Process for the preparation of a bifunctional catalyst and use for the synthesis of high-density fuels

Abstract

The application discloses a preparation method of a bifunctional catalyst, which comprises the following steps: (1) preparing a niobium tartrate aqueous solution; (2) dissolving diammonium hydrogen phosphate in water; (3) mixing the solutions and adjusting the pH value by using an acid; (4) adding an aqueous solution of cetyltrimethylammonium bromide; (5) hydrothermally crystallizing in a high-pressure hydrothermal kettle for a period of time, then filtering and drying the obtained solid; (6) uniformly mixing a metal salt solution; (7) mixing the dried solid in step (5) into the metal salt solution in step (6) at a certain temperature and mixing for a period of time; and (8) drying and calcining the obtained solid after separation, so that the bifunctional catalyst is obtained. The application further discloses a use of the bifunctional catalyst prepared by the preparation method in catalyzing a one-pot solvent-free reaction of a lignin derivative to obtain a polycyclic alkane fuel.

Description

Technical Field

[0001] This invention belongs to the field of organocatalytic synthesis, specifically relating to MO with controllable adjustment of metal and acid centers. x Preparation method of / NbOPO4 bifunctional catalyst and its application in one-pot solventless synthesis of high-density fuels. Background Technology

[0002] "One generation of power, one generation of equipment"—fuel performance determines the performance level of engines and aircraft. As new aircraft develop towards higher altitudes, faster speeds, and farther ranges, higher demands are placed on the fuels that power them, urgently requiring the development of high-energy-density hydrocarbon fuels. Furthermore, given a fixed fuel tank volume, increasing fuel density allows for a greater mass of fuel to be carried, which is one of the most effective technical approaches to achieving extended flight range. Simultaneously, increasing fuel density facilitates aircraft miniaturization or reduces fuel tank volume, providing ample space for electronic equipment and other components.

[0003] However, with the continuous exploitation of oil resources, the rapid development of various industries leading to a significant increase in demand for liquid fuels, and a series of problems caused by fossil fuels, the development of new, economical, and energy-saving liquid fuels is an urgent issue to be addressed. Research on using renewable biomass feedstocks to replace fossil fuels in the synthesis of high-density fuels has gradually gained widespread attention. Throughout the fuel's life cycle, biomass-derived biojet fuels can reduce carbon emissions by up to 80%. Biomass derivatives have unsaturated carbon-carbon bonds and / or oxygen-containing groups of no more than one ring, thus requiring multi-step reaction synthesis to obtain polycyclic hydrocarbons. First, carbon-carbon (CC) coupling is needed to construct polycyclic oxygen-containing fuel precursors; second, the polycyclic oxygen-containing fuel precursors undergo hydrodeoxygenation to remove oxygen and saturate the C=C bonds, thereby obtaining polycyclic alkanes. Perhydrofluorene is a tricyclic hydrocarbon with a density reaching 1.012 g / mL at 20°C, making it a high-performance, high-density fuel that can also be used as an additive to increase the density of existing aerospace fuels.

[0004] Current research on one-pot synthesis of alkanes from biomass derivatives mainly focuses on straight-chain alkanes and monocyclic or bicyclic alkanes, while catalytic studies on tricyclic and larger alkanes are relatively limited. The literature ChemSusChem, 2017, 10, 747-753, demonstrates the one-pot production of branched C4 hydrocarbons from diesel fuels using furfural and 2-methylfuran as feedstocks via hydroxyalkylation and hydrodeoxygenation on a bifunctional Pd / NbOPO4 catalyst. 15Straight-chain alkanes are used, but the hydrodeoxygenation reaction requires the addition of cyclohexane solvent to disperse the oxygen-containing intermediates, resulting in a reaction time of up to 17 hours. Furthermore, straight-chain alkanes have a relatively lower density compared to cyclohexanes. Reference Fuel, 2023, 334, 126634, describes a one-pot method using a Pt / Hβ catalyst to catalyze the alkylation and hydrodeoxygenation of phenol and cyclohexanol to prepare bicyclic and tricyclic alkanes. However, the resulting bicyclic alkanes have a high proportion, which reduces the final fuel density to some extent, and the entire reaction system needs to be carried out in cyclohexane solvent, resulting in a reaction time of up to 16 hours. Although these one-pot reaction routes can simplify the reaction process and improve energy efficiency, the use of a large amount of additional solvent still leads to relatively high energy consumption. Clearly, the catalysts prepared in these studies have poor performance, resulting in a slow overall reaction rate.

[0005] The synthesis of polycyclic fuels from biomass platform molecules mainly involves a two-step process. The first step involves increasing the carbon number of the target molecule through a C-C coupling reaction to obtain an oxygen-containing fuel intermediate. The second step, during hydrodeoxygenation, uses a hydrogenation catalyst and an acid catalyst to generate a series of polycyclic alkane fuels from the oxygen-containing intermediate. The literature Fuel, 2024, 360, 130570, reports a one-pot solventless sequential synthesis method for obtaining fuels mainly composed of perhydrofluorene and dicyclohexylmethane from lignin derivatives under the synergistic catalytic system of NbOPO4-IB and Ru / C, catalyzing the C-C coupling of phenol and benzyl alcohol to obtain an oxygen-containing fuel intermediate. Subsequently, Ru / C is introduced during hydrodeoxygenation. The literature (SustainableEnergy Fuels, 2022, 6, 1616-1624.) reports the process of obtaining an aldol condensation product from vanillin and cyclohexanone under the catalysis of sulfated titanium dioxide nanofibers. After purification by column chromatography, Pd / C and HY catalysts were introduced during the hydrodeoxygenation process, and the product was further converted into a mixture of perhydrofluorene and dicyclohexylmethane using cyclohexane as a solvent. Patent CN115920934A reports that the NbOPO4 catalyst has excellent acidity for catalyzing alkylation reactions. However, to obtain polycyclic alkane fuels, the reactor needs to be reopened after the alkylation reaction, and a Ru / C catalyst needs to be added to the reactor. Only by physically mixing NbOPO4 and Ru / C can the hydrodeoxygenation reaction be completed to obtain polycyclic alkane fuels.

[0006] The two-step catalytic reaction to produce polycyclic alkane jet fuel is cumbersome, requiring different catalysts at different reaction stages, resulting in high costs. Furthermore, the method of adding acid and metal catalysts in batches into the reaction vessel to catalyze CC coupling and hydrodeoxygenation processes leads to energy waste and difficulties in catalyst separation. In addition, the reaction must be carried out in a solvent.

[0007] To address the aforementioned problems, this invention is proposed. Summary of the Invention

[0008] To address the shortcomings and drawbacks of the existing technology, this invention prepares MO. x / NbOPO4 bifunctional catalyst; using this catalyst, high-density polycyclic alkane fuels can be synthesized in a one-pot solvent-free process. The feedstock consists of phenolic compounds and / or aromatic alcohols extracted from biomass lignin.

[0009] The technical solution of the present invention is as follows:

[0010] The first aspect of this invention discloses a method for preparing a bifunctional catalyst, comprising the following steps:

[0011] (1) Mix niobium source, tartaric acid and water evenly to obtain niobium tartrate aqueous solution;

[0012] (2) Dissolve diammonium hydrogen phosphate in water;

[0013] (3) Mix the solutions obtained in steps (1) and (2) and adjust the pH value with acid;

[0014] (4) Add an aqueous solution of hexadecyltrimethylammonium bromide to the mixture from step (3);

[0015] (5) The mixture obtained in step (4) is hydrothermally crystallized in a high-pressure hydrothermal reactor for a period of time, and then filtered to obtain a solid and dried.

[0016] (6) Mix the metal salt solution thoroughly;

[0017] (7) At a certain temperature, the solid material dried in step (5) is mixed into the metal salt solution in step (6) and mixed for a period of time;

[0018] (8) The solid obtained by separating the mixture in step (7) is dried and then calcined to obtain the bifunctional catalyst.

[0019] Preferably, the niobium source in step (1) is niobium hydroxide, and the mass ratio of the niobium source to tartaric acid is 1:(1-5); in step (3), the pH value is adjusted with phosphoric acid so that the pH value is not greater than 2, preferably the pH value is equal to 1.

[0020] Preferably, the concentration of the aqueous solution of hexadecyltrimethylammonium bromide (CTAB) in step (4) is 5wt%-10wt%, and the mass ratio of hexadecyltrimethylammonium bromide to niobium hydroxide is 7:25. The main purpose of adding hexadecyltrimethylammonium bromide is to create pores in the catalyst; other surfactants can also be used as catalysts for pore creation.

[0021] Preferably, the hydrothermal crystallization time of the mixture in step (5) is 12-26 hours and the temperature is 100-200℃; the drying is carried out at 60-120℃ for 6-24 hours.

[0022] Preferably, the metal salt solution in step (6) is one or more of the following metal salts: Pt, Pd, Ir, Ru, Rh, Au, Ni, Cu, Zn, Co, and Fe.

[0023] Preferably, the mixing temperature in step (7) is 25-100℃ and the time is 1-10h; wherein the amount of metal salt solution added is 0.5-6.0wt% of the metal in the solid.

[0024] Preferably, the calcination temperature in step (8) is 350-650℃ and the time is 3-10h.

[0025] The second aspect of this invention discloses the use of the bifunctional catalyst prepared by the aforementioned method for catalyzing a one-pot solventless reaction of lignin derivatives to obtain polycyclic alkane fuels.

[0026] Preferably, the lignin derivative is a phenolic compound and / or an aromatic alcohol compound. Phenolic compounds mainly include phenol, anisole, guaiacol, etc., and aromatic alcohols mainly include benzyl alcohol, diphenyl ether, etc.

[0027] Preferably, the one-pot solventless reaction to obtain polycyclic alkane fuel includes alkylation and hydrodeoxygenation. The alkylation reaction conditions are: temperature 100-160℃, time 1-10h, and rotation speed >300rpm; the hydrodeoxygenation reaction conditions are: temperature 100-200℃, time 1-10h, and rotation speed >600rpm; no solvent is added during the entire reaction process. The bifunctional catalyst is used to catalyze the one-pot solventless reaction of lignin derivatives to obtain polycyclic alkane fuel, which actually includes two steps: catalytic alkylation and catalytic hydrodeoxygenation. The catalyst of this invention can catalyze both alkylation and hydrodeoxygenation reactions, thus playing a bifunctional role. The obtained polycyclic alkane fuel is perhydrofluorene, dicyclohexylmethane, or a mixture thereof.

[0028] The beneficial effects of this invention are:

[0029] 1. The preparation method of the present invention introduces metal during the preparation of NbOPO4 support, and uses NbOPO4·nH2O as a support to impregnate metal salt solution to prepare MO with different metal impregnation amounts. x / NbOPO4 catalyst (MO x / NbOPO4 means MO x (Loaded on NbOPO4 support). Characterization shows that the catalyst MO x / NbOPO4 contains different forms of active MO, such as MO2 and MO-Nb.x Species. Strong metal-acid interactions cause active metal sites to preferentially load onto Brønsted acid sites. The applicant discovered 3 wt% RuO x Each Ru site on the NbOPO4 catalyst (3wt% here represents the mass of metallic Ru in the molecule and the mass of NbOPO4 in the denominator) matches approximately 2.53 Brønsted acid sites, achieved through alternating stacks of NbOPO4 and directionally distributed RuO4. x A clear division of labor generates a strong synergistic effect, thereby developing ordered and enriched active sites. This results in highly efficient catalytic activity for the one-pot solventless reaction of lignin derivative platform molecules such as phenol and benzyl alcohol to produce high-density polycyclic alkane fuels. (Note: 3wt% MO) x / NbOPO4 catalyst, here 3wt% (where molecule A is the mass of metal M, and denominator is the mass of NbOPO4).

[0030] 2. The bifunctional catalyst obtained by the preparation method of this invention is in the form of nanosheets, and the support NbOPO4 has abundant surface defects and is directionally anchored to MO. x At the edge position. It is used to catalyze the one-pot solventless generation of a mixture of perhydrofluorene and / or dicyclohexylmethane from platform molecules of lignin derivatives such as phenol and benzyl alcohol, yielding high-density polycyclic alkane fuels; the reaction process involves alkylation and hydrodeoxygenation, and the catalyst plays a dual-function role, acting as a catalyst in both alkylation and hydrodeoxygenation reactions.

[0031] 3. The preparation method of this invention is an innovation and improvement based on the preparation of NbOPO4 in patent CN115920934A. Since NbOPO4 has excellent acidity for catalyzing alkylation reactions, NbOPO4·nH2O is used as a carrier to impregnate a metal salt solution to prepare MO with different metal impregnation amounts. x A bifunctional catalyst of NbOPO4. The bifunctional catalyst of this invention simultaneously provides hydrogenation and acidification sites on a single catalyst, functioning as two catalytically active sites within a single reaction vessel, i.e., bifunctionality; its abundant... Acids accelerate the alkylation of oxygen-containing reactants to form fuel intermediates; in the hydrodeoxygenation step, some MO... x In-situ reduction to metal M, along with the synergistic acidic sites, rapidly converts oxygen-containing intermediates into polycyclic alkanes such as perhydrofluorene and dicyclohexylmethane, thereby increasing the reaction rate. The bifunctional catalyst of this invention exhibits excellent metal-acid balance, achieving high yields and short reaction times for the one-pot solventless reaction of lignin derivatives (phenol and benzyl alcohol) to produce high-density fuels such as perhydrofluorene, demonstrating excellent catalytic activity and serving as a bifunctional catalytic agent. Attached Figure Description

[0032] Figure 1 It is the 3wt% RuO prepared by the process.x Scanning electron microscope (SEM) image of / NbOPO4.

[0033] Figure 2 It is the 3wt% RuO prepared by the process. x Transmission electron microscopy (TEM) image of / NbOPO4.

[0034] Figure 3 The NbOPO4 and 1-4wt% RuO were prepared by the process. x X-ray diffraction (XRD) image of NbOPO4.

[0035] Figure 4 The NbOPO4 and 1-4wt% RuO were prepared by the process. x / NbOPO4 reflects the pyridine infrared spectrum of Brønsted acid and Lewis acid.

[0036] Figure 5 It is the 1-4 wt% RuO prepared by the process. x / NbOPO4 was analyzed by hydrogen temperature-programmed desorption (H2-TPD) of accessible metal sites. Detailed Implementation

[0037] The present invention will now be described in detail with reference to some specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The embodiments shown in the embodiments are preferred solutions, but the present invention is not limited to the preferred solutions.

[0038] Example 1: Preparation of a bifunctional catalyst. Using RuO x Taking NbOPO4 as an example, the percentage of metallic Ru to NbOPO4 is 1 wt%, 2 wt%, 3 wt%, and 4 wt%. The steps are as follows:

[0039] (1) Under continuous magnetic stirring, 8.9 g of niobium hydroxide was slowly dissolved in an aqueous solution containing 18.75 g of tartaric acid; then the solution was transferred to a 100 mL volumetric flask; 0.66 g of diammonium hydrogen phosphate was dissolved in 10 mL of deionized water; 20 mL of tartaric acid solution was added to the diammonium hydrogen phosphate solution under vigorous stirring; the pH was adjusted to about 1 with phosphoric acid; an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) (which was prepared by dissolving 0.5 g of CTAB in 7.5 mL of distilled water, with a concentration of 6.25 wt%) was added dropwise to the mixed solution; the resulting solution was stirred at 45 °C for 10 h, and then hydrothermally crystallized at 160 °C for 24 h in an autoclave; after cooling, the solid was filtered, washed with distilled water, and dried at 105 °C for 5 h to remove moisture to obtain NbOPO4.nH2O powder;

[0040] Repeat the above steps to obtain NbOPO4.nH2O powder, and then calcine it at 500℃ for 5h to obtain calcined NbOPO4;

[0041] (2) Weigh 1g of ruthenium chloride and dissolve it in water. Then transfer the solution to a 100mL volumetric flask. The concentration of the ruthenium chloride solution is 0.01g / mL. Take 5mL of the 0.01g / mL ruthenium chloride solution and add it to the NbOPO4.nH2O powder obtained in step (1). Then add 15mL of deionized water and heat in a water bath at 65℃ for 3h. Then dry in a drying oven at 105℃ for 10h. Calcinate the dried powder in air at a rate of 5℃ / min to 500℃ and hold for 5h to remove the organic solvent. This yields 2wt% RuO x / NbOPO4 (2wt% here, the mass percentage of metallic Ru in NbOPO4 is 2%. The same applies below) catalyst; by changing the volume of the 0.01 g / mL ruthenium chloride solution, the impregnation amount was changed to obtain 1wt% RuO x / NbOPO4, 3wt%RuO x / NbOPO4 and 4wt%RuO x / NbOPO4.

[0042] Figure 1 and Figure 2 The 3wt% RuO prepared x Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of / NbOPO4. From Figure 1 As can be seen, the SEM image shows 3wt% RuO x / NbOPO4 consists of densely packed and randomly oriented, uniformly spherical layered nanosheets; from Figure 2 As can be seen, the TEM image shows RuO x The presence of nanoparticles and the corresponding average particle size of approximately 2 nm, RuO x Preferential loading occurs at the edges of layered nanosheets; that is, the NbOPO4 sheets have numerous defect sites around them, which can serve as preferential nucleation sites, thus forming significant RuO₂. x Particles on the surface of / NbOPO4.

[0043] Figure 3 The prepared NbOPO4 and 1-4wt% RuO x X-ray diffraction (XRD) pattern of the NbOPO4 sample. Figure 3It can be seen that with the increase of Ru impregnation amount, the diffraction peaks remain the same compared with NbOPO4, the crystallinity increases slightly, and the degree of shift of 2θ=28.4° to lower angles gradually increases. This may be the reason that the content of Ru-O-Nb bonds is increasing and the degree of interaction of Ru-O-Nb bonds is gradually increasing. The diffraction peaks of RuO2 are determined by 2θ=35.1°(101) and 54.2°(211) (PDF#40-1290), indicating that Ru particles have been successfully deposited on the surface of the support, and Ru exists mainly in two forms: RuO2 and Ru-O-Nb. With the increase of Ru impregnation amount, the diffraction peaks of RuO2 become more obvious.

[0044] Figure 4 and Figure 5 The prepared NbOPO4 and 1-4wt% RuO x Pyridine Fourier Transform Infrared Spectroscopy (Py-IR) and Hydrogen Temperature Programmed Desorption (H2-TPD) assay of the / NbOPO4 sample. Figure 4 The 1wt% RuO calculated from the Py-IR data x / NbOPO4, 2wt%RuO x / NbOPO4, 3wt%RuO x / NbOPO4 and 4wt%RuO x The Brønsted acid content of / NbOPO4 was 58.13 μmol gcat. -1 36.41 μmol gcat -1 23.46 μmol gcat -1 and 20.22 μmol gcat -1 ;according to Figure 5 The 1wt% RuO calculated from H2-TPD data x / NbOPO4, 2wt%RuO x / NbOPO4, 3wt%RuO x / NbOPO4 and 4wt%RuO x The number of accessible metal centers of / NbOPO4 was 39.50 μmol gcat. -1 48.23 μmol gcat -1 59.37 μmol gcat -1 and 60.89 μmol gcat -1 This indicates that as the loading increases, the number of Brønsted acid sites gradually decreases while the metal content gradually increases.

[0045] Table 1 presents quantitative data on the metal acid sites of the bifunctional catalyst prepared in the examples. The applicant found that, as a bifunctional catalyst, the conversion of benzyl alcohol during alkylation, the selectivity of the oxygen-containing intermediate benzylphenol, and the conversion of benzylphenol, the selectivity of perhydrofluorene, and even the product distribution during hydrodeoxygenation are closely related to the synergistic effect of the metal and acid centers. The metal-acid balance (MAB), i.e., the ratio of surface metal sites to Brønsted acid sites (nRu / nBAS, taking metal Ru as an example), can determine the alkylation, hydrodeoxygenation activity, and product distribution in a one-pot solventless conversion process. Only the concentration of Brønsted acid sites was used in the MAB calculation because they are mainly responsible for the alkylation of phenol and benzyl alcohol and the alcohol dehydration process during hydrodeoxygenation. To study the effect of MAB on the catalytic activity of the catalyst, the MAB was adjusted by changing the loading of metal Ru; the results showed that as the metal Ru loading increased from 1 wt% to 4 wt%, the MAB varied between 0.68 and 3.01, thus quantitatively studying the RuO2 content. x The / NbOPO4 catalyst exhibits a synergistic effect on the one-pot solventless conversion of benzyl alcohol and phenol to polycyclic alkylate fuels. For this reaction system, there is no rate-limiting step; the alkylation and hydrodeoxygenation reactions occur sequentially. Therefore, a suitable metal-Ru and acid balance (MAB) is required for the bifunctional catalyst. The applicant unexpectedly discovered that low Ru loading is insufficient to provide enough metal sites for effective hydrodeoxygenation, and excessive Ru particles can block the channels and pores of the acidic support, inhibiting the alkylation reaction. This is because as the metal loading increases, the number of metal sites gradually increases, while the number of Brønsted acid sites gradually decreases. Therefore, a suitable MAB is necessary to achieve the bifunctional catalytic effect.

[0046] Table 1 1-4wt% RuO x The amount of Brønsted acid, the amount of metal, and the nRu / nBAS content of the / NbOPO4 catalyst

[0047] serial number catalyst B acid content (μmol / g) Metal content (μmol / g) nRu / nBAS 1 <![CDATA[1wt%RuO x / NbOPO4]]> 58.13 39.50 0.68 2 <![CDATA[2wt%RuO x / NbOPO4]]> 36.41 48.23 1.32 3 <![CDATA[3wt%RuO x / NbOPO4]]> 23.46 59.37 2.53 4 <![CDATA[4wt%RuO x / NbOPO4]]> 20.22 60.89 3.01

[0048] Following the steps in Example 1, 3wt% PtO was prepared. x / NbOPO4 and 3wt%NiO x / NbOPO4 bifunctional catalyst.

[0049] For comparison, 3wt% RuO was prepared x / S-NbOPO4. The steps are as follows: calcining the NbOPO4.nH2O powder obtained in step (1) of Example 1 at 500℃ for 5h to obtain calcined NbOPO4; adding 7.5mL of 0.01g / mL ruthenium chloride solution, then adding 15mL of deionized water, and stirring at 65℃ in a water bath for 3h; then drying at 105℃ for 10h in a drying oven; calcining the obtained dried powder at 500℃ in an air atmosphere, and raising the temperature at a rate of 5℃ / min and holding for 5h to remove organic solvent; thus obtaining 3wt% RuO x / S-NbOPO4 catalyst.

[0050] Example 2: High-density fuel was prepared by a one-pot solventless reaction of lignin-derived molecules phenol and benzyl alcohol using the above-mentioned catalyst in a 50 mL stainless steel batch reactor. The steps were as follows: 139.8 mmol of phenol, 34.8 mmol of benzyl alcohol, and 0.6 g of the above-mentioned catalyst were added to the reactor, with the catalyst accounting for 3.5 wt% of the reactants. The temperature was raised to 130 °C and the alkylation reaction was carried out in air at a stirring speed of 800 rpm for 2 h. Then, the reactor was purged three times with N2 to ensure airtightness, followed by three purgings with H2. H2 was then introduced at 6 MPa, and the temperature was raised to 160 °C under H2 atmosphere, with a stirring speed of 800 rpm for 1 h for hydrodeoxygenation. After the reaction, the reaction mixture was extracted using a syringe, and the extracted solution was squeezed into a chromatographic vial using a filter head containing an organic filter membrane for chromatographic analysis. The product was then subjected to vacuum distillation to obtain fuel samples, and its fuel performance was tested. The results are shown in Table 2 below.

[0051] Table 2 Hydrodeoxygenation reaction of phenol and benzyl alcohol in one-pot solventless reaction catalyzed by different catalysts.

[0052] Serial Number catalyst perhydrofluorene and dicyclohexylmethane yield 1 <![CDATA[1wt%RuO x / NbOPO4]]> 3.8 2 <![CDATA[2wt%RuO x / NbOPO4]]> 45.9 3 <![CDATA[3wt%RuO x / NbOPO4]]> 78.3 4 <![CDATA[4wt%RuO x / NbOPO4]]> 58.2 5 <![CDATA[3wt%RuO x / S-NbOPO4]]> 18.0 6 <![CDATA[3wt%PtO x / NbOPO4]]> 51.0 7 <![CDATA[3wt%NiO x / NbOPO4]]> 30.0 8 <![CDATA[NbOPO4]]> 0 9 <![CDATA[NbOPO4+Ru / C]]> 6.1 10 <![CDATA[NbOPO4+Ru / C]]> 82.0

[0053] [Note] In Table 2, catalyst NbOPO4 in item 8 is calcined NbOPO4 obtained by calcination at 500℃ for 5 h. Catalyst NbOPO4+Ru / C in item 9 is the yield of the catalyst of patent CN115920934A under these experimental conditions. Catalyst NbOPO4+Ru / C in item 10 is the yield of the catalyst of patent CN115920934A after alkylation reaction, followed by hydrodeoxygenation reaction at 180℃ for 6-10 h.

[0054] As can be seen from Table 2, RuO x NbOPO4 exhibits superior activity compared to other MOs. x / NbOPO4 activity; 3wt% RuO x / NbOPO4 has the best activity.

[0055] Table 2 also shows that 3wt% RuOx / S-NbOPO4 vs. 3wt%RuO x The significant decrease in the activity of / NbOPO4 is likely due to the weak interaction between Ru and the calcined NbOPO4 support during the impregnation process. This indicates that the bifunctional catalyst prepared by the method of the present invention exhibits excellent activity.

[0056] Table 2 also shows that NbOPO4 catalyst alone cannot carry out the hydrodeoxygenation reaction to obtain the final product, polycyclic alkane fuel. A Ru / C catalyst needs to be added after the alkylation reaction, and NbOPO4 and Ru / C need to be physically mixed to jointly complete the hydrodeoxygenation reaction and obtain polycyclic alkane fuel. Furthermore, the final fuel yield under the experimental conditions (alkylation reaction at 130℃ for 2 h; hydrodeoxygenation reaction at 160℃, 6 MPa for 1 h) is still relatively low (6.1%). To obtain a higher fuel yield, a Ru / C catalyst needs to be added after the alkylation reaction, and the hydrodeoxygenation reaction should be carried out at a higher temperature of 180℃ for 6-10 h to overcome the energy barrier of the hydrodeoxygenation reaction. That is, with a molar ratio of phenol to benzyl alcohol of 4:1, after alkylation reaction at 130℃ for 2 h, the Ru / C catalyst needs to be added, and the hydrodeoxygenation reaction should be carried out at 180℃ for 6-10 h to obtain a higher yield of perhydrofluorene and dicyclohexylmethane (82.0%). This indicates that a catalyst containing only NbOPO4 does not have bifunctional properties, while the MO of this invention... x / NbOPO4 catalyst has a dual function.

[0057] 3wt% RuO x The final product obtained from / NbOPO4, after vacuum distillation, yielded a fuel composition of 76% total hydrogen fluorene, 11% dicyclohexylmethane, 3% other bicyclic products, and 10% other tricyclic products. The measured fuel density was 0.9594 g / mL.

[0058] The foregoing description is merely intended to detail specific embodiments of the present invention, but the technical solutions proposed in this invention are not limited to the methods described above. All equivalent modifications and variations made by those skilled in the art to the technology proposed in this invention without departing from its basic principles should be covered within the scope of the claims of this invention.

Claims

1. The use of a bifunctional catalyst for catalyzing a one-pot solventless reaction of lignin derivatives to obtain polycyclic alkane fuels; characterized in that, The lignin derivatives are phenolic compounds and / or aromatic alcohols; the one-pot solventless reaction to obtain polycyclic alkane fuels includes alkylation and hydrodeoxygenation reactions; the alkylation reaction conditions are: temperature 100-160℃, time 1-10h, rotation speed >300rpm; the hydrodeoxygenation reaction conditions are: temperature 100-200℃, time 1-10h, rotation speed >600rpm; The preparation method of the bifunctional catalyst includes the following steps: (1) Mix niobium source, tartaric acid and water evenly to obtain niobium tartrate aqueous solution; (2) Dissolve diammonium hydrogen phosphate in water; (3) Mix the solutions obtained in steps (1) and (2) and adjust the pH value with acid; (4) Add an aqueous solution of hexadecyltrimethylammonium bromide to the mixture from step (3); (5) The mixture obtained in step (4) is hydrothermally crystallized in a high-pressure hydrothermal reactor for a period of time, and then filtered to obtain a solid for drying; (6) Mix the metal salt solution evenly; the metal salt solution is a Ru metal salt solution, wherein the amount of Ru metal salt solution added is 2-4 wt% of the metal in the solid; (7) At a certain temperature, the solid material dried in step (5) is mixed into the metal salt solution in step (6) and mixed for a period of time; (8) The solid obtained by separating the mixture in step (7) is dried and then calcined to obtain the bifunctional catalyst.

2. The use according to claim 1, characterized in that, In step (1), the niobium source is niobium hydroxide, and the mass ratio of the niobium source to tartaric acid is 1:(1-5); in step (3), the pH value is adjusted with phosphoric acid so that the pH value is not greater than 2.

3. The use according to claim 2, characterized in that, The aqueous solution of hexadecyltrimethylammonium bromide (CTAB) in step (4) has a concentration of 5wt%-10wt%, and the mass ratio of hexadecyltrimethylammonium bromide to niobium hydroxide is 7:

25.

4. The use according to claim 1, characterized in that, Step (5) The hydrothermal crystallization time of the mixture is 12-26h, and the temperature is 100-200℃; the drying is carried out at 60-120℃ for 6-24h.

5. The use according to claim 1, characterized in that, Step (7) The mixing temperature is 25-100℃ and the time is 1-10h.

6. The preparation method according to claim 1, characterized in that, The calcination temperature in step (8) is 350-650℃ and the time is 3-10h.

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