A process for the conversion of alkylaluminum to produce alpha-trihydroaluminum

Abstract

This invention provides a method for preparing α-aluminum trihydride by alkylaluminum conversion, comprising: Step 1, thoroughly dispersing micron-sized aluminum powder and trialkylaluminum in a solvent under the action of a stirring paddle in a mixing tank to obtain a suspension; Step 2, transferring the suspension to a reactor equipped with an internal microbubble generator for hydrogenation reaction with hydrogen gas, followed by vacuum flash evaporation to obtain dialkylaluminum hydride; Step 3, adding dialkylaluminum hydride and micron-sized aluminum powder to a solvent for hydrogenation reaction with hydrogen gas, filtering, washing the filter cake, and drying to obtain α-aluminum trihydride. The synthesis method of this invention solves the problems of high product cost, large solvent consumption, harsh synthesis conditions, and operational hazards associated with traditional aluminum trihydride synthesis routes. It achieves a high yield of α-aluminum trihydride, providing a guarantee for its wider application and demonstrating significant economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials synthesis technology, specifically relating to a method for preparing α-aluminum trihydride by alkyl aluminum conversion. Background Technology

[0002] Aluminum trihydride (ACH) is characterized by its high hydrogen content, high heat of combustion, small molecular weight of combustion products, and non-toxicity. Since its inception, it has been considered an ideal fuel for next-generation solid propellants to improve their energy performance. For the past half-century, it has been used as a rocket propellant, a strong reducing agent, and a polymerization catalyst. Until 2005, ACH was reported as a highly promising high-performance hydrogen storage material, attracting the attention of researchers in the hydrogen storage field. The thermal decomposition temperature of ACH can be further reduced through modification. In recent years, with the rapid development of hydrogen energy and fuel cell research, the research and application of ACH have received increasing attention. ACH has a relative molecular mass of 30.0 and a density of 1.48 g·cm³. -3 With a volumetric hydrogen storage density of 0.148 kg H₂ / L (more than twice the density of liquid hydrogen) and a mass hydrogen storage density of 10.08 wt.%, aluminum trihydride is considered suitable as a hydrogen storage material, a hydrogen source for fuel cells, and a polymerization catalyst. Adding it to propellants can also improve specific impulse. Aluminum trihydride possesses seven non-solventizable crystal types: α, α′, β, δ, ξ, θ, and γ. Considering all factors, α-aluminum trihydride is the most stable at room temperature and offers the highest relative safety during use, making it the most valuable for development and application. However, the standard preparation and synthesis conditions for aluminum hydride are extremely demanding, and obtaining high-purity α-aluminum trihydride is extremely difficult, severely hindering its further development and application.

[0003] Currently, domestic and international research on the synthesis and preparation of α-aluminum trihydride mainly includes liquid-phase synthesis, dry synthesis, supercritical methods, and electrochemical synthesis. These methods mostly require medium-high temperature or high-pressure environments, posing safety risks and involving complex preparation processes. Chinese patent CN106986306A discloses a method for preparing high-purity α-aluminum trihydride by using lithium aluminum hydride to catalytically reduce aluminum chloride. Chinese patent CN109970030A discloses a synthesis process for α-aluminum trihydride where the diethyl ether solvent used in the preparation process can be directly recovered without distillation, reducing the raw material cost and energy consumption of α-aluminum trihydride. Chinese patent CN113072041A discloses a method for preparing fine-particle α-aluminum trihydride by coating α-aluminum trihydride with a gel material followed by grinding to obtain fine-particle α-aluminum trihydride. Chinese patent CN106957046A discloses an improved process for preparing α-aluminum trihydride, which uses graphene to activate the reaction solution, improving production safety.

[0004] A comparison of the aforementioned patents reveals that the preparation processes of α-aluminum trihydride are either relatively complex, or the raw materials are difficult to obtain, requiring large quantities of specially treated organic reagents, resulting in high costs, or the preparation efficiency is low, making large-scale mass production difficult. This severely limits the widespread promotion and application of α-aluminum trihydride. Therefore, finding a simple, efficient, and low-energy-consumption method for preparing α-aluminum trihydride is an urgent problem that needs to be solved for practical applications. Summary of the Invention

[0005] This invention provides a method for preparing α-aluminum trihydride by alkyl aluminum conversion, aiming to solve the problems of existing α-aluminum trihydride preparation processes being complex, requiring harsh synthesis conditions, consuming large amounts of energy, using large quantities of solvent, having high production costs, low yields, posing operational hazards, and being difficult to achieve industrial-scale production.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for preparing α-aluminum trihydride by conversion of alkyl aluminum, the specific steps of which are as follows:

[0008] Step 1: Micron-sized aluminum powder and trialkyl aluminum are thoroughly stirred and dispersed in a solvent under the action of a high-efficiency stirring paddle in a mixing tank to obtain a suspension;

[0009] Step 2: The suspension obtained in Step 1 is transported to a reactor equipped with a high-efficiency microbubble generator, where it undergoes a hydrogenation reaction with hydrogen gas and is then flash-evaporated under reduced pressure to obtain dialkyl aluminum hydride.

[0010] Step 3: Add the dialkyl aluminum hydride obtained in Step 2 and micron-sized aluminum powder to the solvent, perform a hydrogenation reaction with hydrogen gas, filter, wash the filter cake, and dry to obtain α-aluminum trihydride.

[0011] Further, in step 1, the trialkylaluminum is selected from any one or more of trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0012] Furthermore, in steps 1 and 3, the particle size of the micron-sized aluminum powder is 60-130 μm.

[0013] Furthermore, in step 1, the molar ratio of micron-sized aluminum powder to trialkylaluminum is 1:0.2 to 1.2.

[0014] Furthermore, in steps 1 and 3, the solvents are each independently selected from any one or more of toluene, tetrahydrofuran, benzene, and n-hexane.

[0015] Furthermore, in step 1, the ratio of the amount of micron-sized aluminum powder to the volume of the solvent is 1 mol: 0.8 L to 3.6 L.

[0016] Furthermore, in step 1, stirring is carried out at 0–80°C for 0.5–3 hours.

[0017] Furthermore, in step 2, the hydrogen pressure is 0.1–3 MPa.

[0018] Furthermore, in step 2, the reaction time of the hydrogenation reaction is 1 to 10 hours and the reaction temperature is 0 to 80°C.

[0019] Furthermore, in step 2, the temperature of the reduced pressure flash evaporation is 30–100°C, and the pressure is 0.1–0.8 bar.

[0020] Furthermore, in step 3, the molar ratio of micron-sized aluminum powder to dialkyl aluminum hydride is 1:0.2 to 1.2.

[0021] Furthermore, in step 3, the hydrogen is supplied by a self-aspirating high-efficiency stirred tank, the molar ratio of dialkyl aluminum hydride to hydrogen is 1:5 to 9, the hydrogenation reaction is carried out at 40 to 120°C, and the reaction time is 2 to 20 hours.

[0022] Furthermore, in step 3, the filter cake is washed with toluene.

[0023] Furthermore, in step 3, the drying method is vacuum drying, and the drying temperature is 40–100°C.

[0024] The present invention provides a method for preparing α-aluminum trihydride by conversion of alkyl aluminum, which has the following beneficial effects:

[0025] 1. The synthesis method of this invention solves the problems of high product cost, large solvent consumption, harsh synthesis conditions, and dangerous operation in the traditional aluminum trihydride synthesis route. It has a high yield of α-aluminum trihydride, which provides a guarantee for the wider application of α-aluminum trihydride and has significant economic and social benefits.

[0026] 2. The alkyl aluminum raw material used in the synthesis method of the present invention overcomes the problems of the raw material AlCl3 containing impurities such as FeCl3, which are difficult to purify and sensitive to moisture in the air, in the prior art. It reduces equipment requirements and process operation difficulty, and the resulting product has high yield and good quality.

[0027] 3. The raw materials alkyl aluminum and hydrogen used in the synthesis method of the present invention are easy to recover and can be recycled, which greatly reduces the production cost of α-aluminum trihydride. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the synthesis process of dialkyl aluminum hydride according to the present invention;

[0029] Figure 2 This is a schematic diagram of the synthesis process of α-aluminum trihydride according to the present invention;

[0030] Figure 3 This is the XRD pattern of the product α-aluminum trihydride obtained in Example 2 of the present invention;

[0031] Figure 4 This is an SEM image of the product α-aluminum trihydride obtained in Example 2 of the present invention. Detailed Implementation

[0032] The present invention will be described in detail below through embodiments, and the features and advantages of the present invention will become clearer and more explicit with these descriptions. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a method for preparing α-aluminum trihydride by conversion of alkyl aluminum, comprising the following steps:

[0034] Step 1: Micron-sized aluminum powder with a certain particle size and trialkyl aluminum are thoroughly stirred and dispersed in a solvent under the action of a stirring paddle in a mixing tank to obtain a suspension.

[0035] In a preferred embodiment, the trialkylaluminum is selected from any one or more of trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0036] In a preferred embodiment, the particle size of the micron-sized aluminum powder is 60-130 μm.

[0037] In a preferred embodiment, the molar ratio of micron-sized aluminum powder to trialkylaluminum is 1:0.2 to 1.2.

[0038] In a preferred embodiment, the solvent is selected from any one or more of toluene, tetrahydrofuran, benzene, and n-hexane.

[0039] In a preferred embodiment, the molar ratio of micron-sized aluminum powder to the volume of the solvent is 1 mol: 0.8 L to 3.6 L.

[0040] In a preferred embodiment, stirring is carried out at 0–80°C for 0.5–3 hours.

[0041] Step 2: The suspension obtained in Step 1 is transported to a reactor equipped with a high-efficiency microbubble generator to undergo a hydrogenation reaction with hydrogen gas, followed by vacuum flash evaporation to obtain dialkyl aluminum hydride.

[0042] In a preferred embodiment, the hydrogen pressure is 0.1–3 MPa.

[0043] In a preferred embodiment, the hydrogenation reaction takes 1 to 10 hours and the reaction temperature is 0 to 80°C.

[0044] In a preferred embodiment, the temperature of the reduced pressure flash evaporation is 30–100°C, and the pressure is 0.1–0.8 bar.

[0045] Step 3: Add the dialkyl aluminum hydride obtained in Step 2 and micron-sized aluminum powder to the solvent, perform a hydrogenation reaction with hydrogen gas, filter, wash the filter cake, and dry to obtain α-aluminum trihydride.

[0046] In a preferred embodiment, the molar ratio of micron-sized aluminum powder to dialkyl aluminum hydride is 1:0.2 to 1.2.

[0047] In a preferred embodiment, the solvent is selected from any one or more of toluene, tetrahydrofuran, benzene, and n-hexane.

[0048] In a preferred embodiment, hydrogen is supplied by a self-aspirating high-efficiency stirred tank.

[0049] In a preferred embodiment, the molar ratio of dialkylaluminum hydride to hydrogen is 1:5 to 9.

[0050] In a preferred embodiment, the hydrogenation reaction is carried out at 40–120°C for 2–20 h.

[0051] In a preferred embodiment, the filter cake is washed with toluene.

[0052] In a preferred embodiment, the drying method is vacuum drying, and the drying temperature is 40-100℃.

[0053] Example 1

[0054] In this embodiment, α-aluminum trihydride was prepared according to the following steps:

[0055] S1-1: Weigh 27g of micron-sized aluminum powder and 18g of trimethylaluminum in a glove box.

[0056] S1-2: Add 2L of toluene to the mixing tank.

[0057] S1-3: Add 27g of micron-sized aluminum powder and 18g of trimethylaluminum weighed in S1-1 to the mixing tank, and mechanically stir for 2 hours at a speed of 300r / min and a temperature of 30℃ to obtain a suspension.

[0058] S2-1: The suspension obtained in S1-3 is transported to the reactor.

[0059] S2-2: The reactor is equipped with a high-efficiency microbubble generator, and the reactor is input with a hydrogen pressure of 1.5 MPa.

[0060] S2-3: The hydrogenation reaction proceeds for 2 hours, with the reactor temperature maintained at 30°C.

[0061] S2-4: After the reaction was completed, 21.5 g of dimethylaluminum hydride was obtained by flash evaporation under reduced pressure at 0.3 bar and 30 °C.

[0062] S3-1: Weigh 54g of micron-sized aluminum powder into the glove box.

[0063] S3-2: Add 4L of toluene to the stirred tank.

[0064] S3-3: Add the 54g of micron-sized aluminum powder weighed in S3-1 and the 21.5g of dimethyl aluminum hydride obtained in S2-4 into a stirred tank.

[0065] S3-4: 6g of hydrogen is supplied to the self-priming high-efficiency stirred tank and stirred for 2 hours at 40℃.

[0066] S3-5: After filtration, the filter cake was washed with toluene and placed in a vacuum drying oven at 45°C for 3 hours to obtain 21g of aluminum trihydride. The yield was 93.3%, the product purity was 98.7%, and the average particle size was 105μm.

[0067] Example 2

[0068] In this embodiment, α-aluminum trihydride was prepared according to the following steps:

[0069] S1-1: Weigh 108g of micron-sized aluminum powder and 72g of trimethylaluminum in a glove box.

[0070] S1-2: Add 8L of toluene to the mixing tank.

[0071] S1-3: Add 108g of micron-sized aluminum powder and 72g of trimethylaluminum weighed in S1-1 to the mixing tank, and mechanically stir for 4 hours at a speed of 300r / min and a temperature of 30℃ to obtain a suspension.

[0072] S2-1: The suspension obtained in S1-3 is transported to the reactor.

[0073] S2-2: The reactor is equipped with a high-efficiency microbubble generator, and the reactor is input with a hydrogen pressure of 1.5 MPa.

[0074] S2-3: The hydrogenation reaction was carried out for 4 hours, and the reactor temperature was maintained at 30℃.

[0075] S2-4: After the reaction was completed, the product was flash evaporated under reduced pressure at 0.3 bar and 30 °C to obtain 86.1 g of dimethyl aluminum hydride.

[0076] S3-1: Weigh 216g of micron-sized aluminum powder in the glove box.

[0077] S3-2: Add 16L of toluene to the stirred tank.

[0078] S3-3: Add 216g of micron-sized aluminum powder weighed in S3-1 and 86.1g of dimethylaluminum hydride obtained in S2-4 into a stirred tank.

[0079] S3-4: 24g of hydrogen is supplied to the self-priming high-efficiency stirred tank, and the reaction is carried out at 40℃ for 4 hours.

[0080] S3-5: After filtration, the filter cake was washed with toluene and placed in a vacuum drying oven at 45°C for 5 hours to obtain 86.6 g of aluminum trihydride. The yield was 96.2%, the product purity was 99.2%, and the average particle size was 118 μm.

[0081] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0082] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the conversion of alkylaluminum to produce α-trihydroaluminum, characterized in that, The method comprises the following steps: Step 1: micron-sized aluminum powder and trialkyl aluminum are fully stirred and dispersed in a solvent in a batching tank under the action of stirring blades, to obtain a suspension, wherein the molar ratio of micron-sized aluminum powder to trialkyl aluminum is 1:0.2-1.2; Step 2: the suspension obtained in Step 1 is transported to a reactor provided with a micro-bubble generating device, and hydrogenation reaction is performed with hydrogen, and then flash evaporation is performed under reduced pressure, to obtain dialkyl aluminum hydride; wherein the hydrogen pressure is 0.1-3 MPa, the reaction time of the hydrogenation reaction is 1-10 h, and the reaction temperature is 0-80℃; Step 3: the dialkyl aluminum hydride obtained in Step 2 and micron-sized aluminum powder are added to a solvent, and hydrogenation reaction is performed with hydrogen, then filtration is performed, the filter cake is washed and dried, to obtain α-trihydroaluminum; wherein the molar ratio of micron-sized aluminum powder to dialkyl aluminum hydride is 1:0.2-1.2, the hydrogen is transported by self-suction gas high-efficiency stirred tank, the molar ratio of dialkyl aluminum hydride to hydrogen is 1:5-9, and the hydrogenation reaction is performed at 40-120℃, and the reaction time is 2-20 h.

2. The process for the conversion of aluminum alkyls to produce a-trihydroaluminum according to claim 1, characterized in that, In Step 1, the trialkyl aluminum is selected from any one or more of trimethyl aluminum, triethyl aluminum and triisobutyl aluminum.

3. The method of claim 1, wherein the aluminum alkyl is converted to α-trihydroaluminum. In Step 1 and Step 3, the particle size of the micron-sized aluminum powder is 60-130 μm.

4. The method of claim 1, wherein the aluminum alkyl is converted to α-trihydroaluminum. In Step 1 and Step 3, the solvent is independently selected from any one or more of toluene, tetrahydrofuran, benzene and n-hexane.

5. The method of claim 1, wherein the aluminum alkyl is converted to α-trihydroaluminum. In Step 1, the stirring is performed at 0-80℃, and the stirring time is 0.5-3 h.

6. The method of claim 1, wherein the aluminum alkyl is converted to α-trihydroaluminum. In Step 2, the temperature of the flash evaporation under reduced pressure is 30-100℃, and the pressure is 0.1-0.8 bar.

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