Preparation of high-activity monatomic catalyst and application of high-activity monatomic catalyst in hydrodeoxygenation of guaiacol

Abstract

The invention discloses a monatomic catalyst for preparing cyclohexanol, and particularly relates to a catalyst for loading metal ruthenium on an ordered mesoporous carbon-titanium dioxide carrier. The catalyst only selectively adsorbs methoxy monofunctional groups in the hydrodeoxygenation reaction of guaiacol, so that high-efficiency and high-selectivity production of single product cyclohexanol is realized. According to the preparation method of the novel monatomic catalyst and the application of the monatomic catalyst in cyclohexanol synthesis, the size of a metal center is regulated and controlled by adopting a defect induction strategy, the overall adsorption capacity of guaiacol substrate molecules can be moderately weakened in the reaction for preparing cyclohexanol through guaiacol hydrodeoxygenation, and the yield of cyclohexanol is increased. Only methoxy monofunctional groups are selectively adsorbed, and C-O bonds are effectively broken, so that high-selectivity production of a single product cyclohexanol is realized. According to the technical scheme, the problems of harsh reaction conditions, low conversion rate, low product selectivity and the like in the prior art are effectively solved, the utilization rate of biomass resources is remarkably increased, and a solid foundation is laid for producing environment-friendly chemicals.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and in particular to a single-atom catalyst for preparing cyclohexanol, a preparation method and applications. Background Art

[0002] As a key chemical solvent and chemical raw material, cyclohexanol plays a vital role in the chemical industry. It is not only an intermediate in the production of important chemical products such as hexamethylenediamine, nylon 6-caprolactam, and nylon 6-6 adipic acid, but is also widely used in a variety of fields, including textiles, pharmaceuticals, and perfumes. Traditional cyclohexanol synthesis methods mainly rely on the direct epoxidation of cyclohexane. However, this method is usually carried out under high temperature and high pressure conditions, resulting in low conversion rates and the production of a large number of by-products. Therefore, designing a new, efficient and green cyclohexanol synthesis route that uses renewable carbon resources as raw materials to reduce dependence on fossil fuels is of great significance for achieving sustainable economic and social development.

[0003] Guaiacol, an aromatic compound derived from lignin, can be converted into a variety of important chemicals, including catechol, cyclohexanol, benzene, and cyclohexane, through a hydrodeoxygenation process. However, due to the complex molecular structure of guaiacol and the presence of multiple reducible functional groups (such as methoxy and phenolic hydroxyl groups), its conversion process typically requires multiple steps, resulting in low yields of single products. In addition, the difference in bond energies of different CO bonds increases the difficulty of selectively cleaving specific CO bonds, thus posing challenges to achieving high conversion rates of guaiacol and highly selective production of cyclohexanol.

[0004] In the research on the hydrodeoxygenation of guaiacol to cyclohexanol, relevant patents such as CN110606800A reported on a nano-spherical carbon-coated molybdenum nitride catalyst. This catalyst showed high conversion and selectivity in the reaction, but required harsh conditions exceeding 500°C. Patent CN111992213A introduced a core-shell catalyst with cobalt as the active center, but the mass fraction of cobalt metal in the active center was high (10%), and the amount of metal used was large. Patent CN113731441A proposed a graphene-supported metal cobalt catalyst, but its synthesis process involved the use of strong oxidants such as concentrated sulfuric acid and hydrazine hydrate, and the synthesis steps were relatively complicated. In addition, CN115672377A reported a nitrogen-doped carbon-supported cobalt catalyst. Although it showed good conversion and selectivity, it used toxic and environmentally unfriendly n-decane as a solvent. Summary of the Invention

[0005] In view of the numerous deficiencies in the prior art, the primary technical problem of the present invention is to address the numerous issues encountered in the hydrodeoxygenation of guaiacol to produce cyclohexanol, including harsh reaction conditions, low conversion, low product selectivity, excessive metal usage, complex catalyst synthesis steps, toxicity, and environmental unfriendliness. Therefore, the present invention provides a method for preparing a novel single-atom catalyst and its application in cyclohexanol synthesis. By employing a defect-inducing strategy to regulate the size of the metal center, the overall adsorption capacity of the guaiacol substrate molecule is moderately weakened, resulting in selective adsorption of only the methoxyl group and effective cleavage of the CO bond, thereby achieving highly selective production of the single product, cyclohexanol. This significantly improves the harsh reaction conditions, low conversion, and low product selectivity encountered in the prior art, promotes the efficient utilization of biomass resources, and lays a solid foundation for the production of environmentally friendly chemicals.

[0006] To achieve the above objectives, the present invention provides a single-atom catalyst for preparing cyclohexanol, which is an ordered mesoporous carbon-titania supported ruthenium-containing catalyst with the ability to selectively adsorb methoxy monofunctional groups, thereby achieving highly selective production of a single product, cyclohexanol.

[0007] Specifically, the catalyst includes ruthenium, titanium, carbon and oxygen elements, wherein the content of titanium dioxide is 60% and the content of carbon is 40%.

[0008] Furthermore, the loading amount of ruthenium in the catalyst is 0.2-3 wt%.

[0009] The present invention provides a method for preparing a single-atom catalyst for preparing cyclohexanol, comprising the following steps:

[0010] Phenolic resin was prepared in advance: using amphiphilic triblock copolymer F127 as a template, phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, an ordered mesoporous carbon-titanium dioxide composite support material named TiO2-C was obtained by inducing self-assembly by solvent evaporation and high-temperature calcination;

[0011] The ordered mesoporous carbon-titania composite support material is impregnated in a ruthenium trichloride-ethanol solution, with ruthenium trichloride as a precursor, and subjected to post-impregnation and hydrogen reduction to obtain a ruthenium-containing mesoporous carbon-titania catalyst, named Ru / TiO2-C.

[0012] The further step includes: preparing phenolic resin in advance, specifically, uniformly dispersing the carbon source and the auxiliary agent in the organic solution of the alkaline catalyst, fully stirring at 30-70° C. to obtain a low molecular weight polymer of phenol and formaldehyde, and then adjusting the pH value to obtain a low molecular weight phenolic resin polymer.

[0013] Furthermore, using the amphiphilic triblock copolymer F127 as a template, phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, an ordered mesoporous carbon-titanium dioxide composite support material was obtained after solvent evaporation-induced self-assembly and high-temperature calcination, and was named TiO2-C. Specifically, the amphiphilic triblock copolymer F127 was used as a template, phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, and solvent evaporation-induced self-assembly and high-temperature calcination at 600°C for 2h were used, and then washed three times with deionized water and anhydrous ethanol to remove inorganic salts, thereby obtaining an ordered mesoporous carbon-titanium dioxide composite support material, and was named TiO2-C.

[0014] Another preferred embodiment of the present invention provides a specific application of the single-atom catalyst in catalyzing the selective hydrodeoxygenation of guaiacol to produce cyclohexanol, comprising the following steps:

[0015] Deionized water solvent, guaiacol, and ruthenium-mesoporous carbon-titanium dioxide composite catalyst were added to a high-pressure reactor, which was sealed and purged with hydrogen three times to remove residual air.

[0016] The hydrogen pressure in the kettle was maintained, and the mixture was stirred and cooled to room temperature after the reaction was completed. The mixture was extracted three times with ethyl acetate and dried over anhydrous magnesium sulfate to finally obtain cyclohexanol.

[0017] Technical effects:

[0018] In the catalytic system of the present invention, ruthenium (Ru) serves as the active center. By adjusting its loading to promote its interaction with the titanium dioxide support, the concentration of surface defect oxygen is modulated, thereby changing the coordination environment and electronic structure of ruthenium, thereby affecting the adsorption configuration and adsorption energy of the substrate molecule guaiacol. When the metal loading is 0.2% by mass, the size of the ruthenium becomes a single atom state, and the selectivity of the cyclohexanol prepared at this time reaches 100%, and its activity is significantly better than that of other catalysts (TOF = 182h -1 This result indicates that the single-atom catalyst is favorable for the adsorption of methoxy groups in guaiacol both spatially and electronically, thereby significantly improving the selectivity for cyclohexanol.

[0019] In addition, after cyclic reaction experiments, the initial rate, conversion rate and selectivity of the ruthenium single-atom catalyst catalytic reaction did not show a significant decrease, indicating its excellent stability.

[0020] The catalyst of the present invention is relatively simple to prepare, employing common solvent volatilization-induced self-assembly, calcination, impregnation, and reduction steps. This preparation method is easily implemented in existing industrial systems, significantly reducing the cost of catalyst synthesis.

[0021] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy (CS-HAADF-STEM) image of a 0.2% Ru / TiO2-C catalyst according to a preferred embodiment of the present invention;

[0023] Figure 2 is the X-ray diffraction pattern (XRD) of a series of Ru / TiO2-C catalysts;

[0024] Figure 3 (a) N2 adsorption isotherms and (b) pore size distribution curves of a series of Ru / TiO2-C catalysts;

[0025] Figure 4 This is a cycle stability test diagram of 0.2% Ru / TiO2-C, a preferred embodiment of the present invention;

[0026] Figure 5 This is a graph showing the cyclohexanol production rate in each cycle of a 0.2% Ru / TiO2-C reaction, a preferred embodiment of the present invention;

[0027] Table 1 shows the catalytic performance of a series of Ru / TiO2-C catalysts in the production of cyclohexanol from guaiacol;

[0028] Table 2 shows the catalytic performance of a preferred embodiment of the present invention, 0.2% Ru / TiO2-C catalyst, in producing cyclohexanol on different substrates. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] In the following description, specific details, such as certain internal procedures and techniques, are provided for purposes of illustration and not limitation to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0031] Example 1:

[0032] This example provides a single-atom catalyst for the preparation of cyclohexanol. Specifically, the catalyst is suitable for the selective hydrodeoxygenation reaction of guaiacol and is characterized by loading different amounts of ruthenium (Ru) onto an ordered mesoporous carbon-titania composite support. By regulating the size of the metal center, the overall adsorption capacity of the guaiacol substrate molecule is moderately weakened, resulting in selective adsorption of only the methoxyl group and effective cleavage of the CO bond, thereby achieving high selectivity for the single product, cyclohexanol. The catalyst comprises ruthenium, titanium, carbon, and oxygen, with a titanium dioxide content of 60%, a carbon content of 40%, and a ruthenium loading of 0.2-3wt%.

[0033] The present invention also provides a method for preparing the above catalyst, which specifically comprises the following steps:

[0034] S1: preparing phenolic resin (PF) in advance, specifically comprising the steps of uniformly dispersing a carbon source and an additive in an organic solution of an alkaline catalyst; fully stirring at 30-70° C. to obtain a low molecular weight polymer of phenol and formaldehyde, and adjusting the pH value to 7 to obtain a low molecular weight phenolic resin polymer;

[0035] S2: Using the amphiphilic triblock copolymer F127 as a template, the above-prepared PF as a carbon source, and titanium tetrachloride (TiCl4) as a titanium source, after solvent evaporation-induced self-assembly (EISA) and high-temperature calcination at 600°C, an ordered mesoporous carbon-titania composite support material was obtained, named TiO2-C;

[0036] S3: The ordered mesoporous carbon-titania composite support material described in step S2 is impregnated in a ruthenium trichloride-ethanol solution, using ruthenium trichloride as a precursor. By changing the concentration of the ruthenium precursor solution, a series of mesoporous carbon-titania catalysts with different ruthenium contents are obtained through post-impregnation and hydrogen reduction. The ratio of ruthenium metal content is 0.2%-3% wt%, and is named Ru / TiO2-C.

[0037] Its characteristic spherical aberration corrected high-angle annular dark field scanning transmission electron microscope (CS-HAADF-STEM) is shown in Figure 1 shown.

[0038] In addition, the present invention also proposes the use of the above catalyst in the hydrodeoxygenation of guaiacol to produce cyclohexanol. The specific reaction steps are as follows:

[0039] S1: 5 mg of deionized water solvent, 125 mg of guaiacol, and 125 mg of 0.2% ruthenium-mesoporous carbon-titanium dioxide catalyst were added to an autoclave, which was sealed and flushed with 1 MPa hydrogen three times to remove residual air;

[0040] S2: Maintaining the hydrogen pressure in the autoclave at 1 MPa, reacting at 210° C. with a stirring speed of 800 rpm for 3.5 h, cooling to room temperature, extracting three times with 4.5 g of ethyl acetate, and drying over anhydrous magnesium sulfate to obtain cyclohexanol.

[0041] The following specific examples will illustrate the preparation method, characterization and application of mesoporous carbon-titanium dioxide catalysts with different ruthenium contents.

[0042] Example 2:

[0043] Catalyst preparation and characterization are as follows:

[0044] A low-order phenolic resin was prepared in advance: 1.5 g of phenol and 28 g of formaldehyde were uniformly dispersed in an ethanol solution of sodium hydroxide, and the mixture was stirred at 50° C. to obtain a low molecular weight polymer of phenol and formaldehyde. The pH value was further adjusted to 7 to obtain a low-order phenolic resin polymer (PF).

[0045] Next, 1.0g of deionized water, 8.0g of ethanol, and 1.5g of F127 were weighed into a thermostatically controlled beaker A at 40°C and stirred for 30 minutes. In a low-temperature jacketed beaker B at -1°C, 0.5g of deionized water and 7.5g of ethanol were added, followed by a quick pipette transfer of 1.0mL of TiCl4. After stirring for 30 minutes, the pale yellow solution in beaker B was added to beaker A and stirred for another 30 minutes. 5.0g of the prepared PF was then added dropwise to beaker A, causing the solution to rapidly turn reddish-brown. After stirring for another 30 minutes, the solution was evenly coated onto a clean glass watch glass using a dropper. The solution was then air-dried for a period of time before being prepolymerized in a forced air drying oven. The temperature was raised to 40°C over a 1-minute period, the solvent evaporated over 12 hours, and then the temperature was rapidly raised to 100°C for 24 hours. After cooling to room temperature, a yellow, transparent film of polymer was obtained by scraping. The film was cut into pieces and transferred to a quartz boat, calcined in a high-purity nitrogen atmosphere, maintained at 350°C for 5 hours to remove the surfactant, calcined at 600°C for 2 hours for carbonization, and finally washed three times with deionized water and anhydrous ethanol to remove NaCl inorganic salts, ultimately obtaining a mesoporous carbon-titanium dioxide composite carrier material, named TiO2-C.

[0046] Weigh 200mg of the ground TiO2-C support. Use a pipette to pipette 420μL of a 0.002g / L ruthenium trichloride-ethanol solution. Add the solution evenly to the support and cover with plastic wrap. After sonication for 20 minutes, place the beaker in a 40°C vacuum drying oven and dry for 24 hours. The dried material is then placed in an atmosphere of H2 / N2 with a 1 / 4 volume ratio and heated to 200°C at a rate of 1°C / min for 2 hours for reduction. After preparation, the material is weighed at room temperature to yield a ruthenium-loaded mesoporous carbon-titanium oxide composite, designated Ru / TiO2-C.

[0047] To investigate the ruthenium loading, inductively coupled plasma optical emission spectroscopy (Varian VISTA-MPX) was used to analyze and calculate the metal loading of the catalyst before the reaction. The catalyst required pretreatment prior to testing. The specific steps were as follows: the catalyst powder was dissolved in a pre-prepared aqua regia solution, heated and concentrated, then diluted to volume. The prepared solution was then directly tested for Ru ion concentration. The Ru loading of the catalyst was ultimately determined to be 0.2 wt%, and the catalyst was ultimately designated 0.2% Ru / TiO2-C.

[0048] Its characteristic X-ray diffraction (XRD) pattern is shown in Figure 2 .

[0049] Its characteristic N2 adsorption isotherm and pore size distribution curve are shown in Figure 3 .

[0050] The applications of catalysts are as follows:

[0051] The selective hydrodeoxygenation of guaiacol to prepare cyclohexanol specifically comprises the following steps:

[0052] S1: The reaction was carried out in a 50 mL Parr autoclave. 5 mg of deionized water, 125 mg of guaiacol, and 125 mg of 0.2% Ru / TiO2-C catalyst were added to the autoclave. The autoclave was sealed and flushed with 1 MPa hydrogen three times to remove residual air.

[0053] S2: Maintaining the hydrogen pressure in the autoclave at 1 MPa, reacting at 210° C. with a stirring speed of 800 rpm for 3.5 h, cooling to room temperature, extracting three times with 4.5 g of ethyl acetate, and drying over anhydrous magnesium sulfate to obtain cyclohexanol.

[0054] Example 3:

[0055] A low-order phenolic resin was prepared in advance: 1.5 g of phenol and 28 g of formaldehyde were uniformly dispersed in an ethanol solution of sodium hydroxide, and the mixture was stirred at 50° C. to obtain a low molecular weight polymer of phenol and formaldehyde. The pH value was further adjusted to 7 to obtain a low-order phenolic resin polymer (PF).

[0056] Next, 1.0g of deionized water, 8.0g of ethanol, and 1.5g of F127 were weighed into a thermostatically controlled beaker A at 40°C and stirred for 30 minutes. In a low-temperature jacketed beaker B at -1°C, 0.5g of deionized water and 7.5g of ethanol were added, followed by a quick pipette transfer of 1.0mL of TiCl4. After stirring for 30 minutes, the pale yellow solution in beaker B was added to beaker A and stirred for another 30 minutes. 5.0g of the prepared PF was then added dropwise to beaker A, causing the solution to rapidly turn reddish-brown. After stirring for another 30 minutes, the solution was evenly coated onto a clean glass watch glass using a dropper. The solution was then air-dried for a period of time before being prepolymerized in a forced air drying oven. The temperature was raised to 40°C over a 1-minute period, the solvent evaporated over 12 hours, and then the temperature was rapidly raised to 100°C for 24 hours. After cooling to room temperature, a yellow, transparent film of polymer was obtained by scraping. The film was cut into pieces and transferred to a quartz boat, calcined in a high-purity nitrogen atmosphere, maintained at 350°C for 5 hours to remove the surfactant, calcined at 600°C for 2 hours for carbonization, and finally washed three times with deionized water and anhydrous ethanol to remove NaCl inorganic salts, ultimately obtaining a mesoporous carbon-titanium dioxide composite carrier material, named TiO2-C.

[0057] Weigh 200mg of the ground TiO2-C support and pipette 420μL of a 0.005g / L ruthenium trichloride-ethanol solution. Add the solution evenly to the support and cover with plastic wrap. After sonication for 20 minutes, dry the beaker in a 40°C vacuum oven for 24 hours. The dried material is then placed in an atmosphere of 1 / 4 H2 / N2 by volume and heated to 200°C at a rate of 1°C / min for 2 hours for reduction. After preparation, the material is weighed at room temperature to yield a ruthenium-loaded mesoporous carbon-titania composite, designated Ru / TiO2-C.

[0058] To investigate the ruthenium loading, inductively coupled plasma optical emission spectroscopy (Varian VISTA-MPX) was used to analyze and calculate the metal loading of the catalyst before the reaction. The catalyst required pretreatment prior to testing. The specific steps were as follows: the catalyst powder was dissolved in a pre-prepared aqua regia solution, first heated and concentrated, then diluted to volume. The prepared solution was then directly tested for Ru ion concentration. The Ru loading of the catalyst was ultimately determined to be 0.5 wt%, and the catalyst was ultimately designated 0.5% Ru / TiO2-C.

[0059] The application process of the catalyst is shown in Example 2.

[0060] Its characteristic X-ray diffraction (XRD) pattern is shown in Figure 2 .

[0061] Its characteristic N2 adsorption isotherm and pore size distribution curve are shown in Figure 3 .

[0062] Example 4:

[0063] A low-order phenolic resin was prepared in advance: 1.5 g of phenol and 28 g of formaldehyde were uniformly dispersed in an ethanol solution of sodium hydroxide, and the mixture was stirred at 50° C. to obtain a low molecular weight polymer of phenol and formaldehyde. The pH value was further adjusted to 7 to obtain a low-order phenolic resin polymer (PF).

[0064] Next, 1.0g of deionized water, 8.0g of ethanol, and 1.5g of F127 were weighed into a thermostatically controlled beaker A at 40°C and stirred for 30 minutes. In a low-temperature jacketed beaker B at -1°C, 0.5g of deionized water and 7.5g of ethanol were added, followed by a quick pipette transfer of 1.0mL of TiCl4. After stirring for 30 minutes, the pale yellow solution in beaker B was added to beaker A and stirred for another 30 minutes. 5.0g of the prepared PF was then added dropwise to beaker A, causing the solution to rapidly turn reddish-brown. After stirring for another 30 minutes, the solution was evenly coated onto a clean glass watch glass using a dropper. The solution was then air-dried for a period of time before being prepolymerized in a forced air drying oven. The temperature was raised to 40°C over a 1-minute period, the solvent evaporated over 12 hours, and then the temperature was rapidly raised to 100°C for 24 hours. After cooling to room temperature, a yellow, transparent film of polymer was obtained by scraping. The film was cut into pieces and transferred to a quartz boat, calcined in a high-purity nitrogen atmosphere, maintained at 350°C for 5 hours to remove the surfactant, calcined at 600°C for 2 hours for carbonization, and finally washed three times with deionized water and anhydrous ethanol to remove NaCl inorganic salts, ultimately obtaining a mesoporous carbon-titanium dioxide composite carrier material, named TiO2-C.

[0065] Weigh 200mg of the ground TiO2-C support and pipette 420μL of a 0.01g / L ruthenium trichloride-ethanol solution. Add the solution evenly to the support and cover with plastic wrap. After sonication for 20 minutes, dry the beaker in a 40°C vacuum oven for 24 hours. The dried material is then placed in an atmosphere of 1 / 4 H2 / N2 by volume and heated to 200°C at a rate of 1°C / min for 2 hours for reduction. After preparation, the material is weighed at room temperature to yield a ruthenium-loaded mesoporous carbon-titania composite, designated Ru / TiO2-C.

[0066] To investigate the ruthenium loading, inductively coupled plasma optical emission spectroscopy (Varian VISTA-MPX) was used to analyze and calculate the metal loading of the catalyst before the reaction. The catalyst required pretreatment prior to testing. The specific steps were as follows: The catalyst powder was dissolved in a pre-prepared aqua regia solution, first heated and concentrated, then diluted to volume. The prepared solution was then directly tested for Ru ion concentration. The Ru loading of the catalyst was ultimately determined to be 1 wt%, and the catalyst was ultimately named 1% Ru / TiO2-C.

[0067] The application process of the catalyst is shown in Example 2.

[0068] Its characteristic X-ray diffraction (XRD) pattern is shown in Figure 2 .

[0069] Its characteristic N2 adsorption isotherm and pore size distribution curve are shown in Figure 3 .

[0070] Example 4:

[0071] Prepare low-order phenolic resin in advance, the specific steps are as follows:

[0072] 1.5 g of phenol and 28 g of formaldehyde were uniformly dispersed in an ethanol solution of sodium hydroxide, and the mixture was stirred at 50° C. to obtain a low molecular weight polymer of phenol and formaldehyde. The pH value was further adjusted to 7 to obtain a low-order phenolic resin polymer (PF).

[0073] Next, 1.0g of deionized water, 8.0g of ethanol, and 1.5g of F127 were weighed into a thermostatically controlled beaker A at 40°C and stirred for 30 minutes. In a low-temperature jacketed beaker B at -1°C, 0.5g of deionized water and 7.5g of ethanol were added, followed by a quick pipette transfer of 1.0mL of TiCl4. After stirring for 30 minutes, the pale yellow solution in beaker B was added to beaker A and stirred for another 30 minutes. 5.0g of the prepared PF was then added dropwise to beaker A, causing the solution to rapidly turn reddish-brown. After stirring for another 30 minutes, the solution was evenly coated onto a clean glass watch glass using a dropper. The solution was then air-dried for a period of time before being prepolymerized in a forced air drying oven. The temperature was raised to 40°C over a 1-minute period, the solvent evaporated over 12 hours, and then the temperature was rapidly raised to 100°C for 24 hours. After cooling to room temperature, a yellow, transparent film of polymer was obtained by scraping. The film was cut into pieces and transferred to a quartz boat, calcined in a high-purity nitrogen atmosphere, maintained at 350°C for 5 hours to remove the surfactant, calcined at 600°C for 2 hours for carbonization, and finally washed three times with deionized water and anhydrous ethanol to remove NaCl inorganic salts, ultimately obtaining a mesoporous carbon-titanium dioxide composite carrier material, named TiO2-C.

[0074] Weigh 200mg of the ground TiO2-C support and pipette 420μL of a 0.03g / L ruthenium trichloride-ethanol solution. Add the solution evenly to the support and cover with plastic wrap. After sonication for 20 minutes, dry the beaker in a 40°C vacuum oven for 24 hours. The dried material is then placed in an atmosphere of H2 / N2 with a 1 / 4 volume ratio and heated to 200°C at a rate of 1°C / min for 2 hours. After preparation, the material is weighed at room temperature to yield a ruthenium-loaded mesoporous carbon-titania composite, designated Ru / TiO2-C.

[0075] To investigate the ruthenium loading, inductively coupled plasma optical emission spectroscopy (Varian VISTA-MPX) was used to analyze and calculate the metal loading of the catalyst before the reaction. The catalyst required pretreatment prior to testing. The specific steps were as follows: the catalyst powder was dissolved in a pre-prepared aqua regia solution, heated and concentrated, then diluted to volume. The prepared solution was then directly tested for Ru ion concentration. The Ru loading of the catalyst was ultimately determined to be 3 wt%, and the catalyst was ultimately named 3% Ru / TiO2-C.

[0076] The application process of the catalyst is shown in Example 2.

[0077] Its characteristic X-ray diffraction (XRD) pattern is shown in Figure 2 .

[0078] Its characteristic N2 adsorption isotherm and pore size distribution curve are shown in Figure 3 .

[0079] Product Analysis:

[0080] The liquid products were detected by Agilent 7890B gas chromatograph and separated using a chromatographic column model HP-5. The gas chromatography conditions included: split ratio 10:1, temperature 290°C, and nitrogen as carrier gas (3 mL min -1 ), temperature programmed heating (50°C, hold for 1 min, increase the temperature to 85°C at 2°C / min, hold for 2 min, then increase the temperature to 310°C at 20°C / min, hold for 2 min).

[0081] The conversion rate and product selectivity of the reactants were calculated based on the peak area data. Each reaction was repeated three times and the average value was calculated with an error of 5% or less. The initial reaction rate r0 value and TOF data were calculated when the conversion rate was less than 20%.

[0082] The conversion rate of guaiacol and the selectivity of the product were calculated by the following formula:

[0083] Conversion rate: Conv. (%) = [(n0-n t ) / n0]×100%

[0084] Selectivity: Sel.(%)=[n T / (n0-n t )]×100%

[0085] Where n0 is the initial amount of reactants before the reaction; n t is the amount of reactant remaining after reaction th; n T is the amount of the target product after reaction th.

[0086] The TOF (turnover frequency) calculation formula of the reaction is:

[0087] Where N is the molar ratio of the reaction substrate to the metal; t is the reaction time; X is the conversion rate of the substrate after reaction time th; τ is the exposure rate of the active metal.

[0088] The conversion rates and selectivities of the above-mentioned embodiments and the existing catalysts are shown in Table 1. It can be seen that the catalysts of the embodiments of the present invention have much higher conversion rates and selectivities than the existing technologies.

[0089] The results of the conversion rate and selectivity of the dehydrogenation and oxygenation reaction of guaiacol derivatives with various substituents by the catalyst in Example 2 are shown in Table 2. It can be seen that the catalyst in Example 2 of the present invention has good substrate universality.

[0090] The results of the cycle experiment on the total conversion rate, cyclohexanol yield and methanol yield of the catalyst in the dehydrogenation and oxygenation reaction of guaiacol in Example 2 are as follows: Figure 4 The rate of cyclohexanol formation in each cycle of selective hydrogenation of guaiacol is as follows: Figure 5 It can be seen that the catalyst of Example 2 of the present invention has very good cycle stability.

[0091] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A single-atom catalyst for preparing cyclohexanol, characterized in that: The catalyst is a ruthenium-containing catalyst supported on ordered mesoporous carbon-titania, which can selectively adsorb only the methoxyl functional group to achieve high selectivity for the single product cyclohexanol.

2. The single-atom catalyst for preparing cyclohexanol according to claim 1, wherein: The catalyst comprises ruthenium, titanium, carbon and oxygen elements, wherein the content of titanium dioxide is 60% and the content of carbon is 40%.

3. The single-atom catalyst for preparing cyclohexanol according to claim 1, wherein: The loading amount of Ru in the catalyst is 0.2-3 wt%.

4. A method for preparing a single-atom catalyst for preparing cyclohexanol according to any one of claims 1 to 3, characterized in that: The following steps are involved: Phenolic resin was prepared in advance: using amphiphilic triblock copolymer F127 as a template, phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, an ordered mesoporous carbon-titanium dioxide composite support material was prepared through solvent evaporation-induced self-assembly and high-temperature calcination, named TiO2-C; The ordered mesoporous carbon-titania composite support material is impregnated in a ruthenium trichloride-ethanol solution, with ruthenium trichloride as a precursor, and subjected to post-impregnation and hydrogen reduction to obtain a ruthenium-containing mesoporous carbon-titania catalyst, named Ru / TiO2-C.

5. The method for preparing a single-atom catalyst for preparing cyclohexanol according to claim 4, wherein: The phenolic resin is prepared in advance, specifically comprising: selecting a carbon source and an auxiliary agent, uniformly dispersing them in an organic solution of an alkaline catalyst, stirring them thoroughly to obtain a low molecular weight polymer of phenol and formaldehyde, and then adjusting the pH value to 7 to obtain a low molecular weight phenolic resin polymer.

6. The method for preparing a single-atom catalyst for preparing cyclohexanol according to claim 5, wherein: The carbon source and the auxiliary agent are uniformly dispersed in the organic solution of the alkaline catalyst and fully stirred at 30-70° C. to obtain a low molecular weight polymer of phenol and formaldehyde.

7. The method for preparing a single-atom catalyst for preparing cyclohexanol according to claim 5, wherein: When the phenolic resin is prepared in advance, after obtaining a low molecular weight polymer of phenol and formaldehyde, the pH value is adjusted to 7 to obtain a low-order phenolic resin polymer.

8. The method for preparing a single-atom catalyst for preparing cyclohexanol according to claim 4, wherein: The preparation process comprises the following steps: using an amphiphilic triblock copolymer F127 as a template, a phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, and subjecting the material to solvent volatilization-induced self-assembly and high-temperature calcination to obtain an ordered mesoporous carbon-titanium dioxide composite support material, which is named TiO2-C. The process comprises the following steps: using an amphiphilic triblock copolymer F127 as a template, a phenolic resin as a carbon source, and titanium tetrachloride as a titanium source, subjecting the material to solvent volatilization-induced self-assembly and high-temperature calcination at 600°C for 2 hours, and washing the material three times with deionized water and anhydrous ethanol to remove inorganic salts, to obtain an ordered mesoporous carbon-titanium dioxide composite support material, which is named TiO2-C.

9. Use of the single-atom catalyst for preparing cyclohexanol according to any one of claims 1 to 3 in catalyzing the selective hydrodeoxygenation of guaiacol to prepare cyclohexanol.

10. The use according to claim 9, characterized in that: The following steps are involved: Deionized water solvent, guaiacol, and ruthenium-mesoporous carbon-titanium dioxide composite catalyst were added to a high-pressure reactor, which was then sealed and purged with hydrogen three times to remove residual air. The hydrogen pressure in the kettle was maintained, and after the reaction was completed by stirring, the mixture was cooled to room temperature, extracted three times with ethyl acetate, and dried over anhydrous magnesium sulfate to prepare cyclohexanol.

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