Process for the preparation of alkylaluminoxanes and their use

Abstract

The application provides a preparation method of alkylaluminoxane and application thereof. The preparation method provided by the application uses ketone compounds to react with alkylaluminum to prepare alkylaluminoxane, avoids the introduction of water, is mild and controllable, has high product yield, and is cheap in raw materials. In addition, unlike the crystallization hydration method which produces a large amount of inorganic salt impurities and is complicated in post-treatment, the preparation method provided by the application has few by-products and is easy to separate and purify. Meanwhile, by adding boron trihalide as an initiator, the chain length of the prepared alkylaluminoxane is suitable, and the alkylaluminoxane prepared by the preparation method provided by the application has high yield. In particular, the alkylaluminoxane, especially methylaluminoxane, prepared by the preparation method provided by the application is used as a cocatalyst and is used in combination with a metallocene catalyst to catalyze ethylene polymerization, and it is found that the cocatalytic performance is excellent.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and particularly relates to a preparation method of alkylaluminoxane and application thereof. Background Art

[0002] Since its discovery, alkylaluminoxane has become the most important cocatalyst for olefin polymerization or oligomerization catalytic systems such as metallocene catalysts, vinyl polymerization catalysts (FI catalysts) and late transition metal catalysts, greatly promoting the development of the polyolefin industry. Before alkylaluminoxane was discovered, the activity of metallocene catalysts was very low when using alkylaluminum as a cocatalyst, but the catalytic activity of the metallocene catalyst system with alkylaluminoxane as a cocatalyst was very high. In particular, the combination of alkylaluminoxane and metallocene catalyst has made it possible to produce many high-performance polyolefin materials (such as mPE, mPP, mEPDM, POE, etc.) with precise and adjustable microstructures. These materials have huge application potential in various aspects such as military industry, national defense, medical treatment, energy, and people's production and life. At present, although cocatalysts such as borane and borate have appeared, alkylaluminoxane still plays an indispensable role in the field of homogeneous olefin polymerization.

[0003] Traditional methods generally use a hydrolysis method to react alkyl aluminum with water to obtain a low molecular weight polymer, i.e., an alkyl aluminoxane. The reaction involved in this method is a rapid, highly exothermic reaction. Depending on the source of the water, the hydrolysis method can be divided into two major categories: the free hydration method and the crystallization hydration method. Among them, the free hydration method is to introduce water in different states such as gas, liquid, and solid into a reactor. For example, water is dispersed in an inert solvent using a static mixer or mechanical emulsification method, introduced using nitrogen to carry water vapor (US4937363), introduced by atomizing equipment to convert water into a mist (CN102190677B), or directly reacted on an ice surface (US5087713). The common feature of this type of method is that the alkyl aluminum reacts directly with free water, the reaction is very violent, and there are high requirements for process control and equipment, but the reproducibility between batches is poor.

[0004] Crystallization hydration method refers to that the moisture required for reaction is introduced into reaction system with the form of crystal hydrate (US 5902891, CN102286012B) or the inert carrier (CN 102675494 B) of absorption certain water, reaction rate depends on the precipitation rate of crystallization water, the reaction of inorganic crystallization water and alkyl aluminum is not as violent as the reaction of free water and alkyl aluminum, therefore compared to free hydration method, crystallization hydration method reaction process is easier to control, process operation is simple, equipment investment cost is low, but this synthetic method can produce the porous reaction residue such as a large amount of inorganic salts, this residue can adsorb methylaluminoxane product and excessive alkyl aluminum raw material, cause a large amount of losses of product, reaction yield is lower. In addition, although can pass through washing reaction residue, improve the rate of recovery of aluminum-containing raw material and product, the introducing of inert solvent and washing operation, can further increase the complexity and production energy consumption of flow process.

[0005] Therefore, it is urgent to find a more efficient method for preparing alkylaluminoxanes. Summary of the Invention

[0006] In view of this, the present invention aims to provide a preparation method of alkylaluminoxane and its application. The preparation method is simple and feasible, flexible in operation, safe and controllable in the preparation process, and high in product yield.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing an alkylaluminoxane, comprising:

[0009] A ketone compound and an alkyl aluminum are reacted in the presence of an initiator to obtain an alkyl aluminumoxane;

[0010] The initiator is selected from boron trihalides.

[0011] Preferably, the initiator is selected from boron tribromide.

[0012] Preferably, the ketone compound is selected from acetophenone and / or benzophenone.

[0013] Preferably, the alkyl aluminum is selected from any one or more of trimethyl aluminum, triethyl aluminum or triisobutyl aluminum.

[0014] Preferably, the molar ratio of the ketone compound, alkyl aluminum and initiator is (1-5):1:(0.01-0.015).

[0015] Preferably, the reaction temperature is 80-110° C. and the reaction time is 10-12 h.

[0016] Preferably, the reaction is carried out in an inert atmosphere.

[0017] Preferably, the reaction is also carried out in the presence of a solvent.

[0018] Preferably, the solvent is selected from any one or more of toluene, p-xylene, o-xylene or mesitylene.

[0019] Preferably, the reaction is carried out by dropwise adding a mixed solution of the ketone compound and the solvent into a mixed solution of the alkyl aluminum, the initiator and the solvent.

[0020] Preferably, the mass ratio of the ketone compound to the solvent is 1:(2-2.5).

[0021] Preferably, the mass ratio of the alkyl aluminum to toluene is 1:(2-2.5).

[0022] Preferably, the dropping speed is 1 to 5 drops / s.

[0023] In a second aspect, the present invention provides a use of the alkylaluminoxane prepared by the above preparation method as a co-catalyst in catalyzing ethylene polymerization.

[0024] Preferably, the main catalyst in the ethylene polymerization is selected from metallocene catalysts.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The preparation method provided by the present invention uses a ketone compound to react with an alkyl aluminum (preferably trimethyl aluminum) to prepare an alkyl aluminoxane (preferably methyl aluminoxane, MAO), which avoids the introduction of water, has a mild and controllable reaction, a high product yield, and cheap raw materials. In addition, unlike the crystallization hydration method, which produces a large amount of inorganic salt impurities and has cumbersome post-processing, the preparation method provided by the present invention has few by-products and is easy to separate and purify. At the same time, the present invention adds a boron trihalide BX3 (such as BBr3) as an initiator to make the chain length of the prepared alkyl aluminoxane suitable. While having a higher yield, the alkyl aluminoxane prepared by the preparation method provided by the present invention, especially methyl aluminoxane, can be used as a co-catalyst and used in combination with a metallocene catalyst to catalyze ethylene polymerization. It was found that its co-catalytic performance is excellent.

[0027] Tests have shown that the yield of methylaluminoxane prepared by the preparation method provided by the present invention is relatively high, reaching up to 72.4%. In addition, ethylene polymerization was catalyzed by using a toluene solution of the prepared methylaluminoxane as a co-catalyst and zirconocene dichloride as the main catalyst, and the catalytic activity was found to be as high as 1.45×10 7 gpp / mol·Zr·h. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In view of the problems in the prior art of preparing alkyl aluminoxanes by traditional hydrolysis methods, which have high requirements for reaction equipment or high energy consumption and complex processes, the present invention has developed a non-hydrolysis-based alkyl aluminoxane synthesis technology, which mainly prepares alkyl aluminoxanes by reacting alkyl aluminum with ketone-containing compounds.

[0030] It should be noted that the prior art hydrolysis method relies on oxygen-hydrogen bond reactions to prepare alkylaluminoxanes. This reaction is highly reactive, extremely violent, uncontrollable, dangerous, and requires high equipment. Therefore, this type of reaction must be carried out at a relatively low temperature to reduce its reactivity and ensure safety. In contrast, the present invention uses the Al in the alkyl aluminum to react with the carbonyl group in the ketone compound. Compared to oxygen-hydrogen bonds, the reactivity of carbon-oxygen bonds is lower. Therefore, the reaction of the present invention can be carried out at room temperature and is easy to control.

[0031] In the present invention, the preparation method of alkylaluminoxane comprises the following steps:

[0032] A ketone compound and an alkyl aluminum are reacted in the presence of an initiator to obtain an alkyl aluminumoxane.

[0033] Wherein, the ketone compound is selected from acetophenone and / or benzophenone, preferably acetophenone; the alkyl aluminum is selected from any one or more of trimethylaluminum, triethylaluminum or triisobutylaluminum, preferably trimethylaluminum; the initiator is selected from boron trihalide, preferably boron tribromide.

[0034] In some embodiments of the present invention, the ketone compound and alkyl aluminum are reacted in the presence of an initiator at 80-110°C for 10-12 hours, preferably at 90-100°C for 10-11 hours. In the present invention, the ketone compound and alkyl aluminum need to react in a certain ratio. If the ketone compound is too little, the yield will be affected, and if it is too much, the chain length of the prepared MAO will be too long, affecting the co-catalytic activity. At the same time, the initiator is used to control the chain length of the alkyl aluminoxane within an appropriate range to avoid the chain length of the alkyl aluminoxane being too long, causing it to form a colloidal substance, thereby reducing its yield and co-catalytic performance. Therefore, the amount of initiator used also needs to be within an appropriate range. Therefore, after screening, the present invention controls the molar ratio of the ketone compound, alkyl aluminum and initiator to be (1-5):1:(0.01-0.015), preferably (2-4):1:(0.03-0.012), and more preferably (2.5-3.5):1:(0.05-0.010).

[0035] In some embodiments of the present invention, the reaction is preferably carried out in an inert atmosphere. The present invention has no particular limitation on the inert atmosphere, and any atmosphere familiar to those skilled in the art may be used, such as nitrogen, argon, etc. In some embodiments of the present invention, the inert atmosphere is high-purity nitrogen with a purity of 3N or above or other high-purity inert gas.

[0036] In some embodiments of the present invention, the reaction is further carried out in the presence of a solvent, which is used to provide a liquid environment and can be specifically selected from any one or more of toluene, p-xylene, o-xylene or mesitylene.

[0037] Because the reaction between the ketone compound and the alkylaluminum is an exothermic reaction, to avoid excessive reaction intensity and difficulty in control, in some preferred embodiments of the present invention, the reaction is carried out by dropwise adding a mixed solution of the ketone compound and solvent to a mixed solution of the alkylaluminum, initiator, and solvent. The mass ratio of the ketone compound to the solvent is 1:(2-2.5), preferably 1:(2.1-2.3); the mass ratio of the alkylaluminum to toluene is 1:(2-2.5), preferably 1:(2.1-2.3). Furthermore, considering both production efficiency and reaction safety, the dropwise addition rate can be 1-5 drops / s, preferably 1-4 drops / s, and more preferably 1-2 drops / s. In the present invention, the dropwise addition can be carried out at room temperature. In the present invention, after the dropwise addition is completed, the temperature is preferably raised to 80-110°C for the reaction. In the present invention, the reaction is preferably carried out with stirring at a rate of 200-300 r / min, preferably 220-280 r / min, and more preferably 250-260 r / min.

[0038] In the present invention, after the reaction is completed and the reaction system is cooled to room temperature, the solid in the reaction system is preferably filtered out to obtain a solution containing alkylaluminoxane for subsequent use.

[0039] In some specific embodiments of the present invention, the method for preparing the alkylaluminoxane comprises the following steps:

[0040] Under the protection of inert gas, a certain amount of ketone compound (such as acetophenone) is added to toluene, and then slowly added dropwise to a toluene solution of trimethylaluminum with a certain amount of initiator BX3 (such as BBr3) at room temperature. After the addition is completed, the temperature is raised to 80-110°C and the reaction is continued with stirring for 10-12 hours. After that, the solid in the reaction system is filtered out to prepare a toluene solution of methylaluminoxane.

[0041] In the present invention, the room temperature is "15 to 30°C", preferably 25°C.

[0042] The above preparation method provided by the present invention has the following advantages:

[0043] (1) The preparation method is simple and feasible, the operation is flexible, and the preparation process is safe and controllable;

[0044] (2) The yield of alkylaluminoxane is high and the co-catalytic performance is excellent;

[0045] (3) Since alkyl aluminum (especially trimethyl aluminum) reacts violently with water, the concentration of the conventionally used alkyl aluminum solution is 1%. However, the alkyl aluminum solution used in the present invention (i.e., the mixed solution of alkyl aluminum and solvent) does not need to be very dilute (it can be 30-35 wt%). The increase in its concentration is not only beneficial to improving the production capacity of the device, but also helps to reduce the subsequent solvent processing volume;

[0046] (4) Unlike the crystallization hydration method, which produces a large amount of inorganic salt impurities and requires cumbersome post-processing, the preparation method provided by the present invention produces fewer by-products and is easy to separate and purify.

[0047] The alkylaluminoxanes prepared in the present invention, particularly methylaluminoxane, can be used as cocatalysts in catalyzing ethylene polymerization. Therefore, the present invention can utilize alkylaluminoxanes as cocatalysts in combination with metallocene catalysts (such as zirconocene dichloride, titanocene dichloride, or hafnocene dichloride) as the main catalyst to catalyze ethylene polymerization. Results indicate that alkylaluminoxanes exhibit excellent cocatalytic performance.

[0048] In some embodiments of the present invention, ethylene polymerization is catalyzed by using a toluene solution of methylaluminoxane as a cocatalyst and zirconocene dichloride as a main catalyst, and the catalytic activity can reach up to 1.45×10 7This further proves that the alkylaluminoxane prepared by the preparation method provided by the present invention has excellent co-catalytic performance.

[0049] In order to further illustrate the present invention, the following examples are provided for detailed description. The experimental raw materials used in the following examples of the present invention are all commonly available commercial products.

[0050] The specific conditions for catalyzing ethylene polymerization in the following examples and comparative examples are:

[0051] T = 60 ° C, t = 0.5 h; Al / Zr = 1500; V (toluene) = 50 mL; P (ethylene) = 1 atm;

[0052] n(MAO)=4.5*10 -3 mol; n(CpZrCl2)=3*10 -6 mol.

[0053] Example 1

[0054] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 14.42g acetophenone (0.12mol) was weighed, 5g toluene was added to prepare a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0055] The toluene solution of methylaluminoxane in the three-necked flask was distilled under reduced pressure at 40°C to remove the toluene solvent, and then the temperature was raised to 80°C and distilled under reduced pressure to remove the tert-butylbenzene by-product (detected as tert-butylbenzene by nuclear magnetic resonance hydrogen spectrum). The weight was 16.11 g, and the mass of the residue in the three-necked flask was 3.99 g.

[0056] According to the law of conservation of mass, the total mass of the raw materials is: 7.2g + 14.42g = 21.62g (BBr3 is the catalyst, and its mass remains unchanged before and after the reaction). The theoretical value of the total mass of the product is 21.62g, and the mass of the by-product tert-butylbenzene is 16.11g (0.12mol). That is, 5.51g of MAO is theoretically produced, and 3.99g of MAO is actually obtained. The yield is 3.99 / 5.51×100% = 72.4%.

[0057] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 1.42×107 gpp / mol·Zr·h.

[0058] Example 2

[0059] Under inert gas protection, 7.2g TMA (0.1mol), 1.17g BCl3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 14.42g acetophenone (0.1mol) was weighed, 5g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0060] The yield was calculated using the same method as in Example 1. The yield was 70.4%.

[0061] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 1.38×10 7 gpp / mol·Zr·h.

[0062] Example 3

[0063] Under inert gas protection, 7.2 g TMA (0.1 mol), 3.91 g BI3 (0.01 mol), and 15 g toluene were weighed in a 100 mL three-necked flask and stirred at 200 r / min. Then, 14.42 g acetophenone (0.1 mol) was weighed, 5 g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100 mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100 ° C. and the reaction was continued with stirring for 10 h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0064] The yield was calculated using the same method as in Example 1. The yield was 72.2%.

[0065] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 1.45×10 7 gpp / mol·Zr·h.

[0066] Example 4

[0067] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 21.86g benzophenone (0.12mol) was weighed, 5g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0068] The yield was calculated using the same method as in Example 1. The yield was calculated to be 68.2%.

[0069] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 0.89×10 7 gpp / mol·Zr·h.

[0070] Example 5

[0071] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 14.42g acetophenone (0.12mol) was weighed, 5g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 120°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0072] The yield was calculated in the same manner as in Example 1, and the yield was 45.1%.

[0073] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 4.38×10 6 gpp / mol·Zr·h.

[0074] Example 6

[0075] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 14.42g acetophenone (0.12mol) was weighed, 5g toluene was added to prepare a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the stirring reaction was continued for 6h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0076] The yield was calculated using the same method as in Example 1. The yield was 52.8%.

[0077] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 7.25×10 6 gpp / mol·Zr·h.

[0078] Example 7

[0079] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 72.09g acetophenone (0.6mol) was weighed, 5g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0080] The yield was calculated in the same manner as in Example 1, and the yield was 68.7%.

[0081] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 1.02×10 5 gpp / mol·Zr·h.

[0082] Comparative Example 1

[0083] Under inert gas protection, 7.2g TMA (0.1mol), 2.5g BBr3 (0.01mol), and 15g toluene were weighed in a 100mL three-necked flask and stirred (200r / min). Then, 61.06g benzoic acid (0.5mol) was weighed, 5g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0084] The yield was calculated using the same method as in Example 1. The yield was 37.1%.

[0085] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 0.38×10 7 gpp / mol·Zr·h.

[0086] Comparative Example 2

[0087] Under inert gas protection, 7.2 g TMA (0.1 mol), 1.42 g CH3I (0.01 mol), and 15 g toluene were weighed in a 100 mL three-necked flask and stirred at 200 r / min. Then, 14.42 g acetophenone (0.12 mol) was weighed, 5 g toluene was added to form a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100 mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100°C and the reaction was continued with stirring for 10 hours. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0088] The yield was calculated in the same manner as in Example 1, and the yield was 54.1%.

[0089] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization with a catalytic activity of 1.08×10 5 gpp / mol·Zr·h.

[0090] Comparative Example 3

[0091] Under inert gas protection, 7.2 g TMA (0.1 mol) and 15 g toluene were weighed in a 100 mL three-necked flask and stirred at 200 r / min. Then, 14.42 g acetophenone (0.12 mol) was weighed, 5 g toluene was added to prepare a solution, and then transferred to a constant pressure dropping funnel. The solution was slowly added dropwise to the 100 mL three-necked flask at a rate of 1 drop / s at room temperature. After the addition was completed, the temperature was raised to 100 ° C. and the reaction was continued with stirring for 10 h. After the reaction was completed, the heating was turned off. After the system was cooled to room temperature, the solid impurities generated in the reaction system were filtered out to prepare a toluene solution of methylaluminoxane.

[0092] The yield was calculated using the same method as in Example 1. The yield was 72.4%.

[0093] The toluene solution of methylaluminoxane was used as a cocatalyst and zirconocene dichloride as the main catalyst to catalyze ethylene polymerization. No polyethylene was produced and the catalytic activity was 1.38×10 6 gpp / mol·Zr·h.

[0094] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an alkylaluminoxane, characterized in that: include: A ketone compound and an alkyl aluminum are reacted in the presence of an initiator to obtain an alkyl aluminumoxane; The initiator is selected from boron tribromide; The ketone compound is selected from acetophenone and / or benzophenone; The alkyl aluminum is selected from any one or more of trimethyl aluminum, triethyl aluminum or triisobutyl aluminum.

2. The preparation method according to claim 1, characterized in that The molar ratio of the ketone compound, alkyl aluminum and initiator is (1-5):1:(0.01-0.015).

3. The preparation method according to claim 1 or 2, characterized in that The reaction temperature is 80-110° C. and the reaction time is 10-12 h.

4. The preparation method according to claim 1, characterized in that The reaction is carried out in an inert atmosphere.

5. The preparation method according to claim 1, characterized in that The reaction is also carried out in the presence of a solvent; The solvent is selected from any one or more of toluene, p-xylene, o-xylene or mesitylene.

6. The preparation method according to claim 5, characterized in that The reaction is carried out by dropwise adding a mixed solution of a ketone compound and a solvent into a mixed solution of an alkyl aluminum, an initiator and a solvent.

7. The preparation method according to claim 6, characterized in that The mass ratio of the ketone compound to the solvent is 1:(2-2.5); The mass ratio of the alkyl aluminum to toluene is 1:(2-2.5); The dropping speed is 1 to 5 drops / s.