Method for preparing high-density coal-based jet fuel by taking fluorene and benzaldehyde as raw materials

Abstract

The invention discloses a method for preparing high-density coal-based jet fuel by taking fluorene and benzaldehyde as raw materials. The method comprises the following specific steps: 1, reacting a fluorene compound with benzaldehyde under the catalysis of alkali to generate a compound with a tetracyclic structure; and 2, dissolving the compound with the tetracyclic structure in an alkane solvent, and carrying out hydrogenation in a hydrogenation kettle or a fixed bed under the action of a metal catalyst to generate the high-density coal-based jet fuel. The high-density coal-based jet fuel can be completely prepared from the fluorene compound and benzaldehyde extracted from coal tar components in a high-yield mode through a two-step method, the density of the high-density coal-based jet fuel is larger than 0.90 g / cm < 3 >, and the high-density coal-based jet fuel is an aviation kerosene alkane compound with excellent performance; according to the whole route, the coal base is used as the raw material, the raw material source is wide, the cost is low, industrial production is more facilitated, and high-end and high-value coal products are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of compound organic synthesis, and particularly relates to a method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials. Background Art

[0002] High-density hydrocarbon fuels generally refer to artificially synthesized alkane fuels with a density greater than 0.80 g / cm 3 , which provide important power guarantees for various aerospace vehicles such as missiles, rockets, and fighter jets, and are the research focus in the field of propellants. Currently, the main source of jet fuel is petroleum. How to ensure China's growing demand for jet fuel has become an important research topic in the post-petroleum era. With the development of aviation technology, the continuous upgrading of engines, and the increasing requirements for environmental protection at home and abroad. In view of the different requirements for fuel quality indicators of military and civilian aircraft in China, the key performance parameters (including indicators such as density, freezing point, lubricity, and thermal oxidation stability) of kerosene fractions are scientifically adjusted and optimized in system with reference to the international general jet fuel standard system, so as to develop qualified products that meet the aviation fuel technical specifications. From a global perspective, the processes used to produce jet fuel mainly depend on the nature of the raw materials. Therefore, in order to further expand this market share and improve profitability, seeking jet fuels with low sulfur, low corrosiveness, and high stability is the ultimate goal.

[0003] Wash oil is a primary processed product obtained by distilling high-temperature coal tar, rich in bicyclic or tricyclic aromatic compounds such as fluorene, acenaphthene, methylnaphthalene, dimethylnaphthalene, and pyrene. Currently, it is mainly used as raw material oil for carbon black, fuel oil, and asphalt blending oil, or crude products such as fluorene are separated, with poor economy. Coupled with China's fossil energy structure being rich in coal and poor in oil, with coal reserves ranking second in the world only after the United States. Producing clean energy and alternative petrochemical products from coal chemical industry is an important way to solve or alleviate China's energy shortage. Due to the high prices of world crude oil and fuel oil in the near future, wash oil is widely used as a blending component for fuel oil, and the high sulfur and nitrogen content it contains will pollute the environment. Therefore, a method for producing clean fuel using wash oil is needed to solve the environmental protection problem and thus improve the economic value of wash oil. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials. This method has simple steps and high yield, and can produce high-density coal-based jet fuel.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials, comprising the following steps:

[0006] S1. Dissolve the fluorene compound 1 and benzaldehyde in an organic solvent, and react under the catalysis of a basic catalyst to form a compound 3 with a four-ring structure.

[0007]

[0008] S2. Dissolve the compound 3 with a four-ring structure in an alkane solvent, and carry out hydrogenation in a hydrogenation autoclave or a fixed bed under the catalysis of a metal catalyst to produce a high-density coal-based jet fuel 4.

[0009]

[0010] Preferably, in step S1, the reaction temperature is 100 - 200 °C, and the reaction time is 4 - 72 h.

[0011] Preferably, in step S1, the basic catalyst is one of KF / Al2O3, Mg-Al hydrotalcite, NaOH, KOH, LiOH, CsOH, RbOH, CaO, MgO, ZnO.

[0012] Preferably, in step S1, the molar ratio between the fluorene compound 1 and benzaldehyde is 1:1.1; the dosage of the basic catalyst is 20% of the mass of the fluorene compound 1.

[0013] Preferably, in step S1, the organic solvent is selected from one of dichloromethane, cyclohexane, dimethyl sulfoxide, N,N-dimethylformamide, acetone, N-methylpyrrolidone, propylene carbonate, and the concentration range of the fluorene compound 1 is 0.5 - 1 mol / L.

[0014] Preferably, in step S2, the mass ratio between the dosage of the metal catalyst and the compound 3 with a four-ring structure is (0.001 - 1):1.

[0015] Preferably, in step S2, the metal catalyst is selected from one of commercial Raney nickel, commercial Raney cobalt, Pt / C, Pd / C, Ru / C, Rh / C, Ni-W / Al2O3, Ni-Mo / Al2O3, Ni / Al2O3, wherein the active metal loading of Pt / C, Pd / C, Ru / C, Rh / C is 3 - 8 wt%; in Ni-W / Al2O3, Ni and W respectively account for 12 - 20% and 4 - 12% of the mass of Ni-W / Al2O3; in Ni-Mo / Al2O3, Ni and Mo respectively account for 8 - 20% and 4 - 16% of the mass of Ni-Mo / Al2O3; in Ni / Al2O3, Ni accounts for 28 - 36% of the mass of Ni / Al2O3.

[0016] Preferably, in step S2, the alkane solvent is cyclohexane or n-hexane, the concentration of compound 3 with a four-ring structure in the hydrogenation autoclave is 0.01 - 10 mol / L, and the concentration of compound 3 with a four-ring structure in the fixed bed is 1 - 20 wt%.

[0017] Preferably, in step S2, when the hydrogenation reaction is carried out in an autoclave, the reaction temperature is 120 - 300 °C, the reaction time is 4 - 12 h, and the hydrogen pressure is 1 - 6 MPa; when the hydrogenation reaction is carried out in a fixed bed, the average reaction temperature is 160 - 350 °C, the reaction pressure is 0.5 - 4 MPa, the molar ratio of hydrogen to compound 3 with a four-ring structure is (200 - 1000):1, and the liquid hourly space velocity is 0.1 - 1 h -1 .

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention can completely achieve the preparation of high-density coal-based jet fuel with high yields of fluorene compounds and benzaldehyde extracted from coal tar components through a two-step method. Its density is greater than 0.90 g / cm 3 , and it is an alkane compound of aviation kerosene with relatively excellent performance;

[0020] (2) The entire route uses coal-based raw materials, has a wide range of raw material sources, low costs, is more conducive to industrial production, and realizes the high-end and high-value of coal products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 . MS spectrum of compound 3 with a four-ring structure prepared in Example 22;

[0022] Figure 2 . GC spectrum of compound 3 with a four-ring structure prepared in Example 22;

[0023] Figure 3 . 1 HNMR spectrum of compound 3 with a four-ring structure prepared in Example 22;

[0024] Figure 4 . 13 C NMR spectrum of compound 3 with a four-ring structure prepared in Example 22;

[0025] Figure 5 . MS spectrum of the hydrogenation product 4 prepared in Example 71;

[0026] Figure 6 . GC spectrum of the hydrogenation product 4 prepared in Example 71;

[0027] Figure 7The hydrogenation product 4 obtained in Example 71 1 HNMR spectrum;

[0028] Figure 8 The hydrogenation product 4 obtained in Example 71 13 C NMR spectrum. Detailed implementation mode

[0029] The present invention will be further described in detail below with reference to the embodiments.

[0030] In the following embodiments, unless otherwise specified, the reagents used can be purchased commercially or obtained in the manner reported in known literature.

[0031] Embodiment

[0032] A method for preparing high-density coal-based jet fuel from fluorene and benzaldehyde, comprising the following steps:

[0033] S1. Dissolve fluorene compound 1 (1 mmol, 0.166 g) and benzaldehyde (1.1 mmol, 0.102 mL) in 1 mL of organic solvent, and react under the catalysis of a basic catalyst to form a compound 3 with a four-ring structure; the reaction temperature is between 100-200 °C, and the reaction time is between 4-72 h; the dosage of the basic catalyst is 20% of the mass of fluorene compound 1;

[0034]

[0035] S2. When the hydrogenation reaction is carried out in a reaction kettle, dissolve the compound 3 with a four-ring structure (2740 mg, 10 mmol) in 20 mL of an alkane solvent, and react under the catalysis of 137 mg of a metal catalyst (active metal loading 5 wt%) at 120-300 °C and 2 MPa hydrogen pressure for 4-12 h to generate high-density coal-based jet fuel 4.

[0036] When the hydrogenation reaction is carried out in a fixed bed, the reaction conditions are as follows: hydrogen is used as the raw material gas, and a cyclohexane solution containing 1-20 wt% of the compound 3 with a four-ring structure (2740 mg, 10 mmol) is used as the raw material liquid. The molar ratio of hydrogen to the compound 3 with a four-ring structure in the reaction is (200-1000):1, the reaction temperature range is 160-350 °C, the reaction pressure is 0.5-4 MPa, and the liquid volume space velocity is 0.1-1 h -1 . A stainless steel reaction tube is used as the reactor, with an outer diameter of 20 mm, an inner diameter of 8 mm, a length of 300 mm, a catalyst loading of 0.5 g. After the reaction tail gas is condensed and separated, a Fuli GC9790PLUS gas chromatograph is used to quantitatively analyze the product.

[0037]

[0038] Examples 1-33 differ in the catalyst, reaction temperature, solvent, and reaction time in step S1. The specific parameters are shown in Table 1 below:

[0039] Table 1. Effects of Catalyst, Temperature, Solvent, and Time on the Alkylation Reaction

[0040]

[0041]

[0042] As can be seen from the results in Table 1, the basic catalysts KOH, NaOH, LiOH, CsOH, RbOH, and CaO showed good catalytic performance in the reaction of fluorene compounds with benzaldehyde and achieved a medium to high yield. Among them, CaO had the best catalytic performance. The yield of the dimerization product reached 97% after reacting at 200 °C for 6 h. Through the screening of different solvents, it was found that NMP and DMF had relatively good effects on this reaction. However, considering energy consumption and the ease of subsequent product separation, DMF was selected as the solvent. Through the screening of different reaction times, it was found that prolonging the time did not increase the product yield. The yield of the dimerization product was 97% after reacting for 72 h, which was not much different from the result of reacting for 6 h.

[0043] Since the service life of the catalyst needs to be investigated in practical applications, the recycling of CaO was studied using DMF as the solvent and reacting at 200 °C for 6 h. After each reaction, CaO reacts with the water generated by the reaction. Therefore, it needs to be calcined at 500 °C for 4 h (2 °C / min) before each cycle. After the calcination is completed, the next cycle continues. As can be seen from the results in Table 2, the yield did not change significantly after CaO was recycled four times, indicating that this reaction system can be reused.

[0044] Table 2. CaO Recycling Experiment

[0045]

[0046]

[0047] The MS spectrum of compound 3 prepared in Example 22 is as Figure 1 shown. It can be seen from the figure that the maximum mass-to-charge ratio of the molecular ion peak of this substance is m / z = 254. The relative molecular mass of fluorene is 166, and the relative molecular mass of benzaldehyde is 106. Fluorene and benzaldehyde condense and dehydrate to form product 3, and the relative molecular mass of compound 3 is 254. Therefore, this product may be the target product 3, and subsequent nuclear magnetic resonance is needed for auxiliary verification.

[0048] The GC spectrum of the product of compound 3 prepared in Example 22 is asFigure 2 As shown in the figure. The inlet temperature of the gas chromatography was set at 270 °C, the initial temperature of the column oven was set at 40 °C, the heating rate was 15 °C / min, and it was heated to 280 °C and held for 5 min. The substance eluting at 8.9 min in the GC chromatogram was the internal standard n-tridecane, and the substance eluting at 19.4 min was Compound 3.

[0049] For the addition product 3 prepared in Example 22 1 The 1H NMR spectrum was as Figure 3 shown. 1 1H NMR (600 MHz, Chloroform-d) δ 7.86 (d, J = 7.5 Hz, 1H), 7.83–7.72 (m, 3H), 7.67 (dd, J = 7.8, 3.6 Hz, 3H), 7.54 (t, J = 7.5 Hz, 2H), 7.47 (q, J = 7.7 Hz, 2H), 7.40 (dt, J = 11.8, 7.5 Hz, 2H), 7.14 (t, J = 7.6 Hz, 1H).

[0050] For the addition product 3 prepared in Example 22 13 The 13C NMR spectrum was as Figure 4 shown. 13 13C NMR (151 MHz, Chloroform-d) δ 141.33, 139.57, 139.27, 136.97, 136.63, 136.56, 129.35, 128.62, 128.60, 128.29, 128.10, 127.35, 127.07, 126.74, 124.49, 120.34, 119.80, 119.67.

[0051] In Examples 34 - 54, the tetracyclic structure compound obtained in Example 22 was hydrogenated in a reaction kettle, and the differences were the different catalysts, reaction temperatures, solvents, and reaction times in step S2. The specific parameters are shown in Table 3 below:

[0052] Table 3. Effects of Catalyst, Temperature, Solvent, and Time on the Hydrogenation Reaction (Hydrogenation Kettle)

[0053]

[0054]

[0055] As can be seen from the results in Table 3, there are differences in the hydrogenation capabilities of different metal catalysts. Among them, metals Rh, Pt, Ru, and Pd exhibit relatively good activities. Considering the prices of various precious metals, Ru / C was selected in the present invention for subsequent condition screening. When screening solvents, it was found that both n-hexane and cyclohexane had good effects. However, since n-hexane had a better effect on the separation of subsequent products, n-hexane was used as the hydrogenation solvent. It should be noted that when the temperature rose to 300 °C, non-precious metals also had a relatively good product yield. Considering the limitation of the reaction temperature of the hydrogenation autoclave and the possibility of subsequent large-scale production, a fixed bed was decided to be used to further evaluate the hydrogenation performance of the catalyst. To sum up, the highest yield of 90% was obtained when using n-hexane as the solvent in the hydrogenation autoclave at 180 °C for 8 h, and the optimal conditions for the hydrogenation reaction were thus obtained.

[0056] It was desired to explore the service life of the catalyst in practical applications. Therefore, using n-hexane as the solvent, the reaction was carried out at 180 °C for 8 h, and the recycling of Ru / C was studied. As can be seen from the results in Table 4, there was no obvious change in the yield after Ru / C was recycled four times, indicating that this reaction system could be reused.

[0057] Table 4. Hydrogenation recycling experiments

[0058]

[0059] Examples 59 - 103 involved hydrogenating the compound with a four-ring structure obtained in Example 22 in a fixed bed. The differences were the catalyst, the concentration of the compound with a four-ring structure 3, the reaction temperature, the liquid hourly space velocity, the reaction pressure, and the molar ratio between hydrogen and the compound with a four-ring structure 3 (i.e., the hydrogen-oil ratio in Table 5) in step S2. The specific parameters are shown in Table 5 below:

[0060] Table 5. Influence of different parameters on the hydrogenation reaction (fixed bed)

[0061]

[0062]

[0063] As can be seen from the results in Table 5, there are differences in the hydrogenation capabilities of catalysts with different metal loadings. Among them, 10% Ni - 10% Mo / Al2O3 exhibits relatively good activity. When screening the substrate concentration, it was found that the raw material concentration of 5 wt% had the best effect and a relatively high conversion rate, which was beneficial for the subsequent separation of products. Therefore, a raw material concentration of 5 wt% was adopted. When screening different temperatures, it was found that when the temperature rose above 260 °C, the product yield decreased. Considering energy consumption and the comparison of yields, 180 °C was selected as the optimal reaction temperature in the present invention. When screening different liquid hourly space velocities, it was found that changing the space velocity did not affect the yield. Considering the possibility of long-term production in this fixed bed, a space velocity of 0.5 h was selected.-1 。The hydrogen-oil ratios were screened, and it was found that the hydrogen-oil ratio did not affect the product yield. Considering the raw material economy, a hydrogen-oil ratio of 200:1 was selected. Different hydrogen pressures were screened, and it was found that the yield of this reaction was the highest when the pressure was 3 Mpa. When the pressure was further increased, the product yield remained unchanged. In summary, in the fixed bed, the catalyst loading was 0.5 g, the temperature was 180 °C, the feed concentration was 5 wt%, and the liquid hourly space velocity was 0.5 h -1 , the hydrogen pressure was 3 Mpa, the hydrogen-oil ratio was 200:1, the yield was relatively high at 94%, and the catalyst life was 200 h, thus obtaining the optimal conditions for the hydrogenation reaction.

[0064] The MS spectrum of the hydrogenation product 4 prepared in Example 71 is as Figure 5 shown. It can be seen from the figure that the maximum mass-to-charge ratio of the molecular ion peak of this substance is m / z = 274. The relative molecular mass of compound 3 is 254, and the relative molecular mass of the fully hydrogenated product should be 274. The GC-MS result shows that the maximum molecular weight is 274. Therefore, this product may be the target addition product 4, and NMR is needed for auxiliary verification later.

[0065] The GC spectrum of the hydrogenation product 4 prepared in Example 71 is as Figure 6 shown. The injection port temperature of the gas chromatography was set at 270 °C, the initial temperature of the column oven was set at 40 °C, the heating rate was 15 °C / min, and it was heated to 280 °C and held for 5 min. The substance eluting at 8.9 min in the GC chromatogram is the internal standard n-tridecane, and the substances eluting at 15.1 / 15.6 / 16.3 min are the addition product 4.

[0066] The 1 H NMR spectrum of the hydrogenation product 4 prepared in Example 71 is as Figure 7 shown. 1 H NMR(600 MHz, Chloroform-d) δ 1.95–1.86 (m, 1H), 1.86–1.77 (m, 2H), 1.68–1.38 (m, 4H), 1.37 (s, 1H), 1.33–1.11 (m, 7H), 1.03 (t, J = 11.7 Hz, 1H), 0.89 (ddq, J = 47.2, 24.0, 13.1, 11.7 Hz, 2H).

[0067] The 13 C NMR spectrum of the hydrogenation product 4 prepared in Example 71 is as Figure 8 shown. 13 C NMR(151 MHz, Chloroform-d) δ 47.72, 45.91, 45.33, 35.77, 34.44, 33.51, 29.34, 29.32, 26.17, 26.07, 26.05, 26.04, 25.91.

[0068] The high-density coal-based jet fuel obtained in Example 71 was compared with traditional petroleum-based fuels (JP-10, RJ-4, RJ-4-I, RJ-5, and RJ-7) in terms of properties. It was found that while maintaining key properties such as density, calorific value, and freezing point, the difficulty and cost of synthesis were significantly reduced.

[0069] Table 6. Comparison of the properties of different fuels

[0070]

[0071] As can be seen from the examples in Table 6, through a two-step method, it is possible to controllably increase the ring and hydrogenate coal tar components and benzaldehyde to prepare high-density coal-based jet fuel. The density of the prepared high-density aviation fuel is 0.9611 g / cm 3 , the viscosity is 47.5 mPa·s, the calorific value is 46.68 MJ / L, and the freezing point is -54°C; it is a jet fuel with relatively excellent performance. The entire route uses the coal tar component fluorene as the raw material, which is a new type of green and environmentally friendly route and does not produce harmful substances.

[0072] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials, characterized in that: The following steps are involved: S1, dissolving the fluorene compound 1 and benzaldehyde in an organic solvent, and reacting them under the catalysis of an alkaline catalyst to generate a compound 3 having a tetracyclic structure; S2. Dissolving the compound 3 having a tetracyclic structure in an alkane solvent, and hydrogenating it in a hydrogenation reactor or a fixed bed under the catalysis of a metal catalyst to generate a high-density coal-based jet fuel 4.

2. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S1, the reaction temperature is 100-200°C and the reaction time is 4-72h.

3. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S1, the alkaline catalyst is one of KF / Al2O3, Mg-Al hydrotalcite, NaOH, KOH, LiOH, CsOH, RbOH, CaO, MgO, and ZnO.

4. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 3, characterized in that: In step S1, the molar ratio of the fluorene compound 1 to benzaldehyde is 1:1.1; the amount of the alkaline catalyst used is 20% of the mass of the fluorene compound 1.

5. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S1, the organic solvent is selected from one of dichloromethane, cyclohexane, dimethyl sulfoxide, N,N-dimethylformamide, acetone, N-methylpyrrolidone, and propylene carbonate, and the concentration range of the fluorene compound 1 is 0.5-1 mol / L.

6. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S2, the mass ratio between the amount of the metal catalyst and the compound 3 having a tetracyclic structure is (0.001-1):

1.

7. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S2, the metal catalyst is selected from one of commercial Raney nickel, commercial Raney cobalt, Pt / C, Pd / C, Ru / C, Rh / C, Ni-W / Al2O3, Ni-Mo / Al2O3, and Ni / Al2O3, wherein the active metal loading of Pt / C, Pd / C, Ru / C, and Rh / C is 3-8wt%; in the Ni-W / Al2O3, Ni and W account for 12-20% and 4-12% of the mass of Ni-W / Al2O3, respectively; in Ni-Mo / Al2O3, Ni and Mo account for 8-20% and 4-16% of the mass of Ni-Mo / Al2O3, respectively; in the Ni / Al2O3, Ni accounts for 28-36% of the mass of Ni / Al2O3.

8. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S2, the alkane solvent is cyclohexane or n-hexane, the concentration of the compound 3 having a tetracyclic structure in the hydrogenation reactor is 0.01-10 mol / L, and the concentration of the compound 3 having a tetracyclic structure in the fixed bed is 1-20 wt%.

9. The method for preparing high-density coal-based jet fuel using fluorene and benzaldehyde as raw materials according to claim 1, characterized in that: In step S2, when the hydrogenation reaction is carried out in a reactor, the reaction temperature is 120-300° C., the reaction time is 4-12 h, and the hydrogen pressure is 1-6 MPa; when the hydrogenation reaction is carried out in a fixed bed, the average reaction temperature is 160-350° C., the reaction pressure is 0.5-4 MPa, the molar ratio of hydrogen to the compound 3 having a tetracyclic structure is (200-1000): 1, and the liquid volume space velocity is 0.1-1 h -1 .

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