A core-shell molecular sieve-encapsulated Ni metal catalyst, its preparation method and application

Abstract

This invention provides a core-shell molecular sieve-encapsulated Ni metal catalyst, its preparation method, and its application, addressing the low efficiency of cyclohexanol production via hydrodeoxygenation of phenolic compounds. This invention utilizes a two-stage hydrothermal synthesis method to encapsulate metallic Ni into the molecular sieve framework, preparing a Ni-encapsulated core-shell Silicalite-1 molecular sieve catalyst. A single hydrothermal synthesis yields the nano-molecular sieve Silicalite-1. Using Silicalite-1 as a seed crystal, a template agent is added, followed by a second hydrothermal synthesis to allow the molecular sieve to grow and recrystallize on the surface of the Silicalite-1 seed crystal. During this second hydrothermal growth process, an amino-complexed metal precursor is added, causing the metal precursor nanoclusters to coat the interior of the molecular sieve pores. Through this in-situ complex-assisted synthesis strategy, uniformly dispersed Ni metal particles within the nanocrystalline molecular sieve shell, along with a hierarchical porous core-shell structure suitable for molecular diffusion, are used to catalyze the efficient hydrodeoxygenation of phenolic compounds to cyclohexanol, achieving a phenolic compound conversion rate of up to 98.9% and a cyclohexanol selectivity of up to 99.1%.

Description

Technical Field

[0001] This invention belongs to the field of catalysts and relates to a molecular sieve catalyst with a core-shell structure of encapsulated single metal Ni nanoparticles. Specifically, it relates to a core-shell molecular sieve encapsulated Ni metal catalyst, its preparation method, and its application. Background Technology

[0002] Fossil fuels are the most basic industrial raw materials in the world today. With economic development, people's demand for fossil fuels continues to expand. However, fossil fuels are constrained by their non-renewable nature, prompting people to conduct in-depth research on the industrial utilization of other renewable and clean energy sources, including the development and utilization of biomass resources. Chem Soc Rev. 2021, 50, 6042). Lignocellulose is widely present in biomass and is crucial for the sustainable production of fuels and high-value-added chemicals. However, biomass-derived molecules contain high levels of oxygen and unsaturated groups, resulting in low calorific value and corrosiveness, which limits their further industrial applications. Catalytic hydrogenation of biomass derivatives is an effective solution to these problems. J Catal. 2021, 398, 76). Lignocellulose contains cellulose, hemicellulose, and lignin. Phenolic compounds, as aromatic derivatives of lignin, are monomers obtained through rapid pyrolysis of lignin, mainly including guaiacol and syringyl compounds, which can be converted into many high-value-added fine chemical products through subsequent hydrogenation (deoxygenation). ACS Catal. 2019, 9, 4, 3551). Among the many fine chemicals derived from phenolic compounds, cyclohexanol is an important and economically viable product. Cyclohexanol is a crucial intermediate in the production of fragrances, plasticizers, pharmaceuticals, and polymers, with wide applications. Therefore, phenolic compounds can be converted to cyclohexanol through catalytically controlled hydrodeoxygenation. Developing a highly efficient and selective catalyst for the synthesis of cyclohexanol from guaiacol is of great significance. Appl Catal A: Gen. 2017, 529, 20).

[0003] Among numerous catalysts for the hydrogenation and deoxygenation of phenolic compounds, bifunctional catalysts possessing both metal and acid centers have been widely reported. In particular, bifunctional catalysts constructed by supporting metals on molecular sieves have shown excellent activity in the hydrogenation (deoxygenation) of phenolic compounds to cyclohexanol. Molecular sieves, due to their large specific surface area and large pore volume, are widely used in catalytic conversion. Metal centers are mainly associated with hydrogenation and hydrogenolysis reactions, while acid centers on the molecular sieve surface catalyze dehydration and methanol removal. Due to their wide availability and low cost, non-noble metal catalysts, represented by Ni and Co, have exhibited excellent hydrogenation activity. RSC Adv June 26, 2016 ChenSusChem August 18, 2015 Fuel 2022,327, 125115 Appl Clay Sci 2021, 203, 106003).

[0004] Patent CN 114558612 A discloses a hierarchical porous ZSM-5 molecular sieve-encapsulated Pt-Ni bimetallic catalyst, its preparation method, and its applications. This catalyst is used for the efficient catalytic hydrogenation and deoxygenation of phenolic compounds. Using the Pt-Ni bimetallic catalyst as the active center, the adsorption and activation of hydrogen species by a small amount of noble metal Pt significantly enhances the hydrogenation activity of the Ni metal center. Through an in-situ complex-assisted synthesis strategy, the metal can be fixed inside the micropores of the nanocrystalline molecular sieve, significantly inhibiting the aggregation of the metal active center during preparation and reaction, and improving its dispersion. Furthermore, by utilizing the dynamic pH adjustment process of the molecular sieve synthesis solution from base-acid-base, the encapsulation of the Pt-Ni bimetallic catalyst within the ZSM-5 molecular sieve nanocrystals is achieved. This catalyst can efficiently convert phenolic compounds into cyclohexane through hydrogenation and deoxygenation.

[0005] It is worth noting that the introduction of additional acidic sites into molecular sieves leads to the easy removal of hydroxyl groups from guaiacol, generating cyclohexane and reducing the selectivity of the target product cyclohexanol. Although the wet impregnation method is simple and low-cost for introducing metal active centers, the Oswald ripening process during the preparation and reaction of the metal centers easily leads to their agglomeration and loss of metal active sites during the reaction, further reducing the utilization efficiency of the metal active sites. Furthermore, metal catalysts supported on microporous molecular sieves suffer from reduced utilization efficiency of active sites within the catalyst channels due to the diffusion limitation imposed by the limited microporous structure. Chem Eng J. 2020, 397, 125484).

[0006] Therefore, it is crucial to obtain a catalyst with high catalytic activity, low cost, uniform and stable metal site distribution, and suitable hierarchical pore structure for the hydrogenation and deoxygenation of phenolic compounds to prepare cyclohexanol. Summary of the Invention

[0007] In the hydrodeoxygenation reaction of phenolic compounds, this application addresses the problems of metal center agglomeration and loss of metal active sites in conventional molecular sieve-supported single metal catalysts, as well as the significant diffusion restriction of phenolic compounds by traditional microporous molecular sieves. It proposes a core-shell molecular sieve-encapsulated Ni metal catalyst, its preparation method, and its application.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for preparing a core-shell molecular sieve-encapsulated Ni metal catalyst, the method comprising the following steps: (1) Prepare a Ni-ethylenediamine complex solution by dissolving a nickel source and ethylenediamine in water; (2) After the Ni-ethylenediamine complex solution, template agent I and Silicalite-1 nanocrystalline seed molecular sieve from step (1) are mixed evenly, hydrothermal reaction I is carried out again. After the reaction is completed, the product is post-treated to remove impurities and dried to obtain the molecular sieve precursor. (3) The molecular sieve precursor obtained in step (2) is subjected to a reduction reaction after high-temperature oxidation to obtain a core-shell Silicalite-1 molecular sieve encapsulating Ni nanoparticles.

[0009] Further, the preparation method of Silicalite-1 nanocrystalline seed molecular sieve in step (2) is as follows: template agent II, silicon source and water system are subjected to hydrothermal reaction II. After the reaction is completed, the product is post-treated to remove impurities and calcined to obtain Silicalite-1 nanocrystalline seed molecular sieve.

[0010] Furthermore, the template agent II includes one or both of tetrapropylammonium bromide and tetrapropylammonium hydroxide; the silicon source is one or more of fumed silica, soluble inorganic silicates, organosilicates, silicic acid, and silica sol.

[0011] Further, the molar ratio of template agent II, silicon source and water is (0.5~1):(1~5):(30~55); the temperature of hydrothermal reaction II is 100~250℃ and the time is 1~6 days; after hydrothermal reaction II, drying and calcination are carried out; the calcination conditions are in an oxygen-containing atmosphere, the temperature is 300~650℃ and the time is 2~8h.

[0012] Further, in step (1), the molar ratio of nickel source, ethylenediamine and water is (0.5~2):(2~6):(55~75), and the nickel source is nickel nitrate, nickel sulfate, nickel chloride or its hydrate.

[0013] Further, in step (2), template agent I is one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide and tetrabutylphosphine hydroxide; the mass ratio of Ni-ethylenediamine complex, template agent I and Silicalite-1 nanocrystalline seed molecular sieve is (0.2~2.3):(10~40):(0.5~2).

[0014] Furthermore, in step (2), the temperature of hydrothermal reaction I is 100~250℃ and the time is 0.5~3 days.

[0015] Furthermore, in step (3), the high-temperature oxidation is carried out in an oxygen-containing atmosphere at a temperature of 300~650℃ for 2~8h; the reduction reaction is carried out in a hydrogen atmosphere at a temperature of 200~600℃ for 1~6h.

[0016] Furthermore, the core-shell molecular sieve encapsulated Ni metal catalyst prepared by the above method.

[0017] Furthermore, the core-shell molecular sieve-encapsulated Ni metal catalyst has an MFI crystal structure, which is a hierarchical porous core-shell structure that combines micropores and mesopores; the Ni nanoparticles loaded in the core-shell molecular sieve-encapsulated Ni metal catalyst have a particle size of 1~10nm and a Ni loading of 3~7%.

[0018] Furthermore, in one embodiment of the present invention, the particle size of the core-shell molecular sieve-encapsulated Ni metal catalyst is 100 nm to 800 nm; the specific surface area of ​​the catalyst is 200 to 800 m². 2 / g, pore volume 0.2~0.8cm³ 3 / g.

[0019] Furthermore, the application of the above-mentioned core-shell molecular sieve-encapsulated Ni metal catalyst in the catalytic hydrogenation and deoxygenation of phenolic compounds to prepare cyclohexanol is discussed.

[0020] The reaction mechanism of this invention is as follows: In the first hydrothermal reaction, the template agent acts as a structure guide, combining with the silicon source to form a molecular sieve with a specific structure. At this time, the template agent occupies the molecular sieve channels, and is removed by washing and calcination, forming a porous pure silicon molecular sieve. In the second hydrothermal reaction, the template agent, Ni-ethylenediamine complex, and the already formed Silicalite-1 nanocrystal seed molecular sieve are added together. The alkalinity of the template agent can dissolve the center of the Silicalite-1 nanocrystal seed molecular sieve, forming a hollow structure. The dissolved silicon and template agent can then grow again on the surface of the Silicalite-1 nanocrystal seed molecular sieve. In the second hydrothermal process, the template agent provides alkalinity and acts as a template agent. The added Ni-ethylenediamine complex complexes in situ within the molecular sieve channels and grows dispersedly. After washing and calcination, a core-shell structure molecular sieve encapsulating Ni metal is formed. The hollow catalyst after dissolution and recrystallization has a hierarchical porous structure, less carbon deposition, high reproducibility, and significantly improved catalytic performance.

[0021] The beneficial effects of this invention are: (1) The core-shell molecular sieve-encapsulated Ni metal catalyst prepared in this invention enhances the interaction between the metal and the molecular sieve framework, avoids the agglomeration of metal active centers during preparation and the loss of metal active sites during reaction, and improves the dispersion of metal.

[0022] (2) In the catalyst of the present invention for the hydrogenation and deoxygenation reaction of phenolic compounds, by using Ni as the metal active center and utilizing the excellent adsorption and activation properties of Ni active sites for hydrogen, the reaction rate of hydrogenation and deoxygenation reaction of phenolic compounds is significantly improved.

[0023] (3) The multi-level porous core-shell Silicalite-1 core-shell molecular sieve encapsulating Ni metal catalyst prepared by the present invention finally realizes the efficient hydrogenation and deoxygenation conversion process of phenolic compounds, and is used to catalyze the efficient hydrogenation and deoxygenation of phenolic compounds to prepare cyclohexanol. The conversion rate of phenolic compounds is as high as 98.9%, and the selectivity of cyclohexanol is as high as 99.1%.

[0024] (4) The preparation method of the present invention is simple, the raw materials are cheap and readily available, and it has broad application prospects in the efficient hydrogenation and deoxygenation of phenolic compounds to prepare cyclohexanol. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is the XRD pattern of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 3 of this invention.

[0027] Figure 2 This is a TEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 3 of this invention.

[0028] Figure 3 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 3 of this invention.

[0029] Figure 4 This is a particle size distribution diagram of the Ni metal catalyst encapsulated in a core-shell molecular sieve prepared in Example 3 of the present invention.

[0030] Figure 5 This is the XRD pattern of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 5 of this invention.

[0031] Figure 6 This is a TEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 5 of this invention.

[0032] Figure 7 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 5 of this invention.

[0033] Figure 8 This is a metal particle size distribution diagram of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 5 of the present invention.

[0034] Figure 9 This is the XRD pattern of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 7 of this invention.

[0035] Figure 10 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 7 of this invention.

[0036] Figure 11 This is the XRD pattern of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 10 of this invention.

[0037] Figure 12 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 10 of this invention.

[0038] Figure 13 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 11 of this invention.

[0039] Figure 14 This is a SEM image of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 14 of this invention.

[0040] Figure 15 This is a metal particle size distribution diagram of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 14 of the present invention.

[0041] Figure 16 This is the XRD pattern of the Ni metal catalyst encapsulated in a core-shell molecular sieve prepared in Example 16 of this invention.

[0042] Figure 17 This is the XRD pattern of the core-shell molecular sieve-encapsulated Ni metal catalyst prepared in Example 22 of this invention.

[0043] Figure 18 This is a TEM image of the commercial ZSM-5 molecular sieve catalyst with supported metal prepared in Comparative Example 1.

[0044] Figure 19 This is a metal particle size distribution diagram of the commercial ZSM-5 molecular sieve catalyst with supported metal prepared in Comparative Example 1 of this invention.

[0045] Figure 20 This is a SEM image of the metal-loaded Silicalite-1 molecular sieve prepared in Comparative Example 2 of this invention.

[0046] Figure 21This is a SEM image of the metal-loaded core-shell Silicalite-1 molecular sieve prepared in Comparative Example 3 of this invention.

[0047] Figure 22 a is a comparison graph showing the conversion rates of guaiacol hydrodeoxygenation at 150°C, 175°C, and 200°C for the catalysts obtained in Examples 3, 11, 16, and Comparative Example 1 of this invention. Figure 22 b is a comparison graph showing the selectivity of cyclohexanol in the guaiacol hydrodeoxygenation products of the catalysts obtained in Examples 3, 11, 16, and Comparative Example 1 at 150°C, 175°C, and 200°C.

[0048] Figure 23 This is a comparison chart of the cyclohexanol yields of the catalysts obtained in Examples 3, 11, 16, and Comparative Example 1 during the hydrogenation reaction of phenol at 150°C, 175°C, and 200°C.

[0049] Figure 24 a is a comparison graph showing the conversion rates of guaiacol hydrodeoxygenation at 150°C, 175°C, and 200°C for the catalysts obtained in Examples 1, 3, 6, and Comparative Example 2. Figure 24 b is a comparison graph showing the selectivity of cyclohexanol in the guaiacol hydrodeoxygenation products of the catalysts obtained in Examples 1, 3, 6, and Comparative Example 2 at 150°C, 175°C, and 200°C.

[0050] Figure 25 a is a comparison graph of the conversion rates of guaiacol hydrodeoxygenation of the catalysts obtained in Example 3, Example 18, Example 23 and Comparative Example 3 at 150℃, 175℃ and 200℃; Figure 25 b is a comparison graph showing the selectivity of cyclohexanol in the guaiacol hydrodeoxygenation products of Examples 3, 18, 23, and Comparative Example 3 at 150°C, 175°C, and 200°C. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that: In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0052] Unless otherwise stated, in this instruction manual, "more" in "multiple", "multi-variety", "multiple", etc., means a value of 2 or more.

[0053] Unless otherwise specified, "%" in this instruction manual refers to the percentage content by mass.

[0054] The temperature referred to as "room temperature" in this article is generally between 10℃ and 40℃.

[0055]

Examples 1-5

[0056] Weigh 2g of Ni(NO3)2·6H2O and add it to deionized water to prepare a metal precursor solution with a total mass of 10g. Stir for 30min to mix it evenly. Take 5g of the above-prepared metal precursor solution and add 920μL of ethylenediamine solution. Stir at room temperature for 30min to obtain a Ni-ethylenediamine complex solution.

[0057] Take a certain amount of Ni-ethylenediamine complex solution and slowly add it to 20g of tetrapropylammonium hydroxide (25% TPAOH solution). The solution is clear. Stir at room temperature for 30min. Then add 1g of Silicalite-1 nanocrystalline seed molecular sieve and stir at room temperature for 5min to mix it evenly.

[0058] The synthesis solution was transferred to a hydrothermal reactor for secondary hydrothermal treatment. The static hydrothermal treatment was carried out at 170°C for 24 hours. The resulting hydrothermal product was centrifuged, washed four times with deionized water, and dried in an oven at 120°C for 6 hours to obtain the molecular sieve precursor.

[0059] The obtained molecular sieve precursor was calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours, and then reduced in a hydrogen atmosphere in a reduction furnace at 550°C for 4 hours to obtain the hierarchical porous core-shell Silicalite-1 molecular sieve catalyst encapsulated with single metal Ni.

[0060] The mass of the Ni-ethylenediamine complex solution used in Example 1 was 0.866 g, and the loading amount calculated based on metallic Ni was 3%.

[0061] The mass of the Ni-ethylenediamine complex solution used in Example 2 was 1.155 g, and the loading amount calculated based on metallic Ni was 4%.

[0062] The mass of the Ni-ethylenediamine complex solution used in Example 3 was 1.443 g, and the loading amount calculated based on metallic Ni was 5%.

[0063] The mass of the Ni-ethylenediamine complex solution used in Example 4 was 1.732 g, and the loading amount calculated based on metallic Ni was 6%.

[0064] The mass of the Ni-ethylenediamine complex solution used in Example 5 was 2.021 g, and the loading amount calculated based on metallic Ni was 7%.

[0065] Figure 1 The XRD pattern of Example 3, compared with the PDF card (JCPDS-44-0003) in Jade software, shows that it has a typical MFI molecular sieve crystal form and no diffraction peaks corresponding to single metal Ni were found. Figure 2 The TEM image shown is from Example 3. The catalyst was formed by recrystallization of Silicalite-1 nanocrystals. The Silicalite-1 monomers, with a hierarchical porous core-shell structure, are hexagonal prisms with a size of 160 nm. A small amount of Ni metal can be observed encapsulated within the core-shell Silicalite-1. The molecular sieve catalyst has a specific surface area of ​​373 m². 2 / g, pore volume is 0.42cm³ 3 / g, and the nano-metal particles are dispersed inside the molecular sieve. Figure 3 The image shown is an SEM image of Example 3, which shows its basic hexagonal prism morphology, similar to that of the TEM image. Figure 4 The image shows the particle size distribution of the prepared catalyst. The average particle size of the nano-metal particles obtained by statistical analysis is 4.00 nm.

[0066] Figure 5 The XRD pattern in Example 5 is compared with the PDF card (JCPDS-44-0003) in Jade software. It also belongs to the MFI crystal form. Compared with the standard Ni card, no diffraction peaks of metallic Ni were observed. Figure 6 The TEM image shown in Example 5 reveals a large number of Ni nanoparticles entering the core-shell structure of the Silicalite-1 molecular sieve. Figure 7 The image shown is an SEM image of the catalyst prepared in Example 5, which shows its basic hexagonal prism morphology, similar to that in the TEM image. Figure 8 The figure shows the metal particle size distribution of the catalyst prepared in Example 5. The average particle size of the nano-metal particles obtained by statistics is 5.59 nm.

[0067] Verification showed that the catalyst monomers prepared in Examples 2-4 had an average particle size of 100 nm to 700 nm, and the molecular sieves possessed an MFI structure; the encapsulated nano-metal particles had an average particle size of 1 nm to 10 nm; and the catalyst specific surface area was 200 m². 2 / g~800m 2 / g, pore volume 0.2cm³ 3 / g~0.8cm 3 / g.

[0068]

Examples 6-10

[0069] Weigh 6.5g of tetrapropylammonium hydroxide (25% TPAOH solution) and add it to 7.719g of deionized water. Stir at room temperature, and add 4.16g of TEOS dropwise while stirring. Continue stirring at room temperature for 3 hours. After stirring, transfer the mixed solution to a hydrothermal reactor and perform static hydrothermal treatment at 220℃ for 1.5 days. Centrifuge the hydrothermal product, wash it 4 times with deionized water, dry it in an oven at 120℃ for 6 hours, and calcine it at 650℃ for 2 hours in an air atmosphere in a muffle furnace to obtain the product Silicalite-1 nanocrystalline seed molecular sieve.

[0070] Weigh 2g of Ni(NO3)2·6H2O and add it to deionized water to prepare a Ni precursor solution with a total mass of 10g. Stir for 30min to mix it evenly. Take 5g of the prepared precursor solution and add 920μL of ethylenediamine solution. Stir at room temperature for 30min to obtain a Ni-ethylenediamine complex solution.

[0071] Take 1.443g of Ni-ethylenediamine complex solution and slowly add it to 20g of tetrapropylammonium hydroxide (25% TPAOH solution). The solution is clear. Stir at room temperature for 30min. Then add a certain amount of Silicalite-1 nanocrystalline seed molecular sieve and stir at room temperature for 5min to mix it evenly.

[0072] The synthesis solution was transferred to a hydrothermal reactor for secondary hydrothermal treatment. The static hydrothermal treatment was carried out at 250°C for 12 hours. The resulting hydrothermal product was centrifuged, washed four times with deionized water, and dried in an oven at 120°C for 6 hours to obtain the molecular sieve precursor.

[0073] The obtained molecular sieve precursor was calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours, and then reduced in a hydrogen atmosphere in a reduction furnace at 550°C for 4 hours to obtain the hierarchical porous core-shell Silicalite-1 molecular sieve catalyst encapsulated with single metal Ni.

[0074] In Example 6, the mass of the Silicalite-1 nanocrystalline seed molecular sieve used before the secondary hydrothermal treatment was 0.4 g.

[0075] In Example 7, the mass of the Silicalite-1 nanocrystalline seed molecular sieve used before the secondary hydrothermal treatment was 0.8g.

[0076] In Example 8, the mass of the Silicalite-1 nanocrystalline seed molecular sieve used before the secondary hydrothermal treatment was 1.2g.

[0077] In Example 9, the mass of the Silicalite-1 nanocrystalline seed molecular sieve used before the secondary hydrothermal treatment was 1.6g.

[0078] In Example 10, the mass of the Silicalite-1 nanocrystalline seed molecular sieve used before the secondary hydrothermal treatment was 2g.

[0079] Figure 9 The XRD pattern of Example 7 is compared with the PDF card (JCPDS-44-0003) in Jade software. It can be found that it has a typical MFI molecular sieve crystal form, with small peak width, sharp characteristic peaks, and high crystallinity. Figure 10 The SEM image of Example 7 shows its hexagonal prism-like monomer morphology. Figure 11 The XRD pattern of Example 10, compared with the PDF card (JCPDS-44-0003) in Jade software, shows that it possesses a typical MFI molecular sieve crystal structure, but its full width at half maximum (FWHM) is relatively wide, and its characteristic peaks are low, indicating low crystallinity. This suggests that the amount of Silicalite-1 nanocrystals added affects its secondary crystallinity. Figure 12 The SEM image of Example 10 shows that it has a basic hexagonal prism structure and the molecular sieve has some irregular morphology.

[0080] Verification showed that the catalyst monomers prepared in Examples 6-9 had an average particle size of 100 nm to 700 nm, the molecular sieves had an MFI crystal structure, and the encapsulated nano-metal particles had an average particle size of 1 nm to 10 nm; the catalyst specific surface area was 200 m². 2 / g~800m 2 / g, pore volume 0.2cm³ 3 / g~0.8cm 3 / g.

[0081]

Examples 11-15

[0082] Weigh 4g of tetrapropylammonium hydroxide (25% TPAOH solution) and add it to 5.5g of deionized water. Stir at room temperature, and add 4g of sodium silicate dropwise while stirring. Continue stirring at room temperature for 9 hours. After stirring, transfer the mixed solution to a hydrothermal reactor and statically hydrothermally treat it at 170℃ for 3 days. Centrifuge the hydrothermal product, wash it 4 times with deionized water, dry it in an oven at 120℃ for 6 hours, and calcine it at 550℃ for 6 hours in an air atmosphere in a muffle furnace to obtain the product Silicalite-1 nanocrystalline seed molecular sieve.

[0083] Weigh 0.53g of nickel sulfate and add it to deionized water to prepare a Ni precursor solution with a total mass of 8g. Stir for 30min to mix it evenly. Take 4g of the prepared precursor solution and add 700μL of ethylenediamine solution. Stir at room temperature for 30min to obtain a Ni-ethylenediamine complex solution.

[0084] Take 1.443g of Ni-ethylenediamine complex solution and slowly add it to a certain amount of template agent. The solution is clear. Stir at room temperature for 30min. Then add 1g of Silicalite-1 nanocrystalline seed molecular sieve and stir at room temperature for 5min to mix it evenly.

[0085] The synthesis solution was transferred to a hydrothermal reactor for secondary hydrothermal treatment. The static hydrothermal treatment was carried out at 100°C for 3 days. The obtained hydrothermal product was centrifuged, washed 4 times with deionized water, and dried in an oven at 120°C for 6 hours to obtain the molecular sieve precursor.

[0086] The obtained molecular sieve precursor was calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours, and then reduced in a hydrogen atmosphere in a reduction furnace at 550°C for 4 hours to obtain the hierarchical porous core-shell Silicalite-1 molecular sieve catalyst encapsulated with single metal Ni.

[0087] In Example 11, the template agent slowly added to the 1.443g Ni-ethylenediamine complex solution was tetrapropylammonium hydroxide (25% TPAOH solution), and the added mass was 5g.

[0088] In Example 12, the template agent slowly added to the 1.443g Ni-ethylenediamine complex solution was tetrapropylammonium hydroxide (25% TPAOH solution), and the added mass was 10g.

[0089] In Example 13, the template agent in the 1.443g Ni-ethylenediamine complex solution was tetrapropylammonium hydroxide (25% TPAOH solution), and the added mass was 15g.

[0090] In Example 14, the template agent in the 1.443g Ni-ethylenediamine complex solution was tetrapropylammonium bromide (TPABr), and the added mass was 15g.

[0091] In Example 15, the template agent in the 1.443g Ni-ethylenediamine complex solution was tetrapropylammonium bromide (TPABr), and the added mass was 20g.

[0092] Figure 13 The image shown is a SEM image of Example 11. It can be observed that it has a complete hexagonal prism morphology of Silicalite-1 and a complete molecular sieve surface structure. Figure 14 The image shown is a SEM image of Example 13. It shows that a number of pores were generated on the basic morphology of Silicalite-1. This is the pore appearance formed by the destruction of the molecular sieve by tetrapropylammonium hydroxide (25% TPAOH solution) as a strong base. The core-shell structure can be directly observed from the TEM image. Figure 15 This is a particle size distribution diagram of the catalyst prepared in Example 13, which shows that the particle size of the monomer nanomolecular sieve is 305.02 nm.

[0093] Verification showed that the average particle size of the catalyst monomers prepared in Examples 11-15 was 100 nm to 700 nm. Changing the type of template agent did not affect the crystal form of the molecular sieve. The molecular sieves all had an MFI crystal structure, and the average particle size of the encapsulated nano-metal particles was 1 nm to 10 nm. The catalyst specific surface area was 200 m². 2 / g~800m 2 / g, pore volume 0.2cm³ 3 / g~0.8cm 3 / g.

[0094]

Examples 16-21

[0095] Weigh 8g of tetrapropylammonium hydroxide (25% TPAOH solution) and add it to 10g of deionized water. Stir at room temperature, and add 3.9g of silicic acid dropwise while stirring. Continue stirring at room temperature for 6 hours. After stirring, transfer the mixed solution to a hydrothermal reactor and statically hydrothermally treat it at 100℃ for 6 days. Centrifuge the hydrothermal product, wash it 4 times with deionized water, dry it in an oven at 120℃ for 6 hours, and calcine it at 300℃ for 8 hours in an air atmosphere in a muffle furnace to obtain the product Silicalite-1 nanocrystalline seed molecular sieve.

[0096] Weigh 1.1g of Ni(NO3)2·6H2O and add it to deionized water to prepare a Ni precursor solution with a total mass of 6.2g. Stir for 30min to mix it evenly. Take 3.1g of the prepared precursor solution and add 250μL of ethylenediamine solution. Stir at room temperature for 30min to obtain a Ni-ethylenediamine complex solution.

[0097] Take 1.443g of Ni-ethylenediamine complex solution and slowly add it to 20g of tetrapropylammonium bromide (TPABr). The solution is clear. Stir at room temperature for 30min. Then add 1g of Silicalite-1 nanocrystalline seed molecular sieve and stir at room temperature for 5min to mix it evenly.

[0098] The synthesis solution was transferred to a hydrothermal reactor for secondary hydrothermal treatment. The static hydrothermal treatment was carried out at 170°C for 24 hours. The resulting hydrothermal product was centrifuged, washed four times with deionized water, and dried in an oven at 120°C for 6 hours to obtain the molecular sieve precursor.

[0099] The obtained molecular sieve precursor was calcined in an air atmosphere in a muffle furnace at 300°C for 8 hours, and then reduced in a hydrogen atmosphere in a reduction furnace at a certain temperature for a certain time to obtain a hierarchical porous core-shell Silicalite-1 molecular sieve catalyst encapsulated with single metal Ni.

[0100] The reduction temperature used in Example 16 was 200°C, and the reduction time was 6 hours.

[0101] The reduction temperature used in Example 17 was 300°C, and the reduction time was 4 hours.

[0102] The reduction temperature used in Example 18 was 500°C, and the reduction time was 4 hours.

[0103] The reduction temperature used in Example 19 was 400°C, and the reduction time was 4 hours.

[0104] The reduction temperature used in Example 20 was 400°C, and the reduction time was 3 hours.

[0105] The reduction temperature used in Example 21 was 400°C, and the reduction time was 5 hours.

[0106] Figure 16 The image shows the XRD pattern of the catalyst prepared in Example 16. Comparing it with the PDF card (JCPDS-44-0003) in Jade software, it can be found that it has a typical MFI molecular sieve crystal form. Compared with the standard card of nickel oxide, no obvious diffraction peaks of nickel oxide were observed, which may be due to the high dispersion of nickel oxide in the molecular sieve channels.

[0107] As can be seen from Examples 16-21, the reduction temperature affects the reduction process of the metal, resulting in insufficient reduction of nickel oxide to elemental nickel. The reduction time of 3-5 hours did not change the valence state of the encapsulated metal within the molecular sieve. The average particle size of the prepared catalyst monomer was 200 nm-800 nm, the molecular sieve exhibited MFI crystal form, and the average particle size of the encapsulated nano-metal particles was 1 nm-10 nm. The catalyst specific surface area was 200 m² / m³. 2 / g~800m 2 / g, pore volume 0.2cm³ 3 / g~0.8cm 3 / g.

[0108]

Examples 22-26

[0109] Weigh 5g of tetrapropylammonium bromide (25% TPABr solution) and add it to 6.5g of deionized water. Stir at room temperature, and add 2.7g of propyl silicate dropwise while stirring. Continue stirring at room temperature for 6 hours. After stirring, transfer the mixed solution to a hydrothermal reactor and perform static hydrothermal treatment at 250℃ for 1 day. Centrifuge the hydrothermal product, wash it 4 times with deionized water, dry it in an oven at 120℃ for 6 hours, and calcine it at 550℃ for 4 hours in an air atmosphere in a muffle furnace to obtain the product Silicalite-1 nanocrystalline seed molecular sieve.

[0110] Weigh 1.6g of NiCl2·6H2O and add it to deionized water to prepare a Ni precursor solution with a total mass of 10g. Stir for 30min to mix it evenly. Take 5g of the prepared precursor solution and add 900μL of ethylenediamine solution. Stir at room temperature for 30min to obtain a Ni-ethylenediamine complex solution.

[0111] Take 1.443g of Ni-ethylenediamine complex solution and slowly add it to 20g of tetrabutylphosphine hydroxide (TBOPH). The solution is clear. Stir at room temperature for 30min. Then add 1g of Silicalite-1 nanocrystalline seed molecular sieve and stir at room temperature for 5min to mix it evenly.

[0112] The synthesis solution was transferred to a hydrothermal reactor for secondary hydrothermal treatment. The static hydrothermal treatment was carried out at 170°C for 24 hours. The resulting hydrothermal product was centrifuged, washed four times with deionized water, and dried at a certain temperature for a period of time to obtain the molecular sieve precursor.

[0113] The obtained molecular sieve precursor was calcined in an air atmosphere in a muffle furnace at a certain temperature for a period of time; then reduced in a hydrogen atmosphere in a reduction furnace at 600℃ for 1 hour. This yielded a hierarchical porous core-shell Silicalite-1 molecular sieve catalyst encapsulated with monometallic Ni.

[0114] In Example 22, the drying temperature used after the second hydrothermal synthesis was 110°C and the drying time was 4 hours; the calcination temperature used was 450°C and the calcination time was 4 hours.

[0115] In Example 23, the drying temperature used after the second hydrothermal synthesis was 120°C and the drying time was 4 hours; the calcination temperature used was 550°C and the calcination time was 4 hours.

[0116] In Example 24, the drying temperature used after the second hydrothermal synthesis was 130°C and the drying time was 4 hours; the calcination temperature used was 650°C and the calcination time was 4 hours.

[0117] In Example 25, the drying temperature used after the second hydrothermal synthesis was 120°C and the drying time was 3 hours; the calcination temperature used was 550°C and the calcination time was 3 hours.

[0118] In Example 26, the drying temperature used after the second hydrothermal synthesis was 120°C, and the drying time was 5 hours; the calcination temperature used was 550°C, and the calcination time was 5 hours.

[0119] Figure 17The XRD pattern of the catalyst prepared in Example 22 is shown. Comparison with the PDF card (JCPDS-44-0003) in Jade software reveals that it possesses a typical MFI molecular sieve crystal form. Examples 22-26 demonstrate that when drying and calcination conditions fall within the scope of this invention, the molecular sieve crystal type remains unchanged. The average particle size of the prepared catalyst monomers is 200 nm to 700 nm, the molecular sieve exhibits an MFI crystal form, and the average particle size of the encapsulated nano-metal particles is 1 nm to 10 nm; the catalyst specific surface area is 200 m². 2 / g~800m 2 / g, pore volume 0.2cm³ 3 / g~0.8cm 3 / g.

[0120] Comparative Example 1 In this comparative example, ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 100 (Si / Al=100) (purchased from the catalyst factory of Nankai University) was used as a support to prepare a ZSM-5 supported Ni catalyst by wet impregnation method, with a metallic Ni loading of 5%.

[0121] Weigh 1.24g Ni(NO3)2·6H2O, add 7.76g deionized water, and stir for five minutes at room temperature to prepare Ni metal impregnation solution.

[0122] Weigh 1g of commercial ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 100 (Si / Al=100), and slowly drip 1.8g of the metal impregnation solution prepared in the previous step into the molecular sieve. Stir for two minutes to ensure uniform impregnation of the molecular sieve. Then place it in an oven at 30℃, 60℃, and 120℃ and dry for 6 hours each.

[0123] The dried molecular sieve was ground and placed in a muffle furnace and calcined at 550°C for 6 hours in an air atmosphere; then it was reduced at 550°C for 4 hours in a reduction furnace in a hydrogen atmosphere to obtain a commercially available Ni-supported ZSM-5 molecular sieve (Si / Al=100).

[0124] Figure 18 The image shown is a TEM image of the catalyst prepared in Comparative Example 1. It can be observed that the metal particles significantly agglomerate and are distributed on the catalyst surface. The molecular sieve catalyst has an average particle size of 272 nm, a specific surface area of ​​416 m² / g, and a total pore volume of 0.27 cm³ / g.

[0125] Figure 19 The figure shows the metal particle size distribution of the catalyst prepared in Comparative Example 1. The average particle size of the nano-metal particles obtained by statistics is 8.9 nm.

[0126] Comparative Example 2 In this comparative example, pure silicate-1 nanomolecular sieves were used as a support to prepare a pure silicate-1 supported Ni catalyst using a wet impregnation method. The loading of metallic Ni was 5%. The specific steps are as follows: First, pure silicon Silicalite-1 nanomolecular sieves were prepared as a carrier. 6.5 g of tetrapropylammonium hydroxide (25% TPAOH solution) was weighed and added to 7.719 g of deionized water. The mixture was stirred at room temperature, and 4.16 g of TEOS was added dropwise during stirring. Stirring continued for 6 hours at room temperature. After stirring, the mixture was transferred to a hydrothermal reactor and statically hydrothermally treated at 170 °C for 6 hours. The hydrothermal product was centrifuged, washed four times with deionized water, dried in an oven at 120 °C for 6 hours, and calcined at 550 °C for 6 hours in an air atmosphere in a muffle furnace to obtain the pure silicon Silicalite-1 nanomolecular sieve.

[0127] Weigh 1.24g Ni(NO3)2·6H2O, add 7.76g deionized water, and stir for five minutes at room temperature to prepare Ni metal impregnation solution.

[0128] Weigh 1g of the pure silicon Silicalite-1 nanomolecular sieve prepared above, and slowly drip 1.8g of the prepared Ni metal impregnation solution into the molecular sieve. Stir for five minutes to ensure uniform impregnation of the molecular sieve. Then place it in an oven at 30℃, 60℃, and 120℃ and dry for 6 hours respectively.

[0129] The dried molecular sieve was ground and placed in a muffle furnace and calcined at 550°C for 6 hours in an air atmosphere; then it was reduced at 550°C for 4 hours in a reduction furnace in a hydrogen atmosphere to obtain Ni-loaded pure silicon Silicalite-1 nanomolecular sieve.

[0130] Figure 20 The SEM image for Comparative Example 2 shows a complete hexagonal prism structure with obvious metal clusters attached to the surface. The prepared catalyst exhibits the MFI crystal form, with an average particle size of 245 nm and a mesopore volume of 0.16 cm³. 3 / g, total specific surface area is 383m² 2 / g.

[0131] Comparative Example 3 In this comparative example, a core-shell Silicalite-1 nanomolecular sieve was used as a support to prepare a core-shell Silicalite-1 supported Ni catalyst by a wet impregnation method. The loading of metallic Ni was 5%. The specific preparation steps are as follows: First, pure silicon Silicalite-1 nanocrystalline molecular sieves were prepared as seed crystals. 6.5 g of tetrapropylammonium hydroxide (25% TPAOH solution) was weighed and added to 7.719 g of deionized water. The mixture was stirred at room temperature, and 4.16 g of TEOS was added dropwise during stirring. The mixture was stirred continuously at room temperature for 6 hours. After stirring, the mixed solution was transferred to a hydrothermal reactor and statically hydrothermally treated at 170 °C for 6 hours. The hydrothermal product was centrifuged, washed four times with deionized water, dried in an oven at 120 °C for 6 hours, and calcined at 550 °C for 6 hours in an air atmosphere in a muffle furnace to obtain the pure silicon Silicalite-1 nanocrystalline seed molecular sieve.

[0132] Take 20g of tetrapropylammonium hydroxide (25% TPAOH solution), then add 1g of Silicalite-1 nanocrystalline seed molecular sieve, and stir for 5 minutes at room temperature to mix it evenly.

[0133] The synthesis solution was transferred to a hydrothermal reactor for a second time and statically hydrothermally treated at 170°C for 24 hours. The resulting hydrothermal product was centrifuged, washed four times with water, dried at 120°C for 6 hours, ground, and then calcined in air at 550°C for 6 hours to obtain a core-shell structured Silicalite-1 molecular sieve catalyst.

[0134] Weigh 1.24g Ni(NO3)2·6H2O, add 7.76g deionized water, and stir for five minutes at room temperature to prepare Ni metal impregnation solution.

[0135] Weigh 1g of the core-shell structured Silicalite-1 molecular sieve catalyst prepared above, and slowly drop 1.8g of the prepared Ni metal impregnation solution into the molecular sieve. Stir for five minutes to ensure uniform wetting of the molecular sieve. Then place it in an oven at 30℃, 60℃, and 120℃ for 6 hours each. Grind the dried molecular sieve and place it in a muffle furnace for calcination at 550℃ for 6 hours in air.

[0136] Subsequently, the catalyst was reduced in a reduction furnace at 550°C for 4 hours under a hydrogen atmosphere to obtain the Ni-supported core-shell Silicalite-1 molecular sieve catalyst.

[0137] Figure 21 The image shown is a SEM image of the catalyst prepared in Comparative Example 3. It can be observed that the catalyst has a disrupted porous structure, a basic hexagonal prism structure, and obvious metal agglomerations on the surface. The specific surface area of ​​the catalyst is 395 m². 2 / g, the total pore volume of the catalyst is 0.40 cm³. 3 / g, the mesopore volume of the catalyst is 0.29cm³. 3 / g.

[0138] Application 1 The molecular sieve catalysts prepared in Examples 3, 11, 16, and Comparative Example 1 were used for the hydrodeoxygenation reaction of guaiacol. The specific operation was as follows: 60 ml of n-dodecane, 300 μl of n-pentadecane, and 0.5 g of guaiacol were mixed and stirred thoroughly before being placed in a reactor. 0.05 g of the catalyst was added to the reactor, and H2 was introduced to bring the pressure inside the reactor to 3 MPa. The heating rate was 10 °C / min, and the reaction was carried out at a certain temperature, reaction pressure of 3 MPa, and reaction time of 3 h. The obtained product was analyzed by gas chromatography.

[0139] Figure 22 Figure a compares the conversion rates of guaiacol hydrodeoxygenation at 150°C, 175°C, and 200°C for Examples 3, 11, 16, and Comparative Example 1. As can be seen from the figure, at the same reaction temperature, the core-shell molecular sieve catalyst encapsulated with 5% Ni prepared in Example 3 exhibits the highest conversion rate, reaching 98.9% at 200°C. This catalytic conversion rate is significantly higher than that of the catalysts prepared in Examples 11, 16, and Comparative Example 1. The higher conversion rate of Example 3 compared to the 85% conversion rate of the solid structure in Example 11 is due to the core-shell structure having more mesopores, which facilitates the diffusion of reactant molecules and thus increases the reaction rate. The higher conversion rate of Example 3 compared to Example 16 is because the nickel oxide in Example 16 was not fully reduced to elemental nickel, resulting in a lack of metal active sites and thus lower hydrodeoxygenation activity. The reaction activities of the catalysts prepared in different examples at different temperatures show the same trend: for the same catalyst, the conversion rate increases with increasing reaction temperature.

[0140] Figure 22 Figure b shows a comparison of the selectivity of cyclohexanol in the hydrodeoxygenation reaction of guaiacol in Examples 3, 11, 16, and Comparative Example 1 at 150°C, 175°C, and 200°C. It can be observed that the core-shell molecular sieve catalyst encapsulated with 5% Ni prepared in Example 3 has the highest selectivity, reaching 99.1% after three hours at 200°C. The molecular sieve prepared in Comparative Example 1, due to the presence of Al sites, produces a large amount of cyclohexane, thus reducing the selectivity of cyclohexanol to 62.0%. The molecular sieves prepared in Examples 11 and 16 also exhibit considerably high cyclohexanol selectivity, reaching 97.2% and 96.8%, respectively. Furthermore, the catalysts prepared in different examples show the same pattern in their cyclohexanol selectivity at different temperatures; that is, with the same catalyst at different temperatures, the cyclohexanol selectivity increases with increasing reaction temperature.

[0141] Figure 23This is a comparison graph showing the cyclohexanol yields in the hydrogenation reactions of phenol at 150°C, 175°C, and 200°C for Examples 3, 11, 16, and Comparative Example 1. As shown in the graph, the catalyst synthesized in Example 3 achieved a 92.5% yield of cyclohexanol to phenol hydrogenation in three hours at 200°C, which is higher than the yields of the catalysts synthesized in Examples 11, 16, and Comparative Example 1 under the same reaction conditions. This demonstrates that the catalysts prepared in this invention exhibit equally efficient catalytic conversion performance for the hydrogenation of different phenolic compounds. The cyclohexanol yields of the catalysts prepared in Examples 3, 11, 16, and Comparative Example 1 all increased with increasing reaction temperature. Therefore, for the different catalysts prepared in this invention, increasing the reaction temperature can increase the cyclohexanol yield in the hydrogenation reaction of phenol.

[0142] Application 2 In this application example, cyclohexanol was prepared by catalytic synthesis of guaiacol at 150℃, 175℃, and 200℃ using Examples 1, 3, 6, and Comparative Example 2, respectively. The operation steps were the same as in Application Example 1, and the results are as follows: Figure 24 Figure a compares the conversion rates of guaiacol hydrodeoxygenation at 150°C, 175°C, and 200°C for Examples 1, 3, 6, and Comparative Example 2. The figure shows that Example 3 has the highest conversion rate at the same temperature. Example 1 has a conversion rate of 92%. Example 1 uses a core-shell molecular sieve catalyst encapsulated with 3% Ni. The reduced metal encapsulation may have decreased the number of active metal sites participating in the reaction, leading to a decrease in reaction activity. Example 6 has a conversion rate of 84%, also lower than Example 1. This is because Example 6 added less Silicalite-1 seed crystals during the secondary synthesis, affecting the molecular sieve framework after the secondary hydrothermal synthesis, which is detrimental to metal encapsulation and results in reduced reaction activity. Comparative Example 2 has the lowest conversion rate at only 65%. This is because the Silicalite-1 molecular sieve has a single microporous structure, which is not conducive to the diffusion of reactant molecules in the molecular sieve catalyst. Furthermore, the impregnation method for loading metal leads to metal agglomeration on the molecular sieve surface, preventing the active sites from fully participating in the catalytic reaction.

[0143] Figure 24 b is a comparison chart of the selectivity of cyclohexanol in the hydrodeoxygenation reaction of guaiacol in Examples 1, 3, 6, and Comparative Example 2 at 150°C, 175°C, and 200°C. Example 3 showed the highest selectivity, and the selectivity of cyclohexanol increased with increasing temperature. The catalysts prepared in the other examples also showed the same trend.

[0144] Figure 25a is a comparison chart of the hydrogenation deoxygenation conversion rates of guaiacol in Examples 3, 18, 23, and Comparative Example 3 at 150°C, 175°C, and 200°C. Figure 25 b. Comparison of cyclohexanol selectivity in the guaiacol hydrodeoxygenation reaction of Examples 3, 18, 23, and Comparative Example 3 at 150°C, 175°C, and 200°C. The graph shows that the conversion rates and cyclohexanol selectivities of Examples 3, 18, and 23 at the same temperature are similar. This indicates that in this invention, changing the calcination temperature, drying temperature, metal reduction temperature, and reduction time has little effect on the catalytic reaction results, and all exhibit high catalytic activity. The conversion rate and cyclohexanol selectivity of Comparative Example 3 are 65% and 80%, respectively, which are much lower than the molecular sieves prepared in Examples 3, 18, and 23. This is because the metal agglomerates formed on the surface of the molecular sieve obtained by impregnation with metal are not conducive to the participation of metal active sites in the catalytic process, thus weakening the catalytic performance of the guaiacol hydrodeoxygenation reaction.

[0145] The molecular sieve catalyst provided by this invention can be prepared industrially and can be used for efficient catalysis of the hydrogenation and deoxygenation of phenolic compounds to prepare cyclohexanol.

[0146] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation and deoxygenation of phenolic compounds to cyclohexanol, characterized in that, The method includes the following steps: (1) Prepare a Ni-ethylenediamine complex solution by dissolving a nickel source and ethylenediamine in water; the molar ratio of nickel source, ethylenediamine and water in step (1) is (0.5~2):(2~6):(55~75), and the nickel source is nickel nitrate, nickel sulfate, nickel chloride or its hydrate; (2) After the Ni-ethylenediamine complex solution, template agent I and Silicalite-1 nanocrystalline seed molecular sieve from step (1) are mixed evenly, hydrothermal reaction I is carried out again. After the reaction is completed, the product is post-treated to remove impurities and dried to obtain the molecular sieve precursor. (3) The molecular sieve precursor obtained in step (2) is subjected to a reduction reaction after high-temperature oxidation to obtain a core-shell Silicalite-1 molecular sieve encapsulating Ni nanoparticles; the preparation method of Silicalite-1 nanocrystal seed molecular sieve in step (2) is as follows: template agent II, silicon source and water system are subjected to hydrothermal reaction II, and after the reaction is completed, the product is post-treated to remove impurities and calcined to obtain Silicalite-1 nanocrystal seed molecular sieve.

2. The method for preparing a core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation deoxygenation of phenolic compounds to cyclohexanol according to claim 1, characterized in that, The template agent II includes one or both of tetrapropylammonium bromide and tetrapropylammonium hydroxide; the silicon source is one or more of fumed silica, soluble inorganic silicates, organosilicates, silicic acid and silica sol.

3. The method for preparing a core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation deoxygenation of phenolic compounds to cyclohexanol according to claim 2, characterized in that, The molar ratio of template agent II, silicon source and water is (0.5~1):(1~5):(30~55); the temperature of hydrothermal reaction II is 100~250℃ and the time is 1~6 days; after hydrothermal reaction II, it is dried and calcined; the calcination conditions are in an oxygen-containing atmosphere, the temperature is 300~650℃ and the time is 2~8h.

4. The method for preparing the core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation deoxygenation of phenolic compounds to cyclohexanol according to claim 3, characterized in that, In step (2), template agent I is one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, and tetrabutylphosphine hydroxide; the mass ratio of Ni-ethylenediamine complex, template agent I, and Silicalite-1 nanocrystalline seed molecular sieve is (0.2~2.3):(10~40):(0.5~2); the temperature of hydrothermal reaction I is 100~250℃, and the time is 0.5~3 days.

5. The method for preparing the core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation deoxygenation of phenolic compounds to cyclohexanol according to claim 4, characterized in that, In step (3), the high-temperature oxidation is carried out in an oxygen-containing atmosphere at a temperature of 300-650°C for 2-8 hours; the reduction reaction is carried out in a hydrogen atmosphere at a temperature of 200-600°C for 1-6 hours.

6. A core-shell molecular sieve-encapsulated Ni metal catalyst for catalyzing the hydrogenation and deoxygenation of phenolic compounds to cyclohexanol, prepared by the method according to any one of claims 1 to 5.

7. The core-shell molecular sieve-encapsulated Ni metal catalyst for the catalytic hydrogenation deoxygenation of phenolic compounds to cyclohexanol according to claim 6, characterized in that: The core-shell molecular sieve-encapsulated Ni metal catalyst has an MFI crystal structure, which is a hierarchical porous core-shell structure that combines micropores and mesopores; the Ni nanoparticles loaded in the core-shell molecular sieve-encapsulated Ni metal catalyst have a particle size of 1~10nm and a Ni loading of 3~7%.

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