Process for the removal of aluminium alkyl from alkylaluminoxane and supported metallocene catalyst

Abstract

The application discloses a method for removing alkyl aluminum in alkyl aluminoxane and a supported metallocene catalyst, and relates to the technical field of cocatalysts, and aims to solve the problem that it is difficult to remove alkyl aluminum in alkyl aluminoxane in the prior art. The method for removing alkyl aluminum in alkyl aluminoxane comprises the following steps: obtaining an alkyl aluminoxane solution; passing the alkyl aluminoxane solution into an adsorption column provided with a water-containing carrier, so that the alkyl aluminoxane solution reacts with the water-containing carrier, and a target alkyl aluminoxane solution is obtained; and the content of alkyl aluminum in the target alkyl aluminoxane solution is less than the content of alkyl aluminum in the alkyl aluminoxane solution. The method for removing alkyl aluminum in alkyl aluminoxane provided by the application has a removal effect which is significantly better than that of a traditional vacuum distillation or vacuum drying method, and does not need a vacuum equipment, is safe, and has stable product performance. Meanwhile, the adsorption column carrier can be reused to prepare a high-activity supported metallocene catalyst.

Description

Technical Field

[0001] This application relates to the field of cocatalyst technology, and in particular to a method for removing alkyl aluminum from alkylaluminoxanes and a supported metallocene catalyst. Background Technology

[0002] In the field of metallocene and post-transition metal olefin polymerization catalysis, alkylaluminoxanes are a widely used and highly efficient cocatalyst. Currently, alkylaluminoxanes are mainly synthesized through the controlled hydrolysis of alkylaluminum, and a certain amount of alkylaluminum always remains in the final product. To reduce the alkylaluminum content, vacuum distillation or vacuum drying is commonly used for post-treatment of the product. This process is lengthy, affects the alkylaluminoxane product, and cannot effectively remove the alkylaluminum. Summary of the Invention

[0003] The purpose of this application is to provide a method for removing alkyl aluminum from alkylaluminoxanes and a supported metallocene catalyst, which can efficiently and safely remove alkyl aluminum from alkylaluminoxanes while avoiding damage to product performance.

[0004] To achieve the above objectives, this application provides the following technical solution:

[0005] A method for removing alkylaluminum from alkylaluminoxanes, comprising: Obtain an alkylaluminoxane solution; An alkylaluminoxane solution is passed into an adsorption column packed with an aqueous support, allowing the alkylaluminoxane solution to react with the aqueous support to obtain the target alkylaluminoxane solution. The content of alkyl aluminum in the target alkylaluminoxane solution is reduced by at least 80%, preferably by at least 90%, and more preferably by 95%, compared to the content of alkyl aluminum in the alkylaluminoxane solution.

[0006] Compared with the prior art, the method for removing alkyl aluminum from alkylaluminoxanes provided in this application involves passing the alkylaluminoxane solution through an adsorption column filled with an aqueous support. The water in the aqueous support reacts with the alkyl aluminum in the alkylaluminoxane solution, thereby reducing the content of alkyl aluminum in the target alkylaluminoxane solution to a lower level than that in the alkylaluminoxane solution, which can significantly reduce the content of alkyl aluminum in the alkylaluminoxane solution.

[0007] As can be seen, the method of this application does not require vacuum distillation or vacuum drying, avoiding the safety risks and product thermal damage caused by high-temperature operation. Furthermore, the process is simple, controllable, and easy to implement industrially. Simultaneously, during the removal of alkylaluminum, alkylaluminoxanes are successfully supported on the support surface, transforming it into a support loaded with alkylaluminoxanes. This support can be further used to prepare highly active supported metallocene catalysts, demonstrating good economic and environmental benefits.

[0008] This application also provides an alkylaluminoxane, which is prepared by the method for removing alkylaluminum from the alkylaluminoxane provided in the embodiments of this application.

[0009] Compared with the prior art, the beneficial effects of the alkylaluminoxane provided in this application are the same as the beneficial effects of the above-mentioned method for removing alkylaluminum from alkylaluminoxane, which will not be elaborated here.

[0010] This application also provides a supported metallocene catalyst, comprising: under inert gas protection, using a support in an adsorption column after treating an alkylaluminoxane solution as provided in the embodiments of this application, reacting a metallocene complex with the support in an inert solvent to obtain a supported metallocene catalyst.

[0011] Compared with the prior art, the beneficial effects of the supported metallocene catalyst provided in this application are the same as those of the above-mentioned method for removing alkyl aluminum from alkylaluminoxanes, and will not be elaborated here. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 A flowchart of a purification method for alkylaluminoxanes provided in an embodiment of this application is shown; Figure 2 A schematic diagram of the adsorption column provided in an embodiment of this application is shown; Figure 3 A flowchart illustrating the preparation method of the alkylaluminoxane solution provided in the embodiments of this application is shown; Figure 4 The diagram shows a comparison of the ¹H NMR detection results of methylaluminoxane in the embodiments and comparative examples of this application.

[0013] Figure label: Adsorption column 200, body 210, feed inlet 220, discharge outlet 230, vent 240, solid-liquid separation unit 250, microporous filter plate 251, sand core filter plate 252. Detailed Implementation

[0014] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0015] The accompanying drawings illustrate various structural schematics according to embodiments of this application. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0016] In the context of this application, when a layer / element is referred to as being "on top of" another layer / element, the layer / element can be directly on top of the other layer / element, or there can be an intermediate layer / element between them. Furthermore, if a layer / element is "on top of" another layer / element in one orientation, then when the orientation is reversed, the layer / element can be "below" the other layer / element. To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0017] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0018] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0019] Alkyl aluminum oxanes are highly efficient co-catalysts in the polymerization of metallocene and post-transition metal olefins, and are widely used in the synthesis of high-end polyolefin materials such as metallocene polyethylene, metallocene polypropylene, polyolefin elastomers, metallocene polyolefin lubricants, and cyclic polyolefins. The synthesis of alkyl aluminum oxanes typically employs a controlled hydrolysis reaction of alkyl aluminum. However, because the alkyl aluminum in the reactant is difficult to completely convert during the reaction, a certain amount of alkyl aluminum inevitably remains in the final product. The analytical certificates for commercial-grade alkyl aluminum oxane products clearly indicate the residual content of alkyl aluminum.

[0020] For the removal of alkylaluminum from alkylaluminoxane products, vacuum distillation or vacuum drying are commonly used methods. However, current research indicates that vacuum distillation or vacuum drying alone cannot completely remove alkylaluminum. Figure 4 The ¹H NMR results of methylaluminoxane also confirmed this view. Furthermore, vacuum distillation or vacuum drying processes are time-consuming and labor-intensive, pose high safety risks, and the heating operations during these processes can adversely affect the product performance and storage stability of alkylaluminoxanes.

[0021] Therefore, how to efficiently and safely remove alkylaluminates from alkylaluminoxanes while avoiding damage to product performance has become a pressing technical problem to be solved in this field.

[0022] To overcome the above problems, this application provides a method for removing alkyl aluminum from alkylaluminoxanes. Figure 1 A flowchart illustrating a purification method for alkylaluminoxanes provided in an embodiment of this application is shown. Figure 1 As shown, the method may include: Step 110: Obtain an alkylaluminoxane solution. It is understood that the method for removing alkylaluminum from alkylaluminoxanes provided in this application embodiment can be applied to alkylaluminoxane solutions from various sources, including but not limited to commercially purchased alkylaluminoxane products, and alkylaluminoxane solutions prepared by hydrolysis or non-hydrolysis methods.

[0023] Step 120: The alkylaluminoxane solution is passed through an adsorption column containing an aqueous support, allowing the alkylaluminoxane solution to react with the aqueous support to obtain the target alkylaluminoxane solution. The content of alkylaluminum in the target alkylaluminoxane solution is less than that in the alkylaluminoxane solution, specifically, the content of alkylaluminum in the target alkylaluminoxane solution is reduced by at least 80% compared to that in the alkylaluminoxane solution. It should be noted that the reaction here refers to the chemical reaction between water in the aqueous support and alkylaluminum in the alkylaluminoxane solution. Specifically, alkylaluminum reacts with water to generate alkane gas and aluminum-containing compounds, thereby removing the alkylaluminum from the solution. Simultaneously, alkylaluminoxane molecules can also be chemically bonded to the support surface.

[0024] As can be seen from the above, in the method for removing alkyl aluminum from alkylaluminoxanes provided in this application embodiment, the alkylaluminoxane solution is passed through an adsorption column filled with an aqueous support, and the water in the aqueous support reacts with the alkyl aluminum in the alkylaluminoxane solution, thereby making the content of alkyl aluminum in the target alkylaluminoxane solution less than the content of alkyl aluminum in the alkylaluminoxane solution, thus significantly reducing the content of alkyl aluminum in the alkylaluminoxane solution.

[0025] As can be seen, the method of this application does not require vacuum distillation or vacuum drying, avoiding the safety risks and product thermal damage caused by high-temperature operation. Furthermore, the process is simple, controllable, and easy to implement industrially. Simultaneously, during the removal of alkylaluminum, the surface of the support is loaded with alkylaluminoxanes, transforming it into a support supported on alkylaluminoxanes. This support can be further used to prepare highly active supported metallocene catalysts, exhibiting good economic and environmental benefits.

[0026] In some embodiments, Figure 2 A schematic diagram of the structure of the adsorption column 200 provided in an embodiment of this application is shown. Figure 2 As shown, the adsorption column 200 includes a body 210, an inlet 220, an outlet 230, an exhaust port 240, and a solid-liquid separation unit 250. The inlet 220, outlet 230, and exhaust port 240 are all located on the body 210, while the solid-liquid separation unit 250 is located inside the body 210. The inlet 220 is used to introduce an alkylaluminoxane solution, the outlet 230 is used to discharge the treated target alkylaluminoxane solution, the exhaust port 240 is used to discharge any gases generated during the reaction, and the solid-liquid separation unit 250 is used to separate insoluble solids that may be generated during the reaction. It is understood that the solid-liquid separation method can be decantation, filtration, centrifugation, or gravity sedimentation, etc., and the solid-liquid separation unit 250 can employ known solid-liquid separation structures in the art, such as filter plates, sand cores, sieves, and sedimentation zones, and is not limited thereto.

[0027] In one example, such as Figure 2 As shown, the solid-liquid separation unit 250 may include a microporous filter plate 251 and a sand core filter plate 252. The microporous filter plate 251 is disposed in the upstream region inside the adsorption column 200, and is used to initially separate the treated alkylaluminoxane solution from the insoluble solids generated by the reaction, allowing the solution and a small amount of fine solid particles to pass through and flow into the solid separation and collection area. The sand core filter plate 252 is disposed near the outlet inside the adsorption column 200, and is used to perform final filtration of the initially separated solution, ensuring that the target alkylaluminoxane solution flowing out of the outlet 230 does not contain solid particles, thereby achieving thorough solid-liquid separation.

[0028] In some embodiments, such as Figure 2As shown, the number of adsorption columns 200 can be one. When the number of adsorption columns 200 is one, the method provided in this embodiment of the application may further include: repeatedly passing the alkylaluminoxane solution into the adsorption column 200. It is understood that this repeated passing can be a cyclic passing, that is, the solution flowing out of the outlet 230 is again passed into the same adsorption column 200 through the inlet 220, and this process is repeated multiple times. The specific number of cycles can be determined according to actual needs, for example, it can be 2, 3, 4, 5, 6, or 7 times, etc., and is not limited here, in order to improve the removal effect of alkylaluminum.

[0029] In other embodiments, such as Figure 2 As shown, there can be multiple adsorption columns 200, and these multiple adsorption columns 200 are connected in series. When multiple adsorption columns 200 are connected in series, the method provided in this application embodiment may further include: sequentially passing an alkylaluminoxane solution into each of the multiple adsorption columns 200 to achieve continuous processing and improve processing efficiency.

[0030] In one example, such as Figure 2 As shown, the alkylaluminoxane solution can first pass through the first adsorption column 200, then flow out from the outlet 230 of the first adsorption column 200 and directly enter the inlet 220 of the second adsorption column 200, and so on, until it passes through the last adsorption column 200. The number of adsorption columns 200 connected in series can be determined according to actual needs, such as 2, 3, 4 or 5, etc., and is not limited to this, in order to improve the removal effect.

[0031] In some embodiments, the aforementioned aqueous carrier is a solid material containing a certain amount of water, with water available for reaction present inside or on its surface. Specifically, it can be any spherical or near-spherical aqueous carrier, selected from one or more of aqueous silica gel, aqueous molecular sieves, aqueous alumina, and hydrated polymers. For example, the aqueous carrier can be aqueous silica gel, aqueous molecular sieves, aqueous alumina, hydrated polymers, or combinations thereof.

[0032] In some embodiments, to achieve better alkylaluminum removal, the water content in the aqueous carrier can be controlled. Specifically, the molar ratio of water in the aqueous carrier to alkylaluminum in the alkylaluminoxane solution can be (0.3:1)-(3:1) to avoid problems such as insufficient water in the aqueous carrier due to a low molar ratio, resulting in inadequate removal of alkylaluminum and thus unsatisfactory removal effect, and the potential loss of alkylaluminoxane due to a high molar ratio, changes in the surface properties of the aqueous carrier, or even the generation of excessive insoluble solids. Preferably, the molar ratio can be (0.5:1)-(2:1); more preferably, the molar ratio can be (0.8:1)-(1.5:1).

[0033] In some embodiments, Figure 3 A flowchart illustrating the preparation method of the alkylaluminoxane solution provided in the embodiments of this application is shown. Figure 3 As shown, when the alkylaluminoxane solution is an alkylaluminoxane solution prepared by a controlled hydrolysis reaction of alkylaluminum, the above-mentioned method for obtaining the alkylaluminoxane solution may include: Step 310: Dilute the alkylaluminum with an inert solvent to obtain a diluted alkylaluminum solution. It should be noted that the concentration range of the diluted alkylaluminum can be 1wt%-60wt% to avoid problems such as reduced production efficiency and increased solvent consumption due to excessively low concentration, which would increase costs; and excessively high concentration, which could lead to overly vigorous and uncontrollable reactions, potentially causing localized overheating or uneven product development. Preferably, the concentration range after dilution is 5wt%-50wt%; more preferably, the concentration range is 6wt%-40wt%.

[0034] The aforementioned inert solvent can be an organic solvent that does not undergo significant chemical reaction with alkylaluminum, water, or alkylaluminoxanes under the reaction conditions. As an example, the inert solvent can be one or both of aliphatic and aromatic hydrocarbons. For instance, the inert solvent can be aliphatic hydrocarbons, aromatic hydrocarbons, or combinations of aliphatic and aromatic hydrocarbons. The aromatic hydrocarbons can be one or more of benzene, toluene, xylene, ethylbenzene, cumene, and mesitylene; the aliphatic hydrocarbons can be one or more of pentane, hexane, heptane, octane, and cyclohexane. It should be noted that the inert solvent can be a single solvent or a mixture of different hydrocarbons.

[0035] Step 320: Contact the diluted alkyl aluminum solution with the reaction water to carry out a hydrolysis reaction, obtaining an alkylaluminoxane solution. It is understood that the reaction water here can be any water used to hydrolyze the alkyl aluminum, and its form can be various. For example, the reaction water can be one or more of the following: water of crystallization, solid water, liquid water, water vapor, an emulsion formed by water and an inert solvent, a solution formed by water and a polar solvent, and a mixture of water vapor and an inert gas. Among these, the water of crystallization can be the water of crystallization of copper sulfate, ferrous sulfate, or any other hydrated crystals; solid water can be ice or snow, etc.

[0036] Because the reaction between alkylaluminum and water is extremely vigorous, directly adding liquid water can easily lead to localized overheating, splashing, or even explosion. Therefore, the method of water introduction usually needs to be controlled. Thus, the above-mentioned hydrolysis reaction can be carried out using delivery devices such as micro-syringes, micro-sieve arrays, capillaries or capillary arrays, membrane materials, and microchannel reactors to slowly introduce the reaction water into the reaction system. These devices can disperse water into tiny droplets or molecular streams, ensuring uniform contact with the alkylaluminum dilution solution, thereby achieving a mild and controllable hydrolysis reaction.

[0037] The molar ratio of the total amount of water to the total amount of alkyl aluminum in the above reaction can be from (0.1:1) to (2:1). For example, this molar ratio can be from (0.2:1) to (1.7:1), or from (0.3:1) to (1.5:1), and is not limited thereto. By selecting a molar ratio that meets the above requirements, problems such as insufficient water, incomplete conversion of alkyl aluminum, high alkyl aluminum content in the product, and low product yield can be avoided. Furthermore, excessive water may lead to over-hydrolysis of alkyl aluminum, generating large amounts of insoluble aluminum hydroxide or aluminum oxide, thereby reducing the yield and activity of the alkylaluminoxane.

[0038] The reaction temperature of the above hydrolysis reaction can be -80℃ to 300℃. Preferably, the reaction temperature can be -60℃ to 200℃. More preferably, the reaction temperature can be -40℃ to 180℃, etc.

[0039] The reaction time can range from 0 to 72 hours. Preferably, the reaction time can be 1 to 48 hours; more preferably, it can be 2 to 24 hours. In one example, the reaction process can be monitored by sampling analysis to determine the appropriate reaction time. Specifically, the reaction time can be selected based on factors such as reaction temperature, feeding rate, and the properties of the target product to avoid incomplete reactions due to excessively short reaction times, and low production efficiency and the potential increase in the risk of side reactions due to excessively long reaction times.

[0040] In some embodiments, the alkyl aluminum can be one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum. For example, the alkyl aluminum can be trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, or a combination of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum.

[0041] This application also provides an alkylaluminoxane, prepared by the aforementioned method for removing alkylaluminum from alkylaluminoxanes. The content of alkylaluminum in this alkylaluminoxane is significantly lower than that in commercially available products.

[0042] The beneficial effects of the alkylaluminoxanes provided in this application are the same as those of the above-described methods for removing alkylaluminum from alkylaluminoxanes, and will not be repeated here.

[0043] This application also provides a supported metallocene catalyst, comprising: under inert gas protection, reacting a metallocene complex with a support provided in this application embodiment within an adsorption column after treating an alkylaluminoxane solution in an inert solvent to obtain a supported metallocene catalyst. It is understood that since the aqueous support within the adsorption column has successfully supported alkylaluminoxanes on its surface after the aforementioned removal process, and alkylaluminoxanes are extremely sensitive to air and moisture, rapidly hydrolyzing or even burning upon contact with air, the support must be removed from the adsorption column under inert gas protection to prevent deactivation or safety accidents. This inert gas protection can be achieved by using gases such as nitrogen or argon that do not react with alkylaluminoxanes and metallocene complexes throughout the removal and subsequent operations.

[0044] After the aforementioned removal process, the original water inside the aqueous support has been completely consumed by the reaction with the alkylaluminum in the solution. Simultaneously, a large amount of alkylaluminoxane is chemically bonded to the support surface. Therefore, the support in the adsorption column after treating the alkylaluminoxane solution is essentially a solid material loaded with alkylaluminoxane, rather than the original aqueous support. This support can be directly used as a support for supported metallocene catalysts without the need for an additional alkylaluminoxane loading step.

[0045] The aforementioned metallocene complexes can be any metallocene complex of Group IVB metals, such as titanium, zirconium, and hafnium. As examples, the metallocene complexes can be one or more of various metallocene complexes suitable for olefin polymerization, such as dichlorotitanium, dicyclopentadienyl zirconium dichloride, bis(n-butylcyclopentadienyl) zirconium dichloride, ethylene-bridged bis(indenyl) zirconium dichloride, and methylenesilyl-bridged bis(indenyl) zirconium dichloride. The inert solvent can be one or more of toluene, benzene, xylene, hexane, and heptane.

[0046] In one example, under the protection of an inert gas, the removed support can be added to a reaction vessel containing an inert solvent and stirred to form a suspension; then, a metallocene complex solution pre-dissolved in an inert solvent can be added to the suspension, and the mixture can be stirred and reacted for a period of time at a certain temperature to obtain a supported metallocene catalyst.

[0047] The reaction temperature described above can be selected based on the properties of the specific metallocene complex. For example, the reaction temperature can range from room temperature to 150°C, and preferably, it can be between 25°C and 120°C.

[0048] The reaction time described above can be determined based on factors such as reaction temperature and the concentration of the metallocene complex. For example, the reaction time can be 0.5 h to 24 h, and preferably 1 h to 18 h.

[0049] After the reaction is complete, the solid product can be obtained by filtration. The solid product is then washed with an inert solvent, such as toluene 1 to 3 times followed by hexane 1 to 2 times. The washed solid product is then thoroughly dried to obtain the supported metallocene catalyst.

[0050] As can be seen, the supported metallocene catalyst provided in this application directly utilizes the alkylaluminoxane-supported support obtained in the aforementioned alkylaluminoxane removal process, without the need for an additional alkylaluminoxane loading step. The process is simple and low-cost, and the resulting catalyst has high activity and stable performance, making it highly valuable for industrial applications.

[0051] The present application is further illustrated below by way of embodiments, but these embodiments are not intended to limit the scope of the present application. Experimental methods not specifically described in the following embodiments are performed according to conventional methods and conditions, or as selected in accordance with the product instructions.

[0052] Example 1 In this embodiment, aqueous silica gel is selected as the aqueous carrier, trimethylaluminum is selected as the alkylaluminum, toluene is selected as the inert solvent, distilled water is selected as the reaction water, and the concentration of the alkylaluminum diluent is 8wt%.

[0053] The method for removing alkyl aluminum from alkylaluminoxanes in this embodiment may include the following steps: Step 1: Select a 500ml reaction flask equipped with a high-speed stirrer and thoroughly vacuum dry and purge with nitrogen. Under nitrogen protection, add 300ml of a toluene solution with a concentration of 8wt% trimethylaluminum to the reaction flask, and then lower the temperature of the reaction flask to -40℃ using a cold bath.

[0054] Step 2: Take 3.8 ml of distilled water to make the molar ratio of water to trimethylaluminum 0.7:1, and slowly add the water to the reaction flask using a microsyringe. After adding water, bring the reaction flask to room temperature and continue stirring for 1 hour. After the reaction is complete, filter to remove solid residue under nitrogen protection. The filtrate is concentrated to obtain a methylaluminoxane toluene solution. The molar content of residual trimethylaluminum was determined by pyridine titration to be approximately 1.6%. ¹H NMR analysis of the obtained methylaluminoxane toluene solution yielded the following results: Figure 4 As shown, a characteristic narrow peak representing trimethylaluminum can be observed near δ ≈ 0 ppm, while a broad peak signal of methylaluminoxane can be observed at δ ≈ -0.35 ppm to -0.50 ppm.

[0055] Step 3: Under inert gas protection, the above filtrate flows into the inlet of the adsorption column, ensuring full contact with the aqueous silica gel. The molar ratio of water to residual trimethylaluminum is 1.5:1. The gas generated from the reaction of residual trimethylaluminum and water is discharged through the vent. The treated methylaluminoxane solution and a small amount of insoluble solids flow into the solid separation / collection zone through a microporous filter plate, and finally pass through a sand core filter plate to achieve solid-liquid separation. The methylaluminoxane-toluene solution flowing out of the outlet is the final target alkylaluminoxane solution. The target solution is analyzed by ¹H NMR, and the results are as follows: Figure 4 As shown in the figure. The results show that a typical broad peak signal is retained in the range of δ ≈ -0.35 ppm to -0.50 ppm, indicating that the expected aluminum oxane structure is well preserved and the method of this application does not destroy the core structure of methylaluminoxane. At the same time, the characteristic narrow peak representing trimethylaluminum near δ ≈ 0 ppm is significantly weakened or even almost disappears. The molar content of free trimethylaluminum after treatment cannot be determined by pyridine titration, that is, the content is significantly less than the minimum unit of 0.1% determined by pyridine titration, i.e., less than 0.1%, and the content of trimethylaluminum is reduced by at least 93.8%. This confirms that the method of this application can significantly reduce the content of residual alkyl aluminum in the system.

[0056] Furthermore, under inert gas protection, the silica gel packed inside the adsorption column was removed, and the metallocene complex bis(n-butylcyclopentadienyl)zirconium dichloride was supported on the silica gel. The resulting catalyst exhibited extremely high catalytic activity in the gas-phase polymerization of ethylene, with an activity of approximately 8800 gPE / gCat.

[0057] Example 2 The difference between this embodiment and Example 1 is that the concentration of the alkyl aluminum diluent is 6 wt%; the molar ratio of water to trimethylaluminum is 0.5:1, and the other steps are exactly the same as in Example 1.

[0058] The obtained target methylaluminoxane solution was analyzed by ¹H NMR, and the results were basically consistent with those of Example 1. Figure 4 The NMR spectra at the bottom showed no significant difference. Pyridine titration determined that the molar content of free trimethylaluminum decreased to 0.2% after treatment, representing a reduction of approximately 87.5%.

[0059] Example 3 The difference between this embodiment and Example 1 is that the concentration of the alkyl aluminum diluent is 10 wt%; the molar ratio of water to trimethylaluminum is 1:1; and the other experimental steps are exactly the same as in Example 1.

[0060] The obtained target methylaluminoxane solution was analyzed by ¹H NMR, and the results were basically consistent with those of Example 1. Figure 4 The NMR spectra at the bottom showed no significant difference. Using pyridine titration, the molar content of free trimethylaluminum after treatment could not be determined, but the content of trimethylaluminum decreased by at least 93.8%.

[0061] Example 4 The difference between this embodiment and Example 1 is that the reaction temperature is controlled at -80℃, while the other experimental steps are exactly the same as in Example 1.

[0062] The obtained target methylaluminoxane solution was analyzed by ¹H NMR. The results were basically consistent with those of Example 1, and were significantly improved. Figure 4 The NMR spectra at the bottom showed no significant difference. The molar content of free trimethylaluminum after treatment could not be determined using pyridine titration.

[0063] Example 5 This embodiment follows the same steps as Example 1, except that an aqueous molecular sieve is used instead of aqueous silica gel as the packing material in the adsorption column. The obtained sample was analyzed by ¹H NMR, and the results showed no significant change compared to Example 1. Figure 4 The NMR spectra at the bottom show no significant difference. The molar content of free trimethylaluminum after treatment could not be determined using pyridine titration. This demonstrates that the method of this invention also exhibits excellent results when using other aqueous carriers.

[0064] Example 6 This embodiment follows the same steps as Example 1, except that the methylaluminoxane solution flowing out of the adsorption column outlet is re-injected into the adsorption column for a second and third round of adsorption. The resulting sample was analyzed by ¹H NMR, and the results showed no significant change compared to Example 1. Figure 4 The NMR spectra at the bottom showed no significant difference. The molar content of free trimethylaluminum after treatment could not be determined using pyridine titration.

[0065] Example 7 This embodiment follows the same steps as Example 1, except that two adsorption columns are connected in series. The methylaluminoxane solution exiting the first adsorption column is fed into the inlet of the second adsorption column. The resulting sample is analyzed by ¹H NMR, and the results show no significant change compared to Example 1. Figure 4 The NMR spectra at the bottom showed no significant difference. The molar content of free trimethylaluminum after treatment could not be determined using pyridine titration.

[0066] Example 8 This embodiment is identical to Example 1 in terms of steps, except that triethylaluminum is used instead of trimethylaluminum as the reaction raw material. All other experimental procedures remain completely consistent. The amount of triethylaluminum in the ethylaluminoxane solution obtained after adsorption treatment is extremely low, and the specific content cannot be determined by pyridine titration (i.e. the content is significantly less than the minimum unit of 0.1% determined by pyridine titration), indicating that the present invention has a significant effect on the removal of alkylaluminum.

[0067] Example 9 This embodiment is the same as the steps in Example 1, except that triisobutylaluminum is used instead of trimethylaluminum as the reaction raw material. The other experimental procedures are completely consistent. The amount of triisobutylaluminum in the isobutylaluminoxane solution obtained after adsorption treatment is extremely low, and the specific content cannot be determined by pyridine titration, indicating that the present invention has a significant effect on the removal of alkylaluminum.

[0068] Comparative Example 1 ¹H NMR analysis was performed on methylaluminoxane (MAO) product (10 wt% toluene solution) purchased from Grace Company in the United States. The results are as follows: Figure 4 As shown in the figure. The results show that a set of obvious narrow peak signals can be observed near δ ≈ 0.00 ppm, which belongs to the residual trimethylaluminum (TMA) species in the system. At the same time, a set of broad peak signals can be observed at δ ≈ -0.35 ppm to -0.50 ppm, which is the methylaluminoxane (MAO) species. This indicates that there is obvious trimethylaluminum impurity in the MAO product. The molar content of trimethylaluminum determined by pyridine titration is 1.1%.

[0069] Comparative Example 2 The commercial-grade methylaluminoxane (MAO) toluene solution in Comparative Example 1 was dried under reduced pressure to remove the solvent, and then subjected to ¹H NMR detection. The results are as follows: Figure 4 As shown.

[0070] The results showed a distinct narrow peak signal near δ ≈ 0.00 ppm, which is attributed to residual trimethylaluminum in the system. Reduced pressure drying was not effective in removing the residual trimethylaluminum. Meanwhile, the broad peak signal in the range of δ ≈ -0.35 ppm to -0.50 ppm underwent some changes, indicating that the reduced pressure drying process affected the methylaluminoxane product. The molar content of trimethylaluminum, determined by pyridine titration, was 0.5%, meaning that the trimethylaluminum content decreased by only 54.5% compared to before treatment.

[0071] Example 10 The commercial-grade methylaluminoxane (MAO) toluene solution in Comparative Example 1 was treated with the adsorption treatment method in step 3 of Example 1. The resulting methylaluminoxane solution contained a triisobutylaluminum molar content that could not be determined by pyridine titration, indicating that its content was significantly lower than 0.1%. The obtained sample was analyzed by ¹H NMR, and the results were... Figure 4 The NMR spectra at the bottom show no significant difference. This indicates that the present invention also has a significant effect on the removal of alkyl aluminum from commercial MAO products.

[0072] As shown in Examples 1 to 4 of this application, within the range of parameters such as alkylaluminum concentration, water-aluminum ratio, and reaction temperature defined in this application, a target product with significantly reduced alkylaluminum content can be obtained. Example 5 shows that using different types of aqueous carriers is equally effective. Examples 6 and 7 show that single-column cyclic adsorption and multi-column tandem adsorption can further improve the removal effect. Examples 8 and 9 show that the method of this application is also applicable to different alkylaluminum raw materials such as triethylaluminum and triisobutylaluminum, and a target product with significantly reduced alkylaluminum content can be obtained in all cases. Comparative Examples 1 and 2 show that both the commercial product not treated by the method of this application and the product treated with vacuum drying exhibit obvious alkylaluminum signals. Simultaneously, the broad peak signal of alkylaluminoxanes in the product treated with conventional vacuum drying showed a slight change, confirming the influence of the vacuum drying process on the alkylaluminoxane product.

[0073] According to Example 10 and Comparative Examples 1-2, Example 10 treated the commercial-grade methylaluminoxane (MAO) toluene solution in Comparative Example 1 with the same adsorption method, reducing the residual trimethylaluminum content to below 0.1%, and the broad peak signal of methylaluminoxane did not change significantly; while the molar content of trimethylaluminum in the product of Comparative Example 1 was 1.1%; after conventional vacuum drying treatment, the trimethylaluminum content in Comparative Example 2 only decreased to 0.5% (a reduction of 54.5%), and the broad peak signal of methylaluminoxane changed, indicating structural damage.

[0074] In summary, the results of the above embodiments and comparative examples show that the method for removing alkyl aluminum from alkylaluminoxanes provided in this application can effectively remove alkyl aluminum from the alkylaluminoxane solution while maintaining the core structure of the alkylaluminoxane.

[0075] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. The scope of this application is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this application, and all such substitutions and modifications should fall within the scope of this application.

Claims

1. A method for removing alkyl aluminum from alkylaluminoxanes, characterized in that, include: Obtain an alkylaluminoxane solution; An alkylaluminoxane solution is passed through an adsorption column containing an aqueous support, and the alkylaluminoxane solution reacts with the aqueous support to obtain the target alkylaluminoxane solution. The content of alkyl aluminum in the target alkylaluminoxane solution is reduced by at least 80% compared to the content of alkyl aluminum in the alkylaluminoxane solution.

2. The method according to claim 1, characterized in that, The adsorption column is one in number, and the method further includes: passing the alkylaluminoxane solution into the adsorption column multiple times.

3. The method according to claim 1, characterized in that, The adsorption columns are multiple, and the multiple adsorption columns are connected in series. The method further includes: sequentially passing the alkylaluminoxane solution into each of the multiple adsorption columns.

4. The method according to claim 1, characterized in that, The water-containing carrier is a spherical or near-spherical carrier, and the water-containing carrier is selected from one or more of water-containing silica gel, water-containing molecular sieve, water-containing alumina and high molecular weight hydropolymer.

5. The method according to claim 1, characterized in that, The water content in the aqueous carrier is in a molar ratio of (0.3:1) to (3:1) of the alkyl aluminum oxane solution.

6. The method according to claim 1, characterized in that, The process of obtaining the alkylaluminoxane solution includes: The alkylaluminum was diluted with an inert solvent to obtain a diluted alkylaluminum solution; The alkylaluminum dilution solution is brought into contact with reaction water to carry out a hydrolysis reaction, thereby obtaining an alkylaluminoxane solution.

7. The method according to claim 6, characterized in that, The alkylaluminum is one or more selected from trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum; and / or, The concentration range of the alkyl aluminum diluent is 1 wt%–60 wt%; and / or, The inert solvent is one or more of aliphatic hydrocarbons and aromatic hydrocarbons.

8. The method according to claim 6, characterized in that, The reaction water is one or more of the following: water of crystallization, solid water, liquid water, water vapor, an emulsion formed by water and an inert solvent, a solution formed by water and a polar solvent, and a mixture of water vapor and an inert gas; and / or, The molar ratio of the total amount of reaction water to the total amount of alkyl aluminum is (0.1:1) to (2:1).

9. An alkylaluminoxane, characterized in that, Prepared by the method described in any one of claims 1-8.

10. A supported metallocene catalyst, characterized in that, include: Under inert gas protection, the support in the adsorption column after treating the alkylaluminoxane solution according to any one of claims 1-8 is used to react with the metallocene complex in an inert solvent to obtain a supported metallocene catalyst.

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