CN118221074A - Preparation method of lithium aluminum hydride - Google Patents
Preparation method of lithium aluminum hydride Download PDFInfo
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- CN118221074A CN118221074A CN202410356377.4A CN202410356377A CN118221074A CN 118221074 A CN118221074 A CN 118221074A CN 202410356377 A CN202410356377 A CN 202410356377A CN 118221074 A CN118221074 A CN 118221074A
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- aluminum hydride
- lithium aluminum
- diethyl ether
- lithium
- ether solution
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- -1 lithium aluminum hydride Chemical compound 0.000 title claims abstract description 151
- 239000012280 lithium aluminium hydride Substances 0.000 title claims abstract description 102
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims abstract description 119
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims abstract description 70
- 238000000034 method Methods 0.000 claims abstract description 32
- 239000002244 precipitate Substances 0.000 claims abstract description 31
- 239000000243 solution Substances 0.000 claims abstract description 29
- 239000013078 crystal Substances 0.000 claims abstract description 14
- 239000011259 mixed solution Substances 0.000 claims abstract description 14
- 239000003999 initiator Substances 0.000 claims abstract description 11
- 239000007788 liquid Substances 0.000 claims abstract description 9
- 238000000926 separation method Methods 0.000 claims abstract description 9
- 238000003756 stirring Methods 0.000 claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- 238000001556 precipitation Methods 0.000 claims description 27
- 238000001914 filtration Methods 0.000 claims description 5
- 239000002994 raw material Substances 0.000 abstract description 4
- 238000001308 synthesis method Methods 0.000 abstract description 2
- 239000000126 substance Substances 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 28
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 16
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
- 239000011780 sodium chloride Substances 0.000 description 8
- 239000012535 impurity Substances 0.000 description 6
- 229910000103 lithium hydride Inorganic materials 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 229910010084 LiAlH4 Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 229910020828 NaAlH4 Inorganic materials 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 238000011085 pressure filtration Methods 0.000 description 3
- 229910010082 LiAlH Inorganic materials 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000001603 reducing effect Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- DNEHKUCSURWDGO-UHFFFAOYSA-N aluminum sodium Chemical compound [Na].[Al] DNEHKUCSURWDGO-UHFFFAOYSA-N 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 239000004210 ether based solvent Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- SIAPCJWMELPYOE-UHFFFAOYSA-N lithium hydride Chemical compound [LiH] SIAPCJWMELPYOE-UHFFFAOYSA-N 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B6/00—Hydrides of metals including fully or partially hydrided metals, alloys or intermetallic compounds ; Compounds containing at least one metal-hydrogen bond, e.g. (GeH3)2S, SiH GeH; Monoborane or diborane; Addition complexes thereof
- C01B6/24—Hydrides containing at least two metals; Addition complexes thereof
- C01B6/243—Hydrides containing at least two metals; Addition complexes thereof containing only hydrogen, aluminium and alkali metals, e.g. Li(AlH4)
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The present disclosure discloses a lithium aluminum hydride preparation method, comprising the steps of: s100: placing a proper amount of sodium aluminum hydride, lithium chloride and an initiator into an ether solution, and fully stirring and reacting at normal temperature and normal pressure to obtain a mixed solution; s200: carrying out solid-liquid separation on the mixed solution to obtain an diethyl ether solution containing lithium aluminum hydride and a precipitate; s300: the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a certain temperature to obtain dry lithium aluminum hydride crystals. The method adopts the cheap sodium aluminum hydride and the cheap and easily available lithium chloride of the simple substance synthesis method as raw materials, so that the production cost of the existing lithium aluminum hydride can be reduced.
Description
Technical Field
The invention belongs to the technical field of new energy materials and preparation thereof, and particularly relates to a preparation method of lithium aluminum hydride.
Background
Lithium aluminum hydride is a compound aluminum hydride, the molecular formula of which is LiAlH4, and the molecular weight of which is 37.95. Lithium aluminum hydride is an extremely strong reducing agent in organic synthesis, and particularly has extremely strong reducing property for esters, carboxylic acids and amides. Pure lithium aluminum hydride is relatively stable in dry air at 120 ℃, but explosively decomposes upon water. Lithium aluminum hydride is soluble in ether solvents such as diethyl ether and tetrahydrofuran, has a specific gravity of 0.917, and can be decomposed into lithium hydride, aluminum and hydrogen under vacuum at 130 ℃.
The existing preparation process of lithium aluminum hydride comprises the following steps: ① Slowly dissolving aluminum trichloride in diethyl ether to obtain diethyl ether solution of aluminum trichloride; ② Preparing lithium hydride, lithium aluminum hydride and diethyl ether into suspension; ③ Slowly adding the diethyl ether solution of the aluminum trichloride in ① into the suspension of ② for mixing reaction; ④ After the reaction is finished, carrying out solid-liquid separation to obtain an diethyl ether solution containing lithium aluminum hydride and a lithium chloride byproduct; ⑤ Evaporating and drying the diethyl ether solution containing the lithium aluminum hydride to obtain lithium aluminum hydride crystals.
The reaction equation involved in the preparation process is as follows:
4LiH+AlCl3＝LiAlH4+3LiCl
In the preparation process, a large amount of heat is released no matter the aluminum chloride is dissolved in diethyl ether or the aluminum chloride reacts with lithium hydride, the reaction rate and the temperature need to be strictly controlled, otherwise, explosion is very easy to occur, and the risk is high. In addition, the raw material of the method is lithium hydride obtained by high-temperature hydrogenation of metallic lithium, and as can be seen from the above formula, at least 4 moles of lithium hydride LiH can be used for preparing 1 mole of lithium aluminum hydride LiAlH 4, and the cost is high.
Disclosure of Invention
Aiming at the defects in the prior art, the purpose of the present disclosure is to provide a preparation method of lithium aluminum hydride, which adopts low-cost sodium aluminum hydride and low-cost and easily available lithium chloride of an elemental synthesis method as raw materials, can reduce the production cost of lithium aluminum hydride by at least 50%, has high purity of the prepared product, can recover the solvent, and provides a technical route for industrial mass production.
In order to achieve the above object, the present disclosure provides the following technical solutions:
A method for preparing lithium aluminum hydride, comprising the following steps:
S100: placing a proper amount of sodium aluminum hydride, lithium chloride and an initiator into an ether solution, and fully stirring and reacting at normal temperature and normal pressure to obtain a mixed solution;
S200: carrying out solid-liquid separation on the mixed solution to obtain an diethyl ether solution containing lithium aluminum hydride and a sodium chloride precipitate;
s300: the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a certain temperature to obtain dry lithium aluminum hydride crystals.
Preferably, in step S100, the molar ratio of sodium aluminum hydride to lithium chloride is 1.0:1.0 to 1.1.
Preferably, in step S100, the molar ratio of the sodium aluminum hydride to the initiator is 1.0:0 to 0.1.
Preferably, in step S100, the purity of the sodium aluminum hydride is 95.00% to 99.50%.
Preferably, in step S100, a small amount of lithium aluminum hydride is used as the initiator.
Preferably, in step S200, the solid-liquid separation of the mixed solution includes, but is not limited to, any one of the following methods: standing for precipitation, centrifuging and filtering at positive pressure.
Preferably, in step S300, the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a temperature of 30 to 90 ℃.
Preferably, in step S300, the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a temperature of 70-90 ℃.
Preferably, in step S300, the diethyl ether solution containing lithium aluminum hydride is depressurized to-0.1 to-0.01 Mpa.
Preferably, in step S300, the diethyl ether solution containing lithium aluminum hydride is depressurized to-0.04 to-0.02 Mpa.
Compared with the prior art, the beneficial effects that this disclosure brought are:
1. The method has mild reaction, no obvious temperature change in the whole reaction process, no requirement on a heat dissipation system, and simple and safe reaction;
2. The method has higher utilization rate of expensive lithium sources, almost 1 mol of lithium chloride can generate 1 mol of lithium aluminum hydride, and the comprehensive cost is lower.
Drawings
FIG. 1 is a flow chart of a method for preparing lithium aluminum hydride according to an embodiment of the present disclosure;
Fig. 2 is a diffraction pattern of lithium aluminum hydride crystals prepared by the preparation method shown in fig. 1.
Detailed Description
Specific embodiments of the present disclosure will be described in detail below with reference to fig. 1 to 2. While specific embodiments of the disclosure are shown in the drawings, it should be understood that the disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. Those of skill in the art will understand that a person may refer to the same component by different names. The specification and claims do not identify differences in terms of components, but rather differences in terms of the functionality of the components. As used throughout the specification and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description hereinafter sets forth the preferred embodiments for carrying out the present disclosure, but is not intended to limit the scope of the disclosure in general, as the description proceeds. The scope of the present disclosure is defined by the appended claims.
For the purposes of promoting an understanding of the embodiments of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific examples, without the intention of being limiting the embodiments of the disclosure.
In one embodiment, as shown in fig. 1, the present disclosure provides a method for preparing lithium aluminum hydride, comprising the steps of:
1. The molar ratio is 1:1:0.5 weight ratio of 97% purity sodium aluminum hydride 21.6g, lithium chloride 16.5g, lithium aluminum hydride 0.74g (here, a small amount of lithium aluminum hydride as an initiator, can accelerate the reaction) and anhydrous ether 480g into a reaction kettle, stirring at normal temperature (25 ℃) and normal pressure (one atmosphere pressure) for 4 hours, fully reacting to obtain a mixed solution, and in the stirring process, reacting sodium aluminum hydride and lithium chloride as follows:
NaAlH4+LiCl＝LiAlH4+NaCl
2. Carrying out solid-liquid separation on the mixed solution by any one of standing precipitation, centrifugal filtration and positive pressure filtration to obtain diethyl ether solution containing lithium aluminum hydride and precipitate, wherein the precipitate comprises sodium chloride generated after reaction, lithium chloride which is not completely reacted, a small amount of sodium aluminum hydride and other impurities;
3. The ether solution containing lithium aluminum hydride was decompressed to-0.04 MPa at 70℃and then distilled, whereby 12.93g of dried sodium aluminum hydride crystals were obtained.
In another embodiment, the present disclosure further provides a method for preparing lithium aluminum hydride, including the steps of:
1. the molar ratio is 1:1.05: the proportion of 0.05 is respectively weighing 21.6g of sodium aluminum hydride with the purity of 97%, 17.3g of lithium chloride, 0.74g of lithium aluminum hydride and 480g of anhydrous diethyl ether, putting the materials into a reaction kettle, stirring the materials for 4 hours at normal temperature (25 ℃) and normal pressure (one atmosphere), fully reacting the materials to obtain a mixed solution, and reacting the sodium aluminum hydride with the lithium chloride in the stirring process:
NaAlH4+LiCl＝LiAlH4+NaCl
S200: carrying out solid-liquid separation on the mixed solution by any one of standing precipitation, centrifugal filtration and positive pressure filtration to obtain diethyl ether solution containing lithium aluminum hydride and precipitate, wherein the precipitate comprises sodium chloride generated after reaction, lithium chloride which is not completely reacted, a small amount of sodium aluminum hydride and other impurities;
2. The ether solution containing lithium aluminum hydride was decompressed to-0.04 MPa at 70℃and distilled to obtain 13.57g of dried sodium aluminum hydride crystals.
In another embodiment, the present disclosure further provides a method for preparing lithium aluminum hydride, including the steps of:
1. The molar ratio is 1:1.1: 21.6g of sodium aluminum hydride with the purity of 97%, 17.3g of lithium chloride, 0.74g of lithium aluminum hydride and 480g of anhydrous diethyl ether are put into a reaction kettle according to the proportion of 0.05, stirred for 4 hours at normal temperature (25 ℃) and normal pressure (one atmosphere), and fully reacted to obtain a mixed solution, wherein in the stirring process, the sodium aluminum hydride and the lithium chloride react as follows:
NaAlH4+LiCl＝LiAlH4+NaCl
2. Carrying out solid-liquid separation on the mixed solution by any one of standing precipitation, centrifugal filtration and positive pressure filtration to obtain diethyl ether solution containing lithium aluminum hydride and precipitate, wherein the precipitate comprises sodium chloride generated after reaction, lithium chloride which is not completely reacted, a small amount of sodium aluminum hydride and other impurities;
3. the ether solution containing lithium aluminum hydride was decompressed to-0.04 MPa at 70℃and distilled, whereby 13.64g of dried sodium aluminum hydride crystals were obtained.
The three examples above are sodium aluminum hydride to lithium chloride molar ratios of 1:1 to 1:1.1 portions of lithium aluminum hydride prepared respectively. When the molar ratio of sodium aluminum hydride to lithium chloride is 1:1, yield 82.79%,1:1.05, yield 87.13%,1:1.1, the yield was 87.61% (where the yield=the amount of lithium aluminum hydride actually obtained/the amount of lithium aluminum hydride theoretically produced. Taking the first example as an example, 21.6g of sodium aluminum hydride was used for the reaction, the purity was 97%, converted to 0.3880mol, 0.3880mol of lithium aluminum hydride could be produced according to the theory of the reaction equation, converted to 14.7246g of lithium aluminum hydride by mass, 12.93g of lithium aluminum hydride was actually obtained, 0.74g of lithium aluminum hydride as an initiator was subtracted, and 12.19/14.7246. About. 82.79%. The yields in the subsequent examples were all calculated by this method, and are not described again).
Based on the above three examples, it can be seen that the yield of lithium aluminum hydride gradually increases as the amount of lithium chloride added increases. The molar ratio of the two is 1:1.05 is almost close to the limit, and the benefit of continuously increasing the consumption of lithium chloride is not great. This is because sodium aluminum hydride and lithium chloride are both insoluble in diethyl ether, and the reaction is similar to the solid-solid reaction with diethyl ether as the unreacted medium, and cannot be completely reacted, but there is a boundary effect even if the addition of excessive lithium chloride can promote the forward progress of the reaction. From the aspect of lithium utilization, the molar ratio of sodium aluminum hydride to lithium chloride is optimally 1:1.05.
In another embodiment, the present disclosure further provides a method for preparing sodium aluminum hydride, unlike the previous embodiment, in this embodiment, the molar ratio of the weighed sodium aluminum hydride, lithium chloride and lithium aluminum hydride is 1:1.05:0, the mass is 21.6g, 17.3g and 0g in turn, the rest of the reaction conditions are the same, and finally, 7.08g of dried sodium aluminum hydride crystals are obtained.
In another embodiment, the present disclosure further provides a method for preparing sodium aluminum hydride, unlike the previous embodiment, in this embodiment, the molar ratio of the weighed sodium aluminum hydride, lithium chloride and lithium aluminum hydride is 1:1.05:0.1, 21.6g, 17.3g and 1.48g in order, and the rest of the reaction conditions are the same, and finally, 14.35g of dried sodium aluminum hydride crystals are obtained.
In the two examples, the molar ratio of sodium aluminum hydride to lithium aluminum hydride was 1:0 and 1:0.1, a molar ratio to the sodium aluminum hydride and lithium aluminum hydride of 1:0.05, when the molar ratio of sodium aluminum hydride to lithium aluminum hydride is 1: when the yield of lithium aluminum hydride was 48.08% at 0 and 87.13% at 1:0.05, and 87.40% at 1:0.1, it was found that the yield of lithium aluminum hydride gradually increased with the addition of a small amount of lithium aluminum hydride as an initiator. At 1: the use amount of lithium chloride is increased by 0.05 basically approaching the limit, and the benefit is not great. This is because lithium aluminum hydride acts as an initiator in the reaction, and in the absence of lithium aluminum hydride, the reaction starts slowly, with less than 50% of the sodium aluminum hydride. The reaction proceeds rapidly after a certain amount of lithium aluminum hydride is added. From the cost point of view, the optimal lithium aluminum hydride dosage is 1:0.05.
In another embodiment, the present disclosure further provides a method for preparing lithium aluminum hydride, unlike the previous embodiment, in this embodiment, sodium aluminum hydride with a purity of 95% is used, and the molar ratio is 1:1.05:0.05 g of sodium aluminum hydride 22.0g, lithium chloride 17.3g, lithium aluminum hydride 0.74g, the other reaction conditions were the same, and finally, a dried sodium aluminum hydride crystal of 11.94g was obtained.
In another embodiment, the present disclosure further provides a method for preparing lithium aluminum hydride, unlike the previous embodiment, in this embodiment, sodium aluminum hydride with a purity of 99.5% is used, and the molar ratio is 1:1.05: 21.1g of sodium aluminum hydride of 0.05, 17.3g of lithium chloride, 0.74g of lithium aluminum hydride, and the other reaction conditions were the same, and finally, 15.12g of dried sodium aluminum hydride crystals were obtained.
The molar ratio of sodium aluminum hydride, lithium chloride and lithium aluminum hydride was 1 as described above: 1.05:0.05, and the purity of sodium aluminum hydride is 97% compared with the example, when the purity of sodium aluminum hydride is 95%, the yield of lithium aluminum hydride is 76.25%, when the purity is 97%, the yield is 87.13%, when the purity is 99.5%, the yield is 97.46%. It can be seen that the yield of lithium aluminum hydride increases rapidly as the purity of the sodium aluminum hydride increases. The sodium aluminum hydride synthesized industrially contains aluminum powder, sodium aluminum hexahydride and other impurities, wherein the aluminum powder has a catalytic decomposition effect on lithium aluminum hydride even under the low-temperature condition. Sodium aluminum hydride having a purity of 97% or less, therefore, causes a decrease in the yield of lithium aluminum hydride due to the catalytic action of aluminum powder therein. To increase the yield of lithium aluminum hydride, it is necessary to purify sodium aluminum hydride to remove impurities such as aluminum powder. From the standpoint of cost and process complexity, the sodium aluminum hydride with the purity of more than 95% can be used for meeting the actual production requirements.
In addition, the present disclosure also conducted deformation tests on the above second example, i.e., the reaction temperatures and pressures in steps 3 and were adjusted to 30℃and-0.1 MPa, 50℃and-0.07 MPa, 90℃and-0.02 MPa, respectively. In addition, at a temperature of 90 ℃ or lower, the operation of reducing pressure is required to obtain solid crystals of lithium aluminum hydride, which cannot be efficiently crystallized from diethyl ether. This is due to the fact that lithium aluminum hydride and diethyl ether form a complex, and more energy is required to separate the lithium aluminum hydride from the diethyl ether. If heating alone is required, a high temperature of at least 110 ℃ or higher is required, but a higher crystallization temperature leads to decomposition of lithium aluminum hydride, resulting in a decrease in purity. In order to obtain pure lithium aluminum hydride, a depressurizing operation is necessary.
Table 1 shows the correspondence between temperature and pressure for crystallization of lithium aluminum hydride in diethyl ether.
TABLE 1
| Pressure/temperature | 30℃ | 50℃ | 70℃ | 90℃ |
| 0Mpa | Hardly precipitate out | Hardly precipitate out | Hardly precipitate out | Hardly precipitate out |
| -0.01Mpa | Hardly precipitate out | Hardly precipitate out | Hardly precipitate out | Slowly precipitate out |
| -0.02Mpa | Hardly precipitate out | Hardly precipitate out | Hardly precipitate out | Fast precipitation |
| -0.03Mpa | Hardly precipitate out | Hardly precipitate out | Slowly precipitate out | Fast precipitation |
| -0.04Mpa | Hardly precipitate out | Hardly precipitate out | Fast precipitation | Fast precipitation |
| -0.05Mpa | Hardly precipitate out | Slowly precipitate out | Fast precipitation | Fast precipitation |
| -0.06Mpa | Hardly precipitate out | Fast precipitation | Fast precipitation | Fast precipitation |
| -0.07Mpa | Hardly precipitate out | Fast precipitation | Fast precipitation | Fast precipitation |
| -0.08Mpa | Hardly precipitate out | Fast precipitation | Fast precipitation | Fast precipitation |
| -0.09Mpa | Slowly precipitate out | Fast precipitation | Fast precipitation | Fast precipitation |
| -0.1Mpa | Fast precipitation | Fast precipitation | Fast precipitation | Fast precipitation |
As can be seen from table 1, the lower the temperature, the higher the vacuum level required. The optimal crystallization condition is that the temperature is 70-90 ℃ and the pressure is-0.04 Mpa to-0.02 Mpa from the comprehensive consideration of factors such as energy consumption, efficiency, difficulty in recovering diethyl ether and the like.
Table 2 shows the yield and purity data of lithium aluminum hydride prepared in all the examples above.
TABLE 2
As can be seen from Table 2, the purity of the lithium aluminum hydride prepared by the preparation process of the method is above 98%, and the change of different parameters only affects the yield of the final product. The method is characterized in that the raw materials of sodium aluminum hydride, lithium chloride and sodium chloride byproduct used in the process route are all insoluble in diethyl ether, and the diethyl ether solution obtained by the reaction only contains lithium aluminum hydride, and only lithium aluminum hydride crystals can be obtained through reduced pressure distillation and drying treatment, so that the obtained lithium aluminum hydride has high purity.
Fig. 2 shows the XRD pattern of lithium aluminum hydride obtained for the process of the present invention, and it can be seen that the positions of diffraction peaks in the figure are substantially in one-to-one correspondence with characteristic peaks on standard card PDF 73-0461 (LiAlH 4), in particular, main peaks of 20 °,23 °,27 ° and 30 °, thus indicating that the sample contains only lithium aluminum hydride phase and no other impurities.
Although the present invention has been described above with reference to exemplary embodiments, the scope of protection of the present invention is not limited to the embodiments described above. It will be apparent to persons skilled in the relevant art that various changes and modifications in form and detail can be made therein without departing from the scope and spirit of the invention. The scope of the invention is defined only by the following claims and their equivalents.
Claims (10)
1. A method for preparing lithium aluminum hydride, comprising the following steps:
S100: placing a proper amount of sodium aluminum hydride, lithium chloride and an initiator into an ether solution, and fully stirring and reacting at normal temperature and normal pressure to obtain a mixed solution;
s200: carrying out solid-liquid separation on the mixed solution to obtain an diethyl ether solution containing lithium aluminum hydride and a precipitate;
s300: the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a certain temperature to obtain dry lithium aluminum hydride crystals.
2. The method according to claim 1, wherein, preferably, in step S100, the molar ratio of sodium aluminum hydride to lithium chloride is 1.0:1.0 to 1.1.
3. The method of claim 1, wherein in step S100, the molar ratio of sodium aluminum hydride to initiator is 1.0:0 to 0.1.
4. The production method according to claim 1, wherein in step S100, the purity of the sodium aluminum hydride is 95.00% to 99.50%.
5. The preparation method according to claim 1, wherein in step S100, a small amount of lithium aluminum hydride is used as the initiator.
6. The method according to claim 1, wherein in step S200, the solid-liquid separation of the mixed solution includes, but is not limited to, any of the following methods: standing for precipitation, centrifuging and filtering at positive pressure.
7. The method according to claim 1, wherein in step S300, the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a temperature of 30-90 ℃.
8. The method according to claim 1, wherein in step S300, the diethyl ether solution containing lithium aluminum hydride is distilled under reduced pressure at a temperature of 70-90 ℃.
9. The method according to claim 1, wherein in step S300, the diethyl ether solution containing lithium aluminum hydride is depressurized to-0.1 to-0.01 Mpa.
10. The method according to claim 1, wherein in step S300, the diethyl ether solution containing lithium aluminum hydride is depressurized to-0.04 to-0.02 Mpa.
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