Preparation method and application of high-tension cyclobutane fuel

Abstract

The invention discloses a preparation method and application of a high-tension cyclobutane fuel, and the preparation method comprises the following steps: S1, in the presence of a photocatalyst, oxygen, organic anhydride and alkali, substituted cycloolefin is subjected to photocatalytic oxidation / [2 + 2] cycloaddition to obtain a cyclobutane fuel parent molecule; n is equal to 0, 1 or 2; r1, R2, R3 and R4 are respectively and independently H or-CH3 or-CH2CH3. According to the method, the cyclobutane fuel is directly synthesized from olefin, the target yield is high, the reaction condition is mild, aftertreatment is simple, and the prepared high-tension cyclobutane fuel has the excellent performance of high density, high calorific value and low freezing point at the same time.

Description

Technical Field

[0001] This invention belongs to the field of liquid fuel propellants, and relates to a method for preparing and applying high-strain cyclobutane fuel. More specifically, it relates to a method for preparing high-strain cyclobutane fuel via photocatalytic cycloolefin oxidation / [2+2] one-pot conversion pathway. Background Technology

[0002] High-density hydrocarbon fuels refer to artificially synthesized fuels with a density exceeding 0.8 g / cm³. 3 Alkane fuels have significant applications in the aerospace field. Advanced spacecraft such as rockets, long-range missiles, and supersonic aircraft not only require greater range and payload but also higher fuel tank capacity. Increasing fuel density and volumetric calorific value can effectively improve the propulsion performance of spacecraft. In space-constrained aerospace vehicles, high-density fuels can extend range and increase payload.

[0003] Currently, high-density hydrocarbon fuels are mainly synthesized through thermocatalysis, including alkylation, hydroxyalkylation, Aldol condensation, olefin polymerization, Michael addition, and hydrodeoxygenation. This approach presents several challenges: demanding reaction conditions (high temperature and pressure); low product selectivity and numerous side reactions; and thermodynamic instability, making it difficult to construct high-strain ring structures (such as cyclobutane). High-strain cyclobutane is primarily constructed through a [2+2] cycloaddition reaction, which, according to the Woodward-Hoffmann rule, is thermodynamically forbidden and can only occur under light conditions. Compared to traditional thermocatalytic synthesis routes, photocatalytic cycloaddition reactions offer advantages such as milder reaction conditions and higher product selectivity.

[0004] Currently reported cyclobutane fuels are mainly obtained from the [2+2] reaction of ketenes. For example:

[0005] Patent application No. 201810008691.8 discloses a four-membered ring fuel molecule and its photochemical preparation method: In the presence of a photosensitizer, a substituted cycloene undergoes a cycloaddition reaction to obtain a fuel precursor molecule, which is then hydrogenated and deoxygenated to obtain the four-membered ring fuel molecule; alternatively, in the presence of a photosensitizer, a substituted cycloene and a substituted cycloene undergo a cycloaddition reaction to obtain a fuel precursor molecule, which is then hydrogenated and deoxygenated to obtain the four-membered ring fuel molecule; furthermore, in the presence of a photosensitizer, a substituted cycloene undergoes a cycloaddition reaction to obtain the four-membered ring fuel molecule. This technical solution mainly uses the cycloaddition reaction of the ketone itself or the ketone with a cycloene, resulting in a relatively high yield; however, the method using the substituted cycloene itself for cycloaddition has a low yield.

[0006] Patent application No. 202311275115.7 discloses a one-pot method for preparing high-strength four-membered cycloalkane fuels from cyclic ketones or cyclic alcohols. In the presence of an oxidant and a light source, biomass-derived cyclic ketones or cyclic alcohols undergo a one-pot oxidation / photochemical [2+2] cycloaddition reaction to obtain a four-membered cycloalkane fuel precursor molecule, which is then hydrogenated and deoxygenated to obtain the four-membered cycloalkane fuel molecule. The substrate for this method is a cyclic ketone or cyclic alcohol.

[0007] However, in existing technologies, ketenes are far fewer than alkenes. Conversely, both biomass and non-biomass resources contain abundant cycloolefins, such as cyclopentene, cyclohexene, n-hexene, cycloheptene, myrcene, and turpentine. However, the triplet state energy of simple alkenes is high and difficult to reach; moreover, the triplet state lifetime is short (nanoseconds), resulting in extremely low reaction efficiency and very low yields for direct [2+2] cycloaddition reactions. Therefore, developing methods for the direct synthesis of cyclobutane fuels from alkenes with high yields of the target product is of great significance.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The technical problem to be solved by this invention is to overcome the shortcomings of existing technologies and provide a method for preparing and applying high-strain cyclobutane fuel. This invention employs a one-pot method for preparing high-strain cyclobutane fuel using photocatalytic cycloolefin oxidation / [2+2] cycloaddition. Photocatalysis overcomes the thermodynamic limitations of [2+2] cycloaddition, and high-efficiency reaction is achieved by controlling the excited state of the cycloolefin. The one-pot method simplifies the synthesis process and solves the problem of low yield in the direct synthesis of cyclobutane from olefins.

[0010] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a method for preparing high-strength cyclobutane fuel, comprising the following steps:

[0012] S1: In the presence of a photocatalyst, oxygen, organic acid anhydride, and base, substituted cycloolefins undergo photocatalytic oxidation / [2+2] cycloaddition to yield cyclobutane fuel parent molecules:

[0013]

[0014] S2: Hydrogenation and deoxygenation of the cyclobutane fuel precursor molecule obtained in step S1 yields a high-strain cyclobutane fuel molecule.

[0015]

[0016] Where n = 0, 1, or 2;

[0017] R1, R2, R3, and R4 are each independently H, -CH3, or -CH2CH3.

[0018] Currently, high-density hydrocarbon fuels are mainly synthesized through thermocatalytic reactions, requiring high temperature and pressure, numerous side reactions, high energy consumption, few strained ring structures, and relatively low density. Cyclobutane, on the other hand, is primarily constructed through a [2+2] cycloaddition reaction. This [2+2] cycloaddition reaction is thermodynamically forbidden, and traditional methods require photoexcitation to bring the olefin into the triplet state (T1). However, the triplet state (T1) of simple olefins (such as ethylene) has high energy (~80-100 kcal / mol), making it difficult to achieve, and its short lifetime (nanoseconds) further hinders its direct [2+2] cycloaddition reaction, resulting in extremely low reaction efficiency.

[0019] The patent application with application number 201810008691.8 discloses a scheme in which substituted cycloalkene undergoes a cycloaddition reaction in the presence of a photosensitizer to obtain a four-membered ring fuel molecule. The photosensitizer is cyclopentanone, etc. The reaction mechanism is that the photosensitizer in the excited state under light transfers triplet energy to the substituted cycloalkene to form a cycloalkene triplet state and then initiates [2+2] cycloaddition. However, its triplet energy transfer efficiency is low and the lifetime of the cycloalkene triplet state is short, resulting in a low yield of the [2+2] cycloaddition reaction.

[0020] This invention proposes a one-pot method for preparing high-strain cyclobutane fuel molecules via photocatalytic cycloolefin oxidation / [2+2] cycloaddition. First, photocatalytic cycloolefin oxidation to cycloenone: under light irradiation, conjugated organic polymers activate oxygen via electron and energy transfer to generate highly oxidizing reactive oxygen species, which then oxidize the substituted cycloolefin to cycloenone. Second, in-situ [2+2] cycloaddition to prepare a four-membered ring fuel precursor: the in-situ generated cycloenone is excited by photons to form a triplet cycloenone. The triplet cycloenone collides with ground-state cycloolefin molecules and, via a biradical intermediate, yields the four-membered ring fuel precursor. This process avoids the inefficient triplet energy transfer process and the formation of triplet cycloolefins, thus resulting in higher reaction efficiency. Third, the "one-pot" design: oxidation and cycloaddition are carried out in series in the same reaction system, avoiding the separation of intermediates and improving efficiency.

[0021] In addition, the method of the present invention can be achieved at room temperature and pressure, overcomes thermodynamic barriers through photocatalysis, constructs cyclobutane skeletons with high selectivity, has few side reactions, and utilizes light energy, making it green and efficient.

[0022] The high-strain cyclobutane fuel prepared by this invention utilizes the ring strain of cyclobutane (~26 kcal / mol) to achieve a more compact molecular packing and high volumetric energy density. The release of strain energy increases the enthalpy of combustion, resulting in a high calorific value. Furthermore, cyclobutane derivatives can lower the freezing point by modifying the side chains (e.g., methyl, ethyl), making it suitable for low-temperature environments (such as aerospace fuels). Therefore, the high-strain cyclobutane fuel synthesized by the method of this invention exhibits excellent properties including high density, high calorific value, and low freezing point.

[0023] In a further embodiment, in step S1, the amount of photocatalyst added is 0.05 wt% to 5 wt% of the mass of the reactants, preferably 0.05 wt% to 3 wt%, and more preferably 0.05 wt% to 1 wt%. For example, in some embodiments, it can be 0.05 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0024] In a further embodiment, the photocatalyst is a conjugated organic polymer catalyst synthesized from a first monomer and a second monomer;

[0025] The first monomer is selected from at least one of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine or 1,3,6,8-tetraethynylpyrene; the second monomer is selected from at least one of 2,7-dibromophenanthroline or 3,6-dibromophenanthroline or 2,6-dibromoanthraquinone or 1,5-dibromoanthraquinone or 2,7-dibromo-4,5,9,10-pyrenetetrone.

[0026] The photocatalyst of this invention can not only absorb light of specific wavelengths to form an excited state and transfer energy to the substrate or intermediate, but also modulate the reaction pathway, making the reaction more inclined towards the free radical generation pathway, thus determining the selectivity and efficiency of the product. In this invention, a conjugated organic polymer synthesized from the first and second monomers is used as the photocatalyst, which can promote the generation of reactive oxygen species and enhance the generation of the intermediate cycloenone, thereby achieving in-situ cycloaddition to generate high-strain pure carbocyclobutane with a higher calorific value. This invention also finds that when using traditional photocatalysts, such as TiO2, CdS, and W... 18 O 49 At that time, the yield of cyclobutane fuel precursor was very low, but by using the conjugated organic polymer synthesized from the first and second monomers as a photocatalyst, the yield of cyclobutane fuel precursor was high, reaching more than 80%.

[0027] The method for preparing the conjugated organic polymer catalyst synthesized from the first monomer and the second monomer can be carried out using methods in the prior art.

[0028] In a further embodiment, the preparation method of the photocatalyst includes:

[0029] The first and second monomers were placed in an organic solvent, and cuprous salt, phosphine ligand and palladium catalyst were added. The mixture was heated under a protective atmosphere and refluxed. After the reaction was completed, the mixture was cooled to room temperature. The crude product was collected, washed and vacuum dried to obtain the conjugated organic polymer catalyst.

[0030] The equivalence ratio of the first monomer to the second monomer is 1:1 to 3.

[0031] The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, triethylamine, diethylamine, pyridine, N,N-diisopropylethylamine, toluene, and dioxane.

[0032] The equivalent ratio of the first monomer to the cuprous salt is 1:5 to 15%.

[0033] The cuprous salt is selected from at least one of CuI, CuBr, and CuCl.

[0034] The equivalence ratio of the first monomer to the phosphine ligand is 1:5 to 15%;

[0035] The phosphine-based ligand is triphenylphosphine.

[0036] The equivalence ratio of the first monomer to the palladium catalyst is 1:2.5 to 7.5%.

[0037] Preferably, the palladium catalyst is at least one of Pd(PPh3)2Cl2 and Pd(PPh3)4. The reflux reaction is carried out under a protective atmosphere at a temperature of 80–160°C for a reaction time of 20–36 h.

[0038] In a further embodiment, in step S1, the amount of organic anhydride added is 0.5wt% to 5wt% of the mass of the reactants, preferably 0.5wt% to 3wt%; for example, in some embodiments, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, etc.

[0039] Preferably, the organic anhydride is selected from at least one of formic anhydride, acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, phthalic anhydride, and terephthalic anhydride.

[0040] In a further embodiment, in step S1, the amount of alkali added is 0.005 wt% to 5 wt% of the reactant mass, preferably 0.01 wt% to 3 wt%. For example, in some embodiments, it can be 0.005 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0041] Preferably, the base is selected from at least one of purine, quinoline, pyridine, piperidine, triazole, 2,6-dimethylpyridine, N,N-dimethylpyridine, 4-dimethylaminopyridine, and 3,5-dimethylpyridine.

[0042] In a further embodiment, in step S1, the substituted cycloolefin is selected from cyclopentene, 2-methylcyclopentene, 3-methylcyclopentene, 2-ethylcyclopentene, 3-ethylcyclopentene, 2,2-dimethylcyclopentene, 2,3-dimethylcyclopentene, 3,3-dimethylcyclopentene, 2-methyl-2-ethylcyclopentene, 2-methyl-3-ethylcyclopentene, 2,2-diethylcyclopentene, 2,3-diethylcyclopentene, 3,3-diethylcyclopentene, 2,2-dimethyl-3-ethylcyclopentene, 2-methyl-3,3-diethylcyclopentene, cyclohexene, 2-methylcyclohexene, 3-methylcyclohexene, 2-ethylcyclohexene, 3-ethylcyclohexene, 2,2-dimethylcyclohexene, 2,3-dimethylcyclohexene, 2,4-dimethylcyclohexene, ... Hexene, 3,4-dimethylcyclohexene, 2-methyl-2-ethylcyclohexene, 2-methyl-3-ethylcyclohexene, 2-methyl-4-ethylcyclohexene, 3-methyl-4-ethylcyclohexene, 2,2-diethylcyclohexene, 2,3-diethylcyclohexene, 2,4-diethylcyclohexene, 3,4-diethylcyclohexene, 2,2,3-trimethylcyclohexene, 2,2,4-trimethylcyclohexene, 2,3,4-trimethylcyclohexene, 2,2,3-triethylcyclohexene, 2,2,4-triethylcyclohexene, 2,3,4-triethylcyclohexene, 2,2-dimethyl-3-ethylcyclohexene, 2,2-dimethyl-4-ethylcyclohexene, 2,3-dimethyl-4-ethylcyclohexene, 2-methyl-3,3-diethylcyclohexene 2-Methyl-3,4-triethylcyclohexene, 2-methyl-4,4-diethylcyclohexene, cycloheptene, 2-methylcycloheptene, 3-methylcycloheptene, 4-methylcycloheptene, 2,2-dimethylcycloheptene, 2,3-dimethylcycloheptene, 2,4-dimethylcycloheptene, 2,5-dimethylcycloheptene, 3,3-dimethylcycloheptene, 3,4-dimethylcycloheptene, 3,5-dimethylcycloheptene, 4,4-dimethylcycloheptene, 2-ethylcycloheptene, 3-ethylcycloheptene, 4-ethylcycloheptene, 2,2-diethylcycloheptene, 2,3-diethylcycloheptene, 2,4-diethylcycloheptene, 2,5-diethylcycloheptene, 3,3'-diethylcycloheptene, 3,4-diethylcycloheptene, 3,5-diethylcycloheptene 4,4-Diethylcycloheptene, 2,2,3-Trimethylcycloheptene, 2,2,4-Trimethylcycloheptene, 2,2,5-Trimethylcycloheptene, 2,3,4-Trimethylcycloheptene, 2,3,5-Trimethylcycloheptene, 2,3,6-Trimethylcycloheptene, 2,4,5-Trimethylcycloheptene, 3,3,4-Trimethylcycloheptene, 3,3,5-Trimethylcycloheptene, 3,4,5-Trimethylcycloheptene, 2,2,3-Triethylcycloheptene, 2,2,4-Triethylcycloheptene, 2,2,5-Triethylcycloheptene, 2,3,4-Triethylcycloheptene, 2,3,5-Triethylcycloheptene, 2,3,6-Triethylcycloheptene, 2,4,5-Triethylcycloheptene, 3,3,4-Triethylcycloheptene, 3,3...At least one of the following: 5-triethylcycloheptene, 3,4,5-triethylcycloheptene, 2,2-dimethyl-3-ethylcycloheptene, 2,2-dimethyl-4-ethylcycloheptene, 2,2-dimethyl-5-ethylcycloheptene, 2,3-dimethyl-4-ethylcycloheptene, 2-methyl-3,3-diethylcycloheptene, 2-methyl-3,4-diethylcycloheptene, 2-methyl-4,5-diethylcycloheptene, 3,3-dimethyl-4-ethylcycloheptene, 3,3-dimethyl-5-ethylcycloheptene, 3,4-dimethyl-5-ethylcycloheptene, and 3-methyl-4,5-diethylcycloheptene.

[0043] In a further embodiment, in step S1, the photocatalytic oxidation / [2+2] cycloaddition reaction conditions are: the light source is a high-pressure mercury lamp or xenon lamp of 200-500W; in some embodiments, the light source can be a high-pressure mercury lamp or xenon lamp of 200W, 250W, 300W, 350W, 400W, 450W, 500W, etc.

[0044] The reaction temperature is 0–40°C, preferably 0–30°C; in some embodiments, the reaction temperature can be 0°C, 10°C, 20°C, 30°C, 40°C, etc.

[0045] The reaction time is 5 to 48 hours, preferably 5 to 36 hours, and more preferably 5 to 24 hours; in some embodiments, the reaction time can be 5 hours, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 ​​hours, etc.

[0046] In a further embodiment, in step S2, the reaction conditions for the hydrogenation and deoxygenation of the high-tension cyclobutane fuel precursor molecule are as follows: with the aid of a catalyst, the reaction temperature is controlled at 120-180°C, preferably 140-180°C. In some embodiments, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc.

[0047] The hydrogen pressure is 4–7 MPa; in some embodiments, it can be, for example, 4 MPa, 5 MPa, 6 MPa, 7 MPa, etc.

[0048] The reaction time is 12 to 48 hours, preferably 24 to 48 hours; in some embodiments, it can be, for example, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 ​​hours, etc.

[0049] In a further embodiment, the catalyst is a supported catalyst formed by loading a metal onto a support;

[0050] Preferably, the metal is selected from at least one of copper, nickel, gold, platinum and palladium;

[0051] Preferably, the carrier is selected from at least one of SBA-15, HZSM-5, Al2O3, SiO2, Hβ, or HY.

[0052] Secondly, the present invention provides a high-strain cyclobutane fuel obtained by the preparation method described above; the structure of the high-strain cyclobutane fuel is shown below:

[0053]

[0054] Where n = 0, 1, or 2;

[0055] R1, R2, R3, and R4 are each independently H, -CH3, or -CH2CH3.

[0056] Preferably, when n=1, the density of the obtained high-strength cyclobutane fuel molecules is 0.86–0.95 g / cm³. 3 Its freezing point is not higher than -55℃ and its mass calorific value is not lower than 42.4 MJ / kg.

[0057] Thirdly, the present invention provides an application of the method for preparing high-strength cyclobutane fuel as described above in the preparation of aircraft propellants.

[0058] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0059] 1. The method for preparing high-strain cyclobutane fuel of the present invention overcomes the limitations of traditional thermocatalytic synthesis of high-density fuels and overcomes the thermodynamic prohibition problem of simple olefin [2+2] cycloaddition reactions. The present invention utilizes photocatalysis to overcome the thermodynamic limitations of [2+2] cycloaddition, achieving efficient reactions by controlling the excited state of cycloolefins. The "one-pot" design simplifies the synthesis process, directly obtaining high-strain cyclobutane fuel, avoiding the separation of intermediates, and improving efficiency.

[0060] 2. In the preparation method of the present invention, high-strain cyclobutane fuel is directly synthesized using substituted cycloolefins as substrates, and a conjugated organic polymer is used as a photocatalyst. The amounts of photocatalyst, organic acid anhydride and base are appropriate, thereby greatly improving the yield of cyclobutane fuel parent molecules, which can reach more than 80%.

[0061] 3. The high-tension cyclobutane fuel molecule in this invention is prepared by photocatalytic oxidation / [2+2] cycloaddition and hydrogenation deoxygenation reaction at room temperature and pressure. The preparation process is simple, the reaction conditions are mild, the energy consumption is low, it is a green synthesis, the target yield is high, and it has good universality for various substituted cycloolefins, and has high industrial application value.

[0062] 4. The high-strength cyclobutane structure fuel molecules synthesized by the preparation method of the present invention have excellent properties such as high density, high calorific value and low freezing point. Its volumetric calorific value is higher than that of general liquid hydrocarbon fuels. For spacecraft with a fixed fuel tank volume, it can effectively increase the fuel capacity and meet the application requirements of long range, high speed and large payload. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0064] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0065] In this embodiment of the invention, the photocatalyst is at least one of a conjugated organic polymer catalyst synthesized from a first monomer and a second monomer. The first monomer is 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (A) or 1,3,6,8-tetraethynylpyrene (B); the second monomer is 2,7-dibromophenanthroquinone (C) or 3,6-dibromophenanthroquinone (D) or 2,6-dibromoanthraquinone (E) or 1,5-dibromoanthraquinone (F) or 2,7-dibromo-4,5,9,10-pyrenetetrone (G). For the sake of brevity, each monomer is represented by an English letter in the following embodiments.

[0066] The conjugated polymers in the examples were prepared using the Sonogashira Hagihara cross-coupling reaction. AC is used as an example below:

[0067] Toluene and triethylamine were added to a mixture of C, A, triphenylphosphine, and cuprous iodide, wherein the equivalent ratio of A to C was 1:1.5, the equivalent ratio of A to cuprous iodide was 1:10%, and the equivalent ratio of A to triphenylphosphine was 1:10%. The mixture was degassed under an inert gas-vacuum atmosphere, and then Pd(PPh3)2Cl2 was immediately added, with an equivalent ratio of A to Pd(PPh3)2Cl2 of 1:5%; this mixture was then degassed again under an inert gas-vacuum atmosphere. Subsequently, the mixture was stirred in an oil bath at 120°C for 24 hours under an inert gas atmosphere. After the reaction was complete and cooled to ambient temperature, the precipitate was collected by vacuum filtration, washed, and the filtrate was washed until colorless. The filter cake was collected and dried at 80°C for 8 hours to obtain a solid powder, which is the AC conjugated organic polymer catalyst.

[0068] The preparation of AD crosslinked polymers, AE crosslinked polymers, AF crosslinked polymers, AG crosslinked polymers, BC crosslinked polymers, BD crosslinked polymers, BE crosslinked polymers, BF crosslinked polymers, and BG crosslinked polymers all follow the methods described above.

[0069] Example 1

[0070] S1, Synthesis reaction of high-strain cyclobutane fuel parent molecule:

[0071] In a 25 mL single-port jacketed glass reactor, 2 g of cyclopentene, 0.3 wt% AC crosslinked polymer photocatalyst, 0.5 wt% acetic anhydride, and 0.03 wt% 2,6-dimethylpyridine were added. Circulating cooling water was introduced under magnetic stirring, and oxygen was bubbled throughout the reaction. The reactor was irradiated with a high-pressure mercury lamp for 24 h. Gas chromatography-mass spectrometry was used to analyze the reaction solution, qualitatively identify the products, and determine the reaction yield.

[0072] Examples 2-31 were carried out according to the method of Example 1 and the conditions in Table 1.

[0073] Table 1 Synthesis Reactions of High-Tension Cyclobutane Fuel Parent Molecule

[0074]

[0075]

[0076]

[0077] Results analysis:

[0078] As can be seen from the table above, in the schemes of Examples 1-31, the yield of high-strength cyclobutane fuel precursor molecules all reached over 80%, and the yields of Examples 4, 8 and 12 even reached over 95%.

[0079] Example 32

[0080] S2, Hydrodeoxygenation reaction of high-strength cyclobutane fuel parent molecules:

[0081] The fuel precursor molecule obtained in Example 1, along with 2g of Pd / C and 5g of HY catalyst, was added to a 100mL high-pressure reactor. The reactor was sealed, and the air was purged with nitrogen 2-3 times. Then, hydrogen gas at 5.5MPa was introduced, and the temperature was raised to 140℃ with stirring. The reaction was carried out for 24 hours. The reaction solution was analyzed by gas chromatography-mass spectrometry to identify the products and calculate the reaction yield.

[0082] Results: The fuel parent molecules were completely converted, and the yield of cyclobutane fuel molecules (target molecules) was 88%.

[0083] Examples 33-46 follow the method of Example 32, carrying out the hydrogenation and deoxygenation reaction of cyclobutane fuel parent molecules according to the conditions in Table 2.

[0084] Table 2 Hydrodeoxygenation of High-Tension Cyclobutane Fuel Parent Molecules

[0085]

[0086] As can be seen from the table above, the yield of high-strength cyclobutane fuel molecules in Examples 32-46 is all above 80%, with the yield in Examples 35-46 reaching above 90% and that in Example 41 reaching 95%.

[0087] The reaction process for preparing high-strain cyclobutane fuel in Examples 1 and 39 is as follows:

[0088]

[0089] The reaction process for preparing high-strain cyclobutane fuel in Examples 2 and 43 is as follows:

[0090]

[0091] Comparative Example 1

[0092] Compared with Example 1, the difference in this comparative example is the use of a different photocatalyst; all other conditions are the same. The specific results are as follows:

[0093] When using a conventional TiO2 photocatalyst, the yield of cyclobutane fuel precursor is 5%.

[0094] When using a CdS photocatalyst, the yield of cyclobutane fuel precursor is 9%;

[0095] Using W 18 O 49 When using a photocatalyst, the yield of cyclobutane fuel precursor is 15%.

[0096] Comparative Example 2

[0097] Compared with Example 2, the difference in this comparative example is the use of a different olefin feedstock; all other conditions are the same. The specific results are as follows:

[0098] Under the same reaction conditions, when the olefin feedstock is n-pentene, the yield of cyclobutane fuel parent material is 5.5%;

[0099] Under the same reaction conditions, when the olefin feedstock is n-hexene, the yield of cyclobutane fuel parent material is 3.4%.

[0100] Under the same reaction conditions, when the olefin feedstock is n-heptene, the yield of cyclobutane fuel parent material is 2.5%.

[0101] It can be seen that the overall yield of straight-chain olefins in this reaction system is very low. Therefore, substituted cyclic olefins are used as olefin feedstocks in this invention.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing high-strain cyclobutane fuel, characterized in that, Includes the following steps: S1: In the presence of a photocatalyst, oxygen, organic acid anhydride, and base, substituted cycloolefins undergo photocatalytic oxidation / [2+2] cycloaddition to yield cyclobutane fuel parent molecules: S2: Hydrogenation and deoxygenation of the cyclobutane fuel precursor molecule obtained in step S1 yields a high-strain cyclobutane fuel molecule. Where n = 0, 1, or 2; R1, R2, R3, and R4 are each independently H, -CH3, or -CH2CH3.

2. The method for preparing high-strength cyclobutane fuel according to claim 1, characterized in that, In step S1, the photocatalyst is a conjugated organic polymer catalyst synthesized from a first monomer and a second monomer; preferably, the preparation method of the photocatalyst includes: The first and second monomers were placed in an organic solvent, and cuprous salt, phosphine ligand and palladium catalyst were added. The mixture was heated under a protective atmosphere and refluxed. After the reaction was completed, the mixture was cooled, and the crude product was collected, washed and dried to obtain the conjugated organic polymer catalyst. Preferably, the equivalence ratio of the first monomer to the second monomer is 1:1 to 3; Preferably, the first monomer is selected from at least one of 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine or 1,3,6,8-tetraethynylpyrene; and the second monomer is selected from at least one of 2,7-dibromophenanthroline or 3,6-dibromophenanthroline or 2,6-dibromoanthraquinone or 1,5-dibromoanthraquinone or 2,7-dibromo-4,5,9,10-pyrenetetrone.

3. The method for preparing high-strength cyclobutane fuel according to claim 1 or 2, characterized in that, In step S1, the amount of photocatalyst added is 0.05% to 5% of the reactant mass.

4. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-3, characterized in that, In step S1, the amount of organic acid anhydride added is 0.5% to 3% of the reactant mass; Preferably, the organic anhydride is selected from at least one of formic anhydride, acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, phthalic anhydride, and terephthalic anhydride.

5. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-4, characterized in that, In step S1, the amount of alkali added is 0.005% to 5% of the reactant mass; Preferably, the base is selected from at least one of purine, quinoline, pyridine, piperidine, triazole, 2,6-dimethylpyridine, N,N-dimethylpyridine, 4-dimethylaminopyridine, and 3,5-dimethylpyridine.

6. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-5, characterized in that, In step S1, the substituted cycloolefin is selected from cyclopentene, 2-methylcyclopentene, 3-methylcyclopentene, 2-ethylcyclopentene, 3-ethylcyclopentene, 2,2-dimethylcyclopentene, 2,3-dimethylcyclopentene, 3,3-dimethylcyclopentene, 2-methyl-2-ethylcyclopentene, 2-methyl-3-ethylcyclopentene, 2,2-diethylcyclopentene, 2,3-diethylcyclopentene, 3,3-diethylcyclopentene, 2,2-dimethyl-3-ethylcyclopentene, 2-methyl-3,3-diethylcyclopentene, cyclohexene, 2-methylcyclohexene, 3-methylcyclohexene, 2-ethylcyclohexene, 3-ethylcyclohexene, 2,2-dimethylcyclohexene, 2,3-dimethylcyclohexene, 2,4-dimethylcyclohexene, 3,4-dimethylcyclohexene, 2 ... -Dimethylcyclohexene, 2-methyl-2-ethylcyclohexene, 2-methyl-3-ethylcyclohexene, 2-methyl-4-ethylcyclohexene, 3-methyl-4-ethylcyclohexene, 2,2-diethylcyclohexene, 2,3-diethylcyclohexene, 2,4-diethylcyclohexene, 3,4-diethylcyclohexene, 2,2,3-trimethylcyclohexene, 2,2,4-trimethylcyclohexene, 2,3,4-trimethylcyclohexene, 2,2,3-triethylcyclohexene, 2,2,4-triethylcyclohexene, 2,3,4-triethylcyclohexene, 2,2-dimethyl-3-ethylcyclohexene, 2,2-dimethyl-4-ethylcyclohexene, 2,3-dimethyl-4-ethylcyclohexene, 2-methyl-3,3-diethylcyclohexene, 2-methyl 2-Methyl-4,4-diethylcyclohexene, cycloheptene, 2-methylcycloheptene, 3-methylcycloheptene, 4-methylcycloheptene, 2,2-dimethylcycloheptene, 2,3-dimethylcycloheptene, 2,4-dimethylcycloheptene, 2,5-dimethylcycloheptene, 3,3-dimethylcycloheptene, 3,4-dimethylcycloheptene, 3,5-dimethylcycloheptene, 4,4-dimethylcycloheptene, 2-ethylcycloheptene, 3-ethylcycloheptene, 4-ethylcycloheptene, 2,2-diethylcycloheptene, 2,3-diethylcycloheptene, 2,4-diethylcycloheptene, 2,5-diethylcycloheptene, 3,3'-diethylcycloheptene, 3,4-diethylcycloheptene, 3,5-diethylcycloheptene, 4 4-Diethylcycloheptene, 2,2,3-Trimethylcycloheptene, 2,2,4-Trimethylcycloheptene, 2,2,5-Trimethylcycloheptene, 2,3,4-Trimethylcycloheptene, 2,3,5-Trimethylcycloheptene, 2,3,6-Trimethylcycloheptene, 2,4,5-Trimethylcycloheptene, 3,3,4-Trimethylcycloheptene, 3,3,5-Trimethylcycloheptene, 3,4,5-Trimethylcycloheptene, 2,2,3-Triethylcycloheptene, 2,2,4-Triethylcycloheptene, 2,2,5-Triethylcycloheptene, 2,3,4-Triethylcycloheptene, 2,3,5-Triethylcycloheptene, 2,3,6-Triethylcycloheptene, 2,4,5-Triethylcycloheptene, 3,3,4-Triethylcycloheptene, 3,3...At least one of the following: 5-triethylcycloheptene, 3,4,5-triethylcycloheptene, 2,2-dimethyl-3-ethylcycloheptene, 2,2-dimethyl-4-ethylcycloheptene, 2,2-dimethyl-5-ethylcycloheptene, 2,3-dimethyl-4-ethylcycloheptene, 2-methyl-3,3-diethylcycloheptene, 2-methyl-3,4-diethylcycloheptene, 2-methyl-4,5-diethylcycloheptene, 3,3-dimethyl-4-ethylcycloheptene, 3,3-dimethyl-5-ethylcycloheptene, 3,4-dimethyl-5-ethylcycloheptene, and 3-methyl-4,5-diethylcycloheptene.

7. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-6, characterized in that, In step S1, the photocatalytic oxidation / [2+2] cycloaddition reaction conditions are: a high-pressure mercury lamp or xenon lamp with a light source of 200-500W, a reaction temperature of 0-40℃, and a reaction time of 5-48h.

8. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-7, characterized in that, In step S2, the reaction conditions for the hydrogenation and deoxygenation of the high-tension cyclobutane fuel precursor molecule are as follows: with the aid of a catalyst, the reaction temperature is controlled at 120-180℃, the hydrogen pressure is 4-7MPa, and the reaction time is 12-48h.

9. The method for preparing high-strength cyclobutane fuel according to any one of claims 1-8, characterized in that, The catalyst is a supported catalyst formed by loading a metal onto a support; Preferably, the metal is selected from at least one of copper, nickel, gold, platinum and palladium; Preferably, the carrier is selected from at least one of SBA-15, HZSM-5, Al2O3, SiO2, Hβ, or HY.

10. The application of a method for preparing high-tension cyclobutane fuel as described in any one of claims 1-9 in the preparation of aircraft propellants.

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