Supported metallocene catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of olefin polymerization, and discloses a supported metallocene catalyst as well as a preparation method and application thereof, and the catalyst comprises a porous carrier, a metallocene compound, a promoter and a sustained release polymer. According to the supported metallocene catalyst disclosed by the invention, the sustained-release monomer is added in the preparation process, so that the catalyst has the characteristic of low initial activity, and the long-term total polymerization activity of the catalyst can be improved. The supported metallocene catalyst provided by the invention can reduce the blocking risk of a catalyst feeding pipeline and significantly improve the operation stability of a polyolefin device.

Description

Technical Field

[0001] The present invention relates to the technical field of olefin polymerization, and more specifically, to a supported metallocene catalyst and a preparation method and application thereof. Background Art

[0002] Compared with traditional Ziegler-Natta catalysts, metallocene polyolefin catalysts are single-active site catalysts that can precisely customize the molecular structure of the polymer, including relative molecular mass and its distribution, comonomer content and its distribution on the molecular chain, etc.

[0003] The loaded metallocene polyolefin catalyst can significantly reduce the initial polymerization activity, but still has the characteristics of high initial activity and intense heat release. This metallocene catalyst with high initial activity has the following problems: for example, in the polymerization reaction in the presence of polymerization monomers, the solid catalyst particles are easily broken, resulting in a large amount of polymer fine powder. At the same time, the excessively high temperature inside the polymer particles causes the particles to agglomerate and induce agglomeration, which in severe cases will cause the device to shut down. In addition, the agglomeration of polymer particles causes the catalyst active center to be densely wrapped, resulting in an increase in the diffusion resistance of the polymerization monomers, and thus the catalyst activity decays rapidly.

[0004] During the preparation of the loaded metallocene catalyst, the co-catalyst has been added, and the polymerization reaction starts immediately after contacting the monomer. Since the metallocene catalyst has a high initial activity, it is difficult to smoothly transport the catalyst to the reactor to avoid clogging of the delivery pipeline. The main solutions are: one is to use an inert gas or solvent as part or all of the delivery medium to transport the catalyst to the reactor to reduce the concentration of polymerized monomers during the delivery process, but this method will increase the burden on the subsequent separation and recovery modules; another way is to use polymerized monomers as the delivery medium, by lowering the temperature of the delivery medium or increasing its flow rate, to reduce the activity of the catalyst in the delivery stage. However, the above measures cannot completely solve the problem of easy clogging of the feed.

[0005] Patent CN109906234A discloses a method for feeding a metallocene catalyst, wherein a metallocene catalyst supported by silica suspended in aliphatic hydrocarbons and / or oil is transported to a solution or slurry polymerization reactor without prepolymerization at a speed of at least 1 m / s, and the transport medium (propylene monomer) is controlled at a temperature of at least 50°C. This method can reduce or lower the agglomeration and blockage problems during the transport process. The patent application has certain requirements for the flow rate of the transport medium. The usual practice is to increase the flow rate of the transport medium or reduce the inner diameter of the transport pipeline. Increasing the flow rate of the transport medium may have a certain impact on the composition control of the main reactor, while reducing the size of the transport pipeline involves changes in the device. Patent CN113039212A discloses the use of nitrogen, argon, ethane, propane and mixtures thereof as transport media to transport a catalyst system containing a metallocene catalyst to a gas phase polymerization reactor. The introduction of an inert medium will have a certain impact on the composition control in the reactor. Summary of the invention

[0006] The purpose of the present invention is to provide a supported metallocene catalyst and a preparation method and application thereof in view of the current state of the prior art. The supported metallocene catalyst of the present invention releases its activity slowly when in contact with a polymerization monomer, has the characteristics of low initial activity and does not affect the overall polymerization activity, can directly use the polymerization monomer as a conveying medium, can effectively reduce or avoid the clogging problem of the feeding equipment or reactor caused by the initial violent reaction of the catalyst, and significantly improves the operating stability of the polyolefin device.

[0007] The first aspect of the present invention provides a supported metallocene catalyst, which comprises: a porous carrier, a metallocene compound, a co-catalyst and a slow-release polymer.

[0008] The second aspect of the present invention provides a method for preparing the above catalyst, the preparation method comprising:

[0009] (1) reacting the porous support and the co-catalyst in the presence of a first solvent;

[0010] (2) contacting and reacting the support obtained in step (1) with a metallocene compound solution in the presence of a first solvent;

[0011] (3) in the presence of a second solvent and the carrier obtained in step (2), polymerizing the first slow-release monomer to obtain a supported metallocene catalyst;

[0012] Optionally (4) in the presence of the second solvent and the supported metallocene catalyst obtained in the previous step, polymerizing the second slow-release monomer to obtain a slow-release reinforced supported metallocene catalyst;

[0013] Optional (5) Repeat step (4).

[0014] The third aspect of the present invention provides use of the above catalyst in the preparation of polyolefins.

[0015] The technical solution of the present invention has the following beneficial effects:

[0016] (1) The supported metallocene catalyst of the present invention has the characteristics of low initial activity due to the addition of a slow-release monomer during the preparation process, and can improve the long-term total polymerization activity of the catalyst.

[0017] (2) The supported metallocene catalyst of the present invention can reduce the risk of catalyst feed line blockage and significantly improve the operating stability of the polyolefin device.

[0018] (3) Since the catalyst of the present invention has the characteristic of low initial activity, its initial reaction when in contact with the polymerization monomer is relatively mild, and the prepared polymer powder has the characteristics of low fine powder rate and agglomeration rate, thereby improving the operating stability of the device.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] The first aspect of the present invention provides a supported metallocene catalyst, which comprises: a porous carrier, a metallocene compound, a co-catalyst and a slow-release polymer.

[0022] According to the present invention, preferably, the porous carrier comprises an inorganic porous carrier or an organic porous carrier;

[0023] The inorganic porous carrier is preferably at least one of a silica carrier, an aluminum oxide carrier and a magnesium chloride carrier; the silica carrier preferably includes a silica gel carrier and / or a silica carrier;

[0024] The organic porous carrier is preferably a functionalized polyolefin carrier, and more preferably a polyethylene powder particle carrier and / or a polypropylene powder particle carrier.

[0025] According to the present invention, preferably, the metallocene compound is a non-bridged metallocene compound as shown in formula I or a bridged metallocene compound as shown in formula II;

[0026] Ar1 Ar2M1Q1 Q2 Formula Ⅰ; T Ar3 Ar4M2 Q3Q4 Formula II;

[0027] Wherein, M1 and M2 are each independently selected from elements of Groups 3 to 5 of the Periodic Table of Elements, preferably transition metals of Group 4, most preferably zirconium, titanium, hafnium or vanadium;

[0028] Q1, Q2, Q3 and Q4 are all sigma ligands, and are each independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl group, a phenyl group or a benzyl group;

[0029] Ar1, Ar2, Ar3 and Ar4 are each independently selected from cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, substituted cyclopentadienyl, substituted indenyl, substituted tetrahydroindenyl or substituted fluorenyl; wherein the substituent is selected from at least one of a hydrocarbon group, a silyl group, a hydrocarbon group in which one or more hydrogen atoms and / or one or more carbon atoms are replaced by heteroatoms, and a silyl group in which one or more hydrogen atoms and / or one or more carbon atoms are replaced by heteroatoms, and the heteroatoms are selected from at least one of B, P, S and N;

[0030] Preferably, the substituents in the substituted cyclopentadienyl, substituted indenyl, substituted tetrahydroindenyl and substituted fluorenyl are optionally cyclic;

[0031] The T group is a bridging group selected from a divalent bridge -R'1R'2C-, -R'1C=CR'2-, -R'1R'2C-C R'3R'4-, -R'1R'2Si-, -R'1R'2Si-Si R'3R'4-, -R'1R'2Ge-, -R'1R'2Ge-Ge R'3R'4-, -R'1R'2C-Ge R'3R'4-, -R'1R'2Si-Ge R'3R'4- or -R'1R'2Si-CR'3R'4-; wherein R'1, R'2, R'3 and R'4 are each independently selected from a hydrogen atom, a hydrocarbon group, a silyl group, a germyl group, a hydrocarbon group in which one or more carbon atoms are substituted by a heteroatom, a silyl group in which one or more carbon atoms are substituted by a heteroatom or a germyl group in which one or more carbon atoms are substituted by a heteroatom, and the heteroatom is at least one of B, O, S, P and N;

[0032] The T group is most preferably -CH2-, -CH2CH2-, -C(CH3)2-, -SiMe2-, -SiPh2-, -SiMePh-, -Si(CH3)2-CH2-, -SiPh2-CH2-, -Si(Me3)2-SiPh2- or -SiMePh-CH2-.

[0033] In the present invention, the substitution in the substituted cyclopentadienyl, substituted indenyl, substituted tetrahydroindenyl and substituted fluorenyl means that one or more hydrogens are replaced.

[0034] In the present invention, M1 and M2 may be the same or different; Q1, Q2, Q3 and Q4 may be the same, at least one may be different from the others or all may be different; Ar1, Ar2, Ar3 and Ar4 may be the same, at least one may be different from the others or all may be different; R'1, R'2, R'3 and R'4 may be the same, at least one may be different from the others or all may be different.

[0035] According to the present invention, the cocatalyst refers to any compound capable of converting the metallocene compound into an active center. Preferably, the cocatalyst comprises an alkylaluminoxane compound and / or a boron-containing compound; preferably, a C1-C10 alkylaluminoxane and / or an organic borate; the C1-C10 alkylaluminoxane is more preferably at least one selected from methylaluminoxane, ethylaluminoxane and butylaluminoxane; the organic borate is more preferably at least one selected from tetraphenylborate, tetrakis(p-phenyl)borate, tetrakis(o-,p-dimethylphenyl)borate, tetrakis(p-trifluoromethylphenyl)borate, tetrakis(pentafluorophenyl)borate, tetrakis(perfluorobiphenyl)borate and tetrakis(perfluoronaphthyl)borate;

[0036] The cation of the organic borate is an organic cation, and the organic cation is preferably at least one of trialkylammonium ion, alkylanilinium ion, tetraalkylphosphonium ion, tetraphenylphosphonium ion and phenylcarbonium;

[0037] The cocatalyst is most preferably methylaluminoxane and / or ethylaluminoxane.

[0038] According to the present invention, preferably, the monomer for synthesizing the sustained-release polymer is selected from at least one of C2-16 monoolefins and C2-16 polyolefins; preferably at least one of propylene, ethylene, butene, pentene, hexene, octene and styrene.

[0039] According to the present invention, preferably, the number average molecular weight of the sustained-release polymer is ≥2000.

[0040] According to the present invention, preferably, based on the total weight of the supported metallocene catalyst, the content of the slow-release polymer is 1 to 95 wt%, preferably 10 to 90 wt%, and more preferably 15-60 wt%; the content of the porous carrier is 1 to 90 wt%, preferably 5 to 80 wt%; the content of the metallocene compound is 0.1 to 10 wt%, preferably 0.1 to 5 wt%; the content of the co-catalyst is 0.1 to 20 wt%, preferably 0.1 to 10 wt%; and the sum of the percentage contents of each component is 100%.

[0041] The second aspect of the present invention provides a method for preparing the above catalyst, the preparation method comprising:

[0042] (1) reacting the porous support and the co-catalyst in the presence of a first solvent;

[0043] (2) contacting and reacting the support obtained in step (1) with a metallocene compound solution in the presence of a first solvent;

[0044] (3) in the presence of a second solvent and the carrier obtained in step (2), polymerizing the first slow-release monomer to obtain a supported metallocene catalyst;

[0045] Optionally (4) in the presence of the second solvent and the supported metallocene catalyst obtained in the previous step, polymerizing the second slow-release monomer to obtain a slow-release reinforced supported metallocene catalyst;

[0046] Optional (5) Repeat step (4).

[0047] According to the present invention, preferably, in step (1), the reaction temperature is 30 to 80° C. and the reaction time is 3 to 6 hours;

[0048] In step (2), the reaction temperature is 0 to 100° C.; the solvent for preparing the metallocene compound solution is selected from at least one of toluene, benzene, xylene, hexane, heptane and cyclohexane, preferably selected from toluene and / or hexane;

[0049] In step (3), the polymerization reaction temperature is 0 to 100° C. and the time is 0.1 to 6 hours;

[0050] In step (4), the polymerization reaction temperature is 0 to 100° C. and the time is 0.1 to 6 hours;

[0051] The first solvent is selected from aromatic hydrocarbons and / or aliphatic hydrocarbons, preferably at least one selected from toluene, benzene, xylene, hexane, heptane and cyclohexane;

[0052] The second solvent is selected from aromatic hydrocarbons and / or aliphatic hydrocarbons, preferably at least one selected from toluene, benzene, xylene, hexane, heptane and cyclohexane;

[0053] Preferably, each step in the preparation method is carried out under an inert gas atmosphere.

[0054] According to the present invention, preferably, the first slow-release monomer and the second slow-release monomer are each independently selected from at least one of C2-16 monoolefins and C2-16 polyolefins; preferably at least one of propylene, ethylene, butene, pentene, hexene, octene and styrene.

[0055] In the present invention, the first solvent and the second solvent may be the same or different, and the first slow-release monomer and the second slow-release monomer may be the same or different.

[0056] In the present invention, preferably, in step (1), after the porous carrier and the promoter react, they can be washed and dried to obtain a solid powder loaded with the promoter; or they can be directly used in the reaction in the subsequent step (2) without washing and drying. The washing can be performed several times with the first solvent mentioned above, and the drying can be vacuum drying.

[0057] In step (2), after the metallocene compound solution is dripped, the reaction time is 1 to 120 minutes; a slurry containing a metallocene compound-supported solid is obtained, and a solid is obtained after solvent washing and drying (or not drying).

[0058] In step (4), the supported metallocene catalyst obtained in the previous step may be washed or not before drying, and the solvent used for washing is an aromatic hydrocarbon and / or an aliphatic hydrocarbon, preferably at least one of toluene, benzene, xylene, hexane, heptane and cyclohexane. In step (5), the number of repetitions is ≥ 1.

[0059] In the present invention, as a preferred embodiment, steps (3) to (5) in the preparation method of the present invention can be specifically selected from the following embodiment 1 or embodiment 2:

[0060] Embodiment 1: (3) adding the first slow-release monomer solution to the reactor containing the carrier obtained in step (2), stirring and mixing, to obtain a supported metallocene catalyst;

[0061] Optional (4) adding the second slow-release monomer solution to the reactor containing the supported metallocene catalyst obtained in the previous step, stirring and mixing, to obtain a slow-release reinforced supported metallocene catalyst;

[0062] Optional (5) Repeat step (4).

[0063] Embodiment 2: (3) adding a second solvent to a reactor containing the carrier obtained in step (2), and then adding the first slow-release monomer, stirring and mixing, to obtain a supported metallocene catalyst;

[0064] Optional (4) adding a second solvent to the reactor containing the supported metallocene catalyst obtained in the previous step, and then adding a second slow-release monomer, stirring and mixing, to obtain a slow-release reinforced supported metallocene catalyst;

[0065] Optional (5) Repeat step (4).

[0066] In the first embodiment, the solvent for preparing the first slow-release monomer solution is preferably the second solvent, and the concentration of the first slow-release monomer in the first slow-release monomer solution is less than 95 wt %, preferably 2 to 60 wt %;

[0067] In the above-mentioned Embodiment 1 and Embodiment 2, the temperature of stirring and mixing is 0-100°C, and the time is 0.1-6 hours; the solvent for preparing the second slow-release monomer solution is preferably the second solvent, and the concentration of the second slow-release monomer in the second slow-release monomer solution is <95wt%, preferably 2-60wt%; the supported metallocene catalyst obtained in the previous step can be washed or not before drying, and the solvent used for washing is aromatic hydrocarbons and / or aliphatic hydrocarbons, preferably at least one of toluene, benzene, xylene, hexane, heptane and cyclohexane. In step (5), the number of repetitions is ≥1.

[0068] In the present invention, in the above preparation method, when step (4) is repeatedly performed, the second sustained-release monomer used in each repetition may be the same as or different from the second sustained-release monomer used in the previous repetition.

[0069] In the present invention, preferably, in the preparation method of the present invention, when the sustained-release monomer is added repeatedly for multiple times, the adding methods thereof may be the same or different.

[0070] The third aspect of the present invention provides use of the above catalyst in the preparation of polyolefins.

[0071] According to the present invention, preferably, the mixture containing the above catalyst and polymerization monomer is directly introduced into the main reactor without passing through the prepolymerization reactor; the polymerization monomer is a gas phase or liquid phase polymerization monomer.

[0072] According to the present invention, preferably, the polymerization temperature in the main reactor is 0 to 100°C, preferably 20 to 80°C.

[0073] In the present invention, the used polymerization reactor for preparing polyolefin includes but is not limited to pipeline reactor, loop reactor, kettle reactor, horizontal reactor, fluidized bed reactor or multiphase multi-zone reactor. According to whether prepolymerization is carried out in the reactor, it can be divided into prepolymerization reactor and main reactor.

[0074] In the present invention, the polymerization reaction used to prepare the polyolefin includes at least one of copolymerization and homopolymerization, and the polymerization monomer is particularly a C2-C 16 At least one of hydrocarbon and aromatic compounds, preferably C2-C 16 One or more olefin monomers, such as ethylene, propylene, butene-1, hexene-1, octene-1, propadiene, C3-C 12 At least one of cycloolefins, 1,3-butadiene, 1,4-butadiene, 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, vinylcyclopentane and vinylcyclohexane.

[0075] The present invention is further described below by examples:

[0076] The polymerization activity was obtained by calculating the molar ratio of the polymer to the active metal Zr in the catalyst.

[0077] Screening: The polymer powder was screened using a German FRITSCH vibration screening machine, and the proportion of polymer with a particle size of less than 0.18 mm was taken as the fine powder rate, and the proportion of polymer with a particle size of more than 2 mm was taken as the agglomeration rate.

[0078] Example 1

[0079] Catalyst preparation

[0080] Step a: Add 40 g of silica carrier and 35 ml of toluene to a 250 ml glass bottle replaced with nitrogen, heat the system to 50°C, dropwise add a toluene solution of methylaluminoxane (MAO) (containing 14.7 g MAO), react for 4 hours, filter, wash 3 times with 35 ml of toluene, and drain to obtain a white carrier with good fluidity.

[0081] Step b: Add 40 g of the above-prepared catalyst-supporting carrier into a 500 ml glass bottle replaced with nitrogen, add 60 ml of toluene, start stirring, and dropwise add 40 ml of a toluene solution of rac-vinylbisindenyl zirconium dichloride (Beijing Bailingwei Technology Co., Ltd.) at room temperature, the molar ratio of MAO to rac-vinylbisindenyl zirconium dichloride is 100:1 (MAO:Zr). After the dropwise addition, react for 30 minutes under stirring, filter, wash with 60 ml of hexane, filter, and dry to obtain a light yellow powder with good fluidity, i.e., a metallocene compound-supported solid.

[0082] Step c: Put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then introduce 67g of hexane solution of butene with a concentration of 10wt%, maintain the operating temperature at 30°C, start stirring and mixing for 30min; then after drying, introduce 67g of hexane solution of butene with a concentration of 10wt%, maintain the operating temperature at 30°C, start stirring and mixing for 30min. Skim off the supernatant, cool to 20°C, wash with hexane, replace with nitrogen several times, and then remove the solvent in vacuum to prepare a supported metallocene catalyst MET-1 with a mass of 53.40g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.17wt%, the content of the cocatalyst MAO is 7.85wt%, the slow-release polymer is 24.08wt%, and the balance is a porous carrier.

[0083] Small scale polymerization experiment

[0084] In a 5L stainless steel autoclave, after nitrogen purging and multiple replacements with propylene, 2L of liquid propylene was added, the temperature was raised to 60°C, 2mL (0.9mol / L) of triisobutylaluminum hexane solution and 100mg of the above MET-1 catalyst were pressed into the reactor with high-pressure nitrogen, and after reacting for 5min, 0.5mL of ethanol was added to deactivate the catalyst. The temperature was lowered, vented, and dried to obtain a polymer powder.

[0085] The polymerization activity data are shown in Table 1.

[0086] Example 2

[0087] Catalyst preparation

[0088] The difference between this embodiment and embodiment 1 is only step c: all the metallocene compound supported solid prepared in step b is placed in a 500ml glass bottle replaced with nitrogen, and then 134g of a hexane solution of butene with a concentration of 10wt% is introduced, the operating temperature is maintained at 30°C, and stirring and mixing is started for 30min. The supernatant is skimmed off, the temperature is lowered to 20°C, and the mixture is washed with hexane, replaced with nitrogen for multiple times, and then the solvent is removed in vacuo to prepare a supported metallocene catalyst MET-2 with a mass of 53.30g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.12wt%, the content of the cocatalyst MAO is 7.96wt%, the slow-release polymer is 24.04wt%, and the balance is a porous carrier.

[0089] Small scale polymerization experiment

[0090] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-2 catalyst. The data are shown in Table 1.

[0091] Example 3

[0092] Catalyst preparation

[0093] The difference between this embodiment and embodiment 1 is only step c: put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then pass 67g of hexane solution of butene with a concentration of 10wt%, maintain the operating temperature at 30℃, start stirring and mixing for 30min; then after drying, pass 67g of hexane solution of propylene with a concentration of 10wt%, maintain the operating temperature at 30℃, start stirring and mixing for 30min. Skim off the supernatant, cool to 20℃, wash with hexane, replace with nitrogen several times, and then remove the solvent in vacuum to prepare a supported metallocene catalyst MET-3 with a mass of 53.34g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.13wt%, the content of the cocatalyst MAO is 7.90wt%, the slow-release polymer is 23.95wt%, and the balance is the porous carrier.

[0094] Small scale polymerization experiment

[0095] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-3 catalyst. The data are shown in Table 1.

[0096] Example 4

[0097] Catalyst preparation

[0098] The difference between this embodiment and embodiment 1 is only step c: put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then pass 134g of propylene hexane solution with a concentration of 10wt%, maintain the operating temperature at 30°C, start stirring and mixing for 30min. Skim off the supernatant, cool to 20°C, wash with hexane, replace with nitrogen several times, and then remove the solvent in vacuum to prepare a supported metallocene catalyst MET-4 with a mass of 53.45g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.20wt%, the content of the cocatalyst MAO is 7.65wt%, the slow-release polymer is 24.13wt%, and the balance is the porous carrier.

[0099] Small scale polymerization experiment

[0100] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-4 catalyst. The data are shown in Table 1.

[0101] Example 5

[0102] Catalyst preparation

[0103] The difference between this embodiment and embodiment 1 is only step c: put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then pass 200g of propylene hexane solution with a concentration of 10wt%, maintain the operating temperature at 30℃, start stirring and mixing for 30min; then after drying, pass 200g of propylene hexane solution with a concentration of 10wt%, maintain the operating temperature at 30℃, start stirring and mixing for 30min. Skim off the supernatant, cool to 20℃, wash with hexane, replace with nitrogen several times, and then remove the solvent in vacuum to prepare a supported metallocene catalyst MET-5 with a mass of 79.71g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 0.82wt%, the content of the cocatalyst MAO is 5.34wt%, the slow-release polymer is 49.08wt%, and the balance is the porous carrier.

[0104] Small scale polymerization experiment

[0105] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 200 mg of MET-5 catalyst. The data are shown in Table 1.

[0106] Example 6

[0107] Catalyst preparation

[0108] The difference between this embodiment and embodiment 1 is only step c: put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then introduce 200ml of hexane, and then slowly introduce 14g of ethylene continuously, maintain the operating temperature at 30°C, and start stirring and mixing for 30min. Skim off the supernatant, cool to 20°C, wash with hexane, replace with nitrogen several times, and then remove the solvent in vacuum to prepare a supported metallocene catalyst MET-6, with a mass of 54.11g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.21wt%, the content of the cocatalyst MAO is 7.94wt%, the slow-release polymer is 24.58wt%, and the balance is the porous carrier.

[0109] Small scale polymerization experiment

[0110] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-6 catalyst. The data are shown in Table 1.

[0111] Example 7

[0112] Catalyst preparation

[0113] The difference between this embodiment and embodiment 1 is only step c: put all the metallocene compound supported solid prepared in step b into a 500ml glass bottle replaced with nitrogen, then introduce 200ml of hexane, introduce 6g of ethylene slowly and continuously again, maintain the operating temperature at 30°C, start stirring and mixing for 30min; then after drying, introduce 200ml of hexane, introduce 8g of ethylene slowly and continuously again, maintain the operating temperature at 30°C, start stirring and mixing for 30min. Skim off the supernatant, cool to 20°C, wash with hexane, replace with nitrogen several times, then remove the solvent in vacuum, and prepare a supported metallocene catalyst MET-7, with a mass of 53.92g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.22wt%, the content of the cocatalyst MAO is 7.67wt%, the slow-release polymer is 24.61wt%, and the balance is the porous carrier.

[0114] Small scale polymerization experiment

[0115] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-7 catalyst. The data are shown in Table 1.

[0116] Comparative Example 1

[0117] Catalyst preparation

[0118] The difference between this comparative example and Example 1 is only step c: all the metallocene compound supported solid prepared in step b is placed in a 500 ml glass bottle replaced with nitrogen, and then 200 ml of hexane is introduced and stirred for 30 min. The supernatant is skimmed off, the temperature is lowered to 20° C., and washed with hexane, replaced with nitrogen several times, and then the solvent is removed in vacuo to prepare a supported metallocene catalyst MET-1-C with a mass of 40.54 g, wherein, based on the total weight of the supported metallocene catalyst, the content of the metallocene compound is 1.45 wt%, the content of the cocatalyst MAO is 10.3 wt%, the sustained-release polymer is 0 wt%, and the remainder is a porous carrier.

[0119] The supported metallocene catalyst MET-1-C was prepared.

[0120] Small scale polymerization experiment

[0121] The polymerization experiment was the same as that of Example 1, except that 100 mg of MET-1 catalyst was replaced by 100 mg of MET-1-C catalyst. The data are shown in Table 1.

[0122] Example 8

[0123] Pilot polymerization experiment

[0124] MET-1 catalyst slurry (30wt%) at a flow rate of 4g / h and triisobutylaluminum hexane solution (0.3mol / L) at a flow rate of 60mL were mixed with 15kg / h of liquid propylene at 20℃ and then entered the 75L loop reactor. At the same time, 15kg / h of liquid propylene entered the loop reactor through the axial flow pump flushing port. The reaction temperature was 70℃, and the discharge valve was controlled by the reactor pressure to perform intermittent discharge. The generated polymer powder was separated from the unreacted propylene monomer by flash evaporation, and then deactivated and dried.

[0125] The polymerization activity and screening data are shown in Table 1.

[0126] Example 9

[0127] Same as Example 8, except that the catalyst used is MET-2. The data are shown in Table 1.

[0128] Example 10

[0129] Same as Example 8, except that the catalyst used is MET-3. See Table 1 for data.

[0130] Embodiment 11

[0131] Same as Example 8, except that the catalyst used is MET-4. The data are shown in Table 1.

[0132] Example 12

[0133] Same as Example 8, except that the catalyst used is MET-5 and the catalyst slurry flow rate is 5.5 g / h. The data are shown in Table 1.

[0134] Embodiment 13

[0135] Same as Example 8, except that the catalyst used is MET-6. See Table 1 for data.

[0136] Embodiment 14

[0137] Same as Example 8, except that the catalyst used is MET-7. See Table 1 for data.

[0138] Comparative Example 2

[0139] Same as Example 8, except that the catalyst used is MET-1-C and the catalyst slurry flow rate is 3.0 g / h. See Table 1 for data.

[0140] Table 1

[0141]

[0142]

[0143] As can be seen from the table, the supported metallocene catalyst obtained by adding a slow-release monomer during the preparation process has the characteristics of low initial activity and can improve the long-term total polymerization activity of the catalyst. It is important that the supported metallocene catalyst prepared by this method can reduce the risk of catalyst feed line blockage and significantly improve the operational stability of the polyolefin device. In addition, the present invention surprisingly found that because the catalyst has the characteristics of low initial activity, its initial contact reaction with the polymerization monomer is relatively mild, and the prepared polymer powder has the characteristics of low fine powder rate and low agglomeration rate, thereby improving the operational stability of the device.

[0144] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A supported metallocene catalyst, characterized in that: The catalyst comprises a porous carrier, a metallocene compound, a co-catalyst and a slow-release polymer.

2. The catalyst according to claim 1, wherein The porous carrier includes an inorganic porous carrier or an organic porous carrier; The inorganic porous carrier is preferably at least one of a silica carrier, an aluminum oxide carrier and a magnesium chloride carrier; the silica carrier preferably includes a silica gel carrier and / or a silica carrier; The organic porous carrier is preferably a functionalized polyolefin carrier, and more preferably a polyethylene powder particle carrier and / or a polypropylene powder particle carrier.

3. The catalyst according to claim 1, wherein The metallocene compound is a non-bridged metallocene compound of formula I or a bridged metallocene compound of formula II; Ar1 Ar2M1Q1 Q2 Formula Ⅰ; T Ar3 Ar4M2 Q3Q4 Formula II; Wherein, M1 and M2 are each independently selected from elements of Groups 3 to 5 of the Periodic Table of Elements, preferably transition metals of Group 4, most preferably zirconium, titanium, hafnium or vanadium; Q1, Q2, Q3 and Q4 are all sigma ligands, and are each independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, a C1-C6 alkyl group, a phenyl group or a benzyl group; Ar1, Ar2, Ar3 and Ar4 are each independently selected from cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, substituted cyclopentadienyl, substituted indenyl, substituted tetrahydroindenyl or substituted fluorenyl; wherein the substituent is selected from at least one of a hydrocarbon group, a silyl group, a hydrocarbon group in which one or more hydrogen atoms and / or one or more carbon atoms are replaced by heteroatoms, and a silyl group in which one or more hydrogen atoms and / or one or more carbon atoms are replaced by heteroatoms, and the heteroatoms are selected from at least one of B, P, S and N; Preferably, the substituents in the substituted cyclopentadienyl, substituted indenyl, substituted tetrahydroindenyl and substituted fluorenyl are optionally cyclic; The T group is a bridging group selected from a divalent bridge -R'1R'2C-, -R'1C=CR'2-, -R'1R'2C-C R'3R'4-, -R'1R'2Si-, -R'1R'2Si-Si R'3R'4-, -R'1R'2Ge-, -R'1R'2Ge-Ge R'3R'4-, -R'1R'2C-Ge R'3R'4-, -R'1R'2Si-Ge R'3R'4- or -R'1R'2Si-CR'3R'4-; wherein R'1, R'2, R'3 and R'4 are each independently selected from a hydrogen atom, a hydrocarbon group, a silyl group, a germyl group, a hydrocarbon group in which one or more carbon atoms are substituted by a heteroatom, a silyl group in which one or more carbon atoms are substituted by a heteroatom or a germyl group in which one or more carbon atoms are substituted by a heteroatom, and the heteroatom is at least one of B, O, S, P and N; The T group is most preferably -CH2-, -CH2CH2-, -C(CH3)2-, -SiMe2-, -SiPh2-, -SiMePh-, -Si(CH3)2-CH2-, -SiPh2-CH2-, -Si(Me3)2-SiPh2- or -SiMePh-CH2-.

4. The catalyst according to claim 1, wherein The cocatalyst comprises an alkylaluminoxane compound and / or a boron-containing compound; preferably a C1-C10 alkylaluminoxane and / or an organic borate; the C1-C10 alkylaluminoxane is more preferably at least one selected from methylaluminoxane, ethylaluminoxane and butylaluminoxane; the organic borate is more preferably at least one selected from tetraphenylborate, tetrakis(p-phenyl)borate, tetrakis(o-,p-dimethylphenyl)borate, tetrakis(p-trifluoromethylphenyl)borate, tetrakis(pentafluorophenyl)borate, tetrakis(perfluorobiphenyl)borate and tetrakis(perfluoronaphthyl)borate; The cation of the organic borate is an organic cation, and the organic cation is preferably at least one of trialkylammonium ion, alkylanilinium ion, tetraalkylphosphonium ion, tetraphenylphosphonium ion and phenylcarbonium; The cocatalyst is most preferably methylaluminoxane and / or ethylaluminoxane.

5. The catalyst according to claim 1, wherein The monomer for synthesizing the sustained-release polymer is selected from at least one of C2-16 monoolefins and C2-16 polyolefins; preferably at least one of propylene, ethylene, butene, pentene, hexene, octene and styrene.

6. The catalyst according to claim 1, wherein The number average molecular weight of the sustained-release polymer is ≥2000.

7. The catalyst according to claim 1, wherein Based on the total weight of the supported metallocene catalyst, the content of the slow-release polymer is 1 to 95wt%, preferably 10 to 90wt%, and more preferably 15-60wt%; the content of the porous carrier is 1 to 90wt%, preferably 5 to 80wt%; the content of the metallocene compound is 0.1 to 10wt%, preferably 0.1 to 5wt%; the content of the co-catalyst is 0.1 to 20wt%, preferably 0.1 to 10wt%; the sum of the percentage content of each component is 100%.

8. The method for preparing a catalyst according to any one of claims 1 to 6, characterized in that: The preparation method comprises: (1) reacting the porous support and the co-catalyst in the presence of a first solvent; (2) contacting and reacting the support obtained in step (1) with a metallocene compound solution in the presence of a first solvent; (3) in the presence of a second solvent and the carrier obtained in step (2), polymerizing the first slow-release monomer to obtain a supported metallocene catalyst; Optionally (4) in the presence of the second solvent and the supported metallocene catalyst obtained in the previous step, polymerizing the second slow-release monomer to obtain a slow-release reinforced supported metallocene catalyst; Optional (5) Repeat step (4).

9. The preparation method according to claim 8, wherein: In step (1), the reaction temperature is 30 to 80° C. and the reaction time is 3 to 6 hours; In step (2), the reaction temperature is 0 to 100° C.; the solvent for preparing the metallocene compound solution is selected from at least one of toluene, benzene, xylene, hexane, heptane and cyclohexane, preferably selected from toluene and / or hexane; In step (3), the polymerization reaction temperature is 0 to 100° C. and the time is 0.1 to 6 hours; In step (4), the polymerization reaction temperature is 0 to 100° C. and the time is 0.1 to 6 hours; The first solvent is selected from aromatic hydrocarbons and / or aliphatic hydrocarbons, preferably at least one selected from toluene, benzene, xylene, hexane, heptane and cyclohexane; The second solvent is selected from aromatic hydrocarbons and / or aliphatic hydrocarbons, preferably at least one selected from toluene, benzene, xylene, hexane, heptane and cyclohexane; Preferably, each step in the preparation method is carried out under an inert gas atmosphere.

10. The preparation method according to claim 8, wherein: The first slow-release monomer and the second slow-release monomer are each independently selected from at least one of C2-16 monoolefins and C2-16 polyolefins; preferably at least one of propylene, ethylene, butene, pentene, hexene, octene and styrene.

11. Use of the catalyst according to any one of claims 1 to 7 in the preparation of polyolefins.

12. The use according to claim 11, wherein: The mixed material containing the catalyst according to any one of claims 1 to 7 and polymerization monomers is directly introduced into the main reactor without passing through a prepolymerization reactor; the polymerization monomers are gas phase or liquid phase polymerization monomers.

13. The use according to claim 12, wherein: The polymerization temperature in the main reactor is 0 to 100°C, preferably 20 to 80°C.

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