Preparation method and application of efficient titanium dioxide nanosheet flower supported Ru catalyst

Abstract

The application discloses a preparation method of a high-efficiency Ru catalyst loaded on TiO2 nanosheet flowers and application thereof, and comprises the following steps: synthesizing a titanate by a solvothermal method, etching and acid-treating the titanate, obtaining a nanosheet flower TiO2 carrier by calcining, and loading active metal ruthenium by an impregnation chemical reduction method to obtain a final catalyst Ru / TiO2; compared with other supported catalysts for benzene hydrogenation reaction, the catalyst has a unique flower-shaped structure formed by nanosheet assembly and good hydrophilicity, the flower-shaped nanosheet structure can support the active component ruthenium, improve the mechanical strength of the catalyst, meanwhile, the carrier surface has rich pore structures, which can improve the heat conductivity of the catalyst, prevent sintering inactivation caused by local overheating of the catalyst, improve the stability of the catalyst, and the carrier with good hydrophilicity can promote the rapid desorption of products such as cyclohexene, and improve the cyclohexene selectivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of catalysts required for the selective hydrogenation of benzene to cyclohexene, and relates to a preparation method of a high-efficiency titanium dioxide nanosheet flower-supported Ru catalyst and application thereof. BACKGROUND

[0002] Cyclohexene is an extremely important industrial raw material, which is not only applied to the production of chemicals such as cyclohexanol, nylon and polyamide, but also has a wide range of applications in the fields of electronics, electrical appliances, medicine and the like, and has extremely high economic value and wide industrial use. At present, there are mainly four methods for producing cyclohexene, namely, dehydrogenation of cyclohexane, oxidation of cyclohexane, dehydration of cyclohexanol and partial hydrogenation of benzene, but the first three methods have unavoidable problems such as high energy consumption, high cost, difficulty in recycling of waste liquid and waste gas and low product yield. Compared with other synthesis routes, the partial hydrogenation of benzene to cyclohexene has the characteristics of low energy consumption, green environmental protection and recyclable by-product cyclohexane, and is an environmentally friendly and energy-efficient production route.

[0003] From the perspective of thermodynamics, selective hydrogenation of benzene can generate cyclohexane in one step or generate cyclohexene first, and then the cyclohexene is deeply hydrogenated to generate cyclohexane. Therefore, in order to obtain more cyclohexene, we can only study it from the perspective of kinetics, that is, to reduce the rate of cyclohexene re-hydrogenation to cyclohexane and to accelerate the desorption of cyclohexene to avoid deep hydrogenation to cyclohexane. In the current research, the non-supported Ru-Zn catalyst has the best performance in the reaction, but the non-supported Ru-based catalyst directly consumes a large amount of noble metal Ru, and has problems such as high cost and easy aggregation of active components. Therefore, in the past ten years, supported Ru catalysts have become a research hotspot. In supported Ru-based catalysts, the structure of the carrier is directly related to the catalytic performance. A good carrier has a large specific surface area and a special pore structure size, which can improve the dispersion of the active component and improve the catalytic efficiency, and can also increase the mechanical strength of the catalyst as the skeleton of the active component. In addition, the hydrophilicity of the carrier directly affects whether the cyclohexene can be quickly desorbed from the reaction system, and also directly determines the performance of the catalyst. In summary, in order to improve the selectivity, activity and stability of the catalyst, it is crucial to explore the synthesis of carriers with stable structure and excellent morphology.

[0004] In the current research, there are related patents that disclose Ru-based catalysts and preparation methods for the preparation of cyclohexene by partial hydrogenation of benzene. For example, patent CN116764629A discloses a supported catalyst using reduced graphene oxide as a carrier. The carrier in this method significantly reduces the amount of noble metal in the catalyst, and can avoid the growth and agglomeration of ruthenium particles after long-term use, thereby significantly improving the stability of the catalyst.

[0005] At present, the research on catalyst carrier is mostly focused on the selection of the carrier, and the research on the specific carrier morphology is less. However, for the performance of the supported catalyst, the optimization of the carrier structure is crucial, and the carrier with specific morphology directly affects the dispersion of the active component Ru, and then affects the stability of the catalyst and the benzene conversion rate and the cyclohexene selectivity. Therefore, it is of great significance to develop a catalyst with unique morphology, strong stability, excellent catalytic performance and easy industrial production and application. SUMMARY

[0006] The present application aims to overcome the above technical problems, and provides a preparation method of a high-efficiency Ru catalyst supported by TiO2 nanosheet flower and application thereof. First, titanate is synthesized by a solvothermal method, and is etched and acid-treated, and then TiO2 carrier is obtained by calcination, and then Ru / TiO2 material is synthesized by impregnation-chemical reduction method. The carrier has a unique flower structure formed by nanosheet assembly and excellent hydrophilicity. The flower-shaped nanosheet structure has a certain support and heat conduction function for the active component Ru, prevents Ru from being prematurely deactivated in the reaction process, improves the stability of the catalyst, and the carrier with good hydrophilicity can promote the rapid desorption of cyclohexene and other products, improves the cyclohexene selectivity, and the prepared catalyst Ru is uniformly distributed on the nanosheet, has high dispersion, uses less noble metal Ru, reduces the amount of noble metal, and reduces the production cost.

[0007] The technical scheme adopted by the present application is as follows:

[0008] A preparation method of a high-efficiency Ru catalyst supported by TiO2 nanosheet flower, which is performed according to the following steps in sequence:

[0009] S1, uniformly mix diethylenetriamine and glycerol to obtain solution A, then add titanium isopropoxide dropwise into solution A and stir uniformly, transfer the mixed solution to a reaction kettle and react at 200 DEG C for 24h, obtain white precipitate, then wash with ethanol for 3-4 times and dry;

[0010] S2, mix the white precipitate obtained in step S1 with 1M NaOH solution to obtain solution B, transfer solution B to a reaction kettle after stirring for 30min, react at 140 DEG C for 10h, wash the obtained product with water until neutral, then add 0.5M hydrochloric acid to obtain solution C, mix uniformly, stand for 12h, centrifugal wash and dry the obtained precipitate, and then calcine to obtain TiO2 carrier;

[0011] S3, disperse the TiO2 carrier into water, add ruthenium compound dropwise, stir for 1h, then add NaBH4 solution dropwise to obtain precipitate, centrifugal wash the precipitate, vacuum dry, and then the catalyst is obtained.

[0012] As a limitation of the present invention, the catalyst comprises an active component Ru and a support TiO2 material, wherein the mass of Ru is 2-10 wt% of TiO2.

[0013] As a second limitation of the present invention, in step S1, the molar ratio of diethylenetriamine, glycerol and titanium isopropoxide is 1:383.64:5.55.

[0014] As a third limitation of the present invention, in step S2, the mass ratio of the white precipitate to sodium hydroxide and hydrochloric acid is 1:8:7.3.

[0015] As a fourth limitation of the present invention, in step S2, the calcination temperature is 500-600℃ and the calcination time is 2h.

[0016] As a fifth limitation of the present invention, in step S3, the ruthenium compound is ruthenium trichloride, and the molar amount of NaBH4 is four times the molar amount of Ru loaded in the catalyst.

[0017] As a sixth limitation of the present invention, the catalyst is defined as a flower-shaped nanosheet structure with a thickness of approximately 10 nm.

[0018] The present invention also provides an application of a highly efficient titanium dioxide nanosheet-supported Ru catalyst, which is used in the selective hydrogenation of benzene to cyclohexene.

[0019] The technical solution described above in this invention, as a whole, involves interconnected and interdependent steps that ultimately affect the morphology, structure, and performance of the catalyst. This invention first synthesizes titanate using a solvothermal method, followed by etching and acid treatment. During this process, sodium hydroxide increases the pH of the solution, leading to the formation of titanate ions (TiO3). 2- The reaction proceeds, and titanate ions gradually aggregate to form a core. Nanosheets then undergo directional bonding and grow around the core, resulting in a unique flower-like TiO2 support formed by nanosheet assembly. Subsequently, Ru / TiO2 materials are synthesized using an impregnation-chemical reduction method. The flower-like support with unique nanosheet assembly prepared in this invention not only possesses excellent hydrophilicity, but this structure also provides support and thermal conductivity for the active component ruthenium, preventing premature deactivation of ruthenium during the reaction and improving catalyst stability. The good hydrophilicity of the support promotes rapid desorption of products such as cyclohexene, improving cyclohexene selectivity. Simultaneously, the prepared catalyst exhibits uniform Ru distribution on the nanosheets with high dispersion, using less precious metal Ru, thus reducing the amount of precious metal and lowering production costs. This catalyst solves the problem of large Ru content and easy agglomeration and deactivation in traditional unsupported catalysts. It is used in the selective hydrogenation of benzene to cyclohexene, exhibiting advantages such as high conversion rate and good cyclohexene selectivity.

[0020] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0021] 1. The nanosheet-like TiO2 support synthesized in this invention possesses a unique flower-like structure formed by the assembly of nanosheets. This structure serves as a support for the overall catalyst material, improving the catalyst's mechanical strength, promoting its thermal conductivity, and preventing sintering deactivation caused by localized overheating during the reaction. Furthermore, this structure avoids the problem of low utilization of active components due to the stacking of two-dimensional nanosheets, increases the effective contact between the catalyst and reactants and intermediates, and enhances catalytic efficiency.

[0022] 2. The Ru / TiO2 material synthesized in this invention utilizes the unique texture of nanosheets and the rich pore structure on the surface after etching and acidification to improve the internal diffusion of H2 and the liquid-solid diffusion of cyclohexene in the reaction process, promoting the four-phase reaction of gas-solid-water-oil in the selective hydrogenation of benzene; at the same time, the hydrophilicity of the support increases after etching, which is beneficial to promoting the release of cyclohexene from the reaction system and improving the selectivity of the catalyst.

[0023] 3. In the Ru / TiO2 material synthesized in this invention, the active component Ru is uniformly distributed on the nanosheets, exhibiting high dispersion. It uses less precious metal Ru, thereby reducing the amount of precious metal required and thus lowering production costs, and has broad prospects for industrial application.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the Ru / TiO2 material prepared in Example 1;

[0026] Figure 2 This is a transmission electron microscope image of the Ru / TiO2 material prepared in Example 1;

[0027] Figure 3 The energy spectrum of the Ru / TiO2 material prepared in Example 1 is shown below.

[0028] Figure 4 This is a water contact angle diagram of the Ru / TiO2 material prepared in Example 1;

[0029] Figure 5 The X-ray diffraction pattern of the Ru / TiO2 material prepared in Example 1 is shown below. Detailed Implementation

[0030] In the following examples, the diethylenetriamine was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number D100058-25mL; glycerol was purchased from Tianjin Kemeio Chemical Reagent Co., Ltd., specification AR / 500mL; and titanium isopropoxide was purchased from Beijing Innocare Technology Co., Ltd., product number A34013-500mL. Unless otherwise specified, existing experimental and detection methods were used in the following examples.

[0031] Example 1: A method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst

[0032] The catalyst described in this embodiment includes an active component Ru and a support TiO2 material, wherein the mass of Ru is 10 wt% of TiO2.

[0033] The preparation process in this embodiment is carried out in the following order:

[0034] S1. Add 0.0011 mol diethylenetriamine to 0.422 mol glycerol and stir for 5 minutes until evenly dispersed. Then add 0.0061 mol titanium isopropoxide dropwise and stir for 20 minutes until the sample is homogeneous. Solvothermal treatment at 200℃ for 24 hours. The white precipitate obtained by centrifugation is washed 3-4 times with ethanol and then dried overnight.

[0035] S2. Add 20 mL of NaOH solution (1 mol / L) to 0.1 g of white precipitate, mix well, and then solvothermal at 140 °C for 12 h. Wash with water until pH is neutral, add 40 mL of hydrochloric acid (0.5 mol / L), mix well, and let stand for 12 h. Then wash and dry the precipitate. After drying, calcine the precipitate at 500 °C for 2 h to obtain TiO2 nanosheet support, denoted as TiO2-a.

[0036] S3. Disperse 1g TiO2-a in water (denoted as the carrier solution). Weigh 0.27g RuCl3·H2O and 0.16g NaBH4 and dissolve them separately in a small amount of water. Add ruthenium trichloride solution dropwise to the carrier solution while stirring at 800rpm / min. After stirring for 10min, add NaBH4 solution dropwise and continue stirring for 30min. Wash with deionized water until residual Cl is removed. - After drying, Ru / TiO2-a is obtained.

[0037] The catalyst prepared in this embodiment underwent a series of performance tests, as detailed below.

[0038] like Figure 1 The image shows a scanning electron microscope image of the Ru / TiO2 material prepared in Example 1. The image reveals a unique flower-like structure formed by the assembly of nanosheets.

[0039] likeFigure 2 As shown in the transmission electron microscope image of the Ru / TiO2 material prepared in Example 1, it can be seen that the ruthenium active component is uniformly distributed on the surface of the nanosheets, and the distribution is relatively uniform without agglomeration.

[0040] from Figure 3 The energy dispersive spectroscopy (EDS) spectrum shows that the ruthenium active component is uniformly distributed on the nanosheets, which is consistent with the transmission electron microscopy (TEM) characterization results.

[0041] from Figure 4 The water contact angle diagram shows that the Ru / TiO2 catalyst has strong hydrophilicity.

[0042] like Figure 5 As shown in the XRD pattern of the Ru / TiO2 material prepared in Example 1, TiO2 exhibits tetragonal TiO2 (t-TiO2) diffraction peaks (101), (103), (004), (112), (200) and (204) at 25.3°, 36.9°, 37.8°, 38.6°, 48.1° and 62.7° (PDF#21-1272), indicating that the sample has a good crystal structure.

[0043] Example 2: A method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst

[0044] The catalyst described in this embodiment includes an active component Ru and a support TiO2 material, wherein the mass of Ru is 10 wt% of TiO2.

[0045] The preparation process in this embodiment is carried out in the following order:

[0046] S1. Add 0.0011 mol diethylenetriamine to 0.422 mol glycerol and stir for 5 minutes until evenly dispersed. Then add 0.0061 mol titanium isopropoxide dropwise and stir for 20 minutes until the sample is homogeneous. Solvothermal treatment at 200℃ for 24 hours. The white precipitate obtained by centrifugation is washed 3-4 times with ethanol and then dried overnight.

[0047] S2. Add 20 mL of NaOH solution (1 mol / L) to 0.1 g of white precipitate, mix well, and then solvothermal at 140 °C for 12 h. Wash with water until pH is neutral, add 40 mL of hydrochloric acid (0.5 mol / L), mix well, and let stand for 12 h. Then wash and dry the precipitate. After drying, calcine the precipitate at 600 °C for 2 h to obtain TiO2 nanosheet support, denoted as TiO2-b.

[0048] S3. Disperse 1g TiO2-b in water (denoted as the carrier solution). Weigh 0.27g RuCl3·H2O and 0.16g NaBH4 and dissolve them separately in a small amount of water. Add ruthenium trichloride solution dropwise to the carrier solution while stirring at 800rpm / min. After stirring for 10min, add NaBH4 solution dropwise and continue stirring for 30min. Wash with deionized water until residual Cl is removed. - After drying, Ru / TiO2-b is obtained.

[0049] Example 3: A method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst

[0050] The catalyst described in this embodiment includes an active component Ru and a support material TiO2, wherein the mass of Ru is 2 wt% of TiO2.

[0051] The preparation process in this embodiment is carried out in the following order:

[0052] S1. Add 0.0011 mol diethylenetriamine to 0.422 mol glycerol and stir for 5 minutes until evenly dispersed. Then add 0.0061 mol titanium isopropoxide dropwise and stir for 20 minutes until the sample is homogeneous. Solvothermal treatment at 200℃ for 24 hours. The white precipitate obtained by centrifugation is washed 3-4 times with ethanol and then dried overnight.

[0053] S2. Add 20 mL of NaOH solution (1 mol / L) to 0.1 g of white precipitate, mix well, and then solvothermal at 140 °C for 12 h. Wash with water until pH is neutral, add 40 mL of hydrochloric acid (0.5 mol / L), mix well, and let stand for 12 h. Then wash and dry the precipitate. After washing, calcine the precipitate at 550 °C for 2 h to obtain TiO2 nanosheet support, denoted as TiO2-c.

[0054] S3. Disperse 1g TiO2-c in water, then weigh out 0.05g RuCl3·H2O and 0.03g NaBH4 and dissolve them in a small amount of water respectively. Add ruthenium trichloride solution dropwise to the carrier solution while stirring at 800rpm / min. After stirring for 10min, add NaBH4 solution dropwise and continue stirring for 30min. Wash with deionized water until residual Cl is removed. - After drying, Ru / TiO2-c is obtained.

[0055] Comparative Example 1

[0056] The carrier used in Example 1 was replaced with the intermediate white precipitate (the carrier is denoted as TiO2-d) prepared in step S1. Step S2 was not performed, and the rest of the preparation process was the same as in Example 1.

[0057] Comparative Example 2

[0058] The carrier used in Example 1 was replaced with a sample that was washed to neutrality with NaOH solvent (the carrier is denoted as TNs-e). That is, step S2 was not acidified, and the product obtained by direct calcination was used as the carrier. The rest of the preparation process was the same as in Example 1.

[0059] Comparative Example 3

[0060] The support used in Example 1 was replaced with a commercial anatase TiO2 support sample (the support is denoted as TiO2-f), and the rest of the preparation process was the same as in Example 1, that is, step S3 was performed directly.

[0061] The activity and selectivity of the catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were determined:

[0062] The performance testing of the liquid-phase benzene selective hydrogenation catalyst was conducted in a YZPR series 0.25L high-temperature and high-pressure reactor from Yanzheng Instruments Co., Ltd. First, 0.5g of Ru / TiO2 catalyst, 60mL of H2O, and 12g of ZnSO4·7H2O were added to the reactor. Among numerous additives, ZnSO4·7H2O is widely considered the best additive for effectively improving the selectivity of cyclohexene. Then, 30mL of benzene was added to the storage tank. After purging the reactor and storage tank with hydrogen five times, the temperature was raised at a rate of 5℃ / min. When the temperature reached 140℃, the hydrogen pressure was maintained at 4.0 MPa, and the mixture was stirred at 800 rpm for 4 hours for pretreatment. Then, 30mL of benzene was added through the storage tank, and timing was started, adjusting the hydrogen pressure to 5.0 MPa. Samples were taken every 5 minutes, and the contents of benzene, cyclohexene, and cyclohexane in the oil phase were analyzed using gas chromatography. The product concentration was calculated using area correction and normalization, and then the corresponding conversion rate and cyclohexene selectivity were obtained.

[0063] The catalytic performance obtained in each embodiment is shown in the table below.

[0064] Example Catalyst Reaction time / min Benzene conversion / % Cyclohexene selectivity / % Cyclohexene yield / % Example 1 [Ru / TiO2-a] 30 73.2 58.0 42.5 Example 2 [Ru / TiO2-b] 50 84.0 62.9 52.8 Example 3 [Ru / TiO2-c] 60 81.8 43.1 35.3 Comparative Example 1 [Ru / TiO2-d] 60 38.3 58.6 22.4 Comparative Example 2 Ru / TNs-e 30 86.5 28.7 24.8 Comparative Example 3 [Ru / TiO2-f] 50 42.1 67.6 28.5

[0065] As is well known, the catalytic performance of selective hydrogenation of benzene to cyclohexene is mainly evaluated by considering reaction time, benzene conversion, cyclohexene selectivity, and cyclohexene yield. The catalysts provided in the embodiments and comparative examples of this invention underwent catalytic performance testing. The highest cyclohexene yield was used as the comparison point. From the table above, it can be seen that the cyclohexene yields of the three examples are all higher than those of the comparative examples. Specifically, the cyclohexene yield of Example 2 reached 52.8%. This shows that the ruthenium-based catalyst obtained by this method can achieve high benzene conversion and cyclohexene selectivity, fully meeting the requirements of industrial synthesis, proving that the catalyst in this invention has high industrial application value. The difference in cyclohexene yield between Example 1 and Comparative Examples 1 and 2 demonstrates that the preparation method developed in this invention facilitates the desorption of cyclohexene from the reaction system, improving cyclohexene selectivity and yield.

[0066] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst, characterized in that, Follow these steps in sequence: S1. Mix diethylenetriamine and glycerol evenly to obtain solution A. Then, add titanium isopropoxide dropwise into solution A and stir evenly. Transfer the mixture to a reaction vessel and react at 200°C for 24 hours. The resulting white precipitate is then washed 3-4 times with ethanol and dried. S2. The white precipitate obtained in step S1 is mixed with 1M NaOH solution to obtain solution B. Solution B is stirred for 30 min and then transferred to a reaction vessel. It is reacted at 140℃ for 10 h. The product is washed with water until neutral and then added to 0.5 M hydrochloric acid to obtain solution C. After mixing evenly, it is allowed to stand for 12 h. After centrifugation, washing and drying, the precipitate is calcined to obtain TiO2 support. S3. Disperse the TiO2 support in water, add ruthenium compound dropwise, stir for 1 hour, and then add NaBH4 solution dropwise to obtain a precipitate. The precipitate is washed by centrifugation and dried under vacuum to obtain the catalyst.

2. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: The catalyst comprises an active component Ru and a support TiO2 material, wherein the mass of Ru is 2-10 wt% of TiO2.

3. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: In step S1, the molar ratio of diethylenetriamine, glycerol and titanium isopropoxide is 1:383.64:5.

55.

4. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: In step S2, the mass ratio of the white precipitate to sodium hydroxide and hydrochloric acid is 1:8:7.

3.

5. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: In step S2, the calcination temperature is 500-600℃ and the calcination time is 2h.

6. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: In step S3, the ruthenium compound is ruthenium trichloride, and the molar amount of NaBH4 is four times the molar amount of Ru loaded in the catalyst.

7. The method for preparing a highly efficient titanium dioxide nanosheet-supported Ru catalyst according to claim 1, characterized in that: The catalyst is a flower-shaped nanosheet structure with a thickness of approximately 10 nm.

8. The application of the catalyst obtained by the preparation method according to any one of claims 1-7, characterized in that: The catalyst is used in the selective hydrogenation of benzene to produce cyclohexene.

Images