Process for the preparation of modified alkylaluminoxanes and use thereof
Modified alkylaluminoxanes were prepared by reacting nitrogen dioxide gas with alkylaluminum solution and controlling the temperature and pressure. This solved the problem of reaction instability in the prior art and achieved a high-yield and highly active olefin polymerization catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WANHUA CHEM GRP CO LTD
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-05
AI Technical Summary
In existing methods for preparing alkylaluminoxanes, the hydrolysis reaction rapidly releases a large amount of heat, leading to unstable and difficult-to-control reactions. In contrast, non-hydrolysis methods involve vigorous reactions and complex synthesis, which are not conducive to large-scale production.
Modified alkylaluminoxanes are prepared by reacting nitrogen dioxide gas with alkylaluminum solution at specific temperature and pressure, mixing through a bottom tube or gas distributor, and combining a batch, tubular, or microchannel reactor to control the reaction temperature and rapidly remove heat. Post-processing methods include heating, evaporation, and filtration.
The reaction process is stable and controllable, with reduced byproducts and a product yield of up to 98%. As a co-catalyst, it exhibits high catalytic activity in olefin polymerization, and the process is simple and easy to scale up.
Smart Images
Figure BDA0005170371680000021 
Figure BDA0005170371680000051 
Figure BDA0005170371680000052
Abstract
Description
Technical Field
[0001] This invention relates to the field of olefin polymerization, and more specifically to the field of olefin polymerization catalysts. Background Technology
[0002] Aluminoxanes (MAO) and modified aluminoxanes (MMAO) are mainly used as co-catalysts in olefin polymerization reactions. They are products of partial hydrolysis of alkyl aluminum compounds, and their actual structure is a mixture of various partially hydrolyzed products, making their specific composition quite complex. Aluminoxanes possess properties such as R(-Al(-R)-O). n The structure is -Al-R2, where R substituents can be alkyl or alkoxy groups.
[0003] The preparation methods of aluminum oxanes and modified aluminum oxanes include hydrolysis, indirect hydrolysis and non-hydrolysis.
[0004] US Patent 4772736A discloses a method for preparing alkylaluminoxanes. This method involves directly introducing water into an alkylaluminum solution, with the water inlet pipe outlet very close to a stirring paddle. This ensures that the water disperses immediately upon exiting the pipe outlet due to the shear force of the paddle, thus reducing side reactions. However, this method still fails to address the problem of the rapid release of a large amount of heat during the reaction of water with alkylaluminum.
[0005] Chinese patent CN1209080A discloses a method for converting a precursor composition into a catalytically suitable aluminoxane composition in a non-hydrolytic manner. The intermediate precursor is formed by reacting a trialkylaluminum compound or a mixture of trialkylaluminum compounds with a compound containing a carbon-oxygen bond, such as an alcohol, ketone, carboxylic acid, or carbon dioxide. The catalytically suitable aluminoxane composition obtained by this non-hydrolytic method is essentially free of trimethylaluminum. However, in the process of synthesizing the intermediate precursor, the trialkylaluminum compound is directly mixed with the compound containing a carbon-oxygen bond, resulting in a violent reaction, easy temperature runaway, and inability to be directly scaled up.
[0006] Chinese patent CN116515018A discloses a method for preparing alkylaluminoxanes. This method involves mixing a porous material, toluene, and water to obtain a mixed system, which is then added dropwise to a toluene solution of trimethylaluminum to initiate the reaction. This method utilizes the slow release of water from the porous material, making the reaction milder and safer. However, the fabrication process of the porous material is complex, which is not conducive to practical applications. Summary of the Invention
[0007] To address the problems existing in the prior art, this invention provides a method for preparing modified alkylaluminoxanes and their application in olefin polymerization. This method can slow down the reaction rate of alkylaluminum, making the reaction process stable and controllable, thereby reducing the generation of by-products, and the product has high catalytic activity.
[0008] To achieve this objective, the present invention adopts the following technical solution:
[0009] A method for preparing a modified alkylaluminoxane includes the following steps:
[0010] (1) Cool the alkylaluminum or alkylaluminum solution in the reaction vessel;
[0011] (2) Nitrogen dioxide gas is introduced into the reaction vessel to react with alkyl aluminum or alkyl aluminum solution;
[0012] (3) Modified alkylaluminoxane and trimethylamine were obtained after post-treatment.
[0013] The alkylaluminum described in this invention is one or more alkylaluminum compounds containing C1 to C12 alkyl groups. Preferably, the alkylaluminum includes one or more of trimethylaluminum, triethylaluminum, trihexylaluminum, and trioctylaluminum.
[0014] The alkylaluminum solution of the present invention has an alkylaluminum mass fraction of 10% to 70%, preferably 10% to 50%.
[0015] The solvent in the alkyl aluminum solution of the present invention can be one or more of C5-C20 alkane solvents and benzene series solvents; preferably, the solvent is one or more of methylcyclohexane, cyclohexane, isoalkanes, toluene, and xylene; more preferably, the solvent is methylcyclohexane and / or isoalkanes.
[0016] In this invention, the reaction temperature of step (2) is -10 to 50°C and the reaction pressure is 0 to 3 MPa (G); preferably, the reaction temperature is 0 to 20°C and the reaction pressure is 0.2 to 2 MPa (G).
[0017] In this invention, the molar ratio of nitrogen dioxide gas feed rate to alkyl aluminum in step (2) is 1:1 to 3:1.
[0018] As a preferred embodiment, in this invention, nitrogen dioxide is introduced into the reactor using a bottom-insertion pipe or a gas distributor to improve the rapid mixing effect of nitrogen dioxide gas and alkyl aluminum solution.
[0019] As a preferred embodiment, the reactor described in this invention can be one or more of the following: a batch reactor, a tubular reactor, or a microchannel reactor. The reactor has a heat transfer function and is required to quickly remove the heat released by the reaction to maintain a constant reaction temperature.
[0020] As a preferred embodiment, the post-processing method for the product at the reactor outlet in this invention includes one or more of the following: heating, evaporation and concentration, filtration, washing, crystallization, and condensation, with heating, filtration, and condensation being the preferred methods.
[0021] Without being limited by any theory, the possible reaction mechanism of this invention is as follows:
[0022]
[0023] This invention provides a modified alkylaluminoxane prepared by the method described above, which can be used as a co-catalyst in the field of olefin polymerization.
[0024] The modified alkylaluminoxanes obtained by the method of the present invention have a yield of over 85%, with a maximum of 98%.
[0025] The byproduct trimethylamine obtained by the method of this invention can be sold directly.
[0026] The present invention has the following beneficial effects: The method for preparing modified aluminoxane provided by the present invention uses nitrogen dioxide as a reactant. The reaction process is mild and controllable, which can maintain the uniform reaction, avoid local hot spots, and reduce over-reaction or incomplete reaction. The product yield can reach up to 98%. The method has a short process flow, is easy to scale up, and exhibits higher catalytic activity when used as a co-catalyst in olefin polymerization reactions, showing significant advantages.
[0027] The modified alkylaluminoxane provided by this invention can be used as a co-catalyst in the field of olefin polymerization. It can be directly combined with a single-center catalyst, exhibits high catalytic activity, and produces trimethylamine as a byproduct while generating the modified aluminoxane, thus having high practical application value. Detailed Implementation
[0028] The embodiments of the present invention are described in detail below. These embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in existing literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.
[0029] In this embodiment, the aluminum content of the modified aluminoxane product was determined by titration. The specific method is as follows: Weigh mg of the product under a nitrogen atmosphere (e.g., in a glove box) and add ethanol for alcoholysis. Add dilute nitric acid to the alcoholysis mixture and digest until transparent. Take out the aqueous phase of the above mixture and dilute it to a 250 mL volumetric flask to obtain a digested aluminum nitrate aqueous solution. Add 20 mL of EDTA disodium aqueous solution (c2) and 10 mL of aluminum nitrate aqueous solution to an Erlenmeyer flask. Heat the above mixture at 160°C for 6 min and then allow it to return to room temperature. Add 25 mL of 20% hexamethylenetetramine aqueous solution to the Erlenmeyer flask, then add 2 drops of xylenol orange indicator. The liquid in the Erlenmeyer flask turns yellow. Add zinc nitrate aqueous solution (c1) dropwise to the Erlenmeyer flask using an acid burette until the yellow color just turns purple and does not fade within 1 min, indicating that the titration is complete. Record the volume V of zinc nitrate aqueous solution consumed.
[0030] The aluminum content in the product can be obtained using the formula w%=(20×c2-V×c1) / 10*250*27 / 1000 / m.
[0031] The mass fraction and yield of modified alkylaluminoxane can be calculated from the aluminum content in the product.
[0032] The main raw material information is shown in Table 1:
[0033] Table 1
[0034] chemicals source Specification Trimethylaluminum Inokai As needed Triethylaluminum Inokai As needed Trioctyl aluminum Inokai As needed Toluene Inokai AR xylene Inokai AR Nitrogen Air Liquide High purity Methylcyclohexane Inokai AR Nitrogen dioxide Inokai AR
[0035] Example 1
[0036] 45g of trimethylaluminum (a 10% mass fraction isoparaffin solution) was added to the reactor, with the liquid level above the nitrogen dioxide inlet. The reactor temperature was slowly lowered to -10℃, and stirring was started. 2.87g of nitrogen dioxide gas was added to the reactor through a bottom-insertion pipe. The pressure was stabilized at 1.5MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at -10℃ by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5h. The product was filtered and cooled to 20℃ to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 3.60%, and the yield was 94.30%.
[0037] Example 2
[0038] 45g of trimethylaluminum (70% toluene solution) was added to the reactor, with the liquid level above the nitrogen dioxide inlet. The reactor temperature was slowly raised to 50°C, and stirring was started. 40.21g of nitrogen dioxide gas was added to the reactor through a bottom-insertion pipe. The pressure was stabilized at 0.2MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at 50°C by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5 hours. The product was heated, filtered, and cooled to 20°C to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 27.14%, and the yield was 89.40%.
[0039] Example 3
[0040] 45g of trimethylaluminum (30% methylcyclohexane solution) was added to the reactor, with the liquid level above the nitrogen dioxide inlet. The reactor temperature was slowly raised to 10°C, and stirring was started. 17.23g of nitrogen dioxide gas was added to the tubular reactor through a bottom-insertion pipe. The pressure was stabilized at 0.5MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at 10°C by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5 hours. The product was condensed, filtered, and cooled to 20°C to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 11.70%, and the yield was 98.11%.
[0041] Example 4
[0042] 38g of triethylaluminum (30% cyclohexane solution) was added to the reactor, with the triethylaluminum level above the nitrogen dioxide inlet. The reactor temperature was slowly raised to 20°C, and stirring was started. 13.78g of nitrogen dioxide gas was added to the reactor through a bottom-insertion pipe. The pressure was stabilized at 0.5MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at 20°C by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5 hours. The product was heated, filtered, and cooled to 20°C to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 7.61%, and the yield was 95.50%.
[0043] Example 5
[0044] 50g of trioctylaluminum (30% cyclohexane solution) was added to the reactor, with the liquid level above the nitrogen dioxide inlet. The reactor temperature was slowly raised to 30°C, and stirring was started. 2.82g of nitrogen dioxide gas was added to the tubular reactor through a bottom-insertion pipe. The pressure was stabilized at 3.0MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at 30°C by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5 hours. The product was heated, filtered, and cooled to 20°C to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 2.46%, and the yield was 92.35%.
[0045] Comparative Example 1
[0046] 45g of trimethylaluminum (30% methylcyclohexane solution) was added to the reactor, with the liquid level above the nitrogen dioxide inlet. The reactor temperature was slowly raised to 10°C, and stirring was started. 17.23g of nitrogen dioxide gas was directly introduced into the reactor. The pressure was stabilized at 0.5MPa(G) by controlling the nitrogen dioxide feed rate, and the reaction temperature was maintained at 10°C by controlling the oil bath in the reactor jacket. After the nitrogen dioxide feed was completed, the reaction continued for 1.5 hours. The product was condensed, filtered, and cooled to 20°C to obtain a modified alkylaluminoxane solution. The aluminum content in the product was measured to be 8.05%, and the yield was 67.48%.
[0047] Examples 6-10 and Comparative Example 2
[0048] The MAO / MMAO described in Examples 1-5 and Comparative Example 1 were used as co-catalysts to catalyze the polymerization of ethylene / 1-octene.
[0049] The main catalyst is a compound as shown in formula (I), which can be synthesized according to the method described in patent CN115710326B. All materials and reagents used are commercially available.
[0050]
[0051] 1.0 L of dried isoparaffin solvent was added to a 2.5 L stainless steel high-pressure polymerization reactor. The temperature was raised to 150 °C, and after stirring for 30 min, the reactor was cleaned and the solvent was drained. The reactor was then dried under vacuum at 170 °C for 2 h, and then purged with nitrogen. 0.8 L of isoparaffin and 0.2 L of n-octene were added to the reactor, along with the main catalyst of formula (I). The corresponding amount of modified alkylaluminoxane product was added according to the Al / M ratio described in Table 2. After heating to the polymerization temperature, 3 MPa (G) ethylene was introduced to start the reaction. After reacting for 6 min, the reactor pressure was released, and the reaction liquid was released into ethanol. The resulting solid was filtered out, dried in a vacuum oven at 40 °C, and weighed. The results are shown in Table 2.
[0052] Table 2
[0053]
[0054] The above description is only a partial embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a modified alkylaluminoxane, comprising the following steps: (1) Cool the alkylaluminum or alkylaluminum solution in the reaction vessel; (2) Nitrogen dioxide gas is introduced into the reaction vessel to react with alkyl aluminum or alkyl aluminum solution; (3) Modified alkylaluminoxane and trimethylamine were obtained after post-treatment.
2. The method according to claim 1, characterized in that, The alkylaluminum is one or more of alkylaluminum compounds containing C1 to C12 alkyl groups; preferably, the alkylaluminum includes one or more of trimethylaluminum, triethylaluminum, trihexylaluminum, and trioctylaluminum.
3. The method according to claim 1 or 2, characterized in that, The alkylaluminum solution contains 10% to 70% by mass, preferably 10% to 50%.
4. The method according to any one of claims 1-3, characterized in that, The reaction temperature in step (2) is -10 to 50°C and the reaction pressure is 0 to 3 MPa (G); preferably, the reaction temperature is 0 to 20°C and the reaction pressure is 0.2 to 2 MPa (G).
5. The method according to any one of claims 1-4, characterized in that, In step (2), the molar ratio of nitrogen dioxide gas feed rate to alkyl aluminum is 1:1 to 3:
1.
6. The method according to any one of claims 1-5, characterized in that, The solvent in the alkyl aluminum solution is one or more of C5-C20 alkane solvents and benzene series solvents; preferably, the solvent is one or more of methylcyclohexane, cyclohexane, isoalkanes, toluene, and xylene; more preferably, the solvent is methylcyclohexane and / or isoalkanes.
7. The method according to any one of claims 1-6, characterized in that, The nitrogen dioxide enters the reactor via a bottom-insertion pipe or a gas distributor.
8. The method according to any one of claims 1-7, characterized in that, The reactor is one or more of the following: batch reactor, tubular reactor, and microchannel reactor.
9. The method according to any one of claims 1-8, characterized in that, The post-processing method includes one or more of the following: evaporation and concentration, filtration, washing, crystallization, and condensation.
10. The application of the modified alkylaluminoxane prepared by the method according to any one of claims 1-9 in olefin polymerization.