Separation and purification method and application of polyolefin catalyst

Abstract

The invention discloses a separation and purification method of a polyolefin catalyst, which adopts an overflow separation technology and comprises the following steps: firstly, adding a catalyst crude product and a solvent into a container A, fully mixing to prepare a suspension liquid, then enabling the suspension liquid to flow into a container B from the bottom at a certain speed, and rising along with the liquid level to obtain the polyolefin catalyst. Catalyst product particles and impurity particles are slowly diffused in the solvent and directionally move in the vertical direction to form different particle distributions, that is, a product particle enrichment area is formed above the container B, an impurity particle enrichment area is formed below the container B, the product particles overflow into the container C under the driving of fluid, and the product particles are separated from the container C; and carrying out solid-liquid separation to obtain the high-purity polyolefin catalyst. The method is easy to implement, the device is simple in structure, the technological process is stable, the purification problem of the slightly-soluble catalyst is solved, the method is particularly suitable for separation and purification of the slightly-soluble multi-component catalyst with the same particle size, and the preparation requirement of a high-quality polyolefin material is met.

Description

Technical Field

[0001] The invention relates to the field of polyolefin materials, and in particular to a separation and purification method of a polyolefin catalyst and application thereof. Background Art

[0002] Polyolefin materials, such as polyethylene, polypropylene, and olefin copolymers, are produced by homopolymerization or copolymerization of olefin monomers. Polyolefin catalysts play a vital role in the production of polyolefin materials.

[0003] Polyolefin catalysts can be divided into metallocene catalysts and non-metallocene catalysts, which are composed of a ligand part and a transition metal (such as titanium, zirconium, hafnium, etc.) part. These catalysts can be prepared by different methods, including solution method, gas phase method and solid phase method, and most of the catalysts obtained are in the form of solid particles. During the preparation process, due to the factors of feed ratio, reaction mechanism and process conditions, residual inorganic impurity components are inevitable, which reduces the purity of the catalyst. These inorganic impurities come from by-products or residual raw materials, such as lithium chloride, sodium chloride, magnesium chloride, zirconium chloride, hafnium chloride, etc., which will continue to remain in the polymer and affect the product performance. Therefore, the purification of the catalyst is an important research direction.

[0004] At present, there are two methods for purifying catalysts: physical purification and chemical purification. Physical purification methods include filtration, pulping, centrifugation and washing, while chemical purification methods include solvent extraction, complex precipitation and chemical reaction.

[0005] Patent CN107973868B discloses a scrubber and a method for purifying a polyolefin catalyst, wherein a crude product slurry and a solvent are filtered and washed through a filter plate containing micropores to remove impurities in the crude product. The impurities are required to be soluble in the solvent. For insoluble impurities, this solution is not applicable and cannot be filtered and separated.

[0006] Patent CN113880977B discloses a method for preparing an olefin polymerization catalyst, which uses a method of filtering a catalyst solution to remove lithium chloride or other insolubles, and the filtrate is concentrated, crystallized, filtered, and then processed to obtain a product powder. This method requires that the catalyst has good solubility in the solvent, while a catalyst with poor solubility needs to add an excessive amount of solvent to dissolve it, which increases the amount of waste liquid dramatically, has poor processability, is cumbersome to operate, has low production efficiency, and is costly.

[0007] Patent CN111683953A discloses a method for preparing a metallocene compound, which uses a distillation process to remove inorganic salts and high-boiling impurities to obtain a high-purity fraction product. This method is only applicable to low-boiling organic metal compounds.

[0008] These methods can effectively remove inorganic impurities in product particles, but the process is limited and the effect of purifying slightly soluble catalysts is poor. Therefore, it is urgent to develop a high-purity, low-cost purification method for polyolefin catalysts to meet the needs of industrial scale-up. Summary of the invention

[0009] In order to solve the above technical problems, the present invention proposes a method for separating and purifying a polyolefin catalyst, which adopts an "overflow separation" technology to obtain a high-purity polyolefin catalyst.

[0010] Another object of the present invention is to provide the use of the polyolefin catalyst prepared by the separation and purification method in the preparation of polyolefin.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0012] A method for separating and purifying a polyolefin catalyst comprises the following steps:

[0013] (1) Adding a crude polyolefin catalyst and a solvent into a container A, stirring and dispersing, and preparing a suspension;

[0014] (2) The suspension in container A flows into container B from the bottom of container B, and the liquid level in container B rises slowly;

[0015] (3) The liquid level in container B rises to the top and overflows into container C through an overflow pipeline located at the top of container B, where solid-liquid separation is performed and the solvent is removed to obtain a solid powder;

[0016] (4) Drying the solid powder obtained in the container C to obtain a high-purity polyolefin catalyst.

[0017] In some specific embodiments, the solvent in step (1) is an ultra-dry solvent selected from one or more of alkane, ether, and aromatic solvents.

[0018] In some specific embodiments, the solvent in step (1) is selected from one or more of diethyl ether, cyclopentyl methyl ether, butyl ether, n-hexane, cyclohexane, methylcyclohexane, n-heptane, toluene, xylene, and tetrahydrofuran.

[0019] In some specific embodiments, the mass ratio of the crude catalyst to the solvent is 1-50:100, for example, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95, etc.

[0020] In some specific embodiments, the stirring speed in the step (1) is 50-500 rpm, for example, 60 rpm, 80 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc., and the stirring time is 0.5-5 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.

[0021] In some specific embodiments, the flow rate of the suspension from the bottom of container B into container B in step (2) is 0.001-20 L / min, for example, 0.001 L / min, 0.01 L / min, 0.1 L / min, 0.5 L / min, 1 L / min, 3 L / min, 5 L / min, 8 L / min, 10 L / min, 15 L / min, 20 L / min, etc., preferably 0.01-10 L / min.

[0022] In some specific embodiments, the content of inorganic impurity particles in the crude catalyst is 0.5-15wt%, for example, 0.6wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, etc.

[0023] In some specific embodiments, the polyolefin catalyst is selected from a metallocene catalyst or a non-metallocene catalyst.

[0024] In some specific embodiments, the aspect ratio of the container B is 1-1000:1, for example 5:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1, 800:1, 850:1, 900:1, 950:1, etc., preferably 20-100:1.

[0025] In some specific embodiments, the drying temperature in step (4) is 30-100°C, for example, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc., and the drying time is 2-24h, for example, 3h, 5h, 6h, 8h, 10h, 12h, 15h, 18h, 20h, 23h, etc.

[0026] On the other hand, the polyolefin catalyst obtained by the above-mentioned method for separating and purifying the polyolefin catalyst is used in the preparation of polyolefin.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The separation and purification method of the polyolefin catalyst proposed by the present invention solves the purification problem of slightly soluble catalysts and is particularly suitable for the separation and purification of slightly soluble multi-component catalysts with the same particle size.

[0029] The separation and purification method of the present invention adopts the "overflow separation" technology. First, the crude catalyst and the solvent are added to the container A in a certain mass ratio, and are fully mixed to form a suspension. Then, the suspension flows from the bottom to the container B at a certain rate. As the liquid level rises, the product particles and the impurity particles slowly diffuse in the solvent and move in a directional manner in the vertical direction to form different particle distributions, that is, a product particle enrichment zone is formed above the container B, and an impurity particle enrichment zone is formed below the container B. Driven by the fluid, the product particles overflow into the container C, and a high-purity polyolefin catalyst is obtained by solid-liquid separation to meet the preparation requirements of high-quality polyolefin materials.

[0030] The solution of the invention is easy to implement, the device structure is simple, the process flow is stable, and it can be widely used in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the separation and purification device of the polyolefin catalyst of the present invention.

[0032] Figure 2 The present invention is a schematic flow diagram of the separation and purification method of the polyolefin catalyst.

[0033] Among them, 1-container A, 2-container B, 3-container C, 4-container B feed pipeline, 5-overflow pipeline, 6-catalyst product particles, 7-impurity particles. DETAILED DESCRIPTION

[0034] The present invention is further described below through specific implementation methods. The embodiments of the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0035] like Figure 1 , Figure 2As shown, the separation and purification method of the polyolefin catalyst of the present invention adopts the "overflow separation" technology, including the steps of mixing ingredients, overflow separation, and solvent removal. First, the crude catalyst including the catalyst product particles 6 and the impurity particles 7 and the solvent are added to the container A1 at a certain mass ratio, and are fully mixed to prepare a suspension. Then, the suspension flows from the feed pipeline 4 located at the bottom of the container B2 to the container B2 at a certain rate. As the liquid level rises, the product particles 6 and the impurity particles 7 slowly diffuse in the solvent and move in a directional manner in the vertical direction to form different particle distributions, that is, a product particle enrichment zone is formed above the container B, and an impurity particle enrichment zone is formed below the container B. Driven by the fluid, the product particles 6 overflow into the container C3 through the overflow pipeline 5 located at the top of the container B. The solid-liquid separation and solvent removal are performed to obtain a high-purity polyolefin catalyst to meet the preparation requirements of high-quality polyolefin materials.

[0036] Among them, the discharge pipeline of container A is connected to the feed pipeline of container B. The position of the discharge pipeline of container A is not particularly limited and can be located at the top, middle or bottom of container A, preferably at the bottom. Those skilled in the art can understand that a feed pump can be set between the discharge pipeline of container A and the feed pipeline of container B to pump the prepared suspension in container A into container B.

[0037] Those skilled in the art will appreciate that a stirring mechanism, such as a stirring paddle, is also provided in the container A for fully stirring and mixing to form a suspension.

[0038] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0039] The materials and reagents used in the following examples were purchased from commercial sources, including:

[0040] Raw material 1: AR, Shanghai Shenze Chemical Technology Co., Ltd.;

[0041] Raw material 2: AR, Innochem;

[0042] Raw material 3: AR, Innochem;

[0043] n-Hexane: AR, Innochem;

[0044] Ether: AR, Innochem;

[0045] n-Butyl lithium: AR, Innochem;

[0046] Tetrahydrofuran: AR, Innochem;

[0047] Hafnium tetrachloride: AR, Innochem;

[0048] In the following examples and comparative examples: the metal impurity content is calculated using the ICP test results; the polymerization activity is obtained by polymerization experiments using the catalysts obtained in each example and comparative example, and the polymerization process refers to "Example 8 in Patent CN113880977B"; "wt%" means mass percentage; the remaining experimental methods are conventional methods unless otherwise specified; the processes involving the catalysts are all carried out under a nitrogen atmosphere.

[0049] [Preparation Example]

[0050] Catalyst synthesis process:

[0051]

[0052] Preparation of crude catalyst I

[0053] (1) 1 kg of raw material 1 (1.0 eq) and 0.762 kg of raw material 2 (1.0 eq) were added to 100 L of ether, cooled to -78°C, and stirred for 1 h; 2.76 L of n-butyl lithium (2.5 M, 2.2 eq) n-hexane solution was added, stirred at low temperature for 5 h, and then 0.795 kg of raw material 3 (1.0 eq) was added, and stirring was continued for 36 h; then the temperature was slowly raised to 25°C, stirred for 10 h, and the reaction was completed. The filter cake was obtained by filtration, collection, and drying to obtain ligand 4.

[0054] (2) Weigh 0.8 kg of ligand 4 (1.0 eq) and add it to 70 L of ether, and stir at 0°C for 1 h; add 0.9 L of n-butyl lithium (2.5 M, 2.0 eq) in n-hexane, and continue to react at 0°C for 36 h to obtain a red suspension; add 0.25 kg of hafnium tetrachloride fine powder (1.0 eq) to the suspension, and stir at 25°C for 16 h; after the reaction is completed, filter through a centrifuge, wash the powder three times with 10 L of n-hexane respectively, and dry the powder to obtain a crude catalyst 1.

[0055] The impurity contents of the crude catalyst 1 are LiCl: 13.5 wt %, ZrCl4: 0.5 wt %.

[0056] Preparation of crude catalyst II

[0057] The preparation steps are basically the same as those for the crude catalyst I, with the only difference being that in step (2), after the reaction is completed, the powder is filtered through a centrifuge, 50 L of tetrahydrofuran is added to the powder and the mixture is thoroughly washed and mixed for 5 h, then filtered, the powder is washed three times with 10 L of n-hexane, and the powder is dried to obtain the crude catalyst II.

[0058] The impurity contents of the crude catalyst II are LiCl: 7.8 wt %, ZrCl4: 0.5 wt %.

[0059] [Example 1]

[0060] The crude catalyst I was separated and purified according to the following steps:

[0061] (1) Under nitrogen atmosphere, 10 kg of crude catalyst and 100 kg of n-hexane were added to container A, stirring was started, the speed was adjusted to 200 rpm, the stirring time was 3 h, and the mixture was fully mixed to prepare a suspension;

[0062] (2) Open the bottom valves of container A and container B, start the feed pump, set the flow rate to 1 L / min, and the suspension fluid continuously enters container B, wherein the aspect ratio of container B is 20:1;

[0063] (3) The liquid level in container B rises slowly. After reaching the top of the container, the suspension overflows into container C and is filtered to obtain a polyolefin catalyst.

[0064] Experimental results: impurity content, LiCl: 0.019wt%, ZrCl4: 0.004wt%; polymerization activity: 7.1×10 7 g / (mol×min), polymer molecular weight: 82430 g / mol, octene insertion rate: 33 wt%.

[0065] [Example 2]

[0066] The same crude catalyst and purification method as in Example 1 were used, with the only differences being that the solvent was ether, the feed pump flow rate was 5 L / min, the aspect ratio of container B was 100:1, the rotation speed was 50 rpm, and the stirring time was 5 h.

[0067] Experimental results: impurity content, LiCl: 0.012wt%, ZrCl4: 0.002wt%; polymerization activity: 7.2×10 7 g / (mol×min), polymer molecular weight: 84324 g / mol, octene insertion rate: 34 wt%.

[0068] [Example 3]

[0069] The same crude catalyst and purification method as in Example 1 were used, with the only difference being that crude catalyst II was selected, the solvent was butyl ether, the feed pump flow rate was 0.01 L / min, and the mass of the crude catalyst was 40 kg.

[0070] Experimental results: impurity content, LiCl: 0.015wt%, ZrCl4: 0.002wt%; polymerization activity: 7.1×10 7 g / (mol×min), polymer molecular weight: 83541 g / mol, octene insertion rate: 32 wt%.

[0071] [Example 4]

[0072] The same crude catalyst and purification method as in Example 1 were used, with the only difference being that the solvent was toluene, the feed pump flow rate was 8 L / min, the mass of the crude catalyst was 1 kg, the rotation speed was 500 rpm, and the stirring time was 0.5 h.

[0073] Experimental results: impurity content, LiCl: 0.012wt%, ZrCl4: 0.001wt%; polymerization activity: 7.3×10 7 g / (mol×min), polymer molecular weight: 80056 g / mol, octene insertion rate: 30 wt%.

[0074] [Example 5]

[0075] The same crude catalyst and purification method as in Example 1 were used, with the only difference being that the solvent was n-heptane, the mass of the crude catalyst was 5 kg, the aspect ratio of container B was 50:1, and the stirring time was 4 h.

[0076] Experimental results: impurity content, LiCl: 0.020wt%, ZrCl4: 0.004wt%; polymerization activity: 7.2×10 7 g / (mol×min), polymer molecular weight: 81974 g / mol, octene insertion rate: 31 wt%.

[0077] [Example 6]

[0078] The same crude catalyst and purification method as in Example 1 were used, the only difference being that the solvent was xylene, the mass of the crude catalyst was 50 kg, the aspect ratio of container B was 1000:1, and the stirring time was 5 h.

[0079] Experimental results: impurity content, LiCl: 0.022wt%, ZrCl4: 0.004wt%; polymerization activity: 7.2×10 7 g / (mol×min), polymer molecular weight: 82874 g / mol, octene insertion rate: 32 wt%.

[0080] [Example 7]

[0081] The same crude catalyst and purification method as in Example 1 were used, with the only difference being that crude catalyst II was selected, the mass of the crude catalyst was 1 kg, the aspect ratio of container B was 1000:1, and the stirring time was 5 h.

[0082] Experimental results: impurity content, LiCl: 0.021wt%, ZrCl4: 0.004wt%; polymerization activity: 7.3×10 7g / (mol×min), polymer molecular weight: 83247 g / mol, octene insertion rate: 31 wt%.

[0083] [Example 8]

[0084] The same crude catalyst and purification method as in Example 1 were used, the only difference being that the feed pump flow rate was 0.2 L / min and the mass of the crude catalyst was 20 kg.

[0085] Experimental results: impurity content, LiCl: 0.014wt%, ZrCl4: 0.001wt%; polymerization activity: 7.1×10 7 g / (mol×min), polymer molecular weight: 82756 g / mol, octene insertion rate: 31 wt%.

[0086] [Example 9]

[0087] The same crude catalyst and purification method as in Example 1 were used, the only difference being that crude catalyst II was selected, the feed pump flow rate was 0.001 L / min, and the mass of the crude catalyst was 20 kg.

[0088] Experimental results: impurity content, LiCl: 0.018wt%, ZrCl4: 0.004wt%; polymerization activity: 7.2×10 7 g / (mol×min), polymer molecular weight: 83014 g / mol, octene insertion rate: 31 wt%.

[0089] [Example 10]

[0090] The same crude catalyst and purification method as in Example 1 were used, with the only difference being that crude catalyst II was selected, the stirring speed was 300 rpm, the feed pump flow rate was 20 L / min, and the mass of the crude catalyst was 1 kg.

[0091] Experimental results: impurity content, LiCl: 0.011wt%, ZrCl4: 0.001wt%; polymerization activity: 7.1×10 7 g / (mol×min), polymer molecular weight: 82007 g / mol, octene insertion rate: 32 wt%.

[0092] [Comparative Example 1]

[0093] The same crude catalyst and purification method as in Example 1 were used, the only difference being that the aspect ratio of container B was 0.5:1.

[0094] Experimental results: impurity content, LiCl: 10.5wt%, ZrCl4: 0.4wt%; polymerization activity: 6.1×10 6g / (mol×min), polymer molecular weight: 80765 g / mol, octene insertion rate: 29 wt%.

[0095] [Comparative Example 2]

[0096] (1) Under nitrogen atmosphere, 10 kg of crude catalyst II and 100 kg of n-hexane were added to container A, stirring was started, the speed was adjusted to 200 rpm, the stirring time was 3 h, and the mixture was fully mixed to prepare a suspension;

[0097] (2) The suspension is directly transferred to container C and filtered to obtain the polyolefin catalyst.

[0098] Experimental results: impurity content, LiCl: 7.3wt%, ZrCl4: 0.5wt%; polymerization activity: 6.3×10 6 g / (mol×min), polymer molecular weight: 81182 g / mol, octene insertion rate: 29 wt%.

[0099] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for separating and purifying a polyolefin catalyst, characterized in that: The steps include: (1) Adding a crude polyolefin catalyst and a solvent into a container A, stirring and dispersing, and preparing a suspension; (2) The suspension in container A flows into container B from the bottom of container B, and the liquid level in container B rises slowly; (3) The liquid level in container B rises to the top and overflows into container C through an overflow pipeline located at the top of container B, where solid-liquid separation is performed and the solvent is removed to obtain a solid powder; (4) Drying the solid powder obtained in the container C to obtain a high-purity polyolefin catalyst.

2. The method for separating and purifying a polyolefin catalyst according to claim 1, characterized in that: The solvent in step (1) is an ultra-dry solvent selected from one or more of alkane, ether and aromatic solvents.

3. The method for separation and purification of a polyolefin catalyst according to claim 2, characterized in that: The solvent in step (1) is selected from one or more of diethyl ether, cyclopentyl methyl ether, butyl ether, n-hexane, cyclohexane, methylcyclohexane, n-heptane, toluene, xylene, and tetrahydrofuran.

4. The method for separating and purifying a polyolefin catalyst according to any one of claims 1 to 3, characterized in that: The mass ratio of the crude catalyst to the solvent is 1-50:

100.

5. The method for separation and purification of a polyolefin catalyst according to claim 4, characterized in that: The stirring speed in step (1) is 50-500 rpm, and the stirring time is 0.5-5 h.

6. The method for separation and purification of a polyolefin catalyst according to claim 1, characterized in that: In the step (2), the flow rate of the suspension flowing from the bottom of container B into container B is 0.001-20 L / min, preferably 0.01-10 L / min.

7. The method for separating and purifying a polyolefin catalyst according to claim 4, characterized in that: The content of inorganic impurity particles in the crude catalyst is 0.5-15wt%.

8. The method for separation and purification of a polyolefin catalyst according to claim 7, characterized in that: The polyolefin catalyst is selected from a metallocene catalyst or a non-metallocene catalyst.

9. The method for separating and purifying a polyolefin catalyst according to claim 1, characterized in that: The aspect ratio of the container B is 1-1000:1, preferably 20-100:1; Preferably, the drying temperature in step (4) is 30-100° C., and the drying time is 2-24 h.

10. Use of the polyolefin catalyst obtained by the method for separation and purification of a polyolefin catalyst according to any one of claims 1 to 9 in the preparation of polyolefin.

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