A hydrophobic catalyst for the hydrogention of alpha, beta-unsaturated aldehydes in aqueous phase and a process for its preparation

Abstract

The application relates to the technical field of catalytic materials, and discloses an alpha, beta-unsaturated aldehyde aqueous-phase hydrogenation hydrophobic catalyst and a preparation method thereof, which comprises the following preparation steps: mixing a silane coupling agent, a carbon nanotube carrier, toluene and deionized water, reacting, then performing ultraviolet irradiation, and obtaining the carbon nanotube carrier with a hydrophobic inner cavity; mixing the carbon nanotube carrier with a hydrophobic inner cavity and a metal precursor methanol solution, performing vacuum adsorption, releasing the vacuum, performing filtration, washing, drying, sintering, and cooling to room temperature, and obtaining the aqueous-phase hydrogenation hydrophobic catalyst. The aqueous-phase hydrogenation hydrophobic catalyst takes the active metal loaded in the inner cavity of the carbon nanotube carrier with a hydrophobic inner cavity as a hydrogen gas activation center, takes the oxygen vacancy provided by the nanometer titanium dioxide on the surface of the carbon nanotube carrier with a hydrophobic inner cavity as an activation center of alpha, beta-unsaturated aldehyde, and reduces the competitive adsorption of hydrogen gas and alpha, beta-unsaturated aldehyde at the same active site.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, specifically to an α,β-unsaturated aldehyde aqueous-phase hydrogenation hydrophobic catalyst and its preparation method. Background Technology

[0002] Selective hydrogenation of α,β-unsaturated aldehydes is an important reaction in the fine chemical industry, and its hydrogenation products, unsaturated alcohols, are widely used in the fragrance, pharmaceutical intermediates, and cosmetics industries. However, this reaction faces significant challenges in selectivity control. C=C hydrogenation in α,β-unsaturated aldehydes is generally superior to C=O hydrogenation. Furthermore, with existing supported metal catalysts (such as nickel, cobalt, and copper-based catalysts), the C=C bonds in α,β-unsaturated aldehyde molecules typically tend to undergo conjugated adsorption with metal sites on the surface of traditional supported metal catalysts, resulting in preferential hydrogenation of C=C and leading to saturated aldehydes or saturated alcohols as products. Therefore, it is difficult to improve the selectivity for unsaturated alcohols.

[0003] To overcome the aforementioned selectivity challenges, researchers have developed various strategies: modulating the electronic structure of metal active sites, such as constructing bimetallic catalysts or introducing Lewis acid sites to enhance the activation ability of C=O; utilizing the interaction between the support and the metal to control the geometric configuration; and employing organic solvents or water-organic two-phase systems to regulate the reaction microenvironment. In recent years, water has received widespread attention as a green reaction medium in the field of catalytic hydrogenation. Studies have shown that water molecules can promote proton transfer by forming intermolecular hydrogen bond networks, thereby improving the hydrogenation selectivity of C=O bonds. However, aqueous systems face a core contradiction: the extremely low solubility of hydrogen in water limits the effective contact between reactants and catalysts in the aqueous phase, resulting in low mass transfer efficiency. Therefore, developing a catalyst with high selectivity, high activity, and good aqueous phase dispersion / mass transfer performance, and establishing a simple and controllable preparation method, is of great significance for promoting the industrial application of aqueous hydrogenation of α,β-unsaturated aldehydes. Summary of the Invention

[0004] This invention provides a hydrophobic catalyst for the aqueous hydrogenation of α,β-unsaturated aldehydes and its preparation method, which solves the problems that the C=C bonds in α,β-unsaturated aldehyde molecules usually tend to undergo conjugated adsorption with metal sites on the surface of traditional supported metal catalysts, resulting in preferential hydrogenation of C=C and limited effective contact between reactants and catalysts in the aqueous phase due to the extremely low solubility of hydrogen in water, leading to low mass transfer efficiency.

[0005] The technical solution of the present invention:

[0006] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0007] S1. Mix silane coupling agent, carbon nanotube carrier, toluene and deionized water, and react under vacuum and stirring. Then filter, wash, dry and finally irradiate with ultraviolet light to obtain a carbon nanotube carrier with a hydrophobic inner cavity.

[0008] S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor are mixed, and after vacuum adsorption, the vacuum is released, filtered, washed, dried, and placed in a sintering furnace for sintering. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation is obtained.

[0009] The carbon nanotube carrier is obtained by synthesizing a porous carbon layer on the surface of carbon nanotubes and then loading nano-titanium dioxide in situ.

[0010] Further, step S1 specifically includes:

[0011] The silane coupling agent, carbon nanotube carrier, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.06 to -0.02 MPa and stirred at 50-60°C for 3-4 hours. After releasing the vacuum, the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in an oven at 60°C for 10 hours and then placed in a quartz reaction vessel for ultraviolet irradiation to obtain a carbon nanotube carrier with a hydrophobic inner cavity.

[0012] Furthermore, during the above reaction process, a vacuum of -0.06 to -0.02 MPa is applied, which makes it easier for the silane coupling agent to enter the inner cavity of the carbon nanotube support. The silanol groups generated by the hydrolysis of the silane coupling agent can be chemically bonded to the hydroxyl groups on the carbon nanotube support, so that the silane coupling agent is grafted onto the outer surface and inner cavity surface of the carbon nanotube support.

[0013] Furthermore, the carbon nanotube carrier is placed in a quartz reaction dish and irradiated with ultraviolet light. The nano-titanium dioxide contained on the surface of the carbon nanotube carrier has a photocatalytic effect. The photocatalytic effect of the nano-titanium dioxide is used to degrade the silane coupling agent exposed on the surface of the carbon nanotube carrier, so that the outer surface of the carbon nanotube carrier is restored to hydrophilicity.

[0014] It should also be noted that by controlling the ultraviolet irradiation time, wavelength and intensity, the porous carbon layer on the surface of the composite carbon nanotube carrier can weaken the ultraviolet light, thus limiting the penetration depth of the ultraviolet light. The silane coupling agent on the inner surface of the carbon nanotube carrier cannot be degraded, thereby restoring the hydrophilicity of the outer surface of the carbon nanotube carrier and maintaining the hydrophobicity of the inner cavity, resulting in a carbon nanotube carrier with a hydrophobic inner cavity.

[0015] Furthermore, the ratio of the silane coupling agent, carbon nanotube carrier, toluene, and deionized water is (2.5-3)g:(1-1.4)g:(120-130)mL:(10-20)mL.

[0016] Furthermore, the silane coupling agent is selected from any one of octyltrimethoxysilane, isobutyltriethoxysilane, and aminopropyltriethoxysilane.

[0017] Furthermore, the ultraviolet light irradiation specifically refers to: 250-350nm, 20-50mW / cm². 2 Irradiate with ultraviolet light for 15-22 hours.

[0018] Furthermore, step S2 specifically includes:

[0019] A hydrophobic carbon nanotube support with an inner cavity was mixed with a methanol solution containing a metal precursor. The mixture was then evacuated to -0.06 to -0.02 MPa and subjected to vacuum adsorption for 2-3 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, and dried at 80-90℃ for 10-18 hours. The mixture was then placed in a reactor, and nitrogen and hydrogen were introduced. The temperature was increased to 400-500℃ at a rate of 2-3℃ / min, and the mixture was sintered at a constant temperature for 4-5 hours. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation was obtained.

[0020] Furthermore, in the above reaction process, the hydrophobic carbon nanotube support with an inner cavity is mixed with a methanol solution containing a metal precursor. Utilizing methanol with low surface tension, a vacuum of -0.06 to -0.02 MPa is applied to allow the methanol solution containing the metal precursor to enter the cavity of the hydrophobic carbon nanotube support. The solution is then washed with methanol and deionized water to remove the metal salts adsorbed on the surface of the hydrophobic carbon nanotube support. After drying at 80-90℃ for 10-18 hours, methanol and free water within the cavity of the carbon nanotube support are removed. Subsequently, nitrogen and hydrogen are introduced, and the solution is sintered and reduced at 400-500℃ for 4-5 hours to achieve the attachment of an active metal (M) with a particle size of 5-10 nm on the inner surface of the carbon nanotube support, thus obtaining an aqueous hydrophobic catalyst for hydrogenation.

[0021] Furthermore, the ratio of the hydrophobic carbon nanotube carrier in the cavity to the methanol solution of the metal precursor is (1.5-2) g:(100-120) mL.

[0022] Furthermore, the metal precursor methanol solution is prepared by mixing the metal precursor and methanol in a ratio of (0.3-0.4)g:(80-120)mL.

[0023] Furthermore, the metal precursor is selected from any one of nickel nitrate, cobalt nitrate, and copper chloride.

[0024] Furthermore, the volume ratio of nitrogen to hydrogen is 1:(8-10).

[0025] Furthermore, the carbon nanotube carrier is specifically prepared by the following steps:

[0026] A1. Mix carbon nanotubes, glucose, tannic acid and ethanol evenly. After stirring, filter and dry. Place in a tube furnace, add potassium hydroxide solution, and purge with nitrogen gas. Carbonize at 750-850℃ for 3-4 hours. Cool to room temperature, remove, wash and dry to obtain porous carbon-coated carbon nanotubes.

[0027] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon nanotubes coated with a carbon layer, place on a magnetic stirrer, stir at 80-100 r / min for 40-50 min, place in a reaction vessel, react at 175-185℃ for 22-24 h, cool to room temperature, collect the solid by filtration, wash the solid, dry it, and obtain the carbon nanotube support.

[0028] Furthermore, in the A1 reaction process described above, tannic acid contains a large number of phenolic hydroxyl groups, which act as a linker to adhere glucose to the surface of carbon nanotubes. After high-temperature carbonization, the glucose decomposes to form a dense carbon layer. Potassium hydroxide solution acts as an activator to form channels on the surface of the dense carbon layer, thereby achieving the synthesis of a porous carbon layer on the surface of carbon nanotubes and obtaining carbon nanotubes coated with a porous carbon layer.

[0029] Furthermore, in the above A2 reaction process, the porous carbon layer on the surface of the carbon nanotube coated with the porous carbon layer has a rich pore structure and high adsorption performance. It can adsorb titanium hydroxide produced by the hydrolysis of tetrabutyl titanate into the pores of the porous carbon layer. Through hydrothermal reaction, titanium hydroxide dehydrates and condenses to form titanium dioxide crystals. As the reaction proceeds, the crystals grow, and hydrofluoric acid can regulate the crystal growth, so as to form nano-titanium dioxide with a particle size of 10-20 nm on the surface of the carbon nanotube coated with the porous carbon layer, thus obtaining a carbon nanotube carrier.

[0030] Further, in step A1, the ratio of the amount of carbon nanotubes, glucose, tannic acid, ethanol and potassium hydroxide solution is (1.1-1.3)g:(0.5-0.7)g:(0.1-0.3)g:(140-160)mL:(2-3)mL.

[0031] Further, in step A2, the ratio of the amount of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is (0.9-1.1) mL:(90-110) mL:(0.2-0.3) mL:(1.4-1.6) g.

[0032] Furthermore, the carbon nanotubes have a thickness of 3-20 nm, a length of 100-600 nm, and a diameter of 30-100 nm.

[0033] The present invention has the following beneficial effects:

[0034] (1) In the technical solution of the present invention, the carbon nanotube support is obtained by synthesizing a porous carbon layer on the surface of carbon nanotubes and then loading nano-titanium dioxide in situ. On the one hand, the synthesized porous carbon layer has high adsorption performance, which is conducive to synthesizing nano-titanium dioxide on the surface of carbon nanotubes and avoiding the inertness of the carbon nanotube surface, which makes it difficult to synthesize uniformly distributed and firmly bonded nano-titanium dioxide on the surface of carbon nanotubes. The oxygen vacancies contained in the synthesized nano-titanium dioxide preferentially undergo strong coordination with the C=O double bond in α,β-unsaturated aldehydes, so that the C=O double bond is close to the catalyst, realizing the selective hydrogenation of α,β-unsaturated aldehydes to form unsaturated alcohols. Moreover, the synthesized porous carbon layer can reflect and weaken ultraviolet light, so that the penetration depth of ultraviolet light is limited, preventing the silane coupling agent on the inner surface of the carbon nanotube support from being degraded, and improving the catalytic conversion rate and the selectivity of unsaturated alcohol products in the aqueous hydrogenation reaction of α,β-unsaturated aldehydes.

[0035] On the other hand, the nano-titanium dioxide formed on the surface of carbon nanotubes coated with porous carbon layers interacts strongly with the C=O double bonds in α,β-unsaturated aldehydes, bringing the C=O double bonds close to the catalyst. This enables selective hydrogenation of α,β-unsaturated aldehydes to form unsaturated alcohols. Furthermore, nano-titanium dioxide can generate active free radicals under ultraviolet light irradiation, which easily oxidize and destroy the hydrophobic carbon layer on the surface of the carbon nanotube support. This restores the hydrophilicity of the outer surface of the carbon nanotube support while maintaining the hydrophobicity of the inner cavity. As a result, oxygen vacancies on the surface of the hydrophobic catalyst for aqueous hydrogenation can activate α,β-unsaturated aldehydes, thereby improving the selectivity of unsaturated alcohols.

[0036] (2) In the technical solution of the present invention, the outer surface of the hydrophobic carbon nanotube carrier prepared in step S1 is restored to hydrophilicity, while the inner cavity remains hydrophobic. The hydrophobic carbon layer contained in the inner cavity surface of the carbon nanotube carrier can effectively enrich hydrogen in the nanotube and activate it with active metal. This avoids the extremely low solubility of hydrogen in water, which restricts the contact between the reactants and the catalyst in the aqueous phase and affects the yield of the hydrogenation product unsaturated alcohol. In addition, the hydrophobic carbon layer can effectively inhibit the leaching of active metal in the aqueous phase and improve the stability of the catalyst in the aqueous phase.

[0037] (3) In the technical solution of the present invention, the aqueous hydrogenation hydrophobic catalyst prepared in step S2 utilizes vacuum adsorption to allow the metal precursor methanol solution to enter the inner cavity of the hydrophobic carbon nanotube support cavity, and after drying and reduction, the aqueous hydrogenation hydrophobic catalyst is obtained.

[0038] The hydrophobic catalyst for aqueous hydrogenation utilizes an active metal supported on a hydrophobic carbon nanotube support as the hydrogen activation center, and oxygen vacancies provided by nano-titanium dioxide on the surface of the hydrophobic carbon nanotube support as the activation center for α,β-unsaturated aldehydes. This reduces the competitive adsorption of hydrogen and α,β-unsaturated aldehydes at the same active site. Simultaneously, the catalyst's unique hydrophobic hollow tubular structure enables local hydrogen enrichment, creating a highly efficient reaction microenvironment suitable for aqueous hydrogenation. Therefore, the synergistic effect of the dual active sites and the local hydrogen enrichment significantly improves the catalytic conversion rate and unsaturated alcohol product selectivity of the aqueous hydrogenation reaction of α,β-unsaturated aldehydes. Furthermore, the catalyst preparation method is simple, and the raw materials are inexpensive and readily available, facilitating large-scale production. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating the working principle of the aqueous hydrogenation hydrophobic catalyst of the present invention. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0042] The carbon nanotubes are large-diameter, thin-walled, multi-walled carbon nanotubes with an outer diameter of 30-60 nm, an inner diameter of 20-50 nm, a length of 1-10 μm, and a specific surface area >200 m². 2 / g, purchased from Shanghai Liantian Materials Technology Co., Ltd.

[0043] The silane coupling agent is octyltrimethoxysilane.

[0044] The metal precursor is nickel nitrate.

[0045] Example 1

[0046] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0047] S1. Octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.06 MPa and stirred at 50°C for 3 hours. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 hours and then placed in a quartz reaction vessel. The reaction was then carried out at 250 nm and 20 mW / cm². 2The carbon nanotube carrier with a hydrophobic inner cavity was obtained by irradiation with ultraviolet light for 15 hours; the ratio of octyltrimethoxysilane, carbon nanotube carrier, toluene and deionized water was 2.5g:1g:120mL:10mL.

[0048] S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.06 MPa for 2 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 80°C for 10 hours, placed in a reactor, and purged with nitrogen and hydrogen in a volume ratio of 1:8. The temperature was increased to 400°C at a rate of 2°C / min, and sintered at this temperature for 4 hours. After cooling to room temperature, an aqueous hydrophobic catalyst was obtained. The ratio of the hydrophobic carbon nanotube support with an inner cavity to the methanol solution of the metal precursor was 1.5 g: 100 mL. The methanol solution of the metal precursor was prepared by mixing the metal precursor and methanol in a ratio of 0.3 g: 80 mL. The metal precursor was nickel nitrate.

[0049] The carbon nanotube carrier is prepared by the following steps:

[0050] A1. Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 750°C for 3 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.1 g: 0.5 g: 0.1 g: 140 mL: 2 mL.

[0051] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon-coated carbon nanotubes, place on a magnetic stirrer, stir at 80 r / min for 40 min, place in a reaction vessel, react at 175℃ for 22 h, cool to room temperature, collect the solid by filtration, wash the solid three times with deionized water and three times with ethanol, dry in an oven at 70℃ for 10 min to obtain the carbon nanotube support; the ratio of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is 0.9 mL:90 mL:0.2 mL:1.4 g.

[0052] Example 2

[0053] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0054] S1. Octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.04 MPa and stirred at 55°C for 3.5 h. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 h and placed in a quartz reaction vessel. The reaction was then carried out at 300 nm and 35 mW / cm². 2 Irradiation under ultraviolet light for 18 hours yielded a carbon nanotube carrier with a hydrophobic interior; the ratio of octyltrimethoxysilane, carbon nanotube carrier, toluene, and deionized water was 2.8 g: 1.2 g: 125 mL: 15 mL.

[0055] S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.04 MPa and held under pressure for 2.5 h. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 85 °C for 16 h, placed in a reactor, and purged with nitrogen and hydrogen gas at a volume ratio of 1:9. The temperature was increased to 450 °C at a rate of 2.5 °C / min, and sintered at this temperature for 4.5 h. After cooling to room temperature, an aqueous hydrophobic hydrogenation catalyst was obtained. The ratio of the hydrophobic carbon nanotube support with an inner cavity to the methanol solution of the metal precursor was 1.8 g: 110 mL. The methanol solution of the metal precursor was prepared by mixing the metal precursor and methanol at a volume ratio of 0.35 g: 100 mL. The metal precursor was nickel nitrate.

[0056] The carbon nanotube carrier is prepared by the following steps:

[0057] A1. Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 3.5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.2 g: 0.6 g: 0.2 g: 150 mL: 2.5 mL.

[0058] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon-coated carbon nanotubes, place on a magnetic stirrer, stir at 90 r / min for 45 min, place in a reaction vessel, react at 180℃ for 23 h, cool to room temperature, collect the solid by filtration, wash the solid 3 times with deionized water and 3 times with ethanol, dry in a 70℃ oven for 10 min to obtain the carbon nanotube support; the ratio of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is 1 mL:100 mL:0.25 mL:1.5 g.

[0059] Example 3

[0060] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0061] S1. Octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.02 MPa and stirred at 60°C for 4 hours. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 hours and placed in a quartz reaction vessel. The reaction was then carried out at 350 nm and 50 mW / cm². 2 The carbon nanotube carrier with a hydrophobic interior was obtained by irradiation with ultraviolet light for 22 hours; the ratio of silane coupling agent, carbon nanotube carrier, toluene and deionized water was 3g:1.4g:130mL:20mL.

[0062] S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.02 MPa for 3 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 90°C for 18 hours, placed in a reactor, and purged with nitrogen and hydrogen gas at a volume ratio of 1:10. The temperature was increased to 500°C at a rate of 3°C / min, and sintered at this temperature for 5 hours. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation was obtained. The ratio of the hydrophobic carbon nanotube support with an inner cavity to the methanol solution of the metal precursor was 2 g:120 mL. The methanol solution of the metal precursor was prepared by mixing the metal precursor and methanol at a ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0063] The carbon nanotube carrier is prepared by the following steps:

[0064] A1. Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 850°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.3 g: 0.7 g: 0.3 g: 160 mL: 3 mL.

[0065] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon-coated carbon nanotubes, place on a magnetic stirrer, stir at 100 r / min for 50 min, place in a reaction vessel, react at 185℃ for 24 h, cool to room temperature, filter to collect the solid, wash the solid 3 times with deionized water and 3 times with ethanol, dry in a 70℃ oven for 10 min to obtain the carbon nanotube carrier; the ratio of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is 1.1 mL: 110 mL: 0.3 mL: 1.6 g.

[0066] Comparative Example 1

[0067] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0068] S1. Octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.02 MPa and stirred at 60°C for 4 hours. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 hours and placed in a quartz reaction vessel. The reaction was then carried out at 350 nm and 50 mW / cm². 2 The carbon nanotube carrier with a hydrophobic inner cavity was obtained by irradiation under ultraviolet light for 22 hours; the ratio of octyltrimethoxysilane, carbon nanotube carrier, toluene and deionized water was 3g:1.4g:130mL:20mL.

[0069] S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.02 MPa for 3 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 90°C for 18 hours, placed in a reactor, and purged with nitrogen and hydrogen gas at a volume ratio of 1:10. The temperature was increased to 500°C at a rate of 3°C / min, and sintered at this temperature for 5 hours. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation was obtained. The ratio of the hydrophobic carbon nanotube support with an inner cavity to the methanol solution of the metal precursor was 2 g:120 mL. The methanol solution of the metal precursor was prepared by mixing the metal precursor and methanol at a ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0070] The carbon nanotube carrier is prepared by the following steps:

[0071] Tetrabutyl titanate and deionized water were mixed and stirred until homogeneous. Hydrofluoric acid and carbon nanotubes were added, and the mixture was placed on a magnetic stirrer and stirred at 100 r / min for 50 min. The mixture was then placed in a reaction vessel and reacted at 185 °C for 24 h. After cooling to room temperature, the solid was collected by filtration. The solid was washed three times with deionized water and three times with ethanol, and then dried in an oven at 70 °C for 10 min to obtain the carbon nanotube support. The ratio of tetrabutyl titanate, deionized water, hydrofluoric acid, and porous carbon-coated carbon nanotubes was 1.1 mL: 110 mL: 0.3 mL: 1.6 g.

[0072] Comparative Example 2

[0073] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0074] S1. Octyltrimethoxysilane, porous carbon-coated carbon nanotubes, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.02 MPa and stirred at 60°C for 4 hours. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 hours and then placed in a quartz reaction vessel. The reaction was carried out at 350 nm and 50 mW / cm². 2 Irradiation under ultraviolet light for 22 hours yielded carbon nanotubes with a porous carbon layer coated with a hydrophobic inner cavity; the ratio of octyltrimethoxysilane, porous carbon-coated carbon nanotubes, toluene, and deionized water was 3g:1.4g:130mL:20mL.

[0075] S2. Carbon nanotubes coated with a porous carbon layer with a hydrophobic inner cavity and a methanol solution containing a metal precursor were mixed. The mixture was then evacuated to -0.02 MPa and subjected to vacuum adsorption for 3 hours. After releasing the vacuum, the mixture was filtered, washed five times with methanol, and three times with deionized water. It was dried at 90°C for 18 hours and placed in a reactor. Nitrogen and hydrogen were introduced at a volume ratio of 1:10. The temperature was increased to 500°C at a rate of 3°C / min and sintered at this temperature for 5 hours. The mixture was then cooled to room temperature to obtain an aqueous hydrophobic hydrogenation catalyst. The ratio of the porous carbon nanotubes coated with a hydrophobic inner cavity to the methanol solution containing the metal precursor was 2 g:120 mL. The methanol solution containing the metal precursor was prepared by mixing the metal precursor and methanol at a volume ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0076] Porous carbon-coated carbon nanotubes are prepared by the following steps:

[0077] Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 850°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.3 g: 0.7 g: 0.3 g: 160 mL: 3 mL.

[0078] Comparative Example 3

[0079] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0080] S1. Octyltrimethoxysilane, TiO2 nanotubes, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.02 MPa and stirred at 60°C for 4 hours. The vacuum was released, and the mixture was filtered, washed three times with toluene, and then three times with deionized water. It was dried in a 60°C oven for 10 hours and then placed in a quartz reaction vessel. The reaction was then carried out at 350 nm and 50 mW / cm². 2 TiO2 nanotubes with hydrophobic inner cavities were obtained by irradiation with ultraviolet light for 22 hours; the ratio of octyltrimethoxysilane, TiO2 nanotubes, toluene and deionized water was 3g:1.4g:130mL:20mL.

[0081] S2. The hydrophobic TiO2 nanotubes with an inner cavity and the methanol solution of the metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.02 MPa for 3 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 90°C for 18 hours, placed in a reactor, and purged with nitrogen and hydrogen gas at a volume ratio of 1:10. The temperature was increased to 500°C at a rate of 3°C / min, and sintered at this temperature for 5 hours. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation was obtained. The ratio of the hydrophobic TiO2 nanotubes with an inner cavity to the methanol solution of the metal precursor was 2 g:120 mL. The methanol solution of the metal precursor was prepared by mixing the metal precursor and methanol at a ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0082] TiO2 nanotubes are prepared by the following steps:

[0083] 1.5 g of nano-titanium dioxide was mixed evenly with 112 mL of an aqueous solution containing 44 g of sodium hydroxide and 41 g of sodium dihydrogen phosphate. The mixture was then placed in a hydrothermal reactor and reacted at 150 °C for 55 h. After cooling to room temperature, the product was collected by filtration. The product was washed three times with deionized water and dried in an oven at 60 °C for 20 h. The product was then added to 3.5 mL of 36% concentrated hydrochloric acid and 750 mL of deionized water, stirred evenly, and allowed to stand for 100 h. The product was collected by filtration and washed three times with deionized water. After drying in an oven at 120 °C for 8 h, the product was placed in a sintering furnace and calcined at 600 °C for 2 h. After cooling to room temperature, TiO2 nanotubes were obtained.

[0084] Comparative Example 4

[0085] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0086] S1. Octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water were mixed and stirred evenly. The mixture was then evacuated to -0.02 MPa and stirred at 60°C for 4 hours. After releasing the vacuum, the mixture was filtered, washed three times with toluene, and then washed three times with deionized water. Finally, it was dried in an oven at 60°C for 10 hours to obtain hydrophobically modified carbon nanotube support. The ratio of octyltrimethoxysilane, carbon nanotube support, toluene, and deionized water was 3 g: 1.4 g: 130 mL: 20 mL.

[0087] S2. The hydrophobically modified carbon nanotube support and the metal precursor methanol solution were mixed, and the mixture was vacuum-adsorbed to -0.02 MPa for 3 hours. After releasing the vacuum, the mixture was filtered, washed 5 times with methanol and 3 times with deionized water, dried at 90°C for 18 hours, placed in a reactor, and purged with nitrogen and hydrogen gas at a volume ratio of 1:10. The temperature was increased to 500°C at a rate of 3°C / min, and sintered at this temperature for 5 hours. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation was obtained. The ratio of hydrophobically modified carbon nanotube support to metal precursor methanol solution was 2 g:120 mL. The metal precursor methanol solution was prepared by mixing the metal precursor and methanol at a ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0088] The carbon nanotube carrier is prepared by the following steps:

[0089] A1. Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 850°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.3 g: 0.7 g: 0.3 g: 160 mL: 3 mL.

[0090] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon-coated carbon nanotubes, place on a magnetic stirrer, stir at 100 r / min for 50 min, place in a reaction vessel, react at 185℃ for 24 h, cool to room temperature, filter to collect the solid, wash the solid 3 times with deionized water and 3 times with ethanol, dry in a 70℃ oven for 10 min to obtain the carbon nanotube carrier; the ratio of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is 1.1 mL: 110 mL: 0.3 mL: 1.6 g.

[0091] Comparative Example 5

[0092] A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst for hydrogenation includes the following preparation steps:

[0093] A carbon nanotube support and a methanol solution containing a metal precursor were mixed, and the mixture was vacuum-adsorbed to -0.02 MPa for 3 hours. After releasing the vacuum, the mixture was filtered, washed five times with methanol and three times with deionized water, dried at 90°C for 18 hours, and placed in a reactor. Nitrogen and hydrogen gases were introduced at a volume ratio of 1:10, and the temperature was increased to 500°C at a rate of 3°C / min. The mixture was then sintered at this temperature for 5 hours and cooled to room temperature to obtain an aqueous hydrophobic catalyst for hydrogenation. The ratio of carbon nanotube support to methanol solution containing a metal precursor was 2 g:120 mL. The methanol solution containing the metal precursor was prepared by mixing the metal precursor and methanol at a ratio of 0.4 g:120 mL. The metal precursor was nickel nitrate.

[0094] The carbon nanotube carrier is prepared by the following steps:

[0095] A1. Carbon nanotubes, glucose, tannic acid, and ethanol were mixed evenly and stirred at 70°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 20 min. The mixture was then placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 850°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain porous carbon nanotubes coated with a carbon layer. The ratio of carbon nanotubes, glucose, tannic acid, ethanol, and potassium hydroxide solution was 1.3 g: 0.7 g: 0.3 g: 160 mL: 3 mL.

[0096] A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon-coated carbon nanotubes, place on a magnetic stirrer, stir at 100 r / min for 50 min, place in a reaction vessel, react at 185℃ for 24 h, cool to room temperature, filter to collect the solid, wash the solid 3 times with deionized water and 3 times with ethanol, dry in a 70℃ oven for 10 min to obtain the carbon nanotube carrier; the ratio of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is 1.1 mL: 110 mL: 0.3 mL: 1.6 g.

[0097] The performance of the aqueous hydrogenation hydrophobic catalysts prepared in Examples 1-3 and Comparative Examples 1-5 was tested.

[0098] The aqueous hydrophobic catalysts prepared above were used for the selective catalytic hydrogenation of citral, cinnamaldehyde, and furfural in the aqueous phase. The catalytic hydrogenation activity was evaluated in a 250 mL high-pressure reactor. The citral reaction system consisted of 0.3 g of the prepared aqueous hydrophobic catalyst, 0.7 mL of citral, and 50 mL of deionized water. The reaction was carried out at 120 °C, 1.5 MPa hydrogen pressure, and 750 r / min stirring speed for 5 h.

[0099] The cinnamaldehyde reaction system consisted of 1g of the aqueous hydrophobic catalyst prepared above, 1mL of cinnamaldehyde and 60mL of deionized water, reacted at 80℃, 1.5MPa hydrogen pressure and 900r / min stirring speed for 4h.

[0100] The furfural reaction system consisted of 0.6 g of the aqueous hydrophobic catalyst prepared above, 1 mL of furfural, and 80 mL of deionized water. The reaction was carried out at 90 °C, 0.5 MPa hydrogen pressure, and 950 r / min stirring speed for 6 h.

[0101] After the reaction was completed, the mixture was centrifuged and the reaction product was taken. The product was detected by gas chromatography, and the conversion rate, selectivity and yield were measured.

[0102] The test results are shown in Table 1 below.

[0103] Table 1. Performance testing of the aqueous hydrophobic catalysts prepared in Examples 1-3 and Comparative Examples 1-5.

[0104]

[0105] Table 2 Performance testing of the aqueous hydrophobic catalysts prepared in Examples 1-3 and Comparative Examples 1-5

[0106]

[0107] Table 3 Performance testing of the aqueous hydrophobic catalysts prepared in Examples 1-3 and Comparative Examples 1-5

[0108]

[0109] As can be seen from the data in Table 1, the aqueous hydrogenation hydrophobic catalysts prepared in Examples 1-3, using the active metal supported in the inner cavity of the hydrophobic carbon nanotube support as the hydrogen activation center and the oxygen vacancies provided by the nano-titanium dioxide on the surface of the hydrophobic carbon nanotube support as the activation center of the α,β-unsaturated aldehyde, significantly improved the catalytic conversion rate and the selectivity of unsaturated alcohol products in the aqueous hydrogenation reaction of α,β-unsaturated aldehydes.

[0110] Comparative Example 1 replaced the porous carbon layer-coated carbon nanotubes with a hydrophobic catalyst prepared from carbon nanotubes for the hydrogenation catalysis of α,β-unsaturated aldehydes. The yield of the hydrogenation product, unsaturated alcohol, decreased, demonstrating that the synthesized porous carbon layer has high adsorption performance, which is beneficial for the synthesis of nano-titanium dioxide on the carbon nanotube surface. This avoids the inertness of the carbon nanotube surface, which makes it difficult to synthesize uniformly distributed and firmly bonded nano-titanium dioxide on the carbon nanotube surface. The oxygen vacancies in the synthesized nano-titanium dioxide preferentially undergo strong coordination with the C=O double bonds in the α,β-unsaturated aldehydes, making the C=O double bonds close to the catalyst, achieving selective hydrogenation of α,β-unsaturated aldehydes to form unsaturated alcohols. Furthermore, the synthesized porous carbon layer can reflect and weaken ultraviolet light, limiting the penetration depth of ultraviolet light and preventing the degradation of the silane coupling agent on the inner surface of the carbon nanotube support. This improves the catalytic conversion rate and the selectivity of the unsaturated alcohol product in the aqueous hydrogenation reaction of α,β-unsaturated aldehydes.

[0111] Comparative Example 2 replaced the carbon nanotube support with a porous carbon layer-coated carbon nanotube to prepare an aqueous hydrogenation hydrophobic catalyst for the hydrogenation catalysis of α,β-unsaturated aldehydes. The yield of the hydrogenation product, unsaturated alcohol, decreased, demonstrating that the nano-titanium dioxide formed on the surface of the porous carbon layer-coated carbon nanotubes has a strong coordination interaction with the C=O double bonds in the α,β-unsaturated aldehydes. This allows the C=O double bonds to be close to the catalyst, achieving selective hydrogenation of α,β-unsaturated aldehydes to form unsaturated alcohols. Furthermore, the nano-titanium dioxide can generate active free radicals under ultraviolet light irradiation, which easily oxidize and destroy the hydrophobic carbon layer on the surface of the carbon nanotube support. This restores the hydrophilicity of the outer surface of the carbon nanotube support while maintaining the hydrophobicity of the inner cavity. This allows the oxygen vacancies on the surface of the aqueous hydrogenation hydrophobic catalyst to activate α,β-unsaturated aldehydes and improve the selectivity of unsaturated alcohols.

[0112] Comparative Example 3 used an aqueous hydrogenation hydrophobic catalyst prepared by replacing the carbon nanotube support with TiO2 nanotubes for the hydrogenation catalysis of α,β-unsaturated aldehydes. The yield of the hydrogenation product, unsaturated alcohol, decreased, demonstrating that TiO2 nanotubes have high UV light penetration. When irradiated with UV light, the silane coupling agent inside the TiO2 nanotubes was also degraded. The TiO2 nanotubes lost their hydrophilic outer surface and hydrophobic inner cavity structure, resulting in a decrease in the catalytic conversion rate and selectivity of the unsaturated alcohol product in the aqueous hydrogenation reaction of α,β-unsaturated aldehydes.

[0113] In Comparative Example 4, the aqueous hydrophobic catalyst prepared without UV irradiation in step S1 was used for the hydrogenation catalytic reaction of α,β-unsaturated aldehydes. The yield of the hydrogenation product, unsaturated alcohol, decreased, demonstrating that UV irradiation of the nano-titanium dioxide on the carbon nanotube support surface exhibits photocatalytic activity. The photocatalytic activity of nano-titanium dioxide degrades the silane coupling agent exposed on the carbon nanotube support surface, restoring the hydrophilicity of the outer surface of the carbon nanotube support while preventing the degradation of the silane coupling agent on the inner cavity surface. This achieves the restoration of hydrophilicity on the outer surface of the carbon nanotube support while maintaining hydrophobicity in the inner cavity. The hydrophobic carbon layer on the inner cavity surface effectively enriches hydrogen within the nanotubes, allowing it to be activated by the active metal. This avoids the extremely low solubility of hydrogen in water, which limits the contact between the reactants and the catalyst in the aqueous phase, thus affecting the yield of the hydrogenation product, unsaturated alcohol. Furthermore, the hydrophobic carbon layer effectively inhibits the leaching of the active metal in the aqueous phase, improving the catalyst's stability in the aqueous phase.

[0114] Comparative Example 5 replaced the hydrophobic carbon nanotube support with a hydrophobic catalyst for aqueous hydrogenation prepared using a carbon nanotube support. This catalyst was used for the hydrogenation catalysis of α,β-unsaturated aldehydes, resulting in a decrease in the yield of the hydrogenation product, unsaturated alcohol. This demonstrates that the hydrophobic catalyst for aqueous hydrogenation utilizes the active metal supported within the hydrophobic carbon nanotube support as the hydrogen activation center, and the oxygen vacancies provided by nano-titanium dioxide on the surface of the hydrophobic carbon nanotube support as the activation center for α,β-unsaturated aldehydes. Simultaneously, the catalyst's unique hydrophobic hollow tubular structure enables local hydrogen enrichment, constructing a highly efficient reaction microenvironment suitable for aqueous hydrogenation. Therefore, the combined effect of the synergistic enhancement of the two active sites and the local enrichment of hydrogen significantly improves the catalytic conversion rate and the selectivity of the unsaturated alcohol product in the aqueous hydrogenation reaction of α,β-unsaturated aldehydes.

[0115] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0116] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst, characterized in that, The preparation steps include the following: S1. Mix silane coupling agent, carbon nanotube carrier, toluene and deionized water, and react under vacuum and stirring. Then filter, wash, dry and finally irradiate with ultraviolet light to obtain a carbon nanotube carrier with a hydrophobic inner cavity. S2. The hydrophobic carbon nanotube support with an inner cavity and the methanol solution of the metal precursor are mixed, and after vacuum adsorption, the vacuum is released, filtered, washed, dried, and placed in a sintering furnace for sintering. After cooling to room temperature, an aqueous hydrophobic catalyst for hydrogenation is obtained. The metal precursor methanol solution is prepared by mixing the metal precursor and methanol in a ratio of (0.3-0.4) g:(80-120) mL. The metal precursor is selected from any one of nickel nitrate, cobalt nitrate, and copper chloride; The carbon nanotube carrier is obtained by synthesizing a porous carbon layer on the surface of carbon nanotubes and then loading nano-titanium dioxide in situ. The carbon nanotube carrier is prepared by the following steps: A1. Mix carbon nanotubes, glucose, tannic acid and ethanol evenly. After stirring, filter and dry. Place in a tube furnace, add potassium hydroxide solution, and purge with nitrogen gas. Carbonize at 750-850℃ for 3-4 hours. Cool to room temperature, remove, wash and dry to obtain porous carbon-coated carbon nanotubes. A2. Mix tetrabutyl titanate and deionized water, stir until homogeneous, add hydrofluoric acid and porous carbon nanotubes coated with a carbon layer, place on a magnetic stirrer, stir at 80-100 r / min for 40-50 min, place in a reaction vessel, react at 175-185℃ for 22-24 h, cool to room temperature, collect the solid by filtration, wash the solid, dry it, and obtain the carbon nanotube support.

2. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, Step S1 specifically involves: The silane coupling agent, carbon nanotube support, toluene, and deionized water were mixed and stirred until homogeneous. The mixture was then evacuated to -0.06 to -0.02 MPa and stirred at 50-60°C for 3-4 hours. After releasing the vacuum, the mixture was filtered, washed with toluene and deionized water, dried, and placed in a quartz reaction vessel for ultraviolet irradiation to obtain a carbon nanotube support with a hydrophobic inner cavity.

3. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, The ratio of the silane coupling agent, carbon nanotube carrier, toluene, and deionized water is (2.5-3) g:(1-1.4) g:(120-130) mL:(10-20) mL; The silane coupling agent is selected from any one of methyltrimethoxysilane, octyltrimethoxysilane, and isobutyltriethoxysilane; The ultraviolet light irradiation specifically refers to: 250-350nm, 20-50mW / cm². 2 Irradiate with ultraviolet light for 15-22 hours.

4. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, Step S2 is as follows: A hydrophobic carbon nanotube support with an inner cavity was mixed with a methanol solution containing a metal precursor. The mixture was then evacuated to -0.06 to -0.02 MPa and subjected to vacuum adsorption for 2-3 hours. After releasing the vacuum, the mixture was filtered, washed with methanol and deionized water, and dried at 80-90℃ for 10-18 hours. The mixture was then placed in a reactor, and nitrogen and hydrogen were introduced. The temperature was increased to 400-500℃ at a rate of 2-3℃ / min, and the mixture was sintered at a constant temperature for 4-5 hours. After cooling to room temperature, an aqueous hydrophobic hydrogenation catalyst was obtained.

5. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, The ratio of the hydrophobic carbon nanotube carrier in the cavity to the methanol solution of the metal precursor is (1.5-2) g:(100-120) mL.

6. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, In step A1, the ratio of carbon nanotubes, glucose, tannic acid, ethanol and potassium hydroxide solution is (1.1-1.3)g:(0.5-0.7)g:(0.1-0.3)g:(140-160)mL:(2-3)mL.

7. The method for preparing an α,β-unsaturated aldehyde aqueous-phase hydrophobic catalyst according to claim 1, characterized in that, In step A2, the ratio of the amount of tetrabutyl titanate, deionized water, hydrofluoric acid and porous carbon-coated carbon nanotubes is (0.9-1.1) mL:(90-110) mL:(0.2-0.3) mL:(1.4-1.6) g.

8. An aqueous hydrophobic catalyst prepared by the method for preparing an α,β-unsaturated aldehyde aqueous hydrophobic catalyst according to any one of claims 1-7.

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