A metallocene catalyst for ethylene polymerization and its application

Abstract

The present invention provides a metallocene catalyst for ethylene polymerization and its application. The catalyst comprises a carrier and an active component supported on the carrier; the active component comprises a metallocene compound and an alkylaluminum compound. The carrier is a porous polymer microsphere modified with tertiary amino groups, wherein the cyano groups account for 1 to 10% by weight of the carrier, and the tertiary amino groups account for 1 to 25% by weight of the carrier. The catalyst has excellent ethylene polymerization activity and can produce polyethylene products with high molecular weight and enhanced crystallinity. It can also reduce the amount of co-catalyst used, thereby lowering the production cost of polyethylene.

Description

Technical Field

[0001] The invention belongs to the field of industrial catalysis and relates to a metallocene catalyst for ethylene polymerization and application thereof. Background Art

[0002] Polyethylene is one of the most produced, widely used, and fastest-growing general-purpose resins. It is widely used in packaging, concentrates, construction, automotive, and other aspects of life and production. Catalyst technology has evolved through several stages, including Ziegler-Natta, metallocene, and late-transition metal catalysts. These catalysts have produced a wide variety of products, expanding the production and application scope of the polyolefin industry.

[0003] In the existing technology, the polymerization activity of metallocene catalysts used in ethylene polymerization is not good, and it is difficult to obtain polyethylene products with high molecular weight and excellent crystallization properties. In addition, a large amount of co-catalysts need to be added to the polymerization reaction to assist in catalysis, which will further increase the production cost of polyethylene.

[0004] Therefore, it is of great significance to develop a catalyst for ethylene polymerization that can obtain high molecular weight polyethylene with good crystallization performance and low production cost. Summary of the Invention

[0005] The present invention provides a metallocene catalyst for ethylene polymerization. The catalyst has excellent ethylene polymerization activity and can obtain a polyethylene product with high molecular weight and good crystallization performance. The catalyst can also avoid reducing the amount of co-catalyst used and reduce reaction costs.

[0006] The present invention also provides an application of a metallocene catalyst for ethylene polymerization in an ethylene polymerization reaction. The metallocene catalyst for ethylene polymerization is used to catalyze the ethylene polymerization reaction to obtain polyethylene with high molecular weight and good crystallinity, and can also reduce the amount of co-catalyst used and reduce the polyethylene production cost.

[0007] The present invention provides a metallocene catalyst for ethylene polymerization, comprising a carrier and an active component supported on the carrier;

[0008] The active components include metallocene compounds and alkyl aluminum compounds;

[0009] The carrier is a porous polymer microsphere modified with cyano and tertiary amino groups;

[0010] The mass content of the cyano group in the carrier is 1 to 10%, and the mass content of the tertiary amino group in the carrier is 1 to 25%.

[0011] The metallocene catalyst for ethylene polymerization as described above, wherein the molar ratio of the tertiary amino group to the cyano group is (1-20):1.

[0012] The metallocene catalyst for ethylene polymerization as described above, wherein the catalyst comprises, by mass percentage, 0.1-5% of a metallocene compound, 10-36% of an alkyl aluminum compound, and 59-89.9% of a carrier.

[0013] The metallocene catalyst for ethylene polymerization as described above, wherein the Al / N molar ratio in the catalyst is (1 to 10):1; and / or

[0014] The Al / Ti molar ratio in the catalyst is (1-30):1.

[0015] The metallocene catalyst for ethylene polymerization as described above, wherein the average pore size of the carrier is 12 to 25 nm; and / or,

[0016] The average diameter of the carrier is 4 to 6 μm.

[0017] The metallocene catalyst for ethylene polymerization as described above, wherein the carrier is obtained by polymerization reaction of porous polymer microspheres with a cyano group-containing olefin compound and a tertiary amino group-containing olefin compound;

[0018] The tertiary amino group-containing olefin compound is selected from at least one of N,N-dimethyl-3-butene-1-amine, N,N-dimethyl-2-methyl-3-butene-1-amine, N,N-dimethyl-4-pentene-1-amine, N,N-dimethyl-4-aminostyrene, N,N-diethyl-4-aminostyrene, and 4-allyl-N,N-dimethylaniline.

[0019] The metallocene catalyst for ethylene polymerization as described above, wherein the cyano group-containing olefin compound is selected from 4-cyanostyrene.

[0020] The metallocene catalyst for ethylene polymerization as described above, wherein the metallocene compound is selected from the compound represented by formula (II):

[0021] (Cp) x TiCl y Formula (II);

[0022] wherein Cp is selected from cyclopentadienyl or a cyclopentadienyl derivative; x is selected from 1 or 2; and y is selected from 2 or 3.

[0023] The present invention also provides a use of any of the above metallocene catalysts for ethylene polymerization in an ethylene polymerization reaction.

[0024] The metallocene catalyst for ethylene polymerization of the present invention uses porous polymer microspheres modified with tertiary amino groups and cyano groups as carriers to load active components such as metallocene and alkyl aluminum compounds, and controls the content of tertiary amino groups and cyano groups in the carriers, so that the catalyst has excellent ethylene polymerization activity, thereby being able to obtain polyethylene products with high molecular weight and good crystallinity.

[0025] When the metallocene catalyst for ethylene polymerization of the present invention is used in ethylene polymerization reaction, it can efficiently catalyze ethylene polymerization to obtain a polyethylene product with high molecular weight and good crystallinity, and can effectively reduce the amount of co-catalyst used, thereby reducing the production cost of polyethylene. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0027] The present invention provides a metallocene catalyst for ethylene polymerization, which comprises a carrier and an active component supported on the carrier;

[0028] Wherein, the active components include metallocene compounds and alkyl aluminum compounds;

[0029] The carrier is a porous polymer microsphere modified by cyano and tertiary amino groups, wherein the mass content of the cyano groups in the carrier is 1-10%, and the mass content of the tertiary amino groups in the carrier is 1-25%.

[0030] The inventors discovered that when porous polymer microspheres modified with cyano and tertiary amino groups are used as a carrier, with the cyano group content of the carrier being 1-10% by mass and the tertiary amino group content being 1-25% by mass, and when the carrier is loaded with active components such as a metallocene compound and an alkylaluminum compound, the catalyst exhibits superior ethylene polymerization activity, resulting in polyethylene products with higher molecular weight and improved crystallinity. This may be due to the fact that the porous polymer microsphere carrier modified with tertiary amino groups can coordinate with the strongly acidic substances produced during the polymerization process, and the cyano groups can effectively regulate the distribution of the catalyst's active centers, thereby increasing the catalyst's polymerization activity. Furthermore, the catalyst's high polymerization activity allows for better linear copolymerization of ethylene, resulting in polyethylene products with higher molecular weight and improved crystallinity.

[0031] Furthermore, porous polymer microspheres are spherical polymer particles with a porous structure, produced through polymer synthesis. Porous polymer microspheres have numerous pores, low density, large specific surface area, and excellent acid-base stability, allowing them to carry more active components and thus enhance the catalyst's excellent catalytic activity.

[0032] Furthermore, the molar ratio of the tertiary amino group to the cyano group is (1-20): 1. The polymerization activity of the catalyst can be regulated by adjusting the molar ratio of the tertiary amino group to the cyano group according to different actual needs, thereby obtaining polyethylene products meeting different molecular weights and crystallization properties.

[0033] In a specific embodiment, the catalyst comprises, by weight, 0.1-5% of a metallocene compound, 10-36% of an alkyl aluminum compound, and 59-89.9% of a carrier. Within this composition range, the catalyst has good catalytic activity.

[0034] The present invention does not impose any specific limitation on the selection of alkyl aluminum, and any alkyl aluminum compound commonly used in the art can be used. For example, the alkyl aluminum compound can be selected from one or more of methylaluminoxane, ethyl-modified methylaluminoxane, or isobutyl-modified methylaluminoxane.

[0035] In a specific embodiment, the Al / N molar ratio in the catalyst is (1-10):1; and / or the Al / Ti molar ratio in the catalyst is (1-30):1. Specifically, the Al / N molar ratio and the Al / Ti molar ratio in the catalyst can be controlled by adjusting the molar ratio of the aluminum element to the cyano group in the alkyl aluminum compound and by adjusting the molar ratio of the metallocene compound to the cyano group, respectively, thereby imparting the catalyst with excellent polymerization activity.

[0036] In one specific embodiment, the average pore size of the support is 12 to 25 nm; and / or the average diameter of the support is 4 to 6 μm. When the average pore size and average diameter of the support are within the above ranges, the support has sufficient pores and specific surface area to support the active component, thereby providing the catalyst with excellent catalytic activity.

[0037] The catalyst carrier of the present invention is obtained by polymerization reaction of porous polymer microspheres with olefin compounds containing cyano groups and olefin compounds containing tertiary amino groups;

[0038] Among them, the tertiary amino group-containing olefin compound is selected from at least one of N,N-dimethyl-3-butene-1-amine, N,N-dimethyl-2-methyl-3-butene-1-amine, N,N-dimethyl-4-pentene-1-amine, N,N-dimethyl-4-aminostyrene, N,N-diethyl-4-aminostyrene, and 4-allyl-N,N-dimethylaniline.

[0039] Furthermore, the cyano group-containing olefin compound is selected from 4-cyanostyrene.

[0040] The metallocene compound of the present invention is selected from the compound represented by formula (II):

[0041] (Cp) x TiCl y Formula (II);

[0042] wherein Cp is selected from cyclopentadienyl or a cyclopentadienyl derivative; x is selected from 1 or 2; and y is selected from 2 or 3.

[0043] When x is 1, the compound represented by formula (II) is a monometallocene compound, and when x is 2, the compound represented by formula (II) is a dimetallocene compound. The compound represented by formula (II) has a better bonding effect with the support, which can make the catalyst have better catalytic activity.

[0044] The catalyst support of the present invention can be prepared by a two-step seed swelling method commonly used in the art, which specifically comprises the following steps:

[0045] 1) mixing styrene, ethanol, ethylene glycol monomethyl ether, azobisisobutyronitrile, and polyvinyl pyrrolidone in a mass ratio of 10:44:44:0.1:2, and polymerizing at 60-80° C. and a stirring speed of 60-120 rpm for 12-24 hours to obtain polyethylene seed microspheres;

[0046] 2) dispersing the styrene seed microspheres using the dispersion liquid to obtain a seed emulsion;

[0047] 3) dispersing the swelling agent with a dispersing liquid to obtain a swelling agent emulsion; mixing the seed emulsion with the swelling agent and swelling the mixture to obtain an activated seed emulsion;

[0048] 4) using a dispersant to disperse the mixed solution containing the comonomer, the initiator, and the porogen to obtain an emulsion containing the comonomer, the initiator, and the porogen;

[0049] The comonomers include styrene, divinylbenzene, olefin compounds containing cyano groups, and olefin compounds containing tertiary amino groups.

[0050] 5) adding an emulsion containing a comonomer, an initiator, and a porogen to the activated seed emulsion and causing the emulsion to swell to obtain a swollen microsphere emulsion;

[0051] 6) The swollen microsphere emulsion is placed in a separatory funnel and allowed to stand for separation to separate the unswollen residual monomers. The stabilizer solution is added to the separated swollen microsphere emulsion, mixed, and centrifuged. The solid obtained after centrifugation is dried to obtain porous polymer microspheres modified with cyano groups and tertiary amino groups.

[0052] Furthermore, the dispersion liquid is an ethanol aqueous solution of sodium dodecylbenzenesulfonate with a mass fraction of 0.25 wt %, wherein the mass ratio of ethanol to water is 5:1.

[0053] Furthermore, in the above-mentioned dispersion process, ultrasound can be used to assist the dispersion, and the ultrasound time is 0.5 to 2 hours;

[0054] In a specific embodiment, the mass ratio of the dispersion in step 2) to the styrene seed microspheres is 1:(0.02-0.1).

[0055] In a specific embodiment, the swelling agent in step 3) is selected from 1-chlorododecane, and the mass ratio of 1-chlorododecane to the dispersion is (0.01-0.1):1. To better swell the seed solution in the swelling agent, the seed solution can be swollen at 25-35°C and 80-120 rpm for 12-24 hours.

[0056] In a specific embodiment, in step 4), the mass ratio of the comonomer, initiator, porogen and dispersion is 10:0.1:10:(30-60).

[0057] Specifically, the initiator is selected from dibenzoyl peroxide, and the porogen is selected from toluene, n-heptane or other inert solvents that do not react with the comonomer.

[0058] In a specific embodiment, the swelling in step 5) is mixed at 25-35° C. and 80-120 rpm for 12-24 hours.

[0059] In one specific embodiment, the stabilizer solution in step 6) is a 5% by mass polyvinylpyrrolidone emulsion, and the mass ratio of the swellable microsphere emulsion to the stabilizer emulsion is 1:2. The swellable microsphere emulsion and the stabilizer solution are mixed at 60-80°C for 12-24 hours to complete polymerization. After centrifugation, the resulting solid is washed with ethanol and an aqueous solution, extracted with dichloromethane, and then vacuum dried at 50-80°C.

[0060] The present invention also provides a method for preparing a metallocene catalyst for ethylene polymerization, the method comprising the following steps:

[0061] 1) mixing porous polymer microspheres modified with cyano groups and tertiary amino groups, an alkyl aluminum compound, and a solvent to obtain a mixed solution;

[0062] 2) Adding a metallocene compound to the mixed solution to obtain a metallocene catalyst for ethylene polymerization.

[0063] Furthermore, the solvent in step 1) is selected from n-hexane or toluene;

[0064] The mixing in step 1) is carried out at 20-100° C. for 1-24 hours.

[0065] Furthermore, the mixed solution in step 2) is subjected to a temperature of 20-100° C. for 1-24 hours. After the metallocene compound is added to the mixed solution and the reaction is completed, post-treatment is required. The post-treatment includes: filtration under nitrogen protection, washing the solid particles with toluene and hexane in sequence, and vacuum drying at 60-80° C. for 12-24 hours to finally obtain a metallocene catalyst for ethylene polymerization.

[0066] The present invention also provides a use of a metallocene catalyst for ethylene polymerization in an ethylene polymerization reaction. When used in an ethylene polymerization reaction, the metallocene catalyst can efficiently catalyze the polymerization of ethylene, thereby producing a high molecular weight polyethylene product with good crystalline properties. Furthermore, the metallocene catalyst can effectively reduce the amount of co-catalyst used, thereby lowering the production cost of the polyethylene.

[0067] Specifically, the ethylene polymerization reaction includes: mixing a metallocene catalyst for ethylene polymerization, a co-catalyst and a solvent, and then introducing ethylene to obtain a polyethylene product.

[0068] Furthermore, in order to make the ethylene polymerization reaction proceed more fully, the molar ratio of the co-catalyst to the metallocene catalyst for ethylene polymerization can be controlled to be (500-2000):1, and the polymerization pressure can be 1-60 atm.

[0069] The ethylene polymerization catalyst and its application provided by the present invention will be further described in detail below through specific examples.

[0070] It should be noted that, in the following examples, unless otherwise specified, the raw materials used can be obtained by commercial purchase or conventional methods, and the experimental methods without specific conditions are conventional methods and conventional conditions well known in the art.

[0071] Example 1

[0072] 1. The preparation method of the catalyst of this embodiment comprises the following steps:

[0073] 1) A 250ml four-necked reaction flask was equipped with a mechanical stirrer, a reflux condenser, a nitrogen vent tube, and a temperature detector. 15g of styrene, 66g of ethanol, 66g of ethylene glycol monomethyl ether, 0.15g of azobisisobutyronitrile, and 3g of polyvinylpyrrolidone (PVPK-30) were then added to the flask. Mechanical stirring was performed at 60-120 rpm, and polymerization was carried out under nitrogen in a water bath at 60-80°C for 24 h. After completion of the reaction, the reaction slurry was centrifuged at 5000 rpm to remove unreacted monomer and solvent from the upper layer. A mixture of water and ethanol (1:1 by mass) was added to the precipitated particles, and ultrasonic dispersion was performed for 5 min. Centrifugation was then repeated 4-5 times to remove the stabilizer from the precipitated particles. The precipitate was vacuum dried at room temperature for 24 h to obtain polystyrene seed microspheres with a particle size of 2.2 μm.

[0074] 2) adding 0.225 g of sodium lauryl sulfate, 15 g of ethanol, and 75 g of deionized water into a 250 ml conical flask to prepare a sodium lauryl sulfate ethanol aqueous solution with a mass fraction of 0.25 wt%;

[0075] Take 25g of 0.25wt% sodium lauryl sulfate ethanol aqueous solution and add it to a 250ml conical flask. At the same time, add 0.5g of 1-chlorododecane and ultrasonically disperse it for 30min to make it well emulsified.

[0076] Place 25g of sodium dodecyl sulfate in ethanol in a 250ml Erlenmeyer flask, add 0.5g of the polystyrene seed microspheres prepared in step 1), and ultrasonically disperse for 30 minutes. Transfer the ultrasonically emulsified 1-chlorododecane and polystyrene emulsion to a 250ml Erlenmeyer flask, mix, and seal the flask with a rubber stopper. Place the sealed flask in an oscillator at 80 rpm at 30°C and allow to swell for approximately 12 hours.

[0077] Take 40g of a 0.25wt% sodium dodecyl sulfate ethanol solution, add 3g of styrene, 10g of divinylbenzene, 3g of 4-cyanostyrene, 3.5g of 4-dimethylaminostyrene, toluene, n-heptane, and benzoyl peroxide, and ultrasonically emulsify for approximately 60 minutes to perform the first swelling step. After the first swelling step is completed, add the mixture to a conical flask and continue swelling at 30°C and 80 rpm for 12 hours to separate the unswollen monomer. The reaction solution is then transferred to a 125ml separatory funnel and allowed to stand for three layers. The middle and lower layers of the reaction solution are removed and weighed. The middle and lower layers contain the swollen polymerized monomers and the seed carrier.

[0078] 3) Add 2.5 g of polyvinyl pyrrolidone and 47.5 g of deionized water to a 100 ml conical flask and dissolve the solution under magnetic stirring to obtain 50 g of a 5 wt % polyvinyl pyrrolidone aqueous solution;

[0079] The middle and lower reaction layers separated by a separatory funnel were transferred to a 250 ml conical flask. A 5 wt% polyvinylpyrrolidone solution was added based on the weight of the middle and lower reaction layers, with the mass ratio of the middle and lower reaction layers to the polyvinylpyrrolidone solution being 1:2. Nitrogen was then blown through the liquid surface for 30 minutes to displace air from the solution. Polymerization was then carried out in an oscillator at 70°C and 80 rpm for 24 hours to produce unpurified porous polymer microspheres. After polymerization, the solution was cooled and centrifuged to remove the unreacted upper layer. Deionized water and ethanol (1:1 mass ratio) were then added and washed by repeated centrifugation 4-5 times. The washed solid particles were then dried in a vacuum oven at 60°C. The dried solid particles were then extracted with dichloromethane in a Soxhlet extractor for 48 hours to remove linear polystyrene and solvent. Finally, the extracted solid particles were dried in a vacuum oven at 60°C to produce porous polymer microspheres with an average diameter of 5.4 μm and an average pore size of 13.5 nm. The mass content of the cyano group in the porous polymer microspheres is 3%, the mass content of the tertiary amino group is 5%, and the molar ratio of the cyano group to the tertiary amino group is 1:1.

[0080] 4) After the porous polymer microspheres obtained in step 3) were vacuum dried at 60 ° C for 12 hours, 1g of porous polymer microspheres was added to a 100ml Schlenk filter reactor under anhydrous and oxygen-free conditions, 30mL of toluene was added as a solvent, and 2g of methylaluminoxane (MAO) was added after magnetic stirring and mixing at 50 ° C. The mixture was stirred for about 12 hours, and the reactor was inverted for suction filtration and washed with toluene 2-3 times to remove excess co-catalyst. A toluene solution of the configured Cp2TiCl2 (Cp is cyclopentadiene) metallocene catalyst was then added with a syringe. After magnetic stirring for 12 hours at 50 ° C, the reactor was inverted for suction filtration, washed with toluene 3 times and then washed with n-hexane 1-2 times. The solid was vacuum-dried to obtain the catalyst and stored in an ampoule. Sampling and testing using the ICP method (reference HG / T 5763-2020) showed that the titanium content in the catalyst was 0.66wt%. The Al / N molar ratio in the catalyst is 10:1, and the Al / Ti molar ratio is 30:1. The catalyst comprises, by weight, 3% of a metallocene compound, 15% of an alkyl aluminum compound, and 82% of a carrier.

[0081] 2. The ethylene polymerization reaction of this embodiment comprises the following steps:

[0082] 1) A 100 mL autoclave was vacuum dried at 70°C for 30 min, and the atmosphere was replaced with nitrogen and ethylene three times.

[0083] 2) Under vacuum conditions, 20 mL of n-hexane was added to the autoclave, followed by the addition of MAO and 10 μmol of a toluene suspension of the catalyst prepared in this example, wherein the molar ratio of MAO to the Al:Ti of the catalyst was 1500:1. The pipeline was flushed with a small amount of hexane, the system was sealed, stirring was started, the temperature was raised to 50°C, ethylene was introduced, and polymerization was performed for 1 hour. During the reaction, the polymerization pressure was controlled not to exceed 5 atm. After the polymerization was completed, the pressure was released, the mixture was quenched with acidified ethanol while stirring, filtered, and vacuum dried to constant weight to obtain a polyethylene product. The obtained polyethylene product was tested and characterized, and the number average molecular weight of the polyethylene was 4.4×10 5 g / mol, melting point is 127.2℃.

[0084] Example 2

[0085] 1. The preparation method of the catalyst in this example is basically the same as that in Example 1, except that 3 g of 4-cyanostyrene and 8 g of 4-dimethylaminostyrene are added in step 2). The resulting porous polymer microspheres have an average diameter of 5.8 μm and an average pore size of 14.8 nm. The mass content of cyano groups in the porous polymer microspheres is 2.4%, the mass content of tertiary amino groups is 10.5%, and the molar ratio of cyano groups to tertiary amino groups is 1:2.1.

[0086] 2. The steps of the ethylene polymerization reaction in this embodiment are basically the same as those in Example 1, except that the catalyst in Example 1 is replaced by the catalyst in this embodiment.

[0087] The molecular weight of the polyethylene obtained in this example is 9.1×10 5 g / mol, melting point is 130.7℃.

[0088] Example 3

[0089] 1. The preparation method of the catalyst in this example is basically the same as that in Example 1, except that 3 g of 4-cyanostyrene and 16 g of 4-dimethylaminostyrene are added in step 2). The resulting porous polymer microspheres have an average diameter of 5.4 μm and an average pore size of 14.5 nm. The mass content of cyano groups in the porous polymer microspheres is 1.8%, the mass content of tertiary amino groups is 14%, and the molar ratio of cyano groups to tertiary amino groups is 1:4.

[0090] 2. The steps of the ethylene polymerization reaction in this embodiment are basically the same as those in Example 1, except that the catalyst in Example 1 is replaced by the catalyst in this embodiment.

[0091] The molecular weight of the polyethylene obtained in this example is 3.2×10 6 g / mol, melting point 135.5℃.

[0092] Example 4

[0093] The preparation method of the catalyst in this example is essentially the same as that in Example 1, except that 3 g of 4-cyanostyrene and 23 g of 4-dimethylaminostyrene are added in step 2). The resulting porous polymer microspheres have an average diameter of 5.9 μm and an average pore size of 15.5 nm. The cyano group content in the porous polymer microspheres is 1.5% by mass, the tertiary amino group content is 18.9% by mass, and the molar ratio of cyano groups to tertiary amino groups is 1:6.8.

[0094] 2. The steps of the ethylene polymerization reaction in this embodiment are basically the same as those in Example 1, except that the catalyst in Example 1 is replaced by the catalyst in this embodiment.

[0095] The molecular weight of the polyethylene obtained in this example is 1.7×10 6 g / mol, melting point is 133.5℃.

[0096] Example 5

[0097] 1. The preparation method of the catalyst in this example is basically the same as that in Example 1, except that 3 g of 4-cyanostyrene and 30 g of 4-dimethylaminostyrene are added in step 2). The resulting porous polymer microspheres have an average diameter of 5.2 μm and an average pore size of 15.2 nm. The mass content of cyano groups in the porous polymer microspheres is 1.3%, the mass content of tertiary amino groups is 19%, and the molar ratio of cyano groups to tertiary amino groups is approximately 1:8.8.

[0098] 2. The steps of the ethylene polymerization reaction in this embodiment are basically the same as those in Example 1, except that the catalyst in Example 1 is replaced by the catalyst in this embodiment.

[0099] The molecular weight of the polyethylene obtained in this example is 1.2×10 6 g / mol, melting point is 132.3℃.

[0100] Example 6

[0101] 1. The preparation method of the catalyst in this embodiment is consistent with that in embodiment 2.

[0102] 2. The steps of the ethylene polymerization reaction in this embodiment are basically the same as those in Example 2, except that the molar ratio of MAO to Al:Ti in the catalyst is 800:1.

[0103] The molecular weight of the polyethylene obtained in this example is 2.1×10 6 g / mol, melting point is 133.6℃.

[0104] Comparative Example 1

[0105] 1. The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), 4-dimethylaminostyrene is not added, and the average pore size of the obtained porous polymer microsphere carrier is 10.3 nm and the average diameter is 4.9 μm.

[0106] 2. The ethylene polymerization reaction of this comparative example comprises the following steps:

[0107] 1) A 100 mL autoclave was vacuum dried at 70°C for 30 min, and the atmosphere was replaced with nitrogen and ethylene three times.

[0108] 2) Under vacuum conditions, 20 mL of n-hexane was added to the autoclave, followed by the addition of MAO, 10 μmol of a toluene suspension of the catalyst obtained in this comparative example, and 4-dimethylaminostyrene, wherein the molar ratio of MAO to the Al:Ti of the catalyst was 1500:1, and the molar ratio of the added 4-methylaminostyrene to the cyano group in the catalyst was 1:1; the pipeline was flushed with a small amount of hexane, the system was sealed, stirring was started, the temperature was raised to 50°C, ethylene was introduced, and polymerization was carried out for 1 hour. During the reaction, the polymerization pressure was controlled not to exceed 5 atm. After the polymerization was completed, the pressure was released, the product was quenched with acidified ethanol under stirring, filtered, and vacuum dried to constant weight to obtain a polyethylene product. The obtained polyethylene product was tested and characterized, and the molecular weight of the polyethylene was 1.2×10 5 g / mol, melting point is 124.3℃.

[0109] Comparative Example 2

[0110] 1. The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), 4-dimethylaminostyrene is not added, and the average pore size of the obtained porous polymer microsphere carrier is 10.3 nm and the average diameter is 4.1 μm.

[0111] 2. The ethylene polymerization reaction of this comparative example comprises the following steps:

[0112] 1) A 100 mL autoclave was vacuum dried at 70°C for 30 min, and the atmosphere was replaced with nitrogen and ethylene three times.

[0113] 2) Under vacuum conditions, 20 mL of n-hexane was added to the autoclave, followed by the addition of MAO, 10 μmol of a toluene suspension of the catalyst obtained in this comparative example, and 4-dimethylaminostyrene, wherein the molar ratio of MAO to the Al:Ti of the catalyst was 1500:1, and the molar ratio of the added 4-methylaminostyrene to the cyano group in the catalyst was 5:1; the pipeline was flushed with a small amount of hexane, the system was sealed, stirring was started, the temperature was raised to 50°C, ethylene was introduced, and polymerization was carried out for 1 hour. During the reaction, the polymerization pressure was controlled not to exceed 5 atm. After the polymerization was completed, the pressure was released, the product was quenched with acidified ethanol under stirring, filtered, and vacuum dried to constant weight to obtain a polyethylene product. The obtained polyethylene product was tested and characterized, and the molecular weight of the polyethylene was 1.6×10 5 g / mol, melting point is 125.3℃.

[0114] Comparative Example 3

[0115] 1. The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), 4-dimethylaminostyrene is not added, and the average pore size of the obtained porous polymer microsphere carrier is 10 nm and the average diameter is 3.5 μm.

[0116] 2. The ethylene polymerization reaction of this comparative example comprises the following steps:

[0117] 1) A 100 mL autoclave was vacuum dried at 70°C for 30 min, and the atmosphere was replaced with nitrogen and ethylene three times.

[0118] 2) Under vacuum conditions, 20 mL of n-hexane was added to the autoclave, followed by the addition of MAO, 10 μmol of a toluene suspension of the catalyst obtained in this comparative example, and 4-dimethylaminostyrene, wherein the molar ratio of MAO to the Al:Ti of the catalyst was 1500:1, and the molar ratio of the added 4-methylaminostyrene to the cyano group in the catalyst was 15:1; the pipeline was flushed with a small amount of hexane, the system was sealed, stirring was started, the temperature was raised to 50°C, ethylene was introduced, and polymerization was carried out for 1 hour. During the reaction, the polymerization pressure was controlled not to exceed 5 atm. After the polymerization was completed, the pressure was released, the product was quenched with acidified ethanol under stirring, filtered, and vacuum dried to constant weight to obtain a polyethylene product. The obtained polyethylene product was tested and characterized, and the molecular weight of the polyethylene was 7.9×10 5 g / mol, melting point is 129.5℃.

[0119] By comparing the above examples with the comparative examples, it can be seen that the metallocene catalyst for ethylene polymerization of the present invention is used in ethylene polymerization reaction to obtain polyethylene with higher molecular weight and higher crystallinity (high melting point) at a low amount of co-catalyst.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metallocene catalyst for ethylene polymerization, characterized in that It includes a carrier and an active component loaded on the carrier; The active components include metallocene compounds and alkyl aluminum compounds; The carrier is a porous polymer microsphere modified with cyano and tertiary amino groups; The mass content of the cyano group in the carrier is 1 to 10%, and the mass content of the tertiary amino group in the carrier is 1 to 25%.

2. The metallocene catalyst for ethylene polymerization according to claim 1, wherein The molar ratio of the tertiary amino group to the cyano group is (1-20):

1.

3. The metallocene catalyst for ethylene polymerization according to claim 1 or 2, characterized in that The catalyst comprises, by weight percentage, 0.1 to 5 percent of a metallocene compound, 10 to 36 percent of an alkyl aluminum compound, and 59 to 89.9 percent of a carrier.

4. The metallocene catalyst for ethylene polymerization according to claim 1 or 2, characterized in that The Al / N molar ratio in the catalyst is (1-10):1; and / or, The Al / Ti molar ratio in the catalyst is (1-30):

1.

5. The metallocene catalyst for ethylene polymerization according to claim 1 or 2, characterized in that The average pore size of the carrier is 12 to 25 nm; and / or, The average diameter of the carrier is 4 to 6 μm.

6. The metallocene catalyst for ethylene polymerization according to claim 1 or 2, characterized in that The carrier is obtained by polymerization reaction of porous polymer microspheres with olefin compounds containing cyano groups and olefin compounds containing tertiary amino groups; The tertiary amino group-containing olefin compound is selected from at least one of N,N-dimethyl-3-butene-1-amine, N,N-dimethyl-2-methyl-3-butene-1-amine, N,N-dimethyl-4-pentene-1-amine, N,N-dimethyl-4-aminostyrene, N,N-diethyl-4-aminostyrene, and 4-allyl-N,N-dimethylaniline.

7. The metallocene catalyst for ethylene polymerization according to claim 6, characterized in that The cyano group-containing olefin compound is selected from 4-cyanostyrene.

8. The metallocene catalyst for ethylene according to claim 1 or 2, characterized in that The metallocene compound is selected from the compound represented by formula (II): (Cp) x TiCl y Formula (II); wherein Cp is selected from cyclopentadienyl or a cyclopentadienyl derivative; x is selected from 1 or 2; and y is selected from 2 or 3.

9. Use of the metallocene catalyst for ethylene polymerization according to any one of claims 1 to 8 in ethylene polymerization reactions.