A method for preparing high-density low-freezing-point fuel by one-pot method using biomass derivative as raw material

Abstract

The application discloses a method for preparing high-density low-freezing-point fuel by one-pot method with biomass derivative as raw material, which comprises the following steps: (1) preparing protonated titanate catalyst; (2) mixing the protonated titanate catalyst obtained in step (1), a ruthenium-based catalyst and a reaction raw material biomass derivative, and performing aldol condensation reaction under nitrogen atmosphere; (3) after the aldol condensation reaction is completed, performing hydrogenation and deoxidation reaction under hydrogen atmosphere; (4) after the hydrogenation and deoxidation reaction is completed, the high-density low-freezing-point fuel is obtained. The method of the application realizes high selectivity of target fuel product under more moderate conditions under the condition of simplifying the reaction system, and is more convenient to operate and saves reaction cost.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing high-density, low-freezing-point fuels in a one-pot process using biomass derivatives as raw materials. Background Technology

[0002] Liquid jet fuel is an important type of aviation fuel used in turbojet, turbofan, and ramjet engines, primarily serving as an energy source for aircraft. Fuel energy is a key factor determining an aircraft's range. High-density aviation fuels with a density greater than 0.85 g / mL possess a high volumetric calorific value, allowing for greater propulsion power within a given fuel tank volume, significantly increasing the aircraft's range or payload capacity. Currently, typical high-density fuels widely used in the aerospace field, such as JP-10, RJ-5, and RJ-7, are mainly synthesized from petroleum-based feedstocks. The preparation of high-density jet fuels using renewable and sustainable biomass as raw materials is gradually attracting attention.

[0003] The properties of fuel components are closely related to the fuel's structure. Based on the structure-activity relationship of hydrocarbons, cycloalkanes with the same number of carbon atoms have higher densities than alkanes. Furthermore, the number of rings is also a factor affecting the density of cycloalkanes; polycyclic alkanes have significantly higher densities than bicyclic and monocyclic alkanes. The synthesis of polycyclic alkanes from biomass mainly involves two steps. First, using cyclic biomass-based feedstocks, carbon numbers are increased through reactions such as alkylation, olefin polymerization, aldol condensation, Michael addition, and DA addition using acid / base catalysts to achieve C / C bond coupling. Then, hydrogenation / hydrodeoxygenation reactions using metal catalysts achieve intramolecular cyclization, resulting in fuels with polycyclic ring structures. However, as the molecular ring structure of the fuel increases, its low-temperature properties deteriorate. High-performance aerospace fuels must consider not only density properties but also a range of other properties such as calorific value, freezing point, viscosity, flash point, and thermal stability. Many biomass fuels have shortcomings. For example, while all-hydrofluorene has a high density of 0.96 g / mL, its low-temperature properties are poor, with a freezing point of only -15°C. It can only be used as a fuel additive, and its overall performance cannot compare with traditional petroleum-based high-density fuels such as RJ-4 and JP-10, which significantly limits its practical application. Therefore, synthesizing high-density, low-freezing-point jet fuels based on biomass is crucial.

[0004] Ma et al. catalyzed the aldol condensation of cyclopentanone and vanillin under solvent-free conditions using a lactic acid ethanolamine ionic liquid, followed by hydrodeoxygenation using a 5% Pd / Nb2O5 catalyst to obtain a mixture of C12 and C19 polycyclic alkanes with a density of 0.89 g / mL and a freezing point less than -60 °C (J Energy Chem, 2023, 79, 22-30). Zhang et al. used cyclopentanol as a starting material and obtained a mixture of C10 and C15 polycyclic alkanes with decahydronaphthalene as the main product through three steps: dehydration, oligomerization / rearrangement, and hydrodeoxygenation, with a density of 0.896 g / mL and a freezing point of -37 °C (ACS Sustainable Chem Eng, 2016, 4, 6160-6166). Zhang et al. used methylbenzaldehyde and methyl isobutyl ketone derived from cellulose as raw materials and K2CO3 / Al2O3 as catalysts to react and obtain an aldol condensate product. Then, under Pt / C catalysis, they obtained branched octahydroindene with a freezing point of -45.3 to -33 °C and a density of 0.857-0.944 g / mL (ACS Sustainable Chem Eng, 2019, 7, 12023-12031). However, the above process for preparing high-density fuels is carried out in two or more different reaction vessels and involves one or more separation processes, which not only wastes energy but also causes material loss during transfer. The condensation step disclosed in ACS Sustainable Chem Eng, 2019, 7, 12023-12031 has very low selectivity and the hydrodeoxygenation temperature is high, at 180 °C or above.

[0005] To better apply this technology to industrial production and simplify reaction processes, it is crucial to efficiently integrate multiple reaction steps. This invention is proposed to address this need. Summary of the Invention

[0006] This invention provides a one-pot selective synthesis method for high-density, low-freezing-point jet fuel using biomass derivatives as raw materials. The fuel product obtained by this method has a density of not less than 0.940 g / mL and a freezing point of not more than -41°C, and can be used as a high-performance jet fuel, improving the energy density of the fuel and enhancing its low-temperature flow properties.

[0007] The technical solution of the present invention is as follows:

[0008] This invention discloses a one-pot method for preparing high-density, low-freezing-point fuel from biomass derivatives, comprising the following steps:

[0009] (1) Preparation of protonated titanate catalyst;

[0010] (2) The protonated titanate catalyst, the ruthenium-based catalyst, and the biomass derivatives obtained in step (1) are mixed and subjected to aldol condensation reaction under a nitrogen atmosphere;

[0011] (3) After the aldol condensation reaction is completed, a hydrogenation deoxygenation reaction is carried out in a hydrogen atmosphere;

[0012] (4) After the hydrogenation and deoxygenation reaction is completed, the high-density, low-freezing-point fuel is obtained.

[0013] Preferably, in step (2), the protonated titanate catalyst accounts for 1 to 10 wt% of the reactants; and the ruthenium-based catalyst accounts for 1 to 5 wt% of the reactants.

[0014] Preferably, the aldol condensation reaction in step (2) is carried out at a temperature of 60~110℃ for 0.5~2.5h and a nitrogen pressure of 0.1~1MPa.

[0015] Preferably, the temperature of the hydrogenation deoxygenation reaction in step (3) is 80~180℃, the time is 0.5~8h, and the hydrogen pressure is 2~6MPa.

[0016] Preferably, in step (2), the alkyl-substituted benzaldehyde is one or both of 2-methylbenzaldehyde or 4-methylbenzaldehyde, and the ruthenium-based catalyst is Ru / Al2O3.

[0017] Preferably, the preparation method of the protonated titanate catalyst in step (1) includes the following steps: adding titanium dioxide powder to sodium hydroxide solution, mixing evenly, and then carrying out hydrothermal reaction to separate and obtain solid titanate catalyst; adding the obtained solid titanate catalyst to nitric acid solution, mixing, and then vacuum drying, which is the protonated titanate catalyst.

[0018] Preferably, the mass ratio of titanium dioxide powder to sodium hydroxide is 1:(10~15), the mixing time is 0.5~5h, the hydrothermal reaction temperature is 100~200℃ and the time is 12~26h, and the concentration of sodium hydroxide solution is 5~15mol / L; the mass ratio of titanate catalyst solid to nitric acid solution is 1 (g):(100~300) (ml), the concentration of nitric acid solution is (0.01~0.5)mol / L, and the vacuum drying temperature is 60~120℃ and the time is 6~24h.

[0019] Preferably, the biomass derivatives used as raw materials in step (2) are alkyl-substituted benzaldehyde and cyclopentanone, wherein the molar ratio of alkyl-substituted benzaldehyde to cyclopentanone is (15~1):1.

[0020] Preferably, the alkyl-substituted benzaldehyde is one or both of 2-methylbenzaldehyde or 4-methylbenzaldehyde.

[0021] Preferably, the high-density, low-freezing-point fuel has a density of not less than 0.940 g / mL and a freezing point of not more than -41°C.

[0022] The beneficial effects of this invention are:

[0023] This invention proposes for the first time a highly efficient synergistic catalytic reaction of methylbenzaldehyde and cyclopentanone based on protonated titanate catalyst (PTNT) and Ru / Al₂O₃ to prepare high-density, low-freezing-point fuel from biomass derivatives in a one-pot process. In this method, the biomass derivatives methylbenzaldehyde and cyclopentanone undergo aldol condensation and hydrodeoxygenation in a one-pot process under the synergistic catalysis of PTNT and Ru / Al₂O₃, eliminating the need for separation and purification of intermediates. In the aldol condensation step, PTNT facilitates the activation of the condensation reaction between methylbenzaldehyde and cyclopentanone to generate a C13 bicyclic condensation product, while the introduction of Ru / Al₂O₃ does not affect the condensation activity of the PTNT catalyst. In the hydrodeoxygenation step, Ru / Al₂O₃ acts on the hydrogenation of the C13 bicyclic condensation product, while PTNT effectively activates the CO bond, accelerating the intermolecular dehydration rate of oxygen-containing intermediates and significantly shortening the hydrodeoxygenation reaction time. The method of this invention eliminates the need for separating and purifying intermediates, yielding high-density, low-freezing-point jet fuel in a one-pot, two-step reaction. Furthermore, the reaction temperature is relatively low, and the product yield can reach over 80.0%. This method is significantly superior to existing techniques. Therefore, the method of this invention, while simplifying the reaction system, achieves high selectivity in obtaining the target fuel product under milder conditions, is more convenient to operate, and saves reaction costs. The alkyl-substituted benzaldehyde and cyclopentanone, the reaction raw materials of this invention, are obtained from biomass, which provides broad possibilities for further development of green synthesis. The alkyl-substituted benzaldehyde and cyclopentanone, the reaction raw materials of this invention, can also be derived from petroleum-based raw materials with the same effect. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the one-pot method for preparing high-density, low-freezing-point jet fuel according to the present invention.

[0025] Figure 2 The image shows a scanning electron microscope (SEM) image of the PTNT prepared in Example 1.

[0026] Figure 3 This is a transmission electron microscope (TEM) image of PTNT from Example 1.

[0027] Figure 4 The images show the pyridine infrared spectra (Py-IR) of PTNT from Example 1 at different temperatures.

[0028] Figure 5 The ammonia adsorption-desorption spectrum (NH3-TPD) of PTNT in Example 1 is shown. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The implementation schemes in the embodiments are merely preferred solutions, but the present invention is not limited to the preferred solutions.

[0030] Example 1: Preparation of PTNT, the steps are as follows:

[0031] (1) Weigh 28g of sodium hydroxide granules and dissolve them in 70mL of water, stirring until well mixed;

[0032] (2) Add 2g of titanium dioxide powder to the sodium hydroxide solution in step (1) and stir for 1.5h;

[0033] (3) The mixture obtained in step (2) was placed in a hydrothermal reactor and hydrothermally heated at 150°C for 24 hours. After washing and filtration, solid titanate catalyst was obtained.

[0034] (4) Add 2g of the titanate catalyst solid obtained in step (3) to 300mL of 0.5mol / L nitric acid solution, stir vigorously for 12h, and dry in vacuum at 80℃ for 12h to obtain PTNT with abundant medium-strong acid sites.

[0035] Figure 1 This is a scanning electron microscope (SEM) image of the prepared PTNT. Figure 2 This is a transmission electron microscope (TEM) image of the prepared PTNT. Figure 3 These are the pyridine infrared spectra (Py-IR) of the prepared PTNT at different temperatures. Figure 4 This is the ammonia adsorption-desorption spectrum (NH3-TPD) of the prepared PTNT. From Figure 1 SEM and Figure 2 TEM images show that PTNT possesses a uniform multi-walled hollow tubular structure, which provides more active sites for contact with reactant molecules; from Figure 3 Py-IR spectra and Figure 4 The NH3-TPD spectrum shows that the prepared PTNT has abundant medium-strong acid sites and medium-strong Brønsted acid sites, with a high Brønsted / Lewis ratio. The abundance of medium-strong Brønsted acid sites is not only conducive to the condensation reaction, but also to accelerating the intramolecular dehydration rate of oxygen-containing intermediates.

[0036] Example 2-19: Preparation of condensation products.

[0037] The preparation of the C13 bicyclic condensation product includes the following steps: PTNT prepared in Example 1, biomass derivative 2-methylbenzaldehyde, and cyclopentanone are added to a high-temperature and high-pressure reactor, and the reaction is carried out under a N2 atmosphere of 0.1 MPa. The specific parameters and the yield of the C13 bicyclic condensation product are shown in Table 1 below.

[0038] Table 1

[0039]

[0040] Table 1 shows that the highest overall yield of the C13 bicyclic condensation product was obtained when the molar ratio of 2-methylbenzaldehyde to cyclopentanone was 10:1, the amount of PTNT was 3 wt%, the reaction temperature was 100℃, and the reaction time was 2 h. The obtained C13 bicyclic condensation product is... The number is C13-1.

[0041] Example 20: Same as Example 5, but the raw materials are 4-methylbenzaldehyde and cyclopentanone.

[0042] The preparation of the C13 bicyclic condensation product included the following steps: 3 wt% PTNT, 208 mmol of 4-methylbenzaldehyde, and 20.8 mmol of cyclopentanone were added to a high-temperature, high-pressure reactor. The reaction was carried out at 100°C for 2 hours under a 0.1 MPa N2 atmosphere. The yield of the C13 bicyclic condensation product was 82.7%. The obtained C13 bicyclic condensation product was... The number is C13-2.

[0043] Examples 21-22: Same as Example 5, but with the addition of Ru / Al2O3 or Ru / C to carry out a condensation reaction.

[0044] The preparation of C13 bicyclic condensation products includes the following steps: 1.5 wt% of ruthenium-based catalyst Ru / Al2O3 or Ru / C, 3 wt% PTNT, 208 mmol 2-methylbenzaldehyde, and 20.8 mmol cyclopentanone were added to a high-temperature and high-pressure reactor. The reaction was carried out under a 0.1 MPa N2 atmosphere, at 600 rpm and 100 °C for 2 h. The yield of C13 bicyclic condensation products is shown in Table 2.

[0045] Table 2

[0046]

[0047] As shown in Table 2, the addition of Ru / Al2O3 does not reduce the condensation activity of PTNT, and the yield of the C13 bicyclic condensation product remains unchanged at 81.3%; however, the addition of Ru / C reduces the condensation activity of PTNT, and the yield of the C13 bicyclic condensation product decreases. Therefore, Ru / Al2O3 catalyst is selected for the hydrodeoxygenation step in this invention.

[0048] Examples 23-25: One-pot selective synthesis of high-density, low-freezing-point polycyclic alkanes, comprising the following steps: 3 wt% PTNT, 1.5 wt% Ru / Al₂O₃, 208 mmol of methylbenzaldehyde at different methyl positions, and 20.8 mmol of cyclopentanone were added to a high-temperature, high-pressure reactor. The reaction was first carried out at 100°C and 0.1 MPa N₂ for 2 h; then at 120°C and 6 MPa H₂ for 3–6 h. After the reaction was complete, the product was collected, purified by vacuum distillation, and its density and freezing point were determined. Relevant process parameters, reaction results, and product characteristics are shown in Table 3.

[0049] Table 3

[0050]

[0051] Table 3 shows that, in the presence of both PTNT and Ru / Al2O3, the C13-1 bicyclic condensation product synthesized from 2-methylbenzaldehyde and cyclopentanone is then hydrogenated and deoxygenated to prepare polycyclic alkanes (structural formula: [insert structural formula here]). It is easily achieved that, with a hydrodeoxygenation time of 3 hours, the yield of polycyclic alkanes can reach 80.6%. Under the optimal conditions for the preparation of polycyclic alkanes from the C13-1 bicyclic condensation product synthesized from 2-methylbenzaldehyde and cyclopentanone via hydrodeoxygenation, the C13-2 bicyclic condensation product synthesized from 4-methylbenzaldehyde and cyclopentanone cannot be completely converted into polycyclic alkanes; however, by extending the hydrodeoxygenation reaction time to 6 hours, C13-2 can be completely converted into polycyclic alkanes (structural formula: [structural formula missing]). Furthermore, the yield is relatively high. Table 3 also shows that polycyclic alkanes obtained by hydrodeoxygenation of C13-1 and C13-2 have similar densities and freezing points, and can be used as fuel component additives to improve the fuel's temperature and low-temperature fluidity.

[0052] Examples 26-36: The raw material was 4-methylbenzaldehyde, and Ru / Al2O3 was added to the reaction system of Example 20. After the condensation reaction in Example 20 was completed, the reaction conditions were adjusted to carry out a hydrodeoxygenation reaction to prepare high-density, low-freezing-point fuel. Specific parameters and the selectivity of the hydrodeoxygenation products of the C13-2 bicyclic condensation product are shown in Table 4.

[0053] Table 4:

[0054]

[0055] As shown in Table 4, the C13-2 bicyclic condensation product can be completely converted into polycyclic alkanes when the reaction temperature is ≥120℃, the hydrogen pressure is 6MPa, and the reaction time is ≥3h. This indicates that the conditions for the hydrogenation and deoxygenation of the bicyclic condensation product 13-2 from 4-methylbenzaldehyde are slightly more stringent.

[0056] Comparative Example 1: After the reaction in Example 20 was completed, the catalyst PTNT was removed by centrifugation; Ru / Al2O3 was added, and the reaction was carried out at 120°C and 6 MPa H2 for 3 h for hydrodeoxygenation. The selectivity of the bicyclic condensation product for hydrodeoxygenation is shown in Table 5.

[0057] Table 5:

[0058]

[0059] As shown in Table 5, after centrifuging to remove the catalyst PTNT, adding Ru / Al2O3, and reacting at 120℃ and 6MPa H2 for 3 hours, the selectivity for hydrodeoxygenation of the bicyclic condensation product to obtain polycyclic alkanes was very low. However, Example 27 shows that the presence of PTNT accelerated the hydrodeoxygenation reaction rate of the C13 bicyclic condensation product with 100% selectivity, yielding highly selective polycyclic alkanes in a short time. This indicates that PTNT and Ru / Al2O3 have a synergistic effect in the hydrodeoxygenation step, accelerating the intermolecular dehydration rate of oxygen-containing intermediates and significantly shortening the hydrodeoxygenation reaction time while improving the selectivity of polycyclic alkanes.

[0060] The above description is only used to detail the specific embodiments of the present invention, but the technical solutions proposed by the present invention are not limited to the above methods. All equivalent modifications and variations made by those skilled in the art to the technology proposed by the present invention without departing from the basic principles of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing high-density, low-freezing-point fuel in a one-pot process using biomass derivatives as raw materials, characterized in that, Includes the following steps: (1) Preparation of protonated titanate catalyst; The preparation method of protonated titanate catalyst includes the following steps: adding titanium dioxide powder to sodium hydroxide solution and mixing evenly, then carrying out hydrothermal reaction, and separating to obtain solid titanate catalyst; adding the obtained solid titanate catalyst to nitric acid solution and mixing, and then vacuum drying, which is the protonated titanate catalyst; (2) The protonated titanate catalyst, the ruthenium-based catalyst, and the biomass derivatives obtained in step (1) are mixed and subjected to aldol condensation under a nitrogen atmosphere; the ruthenium-based catalyst is Ru / Al2O3; the aldol condensation reaction temperature is 80~110℃, the time is 0.5~2.5h, and the nitrogen pressure is 0.1~1MPa; the biomass derivatives are alkyl-substituted benzaldehyde and cyclopentanone, wherein the molar ratio of alkyl-substituted benzaldehyde to cyclopentanone is (6-15):1; (3) After the aldol condensation reaction is completed, a hydrogen deoxygenation reaction is carried out in a hydrogen atmosphere; the temperature of the hydrogen deoxygenation reaction is 120~160℃, the time is 3~8h, and the hydrogen pressure is 4~6MPa. (4) After the hydrogenation and deoxygenation reaction is completed, the high-density, low-freezing-point fuel is obtained.

2. The method according to claim 1, characterized in that, In step (2), the protonated titanate catalyst accounts for 1 to 10 wt% of the reactants; the ruthenium-based catalyst accounts for 1 to 5 wt% of the reactants.

3. The method according to claim 1, characterized in that, The mass ratio of titanium dioxide powder to sodium hydroxide is 1:(10~15), the mixing time is 0.5~5h, the hydrothermal reaction temperature is 100~200℃, the time is 12~26h, and the concentration of sodium hydroxide solution is 5~15mol / L; the mass ratio of titanate catalyst solid to nitric acid solution is 1 (g):(100~300) (ml), the concentration of nitric acid solution is (0.01~0.5)mol / L, and the vacuum drying temperature is 60~120℃, the time is 6~24h.

4. The method according to claim 1, characterized in that, The alkyl-substituted benzaldehyde is one or both of 2-methylbenzaldehyde or 4-methylbenzaldehyde.

5. The method according to claim 1, characterized in that, The density of the high-density, low-freezing-point fuel is not less than 0.940 g / mL, and the freezing point is not higher than -41°C.

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