A process for preparing a low-energy-consumption nano-confined NaAlH4 hydrogen storage material capable of low-pressure cycling

Abstract

The application discloses a process method for preparing a nano-limited NaAlH4 hydrogen storage material capable of low-pressure circulation with low energy consumption, and comprises the following preparation steps: (1) pretreating selected two-dimensional carrier materials; (2) placing aluminum powder, sodium, triethylaluminum and an organic solvent into a high-pressure reaction kettle in an argon-filled glove box; (3) dispersing the pretreated two-dimensional carrier materials in the organic solvent, and sealing the reaction kettle; (4) placing the reaction kettle in an ultrasonic machine for ultrasonic mixing and dispersion; (5) vacuumizing the reaction kettle, filling hydrogen into the reaction kettle, heating the reaction kettle at a certain heating rate, and keeping for a period of time; (6) after the reaction is completed, cooling the reaction kettle to room temperature, and discharging the remaining hydrogen pressure; (7) placing the mixture under dynamic vacuum for solvent removal and drying, and obtaining the nano-limited NaAlH4. Through the above method, the pressure and temperature of the loading process are effectively reduced, and the synthesis of NaAlH4 and nano-loading are combined.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage materials technology, and in particular to a low-energy-consumption process for preparing nano-confined NaAlH4 hydrogen storage materials that can be cycled under low pressure. Background Technology

[0002] Against the backdrop of the "dual carbon" goal, hydrogen energy, as a carbon-free clean energy source, has received widespread attention from governments, industries, and academia worldwide, and has experienced rapid development in recent years. As a crucial link in the hydrogen energy industry chain, hydrogen storage connects upstream hydrogen production with downstream hydrogen applications, playing a vital role in the storage, transportation, and portable application of hydrogen energy. However, achieving high-density and safe hydrogen storage remains one of the technological bottlenecks restricting the development of hydrogen energy. Compared with traditional high-pressure and liquid hydrogen storage methods, solid-state hydrogen storage does not require ultra-high pressure or cryogenic storage conditions, offers higher storage and transportation safety, and stores hydrogen in the form of hydrogen atoms within solid materials, resulting in higher hydrogen storage density.

[0003] Among numerous solid-state hydrogen storage materials, NaAlH4 possesses a higher hydrogen density (5.5 wt% hydrogen release in the first two steps) than hydrogen storage alloys and a milder hydrogen release temperature (~200℃) than magnesium hydride and borohydrides, making it more valuable for applications overall. For a long time, NaAlH4 was considered a non-recyclable hydrogen storage material, limiting its development, until Borislav... Manfred Schwickardi and others discovered the recyclability of NaAlH4 under titanium-based catalysis. Since then, researchers have conducted extensive studies on improving the recyclability and hydrogen absorption / desorption performance of NaAlH4, including catalyst design and the nano-sizing of NaAlH4, and have made significant progress.

[0004] However, in most reports, the re-hydrogenation of NaAlH4 dehydrogenation products still requires relatively high hydrogen pressure (10 MPa). Some studies have achieved re-hydrogenation of NaAlH4 dehydrogenation products under relatively low hydrogen pressure by confining NaAlH4 nanoparticles in porous carbon materials, but the loading capacity of NaAlH4 is very limited due to the specific surface area and pore volume limitations of the porous carbon materials. Furthermore, the melt loading method used in these studies requires high temperatures (>180℃) and hydrogen pressures (>15 MPa), leading to high energy consumption and safety risks in production processes. Therefore, it is necessary to adjust the structure of the support material for nano-confined NaAlH4 and regulate the methods and conditions for loading NaAlH4 to further improve the hydrogen storage performance of nano-confined NaAlH4 hydrogen storage materials and enhance the economy and safety of the production process.

[0005] In addition, in the literature and in existing patents, most of them are directly using commercial NaAlH4 as raw material, and by means of melting or solution loading, the NaAlH4 is nano-confined in porous or two-dimensional support materials. The synthesis and loading of NaAlH4 are separate, and pressurization and temperature rise are required, which produces two-step energy consumption, increases the risk of exposure of the air-sensitive material, and lengthens the process flow.

[0006] Based on the above research, the synthesis method of nano-confined NaAlH4 in the prior art needs to be further improved, and this aspect is currently a market blank point, and has very high market research and market promotion value. SUMMARY

[0007] The technical problem solved by the present application is to provide a low-energy-consumption preparation method for nano-confined NaAlH4 hydrogen storage material, which effectively reduces the pressure and temperature of the loading process, and combines the synthesis and nano-loading of NaAlH4.

[0008] To solve the above technical problems, one technical solution adopted by the present application is to provide a process method for preparing a nano-confined NaAlH4 hydrogen storage material with low pressure circulation and low energy consumption, comprising the following preparation steps:

[0009] (1) pretreating the selected two-dimensional carrier material;

[0010] (2) placing aluminum powder, small pieces of sodium, and triethylaluminum in a high-pressure reaction kettle in an argon-filled glove box, and adding an organic solvent;

[0011] (3) further dispersing the pretreated two-dimensional carrier material in the above organic solvent, and sealing the reaction kettle;

[0012] (4) placing the reaction kettle in an ultrasonic machine for 1-3 hours of mixing and dispersion;

[0013] (5) vacuumizing the reaction kettle, filling hydrogen into the reaction kettle, heating the reaction kettle to 130-160℃ at a certain heating rate, and keeping for a period of time;

[0014] (6) after the reaction is completed, cooling the reaction kettle to room temperature, and discharging the remaining hydrogen pressure;

[0015] (7) placing the mixture under dynamic vacuum for solvent removal and drying treatment to obtain the nano-confined NaAlH4 of the present application;

[0016] (8) performing related performance tests.

[0017] Based on the above technical scheme, the selection of the NaAlH4 carrier material in the prior art is mostly three-dimensional porous material, the inventor finds that the three-dimensional porous material is prone to the problem that the material cannot effectively enter the pores, and it is difficult to achieve sufficient loading, in the present invention, a two-dimensional carrier is innovatively selected, and it is necessary to ensure that the two-dimensional carrier does not react with the reaction raw materials at a temperature of 100-200 DEG C, the surface has no oxidizing groups, and there is an electronic interaction between the two-dimensional carrier and NaAlH4, and the two-dimensional carrier has a light weight and a large specific surface area, therefore, the selection of the carrier material is crucial; in the present invention, the synthesis of NaAlH4 and the nano-loading are combined, and the nano-limited NaAlH4 is directly synthesized, the electronic interaction between the graphene and the NaAlH4 at the hydrogen pressure and the specific temperature makes the reaction-generated NaAlH4 directly and sufficiently dispersed on the two-dimensional carrier material.

[0018] Preferably, in the pretreatment process in the above step (1), the two-dimensional carrier material is placed in a H2 / Ar mixed gas stream or under dynamic vacuum, and is kept at 700-900 DEG C for 1-3 hours.

[0019] Preferably, in the above step (1), the two-dimensional carrier material is graphene or h-BN.

[0020] Preferably, in the above step (2), the molar ratio of the aluminum to triethylaluminum is 250:1-200:1, and the molar ratio of the aluminum to sodium is 1.

[0021] Preferably, in the above step (2), the molar number of the aluminum to the volume (L) of the organic solvent is 0.2-2.0.

[0022] Preferably, in the above step (2), the organic solvent is selected from tetrahydrofuran and ethylene glycol dimethyl ether.

[0023] Preferably, in the above step (2), the purity of the aluminum powder and the sodium is not less than 99%, and the sodium is stored by being immersed in kerosene or liquid paraffin, and is cut into small pieces after being cleaned by using the organic solvent.

[0024] Preferably, in the above step (3), the mass ratio of the aluminum to the two-dimensional carrier is 0.1-4.5.

[0025] Preferably, in the above step (5), the heating rate is controlled to be 2-10 DEG C / min.

[0026] Preferably, in the above step (5), the hydrogen pressure is 7-12 MPa, and the holding time of the reaction kettle is 6-12 hours.

[0027] The present invention has the following beneficial effects:

[0028] The present application is based on the technical defects of high requirement of melting load condition, high energy consumption of NaAlH4 synthesis and load separation, high risk of exposure of air-sensitive materials and the like in the development and promotion process of NaAlH4 in the prior art, and innovatively proposes a low-energy preparation method, which combines the synthesis and nano-loading of NaAlH4 into one, compared with the melting and loading method in the prior art, the present application reduces the pressure and temperature of the loading process while ensuring the loading effect, directly synthesizes hydrogen absorption and desorption energy better nano-confined NaAlH4 in one step without increasing energy consumption, at the same time, the process of the present application reduces the exposure risk of air-sensitive materials in the preparation process, shortens the production process, reduces the corresponding equipment operation and production cost, and has good technical popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the XRD spectrum of the product obtained in Example 1 of the present application;

[0030] Figure 2 is the TEM electron microscope morphology photo of the product obtained in Example 1 of the present application;

[0031] Figure 3 is the isothermal hydrogen desorption curve of the product obtained in Example 1 of the present application;

[0032] Figure 4 is the hydrogen desorption curve of the product obtained in Example 1 of the present application after hydrogenation in the cycle process;

[0033] Figure 5 is the heating and hydrogen desorption curve of Example 1, Comparative Example 1 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present application are described in detail below, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application is more clearly and explicitly defined.

[0035] Example 1:

[0036] Graphene is selected as a two-dimensional carrier material, graphene is placed in a tube furnace connected to a dynamic vacuum, heated to 800℃ at a heating rate of 5℃ / min, and heat treated for 2 hours; after pre-treatment, cool to room temperature, collect the pretreated graphene and place it in an argon glove box for standby;

[0037] 270mg of aluminum powder is weighed and placed in a 100ml high-pressure reaction kettle, the sodium block immersed in liquid paraffin is taken out, the surface is cleaned with tetrahydrofuran THF, and then cut into small pieces, 230mg is weighed and placed in the reaction kettle;

[0038] Into a reactor, 13 uL of triethylaluminum and 50 mL of tetrahydrofuran were added, and then 540 mg of pretreated graphene was weighed into the mixture, and the reactor was sealed and taken out of the glove box;

[0039] The sealed reactor was placed in an ultrasonic machine for ultrasonic treatment for 1 hour, and the reactants were fully dispersed in the carrier material. Then, the reactor was vacuumized, 7 MPa of hydrogen was filled into the reactor, and the reactor was heated to 140℃ at a heating rate of 5℃ / min and kept for 10 hours;

[0040] After the above reaction was completed, the reactor was cooled to room temperature, the residual hydrogen pressure was discharged, the reaction mixture was collected, and was dried under dynamic vacuum for 12 hours to obtain 1.03 g of product, which was a low-energy-consumption prepared low-pressure-circulating nano-confined NaAlH4 of the application.

[0041] Comparative Example 1:

[0042] Different from Example 1, no graphene carrier material was added in the present comparative example, and the rest of the preparation was the same;

[0043] Comparative Example 2:

[0044] Commercial NaAlH4 (purchased from Xi'an Qiyue Bio) was directly used as a raw material, and a two-step melting loading method in the prior art was used. 0.4 g of porous carbon carrier material was ground with 0.1 g of NaAlH4 in an argon atmosphere glove box, and then was sealed into a reactor. The reactor was vacuumized, 10 MPa of hydrogen was filled into the reactor, and the reactor was heated to 185℃ and kept for 2 hours for melting loading. After the reactor was cooled to room temperature, it was moved into a glove box, and the nano-confined NaAlH4 hydrogen storage material of the present comparative example was collected.

[0045] The performance of the related products was tested, at least including:

[0046] (1) XRD spectrum: measured by an X-ray diffractometer, D8 advance, Bruker AXS, USA, using Cu Kα (λ = 1.542°) diffraction, voltage 40 KV, current 40 mA, and the test angle range was 20-80°;

[0047] (2) TEM electron microscope: the projection electron microscope used was Philips CM200, and the sample was pretreated before testing: the sample powder was ultrasonically dispersed in ether for 5 minutes, then the suspension was dropped on a carbon-coated TEM copper net, and was dried in an argon-filled glove box. When testing, the TEM copper net was quickly transferred into the microscope to minimize the contact with air.

[0048] (3) Isothermal hydrogen desorption curve: the equipment used is HPSA-auto high-pressure full-automatic gas adsorption instrument, the hydrogen desorption test is carried out under static vacuum, the hydrogen desorption temperature is 140, 160, 180 and 200℃ respectively, and the test time is 1 hour or the hydrogen desorption curve is obviously flat.

[0049] (4) Hydrogen desorption curve in a cycle process: the equipment used is HPSA-auto high-pressure full-automatic gas adsorption instrument, the hydrogen desorption test is carried out under static vacuum, the hydrogen desorption temperature is 180℃, the test time is 1 hour, and the hydrogenation condition in the cycle process is that the hydrogenation temperature is 100℃ and the pressure is 5.5 MPa.

[0050] (5) Heating hydrogen desorption curve: the equipment used is HPSA-auto high-pressure full-automatic gas adsorption instrument, the hydrogen desorption test is carried out under static vacuum, the heating rate is 2℃ / min, and the temperature range is 50-300℃.

[0051] Figure 1 The XRD spectrum of the product obtained in Example 1 is obtained, and it can be seen that the peak shape is obvious and the material composition is determined.

[0052] Figure 2 The TEM electron microscope photo of the product obtained in Example 1 is obtained, and it can be seen that the loading morphology is good.

[0053] Figure 3 The hydrogen desorption of the product obtained in Example 1 at different temperatures is obtained, wherein the black curve is the hydrogen desorption at 140℃, the red curve is the hydrogen desorption at 160℃, the blue curve is the hydrogen desorption at 180℃, and the green curve is the hydrogen desorption at 200℃, and it can be seen that the hydrogen desorption rate is faster with the increase of temperature.

[0054] Figure 4 The hydrogen desorption cycle of the product obtained in Example at 180℃ is obtained, and it can be seen that after the first hydrogen desorption, the hydrogen desorption amount in the subsequent multiple hydrogen absorption and desorption cycles is very small, and the cycle hydrogenation condition of the present embodiment is only a hydrogenation temperature of 100℃ and a pressure condition of 5.5 MPa, which is obviously lower than the cycle hydrogenation condition in the prior art.

[0055] Figure 5 The heating hydrogen desorption curve of the product obtained in Example 1, Comparative Example 1 and Comparative Example 2 is obtained, wherein the blue curve corresponds to the hydrogen desorption of Example 1, the black curve corresponds to the hydrogen desorption of Comparative Example 1, and the red curve corresponds to the hydrogen desorption of Comparative Example 2, and it can be obviously seen that the nano-limited NaAlH4 obtained according to the preparation process of the present embodiment can obtain almost the same unit NaAlH4 hydrogen desorption amount at a lower temperature under the same conditions.

[0056] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A process for the low energy production of a nanoconstrained NaAlH4 hydrogen storage material that can be cycled at low pressure, characterized in that, The preparation steps include: (1) pre-treating the selected two-dimensional carrier material; (2) in an argon-filled glove box, placing aluminum powder, sodium and triethylaluminum in a high-pressure reaction kettle, and adding an organic solvent; (3) dispersing the pre-treated two-dimensional carrier material in the organic solvent, and sealing the reaction kettle; (4) placing the reaction kettle in an ultrasonic machine for 1-3 hours of ultrasonic mixing and dispersion; (5) vacuumizing the reaction kettle, filling hydrogen into the reaction kettle, heating the reaction kettle to 130-160°C at a certain heating rate, and keeping for a period of time; (6) after the reaction is completed, cooling the reaction kettle to room temperature, and discharging the remaining hydrogen pressure; (7) placing the mixture under dynamic vacuum for solvent removal and drying treatment to obtain nano-confined NaAlH4; (8) performing related performance tests; In the above step (1), the pre-treatment process is to place the two-dimensional carrier material in a H2 / Ar mixed gas stream or under dynamic vacuum, and heat at 700-900°C for 1-3 hours; in the above step (2), the molar ratio of aluminum to triethylaluminum is 250:1-200:1, and the molar ratio of aluminum to sodium is 1; in the above step (5), the hydrogen pressure filled is 7-12 MPa, and the holding time of the reaction kettle is 6-12 hours.

2. The process for preparing low pressure cycleable nanoconfined NaAlH4 hydrogen storage material with low energy consumption according to claim 1, characterized in that: In the above step (1), the two-dimensional carrier material is graphene or h-BN.

3. The process for preparing low pressure cycleable nanoconfined NaAlH4 hydrogen storage material with low energy consumption according to claim 1, characterized in that: In the above step (2), the molar number of aluminum to the volume of organic solvent is 0.2-2.0 mol / L.

4. The process of claim 1, wherein the process is characterized in that: In the above step (2), the organic solvent is selected from tetrahydrofuran or ethylene glycol dimethyl ether.

5. The process of claim 1, wherein the process is characterized in that: In the above step (2), the purity of aluminum powder and sodium is not less than 99%, and sodium is stored by being immersed in kerosene or liquid paraffin, and is cut into small pieces after being washed with the organic solvent.

6. The process of claim 1, wherein the process is characterized in that: In the above step (3), the mass ratio of aluminum to two-dimensional carrier is 0.1-4.

5.

7. The process of claim 1, wherein the process is characterized in that: In the above step (5), the heating rate is controlled at 2-10°C / min.

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