A ruthenium-based catalyst, its preparation method and use

Abstract

A ruthenium-based catalyst is disclosed, which is ruthenium metal particles supported on the exposed (101) crystal plane of nanostructured TiO2. The preparation method of the ruthenium-based catalyst and the use thereof for catalyzing polycyclic aromatic hydrocarbons to obtain fuel in one step are also disclosed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic catalytic synthesis, and particularly relates to a ruthenium-based catalyst, a preparation method thereof and a use thereof for catalyzing one-step hydrogenation conversion of polycyclic aromatic hydrocarbons to synthesize high-energy-density fuels. BACKGROUND

[0002] With the development of aerospace technology, the demand for high-performance aerospace fuels is increasing. At the same time, the vigorous development of hypersonic aircraft also puts forward higher requirements for the performance of new aerospace fuels. Compared with traditional jet fuel, high-energy-density endothermic jet fuel has higher density, greater volumetric heat value and excellent thermal oxidative stability, which can greatly enhance the range, flight distance and load of the aircraft in the limited tank volume. Therefore, the development of high-density endothermic jet fuel is of great significance to enhance national defense strength.

[0003] One of the important methods to improve the energy density of fuel is to improve the density of fuel, and one of the preferred methods is to construct saturated polycyclic compound components with excellent performance. Polycyclic aromatic hydrocarbons (PAHs), such as acenaphthene, fluorene, phenanthrene, etc., exist in large quantities in petroleum residues, shale oil, coal tar and biomass, and their carbon number (C9-C 15 ) is consistent with that of aviation fuel. These aromatic hydrocarbons can produce aviation fuel with high density, good thermal oxidative stability and low-temperature performance after deep hydrogenation. During the hydrogenation saturation process of polycyclic aromatic hydrocarbons, stereoisomerism exists, and the properties of different isomers are also different; for example, both cis-decahydronaphthalene and trans-decahydronaphthalene are products of deep hydrogenation of naphthalene, but the density of cis-decahydronaphthalene is greater than that of trans-decahydronaphthalene (0.899 g·mL -1 vs. 0.866 g·mL -1 ), and cis-decahydronaphthalene has higher cetane number (42 vs. 32), volumetric net heat of combustion (38.3 MJ·L -1 vs. 37.2 MJ·L -1 ) and better reactivity. Similarly, the density of the cis stereoisomer of 2-methyldecahydronaphthalene is greater than that of the trans isomer, and the heat of combustion is 5-10 kJ·mol -1 (Catalysis Today, 2019, 329: 94-101). Generally, cis isomers have excellent combustion performance and are preferred fuel components.

[0004] Due to the high resonance energy and steric hindrance of polycyclic aromatic hydrocarbons, the reaction activity is poor, and it is difficult to saturate to form polycyclic alkanes. Although non-noble metal (Ni, Co, Mo, etc.) catalysts are low in price and widely used, their relatively low activity limits their application in polycyclic aromatic hydrocarbon hydrogenation saturation. Noble metals (Pt, Pd, Ru, etc.) have good hydrogen dissociation ability and can carry out hydrogenation saturation reaction under relatively mild conditions. Ru as a hydrogenation active metal has excellent selectivity to cis-product. Therefore, the development of Ru-based hydrogenation catalyst is an important technical approach to realize the upgrading of aviation fuel. SUMMARY

[0005] In order to solve the above-mentioned problems and shortcomings of the prior art, the present application discloses a ruthenium-based catalyst, wherein ruthenium metal nanoparticles are loaded on the exposed (101) crystal face of nanostructured TiO2. The preparation method of the present application uses tetrabutyl titanate as the titanium source to prepare anatase titanium dioxide with different crystal faces and oxygen vacancy contents during the preparation of the titanium dioxide carrier, and further prepares a Ru catalyst with a controllable crystal face orientation TiO2 carrier with different oxygen vacancy contents. The applicant found that moderate oxygen vacancy content, such as 14.0%, and exposure of (101) crystal face have very high catalytic performance for polycyclic aromatic hydrocarbon hydrogenation reaction; when applied in the catalytic reaction of one-step hydrogenation conversion of polycyclic aromatic hydrocarbons to synthesize high-energy-density endothermic aviation fuel, a high hydrogenation rate and a high cis-hydrogenated product can be obtained at a relatively low temperature, such as about 60℃.

[0006] The technical scheme of the present application is as follows:

[0007] The first aspect of the present application discloses a ruthenium-based catalyst, wherein ruthenium metal particles are loaded on the exposed (101) crystal face of nanostructured TiO2.

[0008] Preferably, the nanostructured TiO2 is a nanoparticle or a nanosheet; the oxygen vacancy content of the nanostructured TiO2 is 13.5-14.5%, preferably 14.0%.

[0009] Preferably, the loading amount of ruthenium metal particles is 2.5-3.5wt% of the total amount of catalyst.

[0010] Preferably, the ruthenium metal particles are not greater than 2nm.

[0011] The second aspect of the present application discloses a preparation method of the ruthenium-based catalyst, comprising the following steps:

[0012] (1) mixing a titanium source and a structure directing agent uniformly to obtain an aging solution;

[0013] (2) hydrothermally crystallizing the aging solution, then filtering and drying the solid to obtain a solid;

[0014] (3) calcining the obtained solid to obtain TiO2;

[0015] (4) high-temperature reduction of the obtained TiO2 in a H2 / Ar mixed atmosphere to obtain TiO2 with different oxygen vacancies and different crystal face orientations;

[0016] (5) preparation of a ruthenium source into an aqueous solution;

[0017] (6) mixing the TiO2 obtained in step (4) with deionized water, adding the aqueous solution of the ruthenium source in step (5) and mixing uniformly at a certain temperature, and drying to obtain a solid;

[0018] (7) reduction of the obtained solid in a H2 / Ar mixed atmosphere; namely, the ruthenium-based catalyst is obtained.

[0019] Preferably, the titanium source in step (1) is tetrabutyl titanate; and the structure-directing agent is one or both of acetic acid and hydrofluoric acid.

[0020] Preferably, if the structure-directing agent is acetic acid, the volume ratio of tetrabutyl titanate to acetic acid is 1:(3-5), preferably 1:4; and if the structure-directing agent is hydrofluoric acid, the volume ratio of 40wt% hydrofluoric acid to tetrabutyl titanate is 1:(4-6), preferably 1:5.

[0021] Preferably, the hydrothermal crystallization conditions in step (2) are 180-220℃ for 12-36h, preferably 200℃ for 24h; the calcination temperature in step (3) is 300-500℃ for 2-6h, preferably 400℃ for 4h; the reduction temperature in step (7) is 200-600℃ for 0.5-3h, preferably 400℃ for 2h; and the content of H2 in the H2 / Ar atmosphere is about 10v / v%.

[0022] Preferably, the reduction temperature in step (4) is 100-800℃ for 2-6h; and the content of H2 in the H2 / Ar atmosphere is about 10v / v%.

[0023] Preferably, the ruthenium source in step (5) is a soluble ruthenium salt, and the concentration of the aqueous solution of the ruthenium source is (0.005-0.020)g / mL, preferably 0.010g / mL; and the mixing and drying temperature in step (6) is 80-100℃, preferably 90℃.

[0024] The third aspect of the present application discloses the use of the ruthenium-based catalyst for catalyzing polycyclic aromatic hydrocarbons at low temperature in one step to improve hydrogenation yield and increase the production of cis-perhydrogenated fuel products. The fuel is a high-energy high-density fuel, such as one or more of perhydroacenaphthene, perhydrofluorene and decalin.

[0025] The present application has the following beneficial effects:

[0026] 1. The ruthenium-based catalyst of the present application, ruthenium metal particles are supported on the exposed (101) crystal plane of nanostructured TiO2, the support TiO2 has moderate oxygen vacancy content, such as about 14.0%, and has strong metal-support interaction. The Ru catalyst particles supported on TiO2(101) prepared at 400℃ are used for the catalytic one-step hydrogenation of polycyclic aromatic hydrocarbons to obtain fuel, and the synergistic effect of the two makes the hydrogenation reaction obtain a higher hydrogenation rate (0.18 μmol·min -1 ·g -1 ) and the highest selectivity (95.0%) of cis-perhydro product at about 60℃; deep hydrogenation saturation of polycyclic aromatic hydrocarbons at near room temperature can be achieved.

[0027] 2. The preparation method of the ruthenium-based catalyst of the present application, tetrabutyl titanate is used as the titanium source, the preparation process is simple and efficient, and different crystal plane orientations of TiO2 are obtained by changing the structure-directing agent in the synthesis process. The interaction ability of TiO2(101) with Ru is stronger than that of TiO2(001), which can prevent Ru nanoparticles from agglomerating during the reaction, resulting in a decrease in hydrogenation activity.

[0028] 3. The preparation method of the ruthenium-based catalyst of the present application, different contents of oxygen vacancies are manufactured by high-temperature reduction, and sodium borohydride is avoided. After high-temperature treatment, the support TiO2 is still in an anatase phase. This indicates that the crystal structures of the support and the catalyst are not changed, and it is indicated that the reduction temperature has little effect on the crystal structure. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a scanning electron microscope (SEM) photo of TiO2-NP prepared in Example 1.

[0030] Figure 2 is a scanning electron microscope (SEM) photo of TiO2-NS prepared in Example 2.

[0031] Figure 3 is an X-ray diffraction (XRD) picture of the Ru catalyst prepared in Examples 1-6

[0032] Figure 4 is an X-ray photoelectron spectroscopy (XPS) picture of the Ru catalyst prepared in Examples 1-6. DETAILED DESCRIPTION

[0033] The present application will be described in detail below in conjunction with some specific embodiments. These examples are only used to illustrate the present application, and are not used to limit the scope of the present application. The embodiments in the examples are only preferred schemes, but the present application is not limited to the preferred schemes.

[0034] Example 1: Preparation of ruthenium-based catalyst, acetic acid as structure-directing agent, reduction temperature of support TiO2 400℃. The steps are as follows:

[0035] (1) 5 mL of tetrabutyl titanate was added to 20 mL of glacial acetic acid under stirring at room temperature; after stirring for 30 min, it was transferred to a 100 mL polytetrafluoro-lined autoclave and hydrothermally crystallized at 200℃ for 24 h;

[0036] (2) After natural cooling to room temperature, the obtained solid was washed with anhydrous ethanol three times and dried at 80℃ overnight;

[0037] (3) The collected solid powder was ground and calcined in a muffle furnace at a temperature increasing rate of 5℃·min -1 -1 at 400℃ for 4 h; the obtained sample was named TiO2-NP;

[0038] (4) TiO2 was pretreated at 400℃ for 4 h using 10 v / v% of H2 / Ar (150 mL·min -1 -1); the sample was labeled as TP-400;

[0039] (5) 0.5 g of ruthenium chloride was dissolved in 50 mL of ultrapure water to prepare a 0.01 g·mL -1 -1 ruthenium chloride aqueous solution;

[0040] (6) The solid TP-400 obtained in step (4) was added to a 100 mL beaker, 20 mL of deionized water was added; 3.1 mL of the solution in step (5) was added, and the solid powder was obtained by stirring and drying at 90℃;

[0041] (7) The solid powder obtained in step (6) was reduced at 400℃ for 1 h in a 10 v / v% H2 / Ar atmosphere (150 mL·min -1 -1) at a temperature increasing rate of 5℃·min -1 -1; thus the ruthenium-based catalyst was obtained and labeled as Ru / TP-400.

[0042] Example 2: Preparation of ruthenium-based catalyst, acetic acid as structure-directing agent, reduction temperature 200℃.

[0043] The conditions and steps were the same as in Example 1, but the reduction temperature in step (4) was 200℃, and the sample was labeled as TP-200; thus the ruthenium-based catalyst was obtained and labeled as Ru / TP-200.

[0044] Example 3: Preparation of ruthenium-based catalyst, acetic acid as structure-directing agent, reduction temperature 600℃.

[0045] The conditions and steps were the same as in Example 1, but the reduction temperature in step (4) was 600°C, and the sample was designated TP-600; the ruthenium-based catalyst was obtained and designated Ru / TP-600.

[0046] Example 4: Preparation of a ruthenium-based catalyst, using hydrofluoric acid as a structure directing agent, and a reduction temperature of 200°C.

[0047] The conditions and steps were the same as in Example 1, but in step (1), 25 mL of tetrabutyl titanate was added to a 100 mL polytetrafluoroethylene liner, followed by the careful and slow addition of 4 mL of a 40 wt% solution of hydrofluoric acid; the sample obtained after step (3) was designated TiO2-NS; the reduction temperature in step (4) was 200°C, and the sample was designated TS-200; the ruthenium-based catalyst was obtained and designated Ru / TS-200.

[0048] Example 5: Preparation of a ruthenium-based catalyst, using hydrofluoric acid as a structure directing agent, and a reduction temperature of 400°C.

[0049] The conditions and steps were the same as in Example 4, but the reduction temperature in step (4) was 400°C, and the sample was designated TS-400; the ruthenium-based catalyst was obtained and designated Ru / TS-400.

[0050] Example 6: Preparation of a ruthenium-based catalyst, using hydrofluoric acid as a structure directing agent, and a reduction temperature of 600°C.

[0051] The conditions and steps were the same as in Example 4, but the reduction temperature in step (4) was 600°C, and the sample was designated TS-600; the ruthenium-based catalyst was obtained and designated Ru / TS-600.

[0052] Figure 1 is a scanning electron microscope (SEM) photograph of TiO2-NP obtained in Example 1, Figure 2 is a scanning electron microscope (SEM) photograph of TiO2-NS obtained in Example 4. Figure 3 is an X-ray diffraction (XRD) pattern of Ru catalyst obtained in Examples 1-6. Figure 4 is an X-ray photoelectron spectroscopy (XPS) image of Ru catalyst obtained in Examples 1-6.

[0053] From the SEM of Figure 1 and Figure 2 it can be seen that the TiO2-NP obtained have a nanoparticle structure, and the TiO2-NS have a nanosheet structure. From the XRD pattern of Figure 3 it can be seen that the (101) plane is the main exposed plane of TiO2-NP, and the exposure of the (001) plane increases in TiO2-NS. From the XPS image of Figure 4The XPS spectrum of Ru / TP-400 prepared in Example 1 can be seen that the binding energy of Ru species is high, which means that there is a stronger interaction between Ru and TiO2; the higher Ru δ+ species is beneficial to the hydrogenation of polycyclic aromatic hydrocarbons. Table 1 is the Ru 3d spectrum results of the catalysts prepared in Examples 1-6, which further proves that the Ru δ+ species of Ru / TP-400 has high binding energy.

[0054] Table 1 Ru 3d spectrum results of the catalysts prepared in Examples 1-6

[0055]

[0056] Example 7: One-step hydroconversion of polycyclic aromatic hydrocarbons to high-energy fuel, using Ru-based catalysts of Examples 1-6, the steps are:

[0057] 2g acenaphthene and 90mL decalin were added to a 250mL high-temperature and high-pressure reaction kettle; hydrogen pressure 4MPa, heated to 150℃, reaction time 0-3h, rotation speed 600rpm.

[0058] Using the Ru catalysts of Examples 1-6, the conversion rate, yield, and product selectivity achieved are shown in Table 2.

[0059] Table 2 Comparison of catalytic results of Ru-based catalysts of Examples 1-6

[0060]

[0061] As can be seen from Table 2, the activity of Ru catalysts with TiO2-NP as carrier is significantly higher than that of Ru catalysts with TiO2-NS as carrier.

[0062] Example 8: Hydrogenation saturation of polycyclic aromatic hydrocarbons at low temperature.

[0063] In order to further explore the activity of Ru catalysts with TiO2-NP as carrier, polycyclic aromatic hydrocarbon hydrogenation saturation was carried out at 100℃ and 60℃, and the results are shown in Table 3

[0064] Table 3 Comparison of catalytic results of Ru-based catalysts of Examples 1-3 at different temperatures

[0065]

[0066] As can be seen from Table 3, the activities of the catalysts are not much different at 100℃; but after further reducing the temperature to 60℃, the activity of the Ru / TP-400 catalyst is still higher, and a higher cis-product selectivity is obtained, and the Ru / TP-400 has the best catalytic activity at 60℃ compared with the Ru / TP-200 and Ru / TP-600.

[0067] Comparative Example: Achieving the hydrogenation saturation of the tricyclic polycyclic aromatic hydrocarbon at near room temperature of 60℃; using the catalyst in the literature ChemNanoMat, e202400092. for comparison. Comparing the catalytic activity of the catalysts (Ru / TiO2 vs. Ru / TP-400 of Example 1) from the product selectivity and reactant conversion rate (hydrogenation reaction conditions: 2gacenaphthene, 60℃, 4MPa hydrogen, 0.4g catalyst);

[0068] The results are: at a hydrogenation temperature of 60℃, the catalyst in the literature ChemNanoMat, e202400092. has an acenaphthene conversion rate of 0% and a cis-product selectivity of 0%; while the acenaphthene conversion rate of the present application is 100% and the cis-product selectivity is 95.0%.

[0069] Therefore, the catalytic activity of the Ru-based catalyst of the present application is significantly higher than that of the prior art catalyst, and the selectivity of the cis-perhydrogen product is also significantly higher.

[0070] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. Use of a ruthenium-based catalyst for the catalytic one-step production of fuel from polycyclic aromatic hydrocarbons, characterized in that, The fuel is one or more of perhydroacenaphthylene, perhydrofluorene, and decalin; the ruthenium-based catalyst is ruthenium metal particles supported on an exposed (101) crystal plane of nanostructured TiO2; the nanostructured TiO2 is nanoparticles or nanosheets; the nanostructured TiO2 has an oxygen vacancy content of 13.5-14.5%; The preparation method of the ruthenium-based catalyst comprises the following steps: (1) uniformly mixing a titanium source and a structure-directing agent to obtain an aging solution; the structure-directing agent is one or both of acetic acid and hydrofluoric acid; (2) hydrothermally crystallizing the aging solution, then filtering and drying the solid to obtain a solid product; (3) calcining the obtained solid product to obtain TiO2; (4) reducing the obtained TiO2 in a H2 / Ar mixed atmosphere to obtain TiO2 with different oxygen vacancies and different crystal plane orientations; (5) preparing a ruthenium source into an aqueous solution; (6) mixing the TiO2 obtained in step (4) with deionized water, then adding the aqueous solution of the ruthenium source in step (5) and uniformly mixing at a certain temperature, and then drying to obtain a solid product; (7) reducing the obtained solid product in a H2 / Ar mixed atmosphere; thus the ruthenium-based catalyst is obtained.

2. Use according to claim 1, characterized in that, The ruthenium metal particles are not greater than 2 nm.

3. Use according to claim 1, characterized in that, The titanium source in step (1) is tetrabutyl titanate.

4. Use according to claim 1, characterized in that, If the structure-directing agent is acetic acid, the volume ratio of tetrabutyl titanate to acetic acid is 1: (3-5); if the structure-directing agent is hydrofluoric acid, the volume ratio of 40wt% hydrofluoric acid to tetrabutyl titanate is 1: (4-6).

5. Use according to claim 1, characterized in that, The hydrothermal crystallization conditions in step (2) are 180-220℃ for 12-36h; the calcination temperature in step (3) is 300-500℃ for 2-6h; and the reduction temperature in step (7) is 200-600℃ for 0.5-3h.

6. Use according to claim 1, characterized in that, The reduction temperature in step (4) is 100-800℃ for 2-6h.

7. Use according to claim 1, characterized in that, The ruthenium source in step (5) is a soluble ruthenium salt, and the concentration of the aqueous solution of the ruthenium source is (0.005-0.020) g / mL.

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