A catalyst for efficient catalytic conversion of primary and secondary hydrogen, preparation method and application

Abstract

The application provides a catalyst for efficient catalytic conversion of primary and secondary hydrogen, a preparation method and application. The catalyst is composed of M-FeF3 / C, the mass of M accounts for 1-5% of the total mass of the catalyst; wherein: FeF3 exists in the form of hydroxyl iron fluoride; M is selected from one or both of Mn elements and Ni elements; and C is a porous carbon rod carrier. The catalyst has a porous carbon rod as a carrier, a metal modified hydroxyl iron fluoride as an active phase, is applied to a primary and secondary hydrogen catalytic conversion process under a reaction condition of 20K-77K, has a conversion rate of greater than or equal to 98%, high reaction activity, a wide applicable temperature range, good environmental applicability and potential application value.

Description

Technical Field

[0001] This invention belongs to the field of energy and chemical engineering, and relates to the catalysis of n- and secondary hydrogen, specifically to a catalyst for the efficient catalytic conversion of n- and secondary hydrogen, its preparation method, and its application. Background Technology

[0002] Hydrogen energy is an abundant, green, low-carbon, and widely applicable secondary energy source. It bridges the gap between renewable energy sources such as wind and solar power and end-use energy, and is an important component of the future energy system. In the entire hydrogen energy industry chain—from production and storage to transportation and application—the safe and efficient storage and transportation of hydrogen are key bottlenecks restricting its use as an energy source. Hydrogen exists in various forms, including gaseous, liquid, and solid. Liquid hydrogen, with its advantages of easy storage and large expansion rate upon vaporization, has become one of the important methods for hydrogen energy use and storage.

[0003] Hydrogen molecules exist in two quantum spin isomers: orthohydrogen and parahydrogen. At room temperature, hydrogen gas is approximately composed of 75% orthohydrogen and 25% parahydrogen. As the temperature decreases, orthohydrogen, with its high-energy ground state, spontaneously transforms into the lower-energy parahydrogen, leading to a continuous increase in parahydrogen concentration. At 77 K, the orthohydrogen content is 51%, and the parahydrogen content is 49%; at the liquid hydrogen temperature of 20.4 K, the parahydrogen content reaches 99.8%. Hydrogen liquefaction is an exothermic process. Because the heat released during the conversion of orthohydrogen and parahydrogen is greater than the latent heat of vaporization of liquid hydrogen, liquid hydrogen evaporation occurs, resulting in an increase in pressure within the storage tank. To reduce losses and energy consumption during hydrogen liquefaction and to extend the time for lossless storage of liquid hydrogen as much as possible, the conversion of hydrogen to its orthohydrogen and parahydrogen states must be completed simultaneously with hydrogen liquefaction. However, the conversion of orthohydrogen and parahydrogen is an extremely slow process; therefore, catalysts are needed to accelerate the conversion rate of orthohydrogen to parahydrogen.

[0004] Currently, the main catalysts used for the conversion of n- and secondary hydrogen in liquid hydrogen production are hydrated iron oxide catalysts. However, iron-based catalysts suffer from problems such as narrow applicable temperature windows and low catalytic activity. Therefore, it is particularly urgent to develop n- and secondary hydrogen conversion catalysts with a wide temperature range and high performance. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a catalyst, preparation method and application for high-efficiency catalytic conversion of n- and para-hydrogen, and to solve the technical problems of narrow applicable temperature range and low reaction activity of the catalyst in the existing technology.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A catalyst with the composition M-FeF3 / C: M accounts for 1% to 5% of the total mass of the catalyst.

[0008] in:

[0009] FeF3 exists in the form of ferric hydroxyfluoride;

[0010] M is selected from one or both of the elements Mn and Ni;

[0011] C represents a porous carbon rod support.

[0012] This invention also protects a method for preparing the catalyst as described above, which employs an in-situ supported process and is carried out according to the following steps:

[0013] Step 1: Under conditions of 45℃~80℃, [the mixture] contains M and Fe 3+ A fluorinating agent is added dropwise to a polyol solution, and the mixture is stirred vigorously for 2–12 hours. Then, a porous carbon rod is added, and the mixture is allowed to stand for 12–24 hours to obtain a solid-liquid mixture.

[0014] Step 2: After dehydration and drying of the solid-liquid mixture obtained in Step 1, heat-treat it at 300℃~450℃ under an inert atmosphere for 2~6 hours to obtain the catalyst.

[0015] The present invention also has the following technical features:

[0016] In step one, M exists in the form of nitrate, acetate, and / or sulfate of element M; the Fe 3+ It exists in the form of ferric nitrate or ferric acetate.

[0017] In step one, the polyol is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

[0018] In step one, the fluorinating agent is an aqueous solution of hydrogen fluoride or an alcohol solution.

[0019] In step one, the Fe 3+ The molar ratio of hydrogen fluoride in the fluorinating reagent to hydrogen fluoride is 1:(3-10).

[0020] In step one, the mass concentration of the fluorinating reagent is 20% to 50%.

[0021] In step two, the inert atmosphere is nitrogen or argon.

[0022] The catalysts described above are used in the catalytic conversion of n- and para-hydrogen.

[0023] The aforementioned secondary hydrogen catalytic conversion reaction is a secondary hydrogen catalytic conversion reaction under conditions of 20K to 77K.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (I) The catalyst of this invention uses porous carbon rods as a support and metal-modified hydroxy fluoride iron as the active phase. It is applied to the catalytic conversion of n- and para-hydrogen under reaction conditions of 20K to 77K. The conversion rate is ≥98%, the reaction activity is high, the applicable temperature range is wide, the environmental adaptability is good, and it has potential application value.

[0026] (II) The present invention uses an in-situ supported process to prepare the catalyst, which has fewer steps and a simpler process, making it suitable for industrial production and application.

[0027] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, all raw materials used in this invention are known in the prior art, meaning that all raw materials used in this invention are commercially available.

[0029] The overall technical concept of this invention is as follows: By introducing ferromagnetic and paramagnetic metallic elements and non-metallic elements with strong electronegativity, the spin catalytic conversion process is accelerated by modulating the nuclear spin direction of hydrogen molecules under low-temperature conditions. At the same time, using porous carbon rods with large pore size, high specific surface area, and high strength as a support, the loading of the active phase of the catalyst is increased, the diffusion coefficient of hydrogen molecules on the catalyst surface is improved, the catalyst flow resistance is reduced, the catalytic conversion efficiency of positive and negative hydrogen is improved, and the reaction temperature range is broadened.

[0030] It should be noted that this invention uses porous carbon rods as a carrier and employs an in-situ loading process to prepare M-FeF3 / C. The porous carbon rods are commercially available products with a specific surface area ≥500 m². 2 / g, pore volume ≥1.1cm³ 3 / g, particle size approximately 2-3mm, average pore size approximately 15nm, particle strength ≥400N / cm 2 Wear is less than 0.5%.

[0031] Meanwhile, the n-parahydrogenation catalyst of this invention uses an isothermal reactor and employs chromatography to evaluate its performance. Of course, this invention can also be applied using an adiabatic or continuous reactor.

[0032] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0033] Example 1:

[0034] This embodiment provides a method for preparing a catalyst, which is carried out according to the following steps: 0.1M manganese sulfate, 0.1M nickel nitrate and 1.0M ferric nitrate are dissolved in 1000mL of ethylene glycol solvent. Under stirring at 80℃, 40wt% hydrofluoric acid is added dropwise to the above solution. After the addition is completed, stirring is continued for 12 hours. Then, 103g of porous carbon rod is added and allowed to stand for 24 hours. The resulting solid-liquid mixture is then dehydrated and dried under reduced pressure and heat-treated under argon at 450℃ for 4 hours to obtain catalyst A.

[0035] Example 2:

[0036] This embodiment provides a method for preparing a catalyst, which is carried out according to the following steps: 0.1M nickel nitrate and 2M ferric acetate are dissolved in 1000mL propylene glycol solvent. Under stirring at 60°C, 20% hydrofluoric acid is added dropwise to the above solution. After the addition is completed, stirring is continued for 2 hours. Then, 355g of porous carbon rod is added, and the mixture is allowed to stand for 12 hours. The resulting solid-liquid mixture is then dehydrated and dried under reduced pressure, and then heat-treated at 300°C under argon for 2 hours to obtain catalyst B.

[0037] Example 3:

[0038] This embodiment provides a method for preparing a catalyst, which is carried out according to the following steps: 0.2M manganese acetate and 3M ferric nitrate are dissolved in 1000mL of ethylene glycol solvent. Under stirring at 45°C, 50% hydrofluoric acid is added dropwise to the above solution. After the addition is completed, stirring is continued for 6 hours. Then, 200g of porous carbon rod is added, and the mixture is allowed to stand for 12 hours. The resulting solid-liquid mixture is then dehydrated under reduced pressure and dried, and then heat-treated at 350°C under nitrogen for 6 hours to obtain catalyst C.

[0039] Example 4:

[0040] This embodiment provides an application of the catalysts given in Examples 1 to 3 for the catalytic conversion of n- and para-hydrogen.

[0041] An isothermal reactor was used, and the reaction was carried out in a low-temperature Dewar flask at 77 K and 20 K, respectively, with a volume hourly space velocity of 75,000 h⁻¹. -1 The secondary hydrogen content was determined using a gas chromatography-TCD detector. The catalytic performance of catalysts A, B, and C obtained in Examples 1-3 for the n- and secondary hydrogen reactions is shown in Table 1.

[0042] Table 1. Catalytic conversion performance of different catalysts for n- and secondary hydrogenation

[0043]

[0044] As shown in Table 1, the catalysts for the efficient catalytic conversion of n- and secondary hydrogen given in Examples 1 to 3, when applied to the catalytic conversion reaction of n- and secondary hydrogen under conditions of 20K to 77K, have a conversion efficiency of more than 98%, and have potential application value.

Claims

1. A method for preparing a catalyst, characterized in that, This method employs an in-situ loading process and is carried out according to the following steps: Step 1: Under conditions of 45℃~80℃, [the mixture] contains M and Fe 3+ A fluorinating agent is added dropwise to a polyol solution, and the mixture is stirred vigorously for 2 to 12 hours. Then, a porous carbon rod is added, and the mixture is allowed to stand for 12 to 24 hours to obtain a solid-liquid mixture. Step 2: After dehydration and drying of the solid-liquid mixture obtained in Step 1, heat-treat it at 300℃~450℃ under an inert atmosphere for 2~6 hours to obtain the catalyst. The catalyst has the following composition: M-FeF3 / C, where M accounts for 1% to 5% of the total mass of the catalyst. in: FeF3 exists in the form of ferric hydroxyfluoride; M is selected from one or both of the elements Mn and Ni; C represents a porous carbon rod support.

2. The method for preparing the catalyst according to claim 1, characterized in that, In step one, M exists in the form of nitrate, acetate, and / or sulfate of element M; the Fe 3+ It exists in the form of ferric nitrate or ferric acetate.

3. The method for preparing the catalyst according to claim 1, characterized in that, In step one, the polyol is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

4. The method for preparing the catalyst according to claim 1, characterized in that, In step one, the fluorinating agent is an aqueous solution of hydrogen fluoride or an alcohol solution.

5. The method for preparing the catalyst according to claim 1, characterized in that, In step one, the Fe 3+ The molar ratio of hydrogen fluoride in the fluorinating reagent to hydrogen fluoride is 1:(3-10).

6. The method for preparing the catalyst according to claim 1, characterized in that, In step one, the mass concentration of the fluorinating reagent is 20% to 50%.

7. The method for preparing the catalyst according to claim 1, characterized in that, In step two, the inert atmosphere is nitrogen or argon.

8. The catalyst prepared by the method described in claim 1 is used for the catalytic conversion reaction of n- and para-hydrogen.

9. The application as described in claim 8, characterized in that, The aforementioned secondary hydrogen catalytic conversion reaction is a secondary hydrogen catalytic conversion reaction under conditions of 20K to 77K.

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