JP2024050246A - Method for treating trialkylaluminum-containing residue - Google Patents

Abstract

[Problem] To provide a method for treating residues generated after the distillation and recovery of trialkylaluminum in the reaction for producing trialkylaluminum. [Solution] The present invention provides a method for treating trialkylaluminum-containing residues generated in the production process of trialkylaluminum, which allows them to be safely handled, and includes a step of subjecting the residue to reduced pressure distillation to distill off the trialkylaluminum contained therein. [Selected Figures] None

Description

The present invention provides a method for treating the residue generated after the reaction to produce trialkylaluminum.

As a representative Lewis acid, alkylaluminum has high industrial value and is used as a polymerization promoter for plastics, synthetic rubber, etc. In recent years, with the rapid growth of the electronic materials field, it has also been used as a raw material for insulating films of semiconductors and compound semiconductors. In general, alkylaluminum is a very dangerous substance to handle, and is known to spontaneously combust when exposed to air and to react explosively when in contact with water. Among alkylaluminums, trimethylaluminum (TMAL) in particular is extremely reactive, so a method for safely handling and manufacturing it is desirable.

A simple method for obtaining trialkylaluminum is to react aluminum powder with an alkyl halide (e.g., methyl chloride, methyl bromide) to obtain alkylaluminum sesquihalide (Me ₃ Al ₂ X _3, X = Cl, Br), which is then reduced with an alkali metal or alkaline earth metal (Non-Patent Document 1). Another method is to react an alloy containing aluminum with an alkyl halide in an organic solvent in the presence of a catalyst (Patent Document 1, Patent Document 2). The trialkylaluminum produced by these reactions has generally been separated and recovered by vacuum distillation. The residue left after distillation contains a slurry consisting of trialkylaluminum that could not be recovered, unreacted aluminum or alloy containing aluminum, inorganic salts (salts consisting of alkali metals or alkaline earth metals and halogens), and the organic solvent used in the reaction. This slurry contains trialkylaluminum, so appropriate measures, including detoxification, are required.

Generally, filtration is known as a method for treating the residue after distillation and recovery of alkylaluminum such as trialkylaluminum (Patent Document 3, Patent Document 4). As mentioned above, since a significant amount of alkylaluminum remains in the residue, the filtration must be carried out in an inert gas atmosphere, and a specialized, expensive filter with high sealing properties must be used. In addition, alkylaluminum spontaneously combusts when exposed to air, which can lead to complicated maintenance of the filter and troubleshooting operations, and can place a heavy burden on workers.

Therefore, in the production method of trialkylaluminum, the development of a method for safely and efficiently disposing of the residue obtained after the distillation and recovery of trialkylaluminum is desirable.

Japanese Patent Application Laid-Open No. 09-136890 JP 2018-135300 A JP 2010-116339 A JP 2011-84507 A

A. V. Grosse, et.al., J. Orｇ. Chem., 05, 2.106-121

The present invention provides a new method for treating the distillation residue generated after the distillation and recovery of trialkylaluminum in the production method of trialkylaluminum.

In order to solve the above problems, the inventors have come up with a method of treating the residue in which trialkylaluminum is recovered by distillation in the production reaction of trialkylaluminum, and then the residue in the reaction apparatus is subjected to a distillation process again for a purpose other than the distillation purification carried out for the purpose of obtaining trialkylaluminum, and the trialkylaluminum is distilled off from the residue to render it harmless.

Therefore, this application includes the following inventions.
(1) A method for treating a trialkylaluminum-containing residue generated in a method for producing trialkylaluminum, comprising the step of subjecting the residue to reduced pressure distillation to remove the trialkylaluminum contained therein.
(2) The method according to (1), wherein the reduced pressure distillation is carried out at a vacuum level of 0.5 to 3 kPaA.
(3) The method according to (1) or (2), wherein the reduced pressure distillation is carried out at an internal temperature of 60 to 160° C.
(4) The method according to any one of (1) to (3), wherein the reduced pressure distillation is continued for an additional 30 minutes to 3 hours from the point at which no more components are distilled off.
(5) The method according to any one of (1) to (4), wherein the method for producing trialkylaluminum comprises reacting a mixed composition containing aluminum and a metal serving as a reducing agent and/or an alloy thereof with an alkyl halide in an organic solvent.
(6) The method according to (5), wherein the organic solvent is a hydrocarbon solvent.
(7) The method according to (6), wherein the hydrocarbon solvent is at least one selected from the group consisting of saturated hydrocarbon solvents having 5 to 18 carbon atoms and aromatic hydrocarbon solvents having 6 to 12 carbon atoms.
(8) The method according to (6) or (7), wherein the organic solvent is n-dodecane.
(9) The method according to any one of (1) to (8), wherein the trialkylaluminum is trimethylaluminum.

Previous methods for treating trialkylaluminum-containing residues had issues to be resolved not only in terms of safety, but also in terms of costs, equipment, number of steps, and operability. The present invention makes it possible to treat trialkylaluminum-containing residues more safely and efficiently, while minimizing capital investment and labor costs, compared to previously known methods. In addition, the amount of organic matter contained in the residue can be reduced, which reduces the number of steps required for subsequent processing, thereby reducing costs and saving energy required for disposal. In addition, the present invention allows the organic solvent used in the reaction to be recovered and reused, which is also effective in reducing solvent costs and processing costs.

The trialkylaluminum-containing residue generated in the method for producing trialkylaluminum can be subjected to reduced pressure distillation to remove the trialkylaluminum. Examples of trialkylaluminum include trimethylaluminum, triethylaluminum, triisobutylaluminum, etc., with trimethylaluminum being particularly preferred.

The conditions for the vacuum distillation of the present invention are not particularly limited, but conditions under which trialkylaluminum is efficiently distilled off are preferred. For example, the degree of vacuum may be set to a range of 0.1 to 10 kPaA, preferably 0.5 to 3 kPaA. The temperature inside the apparatus during vacuum distillation may be 60 to 200°C, preferably 80 to 160°C. The final content of trialkylaluminum remaining in the residue may be reduced to a maximum of 0.1% by weight, more preferably to a maximum of about 0.05% by weight, and most preferably to a maximum of 0.03% by weight, so that it can be safely handled. For this reason, the vacuum distillation may be continued for an additional 10 minutes to 10 hours, preferably 30 minutes to 3 hours, more preferably 1 to 2 hours, from the point at which no components are left to be distilled off.

In addition, in the above-mentioned method for distilling off trialkylaluminum, when an organic solvent is used in the production of trialkylaluminum, the organic solvent contained in the residue can also be distilled off. In order to reduce the amount of waste, the final content of the organic solvent contained in the residue may be reduced to a maximum of about 50% by weight, more preferably to a maximum of 10% by weight, and most preferably to about 1% by weight. Furthermore, the distilled off organic solvent can be reused as a reaction solvent for trialkylaluminum.

In the present invention, the method for producing trialkylaluminum is not particularly limited, and any method may be used as long as it includes a step of distilling and separating the trialkylaluminum after its production for the purpose of purification. Specific production methods include, for example, (i) a method of producing trialkylaluminum by reacting a mixed composition containing aluminum and a metal serving as a reducing agent and/or an alloy thereof with an alkyl halide in an organic solvent, (ii) a method of contacting an alkylaluminum sesquihalide synthesized from aluminum and an alkyl halide, etc. with sodium or magnesium to obtain trimethylaluminum by reduction, and (iii) a method of activating aluminum with alkylaluminum and hydrogen, reacting it with an unsaturated hydrocarbon, and obtaining trialkylaluminum by a substitution reaction. In all of these methods, aluminum and a metal serving as a reducing agent are used, and therefore inorganic salts of these are generated in the residue after the reaction and remain in the reaction vessel, so a process for treating these is essential.

For example, when an alkyl chloride is used as a reactant and sodium is used as a reducing agent, sodium chloride is produced, and when magnesium is used, magnesium chloride is produced. Since 1.5 to 3.0 moles of these inorganic salts are produced for every mole of trialkylaluminum produced, processes including the treatment of these salts are necessary when synthesizing trialkylaluminum industrially. Therefore, by reducing the amount of trialkylaluminum contained in the residue, the treatment method for the subsequent process can be improved in an extremely safe and efficient manner.

A particularly preferred method for producing trialkylaluminum is one in which a mixed composition containing aluminum or a metal serving as a reducing agent and/or an alloy thereof as described above in (i) is reacted with an alkyl halide in an organic solvent to produce trialkylaluminum, taking into consideration the safety of the raw materials used, the number of reaction steps, and inorganic salts remaining in the residue after the reaction and the method for post-treating them.

The mixed composition containing aluminum and a metal serving as a reducing agent and/or their alloys used in the above reaction can be, for example, a mixed composition or alloy containing 20 to 99% by weight of aluminum, with the aluminum content being more preferably 30 to 70% by weight, and even more preferably 35 to 50% by weight. Specific examples of the metal serving as a reducing agent include alkali metals such as lithium, sodium, and potassium, and alkaline earth metals such as beryllium, magnesium, and calcium, and magnesium is more preferred. The alloy containing aluminum and a metal serving as a reducing agent may be any metal that forms an alloy with aluminum, such as a lithium alloy, a sodium alloy, a potassium alloy, a magnesium alloy, a calcium alloy, a barium alloy, and a strontium alloy. An aluminum-magnesium alloy is particularly preferred as an alloy.

The mixed composition of aluminum and a metal serving as a reducing agent and/or their alloys can be used in the reaction after being pulverized, although there is no particular limitation. For the pulverization, a conventional method such as a ball mill, a bead mill, or a jet mill can be used. When using a powder for the reaction, the particle size is not particularly limited, but is preferably 1 μm to 1000 μm, and more preferably 5 to 500 μm.

Any commonly available alkyl halide can be used, such as methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, isobutyl chloride, isobutyl bromide, isobutyl iodide, etc. Of the above, methyl chloride is preferred.

There are no particular limitations on the amount of alkyl halide used, but it is sufficient to use 32 mol or more per mol of aluminum in the aluminum or its alloy, and it is preferable to use 32 mol or more and 54 mol or less, and more preferably 32.5 mol or more and 43.5 mol or less.

The reaction may be carried out in a batch, semi-batch or continuous manner without any particular restrictions. As the reaction apparatus, a vertical or horizontal pressure-resistant reaction vessel may be used. For example, a pressure-resistant autoclave equipped with a stirrer may be used. As the stirring blade, any commonly known type may be used, such as a propeller, a turbine, a triple-swept blade, a large blade, etc. Furthermore, a homogenizer may also be used.

The alkyl halide may be fed into the reactor continuously or intermittently. When the alkyl halide is fed continuously, the reaction is exothermic, so it is necessary to control the amount fed and the heating temperature to prevent an excessive rise in temperature. When the alkyl halide is fed intermittently, it is preferable to heat the reaction after feeding the alkyl halide and carry out the reaction until the exothermic reaction ends. When feeding intermittently, the above reaction may be repeated. In the present invention, it is preferable to suspend a mixed composition containing aluminum and a metal serving as a reducing agent and/or an alloy thereof in a solvent to form a slurry and feed the alkyl halide.

The reaction temperature is not particularly limited, but is preferably 20°C to 200°C, and more preferably 60°C to 160°C. The reaction time is not particularly limited, but is preferably 1 to 12 hours, and more preferably 3 to 8 hours.

A solvent can be used for the reaction, for example, a hydrocarbon. The solvent is preferably a hydrophobic and poorly reactive hydrocarbon solvent, and examples of such organic solvents include at least one selected from the group consisting of saturated hydrocarbons and aromatic hydrocarbons.

The hydrocarbon solvent preferably has a boiling point in the range of 30°C or higher and 250°C or lower. The saturated hydrocarbon solvent may be a substituted or unsubstituted linear saturated hydrocarbon having 5 to 18 carbon atoms, or a substituted or unsubstituted cyclic saturated hydrocarbon. It may also contain paraffin oil or a mixture thereof.

Specific examples of the saturated hydrocarbon solvent include n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, o-menthane, m-menthane, p-menthane, decahydronaphthalene, paraffins C _n H _2n+2 , isoparaffins C _n H _2n+2 , etc. n-Dodecane is particularly preferred.

As the aromatic hydrocarbon used as the solvent, an aromatic hydrocarbon having a substituent selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, and an alkylene group having 2 to 8 carbon atoms, or an unsubstituted aromatic hydrocarbon is preferred.

Examples of alkyl groups having 1 to 8 carbon atoms that are substituents of aromatic hydrocarbons include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, neohexyl, tert-hexyl, n-heptyl, isoheptyl, neoheptyl, tert-heptyl, n-octyl, isooctyl, neooctyl, and tert-octyl groups.

Examples of cycloalkyl groups having 3 to 8 carbon atoms that are substituents of aromatic hydrocarbons include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.

Examples of alkylene groups having 2 to 8 carbon atoms that are substituents of aromatic hydrocarbons include ethylene, propylene, butylene, pentene, hexene, heptene, and octene groups.

Specific examples of the aromatic hydrocarbons include cumene, o-cumene, m-cumene, p-cumene, propylbenzene, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, 1-phenylpentane, 1-phenylheptane, 1-phenyloctane, 1,2-diethylbenzene, 1,4-diethylbenzene, mesitylene, 1,3-di-tert-butylbenzene, 1,4-di-tert-butylbenzene, di-n-pentylbenzene, tri-tert-butylbenzene, cyclohexylbenzene, indane, and tetralin.

The amount of the solvent used is not particularly limited, but can be, for example, in the range of 0.1 mol or more and 100 mol or less relative to the aluminum contained in the mixed composition containing 1 mol of aluminum and a metal serving as a reducing agent and/or an alloy thereof, and is preferably in the range of 1 mol or more and 10 mol or less.

The reaction of the alkyl halide with the mixed composition containing aluminum and a metal serving as a reducing agent and/or their alloys may be carried out in the presence of a nitrogen-containing organic compound. A nitrogen-containing organic compound is a compound containing one or more nitrogen atoms. Examples of the nitrogen-containing organic compound include amine compounds, heterocyclic compounds containing a nitrogen atom, and amide compounds. Two or more of these nitrogen-containing organic compounds may be used in combination.

Examples of amine compounds include aliphatic amine compounds, aromatic amine compounds, and heterocyclic compounds containing nitrogen atoms.

Examples of the aliphatic amine compound include primary amines such as methylamine, ethylamine, butylamine, amylamine, isoamylamine, cyclohexylamine, hexamethylenediamine, spermidine, spermine, and amantadine; secondary amines such as dimethylamine, diethylamine, diisopropylamine, dibutylamine, diisobutylamine, diamylamine, and dicyclohexylamine; and tertiary amines such as trimethylamine, triethylamine, tributylamine, triisobutylamine, triethanolamine, tricyclohexylamine, and N,N-diisopropylethylamine. In the present invention, it is particularly preferable to use a tertiary amine.

Aromatic amine compounds include aniline, N,N-dimethylaniline, phenethylamine, toluidine, catecholamine, 1,8-bis(dimethylamino)naphthalene, etc.

Heterocyclic compounds containing a nitrogen atom include saturated heterocyclic compounds such as pyrrolidine, piperidine, piperazine, morpholine, quinuclidine, and 1,4-diazabicyclo[2.2.2]octane, and unsaturated heterocyclic compounds such as pyrazole, imidazole, pyridine, 2-methylpyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, 2,6-diethylpyridine, 2,6-diisopropylpyridine, 2,2-bipyridine, pyridazine, pyrimidine, pyrazine, oxazole, thiazole, 4-dimethylaminopyridine, indole, quinoline, isoquinoline, purine, imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-butylimidazole. In the present invention, it is preferable to use unsaturated heterocyclic compounds.

The amount of nitrogen-containing organic compounds present may be 1 mol or less per mol of aluminum contained in the mixed composition containing aluminum and a metal that serves as a reducing agent and/or an alloy thereof, but is preferably in the range of 0.001 mol to 0.2 mol, more preferably 0.001 mol to 0.1 mol, and even more preferably 0.01 mol to 0.08 mol.

The effect of nitrogen-containing organic compounds in the reaction of alkyl halides with mixed compositions containing aluminum and reducing metals and/or alloys thereof is believed to be due to the formation of a complex between the nitrogen-containing organic compounds and the compounds of aluminum, magnesium, and chlorine produced by the reaction, thereby constructing a reaction system that promotes the production of trialkylaluminum. However, the entire mechanism has not yet been elucidated, and the present invention is not bound by this speculation.

In the reaction of a mixed composition containing aluminum and a metal that serves as a reducing agent and/or an alloy thereof with an alkyl halide, in addition to the nitrogen-containing organic compound, at least one additive selected from the group consisting of alkylaluminum compounds, iodine, bromine, and halogenated compounds can be present.

Examples of alkylaluminum compounds include trialkylaluminum, alkylaluminum sesquichloride, dialkylaluminum chloride, and alkylaluminum dichloride. By adding an alkylaluminum compound, the aluminum surface is activated, improving the trialkylaluminum selectivity and trialkylaluminum conversion rate.

The amount of alkylaluminum compound added is preferably in the range of 0.001 mol or more and 0.20 mol or less per 1 mol of aluminum in the aluminum-magnesium alloy, and more preferably in the range of 0.01 mol or more and 0.10 mol or less.

Examples of halogenated compounds as additives include methyl iodide, ethyl iodide, ethyl bromide, and methyl bromide. By adding iodine, bromine, and/or a halogenated compound, the reaction conversion rate of aluminum in step (1) is improved, and the trialkylaluminum selectivity and trialkylaluminum conversion rate are improved.

The amount of iodine, bromine, or a halogenated compound added is preferably in the range of 0.001 mol or more and 0.2 mol or less per mol of aluminum in the mixed composition containing aluminum and a metal that serves as a reducing agent and/or an alloy thereof, and more preferably in the range of 0.01 mol or more and 0.1 mol or less.

As an additive, it is preferable to use an alkylaluminum compound in combination with iodine, bromine, or a halogenated compound, since this improves the trialkylaluminum selectivity and trialkylaluminum conversion rate. In particular, a combination of a dialkylaluminum halide and iodine is preferable as the alkylaluminum, and when the alkyl halide raw material is methyl chloride and the trialkylaluminum product is trimethylaluminum, it is preferable that the dialkylaluminum halide is dimethylaluminum chloride and the additive is a combination of dimethylaluminum chloride and iodine.

All documents referred to herein are incorporated herein by reference in their entirety.

The examples of the present invention described below are for illustrative purposes only and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is limited only by the claims. Modifications of the present invention, such as additions, deletions, and substitutions of constituent elements of the present invention, may be made without departing from the spirit of the present invention.

The present invention will be described in more detail below with reference to examples, but these are not intended to limit the present invention in any way.

[Example 1]
A 1.5 L reactor equipped with a stirring mechanism and a piping for discharging the residue was purged with nitrogen. Then, an aluminum-magnesium alloy (92.3 g, 39.2 g, 1.45 mol in terms of aluminum) with a median diameter of 90 μm, n-dodecane (308.9 g, 1.81 mmol), iodine (11.1 g, 0.04 mmol), and 2,6-dimethylpyridine (5.5 g, 0.05 mmol) were added and stirred, and the temperature was raised to 150°C. After the temperature was raised, methyl chloride was added to start the reaction. The reaction was terminated when the heat generation ceased, and the introduction of methyl chloride was stopped. The introduction time of methyl chloride was 7 hours, and the introduction amount was 264.2 g (3.59 mol per 1 mol of aluminum). After cooling the reaction liquid, trimethylaluminum was recovered by vacuum distillation. The vacuum distillation was performed under conditions of a vacuum of 3.0 kPaA, and the end point was when the internal temperature reached 110°C. The amount of TMAL in the distillate was 62.7 g, n-dodecane was 6.2 g, and dimethylaluminum chloride (DMAC) was 14.2 g as a by-product. Next, in order to distill off the TMAL component and n-dodecane remaining in the bottom, the vacuum was kept at 1.0 kPaA and the internal temperature was kept at 90°C, and the end point was set to 1 hour from the time when distillation ceased. The amount of TMAL in the distillate was 8.5 g, the amount of DMAC was 1.9 g, and n-dodecane was 300.7 g. After the vacuum distillation, the temperature was returned to room temperature, and the bottom discharge pipe was removed in the air. The total amount of bottom was removed was 203.3 g, the alkylaluminum content was 0.03 wt%, and the n-dodecane content was 0.96 wt% (wet basis).

[Example 2]
A 1.5 L reactor equipped with a stirring mechanism and a piping for discharging the residue was purged with nitrogen. Then, aluminum powder (38.3 g, 1.46 mol) with a median diameter of 73.5 μm, magnesium powder (69.3 g, 2.85 mmol) with a median diameter of 450 μm, n-dodecane (309.1 g, 1.81 mmol), iodine (11.1 g, 0.04 mmol), and 2,6-dimethylpyridine (5.5 g, 0.05 mmol) were added and stirred, and the temperature was raised to 150°C. After the temperature was raised, methyl chloride was added to start the reaction. The reaction was terminated when the heat generation ceased, and the introduction of methyl chloride was stopped. The introduction time of methyl chloride was 7 hours, and the introduction amount was 264.7 g (3.59 mol per 1 mol of aluminum). After cooling the reaction liquid, trimethylaluminum was subsequently recovered by vacuum distillation. The vacuum distillation was performed under conditions of a vacuum of 3.0 kPaA, and the end point was when the internal temperature reached 110°C. The amount of TMAL in the distillate was 50.4 g, and n-dodecane was 3.1 g. Next, in order to distill off the TMAL component and n-dodecane remaining in the bottom, the vacuum was increased stepwise to 1.0 kPaA and the internal temperature to 160°C, and the end point was set to 1 hour from when distillation ceased. The amount of TMAL in the distillate was 12.6 g, and n-dodecane was 304.9 g. After the vacuum distillation, the temperature was returned to room temperature, and the bottom discharge pipe was removed in the air. The total amount of bottom removed was 224.0 g, the alkylaluminum content was 0.02 wt%, and the n-dodecane content was 0.50 wt% (wet basis).

Claims (9)

A method for treating trialkylaluminum-containing residues generated in a method for producing trialkylaluminum, comprising the step of subjecting the residues to reduced pressure distillation to remove the trialkylaluminum contained therein. The method according to claim 1, wherein the reduced pressure distillation is carried out at a vacuum level of 0.5 to 3 kPaA. The method according to claim 1, wherein the vacuum distillation is carried out at an internal temperature of 60 to 160°C. The method according to claim 1, wherein the vacuum distillation is continued for an additional 30 minutes to 3 hours from the point when no more components are left to be distilled off. The method according to claim 1, wherein the method for producing trialkylaluminum comprises reacting a mixed composition containing aluminum and a metal serving as a reducing agent and/or an alloy thereof with an alkyl halide in an organic solvent. The method of claim 5, wherein the organic solvent is a hydrocarbon solvent. The method according to claim 6, wherein the hydrocarbon solvent is at least one selected from the group consisting of saturated hydrocarbon solvents having 5 to 18 carbon atoms and aromatic hydrocarbon solvents having 6 to 12 carbon atoms. The method of claim 6, wherein the organic solvent is n-dodecane. The method of claim 1, wherein the trialkylaluminum is trimethylaluminum.