Magnesium-based hydrogen storage material limited by 5A zeolite molecular sieve and preparation method of magnesium-based hydrogen storage material

Abstract

The invention relates to the technical field of hydrogen storage materials, in particular to a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material and a preparation method thereof.The preparation method comprises the following steps that water is added into a 5A zeolite molecular sieve for ball milling, roasting is conducted after heating dehydration is conducted, then a modifier 3-aminopropyl phosphonic acid is added for ball milling, heat treatment is conducted, and the modified 5A zeolite molecular sieve is obtained; magnesium is added into the modified 5A zeolite molecular sieve for ball milling, and then the magnesium-based hydrogen storage material limited by the 5A zeolite molecular sieve is obtained through pressure forming. The 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve is used as a protective layer on the surface of the magnesium-based hydrogen storage material block, magnesium in the material can be prevented from being oxidized and passivated or spontaneously combusted when the material is stored in air, and meanwhile, the 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve is used as a dispersing agent which does not hinder hydrogen diffusion among magnesium particles in the magnesium-based hydrogen storage material block; and the hydrogen absorption / hydrogen desorption rate can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage materials, and in particular to a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material and a preparation method thereof. Background Art

[0002] The storage of hydrogen is an important part of hydrogen energy application. Magnesium metal is abundant in resources and has a high hydrogen storage density, making it one of the most promising solid hydrogen storage materials. However, magnesium is easily oxidized and has a slow hydrogen absorption / desorption rate, which restricts its practical application as a hydrogen storage material.

[0003] Magnesium is a relatively active alkaline earth metal. When placed in the air, the surface of magnesium particles is easily oxidized by oxygen and water in the air, forming a dense magnesium oxide / magnesium hydroxide film and being passivated, so that when absorbing / desorbing hydrogen, it is necessary to undergo multiple activations to destroy the passivation film before normal absorption / desorption of hydrogen. If the magnesium powder is nano-scale, the oxidation reaction in the air is more intense, can spontaneously combust, and even explode, which is very unsafe. Furthermore, during the high-temperature absorption / desorption of hydrogen, magnesium is also prone to react with carbon dioxide impurities in hydrogen to form magnesium oxide and magnesium carbide, resulting in a decrease in the absorption / desorption of hydrogen activity. Although the problem of being oxidized by carbon dioxide during the absorption / desorption of hydrogen can be alleviated to a certain extent by increasing the purity of hydrogen and reducing the content of carbon dioxide impurities, this is bound to increase the production cost of hydrogen. After magnesium reacts with oxidizing gases such as oxygen, water, and carbon dioxide, the generated magnesium oxide, magnesium hydroxide, and magnesium carbide have no hydrogen storage capacity, and are difficult to be reduced to magnesium by hydrogen, resulting in a decrease in the hydrogen storage capacity of magnesium-based hydrogen storage materials.

[0004] Adding a catalyst can increase the rate of hydrogen absorption / desorption of magnesium. However, catalysts generally do not have hydrogen storage capacity. The greater the amount added, the lower the hydrogen storage capacity of the material. Nano-sizing can also effectively increase the rate of hydrogen absorption / desorption of magnesium. Nano-sizing can increase the lattice defects on the surface of magnesium and shorten the diffusion distance of hydrogen atoms in the solid phase. Therefore, even without adding a catalyst, magnesium has good hydrogen absorption / desorption performance. However, after nano-sizing, magnesium is more likely to react with oxidizing gases, so that nano-sizing magnesium cannot be exposed to the air, otherwise it will spontaneously combust and explode, and needs to be stored in an inert gas. In addition, nano-magnesium particles are easy to melt and become larger particles during the process of hydrogen absorption / desorption at high temperatures, which reduces the hydrogen absorption / desorption kinetics.

[0005] When magnesium is nano-sized by ball milling, the commonly used solid granular dispersants (such as graphite and talcum powder, etc.) have no pores. When the powder is pressurized and formed, hydrogen cannot pass through the non-porous solid particles during the hydrogen absorption / desorption process, which hinders hydrogen mass transfer. If a porous zeolite molecular sieve is used as a dispersant, it will not hinder hydrogen mass transfer, but the pore opening of the zeolite molecular sieve is generally large. When it is used as the surface layer of the magnesium-based hydrogen storage material block, it cannot play the role of isolating air / carbon dioxide. Therefore, there is an urgent need for 5A zeolite molecular sieve surface modification technology that can effectively block oxygen, water and carbon dioxide molecules for the confinement of magnesium-based hydrogen storage materials to solve the problem of magnesium being easily oxidized and increase the hydrogen absorption / desorption rate of magnesium. Summary of the invention

[0006] The purpose of the present invention is to provide a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material and a preparation method thereof, which effectively solves the problem that the magnesium-based hydrogen storage material is easily oxidized and has a slow hydrogen absorption / desorption rate.

[0007] To achieve the above object, the present invention provides a method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material, comprising the following steps: S1, adding water to ball-mill the 5A zeolite molecular sieve, then heating and dehydrating it and calcining it to obtain the calcined 5A zeolite molecular sieve; S2, adding a modifier 3-aminopropylphosphonic acid to the calcined 5A zeolite molecular sieve obtained in S1 and ball milling to obtain a solid product; S3, heat treating the solid product obtained in S2 to obtain a modified 5A zeolite molecular sieve; S4, adding the modified 5A zeolite molecular sieve obtained in S3 to magnesium for ball milling, and then pressurizing to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0008] Preferably, in S1, the ball milling is performed at a ball milling speed of 420 to 600 r / min and a ball milling time of 1 to 3 h.

[0009] More preferably, the ball milling speed is 540 r / min and the ball milling time is 2 h.

[0010] Preferably, in S1, the heating dehydration is performed at a temperature of 130 to 160° C. and a time of 1 to 3 h.

[0011] More preferably, the heating dehydration temperature is 150° C. and the heating dehydration time is 2 h.

[0012] Preferably, in S1, the calcination is performed at a temperature of 360 to 390° C. and a time of 2 to 4 h.

[0013] More preferably, the calcination temperature is 380° C. and the calcination time is 3 h.

[0014] Preferably, in S2, the mass ratio of 5A zeolite molecular sieve to the modifier 3-aminopropylphosphonic acid is 1:0.048 to 1:0.288.

[0015] More preferably, the mass ratio of 5A zeolite molecular sieve to the modifier 3-aminopropylphosphonic acid is 1:0.192.

[0016] Preferably, in S2, the ball milling is performed at a ball milling speed of 240 to 420 r / min and a ball milling time of 0.5 to 1.5 h.

[0017] More preferably, the ball milling speed is 360 r / min and the ball milling time is 1 h.

[0018] Preferably, in S3, the heat treatment is performed at a temperature of 260 to 290° C. and a time of 1 to 3 h.

[0019] More preferably, the heat treatment temperature is 280° C. and the heat treatment time is 2 h.

[0020] Preferably, in S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.25.

[0021] More preferably, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.18.

[0022] Preferably, in S4, the ball milling is performed at a ball milling speed of 360 to 480 r / min and a ball milling time of 2 to 4 h.

[0023] More preferably, the ball milling speed is 420 r / min and the ball milling time is 3 h.

[0024] Preferably, in S4, the pressure applied during the press forming is 700-1000 MPa.

[0025] More preferably, the applied pressure is 900 MPa.

[0026] The 5A zeolite molecular sieve confined magnesium-based hydrogen storage material is prepared by the above-mentioned preparation method of the 5A zeolite molecular sieve confined magnesium-based hydrogen storage material.

[0027] Technical principle of the present invention: First, 5A zeolite molecular sieve is ball-milled with water. During the ball-milling process, the particles of 5A zeolite molecular sieve become smaller, and the broken bonds (-Si-O-, -Al-O-, -Si- and -Al-) on the outer surface react with water to form hydroxylation (combining with -H or -OH in water to form -Si-OH and -Al-OH). Then, it is heated for dehydration (removing free water in 5A zeolite molecular sieve after ball-milling), calcined (removing crystal water in 5A zeolite molecular sieve and organic template agent remaining during synthesis), and then the modifier 3-aminopropylphosphonic acid is added for ball-milling. During the ball-milling process, a part of 3-aminopropylphosphonic acid undergoes condensation reaction with the hydroxyl groups on the surface of 5A zeolite molecular sieve, thereby anchoring on the outer surface of 5A zeolite molecular sieve, and the remaining 3-aminopropylphosphonic acid accumulates on it. In the subsequent heat treatment process, 3-aminopropylphosphonic acid is further ordered (similar to crystallization), and the water generated in the condensation reaction is removed. Then, the modified 5A zeolite molecular sieve is added to the magnesium for ball milling. During the ball milling process, the modified 5A zeolite molecular sieve disperses the magnesium powder, preventing the magnesium particles from "cold welding" (welding without high-temperature melting under high pressure) to form larger particles, which is conducive to grinding the magnesium powder to the nanoscale. Finally, the magnesium-based hydrogen storage material block confined by the 5A zeolite molecular sieve is obtained by pressure molding.

[0028] Among them, the outer surface of the 5A zeolite molecular sieve is a relatively dense 3-aminopropylphosphonic acid molecular layer, with larger pores (4.21 Å) inside. Hydrogen molecules with smaller kinetic diameters (kinetic diameter 2.89 Å) can easily pass through, while oxygen, water and carbon dioxide molecules with larger kinetic diameters (kinetic diameters are 3.46 Å, 3.2 Å, and 3.3 Å, respectively) are difficult to pass through.

[0029] The 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve segregated to the surface of the magnesium-based hydrogen storage material block confined by the 5A zeolite molecular sieve during the high-pressure molding process can prevent oxygen and water molecules in the air from passing through, playing the role of isolating the air, thereby preventing the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve from being oxidized and passivated or spontaneously combusted during storage. During the hydrogen absorption process, the 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve can also prevent carbon dioxide from entering the interior of the block, thereby preventing magnesium from being oxidized by carbon dioxide; during the hydrogen absorption / desorption process, in the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve, hydrogen can pass through the 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve solid particles, which is beneficial to improve the hydrogen absorption / desorption rate of the material.

[0030] Compared with the prior art, the magnesium-based hydrogen storage material provided by the present invention has the following beneficial effects: (1) The present invention obtains a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material block by pressure molding, wherein the surface layer of the block is a 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid. Oxygen and water molecules in the air are difficult to pass through the 3-aminopropylphosphonic acid modified layer, thereby preventing the 5A zeolite molecular sieve confined magnesium-based hydrogen storage material from being oxidized, self-ignited, and passivated during storage, without the need to place it in an inert protective gas.

[0031] (2) The 3-aminopropylphosphonic acid-modified 5A zeolite molecular sieve on the surface of the magnesium-based hydrogen storage material block confined by the 5A zeolite molecular sieve of the present invention can prevent carbon dioxide impurities in hydrogen from entering the interior of the block during the hydrogen absorption process, thereby preventing magnesium from being oxidized by carbon dioxide.

[0032] (3) In the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve provided by the present invention, hydrogen can pass through the solid particle dispersant composed of the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid, which is beneficial to improve the hydrogen absorption / desorption rate.

[0033] (4) The 3-aminopropylphosphonic acid modified layer on the outer surface of the 5A zeolite molecular sieve in the present invention has good plasticity and adhesion, which can prevent the magnesium-based hydrogen storage material block confined in the 5A zeolite molecular sieve from breaking due to volume expansion when magnesium absorbs hydrogen.

[0034] (5) In the preparation method provided by the present invention, 3-aminopropylphosphonic acid is anchored on the outer surface of 5A zeolite molecular sieve by solid phase reaction ball milling. The synthesis method is simple and does not generate waste liquid. By adjusting the amount of 3-aminopropylphosphonic acid, the barrier properties of the 3-aminopropylphosphonic acid layer on the outer surface of 5A zeolite molecular sieve to oxygen and water in the air and carbon dioxide in hydrogen can be regulated.

[0035] (6) In the preparation method provided by the present invention, 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid is used as a dispersant for magnesium, which can effectively prevent the magnesium particles from "cold welding" into larger particles during the ball milling process, making it easy to grind the magnesium powder to the nanometer level. In the subsequent high-temperature hydrogen absorption / desorption process, the dispersant can also prevent the magnesium particles from melting and merging into larger particles.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the X-ray diffraction pattern of 5A zeolite molecular sieve in Example 1 of the present invention; Figure 2 is the X-ray diffraction pattern of 3-aminopropylphosphonic acid in Example 1 of the present invention; Figure 3 is the X-ray diffraction pattern of magnesium in Example 1 of the present invention; Figure 4is an X-ray diffraction pattern of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve in Example 1 of the present invention; Figure 5 This is a scanning electron microscope image of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve in Example 1 of the present invention; Figure 6 It is a kinetic curve diagram of the adsorption of CO2 at 25°C by the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid in Example 1 of the present invention and the unmodified 5A zeolite molecular sieve in Comparative Example 1; Figure 7 This is a graph showing the hydrogen absorption kinetics of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Example 1 of the present invention in hydrogen containing 0.5 vol.% CO2 at 170°C; Figure 8 This is a graph showing the hydrogen absorption kinetics of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Example 1 of the present invention in hydrogen containing 0.5 vol.% CO2 at 240°C; Fig. 9 This is a graph of the cyclic hydrogen absorption / desorption of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Example 1 of the present invention in a hydrogen gas containing 0.5 vol.% CO2 at 280°C; Fig.10 This is a graph of the cyclic hydrogen absorption / desorption of the magnesium-based hydrogen storage material confined by the unmodified 5A zeolite molecular sieve in Comparative Example 1 of the present invention in a hydrogen gas containing 0.5 vol.% CO2 at 280°C; Fig.11 This is a graph of the cyclic hydrogen absorption / desorption curve of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Example 2 of the present invention at 280°C in hydrogen containing 0.5 vol.% CO2. DETAILED DESCRIPTION

[0038] A method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material comprises the following steps: S1, adding water to ball-mill the 5A zeolite molecular sieve, then heating and dehydrating it and calcining it to obtain the calcined 5A zeolite molecular sieve; In S1, the ball milling speed is 420-600 r / min, and the ball milling time is 1-3 h.

[0039] In S1, the heating dehydration is carried out at a temperature of 130 to 160° C. and a time of 1 to 3 h.

[0040] In S1, the calcination temperature is 360-390° C. and the calcination time is 2-4 h.

[0041] S2. Adding a modifier, 3-aminopropylphosphonic acid, to the calcined 5A zeolite molecular sieve obtained in S1, and ball milling to obtain a solid product.

[0042] In S2, the mass ratio of 5A zeolite molecular sieve to the modifier is 1:0.048 to 1:0.288.

[0043] In S2, the ball milling speed is 240-420 r / min, and the ball milling time is 0.5-1.5 h.

[0044] S3. Heat-treating the solid product obtained in S2 to obtain a modified 5A zeolite molecular sieve.

[0045] In S3, the heat treatment is performed at a temperature of 130 to 160° C. and for a time of 1 to 3 h.

[0046] S4, adding the modified 5A zeolite molecular sieve obtained in S3 to magnesium for ball milling, and then pressurizing to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0047] In S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.25.

[0048] In S4, the ball milling speed is 360-480 r / min and the ball milling time is 1-4 h.

[0049] In S4, the pressure forming is performed at a pressure of 700 to 1000 MPa.

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0051] Example 1 A method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material comprises the following steps: S1. Add 6.0 mL of deionized water to 3.000 g of 5A zeolite molecular sieve (<10 μm, Sigma-Aldrich 233676), load into the ball mill of a planetary ball mill (ND8-1L, Nanjing Nanda Tianzun Electronics Co., Ltd., ball mill volume 100 mL, grinding ball material is sintered zirconium dioxide, the ratio of the number of grinding balls with diameters of 9 mm, 5 mm, and 3 mm is 20:40:40, the ratio of rotation to revolution during operation is 2:1, and the machine is stopped for cooling for 5 min after every 5 min of forward rotation and 5 min of reverse rotation), and then ball milled on the planetary ball mill at a ball mill speed of 540 r / min for 2 h.

[0052] The ball-milled 5A zeolite molecular sieve was then transferred into a 5 mL glass bottle, heated and dehydrated at 150°C in a forced air oven for 2 h, and then the glass bottle was taken out, the bottle cap was screwed on, and the bottle was cooled to room temperature.

[0053] Then, in a glove box (Lab2000, Itex Inert Gas Systems Co., Ltd., oxygen content <0.1 ppm, water content <0.1 ppm) protected by argon (purity 99.999%), 2.000 g of the 5A zeolite molecular sieve that had been heated and dehydrated was loaded into the sample cell of a high-pressure gas adsorption instrument (PCT-Pro 2000, Setram Instruments, France), and then the high-pressure gas adsorption instrument was evacuated to <0.001 atm, filled with oxygen to 3 atm, and then heated to 380°C and calcined for 3 h. During this period, the vacuum was evacuated and oxygen was filled to 3 atm every 15 minutes, and then cooled to room temperature to obtain the calcined 5A zeolite molecular sieve.

[0054] S2. In an argon-filled glove box, 0.288 g of the modifier 3-aminopropylphosphonic acid (APPA, CAS No. 13138-33-5, NH2(CH2)3P(O)(OH)2, purity 99%) and 1.500 g of the calcined 5A zeolite molecular sieve obtained in S1 were loaded into a ball mill, and then ball milled on a planetary ball mill at a ball mill speed of 360 r / min for 1 h to obtain a solid product.

[0055] S3. The solid product obtained in S2 is loaded into the sample cell of a high-pressure gas adsorption instrument, and then the high-pressure gas adsorption instrument is evacuated to <0.001 atm, filled with helium to 5 atm, and then heated to 280°C for heat treatment for 2 h. During this period, the vacuum is evacuated and helium is filled to 5 atm every 15 minutes, and then cooled to room temperature to obtain the modified 5A zeolite molecular sieve.

[0056] S4. In an argon-filled glove box, 1.500 g of magnesium (particle size <74 μm, purity 99%) and 0.265 g of the modified 5A zeolite molecular sieve obtained in step S3 were loaded into a ball mill, and then ball milled for 3 h on a planetary ball mill at a ball mill speed of 420 r / min. After ball milling, in an argon-filled glove box, 0.600 g was loaded into a tablet press (769YP-15A powder tablet press) mold, and then pressed into a cylinder with a diameter of 5 mm at a pressure of 900 MPa on the tablet press to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0057] Example 2 The difference between this embodiment and embodiment 1 is that the ball milling intensity of the 5A zeolite molecular sieve in step S1 is reduced, the ball milling speed is 420 r / min, and the ball milling time is 1 h. The remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0058] Example 3 The difference between this embodiment and embodiment 1 is that the ball milling intensity of the 5A zeolite molecular sieve in step S1 is increased, the ball milling speed is 600 r / min, and the ball milling time is 3 h. The remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0059] Example 4 The difference between this embodiment and embodiment 1 is that the amount of the modifier 3-aminopropylphosphonic acid in step S2 is reduced to 0.072 g, and the remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve.

[0060] Example 5 The difference between this embodiment and embodiment 1 is that the amount of the modifier 3-aminopropylphosphonic acid in step S2 is increased, the amount of 3-aminopropylphosphonic acid is 0.432 g, and the remaining operations are the same as the steps in embodiment 1 to obtain a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material.

[0061] Example 6 The difference between this embodiment and embodiment 1 is that the intensity of heating dehydration and calcination in step S1 and heat treatment in step S3 is reduced. In S1, heating dehydration is performed at 130°C for 1 h and calcination is performed at 360°C for 2 h. In S3, heat treatment is performed at 260°C for 1 h. The remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0062] Example 7 The difference between this embodiment and embodiment 1 is that the intensity of heating dehydration and calcination in step S1 and heat treatment in step S3 is increased. In S1, heating dehydration is performed at 160°C for 3 h and calcination is performed at 390°C for 4 h. In S3, heat treatment is performed at 290°C for 3 h. The remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0063] Example 8 The difference between this embodiment and embodiment 1 is that the mixed ball milling intensity of magnesium and 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid in step S4 is reduced, the ball milling speed is 360 r / min, the ball milling time is 2 h, and the remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0064] Example 9 The difference between this embodiment and embodiment 1 is that the mixed ball milling intensity of magnesium and 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid in step S4 is increased, the ball milling speed is 480 r / min, the ball milling time is 4 h, and the remaining operations are the same as the steps in embodiment 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0065] Example 10 The difference between this embodiment and Example 1 is that the amount of 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid in step S4 is reduced, and the amount of modified 5A zeolite molecular sieve is 0.079 g. The remaining operations are the same as the steps in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0066] Embodiment 11 The difference between this embodiment and Example 1 is that the amount of 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid in step S4 is increased, the amount of modified 5A zeolite molecular sieve is 0.375 g, and the remaining operations are the same as the steps in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0067] Example 12 The difference between this embodiment and embodiment 1 is that: In S1, 9.0 mL of deionized water was added to 5A zeolite molecular sieve, ball milled at 480 r / min for 3 h, heated for dehydration at 140 °C for 3 h, and calcined at 370 °C for 4 h; In S2, the amount of the modifier 3-aminopropylphosphonic acid added was 0.144 g, and the ball milling was carried out at a speed of 300 r / min for 1.5 h; In S3, heat treatment was performed at 270 °C for 3 h; In S4, the amount of modified 5A zeolite molecular sieve added was 0.167 g; The remaining operations are the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0068] Example 13 The difference between this embodiment and embodiment 1 is that: In S1, 3.0 mL of deionized water was added to 5A zeolite molecular sieve, ball milled for 1 h, heated for dehydration for 1 h, and calcined for 2 h; In S2, ball milling was performed at 420 r / min for 0.5 h; In S3, heat treatment was performed for 1 h; In S4, ball milling for 2 h; The remaining operations are the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0069] Embodiment 14 The difference between this embodiment and embodiment 1 is that: In S1, ball milling was performed for 3 h, heating and dehydration was performed for 3 h, and calcination was performed for 4 h; In S2, ball milling was performed for 1.5 h; In S3, heat treatment was performed for 3 h; In S4, ball milling for 4 h; The remaining operations are the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0070] Comparative Example 1 The difference between this comparative example and Example 1 is that no modifier is used to modify the 5A zeolite molecular sieve, that is, 3-aminopropylphosphonic acid is not added in step S2, and the remaining operations are the same as those in Example 1 to obtain an unmodified 5A zeolite molecular sieve confined magnesium-based hydrogen storage material.

[0071] Test Example 1 a. X-ray diffraction test The raw materials 5A zeolite molecular sieve, 3-aminopropylphosphonic acid, magnesium and the prepared 5A zeolite molecular sieve confined magnesium-based hydrogen storage material in Example 1 were subjected to X-ray diffraction tests (Japan Rigaku Smartlab X-ray diffractometer, Cu target Kα ray, scanning step size 0.01°, scanning speed 2° / min), and the results were as follows: Figure 1 to Figure 4 shown.

[0072] Depend on Figure 1 to Figure 3 It can be seen that the raw materials 5A zeolite molecular sieve, 3-aminopropylphosphonic acid and magnesium are all relatively pure crystals; Figure 4 It can be seen that the magnesium crystallite size in the magnesium-based hydrogen storage material confined by the prepared 5A zeolite molecular sieve is 36 nm (calculated using the Scherrer formula based on the 36.5° diffraction peak). The diffraction peaks of 5A zeolite molecular sieve and 3-aminopropylphosphonic acid are almost unobservable due to their small crystallites and low content.

[0073] b. Scanning electron microscope observation A scanning electron microscope photograph of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve obtained in Example 1 (taken by a SU3500 VP scanning electron microscope of Hitachi, Japan) is shown in FIG. Figure 5 As shown by Figure 5 It can be seen that the particles of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve are nanometer-sized.

[0074] c. Carbon dioxide adsorption test The 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid obtained in step S3 of Example 1 and the unmodified 5A zeolite molecular sieve obtained in step S3 of Comparative Example 1 were respectively taken, and the CO2 adsorption amount of the two was measured at 25°C in a high-pressure gas adsorption instrument as a function of adsorption time. Figure 6 As shown. Figure 6 It can be seen that after modification with 3-aminopropylphosphonic acid, CO2 can hardly enter the 5A zeolite molecular sieve.

[0075] d. Hydrogen absorption / desorption performance test The hydrogen absorption / desorption performance test method of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve prepared in Example 1 is as follows: using a high-pressure gas adsorption instrument (PCT-Pro 2000, Sethram, France), the material is tested for changes in hydrogen absorption / desorption over time at a certain temperature and initial pressure, hydrogen absorption / desorption isotherms, and cyclic hydrogen absorption / desorption stability; during the test, the solid sample mass is 300 mg, the initial hydrogen absorption pressure is 2.5 MPa, the reference volume is 17.10 mL, the initial hydrogen desorption pressure is 0.01 MPa, and the reference volume is 176.09 mL. When testing the carbon dioxide adsorption of the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid, the initial carbon dioxide pressure is 80 kPa and the reference volume is 17.10 mL.

[0076] The 5A zeolite molecular sieve confined magnesium-based hydrogen storage material obtained in Example 1 has a hydrogen absorption kinetic curve as shown in FIG. Figure 7 As shown by Figure 7 It can be seen that the saturated hydrogen absorption capacity can be reached at 170℃ and 2 min; the hydrogen release kinetic curve is as follows Figure 8 As shown by Figure 8 It can be seen that hydrogen can be completely released at 240°C in 8 min, indicating that the material has a lower hydrogen absorption / desorption temperature and a faster hydrogen absorption / desorption rate.

[0077] The magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve obtained in Example 1 was placed in air for 7 days, and then the cyclic hydrogen absorption / desorption curve at 280°C in hydrogen containing 0.5 vol.% CO2 was measured by a high-pressure gas adsorption instrument. Fig. 9 shown.

[0078] The unmodified 5A zeolite molecular sieve confined magnesium-based hydrogen storage material in Comparative Example 1 was placed in air for 7 days, and then the cyclic hydrogen absorption / desorption curve at 280°C in hydrogen containing 0.5 vol.% CO2 was measured by a high-pressure gas adsorption instrument. Fig.10 shown.

[0079] The 5A zeolite molecular sieve confined magnesium-based hydrogen storage material in Example 2 has a cyclic hydrogen absorption / desorption curve at 280°C in hydrogen containing 0.5 vol.% CO2, as shown in FIG. Fig.11 shown.

[0080] Depend on Fig. 9 and Fig.10 By comparison, it can be seen that the amount of hydrogen absorbed / released by the material in Example 1 after 20 cycles is almost unchanged and basically stabilized at 6.2 wt%, while the amount of hydrogen absorbed / released by the material in Comparative Example 1 (without 3-aminopropylphosphonic acid) decreases rapidly (to 0.1 wt%). This indicates that the modification of the surface of 5A zeolite molecular sieve with 3-aminopropylphosphonic acid is crucial to prevent CO2 molecules from entering the material and reacting with magnesium.

[0081] Depend on Fig.11 It can be seen that with the increase in the number of hydrogen absorption / desorption cycles, the hydrogen absorption / desorption amount of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Example 2 decreases significantly, and then tends to stabilize. The 20th hydrogen absorption / desorption amount is 2.2wt%, and its anti-CO2 oxidation performance is worse than that in Example 1, that is, when the ball milling intensity of the 5A zeolite molecular sieve in step S1 is low, its particles are larger, resulting in the surface of the magnesium-based hydrogen storage material block confined by the 5A zeolite molecular sieve being insufficient to form a complete protective layer, which is not conducive to preventing CO2.

[0082] The magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve in Examples 1 to 14 and Comparative Example 1 was tested for cyclic hydrogen absorption / desorption in hydrogen containing 0.5 vol.% CO2 at 280°C, and the 20th hydrogen absorption / desorption amount was obtained, which is summarized in Table 1.

[0083] Table 1 Data table of the 20th hydrogen absorption / desorption of materials in Examples 1 to 14 and Comparative Example 1

[0084] It can be seen from the data of Examples 1 and 3 that the material performance of Example 3 is slightly worse than that of Example 1, that is, when the 5A zeolite molecular sieve is over-ball-milled in step S1, its particles are too small and the 3-aminopropylphosphonic acid modification layer on the outer surface becomes thinner, which is not conducive to preventing CO2 molecules from diffusing in.

[0085] It can be seen from the data of Examples 1 and 4 that the material performance of Example 4 is worse than that of Example 1, that is, when the amount of 3-aminopropylphosphonic acid used in step S2 is too small, the 3-aminopropylphosphonic acid modification layer on the outer surface of the 5A zeolite molecular sieve is too thin, which is not conducive to preventing CO2.

[0086] It can be seen from the data of Examples 1 and 6 that the performance of Example 6 is worse than that of Example 1, that is, when the heating dehydration and calcination in step S1 are insufficient and the heat treatment in step S3 is insufficient, the outer surface of the 5A zeolite molecular sieve is not conducive to preventing CO2 due to the presence of impurities such as water and the insufficient degree of ordering of 3-aminopropylphosphonic acid.

[0087] It can be seen from the data of Examples 1 and 8 that the material properties of Example 8 are lower than those of Example 1, that is, the ball milling intensity in step S4 is not large enough and the magnesium particle size is large, which is not conducive to increasing the amount of hydrogen absorbed / released.

[0088] It can be seen from the data of Example 1 and Example 10 that the material performance of Example 10 is lower than that of Example 1, that is, the amount of dispersant used in step S4 is too small and the magnesium particle size is large, which is not conducive to increasing the amount of hydrogen absorbed / released.

[0089] The material properties in Examples 5, 7, 9, 11, 12 and 14 are similar to those in Example 1, and the performance of Example 13 is slightly lower than that of Example 1.

[0090] Therefore, the present invention adopts the above-mentioned 5A zeolite molecular sieve confined magnesium-based hydrogen storage material and its preparation method, and 3-aminopropylphosphonic acid can be modified on the outer surface of the 5A zeolite molecular sieve by ball milling; the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid is used as a dispersant, which is conducive to grinding the magnesium powder to nanometer level; the obtained 5A zeolite molecular sieve confined magnesium-based hydrogen storage material block is not easily oxidized by air when placed in the air, and is not easily oxidized by CO2 impurities in hydrogen during hydrogen absorption; under the confining effect of the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid, magnesium has a faster hydrogen absorption / desorption rate and a more stable cyclic hydrogen absorption / desorption performance.

[0091] The preferred process conditions for preparing magnesium-based hydrogen storage materials confined in 5A zeolite molecular sieve are as follows: the ball milling speed of 5A zeolite molecular sieve with water is 540 r / min, the ball milling time is 2 h, the heating dehydration temperature is 150°C, the dehydration time is 2 h, the calcination temperature is 380°C, the calcination time is 3 h, and then the ball milling speed of adding 3-aminopropylphosphonic acid is 360 r / min, the ball milling time is 1 h, and the mass ratio of 5A zeolite molecular sieve to 3-aminopropylphosphonic acid is 1:0.192; the heat treatment temperature is 280°C, and the heat treatment time is 2 h; the ball milling speed of adding magnesium is 420 r / min, the ball milling time is 3 h, and the mass ratio of magnesium to 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid is 1:0.18.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material, characterized in that: The following steps are included: S1, adding water to ball-mill the 5A zeolite molecular sieve, heating and dehydrating it, and then calcining it to obtain the calcined 5A zeolite molecular sieve; S2, adding a modifier 3-aminopropylphosphonic acid to the calcined 5A zeolite molecular sieve obtained in S1 and ball milling to obtain a solid product; S3, heat treating the solid product obtained in S2 to obtain a modified 5A zeolite molecular sieve; S4, adding the modified 5A zeolite molecular sieve obtained in S3 to magnesium for ball milling, and then pressurizing to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

2. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S1, the ball milling speed is 420-600 r / min, and the ball milling time is 1-3 h.

3. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S1, the heating dehydration is carried out at a temperature of 130 to 160° C. and a time of 1 to 3 h.

4. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S1, the calcination temperature is 360-390° C. and the calcination time is 2-4 h.

5. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S2, the mass ratio of 5A zeolite molecular sieve to the modifier 3-aminopropylphosphonic acid is 1:0.048 to 1:0.

288.

6. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S2, the ball milling speed is 240-420 r / min, and the ball milling time is 0.5-1.5 h.

7. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S3, the heat treatment is performed at a temperature of 260 to 290° C. and for a time of 1 to 3 h.

8. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.

25.

9. The method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to claim 1, characterized in that: In S4, the ball milling speed is 360-480 r / min and the ball milling time is 2-4 h. 10 . The 5A zeolite molecular sieve confined magnesium-based hydrogen storage material prepared according to the method for preparing a 5A zeolite molecular sieve confined magnesium-based hydrogen storage material according to any one of claims 1 to 9.

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