A magnesium-based hydrogen storage material added with natural coke and transition metal and a preparation method thereof

Abstract

The application relates to the technical field of hydrogen storage materials, in particular to a magnesium-based hydrogen storage material added with natural coke and transition metals and a preparation method thereof. The preparation method is as follows: under a protective atmosphere, the natural coke is ball milled, transition metal small balls serving as catalyst precursors are added and mixed and ball milled, then the remaining transition metal small balls after ball milling are separated out, and finally magnesium powder is added and mixed and ball milled, so that the magnesium-based hydrogen storage material added with natural coke and transition metals is prepared. The transition metal falling off the transition metal small balls is transferred to the surface of magnesium particles with the natural coke as a carrier, so that the dispersion degree of the transition metal catalyst is improved, and the catalytic effect of the transition metal catalyst is improved; and the dispersion effect and the grinding medium effect of the natural coke on the magnesium powder ball milling make the magnesium powder easy to be nanometerized, so that the technical problems that the solid catalyst is difficult to be highly dispersed by the ball milling method and the magnesium powder is difficult to be nanometerized are solved, and the hydrogen absorption and hydrogen release kinetic performance of the magnesium can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen storage materials, in particular to a magnesium-based hydrogen storage material added with natural coke and transition metals and a preparation method thereof. BACKGROUND

[0002] Hydrogen energy is chemical energy released by chemical reaction of hydrogen and oxygen. Hydrogen energy is considered as a potential clean energy because of its advantages of high energy density, reaction product only water, abundant resources and sustainable development, and has become a research hotspot. The hydrogen storage link is crucial to the practical application of hydrogen energy. Hydrogen storage can use solid materials, among which magnesium-based hydrogen storage materials are favored by researchers because of the characteristics of abundant magnesium resources and high hydrogen storage density.

[0003] The hydrogen absorption and desorption kinetics of magnesium-based hydrogen storage materials composed of magnesium elements is poor, which restricts its practical application in hydrogen energy. Adding transition metal catalyst by ball milling and reducing the particle size of magnesium powder are common technical means to improve the kinetics of magnesium-based hydrogen storage materials.

[0004] However, when adding transition metal catalyst by ball milling, the transition metal catalyst is generally compounded with magnesium particles in the form of micron / nanometer particles, resulting in low dispersion degree of the catalyst on the surface of magnesium particles and poor catalytic effect.

[0005] When reducing the particle size of magnesium powder by ball milling, dispersants need to be added to prevent "cold welding" between magnesium particles during ball milling. However, common dispersants such as graphite powder, talc powder and organic solvents do not have significant grinding medium effect, making it difficult to nanoize magnesium powder.

[0006] Therefore, the current technical means of adding transition metal catalyst by ball milling and reducing the particle size of magnesium powder have the technical problems of low dispersion degree of transition metal catalyst and difficulty in nanoizing magnesium powder, which results in ineffective improvement of the hydrogen absorption and desorption kinetics of magnesium-based hydrogen storage materials. SUMMARY

[0007] The present application aims to overcome the shortcomings of the prior art and provides a magnesium-based hydrogen storage material added with natural coke and transition metals and a preparation method thereof, which solves the technical problems of low dispersion degree of catalyst added by ball milling and difficulty in nanoizing magnesium powder.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] The present application provides a preparation method of a magnesium-based hydrogen storage material added with natural coke and transition metals, comprising the following steps:

[0010] Under a protective atmosphere, the natural coke is ball milled to obtain natural coke powder; then the transition metal small balls as catalyst precursors are added into the natural coke powder for mixed ball milling, and then the remaining transition metal small balls after the ball milling are separated to obtain the natural coke loaded with transition metal; finally, the magnesium powder is added into the natural coke loaded with transition metal for mixed ball milling to obtain the magnesium-based hydrogen storage material added with natural coke and transition metal.

[0011] In the magnesium-based hydrogen storage material, the mass percentage of each component is as follows: 3.9wt%-7.2wt% of natural coke, 0.7wt%-1.7wt% of transition metal, and 91.2wt%-94.9wt% of magnesium, and the transition metal is at least one of iron, cobalt and nickel.

[0012] The present application transfers the transition metal ground from the transition metal small balls to the surface of magnesium particles by taking the natural coke as a carrier, so as to improve the dispersion degree of the transition metal catalyst and enhance the catalytic effect of the transition metal catalyst; and the dispersion effect and grinding medium effect of the natural coke on the magnesium powder ball milling make the magnesium powder easy to be nano-sized, so as to solve the technical problems that the solid catalyst is difficult to be highly dispersed by the ball milling method and the magnesium powder is difficult to be nano-sized, and effectively improve the hydrogen absorption and desorption kinetic performance of magnesium.

[0013] Optionally, the ball milling speed of the natural coke ball milling alone is 480r / min-600r / min, and the ball milling time is 0.5h-1.5h. Further preferably, the ball milling speed is 540r / min, and the ball milling time is 1h.

[0014] Optionally, the ball milling speed of the transition metal small balls added into the natural coke powder for mixed ball milling is 240r / min-360r / min, and the ball milling time is 2h-4h. Further preferably, the ball milling speed is 300r / min, and the ball milling time is 3h.

[0015] Optionally, the mass ratio of the transition metal small balls to the natural coke powder is 2-5:1. Further preferably, the mass ratio of the transition metal small balls to the natural coke powder is 3:1.

[0016] Optionally, the ball milling speed of the magnesium powder added into the natural coke loaded with transition metal for mixed ball milling is 360r / min-480r / min, and the ball milling time is 1h-3h.

[0017] The present application also provides a magnesium-based hydrogen storage material added with natural coke and transition metal, which is prepared by the above preparation method.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] (1) The present application transfers the transition metal ground from the transition metal small ball to the surface of magnesium particles with natural coke as the carrier, so as to improve the dispersion degree of the transition metal catalyst and promote the catalytic effect of the transition metal catalyst; and the dispersion effect and grinding medium effect of the natural coke on the magnesium powder ball milling make the magnesium powder easy to be nano-sized, so that the technical problems of the difficulty in realizing the high dispersion of the solid catalyst and the nano-sized magnesium powder by the ball milling method are solved, and the hydrogen absorption and desorption kinetic performance of the magnesium can be effectively improved.

[0020] Specifically, the transition metal catalyst added to the surface of the magnesium particles is ground from the transition metal small ball, and compared with the conventional micron / nano-sized transition metal catalyst particles, the transition metal catalyst ground from the transition metal small ball has high dispersion degree and high catalytic activity. The natural coke is used as the grinding aid for the magnesium powder ball milling, the natural coke has high hardness, has good grinding medium effect on the magnesium powder, and has good dispersion effect on the magnesium powder, so that the "cold welding" between the magnesium particles can be prevented, and thus the magnesium powder is easy to be ground to the nano-sized, and the hydrogen absorption / desorption rate of the magnesium can be improved.

[0021] (2) In the process of the hydrogen absorption / desorption of the magnesium-based hydrogen storage material at high temperature, the natural coke has good confinement effect on the magnesium particles, so that the fusion and growth between the magnesium particles can be prevented, and the hydrogen absorption / desorption kinetic performance of the magnesium can be stabilized.

[0022] (3) The natural coke has poor thermal stability, has flammability, and has low chemical reactivity, and is generally used as low-value fuel, while the present application innovatively applies the natural coke to the preparation of the magnesium-based hydrogen storage material with high performance, so that the natural coke can be used in high-value way. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 An X-ray diffraction spectrum of the magnesium powder provided by the present application.

[0024] Figure 2 A scanning electron microscope photo of the natural coke after ball milling obtained from Example 1 provided by the present application.

[0025] Figure 3 A scanning electron microscope photo of the magnesium-based hydrogen storage material prepared in Example 1 provided by the present application.

[0026] Figure 4 A distribution diagram of the nickel element in the magnesium-based hydrogen storage material prepared in Example 1 provided by the present application.

[0027] Figure 5 A transmission electron microscope photo of the magnesium-based hydrogen storage material prepared in Example 1 provided by the present application.

[0028] Figure 6 An X-ray diffraction spectrum of the magnesium-based hydrogen storage material prepared in Example 1 provided by the present application.

[0029] Figure 7 The hydrogen absorption kinetics curve of the magnesium-based hydrogen storage material prepared by the example 1 of the present application at 200℃ is shown in the following figure.

[0030] Figure 8 The hydrogen desorption kinetics curve of the magnesium-based hydrogen storage material prepared by the example 1 of the present application at 300℃ is shown in the following figure.

[0031] Figure 9 The hydrogen absorption / desorption isotherm of the magnesium-based hydrogen storage material prepared by the example 1 of the present application at 300℃ is shown in the following figure.

[0032] Figure 10 The hydrogen absorption / desorption kinetics curve of the magnesium-based hydrogen storage material prepared by the example 1 of the present application at 300℃ is shown in the following figure. DETAILED DESCRIPTION

[0033] In order to solve the above technical problems, the present application provides a magnesium-based hydrogen storage material added with natural coke and transition metal and a preparation method thereof, and the technical solutions and examples of the present application are described in detail in combination with the drawings.

[0034] The technical principle of the present application is that: the transition metal small balls are used as the precursor of the transition metal catalyst, the zirconium dioxide with high mechanical strength is used as the grinding medium, and the natural coke is used as the catalyst carrier. The natural coke particles with graphite-like sheet structure are ground into small sheet particles, and the specific surface area is increased. At the same time, the transition metal removed from the transition metal small balls is adsorbed on the surface of the small natural coke particles in the form of single atom / atomic cluster. Then, the magnesium powder is added for mixing and ball milling. The small natural coke particles with hard texture have good grinding medium effect on the magnesium particles with soft texture, which is beneficial to reduce the particle size of the magnesium powder. In addition, the small natural coke particles have good dispersion effect on the magnesium powder, which can prevent the "cold welding" between the magnesium particles and is also beneficial to reduce the particle size of the magnesium powder, so that the magnesium powder is easily ground to the nanoscale, and then the diffusion distance of hydrogen atoms in the magnesium crystal during the hydrogen absorption / desorption process of the magnesium is shortened, and the hydrogen absorption / desorption rate of the magnesium is improved. At the same time, the transition metal catalyst on the surface of the natural coke particles in the form of single atom / atomic cluster is compounded with the magnesium particles during the ball milling process. Compared with the micron / nanoscale particulate transition metal catalyst, this reduces the amount of the transition metal catalyst and improves the catalytic effect of the transition metal catalyst on the hydrogen absorption / desorption of the magnesium. The high dispersion of the transition metal catalyst and the nanoscale of the magnesium powder are both beneficial to improve the hydrogen absorption / desorption kinetics performance of the magnesium.

[0035] Natural coke is the product of coking of caking bituminous coal under natural conditions by magma contact, and the gas pores and cracks of the natural coke generally enclose gas, and the natural coke is non-caking when heated, has combustion and explosion property, poor thermal stability and low chemical activity, and has low utilization value. The natural coke has the characteristics of similar graphite sheet structure and hard texture, and is used as a carrier of transition metal catalyst and a grinding aid for magnesium powder ball milling.

[0036] The natural coke used in the present application is produced in Xulou minefield of Tengxian coalfield in Shandong, and is 1 / 3 coking coal metamorphosed by magma contact, has hard texture, and has a Hardgrove grindability index of only 34.5. The industrial analysis and element analysis data of the natural coke are shown in Table 1. The natural coke is crushed to a particle size of <0.074 mm by a jaw crusher and a vibration mill for application in the present application.

[0037] Table 1 Statistical table of analysis data of the natural coke

[0038]

[0039] Note: M ad —air-dried moisture, A d —dry ash, V daf —dry ash-free volatile matter, C daf —dry ash-free fixed carbon; C d —carbon content on dry basis, H d —hydrogen content on dry basis, N d —nitrogen content on dry basis, S t,d —total sulfur content on dry basis, O d —oxygen content on dry basis; R r —average random reflectance of vitrinite; Q gr,d —dry basis gross calorific value; α—CO2 reactivity; ARD—apparent density; HGI—Hardgrove grindability index.

[0040] The purity of the magnesium used in the present application is 98.5wt%, and the particle size is <0.074 mm, and the X-ray diffraction spectrum thereof is shown in Figure 1 The instrument used in the X-ray diffraction analysis is a SmartLab X-ray diffractometer of RIGAKU Corporation of Japan, a copper target Kα ray is used, the scanning step is set to 0.01°, and the scanning speed is set to 2° / min. Figure 1 It can be known from

[0041] The equipment for carrying out the ball milling treatment of the present application is a planetary ball mill. The model of the planetary ball mill is ND8-1L, which is produced by Nanjing Nandatianzun Electronics Co., Ltd. The specific configuration of the planetary ball mill is as follows: 4 ball milling jars are installed, each ball milling jar has a volume of 100 mL, the material of the lining and the grinding balls in the ball milling jar is sintered zirconium dioxide, the number ratio of the grinding balls with diameters of 9 mm, 5 mm and 3 mm is 20:40:40, the rotation speed ratio of the self-rotation and the revolution is 2:1, the self-rotation and the revolution are in the same direction, and the revolution is stopped and cooled for 5 minutes after each forward rotation of 5 minutes and reverse rotation of 5 minutes.

[0042] The inert protective gas in the ball milling jar of the present application is preferably argon with a purity of 99.999 vol%.

[0043] The ball milling jar loading and unloading operations of the present application are carried out in an argon-filled glove box. The glove box is Lab2000 type, which is produced by Yitex Inert Gas System Co., Ltd. The purity of the argon filled in the glove box is 99.999 vol%, the oxygen content in the glove box is <0.1 ppm, and the water content is <0.1 ppm.

[0044] The hydrogen absorption / desorption properties of the magnesium-based hydrogen storage material are tested to evaluate the hydrogen storage performance thereof. The specific testing method is as follows:

[0045] The hydrogen absorption / desorption properties of the material are tested by using a high-pressure gas adsorption instrument. The high-pressure gas adsorption instrument is PCT-Pro2000 type, which is produced by Saicrtec Instruments Co., Ltd. The hydrogen absorption kinetics curve of the material at 200℃, the hydrogen desorption kinetics curve at 300℃, the hydrogen absorption / desorption kinetics curve at 300℃, and the hydrogen absorption / desorption isotherm at 300℃ are tested. During the testing, the mass of the solid sample is 300 mg, the hydrogen absorption reference volume is 17.10 mL, the hydrogen desorption reference volume is 176.09 mL, and the free volume of the sample cell is about 11.5 mL at room temperature; during the kinetics testing, the initial pressure for hydrogen absorption is 2.5 MPa, and the initial pressure for hydrogen desorption is 0.01 MPa; during the hydrogen absorption isotherm testing, the final pressure is 2.0 MPa.

[0046] The present application is described in detail below through specific examples, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application. In each of the following examples, the method is a conventional method unless otherwise specified; and the reagents and materials can be purchased on the market unless otherwise specified.

[0047] Example 1

[0048] The present embodiment provides a magnesium-based hydrogen storage material, and the preparation method is as follows:

[0049] Step one, separate ball milling of natural coke.

[0050] In an argon-filled glove box, 0.122 g of the natural coke with the analysis data as shown in Table 1 was loaded into a ball mill jar, and the ball mill jar was filled with argon to 3 atm, and then ball milling was performed on a planetary ball mill at a rotation speed of 540 r / min for 1 h to obtain natural coke powder.

[0051] Step two, mixing and ball milling of transition metal pellets and natural coke powder.

[0052] In an argon-filled glove box, 90 nickel metal pellets with a diameter of 1.0 mm were added into the ball mill jar containing the obtained natural coke powder in step one, and the ball mill jar was filled with argon to 3 atm, and then ball milling was performed on a planetary ball mill at a rotation speed of 300 r / min for 3 h; and then in an argon-filled glove box, the remaining nickel metal pellets after ball milling were separated out by sieving to obtain natural coke loaded with transition metal.

[0053] The purity of nickel in the nickel metal pellets was 99.5 wt%; the sieves used for removing the remaining nickel metal pellets after ball milling were sieves with a pore size of 1.4 mm and 0.5 mm, and the nickel metal pellets in between the two pore sizes were removed by sieving, and the mass of the milled nickel was the difference between the mass of the nickel metal pellets before and after ball milling, and the mass of the milled nickel in this example was 0.031 g.

[0054] Step three, mixing and ball milling of magnesium powder and natural coke loaded with transition metal.

[0055] In an argon-filled glove box, 1.880 g of magnesium powder was added into the ball mill jar containing the obtained natural coke loaded with transition metal in step two, and the ball mill jar was filled with argon to 3 atm, and then ball milling was performed on a planetary ball mill at a rotation speed of 420 r / min for 2 h to obtain a magnesium-based hydrogen storage material.

[0056] The mass proportions of natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example were 6.0 wt%, 1.5 wt% and 92.5 wt% respectively.

[0057] The natural coke powder obtained after ball milling in this example and the prepared magnesium-based hydrogen storage material were taken for morphology observation, and the prepared magnesium-based hydrogen storage material was subjected to nickel element distribution analysis, transmission electron microscope observation, crystal structure analysis, hydrogen absorption / desorption kinetics test, hydrogen absorption / desorption isotherm determination and cyclic hydrogen absorption / desorption stability test.

[0058] The scanning electron microscope photograph of the natural coke powder obtained after ball milling in this example is shown in Figure 2 The instrument used for scanning electron microscope observation was a scanning electron microscope S-570 of Hitachi, Japan, which was equipped with an energy-dispersive spectrometer and could be used for element analysis. Figure 2It can be seen that the natural coke powder after ball milling is <1 μm, most of which is <0.1 μm.

[0059] The scanning electron microscope photograph of the magnesium-based hydrogen storage material of the present example is shown in Fig. 1. It can be seen that the particles of the magnesium-based hydrogen storage material are nanoscale. Figure 3 The distribution of the nickel element in the magnesium-based hydrogen storage material is shown in Fig. 2. It can be seen that the nickel element is uniformly distributed in the material. Figure 4

[0060] The transmission electron microscope photograph of the magnesium-based hydrogen storage material of the present example is shown in Fig. 3. The instrument used for transmission electron microscope observation is H-800 transmission electron microscope of Japan Hitachi Company. The accelerating voltage is 200 kV. Figure 5 It can be seen that the particles of the magnesium-based hydrogen storage material are nanoscale, and most of the particles are hexagonal. Figure 5

[0061] The X-ray diffraction spectrum of the magnesium-based hydrogen storage material of the present example is shown in Fig. 4. It can be seen that the natural coke in the material is in amorphous state, and the magnesium is still in crystalline state, but the magnesium grain size after ball milling is significantly reduced compared with the raw material magnesium. The grain size calculated by Scherrer formula according to the diffraction peak at 36.5° is 28 nm. Figure 6

[0062] The hydrogen absorption kinetics curve of the magnesium-based hydrogen storage material of the present example at 200°C is shown in Fig. 5, which is the curve of "Example 1" in Fig. 5. It can be seen that the saturated hydrogen absorption amount of 6.3wt% can be reached at 2 min. The hydrogen desorption kinetics curve at 300°C is shown in Fig. 6. It can be seen that the hydrogen can be completely desorbed at 7 min. Figure 7 Figure 8

[0063] The hydrogen absorption / desorption isotherm of the magnesium-based hydrogen storage material of the present example at 300°C is shown in Fig. 7. It can be seen that the hydrogen absorption / desorption plateau pressure is 0.5 MPa, the pressure difference is 0.15 MPa, and the length of the pressure plateau is 5.5wt% of hydrogen content. Figure 9

[0064] The hydrogen absorption / desorption kinetics curve of the magnesium-based hydrogen storage material of the present example at 300°C is shown in Fig. 8. It can be seen that the hydrogen absorption / desorption amount of the material does not attenuate at 45 cycles. Figure 10

[0065] Example 2

[0066] The difference between the present example and Example 1 is that the amount of the natural coke used as the raw material is reduced. The amount of the natural coke used in the present example is reduced to 0.102 g, and the magnesium-based hydrogen storage material is prepared.

[0067] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in the present example is 5.1wt%, 1.3wt% and 93.6wt% respectively.

[0068] ​​​​​​​The hydrogen absorption kinetics curve of the magnesium-based hydrogen storage material prepared in this example at 200℃ is shown in Figure 2. Figure 5 As shown in the "Example 2" curve, the hydrogen absorption amount reaches 6.3wt% at 12 minutes, which is the saturated hydrogen absorption amount. Compared with Example 1, the amount of natural coke is reduced, and the hydrogen absorption rate is slowed down.

[0069] Example 3

[0070] The difference between this example and Example 1 is that the amount of natural coke is reduced to 0.078g, and the magnesium-based hydrogen storage material is prepared.

[0071] The contents of natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example are 3.9wt%, 1.2wt% and 94.9wt%, respectively.

[0072] The hydrogen absorption kinetics curve of the magnesium-based hydrogen storage material prepared in this example at 200℃ is shown in Figure 2. Figure 5 As shown in the "Example 3" curve, the hydrogen absorption amount is 5.9wt% at 12 minutes, which is not saturated. Compared with Example 1, the hydrogen absorption rate is significantly slowed down, that is, the less the amount of natural coke, the slower the hydrogen absorption rate of the magnesium-based hydrogen storage material.

[0073] Example 4

[0074] The difference between this example and Example 1 is that the amount of natural coke is increased to 0.149g, and the magnesium-based hydrogen storage material is prepared.

[0075] The contents of natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example are 7.2wt%, 1.6wt% and 91.2wt%, respectively.

[0076] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200℃ is determined, and the hydrogen absorption amount reaches 6.2wt% at 2 minutes, which is the saturated hydrogen absorption amount. Compared with Example 1, it can be seen that adding too much natural coke is not beneficial to improving the hydrogen absorption kinetics performance.

[0077] Example 5

[0078] The difference between this example and Example 1 is that the amount of magnesium is increased to 2.360g, and the magnesium-based hydrogen storage material is prepared.

[0079] The contents of natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example are 4.9wt%, 1.2wt% and 93.9wt%, respectively.

[0080] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200℃ is determined, and the hydrogen absorption amount is 5.3wt% at 12 minutes, which is not saturated.

[0081] Example 6

[0082] The difference between this example and Example 1 is that the ball milling speed is reduced and the ball milling time is decreased, the ball milling speed of Step 1 is 480 r / min, the ball milling time is 0.5 h, the ball milling speed of Step 2 is 240 r / min, the ball milling time is 2 h, the ball milling speed of Step 3 is 360 r / min, and the ball milling time is 1 h, and the magnesium-based hydrogen storage material is prepared.

[0083] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.1 wt%, 0.7 wt% and 93.2 wt% respectively.

[0084] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption amount is 3.1 wt% when the saturation is not reached after 12 min of hydrogen absorption.

[0085] Example 7

[0086] The difference between this example and Example 1 is that the ball milling time is decreased, the ball milling time of Step 1 is 0.5 h, the ball milling time of Step 2 is 2 h, and the ball milling time of Step 3 is 1 h, and the magnesium-based hydrogen storage material is prepared.

[0087] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.0 wt%, 1.3 wt% and 92.7 wt% respectively.

[0088] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption amount is 4.3 wt% when the saturation is not reached after 12 min of hydrogen absorption.

[0089] Example 8

[0090] The difference between this example and Example 1 is that the ball milling time is increased, the ball milling time of Step 1 is 1.5 h, the ball milling time of Step 2 is 4 h, and the ball milling time of Step 3 is 3 h, and the magnesium-based hydrogen storage material is prepared.

[0091] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.0 wt%, 1.6 wt% and 92.4 wt% respectively.

[0092] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the saturation is reached after 2 min of hydrogen absorption, and the hydrogen absorption amount is 6.2 wt%.

[0093] Example 9

[0094] The difference between this example and example 1 is that the ball milling speed is increased and the ball milling time is increased, the ball milling speed of step one is 600 r / min, the ball milling time is 1.5 h, the ball milling speed of step two is 360 r / min, the ball milling time is 4 h, the ball milling speed of step three is 480 r / min, and the ball milling time is 3 h, to prepare the magnesium-based hydrogen storage material.

[0095] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.0 wt%, 1.7 wt% and 92.3 wt% respectively.

[0096] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 2 min, and the hydrogen absorption amount is 6.1 wt%.

[0097] Example 10

[0098] The difference between this example and example 1 is that the ball milling speed is increased and the ball milling time is reduced, the ball milling speed of step one is 600 r / min, the ball milling time is 0.5 h, the ball milling speed of step two is 360 r / min, the ball milling time is 2 h, the ball milling speed of step three is 480 r / min, and the ball milling time is 1 h, to prepare the magnesium-based hydrogen storage material.

[0099] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.0 wt%, 1.5 wt% and 92.5 wt% respectively.

[0100] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 2 min, and the hydrogen absorption amount is 6.2 wt%.

[0101] Example 11

[0102] The difference between this example and example 1 is that the ball milling speed is reduced and the ball milling time is increased, the ball milling speed of step one is 480 r / min, the ball milling time is 1.5 h, the ball milling speed of step two is 240 r / min, the ball milling time is 4 h, the ball milling speed of step three is 360 r / min, and the ball milling time is 3 h, to prepare the magnesium-based hydrogen storage material.

[0103] The content of the natural coke, nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example is 6.0 wt%, 1.4 wt% and 92.6 wt% respectively.

[0104] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 2 min, and the hydrogen absorption amount is 6.1 wt%.

[0105] Example 12

[0106] The difference between this example and example 1 is that the transition metal used as catalyst is iron, i.e. iron metal pellets are used instead of nickel metal pellets, to prepare the magnesium-based hydrogen storage material.

[0107] The contents of natural coke, iron and magnesium in the magnesium-based hydrogen storage material prepared in this example are 6.0wt%, 1.7wt% and 92.3wt% respectively.

[0108] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 12 min, with the hydrogen absorption amount being 5.7wt%.

[0109] Example 13

[0110] The difference between this example and example 1 is that the transition metal used as catalyst is cobalt, i.e. cobalt metal pellets are used instead of nickel metal pellets, to prepare the magnesium-based hydrogen storage material.

[0111] The contents of natural coke, cobalt and magnesium in the magnesium-based hydrogen storage material prepared in this example are 6.0wt%, 1.2wt% and 92.8wt% respectively.

[0112] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 2 min, with the hydrogen absorption amount being 5.9wt%.

[0113] Example 14

[0114] The difference between this example and example 1 is that the transition metal used as catalyst is a mixture of iron, cobalt and nickel in equal atomic ratio, i.e. 30 iron metal pellets and 30 cobalt metal pellets are used instead of 60 nickel pellets, and 30 nickel metal pellets are retained, to prepare the magnesium-based hydrogen storage material.

[0115] The contents of natural coke, iron-cobalt-nickel and magnesium in the magnesium-based hydrogen storage material prepared in this example are 6.0wt%, 1.6wt% and 92.4wt% respectively.

[0116] The hydrogen absorption kinetics of the magnesium-based hydrogen storage material prepared in this example at 200°C is determined, and the hydrogen absorption reaches saturation in 2 min, with the hydrogen absorption amount being 6.1wt%.

[0117] Comparative Example 1

[0118] The difference between this example and example 1 is that the raw material is only magnesium powder, without natural coke and transition metal, and the specific steps are as follows:

[0119] In an argon-filled glove box, 1.880 g of magnesium powder is added to a ball mill tank, and the ball mill tank is filled with argon to 3 atm, and then ball milling is carried out in a planetary ball mill at a speed of 420 r / min for 2 h to prepare the magnesium-based hydrogen storage material.

[0120] The magnesium-based hydrogen storage material prepared in the present comparative example was measured for hydrogen absorption kinetics at 200°C and hydrogen desorption kinetics at 300°C. The hydrogen absorption amount at 200°C for 12 min was only 0.2 wt%, and the hydrogen desorption amount at 300°C for 12 min was only 0.1 wt%. It was observed that the magnesium powder without natural coke and transition metal would be "cold-welded" to the milling balls and the inner surface of the milling jar during the ball milling.

[0121] The statistical results of the composition of the magnesium-based hydrogen storage materials prepared in Examples 1-14 and Comparative Example 1 are shown in Table 2.

[0122] Table 2 Statistical results of the composition of the magnesium-based hydrogen storage materials

[0123]

[0124]

[0125] The statistical results of the hydrogen absorption performance of the magnesium-based hydrogen storage materials in Examples 1-14 and Comparative Example 1 at 200°C are shown in Table 3.

[0126] Table 3 Statistical results of the hydrogen absorption performance of the magnesium-based hydrogen storage materials at 200°C

[0127]

[0128] From the above experimental results, it can be seen that the hydrogen storage performance of the magnesium-based hydrogen storage materials in Examples 1-14 is significantly improved compared to that of Comparative Example 1, and the hydrogen storage performance of the magnesium-based hydrogen storage material in Example 1 is the best.

[0129] In combination with Figures 2 to 8 , it is shown that using transition metal small balls as the precursor of the transition metal catalyst and natural coke as the carrier of the transition metal catalyst, and using ball milling to grind the transition metal from the surface of the small balls, a highly dispersed transition metal catalyst can be obtained. Using natural coke as the grinding aid for the magnesium powder, its good dispersion and grinding medium effect can prevent "cold welding" between magnesium particles, and the magnesium powder can be easily ground to the nanoscale, which can effectively improve the hydrogen absorption / desorption kinetics of magnesium. That is, the preparation method of the magnesium-based hydrogen storage material provided by the present application can solve the technical problems of difficult realization of high dispersion of the transition metal catalyst and nanoscale of the magnesium powder, and effectively improve the hydrogen storage performance of the magnesium-based hydrogen storage material.

[0130] The preferred process conditions for preparing the magnesium-based hydrogen storage material with high hydrogen absorption rate, high hydrogen absorption amount and high hydrogen release rate are as follows: the transition metal is nickel, the ball milling speed of the natural coke alone is 540 r / min, the ball milling time is 1 h, the ball milling speed of the mixing ball milling of the transition metal small balls and the natural coke is 300 r / min, the ball milling time is 3 h, the ball milling speed of the mixing ball milling of the magnesium powder and the natural coke loaded with the transition metal is 420 r / min, the ball milling time is 2 h, and the preferred composition of the magnesium-based hydrogen storage material is that the natural coke, the nickel and the magnesium respectively account for 6.0 wt%, 1.5 wt% and 92.5 wt%.

[0131] The above description is only the preferred embodiments of the present application, and the above specific embodiments are not the limitation of the present application. Various modifications and changes can occur within the technical concept of the present application, and any modification, change or equivalent replacement made by those skilled in the art according to the above description shall fall within the protection scope of the present application.

Claims

1. A method for producing a magnesium-based hydrogen storage material added with natural coke and a transition metal, characterized by, The method comprises the following steps: ball-milling natural coke under a protective atmosphere to obtain natural coke powder; adding transition metal balls into the natural coke powder obtained by ball-milling to perform mixed ball-milling under a protective atmosphere, and then separating the remaining transition metal balls after ball-milling to obtain natural coke loaded with transition metal; adding magnesium powder into the natural coke loaded with transition metal obtained by ball-milling to perform mixed ball-milling under a protective atmosphere, thereby preparing magnesium-based hydrogen storage material added with natural coke and transition metal; wherein the mass ratio of each component in the magnesium-based hydrogen storage material is: natural coke 3.9wt%-7.2wt%, transition metal 0.7wt%-1.7wt%, and magnesium 91.2wt%-94.9wt%, and the transition metal is at least one of iron, cobalt and nickel; the ball-milling speed of the natural coke alone is 480r / min-600r / min, and the ball-milling time is 0.5h-1.5h; the ball-milling speed of the mixed ball-milling of the transition metal balls and the natural coke powder is 240r / min-360r / min, and the ball-milling time is 2h-4h; the ball-milling speed of the mixed ball-milling of the magnesium powder and the natural coke loaded with transition metal is 360r / min-480r / min, and the ball-milling time is 1h-3h.

2. The method for preparing the magnesium-based hydrogen storage material according to claim 1, characterized in that, the mass ratio of the transition metal balls to the natural coke powder is 2-5:

1.

3. A magnesium-based hydrogen storage material, characterized in that, The magnesium-based hydrogen storage material is prepared by the method according to any one of claims 1-2.

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