A method for regenerating lithium borohydride from an aluminum-based material

Abstract

This invention discloses a method for regenerating lithium borohydride using aluminum-based materials. The method involves simultaneously adding rare-earth-aluminum intermetallic compounds and lithium oxide, followed by solid-phase ball milling of aluminum and lithium metaborate dihydrate in a ball mill jar under non-oxidizing atmosphere or vacuum conditions to regenerate lithium borohydride. The addition of rare-earth-aluminum intermetallic compounds and lithium oxide additives improves ball milling efficiency, removes the aluminum oxide passivation layer, improves positive and negative hydrogen conversion, promotes lithium borohydride formation, and increases the yield of lithium borohydride. The rare-earth-aluminum intermetallic compound additives include inexpensive Al2Ce, Al3Ce, and Al... 11 One or more of Ce3, Al2La, and Al3La. This invention has the advantages of simple process, low cost, and easy industrialization.

Description

Technical Field

[0001] This invention relates to the field of irreversible hydrogen storage material regeneration, specifically to a method for regenerating lithium borohydride from aluminum-based materials. Background Technology

[0002] If the challenges of efficient and safe hydrogen production, storage, transportation, and fuel cell conversion can be overcome, hydrogen has the potential to meet future energy needs in a zero-carbon and zero-pollution manner. Hydrogen storage is particularly advantageous due to its easy diffusion and ultra-low density under standard conditions. Compared to the reversible storage of complex coordination hydrides, irreversible hydrogen storage, especially lithium borohydride hydrolysis, has inherent advantages such as high hydrogen release capacity, fast hydrogen production rate, mild operating conditions, and high safety. The hydrolysis of lithium borohydride proceeds as follows:

[0003] LiBH4 + (2+x)H2O → LiBO2·xH2O + 4H2 (1)

[0004] The reaction is irreversible, meaning the hydrolysis byproducts cannot be regenerated through direct hydrogenation. Currently, the industrial method for preparing lithium borohydride involves reflux heating lithium halides (such as lithium chloride) and sodium borohydride in diethyl ether or isopropylamine. However, the cost of lithium borohydride synthesized by this method is too high, limiting its practical application in hydrogen production via hydrolysis. Therefore, there is an urgent need to develop a method for regenerating lithium borohydride from its hydrolysis byproducts (LiBO2·xH2O).

[0005] Previously, lithium borohydride regeneration was based on converting the BO bonds in LiBO₂·xH₂O into BH bonds. However, the high energy barrier between BO bond breaking and BH bond formation meant the reaction typically required expensive strong reducing agents (such as magnesium hydride). Regenerating lithium borohydride by ball milling magnesium hydride and anhydrous lithium metaborate yields high regeneration rates. It is worth noting that the true hydrolysis product of lithium borohydride is hydrated lithium metaborate (LiBO₂·xH₂O) or an aqueous solution of lithium metaborate. The above method requires dehydration of hydrated lithium metaborate at temperatures above 470°C before regeneration, leading to high energy consumption and increased costs.

[0006] Patent CN108285131A discloses a method for preparing lithium borohydride using room-temperature solid-phase ball milling. LiBO₂·2H₂O is directly ball-milled with magnesium hydride under an argon atmosphere, successfully regenerating lithium borohydride. However, the presence of water of crystallization necessitates the consumption of expensive magnesium hydride, requiring twice the amount compared to using anhydrous lithium metaborate. To reduce costs, cheaper magnesium is used instead of magnesium hydride under similar conditions, reacting with LiBO₂·2H₂O, but the formation kinetics are slower, resulting in low lithium borohydride yields. Patent CN 115784158A discloses a method for regenerating lithium borohydride using a rare-earth-magnesium alloy. This method regenerates lithium borohydride with a rare-earth-magnesium alloy and LiBO₂·2H₂O, improving the formation kinetics of lithium borohydride to some extent. For large-scale applications of lithium borohydride hydrolysis, further cost reduction and the development of new, cheaper reducing agents are still necessary. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for regenerating lithium borohydride using aluminum-based materials. This invention regenerates lithium borohydride in a one-step process by directly ball milling a mixture of lithium metaborate dihydrate, aluminum, rare-earth-aluminum intermetallic compounds, and lithium oxide at room temperature and pressure. This method offers advantages such as simple process, low cost, and ease of industrialization. Specifically, the addition of rare-earth-aluminum intermetallic compounds aims to address the high dissociation energy (>1 eV) of hydrogen on the aluminum surface, promoting the conversion between positive and negative hydrogen atoms, improving ball milling efficiency, and facilitating the formation of lithium borohydride. The addition of lithium oxide aims to break down the aluminum oxide passivation layer, improve diffusion mass transfer, and enhance the regeneration kinetics of lithium borohydride.

[0008] This invention provides a method for regenerating lithium borohydride from aluminum-based materials, comprising the following steps:

[0009] Lithium borohydride can be regenerated by loading lithium metaborate dihydrate, aluminum, rare earth-aluminum intermetallic compounds, and lithium oxide into a ball mill jar and ball milling them under a non-oxidizing atmosphere or vacuum conditions. Pure solid lithium borohydride can then be obtained by purification with diethyl ether.

[0010] In the above scheme, the rare earth-aluminum intermetallic compound is Al2Ce, Al3Ce, or Al 11 One or more of Ce3, Al2La, and Al3La are selected. The rare earth element cerium is mixed with aluminum in a molar ratio of Al:Ce = 2:1, 3:1, or 11:3, or the rare earth element lanthanum is mixed with aluminum in a molar ratio of Al:La = 2:1 or 3:1, through a smelting method. The smelting temperature is controlled at 80-100°C above the corresponding alloy liquidus temperature, and the smelting time is 4-6 minutes. Rare earth-aluminum intermetallic compounds with high rare earth content are more likely to yield a pure phase.

[0011] In the above scheme, the molar ratio of lithium metaborate dihydrate, aluminum, rare earth-aluminum intermetallic compound and lithium oxide is 1:(3.875-3):(1 / 36-1 / 3):2 / 3.

[0012] All ball milling processes proposed in this invention are performed at room temperature.

[0013] Preferably, the molar ratio of lithium oxide to lithium metaborate dihydrate is 2 / 3:1.

[0014] Preferably, the rare earth-aluminum intermetallic compound is Al2Ce or Al2La. The molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce or Al2La, and lithium oxide is 1:(3.875-3):(1 / 24-1 / 3):2 / 3.

[0015] In the above scheme, the rare earth-aluminum intermetallic compound is most preferably Al2Ce, the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3.75:1 / 12:2 / 3, and the ball milling time is 10h.

[0016] Preferably, the non-oxidizing atmosphere is one of argon, hydrogen, or a mixture of argon and hydrogen. The pressure of the non-oxidizing atmosphere inside the ball mill jar is 0-2 MPa.

[0017] Preferably, the ball-to-material ratio in the ball milling process is 30-50:1, and the ball milling time is 5-10 hours.

[0018] Preferably, the ball milling process uses a vibrating ball mill with a rotation speed of 1000-1200 r / min.

[0019] Preferably, the vacuum level of the vacuum condition is below 10 Pa.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) Compared with existing technologies, this invention uses an aluminum-based reducing agent, avoiding the use of expensive magnesium hydride, making it suitable for mass production. Al is more abundant, cheaper, and more stable than Mg, and more importantly, it can be oxidized to a higher valence state (Al). 3+ This provides more electrons, converting more lithium metaborate dihydrate into lithium borohydride.

[0022] (2) Based on the use of aluminum-based reducing agents, rare earth-aluminum intermetallic compounds are used as additives to partially replace aluminum. The addition of a small amount of rare earth-aluminum intermetallic compounds significantly improves the yield of lithium borohydride. The improved regeneration rate is due to the following reasons: First, rare earth-aluminum intermetallic compounds have hard and brittle properties. As grinding aids, they solve the problem of aluminum sticking to the mill and agglomerating due to its high plasticity, thus improving ball milling efficiency. Second, the addition of a small amount of rare earth-aluminum intermetallic compounds introduces hydrogen-loving rare earth elements, which improves the dissociation of hydrogen formed in situ, promotes the conversion between positive and negative hydrogen, promotes the formation of lithium borohydride, and improves the yield of lithium borohydride. Third, the addition of lithium oxide in this invention breaks the dense aluminum oxide passivation layer, improves diffusion mass transfer, improves the regeneration kinetics of lithium borohydride, and improves the yield of lithium borohydride. Fourth, light rare earth elements lanthanum and cerium have low electronegativity and strong reducing properties, and can also provide electrons to reduce lithium metaborate dihydrate. Furthermore, the rapid development of the permanent magnet materials industry has led to a large stockpile of La and Ce, the rare earth elements with the richest reserves, resulting in low prices. Their use can not only reduce the amount of Al used but also promote the balanced application of rare earth elements.

[0023] (3) The present invention directly uses hydrated lithium metaborate, avoiding the high-temperature dehydration process of 470°C, reducing energy consumption and cost; the crystal water in hydrated lithium metaborate is used as the hydrogen source for the regeneration of lithium borohydride, that is, the positive hydrogen of the crystal water is converted into the negative hydrogen in lithium borohydride, without the need to introduce expensive hydrogen sources such as magnesium hydride.

[0024] (4) The present invention achieves the regeneration of lithium borohydride by high-energy ball milling at room temperature. Rare earth aluminum intermetallic compound and lithium oxide are added, and the yield reaches 10.4% after ball milling for 10 hours, which is about 35 times that of pure aluminum (0.3%). Attached Figure Description

[0025] Figure 1 The images show the FTIR spectra of the ball-milled products of lithium metaborate dihydrate, aluminum, and lithium oxide in the present invention. The spectral lines in the images correspond to: 1) Comparative Example 1; 2) Comparative Example 2; 3) Comparative Example 3.

[0026] Figure 2 The graph shows the lithium borohydride yield of the ball-milled products of Comparative Examples 1-3 of this invention.

[0027] Figure 3 The images show the FTIR spectra of the ball-milled products of lithium metaborate dihydrate and rare earth-aluminum alloy in the present invention. The spectral lines in the images correspond to: 1) Comparative Example 4; 2) Comparative Example 5; 3) Comparative Example 6; 4) Comparative Example 7; 5) Comparative Example 8.

[0028] Figure 4 The graph shows the lithium borohydride yield of the ball-milled products of Comparative Examples 1 and 4-8 in this invention.

[0029] Figure 5The images show the FTIR spectra of lithium metaborate dihydrate, aluminum, rare earth-aluminum intermetallic compounds, and lithium oxide ball-milled products in the present invention. The spectral lines in the images correspond to: 1) Comparative Example 1; 2) Example 1; 3) Example 2; 4) Example 3; 5) Example 4; 6) Example 5.

[0030] Figure 6 The graph shows the lithium borohydride yield of the ball-milled products of Comparative Example 1, Example 1, and Example 2 of the present invention.

[0031] Figure 7 The image shows the FTIR spectrum of the product of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide ball-milled for 5 hours in Example 6 of the present invention.

[0032] Figure 8 The images show the FTIR spectra of the ball-milled products of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide in the present invention. The spectral lines in the images correspond to: 1) Example 7; 2) Example 1; 3) Example 8; 4) Example 9; 5) Example 10.

[0033] Figure 9 The graph shows the lithium borohydride yield of the ball-milled products of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide in Examples 1, 7-10 of the present invention.

[0034] Figure 10 The images show the FTIR spectra of the ball-milled products of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide in the present invention. The spectral lines in the images correspond to: 1) Example 11; 2) Example 1; 3) Example 12.

[0035] Figure 11 The graph shows the lithium borohydride yield of the ball-milled products from Examples 1, 11, and 12 of this invention. Detailed Implementation

[0036] The following examples further illustrate specific implementations of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0037] The specific purification process was not described in the examples; the following method was used: In an argon-atmospheric glove box, the ball-milled mixture was dissolved in diethyl ether that had been dehydrated by sodium distillation, filtered to obtain a clear filtrate, and then vacuum-dried to obtain pure lithium borohydride powder. The yield was finally quantified using iodine titration. The ball-milled products in the examples and comparative examples were analyzed using Fourier transform infrared spectroscopy (FT-IR).

[0038] All ball milling in the examples was performed at room temperature.

[0039] Comparative Example 1

[0040] First, in a 1 atm argon atmosphere glove box, 0.4429 g of lithium metaborate dihydrate and 0.5571 g of aluminum were weighed at a molar ratio of 1:4, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 1 Curve 1 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 1 Curve 1 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 1 δ) and stretching vibration ( Figure 1 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification using diethyl ether that had been dehydrated by sodium distillation, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 0.3% (…). Figure 2 ).

[0041] Comparative Example 2

[0042] First, in a 1 atm argon atmosphere glove box, 0.4016 g of lithium metaborate dihydrate, 0.5052 g of aluminum, and 0.0933 g of lithium oxide were weighed according to a molar ratio of 1:4:2 / 3, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 1 Curve 2 shows the FTIR spectrum of the ball-milled product in this comparative example. Compared to... Figure 1 Curve 1 corresponds to the stretching vibration of the BH bond in lithium borohydride. Figure 1 δ) and stretching vibration ( Figure 1 The absorption intensity of the ν) peak in the figure was significantly enhanced, indicating that the addition of lithium oxide promoted the formation of lithium borohydride and significantly improved the yield of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether after sodium distillation and quantification by iodine titration. The regeneration rate of lithium borohydride in this comparative example was 4.2%, which was higher than the yield of 0.3% in Comparative Example 1. Figure 2 ).

[0043] Comparative Example 3

[0044] First, in a 1 atm argon atmosphere glove box, 0.3673 g of lithium metaborate dihydrate, 0.4621 g of aluminum, and 0.1706 g of lithium oxide were weighed according to a molar ratio of 1:4:4 / 3, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 1 Curve 3 shows the FTIR spectrum of the ball-milled product in this comparative example. Compared to... Figure 1 Curve 1 corresponds to the stretching vibration of the BH bond in lithium borohydride. Figure 1 δ) and stretching vibration ( Figure 1 The absorption intensity of the ν) absorption peak was significantly enhanced, indicating that the addition of lithium oxide promoted the formation of lithium borohydride and significantly improved the yield of lithium borohydride. Finally, pure lithium borohydride was obtained by purification using diethyl ether after sodium distillation to remove water, and quantification was performed by iodine titration. The regeneration rate of lithium borohydride in this comparative example was 2.0%, which was higher than the yield of 0.3% in comparative example 1, but lower than the yield of 4.2% in comparative example 2. Figure 2 This indicates that adding too much lithium oxide actually reduces the yield.

[0045] Comparative Example 4

[0046] First, in a 1 atm argon atmosphere glove box, weigh 0.3135 g of lithium metaborate dihydrate and 0.6865 g of Al according to a molar ratio of 1:11 / 42. 11 Ce3, with a ball-to-material ratio of 50:1, was loaded into a ball mill jar, and the lid was sealed tightly. Next, the jar was placed directly into a QM-3C oscillating ball mill and ball-milled at 1000 rpm for 10 hours to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 minutes followed by a 30-minute pause. The milled product was then characterized by FTIR. Figure 3 Curve 1 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 3 Curve 1 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 3 δ) and stretching vibration ( Figure 3 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether that had been dehydrated by sodium distillation, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 0.7% (…). Figure 4 ).

[0047] Comparative Example 5

[0048] First, in a 1 atm argon atmosphere glove box, 0.2974 g of lithium metaborate dihydrate and 0.7026 g of Al3Ce were weighed at a molar ratio of 1:11 / 12, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 3 Curve 2 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 3 Curve 2 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 3 δ) and stretching vibration ( Figure 3 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether that had been dehydrated by sodium distillation, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 0.7% (…). Figure 4 ).

[0049] Comparative Example 6

[0050] First, in a 1 atm argon atmosphere glove box, 0.2656 g of lithium metaborate dihydrate and 0.7344 g of Al₂Ce were weighed at a molar ratio of 1:11 / 9, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 3 Curve 3 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 3 Curve 3 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 3 δ) and stretching vibration ( Figure 3 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether after sodium distillation to remove water, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 1.3% (…). Figure 4 ).

[0051] Comparative Example 7

[0052] First, in a 1 atm argon atmosphere glove box, 0.2986 g of lithium metaborate dihydrate and 0.7014 g of Al3La were weighed at a molar ratio of 1:11 / 12, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 3 Curve 4 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 3 Curve 4 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 3 δ) and stretching vibration ( Figure 3 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether that had been dehydrated by sodium distillation, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 0.9% (…). Figure 4 ).

[0053] Comparative Example 8

[0054] First, in a 1 atm argon atmosphere glove box, 0.2668 g of lithium metaborate dihydrate and 0.7332 g of Al₂La were weighed at a molar ratio of 1:11 / 9, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 3 Curve 5 in the middle is the FTIR spectrum of the ball-milled product of this comparative example. Figure 3 Curve 5 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A weak stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 3 δ) and stretching vibration ( Figure 3 The ν) absorption peak indicates the formation of a very small amount of lithium borohydride. Finally, pure lithium borohydride was obtained by purification with diethyl ether that had been dehydrated by sodium distillation, and quantification was performed by iodine titration. The regeneration rate of this comparative lithium borohydride was only 0.9% (…). Figure 4 ).

[0055] Example 1

[0056] First, in a 1 atm argon atmosphere glove box, 0.3846 g of lithium metaborate dihydrate, 0.4536 g of aluminum, 0.0725 g of Al₂Ce, and 0.0893 g of lithium oxide were weighed according to a molar ratio of 1:3.75:1 / 12:2 / 3, with a ball-to-material ratio of 50:1. The mixture was then placed into a ball mill jar, and the lid was sealed tightly. Next, the ball mill jar was directly placed in a QM-3C vibrating ball mill and ball-milled at 1000 r / min for 10 h to regenerate lithium borohydride. To prevent overheating, the milling process was repeated for 30 min, followed by a 30 min pause. Finally, the ball-milled product was characterized by FTIR. Figure 5 Curve 2 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 5 Curve 2 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 5 δ) and stretching vibration ( Figure 5 The ν) absorption peak in the image confirms the successful regeneration of lithium borohydride. It is worth noting that the infrared absorption peak intensity of the BH bond in lithium borohydride after the addition of Al₂Ce and lithium oxide is much stronger than that using only elemental aluminum (Comparative Example 1) or Al₂Ce (Comparative Example 6), and also stronger than that using a mixture of elemental aluminum and lithium oxide (Comparative Examples 2 and 3). This indicates that the simultaneous addition of Al₂Ce and lithium oxide greatly promotes the formation of lithium borohydride and significantly improves its yield. In Al₂O₃, Al and O exhibit both tetrahedral and octahedral coordination, while LiAlO₂ only exhibits tetrahedral coordination. Compared to... Figure 5 The Al-O bond stretching vibration peaks (750-900 cm⁻¹) in the AlO₄ unit in curves 1 and 2 are shown in the figure. -1 The absorption intensity increases, and the stretching vibration peak of the eight-coordinate Al-O bond (750-900 cm⁻¹) appears. -1 The weakening absorption intensity indicates that the introduction of lithium oxide led to the formation of LiAlO2. The introduction of lithium oxide can break the dense Al2O3 passivation layer, improve diffusion mass transfer, and thus increase the yield of lithium borohydride. Finally, pure lithium borohydride was obtained by purification using diethyl ether after sodium distillation to remove water, and quantification was performed by iodine titration. The regeneration rate of lithium borohydride in this example was 10.4%. Figure 6 The yield was significantly higher than that of Comparative Example 1 (0.3%) and Comparative Example 2 (4.2%), and approximately 35 times that of Comparative Example 1, consistent with the FTIR results.

[0057] Example 2

[0058] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that Al2Ce is replaced with Al2La, and the molar ratio of lithium metaborate dihydrate, aluminum, Al2La and lithium oxide is 1:3.75:1 / 12:2 / 3.

[0059] Figure 5 Curve 3 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 5 Curve 3 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 5 δ) and stretching vibration ( Figure 5 The infrared absorption peak (ν) in the figure confirms the successful regeneration of lithium borohydride. With the addition of Al₂La and lithium oxide, the infrared absorption peak intensity of the BH bond in lithium borohydride is significantly stronger than that using only elemental aluminum (Comparative Example 1) or Al₂La (Comparative Example 8), and also stronger than that using a mixture of elemental aluminum and lithium oxide (Comparative Examples 2 and 3). This indicates that the simultaneous addition of Al₂La and lithium oxide greatly promotes the formation of lithium borohydride and significantly improves its yield. Similarly, compared to... Figure 5 The Al-O bond stretching vibration peaks (750-900 cm⁻¹) in the AlO₄ unit in curves 1 and 3 are shown in the figure. -1 The absorption intensity increases, and the stretching vibration peak of the eight-coordinate Al-O bond (750-900 cm⁻¹) appears. -1 The weakening absorption intensity indicates the formation of LiAlO2. Further evidence shows that the introduction of lithium oxide can break the dense Al2O3 passivation layer, promote the formation of lithium borohydride, and improve the regeneration rate of lithium borohydride. Through purification and quantitative analysis, the regeneration rate of lithium borohydride in this example is 8.9%. Figure 6 The yield was much higher than that of Comparative Example 1 (0.3%), and about 30 times that of Comparative Example 1, consistent with the FTIR results.

[0060] Example 3

[0061] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that Al2Ce is replaced with Al3Ce, and the molar ratio of lithium metaborate dihydrate, aluminum, Al3Ce and lithium oxide is 1:3.67:1 / 12:2 / 3.

[0062] Figure 5 Curve 4 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 5 Curve 4 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 5δ) and stretching vibration ( Figure 5 The infrared absorption peak (ν) in the figure confirms the successful regeneration of lithium borohydride. The infrared absorption peak intensity of the BH bond in lithium borohydride after the addition of Al3Ce and lithium oxide is also much stronger than that using only elemental aluminum (Comparative Example 1) or Al3Ce (Comparative Example 5), indicating that Al3Ce and lithium oxide promote the formation of lithium borohydride and significantly improve its yield.

[0063] Example 4

[0064] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that Al2Ce is replaced with Al3La, and the molar ratio of lithium metaborate dihydrate, aluminum, Al3La and lithium oxide is 1:3.67:1 / 12:2 / 3.

[0065] Figure 5 Curve 5 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 5 Curve 5 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 5 δ) and stretching vibration ( Figure 5 The infrared absorption peak (ν) in the figure confirms the successful regeneration of lithium borohydride. The infrared absorption peak intensity of the BH bond in lithium borohydride after the addition of Al3La and lithium oxide is also much stronger than that using only elemental aluminum (Comparative Example 1) or Al3La (Comparative Example 7), indicating that Al3La and lithium oxide promote the formation of lithium borohydride and significantly improve its yield.

[0066] Example 5

[0067] A method for regenerating lithium borohydride from aluminum-based materials is basically the same as in Example 1, except that Al2Ce is replaced with Al. 11 Ce3, and lithium metaborate dihydrate, aluminum, Al 11 The molar ratio of Ce3 to lithium oxide is 1:3.61:1 / 36:2 / 3.

[0068] Figure 5 Curve 6 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 5 Curve 6 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 5 δ) and stretching vibration ( Figure 5 The ν) absorption peak in the image confirms the successful regeneration of lithium borohydride. Al was added. 11After Ce3 and lithium oxide, the infrared absorption peak intensity of the BH bond in lithium borohydride is also much stronger than that using only elemental aluminum (Comparative Example 1) or Al. 11 Ce3 (Comparative Example 4) indicates that Al 11 Ce3 and lithium oxide promote the formation of lithium borohydride, significantly improving the yield of lithium borohydride.

[0069] Example 6

[0070] A method for regenerating lithium borohydride from aluminum-based materials is basically the same as that in Example 1, except that the ball milling time is 5 hours.

[0071] Figure 7 The image shows the FTIR spectrum of the ball-milled product in this embodiment. Figure 7 It was observed that in the range of 2200-2450cm -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 7 δ) and stretching vibration ( Figure 7 The presence of the ν) absorption peak confirms successful regeneration of lithium borohydride. Quantitative analysis using purified iodine titration showed a lithium borohydride regeneration rate of 8.5% in this example, slightly lower than the 10.4% yield achieved by ball milling for 10 hours.

[0072] Example 7

[0073] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that the amount of Al2Ce replacing Al is reduced, i.e., the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3.875:1 / 24:2 / 3.

[0074] Figure 8 Curve 1 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 8 Curve 1 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 8 δ) and stretching vibration ( Figure 8 The presence of the ν) absorption peak in Example 1 confirms successful regeneration of lithium borohydride. The infrared characteristic absorption peak intensity of lithium borohydride is slightly lower than that of Example 1. Figure 8 In curve 2, the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide was 1:3.75:1 / 12:2 / 3. Quantification was performed by titration with purified iodine. The remanufacturing rate of lithium borohydride in this example was 7.1%. Figure 9The yield was 10.4%, lower than that of Example 1, consistent with the FTIR results. These results indicate that when the molar ratio of Al₂Ce to lithium metaborate dihydrate is less than 1 / 12, the yield of lithium borohydride increases with the increase of Al₂Ce substitution for Al.

[0075] Example 8

[0076] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that the amount of Al2Ce replacing Al is increased, and the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3.625:3 / 24:2 / 3.

[0077] Figure 8 Curve 3 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 8 Curve 3 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 8 δ) and stretching vibration ( Figure 8 The presence of the ν) absorption peak in Example 1 confirms successful regeneration of lithium borohydride. The infrared characteristic absorption peak intensity of lithium borohydride is also slightly lower than that of Example 1. Figure 8 In curve 2, the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide was 1:3.75:1 / 12:2 / 3. Quantification was performed by titration with purified iodine. The remanufacturing rate of lithium borohydride in this example was 9.5%. Figure 9 The yield was 10.4%, lower than that of Example 1, which is consistent with the FTIR results.

[0078] Example 9

[0079] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that the amount of Al2Ce replacing Al is increased, and the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3.5:1 / 6:2 / 3.

[0080] Figure 8 Curve 4 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 8 Curve 4 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 8 δ) and stretching vibration ( Figure 8 The presence of the ν) absorption peak in Example 1 confirms successful regeneration of lithium borohydride. The infrared characteristic absorption peak intensity of lithium borohydride is lower than that of Example 1. Figure 8In curve 2, the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce, and lithium oxide was 1:3.75:1 / 12:2 / 3. Quantification was performed by titration with purified iodine. The remanufacturing rate of lithium borohydride in this example was 8.8%. Figure 9 The yield was 10.4%, lower than that of Example 1, which is consistent with the FTIR results.

[0081] Example 10

[0082] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as in Example 1, except that the amount of Al2Ce replacing Al is increased, and the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3:1 / 3:2 / 3.

[0083] Figure 8 Curve 5 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 8 Curve 5 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 8 δ) and stretching vibration ( Figure 8 The presence of the ν) absorption peak confirms successful regeneration of lithium borohydride. When the molar ratio of Al₂Ce to lithium oxide is higher than 1 / 12, the intensity of the infrared characteristic absorption peak of lithium borohydride gradually decreases with increasing Al₂Ce substitution of Al. Quantitative analysis using purified iodine titration showed that the regeneration rate of lithium borohydride in this example was 7.4%. Figure 9 The results of Examples 8-10 show that when the molar ratio of Al2Ce to lithium oxide is higher than 1 / 12, the yield of lithium borohydride gradually decreases as the amount of Al2Ce replacing Al increases, which is consistent with the FTIR results.

[0084] Example 11

[0085] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as that in Example 1 (with an excess of 37.5% of reducing agent (Al+Al2Ce)), except that the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:3.409:0.0758:2 / 3 (i.e., an excess of 25% of reducing agent (Al+Al2Ce)).

[0086] Figure 10 Curve 1 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 10 Curve 1 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 10 δ) and stretching vibration ( Figure 10The presence of the ν) absorption peak in Example 1 confirms successful regeneration of lithium borohydride. The infrared characteristic absorption peak intensity of lithium borohydride is lower than that of Example 1. Figure 10 In curve 2 (with an excess of 37.5% reducing agent), the remanufacturing rate of lithium borohydride in this example was 3.5% by titration with purified iodine. Figure 11 The yield was 10.4%, lower than that of Example 1, consistent with the FTIR results. These results indicate that when the excess of the reducing agent (Al+Al₂Ce) is less than or equal to 37.5%, the yield of lithium borohydride increases with increasing reducing agent dosage. This is because initially, when the reducing agent dosage is low, increasing the dosage significantly improves the powder sticking and agglomeration phenomenon, and the excess (Al+Al₂Ce) allows for better contact between reactants, thus contributing to increased yield.

[0087] Example 12

[0088] A method for regenerating lithium borohydride using aluminum-based materials is basically the same as that in Example 1 (with an excess of 37.5% of reducing agent (Al+Al2Ce)), except that the molar ratio of lithium metaborate dihydrate, aluminum, Al2Ce and lithium oxide is 1:4.091:0.0909:2 / 3 (i.e., an excess of 50% of reducing agent (Al+Al2Ce)).

[0089] Figure 10 Curve 3 is the FTIR spectrum of the ball-milled product in this embodiment. Figure 10 Curve 3 shows that in the range of 2200-2450cm... -1 and 1126cm -1 A strong stretching vibration corresponding to the BH bond in lithium borohydride was observed at this location. Figure 10 (δ) and stretching vibration) Figure 10 The presence of the ν) absorption peak in Example 1 confirms successful regeneration of lithium borohydride. The infrared characteristic absorption peak intensity of lithium borohydride is slightly lower than that of Example 1. Figure 10 In curve 2 (with an excess of 37.5% reducing agent), the remanufacturing rate of lithium borohydride in this example was 8.8% by titration with purified iodine. Figure 11 The yield was 10.4% lower than that of Example 1, consistent with the FTIR results. These results indicate that when the excess of reducing agent (Al+Al2Ce) exceeds 37.5%, the yield of lithium borohydride decreases slightly with increasing reducing agent content. This is because the excessive use of reducing agent reduces the amount of lithium metaborate dihydrate, resulting in less effective contact and lower solid-phase reaction efficiency.

[0090] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.

Claims

1. A method for regenerating lithium borohydride using aluminum-based materials, characterized in that, Includes the following steps: Lithium borohydride can be regenerated by loading lithium metaborate dihydrate, aluminum, rare earth-aluminum intermetallic compounds, and lithium oxide into a ball mill jar and performing ball milling under non-oxidizing atmosphere or vacuum conditions.

2. The method according to claim 1, characterized in that, The rare earth-aluminum intermetallic compound is Al2Ce, Al3Ce, or Al 11 One or more of Ce3, Al2La, and Al3La.

3. The method according to claim 1, characterized in that, The rare earth-aluminum intermetallic compound is obtained by melting light rare earth cerium and aluminum in a molar ratio of Al:Ce = 2:1, 3:1, or 11:3, or by melting light rare earth lanthanum and aluminum in a molar ratio of Al:La = 2:1 or 3:

1. The melting temperature is controlled at 80-100°C above the corresponding alloy liquidus temperature, and the melting time is 4-6 minutes.

4. The method according to claim 1, characterized in that, The molar ratio of lithium metaborate dihydrate, aluminum, rare earth-aluminum intermetallic compound and lithium oxide is 1:(3.875-3):(1 / 36-1 / 3):2 / 3.

5. The method according to claim 1, characterized in that, The ball milling process described is a solid-phase ball milling method.

6. The method according to claim 1, characterized in that, The ball milling process is performed using a vibrating ball mill with a rotation speed of 1000-1200 r / min and a ball-to-material ratio of 30-50:

1.

7. The method according to claim 1, characterized in that, The ball milling process is carried out at room temperature for 5-10 hours.

8. The method according to claim 1, characterized in that, The non-oxidizing atmosphere is one of argon atmosphere, hydrogen atmosphere, or a mixture of argon and hydrogen atmosphere.

9. The method according to claim 1, characterized in that, The pressure of the non-oxidizing atmosphere inside the ball mill jar is 0-2 MPa.

10. The method according to any one of claims 1-9, characterized in that, The vacuum level of the vacuum condition is below 10 Pa.

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