Method for preparing hydrogen

Abstract

The invention discloses a method for preparing hydrogen. The method comprises the following steps: mixing alkali metal which is inactive at normal temperature with hydride, coating the hydride on the surface of the alkali metal to form a coating layer, and preparing a hydride / alkali metal mixture; and contacting the hydride / alkali metal mixture with water, so that the water respectively reacts with the hydride and the alkali metal in sequence to prepare the hydrogen. The hydrogen preparation method provided by the invention is low in cost, reduces the use cost of hydrogen, is simple and easy to operate and control, and can simply and efficiently prepare hydrogen; in addition, the method does not need any complex pretreatment, and efficient on-site preparation can be achieved. According to the invention, a hydrogen source can be provided for portable and wearable electronic equipment, electric energy is provided in combination with a fuel cell, the endurance time of the electronic equipment can be greatly prolonged, and the hydrogen power generation device is suitable for outdoor, field and some military fields, and is used as a power supply in combination with the fuel cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by hydrolysis, and particularly relates to a simple and low-cost method for on-site hydrogen production. Background Art

[0002] The depletion of global fossil fuels and the extensive use of fossil fuels have caused serious environmental pollution and energy crises. Hydrogen, as a clean and high-energy fuel, can greatly alleviate environmental pollution and energy crises. Currently, the methods for hydrogen production mainly include: steam methane reforming, electrolysis, biomass gasification, coal gasification, fermentation, and so on. The advantages of the above hydrogen production methods are that they can produce hydrogen industrially and in large quantities. However, for lightweight, portable, and wearable electronic devices, the above hydrogen production methods still require storage. Generally, pressurized storage using steel cylinders is required, which greatly increases the mass and volume of portable devices and is not conducive to the application of the above lightweight and portable electronic devices. Therefore, developing a lightweight, low-cost, and on-site hydrogen production method has great market prospects.

[0003] Aluminum can react with acids and alkalis to produce a large amount of hydrogen. At the same time, aluminum also has the advantages of low cost, rich reserves, and easy recycling. Therefore, hydrogen production from aluminum is a potential means for low-cost and rapid on-site hydrogen production. However, when aluminum comes into contact with water, an oxide layer is easily formed on the outer surface of the aluminum metal, which prevents aluminum from further reacting to produce hydrogen. Based on this, researchers in this field have established various methods to initiate the reaction of aluminum with water. These strategies include pretreatment of aluminum (such as ball milling), molten aluminum alloy, addition of hydroxide promoters, oxide and salt promoters, steam method, plasma modification of aluminum, and so on. Although the above methods can promote hydrogen production from aluminum, there are still many disadvantages. For example:

[0004] 1) Ball milling requires a large amount of additional energy input, which will increase the overall production cost; at the same time, factors such as particle size, milling time, and impurities in aluminum will all affect hydrogen production from aluminum. The influencing factors are complex and difficult to control. Pretreatment such as ball milling and high-temperature treatment are required, and the process is complex.

[0005] 2) The high operating temperature of molten aluminum alloy, and the processing and control of the molten state increase the complexity and cost of the process.

[0006] 3) Adding hydroxide promoters can enhance hydrogen production from aluminum, but the concentration of the promoter needs to be precisely controlled because it will affect the stability and efficiency of the reaction. The availability and cost of hydroxide promoters may also limit large-scale applications.

[0007] 4) High cost, which increases the use cost of hydrogen.

[0008] Therefore, the development of a simple, easy-to-control, and low-cost aluminum-based hydrogen production technology is of great help in promoting the development and utilization of hydrogen, alleviating the energy crisis and environmental pollution, and is also the long-term goal of researchers in the industry. Summary of the Invention

[0009] The main object of the present invention is to provide a simple and low-cost method for on-site hydrogen production to overcome the deficiencies in the prior art.

[0010] To achieve the aforementioned invention object, the technical solutions adopted by the present invention include:

[0011] An embodiment of the present invention provides a method for hydrogen production, which includes:

[0012] Mix an alkali metal that is inactive at room temperature with a hydride, so that the hydride coats the surface of the alkali metal to form a coating layer, and obtain a hydride / alkali metal mixture;

[0013] Contact the hydride / alkali metal mixture with water, so that water reacts with the hydride and the alkali metal respectively in sequence, and obtain hydrogen.

[0014] An embodiment of the present invention also provides an application of the aforementioned method for hydrogen production in preparing a hydrogen source for wearable electronic devices.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0016] 1) The method for hydrogen production provided by the present invention has a low cost, reduces the use cost of hydrogen, is simple and easy to operate and control, and can produce hydrogen simply and efficiently; moreover, the method of the present invention does not require any complex pretreatment and can be efficiently prepared on-site;

[0017] 2) The method for hydrogen production provided by the present invention can provide a hydrogen source for portable and wearable electronic devices, combine with a fuel cell to provide electrical energy, and can greatly extend the battery life of the above-mentioned electronic devices, and is suitable for outdoor, field, and certain military fields, and is used as a power source in combination with a fuel cell. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a roadmap for hydrogen production by reacting water with a NaH / Al mixed powder in the present invention;

[0020] Figure 2a and Figure 2b are SEM images of Al particles at different method multiples before mixing in a typical embodiment of the present invention;

[0021] Figure 2c and Figure 2d are SEM images of NaH at different magnification multiples before mixing in a typical embodiment of the present invention;

[0022] Figure 2e is the SEM image of the NaH / Al mixed powder in a typical embodiment of the present invention;

[0023] Figure 2f 、 Figure 2g 、 Figure 2h are elemental analysis diagrams of the NaH / Al mixed powder in a typical embodiment of the present invention;

[0024] Figure 2i is the XRD pattern of aluminum before mixing in a typical embodiment of the present invention;

[0025] Figure 2j is the XRD pattern of NaH before mixing in a typical embodiment of the present invention;

[0026] Figure 2k is the XRD pattern of the NaH / Al mixed powder in a typical embodiment of the present invention;

[0027] Figure 3a is the relationship diagram between temperature and hydrogen production volume at different water flow rates in a typical embodiment of the present invention;

[0028] Figure 3b 、 Figure 3c are schematic diagrams of the total hydrogen production and the highest temperature at different water flow rates in a typical embodiment of the present invention;

[0029] Figure 4a is the relationship diagram of hydrogen generation amount over time at different ratios of NaH to Al in a typical embodiment of the present invention;

[0030] Figure 4b is the schematic diagram of the total hydrogen production at different ratios of NaH to Al in a typical embodiment of the present invention;

[0031] Figure 4c is the relationship diagram of hydrogen production rate at different ratios of NaH to Al in a typical embodiment of the present invention;

[0032] Figure 5a is the relationship diagram between hydrogen production amount and time at different aluminum foil sizes in a typical embodiment of the present invention;

[0033] Figure 5b Schematic diagram of total hydrogen production of different aluminum foil sizes in a typical embodiment of the present invention;

[0034] Figure 5c and Figure 5d In a typical embodiment of the present invention, when the ratio of NaH to Al is 1:1.5, it is a graph showing the influence relationship of lake water, ultrapure water and tap water on hydrogen production. Detailed implementation manners

[0035] As mentioned above, in view of the deficiencies of the prior art, the inventors of this case, through long-term research and a large number of practices, proposed the technical solution of the present invention. The method provided mainly is a method for producing hydrogen by using hydrides and alkali metals that are inactive at room temperature such as Al. The following will further explain the technical solution, its implementation process and principle, etc.

[0036] A method for producing hydrogen provided by one aspect of the embodiments of the present invention includes:

[0037] Mix an alkali metal that is inactive at room temperature with a hydride so that the hydride coats the surface of the alkali metal to form a coating layer, obtaining a hydride / alkali metal mixture;

[0038] Contact the hydride / alkali metal mixture with water, and make the water react with the hydride and the alkali metal respectively in sequence to produce hydrogen.

[0039] In some embodiments, the molar ratio of the alkali metal to the hydride is 0.6:1 to 1:1.7.

[0040] In some embodiments, the alkali metal can be aluminum, such as aluminum particles, and the particle size of the aluminum particles is 1 to 500 μm.

[0041] In some embodiments, the hydride can be sodium hydride, but is not limited thereto. For example, it can also be one or a combination of magnesium hydride, calcium hydride, etc.

[0042] In some embodiments, the thickness of the coating layer is 1 to 200 μm.

[0043] Further, the method for producing hydrogen includes: adding water to the hydride / alkali metal mixture, and making the water react with the hydride and the alkali metal at 31 to 170 °C respectively to produce hydrogen.

[0044] Further, the flow rate of the water is 15 to 500 μL / min.

[0045] Further, the water includes at least any one of lake water, ultrapure water, tap water, etc., but is not limited thereto.

[0046] Furthermore, the alkali metal includes aluminum foil, and the size of the aluminum foil is 1 mm 2 ~20mm 2 .

[0047] In some typical implementations, the present invention provides a method for producing hydrogen by reacting water with NaH / Al mixed powder. Figure 1 This is a roadmap and basic mechanism diagram of this hydrogen production method. When water comes into contact with NaH / Al mixed powder, water first reacts with NaH to produce NaOH (reaction formula (1)), while a large amount of reaction heat increases the temperature of the environment. NaOH and water attack Al at a higher temperature to induce hydrolysis of aluminum and produce more hydrogen and more heat (reaction formula (2)). Therefore, NaH acts as a promoter to react with water to generate NaOH and heat. The presence of NaOH ensures that Al always has a fresh surface to react with NaOH. The presence of a large amount of reaction heat ensures that NaOH and Al can further react to generate hydrogen. At the same time, the reaction of NaOH and Al also releases a large amount of reaction heat to promote the further reaction of NaH / Al mixed powder with water to generate hydrogen.

[0048] NaH+H2O→NaOH+H2 Reaction formula (1)

[0049] Al+3H2O→Al(OH)3+H2 Reaction formula (2)

[0050] Furthermore, the hydrogen yield of the method is above 60%.

[0051] In summary, the method provided by the present invention is low in cost, reduces the cost of using hydrogen, is simple and easy to operate and control, and can produce hydrogen simply and efficiently; and the method of the present invention does not require any complicated pretreatment and can be efficiently prepared on-site.

[0052] Another aspect of an embodiment of the present invention further provides an application of the aforementioned method for producing hydrogen. For example, producing hydrogen from aluminum is a portable, on-site, in-situ hydrogen production method that can provide a hydrogen source for portable and wearable electronic devices, and further provide electrical energy with the help of fuel cells. It is only expected to significantly extend the battery life of electronic devices, bringing great convenience to people's lives and work, and is suitable for outdoor, field, and certain military fields, combined with fuel cells as a power source.

[0053] In order to make the above-mentioned objects, features and advantages of the present invention more understandable, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification and the drawings.

[0054] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] Unless otherwise specified, the raw materials and reagents in the embodiments of the present application are all purchased through commercial channels.

[0056] Example 1

[0057] The method for producing hydrogen by reacting water with the NaH / Al mixed powder in this example includes:

[0058] First, the aluminum particles are fully mixed with NaH, and the molar ratio between the two can be 0.6:1 to 1:1.7, so that NaH coats the surface of the aluminum particles to form a coating layer (the thickness can be 1 to 200 μm), and the NaH / Al mixed powder is obtained. The above-mentioned mixed powder is placed in a sample bottle. Then, a micro-injection pump is used to drop water into the NaH / Al mixed powder through a thin tube above the sample bottle for reaction. Another thin tube of the sample bottle is directly connected to a gas detector to detect the rate and total volume of the generated hydrogen, and further calculate the hydrogen production rate. When water contacts the NaH / Al mixed powder, water first reacts with NaH to produce NaOH, and at the same time, a large amount of reaction heat raises the temperature of the environment. NaOH and water attack Al at a higher temperature to initiate the hydrolysis of aluminum and generate more hydrogen and more heat. Therefore, NaH acts as a promoter, reacting with water to generate NaOH and heat. The presence of NaOH ensures that Al always has a fresh surface to react with NaOH. The presence of a large amount of reaction heat ensures that NaOH and Al can further react to generate hydrogen. At the same time, the reaction between NaOH and Al also releases a large amount of reaction heat to promote the further reaction of the NaH / Al mixed powder with water to generate hydrogen.

[0059] As Figures 2a - 2k shown, the results of the characterization and structural analysis of Al before and after mixing with NaH by the inventors of this case are presented. Specifically:

[0060] Figure 2a and Figure 2b are SEM images of Al particles at different magnification factors. It can be observed from the SEM that the shape of Al is spherical, and the size is concentrated between dozens of microns and hundreds of microns. Figure 2c and Figure 2d are SEM images of NaH at different magnification factors before mixing. It can be seen from Figure 2c that the structure of NaH presents an ear-like shape.Figure 2d At a larger method magnification, the edges of NaH show obvious melting and collapse in structure. This is mainly because the reaction between NaH and water is highly active, and water vapor in the air can react directly with NaH. Therefore, when extracting samples for detection, NaH reacts immediately with water in the air and produces NaOH.

[0061] Figure 2e is the structure after mixing NaH and Al. It can be clearly seen that the spherical Al particles are significantly covered by NaH. At the same time, from Figures 2e - 2h the elemental analysis, it can also be clearly seen that the Al particles are wrapped by NaH. Therefore, the NaH outside the Al particles can form a shielding layer to protect the Al particles from direct contact with water and the environment. The mixed powder of NaH and Al provides a suitable environment to support and improve the hydrolysis ability of aluminum. By mixing with NaH, Al can be easily hydrolyzed while producing more hydrogen.

[0062] Figure 2i , Figure 2j , Figure 2k shows the XRD patterns of Al and NaH before and after mixing. Figure 2i shows the XRD peaks of Al before mixing. Comparing with the JCPDS card number (00-004-0787), it is confirmed that Al is in the cubic phase. Figure 2j is the XRD pattern of NaH before mixing, indicating that NaH is in the cubic phase, which is consistent with the JCPDS card number (03-065-9247). In addition, small and weak peaks of NaOH are also observed in Figure 2j , which shows the orthorhombic phase of NaOH and is consistent with the JCPDS card number (00-035-1009). The XRD pattern of the small and weak peaks of NaOH is due to the air sensitivity of NaH, because it reacts immediately when exposed to air and produces a small amount of NaOH. The positions of the XRD peaks of the mixed Al and NaH powders are as shown in Figure 2k . It is observed that the XRD peaks belong to Al, NaH, and NaOH, which confirms their cubic and orthorhombic structures. The XRD peaks represent the three-phase crystal structure in the hydrogen production system of the Al and NaH mixed powder. The peak of Al does not shift, indicating that Na and Al do not replace each other, which means that NaH only covers the outer surface of the Al particles to protect Al from the environment and support the hydrolysis ability of Al under normal conditions. In addition, compared with the NaOH peak shown in the XRD pattern of NaH, the peak formed due to NaOH is relatively low and slightly disappears. This may be due to the lower concentration of NaOH after mixing with Al. The XRD results are consistent with the SEM analysis and EDS analysis results.

[0063] The inventors of this case conducted the following research on the process conditions of this embodiment:

[0064] I. Influence of water flow rate and temperature on hydrogen production

[0065] Figures 3a - 3c The influence of water flow rate and temperature on hydrogen generation is shown. Figure 3a The relationship between temperature and hydrogen production volume (mL) at different water flow rates is shown. As Figure 3a shown, temperature and water flow rate significantly affect the volume of hydrogen produced from the mixture of NaH and Al powders. Through a series of experiments, the inventors of this case found that the water flow rate is 15 - 500 μL / min, and the optimal water flow rate is 50 - 100 μL / min. Because compared with other water flow rates, it generates more hydrogen in a more controllable manner within the temperature range of 31 - 80 °C. In addition, a water flow rate of 375 μL / min can produce more hydrogen within the temperature range of 31 - 170 °C, while the water flow rate of 15 μL / min produces the least amount of hydrogen.

[0066] Figure 3b The total hydrogen production at different water flow rates is shown, where A = (15 μL / min), B = (35 μL / min), C = (75 μL / min), D = (200 μL / min), E = (375 μL / min). Figure 3c The maximum temperature reached at different water flow rates is shown. The hydrogen production amounts corresponding to water flow rates of 15 μL / min, 35 μL / min, 75 μL / min, 200 μL / min, 375 μL / min, and 500 μL / min are 22 mL, 95 mL, 156 mL, 175 mL, 186 mL, and 232 mL respectively. At the same time, the corresponding maximum temperatures are 51 °C, 72 °C, 80 °C, 102 °C, 130 °C, and 169 °C respectively.

[0067] II. Hydrogen production performance at different ratios of Al to NaH

[0068] Figures 4a - 4c The influence of different ratios of Al to NaH on hydrogen production is shown. Figure 4a The hydrogen production amount over time at different ratios of Al to NaH is shown. It can be clearly seen from Figure 4a this that pure NaH produces less hydrogen. When Al is added, due to the hydrolysis of Al, a significant increase in the hydrogen production amount is detected. Figure 4cShows the hydrogen production rates at different ratios of Al to NaH. Compared with single-component NaH and Al, the mixture of NaH and Al has a higher hydrogen production rate. The hydrogen production rates corresponding to the ratios of NaH to Al of 1:0.6, 1:0.7, 1:1, 1:1.5, 1:1.7, and 1:2 are 98%, 94%, 93%, 95%, 84%, and 73% respectively. When the ratio of NaH to Al is 0:1, the hydrogen production rate is 0%, which is because there is no NaH on the Al particles and hydrogen cannot be produced.

[0069] Figure 4b Shows the relationship of the total hydrogen production amounts at different ratios of NaH and Al. It can be noted that the total hydrogen production amount of the single Al component is 0. This is mainly because Al cannot react with water to produce hydrogen at normal temperature and pressure. In addition, for the single NaH component, the total hydrogen production amount is also relatively small. On the other hand, the total hydrogen production amounts corresponding to the ratios of NaH to Al of 1:0.6, 1:0.7, 1:1, 1:1.5, 1:1.7, and 1:2 are 87 mL, 93 mL, 116 mL, 156 mL, 158 mL, and 160 mL respectively. Therefore, only when Al and NaH exist simultaneously can they have the ability to produce a large amount of hydrogen.

[0070] III. Hydrogen production performance of aluminum foils of different sizes, lake water, ultrapure water, and tap water

[0071] Figures 5a - 5d Shows the total hydrogen production amounts of hydrogen generation under different sizes of aluminum foils and the influence of lake water, ultrapure water, and tap water as water sources on the total hydrogen production amount. Figure 5a Is the relationship between the hydrogen production amount (volume) and time under different sizes of aluminum foils (2.5×0.5 cm, 0.5×0.5 cm, 0.3×0.3 cm, 0.4×0.4 cm, 0.2×0.1 cm), where the ratio of NaH to the Al foil is 1:0.7. It can be observed that all sizes of aluminum foils will produce hydrogen only when NaH is added. Figure 5b Is the total hydrogen production amounts of different sizes of aluminum foils, where the ratio of NaH to the Al foil is fixed at 1:0.7. From Figure 5b It can be seen that when the sizes of the aluminum foils are 2.5×0.5 cm, 0.5×0.5 cm, 0.3×0.3 cm, 0.4×0.4 cm, and 0.2×0.1 cm, the corresponding total hydrogen production amounts are 62 mL, 87 mL, 95 mL, 69 mL, and 88 mL respectively. In addition, compared with other sizes of aluminum foils, the 0.3×0.3 cm-sized aluminum foil produces more hydrogen.

[0072] Figure 5c and Figure 5dIt shows the influence of using lake water, ultrapure water and tap water on the total hydrogen production when the ratio of NaH to Al is 1:1.5. In this embodiment, different types of water are used, such as the water of Dushu Lake in Suzhou, tap water and ultrapure water prepared in the laboratory. It can be seen that the volumes of hydrogen produced by the water of Dushu Lake and tap water are close to that produced by the ultrapure water prepared in the laboratory, which are 153 mL and 156 mL respectively. Therefore, the technology for producing hydrogen based on the mixture of Al and NaH powders is suitable for simple and rapid hydrogen production outdoors and in harsh environmental areas.

[0073] In addition, the inventor of this case also referred to the foregoing embodiments and conducted tests with other raw materials, process operations and process conditions described in this specification, and all obtained relatively ideal results.

[0074] All aspects, embodiments, features and examples of the present invention should be regarded as illustrative in all respects and are not intended to limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications and uses.

[0075] Although the present invention has been described with reference to the illustrative embodiments, those skilled in the art will understand that various other changes, omissions and / or additions can be made without departing from the spirit and scope of the present invention and elements of the embodiments can be replaced with substantial equivalents. In addition, many modifications can be made without departing from the scope of the present invention to adapt a particular situation or material to the teachings of the present invention. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed for carrying out the present invention, but is intended to cover all embodiments falling within the scope of the appended claims.

Claims

1. A method for producing hydrogen, characterized in that, Comprising: Mixing an alkali metal that is inactive at room temperature with a hydride so that the hydride coats the surface of the alkali metal to form a coating layer, thereby obtaining a hydride / alkali metal mixture; Bringing the hydride / alkali metal mixture into contact with water, and reacting water with the hydride and the alkali metal successively to produce hydrogen gas.

2. The method for producing hydrogen according to claim 1, characterized in that: The molar ratio of the alkali metal to the hydride is 0.6:1 to 1:1.

7.

3. The method for producing hydrogen according to claim 1, wherein: The alkali metal includes aluminum particles, and the particle size of the aluminum particles is 1 to 500 μm.

4. The method for producing hydrogen according to claim 1, characterized in that: The hydride includes any one or a combination of two or more of sodium hydride, magnesium hydride, and calcium hydride.

5. The method for producing hydrogen according to claim 1, characterized in that: The thickness of the coating layer is 1 to 200 μm.

6. The method for producing hydrogen according to claim 1, characterized in that, Comprising: Adding water to the hydride / alkali metal mixture, and reacting water with the hydride and the alkali metal at 31 to 170 °C to produce hydrogen gas.

7. The method for producing hydrogen according to claim 6, characterized in that: The flow rate of the water is 15 to 500 μL / min; and / or the water includes at least any one of lake water, ultrapure water, and tap water.

8. The method for producing hydrogen according to claim 1, characterized in that: The alkali metal includes aluminum foil, and the size of the aluminum foil is 1 mm 2 ~20 mm 2 .

9. The method for producing hydrogen according to claim 1, wherein: The hydrogen production rate of the method is above 60%.

10. Use of the method for producing hydrogen according to any one of claims 1-9 in the preparation of a hydrogen source for a wearable electronic device.

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