Method for regenerating sodium borohydride

Abstract

The invention relates to a method for regenerating sodium borohydride, which comprises the following steps: pretreating reactants, which comprise sodium tetraborate hydrate (Na2B4O7. XH2O, 0lt; x < = 10), a metal salt and a reducing agent; and the pretreated reactants are subjected to a reaction through a ball milling method, wherein the metal salt comprises NaHCO2, KHCO2, LiHCO2, NaHCO3, Na2CO3, NaOH, KHCO3, K2CO3, LiHCO3, Li2CO3, Na2O2, NaH or a combination of the NaHCO2, KHCO2, LiHCO2, NaHCO3, NaHCO3, Na2CO3, NaOH, KHCO3, K2CO3, LiHCO3, Li2CO3, Na2O2 and NaH.

Description

Cross - Reference to Related Applications

[0001] This application claims the priority and benefit of Korean Patent Application No. 10 - 2023 - 0127014, filed with the Korean Intellectual Property Office on September 22, 2023, the entire content of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention discloses a method for regenerating sodium borohydride. Background Art

[0003] In order to use sodium borohydride (SBH) as a hydrogen storage material for hydrogen extraction, regeneration and production are crucial.

[0004] To reduce the boron complex, the product of the sodium borohydride hydrolysis reaction, conventional SBH regeneration methods require harsh conditions of high pressure and high temperature.

[0005] Recently, the ball - milling method has been proposed to alleviate these harsh conditions. However, this method uses very expensive materials such as sodium hydride (NaH) for reduction and has limitations in low yield.

[0006] The statements in this section merely provide background information related to the present invention and do not constitute prior art. Summary of the Invention

[0007] Embodiments provide a method for regenerating sodium borohydride (NaBH 4 ), which can reduce the cost of sodium borohydride, has a high regeneration rate, and increases the convenience of regeneration.

[0008] According to one embodiment, the method for regenerating sodium borohydride includes pre - treating reactants, the reactants including sodium tetraborate hydrate (Na 2 B 4 O 7 ·xH 2 O, 0 < x ≤ 10), a metal salt, and a reducing agent; and reacting the pre - treated reactants by a ball - milling method, wherein the metal salt includes sodium formate (NaHCO 2 ), potassium formate (KHCO 2 ), lithium formate (LiHCO 2 ), sodium bicarbonate (NaHCO 3 ), sodium carbonate (Na 2 CO 3 ), sodium hydroxide (NaOH), potassium bicarbonate (KHCO 3 ), potassium carbonate (K 2 CO 3), lithium bicarbonate (LiHCO 3 )、Lithium carbonate (Li 2 CO 3 ), sodium peroxide (Na 2 O 2 ), sodium hydride (NaH), or a combination thereof.

[0009] Sodium tetraborate hydrate can be sodium borohydride (NaBH 4 ) products of hydrolysis reactions.

[0010] The metal salt may include NaHCO 2 , the NaHCO 2 It can be sodium borohydride (NaBH 4 )'s hydrolysis reaction product.

[0011] Sodium borohydride (NaBH 4 ) can be carried out in the presence of an acid catalyst.

[0012] The reducing agent may include metal magnesium (Mg), silicon (Si), aluminum (Al), sodium aluminum hydride (NaAlH 4 ), magnesium-containing alloys or combinations thereof.

[0013] The reactants may include sodium tetraborate hydrate, a metal salt, and a reducing agent in a molar ratio ranging from 1:0.5:10 to 1:4:40.

[0014] In the reactants, the molar ratio of the metal salt to the sodium tetraborate hydrate may be in the range of 0.5: 1 to 4: 1. In addition, in the reactants, the molar ratio of the reducing agent to the sodium tetraborate hydrate may be in the range of 10: 1 to 40: 1.

[0015] Pretreatment may include a dehydration process.

[0016] The dehydration process may be performed at a temperature ranging from 0° C. to 300° C. and a pressure ranging from 0.01 atmospheres to 3 atmospheres.

[0017] The dehydration process can be carried out in argon (Ar), nitrogen (N 2 ), air, hydrogen (H 2 ) or a combination thereof.

[0018] The ball milling method may be performed at a rotation speed ranging from 450 rpm to 1200 rpm for 2 hours to 36 hours.

[0019] The ball milling method can be carried out at an initial H range of 5 bar to 70 bar. 2 Under pressure 。

[0020] Sodium borohydride can be used to extract hydrogen through a hydrolysis reaction.

[0021] The regeneration rate of sodium borohydride by this regeneration method can be 50% or more.

[0022] The method for regenerating sodium borohydride according to one embodiment can reduce the cost of sodium borohydride, improve the regeneration rate and increase the convenience of regeneration. Therefore, sodium borohydride can be effectively used to extract hydrogen through a hydrolysis reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a graph showing the analysis results of a hydrolysis reaction product of sodium borohydride, which is used as a reactant in the method for regenerating sodium borohydride according to Example 2, using an X-ray diffraction (XRD) method.

[0024] Figure 2 1 is a diagram showing the analysis results of a hydrolysis reaction product of sodium borohydride using Fourier transform infrared spectroscopy (FT-IR), wherein the hydrolysis reaction product of sodium borohydride is used as a reactant in the method for regenerating sodium borohydride according to Example 2.

[0025] Figure 3 It is shown that the use 13 A graph showing the results of C NMR analysis of a hydrolysis reaction product of sodium borohydride, wherein the hydrolysis reaction product of sodium borohydride is used as a reactant in the method for regenerating sodium borohydride according to Example 2.

[0026] Figure 4 A graph showing the regeneration rate of sodium borohydride according to the method of regenerating sodium borohydride according to Examples 1 and 2 and Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0027] The advantages, features and aspects to be described below become apparent through the following description of the embodiments with reference to the accompanying drawings presented below. However, the embodiments should not be construed as being limited to the embodiments set forth herein. Although not specifically defined, all terms used in the present invention, including technical and scientific terms, have meanings understood by those of ordinary skill in the art. Unless explicitly defined, terms defined in general dictionaries shall not be interpreted ideally or exaggeratedly. In addition, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising" shall be understood to include the elements but not exclude any other elements.

[0028] In addition, unless otherwise specified, the singular includes the plural.

[0029] An embodiment provides a method for the regeneration of sodium borohydride.

[0030] Sodium borohydride (NaBH 4 ) is used to extract hydrogen through a hydrolysis reaction, and the regeneration using the hydrolysis reaction products is very important for the practical application of hydrogen extraction technology.

[0031] For example, the hydrolysis reaction for hydrogen extraction using sodium borohydride is shown in Reaction Scheme 1. [Reaction Scheme 1] NaBH 4 +0.5HCOOH+(3.5)H 2 O→0.5NaHCO 2 +0.25(Na 2 B 4 O 7 ·5H 2 O)+4H 2 +0.5H 2 O

[0032] Referring to Reaction Scheme 1, the hydrolysis reaction of sodium borohydride using an acid catalyst can have products such as sodium tetraborate pentahydrate and NaHCO 2 . Reaction Scheme 1 only shows examples of the products of the hydrolysis reaction of sodium borohydride using an acid catalyst, but the products of the hydrolysis reaction of sodium borohydride according to the embodiment are not limited to the products of Reaction Scheme 1.

[0033] The acid catalyst may include formic acid, but is not limited thereto.

[0034] An embodiment provides a method for regenerating sodium borohydride using the hydrolysis reaction products of sodium borohydride (specifically, the products of the hydrolysis reaction of sodium borohydride using an acid catalyst).

[0035] The method for regenerating sodium borohydride according to an embodiment includes pretreating reactants including sodium tetraborate hydrate (Na 2 B 4 O 7 ·xH 2 O, 0 < x ≤ 10), a metal salt, and a reducing agent. The method further includes reacting the pretreated reactants by ball milling. In certain embodiments, the metal salt may include sodium formate (NaHCO 2 ), potassium formate (KHCO 2 ), lithium formate (LiHCO 2 ), sodium bicarbonate (NaHCO 3 ), sodium carbonate (Na2 CO 3 ), sodium hydroxide (NaOH), potassium bicarbonate (KHCO 3 ), potassium carbonate (K 2 CO 3 ), lithium bicarbonate (LiHCO 3 )、Lithium carbonate (Li 2 CO 3 ), sodium peroxide (Na 2 O 2 ), sodium hydride (NaH), or a combination thereof.

[0036] The method of regenerating sodium borohydride can advantageously reduce the cost of sodium borohydride, improve the regeneration rate and increase the convenience of regeneration. Since the sodium borohydride can be effectively used to extract hydrogen through a hydrolysis reaction, it can contribute to the development of hydrogen extraction technology or hydrogen storage technology using sodium borohydride.

[0037] Specifically, the metal salt may include NaHCO 2 , KHCO 2 、LiHCO 2 、NaHCO 3 、Na 2 CO 3 , NaOH, KHCO 3 , K 2 CO 3 、LiHCO 3 , Li 2 CO 3 、Na 2 O 2 , NaH or a combination thereof. Among these metal salts, in certain embodiments, NaHCO 2 、Na 2 CO 3 , NaOH, Na 2 O 2 , NaH or a combination thereof. In a specific embodiment, NaHCO 2 .

[0038] The metal salt may be added as an additive to react with the hydrolysis reaction product of sodium tetraborate hydrate or sodium borohydride. Alternatively, in certain embodiments, because the metal salt (e.g., NaHCO 2 ) is also a product of the sodium borohydride hydrolysis reaction used for hydrogen extraction, so the product of the hydrolysis reaction can be used directly for regeneration without adding a separate additive.

[0039] According to one embodiment, NaHCO is used 2Inexpensive materials such as NaHCO can be used to regenerate sodium borohydride instead of expensive materials such as NaH, thereby reducing the price of sodium borohydride. 2 When a metal salt such as sodium borohydride is used as a cheap material, a high regeneration rate can be ensured by a simple pretreatment before the reactants are reacted. In addition, even when the hydrolysis reaction product of sodium borohydride is directly used to regenerate sodium borohydride, the regeneration can be more conveniently achieved without the need to separately separate and purify the compound because an extremely high regeneration rate is ensured by pretreatment.

[0040] Reducing agents may include metals such as Mg, Si, Al, NaAlH 4 , Mg-containing alloys or a combination thereof.

[0041] The reactants may include sodium tetraborate hydrate, a metal salt, and a reducing agent in a molar ratio ranging from 1:0.5:10 to 1:4:40 or 1:1:20 to 1:3:30. When the reactants have a composition ratio within this range, a high regeneration rate may be ensured.

[0042] The molar ratio of the metal salt to the sodium tetraborate hydrate may be in the range of 0.5: 1 to 4: 1, in the range of 1: 1 to 3: 1, or in the range of 2: 1 to 3: 1. In addition, the molar ratio of the reducing agent to the sodium tetraborate hydrate may be in the range of 10: 1 to 40: 1, in the range of 20: 1 to 30: 1, or in the range of 20: 1 to 27: 1. When the two components of the reactants have respective molar ratios within this range, a high regeneration rate may be ensured.

[0043] The pretreatment of the reactants may include a dehydration process. The dehydration process is a process for dehydrating the reactants, especially sodium tetraborate hydrate.

[0044] When pretreatment is performed before the reaction by ball milling, a high regeneration rate can be ensured even if a cheap material is used as the metal salt. In addition, when the product after the sodium borohydride hydrolysis reaction is directly used as the metal salt for the regeneration reaction, an extremely high regeneration rate can be ensured by the pretreatment.

[0045] Specifically, the dehydration process may be performed at a temperature in the range of 0°C to 300°C or in the range of 100°C to 200°C, and at a pressure in the range of 0.01 atmosphere to 3 atmospheres or in the range of 0.01 atmosphere to 1 atmosphere. 2 , air, H 2 When the dehydration process is carried out within this condition range, a high regeneration rate can be ensured.

[0046] The ball milling method is to grind zirconium dioxide (ZrO 2), iron (Fe), etc. are mixed with the reactants, namely sodium tetraborate hydrate, metal salt and reducing agent.

[0047] The ball milling method can be carried out at a rotation speed in the range of 450 rpm to 1200 rpm or in the range of 600 rpm to 1100 rpm for 2 hours to 36 hours or 4 hours to 30 hours. In addition, the method can be carried out at an initial H in the range of 5 bar to 70 bar or in the range of 10 bar to 50 bar. 2 When the ball milling process is carried out within the conditions, a high regeneration rate can be ensured.

[0048] The method for regenerating sodium borohydride according to one embodiment can achieve a sodium borohydride regeneration rate greater than or equal to 50%, or greater than or equal to 60%. In addition, when the hydrolysis reaction product of sodium borohydride (e.g., sodium tetraborate hydrate and metal salts such as NaHCO) is directly used, 2 When sodium borohydride is regenerated using an acid catalyst (such as 2-nitrogen, ...

[0049] Therefore, the method of regenerating sodium borohydride according to one embodiment can reduce the price of sodium borohydride and ensure a high regeneration rate thereof, and the sodium borohydride can be effectively used to extract hydrogen through a hydrolysis reaction.

[0050] The embodiments will be described in more detail below with reference to examples. However, these examples are exemplary, and the scope of the claims is not limited thereto. Method for regenerating sodium borohydride Example 1

[0051] NaHCO 2 (99%, Sigma Aldrich) and Mg were added as sodium borohydride (NaBH 4 ) is a hydrolysis product of sodium tetraborate decahydrate (Na 2 B 4 O 7 10H 2 O) to prepare the reactants, and then a dehydration process was performed at 170°C and 1 atmosphere. Here, the reactants were prepared by using sodium tetraborate decahydrate, NaHCO 2 and Mg.

[0052] Subsequently, the dehydrated reactants were reacted by ball milling to regenerate sodium borohydride. Here, the ball milling was carried out at room temperature and an initial H pressure of 20 bar. 2 The cycle was carried out at 450 rpm for 12 hours under pressure. Example 2

[0053] Mg is added to the sodium borohydride (NaBH) 4 ) hydrolysis reaction products are sodium tetraborate pentahydrate (Na 2 B 4 O 7 ·5H 2 O) and NaHCO 2 The reactants were prepared by using sodium borate pentahydrate, NaHCO in a molar ratio of 1:2:22.5. 2 and Mg.

[0054] Subsequently, the dehydrated reactants were reacted by ball milling to regenerate sodium borohydride. Here, the ball milling was carried out at room temperature and an initial H pressure of 20 bar. 2 The cycle was carried out at 450 rpm for 12 hours under pressure. Comparative Example 1

[0055] NaH and Mg were added as sodium borohydride (NaBH 4 ) is a hydrolysis product of sodium tetraborate decahydrate (Na 2 B 4 O 7 10H 2 O) to prepare a reactant. Here, the reactant is prepared by using sodium tetraborate decahydrate, NaH and Mg in a molar ratio of 1:2:22.5.

[0056] The reactants were then subjected to a ball milling process to regenerate sodium borohydride. The ball milling process was carried out at room temperature and an initial H pressure of 20 bar. 2 The cycle was carried out at 450 rpm for 12 hours under pressure. Comparative Example 2

[0057] Sodium borohydride was regenerated in the same manner as in Comparative Example 1, except that a dehydration process was additionally performed at 170° C. and a pressure of 1 atmosphere before the reactant of Comparative Example 1 was reacted by a ball milling method. Comparative Example 3

[0058] Sodium borohydride was regenerated in the same manner as in Example 1, except that the dehydration process was omitted. Comparative Example 4

[0059] Sodium borohydride was regenerated in the same manner as in Example 2, except that the dehydration process was omitted. Review 1: NaBH 4 Analysis of hydrolysis reaction products

[0060] In Example 2, sodium borohydride (NaBH 4 ) is used as a reactant. Here, sodium borohydride (NaBH 4 ) is shown in Reaction Scheme 1. [Reaction Scheme 1] NaBH 4 +0.5HCOOH+(3.5)H 2 O→0.5NaHCO 2 +0.25(Na 2 B 4 O 7 ·5H 2 O)+4H 2 +0.5H 2 O

[0061] Here, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and 13 C NMR analysis of the product after sodium borohydride hydrolysis reaction showed that Figures 1 to 3 shown.

[0062] Figure 1 is a graph showing the analysis results of a hydrolysis reaction product of sodium borohydride, which is used as a reactant in the method for regenerating sodium borohydride according to Example 2, using an X-ray diffraction (XRD) method.

[0063] Figure 2 is a graph showing the analysis results of a hydrolysis reaction product of sodium borohydride, which is used as a reactant in the method for regenerating sodium borohydride according to Example 2, using Fourier transform infrared spectroscopy (FT-IR).

[0064] Figure 3 It is shown that the use 13 A graph showing the results of C NMR analysis of a hydrolysis reaction product of sodium borohydride, wherein the hydrolysis reaction product of sodium borohydride is used as a reactant in the method for regenerating sodium borohydride according to Example 2.

[0065] Reference Figures 1 to 3 The hydrolysis product of sodium borohydride is sodium tetraborate pentahydrate (Na 2 B 4 O 7 ·5H 2 O) and NaHCO 2 . Review 2: NaBH 4 The regeneration rate

[0066] The regeneration rates of sodium borohydride (SBH) regenerated according to Examples 1 and 2 and Comparative Examples 1 to 4 were measured, and the results are shown in Figure 4 .

[0067] When the regeneration reaction was completed, 300 mg of each product was collected in a glove box and dissolved in 1 ml of 5 wt % KOH solution and 0.2 ml of D 2 O. Measured by 11B NMR spectroscopy with NaBH 4 The regeneration rate was obtained by the degree to which the corresponding peak -40 ppm was converted to the borate peak.

[0068] SBH yield (%) = {(area corresponding to SBH) / (area corresponding to total boron)}×100

[0069] Figure 4 A graph showing sodium borohydride regeneration rates according to the sodium borohydride regeneration methods according to Examples 1 and 2 and Comparative Examples 1 to 4.

[0070] Reference Figure 4 , compared with Comparative Examples 1 and 2 using expensive NaH and NaHCO 2 Compared with Comparative Examples 3 and 4, which were not pretreated but used as metal salts, NaHCO 2 Examples 1 and 2 as metal salts and pre-treated showed significantly high sodium borohydride regeneration rates. 2 When metal salts are used as an alternative to expensive NaH materials and also pretreated, a higher regeneration rate is ensured.

[0071] In addition, the hydrolysis product NaHCO 2 Compared with Example 1, direct use of NaHCO as an additive 2 Example 2 of shows a much higher sodium borohydride regeneration rate. Therefore, when the product itself of the sodium borohydride hydrolysis reaction using an acid catalyst is used, sodium borohydride is regenerated with a high yield.

[0072] While the invention has been described in conjunction with what are presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for regenerating sodium borohydride, the method comprising: Pre-treating reactants, the reactants comprising sodium tetraborate hydrate Na2B4O7·xH2O, a metal salt, and a reducing agent, where 0 < x ≤ 10; and Reacting the pre-treated reactants by ball milling to regenerate sodium borohydride, where the metal salt comprises NaHCO2, KHCO2, LiHCO2, NaHCO3, Na2CO3, NaOH, KHCO3, K2CO3, LiHCO3, Li2CO3, Na2O2, NaH, or a combination thereof.

2. The method according to claim 1, wherein the sodium tetraborate hydrate is a product of the hydrolysis reaction of sodium borohydride (NaBH4).

3. The method according to claim 2, wherein the hydrolysis reaction of sodium borohydride (NaBH4) is carried out under an acid catalyst.

4. The method according to claim 1, wherein the metal salt comprises NaHCO2, and where the NaHCO2 is a product of the hydrolysis reaction of sodium borohydride (NaBH4).

5. The method according to claim 4, wherein the hydrolysis reaction of sodium borohydride (NaBH4) is carried out under an acid catalyst.

6. The method according to claim 1, wherein the reducing agent comprises Mg, Si, Al, NaAlH4, a Mg-containing alloy, or a combination thereof.

7. The method according to claim 1, wherein the reactants comprise sodium tetraborate hydrate, metal salt, and reducing agent in a molar ratio in the range of 1:0.5:10 to 1:4:

40.

8. The method according to claim 1, wherein the molar ratio of the metal salt to the sodium tetraborate hydrate in the reactants ranges from 0.5:1 to 4:1, and where the molar ratio of the reducing agent to the sodium tetraborate hydrate in the reactants ranges from 10:1 to 40:

1.

9. The method according to claim 1, wherein the pre-treatment comprises a dehydration process.

10. The method according to claim 9, wherein the dehydration process is carried out in a temperature range of 0°C to 300°C and a pressure range of 0.01 atmospheres to 3 atmospheres.

11. The method according to claim 9, wherein the dehydration process is carried out in an atmosphere comprising Ar, N2, air, H2, or a combination thereof.

12. The method according to claim 1, wherein the ball milling is carried out at a rotational speed in the range of 450 revolutions per minute to 1200 revolutions per minute for 2 hours to 36 hours.

13. The method according to claim 1, wherein the ball milling is carried out at an initial H2 pressure in the range of 5 bar to 70 bar.

14. The method according to claim 1, wherein the sodium borohydride is used to extract hydrogen by hydrolysis reaction.

15. The method according to claim 1, wherein the regeneration rate of the sodium borohydride is more than 50%.

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