A 5A zeolite molecular sieve confined magnesium-based hydrogen storage material and its preparation method

Abstract

The present invention relates to the technical field of hydrogen storage materials, and in particular to a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve and a preparation method thereof, comprising the following steps: ball-milling the 5A zeolite molecular sieve with water, heating and dehydrating the sieve, then adding a modifier 3-aminopropylphosphonic acid and ball-milling, and then heat-treating the modified 5A zeolite molecular sieve; adding magnesium to the modified 5A zeolite molecular sieve and ball-milling, and then press-molding to obtain the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve. The present invention adopts 5A zeolite molecular sieve modified by 3-aminopropylphosphonic acid as a protective layer on the surface of the magnesium-based hydrogen storage material block, which can prevent the magnesium therein from being oxidized and passivated or spontaneously combusting when the material is stored in the air, and at the same time, it is used as a dispersant for hydrogen diffusion without hindrance between magnesium particles in the magnesium-based hydrogen storage material block, which is conducive to improving hydrogen absorption / desorption rate.

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] Hydrogen storage is a crucial component of hydrogen energy applications. Magnesium, with its abundant resources and high hydrogen storage density, is one of the most promising solid hydrogen storage materials. However, magnesium's susceptibility to oxidation and slow hydrogen absorption and desorption rates restrict its practical application as a hydrogen storage material.

[0003] Magnesium is a relatively active alkaline earth metal. When exposed to air, the surface of magnesium particles is easily oxidized by oxygen and water in the air, forming a dense magnesium oxide / magnesium hydroxide film that is passivated. This requires multiple activation steps to destroy the passivation film before hydrogen absorption / desorption can proceed normally. Nanosized magnesium powders undergo a more intense oxidation reaction in air, can spontaneously combust, and even explode, making them highly unsafe. Furthermore, during high-temperature hydrogen absorption / desorption, magnesium easily reacts with carbon dioxide impurities in the hydrogen to form magnesium oxide and magnesium carbide, reducing hydrogen absorption / desorption activity. While increasing the purity of hydrogen and reducing the carbon dioxide impurity content can mitigate the problem of carbon dioxide oxidation during hydrogen absorption / desorption to a certain extent, this inevitably increases hydrogen production costs. The magnesium oxide, magnesium hydroxide, and magnesium carbide formed by magnesium's reaction with oxidizing gases such as oxygen, water, and carbon dioxide lack 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 magnesium's hydrogen absorption and desorption rate. However, catalysts generally lack hydrogen storage capacity, and the greater the amount added, the lower the material's hydrogen storage capacity. Nanocrystallization can also effectively improve magnesium's hydrogen absorption and desorption rate. Nanocrystallization increases lattice defects on the magnesium surface and shortens the diffusion distance of hydrogen atoms within the solid phase. Therefore, even without the addition of a catalyst, magnesium exhibits good hydrogen absorption and desorption properties. However, after nanocrystallization, magnesium is more susceptible to reaction with oxidizing gases, forcing nanocrystallized magnesium to be stored in an inert atmosphere without exposure to air, as it will spontaneously combust and explode. Furthermore, nanomagnesium particles tend to fuse and merge into larger particles during hydrogen absorption and desorption at high temperatures, reducing the absorption and desorption kinetics.

[0005] When nano-sizing magnesium using ball milling, commonly used solid particulate dispersants (such as graphite and talc) lack pores. After the powder is pressurized and formed, hydrogen cannot pass through the non-porous solid particles during hydrogen absorption and desorption, hindering hydrogen mass transfer. Using porous zeolite molecular sieves as dispersants does not hinder hydrogen mass transfer, but zeolite molecular sieves generally have large pore openings. When used as the surface layer of magnesium-based hydrogen storage material blocks, they cannot effectively isolate air and carbon dioxide. Therefore, a 5A zeolite molecular sieve surface modification technology that effectively blocks oxygen, water, and carbon dioxide molecules is urgently needed for the confinement of magnesium-based hydrogen storage materials to address magnesium's susceptibility to oxidation and improve its hydrogen absorption and desorption rates. 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 problems of magnesium-based hydrogen storage materials being easily oxidized and having slow hydrogen absorption / desorption rates.

[0007] To achieve the above object, the present invention provides a method for preparing a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve, comprising the following steps:

[0008] S1, ball-milling 5A zeolite molecular sieve with water, heating and dehydrating, and then calcining to obtain calcined 5A zeolite molecular sieve;

[0009] 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;

[0010] S3, heat-treating the solid product obtained in S2 to obtain a modified 5A zeolite molecular sieve;

[0011] S4. Add the modified 5A zeolite molecular sieve obtained in S3 to magnesium and perform ball milling, and then press-form to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0012] 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.

[0013] More preferably, the ball milling speed is 540 r / min and the ball milling time is 2 h.

[0014] Preferably, in S1, the heating dehydration is performed at a temperature of 130 to 160° C. and a time of 1 to 3 h.

[0015] More preferably, the heating dehydration temperature is 150° C. and the heating dehydration time is 2 h.

[0016] Preferably, in S1, the calcination temperature is 360-390° C. and the calcination time is 2-4 h.

[0017] More preferably, the calcination temperature is 380° C. and the calcination time is 3 h.

[0018] 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.

[0019] More preferably, the mass ratio of 5A zeolite molecular sieve to the modifier 3-aminopropylphosphonic acid is 1:0.192.

[0020] 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.

[0021] More preferably, the ball milling speed is 360 r / min and the ball milling time is 1 h.

[0022] Preferably, in S3, the heat treatment is performed at a temperature of 260 to 290° C. and for a time of 1 to 3 h.

[0023] More preferably, the heat treatment temperature is 280° C. and the heat treatment time is 2 h.

[0024] Preferably, in S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.25.

[0025] More preferably, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.18.

[0026] Preferably, in S4, the ball milling is performed at a speed of 360 to 480 r / min and a time of 2 to 4 h.

[0027] More preferably, the ball milling speed is 420 r / min and the ball milling time is 3 h.

[0028] Preferably, in S4, the pressure forming is performed at a pressure of 700 to 1000 MPa.

[0029] More preferably, the applied pressure is 900 MPa.

[0030] 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.

[0031] Technical principle of the present invention:

[0032] Zeolite 5A is first ball-milled with water. During the milling process, the particles 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). The mixture is then heated for dehydration (to remove free water in the milled zeolite) and calcined (to remove the crystallization water and residual organic template from the synthesis). Finally, the modifier 3-aminopropylphosphonic acid is added and ball-milled. During the milling process, a portion of the 3-aminopropylphosphonic acid undergoes a condensation reaction with the hydroxyl groups on the surface of the zeolite 5A, thereby anchoring it to the outer surface of the zeolite 5A. The remaining 3-aminopropylphosphonic acid accumulates on the surface of the zeolite 5A. During the subsequent heat treatment, the 3-aminopropylphosphonic acid further orders itself (similar to crystallization), and the water produced in the condensation reaction is removed. Modified 5A zeolite is then added to the magnesium and ball-milled. During the milling process, the modified 5A zeolite disperses the magnesium powder, preventing the magnesium particles from "cold welding" (welding under high pressure without high-temperature melting) and forming larger particles, thereby facilitating the grinding of the magnesium powder to the nanoscale. Finally, the material is pressurized to produce a 5A zeolite-confined magnesium-based hydrogen storage material block.

[0033] Among them, the outer surface of 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 of 3.46 Å, 3.2 Å and 3.3 Å, respectively) have difficulty passing through.

[0034] The 3-aminopropylphosphonic acid-modified 5A zeolite molecular sieve, which segregates to the surface of the magnesium-based hydrogen storage material confined within the 5A zeolite molecular sieve during the high-pressure molding process, blocks oxygen and water molecules from the air from passing through, effectively isolating the material from the air. This prevents the magnesium-based hydrogen storage material confined within the 5A zeolite molecular sieve from oxidation, resulting in passivation or spontaneous combustion during storage. During hydrogen absorption, the 3-aminopropylphosphonic acid-modified 5A zeolite molecular sieve also blocks carbon dioxide from entering the mold, preventing magnesium from being oxidized by carbon dioxide. During hydrogen absorption and desorption, hydrogen can pass through the 3-aminopropylphosphonic acid-modified 5A zeolite molecular sieve solid particles within the magnesium-based hydrogen storage material confined within the 5A zeolite molecular sieve, thereby increasing the material's hydrogen absorption and desorption rates.

[0035] Compared with the prior art, the magnesium-based hydrogen storage material provided by the present invention has the following advantages:

[0036] (1) The present invention obtains a block of magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve by pressure molding. The surface layer of the block is 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, which can prevent the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve from being oxidized, spontaneously combusted, and passivated during storage, without the need to place it in an inert protective gas.

[0037] (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.

[0038] (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 improving the hydrogen absorption / desorption rate.

[0039] (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.

[0040] (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 produce 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.

[0041] (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.

[0042] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the X-ray diffraction pattern of 5A zeolite molecular sieve in Example 1 of the present invention;

[0044] Figure 2 is the X-ray diffraction pattern of 3-aminopropylphosphonic acid in Example 1 of the present invention;

[0045] Figure 3 is the X-ray diffraction pattern of magnesium in Example 1 of the present invention;

[0046] Figure 4 is 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;

[0047] 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;

[0048] Figure 6 This is a kinetic curve of the adsorption of CO2 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 at 25°C;

[0049] Figure 7 This is a graph showing the hydrogen absorption kinetics of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve in Example 1 of the present invention at 170°C in hydrogen containing 0.5 vol.% CO2;

[0050] Figure 8 This is a graph showing the hydrogen absorption kinetics of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve in Example 1 of the present invention in hydrogen containing 0.5 vol.% CO2 at 240°C;

[0051] Figure 9 2 is a graph showing the cyclic hydrogen absorption / desorption curve of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve in Example 1 of the present invention in hydrogen containing 0.5 vol.% CO2 at 280°C;

[0052] Figure 10 This is a graph showing the cyclic hydrogen absorption / desorption curve of the magnesium-based hydrogen storage material confined by the unmodified 5A zeolite molecular sieve in Comparative Example 1 of the present invention in hydrogen containing 0.5 vol.% CO2 at 280°C;

[0053] Figure 11 This is a graph showing 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

[0054] A method for preparing a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve comprises the following steps:

[0055] S1, ball-milling 5A zeolite molecular sieve with water, heating and dehydrating, and then calcining to obtain calcined 5A zeolite molecular sieve;

[0056] In S1, the ball milling speed is 420-600 r / min and the ball milling time is 1-3 h.

[0057] In S1, the heating dehydration is carried out at a temperature of 130 to 160° C. and a time of 1 to 3 h.

[0058] In S1, the calcination temperature is 360-390° C. and the calcination time is 2-4 h.

[0059] 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.

[0060] In S2, the mass ratio of 5A zeolite molecular sieve to modifier is 1:0.048 to 1:0.288.

[0061] In S2, the ball milling is performed at a speed of 240 to 420 r / min and a time of 0.5 to 1.5 h.

[0062] S3. Heat-treating the solid product obtained in S2 to obtain a modified 5A zeolite molecular sieve.

[0063] In S3, the heat treatment is performed at a temperature of 130 to 160° C. and for a time of 1 to 3 h.

[0064] S4. Add the modified 5A zeolite molecular sieve obtained in S3 to magnesium and perform ball milling, and then press-form to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0065] In S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.25.

[0066] In S4, the ball milling is performed at a speed of 360 to 480 r / min and a ball milling time of 1 to 4 h.

[0067] In S4, the pressure forming is performed at a pressure of 700 to 1000 MPa.

[0068] The present invention is further described below with reference to the accompanying drawings and examples. Unless otherwise defined, technical or scientific terms used herein shall have the same meanings as those commonly understood by persons of ordinary skill in the art to which the present invention pertains. The above-mentioned features or features described in the specific examples of the present invention may be combined in any manner. These specific examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0069] Example 1

[0070] A method for preparing a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve comprises the following steps:

[0071] S1. Add 6.0 mL of deionized water to 3.000 g of 5A zeolite molecular sieve (<10 μm, Sigma-Aldrich 233676). The mixture was placed in a planetary ball mill (ND8-1L, Nanjing Nanda Tianzun Electronics Co., Ltd., 100 mL jar, sintered zirconia balls, 9 mm, 5 mm, and 3 mm diameter balls in a ratio of 20:40:40, and a 2:1 rotation-to-revolution ratio. The mill was stopped for 5 minutes after every 5 minutes of forward and 5 minutes of reverse rotation). The mill was then milled at 540 r / min for 2 h.

[0072] The ball-milled 5A zeolite molecular sieve was then transferred into a 5 mL glass bottle and heated in a forced air oven at 150°C for dehydration for 2 h. The glass bottle was then taken out, the bottle cap was screwed on, and the bottle was cooled to room temperature.

[0073] Then, in a glove box (Lab2000, E-Tex 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 heated and dehydrated 5A zeolite molecular sieve was loaded into the sample cell of a high-pressure gas adsorption instrument (PCT-Pro 2000, Setteram Instruments, France). The high-pressure gas adsorption instrument was then evacuated to <0.001 atm and filled with oxygen to 3 atm. The temperature was then raised to 380°C and calcined for 3 h. During this period, the vacuum was evacuated and the oxygen was filled to 3 atm every 15 minutes. The sample was then cooled to room temperature to obtain the calcined 5A zeolite molecular sieve.

[0074] 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 placed in a ball mill jar, 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.

[0075] S3. The solid product obtained in S2 is loaded into the sample cell of a high-pressure gas adsorption instrument, and then the sample cell is evacuated to <0.001 atm and filled with helium to 5 atm. The sample cell is then heated to 280°C for 2 h, during which the sample cell is evacuated and filled with helium to 5 atm every 15 min, and then cooled to room temperature to obtain the modified 5A zeolite molecular sieve.

[0076] S4. In an argon-filled glove box, 1.500 g of magnesium (particle size <74 μm, 99% purity) and 0.265 g of the modified 5A zeolite molecular sieve obtained in step S3 were placed in a ball mill, and then ball milled on a planetary ball mill at a speed of 420 r / min for 3 h. After ball milling, 0.600 g of the mixture was placed in a tablet press (769YP-15A powder tablet press) in an argon-filled glove box. The mixture was then pressed into a 5 mm diameter cylinder at a pressure of 900 MPa on the tablet press to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0077] Example 2

[0078] The difference between this embodiment and Example 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 those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0079] Example 3

[0080] The difference between this embodiment and Example 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 Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0081] Example 4

[0082] The difference between this embodiment and Example 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 those in Example 1 to obtain a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve.

[0083] Example 5

[0084] The difference between this embodiment and Example 1 is that the amount of the modifier 3-aminopropylphosphonic acid in step S2 is increased, and the amount of 3-aminopropylphosphonic acid is 0.432 g. The remaining operations are the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by a 5A zeolite molecular sieve.

[0085] Example 6

[0086] The difference between this embodiment and Example 1 is that the intensity of the heating dehydration and calcination in step S1 and the heat treatment in step S3 are reduced. In S1, the dehydration is heated at 130°C for 1 h and calcined at 360°C for 2 h. In S3, the heat treatment is performed at 260°C for 1 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.

[0087] Example 7

[0088] The difference between this embodiment and Example 1 is that the intensity of the heating dehydration and calcination in step S1 and the heat treatment in step S3 are increased. In S1, the dehydration is heated at 160°C for 3 hours and calcined at 390°C for 4 hours. In S3, the heat treatment is performed at 290°C for 3 hours. 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.

[0089] Example 8

[0090] The difference between this embodiment and Example 1 is that the mixed ball milling intensity of magnesium and 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve in step S4 is reduced, the ball milling speed is 360 r / min, and the ball milling time is 2 h. 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.

[0091] Example 9

[0092] The difference between this embodiment and Example 1 is that the mixed ball milling intensity of magnesium and 3-aminopropylphosphonic acid modified 5A zeolite molecular sieve in step S4 is increased, the ball milling speed is 480 r / min, and the ball milling time is 4 h. 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.

[0093] Example 10

[0094] 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 those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0095] Example 11

[0096] 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, and the amount of modified 5A zeolite molecular sieve is 0.375 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.

[0097] Example 12

[0098] The difference between this embodiment and embodiment 1 is that:

[0099] 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;

[0100] In S2, the amount of the modifier 3-aminopropylphosphonic acid added was 0.144 g, and the mixture was ball-milled at 300 r / min for 1.5 h;

[0101] In S3, heat treatment was performed at 270 °C for 3 h;

[0102] In S4, the amount of modified 5A zeolite molecular sieve added was 0.167 g;

[0103] The remaining operations were the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0104] Example 13

[0105] The difference between this embodiment and embodiment 1 is that:

[0106] 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;

[0107] In S2, ball milling was performed at 420 r / min for 0.5 h;

[0108] In S3, heat treatment was performed for 1 h;

[0109] In S4, ball milling for 2 h;

[0110] The remaining operations were the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0111] Example 14

[0112] The difference between this embodiment and embodiment 1 is that:

[0113] In S1, ball milling was performed for 3 h, heating and dehydration were performed for 3 h, and calcination was performed for 4 h;

[0114] In S2, ball milling was performed for 1.5 h;

[0115] In S3, heat treatment was performed for 3 h;

[0116] In S4, ball milling for 4 h;

[0117] The remaining operations were the same as those in Example 1 to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve.

[0118] Comparative Example 1

[0119] 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.

[0120] Test Example 1

[0121] a. X-ray diffraction test

[0122] 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 are as follows: Figures 1 to 4 shown.

[0123] Depend on Figures 1 to 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.

[0124] b. Scanning electron microscope observation

[0125] The scanning electron microscope image of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve prepared in Example 1 (taken by a SU3500 VP scanning electron microscope of Hitachi, Japan) is as follows: Figure 5 As shown by Figure 5 It can be seen that the particles of the magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve are nanometer-sized.

[0126] c. Carbon dioxide adsorption test

[0127] 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 capacity 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.

[0128] d. Hydrogen absorption / desorption performance test

[0129] The hydrogen absorption / desorption performance of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve prepared in Example 1 was tested using a high-pressure gas adsorption instrument (PCT-Pro 2000, Setteram, France). The material's hydrogen absorption / desorption capacity at a specific temperature and initial pressure was measured over time, along with its absorption / desorption isotherms and cyclic absorption / desorption stability. The test was conducted with a solid sample mass of 300 mg, an initial hydrogen absorption pressure of 2.5 MPa, and a reference volume of 17.10 mL. The initial hydrogen desorption pressure was 0.01 MPa and a reference volume of 176.09 mL. The carbon dioxide adsorption capacity of the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid was tested at an initial carbon dioxide pressure of 80 kPa and a reference volume of 17.10 mL.

[0130] The hydrogen absorption kinetic curve of the magnesium-based hydrogen storage material confined by the 5A zeolite molecular sieve obtained in Example 1 is as follows: 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 low hydrogen absorption / desorption temperature and a fast hydrogen absorption / desorption rate.

[0131] 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 using a high-pressure gas adsorption instrument. Figure 9 shown.

[0132] 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 using a high-pressure gas adsorption instrument. Figure 10 shown.

[0133] The 5A zeolite molecular sieve confined magnesium-based hydrogen storage material in Example 2 is subjected to a 280°C cyclic hydrogen absorption / desorption curve in hydrogen containing 0.5 vol.% CO2, as shown in FIG. Figure 11 shown.

[0134] Depend on Figure 9 and Figure 10 By comparison, the hydrogen content of the material in Example 1 remained virtually unchanged after 20 cycles of absorption and desorption, remaining essentially stable at 6.2 wt%. However, the hydrogen content of the material in Comparative Example 1 (which did not use 3-aminopropylphosphonic acid) rapidly decreased (to 0.1 wt%) after these cycles. This indicates that surface modification of the 5A zeolite with 3-aminopropylphosphonic acid is crucial for preventing CO2 molecules from entering the material and reacting with magnesium.

[0135] Depend on Figure 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 hydrogen absorption / desorption amount for the 20th time is 2.2 wt %, 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 insufficient surface area of the magnesium-based hydrogen storage material block confined by the 5A zeolite molecular sieve to form a complete protective layer, which is not conducive to preventing CO2.

[0136] 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 at 280°C in hydrogen containing 0.5 vol.% CO2, and the 20th hydrogen absorption / desorption amount was obtained, which is summarized in Table 1.

[0137] Table 1 Data of the 20th hydrogen absorption / desorption of the materials in Examples 1 to 14 and Comparative Example 1

[0138]

[0139] 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 excessively 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.

[0140] 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.

[0141] 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.

[0142] 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 strong enough and the magnesium particle size is large, which is not conducive to increasing the amount of hydrogen absorbed / released.

[0143] It can be seen from the data of Examples 1 and 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.

[0144] 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.

[0145] 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 the nanoscale; 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 confinement effect of the 5A zeolite molecular sieve modified with 3-aminopropylphosphonic acid, magnesium has a faster hydrogen absorption / desorption rate and more stable cyclic hydrogen absorption / desorption performance.

[0146] The optimal 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 and the ball milling time is 2 h, the heating dehydration temperature is 150℃ and the dehydration time is 2 h, the calcination temperature is 380℃ and the calcination time is 3 h, and then 3-aminopropylphosphonic acid is added and the ball milling speed is 360 r / min and 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℃ and the heat treatment time is 2 h; and the ball milling speed of magnesium is 420 r / min and 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.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve, characterized in that: The following steps are included: S1, ball-milling 5A zeolite molecular sieve with water, heating and dehydrating, and then calcining to obtain calcined 5A zeolite molecular sieve; 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 on the outer surface react with water to form hydroxylation. Then, it is heated and dehydrated to remove the free water in the 5A zeolite molecular sieve after ball-milling. 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; In S2, the mass ratio of 5A zeolite molecular sieve to the modifier 3-aminopropylphosphonic acid is 1:0.048 to 1:0.288; 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 and ball milling, and then press-molding to obtain a magnesium-based hydrogen storage material confined by 5A zeolite molecular sieve; During the ball milling process, the modified 5A zeolite molecular sieve disperses the magnesium powder, preventing the magnesium particles from cold welding to form larger particles, and grinding the magnesium powder to nanometer level. In S4, the mass ratio of magnesium to the modified 5A zeolite molecular sieve is 1:0.05 to 1:0.

25.

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 is performed at a speed of 420 to 600 r / min and a time of 1 to 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 hours.

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 ball milling is performed at a speed of 240 to 420 r / min and a time of 0.5 to 1.5 h.

6. 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. for 1 to 3 hours.

7. 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 is performed at a speed of 360 to 480 r / min and a ball milling time of 2 to 4 h. 8 . 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 7 .

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