FeOOH / C primary- secondary hydrogen conversion catalyst and preparation method thereof

Abstract

The application discloses a FeOOH / C primary-secundary hydrogen conversion catalyst and a preparation method thereof. The FeOOH / C primary-secundary hydrogen conversion catalyst has a FeOOH mass content of 30-90%, a specific surface area of 150-750 m 2 / g, a particle size of 20-60 meshes, and a bulk density of 0.2-0.8 g / mL. The preparation method is as follows: (1) uniformly mixing iron salt, an organic ligand, an organic polymer and a solvent by mass to obtain a precursor mixture; (2) performing a solvothermal reaction on the precursor mixture in a closed container, performing solid-liquid separation, vacuum drying the solid particles, and then calcining the Fe / C composite under an inert atmosphere to obtain a Fe / C composite; (3) adding the Fe / C composite into a proper amount of an aqueous solution containing an oxidant, and performing liquid-phase oxidation under a closed condition until the liquid-phase oxidation is fully performed; and (4) washing, drying, crushing and screening the obtained product to obtain a supported primary-secundary hydrogen conversion catalyst with a FeOOH / C structure. The FeOOH / C primary-secundary hydrogen conversion catalyst has the advantages of low preparation cost, simple production process, low material flow resistance and good catalytic effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid hydrogen, and particularly relates to an FeOOH / C primary-secundary hydrogen conversion catalyst and a preparation method thereof. BACKGROUND

[0002] A hydrogen molecule is composed of two hydrogen atoms with different nuclear spin directions, in which the nuclear spin symmetry is primary hydrogen, and the anti-symmetry is secundary hydrogen. Primary hydrogen and secundary hydrogen can stably exist in liquid and gaseous states. The primary-secundary hydrogen equilibrium concentration of hydrogen is affected by temperature. At room temperature, the content of primary hydrogen in hydrogen accounts for 25%, and the content of secundary hydrogen accounts for 75%, which is called normal hydrogen or standard hydrogen. When the temperature decreases, primary hydrogen spontaneously converts into secundary hydrogen. At the standard boiling point of liquid hydrogen, the content of secundary hydrogen can reach 99.8%. Without the action of an external catalyst, the spontaneous conversion of the primary-secundary state of hydrogen is very slow, and the heat released during the conversion process is greater than the heat of vaporization of liquid hydrogen, which can cause a large amount of vaporization of stored liquid hydrogen. In a liquid hydrogen storage tank, without the action of a catalyst, the heat released by the reaction causes the continuous vaporization of liquid hydrogen, thereby consuming the liquid hydrogen. In order to liquefy hydrogen while completing the conversion of primary hydrogen into secundary hydrogen, a high-performance low-temperature primary-secundary hydrogen conversion catalyst is crucial for the production and storage of liquid hydrogen.

[0003] CN112844443 A uses ordered mesoporous materials such as MCM-41, SBA-15, MCM-48 and CMK-3 as carriers, uses a chemical precipitation method to impregnate, roasts and then shapes to obtain a supported primary-secundary hydrogen conversion catalyst. However, the ordered mesoporous carrier material used in the method is expensive and the preparation is complex, resulting in high catalyst cost. The inorganic carrier used often has a large bulk density, which can easily cause the catalyst to be damaged and the bed to be blocked.

[0004] CN112044457 A uses an impregnation method to load metal active substances on the surface of a non-metal modified porous carrier to obtain a supported primary-secundary hydrogen conversion catalyst. The preparation process is simple, but the content of metal oxides obtained by the method is only 5-30%, the content of active metal is low, and the catalytic effect significantly decreases at high space velocity. The surface acidity of the carrier is adjusted by introducing phosphorus, chlorine and fluorine ions to improve the uniformity of the active component loading. However, the loss of the above ions in the use of the prepared catalyst can cause the deterioration of the quality of liquid hydrogen and have an adverse effect on the reactor. The inorganic carrier used generally has a large bulk density, which can easily cause the catalyst to be damaged and the bed to be blocked.

[0005] The existing supported primary-secundary hydrogen conversion catalysts have problems such as high preparation cost, low active metal content, large bulk density and poor catalytic effect. SUMMARY

[0006] In view of the deficiencies of the prior art, the FeOOH / C primary-secular hydrogen conversion catalyst and a preparation method thereof are provided, the obtained catalyst has low material flow resistance, good catalytic effect, low preparation cost and simple production process.

[0007] The FeOOH / C primary-secular hydrogen conversion catalyst comprises 10%-70% of a carbon carrier and 30%-90% of FeOOH, preferably 70%-90% of FeOOH, based on the mass of the catalyst; the Fe element is uniformly distributed on the carbon carrier, the specific surface area is 150-750 m 2 / g, the particle size is 20-60 mesh, and the bulk density is 0.2-0.8 g / mL.

[0008] The preparation method of the FeOOH / C primary-secular hydrogen conversion catalyst comprises the following steps:

[0009] (1) uniformly mixing iron salt, organic ligand, organic high molecular polymer and solvent by mass to obtain a precursor mixture;

[0010] (2) performing a solvothermal reaction on the precursor mixture in a closed container, cooling to room temperature after the reaction, solid-liquid separation, vacuum drying the solid particles, and then calcining under an inert atmosphere to obtain a Fe / C composite;

[0011] (3) adding the Fe / C composite into a proper amount of aqueous solution containing an oxidizing agent, and performing liquid-phase oxidation reaction under closed conditions until the reaction is fully performed;

[0012] (4) washing, drying, crushing and screening the obtained product to obtain a supported primary-secular hydrogen conversion catalyst with a FeOOH / C structure.

[0013] In the method, the material ratio in step (1) is 1-10 parts of iron salt, 0.5-20 parts of organic ligand, 2-50 parts of organic high molecular polymer and 50-150 parts of solvent by mass.

[0014] In the method, the iron salt in step (1) is one or more of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate or ferrous nitrate.

[0015] In the method, the organic ligand in step (1) is one or a mixture of any proportion of fumaric acid, terephthalic acid, amino terephthalic acid, trimesic acid, amino imidazole or 2-methyl imidazole.

[0016] In the method, the solvent in step (1) is one or a mixture of any proportion of ethanol, N,N-dimethylformamide, dimethyl sulfoxide or water.

[0017] In the method, the organic polymer in step (1) is one of polyvinylpyrrolidone, polymethyl acrylate, chitosan, polyacrylic acid, sodium citrate, sodium oleate, polyethylene glycol or carboxylated polyethylene glycol at both ends, or a mixture of any proportion thereof.

[0018] In the method, the reaction temperature of the solvothermal reaction in step (2) is 60-230°C, the reaction time is 3-30 hours, and the autogenous pressure. The preferred conditions of the solvothermal reaction are: the reaction temperature is 120-200°C, the reaction time is 5-24 hours, and the reaction pressure is autogenous pressure.

[0019] In the method, the solid-liquid separation in step (2) can remove impurities by filtration, centrifugation, natural sedimentation, etc., and the solvent used for washing is one or more of water, anhydrous ethanol, methanol and heptane.

[0020] In the method, the vacuum drying temperature in step (2) is 60-150°C, the vacuum drying time is 6-30 hours, and the vacuum degree is (-0.1)-(-8) kPa. Further preferably, the vacuum drying temperature is 80-130°C, and the vacuum drying time is 10-16 hours.

[0021] In the method, the calcination temperature in step (2) is 350-900°C, and the calcination time is 10-200 minutes. The preferred calcination conditions are: the calcination temperature is 450-650°C, and the calcination time is 20-100 minutes.

[0022] In the method, the inert atmosphere in step (2) is an inert gas and / or nitrogen.

[0023] In the method, the oxidizing agent in step (3) is hydrogen peroxide and / or peroxyacetic acid.

[0024] In the method, the mass ratio of the Fe / C composite to the oxidizing agent in step (3) is 1:1-5 by mass. The mass concentration of the oxidizing agent used is 1-30%, preferably 5-15%.

[0025] In the method, the liquid-phase oxidation conditions of the Fe / C composite and the oxidizing agent in step (3) are: the autogenous pressure, the reaction temperature is 10-150°C, and the reaction time is 1-24 hours. Preferably, the reaction temperature is 20-100°C, and the reaction time is 2-12 hours.

[0026] In the method of the present application, the drying conditions of the catalyst in step (4) are as follows: drying temperature 80-180 DEG C, drying time 3-48 hours, preferably drying temperature 120-150 DEG C, drying time 12-24 hours. The further preferred drying conditions are vacuum drying, vacuum degree (-0.1)-(-8) kPa, drying temperature 120-150 DEG C, drying time 6-12 hours.

[0027] The present application prepares an iron-based metal organic framework material from an iron salt and an organic ligand, and then obtains a Fe / C composite framework material with high metal content by calcination. After moderate liquid-phase oxidation, the Fe in the Fe / C framework material is converted into hydrated iron oxide FeOOH, thereby forming a supported primary and secondary hydrogen conversion catalyst with high metal content and a carbon carrier. The material has excellent primary and secondary hydrogen catalytic conversion effect.

[0028] The FeOOH / C primary and secondary hydrogen conversion catalyst of the present application has high active component content and uniform distribution, low bulk density, and does not contain harmful elements such as sodium, phosphorus, chlorine and fluorine ions, and has high catalytic performance. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 X-ray diffraction pattern of the primary and secondary hydrogen conversion catalyst prepared in Example 1 of the present application.

[0030] Figure 2 X-ray diffraction pattern of the primary and secondary hydrogen conversion catalyst prepared in Comparative Example 1 of the present application.

[0031] Figure 3 Iron element distribution map (white dots represent iron elements) of the primary and secondary hydrogen conversion catalyst prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0032] The method for measuring the FeOOH content of the catalyst of the present application is as follows: hydrochloric acid is used to dissolve the catalyst, the insoluble substance is separated to obtain a carbon carrier, and then the FeOOH content is calculated according to the weight difference before and after dissolution. The specific surface area is tested by the BET method. The bulk density is determined according to SH / T 0958-2017 Determination of Mechanical Tap Density of Shaped Catalysts and Catalyst Carriers. Example 1

[0033] By mass parts, 1 part and nine water of iron nitrate, 0.5 part of trimesic acid and 10 parts of polyethylene glycol were mixed with 100 parts of volume ratio of 1:1:1 of anhydrous ethanol, water, N,N-dimethylformamide. The mixture was placed in a reaction kettle at 150°C for 10h, cooled to room temperature. The product was washed with water and methanol alternately, centrifuged to obtain solid particles, dried at 80°C under vacuum for 12h, and then calcined at 450°C for 30min in an argon atmosphere to obtain a Fe / C composite. The obtained Fe / C composite was added to 15% hydrogen peroxide (mass ratio 1:2) and soaked at 60°C for 5h, then washed with water and separated by filtration, and dried at 120°C for 10h, and sieved to obtain a supported primary and secondary hydrogen conversion catalyst with a FeOOH / C framework structure of 30-40 mesh. The mass content of FeOOH in the obtained catalyst was 88%, the crushing strength was 8-15N / particle, the specific surface area of the material was 688m 2 / g, and the bulk density was 0.4g / mL. The test results of the primary and secondary hydrogen conversion performance of the obtained catalyst are shown in Table 1. Example 2

[0034] By mass parts, 1 part and six water of iron chloride, 1 part of isophthalic acid and 10 parts of polyvinylpyrrolidone were mixed with 100 parts of N,N-dimethylformamide. The mixture was placed in a reaction kettle at 180°C for 10h, cooled to room temperature. The product was washed with water and ethanol alternately, centrifuged to obtain solid particles, dried at 60°C under vacuum for 18h, and then calcined at 550°C for 20min in an argon atmosphere to obtain a Fe / C composite. The obtained Fe / C composite was added to 15% hydrogen peroxide (mass ratio 1:2) and soaked at 60°C for 5h, then washed with water and separated by filtration, and dried at 140°C for 8h, and sieved to obtain a supported primary and secondary hydrogen conversion catalyst with a FeOOH / C framework structure of 30-40 mesh. The mass content of FeOOH in the obtained catalyst was 85%, the crushing strength was 6-13N / particle, the specific surface area of the material was 539m 2 / g, and the bulk density was 0.5g / mL. The test results of the primary and secondary hydrogen conversion performance of the obtained catalyst are shown in Table 1. Example 3

[0035] By mass parts, 1 part and nine water iron sulfate, 1 part of benzene tricarboxylic acid and 12 parts of sodium citrate are mixed with 100 parts of ethylene glycol. The mixture is placed in a reaction kettle at 150℃ for 15h, and cooled to room temperature. After the product is alternately washed with water and ethanol, centrifugal separation is obtained. After drying at 80℃ for 10h, it is necessary to calcine at 450℃ for 60min in an argon atmosphere to obtain a Fe / C composite. The obtained Fe / C composite is added to 15% hydrogen peroxide (mass ratio of 1:2) at 60℃ for 5h, then washed with water and separated by filtration, and dried at 130℃ for 15h, and sieved to obtain a 30-40 mesh FeOOH / C skeleton structure supported catalyst for ortho-para hydrogen conversion. The mass content of FeOOH in the obtained catalyst is 89%, the crushing strength is 6-15N / pellet, the specific surface area of the material is 615m 2 / g, and the bulk density is 0.3g / mL. The test results of the ortho-para hydrogen conversion performance of the obtained catalyst are shown in Table 1.

[0036] Comparative Example 1

[0037] Example 2 in CN 112044457A.

[0038] Comparative Example 2

[0039] Example 1 in CN 112844443 A. Example 4

[0040] The prepared catalyst is loaded into a reaction tube, activated, and completely immersed in a liquid nitrogen bath. After the temperature is stable, the chromatograph is connected. Adjust the space velocity of hydrogen gas through the reaction tube until the flow meter reading is stable, measure the area of the para-hydrogen peak at different space velocities, and repeat the measurement 3 times. According to the calculation formula of para-hydrogen content in GB / T 40045-2021, the para-hydrogen content after catalysis by the catalyst at different space velocities is calculated. The test results of the ortho-para hydrogen conversion performance of the obtained catalyst are shown in Table 1.

[0041] Table 1 Para-hydrogen conversion rate (%)

[0042] L / L / min Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 50 100 99.9 100 100 99.9 300 97.6 97.7 97.6 96.3 96 600 95.7 95.9 95.4 94.1 94.5

[0043] The present application is described by the above examples to illustrate the detailed method of the present application, but the present application is not limited to the above detailed method, that is, it does not mean that the present application must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the scope of protection and disclosure of the present application.

Claims

1. A FeOOH / C secondary hydrogen conversion catalyst, characterized in that: Based on catalyst mass, the catalyst comprises: 10wt%~70wt% carbon support and 70wt%-90wt% FeOOH; catalyst specific surface area is 150-750m². 2 / g, particle size 20-60 mesh, bulk density 0.2-0.8g / mL.

2. The catalyst according to claim 1, characterized in that: Fe elements are evenly distributed on the carbon support.

3. A method for preparing the FeOOH / C secondary hydrogen conversion catalyst according to claim 1 or 2, characterized in that... The process includes the following: (1) mixing iron salt, organic ligand, organic polymer and solvent to obtain a precursor mixture; (2) placing the precursor mixture in a sealed container for a solvothermal reaction, cooling to room temperature after the reaction, separating the solid and liquid, drying the solid particles under vacuum, and then calcining under an inert atmosphere to obtain the Fe / C complex; (3) adding the Fe / C complex to an appropriate amount of aqueous solution containing an oxidant, and calcining under sealed conditions until the liquid phase oxidation reaction is fully carried out; (4) washing, drying, pulverizing and screening the obtained product to obtain the FeOOH / C secondary hydrogen conversion catalyst.

4. The method according to claim 3, characterized in that: The material proportions in step (1) by mass are: 1-10 parts iron salt, 0.5-20 parts organic ligand, 2-50 parts organic polymer, and 50-150 parts solvent.

5. The method according to claim 3, characterized in that: The iron salt mentioned in step (1) is one or more of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate, or ferrous nitrate.

6. The method according to claim 3, characterized in that: The organic ligand in step (1) is one or more of fumaric acid, terephthalic acid, aminoterephthalic acid, pyromellitic acid, aminoimidazole or 2-methylimidazole.

7. The method according to claim 3, characterized in that: The solvent in step (1) is one or more of ethanol, N,N-dimethylformamide, dimethyl sulfoxide, or water.

8. The method according to claim 3, characterized in that: The organic polymer mentioned in step (1) is one or more of the following: polyvinylpyrrolidone, polymethyl acrylate, chitosan, polyacrylic acid, sodium citrate, sodium oleate, polyethylene glycol, or polyethylene glycol with carboxyl groups at both ends.

9. The method according to claim 3, characterized in that: The reaction temperature of the solvothermal reaction in step (2) is 60-230℃, and the reaction time is 3-30 hours.

10. The method according to claim 3, characterized in that: The vacuum drying temperature in step (2) is 60-150℃, the vacuum drying time is 6-30 hours, and the vacuum degree is (-0.1)-(-8)kPa.

11. The method according to claim 3, characterized in that: The calcination temperature in step (2) is 350-900℃ and the calcination time is 10-200 minutes; the inert atmosphere is an inert gas and / or nitrogen.

12. The method according to claim 3, characterized in that: The oxidant in step (3) is hydrogen peroxide and / or peracetic acid.

13. The method according to claim 3, characterized in that: In step (3), the mass ratio of Fe / C complex to oxidant is 1:1 to 5, and the mass concentration of oxidant used is 1-30%.

14. The method according to claim 3, characterized in that: In step (3), the liquid phase oxidation conditions of the Fe / C complex with the oxidant are: under autogenous pressure, reaction temperature 10-150℃, and reaction time 1-24 hours.

15. The method according to claim 3, characterized in that: The drying conditions for the catalyst in step (4) are: drying temperature 80-180℃, drying time 3-48 hours.

16. The application of the FeOOH / C secondary hydrogen conversion catalyst according to claim 1 or 2 in the secondary hydrogen conversion reaction.

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