Method for producing hydrogen

Abstract

To provide a novel method for efficiently producing hydrogen from water.SOLUTION: The method for producing hydrogen according to the invention comprises irradiating water containing a reducing agent with electromagnetic waves to generate hydrogen.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing hydrogen. [Background technology]

[0002] In recent years, there has been concern about rapid global warming due to rising carbon dioxide concentrations in the atmosphere. It is said that the rise in carbon dioxide concentrations is largely due to the combustion of fossil fuels. Therefore, nuclear power and renewable energy (such as light, wind, waves, and geothermal energy) are being sought as alternative energy sources to fossil fuels. However, nuclear power poses the problem of waste disposal, and renewable energy poses issues such as capital investment and unstable energy supplies, making the shift to these energy sources not easy.

[0003] Furthermore, development is underway to use hydrogen as a fuel, which does not generate carbon dioxide when burned. However, when fossil fuels or biomass are used as hydrogen raw materials, carbon dioxide is generated as a by-product during the processing of the raw materials. Therefore, methods have been developed to obtain hydrogen and oxygen by electrolyzing water. However, water electrolysis requires equipment such as a positive electrode, a negative electrode, a separator, and an electrolyte, and has not yet been put to practical use.

[0004] Also, a method has been proposed in which water is decomposed to extract hydrogen and oxygen by combining microwaves, ultraviolet light, and photocatalysis (Patent Document 1). However, this method is complicated because it uses multiple types of electromagnetic waves. Furthermore, a water dissociation method using microwave plasma or plasma arc has been proposed (Patent Documents 2 and 3). However, these methods require high temperatures exceeding 2500°C, resulting in high power consumption. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-12626 [Patent Document 2] Japanese Patent Application Publication No. 56-17902 [Patent Document 3] Special Publication No. 2010-532744 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, currently, an efficient method for producing hydrogen from water has not yet been established. Therefore, an object of the present invention is to provide a new method for efficiently producing hydrogen from water. [Means for solving the problem]

[0007] One embodiment of the present invention is a method for producing hydrogen, as described below. [1] A method for producing hydrogen by irradiating electromagnetic waves onto water to which a reducing agent has been added to generate hydrogen. [2] The method for producing a semiconductor device according to [1] above, wherein the reducing agent contains at least one of a metal and a metal compound. [3] The manufacturing method according to [2] above, wherein the at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, an iron compound, zinc, and a zinc compound. [4] The manufacturing method according to [2] or [3] above, wherein at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, ferrous oxide, and triiron tetroxide. [5] The method according to any one of the above [1] to [5], wherein the reducing agent also serves as an electromagnetic wave absorber. [6] the reducing agent includes a compound in which a powder of at least one of a metal and a metal compound is supported on a carrier; at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, ferrous oxide, and triiron tetroxide; the carrier contains an electromagnetic wave absorbing agent, The manufacturing method according to [5] above, wherein the electromagnetic wave absorber contains at least one of aluminum oxide and silicon oxide. [7] The method according to any one of the above [1] to [4], wherein an electromagnetic wave absorber is further added to the water before the irradiation with electromagnetic waves. [8] The manufacturing method according to [7] above, wherein the electromagnetic wave absorber comprises at least one selected from the group consisting of aluminum oxide, silicon oxide, and silicon carbide. [9] The method for producing the electromagnetic wave absorber according to [8] above, wherein the electromagnetic wave absorber contains at least one of aluminum oxide and silicon oxide.

[10] The method according to any one of the above [7] to [9], wherein the electromagnetic wave absorber contains at least one of mullite and aluminosilicate.

[11] The method according to any one of the above [1] to

[10] , wherein the electromagnetic waves are microwaves. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a new method for efficiently producing hydrogen from water. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a chromatogram of Example 1. [Figure 2] 1 is a chromatogram of Example 2. [Figure 3] 1 is a chromatogram of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, a method for producing hydrogen according to one embodiment of the present invention (hereinafter sometimes referred to as "the method") will be described using an example, but the present invention is not limited to this. In the present specification, ○ to △ (for example, ○°C to △°C) means not less than ○ and not more than △ (not less than ○°C and not more than △°C). Furthermore, in this specification, the terms "comprise" or "comprises" mean that the specified components are included, but do not exclude the presence of other components.

[0011] As described above, this method is a method for producing hydrogen by irradiating electromagnetic waves to water to which a reducing agent has been added to generate hydrogen.

[0012] <Water> The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, and pure water. The form of the water is also not particularly limited, and may be liquid, solid, gas, or a mixture thereof. Furthermore, alkaline ions are required when producing hydrogen by electrolyzing water, but the water used in this method may or may not contain alkaline ions. Furthermore, the water may be natural water containing trace amounts of minerals. Thus, this method makes it possible to produce hydrogen from any type of water.

[0013] <Reducing agent> Examples of the reducing agent include metals and metal compounds. Examples of the metal include iron and zinc. Examples of the metal compound include iron compounds and zinc compounds. Examples of the iron compound include ferrous oxide and triiron tetroxide. Examples of the zinc compound include zinc oxide. One type of reducing agent may be used alone, or two or more types may be used in combination. For example, a mixture of zinc and zinc oxide may be used as the reducing agent.

[0014] From the viewpoint of the temperature during hydrogen production, the reducing agent is preferably at least one of iron, ferrous oxide, triiron tetroxide, and a mixture thereof, and more preferably at least one of iron and ferrous oxide. According to this method, hydrogen can be produced at a lower temperature (e.g., 1500°C or lower, preferably 1000°C or lower, more preferably 900°C or lower, and even more preferably 800°C or lower) compared to conventional methods for producing hydrogen from water, and it will be demonstrated in the examples described below that if the above-mentioned reducing agent is used, hydrogen can be produced at an even lower temperature (e.g., 700°C or lower, 650°C or lower, 600°C or lower).

[0015] In this method, the reducing agent, when represented by M or MO, acts on the basis of stoichiometry as shown in formula (1) or formula (2) in generating hydrogen from water. HO + M → H + MO (1) H2O + MO → H2+ MO2(2)

[0016] Therefore, the ratio of the amount of water to the amount of reducing agent can be determined stoichiometrically based on the amount of hydrogen to be generated from water. When the molar ratio of the reducing agent to the water (water / reducing agent) is greater than 1, unreacted water is likely to remain. On the other hand, when the water / reducing agent (molar ratio) is less than 1, the decomposition of the water proceeds, but excess reducing agent is likely to remain. In practice, since emphasis is often placed on the generation of hydrogen, the water / reducing agent (molar ratio) is, for example, 0.01 to 10, 0.01 to 5, or 0.2 to 3.

[0017] <Electromagnetic waves> The electromagnetic waves are not particularly limited, but examples thereof include sunlight, ultraviolet light, infrared light, and microwaves, and among these, microwaves are preferred.

[0018] The frequency of the microwave is not particularly limited, and may be, for example, 2.45 GHz, 5.8 GHz, 915 MHz, or another frequency in the range of 300 MHz to 300 GHz. That is, the electromagnetic wave may have a wavelength of, for example, 1 mm to 1 m. The intensity of the microwave is not particularly limited, and it is preferable to select an optimum output depending on, for example, the scale of the system to be irradiated with the microwave, specifically, the amount of material (irradiated object) to be irradiated with the microwave and the size of the reactor.

[0019] The microwave irradiation may be continuous or may be intermittent irradiation in which irradiation and pauses are repeated. In this method, when the microwave is irradiated, the temperature of the irradiated object rises, but the microwave irradiation intensity may be adjusted so that the temperature remains constant, or the microwave irradiation intensity may be kept constant and the temperature of the irradiated object may be varied, or the microwave irradiation intensity may be changed in small increments. It is desirable to select an irradiation method that generates hydrogen more efficiently. Specifically, it is desirable to select the irradiation method so that the temperature of the irradiated object during hydrogen generation is as low as possible and the rate of hydrogen generation is as high as possible, that is, so that the input energy of the microwaves irradiated for hydrogen generation (production) is minimized.

[0020] <Electromagnetic wave absorber> In this method, the object to be irradiated preferably contains an electromagnetic wave absorber in addition to the reducing agent. By containing the electromagnetic wave absorber in the object to be irradiated, reflection of the electromagnetic waves is reduced and absorption of the electromagnetic waves by the object to be irradiated is increased. This makes it possible to improve the efficiency of use of the electromagnetic waves as energy for hydrogen production.

[0021] Examples of the electromagnetic wave absorber include aluminum oxide, silicon oxide, carbon, and silicon carbide. Mullite and aluminosilicates containing aluminum oxide and silicon oxide may also be used. Examples of aluminosilicates include salts containing Na, K, Li, Ca, and the like. One type of electromagnetic wave absorber may be used alone, or two or more types may be used in combination.

[0022] The shape of the electromagnetic wave absorber is not particularly limited, and may be, for example, a lump, finer granules, or even finer powder, as long as there are no problems in handling, such as the absorber being too coarse to be introduced into a hydrogen production facility or being too fine to float in the air and make introduction into the hydrogen production facility difficult. The electromagnetic wave absorber may also be a mixture of two or more of these shapes.

[0023] The mullite may be, for example, in the form of a mineral itself, or may be formed into a plate, dish, or other shape, and may be used as is even if a processing agent such as glaze has been used during forming. In this method, when the mullite is used as the electromagnetic wave absorber, for example, a compound in the form of a block, granules, or powder may be introduced into the hydrogen production facility.

[0024] The aluminosilicate may be, for example, an intact mineral or may be formed into a plate or granule shape.

[0025] The method for making the irradiated object contain the electromagnetic wave absorbing agent includes, but is not limited to, the following two methods.

[0026] The first method is a method in which the reducing agent also serves as the electromagnetic wave absorber. This first method can be carried out, for example, by causing the reducing agent to contain a compound in which powder of at least one of the metal and metal compound is supported on a carrier, and then causing the carrier to contain the electromagnetic wave absorber.

[0027] The second method is to further add the electromagnetic wave absorber to the water before the electromagnetic wave irradiation.

[0028] In this method, the electromagnetic wave absorber is added to the irradiated object in order to efficiently raise the temperature of the irradiated object to a desired temperature range. The amount of the electromagnetic wave absorber added is desirably fine-tuned depending on the combination of the frequency of the electromagnetic waves, the irradiation power, and the type of the reducing agent, but is roughly, for example, 0.1 to 2 parts by mass relative to the total mass of the water and the reducing agent (i.e., mass of electromagnetic wave absorber / (mass of water + mass of reducing agent) is 0.1 to 2 parts by mass). By setting the amount of the electromagnetic wave absorber added within this range, it becomes easy to adjust the temperature rise rate of the irradiated object. The amount of the electromagnetic wave absorber added may be, for example, 0.1 to 1.7 parts by mass, or 0.2 to 1.4 parts by mass relative to the total mass of the water and the reducing agent.

[0029] In the hydrogen production equipment, the water, the reducing agent, and, if necessary, the electromagnetic wave absorber that have been introduced may or may not be stirred and mixed, as long as hydrogen is generated from the water. When stirring and mixing is performed, for example, a stirrer may be installed inside the equipment, the equipment may be rotated and rocked, or vibration may be applied to the equipment from the outside to mix the ingredients.

[0030] According to this method, hydrogen can be produced without generating carbon dioxide from the raw material, unlike when fossil fuels or biomass are used as the raw material. [Example]

[0031] Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited or restricted by the following examples and comparative examples.

[0032] [Example 1] 0.51 parts by mass of tap water was placed in a quartz tube measuring 15 mm in inner diameter, 18 mm in outer diameter, and 1700 mm in length, and 1.10 parts by mass of mullite pieces measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in thickness and 2.07 parts by mass of powdered ferrous oxide were added. To remove any remaining air in the headspace of the quartz tube, the top of the quartz tube was evacuated and then filled with nitrogen gas. This procedure was repeated three times to flush the top of the quartz tube with nitrogen gas.

[0033] Next, a completely uninflated balloon for collecting the evolved gas and a pressure gauge for measuring the pressure were attached to the top of the quartz tube. Measuring the pressure is necessary to determine the amount of gas (molar amount) generated by the reaction. While any of a Bourdon tube, manometer, and digital pressure sensor can be used as the pressure gauge, a Bourdon tube was used in this example. These points are the same in the examples and comparative examples described below. The quartz tube with the uninflated balloon attached was placed in a microwave irradiation device manufactured by Fuji Radio Kogyo Co., Ltd., and 2.45 GHz microwaves were irradiated through the quartz tube into the inside of the quartz tube for 50 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W, to 30 W after 10 minutes and to 60 W after 20 minutes, and the microwave irradiation was continued for 30 minutes. At this time, the temperature inside the quartz tube, measured through the quartz tube with an infrared thermography camera, was 350°C to 400°C. During this time, no increase in pressure was observed, but 10 mL of gas accumulated in the balloon. Four samples of gas were collected from the balloon and identified by gas chromatography. Hydrogen gas was detected in all samples (Figure 1).

[0034] [Example 2] The following changes were made to Example 1. Specifically, 2.07 parts by mass of powdered ferrous oxide was replaced with 1 part by mass of iron flakes with a major axis of 3 mm or less. The uninflated quartz tube with the balloon attached was placed in the microwave irradiation device, and 915 MHz microwaves were irradiated through the quartz tube into the interior of the quartz tube for 90 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W to 30 W after 10 minutes, 50 W after 20 minutes, and 80 W after 30 minutes. The microwave irradiation was continued for 60 minutes. The temperature inside the quartz tube, measured through the quartz tube with an infrared thermography camera, was 500°C to 550°C. During this time, no pressure increase was observed, but 5 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography. Hydrogen gas was detected from both samples (Figure 2).

[0035] [Example 3] The following changes were made to Example 1. Specifically, 1.10 parts by mass of mullite flakes measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in thickness were replaced with 2.00 parts by mass of aluminosilicate measuring 3 mm in major axis and 2 mm in minor axis containing 0.5% by mass of Na atoms, and 2.07 parts by mass of powdered ferrous oxide were replaced with a mixture of 0.8 parts by mass of powdered ferrous oxide and 0.2 parts by mass of powdered triiron tetroxide. An uninflated quartz tube with a balloon attached was placed in the microwave irradiation device, and 2.45 GHz microwaves were irradiated through the quartz tube for 30 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W to 50 W after 10 minutes, 80 W after 20 minutes, and 120 W after 30 minutes. The temperature inside the quartz tube, measured through the quartz tube with an infrared thermography camera, was 500°C to 600°C. During this time, no increase in pressure was observed, but 30 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography, and hydrogen gas was detected from both.

[0036] [Example 4] The following changes were made to Example 1. Specifically, 0.3 parts by mass of powdered graphite was used instead of 1.10 parts by mass of mullite flakes measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in thickness, and 0.8 parts by mass of zinc powder was used instead of 2.07 parts by mass of powdered ferrous oxide. A glass rod was placed inside the quartz tube and stirred thoroughly, after which the glass rod was removed. The quartz tube with the uninflated balloon attached was placed in the microwave irradiation device, and 2.45 GHz microwaves were irradiated through the quartz tube into the inside of the quartz tube for 30 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W to 50 W after 10 minutes, 80 W after 20 minutes, and 120 W after 30 minutes. At this time, the temperature inside the quartz tube measured through the quartz tube with an infrared thermography camera was 550°C to 650°C. During this time, no increase in pressure was observed, but 20 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography, and hydrogen gas was detected from both (Figure 3).

[0037] [Example 5] The following changes were made to Example 1. Specifically, 1.10 parts by mass of mullite flakes with a major axis of 8 mm, a minor axis of 5 mm, and a thickness of 1.5 mm were replaced with 0.3 parts by mass of silicon carbide particles with a major axis of 3 mm, a minor axis of 2 mm, and an average particle diameter of 0.5 mm, and 2.07 parts by mass of powdered ferrous oxide were replaced with 0.6 parts by mass of powdered ferrous oxide. The quartz tube with the uninflated balloon was placed in the microwave irradiation device, and microwaves of 2.45 GHz were irradiated through the quartz tube into the interior of the quartz tube for 30 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W to 50 W after 10 minutes, 80 W after 20 minutes, and 120 W after 30 minutes. At this time, the temperature inside the quartz tube measured through the quartz tube with an infrared thermography camera was 500 ° C to 600 ° C. During this time, no increase in pressure was observed, but 30 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography, and hydrogen gas was detected from both.

[0038] [Example 6] The following changes were made to Example 1. Specifically, 1.0 parts by mass of powdered aluminosilicate containing 0.2% by mass of Na atoms and 1.0 parts by mass of mullite flakes measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in thickness were used instead of 1.10 parts by mass of mullite flakes measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in thickness, and 2.0 parts by mass of powdered ferrous oxide were used instead of 2.07 parts by mass of powdered ferrous oxide. The remaining changes were the same as in Example 1. During microwave irradiation, the temperature inside the quartz tube measured with an infrared thermography camera through the quartz tube was 370°C to 450°C. During this time, no pressure increase was observed, but 15 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography. Hydrogen gas was detected from both.

[0039] [Comparative Example 1] The following changes were made to Example 1. Specifically, only 1.5 parts by mass of tap water was placed in the quartz tube. The quartz tube with the uninflated balloon was placed in the microwave irradiation device, and 2.45 GHz microwaves were irradiated through the quartz tube into the interior of the quartz tube for 30 minutes. During the microwave irradiation, the microwave output was gradually increased from 10 W, reaching 30 W after 10 minutes and 80 W after 20 minutes. The output was then maintained at 80 W for 10 minutes. The temperature inside the quartz tube measured through the quartz tube with an infrared thermography camera was 85°C. During this time, no increase in pressure was observed, and the balloon did not inflate. Therefore, the microwave irradiation was terminated 30 minutes after the start. Gas samples were collected from inside the balloon and the upper part of the quartz tube and identified by gas chromatography, but no hydrogen gas was detected in either sample.

[0040] Comparative Example 2 The following changes were made to Example 1. Specifically, only 0.51 parts by mass of tap water and 2.07 parts by mass of powdered ferrous oxide were placed in the quartz tube. The quartz tube with the uninflated balloon was placed in the microwave irradiation device, and a ribbon-shaped electric heater was wrapped around the outside of the quartz tube. The tube was heated at 100V, 80W, for 50 minutes. The temperature inside the quartz tube, measured through the quartz tube with an infrared thermography camera, was 95°C to 100°C. Since there was no sign of further increase, heating with the electric heater was terminated. During this time, no increase in pressure was observed, and no gas accumulated in the balloon. Gas samples from inside the balloon and the upper part of the quartz tube were collected and analyzed by gas chromatography, but no hydrogen gas was detected in either sample.

[0041] Comparative Example 3 The following changes were made to Example 1. Specifically, only 0.7 parts by mass of tap water and 2.10 parts by mass of mullite pieces measuring 8 mm in major axis, 5 mm in minor axis, and 1.5 mm in length were placed in the quartz tube. Other than that, the procedure was the same as in Example 1. During microwave irradiation, the temperature inside the quartz tube measured with an infrared thermography camera through the quartz tube was 350°C to 420°C. During this time, no increase in pressure was observed, but 8 mL of gas accumulated in the balloon. The gas inside the balloon and the gas at the top of the quartz tube were each sampled and identified by gas chromatography, but no hydrogen gas was detected in either sample.

[0042] The results of Examples 1 to 6 and Comparative Examples 1 to 3 are summarized in Table 1 below. In Table 1 below, the amount of electromagnetic wave absorber added ( * 1) is the value calculated by dividing the mass of the electromagnetic wave absorber by the mass of water + the mass of the reducing agent.

[0043] [Table 1]

[0044] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Claims

1. A method for producing hydrogen by irradiating electromagnetic waves onto water to which a reducing agent has been added to generate hydrogen.

2. The method according to claim 1 , wherein the reducing agent includes at least one of a metal and a metal compound.

3. The method according to claim 2 , wherein the at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, an iron compound, zinc, and a zinc compound.

4. The method according to claim 2 , wherein the at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, ferrous oxide, and triiron tetroxide.

5. The manufacturing method according to claim 1 , wherein the reducing agent also serves as an electromagnetic wave absorbing agent.

6. the reducing agent includes a compound in which a powder of at least one of a metal and a metal compound is supported on a carrier; at least one of the metal and the metal compound includes at least one selected from the group consisting of iron, ferrous oxide, and triiron tetroxide; the carrier contains an electromagnetic wave absorbing agent, The manufacturing method according to claim 5 , wherein the electromagnetic wave absorbing agent contains at least one of aluminum oxide and silicon oxide.

7. The method according to any one of claims 1 to 4, further comprising adding an electromagnetic wave absorber to the water before the irradiation with electromagnetic waves.

8. The manufacturing method according to claim 7 , wherein the electromagnetic wave absorbing agent includes at least one selected from the group consisting of aluminum oxide, silicon oxide, and silicon carbide.

9. The manufacturing method according to claim 8 , wherein the electromagnetic wave absorbing agent contains at least one of aluminum oxide and silicon oxide.

10. The method according to claim 9 , wherein the electromagnetic wave absorber includes at least one of mullite and aluminosilicate.

11. The manufacturing method according to any one of claims 1 to 10, wherein the electromagnetic waves are microwaves.

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