Preparation method of high-activity low-cost supported ortho-parahydrogen conversion catalyst

Abstract

The invention discloses a preparation method of a high-activity low-cost supported ortho-parahydrogen conversion catalyst. The preparation method comprises the following steps: S1, preparing a SiO2 pellet template by adopting a Stber method; s2, preparing a methyl methacrylate mixed solution, and adding a SiO2 pellet template; s3, polymerizing to form polymethyl methacrylate; s4, carbonizing the polymethyl methacrylate to obtain a carbon skeleton; s5, preparing an ordered macroporous carbon skeleton; and S6, preparing the supported ortho-parahydrogen conversion catalyst. According to the invention, the problems of harsh preparation conditions, high cost, unfavorable large-scale production and the like of the ortho-parahydrogen conversion catalyst are solved, and the application effect of the ortho-parahydrogen conversion catalyst in the hydrogen liquefaction process is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a high-activity, low-cost supported normal-parahydrogen conversion catalyst. Background Art

[0002] Hydrogen molecules can be divided into two forms: orthohydrogen and parahydrogen, depending on the spin direction of the hydrogen atoms. In orthohydrogen, the two hydrogen atoms spin in the same direction; in parahydrogen, the two hydrogen atoms spin in opposite directions. At room temperature, hydrogen is a mixture of 75% orthohydrogen and 25% parahydrogen. When room temperature hydrogen is liquefied, the resulting liquid hydrogen is in a non-equilibrium state, and orthohydrogen spontaneously converts to parahydrogen in an exothermic process.

[0003] The conversion of orthohydrogen to parahydrogen releases a large amount of conversion heat (706 kJ / Kg at 30 K). This conversion heat is much greater than the latent heat of vaporization of liquid hydrogen (447 kJ / Kg at 30 K). Therefore, it will cause the evaporation of liquid hydrogen, increase the pressure inside the storage tank, and seriously affect the safety and stability of liquid hydrogen during storage and transportation.

[0004] To effectively increase the proportion of parahydrogen in liquid hydrogen, reduce evaporation, and improve safety during liquid hydrogen storage and transportation, a specific ortho-parahydrogen conversion catalyst is required during the hydrogen liquefaction process. This catalyst significantly increases the conversion rate of orthohydrogen to parahydrogen, thereby reducing liquid hydrogen loss.

[0005] Currently, there are some related patented technologies that attempt to solve this problem. For example: Chinese patent CN 115155583 A discloses an electrically supported catalyst for the conversion of ortho-parahydrogen, but its preparation requires high conditions and supporting equipment, which is not conducive to industrial production. Chinese patent CN 117645276 A discloses the use of a single-atom catalyst in the conversion of ortho-parahydrogen. This technical solution uses precious metals, which makes the catalyst cost difficult to control and is not conducive to large-scale commercial use. Chinese patent CN 118079961 A discloses a catalyst, preparation method and application for the efficient catalytic conversion of ortho-parahydrogen. This technical solution uses a large amount of fluorination reagent, which makes water treatment difficult in actual production and causes severe pollution, which is not conducive to catalyst cost control. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a high-activity, low-cost supported para-hydrogen conversion catalyst, so as to solve the problems of harsh preparation conditions, high cost, and disadvantages of large-scale production of para-hydrogen conversion catalysts in the prior art, and to improve their application effect in the hydrogen liquefaction process.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] A method for preparing a high-activity, low-cost supported para-hydrogen conversion catalyst comprises the following steps: S1. Preparation of SiO2 bead templates using the Stöber method; S2. The methyl methacrylate monomer, initiator and acetone solvent were mixed, and after ultrasonic treatment, SiO2 beads were added to the template, and the supernatant was removed after centrifugation; S3 filled with nitrogen to deoxygenate, repeated several times after the prepolymerization reaction in a vacuum oven, then heated to form polymethyl methacrylate, which was then washed with anhydrous ethanol and dried; S4. Carbonizing polymethyl methacrylate under a nitrogen atmosphere to obtain a carbon skeleton; S5. The carbon skeleton is dispersed in an alkaline solution to remove the SiO2 ball template, and then washed and dried after heating to obtain an ordered macroporous carbon skeleton; S6. Immerse the ordered macroporous carbon skeleton in an iron ion solution, ultrasonically treat it, let it stand, adjust the pH value with a precipitant, let it stand again, obtain an active material precursor, and calcine it after washing and drying to obtain a supported normal-para hydrogen conversion catalyst.

[0009] Preferably, step S1 is specifically as follows: first, 5-30 mL of ammonia water, 20-50 mL of deionized water and 50-150 mL of ethanol are mixed to form a mixed solution and transferred to a three-necked flask; then, 10-50 L of ethyl orthosilicate is dissolved in 50-100 mL of ethanol, and the solution is added to the formed mixed solution, vigorously stirred at 40-60° C. for 1-3 hours, and the obtained white suspension is centrifuged and washed with ethanol; finally, dried in air to obtain a spherical SiO2 ball template.

[0010] Preferably, the step S2 is specifically as follows: adding 0.1-0.5 g of methyl methacrylate monomer, 0.01-0.1 g of benzoyl peroxide and 2-5 mL of acetone solvent to a centrifuge tube with a rubber sieve, and ultrasonicating for 10 minutes; then adding 0.5-1 g of SiO2 ball template into the centrifuge tube, centrifuging at 5000-10000 rpm for 30-60 minutes, and then removing the supernatant.

[0011] Preferably, step S3 is specifically as follows: first, nitrogen is filled into the centrifuge tube through a rubber stopper with double holes, and the process is repeated 3 to 5 times; then, the centrifuge tube is placed in a vacuum oven at 50-70° C. for prepolymerization reaction for several hours, and then the temperature is raised to 80° C. for polymerization reaction to form polymethyl methacrylate; then, the mixture is quickly washed with anhydrous ethanol for 3 minutes to remove residual monomers, and the washed polymethyl methacrylate is taken out and dried.

[0012] Preferably, the step S4 specifically comprises: placing polymethyl methacrylate in a tube furnace, carbonizing it at 450-800° C. in a nitrogen atmosphere for 2-5 hours to obtain a carbon skeleton and taking it out.

[0013] Preferably, step S5 is specifically as follows: dispersing the carbon skeleton in 10-40 mL of 0.5-5 M NaOH solution, transferring the resulting suspension to a 50 mL hydrothermal autoclave, and heating at 80-220° C. for 1-5 hours. The resulting product is washed four times with deionized water to remove residual NaOH, and then dried under vacuum conditions to obtain an ordered macroporous carbon skeleton.

[0014] Preferably, step S6 is specifically as follows: immersing the ordered macroporous carbon skeleton in a 0.1-1.0 mol / L iron ion solution, ultrasonicating for 5-240 minutes, then standing for 0.1-24 hours at room temperature and vacuum environment, adjusting the pH of the mixed solution to 8-14 using an alkaline solution, and then standing for 1-36 hours at room temperature and vacuum environment to obtain an active material precursor and washing and drying it; then using a muffle furnace to calcine at a calcination temperature of 300-600°C, a heating rate of 2-10°C / min and a holding time of 1-5 hours to obtain a supported normal-parahydrogen conversion catalyst.

[0015] Preferably, the iron ion solution includes any one of ferric nitrate solution, ferric sulfate solution and ferric chloride solution, and the alkaline solution includes any one of ammonia water, sodium hydroxide solution and potassium hydroxide solution.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0017] The supported ortho-parahydrogen conversion catalyst prepared by the present invention has high activity: the supported ortho-parahydrogen conversion catalyst prepared by the present invention can significantly increase the content of parahydrogen during the hydrogen liquefaction process. This high activity ensures that orthohydrogen can be quickly and effectively converted into parahydrogen during the hydrogen liquefaction process, reduces the evaporation loss of liquid hydrogen, and improves the storage and transportation safety and stability of liquid hydrogen.

[0018] The present invention has low cost for preparing supported n-parahydrogen conversion catalysts: the preparation method of the present invention significantly reduces the manufacturing cost of the catalyst by optimizing the loading ratio of the active substance and using an economical and efficient carrier material (ordered macroporous carbon skeleton). Compared with the existing technology, the use of precious metals is reduced, and the preparation process is simple, which is easy to achieve large-scale industrial production.

[0019] The supported ortho-parahydrogen conversion catalyst prepared by the present invention has a uniform macroporous structure: the uniform macroporous structure can provide a good reaction environment for catalytic conversion, thereby not only increasing the specific surface area of ​​the catalyst, but also making the active material uniformly loaded and fully exposing the active sites, thereby improving the catalytic efficiency.

[0020] The mechanical bonding stability of the supported n-parahydrogen conversion catalyst prepared by the present invention: appropriate calcination temperature and treatment process increase the mechanical bonding stability of the catalyst and the carrier, extend the service life of the catalyst, and reduce the replacement frequency and maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a microscopic morphology of the SiO2 bead template prepared in the present invention; Figure 2 This is a microscopic morphology of the carbon skeleton prepared in the present invention; Figure 3 This is a nitrogen adsorption and desorption curve of the supported normal-parahydrogen conversion catalyst prepared in the present invention; Figure 4 This is a pore size distribution diagram of the supported n-parahydrogen conversion catalyst prepared in the present invention; Figure 5 This is a microscopic morphology of the supported n-parahydrogen conversion catalyst obtained in Example 1 of the present invention; Figure 6 This is a microscopic morphology of the supported n-parahydrogen conversion catalyst obtained in Example 2 of the present invention; Figure 7 The microscopic morphology of the sample obtained for Comparative Example 1; Figure 8 The microscopic morphology of the sample obtained for Comparative Example 2; Figure 9 The microscopic morphology of the sample obtained for comparative example 3; Figure 10 The microscopic morphology of the sample obtained in Comparative Example 4. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] A method for preparing a high-activity, low-cost supported para-hydrogen conversion catalyst comprises the following steps: S1. SiO2 bead templates were prepared using the Stöber method.

[0024] The specific steps are as follows: First, mix 5-30 mL of ammonia water, 20-50 mL of deionized water and 50-150 mL of ethanol to form a mixed solution and transfer it to a three-necked flask; then dissolve 10-50 L of tetraethyl orthosilicate (TEOS) in 50-100 mL of ethanol, add the solution to the formed mixed solution, stir vigorously at 40-60°C for 1-3 hours, centrifuge the obtained white suspension, wash with ethanol; finally, dry in air to obtain a spherical SiO2 ball template.

[0025] S2. Methyl methacrylate monomer, initiator and acetone solvent are mixed, and after ultrasonic treatment, SiO2 bead template is added. The supernatant is removed after centrifugation.

[0026] The microscopic morphology of the SiO2 ball template prepared by the above steps is as follows: Figure 1 shown.

[0027] The specific steps are as follows: Add 0.1-0.5g of methyl methacrylate monomer, 0.01-0.1g of benzoyl peroxide (as initiator) and 2-5mL of acetone solvent to a centrifuge tube with a rubber sieve and ultrasonicate for 10 minutes; then add 0.5-1g of SiO2 ball template to the centrifuge tube, centrifuge at 5000-10000 rpm for 30-60 minutes, remove the tube and remove the supernatant.

[0028] S3. Nitrogen is injected to remove oxygen, and the reaction is repeated several times before prepolymerization in a vacuum oven. The temperature is then raised to polymerize the product to form polymethyl methacrylate, which is then washed with anhydrous ethanol and dried.

[0029] The specific steps are as follows: First, nitrogen is filled into the centrifuge tube through a double-hole rubber stopper to achieve the purpose of freezing, nitrogen filling and deoxygenation, and this is repeated 3 to 5 times; then the centrifuge tube is placed in a vacuum oven at 50-70°C for prepolymerization reaction for several hours, and then the temperature is raised to 80°C for polymerization reaction to form polymethyl methacrylate; then it is quickly washed with anhydrous ethanol for 3 minutes to remove residual monomers, and the washed polymethyl methacrylate is taken out and dried.

[0030] S4. Carbonize polymethyl methacrylate under a nitrogen atmosphere to obtain a carbon skeleton.

[0031] The specific steps are as follows: The polymethyl methacrylate is placed in a tube furnace and carbonized at 450-800° C. for 2-5 hours in a nitrogen atmosphere to obtain a carbon skeleton, which is then taken out.

[0032] The microscopic morphology of the carbon skeleton prepared by the above steps is as follows Figure 2 shown.

[0033] S5. The carbon skeleton is dispersed in an alkaline solution to remove the SiO2 ball template, and then washed and dried after heat treatment to obtain an ordered macroporous carbon skeleton.

[0034] The specific steps are as follows: The carbon skeleton was dispersed in 10-40 mL of 0.5-5 M NaOH solution, the resulting suspension was transferred to a 50 mL hydrothermal autoclave and heated at 80-220°C for 1-5 hours. The resulting product was washed four times with deionized water to remove residual NaOH, and then dried under vacuum conditions to obtain an ordered macroporous carbon skeleton.

[0035] S6. Immerse the ordered macroporous carbon skeleton in an iron ion solution, ultrasonically treat it, let it stand, adjust the pH value with a precipitant, let it stand again, obtain an active material precursor, and calcine it after washing and drying to obtain a supported normal-para hydrogen conversion catalyst.

[0036] The specific steps are as follows: an ordered macroporous carbon skeleton is impregnated as a carrier in a 0.1-1.0 mol / L iron ion solution (which can be any one of ferric nitrate solution, ferric sulfate solution and ferric chloride solution), ultrasonicated for 5-240 minutes, and then allowed to stand at room temperature and vacuum for 0.1-24 hours. An alkaline solution (which can be any one of ammonia water, sodium hydroxide solution and potassium hydroxide solution) is used as a precipitant to adjust the pH of the mixed solution to 8-14, and then allowed to stand at room temperature and vacuum for 1-36 hours to obtain an active material precursor and wash and dry it; then a muffle furnace is used to calcine at a calcination temperature of 300-600°C, a heating rate of 2-10°C / min and a holding time of 1-5 hours to obtain a sample, i.e., a supported normal-parahydrogen conversion catalyst.

[0037] The principles of the present invention are as follows: First, a SiO2 bead template is prepared using a simple Stöber method. The SiO2 bead template does not participate in the polymerization reaction of methyl methacrylate. By introducing the SiO2 bead template, the SiO2 bead template becomes regularly arranged under high-speed centrifugation, while methyl methacrylate fills the interstices between the SiO2 bead templates. Subsequently, polymerization occurs in an oxygen-free environment, forming polymethyl methacrylate. The polymethyl methacrylate in the interstices between the SiO2 bead templates is carbonized under calcination, and the SiO2 bead templates are then removed by chemical treatment with alkaline solution, leaving an ordered carbon skeleton. This ordered macroporous skeleton provides a uniform, ordered, and high-specific-surface-area support for the catalytic active material, which is loaded by impregnation and subsequently calcined to form the catalyst. The supported n-parahydrogen conversion catalyst prepared by this invention exhibits a 3D uniform macroporous structure, providing an optimal reaction environment for catalytic conversion. The uniform loading of the active material fully exposes the active sites, minimizing the active material loading. Furthermore, proper calcination enhances the mechanical stability of the catalyst-support bond.

[0038] The nitrogen adsorption and desorption curve of the supported normal-parahydrogen conversion catalyst prepared by the method of the present invention is as follows: Figure 3 As shown, the pore size distribution is Figure 4The supported normal-parahydrogen conversion catalyst prepared by the method of the present invention can effectively improve the conversion rate of parahydrogen in the liquefaction process, reduce the hydrogen liquefaction time, and improve the hydrogen liquefaction efficiency under the premise of low manufacturing cost of the catalyst material.

[0039] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0040] A method for preparing a high-activity, low-cost supported para-hydrogen conversion catalyst comprises the following steps: S1. Prepare SiO2 bead templates using the Stöber method. First, mix 10 mL of ammonia water, 20 mL of deionized water, and 70 mL of ethanol to form a mixed solution, which is transferred to a three-necked flask. Then, dissolve 10 mL of ethyl orthosilicate in 90 mL of ethanol. This solution is added to the mixed solution and vigorously stirred at 40°C for 2.5 hours. The resulting white suspension is centrifuged and washed four times with ethanol. Finally, the solution is air-dried to obtain spherical SiO2 bead templates.

[0041] S2. Take a 10mL centrifuge tube with a rubber sieve, add 0.2g of methyl methacrylate monomer, 0.02g of benzoyl peroxide, and 2mL of acetone solvent, and sonicate for 10 minutes; then add 1g of SiO2 bead template to the centrifuge tube, centrifuge at 10000rpm for 60 minutes, remove the tube, and remove the supernatant.

[0042] S3. First, fill the centrifuge tube with nitrogen through a double-hole rubber stopper for about 3 minutes to achieve the purpose of freezing, filling with nitrogen and deoxygenating, and repeat 3 to 5 times; then place the centrifuge tube in a vacuum oven at 65°C for prepolymerization for several hours, and then raise the temperature to 80°C for polymerization to form polymethyl methacrylate; then quickly wash with anhydrous ethanol for 3 minutes to remove residual monomers, and take out the white precipitate (polymethyl methacrylate) after washing, and dry it at 90°C for 6 hours.

[0043] S4. Place polymethyl methacrylate in a tube furnace and carbonize it at 550°C under a nitrogen atmosphere for 2 hours to obtain black particles (carbon skeleton), which are then removed.

[0044] S5. The carbon skeleton was dispersed in 35 mL of 2.00 M NaOH solution. The resulting suspension was transferred to a 50 mL hydrothermal autoclave and heated at 80°C for 4 h. The resulting product was washed four times with deionized water to remove residual NaOH and then dried at 60°C under vacuum to obtain an ordered macroporous carbon skeleton.

[0045] S6. Immerse the ordered macroporous carbon skeleton in a 0.6 mol / L ferric nitrate solution, ultrasonicate for 60 minutes, then let it stand at room temperature and vacuum for 1 hour, adjust the pH of the mixed solution to 10 with ammonia water, then let it stand at room temperature and vacuum for 24 hours to obtain an active material precursor and wash and dry it; then use a muffle furnace to calcine at a calcination temperature of 300°C, a heating rate of 2°C / min and a holding time of 2 hours to obtain a supported normal-parahydrogen conversion catalyst. The microscopic morphology of the supported normal-parahydrogen conversion catalyst obtained in this embodiment is as follows: Figure 5 shown. Example 2

[0046] A method for preparing a high-activity, low-cost supported normal-parahydrogen conversion catalyst, steps S1 to S5 are not limited by the method provided by the present invention, and step S6 is specifically as follows: immersing the ordered macroporous carbon skeleton in a 0.5 mol / L ferric nitrate solution, ultrasonically stirring for 10 minutes, then standing for 0.2 hours at room temperature and vacuum environment, adjusting the pH of the mixed solution to 12 with ammonia water, then standing for 24 hours at room temperature environment to obtain an active material precursor and washing and drying; then using a muffle furnace to calcine at a calcination temperature of 300 ° C, a heating rate of 2 ° C / min and a holding time of 2 hours to obtain a sample, i.e., a supported normal-parahydrogen conversion catalyst. The microscopic morphology of the supported normal-parahydrogen conversion catalyst obtained in this embodiment is as follows: Figure 6 shown.

[0047] The present invention will be further described in detail below with reference to specific comparative examples.

[0048] Comparative Example 1 does not add a carrier: Without adding carriers, the active material was directly prepared and calcined to obtain the microscopic morphology of the sample. Figure 7 shown.

[0049] Comparative Example 2 uses commercial activated carbon (40-60 mesh) as a carrier (calcination temperature 550 degrees Celsius): The commercial activated carbon (40-60 mesh) was immersed in a 1 mol / L ferric nitrate solution and ultrasonically stirred for 60 minutes. The mixture was then allowed to stand at room temperature and vacuum for 1 hour. The pH of the mixed solution was adjusted to 10 using ammonia water. The mixture was then allowed to stand at room temperature and vacuum for 12 hours, washed and dried, and calcined in a muffle furnace at a calcination temperature of 550°C, a heating rate of 2°C / min, and a holding time of 2 hours to obtain a sample. The micromorphology of the sample is shown in FIG. Figure 8 shown.

[0050] Comparative Example 3 uses commercial activated carbon (40-60 mesh) as a carrier (calcination temperature 200 degrees Celsius): The commercial activated carbon (40-60 mesh) was immersed in 1 mol / L ferric nitrate solution and ultrasonically stirred for 60 minutes. Then, it was allowed to stand at room temperature and vacuum for 1 hour. The pH of the mixed solution was adjusted to 10 with ammonia water. Then, it was allowed to stand at room temperature and vacuum for 12 hours, washed and dried. The sample was calcined in a muffle furnace at a calcination temperature of 200°C, a heating rate of 2°C / min, and a holding time of 2 hours. Its micromorphology is shown in FIG. Figure 9 shown.

[0051] Comparative Example 4 uses commercial molecular sieve (3A) as a carrier (calcination temperature 200 degrees Celsius): The 3A molecular sieve was immersed in a 0.5 mol / L ferric nitrate solution and ultrasonically stirred for 60 minutes. Then, it was allowed to stand at room temperature and vacuum for 1 hour. The pH of the mixed solution was adjusted to 10 with ammonia water. Then, it was allowed to stand at room temperature and vacuum for 24 hours, washed and dried. The sample was calcined in a muffle furnace at a calcination temperature of 200°C, a heating rate of 2°C / min, and a holding time of 2 hours. Its micromorphology is shown in FIG. Figure 10 shown.

[0052] The catalytic activities of the supported n-parahydrogen catalysts of different samples were tested at liquid nitrogen (80K) and liquid hydrogen temperature ranges (20K), as shown in Table 1 below. The samples prepared by the method of the present invention had a parahydrogen content of 95.1% after conversion at 20K, meeting the requirements for parahydrogen content in liquid hydrogen as specified in the national standard GBT 40061-2021 Technical Specifications for Liquid Hydrogen Production Systems.

[0053] Table 1 Catalytic activity of supported parahydrogen catalysts of different samples .

Claims

1. A method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst, characterized by: The following steps are involved: S1. Preparation of SiO2 bead templates using the Stöber method; S2. The methyl methacrylate monomer, initiator and acetone solvent were mixed, and after ultrasonic treatment, SiO2 beads were added to the template, and the supernatant was removed after centrifugation; S3 filled with nitrogen to deoxygenate, repeated several times after the prepolymerization reaction in a vacuum oven, then heated to form polymethyl methacrylate, which was then washed with anhydrous ethanol and dried; S4. Carbonizing polymethyl methacrylate under a nitrogen atmosphere to obtain a carbon skeleton; S5. The carbon skeleton is dispersed in an alkaline solution to remove the SiO2 ball template, and then washed and dried after heating to obtain an ordered macroporous carbon skeleton; S6. Immerse the ordered macroporous carbon skeleton in an iron ion solution, ultrasonically treat it, let it stand, adjust the pH value with a precipitant, let it stand again, obtain an active material precursor, and calcine it after washing and drying to obtain a supported normal-para hydrogen conversion catalyst.

2. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 1, characterized in that: The step S1 specifically comprises: first mixing 5-30 mL of ammonia water, 20-50 mL of deionized water, and 50-150 mL of ethanol to form a mixed solution, and transferring the mixed solution to a three-necked flask; then dissolving 10-50 L of ethyl orthosilicate in 50-100 mL of ethanol, adding the solution to the formed mixed solution, vigorously stirring at 40-60° C. for 1-3 hours, centrifuging the obtained white suspension, and washing with ethanol; and finally drying in air to obtain a spherical SiO2 ball template.

3. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 1, characterized in that: The step S2 specifically comprises: adding 0.1-0.5 g of methyl methacrylate monomer, 0.01-0.1 g of benzoyl peroxide, and 2-5 mL of acetone solvent to a centrifuge tube with a rubber sieve, and ultrasonicating for 10 minutes; then adding 0.5-1 g of SiO2 bead template to the centrifuge tube, centrifuging at 5000-10000 rpm for 30-60 minutes, and removing the supernatant.

4. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 3, characterized in that: The step S3 specifically comprises: first, nitrogen is filled into the centrifuge tube through a rubber stopper with two holes, and the process is repeated 3 to 5 times; then, the centrifuge tube is placed in a vacuum oven at 50-70° C. for prepolymerization reaction for several hours, and then the temperature is raised to 80° C. for polymerization reaction to form polymethyl methacrylate; then, the polymethyl methacrylate is quickly washed with anhydrous ethanol for 3 minutes to remove residual monomers, and the washed polymethyl methacrylate is taken out and dried.

5. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 1, characterized in that: The step S4 specifically comprises placing polymethyl methacrylate in a tube furnace, carbonizing it at 450-800° C. in a nitrogen atmosphere for 2-5 hours to obtain a carbon skeleton and taking it out.

6. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 1, characterized in that: The step S5 is specifically as follows: dispersing the carbon skeleton in 10-40 mL of 0.5-5 M NaOH solution, transferring the resulting suspension to a 50 mL hydrothermal autoclave, and heating at 80-220° C. for 1-5 hours. The resulting product is washed four times with deionized water to remove residual NaOH, and then dried under vacuum conditions to obtain an ordered macroporous carbon skeleton.

7. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 1, characterized in that: The step S6 is specifically as follows: immersing the ordered macroporous carbon skeleton in a 0.1-1.0 mol / L iron ion solution, ultrasonicating for 5-240 minutes, then standing for 0.1-24 hours at room temperature and vacuum environment, adjusting the pH of the mixed solution to 8-14 using an alkaline solution, and then standing for 1-36 hours at room temperature and vacuum environment to obtain an active material precursor and washing and drying it; then using a muffle furnace to calcine at a calcination temperature of 300-600°C, a heating rate of 2-10°C / min, and a holding time of 1-5 hours to obtain a supported normal-parahydrogen conversion catalyst.

8. The method for preparing a high-activity, low-cost supported n-parahydrogen conversion catalyst according to claim 7, characterized in that: The iron ion solution includes any one of ferric nitrate solution, ferric sulfate solution and ferric chloride solution, and the alkaline solution includes any one of ammonia water, sodium hydroxide solution and potassium hydroxide solution.

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