Iron-based primary and secondary hydrogen conversion catalyst, preparation method and application

Abstract

This invention provides an iron-based secondary hydrogen conversion catalyst, its preparation method, and its application. The catalyst is prepared by treating alumina with N and Mg, and then using the treated alumina as a support. The iron loading is 10-25% of the alumina mass. When used in the secondary hydrogen conversion reaction, the catalyst achieves a conversion rate of 92.6%-98.4%. This invention introduces alkali metal ions onto the surface of the nitrided alumina, forming a thin-shell distribution on the support surface, reducing diffusion resistance and thus improving catalytic activity. Simultaneously, a magnesium-aluminum spinel structure is formed on the modified support surface, providing more tetrahedral defect sites for the active components, further enhancing catalytic activity. The catalyst particle strength is ≥350 N / cm². 2 The wear rate is less than 0.5%, which significantly improves the flow resistance of the catalyst bed under the conditions of positive and negative hydrogen conversion.

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 an iron-based n- and secondary hydrogen conversion catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy is an ideal clean energy source with advantages such as renewability, high energy density, and high calorific value. Hydrogen exists in various forms, including gaseous, liquid, and solid. Liquid hydrogen is easy to store and expands significantly upon vaporization, making it one of the important methods for the use and storage of hydrogen energy.

[0003] Hydrogen molecules exist in two states: orthohydrogen and secondary hydrogen. At room temperature, hydrogen gas is composed of approximately 75% orthohydrogen and 25% secondary hydrogen. As the temperature decreases, orthohydrogen, with its high-energy ground state, spontaneously transforms into secondary hydrogen, which has a lower energy state, leading to a continuous increase in the concentration of secondary hydrogen. When hydrogen gas at room temperature is directly liquefied, the resulting liquid hydrogen is in a non-equilibrium state, and orthohydrogen spontaneously transforms into secondary hydrogen. This process is exothermic. Because the heat released during the orthohydrogen-secondary hydrogen transformation exceeds the latent heat of vaporization of liquid hydrogen, regardless of the insulation performance of the liquid hydrogen storage tank, liquid hydrogen will evaporate, leading to an increase in pressure within the tank. This poses a significant challenge to liquid hydrogen storage. To reduce losses during hydrogen liquefaction and the energy consumption of reliquefaction, and to extend the time for lossless storage of liquid hydrogen as much as possible, the orthohydrogen-secondary hydrogen transformation must be completed simultaneously with hydrogen liquefaction. However, the orthohydrogen-secondary hydrogen transformation is an extremely slow process; therefore, catalysts are needed to accelerate the conversion rate from orthohydrogen to secondary hydrogen.

[0004] Currently, most of the catalysts used for the conversion of n- and secondary hydrogen to liquid hydrogen are iron-based catalysts. However, the iron-based catalysts currently in use have problems such as low catalytic activity and low particle strength, which makes them easy to pulverize. Therefore, it is extremely important to develop high-performance, low-flow-resistance n- and secondary hydrogen conversion catalysts. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an iron-based positive and negative hydrogen conversion catalyst, its preparation method, and its application, thereby solving the technical problems of low catalyst activity, low particle strength, and easy pulverization in existing technologies.

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

[0007] An iron-based secondary hydrogen conversion catalyst is prepared by treating alumina with N and Mg, and then using the treated alumina as a support.

[0008] in:

[0009] The iron loading is 10-25% of the mass of alumina.

[0010] The present invention also has the following technical features:

[0011] Furthermore, the catalyst also includes a catalytic promoter, the content of which is 0.5-5% of the mass of alumina.

[0012] Preferably, the catalyst is one or two of La, Zn, Ba, Sr, Nd, Ni, Cr and Gd.

[0013] Specifically, the iron-based secondary hydrogen conversion catalyst has a particle strength ≥350 N / cm. 2 .

[0014] Preferably, the iron-based secondary hydrogen conversion catalyst is a 2×2mm cylindrical particle.

[0015] This invention also protects a method for preparing the iron-based positive and negative hydrogen conversion catalyst as described above, the method comprising the following steps:

[0016] Step 1: Treat alumina powder with ammonia at 200–450°C for 2–5 hours.

[0017] Step 2: Impregnate the alumina powder obtained in Step 1 with a solution containing magnesium nitrate, stir at room temperature to 80°C for 2 to 4 hours, evaporate to dryness, transfer to an oven at 100 to 120°C for 1 to 3 hours to obtain magnesium-modified alumina.

[0018] Step 3: The magnesium-modified alumina obtained in Step 2 is calcined at a high temperature of 400-650℃ for 2-6 hours.

[0019] Step four: Dissolve the precursor containing iron and catalyst in a solvent to obtain solution A.

[0020] Step 5: Using solution A obtained in step 4 as the impregnation liquid, the product obtained in step 3 is impregnated, the water is removed under reduced pressure, and the product is dried at 100-120℃ for 1-3 hours. Finally, the product is shaped and calcined to obtain the iron-based secondary hydrogen conversion catalyst.

[0021] In step one, the ammonia is ammonia gas, liquid ammonia, ammonia water, or a mixture of ammonia and nitrogen.

[0022] In steps two and four, the solvent is one or two of water, methanol, ethanol, and n-propanol.

[0023] In step two, the magnesium oxide in the magnesium-modified alumina accounts for 2% to 10% of the weight of the alumina.

[0024] The iron-based secondary hydrogen conversion catalysts described above are used in secondary hydrogen catalytic conversion reactions.

[0025] In this application, the conversion rate of the described n- and para-hydrogen catalytic conversion reaction is 92.6% to 98.4%.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) This invention introduces alkali metal ions into the surface of alumina after nitriding treatment, which can form a thin shell distribution on the support surface, reducing diffusion resistance and thus improving catalytic activity; at the same time, a magnesium aluminum spinel structure is formed on the modified support surface, which has more tetrahedral defect sites, providing more loading sites for active components and further improving catalytic activity.

[0028] (II) The catalyst prepared by the method of the present invention has high dispersion of metal components, which improves the catalyst activity. At the same time, the prepared catalyst has high strength, avoiding the pulverization and loss problem of traditional hydrated iron oxide catalysts, and has excellent comprehensive performance.

[0029] (III) The catalyst particles prepared by this invention have high strength, with a particle strength ≥350 N / cm. 2 The wear rate is less than 0.5%, which significantly improves the flow resistance of the catalyst bed under the conditions of positive and negative hydrogen conversion.

[0030] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0031] 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.

[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 an iron-based positive and negative hydrogen conversion catalyst. The method is carried out according to the following steps: 20g of alumina powder is weighed and placed in a quartz tube, and a 25% ammonia-nitrogen mixture is introduced. The temperature is raised to 300℃ and maintained for 4h. 2.5g of magnesium nitrate is dissolved in 40mL of deionized water. The ammonia-treated alumina is added to the magnesium nitrate aqueous solution, the temperature is raised to 60℃, and the mixture is stirred for 3h. The impregnation solution is evaporated to dryness under reduced pressure and dried at 110℃ for 2h. The dried product is calcined at 550℃ for 4h to obtain the modified alumina support ZT-1.

[0035] 11.4 g Fe(NO3)3·9H2O and 0.8 g La(NO3)3 were dissolved in 100 mL of deionized water, and 15 g of support ZT-1 was added. The mixture was stirred and impregnated at 40 °C for 8 h, and the water was gradually evaporated under reduced pressure. The mixture was dried at 110 °C for 2 h. The resulting material was granulated with 2% nitric acid aqueous solution, pressed into 2×2 mm cylindrical particles, and calcined at 500 °C for 4 h to obtain iron-based secondary hydrogen catalytic conversion catalyst CAT-1.

[0036] Example 2:

[0037] This embodiment provides a method for preparing an iron-based positive and negative hydrogen conversion catalyst. The method is carried out according to the following steps: 20g of alumina powder is weighed and placed in a quartz tube, and a 25% ammonia-nitrogen mixture is introduced. The temperature is raised to 400℃ and maintained for 4h. 1.5g of magnesium nitrate is dissolved in 40mL of deionized water. The ammonia-treated alumina is added to the magnesium nitrate aqueous solution, the temperature is raised to 60℃, and the mixture is stirred for 3h. The impregnation solution is evaporated to dryness under reduced pressure, dried at 110℃ for 2h, and the dried product is calcined at 550℃ for 4h to obtain the modified alumina support ZT-2.

[0038] 11.4 g Fe(NO3)3·9H2O and 1.2 g La(NO3)3 were dissolved in 100 mL of deionized water, and 15 g of support ZT-2 was added. The mixture was stirred and impregnated at 40 °C for 8 h, and the water was gradually evaporated under reduced pressure. The mixture was dried at 110 °C for 2 h. The resulting material was granulated with 2% nitric acid aqueous solution, pressed into 2×2 mm cylindrical particles, and calcined at 500 °C for 4 h to obtain the iron-based secondary hydrogen catalytic conversion catalyst CAT-2.

[0039] Example 3:

[0040] This embodiment provides a method for preparing an iron-based positive and negative hydrogen conversion catalyst. The method is carried out according to the following steps: 20g of alumina powder is weighed and placed in a quartz tube, and a 25% ammonia-nitrogen mixture is introduced. The temperature is raised to 450℃ and maintained for 4h. 1.5g of magnesium nitrate is dissolved in 40mL of deionized water. The ammonia-treated alumina is added to the magnesium nitrate aqueous solution, the temperature is raised to 60℃, and the mixture is stirred for 3h. The impregnation solution is evaporated under reduced pressure and dried at 110℃ for 2h. The dried product is calcined at 550℃ for 4h to obtain the modified alumina support ZT-3.

[0041] 7.6 g Fe(NO3)3·9H2O and 1.0 g La(NO3)3 were dissolved in 100 mL of deionized water, and 15 g of support ZT-3 was added. The mixture was stirred and impregnated at 40 °C for 8 h, and the water was gradually evaporated under reduced pressure. The mixture was dried at 110 °C for 2 h. The resulting material was granulated with 2% nitric acid aqueous solution, pressed into 2×2 mm cylindrical particles, and calcined at 500 °C for 4 h to obtain the iron-based secondary hydrogen catalytic conversion catalyst CAT-3.

[0042] Example 4:

[0043] This embodiment provides a method for preparing an iron-based secondary hydrogen conversion catalyst. The method is carried out according to the following steps: 11.4g Fe(NO3)3·9H2O and 1.3g La(NO3)3 are dissolved in 100mL of deionized water, 15g of support ZT-2 is added, and the mixture is stirred and impregnated at 40℃ for 8h. The water is gradually evaporated under reduced pressure, and the mixture is dried at 110℃ for 2h. The resulting material is granulated with 2% nitric acid aqueous solution, pressed into 2×2mm cylindrical particles, and calcined at 500℃ for 4h to obtain the iron-based secondary hydrogen conversion catalyst CAT-4.

[0044] Example 5:

[0045] This embodiment provides a method for preparing an iron-based secondary hydrogen conversion catalyst. The method is carried out according to the following steps: 11.4g Fe(NO3)3·9H2O and 3.4g Cr(NO3)3·9H2O are dissolved in 100mL of deionized water, 15g of support ZT-2 is added, and the mixture is stirred and impregnated at 40℃ for 8h. The water is gradually evaporated under reduced pressure, and the mixture is dried at 110℃ for 2h. The resulting material is granulated with 2% nitric acid aqueous solution, pressed into 2×2mm cylindrical particles, and calcined at 500℃ for 4h to obtain the iron-based secondary hydrogen conversion catalyst CAT-5.

[0046] Example 6:

[0047] This embodiment provides a method for preparing an iron-based secondary hydrogen conversion catalyst. The method is carried out according to the following steps: 11.4g Fe(NO3)3·9H2O and 1.1g Nd(NO3)3·6H2O are dissolved in 100mL of deionized water, 15g of support ZT-2 is added, and the mixture is stirred and impregnated at 40℃ for 8h. The water is gradually evaporated under reduced pressure, and the mixture is dried at 110℃ for 2h. The resulting material is granulated with 2% nitric acid aqueous solution, pressed into 2×2mm cylindrical particles, and calcined at 500℃ for 4h to obtain the iron-based secondary hydrogen conversion catalyst CAT-6.

[0048] Example 7:

[0049] This embodiment demonstrates the application of the iron-based secondary hydrogen conversion catalyst prepared using the preparation methods of the iron-based secondary hydrogen conversion catalysts in Examples 1 to 6 for secondary hydrogen catalytic conversion reactions.

[0050] Specifically, it is described as follows:

[0051] At liquid nitrogen temperature, the CAT-1 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 97.2%, with a conversion rate of 97.2%.

[0052] At liquid nitrogen temperature, the CAT-2 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 98.4%, with a conversion rate of 98.4%.

[0053] At liquid nitrogen temperature, CAT-3 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 92.6%, with a conversion rate of 92.6%.

[0054] At liquid nitrogen temperature, CAT-4 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 94.0%, with a conversion rate of 94.0%.

[0055] At liquid nitrogen temperature, CAT-5 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 94.8%, with a conversion rate of 94.8%.

[0056] At liquid nitrogen temperature, CAT-6 catalyst was loaded into a secondary hydrogen catalytic conversion reactor, and the concentration of 1200 L was determined by gas chromatography. H2 / L 催化剂 The catalyst activity at a space velocity of / min was 95.5%, with a conversion rate of 95.5%.

Claims

1. An iron-based secondary hydrogen conversion catalyst, characterized in that, The catalyst is prepared by treating alumina with N and Mg, and then using the treated alumina as a support to prepare an iron-based secondary hydrogen conversion catalyst. in: The iron loading is 10-25% of the mass of alumina; The preparation method of the iron-based secondary hydrogen conversion catalyst is carried out according to the following steps: Step 1: Treat alumina powder with ammonia at 200–450°C for 2–5 hours; Step 2: Impregnate the alumina powder obtained in Step 1 with a solution containing magnesium nitrate, stir at room temperature to 80°C for 2 to 4 hours, evaporate to dryness, transfer to an oven at 100 to 120°C for 1 to 3 hours to obtain magnesium-modified alumina. Step 3: The magnesium-modified alumina obtained in Step 2 is calcined at a high temperature of 400-650℃ for 2-6 hours; Step 4: Dissolve the precursor containing iron and catalyst in a solvent to obtain solution A; Step 5: Using solution A obtained in step 4 as the impregnation liquid, the product obtained in step 3 is impregnated, the water is removed under reduced pressure, and the product is dried at 100-120℃ for 1-3 hours. Finally, the product is shaped and calcined to obtain the iron-based secondary hydrogen conversion catalyst.

2. The iron-based secondary hydrogen conversion catalyst as described in claim 1, characterized in that, The content of the catalyst is 0.5% to 5% of the mass of alumina.

3. The iron-based secondary hydrogen conversion catalyst as described in claim 2, characterized in that, The catalyst promoter is one or two of La, Zn, Ba, Sr, Nd, Ni, Cr and Gd.

4. The iron-based n-parahydrogen conversion catalyst as described in claim 1, characterized in that, The iron-based secondary hydrogen conversion catalyst has a particle strength ≥350 N / cm. 2 .

5. The iron-based secondary hydrogen conversion catalyst as described in claim 1, characterized in that, In step one, the ammonia is ammonia gas, liquid ammonia, ammonia water, or a mixture of ammonia and nitrogen.

6. The iron-based secondary hydrogen conversion catalyst as described in claim 1, characterized in that, In steps two and four, the solvent is one or two of water, methanol, ethanol, and n-propanol.

7. The application of the iron-based secondary hydrogen conversion catalyst according to any one of claims 1 to 6 in the secondary hydrogen catalytic conversion reaction.

8. The application as described in claim 7, characterized in that, In this application, the conversion rate of the described secondary hydrogen catalytic conversion reaction is 92.6% to 98.4%.