Synthetic method of modified methylaluminoxane

Abstract

The invention discloses a synthetic method of modified methylaluminoxane, which comprises the following steps: (1) in an inert atmosphere, adding an inert solvent into a three-neck bottle, then adding an inert solvent solution of trimethylaluminum, and uniformly stirring; under a freezing condition, dropwise adding the aluminum sulfate suspension into an inert solvent solution of trimethylaluminum, and after dropwise adding, carrying out a stirring reaction to obtain a methylaluminoxane inert solvent mixed solution; or the dropwise adding sequence of the two raw materials is changed. And (2) dropwise adding trialkoxy aluminum or an inert solvent solution of trialkoxy aluminum into the reaction solution of methylaluminoxane obtained in the step (1), heating after dropwise adding, and carrying out stirring reaction. And (3) filtering to remove filter residues, and decompressing the filtrate to remove the solvent, thereby obtaining the modified methylaluminoxane product. And (4) dropwise adding trialkoxy aluminum or an inert solvent solution thereof while dropwise adding the inert solvent solution of the trimethylaluminum in the step (1), or dropwise adding aluminum sulfate containing crystal water or an inert solvent suspension of the aluminum sulfate after mixing the inert solvent solution of the trimethylaluminum and the inert solvent solution of the trimethylaluminum in the step (1) in advance. The method is simple in process, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of metal organic compounds, and particularly relates to a method for synthesizing modified methylaluminoxane. Background Art

[0002] Methylaluminoxane (MAO for short) is a core cocatalyst of metallocene catalyst system and has a very important use in the field of olefin polymerization. The cage-like structure of methylaluminoxane can effectively disperse the negative charge and make it a non-coordinating charge balancer of the metallocene cation active center, showing high activity in olefin polymerization. However, methylaluminoxane has poor solubility and low activity in α-olefin synthesis and POE reaction systems, and the resulting polymer has low yield and unstable quality. The modified methylaluminoxane can overcome these problems in different olefin polymerizations.

[0003] CN101993452A discloses a method for preparing an anti-gel methylaluminoxane solution, which mainly comprises: in an anhydrous nitrogen atmosphere, (1) mixing the crystals with an alkali metal or alkaline earth metal anhydrous hydroxide, adding an organic solvent and stirring; (2) adding trimethylaluminum to the slurry formed in (1), reacting at low temperature; (3) adding halogenated alkylaluminum and stirring, filtering after the reaction is completed, removing solid matter, and obtaining an anti-gel MAO transparent solution. However, the stability of MAO modified by alkali metal or alkaline earth metal is not high, it is very easy to react and cannot be effectively stored for a long time.

[0004] CN118126074A discloses a method for preparing methylaluminoxane and modified methylaluminoxane, which comprises reacting aluminum carboxylate with trimethylaluminum in a solvent at a certain temperature to prepare a methylaluminoxane precursor, then pyrolyzing to obtain methylaluminoxane, and then mixing methylaluminoxane with a long-chain alkyl aluminum, heating, and then using The solvent is diluted to a certain concentration to obtain modified methylaluminoxane. This patent uses long-chain alkyl aluminum to modify methylaluminoxane, and only uses long-chain alkyl to replace part of the methyl groups of the original methylaluminoxane, which has limited impact on product performance.

[0005] The invention provides a process for modifying methylaluminoxane by using alkylaluminoxane. The process is simple and controllable, the product quality is high and stable, and the synthesis method of modified methylaluminoxane suitable for industrial production has good economic and social benefits. Summary of the invention

[0006] The invention provides a method for synthesizing modified methylaluminoxane, which has the advantages of simple and controlled process, low cost, high yield, high and stable product quality and is suitable for industrial production.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows: (1) Under an inert atmosphere, add an inert solvent into a three-necked flask, then add trimethylaluminum, stir evenly, and then, under freezing conditions, Slowly drip After the aluminum sulfate inert solvent suspension is added dropwise, the mixture is stirred and kept cold to react to obtain an inert solvent solution of methylaluminoxane; (2) adding dropwise a solution of trialkoxyaluminum in an inert solvent to the solution of methylaluminoxane in an inert solvent obtained in step (1), and after the addition is complete, heating the mixture and stirring the mixture to react; (3) The reaction solution obtained in step (2) is filtered to remove the filter residue, and the filtrate is decompressed to remove part of the solvent to obtain a modified methylaluminoxane inert solvent solution; or the filtrate is decompressed to remove the solvent to obtain a modified methylaluminoxane solid.

[0008] The step (1) is characterized in that the order of adding aluminum sulfate and the inert solvent solution of trimethylaluminum can be changed. Specifically, under an inert atmosphere, the aluminum sulfate suspension is added to a three-necked flask, stirred evenly, and then the inert solvent solution of trimethylaluminum is slowly added dropwise under freezing conditions. After the addition is completed, the mixture is stirred for reaction to obtain the inert solvent solution of methylaluminoxane.

[0009] In the steps (1) and (2), under freezing conditions, the inert solvent solution of trialkoxyaluminum in step (2) is pre-mixed with the inert solvent solution of trimethylaluminum in step (1) and then the aluminum sulfate suspension is slowly added dropwise. After the addition is completed, the temperature is raised and the reaction is stirred.

[0010] In the steps (1) and (2), under freezing conditions, the inert solvent solution of trialkoxyaluminum and the inert solvent solution of trimethylaluminum are simultaneously and slowly added dropwise to the aluminum sulfate suspension. After the addition is completed, the temperature is raised and the reaction is stirred.

[0011] The aluminum sulfate is aluminum sulfate containing crystal water, the number of crystal water is 3-18, preferably 9-15, and more preferably 14. The particle size of the aluminum sulfate powder is 50-500 mesh, preferably 80-200 mesh.

[0012] The trialkoxy aluminum is trimethoxy aluminum, tripropoxy aluminum, tributoxy aluminum, and trioctoxy aluminum.

[0013] The inert solvent is C4-C15 saturated alkane, benzene or C1-C5 alkyl substituted benzene aromatic hydrocarbon or a mixture thereof, naphtha, kerosene or one or more mixtures thereof; C4-C15 saturated alkane is pentane, hexane, decane, octane, C12 alkane, cyclohexane, cycloheptane, but not limited thereto; the substituted benzene aromatic hydrocarbon is toluene, xylene, ethylbenzene, propylbenzene, but not limited thereto.

[0014] The inert atmosphere includes nitrogen, argon or helium.

[0015] The mass ratio of the trimethylaluminum or trialkoxyaluminum to the inert solvent is (5-40):100.

[0016] The mass ratio of the aluminum sulfate to the inert solvent is (10-40):100.

[0017] The molar ratio of the sum of the moles of aluminum sulfate and trialkoxyaluminum to trimethylaluminum is (0.05-1):1, preferably (0.1-0.3):1; the molar ratio of aluminum sulfate to trialkoxyaluminum is (3-30):1, preferably (4-10):1.

[0018] The freezing conditions are -80 to 5°C, preferably -30 to 0°C.

[0019] The slow dripping time is 1 to 10 hours, preferably 1 to 3 hours.

[0020] The stirring and cold-keeping reaction is carried out at -80 to 10°C, preferably -30 to 10°C, and the reaction time is 0.5 to 24.0 hours, preferably 1 to 5 hours.

[0021] In the step (2), the temperature is raised to 25-120°C at a heating rate of 0.05-20.0°C / min, preferably at a heating rate of 0.2-2°C / min, and preferably at a heating temperature of 60-100°C. The reaction is stirred at a constant temperature of 25-120°C for 1-48.0h, preferably at a constant temperature of 60-100°C for 2-10h. The preparation method of the trialkoxy aluminum is as follows: reacting trialkyl aluminum with an alcohol solution, wherein the molar ratio of the trialkyl aluminum to the alcohol solution is 1:2.5-3.5, the reaction temperature is -30°C-80°C, the trialkyl aluminum is trimethyl aluminum, triethyl aluminum, trioctyl aluminum, preferably trimethyl aluminum, the alcohol of the alcohol solution is a C1-C8 alcohol, the solvent is one or more of C4-C12 alkanes or C7-C10 aromatic hydrocarbons, and the mass concentration of the alcohol solution is 1%-50%; the C4-C12 alkanes are butane, hexane, and dodecane, and the C7-C10 aromatic hydrocarbons are toluene, ethylbenzene, and trimethylbenzene.

[0022] The beneficial effects of the method of the present invention are as follows: (1) The method of the present invention uses aluminum sulfate containing crystal water and trimethylaluminum to carry out a hydrolysis reaction in an inert solvent, and the degree of hydrolysis reaction can be accurately controlled. In particular, different reaction effects can be obtained by using aluminum sulfates with different numbers of crystal water. In practice, the use of aluminum sulfate tetradecahydrate has a significant effect on the yield and activity of the product.

[0023] (2) Methylaluminoxane is modified using trialkoxyaluminum in an inert solution. The modified methylaluminoxane obtained by the reaction has high activity, stable molecular structure, and chemical bonds that are not easily broken.

[0024] (3) The method of the present invention has simple process, low cost and is suitable for industrial production. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments.

[0026] The concentration of trimethylaluminum used in the examples of the present invention and the comparative examples is 10-100%; the nitrogen used in the examples of the present invention and the comparative examples is a high-purity gas with a purity of ≥99.9%; the raw materials or chemical reagents used in the examples of the present invention, unless otherwise specified, are obtained through conventional commercial channels.

[0027] Preparation method of trialkoxyaluminum Example 1: 1 mol of trimethylaluminum was mixed with 2.7 mol of 20% octanol toluene solution for reaction. After mixing, the mixture was stirred and heated to 80° C. for reaction for 4 h to obtain tri-n-octyloxyaluminum solution with a yield of 90%.

[0028] Example 2: 1 mol of triethylaluminum and 2.4 mol of 20% ethanol hexane solution were mixed and reacted. After mixing, the mixture was stirred and heated to 60° C. for 10 hours to obtain a triethoxyaluminum solution with a yield of 80%.

[0029] Example 3 of a method for synthesizing modified methylaluminoxane (step-by-step reaction) (1) Under nitrogen atmosphere, add 30 g (0.045 mol) of aluminum sulfate 18hydrate powder (200 mesh) into a three-necked flask, then add 25 mL of toluene inert solvent, stir evenly, then add 200 mL of 2 mol / L trimethylaluminum in toluene inert solvent solution dropwise through a constant pressure dropping funnel under -50°C freezing conditions. After the addition is complete over 60 min, stir and react at room temperature for 4 h to obtain a methylaluminoxane toluene mixed solution; (2) To the methylaluminoxane toluene mixed solution obtained in step (1), 30 g (0.015 mol) of trioctyloxyaluminum toluene solution was added dropwise through a constant pressure dropping funnel. After 30 min of complete addition, the temperature was raised to 80°C at a rate of 0.5°C / min, and the mixture was stirred at a constant temperature for 4 h. The residue was filtered out, and the filtrate was decompressed to remove the solvent to obtain 15.27 g of modified methylaluminoxane solid.

[0030] The obtained modified methylaluminoxane solid had a purity of 76.03% and a yield of 44.68%.

[0031] Example 4 of a method for synthesizing modified methylaluminoxane (step-by-step reaction) (1) Under nitrogen atmosphere, add 14.87 g (0.025 mol) of aluminum sulfate tetradecahydrate powder (100 mesh) into a three-necked flask, then add 100 mL of hexane inert solvent, stir evenly, and then add 100 mL of 2 mol / L trimethylaluminum hexane solvent solution dropwise through a constant pressure dropping funnel under -50°C freezing conditions. After 120 min of dropwise addition, stir and react for 2 h at room temperature to obtain a modified methylaluminoxane hexane mixed solution; (2) To the mixed solution obtained in step (1), 10 g (0.012 mol) of triethoxyaluminum in hexane solvent solution was added dropwise through a constant pressure dropping funnel. After 50 min of addition, the temperature was raised to 60° C. at a rate of 0.1° C. / min and the mixture was stirred at a constant temperature for 8 h. The residue was filtered out and the solvent was removed from the filtrate under reduced pressure to obtain 10.36 g of modified methylaluminoxane solid.

[0032] The solid content of the obtained modified methylaluminoxane was 85.08% and the yield was 70.66%.

[0033] Example 5 of a Synthesis Method for Modified Methylaluminoxane (One-pot Reaction) Under nitrogen atmosphere, 15.32g (0.03mol) of aluminum sulfate pentahydrate powder (200 mesh) was added to a three-necked flask, and then 25mL of octane solvent was added. After stirring evenly, 100mL of 2mol / L trimethylaluminum octane solvent solution was added dropwise through a constant pressure dropping funnel under -50℃ freezing conditions. The addition was completed in 50min. While adding the trimethylaluminum octane solvent solution, 10g (0.012mol) of tributoxyaluminum octane solution was added dropwise through a constant pressure dropping funnel. The addition was completed in 60min. The temperature was raised to 30℃ at a rate of 5℃ / min, and the reaction was stirred at a constant temperature for 20h. The residue was filtered out, and the filtrate was decompressed to remove the solvent to obtain 8.16g of modified methylaluminoxane solid.

[0034] The solid content of the obtained modified methylaluminoxane was 80.2% and the yield was 51.88%.

[0035] Example 6 of a method for synthesizing modified methylaluminoxane (one-pot reaction) Under nitrogen atmosphere, 15.68g (0.03mol) of aluminum sulfate decahydrate powder (200 mesh) was added to a three-necked flask, and then 25mL of octane solvent was added. After stirring evenly, 100mL of 2mol / L trimethylaluminum octane solvent solution was added dropwise through a constant pressure dropping funnel under -50℃ freezing conditions. The addition was completed in 50min. While adding the octane solvent solution of trimethylaluminum, 3g (0.001mol) of tributoxyaluminum octane solution was added dropwise through a constant pressure dropping funnel. The addition was completed in 60min. The temperature was raised to 30℃ at a rate of 5℃ / min, and the reaction was stirred at a constant temperature for 20h. The residue was filtered out, and the filtrate was decompressed to remove the solvent to obtain 8.91g of modified methylaluminoxane solid.

[0036] The solid content of the obtained modified methylaluminoxane was 75.34% and the yield was 51.02%.

[0037] Example 7 of a method for synthesizing modified methylaluminoxane (one-pot reaction) Under nitrogen atmosphere, 15.77 g (0.035 mol) of aluminum sulfate hexahydrate powder (100 mesh) was added to a three-necked flask, and then 50 mL of xylene solvent was added. After stirring evenly, 200 mL of trimethylaluminum (1 mol / L) and trimethoxyaluminum 0.1 mol / L xylene solution was added dropwise through a constant pressure dropping funnel under -30 °C freezing conditions. The addition was completed over 50 min, and the temperature was raised to 20 °C at a rate of 10 °C / min. The reaction was stirred at a constant temperature for 48 h, and the residue was filtered out. The filtrate was decompressed to remove the solvent to obtain 7.17 g of modified methylaluminoxane solid.

[0038] The obtained modified methylaluminoxane solid had a purity of 60.06% and a yield of 35.22%.

[0039] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be subject to the scope of protection of the claims.

Claims

1. A method for synthesizing modified methylaluminoxane, characterized in that: The following steps are involved: In an inert atmosphere, add an inert solvent into a three-necked flask, then add trimethylaluminum, stir evenly, and then, under freezing conditions, Slowly drip After the aluminum sulfate inert solvent suspension is added dropwise, the mixture is stirred and kept cold to react to obtain an inert solvent solution of methylaluminoxane; Adding dropwise the inert solvent solution of trialkoxyaluminum to the inert solvent solution of methylaluminoxane obtained in step (1), and after the addition is complete, heating the mixture and stirring to react; The reaction solution obtained in step (2) is filtered to remove the filter residue, and the filtrate is decompressed to remove part of the solvent to obtain a modified methylaluminoxane inert solvent solution; or the filtrate is decompressed to remove the solvent to obtain a modified methylaluminoxane solid.

2. The method for synthesizing modified methylaluminoxane according to claim 1, characterized in that: In step (1), the order of adding aluminum sulfate and trimethylaluminum inert solvent solution can be changed. Specifically, under an inert atmosphere, the aluminum sulfate inert solvent suspension is added to a three-necked flask, stirred evenly, and then the trimethylaluminum inert solvent solution is slowly added dropwise under freezing conditions. After the addition is completed, the mixture is stirred for reaction to obtain the inert solvent solution of methylaluminoxane.

3. The method for synthesizing modified methylaluminoxane according to claim 1, characterized in that: In steps (1) and (2), under freezing conditions, the inert solvent solution of trialkoxyaluminum in step (2) is pre-mixed with the inert solvent solution of trimethylaluminum in step (1) and then the inert solvent suspension of aluminum sulfate is slowly added dropwise. After the addition is completed, the temperature is raised and the reaction is stirred; 4. The method for synthesizing modified methylaluminoxane according to claim 1, characterized in that: In steps (1) and (2), under freezing conditions, the inert solvent solution of trialkoxyaluminum and the inert solvent solution of trimethylaluminum are simultaneously and slowly added dropwise to the inert solvent suspension of aluminum sulfate. After the addition is completed, the temperature is raised and the reaction is stirred; 5. The method for synthesizing modified methylaluminoxane according to claims 1 to 4, characterized in that: Aluminum sulfate is aluminum sulfate containing water of crystallization, the number of water of crystallization is 3-18, preferably 9-15, and more preferably 14. The particle size of aluminum sulfate powder is 50-500 mesh, preferably 80-200 mesh. The trialkoxy aluminum is trimethoxy aluminum, tripropoxy aluminum, tributoxy aluminum, and trioctoxy aluminum. The inert solvent is one or more mixtures of C4-C15 saturated alkanes, benzene or C1-C5 alkyl substituted benzene aromatic hydrocarbons or mixtures thereof, naphtha, and kerosene. The C4-C15 saturated alkanes are pentane, hexane, decane, octane, C12 alkane, cyclohexane, and cycloheptane, but are not limited thereto. The aromatic hydrocarbons substituted benzene are toluene, xylene, ethylbenzene, and propylbenzene, but are not limited thereto. The inert atmosphere includes nitrogen, argon, or helium.

6. The method for synthesizing modified methylaluminoxane according to claims 1 to 4, characterized in that: The mass ratio of the trimethylaluminum or trialkoxyaluminum to the inert solvent is (5-40):100; the mass ratio of aluminum sulfate to the inert solvent is (10-40):

100.

7. The method for synthesizing modified methylaluminoxane according to any one of claims 1 to 4, characterized in that: The molar ratio of the sum of the moles of aluminum sulfate and trialkoxyaluminum to trimethylaluminum is (0.05-1):1, preferably (0.1-0.3):1; the molar ratio of aluminum sulfate to trialkoxyaluminum is (3-30):1, preferably (4-10):

1.

8. The method for synthesizing modified methylaluminoxane according to claims 1 to 4, characterized in that: The freezing condition is -80 to 5°C, preferably -30 to 0°C; the slow dripping time is 1 to 10 hours, preferably 1-3 hours; the stirring and cold-keeping reaction is at -80 to 10°C, preferably -30 to 10°C, and the reaction time is 0.5 to 24.0 hours, preferably 1-5 hours.

9. The method for synthesizing modified methylaluminoxane according to any one of claims 1, 3 and 4, characterized in that: The heating is carried out at a heating rate of 0.05-20.0°C / min to 25-120°C, preferably at a heating rate of 0.2-2°C / min, and preferably at a heating temperature of 60-100°C; the constant temperature stirring reaction is carried out at a constant temperature of 25-120°C and a reaction time of 1-48.0h, preferably at a constant temperature of 60-100°C and a reaction time of 2-10h.

10. The method for synthesizing modified methylaluminoxane according to any one of claims 1, 3 and 4, characterized in that: In step (2), the preparation method of the trialkoxy aluminum is: reacting trialkyl aluminum with an alcohol solution, the molar ratio of trialkyl aluminum to the alcohol solution is 1:2.5~3.5, the reaction temperature is -30°C~80°C, the trialkyl aluminum is trimethyl aluminum, triethyl aluminum, trioctyl aluminum, preferably trimethyl aluminum, the alcohol of the alcohol solution is a C1-C8 alcohol, the solvent is one or more of C4-C12 alkanes or C7-C10 aromatic hydrocarbons, and the mass concentration of the alcohol solution is 1%-50%; the C4-C12 alkanes are butane, hexane, and dodecane, and the C7-C10 aromatic hydrocarbons are toluene, ethylbenzene, and trimethylbenzene.