Method for preparing dicyclopropane high-energy fuel by using ionic liquid to catalyze CH2Br2 as carbene precursor

Abstract

The invention discloses a method for preparing a dicyclopropane-based high-energy fuel by using ionic liquid to catalyze CH2Br2 as a carbene precursor, which comprises the following steps: mixing olefin, acetic acid ionic liquid, Zn powder, CH2Br2 and an organic solvent, reacting for a period of time at a certain temperature, and filtering and separating after the reaction is finished to obtain the dicyclopropane-based high-energy fuel. The method is easy to operate, rapid in reaction and high in atom economy, high-purity dicyclopropane high-energy fuel can be obtained, and compared with a CH2I2 carbene precursor, the carbene precursor has the advantages of being high in atom economy, stable in reaction and the like. Accurate synthesis of the dicyclopropane high-energy fuel is beneficial to rapid development of aerospace in China.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-energy fuel synthesis, and particularly relates to a method for preparing bicyclopropane-based high-energy fuel by reacting CH2Br2 as a carbene precursor with olefins in the presence of acetic acid-based ionic liquid catalysis. BACKGROUND

[0002] High-energy fuel is an important guarantee for the development of aerospace field as a power source for space launch. At present, liquid hydrazine, unsymmetrical dimethylhydrazine and other substances are used in carrier rockets, which are extremely volatile, toxic and strongly carcinogenic, thereby leading to extremely high operation and transportation costs and high safety accident risks. Hydrocarbon fuel has become an important direction for the development of rocket propellants due to its greenness and high energy. The torsional tension and angular tension of the three-membered ring make it have high tension energy, and the introduction of the three-membered ring into the hydrocarbon fuel is an important way to improve the energy of the fuel.

[0003] Simmons-Smith cyclopropanation reaction has mild reaction conditions, good repeatability and wide application of substrates. In the literature Industrial & Engineering Chemistry Research 63, 6985-6994 (2024), dicyclopentadiene is used as a substrate and HZSM-5 is used as a catalyst to realize the cyclopropanation of dicyclopentadiene (yield 33.0%). In the literature Chemical Engineering Science 283, 119366 (2024), dicyclopentadiene is used as a substrate and Al-MCM-41 molecular sieve is used as a catalyst to realize the cyclopropanation of dicyclopentadiene (selectivity 55.7%). The above two methods both need to use diethyl zinc, which is highly flammable, and the carbene precursor CH2I2 has poor atom economy. Patent CN 101239881B discloses a method for preparing cyclopropane-based high-energy fuel by catalyzing olefins with zinc copper catalyst. In the method, dicyclopentadiene is used as a reaction substrate, CH2I2 is used as a carbene precursor, and I2 is added at the same time and reacted in ultrasonic. However, CH2I2 is a carbene precursor, which has poor atom economy, and the iodine element is easy to sublimate at room temperature, so the ultrasonic reaction temperature is not easy to control.

[0004] Ionic liquids possess excellent properties, such as low vapor pressure and low volatility, high thermal and electrochemical stability, good solubility, and strong structural designability, and are widely used in the field of catalysis. References include: Green Chemistry 23, 1871-1882 (2024), which used acetate-based ionic liquids to catalyze methanol decomposition by adjusting the anion and cation structures of the ionic liquids; Science Advances 9, 7971 (2023), which used lactate ionic liquids to catalyze the conversion of polylactic acid and polycarbonate; Nature Catalysis 4, 753-762 (2021), which found that proton ionic liquids can modulate interfacial hydrogen bonds, thereby enhancing the electrocatalytic process; and Nature Communications 14, 1457 (2023), which found that ionic liquids and Co single atoms can improve the photocatalytic conversion of CO2.

[0005] To address the aforementioned problems, this invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing dicyclopropane high-energy fuels by reacting CH2Br2, a carbene precursor, with olefins using an acetic acid-based ionic liquid as a catalyst. This method utilizes dicyclopentadiene as a raw material and an ionic liquid as a catalyst to selectively prepare dicyclopropane high-energy fuels, offering advantages such as high selectivity, good atom economy, and mild reaction conditions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing dicyclopropane high-energy fuel using CH2Br2 as a carbene precursor via ionic liquid catalysis involves mixing an olefin, an acetic acid-based ionic liquid catalyst, Zn powder, CH2Br2 as a carbene precursor, and an organic solvent, stirring the mixture at a certain temperature for a period of time, and then separating the solid and liquid phases after the reaction to obtain the dicyclopropane high-energy fuel. The selectivity of the dicyclopropane high-energy fuel is determined using gas chromatography.

[0008] As a preferred embodiment of the present invention, the acetic acid-based ionic liquid specifically includes, but is not limited to, one or more of the following: 1-vinyl-3-ethylimidazolium acetate, 1,3-dimethylimidazolium acetate, 1,3-diethylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, 1-decyl-3-methylimidazolium acetate, and 1-dodecyl-3-methylimidazolium acetate.

[0009] As a preferred embodiment of the present invention, the reaction can be carried out by stirring at a temperature of 50-80°C for 8-24 hours, wherein CH2Br2 is used as a carbene precursor.

[0010] In a preferred embodiment of the present invention, the raw material olefin can be one of dicyclopentadiene, isoprene, norbornene, and 1,7-octadiene. The molar ratio of the olefin to zinc powder can be 1:10-20.

[0011] As a preferred embodiment of the present invention, the catalyst, an acetic acid-based ionic liquid, accounts for 1-10% of the molar amount of zinc powder, preferably 2-8%.

[0012] As a preferred embodiment of the present invention, the molar ratio of the olefin to the carbene precursor CH2Br2 is 1:6-16.

[0013] As a preferred embodiment of the present invention, the organic solvent can be one or two of 1,4-dioxane, acetonitrile, etc. 2-4 mL of organic solvent is added for every 1 mmol of olefin.

[0014] As a preferred embodiment of the present invention, 5 mmol of dicyclopentadiene, 1-5 mmol of acetic acid ionic liquid, 50-80 mmol of zinc powder, 30-60 mmol of CH2Br2, and 10-20 mL of 1,4-dioxane are added to a flask and reacted at 50-80°C for 8-24 hours. After the reaction is completed, the mixture is filtered and separated to obtain dicyclopropane high-energy fuel. The specific reaction equation is shown below. Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing bicyclopropane high-energy fuels using acetic acid-based ionic liquid catalysis with CH2Br2 as a carbene precursor. Compared with protic acid catalysts, the acetic acid-based ionic liquid catalyst used in this invention is less volatile and the reaction process is more stable. Compared with the prior art, the method of this invention has the advantages of good atom economy, mild reaction conditions, and high selectivity for bicyclopropane products.

[0015] The method of this invention utilizes dicyclopentadiene, isoprene and 1,7-octadiene as olefin raw materials and acetic acid-based ionic liquids as catalysts to prepare dicyclopropane high-energy fuels with high selectivity. It has the advantages of high selectivity, good atom economy and mild reaction conditions. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art.

[0018] Example 1 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 3 mmol of 1-vinyl-3-ethylimidazolium acetate, 5 mmol of dicyclopentadiene, and 50 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0019] After the reaction was completed, the mixture was filtered and separated. The conversion rate of dicyclopentadiene was determined to be 97.9% by gas chromatography, and the selectivity of dicyclopropane high-energy fuel was 49.1%.

[0020] Example 2 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 2 mmol of 1,3-dimethylimidazolium acetate, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0021] After the reaction was completed, the mixture was filtered and separated. The conversion rate of dicyclopentadiene was 100% and the selectivity of dicyclopropane high-energy fuel was 91.18% as determined by gas chromatography.

[0022] Example 3 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 3 mmol of 1,3-diethylimidazolium acetate, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0023] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of dicyclopentadiene was 100%, and the selectivity of dicyclopropane high-energy fuel was 90.9%.

[0024] Example 4 Add 20 mL of 1,4-dioxane solvent, 70 mmol of Zn powder, 3 mmol of 1-ethyl-3-methylimidazolium acetate, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 70 °C for 12 h.

[0025] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of dicyclopentadiene was 100%, and the selectivity of dicyclopropane high-energy fuel was 92.9%.

[0026] Example 5 Add 10 mL of 1,4-dioxane solvent, 70 mmol of Zn powder, 1 mmol of 1-propyl-3-methylimidazolium acetate, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 70 °C for 12 h.

[0027] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of dicyclopentadiene was 100%, and the selectivity of dicyclopropane high-energy fuel was 91.6%.

[0028] Example 6 Add 15 mL of 1,4-dioxane solvent, 70 mmol of Zn powder, 2 mmol of 1-hexyl-3-methylimidazolium acetate, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 70 °C for 12 h.

[0029] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of dicyclopentadiene was 100%, and the selectivity of dicyclopropane high-energy fuel was 96.4%.

[0030] Example 7 Add 20 mL of 1,4-dioxane solvent, 80 mmol of Zn powder, 1 mmol of 1-decyl-3-methylimidazolium acetate, 5 mmol of dicyclopentadiene, and 80 mmol of CH2Br2 to a 50 mL flask, and react at 80 °C for 16 h.

[0031] After the reaction was completed, the mixture was filtered and separated. The conversion rate of dicyclopentadiene was 100% and the selectivity of dicyclopropane high-energy fuel was 94.5% as determined by gas chromatography.

[0032] Example 8 Add 10 mL of 1,4-dioxane solvent, 80 mmol of Zn powder, 3 mmol of 1-dodecyl-3-methylimidazolium acetate, 5 mmol of dicyclopentadiene, and 80 mmol of CH2Br2 to a 50 mL flask, and react at 80 °C for 24 h.

[0033] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of dicyclopentadiene was 100%, and the selectivity of dicyclopropane high-energy fuel was 88.6%.

[0034] Example 9 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 2 mmol of 1,3-dimethylimidazolium acetate, 5 mmol of isoprene, and 80 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0035] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the isoprene conversion rate was 99.9% and the selectivity for dicyclopropane high-energy fuel was 86.7%.

[0036] Example 10 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 2 mmol of 1,3-dimethylimidazolium acetate, 5 mmol of norbornadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0037] After the reaction was completed, the mixture was filtered and separated. Gas chromatography was used to determine that the conversion rate of norbornene was 100%, and the selectivity of dicyclopropane high-energy fuel was 76.4%.

[0038] Example 11 Add 20 mL of 1,4-dioxane solvent, 60 mmol of Zn powder, 2 mmol of 1,3-dimethylimidazolium acetate, 5 mmol of 1,7-octadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 60 °C for 8 h.

[0039] After the reaction was completed, the mixture was filtered and separated. The conversion rate of 1,7-octadiene was determined to be 80.2% by gas chromatography, and the selectivity of dicyclopropane high-energy fuel was 30.2%.

[0040] Comparative Example 1 To compare the catalytic effect of ionic liquids, a comparative experiment without a catalyst was conducted.

[0041] Add 20 mL of 1,4-dioxane solvent, 70 mmol of Zn powder, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 70 °C for 24 h.

[0042] After the reaction was completed, the mixture was filtered and separated. The yield of the bicyclopropane high-energy fuel in the organic phase was determined by gas chromatography. The results showed that no cyclic products were formed.

[0043] Comparative Example 2 To compare the catalytic effects of Zn-Cu alginate, a comparative experiment on Zn-Cu alginate catalysis was conducted.

[0044] Add 20 mL of 1,4-dioxane solvent, 40 mmol of Zn-Cu, 5 mmol of dicyclopentadiene, and 60 mmol of CH2Br2 to a 50 mL flask, and react at 70 °C for 24 h.

[0045] After the reaction was completed, the mixture was filtered and separated. The yield of the bicyclopropane high-energy fuel in the organic phase was determined by gas chromatography. The results showed that no cyclic products were formed.

[0046] In summary, the method of this invention is simple to operate, has a rapid reaction, and can obtain high-purity dicyclopropane high-energy fuel. Compared with protonic acid catalysts, it also has advantages such as catalyst stability and less environmental harm. The conversion rate of dicyclopentadiene is close to 100%, and the highest selectivity of dicyclopropane high-energy fuel reaches 96.4%. The precise synthesis of dicyclopropane high-energy fuel will contribute to the rapid development of my country's aerospace industry.

[0047] The above description is merely a specific implementation step of this invention, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing dicyclopropane high-energy fuels using CH2Br2 as a carbene precursor catalyzed by ionic liquid, characterized in that, An olefin, an acetic acid ionic liquid, Zn powder, carbene precursor CH2Br2, and an organic solvent are mixed and reacted at a certain temperature for a period of time. After the reaction is completed, the solid and liquid are separated to obtain a dicyclopropane high-energy fuel.

2. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, The acetic acid ionic liquids include one or more of the following: 1-vinyl-3-ethylimidazolium acetate, 1,3-dimethylimidazolium acetate, 1,3-diethylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, 1-decyl-3-methylimidazolium acetate, and 1-dodecyl-3-methylimidazolium acetate.

3. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, React at 50-80℃ for 8-24 hours.

4. The method for preparing dicyclopropane high-energy fuel using CH2Br2 as a carbene precursor via ionic liquid catalysis as described in claim 1, characterized in that, The olefin is one of dicyclopentadiene, isoprene, norbornadiene, and 1,7-octadiene.

5. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, The molar ratio of the olefin to Zn powder is 1:10-20.

6. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, The acetic acid-based ionic liquid accounts for 1-10% of the molar amount of zinc powder.

7. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, The molar ratio of the olefin to CH2Br2 is 1:6-16.

8. The method for preparing dicyclopropane high-energy fuels using ionic liquid catalysis with CH2Br2 as a carbene precursor as described in claim 1, characterized in that, The organic solvent is one or both of 1,4-dioxane and acetonitrile.

9. The method for preparing dicyclopropane high-energy fuel using CH2Br2 as a carbene precursor via ionic liquid catalysis as described in claim 8, characterized in that, For every 1 mmol of olefin, add 2-4 mL of organic solvent.

Images