KR101113748B1 - Preparation of Complex as a Hydrogen Storaging Material - Google Patents

Abstract

The present invention relates to a method for preparing a hydrogen storage complex, comprising: preparing an aqueous alkali boron hydride solution selected from any one of sodium borohydride, potassium borohydride and lithium borohydride; It provides a method for producing a stable hydrogen storage complex comprising a; reacting the aqueous solution and germanium oxide.

Germanium dioxide, sodium borohydride, hydrogen storage, hydrogen emission

Description

Preparation method of hydrogen storage complex {Preparation of Complex as a Hydrogen Storaging Material}

The present invention relates to a method for producing a hydrogen storage complex. More specifically, the hydrogen storage complex provides a method for producing a stable hydrogen storage complex by dissolving an alkali boron hydride in water, followed by mixing and reacting germanium oxide.

Germanium is a trace metal element belonging to group 4A (Group 14 according to IUPAC classification) together with C (non-metal), Si (metal), Sn (metal), and Pb (metal) on the periodic table. It is used in a variety of industries. Germanium is easily adsorbed to clay minerals, iron oxides and organics in the form of Ge (OH) ₄ to recrystallize. Germanium is +4 and +2 is present in the ^{_{cation, HGeO 2 -, HGeO 3 -}} , GeO 3 2 - also present in anionic form, such as a ^{-, 2} GeS. Germanium is mainly distributed in large quantities by the substitution between germanium and silica in silicate minerals, but non-silicates such as oxide minerals, hydroxide minerals, iron-nickel ores, minerals, sulfide minerals, sulfate minerals, halogen minerals, carbonate minerals, coal, pegmatite, etc. It is also present in minerals. In germanium, among the tetrahedral silicate minerals such as silicon, the minerals associated with relatively weak force such as fluorite and olivine are more easily substituted between silica and germanium than quartz and feldspar.

Hydrogen is a clean energy source with the advantages of high energy density, ease of energy conversion as well as no emissions of environmental pollutants during combustion. As such, the technology of producing, storing and converting hydrogen into electrical energy is important as a way for hydrogen to become a future energy source. For example, as a means of transportation, automobiles absolutely need hydrogen storage technology to safely and conveniently store large amounts of hydrogen to be mounted on automobiles in order to replace the fuel supply from oil to hydrogen. Currently, a method of storing hydrogen includes compressing hydrogen to a high pressure of 350 to 700 atm, or cooling to cryogenic temperature (below -253 ° C.) to make a liquid, but there is a problem in safety such as explosion risk. In addition, there is another method that does not need to worry about safety, such as a method of adsorbing hydrogen to the palladium (Pd) metal is a method of adsorption and storage of hydrogen to other solid materials.

A method of storing hydrogen in a solid state includes a storage method in which a hydrogen storage alloy made of a rare earth metal reacts reversibly with hydrogen to form a metal hydride. For example, titanium-iron alloy, lanthanum-nickel alloy, magnesium-nickel alloy and the like may store hydrogen at 20 to 40 atmospheres at room temperature. However, the hydrogen storage alloy is heavy and expensive, and there is a problem of deterioration of performance due to poisoning and micronization.

Another method of hydrogen storage is to use a carbon material such as carbon nanotubes having a large surface area for inducing hydrogen adsorption or a porous material such as a metal-organic skeleton structure. However, the method using the porous material has a disadvantage in that the adsorption energy of hydrogen is small in storing hydrogen at room temperature. In particular, carbon nanotubes have a large variation in hydrogen storage rate due to length and diameter, the number of carbon walls constituting the tube, purity, crystal phase, etc., and it is difficult to secure a reproducible storage rate. In addition, the metal-organic skeleton structure is heavy and the hydrogen storage rate is lower than the theory because the metal cluster occupies most of the weight and is present as a cluster in the oxidized state of the metal.

Recently, a hydrogen storage method using a hydrogen complex (dihydrogen complex) called Kubas complex has been known. The hydrogen complex does not dissociate the hydrogen molecules to bond to the central metal, but as the bond length between hydrogen and hydrogen (H-H) increases, the hydrogen complex is coordinated in the form of hydrogen molecules to the central metal, thereby storing and releasing hydrogen. Using this property, the possibility of storing hydrogen in the form of the hydrogen complex by dispersing the transition metal in the polymer matrix on an atomic basis has been suggested. However, since the hydrogen complexes aggregate with each other, it is difficult to disperse the transition metals in the polymer matrix on an atomic basis and thus cannot achieve the expected hydrogen storage rate.

Another hydrogen storage method is a method of doping an alkali metal or alkaline earth metal to a carbon material such as fullerene, there is a problem that the hydrogen storage rate is lower than the same volume because the doping amount of the alkali metal or alkaline earth metal is limited.

Accordingly, the present invention provides a method for preparing a stable hydrogen storage complex by dissolving alkali boron hydride, which is an unstable hydrogen storage body, in water and then reacting by mixing germanium oxide.

More specifically, an object of the present invention is to provide a very stable hydrogen storage complex by forming a complex by adding germanium dioxide (GeO ₂ ) to an aqueous alkali boron hydride solution. In addition, an object of the present invention is to be able to confirm the formation of the complex at the same time as the hydrogen emission by the color change according to the reaction.

Hydrogen storage complex for solving the above technical problem is to dissolve the alkali boron hydride in water to make an alkaline boron hydride aqueous solution. Next, germanium dioxide (GeO ₂ ) is added to the germanium and boron reacts to form a combined complex to produce a stable hydrogen storage complex.

The alkali boron hydride is preferably selected from any one of sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), lithium borohydride (LiBH ₄ ).

The content of germanium oxide includes 58 to 85% by weight.

The complex in which the germanium and boron react to each other may further include a step of centrifuging and washing.

It provides a hydrogen storage complex prepared by the above production method.

The hydrogen storage complex includes a sodium borohydride-germanium dioxide complex.

Hereinafter, the present invention will be described in more detail.

Alkaline boron hydride selected from sodium borohydride (NaBH ₄ ), potassium borohydride (KBH ₄ ), lithium borohydride (LiBH ₄ ) is easily dissolved in water at room temperature, but gradually Occurs. At this time, when the catalyst in the metal itself or metal salt state is added, hydrogen is decomposed very rapidly. To this, by adding and reacting germanium dioxide (GeO ₂ ), which is a stable germanium oxide in the air, a complex is formed to form a very stable hydrogen storage body.

Germanium dioxide (GeO ₂ ) does not dissolve in water and exists as a float. However, when reacted with sodium borohydride (NaBH ₄ ) aqueous solution, it turns yellow and rapidly forms a reddish brown complex. The reaction can be confirmed by changing the color of the complex is formed, it can also be confirmed that the hydrogen is released.

More specifically, the reaction between the aqueous solution of boron hydride and germanium dioxide can be confirmed by the change in color. That is, the color changes to yellow as the complexes in which hydrogen is bridged are made, and yellow means that the complexes in which hydrogen is bridged are few. Thereafter, the color of the reaction is changed to reddish brown, which means that many complexes in which hydrogen is bridged. This color change can be visually confirmed by acting as an indicator for the release of hydrogen, it is easy to recognize the danger when using the colorless odorless hydrogen, thereby enabling the safe use of hydrogen.

In addition, since the reaction is expressed in color at the same time the complex is formed over time, it is possible to control the amount of hydrogen over time by the color as a measure.

The germanium dioxide (GeO ₂ ) is supported by reacting in the aqueous solution of boron hydride while changing the content. The content is preferably 58 to 85% by weight, more preferably 68 to 78% by weight. If the content is less than 58% by weight, the color change is slow and it is difficult to obtain a hydrogen-containing complete bridged complex, and if it is more than 85% by weight, the color change is so fast that it is difficult to observe intermediate changes.

The germanium boron complex in which the reaction is terminated is washed with distilled water. The cleaning method is preferably using a centrifuge, it is preferably carried out for 10 to 30 minutes at 6000 to 10000 rpm.

The hydrogen storage complex prepared by the above method is dried for 12 to 24 hours in a vacuum oven at 50 ℃ to 100 ℃.

In the hydrogen storage complex according to the present invention, by mixing germanium oxide in an aqueous solution of borohydride, the rapid exothermic reaction due to unstable reaction can be suppressed and stable, so hydrogen storage is easy.

In addition, the hydrogen storage complex can confirm the hydrogen storage and release by the color change can serve as an indicator. This can solve the safety problem by detecting the risk of the release of colorless odorless pyrophoric hydrogen gas as color change.

In addition, since the color change in the reaction to form the complex indicates the degree of the germanium oxide is bonded with hydrogen, the amount of hydrogen can be controlled over time according to the color change.

Hereinafter, the present invention will be described by way of example for specific description of the present invention, but the present invention is not limited to the following examples.

Example 1

0.18 g (4.78 mmol) of sodium borohydride (NaBH ₄ ) was dissolved in 30 mL of distilled water to prepare an aqueous sodium borohydride solution, and 0.5 g (4.78 mmol) of germanium dioxide (GeO ₂ ) was added thereto and stirred. To react for 4 hours. The reaction solution turned yellow and gradually turned reddish brown, indicating that the reaction was completed. After completing the reaction, the germanium boron complex was centrifuged at 8000 rpm for 20 minutes and purified three times with 10 mL of distilled water. The complex obtained by purification is dried at 50 ° C. in a vacuum oven for 12 hours to remove moisture.

[Example 2]

0.26 g (4.78 mmol) of potassium borohydride (KBH ₄ ) was dissolved in 30 mL of distilled water to prepare an aqueous potassium borohydride solution, and 0.5 g (4.78 mmol) of germanium dioxide (GeO ₂ ) was added thereto and stirred. To react for 4 hours. The reaction solution turned yellow and gradually turned reddish brown, indicating that the reaction was completed. After completing the reaction, the germanium boron complex was centrifuged at 8000 rpm for 20 minutes and purified three times with 10 mL of distilled water. The complex obtained by purification is dried at 50 ° C. in a vacuum oven for 12 hours to remove moisture.

Example 3

Lithium borohydride (LiBH ₄ ) 0.11 g (4.78 mmol) was dissolved in 30 mL of distilled water to prepare a lithium borohydride aqueous solution, and 0.5 g (4.78 mmol) of germanium dioxide (GeO ₂ ) was added thereto and stirred. To react for 4 hours. The reaction solution turned yellow and gradually turned reddish brown, indicating that the reaction was completed. After completing the reaction, the germanium boron complex was centrifuged at 8000 rpm for 20 minutes and purified three times with 10 mL of distilled water. The complex obtained by purification is dried at 50 ° C. in a vacuum oven for 12 hours to remove moisture.

In order to examine the hydrogen emission of the complex prepared by the present invention, the reaction with the metal compound was carried out as in Example 4.

Example 4

0.238 g (0.956 mmol) of Ni (C ₂ H ₃ O) ₂ 4H ₂ O was added to 6 mL of distilled water, followed by stirring to form an aqueous nickel acetate tetrahydrate solution. 0.013 g of sodium borohydride-germanium dioxide complex is added to the aqueous solution, followed by stirring. The reaction solution gradually turns black, and this color change is due to the release of hydrogen as the metal is reduced. Therefore, it was found that the sodium borohydride-germanium dioxide complex prepared according to the present invention can regenerate hydrogen if necessary by contacting with a metal catalyst component as a hydrogen storage medium.

[evaluation]

The germanium boron complexes prepared in the examples of the present invention were characterized by the methods described below.

X-ray diffraction patterns were measured with a D / MAX Ultima III X-ray diffractometer (Rigaku) to confirm the structure and crystallinity of the germanium boron complex. As shown in FIG. 1, as a result of XRD analysis, it was confirmed that a clear crystalline peak was not detected in the XRD spectrum, thereby forming a germanium boron complex having an amorphous structure. The peak of the germanium boron complex structure of the amorphous structure was formed at 2θ values of 25 to 32 ° and 45 to 55 ° and detected by a broadly distributed curve.

The particle size and shape of the powder were observed by scanning electron microscopy (SEM: scanning electron microscopy, JSM-7500F). As can be seen in Figure 2, the germanium boron complex particles could be confirmed that the sphere of a relatively uniform size, the size of the particles was found to be 20 ~ 30 nm.

3 and 4 respectively analyze the solid state ¹ H NMR and ¹¹ B NMR of the germanium boron complex using a 400 MHz Solid-State NMR Spectrometer (Avance 400, Bruker). This is a solid state NMR measurement to determine the presence of hydrogen (H) and boron (B) in the intermediate (germanium boron complex) formed by the reaction between NaBH ₄ aqueous solution and GeO ₂ , and peaks at 4.18 ppm in ¹ H NMR. In ¹¹ B NMR, a peak was found at 1.55 ppm. This confirmed that hydrogen and boron were bonded to the intermediate.

5 is a TGA analysis of the germanium boron complex, TGA-50A (Shimadzu, Japan) was used, it was measured to 900 ℃ at a rate of 10 ℃ / min under nitrogen atmosphere. As a result, the complex had a weight loss of only 5% up to 300 ° C., and a constant weight loss up to 550 ° C. followed by a 15% reduction at 900 ° C. This confirmed that the complex is very stable up to 550 ℃. Therefore, the germanium boron complex prepared by the present invention is stable up to 550 ℃ it can be used at high temperatures when actually used. In addition, there is no possibility of explosion at high temperatures, the range of use can be extended.

FIG. 6 is a DSC of the germanium boron complex, which was used as DSC-60A (Shimadzu, Japan), and measured at 500 ° C. at a rate of 10 ° C./min under a nitrogen atmosphere. As a result, it was confirmed that the crystallization temperature is 238.6 ℃.

1 shows the XRD of the germanium boron complex prepared according to the present invention,

Figure 2 shows an electron micrograph of the germanium boron complex prepared according to the present invention,

Figure 3 shows a solid state ¹ H NMR of the germanium boron complex prepared according to the present invention,

Figure 4 shows a solid state ¹¹ B NMR of the germanium boron complex prepared according to the present invention,

5 shows the TGA of the germanium boron complex prepared according to the present invention,

Figure 6 shows the DSC of the germanium boron complex prepared according to the present invention.

Claims (6)

a) preparing an aqueous alkaline boron hydride solution; b) reacting the germanium oxide in an amount of 58 to 85% by weight in the aqueous solution. The method of claim 1, The alkaline boron hydride aqueous solution is a method of producing a hydrogen storage complex is at least one component selected from any one of sodium borohydride, potassium borohydride, lithium borohydride. delete The method of claim 1, After the step b), further comprising the step of centrifugation and washing. Hydrogen storage complex prepared by the method of any one of claims 1, 2 or 4. The method of claim 5, Wherein said hydrogen storage complex is a sodium borohydride-germanium dioxide complex.

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