A method for synthesizing thermally stable aviation kerosene with 2,5 - hexanedione

Abstract

The present invention belongs to the technical field of aviation fuel preparation, and specifically relates to a method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione. The method comprises the following steps: 1) Using 2,5 - hexanedione as a raw material and an alkali solution as a catalyst, an unsaturated ketone compound with twelve carbon atoms is obtained through an alkali - catalyzed aldol condensation reaction; 2) The unsaturated ketone compound obtained in step 1) undergoes a hydrodeoxygenation reaction under the action of a ternary mixed metal oxide catalyst to obtain a saturated cycloalkane liquid fuel with twelve carbon atoms containing alkyl decalin. The method of the present invention simplifies the current route for preparing alkyl decalin from biomass, and the intermediate products and the final product do not need to undergo a purification / distillation process; significantly reduces the production cost, the raw materials are cheap and easily available, the reaction conditions are mild, and it is suitable for large - scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of aviation fuel preparation, and particularly relates to a method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione. Background Art

[0002] Aviation kerosene is a liquid fuel with a large demand internationally at present and is a strategic material of a country. It is generally composed of straight - chain alkanes, aromatics and naphthenes with carbon numbers ranging from 8 to 16. At present, aviation kerosene is mainly produced from fossil resources (coal and petroleum). Both coal and petroleum are non - renewable energy sources. The synthesis of aviation kerosene and diesel from them will produce a large amount of carbon dioxide during the manufacturing and use processes, causing the greenhouse effect. Moreover, in recent years, with the decreasing of petroleum resources, the crude oil price has been rising continuously. As a large energy - consuming country and a large petroleum - importing country, China's petroleum import volume has been increasing in recent years. The petroleum import dependence in 2019 has exceeded the national security warning line of 50%, and the petroleum import dependence in 2021 has reached 72%. In 2022, facing the complex international environment, the external market environment faced by petroleum import trade has become more severe. According to economic laws, as the petroleum reserves decrease, the price of petroleum products will rise, and biofuels will eventually be cost - competitive and even cheaper than petroleum - derived fuels. Therefore, considering environmental protection, national energy security and potential economic value, it is necessary to vigorously develop biomass aviation kerosene technology.

[0003] The high carbon content (40%) of biomass raw materials can meet the carbon demand of transportation fuels, including gasoline, diesel and aviation kerosene. It is very attractive to produce long - chain diesel (C12 - C22) and aviation kerosene (C8 - C16) from biomass and biomass - derived chemicals. At present, most of the work on synthesizing aviation kerosene - range alkanes by hydrodeoxygenation of biomass internationally focuses on branched - chain or straight - chain alkanes. If cycloalkanes with ring strain can be synthesized, the density of aviation kerosene will be significantly increased, making its performance more excellent; in addition, developing a new reaction route for preparing aviation kerosene from biomass and optimizing and integrating the reaction process will be more conducive to the industrialization of biomass aviation kerosene technology.

[0004] The density of polycyclic alkanes decalin and alkyl - decalin is 0.86 - 0.89 g / mL -1Between 37 and 48, it has a cetane number between 37 and 48 and is an ideal high-density fuel with good combustion performance in steam turbines and diesel engines. Currently, decalin is mainly obtained through the coal route, while there are few reports on obtaining decalin through the biomass route. Our research group has successively synthesized decalin using furfural derivative cyclopentanol and hemicellulose derivative cyclopentanone as raw materials: Cyclopentanol obtains polycyclic alkanes through dehydration, oligomerization / rearrangement, and hydrogenation reactions under mild conditions, with a selectivity of 77% for decalin (ACS Sustainable Chem. Eng., 2016, 4, 6160 - 6166.); Cyclopentanone obtains decalin through self-aldol condensation, hydrodeoxygenation, and isomerization, with a total carbon yield of 74% (ACS Sustainable Chem. Eng., 2019, 7, 17354 - 17361.). In addition, using more biomass platform compounds as reaction substrates to develop reaction routes for preparing aviation kerosene from biomass will be more beneficial to the application of biomass aviation kerosene technology.

[0005] 2,5-Hexanedione is an important organic chemical intermediate and is widely used in fields such as medicine, spices, pesticides, photographic agents, electroplating jets, etc. In recent years, methods for synthesizing 2,5-hexanedione using cellulose have been widely reported. In 2015, Flora Chambon reported the hydrogenation of cellulose to prepare 2,5-hexanedione using ZrW as a catalyst (Appl Catal A - Gen., 2015, 504, 664 - 671.). CN 109896938A uses an aqueous hydrochloric acid - organic solvent two-phase reaction system to directly convert cellulose into 2,5-hexanedione in one step by hydrogenation, with a yield of 66%. Therefore, 2,5-hexanedione can be directly obtained from renewable biomass resources.

[0006] A.T, Bell et al. used an oil - water two-phase system and, under the catalysis of solid base Mg - Al - O, 2,5-hexanedione obtained 3-methyl-2-cyclopenten-1-one with a yield of 98% through an aldol condensation reaction, and then catalytic hydrodeoxygenation was carried out on a fixed bed using Pt / NbOPO4 to synthesize the gasoline additive methylcyclopentane (Green Chem., 2015, 17, 2393 - 2397.). Although methylcyclopentane has a high energy density of 46.8 MJ Kg -1 , its octane number is low and the six-carbon number of methylcyclopentane is not within the diesel composition range. Therefore, the methylcyclopentane obtained by this route has limited application fields and cannot be used alone as aviation fuel.

[0007] Subsequently, Cosimbescu et al. constructed a series of polycyclic alkanes starting from 2,5 - hexanedione (Sustain Energy Fuels., 2021, 5, 3143 - 3159.). 2,5 - Hexanedione gives 50% methylcyclopentenone and 50% oligomers at 95% conversion rate, which can be used as potential compression ignition engine fuels. However, this route has a long reaction time and a low content of polycyclic alkanes. In the same year, Harvey et al. reported the preparation of methylcyclopentadiene from 2,5 - hexanedione through a three - step method, including intramolecular aldol condensation, selective hydrogenation, and dehydration reactions, and then RJ - 4 fuel was prepared through Diels - Alder reaction and hydrogenation reaction (ChemSusChem., 2021, 14, 339 - 343.). This route is cumbersome, and the catalyst RuCl2[P(C6H5)3]3 - NH2(CH2)2NH2 - KOH in the selective hydrogenation process is expensive and complex to prepare, and the final yield of RJ - 4 is only 38%.

[0008] In 2019, our research group reported the one - step synthesis of naphthenic liquid fuels from 2,5 - hexanedione (Joule., 2019, 3, 1028 - 1036.). Under solvent - free conditions, a fixed - bed continuous reactor equipped with a dual - catalyst bed was used to directly synthesize liquid naphthenic fuels mainly composed of C6, C12, and C18 in one step, providing a new, simple, and efficient synthetic route for the preparation of naphthenic liquid fuels from 2,5 - hexanedione. Summary of the Invention

[0009] The object of the present invention is to provide a method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione. Under solvent - free conditions, alkyl decahydronaphthalene aviation kerosene is synthesized through aldol condensation and hydrodeoxygenation reactions under mild conditions (below 160 °C).

[0010] To achieve the above object, the technical solution of the present invention is as follows: A method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione, the method comprising the following steps:

[0011] 1) Using 2,5 - hexanedione as a raw material and an alkali solution as a catalyst, an unsaturated ketone compound with twelve carbon atoms is obtained through base - catalyzed aldol condensation reaction;

[0012] 2) The unsaturated ketone compound obtained in step 1) undergoes hydrodeoxygenation reaction under the action of a ternary mixed metal oxide catalyst to effectively remove carbon - carbon double bonds and carbon - oxygen double bonds, obtaining a saturated naphthenic liquid fuel with twelve carbon atoms containing alkyl decahydronaphthalene.

[0013] In the above technical solution, further, in step 1), the alkali solution is one or more of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and ammonia water; the alkali metal hydroxides are one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; the alkali metal carbonates are one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and cesium carbonate; the alkaline earth metal oxides are one or two of strontium hydroxide and barium hydroxide.

[0014] In the above technical solution, further, in step 2), the ternary mixed oxide catalyst is represented by the formula M1M2M3O x and includes a noble metal component M1 and a metal oxide M2M3O x support, where the noble metal component M1 includes one of platinum, palladium, ruthenium, rhodium, and iridium, the mass fraction of the noble metal component M1 in the catalyst is 0.1 - 3%, and the metal oxide component M2M3O x includes CuCeO x 、CuCoO x 、CuMnO x 、NiCeO x 、NiMnO x 、NiFeO x one of them, and the atomic ratio of metal M2 to M3 is 1 - 10 - 10 - 1.

[0015] In the above technical solution, further, in step 2), the ternary mixed oxide catalyst M1M2M3O x is prepared by the co - precipitation method and the incipient wetness impregnation method. The specific method is as follows:

[0016] (1) The M2M3O x support is prepared by the co - precipitation method: Weigh the metal precursors of M2 and M3 according to the stoichiometric ratio of M2 and M3 and prepare an aqueous metal precursor solution with a concentration range of 0.1 - 10%. Stir at room temperature for 30 minutes, then dropwise add NaOH under stirring and continue stirring for 30 minutes, and then vacuum dry at 40 - 80 °C for 6 - 12 hours to obtain the M2M3O x support;

[0017] (2) The ternary mixed metal oxide catalyst M1M2M3O x is prepared by the incipient wetness impregnation method: Prepare an M1 noble metal precursor solution and add it to M2M3O according to the stoichiometric ratio xImpregnate the carrier with an equal volume, let it stand for more than 8 h, then dry it at 60 - 120 °C for 6 - 24 h, calcine it at 500 - 600 °C for 3 h with a heating rate of 1 °C / min, reduce it with hydrogen at 200 - 350 °C for 1 - 6 h, and after the temperature drops to room temperature, pass nitrogen containing 1% O2 by volume to passivate it for more than 4 h.

[0018] In the above technical solution, further, the metal precursors of M2 and M3 are any two of Cu(NO3)2·3H2O, Ce(NO3)3·6H2O, CoCl2, Mn(NO3)2, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O; the noble metal precursor of M1 is one of H2PtCl6·6H2O, PdCl2, RuCl3, RhCl3, H2IrCl6·6H2O.

[0019] In the above technical solution, further, in step 1), the aldol condensation reaction is carried out under liquid conditions, the feeding concentration of the alkali solution is 0.5 - 5 mol / L -1 , the mass ratio of the added alkali to the mass of the reaction substrate is 1% - 40%, the reaction temperature is 10 - 40 °C, and the reaction time is 1 - 3 h.

[0020] In the above technical solution, further, in step 2), the hydrodeoxygenation reaction uses a batch autoclave reactor, the reaction temperature is 120 - 200 °C, the hydrogen pressure is 3 - 5 MPa, the reaction time is 8 - 18 h, and the mass ratio of the added ternary mixed metal oxide catalyst to the mass of the reactants is between 1% - 20%.

[0021] In the above technical solution, further, in step 1), it also includes extracting and purifying the dodecyl unsaturated ketone compound by vacuum distillation, removing a small amount of water in the product and then feeding it, so that the hydrodeoxygenation reaction realizes complete hydrodeoxygenation under liquid solvent-free conditions.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. Starting from a sustainable biomass route to replace the petroleum-based route;

[0024] 2. Simplify the current biomass preparation route of alkyl decahydronaphthalene, and the intermediate products and the final product do not need to be purified / distilled;

[0025] 3. Significantly reduce the production cost, the raw materials are cheap and easy to obtain, the reaction conditions are mild, and it is suitable for large-scale industrial production;

[0026] 4. The final product contains dodecyl cycloalkanes mainly composed of alkyl decahydronaphthalene, which not only meets the requirements of wide boiling range and high octane number diesel fuel specifications, but also meets the needs of advanced aviation fuels with its high energy density and high thermal stability. Description of the Drawings

[0027] Figure 1 High-resolution mass spectrum of the product alkyl decahydronaphthalene prepared in Example 1;

[0028] Figure 2 Extracted ion chromatogram of the product alkyl decahydronaphthalene prepared in Example 1. Detailed Description of the Invention

[0029] The following examples can enable those of ordinary skill in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

[0030] Unless otherwise specified, the materials used in the examples of the present invention can be obtained through commercial channels or prepared according to conventional methods well-known to those skilled in the art.

[0031] Example 1

[0032] 1. Preparation of the ternary mixed metal oxide catalyst RhCuCeO x :

[0033] 2.171 g of Ce(NO3)3·6H2O and 1.208 g of Cu(NO3)2·3H2O were dissolved in 100 mL of deionized water. After stirring at room temperature for 30 minutes, 100 mL of 0.375 mol / L -1 NaOH solution was added dropwise under vigorous stirring and stirring was continued for 30 minutes. Then, it was vacuum dried at 40°C for 8 hours to obtain the CuCeO x support; an RhCl3 solution was prepared, and 3 g of CuCeO x was impregnated in an equal volume. The content of the noble metal in the catalyst accounted for 0.5 wt%. It was allowed to stand for 10 h, then dried at 80°C for 12 hours and calcined at 600°C for 3 hours with a heating rate of 1°C / min. Then, it was reduced with hydrogen at 300°C for 2 hours. After the temperature was lowered to room temperature, it was passivated with nitrogen containing 1% O2 by volume for 6 hours to obtain the ternary mixed metal oxide catalyst RhCuCeO x .

[0034] 2. Synthesis method:

[0035] 1) In a 500 mL reaction flask, 200 g of 2,5-hexanedione was added, and 300 mL of 2 mol / L -1 KOH solution was added. After stirring at 25°C for 3 hours, an aldol condensation reaction was carried out. Then, 100 mL of saturated NaCl solution was added, and it was extracted three times with 300 mL of tetrahydrofuran. The tetrahydrofuran organic phase was first dried over anhydrous magnesium sulfate, and then the organic phase was rotary evaporated under reduced pressure to separate and recover the tetrahydrofuran solvent. After concentration, about 185 g of the unsaturated ketone product of C12 was obtained;

[0036] 2) Transfer the unsaturated ketone product of C12 into a 1-gallon high-pressure reactor, and add 18.5 g of RhCuCeO x catalyst (catalyst ratio 10 wt%), carry out hydrodeoxygenation reaction, the reaction temperature is 160 °C, the hydrogen charging pressure reaches 5 MPa, react for 16 hours, and the reaction is carried out under liquid solvent-free conditions to obtain a saturated cycloalkane liquid fuel with carbon number twelve containing alkyl decahydronaphthalene.

[0037] The detailed reaction results are shown in Table 1 and Table 2.

[0038] Table 1 Aldol condensation reaction products and yields

[0039]

[0040] Table 2 Hydrodeoxygenation reaction products and yields

[0041]

[0042]

[0043] 3. Physicochemical property test of liquid fuel:

[0044] Table 3 Physicochemical property test results of liquid fuel

[0045]

[0046] After the physicochemical property test, the saturated cycloalkane liquid fuel with carbon number twelve containing alkyl decahydronaphthalene meets the quality and performance requirements of modern jet fuel and has strong thermal stability.

[0047] Example 2-22

[0048] The catalyst preparation method and synthesis method are the same as those in Example 1. The difference is that the metal composition and noble metal content of the ternary mixed metal oxide catalyst are changed. The results are shown in Table 3.

[0049] Table 4 Hydrodeoxygenation reaction activities of different catalysts

[0050]

[0051]

[0052] It can be seen from the data in Table 4 that the ternary mixed metal oxide catalyst has good effects on the hydrodeoxygenation reaction of unsaturated ketone compounds. Among them, when the atomic ratio of metal M2 and M3 is nearly 1:1, a better catalytic effect is achieved. In the industrial production process, to save costs, the Ru noble metal content can be increased to replace Rh or Pd to achieve a similar catalytic effect.

[0053] Examples 23 - 37

[0054] The catalyst preparation method and synthesis method are the same as those in Example 1, except that the reaction conditions in the hydrodeoxygenation process are changed, including the dosage of RhCuCeO x , reaction temperature and reaction time. The results are shown in Table 5.

[0055] Table 5 Influence of hydrodeoxygenation reaction conditions

[0056]

[0057]

[0058] It can be seen from the data in Table 5 that the influence of the catalyst dosage on the reaction activity is relatively significant, and a relatively good yield can be obtained at a dosage of 10 wt%. The reaction temperature has little effect on the yield of alkyl decahydronaphthalene at a relatively high temperature of 160°C - 170°C. Excessive temperature leads to ring cleavage, resulting in a significant decrease in the total yield of cycloalkanes. When the temperature is as low as 120°C, the total yield of alkyl decahydronaphthalene and liquid cycloalkanes decreases significantly. The complete conversion of the raw materials can be achieved when the reaction time reaches 16 hours.

[0059] The above examples are only the preferred examples of the present invention and do not limit the implementation mode. The protection scope of the present invention should be subject to the scope defined by the claims. Based on the above description, other different forms of changes or variations can be made. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for synthesizing thermally stable aviation kerosene with 2,5 - hexanedione, characterized in that: The method includes the following steps: 1) Using 2,5 - hexanedione as a raw material and an alkali solution as a catalyst, an unsaturated ketone compound with twelve carbon atoms is obtained through an alkali - catalyzed aldol condensation reaction; 2) The unsaturated ketone compound obtained in step 1) undergoes a hydrodeoxygenation reaction under the action of a ternary mixed metal oxide catalyst to obtain a saturated cycloalkane liquid fuel with twelve carbon atoms containing alkyl - decalin; In step 2), the ternary mixed metal oxide catalyst is represented by the formula M1M2M3O x and includes a noble metal component M1 and a metal oxide M2M3O x supported on a carrier. The noble metal component M1 includes one of palladium, ruthenium, rhodium, and iridium, and the mass fraction of the noble metal component M1 in the catalyst is 0.1 to 3%. The metal oxide component M2M3O x includes CuCeO x , CuCoO x , CuMnO x , NiCeO x , NiMnO x , NiFeO x and the atomic ratio of metal M2 to M3 is 1:1; In step 2), the hydrodeoxygenation reaction uses a batch autoclave reactor, the reaction temperature is 160 - 180 °C, the hydrogen pressure is 3 - 5 MPa, the reaction time is 12 - 18 hours, and the ratio of the mass of the ternary mixed metal oxide catalyst added to the mass of the reactants is between 10% - 20%.

2. The method for synthesizing thermally stable aviation kerosene from 2,5-hexanedione according to claim 1, characterized in that: In step 1), the alkali in the alkali solution is one or more of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and ammonia water; The alkali metal hydroxides are one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; The alkali metal carbonates are one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and cesium carbonate; The alkaline earth metal hydroxides are one or two of strontium hydroxide and barium hydroxide.

3. The method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione according to claim 1, wherein: In step 2), the ternary mixed metal oxide catalyst M1M2M3O x is prepared by the co-precipitation method and the incipient wetness impregnation method. The specific method is as follows: (1)M2M3O x The carrier is prepared by coprecipitation method: Weigh the metal precursors of M2 and M3 according to the stoichiometric ratio of M2 and M3 and prepare an aqueous solution of metal precursors with a concentration range of 0.1 - 10%. Stir at room temperature for 30 minutes, then add NaOH dropwise under stirring and continue stirring for 30 minutes. Then, vacuum dry at 40 - 80 °C for 6 - 12 hours to obtain M2M3O x Carrier; (2)Ternary mixed metal oxide catalyst M1M2M3O x is prepared by the incipient wetness impregnation method: Prepare a noble metal precursor solution of M1, and add M2M3O x to the carrier by incipient wetness impregnation in an equal volume. Let it stand for more than 8 h, then dry it at 60-120 °C for 6-24 h, calcine it at 500-600 °C for 3 h with a heating rate of 1 °C / min, and then reduce it with hydrogen at 200-350 °C for 1-6 h. After the temperature is lowered to room temperature, pass nitrogen containing 1% O2 by volume to passivate it for more than 4 h.

4. The method for synthesizing heat-stable aviation kerosene from 2,5-hexanedione according to claim 3, wherein: The M1 noble metal precursor is one of PdCl2, RuCl3, RhCl3, and H2IrCl6·6H2O.

5. The method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione according to claim 1, wherein: In step 1), the aldol condensation reaction is carried out under liquid conditions, the feeding concentration of the alkali solution is 0.5 - 5 mol / L -1 , the ratio of the mass of the added alkali to the mass of the reaction substrate is 1% - 40%, the reaction temperature is 10 - 40 °C, and the reaction time is 1 - 3 hours.

6. The method for synthesizing thermally stable aviation kerosene from 2,5 - hexanedione according to claim 1, characterized in that: In step 1), it also includes extraction and vacuum distillation purification of the unsaturated ketone compound with twelve carbon atoms.

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