A long-acting hydrogen separation / purification method based on a segmented heating method

Abstract

The application discloses a long-acting hydrogen separation / purification method based on a segmented heating method, which comprises the following steps: firstly, under the condition of a gas to be purified, hydrogen absorption treatment is performed on a separation / purification alloy; then, under the condition of room temperature, gas washing is performed; finally, under the condition of argon as a carrier gas, hydrogen desorption treatment is performed by using the segmented heating method, high-purity hydrogen is obtained, and the separation and purification of hydrogen are completed. The hydrogen desorption treatment process of the segmented heating method comprises two stages. The atomic ratio of the components of the separation / purification alloy satisfies that Nd is 2-4 at.%, Ni is 7-12 at.%, and the rest is Mg, and the separation / purification alloy needs to be activated before use. The gas to be purified is a mixed gas in which hydrogen is a main gas and nitrogen is an impurity gas, and the volume fraction of the nitrogen is 5 vol%. The hydrogen purity after the separation / purification method is greater than 99.90 vol%; the cycle stability is good; after 10 cycles, the hydrogen absorption amount and hydrogen desorption amount retention rate are greater than 99%, and the hydrogen purity is greater than 99.90 vol%.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage materials technology, specifically to a long-lasting hydrogen separation / purification method based on segmented heating. Background Technology

[0002] Industrial byproduct crude hydrogen gas contains impurities such as N2, CO2, O2, H2O, and CO, making it unsuitable for direct use. Among these impurities, N2 is particularly abundant. Furthermore, due to its chemical inertness, N2 competes with H2 for adsorption via physical adsorption, leading to mass transfer obstacles and a dilution effect—significantly reducing the hydrogen adsorption / desorption rate—and making it impossible to remove using conventional adsorption or catalytic conversion methods. Conventional technologies for purifying crude hydrogen gas primarily involve pressure swing adsorption, membrane separation, and cryogenic adsorption, all of which suffer from complex equipment, high energy consumption, and substantial investment costs.

[0003] To address the technical problems of conventional technologies, hydrogen purification technology based on hydrogen storage alloys with selective hydrogen absorption characteristics can be employed. For example, existing literature 1 (《Study on Hydrogen in Mixed Gas Separated by Rare Earth Hydrogen Storage Alloys》 Rare Metal Materials and Engineering, 2011, 40(2): 0189-0194.) describes the preparation of LaNi by vacuum induction melting. 3.7 Mn 0.4 Al 0.3 Fe 0.4 Co 0.2 Although the alloy can achieve hydrogen absorption and desorption under simulated gas mixture conditions of 54.1% H2 + 32.8% CH4 + 13.1% N2, the purity of H2 in the released gas can only reach 90.7%. While this technical solution demonstrates the feasibility of using hydrogen storage alloys for purifying N2-containing gas mixtures, achieving low energy consumption and good safety by utilizing the dual functions of hydrogen storage and purification, this solution still faces three technical problems besides the fact that the purified hydrogen purity cannot meet the industrial hydrogen technical requirement of ≥99.00%. 1. The high cost caused by using rare earth elements as raw materials; 2. The problem of low theoretical capacity: Specifically, the theoretical hydrogen storage capacity of the hydrogen storage alloy used is only 1.3 wt.%, which directly results in too little purified hydrogen that can be processed and released in a single cycle, far from meeting the requirements of large-scale application. 3. Poisoning problem: Specifically, the hydrogen absorption kinetics of the hydrogen storage alloy is severely deteriorated in a mixed atmosphere containing N2, i.e., it is affected by poisoning. Specifically, the hydrogen absorption time is significantly extended from 60 min in pure H2 to 180 min. In addition, CH4 and N2 impurities have a significant retardation effect on the hydrogen absorption process of the alloy, which seriously affects the actual efficiency of use.

[0004] To address the technical challenges of rare-earth-based hydrogen storage alloys, magnesium-based hydrogen storage materials can be used as purification media to improve purification efficiency and reduce material costs. For example, existing literature 2 ("Hydrogen purification by Mg alloy hydrogen adsorbent", Adsorption 2022, 28: 85–95.) describes the synthesis of fluorinated MgNi alloys via vacuum induction melting combined with impregnation. 0.1 Fe 0.05 Ti 0.05 The alloy itself exhibits hydrogen storage performance of 5.4 wt.% over 20 minutes at 300 ℃ and 1 MPa pure hydrogen pressure. When used as a purification medium, it can achieve a purified H2 purity of 95.1% under a 70% H2 + 30% CO2 mixed gas environment. While this technology solves the raw material and low theoretical capacity problems of rare-earth-based hydrogen storage alloys, it still faces poisoning issues, specifically in the following two aspects: 1. Under the condition of CO2 impurity gas, magnesium-based hydrogen storage alloys are poisoned by CO2, which directly leads to a significant decrease in the hydrogen absorption capacity and reaction rate of the alloy after multiple purifications. The reason is that CO2 reacts with Mg to form MgO. 2. At the same time, since the impurity gas CO2 can compete with H2 for adsorption on the alloy surface, this adsorption is physical adsorption. This phenomenon directly leads to the release of the purified gas, and the physically adsorbed impurity CO2 will be released together with H2. As a result, a small amount of impurity CO2 will inevitably be present in the purified gas, which ultimately makes it impossible to make the purified hydrogen gas meet the technical indicator of ≥99.00% for industrial hydrogen. Therefore, based on the above analysis, it can be seen that the core technical problem of the existing technology is the poisoning issue. Summary of the Invention

[0005] The present invention aims to provide a long-lasting hydrogen separation / purification method based on segmented heating, the basic principle of which is as follows: 1. Utilizing the highly selective chemical adsorption and hydrogenation reaction of magnesium-based hydrogen storage alloys to form hydrides of H2, while impurity gases are not absorbed by the alloy, a segmented heating method is used to first remove impurity gases at low temperatures, and then raise the temperature to high temperatures. By leveraging the characteristic of magnesium-based hydrogen storage alloys to release H2 at high temperatures, the separation and purification of H2 and impurity gases are achieved. 2. To achieve a long-term hydrogen separation / purification method, i.e., to solve the problem of poisoning of magnesium-based hydrogen storage alloys by impurity gases, Mg... 88.5 Ni 8.0 Nd 3.5 As a separation / purification alloy, the Mg2Ni and NdH2 formed after its activation treatment are used as catalytic phases to weaken the competitive adsorption and surface chemical reaction of impurity gases with H2 on the material surface, reduce the poisoning effect of impurity gases, and ensure that the magnesium-based hydrogen storage alloy has good hydrogen absorption and desorption cycle stability under non-high-purity hydrogen conditions mixed with impurity gases.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A long-lasting hydrogen separation / purification method based on segmented heating includes the following steps: First, under the condition of the gas to be purified, the separation / purification alloy is subjected to hydrogen absorption treatment; then, the gas is washed at room temperature; finally, hydrogen is released by segmented heating to obtain high-purity hydrogen, thus completing the separation and purification of hydrogen. The conditions for the hydrogen absorption treatment are: a hydrogen absorption treatment temperature of 300℃, a hydrogen absorption treatment pressure of 3 MPa, and a hydrogen absorption treatment time of 30-60 min. The conditions for gas washing are as follows: the washing gas is high-purity argon; after vacuuming, the washing gas is added to complete one gas washing cycle; the number of gas washing cycles is 3-5; after the last gas washing cycle, vacuuming is performed for 10-30 minutes. The hydrogen release process of the segmented heating method includes two stages. The first stage of hydrogen release treatment is carried out at a temperature of 80-100℃ for 20 minutes. After the carrier gas is free of impurity gases, the second stage of hydrogen release treatment is carried out. The second stage of hydrogen release treatment is carried out at a temperature of 300-350℃ for 10 minutes to complete the release of high-purity hydrogen.

[0007] The atomic ratio of the separated / purified alloy components satisfies that Nd is 2-4 at.%, Ni is 7-12 at.%, and the remainder is Mg. Furthermore, activation treatment is required before use. The activation treatment is performed by sequentially performing hydrogen absorption activation and hydrogen desorption activation, which completes one activation treatment. The number of activation treatments is 5. The conditions for hydrogen absorption activation are: hydrogen pressure of 4 MPa, hydrogen temperature of 350℃, and hydrogen activation time of 2 h. The conditions for hydrogen deactivation activation are: hydrogen deactivation activation pressure of 0.01 MPa, hydrogen deactivation activation temperature of 350℃, and hydrogen deactivation activation time of 10 min.

[0008] The gas to be purified is a mixture of hydrogen as the main gas and nitrogen as the impurity gas, with a nitrogen volume fraction of 1-5 vol%. The hydrogen purified by the separation / purification method has a purity greater than 99.90 vol%. The separation / purification method has good cycle stability. After 10 cycles, the hydrogen absorption and release rates are greater than 99%, and the hydrogen purity is greater than 99.90 vol.

[0009] The technical effects of this invention have been tested and confirmed to be: Compositional analysis and quantitative analysis of the gases released after hydrogen desorption treatment revealed that, after hydrogen absorption treatment in a mixed hydrogen gas containing 5 vol% N2, the Mg-Ni-Nd alloy, based on a segmented heating method, released gases at 100℃ consisting of N2 and Ar, with impurity N2 desorbed and separated; at 350℃, the partial pressure of released H2 was 1.44 × 10⁻⁶. -6 mbar, the partial pressure of N2 is 7.38 × 10 -10 mbar, after conversion, the volume fraction of H2 is 99.95 vol%, and the purity of the separated / purified hydrogen meets the technical specifications for industrial hydrogen.

[0010] Cyclic stability tests showed that, under conditions containing 5 vol% N2 mixed hydrogen gas, the Mg-Ni-Nd alloy retained 99.3% of its hydrogen absorption and 99.1% of its hydrogen release after 10 cycles, demonstrating good cyclic stability. Furthermore, after 10 cycles, the H2 volume fraction of the Mg-Ni-Nd alloy purified by the segmented heating method was 99.94 vol%, with no substantial attenuation in purification effect, indicating that the separation / purification method has long-term effectiveness.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention is a hydrogen separation / purification method based on segmented heating. The first stage hydrogen release treatment achieves complete separation of impurities N2 and H2. The second stage hydrogen release treatment releases high-purity hydrogen with a volume fraction of H2 greater than 99.90 vol% and a purity that meets the technical indicators of industrial hydrogen. 2. Compared with the prior art, the separation / purification method of this invention has long-term effectiveness. Under the conditions of the gas to be purified, it has good resistance to N2 poisoning and cycle stability. After 10 cycles, the hydrogen absorption capacity and hydrogen release capacity are retained at a rate greater than 99%. Furthermore, after 10 cycles, the separation / purification effect does not substantially decrease, and the volume fraction of purified H2 is greater than 99.90 vol%, and the purity still meets the technical indicators of industrial hydrogen. Attached Figure Description

[0012] Figure 1 The composition of the gas released at different temperatures during hydrogen release treatment in Example 1; Figure 2 The partial pressures of H2, Ar and N2 and the volume fraction of H2 after purification are shown in Example 1 when the heating temperature is 350°C. Figure 3 The hydrogen absorption and desorption kinetic curves for Example 1 after 1 cycle and 10 cycles are shown. Figure 4 The partial pressures of H2, Ar and N2 at 350°C after 10 cycles in Example 1, and the volume fraction of H2 after purification; Figure 5 The partial pressures of H2, Ar, and N2 and the volume fractions of H2 and N2 during the heating process in Comparative Example 1 are given. Figure 6 The hydrogen absorption and desorption kinetic curves for Comparative Example 1 after 1 cycle and 10 cycles are shown. Figure 7 The partial pressures of H2, Ar, and N2 at 350℃ after 10 cycles in Comparative Example 1, and the volume fraction of H2 after purification. Detailed Implementation

[0013] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0014] Example 1 A long-lasting hydrogen separation / purification method based on segmented heating includes the following steps: First, under the condition of the gas to be purified, the separation / purification alloy is subjected to hydrogen absorption treatment; then, the gas is washed at room temperature; finally, hydrogen is released by segmented heating to obtain high-purity hydrogen, thus completing the separation and purification of hydrogen.

[0015] The gas to be purified is a mixture of hydrogen as the main gas, nitrogen as the impurity gas, and nitrogen with a volume fraction of 5 vol%. The chemical formula of the separated / purified alloy is Mg. 88.5 Ni 8.0 Nd 3.5 Furthermore, activation treatment is required before use. The Mg88.5 Ni 8.0 Nd 3.5 The alloy and its preparation method are described in the reference (Li Qian, Luo Qun, Sun Xuan, Pan Fusheng, Wang Jingfeng, Chen Yu'an. A multiphase Mg-Ni-Nd hydrogen storage alloy based on in-situ activation method and its preparation method, CN117026003B, 2025-07-11).

[0016] The activation treatment is performed by sequentially performing hydrogen absorption activation and hydrogen release activation, which completes one activation treatment. The number of activation treatments is 5. The conditions for hydrogen absorption activation are: hydrogen pressure of 4 MPa, hydrogen temperature of 350℃, and hydrogen activation time of 2 h. The conditions for hydrogen deactivation activation are: hydrogen deactivation activation hydrogen pressure of 0.01 MPa, hydrogen deactivation activation temperature of 350℃, and hydrogen deactivation activation time of 10 min. The conditions for the hydrogen absorption treatment are: hydrogen absorption treatment temperature of 300℃, hydrogen absorption treatment hydrogen pressure of 3 MPa, and hydrogen absorption treatment time of 30 min. The conditions for gas washing are as follows: the washing gas is high-purity argon; after vacuuming, the washing gas is added to complete one gas washing cycle; the number of gas washing cycles is 3; after the last gas washing cycle, vacuuming is performed with a vacuuming time of 20 minutes. The hydrogen release process of the segmented heating method includes two stages. The first stage of hydrogen release treatment is carried out at a temperature of 100℃ for 20 minutes. After the carrier gas is free of impurity gases, the second stage of hydrogen release treatment is carried out. The second stage of hydrogen release treatment is carried out at a temperature of 350℃ for 10 minutes, which completes the release of high-purity hydrogen.

[0017] To demonstrate the effectiveness of the segmented heating method for hydrogen separation / purification, mass spectrometry was used to detect the composition of the gas released during hydrogen desorption under different temperature conditions, and quantitative analysis was performed. The test results are as follows: Figure 1 and Figure 2 As shown, When the heating temperature is 100℃, the components of the released gas are N2 and Ar, where Ar is the carrier gas introduced during mass spectrometry and N2 is the impurity gas that is separated. When the heating temperature is 200℃, the released gas contains only Ar. The test results show that the impurity gas N2 has been completely separated when the heating temperature is 100℃. When heated to 350℃, the released gas consists of H2 and Ar, and the partial pressure of H2 is 1.44 × 10⁻⁶. -6 mbar, the partial pressure of Ar is 1.69 × 10 -6mbar, the partial pressure of N2 is 7.38 × 10 -10 Under conditions of mbar and without considering the carrier gas Ar, the volume fraction of H2 is calculated to be 99.95 vol%. Test results show that hydrogen purification was successfully achieved, and the purity of the purified hydrogen meets the technical requirement of ≥99.00 vol% for industrial hydrogen.

[0018] To further demonstrate the cyclic stability of the separation / purification method, cyclic performance tests were conducted, and the released gas after cycling was subjected to mass spectrometry for component detection and quantitative analysis. The specific method for the cyclic performance test involved repeatedly performing hydrogen absorption and desorption tests under the conditions of the gas to be purified. One cycle test was completed for each hydrogen absorption and desorption test, and the number of cycles was 10.

[0019] Cyclic performance test results are as follows Figure 3 As shown in Table 1, the hydrogen absorption retention rate is 99.3%, and the hydrogen release retention rate is 99.1%. The mass spectrometry composition of the gas released after circulation is as follows: Figure 4 As shown, when the heating temperature is 350℃, the released gas consists of H2 and Ar, and the partial pressure of H2 is 1.36 × 10⁻⁶. -6 mbar, the partial pressure of Ar is 1.39 × 10 -6 mbar, the partial pressure of N2 is 6.08 × 10 -10 Under the condition of mbar without considering the carrier gas Ar, the volume fraction of H2 is 99.94 vol%, which is not substantially different from the purity of the first hydrogen purification, that is, it meets the technical indicators of industrial hydrogen. Cyclic performance test results show that, under the conditions of the gas to be purified, the separation / purification method of the present invention does not show significant decay in hydrogen absorption / desorption capacity and hydrogen absorption / desorption kinetics after 10 cycles, that is, it has good cyclic stability. Furthermore, the purification effect does not substantially decrease. Therefore, the separation / purification method of the present invention has long-term effectiveness.

[0020] Table 1 Summary of Cyclic Performance Test Results of Separation / Purification Methods To demonstrate the effectiveness of the separation / purification method for the alloy, Comparative Example 1 is provided, which uses a conventional commercial magnesium-based hydrogen storage alloy Mg. 90.5 Ni 9.5 Perform separation / purification operations.

[0021] Comparative Example 1 A hydrogen storage alloy based on conventional commercial magnesium-based alloy Mg 90.5 Ni 9.5The separation / purification method, unless otherwise specified, is the same as in Example 1, except that Mg is used. 90.5 Ni 9.5 Replace Mg 88.5 Ni 8.0 Nd 3.5 As a separation / purification alloy, and hydrogen release treatment is carried out by a one-step heating method; the conditions of the one-step heating method are the same as those of the segmented heating method unless otherwise specified, except that the temperature is directly heated from room temperature to 350°C.

[0022] To demonstrate the effectiveness of the one-step heating method for hydrogen separation / purification, the gas released during hydrogen desorption was analyzed by mass spectrometry, and quantitative analysis was performed. The test results are as follows: Figure 5 As shown, the released gas consists of H2, N2, and Ar, with Ar serving as the carrier gas. N2 is released simultaneously with H2. The partial pressure of H2 is 2.26 × 10⁻⁶. -7 mbar, the partial pressure of Ar is 1.76 × 10 -6 mbar, the partial pressure of N2 is 5.72 × 10 -10 Based on the calculation, without considering the carrier gas Ar, the volume fraction of H2 is 98.85 vol.

[0023] Test results show that the one-step heating method cannot effectively separate impurity N2 gas, and the purity of the purified hydrogen does not meet the technical specifications for industrial hydrogen (≥99.00 vol%).

[0024] To further demonstrate the cycling stability of the one-step heating method, cycling performance tests were conducted, and the released gas after cycling was subjected to mass spectrometry composition detection and quantitative analysis. The cycling performance test results are as follows: Figure 6 As shown in Table 1, the hydrogen absorption retention rate was 69.3%, and the hydrogen release retention rate was 68.9%. The mass spectrometry composition of the gas released after circulation is as follows: Figure 7 As shown, the released gas consists of H2, N2, and Ar, and the partial pressure of H2 is 1.85 × 10⁻⁶. -7 mbar, the partial pressure of Ar is 1.72 × 10 -6 mbar, the partial pressure of N2 is 4.22 × 10 -10 Under the condition of mbar without considering the carrier gas Ar, the volume fraction of H2 is 98.37 vol%, which is 0.48 vol% lower than the purity of the first hydrogen purification. Moreover, after 10 cycles, the purity of the purified hydrogen still does not meet the technical specifications of industrial hydrogen. Cyclic performance test results show that, under the conditions of the gas to be purified, the one-step heating separation / purification method not only exhibits a significant decrease in hydrogen absorption / desorption capacity and hydrogen absorption / desorption kinetics after 10 cycles (i.e., poor cycle stability), but also a significant decrease in purification effect. Therefore, the one-step heating separation / purification method is not long-lasting.

Claims

1. A long-lasting hydrogen separation / purification method based on segmented heating, characterized in that... Includes the following steps: First, under the condition of the gas to be purified, the separation / purification alloy is subjected to hydrogen absorption treatment. Then, the gas is washed at room temperature. Finally, hydrogen is released by segmented heating to obtain high-purity hydrogen, thus completing the separation and purification of hydrogen. The hydrogen release process of the segmented heating method includes two stages. The first stage of hydrogen release treatment is carried out at a temperature of 80-100℃ for 20 minutes. After the carrier gas is free of impurity gases, the second stage of hydrogen release treatment is carried out. The second stage hydrogen release process involves a temperature of 300-350℃ and a duration of 10 minutes to complete the release of high-purity hydrogen. The atomic ratio of the separated / purified alloy components satisfies that Nd is 2-4 at.%, Ni is 7-12 at.%, and the remainder is Mg, and activation treatment is required before use.

2. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 1, characterized in that: The conditions for the hydrogen absorption treatment are: a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3 MPa, and a hydrogen absorption time of 30-60 min.

3. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 1, characterized in that: The conditions for gas washing are as follows: the washing gas is high-purity argon gas; after vacuuming, the washing gas is added to complete one gas washing cycle; the number of gas washing cycles is 3-5; after the last gas washing cycle, vacuuming is performed for 10-30 minutes.

4. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 1, characterized in that: The chemical formula of the separated / purified alloy is Mg. 88.5 Ni 8.0 Nd 3.5 Furthermore, it requires activation before use.

5. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 4, characterized in that: The activation treatment is performed by sequentially performing hydrogen absorption activation and hydrogen release activation, which completes one activation treatment. The number of activation treatments is 5. The conditions for hydrogen absorption activation are: hydrogen pressure of 4 MPa, hydrogen temperature of 350℃, and hydrogen activation time of 2 h. The conditions for hydrogen deactivation activation are: hydrogen deactivation activation pressure of 0.01 MPa, hydrogen deactivation activation temperature of 350℃, and hydrogen deactivation activation time of 10 min.

6. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 1, characterized in that: The gas to be purified is a mixture of hydrogen as the main gas and nitrogen as the impurity gas, with a nitrogen volume fraction of 1-5 vol%.

7. The long-lasting hydrogen separation / purification method based on segmented heating according to claim 1, characterized in that: The hydrogen purified by the separation / purification method has a purity greater than 99.90 vol%. The separation / purification method exhibits good cyclic stability. After 10 cycles, the hydrogen absorption and release rates are maintained at over 99%, and the hydrogen purity is greater than 99.90 vol.

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