Supported monatomic catalyst, its preparation method and application in primary secondary hydrogen conversion

Abstract

This invention relates to a supported single-atom catalyst, its preparation method, and its application in the conversion of n- and secondary hydrogens. The preparation method includes: mixing a salt solution containing a metal precursor with a porous catalyst support, ultrasonicating, drying, and calcining to obtain the supported single-atom catalyst. This catalyst preparation method is simple, highly reproducible, and easy to scale up, and exhibits high activity, high stability, and high mechanical strength in the catalytic conversion of n- and secondary hydrogens. Under conditions of 78 K, 2000 cc(H2) / min / g(catalyst), and 1 atm, the supported single-atom catalyst achieves a catalytic conversion efficiency of up to 93% for n- and secondary hydrogens.

Description

Technical Field

[0001] This invention relates to a supported single-atom catalyst, its preparation method, and its application in the conversion of n- and para-hydrogen, belonging to the field of energy and chemical engineering. Background Technology

[0002] Hydrogen energy is a high-energy-density, clean, and carbon-free secondary energy source. Its large-scale application relies on efficient and economical storage and transportation technologies, and hydrogen liquefaction is a key pathway to achieving this goal. Liquid hydrogen has a volumetric energy density approximately 800 times that of gaseous hydrogen, significantly reducing storage and transportation costs, making it an indispensable resource for the development of aerospace, heavy transportation, and the future hydrogen energy industry. However, hydrogen liquefaction technology has a high technological threshold. A complete hydrogen liquefaction plant involves highly complex cryogenic system engineering, one of the core components of which is the "normal-parahydrogen catalytic conversion." The efficiency of this step directly determines the quality of the final liquid hydrogen product and the overall energy consumption and economic efficiency of the liquefaction system.

[0003] Research on n- and para-hydrogen conversion catalysts began in the 1930s. To improve low-temperature activity, catalysts typically need to be fabricated with high specific surface area and porous structures, but this often sacrifices their mechanical strength. In large-scale industrial plants, catalysts must withstand long-term scouring by high-pressure, high-speed hydrogen gas flows and bed pressure. Insufficient mechanical strength leads to catalyst pulverization and wear, increasing operating resistance. Furthermore, the powder carried out by the gas flow can damage downstream equipment, severely restricting the stable long-term, high-load operation of the plant. The core technologies for high-performance catalysts, especially the next-generation catalysts needed for future large-scale and higher-efficiency liquefaction plants, still need to be mastered. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a supported single-atom catalyst for the catalytic conversion of n- and secondary hydrogen and its application. The catalyst preparation method is simple, highly reproducible, easy to scale up, and has the characteristics of high activity, high stability, and high mechanical strength for the catalytic conversion of n- and secondary hydrogen.

[0005] This invention effectively increases the exposure of active metal sites by highly dispersing the active metal, and regulates the structure and properties of the active metal sites, thereby enhancing the catalytic activity of the catalyst for both n- and para-hydrogenation.

[0006] According to one aspect of this application, a method for preparing a supported single-atom catalyst is provided, the method comprising: A salt solution containing a metal precursor is mixed with a porous catalyst support, ultrasonically treated, dried, and calcined to obtain the supported single-atom catalyst.

[0007] Optionally, the metal in the metal precursor is selected from at least one of iron, manganese, nickel, and cobalt.

[0008] Optionally, in the salt solution containing the metal precursor, the concentration of the metal precursor is 0.1~100 mg / mL.

[0009] Optionally, the preparation method includes: mixing a solution containing a precursor metal salt with a porous catalyst support, loading the active metal onto the surface of the catalyst support by impregnation, deposition-precipitation or other methods, and ensuring full contact by ultrasonic treatment, and then drying and calcining the solid product to obtain the supported single-atom catalyst.

[0010] Optionally, the salt solution of the metal precursor is selected from at least one of the following: iron salts (ferric sulfate, ferric nitrate, ferric chloride, ferrous chloride, ferrous acetate, ferrous sulfate), manganese salts (manganese sulfate, manganese nitrate, manganese chloride, manganese acetate), nickel nitrates (nickel sulfate, nickel nitrate, nickel chloride, nickel acetate), and cobalt salts (cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate).

[0011] Optionally, in the salt solution containing the metal precursor, the solvent is selected from at least one of water, ethanol, methanol, and acetone.

[0012] Optionally, the porous catalyst support is at least one of molecular sieve, alumina, silica, and ion exchange resin.

[0013] Optionally, after mixing the salt solution containing the metal precursor with the porous catalyst support, the step of adding a precipitant thereto is further included.

[0014] Optionally, the precipitant is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, and sodium carbonate; Preferably, the preparation method includes: mixing a salt solution containing a metal precursor with a porous catalyst support, adding a precipitant, ultrasonically treating, drying, and calcining to obtain the supported single-atom catalyst; the content of the precipitant in the solution after adding the precipitant is 0.1~2 mol / L.

[0015] Preferably, the temperature of the ultrasonic treatment is 5~50℃, and the ultrasonic treatment time is 0.5~20h; Preferably, the drying temperature is 25~180℃, the drying time is 1~72h, the calcination temperature is 200~800℃, and the calcination time is 1~24h.

[0016] According to a second aspect of this application, a supported single-atom catalyst is provided, said catalyst being selected from catalysts prepared according to the method described above.

[0017] Optionally, the catalyst has a metal loading of 0.01~10wt%, a particle size of 20~40 mesh, and a specific surface area of ​​50~400 m². 2 / g, crushing strength: 10~15N / particle.

[0018] According to a third aspect of this application, an application of the above-described supported single-atom catalyst in the conversion of n- and secondary hydrogen is provided.

[0019] Optionally, the application includes: First, the catalyst packed in the fixed-bed reactor is activated. Then, a feed gas containing normal hydrogen is introduced to contact the supported single-atom catalyst and react to obtain a product containing secondary hydrogen.

[0020] Optionally, the activation temperature is 100~600℃.

[0021] Optionally, the activation atmosphere is at least one of: vacuuming, nitrogen purging, hydrogen purging, and helium purging.

[0022] Optionally, the reaction is carried out in a low-temperature fixed-bed reactor.

[0023] Optionally, the pressure of the reactor is 0.1~0.5MPa.

[0024] Optionally, the reaction temperature is 21~273K.

[0025] Optionally, the pressure of the reaction gas is 0.1~0.5 MPa.

[0026] Optionally, the space velocity of the reaction gas is 100~3000cc(H2) / min / g (catalyst).

[0027] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention provides a precise, controllable, reliable and highly repeatable method for preparing a supported single-atom catalyst.

[0028] (2) The catalyst provided in this application has strong mechanical strength, and its crushing strength is 10~15N / particle.

[0029] (3) The catalyst provided in this application is used for the catalytic conversion of positive and negative hydrogen. Under the conditions of 78K, 2000cc(H2) / min / g(catalyst) and 1atm, the positive hydrogen conversion efficiency reaches 93%, which is better than the commercial hydrated iron oxide catalyst. Attached Figure Description

[0030] The above and other objects, features, and advantages of the present invention will become readily understood by referring to the accompanying drawings and reading the following detailed description. In the drawings, several embodiments of the invention are shown by way of example rather than limitation, wherein like reference numerals denote like or corresponding parts, wherein: Figure 1 The graph shows the mechanical strength test results of the catalyst prepared in Example 1; Figure 2 The image shows an aberration-corrected electron microscope (AC-HAADF-STEM) image of the catalyst in Example 1, at a scale of 5 nm. Detailed Implementation

[0031] The following examples will help to further understand the present invention, but should not be construed as limiting the scope of protection of the above-described subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. Experimental methods in the following examples that do not specify specific conditions are performed according to conventional methods and conditions, or as selected according to the product instructions.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0033] Example 1 217.2 g of Fe(NO3)3·9H2O was dissolved in 1000 mL of anhydrous ethanol. After the ferric nitrate was fully dissolved, 1000 g of alumina support was poured into the above solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain the 3.0 Fe-N catalyst.

[0034] Figure 1 The graph shows the mechanical strength test results of Example 1; Figure 2 The image shows an aberration-corrected electron microscope (AC-HAADF-STEM) image of the catalyst in Example 1, at a scale of 5 nm.

[0035] Example 2 107.4 g of Fe2(SO4)3 was dissolved in 1000 mL of anhydrous ethanol. After the ferric sulfate was fully dissolved, 1000 g of alumina support was poured into the solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain the 3.0 Fe-S catalyst.

[0036] Example 3 87.2 g of FeCl3 was dissolved in 1000 mL of anhydrous ethanol. After the ferric chloride was fully dissolved, 1000 g of alumina support was poured into the solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain 3.0 Fe-Cl catalyst.

[0037] Example 4 99.7 g of Ni(NO3)2 was dissolved in 1000 mL of anhydrous ethanol. After the nickel nitrate was fully dissolved, 1000 g of alumina support was poured into the solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain the 3.0 Ni-N catalyst.

[0038] Example 5 96.1 g of Mn(NO3)2 was dissolved in 1000 mL of anhydrous ethanol. After the manganese nitrate was fully dissolved, 1000 g of alumina support was poured into the above solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain 3.0 Mn-N catalyst.

[0039] Example 6 217.2 g of Fe(NO3)3·9H2O was dissolved in 1000 mL of anhydrous ethanol. After the ferric nitrate was fully dissolved, 1000 g of molecular sieve (ZSM-5) support was poured into the solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain the 3.0Fe-Z catalyst.

[0040] Example 7 217.2 g of Fe(NO3)3·9H2O was dissolved in 2000 mL of deionized water. After the ferric nitrate was fully dissolved, 1000 g of alumina support was poured into the above solution at room temperature and simultaneously placed in an ultrasonic instrument for ultrasonic treatment. Then, while stirring, 20 mL of ammonia solution (25 wt%) was added dropwise. After ultrasonic treatment for 1 hour, the solid was transferred to an oven and dried at 100 °C for 24 hours. Then, it was transferred to a muffle furnace and calcined at 400 °C for 3 hours to obtain the 3.0 Fe-A catalyst.

[0041] Application Example 1 0.2 g of catalyst was weighed and poured into a fixed-bed reaction tube. The tube was purged with high-purity nitrogen for 5 minutes, followed by purging with high-purity hydrogen at room temperature for 0.5 hours. The temperature was then raised to 450 °C and maintained for 2 hours to remove adsorbed water, air, and other impurities, while simultaneously removing oxygen species from the metal sites, thus activating the catalyst. The reaction tube was then cooled to the desired reaction conditions, and normal hydrogen gas was introduced at room temperature. The reaction conditions were 1 bar, 78 K, and a reaction space velocity of 2000 cc(H2) / min / g(catalyst). The products were analyzed by chromatography.

[0042] The specific results are shown in Tables 1 and 2.

[0043] Table 1 Results of n- and parahydrogenation

[0044] Conversion efficiency = (exit secondary hydrogen content - inlet secondary hydrogen content) / (equilibrium conversion secondary hydrogen content - inlet secondary hydrogen content); the commercial hydrated iron oxide is from Molecular Products Limited, USA.

[0045] As shown in Table 1, the prepared catalyst exhibits excellent conversion efficiency of n- and para-hydrogen.

[0046] Table 2. Stability test of the 3.0Fe-N catalyst (Preparation Example 1) for the conversion of n- and secondary hydrogens.

[0047] After reacting for 12 hours, the catalyst was removed from the reaction tube, reactivated, and subjected to a secondary hydrogen catalytic conversion test.

[0048] Table 2 shows that this type of catalyst has good catalytic stability and can be treated with hydrogen and reused.

[0049] This method prepares a supported single-atom catalyst through co-precipitation. In the catalytic conversion of n- and secondary hydrogen, this invention can effectively increase the exposure of active metal sites by highly dispersing the active metal, and regulate the structure and properties of the active metal sites, thereby improving the catalytic activity of the catalyst in the n- and secondary hydrogen conversion reaction.

[0050] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a supported single-atom catalyst, characterized in that, The preparation method includes: A salt solution containing a metal precursor is mixed with a porous catalyst support, ultrasonically treated, dried, and calcined to obtain the supported single-atom catalyst.

2. The preparation method according to claim 1, characterized in that, The metal in the metal precursor is selected from at least one of iron, manganese, nickel, and cobalt.

3. The preparation method according to claim 1, characterized in that, In the salt solution containing the metal precursor, the concentration of the metal precursor is 0.1~100 mg / mL.

4. The preparation method according to claim 1, characterized in that, In the salt solution containing the metal precursor, the solvent is selected from at least one of water, ethanol, methanol, and acetone.

5. The preparation method according to claim 1, characterized in that, The porous catalyst support is at least one of molecular sieve, alumina, silica, and ion exchange resin.

6. The preparation method according to claim 1, characterized in that, After mixing the salt solution containing the metal precursor with the porous catalyst support, the process also includes the step of adding a precipitant thereto.

7. The preparation method according to claim 6, characterized in that, The precipitant is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, and sodium carbonate. Preferably, the preparation method includes: mixing a salt solution containing a metal precursor with a porous catalyst support, adding a precipitant, ultrasonically treating, drying, and calcining to obtain the supported single-atom catalyst; the content of the precipitant in the solution after adding the precipitant is 0.1~2 mol / L; Preferably, the temperature of the ultrasonic treatment is 5~50℃, and the ultrasonic treatment time is 0.5~20h; Preferably, the drying temperature is 25~180℃, the drying time is 1~72h, the calcination temperature is 200~800℃, and the calcination time is 1~24h.

8. A supported single-atom catalyst, characterized in that, The catalyst is selected from catalysts prepared by the method according to any one of claims 1 to 7.

9. The catalyst according to claim 8, characterized in that, The catalyst has a metal loading of 0.01–10 wt%, a particle size of 20–40 mesh, and a specific surface area of ​​50–400 m². 2 / g, crushing strength: 10~15N / particle.

10. The application of the supported single-atom catalyst according to claim 8 or 9 in the conversion of n- and para-hydrogen.

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