A method for producing aviation fuel and hydrogen by photocatalytic decarboxylation coupling of coconut oil fatty acids to grow carbon chains

Abstract

The present invention relates to a technical field of photocatalytically increasing carbon chain length, and in particular to a method for photocatalytically increasing carbon chain length by decarboxylation coupling of coconut oil fatty acids to produce aviation fuel and co-produce hydrogen. Coconut oil fatty acids and Pt@C3N4 catalysts are added to a photocatalytic reactor, and the atmosphere in the reactor is replaced with an inert gas and then sealed, stirred and mixed, and a decarboxylation coupling reaction occurs under the irradiation of an external light source to produce aviation fuel and co-produce hydrogen. Compared with the existing process, it has the advantages of low catalyst cost, low energy consumption, and no consumption of hydrogen, and the reaction can generate an equivalent amount of hydrogen. The present invention provides a new technical approach for converting low-quality oils and fats to prepare bio-aviation fuel.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytically increasing carbon chain length, and in particular to a method for producing aviation fuel and jointly producing hydrogen by photocatalytically decarboxylating and coupling carbon chain-increasing coconut oil fatty acids. Background Art

[0002] In recent years, with the excessive emission of carbon dioxide, countries around the world are facing an increasingly serious global warming crisis. Biomass-based fuel provides a possible way to reduce CO2 emissions. The use of bio-jet fuel can significantly reduce CO2 emissions in the aviation industry. Jet fuel is a type of fuel produced specifically for aircraft, including aviation gasoline for spark-ignition piston engines and aviation kerosene for gas turbine engines. The basic composition is different hydrocarbons and a small amount of additives. Among these components, long-chain alkanes (C8-C18) are the main components, and also include a small amount of cycloalkanes and some aromatic hydrocarbons and olefins. Alkanes are a class of simple compounds that contain only two elements, carbon and hydrogen, in the molecule. All carbon atoms in the molecule are connected by carbon-carbon single bonds, and the remaining valence bonds are bonded to hydrogen. They are divided into two categories: chain alkanes and cycloalkanes. The general chemical formula of chain alkanes is C n H 2n+2 The general formula of cycloalkanes with a single ring structure is C n H 2n .

[0003] At present, the conversion pathways for renewable bio-jet fuel that have been developed at home and abroad mainly include: the Fischer-Tropsch synthesis conversion pathway, which mainly uses synthesis gas (CO2 and H2) to catalytically convert into hydrocarbon substances as fuel; the sugar substance conversion to aviation fuel pathway, in which sugars can be directly fermented to produce alkane fuels without going through other intermediates; the alcohol substance conversion to aviation fuel pathway, in which sugars and starch can be fermented to produce alcohols, as well as alcohol substances obtained by other pathways, which can be used to produce aviation fuel after a certain conversion process; the oil hydrogenation conversion pathway, which uses oil raw materials to produce aviation fuel through conversion processes such as hydrogenation deoxygenation and isomerization cracking.

[0004] Oil is a common and widely available biomass raw material, including vegetable oils and animal oils, and its composition is similar to fossil fuels. In order to be used directly in the engine, oils usually need to be treated by physical or chemical methods. Physical treatment generally refers to mixed use, but due to the high acid value and viscosity of oils, this will aggravate engine wear and form serious coking. The chemical method mainly includes transesterification and thermal cracking. At present, the transesterification process has been relatively perfected, but the prepared fatty acid methyl ester fuel still has the disadvantages of poor oxidation stability and low-temperature fluidity. The thermal decomposition method also faces the problem of high reaction temperature and excessive experimental risk.

[0005] Decarboxylation is a new technology developed in recent years. The key step is to directly remove the oxygen element in the carboxylic acid molecule through a decarboxylation reaction and convert it into a hydrocarbon compound. It mainly includes methods such as thermal catalytic decarboxylation, electrocatalytic decarboxylation, and photocatalytic decarboxylation. The temperature required for thermal decarboxylation is usually higher than 300 ° C, and metal catalytic reactions such as platinum and palladium are required (Green Chem. 2021, 23, 1114-1129). Electrocatalytic decarboxylation inevitably requires the use of expensive platinum electrodes (ACSSustain. Chem. Eng. 2021, 9, 5288-5297). Photocatalytic decarboxylation shows milder decarboxylation conditions and higher product selectivity, but requires excess hydrogen to participate in the reaction (Nat. Catal. 2020, 3, 170-178). And the research mainly focuses on palm oil, soybean oil, etc., and the fatty acid components contained are mostly C16 and C18. The main fatty acid-rich components of coconut oil are C10, C12 and C14. The difference in carbon chain length between coconut oil and other oils will directly affect the quality of the product and may also have a certain impact on the yield. Summary of the invention

[0006] Based on this, the purpose of the present invention is to provide a method for producing aviation fuel and co-producing hydrogen by photocatalytic decarboxylation coupling of coconut oil fatty acids to grow carbon chains, which has low catalyst cost, low energy consumption, no hydrogen consumption, and can generate equivalent hydrogen in the reaction. The present invention provides a new technical approach for converting low-quality oils and fats into bio-aviation fuel.

[0007] In order to solve the above technical problems of the present invention, the present invention provides the following technical solutions:

[0008] The invention provides a method for producing aviation fuel and jointly producing hydrogen by photocatalytic decarboxylation coupling of coconut oil fatty acid to grow carbon chain. Coconut oil fatty acid and Pt@C3N4 catalyst are added into a photocatalytic reactor, and the atmosphere in the reactor is replaced with an inert gas and then sealed, stirred and mixed, and a decarboxylation coupling reaction occurs under the irradiation of an external light source to produce aviation fuel and jointly produce hydrogen.

[0009] The idea of ​​using the photocatalytic decarboxylation coupling method to produce bio-aviation fuel in the present invention is to first hydrolyze the oil, unify the raw materials into fatty acids, and then perform non-hydrogenation decarboxylation to obtain long-chain alkanes containing 10-22 carbon atoms (reaction formula as follows), and then isomerize the long-chain alkanes to prepare bio-aviation fuel. The present invention can effectively extend the carbon chain length of the oil through coupling reaction under mild conditions, avoid the use of Pt and Pd metals, and generate equivalent H2 during the production process.

[0010]

[0011] Furthermore, the mass ratio of the coconut oil fatty acid to the Pt@C3N4 catalyst is 10-200:1.

[0012] Furthermore, the coconut oil fatty acid is a fatty acid containing 6-12 carbon atoms.

[0013] Furthermore, the coconut oil fatty acid contains at least one of n-hexanoic acid, n-heptanoic acid, n-decanoic acid and lauric acid.

[0014] Furthermore, in the Pt@C3N4 catalyst, the configuration of C3N4 is one or more of α phase, β phase, c phase, p phase and g phase;

[0015] The loading amount of Pt was 0.1-10 wt.% based on C3N4.

[0016] Furthermore, the loading amount of Pt is 0.5-2.0 wt.% based on C3N4.

[0017] Furthermore, the inert gas is one or both of nitrogen and argon.

[0018] Furthermore, the external light source is one or both of ultraviolet LED (wavelength 425nm, 10W) ​​and xenon lamp (150W), preferably ultraviolet LED (wavelength 425nm, 10W).

[0019] Furthermore, the temperature of the decarboxylation coupling reaction is 10-80° C. and the time is 8-30 hours.

[0020] Furthermore, the temperature of the decarboxylation coupling reaction is 25-55° C. and the time is 12-24 hours.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention has developed a method for producing aviation fuel and hydrogen by photocatalytic decarboxylation coupling of coconut oil fatty acids to grow carbon chains. Compared with the existing process, it has the advantages of low catalyst cost, low energy consumption, and no hydrogen consumption, and the reaction can generate equivalent hydrogen. The present invention provides a new technical approach for the conversion of low-quality oils and fats to prepare bio-aviation fuel.

[0023] 2. The reaction conditions of the present invention are mild. The Pt@C3N4 catalyst is used to carry out the photocatalytic deacidification coupling reaction of medium-chain saturated fatty acids. The reaction is carried out under inert atmosphere conditions, which overcomes the disadvantage that the traditional decarboxylation reaction requires a large amount of hydrogen consumption. The low-cost Pt@C3N4 catalyst is used, the reaction time is short, the reaction rate is high, and the reaction selectivity is high. After the reaction is completed, the product separation process is simple, the solid catalyst is easy to recycle, and the entire reaction process is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 is the gas chromatogram of coconut oil fatty acids;

[0026] Figure 2 The gas chromatogram of the product of Example 5 is shown in FIG. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in combination with the drawings and specific implementation methods in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified. The reagents or instruments involved in the present invention without indicating the manufacturer are all common commercial products and can be purchased from the market.

[0029] The Pt@C3N4 catalyst in the following examples of the present invention was prepared by a simple photodeposition method. First, urea was used as a precursor to synthesize g-C3N4. 10 g of urea was placed in a 30 mL crucible with a lid and heated in a muffle furnace at 5 °C min. -1 The temperature was raised to 550 °C at a heating rate of 100 °C and calcined for 3 hours. The light yellow solid obtained after cooling to room temperature was labeled as g-C3N4. 500 mg of g-C3N4 powder and 13.3 mg of H2PtCl6 were dispersed in 10 mL of methanol solution and ultrasonically treated for 10 min to form a uniform suspension. The atmosphere in the reaction apparatus was replaced by vacuum and nitrogen purge five times to remove dissolved O2. A 150 W xenon lamp was used as the light source for irradiation at room temperature for 4 hours to remove Pt 4+ Reduced to metallic Pt. Finally, the suspension was filtered, washed with ultrapure water three times, and dried in vacuum at 60 °C for 2 h. The obtained solid was marked as Pt@C3N4.

[0030] In the present invention, the quantitative analysis of yield is performed using a gas chromatograph (Agilent 7890B), and the chromatographic column is an Agilent HP-5 capillary column (30m*32μm*0.25μm). The qualitative analysis is performed using a gas mass spectrometer Thermo scientific TRACE1310, and the chromatographic column is a Thermoscientific TG-MS capillary column (30m*32μm*0.25μm).

[0031] Embodiment 1:

[0032] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 10 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 58%, and the molar yield of hydrogen was 17 μmol·mL -1 The gas chromatogram of coconut oil fatty acids is shown in Figure 1 .

[0033] Embodiment 2:

[0034] 500 mg of n-heptanoic acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 3 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C12) was calculated to be 60%, and the molar yield of hydrogen was 16 μmol·mL -1 .

[0035] Embodiment 3:

[0036] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 63%, and the molar yield of hydrogen was 20 μmol·mL -1 .

[0037] Embodiment 4:

[0038] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 14 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 67%, and the molar yield of hydrogen was 20 μmol·mL -1 .

[0039] Embodiment 5:

[0040] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 20 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 70%, and the molar yield of hydrogen was 20 μmol·mL -1 The gas chromatogram of the product is shown in Figure 2 .

[0041] Embodiment 6:

[0042] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 0.1 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 52%, and the molar yield of hydrogen was 16 μmol·mL -1 .

[0043] Embodiment 7:

[0044] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 0.1 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 24 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 42%, and the molar yield of hydrogen was 16 μmol·mL -1 .

[0045] Embodiment 8:

[0046] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 0.2 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 46%, and the molar yield of hydrogen was 16 μmol·mL -1 .

[0047] Embodiment 9:

[0048] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 0.5 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 55%, and the molar yield of hydrogen was 19 μmol·mL -1 .

[0049] Embodiment 10:

[0050] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 2.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 63%, and the molar yield of hydrogen was 20 μmol·mL -1 .

[0051] Embodiment 11:

[0052] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 5.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 65%, and the molar yield of hydrogen was 20 μmol·mL -1 .

[0053] Embodiment 12:

[0054] 500 mg of n-decanoic acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 3 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C18) was calculated to be 59%, and the molar yield of hydrogen was 19 μmol·mL -1 .

[0055] Embodiment 13:

[0056] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and argon purging five times, and irradiated at 425 nm LED at 25 ° C for 12 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 62%, and the molar yield of hydrogen was 20 μmol·mL -1 .

[0057] Embodiment 14:

[0058] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and hydrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 3 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 58%, and the molar yield of hydrogen was 19 μmol·mL -1 .

[0059] Embodiment 15:

[0060] 500 mg of n-hexanoic acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 425 nm LED at 25 ° C for 3 h. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10) was calculated to be 62%, and the molar yield of hydrogen was 15 μmol·mL -1 .

[0061] Embodiment 16:

[0062] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 40 ° C for 12 h at 425 nm LED. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 63%, and the molar yield of hydrogen was 3 μmol·mL -1 .

[0063] Embodiment 17:

[0064] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuuming and nitrogen purging five times, and irradiated at 50 ° C for 3 h at 425 nm LED. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 65%, and the molar yield of hydrogen was 3 μmol·mL -1 .

[0065] Embodiment 18:

[0066] 500 mg of coconut oil fatty acid and 5.0 mg of Pt@C3N4 catalyst with a Pt content of 1.0 wt.% were added to a 10 mL photocatalytic reactor. The atmosphere of the reaction tube was replaced by continuous vacuum and nitrogen purging five times, and irradiated at 60 ° C for 12 h at 425 nm LED. After the decarboxylation coupling reaction was completed, the volume was fixed with acetonitrile solvent. The product was analyzed by GC, and the molar yield of long-chain alkanes (C10-C22) was calculated to be 65%, and the molar yield of hydrogen was 3 μmol·mL -1 .

[0067] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Other changes or modifications can be made within the knowledge of ordinary technicians in this field. It is not necessary and impossible to list all the embodiments here. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for producing aviation fuel and hydrogen by photocatalytic decarboxylation coupling of coconut oil fatty acids to grow carbon chains, characterized in that: Coconut oil fatty acids and Pt@C3N4 catalyst are added to a photocatalytic reactor, and the atmosphere in the reactor is replaced with an inert gas and then sealed and stirred to mix evenly. A decarboxylation coupling reaction occurs under the irradiation of an external light source to produce aviation fuel and hydrogen.

2. The method according to claim 1, characterized in that: The mass ratio of the coconut oil fatty acid to the Pt@C3N4 catalyst is 10-200:

1.

3. The method according to claim 1, characterized in that: The coconut oil fatty acid is a fatty acid containing 6 to 12 carbon atoms.

4. The method according to claim 1, characterized in that: The coconut oil fatty acid comprises at least one of n-hexanoic acid, n-heptanoic acid, n-decanoic acid and lauric acid.

5. The method according to claim 1, characterized in that: In the Pt@C3N4 catalyst, the configuration of C3N4 is one or more of α phase, β phase, c phase, p phase and g phase; The loading amount of Pt was 0.1-10 wt.% based on C3N4.

6. The method according to claim 5, characterized in that: The loading amount of Pt was 0.5-2.0 wt.% based on C3N4.

7. The method according to claim 1, characterized in that: The inert gas is one or both of nitrogen and argon.

8. The method according to claim 1, characterized in that: The external light source is one or both of ultraviolet LED and xenon lamp.

9. The method according to claim 1, characterized in that: The temperature of the decarboxylation coupling reaction is 10-80° C. and the time is 8-30 hours.

10. The method according to claim 9, characterized in that: The temperature of the decarboxylation coupling reaction is 25-55° C. and the time is 12-24 hours.

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