Method for producing hydrogen

Abstract

To provide a method for producing hydrogen by a simple method without requiring an insolubilizing auxiliary agent containing an inorganic compound.SOLUTION: The method for producing hydrogen according to the present disclosure is a method for producing hydrogen by reacting an aluminum alloy with an alkaline solution, wherein the alkaline solution contains a surfactant, and the surfactant is an insolubilizing agent that insolubilizes impurities contained in the aluminum alloy. This makes it possible to provide a method for producing hydrogen that does not require an insolubilizing agent containing an inorganic compound and can be carried out by a simple method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing hydrogen, and more particularly to a method for producing hydrogen by reacting an aluminum alloy with an alkaline aqueous solution. [Background technology]

[0002] Patent Document 1 discloses a method for producing hydrogen by reacting an aluminum alloy with an alkaline aqueous solution, in which an insolubilizing agent is added to insolubilize and remove components other than aluminum.

[0003] The insolubilization aid disclosed in Patent Document 1 is a compound containing one or more of CaSO4, CaCO3, CaCl2, Ca(OH)2, MgSO4, MgCl2, Mg(OH)2, FeSO4, FeCO3, FeCl2, and Fe(OH)2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-158693 Summary of the Invention [Problem to be solved by the invention]

[0005] The hydrogen production method disclosed in Patent Document 1 has the following problems.

[0006] In the case of inorganic compounds, the inorganic compounds themselves become impurities when added for the purpose of insolubilizing impurities. These inorganic compounds remain even after heating, and therefore require additional washing steps after the insolubilization step. This not only increases the workload but also generates a large amount of wastewater, such as washing water.

[0007] Aluminum hydroxide, which is generated simultaneously with hydrogen, can be used to make artificial marble, etc., which are used in white, so it is preferable to avoid the inclusion of iron, which may cause coloring. Therefore, it is not preferable to use an iron-based insolubilization aid.

[0008] Among the materials disclosed in Patent Document 1, the hydrochloride and sulfate salts are easy to use due to their high water solubility, but on the other hand, they are highly hygroscopic, and if these remain when aluminum hydroxide is used as a flame retardant for resin, the resin will absorb moisture. Furthermore, a major application of flame-retardant resins is wiring coating materials, and moisture absorption reduces the electrical insulation properties, making them unsuitable for these applications.

[0009] Carbonates with low water solubility cannot be dissolved to a concentration sufficient to provide a sufficient effect, and therefore, even if the resulting aluminum hydroxide is washed with water, it is difficult to dissolve and remove it.

[0010] Furthermore, there is no disclosure of the effect of these inorganic substances in improving the purity of the hydrogen produced.

[0011] The present disclosure has been made to solve such problems, and aims to provide a method for producing hydrogen that does not require an insolubilization aid containing an inorganic compound and can be carried out in a simple manner. [Means for solving the problem]

[0012] The present disclosure provides a method for producing hydrogen by reacting an aluminum alloy with an alkaline solution, the alkaline solution containing a surfactant, which is an insolubilizer that insolubilizes impurities contained in the aluminum alloy. This method does not require an insolubilizer containing an inorganic compound, and can provide a simple method for producing hydrogen.

[0013] The surfactant may be any one of an anionic surfactant, a cationic surfactant, and a nonionic surfactant, or a mixture thereof, thereby enabling efficient removal of metal impurities.

[0014] Furthermore, the surfactant and the solid matter consisting of the impurities may be removed from the alkaline solution, thereby increasing the purity of the sodium aluminate solution.

[0015] Furthermore, aluminum hydroxide may be precipitated by adding CO2 to the alkaline solution, which allows for the precipitation of high-purity aluminum hydroxide. [Effects of the Invention]

[0016] The present disclosure makes it possible to provide a method for producing hydrogen that does not require an insolubilizing agent containing an inorganic compound and that can be carried out in a simple manner. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flowchart of a method for producing hydrogen according to the present disclosure. [Figure 2] 1 is a graph showing the proportions of impurity elements contained in an aqueous aluminum hydroxide solution according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Figure 1 is a flowchart of a method for producing hydrogen according to the present disclosure.

[0019] First, aluminum material is prepared as a raw material (S101). The aluminum material used here can be aluminum alloy chips contained in waste materials.

[0020] Next, the aluminum material is added to the aqueous surfactant solution (S102). This step is preferably carried out using a dissolving device or the like.

[0021] The surfactant is an anionic surfactant, a cationic surfactant, a nonionic surfactant, or a mixture thereof. The use of a surfactant allows the aqueous solution to efficiently penetrate into the gaps between aluminum materials dispersed in the aqueous solution, replacing bubbles that form in the gaps between the aluminum materials with water, thereby improving hydrogen purity. As shown in the examples below, this effect is particularly pronounced with anionic surfactants.

[0022] Furthermore, aluminum alloy chips contained in aluminum materials are generated by cutting, and the surface of the tool used for cutting is coated with oil. Therefore, since the chips have oil components attached, impurities on the chip surface can be effectively removed by using a surfactant aqueous solution.

[0023] Sodium hydroxide (NaOH) is then added to the surfactant aqueous solution in which the aluminum material is dispersed (S103). This step can be performed by adding solid sodium hydroxide to the surfactant aqueous solution, or by adding an aqueous solution of sodium hydroxide to the surfactant aqueous solution. As a result, the aluminum material becomes sodium aluminate as shown in the following formula (1), and dissolves in the aqueous solution. At the same time, high-purity hydrogen is produced by this reaction and is recovered (S203). Al+NaOH+3H2O→Na[Al(OH)4]+3 / 2H2(1)

[0024] In the manufacturing method according to the present disclosure, the aluminum material is dissolved using an alkaline aqueous solution of sodium hydroxide, so that the concentration can be easily adjusted and handling is also easy.

[0025] Note that, as long as an alkaline solution exhibiting an appropriate pH can be prepared, other compounds may be used instead of sodium hydroxide, such as organic compounds such as amines, diamines, triamines, and tetraamines.

[0026] Although the above description cites an example of an aqueous solution in which the solvent is water, the present invention is not limited thereto, and subsequent steps may be carried out using an alkaline aluminate solution in which an alkaline compound is dissolved in an organic solvent. The use of an organic solvent can improve the drying properties of the solution. Furthermore, organic compounds such as the above-mentioned amines, diamines, triamines, and tetraamines are particularly preferred because of their high solubility in polar organic solvents.

[0027] Aluminum materials contain a large amount of impurities that are insoluble in aqueous sodium hydroxide solution, and these impurities precipitate as undissolved residue in the aqueous sodium hydroxide solution. Therefore, solid-liquid separation is performed to separate the undissolved residue from the aqueous solution (S104). This process can be performed using, for example, filter paper, a filter, or a centrifuge. The separated undissolved residue contains concentrated impurity elements, so it can be reused as a source of the detected impurity elements (S204). Organic matter derived from impurities and added surfactants can be removed by heating.

[0028] The aqueous solution obtained by solid-liquid separation is an aqueous solution containing sodium aluminate and a surfactant (S105). Thereafter, the sodium aluminate is reacted with an acidic substance, such as CO2 (carbon dioxide), to precipitate aluminum hydroxide, and the precipitate is dried to obtain high-purity aluminum hydroxide. This step is not limited to the reaction with an acidic substance, and other methods, such as hydrolysis, may also be used.

[0029] Furthermore, in the manufacturing method according to the present disclosure, a surfactant, which is an organic material, is used as the insolubilization aid, and therefore the surfactant can be decomposed and removed by the heat treatment in the drying step described above, and therefore the insolubilization aid is also excellent in terms of removability.

[0030] In this way, a method for producing hydrogen that does not require an insolubilizing agent containing an inorganic compound and can be performed simply and easily can be provided. Furthermore, by using the method for producing hydrogen according to the present disclosure, it is possible to obtain high-purity sodium aluminate and aluminum hydroxide. [Example]

[0031] The present disclosure will be explained below using examples, but is not limited to these.

[0032] The surfactants used in the surfactant aqueous solutions were: Example 1: nonionic surfactant, Example 2: cationic surfactant, and Example 3: anionic surfactant, each used at a concentration of 0.1 wt%. The nonionic surfactant was polyoxyethylene alkyl ether, the cationic surfactant was stearyltrimethylammonium chloride, and the anionic surfactant was linear sodium dodecylbenzene sulfonate (LAS). Details of each surfactant are shown in Table 1. [Table 1]

[0033] The aluminum material used was chips from ADC12 (a type of aluminum die-cast containing 1.5-3.5% Cu and 9.6-12% Si). For comparison, an aqueous solution without surfactant was also prepared. The NaOH concentration, NaOH solution volume, and Al / Na molar ratio were adjusted as shown in Table 2, and the hydrogen purity obtained from each sample was evaluated. The evaluation results of hydrogen purity are also shown in Table 2. [Table 2]

[0034] From the above results, it was found that hydrogen of particularly high purity was obtained in Example 3, in which an anionic surfactant was used.

[0035] 2 shows the proportions of impurity elements contained in the precipitates of Examples 1 to 3 and the Comparative Example after solid-liquid separation. The proportions of the impurity elements examined were Mg, Si, P, S, Cl, K, Sn, Ca, Cr, Mn, Fe, Ni, Cu, and Zn.

[0036] It was confirmed that the concentration of impurities was higher in Example 1 (nonionic surfactant) than in the comparative example. Therefore, it was shown that the addition of a nonionic surfactant has the effect of promoting the dissolution of impurities.

[0037] Example 2 (cationic surfactant) contained Cl as a counter ion, so the Cl concentration was high, and it was confirmed that it was specifically effective against Si compared to the comparative example. This suggests that the impurity Si was dissolved as sodium silicate (Na2SiO3) in the sodium aluminate aqueous solution containing the surfactant, and the cationic surfactant replaced Na, reducing its solubility.

[0038] Example 3 (anionic surfactant) showed a reduced concentration of impurities compared to the comparative example. Anionic surfactants are monovalent cation compounds such as sodium ions, potassium ions, and lithium ions. These cations can easily be substituted with other cations, resulting in polyvalent cations, significantly reducing the solubility of the anionic surfactant. In the production method disclosed herein, many elements other than aluminum become divalent or trivalent cations, and these impurities react with the anionic surfactant, reducing the solubility of the surfactant. Therefore, a solid composed of the anionic surfactant and impurities precipitates, and this solid can be easily removed by filtration.

[0039] The results of Examples 1 to 3 and Comparative Example show that adding a surfactant to an alkaline aqueous solution has the effect of suppressing the dissolution of impurities contained in the aluminum alloy in the alkaline aqueous solution. In particular, anionic surfactants have a remarkable effect of insolubilizing metal impurities.

[0040] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the present disclosure.

Claims

1. A method for producing hydrogen by reacting an aluminum alloy with an alkaline solution, comprising: the alkaline solution contains a surfactant, The surfactant is an insolubilization aid that insolubilizes impurities contained in the aluminum alloy. Methods for producing hydrogen.

2. The surfactant is any one of an anionic surfactant, a cationic surfactant, and a nonionic surfactant, or a mixture thereof. The method for producing hydrogen according to claim 1 .

3. and removing solid matter consisting of the surfactant and the impurities from the alkaline solution. The method for producing hydrogen according to claim 1 or 2.

4. Furthermore, CO ２ by adding aluminum hydroxide, The method for producing hydrogen according to claim 1 or 2.

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