Preparation method of magnesium hydride with controllable particle size and purity, and magnesium hydride particles
By monitoring the temperature of the magnesium powder bed and the hydrogen pressure, a correlation between temperature change characteristics and the degree of hydrogenation was established, solving the problem of difficulty in controlling particle size and purity in the preparation of magnesium hydride, and realizing visualized determination of reaction endpoints and efficient preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 大连富德金煜新能源有限公司
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-15
AI Technical Summary
In existing magnesium hydride preparation technologies, particle size and purity are difficult to control, and the reaction endpoint is not accurately determined, resulting in an unstable preparation process and increased energy consumption.
By monitoring the temperature and hydrogen pressure of the magnesium powder bed, a correlation between temperature change characteristics and the degree of hydrogenation is established. A preset termination temperature range and a target hydrogenation threshold are set to achieve visualized control of the hydrogenation reaction.
This method enables controllable particle size and purity of magnesium hydride, improves the controllability and repeatability of the preparation process, and reduces energy consumption.
Smart Images
Figure CN122035784A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of preparation technology of solid hydrogen storage materials of metal hydrides, and more specifically, to a method for preparing magnesium hydride with controllable particle size and purity, and magnesium hydride particles. Background Technology
[0002] In existing technologies, magnesium-based hydrogen storage materials, especially magnesium hydride, have attracted widespread attention as high-quality solid-state hydrogen storage materials. Common preparation routes mainly fall into two categories: one involves mechanical ball milling combined with hydrogen flow to induce a solid-phase reaction between magnesium and hydrogen under high-speed and long-term milling conditions; the other involves directly loading metallic magnesium powder into a pressure-resistant container and conducting a gas-solid reaction under high temperature and high hydrogen pressure conditions, gradually converting magnesium into magnesium hydride. While the former process can refine particles and accelerate the hydrogenation rate to some extent, the ball milling process inevitably introduces wear debris and oxidative impurities, leading to highly irregular particle morphology and making it difficult to obtain magnesium hydride powder with controllable particle size distribution and high purity. The latter high-temperature and high-pressure gas-solid reaction process typically requires high hydrogen pressure and a long reaction time to achieve a high conversion rate. Furthermore, magnesium hydrogen absorption is a strongly exothermic reaction. Under scale-up conditions, local overheating and temperature gradients are prone to occur inside the bed, resulting in significant differences in reaction rate and degree of hydrogenation at different locations. This leads to a wide particle size distribution and uneven morphology of the resulting magnesium hydride particles. Some particles may still retain an incompletely hydrogenated magnesium core, while others may break into excessively fine powder due to intense exothermic reactions, making subsequent particle size control and performance evaluation more difficult.
[0003] In existing processes, the determination of the endpoint of the hydrogenation process mostly relies on empirically set time or rough experimental data. During the reaction, there is a lack of endpoint control methods to match the purity of magnesium hydride. In actual production, insufficient hydrogenation can easily lead to low purity, or the reaction time can be excessively extended in pursuit of safety, resulting in problems such as increased energy consumption, particle growth, and darkening of color.
[0004] Overall, existing magnesium hydride particle preparation technologies generally suffer from drawbacks in hydrogen storage material applications, such as demanding preparation conditions, difficulty in stable scale-up and reproduction, difficulty in achieving both high purity and controllable particle size, and reliance on empirical judgment for reaction endpoints. There is still a lack of a preparation process that can achieve adjustable particle size, high purity, and controllable reaction process under industrially feasible conditions. Summary of the Invention
[0005] The main objective of this invention is to provide a method for preparing magnesium hydride with controllable particle size and purity, as well as magnesium hydride particles, to solve the problems in the prior art where the particle size and purity of magnesium hydride obtained by hydrogenation reaction are difficult to control, and the endpoint of hydrogenation reaction cannot be accurately quantitatively determined, resulting in low purity of the obtained magnesium hydride or increased energy consumption due to prolonged reaction time.
[0006] To achieve the above objectives, the present invention provides a method for preparing magnesium hydride with controllable particle size and purity. The method includes: step S1, introducing hydrogen gas into a reactor filled with a magnesium powder bed to increase its internal pressure to an initial hydrogen pressure P1; and step S2, heating the reactor with heat-conducting oil in an external heating mechanism and monitoring the temperature T of the magnesium powder bed. bed Once the temperature stabilizes within the target temperature range, hydrogen is continuously introduced to increase the hydrogen pressure inside the reactor to the target hydrogen pressure P2, causing the magnesium powder bed to undergo a hydrogenation reaction with the hydrogen and release heat; in step S3, the temperature T of the magnesium powder bed is monitored. bed Increase to the reaction temperature range T high Within this time, hydrogen gas continues to be introduced and the reaction continues for a preset time period t. high The hydrogen pressure was monitored to meet the target hydrogen pressure P2 with a fluctuation not exceeding 0.2 MPa, and the reaction temperature met the preset temperature range T. oil And when the temperature fluctuation does not exceed 10℃, and the temperature T of the magnesium powder bed is... bed The temperature began to decrease, entering the reaction decay stage; the temperature T of the magnesium powder bed was monitored. bed Descend to the preset termination temperature range T end When the hydrogenation degree is greater than or equal to the target hydrogenation degree threshold XH, stop the hydrogen gas supply and collect the solid product; in step S4, crush and sieve the solid product in sequence to obtain the product that meets the first target particle size range d1 and the first target particle size median D. 50_1 The first target is magnesium hydride with a purity grade of C1.
[0007] Furthermore, the above preparation method also includes: obtaining the correspondence between the temperature change characteristics of the hydrogenation reaction system and the degree of hydrogenation of magnesium hydride, to obtain a first process criterion curve; obtaining the correspondence between the dehydrogenation initiation temperature or dehydrogenation characteristic temperature in the magnesium hydride dehydrogenation test and the degree of hydrogenation of magnesium hydride, to obtain a second criterion curve; and setting a preset termination temperature range T based on the first process criterion curve and the second process criterion curve. end And the target hydrogenation degree threshold XH, to monitor the reaction endpoint in step S3.
[0008] Furthermore, in step S3, a preset termination temperature range T is defined. end The temperature range is 290–380℃; the target hydrogenation degree threshold XH ≥ 90%.
[0009] Further, step S1 includes: filling magnesium powder with a preset initial particle size into the reactor to form a magnesium powder bed of the target filling amount, evacuating the reactor to make the internal pressure of the reactor reach the preset evacuation limit pressure threshold, and then introducing hydrogen gas to increase the hydrogen pressure inside the reactor to the initial hydrogen pressure P1.
[0010] Furthermore, the preset initial particle size of magnesium powder is 10–102 μm; the target loading amount of magnesium powder bed in the reactor is 20–70 vol%; the initial hydrogen pressure P1 is 0.5–1.5 MPa; and the preset evacuation limit pressure threshold is 10–200 Pa.
[0011] Furthermore, the reactor is selected from plug flow reactors, jacketed plug flow reactors, or external coil plug flow reactors.
[0012] Furthermore, step S2 also includes: heating the heat transfer oil to raise its temperature to a preset temperature range T. oil Preset temperature range T oil The target temperature range is 280–330°C; and / or, in step S2, the target temperature range is 280–330°C; the target hydrogen pressure P2 is 2.0–3.0 MPa.
[0013] Furthermore, in step S3, the reaction temperature range T high Temperature range: 410–430℃; preset time period: t high The time is 180–360 minutes.
[0014] Furthermore, step S4 also includes: ball milling or mechanically kneading the product obtained after crushing and screening to obtain a product that meets the second target particle size range d2 and the second target particle size median D. 50_2 Magnesium hydride with a second target purity grade of C2.
[0015] Furthermore, the median D of the first target granularity 50_1 The target hydrogenation degree threshold XH satisfies the relationship (Ia): (Ia); where the median of the first target granularity is D 50_1 The thickness is 60–102 μm; the preset termination temperature range is T. end It satisfies the relationship (Ib) with the first target purity level C1: (Ib); where the preset termination temperature range T end The temperature is 290–380℃; preferably, the first target particle size range d1 is 10–102 μm.
[0016] Furthermore, the median D of the second target granularity 50_2 The target hydrogenation degree threshold XH satisfies the relationship (II-a): (II-a); where the median of the second target granularity is D 50_2 The thickness is 10–20 μm; the preset termination temperature range is T. end The second target purity grade C2 satisfies the relationship (II-b): (II-b); where the preset termination temperature range T endThe temperature is 290–380℃; preferably, the second target particle size range d2 is 10–102 μm.
[0017] To achieve the above objectives, another aspect of the present invention provides magnesium hydride particles, which are prepared by the above-described method for preparing magnesium hydride with controllable particle size and purity provided by the present invention.
[0018] By applying the technical solution of this invention, the endpoint of the hydrogenation reaction can be accurately determined by monitoring pressure and temperature, thereby obtaining magnesium hydride products with target particle size and purity.
[0019] By reasonably setting the preset termination temperature range T end And the target hydrogenation degree threshold XH, and the temperature T of the magnesium powder bed bed The criterion of determining the reaction endpoint when the degree of hydrogenation meets the above conditions transforms the preparation process of magnesium hydride from empirical control to quantifiable control centered on temperature curves. Without increasing the complexity of detection methods, it enables the visual judgment of the completion of the hydrogenation reaction and the on-demand preparation of products with different desired purities, thereby improving the controllability, repeatability, and engineering scale-up applicability of the preparation process. Attached Figure Description
[0020] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:
[0021] Figure 1 A flowchart of the preparation method of magnesium hydride with controllable particle size and purity provided by the present invention is shown;
[0022] Figure 2 The first process criterion curve in this invention is shown;
[0023] Figure 3 The second process criterion curve in this invention is shown. Detailed Implementation
[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the embodiments.
[0025] As described in the background section, existing magnesium hydride preparation processes suffer from difficulties in controlling the particle size and purity of magnesium hydride, and the inability to accurately quantify the endpoint of the hydrogenation reaction. This results in low purity magnesium hydride or increased energy consumption due to prolonged reaction time. To address these technical problems, the first aspect of this invention provides a method for preparing magnesium hydride with controllable particle size and purity, such as... Figure 1As shown, the preparation method includes: step S1, introducing hydrogen gas into a reactor filled with a magnesium powder bed to raise its internal pressure to an initial hydrogen pressure P1; step S2, heating the reactor with heat transfer oil in an external heating mechanism and monitoring the temperature T of the magnesium powder bed. bed Once the temperature stabilizes within the target temperature range, hydrogen is continuously introduced to increase the hydrogen pressure inside the reactor to the target hydrogen pressure P2, causing the magnesium powder bed to undergo a hydrogenation reaction with the hydrogen and release heat; in step S3, the temperature T of the magnesium powder bed is monitored. bed Increase to the reaction temperature range T high Within this time, hydrogen gas continues to be introduced and the reaction continues for a preset time period t. high The hydrogen pressure was monitored to meet the target hydrogen pressure P2 with a fluctuation not exceeding 0.2 MPa, and the reaction temperature met the preset temperature range T. oil And when the temperature fluctuation does not exceed 10℃, and the temperature T of the magnesium powder bed is... bed The temperature began to decrease, entering the reaction decay stage; the temperature T of the magnesium powder bed was monitored. bed Descend to the preset termination temperature range T end When the hydrogenation degree is greater than or equal to the target hydrogenation degree threshold XH, stop the hydrogen gas supply and collect the solid product; in step S4, crush and sieve the solid product in sequence to obtain the product that meets the first target particle size range d1 and the first target particle size median D. 50_1 The first target is magnesium hydride with a purity grade of C1.
[0026] Existing magnesium hydride preparation processes typically rely solely on holding time or operational experience to determine the reaction endpoint. However, the preparation process described in this invention can accurately determine the endpoint of the hydrogenation reaction by monitoring pressure and temperature, thereby obtaining magnesium hydride products with the target particle size and purity.
[0027] The inventors discovered in actual production that temperature is related to the degree or purity of magnesium hydride hydrogenation. They focused on the influence of temperature plateaus, heating slopes, and dropout inflection points at different stages of the hydrogenation reaction between magnesium powder and hydrogen on the degree of magnesium hydride hydrogenation. A correlation was established between temperature change characteristics and the degree of magnesium hydride hydrogenation, forming a process criterion curve with temperature change as the abscissa and the degree of magnesium hydride hydrogenation as the ordinate. Based on this, a target hydrogenation degree threshold XH can be set according to actual needs. Furthermore, in step S3 of the above-mentioned preparation process of this invention, when the temperature T of the magnesium powder bed is monitored... bed Descend to the preset termination temperature range T end When the degree of hydrogenation is greater than or equal to the target hydrogenation threshold XH, the reaction is considered to have reached its endpoint, and the hydrogen supply is stopped to end the reaction. Then, in step S4, the solid product in the reactor is crushed and sieved to obtain magnesium hydride with the target particle size and purity.
[0028] Furthermore, during their research, the inventors discovered that the dehydrogenation initiation temperature or dehydrogenation characteristic temperature in the dehydrogenation test is related to the degree of hydrogenation or purity of magnesium hydride. They focused on the correspondence between the temperature range during dehydrogenation and the degree of hydrogenation of magnesium hydride, establishing a process criterion with the dehydrogenation initiation temperature or dehydrogenation characteristic temperature as the independent variable and the degree of hydrogenation of magnesium hydride as the dependent variable. Based on this, a target hydrogenation degree threshold XH can be set according to actual needs, and the preset termination temperature range T can be avoided. end It falls within the temperature range required for significant hydrogen release, thus achieving the goal of using temperature to reasonably and accurately determine the reaction endpoint.
[0029] By reasonably setting the preset termination temperature range T end And the target hydrogenation degree threshold XH, and the temperature T of the magnesium powder bed bed The criterion of determining the reaction endpoint when the degree of hydrogenation meets the above conditions transforms the preparation process of magnesium hydride from empirical control to quantifiable control centered on temperature curves. Without increasing the complexity of detection methods, it enables the visual judgment of the completion of the hydrogenation reaction and the on-demand preparation of products with different desired purities, thereby improving the controllability, repeatability, and engineering scale-up applicability of the preparation process.
[0030] It should be noted that, in this invention, "the purity or degree of hydrogenation of magnesium hydride" refers to the proportion of magnesium element that has been converted into the magnesium hydride phase in the solid product. This can be obtained by comparing the total amount of hydrogen removed from the sample under programmed temperature conditions with the theoretical amount of hydrogen removed during complete hydrogenation; or by performing phase analysis on the solid product and calculating it in conjunction with the law of conservation of mass. Specifically, using the theoretical hydrogen release amount corresponding to the complete conversion of magnesium to magnesium hydride as the benchmark value, when the ratio of the actual measured hydrogen release amount to the theoretical hydrogen release amount reaches a preset ratio, the corresponding degree of hydrogenation is considered to have been reached. In this invention, "90% or 98% degree of hydrogenation" indicates that the actual hydrogen removal amount reaches 90% or 98% of the theoretical complete hydrogenation removal amount, respectively.
[0031] Unless otherwise specified, in this invention, the first target purity grade C1, the second target purity grade C2, and the target hydrogenation degree threshold XH are used to characterize the quality grade of the product and the reaction completion control index, respectively. The purity grade is the evaluation result of the effective content of magnesium hydride in the final product, and the hydrogenation degree threshold is the minimum conversion ratio requirement used when determining the termination of the reaction. The two can be close in value but do not have to be completely equal.
[0032] In this invention, the amount of hydrogen added to magnesium hydride refers to the weight percentage of hydrogen in magnesium hydride.
[0033] In a preferred embodiment, the preparation method provided by the present invention further includes: obtaining the correspondence between the temperature change characteristics of the hydrogenation reaction system and the degree of hydrogenation of magnesium hydride, to obtain a first process criterion curve; obtaining the correspondence between the dehydrogenation initiation temperature or dehydrogenation characteristic temperature in the magnesium hydride dehydrogenation test and the degree of hydrogenation of magnesium hydride, to obtain a second criterion curve; and setting a preset termination temperature range T based on the first process criterion curve and the second process criterion curve. end And the target hydrogenation degree threshold XH, to monitor the reaction endpoint in step S3.
[0034] Specifically, the method for obtaining the first process criterion curve includes: weighing a magnesium powder sample and placing it in a hydrogenation reactor, introducing hydrogen gas to carry out a hydrogenation reaction, controlling the change in hydrogen pressure during the hydrogenation reaction to be consistent with the hydrogen pressure in the actual preparation process described above, and monitoring the temperature of the hydrogenation reaction system in real time, collecting the products generated at different times, and testing the degree of hydrogenation of magnesium hydride in the product; then plotting the temperature of the hydrogenation reaction system as the abscissa and the degree of hydrogenation of magnesium hydride as the ordinate to obtain the first process criterion curve, for example... Figure 2 .
[0035] For example, the temperature of the hydrogenation reaction system is 415–425℃, preferably 420℃; the hydrogen pressure is the target hydrogen pressure P2 = 2.6–2.9 MPa, preferably 2.8 MPa; the reaction time is 240–360 min, preferably 300 min, after which the product is collected, and the degree of hydrogenation of magnesium hydride in the product is 90%; or, the temperature of the hydrogenation reaction system is 415–425℃, preferably 420℃; the hydrogen pressure is the target hydrogen pressure P2 = 2.6–2.9 MPa, preferably 2.8 MPa; the reaction time is 300–360 min, preferably 360 min, after which the product is collected, and the degree of hydrogenation of magnesium hydride in the product is 98%. Based on the above first process criterion curve, when it is desired to obtain magnesium hydride with a degree of hydrogenation of 90%, the hydrogen gas is introduced to reach the target hydrogen pressure P2 = 2.6–2.9 MPa, preferably 2.8 MPa, and the reaction temperature range T is... high The temperature is set to 415–425℃, preferably 420℃, for a preset reaction time period t. high The reaction time is set to 240–360 min, preferably 300 min; or, when it is desired to obtain magnesium hydride with a hydrogenation degree of 98%, hydrogen gas is introduced to achieve the target hydrogen pressure P2 = 2.6–2.9 MPa, preferably 2.8 MPa, and the reaction temperature range T is set accordingly. high The temperature is set to 415–425℃, preferably 420℃, for a preset reaction time period t. high The time was set to 300-360 min, preferably 360 min, thus achieving the goal of using temperature to reasonably and accurately determine the reaction endpoint.
[0036] Specifically, the method for obtaining the second process criterion curve includes: weighing a magnesium hydride sample and placing it in a dehydrogenation reactor, raising the temperature to remove hydrogen from the magnesium hydride sample, and monitoring the temperature of the dehydrogenation reaction system in real time during the hydrogen removal process; collecting the products generated at different times and testing the degree of hydrogenation of magnesium hydride in the products; then plotting the temperature of the dehydrogenation reaction system on the x-axis and the degree of hydrogenation of magnesium hydride on the y-axis to obtain the second process criterion curve, for example... Figure 3 .
[0037] For example, the initial dehydrogenation temperature of magnesium hydride with a hydrogenation degree of 90% is 380℃, and desorption ends at 450℃, with a measured desorption amount of 6.8%. For magnesium hydride with a hydrogenation degree of 98%, the initial dehydrogenation temperature is 290℃, and the measured desorption amount is 7.5% when heated to 420℃. Based on the second process criterion curve mentioned above, when it is desired to obtain magnesium hydride with a hydrogenation degree of 90%, the temperature T of the magnesium powder bed in step S3 above should be... bed The temperature range of 375–385°C is used as the temperature indicator for the end of the reaction; or, when it is desired to obtain magnesium hydride with a hydrogenation degree of 98%, the temperature T of the magnesium powder bed in step S3 above is set as follows. bed Using 290–300°C as the temperature indicator for the end of the reaction, the completion of the hydrogenation reaction can be visually determined, and products with different desired purities can be prepared on demand.
[0038] In a preferred embodiment, in step S3, a preset termination temperature range T is defined. end The temperature range is 290–380℃; the target hydrogenation degree threshold XH ≥ 90%. Compared to other ranges, the preset termination temperature range T is [not specified]. end Limiting the target hydrogenation degree threshold XH to the above range helps improve the accuracy of determining the endpoint of the hydrogenation reaction.
[0039] In a preferred embodiment, step S1 includes: filling a reactor with magnesium powder having a preset initial particle size to form a magnesium powder bed of the target filling amount; evacuating the reactor to bring the internal pressure to a preset evacuation limit pressure threshold; and then introducing hydrogen gas to raise the hydrogen pressure inside the reactor to the initial hydrogen pressure P1. This treatment method helps reduce residual air in the reactor, improves the efficiency of the hydrogenation reaction, and thus increases the purity of the obtained magnesium hydride.
[0040] To further improve the efficiency and controllability of the hydrogenation reaction and the purity of the obtained magnesium hydride, preferably, the initial particle size of the magnesium powder is 10–102 μm; the target loading amount of the magnesium powder bed in the reactor is 20–70 vol%; the initial hydrogen pressure P1 is 0.5–1.5 MPa; and the preset evacuation limit pressure threshold is 10–200 Pa.
[0041] This invention requires the selection of a reactor suitable for solid-gas phase reactions, especially suitable for the preparation process of magnesium hydride. In a preferred embodiment, the reactor includes, but is not limited to, a plug flow reactor, a jacketed plug flow reactor, or an external coil plug flow reactor.
[0042] In a preferred embodiment, step S2 further includes: heating the heat transfer oil to raise its temperature to a preset temperature range T. oil Preset temperature range T oil The temperature range is 280–330℃. The reactor temperature is controlled by raising the temperature of the heat transfer oil, and compared to other ranges, the preset temperature range T... oil Limiting the temperature within the above range is beneficial for ensuring that the temperature of the magnesium powder bed reaches the temperature required for the hydrogenation reaction, thereby activating the magnesium powder bed, improving the efficiency of the hydrogenation reaction, and thus increasing the purity of the obtained magnesium hydride.
[0043] In a preferred embodiment, in step S2, the target temperature range is 280–330°C; the target hydrogen pressure P2 is 2.0–3.0 MPa. Compared to other ranges, limiting the target temperature range and target hydrogen pressure P2 to the above ranges is beneficial for activating the magnesium powder bed, allowing the activated magnesium powder to undergo a hydrogenation reaction with sufficient hydrogen gas, thereby improving the efficiency of the hydrogenation reaction.
[0044] In a preferred embodiment, in step S3, the reaction temperature range T high Temperature range: 410–430℃; preset time period: t high The reaction time is 180–360 min. Compared to other ranges, the reaction temperature range T... high Limiting the reaction to the above-mentioned range is beneficial for the magnesium powder in the magnesium powder bed to react more fully with the introduced hydrogen gas.
[0045] To further obtain magnesium hydride with the desired particle size and purity, in a preferred embodiment, step S4 further includes: ball milling or mechanically kneading the product obtained after crushing and sieving to obtain magnesium hydride that meets the second target particle size range d2 and the median value of the second target particle size D. 50_2 Magnesium hydride with a second target purity grade of C2.
[0046] The preparation method provided by this invention achieves synergistic process control using particle size parameters as adjustment means and hydrogenation degree and purity parameters as quality indicators. This allows the same reaction equipment to adapt to the differentiated requirements of particle size and purity in different application scenarios under the combined adjustment of the above parameters. In a preferred embodiment, the first target particle size median D... 50_1 The target hydrogenation degree threshold XH satisfies the relationship (Ia): (Ia); where the median of the first target granularity is D 50_1The thickness is 60–102 μm; the preset termination temperature range is T. end It satisfies the relationship (Ib) with the first target purity level C1: (Ib); where the preset termination temperature range T end The temperature is 290–380℃; preferably, the first target particle size range d1 is 10–102 μm.
[0047] The preparation method provided by this invention achieves synergistic process control using particle size parameters as adjustment means and hydrogenation degree and purity parameters as quality indicators. This allows the same reaction equipment to adapt to the differentiated requirements of particle size and purity in different application scenarios under the combined adjustment of the above parameters. In a preferred embodiment, the median second target particle size D... 50_2 The target hydrogenation degree threshold XH satisfies the relationship (II-a): (II-a); where the median of the second target granularity is D 50_2 The thickness is 10–20 μm; the preset termination temperature range is T. end The second target purity grade C2 satisfies the relationship (II-b): (II-b); where the preset termination temperature range T end The temperature is 290–380℃; preferably, the second target particle size range d2 is 10–102 μm.
[0048] A second aspect of this invention also provides magnesium hydride, which is prepared by the above-described method for preparing magnesium hydride with controllable particle size and purity. It should be noted that, due to the specific nature of the materials field and limitations of existing testing and characterization methods, it is difficult to comprehensively and quantitatively characterize the complex microstructure of the obtained magnesium hydride. However, experiments show that the magnesium hydride obtained by this invention has controllable particle size and purity, and the particle size and purity of magnesium hydride are relatively stable between different batches, exhibiting high repeatability and facilitating large-scale production.
[0049] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.
[0050] Example 1
[0051] A method for preparing magnesium hydride with controllable particle size and purity, comprising:
[0052] (1) 7 kg of magnesium powder was packed into a plug flow reactor with a length of 1.3 m to obtain a magnesium powder bed with a target packing amount of 45 vol%. The plug flow reactor was evacuated to make its internal pressure reach the preset evacuation limit pressure threshold of 80 Pa. Then hydrogen was introduced to increase the internal hydrogen pressure to 1 MPa. The preset temperature range T of the heat transfer oil was set. oilThe temperature was set at 295–325°C. Then, stirring was started and the heat transfer oil was heated to 310°C. The temperature T of the magnesium powder bed was detected. bed After stabilization, hydrogen gas is continuously introduced to increase the hydrogen pressure to 2.8 MPa, so that the magnesium powder bed reacts with hydrogen gas and releases heat.
[0053] (2) According to Figure 2 and Figure 3 Given the provided criteria and the desired purity of 90% magnesium hydride, a preset termination temperature range T is set. end The temperature range was 372–388℃, and the target hydrogenation threshold XH was 90%; the temperature T of the magnesium powder bed was monitored. bed The temperature was gradually increased to 420℃, hydrogen gas was continuously introduced, and the reaction was carried out for 300 minutes. The hydrogen pressure was monitored to meet the target hydrogen pressure P2 and the fluctuation did not exceed 0.15 MPa, and the reaction temperature met the preset temperature range T. oil Furthermore, the temperature fluctuation should not exceed 8℃, and the temperature T of the magnesium powder bed should be within a certain range. bed It begins to decline, entering the reaction decay phase;
[0054] The temperature T of the magnesium powder bed was monitored. bed Descend to the preset termination temperature range T end When the hydrogenation level is greater than or equal to the target hydrogenation level threshold XH, stop the hydrogen gas supply;
[0055] (3) Collect the solid products in the plug flow reactor and crush and screen them sequentially to obtain the first target particle size range d1=10~102μm and the first target particle size median D. 50_1 Magnesium hydride with a particle size of 102 μm and a first target purity grade C1 of 89% to 91%;
[0056] The magnesium hydride particles obtained in step (3) are oval-shaped with tiny irregularities on the surface. Laser particle size analyzer measurements show that the particle size ranges from 10 to 300 μm, with a D50 of 102 μm. Nitrogen adsorption analysis reveals that the specific surface area of the magnesium hydride particles is 15 m². 2 / g; The whiteness of the magnesium hydride particles was measured to be 41 by a whiteness meter, and the hydrogenation amount was 7%;
[0057] (4) The magnesium hydride obtained in step (3) is ball-milled at a speed of 280 rpm for 150 min to obtain a particle size that meets the second target particle size range d2 = 10 ~ 102 μm and the median value of the second target particle size D. 50_2 =10μm, second target purity grade C2=98% magnesium hydride;
[0058] The magnesium hydride particles obtained in step (4) have a D50 of 10 μm, whiteness increased to 92, and purity increased to 98%.
[0059] Example 2
[0060] A method for preparing magnesium hydride with controllable particle size and purity, comprising:
[0061] (1) 7 kg of magnesium powder was packed into a plug flow reactor with a length of 1.3 m to obtain a magnesium powder bed with a target packing amount of 50 vol%. The plug flow reactor was evacuated to make its internal pressure reach the preset evacuation limit pressure threshold of 50 Pa. Then hydrogen was introduced to increase the internal hydrogen pressure to 1 MPa. The preset temperature range T of the heat transfer oil was set. oil The temperature was set at 300–320°C. Then, stirring was started and the heat transfer oil was heated to 310°C. The temperature T of the magnesium powder bed was detected. bed After stabilization, hydrogen gas is continuously introduced to increase the hydrogen pressure to 2.8 MPa, so that the magnesium powder bed reacts with hydrogen gas and releases heat.
[0062] (2) According to Figure 2 and Figure 3 Given the provided criteria and the desired purity of 90% magnesium hydride, a preset termination temperature range T is set. end The temperature range was 375–385℃, and the target hydrogenation threshold XH was 90%; the temperature T of the magnesium powder bed was monitored. bed The temperature was gradually increased to 420℃, hydrogen gas was continuously introduced, and the reaction was carried out for 300 minutes. The hydrogen pressure was monitored to meet the target hydrogen pressure P2 and the fluctuation did not exceed 0.2 MPa, and the reaction temperature met the preset temperature range T. oil And the temperature fluctuation should not exceed 10℃, and the temperature T of the magnesium powder bed should be constant. bed The temperature began to decrease, entering the reaction decay stage; the temperature T of the magnesium powder bed was monitored. bed Descend to the preset termination temperature range T end When the hydrogenation level is greater than or equal to the target hydrogenation level threshold XH, stop the hydrogen gas supply;
[0063] (3) Collect the solid products in the plug flow reactor and crush and screen them sequentially to obtain the first target particle size range d1=60~102μm and the first target particle size median D. 50_1 Magnesium hydride with a particle size of 102 μm and a first target purity grade of C1=90%;
[0064] The magnesium hydride particles obtained in step (3) are oval-shaped with tiny irregularities on the surface. Laser particle size analyzer measurements show that the particle size is in the range of 60–102 μm. Nitrogen adsorption method analysis shows that the specific surface area of the magnesium hydride particles is 15 m². 2 / g; The whiteness of the magnesium hydride particles was measured to be 41 by a whiteness meter, and the hydrogenation amount was 7%;
[0065] (4) The magnesium hydride obtained in step (3) is ball-milled at a speed of 300 rpm for 120 min to obtain a particle size that meets the second target particle size range d2 = 10 ~ 102 μm and the median value of the second target particle size D. 50_2 =10μm, second target purity grade C2=98% magnesium hydride;
[0066] The magnesium hydride particles obtained in step (4) have a D50 of 10 μm, whiteness increased to 92, and purity increased to 98%.
[0067] Comparative Example 1
[0068] A method for preparing magnesium hydride, comprising:
[0069] (1) 7 kg of magnesium powder was packed into a plug flow reactor with a length of 1.3 m to obtain a magnesium powder bed with a target packing amount of 50 vol%. The plug flow reactor was evacuated and then hydrogen was introduced to increase the internal hydrogen pressure to 1 MPa. Then the stirring was started and the heat transfer oil was heated to 310 °C. Hydrogen was continued to be introduced to increase the hydrogen pressure to 2.8 MPa, so that the magnesium powder bed and hydrogen could undergo a hydrogenation reaction and release heat.
[0070] (2) The temperature T of the magnesium powder bed was monitored. bed The temperature was gradually increased to 420°C, hydrogen gas was continuously introduced and the reaction was continued for 300 minutes, then the hydrogen gas was stopped and the reaction was terminated.
[0071] (3) Collect the solid products in the plug flow reactor and crush and screen them in sequence to obtain magnesium hydride.
[0072] The magnesium hydride prepared in Comparative Example 1 had a particle size in the range of 20–500 μm, a D50 of 150 μm, a whiteness of 35, and a hydrogenation amount of 6.0%.
[0073] It can be seen that, since Comparative Example 1 did not use bed temperature change as the entry mark of the reaction decay stage and the reaction termination condition, its hydrogenation degree was insufficient under the same reaction time conditions, resulting in a lower hydrogenation amount in Comparative Example 1 than in Example 1. At the same time, Comparative Example 1 did not establish an endpoint control method that matched the target hydrogenation degree during the reaction process. To obtain an acceptable hydrogenation degree, it is usually necessary to extend the reaction time or increase the heat preservation and hydrogen supply, resulting in a higher energy consumption in Comparative Example 1 than in Example 1.
[0074] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:
[0075] This invention achieves its goal by rationally setting a preset termination temperature range T. end And the target hydrogenation degree threshold XH, and the temperature T of the magnesium powder bed bedThe criterion of determining the reaction endpoint when the degree of hydrogenation meets the above conditions transforms the preparation process of magnesium hydride from empirical control to quantifiable control centered on temperature curves. Without increasing the complexity of detection methods, it enables the visual judgment of the completion of the hydrogenation reaction and the on-demand preparation of products with different desired purities, thereby improving the controllability, repeatability, and engineering scale-up applicability of the preparation process.
[0076] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of the invention described herein can be implemented, for example, in orders other than those described herein.
[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing magnesium hydride with controllable particle size and purity, characterized in that, The preparation method includes: Step S1: Hydrogen gas is introduced into the reactor filled with a magnesium powder bed to increase the internal pressure to the initial hydrogen pressure P1. Step S2: The reactor is heated by the heat transfer oil in the external heating mechanism, and the temperature T of the magnesium powder bed is monitored. bed Once the temperature stabilizes within the target temperature range, hydrogen is continuously introduced to increase the hydrogen pressure inside the reactor to the target hydrogen pressure P2, causing the magnesium powder bed to undergo a hydrogenation reaction with the hydrogen and release heat. Step S3, monitor the temperature T of the magnesium powder bed. bed Increase to the reaction temperature range T high Within this time, hydrogen gas continues to be introduced and the reaction continues for a preset time period t. high The hydrogen pressure was monitored to meet the target hydrogen pressure P2 and fluctuate by no more than 0.2 MPa, and the reaction temperature met the preset temperature range T. oil And when the temperature fluctuation does not exceed 10℃, and the temperature T of the magnesium powder bed is... bed The temperature of the magnesium powder bed, T, began to decrease, entering the reaction decay stage; the temperature T was monitored. bed Descend to the preset termination temperature range T end When the hydrogenation degree is greater than or equal to the target hydrogenation degree threshold XH, stop the hydrogen gas flow and collect the solid product. Step S4: The solid product is crushed and sieved sequentially to obtain particles that meet the first target particle size range d1 and the first target particle size median D. 50_1 The magnesium hydride of the first target purity grade C1.
2. The method for preparing magnesium hydride with controllable particle size and purity according to claim 1, characterized in that, The preparation method further includes: obtaining the correspondence between the temperature change characteristics of the hydrogenation reaction system and the degree of hydrogenation of magnesium hydride, to obtain a first process criterion curve; obtaining the correspondence between the dehydrogenation initiation temperature or dehydrogenation characteristic temperature in the magnesium hydride dehydrogenation test and the degree of hydrogenation of magnesium hydride, to obtain a second criterion curve; and setting the preset termination temperature range T according to the first process criterion curve and the second process criterion curve. end And the target hydrogenation degree threshold XH, to monitor the reaction endpoint in step S3.
3. The method for preparing magnesium hydride with controllable particle size and purity according to claim 2, characterized in that, In step S3, the preset termination temperature range T end The temperature is 290–380°C; the target hydrogenation degree threshold XH is ≥90%.
4. The method for preparing magnesium hydride with controllable particle size and purity according to any one of claims 1 to 3, characterized in that, Step S1 includes: filling magnesium powder with a preset initial particle size into the reactor to form a magnesium powder bed with a target filling amount, evacuating the reactor to make the internal pressure of the reactor reach a preset evacuation limit pressure threshold, and then introducing hydrogen gas to increase the hydrogen pressure inside the reactor to the initial hydrogen pressure P1. The preset initial particle size of the magnesium powder is 10-102 μm; the target loading amount of the magnesium powder bed in the reactor is 20-70 vol%; the initial hydrogen pressure P1 is 0.5-1.5 MPa; and the preset evacuation limit pressure threshold is 10-200 Pa. The reactor is selected from plug flow reactors, jacketed plug flow reactors, or external coil plug flow reactors.
5. A method for preparing magnesium hydride with controllable particle size and purity according to any one of claims 1 to 3, characterized in that, Step S2 further includes: heating the heat transfer oil to raise its temperature to the preset temperature range T. oil The preset temperature range T oil 280–330℃; and / or, In step S2, the target temperature range is 280–330°C; the target hydrogen pressure P2 is 2.0–3.0 MPa.
6. A method for preparing magnesium hydride with controllable particle size and purity according to any one of claims 1 to 3, characterized in that, In step S3, the reaction temperature range T high The temperature is 410–430℃; the preset time period t high The time is 180–360 minutes.
7. The method for preparing magnesium hydride with controllable particle size and purity according to claim 4, characterized in that, Step S4 further includes: The products obtained after crushing and screening are ball-milled or mechanically kneaded to obtain particles that meet the second target particle size range d2 and the median second target particle size D. 50_2 The magnesium hydride of the second target purity grade C2.
8. The method for preparing magnesium hydride with controllable particle size and purity according to claim 1, characterized in that, The first target granularity median D 50_1 The target hydrogenation degree threshold XH satisfies the relationship (Ia): (I-a); Wherein, the median of the first target granularity D 50_1 The size is 60–102 μm; The preset termination temperature range T end It satisfies the relationship (Ib) with the first target purity level C1: (I-b); Wherein, the preset termination temperature range T end The temperature ranges from 290 to 380℃. The first target particle size range d1 is 10 to 102 μm.
9. The method for preparing magnesium hydride with controllable particle size and purity according to claim 7, characterized in that, The second target granularity median D 50_2 The target hydrogenation degree threshold XH satisfies the relationship (II-a): (II-a): Wherein, the median of the second target granularity D 50_2 It is 10–20 μm; The preset termination temperature range T end It satisfies the relationship (II-b) with the second target purity level C2: (II-b); wherein, the preset termination temperature range T end The temperature ranges from 290 to 380℃. The second target particle size range d2 is 10 to 102 μm.
10. A magnesium hydride particle, characterized in that, The magnesium hydride particles are prepared by any one of the methods for preparing magnesium hydride with controllable particle size and purity as described in claims 1 to 9.