A method of cleaning a reactor for producing aluminum trihydride

Abstract

The application discloses a cleaning method of a cauldron for preparing aluminum trihydride, which comprises the following steps: (1) under an inert gas atmosphere, adding a polyhalogenated hydrocarbon solvent and an inorganic salt abrasive into the cauldron, and stirring intensively to grind off the wall-bonding substances in the cauldron; (2) emptying the cauldron, and slowly feeding a buffer solution into the cauldron through a bottom pipe in a vacuum-extraction mode, so that the buffer solution is immersed into the cauldron from the bottom of the cauldron; and (3) sequentially using dilute alkali, dilute acid and water to completely immerse the wall-bonding layer, and then washing the cauldron with water. The method can safely and effectively remove the wall-bonding substances on the cauldron.

Description

Technical Field

[0001] This invention belongs to the field of aluminum trihydride preparation technology, specifically relating to a method for cleaning a reactor used in the preparation of aluminum trihydride. Background Technology

[0002] Aluminum trihydride is a metastable binary covalent polymer with a volumetric hydrogen release of 148 g H₂ / L, approximately twice that of liquid hydrogen. Except for α-AlH₃ (unless otherwise specified, aluminum trihydride referred to hereafter is α-AlH₃), its other crystal forms are unstable and exhibit dangerous characteristics such as spontaneous decomposition, decomposition upon contact with air, and decomposition and combustion upon contact with alkaline substances or organic matter containing active groups. From a process flow perspective, the synthesis of aluminum trihydride includes an anhydrous and oxygen-free solvent treatment section, a raw material lithium aluminum hydride refining section, an aluminum trihydride ether complex preparation section, a lithium chloride filtration section, a high-temperature deetherification and crystallization section of the ether complex, and a crude product post-processing section. Whether in the refining section of the raw material lithium aluminum hydride or in the preparation of the aluminum trihydride diethyl ether complex (AlH₃· x In the preparation of Et₂O and the high-temperature deetherification crystallization section, varying degrees of wall formation can occur due to various reasons, including incomplete dissolution of raw materials resulting in small amounts of residue, the inherent properties of aluminum hydride crystals, splashing of ether compounds onto the stirring rod and reactor wall during stirring, and decomposition of crystals on the reactor wall, stirring rod, and stirring blades caused by high bath temperature and long deetherification time. In 5L and smaller-scale synthesis, dangerous wall formations can be removed outdoors by directly adding dilute acid or alkali to multi-necked flasks and stirring blades. However, this method almost always produces a violent hydrogen release reaction, which can lead to localized fires in severe cases. As the synthesis scale increases, the reactor capacity grows, making the above-mentioned reactor cleaning methods unsuitable. Therefore, how to safely and effectively remove wall formations and clean the reactor has become one of the challenges restricting the scale-up of aluminum hydride production.

[0003] There are many methods for cleaning reaction vessels in industry, such as direct water washing, spray washing, frame-type stirring cleaning, solvent dissolution cleaning, and cleaning by removing the vessel lid. However, these methods are risky and inefficient in the field of metal hydrides. Research shows that in the large-scale synthesis of metal hydrides, such as the preparation of lithium aluminum hydride, it is possible to either not wash the vessels or to clean them centrally once a quarter or year. Clearly, this approach is not feasible for aluminum trihydride, because the synthesis of aluminum trihydride, especially in the high-temperature deetherification crystallization section, requires extremely high surface quality from the vessel walls and agitators. The surfaces must be clean, dry, and free of impurities; otherwise, high-purity α-type crystals cannot be crystallized, and in severe cases, it can directly cause the decomposition of crystal nuclei during crystallization, leading to an explosion. Therefore, each reaction vessel must be cleaned after each synthesis. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for cleaning a reactor used in the preparation of aluminum trihydride. The method involves using inorganic salts to grind and remove dangerous wall-forming materials such as aluminum-containing impurities, lithium aluminum hydride residue, non-α-type aluminum trihydride crystals, and incomplete α-type aluminum trihydride crystals adhering to the inner wall of the reactor, stirring rod, and stirring blades in a polyhalogenated hydrocarbon solvent. The reactor is further cleaned using buffer solutions, dilute alkalis, and dilute acids.

[0005] The technical solution of the present invention is as follows:

[0006] A method for cleaning an autoclave used in the preparation of aluminum trihydride includes the following steps:

[0007] (1) Under an inert gas atmosphere, add polyhalogenated hydrocarbon solvent and inorganic salt grinding agent to the reactor and stir vigorously to remove the wall material inside the reactor;

[0008] (2) Empty the vessel and slowly introduce the buffer solution through the bottom tube in a vacuum manner. The buffer solution enters the vessel from the bottom for rinsing.

[0009] (3) Clean the vessel by completely immersing the wall layer with dilute alkali, dilute acid and water in sequence, and then rinse with water.

[0010] Preferably, the polyhalogenated hydrocarbon mentioned in step (1) is one or more of carbon tetrachloride, perchloroethylene, chloroform, etc., and carbon tetrachloride is more preferred.

[0011] Preferably, the inorganic salt abrasive in step (1) is one or more of sodium chloride, sodium sulfate, and zirconium oxide, with sodium chloride being more preferred.

[0012] Preferably, the buffer solution in step (2) is one or more of potassium dihydrogen phosphate-sodium hydroxide, potassium dihydrogen phosphate-potassium hydroxide, sodium dihydrogen phosphate-disodium hydrogen phosphate, acetic acid-sodium acetate aqueous solution, etc., preferably potassium dihydrogen phosphate-sodium hydroxide solution; the buffer solution has a pH of 6-8 and a concentration of 0.05-0.5 mol / L; more preferably, it is a potassium dihydrogen phosphate / sodium hydroxide solution with a pH of 7 and a concentration of 0.1 mol / L.

[0013] Preferably, the soaking time in step (2) is 15-30 minutes, and stirring is performed during soaking.

[0014] Preferably, the vacuuming method described in step (2) is intermittent vacuum or direct vacuuming, preferably intermittent vacuum; the vacuum degree is 0.020MPa-0.098MPa.

[0015] Preferably, the slow liquid injection in step (2) refers to the rate at which the surface of the buffer solution in the reactor rises at a rate not exceeding 50 mm / min, and more preferably 5 mm / min to 25 mm / min.

[0016] Preferably, in step (3), after the dilute alkali, dilute acid, and water completely submerge the wall layer, they are stirred for 5-15 minutes respectively to ensure that the inner wall of the reactor, the stirring rod, and the stirring blades are clean. The dilute alkali is a sodium hydroxide aqueous solution or potassium hydroxide aqueous solution of less than 10 wt.%, more preferably a sodium hydroxide aqueous solution of 3 wt.%; the dilute acid is a hydrochloric acid aqueous solution or phosphoric acid aqueous solution of less than 10 wt.%, more preferably a hydrochloric acid aqueous solution of 5 wt.%.

[0017] Preferably, the reactor is a lithium aluminum hydride dissolving reactor, a lithium aluminum hydride refining reactor, an aluminum trihydride ether preparation reactor, or an aluminum trihydride ether crystallization reactor.

[0018] In the synthesis of aluminum trihydride, the method for cleaning the reactor of the present invention has the following advantages:

[0019] (1) Because polyhalogenated hydrocarbons are not flammable, they can be used as good fire extinguishing agents or flame retardants. When used as a grinding solvent, they can prevent fires from occurring. This is especially important for cleaning large-capacity reactors involving metal hydrides.

[0020] (2) Compared with ceramic grinding media, inorganic salts can reduce wear on the vessel. In addition, inorganic salts are also good extinguishing agents for the ignition of metal hydrides, and can also prevent fires from occurring.

[0021] (3) Inorganic salt abrasives usually contain trace amounts of water, which is beneficial for the passivation of aluminum trihydride on the agglomeration wall and for promoting the gradual decomposition of aluminum trihydride impurities with particularly high activity.

[0022] (4) Polyhalogenated hydrocarbons have a relatively high density, which can effectively separate metal hydrides and abrasives, and can also recover some aluminum trihydride products, thereby increasing the yield.

[0023] (5) Abrasives and polyhalogenated hydrocarbons can be recycled.

[0024] (6) By using the method of introducing buffer solution into the bottom of the intermittent vacuum vessel, the risk of explosion or fire can be prevented from the dangerous wall material coming into large-area contact with the buffer solution in a short period of time, generating a large amount of hydrogen gas. The principle is that under intermittent vacuum, once a large amount of hydrogen gas is generated, the vacuum degree inside the vessel will decrease, and the buffer solution injection rate will automatically decrease or stop, ensuring sufficient safety.

[0025] (7) Whether it is the aluminum lithium hydride dissolving vessel or refining vessel involved in the raw material purification process, or the aluminum trihydride ether preparation vessel or deether crystallization vessel involved in the synthesis of aluminum trihydride, they can all be cleaned by the method of the present invention. This is of great significance to the safety of cleaning reaction vessels after the large-scale alumina trihydride production. Attached Figure Description

[0026] Figure 1This refers to the aluminum trihydride deetherification crystallization vessel before cleaning in Example 1;

[0027] Figure 2 The aluminum trihydride deetherification crystallization vessel after grinding the inorganic salt in step (1) in Example 1;

[0028] Figure 3 This is the aluminum trihydride deetherification crystallization vessel after cleaning in Example 1. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments. The present invention is not limited to the embodiments. Those skilled in the art should understand that any improvement to the present invention, equivalent substitution of raw materials for the products of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0030] Example 1

[0031] Cleaning the 10L aluminum trihydride deetherification crystallization vessel:

[0032] (1) Under a nitrogen atmosphere, 2 kg of sodium chloride and 6 L of carbon tetrachloride were added to a 10 L aluminum trihydride deether crystallization vessel and stirred at 150 rpm for 2 h to remove aluminum-containing impurities, non-α type and defective α type aluminum trihydride crystals and other dangerous wall deposits attached to the inner wall of the reactor, stirring rod, stirring blades and other parts.

[0033] (2) Empty the crystallization vessel, evacuate the crystallization vessel to -0.098MPa, close the vacuum valve, open the liquid inlet valve of the bottom tube, and add the phosphate buffer solution (composed of potassium dihydrogen phosphate and sodium hydroxide, pH=7, concentration of 0.1mol / L) into the vessel through the glass tube placed at the bottom of the vessel. Control the liquid level rise rate to 5mm / min until the buffer solution completely submerges the wall layer, and stir for 15min.

[0034] (3) Discharge the buffer solution, and wash it with 7L of 3% dilute NaOH solution, 5% dilute HCl solution and tap water for 10 minutes in sequence to ensure that the inner wall of the vessel, the stirring rod, the stirring blades, etc. are clean. Finally, rinse with deionized water.

[0035] After grinding in step (1), the densities of sodium chloride, carbon tetrachloride, and aluminum trihydride are different (2.165 g / cm³, respectively). 3 1.595g / cm 3 1.30g / cm 3 ~1.49g / cm 3 It can separate sodium chloride and carbon tetrachloride and recover aluminum trihydride products, thereby increasing the yield.

[0036] Experiments show that the 10L crystallization vessel cleaned by the method of the present invention can be used continuously, and it is easier to crystallize high-purity α-AlH3 during the deetherification crystallization process of aluminum trihydride ether compounds. In contrast, when the crystallization vessel is used for the second time without cleaning, partial decomposition occurs during the crystallization process, and the crystal purity (α-type content) is not high.

[0037] Example 2

[0038] Cleaning the 30L aluminum trihydride ether compound preparation vessel:

[0039] (1) Under a nitrogen atmosphere, 3 kg of sodium sulfate and 20 L of chloroform were added to a 30 L aluminum hydride ether preparation vessel and stirred at 150 rpm for 2 h to remove the lithium aluminum hydride residue, aluminum hydride ether solid, lithium chloride and other dangerous wall-forming materials that adhered to the inner wall of the reaction vessel, stirring rod, stirring blade and other parts.

[0040] (2) Empty the preparation vessel, evacuate the preparation vessel to -0.080MPa, close the vacuum valve, open the liquid inlet valve of the bottom tube of the vessel, and add the phosphate buffer solution (composed of potassium dihydrogen phosphate and sodium hydroxide, pH=7, concentration of 0.1mol / L) into the vessel through the glass tube placed at the bottom of the vessel. Control the liquid level rise rate to 10mm / min until the buffer solution completely submerges the wall layer, and stir for 20min.

[0041] (3) Discharge the buffer solution, and wash it with 20L of 2% dilute NaOH solution, 6% dilute HCl solution and tap water in sequence for 10 minutes with stirring to ensure that the inner wall of the vessel, stirring rod and stirring blade are clean. Finally, rinse with deionized water.

[0042] Experiments show that the method of this invention does not generate a large amount of decomposed hydrogen gas or cause fires during the cleaning of the preparation vessel. The process is simple, safe, and effective. Subsequent experiments separated the hazardous wall deposits from sodium chloride. The hazardous wall deposits release a large amount of hydrogen gas and even ignite upon contact with water. This demonstrates that traditional vessel cleaning methods struggle to balance safety and cleaning objectives.

[0043] Example 3

[0044] Cleaning the 50L aluminum trihydride deetherification crystallization vessel:

[0045] (1) Under a nitrogen atmosphere, 4 kg of sodium chloride and 30 L of carbon tetrachloride were added to a 50 L aluminum trihydride deether crystallization vessel and stirred at 150 rpm for 5 h to remove aluminum-containing impurities, non-α-type crystals and defective α-type crystals and other dangerous wall deposits attached to the inner wall of the reactor, stirring rod, stirring blades and other parts.

[0046] (2) Empty the crystallization vessel, evacuate the crystallization vessel to -0.080MPa, close the vacuum valve, open the liquid inlet valve of the bottom tube, and add the phosphate buffer solution (composed of potassium dihydrogen phosphate and sodium hydroxide, pH=7, concentration of 0.1mol / L) into the vessel through the glass tube placed at the bottom of the vessel. Control the liquid level rise rate to 15mm / min until the buffer solution completely submerges the wall layer, and stir for 20min.

[0047] (3) Discharge the buffer solution, and wash it with 40L of 3% dilute NaOH solution, 5% dilute HCl solution and tap water for 15 minutes in sequence to ensure that the inner wall of the vessel, the stirring rod, the stirring blades, etc. are clean. Finally, rinse with deionized water.

[0048] After grinding, based on the different densities of sodium chloride, carbon tetrachloride, and aluminum trihydride (2.165 g / cm³, respectively)... 3 1.595g / cm 3 1.30g / cm 3 ~1.49g / cm 3 It can separate sodium chloride and carbon tetrachloride and recover aluminum trihydride products, thereby increasing the yield.

[0049] The 50L crystallization vessel cleaned by the method of this invention can be used continuously. During the deetherification and crystallization process of aluminum hydride ether compounds, it is easier to crystallize high-purity α-AlH3. In contrast, when a crystallization vessel that has not been cleaned is used a second time, partial decomposition occurs during the crystallization process, and the crystal purity (α-type content) is not high. Therefore, the method of this invention can also be applied to larger-scale aluminum hydride synthesis reactors.

[0050] Example 4

[0051] Cleaning the 50L lithium aluminum hydride dissolving vessel:

[0052] (1) Under a nitrogen atmosphere, 4 kg of abrasive zirconium oxide and 30 L of perchloroethylene were added to a 50 L lithium aluminum hydride dissolving vessel and stirred at 150 rpm for 4 h to remove dangerous wall-forming materials such as lithium aluminum hydride residues adhering to the inner wall of the reactor, stirring rod, stirring blade, etc.

[0053] (2) Empty the dissolving vessel, evacuate the dissolving vessel to -0.050MPa, close the vacuum valve, open the liquid inlet valve of the bottom tube, and add the phosphate buffer solution (composed of potassium dihydrogen phosphate and potassium hydroxide, pH=7, concentration of 0.1mol / L) into the vessel through the glass tube placed at the bottom of the vessel. Control the liquid level rise rate to 20mm / min until the buffer solution completely submerges the wall layer, and stir for 20min.

[0054] (3) Discharge the buffer solution, and wash it with 40L of 5% dilute NaOH solution, 7% dilute HCl solution and tap water for 15 minutes in sequence to ensure that the inner wall of the vessel, the stirring rod, the stirring blades, etc. are clean. Finally, rinse with deionized water.

[0055] Experiments show that the method of this invention does not generate a large amount of decomposed hydrogen gas or cause fire when cleaning the lithium aluminum hydride dissolving vessel. The process is simple, safe, and effective. Similarly, subsequent experiments separated the hazardous wall deposits from sodium chloride. The hazardous wall deposits release a large amount of hydrogen gas and even ignite upon contact with water. Therefore, traditional vessel cleaning methods struggle to balance safety and cleaning objectives, while the method of this patented invention achieves both and can be applied to larger-scale aluminum trihydride synthesis reactors.

Claims

1. A method for cleaning a reactor for preparing aluminum trihydride, comprising the following steps: (1) under an inert gas atmosphere, adding a polyhalogenated hydrocarbon solvent and an inorganic salt abrasive into the reactor, and stirring vigorously to grind off the wall deposits in the reactor; (2) emptying the reactor, and slowly feeding a buffer solution into the reactor through a bottom pipe in a vacuum extraction mode, and immersing the buffer solution from the bottom of the reactor into the reactor for immersion cleaning; (3) sequentially immersing the wall deposits in dilute alkali, dilute acid and water, and then rinsing with water. The polyhalogenated hydrocarbon in step (1) is one or more of carbon tetrachloride, perchloroethylene and chloroform. The inorganic salt abrasive in step (1) is one or more of sodium chloride, sodium sulfate and zirconium oxide. The polyhalogenated hydrocarbon in step (1) is carbon tetrachloride. The inorganic salt abrasive in step (1) is sodium chloride. The buffer solution in step (2) is one or more of potassium dihydrogen phosphate-sodium hydroxide, potassium dihydrogen phosphate-potassium hydroxide, sodium dihydrogen phosphate-disodium hydrogen phosphate, and acetic acid-sodium acetate aqueous solution.

2. The method of claim 1, wherein, The buffer solution in step (2) has a pH of 6-8 and a concentration of 0.05-0.5 mol / L.

3. The method of claim 1, wherein, The vacuum extraction mode in step (2) is intermittent vacuum or direct vacuum.

4. The method of claim 1, wherein, The vacuum degree in step (2) is 0.020-0.098 MPa.

5. The method according to claim 1 or 4, characterized in that, The slow feeding in step (2) is such that the buffer solution in the reactor rises at a rate of not more than 50 mm / min.

6. The method of claim 1, wherein, The slow feeding in step (2) is such that the buffer solution in the reactor rises at a rate of 5-25 mm / min.

7. The method of claim 1, wherein, The dilute alkali in step (3) is an aqueous solution of sodium hydroxide or potassium hydroxide having a concentration of not more than 10 wt.%; and the dilute acid is an aqueous solution of hydrochloric acid or phosphoric acid having a concentration of not more than 10 wt.%.

8. The method of claim 1, wherein, The dilute alkali in step (3) is an aqueous solution of sodium hydroxide having a concentration of 3 wt.%; and the dilute acid is an aqueous solution of hydrochloric acid having a concentration of 5 wt.%.

9. The method of claim 8, wherein, The reactor is a lithium aluminum hydride dissolving reactor, a lithium aluminum hydride refining reactor, an etherate aluminum trihydride preparing reactor or an etherate aluminum trihydride de-etherating and crystallizing reactor.

10. The method of claim 1, wherein, ​ 11. The method of claim 10, wherein, ​ 12. The method of claim 1, wherein, ​

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