hexane solution of the above compound 2 (875.9 mg, 5.4 mmol, 1.05 equiv.). After addition, allow the reaction to slowly warm up to room temperature and stir for 18 h to obtain a reaction solution.

[0064] The reaction equation is:

[0065]

[0066] (6) Quench the reaction by adding 6 mL of water to the reaction solution, stir the mixture vigorously for 30 minutes, and extract the organic layer of the reaction solution with diethyl ether (20 × 3 mL). Wash the organic layer with water (2 × 30 mL) and saturated sodium chloride solution (1 × 30 mL). Transfer the organic layer to another 250 mL flask, add concentrated HCl (2.2 mL) to produce a bright yellow precipitate, which slowly turns brown during the addition process. Stir the brown suspension vigorously for 30 minutes.

[0067] Dilute the brown suspension by adding 30 mL of water, and then wash the obtained organic layer with water until the washing solution becomes colorless. Add sodium tetrafluoroborate (1.7 g, 15.9 mmol, 3 equiv.) to the washing solution to obtain a bright yellow precipitate.

[0068] Then, extract the washing solution containing the bright yellow precipitate with dichloromethane until the extract is colorless. First, remove part of the solvent from the extracted organic layer under reduced pressure, then add diethyl ether complex of tetrafluoroboric acid (0.86 mL, 5.3 mmol, 1 equiv.), stir the solution until homogeneous, and then wash it with 30 mL of water and 30 mL of 1 M aqueous sodium tetrafluoroborate solution respectively. After that, extract the organic layer with dichloromethane until colorless, then dry the organic layer with solid sodium tetrafluoroborate, filter, and remove the solvent under reduced pressure to obtain a crude product, a yellowish-brown solid product, compound 6.

[0069] (7) Transfer the above compound 6 to a 250 mL round-bottom flask, add ethanol (53.0 mL, 0.1 M), and then slowly add 17.8 mL of concentrated ammonia water. Stir the reaction mixture at room temperature for 6 h to obtain a reaction solution. The reaction equation is:

[0070]

[0071] (8) The above reaction solution was de-ethanolized under reduced pressure, 30 mL of water was added, and the resulting mixture was extracted with diethyl ether (3 × 30 mL). The combined organic layers were washed with 50 mL of saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure, and the crude product was separated and purified by column silica gel chromatography. The eluent was a petroleum ether / ethyl acetate system (100 / 1 - 50 / 1). After removing the solvent, the remaining solid was recrystallized from n-hexane to obtain the white solid compound 7 with a yield of 81% (1.7 g).

[0072] (9) Compound 7 (1.5 g) was dissolved in tetrahydrofuran (20 mL), and then azobisisobutyronitrile (50 mg) was added. The mixture was transferred to an autoclave, evacuated three times under an argon atmosphere, heated to 100 °C and reacted for 24 hours. After the reaction, tetrahydrofuran was evaporated under vacuum conditions, and the resulting product was washed with ethyl acetate and then dried under a vacuum environment to finally obtain the solid monomer compound 8 of the target material, namely POL-acridine photocatalyst.

[0073] The reaction equation is as follows:

[0074]

[0075] The name of the solid monomer 8 is polystyrene-supported 3,6-di-tert-butyl-9-(4-vinylphenyl)acridine. In the structural formula, the range of n is 30 - 150, and * represents the active end point of the polymer chain.

[0076] On this basis, using the above compound 8 as a solid-phase photocatalyst, the decarboxylation reaction of carboxylic acid was catalyzed to prepare hydrocarbon compounds. The specific process is as follows:

[0077] In a 10 mL Schlenk tube, under an inert gas atmosphere, 0.2 mmol of oleic acid, 0.01 mmol of p-chlorothiophenol, 0.02 mmol of POL-acridine were added, 1 mL of dichloromethane was added, and the mixture was stirred and reacted for 24 h under argon, room temperature and 54 W blue light irradiation. The reaction equation is as follows:

[0078]

[0079] After monitoring the reaction by TLC until completion, the reaction solution was filtered to obtain the POL-acridine photocatalyst. Then, a vacuum rotary evaporator was used to remove the reaction solvent under reduced pressure from the filtrate. The product was separated by thin-layer chromatography with petroleum ether as the eluent. The product was a colorless oily liquid, compound 10, with a yield of 96%. The POL-acridine photocatalyst was washed with petroleum ether and recovered. Under the same reaction conditions, a recycling experiment was carried out using the recovered solid-phase POL-acridine photocatalyst. The results showed that the catalyst still maintained excellent catalytic activity after 10 cycles, and the yield of the product did not decrease significantly. The experimental data results are as Figure 11 shown.

[0080] Compound 10 was characterized, and the data are as follows:

[0081] 1 H NMR (400 MHz, Chloroform-d) δ 5.43–5.31 (m, 2H), 2.08–1.91 (m, 4H), 1.37–1.23 (m, 22H), 0.88 (t, J = 6.7 Hz, 6H). 13 C NMR (101 MHz, Chloroform-d) δ 130.4, 130.0, 32.7, 32.0, 32.0, 29.8, 29.8, 29.7, 29.6, 29.6, 29.4, 29.3, 29.2, 29.2, 27.3, 22.8, 14.2. IR (KBr): 2957, 2924, 2854, 1466, 1378, 966, 722 cm -1 . HRMS (ESI) m / z: [M+H] + Calcd. for: C 17 H 35 239.2739; Found 239.2731.

[0082] The NMR spectra are as Figure 1 and Figure 2 shown. The above characterization results indicate that compound 10 is (Z)-heptadec-8-ene.

[0083] Example 2

[0084] The synthesis procedure of the photocatalyst POL-acridine used in this example was the same as that in Example 1. On this basis, the next reaction was carried out. The specific process was as follows:

[0085] (1) In a 10 mL Schlenk tube, under an inert gas atmosphere, 0.2 mmol of linoleic acid, 0.01 mmol of p-chlorothiophenol, and 0.02 mmol of POL-acridine were added. 1 mL of dichloromethane was added, and the mixture was stirred and reacted for 24 h under argon, at room temperature, and under 54 W blue light irradiation. The reaction equation was:

[0086]

[0087] (2) After monitoring the reaction by TLC until completion, the reaction solution was filtered to obtain the POL-acridine photocatalyst. Then, a vacuum rotary evaporator was used to remove the reaction solvent under reduced pressure from the filtrate. The product was separated by thin-layer chromatography, with petroleum ether as the eluent. The product was a colorless oily liquid, compound 12, with a yield of 85%. The POL-acridine photocatalyst was washed with petroleum ether and then recovered.

[0088] Under the same reaction conditions, a recycling experiment was carried out using the recovered solid-phase POL-acridine photocatalyst. The results showed that the catalyst still maintained excellent catalytic activity after 10 cycles, and the yield of the product did not decrease significantly. The experimental data results are as Figure 12 shown.

[0089] Compound 12 was characterized, and the data are as follows:

[0090] 1 H NMR (400 MHz, Chloroform-d) δ 5.48–5.30 (m, 4H), 2.81–2.65 (m, 2H), 2.10–1.93 (m, 4H), 1.37–1.26 (m, 16H), 0.92–0.85 (m, 6H). 13 C NMR (101 MHz, Chloroform-d) δ 130.1, 130.0, 128.0, 127.9, 34.1, 31.5, 29.6, 29.3, 29.1, 29.0, 29.0, 27.2, 27.1, 25.6, 24.6, 22.6, 14.1. IR (KBr): 2925, 2854, 1466, 1270, 966 cm -1 . HRMS (ESI) m / z: [M+H] + Calcd. for: C 17 H 33 237.2582; Found 237.2585.

[0091] The NMR spectra are as Figure 3 and Figure 4 shown. The above characterization results indicate that compound 12 is (6Z,9Z)-heptadeca-6,9-diene.

[0092] Example 3

[0093] The synthesis steps of the photocatalyst POL-acridine used in this example are the same as those in Example 1. On this basis, the next reaction was carried out. The specific process is as follows:

[0094] (1) In a 10 mL Schlenk tube, under an inert gas environment, 0.2 mmol of linolenic acid, 0.01 mmol of p-chlorothiophenol, and 0.02 mmol of POL-acridine were added. 1 mL of dichloromethane was added, and the mixture was stirred and reacted for 24 h under argon, at room temperature, and under 54 W blue light irradiation. The reaction equation is as follows:

[0095]

[0096] (2) After monitoring the completion of the reaction by TLC, the reaction solution was filtered to obtain the POL-acridine photocatalyst. Then, a vacuum rotary evaporator was used to remove the reaction solvent under reduced pressure from the filtrate. Then, the solvent was removed under reduced pressure using a vacuum rotary evaporator, and the product was separated by thin layer chromatography. The eluent was petroleum ether, and the product was a colorless oily liquid compound 14 with a yield of 82%. The POL-acridine photocatalyst was washed with petroleum ether and then recovered.

[0097] Under the same reaction conditions, a recycling experiment was carried out using the recovered solid-phase POL-acridine photocatalyst. The results showed that when the catalyst went through 10 cycles, it could still maintain excellent catalytic activity, and the yield of the product did not decrease significantly. The experimental data results are as Figure 13 shown.

[0098] Compound 14 was characterized, and the data are as follows:

[0099] 1 H NMR (400 MHz, Chloroform-d) δ 5.55–5.26 (m, 6H), 2.87–2.64 (m, 4H), 2.11–1.95 (m, 4H), 1.34–1.24 (m, 10H), 1.00–0.93 (m, 3H), 0.91–0.85 (m, 3H). 13 C NMR (101 MHz, Chloroform-d) δ 131.9, 130.2, 128.2, 128.2, 127.7, 127.1, 34.1, 29.5, 29.1, 29.1, 29.0, 27.2, 25.6, 25.5, 24.6, 20.5, 14.3. IR (KBr): 3011, 2958, 2925, 2854, 1466, 1276, 1262, 966, 744 cm -1 . HRMS (ESI) m / z: [M+H] + Calcd. for: C 17 H 31 235.2426; Found 235.2421.

[0100] The NMR spectra are as Figure 5 and Figure 6As shown above, the above characterization results indicate that Compound 14 is (3Z,6Z,9Z)-heptadeca-3,6,9-triene.

[0101] Example 4

[0102] The synthesis steps of the photocatalyst 3POL-acridine used in this example are the same as those in Example 1. On this basis, the next reaction is carried out. The specific process is as follows:

[0103] (1) In a 10 mL Schlenk tube, under an inert gas atmosphere, 0.2 mmol of myristic acid, 0.01 mmol of p-chlorothiophenol, and 0.02 mmol of POL-acridine are added. 1 mL of dichloromethane is added, and the mixture is stirred and reacted for 24 h under argon, room temperature, and 54 W blue light irradiation. The reaction equation is:

[0104]

[0105] (2) After monitoring the reaction to completion by TLC, the reaction solution is filtered to obtain the POL-acridine photocatalyst. Then, the reaction solvent is removed under reduced pressure using a rotary evaporator. The product is separated by thin-layer chromatography, and the eluent is petroleum ether. The product is a colorless oily liquid, Compound 16, with a yield of 95%. The POL-acridine photocatalyst is washed with petroleum ether and then recovered.

[0106] Under the same reaction conditions, a recycling experiment is carried out using the recovered solid-phase POL-acridine photocatalyst. The results show that when the catalyst undergoes 10 cycles, it can still maintain excellent catalytic activity, and the yield of the product does not decrease significantly. The experimental data results are as Figure 14 shown.

[0107] Compound 16 is characterized, and the data are as follows:

[0108] 1 H NMR(400MHz,Chloroform-d)δ1.32–1.23(m,22H),0.88(t,J=6.7Hz,6H). 13 CNMR(101MHz,Chloroform-d)δ32.0,29.8,29.7,29.4,22.7,14.2.IR(KBr):2957,2923,2853,1467,1275,1261,764,750cm -1 .HRMS(ESI)m / z:[M+H] + Calcd.for:C 13 H 29 185.2269;Found 185.2272.

[0109] The NMR spectrum is as Figures 7 - 8As shown above, the above characterization results indicate that Compound 16 is tridecane.

[0110] Example 5

[0111] The synthesis steps of the photocatalyst POL-acridine used in this example are the same as those in Example 1. On this basis, the next reaction is carried out. The specific process is as follows:

[0112] (1) In a 10 mL Schlenk tube, under an inert gas atmosphere, 0.2 mmol of stearic acid, 0.01 mmol of p-chlorothiophenol, and 0.02 mmol of POL-acridine are added. 1 mL of dichloromethane is added, and the mixture is stirred and reacted for 24 h under argon, at room temperature, and irradiated with 54 W blue light. The reaction equation is:

[0113]

[0114] (2) After monitoring the reaction to completion by TLC, the reaction solution is filtered to obtain the POL-acridine photocatalyst. Then, the reaction solvent is removed under reduced pressure using a rotary evaporator. The product is separated by thin-layer chromatography, and the eluent is petroleum ether. The product is a colorless oily liquid, Compound 18, with a yield of 94%. The POL-acridine photocatalyst is washed with petroleum ether and then recovered.

[0115] Under the same reaction conditions, a recycling experiment is carried out using the recovered solid-phase POL-acridine photocatalyst. The results show that when the catalyst undergoes 10 cycles, it can still maintain excellent catalytic activity, and the yield of the product does not decrease significantly. The experimental data results are as Figure 15 shown.

[0116] Compound 18 is characterized, and the data are as follows:

[0117] 1 H NMR (400 MHz, Chloroform-d) δ 1.35–1.18 (m, 30H), 0.88 (t, J = 6.8 Hz, 6H). 13 C NMR (101 MHz, Chloroform-d) δ 32.0, 29.8, 29.7, 29.5, 22.8, 14.2. IR (KBr): 2957, 2924, 2854, 1466, 1275, 1261, 764, 749 cm -1 . HRMS (ESI) m / z: [M+H] + Calcd. for: C 17 H 37 241.2895; Found 241.2902.

[0118] The NMR spectra are as Figure 9 and Figure 10As shown above, the above characterization results indicate that Compound 18 is n - heptadecane.

[0119] Examples 6 - 15

[0120] Examples 6 - 15 are basically the same as the above - mentioned examples. Using oleic acid as the higher fatty acid for the reaction, different reaction solvents, hydrogen atom transfer catalysts, and photocatalysts are used, and the obtained products are the same. The specific differences are shown in Table 1:

[0121] Table 1 Comparison of implementation differences

[0122]

[0123]

[0124] In the above - mentioned examples, the dosage ratios of the higher fatty acid compound, hydrogen atom transfer catalyst, photocatalyst, and reaction solvent are 0.2 mmol:0.01 mmol:0.02 mmol:1 mL, which is the most preferred dosage ratio, and the reaction time at room temperature is the optimal reaction time of 24 h.

[0125] From the above - mentioned examples, it can be seen that:

[0126] 1. Keeping other conditions unchanged, through the comparison of single - factor variable results, it is found that the catalytic effect of 3,6 - di - tert - butyl - 9 - mesityl acridine or acridine supported on polystyrene is better than that of other non - solid - phase catalysts. p - Chlorothiophenol is better than other hydrogen atom transfer catalysts, and dichloromethane is better than other reaction solvents.

[0127] 2. The yield differences of different higher fatty acid compounds are mainly affected by the following factors:

[0128] 1) Carbon chain length and structure of fatty acids:

[0129] Steric effect: A long carbon chain or branched - chain structure will increase steric hindrance, hinder the contact between reactants and catalytic active centers, and reduce the reaction efficiency;

[0130] Decarboxylation difficulty: Short - chain fatty acids (such as C6 - C10) usually have a lower decarboxylation energy barrier, while long - chain (such as C16 - C18) require higher energy due to stronger van der Waals forces, resulting in yield differences.

[0131] 2) Light absorption and energy transfer:

[0132] Chromophore effect: Fatty acids containing conjugated double bonds (such as linoleic acid) may directly absorb light energy to participate in the reaction or compete with the catalyst for light absorption, interfering with the catalytic process;

[0133] Energy matching: The excited state of the catalyst needs to match the LUMO energy level of the fatty acid, and the HOMO-LUMO energy gaps of different structures affect the electron transfer efficiency.

[0134] 3) Side reaction competition

[0135] Free radical stability: If the alkyl radicals generated by decarboxylation are prone to dimerization or disproportionation (such as tertiary carbon radicals), the yield of the target product will be reduced;

[0136] Over-oxidation: The double bonds of unsaturated fatty acids (such as linoleic acid and linolenic acid) may be oxidized by photo-generated holes to form by-products.

[0137] 3. For the same reaction, the same acridine catalyst without polystyrene loading and with polystyrene loading has comparable reaction effects. The acridine catalyst loaded with polystyrene as a solid-phase catalyst has the advantage of being recyclable.

[0138] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes can be made in its form and details without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing biohydrocarbon compounds by the decarboxylation of organic photocatalytic higher fatty acids, characterized in that, It includes the following steps: S1. Under an inert gas atmosphere, add a higher fatty acid compound, a hydrogen atom transfer catalyst, and a photocatalyst into a reaction solvent, and stir and react for 12 - 24 h under blue light irradiation and at room temperature to obtain a reaction solution; S2. Filter the reaction solution obtained in S1 to obtain a filtrate, and after removing the reaction solvent and purifying the filtrate, obtain a long-chain alkane compound after decarboxylation of the higher fatty acid.

2. The method according to claim 1, wherein In S1, the molar volume ratio of the higher fatty acid compound, the hydrogen atom transfer catalyst, the photocatalyst, and the reaction solvent is: (0.2 - 1.0) mmol : (0.01 - 0.05) mmol : (0.02 - 0.1 mmol) : (1 - 5) mL.

3. The method according to claim 1, characterized in that, The stirring time under blue light irradiation and at room temperature is 24 h; when performing blue light irradiation, use a blue LED lamp, and the power of the LED lamp is 18 W and the wavelength is 460 nm.

4. The method according to claim 1, characterized in that The photocatalyst includes a non-solid-phase photocatalyst and a solid-phase photocatalyst; The non-solid-phase photocatalyst is any one of 3,6-ditert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 2,7-ditert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2-chloro-4-vinylphenyl)acridine, 9-(2-methyl-4-vinylphenyl)acridine, 3,6-ditert-butyl-9-mesityl acridine, 2,7-ditert-butyl-9-mesityl acridine, 9-(2-chlorophenyl)acridine, 9-mesityl acridine, 9-(o-tolyl)acridine, 9-phenylacridine, 9-(2,6-dimethylphenyl)acridine, 9-(4-methoxy-2,6-dimethylphenyl)acridine, 9-(4-fluoro-2,6-dimethylphenyl)acridine, 9-([1,1'-biphenyl]-4-yl)-2,7-dimethylacridine, 9-(2,4,6-triisopropylphenyl)acridine; The solid-phase photocatalyst is any one of 3,6-ditert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 2,7-ditert-butyl-9-(2,6-dimethyl-4-vinylphenyl)acridine, 3,6-ditert-butyl-9-(4-vinylphenyl)acridine, 9-(2,6-dimethyl-4-vinylphenyl)acridine, 9-(2-chloro-4-vinylphenyl)acridine, 9-(2-methyl-4-vinylphenyl)acridine acridine supported by polystyrene; 5. The method according to claim 1, wherein The higher fatty acid compound is any one or several of valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 2-heptyldecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, heneicosanoic acid, behenic acid, tricosanoic acid, lignoceric acid, pentacosanoic acid, cerotic acid, melissic acid, lignoceric acid, oleic acid, linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

6. The method according to claim 1, wherein The reaction solvent is any one of dichloromethane, 1,2-dichloroethane, acetonitrile, ethanol, n-hexane, tetrahydrofuran, toluene, dimethyl sulfoxide, and N,N-dimethylformamide.

7. The method according to claim 1, wherein The hydrogen atom transfer catalyst is any one of p-methylbenzenethiol, p-chlorobenzenethiol, p-methoxybenzenethiol, diphenyl disulfide, 4,4'-dichlorodiphenyl disulfide, 4,4'-dimethoxydiphenyl disulfide, N-tert-butoxycarbonyl-L-cysteine methyl ester, and N-acetyl-L-cysteine ethyl ester.

8. The method according to claim 1, wherein The photocatalyst is 3,6-di-tert-butyl-9-homomesityl acridine or acridine supported on polystyrene. The hydrogen atom transfer catalyst is p-chlorobenzenethiol, and the reaction solvent is dichloromethane.

9. The method according to claim 1, wherein When the photocatalyst is a solid-phase photocatalyst, the solid obtained by filtering the reaction solution obtained in S1 is the solid-phase photocatalyst, which is washed with petroleum ether and then recycled.

10. The method according to claim 1, wherein The photocatalyst is 3,6-di-tert-butyl-9-(4-vinylphenyl)acridine supported on polystyrene, and its preparation steps are as follows: Step 1: Add 4-vinylbenzoic acid, potassium carbonate, and N,N-dimethylformamide to a round-bottom flask, then add methyl iodide, and react at room temperature for 24 h to obtain Compound 2. The reaction equation is as follows; Step 2: Add 1-bromo-3-(tert-butyl)benzene, 3-(tert-butyl)phenol, cesium carbonate, copper(I) iodide, 2,2,6,6-tetramethylheptane-3,5-dione, and N,N-dimethylformamide to the round-bottom flask, and stir and react at 110 °C for 24 h to obtain Compound 5; the reaction equation is as follows: Step 3: Under an argon atmosphere, add Compound 5, anhydrous n-hexane, and N,N,N',N'-tetramethylethylenediamine to the flask, then dropwise add a n-hexane solution of sec-butyllithium under an ice bath condition, raise the temperature to room temperature and stir for 4 h; then cool the flask to -78 °C, under an argon atmosphere, add an anhydrous n-hexane solution of Compound 2, and raise the temperature to room temperature and stir for 18 h to obtain a reaction solution; In the organic layer extracted from the reaction solution, add concentrated HCl to obtain a brown suspension, then stir for 30 minutes, add water for dilution, wash the organic layer with water, add sodium tetrafluoroborate to the obtained washing solution, and then add dichloromethane for extraction; for the organic layer obtained after extraction, first remove part of the solvent under reduced pressure, then add diethyl ether complex of tetrafluoroboric acid, stir the solution until homogeneous, then wash with water and an aqueous solution of sodium tetrafluoroborate respectively, then extract the organic layer with dichloromethane until colorless, and then dry the organic layer with solid sodium tetrafluoroborate, filter and remove the solvent under reduced pressure to obtain Compound 6; The reaction equation is as follows: Step 4: First add Compound 6 to ethanol, then add concentrated ammonia water solution, and stir the reaction mixture at room temperature for 6 h to obtain Compound 7. The reaction equation is: Step 5: Dissolve Compound 7 in tetrahydrofuran, add azobisisobutyronitrile, then place it in an autoclave, under an argon atmosphere, heat to 100 °C and continue to react for 24 hours to obtain Compound 8, which is the POL-acridine photocatalyst. The reaction equation is:

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