Orthohydrogen and parahydrogen conversion catalyst as well as preparation method and application thereof

Abstract

The invention discloses an ortho-parahydrogen conversion catalyst and a preparation method and application thereof.The method at least comprises the steps that a five-component catalyst containing Fe, Co and Ni and containing any two kinds of metal of Mn, Mg, Cr, Cu, Zn, Ga, Sn and Al is prepared, the catalyst is prepared through a hydrothermal method, and the specific steps are as follows: soluble salts of the metal components are dissolved in water and stirred, and a solution A is obtained; preparing a soluble alkaline aqueous solution to obtain a solution B; dropwise adding the solution A into the solution B, or dropwise adding the solution B into the solution A, and controlling the pH value to be 8-13 to obtain a turbid liquid C; placing the suspension C in a hydrothermal kettle for hydrothermal reaction at the reaction temperature of 120-250 DEG C, and filtering, washing and drying after the reaction is finished to obtain the multi-component catalyst containing five metal components. The catalyst prepared by the method can be used for catalyzing ortho-parahydrogen low-temperature conversion reaction and has the remarkable advantage of high catalytic activity, meanwhile, the preparation process is simple, and large-scale production is easy.

Description

Technical Field

[0001] This application relates to a positive and negative hydrogen conversion catalyst, its preparation method, and its application, belonging to the field of catalyst application technology. Background Technology

[0002] Liquid hydrogen, as a highly efficient liquid fuel and cryogenic cold source, has wide applications in chemical production, aerospace engineering, hydrogen fuel cell vehicles, neutron cooling, and particle detection. The large-scale use of hydrogen energy inevitably raises the question of how to efficiently store liquid hydrogen, which is inextricably linked to the chemical and physical properties of the hydrogen molecule.

[0003] The nuclear spins of the two hydrogen atoms in a hydrogen molecule can be parallel or antiparallel, resulting in two spin isomers: positive (positive) and negative (negative). As the temperature decreases, positive hydrogen spontaneously converts to negative (negative), causing the concentration of negative hydrogen to increase. The heat released during this positive-negative conversion exceeds the latent heat of vaporization of liquid hydrogen, leading to its evaporation. To reduce evaporation losses and the energy consumption of reliquefaction, and to extend the time for lossless storage of liquid hydrogen, the positive-negative conversion must be completed simultaneously with hydrogen liquefaction.

[0004] The natural conversion of ortho and parahydrogen is an extremely slow process, so catalysts are needed to accelerate the conversion rate. It is generally believed that the low-temperature conversion of ortho and parahydrogen involves a magnetic mechanism, where hydrogen atoms are transformed by the non-uniform magnetic field of the catalyst. Transition elements (such as iron, nickel, manganese, and chromium) have unpaired electrons in their 3d or 4f shells, making them a primary research focus for low-temperature conversion catalysts of ortho and parahydrogen, such as Cr₂O₃-Al₂O₃, Cr₂O₃+Ni, Cr(OH)₃, Mn(OH)₄, FeOOH, Co(OH)₃, and Ni(OH)₂. In addition, nano-gold, nano-silver, silicon, and activated carbon are also widely studied as low-temperature conversion catalysts for ortho and parahydrogen.

[0005] Currently, the main catalysts used for the conversion of n- and secondary hydrogen in liquid hydrogen production are hydrated iron oxide catalysts. Although hydrated iron oxide catalysts have advantages such as safety and reliability, they still suffer from problems such as a narrow applicable temperature window and low catalytic activity. Therefore, it remains essential to develop low-temperature n- and secondary hydrogen conversion catalysts with high catalytic activity and simple preparation processes. Summary of the Invention

[0006] This application proposes a catalyst for the conversion of n- and para-hydrogen, its preparation method, and its application. The catalyst prepared by this method has high activity and a simple preparation process.

[0007] According to a first aspect of this application, a method for preparing a n-parahydroconversion catalyst is provided, the method comprising: Solution A and solution B were mixed and subjected to a precipitation reaction followed by a hydrothermal reaction to obtain the aforementioned secondary hydrogen conversion catalyst. The solution A includes Fe, Co, Ni, and a soluble metal salt containing any two metal components selected from Mn, Mg, Cr, Cu, Zn, Ga, Sn, and Al. Solution B contains a soluble base.

[0008] Optionally, the hydrothermal reaction conditions are: temperature of 120~250℃ and time of 6~72h.

[0009] Optionally, the temperature of the hydrothermal reaction is independently selected from 250°C, 200°C, 160°C, 140°C, and 120°C, and the time is independently selected from 72 h, 65 h, 60 h, 55 h, 50 h, 40 h, 20 h, 10 h, and 6 h.

[0010] Optionally, the precipitation reaction conditions are 2-90℃, preferably 5-80℃.

[0011] Optionally, the soluble metal salt is at least one selected from nitrates, sulfates, chlorides, and acetates; Preferably, the soluble metal salt in solution A has a mass percentage content of 1-50%, more preferably 5-20 wt%.

[0012] Optionally, in solution A, the ratio of metal atoms in various metal salts is an equimolar ratio.

[0013] Optionally, the soluble alkali is selected from at least one of ammonium carbonate, ammonium bicarbonate, urea, ammonia, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

[0014] Optionally, in the solution B, the mass content of the alkali is 1-50%, preferably 5-30 wt%.

[0015] Optionally, the preparation method includes: (1) Dissolve a soluble metal salt containing Fe, Co, Ni and any two metal components from Mn, Mg, Cr, Cu, Zn, Ga, Sn, and Al in water and stir to obtain solution A; (2) Prepare a soluble alkaline aqueous solution, stir, and obtain solution B; (3) Add solution A dropwise to solution B, or add solution B dropwise to solution A, stir to cause precipitation reaction, control the pH value between 8 and 13, and obtain suspension C; (4) The suspension C obtained in step (3) is placed in a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, the solution is filtered, washed and dried to obtain the positive and negative hydrogen conversion catalyst. Preferably, the dry atmosphere is an air atmosphere or an inert gas atmosphere; the inert gas is nitrogen, argon, or helium. Preferably, the drying temperature is 60~160℃, more preferably 80~140℃; the drying time is 1~48h, more preferably 3~24h.

[0016] According to a second aspect of this application, a secondary hydrogen conversion catalyst is provided, wherein the secondary hydrogen conversion catalyst is selected from any one of the secondary hydrogen conversion catalysts prepared according to the above preparation method.

[0017] According to a third aspect of this application, the above-mentioned secondary hydrogen conversion catalyst is provided for use in catalyzing secondary hydrogen conversion reactions.

[0018] The beneficial effects that this application can produce include: The multi-component metal catalyst of this invention has the characteristics of high entropy effect in thermodynamics, synergistic effect of multiple metal ions, and high dispersion of multiple elements. Therefore, it generates more active sites for low-temperature conversion of n- and para-hydrogen, which significantly improves the n- and para-hydrogen conversion activity of the catalyst. The catalyst preparation process is simple and easy to scale up. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the performance evaluation device for the low-temperature conversion reaction of n- and para-hydrogen in the embodiment described above. Detailed Implementation

[0020] The present application is further illustrated below with reference to specific embodiments. The following descriptions are merely a few embodiments of the present application and are not intended to limit the present application in any way. Although the present application discloses preferred embodiments as follows, they are not intended to limit the present application. Any modifications or variations made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

[0021] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without any special treatment.

[0022] The secondary hydrogen content analysis method involved using a secondary hydrogen conversion catalyst activity evaluation device combined with gas chromatography to detect the secondary hydrogen content. (See attached document). Figure 1 .

[0023] Example 1 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #1.

[0024] Example 2 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 180°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #2.

[0025] Example 3 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and aluminum nitrate (all of the above metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #3.

[0026] Example 4 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and aluminum nitrate (all of the above metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 160°C for 24 hours to obtain catalyst #4.

[0027] Example 5 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and aluminum trichloride (all metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #5.

[0028] Example 6 300g of aqueous solutions containing equimolar amounts of iron nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions are 10% by mass) were placed in a reaction vessel, sealed, stirred, and heated to 40°C. A 15% sodium hydroxide aqueous solution was added dropwise until the pH reached 9, resulting in a suspension containing the five metal salts. The suspension was then placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours. After cooling to room temperature, the precipitate was filtered, washed with water until the pH reached approximately 7, and then dried in air at 140°C for 24 hours to obtain catalyst #6.

[0029] Example 7 300g of aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions are 10% by mass) in an equimolar ratio were placed in a reaction vessel, sealed, stirred, and cooled to 10°C. A 15% sodium hydroxide aqueous solution was added dropwise until the pH reached 9, resulting in a suspension containing the five metal salts. The suspension was then placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours. After cooling to room temperature, the precipitate was filtered, washed with water until the pH reached approximately 7, and then dried in air at 140°C for 24 hours to obtain catalyst #7.

[0030] Comparative Example 1 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and a 10% ferric nitrate aqueous solution was added dropwise until the pH reached 9. The addition was then stopped to obtain an iron-based precipitate. The precipitate was filtered, washed with water until the pH reached approximately 7, and then dried in air at 110°C for 24 hours and calcined in air at 160°C for 6 hours to obtain catalyst #8.

[0031] Comparative Example 2 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions were 10% by mass) were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 100°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #9.

[0032] Comparative Example 3 300g of a 15% sodium hydroxide aqueous solution was placed in a reaction vessel; after sealing, the mixture was stirred and heated to 40°C, and aqueous solutions of ferric nitrate, cobalt nitrate, nickel nitrate, manganese nitrate, and gallium nitrate (all metal salt solutions were 10% by mass) with a metal atomic molar ratio of 1:3:1:2:1 were added dropwise until the pH reached 9, resulting in a suspension containing five metal salts; the suspension was placed in a hydrothermal reactor and hydrothermally treated at 160°C for 24 hours, then cooled to room temperature, the precipitate was filtered, washed with water until the pH reached ≈7, and then dried in air at 140°C for 24 hours to obtain catalyst #10.

[0033] Application examples Catalyst activity evaluation in Figure 1 The reaction was performed using the low-temperature conversion evaluation apparatus for n- and secondary hydrogen shown. 0.5 g of catalyst was weighed and placed in the conversion furnace. The furnace was heated to 110 °C and purged with helium at a flow rate of 10 ml / min for 12 h. Heating and purging were then stopped, and the furnace was allowed to cool to room temperature before being placed in a Dewar flask. The Dewar flask was filled with liquid nitrogen, and once the temperature sensor indicated that the liquid nitrogen temperature had been reached, hydrogen was introduced to perform the n- and secondary hydrogen conversion. The converted hydrogen was then analyzed by gas chromatography for secondary hydrogen content. The reaction temperature was 79 K, the reaction pressure was 1.3 atm, and the hydrogen flow rate was 600 ml / min. The experimental results are shown in Table 1.

[0034] Table 1 Comparison of catalytic performance of different catalysts for the conversion of n- and secondary hydrogen

[0035] As shown in Table 1, under the same experimental conditions, the five-member metal catalysts provided in the embodiments of the present invention all exhibited excellent catalytic activity, which was superior to the reference catalyst.

[0036] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A process for the preparation of a primary-to-secondary hydrogen conversion catalyst, characterized in that, The preparation method comprises: mixing solution A with solution B to perform a precipitation reaction and a hydrothermal reaction, to obtain the primary-sec hydrogen conversion catalyst; the solution A comprises Fe, Co, Ni, and soluble metal salts of any two metal components selected from Mn, Mg, Cr, Cu, Zn, Ga, Sn, and Al; the solution B comprises a soluble base.

2. The production method according to claim 1, characterized by, The hydrothermal reaction is performed at a temperature of 120-250°C for 6-72h.

3. The production method according to claim 1, characterized by, The precipitation reaction is performed at a temperature of 2-90°C, preferably 5-80°C.

4. The method of claim 1, wherein, The soluble metal salt is at least one of nitrate, sulfate, chloride, and acetate. Preferably, the mass percentage of the soluble metal salt in the solution A is 1-50%, preferably 5-20wt%.

5. The preparation method according to claim 1, characterized in that, In the solution A, the metal atoms in the various metal salts are in equimolar ratio.

6. The method of claim 1, wherein, The soluble base is at least one of ammonium carbonate, ammonium bicarbonate, urea, aqueous ammonia, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium hydroxide, and sodium hydroxide.

7. The production method according to claim 6, wherein In the solution B, the mass content of the base is 1-50%, preferably 5-30wt%.

8. The method of claim 1, wherein, The preparation method comprises: (1) dissolving soluble metal salts of Fe, Co, Ni, and any two metal components selected from Mn, Mg, Cr, Cu, Zn, Ga, Sn, and Al in water, and stirring to obtain solution A; (2) preparing a soluble base aqueous solution, and stirring to obtain solution B; (3) adding the solution A to the solution B, or adding the solution B to the solution A, and stirring to perform a precipitation reaction, with the pH value controlled at 8-13, to obtain suspension C; (4) placing the suspension C obtained in step (3) in a hydrothermal kettle to perform a hydrothermal reaction, filtering, washing, and drying after the reaction to obtain the primary-sec hydrogen conversion catalyst. Preferably, the drying atmosphere is an air atmosphere or an inert gas atmosphere; the inert gas is nitrogen, argon, or helium. Preferably, the drying temperature is 60-160°C, preferably 80-140°C; and the time is 1-48h, preferably 3-24h.

9. A primary-to-sec hydrogen conversion catalyst characterized by, The primary-sec hydrogen conversion catalyst is selected from any one of the primary-sec hydrogen conversion catalysts prepared according to the preparation method of any one of claims 1-8.

10. Use of the primary-sec hydrogen conversion catalyst of claim 9 in catalyzing a primary-sec hydrogen conversion reaction.

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