Method for preparing trimethyl aluminum through reaction of triethyl aluminum and chloromethane
By using inexpensive chloromethane and a composite catalyst to activate triethylaluminum, the problems of low conversion rate and high cost in the existing preparation of trimethylaluminum have been solved, achieving high yield and recyclable catalyst use, which has industrialization potential.
Patent Information
- Application Number
- CN202511282018.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-09
- Publication Date
- 2025-11-14
AI Technical Summary
Existing methods for preparing trimethylaluminum have low conversion and yield rates, use expensive bromomethane or iodomethane as methylating agents, have high catalyst costs, and the catalysts are difficult to recycle.
Using inexpensive chloromethane as the methylating agent, a composite catalyst composed of bismuth and zinc halides is used to activate triethylaluminum in a high-pressure liquid-phase reaction. The catalyst can be recycled after the reaction.
The yield of trimethylaluminum was increased to 81%, production costs were reduced, the catalyst can be recycled, and it has industrialization prospects.
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Figure CN120943854A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fine chemicals, and more specifically to a novel method for preparing trimethylaluminum. Background Technology
[0002] Trimethylaluminum, as an important organometallic compound, plays a crucial role in organic catalysis, organic synthesis, polymer chemistry, semiconductor chip manufacturing, and defense technology. In recent years, with the rapid development of novel catalyst systems such as metallocene catalysts, post-transition metal catalysts, and non-metallocene catalysts, trimethylaluminum, as a raw material for the synthesis of its key co-catalyst methylaluminoxane (MAO), has demonstrated increasingly prominent value. In the semiconductor manufacturing field, high-purity trimethylaluminum, due to its excellent chemical properties, has become one of the most important metal-based precursor materials in chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes, mainly used for depositing aluminum nitride and alumina thin films. Furthermore, due to its unique self-ignition properties, trimethylaluminum is widely used in the defense industry for rocket propellants and the research and development of novel energetic materials. With continuous breakthroughs in new materials technology, the application prospects of trimethylaluminum in various industrial fields will become even broader.
[0003] Unlike triethylaluminum and higher alkylaluminum compounds, which can be prepared economically using aluminum, hydrogen, and the corresponding olefins, trimethylaluminum can only be prepared using methyl halides or organometallic compounds as starting materials. The main methods for preparing trimethylaluminum include aluminum reduction, magnesium-aluminum alloy reduction, sodium reduction, Grignard reagent method, and alkyl exchange method. In 1865, Buckton first prepared trimethylaluminum by reacting dimethylmercury with aluminum. Although this method had a high yield, the instability and high toxicity of dimethylmercury limited the reaction to the laboratory stage. Furthermore, the formation of mercury during aluminum reduction made product handling difficult. Trimethylaluminum can also be produced by aluminum reduction with iodomethane, but this method has low conversion rates, long reaction times, and the high cost and instability of iodomethane limits its application. US Pat. No. 2744127 reports a method for synthesizing trimethylaluminum, which involves reacting a 40Al / 60Mg alloy with chloromethane to obtain trimethylaluminum. However, this reaction has a low aluminum conversion rate and generates a large amount of magnesium chloride byproduct that is difficult to handle. Currently, the main industrial production method for trimethylaluminum is the sodium reduction method. This method involves preparing aluminum into shavings, granules, or powder, and reacting it with halomethane under strictly anhydrous and oxygen-free conditions. A small amount of iodine or methylaluminum chloride is added as an initiator. After the reaction, an equimolar equilibrium mixture of monomethylaluminum halide and dimethylaluminum halide and their dimers is generated. An excess of 10% sodium is placed in an organic solvent and stirred at high speed at 90–100°C to produce sodium sand. The sesqui-saturated mixture is then added dropwise to the suspension while stirring. After the reaction is complete, the product is distilled off. This method is the classic method for preparing trimethylaluminum. However, because halomethane undergoes a dehalogenation coupling reaction with aluminum, the selectivity of the reaction is reduced. Furthermore, since aluminum participates in the reaction as a reactant, and the intermediate product generates aluminum upon sodium treatment, the reaction is difficult to proceed. The aluminum precipitate on the sodium surface further reduces the reaction rate, thus significantly reducing the conversion rate. Trimethylaluminum can also be prepared by reacting Grignard reagents with aluminum chloride, but the use of ether solvents makes it difficult to separate trimethylaluminum from the system. Compared with the above methods, the most promising method is to prepare trimethylaluminum by using inexpensive and readily available triethylaluminum as raw material and bismuth-containing metal catalysts via alkyl exchange reaction. However, this method currently commonly uses iodomethane or bromomethane as methylating agents, and the yield is only about 60%, resulting in a high cost.
[0004] This invention provides a novel and efficient method for preparing trimethylaluminum via alkyl exchange reaction. It uses inexpensive and readily available chloromethane as the methylating agent, triethylaluminum as the raw material, and bismuth halide and zinc halide as a composite catalyst. The yield of trimethylaluminum is 81%, and the purity is >99.99%. Summary of the Invention
[0005] To address the problems of low conversion rate and yield of triethylaluminum and high cost of using expensive bromomethane or iodomethane as methylating agents and catalysts in the existing alkyl exchange method for the preparation of trimethylaluminum, this invention provides a new method for the preparation of trimethylaluminum. This method utilizes a high-pressure liquid-phase reaction, employs inexpensive chloromethane as the methylating agent, and uses a composite catalyst composed of a bismuth-containing halide and a zinc-containing halide to efficiently activate the chloromethane, achieving a highly efficient catalytic conversion of triethylaluminum to trimethylaluminum. Furthermore, the catalyst can be recycled in the mother liquor after the reaction.
[0006] The specific process route for preparing trimethylaluminum according to the present invention is as follows:
[0007] A method for preparing trimethylaluminum by reacting triethylaluminum with chloromethane involves using a composite catalyst composed of a bismuth halide and a zinc halide in an anhydrous and oxygen-free organic solvent system to catalyze the reaction of triethylaluminum with chloromethane to obtain trimethylaluminum. After the reaction is completed, the trimethylaluminum product is separated, and the composite catalyst can be reused.
[0008] Furthermore, under anhydrous and oxygen-free conditions, triethylaluminum, an organic solvent, and a composite catalyst consisting of a bismuth-containing halide and a zinc-containing halide were added to a pressure-resistant reaction vessel. Chloromethane was then added, and the reaction was carried out at a certain temperature. After the reaction was completed, trimethylaluminum was obtained by distillation.
[0009] Furthermore, the mother liquor of the remaining catalyst at the bottom of the distillation column is transferred to a pressure-resistant reaction vessel reactor, where triethylaluminum and chloromethane are added. No further catalyst is needed. The reaction is carried out at a certain temperature. After the reaction is completed, trimethylaluminum is obtained at the top of the distillation column from the distillation reaction liquid. The mother liquor of the remaining catalyst at the bottom of the distillation column can be recycled.
[0010] Furthermore, bismuth-containing halides refer to bismuth chloride and bismuth bromide, while zinc-containing halides refer to zinc chloride or zinc bromide; the organic solvent is an alkane (C). n H 2n+2 , Cycloalkanes or aromatic compounds, 6≤n≤18.
[0011] Furthermore, the organic solvent is n-octane, n-decane, n-dodecane, tetrahydronaphthalene, decahydronaphthalene, or a mixed solvent system composed of the above solvents.
[0012] Furthermore, the amount of bismuth-containing halide added is 2-8 mol of the raw material triethylaluminum, and the amount of zinc halide added is 1-10 mol of triethylaluminum.
[0013] Furthermore, the molar ratio of chloromethane to triethylaluminum is 3-12:1, preferably 5-9:1.
[0014] Furthermore, the reaction temperature is 130-160℃, the reaction time is 3-7h, and more preferably the temperature is 140-150℃, the reaction time is 5-6h.
[0015] Furthermore, the yield of trimethylaluminum can reach 81% (based on triethylaluminum), and the product purity is >99.99%.
[0016] The beneficial effects of this invention are:
[0017] (1) The method of the present invention uses a composite catalyst composed of a bismuth-containing halide and a zinc-containing halide to synergistically activate chloromethane, and the yield of trimethylaluminum is up to 81%, which is higher than the existing alkyl exchange method for preparing trimethylaluminum.
[0018] (2) The present invention uses inexpensive and readily available chloromethane as the methylation reagent, instead of more expensive bromomethane or iodomethane, and the yield is also higher than that of existing processes using bromomethane, which greatly reduces the process cost and improves atom economy.
[0019] (3) The catalyst used in this invention can be recycled in the mother liquor, which greatly saves the amount of catalyst and solvent used, further reducing the cost of the method and has the prospect of industrialization. Attached Figure Description
[0020] Figure 1 NMR spectrum of trimethylaluminum 1 H NMR (400Hz, C6D6);
[0021] Figure 2 This is a process flow diagram for trimethylaluminum. Detailed Implementation
[0022] To enable those skilled in the art to better understand the present invention, the present invention will be further illustrated by the following embodiments. However, these embodiments do not limit the scope of the present invention. The technical means used in the embodiments are conventional means well known to those skilled in the art.
[0023] Unless otherwise specified, all experimental methods used in this invention are conventional methods, and all materials and reagents used are commercially available. In the following examples, Examples 1-15 and Comparative Examples 1-3 use a micro-distillation apparatus to collect trimethylaluminum.
[0024] Example 1
[0025] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth chloride (0.0409 g, 6.5 mol%), and zinc bromide (0.0045 g, 1.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction was carried out at 148 °C for 5.2 h. After cooling, the mixture was first subjected to vacuum distillation to remove low-boiling components (chloroethane and chloromethane), and then subjected to atmospheric distillation to obtain 0.1169 g of trimethylaluminum, with a yield of 81%. The purity of the product was tested to be >99.99%.
[0026] Example 2
[0027] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-dodecane, bismuth chloride (0.0315 g, 5 mol%), and zinc bromide (0.0113 g, 2.5 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction was carried out at 150 °C for 5 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1121 g of trimethylaluminum, with a yield of 78%. The purity of the product was tested to be >99.99%.
[0028] Example 3
[0029] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL tetrahydronaphthalene, bismuth chloride (0.0126 g, 2 mol%), and zinc bromide (0.0135 g, 3.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction temperature was 160 °C, and after 4 h, the mixture was cooled. The low-boiling components (chloroethane and chloromethane) were first removed by vacuum distillation, and then by atmospheric distillation to obtain 0.1075 g of trimethylaluminum, with a yield of 75%. The purity of the product was tested to be >99.99%.
[0030] Example 4
[0031] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth chloride (0.0315 g, 5 mol%), and zinc bromide (0.0090 g, 2.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 8:1. The reaction temperature was 145 °C, and after 4 h, the mixture was cooled. The low-boiling components (chloroethane and chloromethane) were first removed by vacuum distillation, and then by atmospheric distillation to obtain 0.1108 g of trimethylaluminum, with a yield of 77%. The purity of the product was tested to be >99.99%.
[0032] Example 5
[0033] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL tetrahydronaphthalene, bismuth chloride (0.0315 g, 5 mol%), and zinc bromide (0.0135 g, 2.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 9:1. The reaction was carried out at 140 °C for 4 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1073 g of trimethylaluminum, with a yield of 75%. The purity of the product was tested to be >99.99%.
[0034] Example 6
[0035] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth bromide (0.0449 g, 5 mol%), and zinc bromide (0.0045 g, 1.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 12:1. The reaction was carried out at 160 °C for 7 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1123 g of trimethylaluminum, with a yield of 78%. The purity of the product was tested to be >99.99%.
[0036] Example 7
[0037] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-octane, bismuth chloride (0.0315 g, 5 mol%), and zinc bromide (0.0090 g, 2.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction was carried out at 135 °C for 5.5 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1095 g of trimethylaluminum, with a yield of 76%. The purity of the product was tested to be >99.99%.
[0038] Example 8
[0039] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-dodecane, bismuth chloride (0.0315 g, 5 mol%), and zinc bromide (0.0090 g, 2.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction was carried out at 140 °C for 4 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1154 g of trimethylaluminum, with a yield of 80%. The purity of the product was tested to be >99.99%.
[0040] Example 9
[0041] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth chloride (0.0504 g, 8 mol%), and zinc bromide (0.0090 g, 2.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 8:1. The reaction was carried out at 140 °C for 4 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1110 g of trimethylaluminum, with a yield of 77%. The purity of the product was tested to be >99.99%.
[0042] Example 10
[0043] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth chloride (0.0378 g, 6 mol%), and zinc bromide (0.0450 g, 10 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 6:1. The reaction was carried out at 140 °C for 4 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1093 g of trimethylaluminum, with a yield of 76%. The purity of the product was tested to be >99.99%.
[0044] Example 11
[0045] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of decahydronaphthalene, bismuth chloride (0.0409 g, 6.5 mol%), and zinc bromide (0.0045 g, 1.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 3.5:1. The reaction was carried out at 148 °C for 5.2 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 0.1041 g of trimethylaluminum, with a yield of 75%.
[0046] Example 12 Scale-up
[0047] Under anhydrous and oxygen-free conditions, triethylaluminum (23.3 g, 0.2 mol), 60 mL of n-decane, bismuth chloride (4.09 g, 6.5 mol%), and zinc bromide (0.0045 g, 1.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction temperature was 148 °C, and the reaction was allowed to proceed for 5.2 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, followed by atmospheric distillation to obtain 11.6 g of trimethylaluminum, with a yield of 80%. The purity of the product was tested to be >99.99%.
[0048] Example 13 Catalyst Application
[0049] The mother liquor remaining after distillation as described in Example 1 was reused in the next round of reaction. Only triethylaluminum (0.2330 g, 2 mmol) and chloromethane were added. The molar ratio of chloromethane to triethylaluminum was 7:1. The reaction temperature was 148°C. After reacting for 5.2 h, the mixture was cooled down. The low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, and then 0.1167 g of trimethylaluminum was obtained by atmospheric distillation. The yield of trimethylaluminum was 81%, and the purity of the product was tested to be >99.99%.
[0050] Comparative Example 1 (without zinc bromide compared to Example 1)
[0051] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, and bismuth chloride (0.0409 g, 6.5 mol%) were added sequentially to a pressure-resistant reaction flask, followed by the addition of chloromethane. The molar ratio of chloromethane to triethylaluminum was 7:1. The reaction temperature was 148 °C, and the reaction was carried out for 5.2 h. After cooling, the low-boiling components (chloroethane and chloromethane) were removed by vacuum distillation, and then 0.1007 g of trimethylaluminum was obtained by atmospheric distillation, with a yield of 70%.
[0052] Comparative Example 2 (The reaction apparatus is different from that of Example 1)
[0053] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, and bismuth chloride (0.0409 g, 6.5 mol%) were added sequentially to a round-bottom flask equipped with an immersion tube. Chloromethane was then introduced through the immersion tube at a molar ratio of 7:1 to triethylaluminum. The addition was completed within 2 hours, and the reaction temperature was 120 °C. After the reaction was completed, the mixture was cooled and then distilled at atmospheric pressure to obtain 0.0880 g of trimethylaluminum, with a yield of 61%.
[0054] Comparative Example 3 (the reaction temperature was changed compared to Example 1)
[0055] Under anhydrous and oxygen-free conditions, triethylaluminum (0.2330 g, 2 mmol), 0.6 mL of n-decane, bismuth chloride (0.0409 g, 6.5 mol%), and zinc bromide (0.0045 g, 1.0 mol%) were added sequentially to a pressure-resistant reaction flask. Chloromethane was then added, with a molar ratio of chloromethane to triethylaluminum of 7:1. The reaction temperature was 25 °C, and after 5.2 h, the mixture was cooled. The low-boiling components (chloroethane and chloromethane) were first removed by vacuum distillation, followed by atmospheric distillation. Almost no trimethylaluminum was formed.
[0056] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing trimethylaluminum by reacting triethylaluminum with chloromethane, characterized in that, In an anhydrous and oxygen-free organic solvent system, a composite catalyst composed of a bismuth-containing halide and a zinc-containing halide is used to catalyze the reaction of triethylaluminum with chloromethane to prepare trimethylaluminum. After the reaction is completed and the trimethylaluminum product is separated, the composite catalyst can be reused.
2. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 1, characterized in that, Under anhydrous and oxygen-free conditions, triethylaluminum, an organic solvent, and a composite catalyst consisting of a bismuth-containing halide and a zinc-containing halide are added to a pressure-resistant reaction vessel. Chloromethane is then added, and the reaction is carried out at a certain temperature. After the reaction is completed, trimethylaluminum is obtained by distillation.
3. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 2, characterized in that, The mother liquor of the remaining catalyst at the bottom of the distillation column is transferred to a pressure-resistant reaction vessel reactor, where triethylaluminum and chloromethane are added. No further catalyst is needed. The reaction is carried out at a certain temperature. After the reaction is completed, the distillation reaction liquid is distilled, and trimethylaluminum is obtained at the top of the column. The mother liquor of the remaining catalyst at the bottom of the distillation column can be recycled.
4. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 1, characterized in that, Halides containing metallic bismuth refer to bismuth chloride and bismuth bromide, while halides containing metallic zinc refer to zinc chloride or zinc bromide; the organic solvent is an alkane (C). n H 2n+2 , Cycloalkanes or aromatic compounds, 6≤n≤18.
5. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 1, characterized in that, The organic solvent is n-octane, n-decane, n-dodecane, tetrahydronaphthalene, decahydronaphthalene, or a mixed solvent system composed of the above solvents.
6. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claims 1 and 4, characterized in that, The amount of bismuth-containing halide added is 2-8 mol of the raw material triethylaluminum, and the amount of zinc halide added is 1-10 mol of triethylaluminum.
7. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 1, characterized in that, The molar ratio of chloromethane to triethylaluminum is 3-12:
1.
8. The method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to claim 1, characterized in that, The reaction temperature is 130-160℃.
9. A method for preparing trimethylaluminum by reacting triethylaluminum and chloromethane according to any one of claims 1-8, characterized in that, The purity of the obtained trimethylaluminum product is >99.99%.