Catalyst as well as preparation method and application thereof

Abstract

The invention provides a catalyst as well as a preparation method and application thereof. The catalyst provided by the invention has a structure as shown in a formula 1, is used for polymerization reaction of olefin, has high catalytic activity, no cyclopentadienyl ring structure and more open space structure, is suitable for high-activity polymerization of large-steric-hindrance polyolefin, and has the catalytic activity of 1097-1420 kg PMP / (mmol Hf.h) when being used for polymerization reaction of 4-methyl-1-pentene. The molecular weight of the prepared poly (4-methyl-1-pentene) material is not less than 3 million g / mol, the molecular weight distribution is 1.5-3.5, the crystallinity is 50%-80%, and the poly (4-methyl-1-pentene) material has excellent mechanical properties and high temperature resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of olefin polymerization, and particularly relates to a catalyst and a preparation method and application thereof. BACKGROUND

[0003] Poly-4-methyl-1-pentene is mainly obtained by polymerization of 4-methyl-1-pentene monomer under the action of a catalyst, and thus the performance of the catalyst directly determines the properties of the poly-4-methyl-1-pentene product.

[0004] At present, the catalysts used for preparing poly-4-methyl-1-pentene mainly include Ziegler-Natta catalysts and metallocene catalysts, but the Ziegler-Natta catalysts have great defects in preparing PMP, such as easy poisoning of active centers by polar atoms, leading to deactivation of the catalyst, multiple active centers, too wide molecular weight distribution of the polymerization product, and poor mechanical properties; the metallocene catalysts have large steric hindrance due to the metallocene structure, and it is difficult for the 4-methyl-1-pentene monomer with large steric hindance to insert, so that the activity of the metallocene catalyst in catalyzing 4-methyl-1-pentene is low, the molecular weight of the polymerization product is also low, and the mechanical properties of the product are also poor. SUMMARY

[0005] The present application provides a catalyst for the polymerization of olefins, which has high catalytic activity and is particularly suitable for high-activity polymerization of polyolefins with large steric hindance.

[0006] The present application also provides a preparation method of the above catalyst, which has short preparation process, simple synthesis method, low-cost and easily-obtained raw materials, high synthesis yield, and industrial application

[0007] The present application also provides a preparation method of polyolefins by using the above catalyst, which can prepare polyolefin products with high molecular weight, narrow molecular weight distribution, and high crystallinity in high activity.

[0008] The present application provides a catalyst, wherein the catalyst has the structure shown in Formula 1:

[0009]

[0010] wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, and R15 are each independently selected from a hydrogen atom or a hydrocarbon group with 1-9 carbon atoms; and R16, R17, and R18 are each independently selected from a hydrocarbon group with 1-9 carbon atoms.

[0011] The catalyst described above, wherein the catalyst has the structure shown in Formula 2:

[0012] The present application provides a catalyst, wherein the catalyst has the structure shown in Formula 1:

[0009]

[0010] wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, and R15 are each independently selected from a hydrogen atom or a hydrocarbon group with 1-9 carbon atoms; and R16, R17, and R18 are each independently selected from a hydrocarbon group with 1-9 carbon atoms.

[0011] The catalyst described above, wherein the catalyst has the structure shown in Formula 2:

[0012]

[0013] R1, R3, and R5 are each independently selected from hydrocarbon groups with 1 to 4 hydrogen atoms or carbon atoms; R16, R17, and R18 are each independently selected from hydrocarbon groups with 1 to 3 carbon atoms.

[0014] In the catalyst described above, R1, R3, and R5 are hydrogen atoms, and R16, R17, and R18 are ethyl atoms;

[0015] Alternatively, R3 is a hydrogen atom, R1 and R5 are methyl groups, and R16, R17, and R18 are ethyl groups;

[0016] Alternatively, R3 is a hydrogen atom, R1 and R5 are isopropyl groups, and R16, R17, and R18 are methyl groups;

[0017] Alternatively, R3 is a hydrogen atom, R1 and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups;

[0018] Alternatively, R1, R3, and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0020] (1) An alkyl diphenyl difluorosilane having the structure shown in Formula 3 and an alkyl aniline having the structure shown in Formula 4 are dispersed in solvent 1 and reacted to obtain intermediate 1 having the structure shown in Formula 5.

[0021] (2) Intermediate 1, alkyllithium and hafnium tetrachloride react in solvent 2 to obtain intermediate 2 having the structure shown in Formula 6;

[0022] (3) Intermediate 2 is reacted with Grignard reagent to obtain the catalyst;

[0023]

[0024]

[0025] In the method described above, an alkaline accelerator is added in step (1), wherein the alkaline accelerator includes at least one of ethylamine, ethylenediamine, triethylamine, dimethylamine, pyridine, potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium bicarbonate, and potassium bicarbonate.

[0026] In the method described above, the molar ratio of the alkyl diphenyl difluorosilane to the alkyl aniline is 1:(2-4).

[0027] In the method described above, the molar ratio of intermediate 1, alkyllithium, and hafnium tetrachloride is 1:(1-2):(1-2);

[0028] In the method described above, the molar ratio of intermediate 2 to Grignard reagent is 1:(3-4).

[0029] In the method described above, solvent 1 includes at least one of N,N-dimethylformamide, tetrahydrofuran, and diethyl ether.

[0030] In the method described above, solvent 2 includes at least one of benzene, toluene, and ethylbenzene.

[0031] In the method described above, the ratio of the amount of alkyl diphenyl difluorosilane to the volume of solvent 1 is 1 mmol: (3-8) ml.

[0032] In the method described above, the ratio of the amount of intermediate 1 to the volume of solvent 2 is 1 mmol: (10-20) ml.

[0033] A third aspect of the present invention provides a method for preparing a polyolefin, comprising the following steps:

[0034] The above-described catalyst or the catalyst obtained according to the above preparation method is used to catalyze the polymerization reaction of polyolefin monomers.

[0035] In the preparation method described above, the molar ratio of the monomer of the polyolefin to the catalyst is (10000-50000):1.

[0036] The catalyst of this invention is used for highly active catalytic polymerization of olefins. The catalyst structure is free of cyclic rings and has a more open spatial structure, making it particularly suitable for highly active polymerization of sterically hindered polyolefins. When used for the polymerization of 4-methyl-1-pentene, the catalytic activity can reach 1097-1420 kg PMP / (mmol Hf·h), and the molecular weight of the prepared poly-4-methyl-1-pentene material is not less than 3 million g / mol, with a molecular weight distribution of 1.5-3.5 and a crystallinity of 50%-80%. It also has excellent mechanical properties and high-temperature resistance. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 The mass spectrum of the catalyst provided in Example 1 of this invention;

[0039] Figure 2The mass spectrum of the catalyst provided in Example 2 of this invention;

[0040] Figure 3 The GPC curve of poly4-methyl-1-pentene prepared by the catalyst according to an embodiment of the present invention is shown.

[0041] Figure 4 The image shows the DSC curve of poly4-methyl-1-pentene prepared by the catalyst according to an embodiment of the present invention.

[0042] Figure 5 The image shows the XRD pattern of poly(4-methyl-1-pentene) prepared by the catalyst according to an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0044] A first aspect of the present invention provides a catalyst having the structure shown in Formula 1:

[0045]

[0046] Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, and R15 are each independently selected from hydrocarbon groups with 1 to 9 hydrogen atoms or carbon atoms; R16, R17, and R18 are each independently selected from hydrocarbon groups with 1 to 9 carbon atoms.

[0047] The hydrocarbon group of the present invention is at least one of unsubstituted alkyl, alkenyl, alkynyl and aryl groups.

[0048] The catalyst of this invention belongs to the hafnium-based catalyst family and is used for the polymerization of olefins. Its molecular structure lacks cyclic structures, resulting in a more open spatial structure, making it more suitable for the high-activity polymerization of sterically hindered polyolefins. Furthermore, the introduction of silicon atoms into the molecular structure is hypothesized to reduce the electron cloud density of the central atom, thereby enhancing the activity of the catalyst's metal center and increasing the rate of polymerization chain growth. Due to the "silicon effect" generated by the silicon atoms, the catalyst's activity can be further improved. In the polymerization of 4-methyl-1-pentene, the catalytic activity can reach as high as 1420 kg PMP / (mmolHf·h), and the resulting poly-4-methyl-1-pentene material has a molecular weight of not less than 3 million g / mol, a molecular weight distribution of 1.5–3.5, and a crystallinity of 50%–80%, exhibiting excellent mechanical properties and high-temperature resistance.

[0049] In one specific embodiment, the catalyst has the structure shown in Formula 2:

[0050]

[0051] R1, R3, and R5 are each independently selected from hydrocarbon groups with 1 to 4 hydrogen atoms or carbon atoms; R16, R17, and R18 are each independently selected from hydrocarbon groups with 1 to 3 carbon atoms.

[0052] When the catalyst of the present invention has the structure described in Formula 2, there are no cyclic structures in the molecular structure, so the space is more open and the steric hindrance is small, which is conducive to the high-activity polymerization of sterically hindered polyolefins.

[0053] In one specific embodiment, R1, R3, and R5 are hydrogen atoms, and R16, R17, and R18 are ethyl atoms;

[0054] Alternatively, R3 is a hydrogen atom, R1 and R5 are methyl groups, and R16, R17, and R18 are ethyl groups;

[0055] Alternatively, R3 is a hydrogen atom, R1 and R5 are isopropyl groups, and R16, R17, and R18 are methyl groups;

[0056] Alternatively, R3 is a hydrogen atom, R1 and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups;

[0057] Alternatively, R1, R3, and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups.

[0058] When a catalyst has the above-mentioned structure, the catalyst has higher activity and better catalytic effect.

[0059] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0060] (1) An alkyl diphenyl difluorosilane having the structure shown in Formula 3 and an alkyl aniline having the structure shown in Formula 4 are dispersed in solvent 1 and reacted to obtain intermediate 1 having the structure shown in Formula 5.

[0061] (2) Intermediate 1, alkyllithium and hafnium tetrachloride react in solvent 2 to obtain intermediate 2 having the structure shown in Formula 6;

[0062] (3) Intermediate 2 reacts with Grignard reagent to obtain the catalyst.

[0063]

[0064] First, an ammonolysis reaction occurs between alkyldiphenyldifluorosilane and alkylaniline. One molecule of alkyldiphenyldifluorosilane reacts with two molecules of alkylaniline, with the silicon atom bonded to two nitrogen atoms, to obtain intermediate 1.

[0065] Then, alkyllithium undergoes a deprotonation reaction with hafnium tetrachloride, followed by a substitution reaction in which the hafnium atom is bonded to two nitrogen atoms, forming intermediate 2 with a four-membered ring structure.

[0066] Finally, intermediate 2 reacts with a Grignard reagent to obtain the catalyst.

[0067] In one specific embodiment, the molar ratio of the alkyl diphenyl difluorosilane to the alkyl aniline is 1:(2-4).

[0068] Furthermore, the molar ratio of intermediate 1, alkyllithium and hafnium tetrachloride is 1:(1-2):(1-2).

[0069] Furthermore, the molar ratio of intermediate 1 to Grignard reagent is 1:(3-4).

[0070] When the molar ratio of the above-mentioned reaction raw materials is within the above-mentioned range, both reaction efficiency and raw material cost can be considered. In one specific embodiment, an alkaline accelerator is also added in step (1), wherein the alkaline accelerator includes at least one of ethylamine, ethylenediamine, triethylamine, dimethylamine, pyridine, and potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium bicarbonate, and potassium bicarbonate.

[0071] HF is formed during the reaction in step 1). Adding an alkaline promoter can react with HF, thereby promoting the forward reaction and increasing the conversion rate.

[0072] In one specific embodiment, solvent 1 includes at least one of N,N-dimethylformamide, tetrahydrofuran, and diethyl ether.

[0073] Furthermore, solvent 1 is N,N-dimethylformamide.

[0074] In one specific embodiment, the ratio of the amount of alkyl diphenyl difluorosilane to the volume of solvent 1 is 1 mmol: (3-8) ml.

[0075] In one specific embodiment, solvent 2 includes at least one of benzene, toluene, and ethylbenzene.

[0076] Furthermore, solvent 2 is toluene.

[0077] In one specific embodiment, the ratio of the amount of intermediate 1 to the volume of solvent 2 is 1 mmol: (10-20) ml.

[0078] In one specific embodiment, the Grignard reagent includes at least one of MeMgCl, MeMgBr, MeMgI, EtMgCl, EtMgBr, and EtMgI.

[0079] In one specific embodiment, the molar ratio of intermediate 1 to Grignard reagent is 1:(3-4).

[0080] Specifically, the preparation method of the catalyst of the present invention includes the following steps:

[0081] (1) Under an inert gas atmosphere, alkyl diphenyl difluorosilane is mixed evenly with alkyl aniline, alkyl aniline and basic accelerator, solvent is added, and the reaction is carried out at 30-90℃ for 12-36h.

[0082] (2) Dissolve intermediate 1 in a solvent, add alkyl lithium at -40-0℃, react at 25-80℃ for 3-8h, cool to room temperature, add hafnium tetrachloride, react at 80-130℃ for 16-30h, and obtain a solution containing intermediate 2.

[0083] (3) Add the Grignard reagent dropwise to the system after the reaction in step (2), and react at 0-50°C for 3-8 hours to obtain the catalyst of the present invention.

[0084] A third aspect of the present invention provides a method for preparing a polyolefin, comprising the following steps:

[0085] The above-described catalyst or the catalyst obtained according to the above preparation method is used to catalyze the polymerization reaction of polyolefin monomers.

[0086] Among them, the monomers of polyolefins are olefins with C2-C8 carbon atoms. The catalyst of the present invention is particularly suitable for the polymerization reaction of sterically hindered monomers, such as 4-methyl-1-pentene.

[0087] In one specific embodiment, the molar ratio of the monomer of the polyolefin to the catalyst is (10000-50000):1.

[0088] The solution provided by the present invention will be further described below with reference to specific embodiments.

[0089] Example 1

[0090] The catalyst preparation method of this embodiment includes the following steps:

[0091] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 24 mmol of 2,6-diisopropylaniline, and 5 g of potassium hydroxide were added sequentially to a bottle with a side arm. 50 mL of N,N-dimethylformamide was then added using a syringe, and the mixture was refluxed at 50 °C for 24 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 96.7%.

[0092] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 30 mL of toluene. 2.2 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to reflux at 40 °C for 5 h and then cooled to room temperature. 2.2 mmol of HfCl4 was added, and the mixture was heated to 100 °C and refluxed for 24 h. The solution was then cooled to room temperature after the reaction.

[0093] (3) Add 7 mmol of methyl magnesium bromide solution dropwise to the reaction solution from the previous step and stir at room temperature for 5 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35 °C, filter, and dry. The catalyst shown in Formula 7, labeled C1, is obtained, with an overall yield of 78.6% for steps (2) and (3).

[0094]

[0095] The characterization data for intermediate 1 are as follows:

[0096] 1 H NMR (CD3Cl, 400MHz): δ (ppm) 1.20 (d, 24H, -CH3), 2.87 (m, 4H, -CH), 4.0 (s, 2H, -NH), 6.87 (s, 6H, N-Ar-H), 7.27-7.50 (m, 10H, Si-Ar-H).

[0097] The characterization data for catalyst C1 are: MS-EI (m / z): 755.4. The mass spectrum is shown below. Figure 1 .

[0098] Example 2

[0099] The preparation method in this embodiment is basically the same as that in Example 1, except that:

[0100] In step (1), 2,6-isopropylaniline was replaced with 2,4,6-tri-tert-butylaniline; the yield of step (1) was 89.6%, and the total yield of steps (2) and (3) was 69.4%.

[0101] The catalyst shown in Formula 8 was obtained and labeled as C2;

[0102]

[0103] The characterization data of intermediate 1 in this embodiment are as follows:

[0104] 1 H NMR (CD3Cl, 400MHz): δ (ppm) 1.35 (s, 54H, -CH3), 4.0 (s, 2H, -NH), 7.26 (s, 4H, N-Ar-H), 7.37-7.55 (m, 10H, Si-Ar-H).

[0105] The characterization data for catalyst C2 are: MS-EI (m / z): 924.3. The mass spectrum is shown below. Figure 2 .

[0106] Example 3

[0107] The preparation method in this embodiment is basically the same as that in Example 1, except that:

[0108] In step (1), 2,6-isopropylaniline was replaced with 2,6-di-tert-butylaniline; the yield of step (1) was 91.6%, and the total yield of steps (2) and (3) was 70.2%.

[0109] The catalyst shown in Formula 9 is obtained and labeled as C3;

[0110]

[0111] The characterization data of catalyst C3 are: MS-EI (m / z): 813.3.

[0112] Example 4

[0113] The preparation method in this embodiment is basically the same as that in Example 1, except that:

[0114] In step (1), 2,6-isopropylaniline was replaced with 2,6-dimethylaniline, and in step (3), methyl magnesium bromide was replaced with ethyl magnesium bromide; the yield of step (1) was 98.4%, and the total yield of steps (2) and (3) was 74.9%.

[0115] The catalyst shown in Formula 10 is obtained and labeled as C4;

[0116]

[0117] The characterization data for catalyst C4 are as follows:

[0118] MS-EI(m / z): 686.2.

[0119] Example 5

[0120] The preparation method in this embodiment is basically the same as that in Example 1, except that:

[0121] Replace 2,6-isopropylaniline in step (1) with aniline, and replace methyl magnesium bromide in step (3) with ethyl magnesium iodide; the yield of step (1) is 98.8%, and the total yield of steps (2) and (3) is 76.8%.

[0122] The catalyst shown in Formula 11 is obtained and labeled as C5;

[0123]

[0124] The characterization data for catalyst C5 are as follows:

[0125] MS-EI(m / z): 630.3.

[0126] Example 6

[0127] The preparation steps of catalyst C1 in this embodiment are as follows:

[0128] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 24 mmol of 2,6-diisopropylaniline, and 5 g of potassium carbonate were added sequentially to a bottle with a side arm. 50 mL of N,N-dimethylformamide was then added using a syringe, and the mixture was refluxed at 30 °C for 24 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 86.0%.

[0129] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 30 mL of toluene. 2.0 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to reflux at 25 °C for 8 h and then cooled to room temperature. 2.0 mmol of HfCl4 was added, and the mixture was heated to 100 °C and refluxed for 24 h. The solution was then cooled to room temperature after the reaction.

[0130] (3) Add 7 mmol of methyl magnesium bromide solution dropwise to the reaction solution from the previous step and stir at room temperature for 5 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35 °C, filter, and dry. Obtain a yellow solid hafnium catalyst with a total yield of 72.1% for steps (2) and (3).

[0131] Example 7

[0132] The preparation steps of catalyst C1 in this embodiment are as follows:

[0133] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 32 mmol of 2,6-diisopropylaniline, and 1.0 g of pyridine were added sequentially to a bottle with a side arm. 50 mL of N,N-dimethylformamide was then added using a syringe, and the mixture was refluxed at 70 °C for 24 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 91.7%.

[0134] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 30 mL of toluene. 3.0 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to reflux at 60 °C for 3 h and then cooled to room temperature. 3.0 mmol of HfCl4 was added, and the mixture was heated to 80 °C and refluxed for 16 h. The solution was then cooled to room temperature after the reaction.

[0135] (3) Add 7 mmol of methyl magnesium bromide solution dropwise to the reaction solution from the previous step, and stir at room temperature for 5 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35 °C, filter, and dry. Obtain a yellow solid hafnium catalyst with a total yield of 70.7% for steps (2) and (3).

[0136] Example 8

[0137] The preparation steps of catalyst C1 in this embodiment are as follows:

[0138] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 40 mmol of 2,6-diisopropylaniline, and 3.0 g of ethylenediamine were added sequentially to a bottle with a side arm. 30 mL of tetrahydrofuran was then added using a syringe, and the mixture was refluxed at 70 °C for 24 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 89.9%.

[0139] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 30 mL of toluene. 4 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to 80 °C and refluxed for 3 h. After cooling to room temperature, 4.0 mmol of HfCl4 was added, and the mixture was heated to 130 °C and refluxed for 20 h. The solution was then cooled to room temperature after the reaction.

[0140] (3) Add 6 mmol of methyl magnesium bromide solution dropwise to the reaction solution from the previous step, and stir at room temperature for 3 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35 °C, filter, and dry. Obtain a yellow solid hafnium catalyst with a total yield of 61.9% for steps (2) and (3).

[0141] Example 9

[0142] The preparation steps of catalyst C1 in this embodiment are as follows:

[0143] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 24 mmol of 2,6-diisopropylaniline, and 10 g of ethylenediamine were added sequentially to a bottle with a side arm. 80 mL of diethyl ether was added using a syringe, and the mixture was refluxed at 90 °C for 36 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 79.4%.

[0144] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 20 mL of toluene. 3 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to 60 °C and refluxed for 5 h. After cooling to room temperature, 3.0 mmol of HfCl4 was added, and the mixture was heated to 100 °C and refluxed for 30 h. The solution was then cooled to room temperature after the reaction.

[0145] (3) Add 8 mmol of methyl magnesium bromide solution dropwise to the reaction solution from the previous step, and stir at 50°C for 8 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35°C, filter, and dry. Obtain a yellow solid hafnium catalyst with a total yield of 69.9% for steps (2) and (3).

[0146] Example 10

[0147] The preparation steps of catalyst C1 in this embodiment are as follows:

[0148] (1) Under a nitrogen atmosphere, 10 mmol of diphenyldifluorosilane, 24 mmol of 2,6-diisopropylaniline, and 7 g of ethylamine were added sequentially to a bottle with a side arm. 50 mL of diethyl ether was then added using a syringe, and the mixture was refluxed at 90 °C for 12 h. After the reaction, the mixture was filtered and distilled under reduced pressure to obtain a pale yellow powder, which was intermediate 1, with a yield of 78.2%.

[0149] (2) Under a nitrogen atmosphere, 2 mmol of intermediate 1 was weighed and dissolved in 40 mL of toluene. 3 mmol of alkyl lithium solution was added dropwise at 0 °C. The mixture was heated to reflux at 60 °C for 5 h and then cooled to room temperature. 3 mmol of HfCl4 was added, and the mixture was heated to 100 °C and refluxed for 30 h. The solution was then cooled to room temperature after the reaction.

[0150] (3) Add 6 mmol of methyl magnesium chloride solution dropwise to the reaction solution from the previous step, and stir at 40°C for 5 h. Evaporate the solvent, wash the solid three times with n-hexane, and collect the filtrate. Crystallize at -35°C, filter, and dry. Obtain a yellow solid hafnium catalyst, with a total yield of 67.7% for steps (2) and (3).

[0151] Comparative Example 1

[0152] This comparative example uses the Ziegler-Natta catalyst as a reference.

[0153] Comparative Example 2

[0154] This comparative example uses a zirconium catalyst as a reference, prepared according to the method described in the reference (Walter, Kaminsky, et al. Photoinduced rac / meso interconversions of bridged bis(indenyl)zirconium dichlorides[J]. Journal of Molecular Catalysis A Chemical, 1996, 112: 37-42.).

[0155] The structural formula of the zirconium catalyst is shown in Formula 12;

[0156]

[0157] Comparative Example 3

[0158] This comparative example uses a non-silicon-containing, non-hafnium-containing catalyst as a reference, prepared according to the methods described in the references (Journal American Chemistry Society 2008, 130, 10354–10368; Organometallics 2011, 30, 3318–3329; ACS Catalysis. 2017, 7, 6930-6937).

[0159] The structural formula of the non-silicon-containing, non-hafnium-ceramsite catalyst is shown in Formula 13;

[0160]

[0161] Experimental Example 1

[0162] In the experimental example, the catalysts used in the above examples and comparative examples were used to catalyze the polymerization reaction of 4-methyl-1-pentene.

[0163] The polymerization of 4-methyl-1-pentene was catalyzed using catalyst C1 from Example 1 as follows: A 500 ml high-pressure polymerization reactor was evacuated from nitrogen three times and then purged with nitrogen to atmospheric pressure. 200 ml of 4-methyl-1-pentene monomer (monomer to hafnium catalyst molar ratio of 30000:1) and 15.6 mmol of triisobutylaluminum were added, and the mixture was stirred at 80°C for half an hour. Subsequently, a toluene solution prepared from 0.052 mmol of catalyst C1 and 0.26 mmol of [Ph3C][B(C6F5)4] was added to the system to initiate polymerization. After 120 min of polymerization, a 10 wt% hydrochloric acid-acidified ethanol solution was added to terminate the polymerization, yielding poly-4-methyl-1-pentene. The poly-4-methyl-1-pentene was filtered, washed three times with ethanol, and then vacuum-dried to constant weight.

[0164] The catalyst activity, polymer molecular weight, molecular weight distribution index, and melting temperature were measured. The formula for calculating the catalyst activity is as follows:

[0165] Act (activity) = m PMP / n Hf

[0166] Where m PMP The mass (g) and n of PMP obtained after polymerization Hf The molar amount (mmol) of Hf in the catalyst added during the polymerization process;

[0167] Methods for testing the molecular weight and molecular weight distribution of polymers: The molecular weight and molecular weight distribution were tested using a 220CV high-temperature gel permeation chromatograph from WATER Corporation, USA. The solvent used was 1,2,4-trichlorobenzene, and the test temperature was 150℃. The molecular weight distribution is the ratio of weight-average molecular weight to number-average molecular weight. (1) Sample preparation: Weigh 5-15 mg of polymer sample into a special sample bottle, add 5 mL of 1,2,4-trichlorobenzene, and use a PL-SP260 (Polymer Laboratories) heating stage for high-temperature sample preparation. The heating temperature is 160℃. 1,2,4-trichlorobenzene is used as the solvent. Generally, after dissolving for 3-5 hours, shake for 1 hour and then filter through a filter gun into a special test bottle for testing. The sample concentration is generally 1-3 mg / mL. (2) Test: The molecular weight and molecular weight distribution were determined on a PL-220 high-temperature gel permeation chromatograph (Polymer Laboratories). 1,2,4-trichlorobenzene was used as the mobile phase. The elution temperature was 150℃ and the flow rate was 1.0 mL / min. The data were processed using the narrow-distribution polystyrene standard universal correction method. The Mark-Houwink parameters used in the calculation were K = 5.91 × 10⁻⁴ and α = 0.69.

[0168] Method for testing melting temperature: The melting temperature and crystallization temperature of the polymer were determined using a differential scanning calorimeter at a heating rate of 20℃ / min and a cooling rate of 20℃ / min. (GB / T 19466.3-2004).

[0169] The catalytic activity of catalyst C1 in Example 1 was 1420 kg PMP / (mmol Hf·h); Figure 3 The GPC curve of poly(4-methyl-1-pentene) prepared with catalyst C1 shows a molecular weight distribution index of 2.23. Figure 4 The DSC curve of poly(4-methyl-1-pentene) prepared using catalyst C1 has a melting temperature of 240.01℃. Figure 5 XRD pattern of poly(4-methyl-1-pentene) prepared using catalyst C1, with a crystallinity of 72.2%.

[0170] The methods for catalyzing the polymerization of 4-methyl-1-pentene using catalysts C2-C5 in Examples 2-5 and catalysts in Comparative Examples 1-3 are consistent with the methods described above. The catalytic activity of the catalysts in the examples and comparative examples and the properties of the polymer products obtained are shown in Table 1.

[0171] Table 1 Catalyst and polymer product data for the examples and comparative examples.

[0172]

[0173]

[0174] As shown in Table 1, the silicon-containing non-hafnium-containing catalyst provided by this invention has higher catalytic activity, significantly higher than that of Ziegler-Natta catalyst, zirconium-containing catalyst and non-silicon-containing non-hafnium-containing metal catalyst. Furthermore, the poly(4-methyl-1-pentene) material prepared using this catalyst has a higher molecular weight (>3 million g / mol), a higher crystallinity (50%–80%), and a better melting temperature, thus endowing the polymer material with superior mechanical properties and high-temperature resistance.

[0175] Experimental Example 2

[0176] In this experimental example, catalyst C1 from Example 1 was used to catalyze the polymerization reaction of 4-methyl-1-pentene.

[0177] The polymerization reaction method in this experimental example is basically the same as that in Experimental Example 1, except that the molar ratio of 4-methyl-1-pentene monomer to catalyst is 10000:1.

[0178] Experimental Example 3

[0179] In this experimental example, catalyst C1 from Example 1 was used to catalyze the polymerization reaction of 4-methyl-1-pentene.

[0180] The polymerization reaction method in this experimental example is basically the same as that in Experimental Example 1, except that the molar ratio of 4-methyl-1-pentene monomer to catalyst is 50000:1.

[0181] The catalytic activity of catalyst C1 in Experimental Examples 2 and 3 and the properties of the polymer products obtained are shown in Table 2.

[0182] Table 2 shows the catalytic activity of catalyst C1 and the properties of the polymer products obtained in Experiments 1-3.

[0183]

[0184]

[0185] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 catalyst, characterized in that, The catalyst has the structure shown in Formula 1: Among them, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, and R15 are each independently selected from hydrocarbon groups with 1 to 9 hydrogen atoms or carbon atoms; R16, R17, and R18 are each independently selected from hydrocarbon groups with 1 to 9 carbon atoms.

2. The catalyst according to claim 1, characterized in that, The catalyst has the structure shown in Formula 2: R1, R3, and R5 are each independently selected from hydrocarbon groups with 1 to 4 hydrogen atoms or carbon atoms; R16, R17, and R18 are each independently selected from hydrocarbon groups with 1 to 3 carbon atoms.

3. The catalyst according to claim 2, characterized in that, R1, R3, and R5 are hydrogen atoms, and R16, R17, and R18 are ethyl atoms; Alternatively, R3 is a hydrogen atom, R1 and R5 are methyl groups, and R16, R17, and R18 are ethyl groups; Alternatively, R3 is a hydrogen atom, R1 and R5 are isopropyl groups, and R16, R17, and R18 are methyl groups; Alternatively, R3 is a hydrogen atom, R1 and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups; Alternatively, R1, R3, and R5 are tert-butyl groups, and R16, R17, and R18 are methyl groups.

4. A method for preparing the catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) An alkyl diphenyl difluorosilane having the structure shown in Formula 3 and an alkyl aniline having the structure shown in Formula 4 are dispersed in solvent 1 and reacted to obtain intermediate 1 having the structure shown in Formula 5. (2) Intermediate 1, alkyllithium and hafnium tetrachloride react in solvent 2 to obtain intermediate 2 having the structure shown in Formula 6; (3) Intermediate 2 is reacted with Grignard reagent to obtain the catalyst; 5. The method according to claim 4, characterized in that, In step (1), an alkaline accelerator is also added, which includes at least one of ethylamine, ethylenediamine, triethylamine, dimethylamine, pyridine, potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, sodium bicarbonate, and potassium bicarbonate.

6. The method according to claim 4 or 5, characterized in that, The molar ratio of the alkyl diphenyl difluorosilane to the alkyl aniline is 1:(2-4).

7. The method according to claim 4 or 5, characterized in that, The molar ratio of intermediate 1, alkyllithium and hafnium tetrachloride is 1:(1-2):(1-2).

8. The method according to claim 4 or 5, characterized in that, The molar ratio of intermediate 1 to Grignard reagent is 1:(3-4).

9. The method according to claim 4 or 5, characterized in that, Solvent 1 includes at least one of N,N-dimethylformamide, tetrahydrofuran, and diethyl ether.

10. The method according to claim 4 or 5, characterized in that, Solvent 2 includes at least one of benzene, toluene, and ethylbenzene.

11. The method according to claim 4 or 5, characterized in that, The ratio of the amount of the alkyl diphenyl difluorosilane to the volume of solvent 1 is 1 mmol: (3-8) ml.

12. The method according to claim 4 or 5, characterized in that, The ratio of the amount of intermediate 1 to the volume of solvent 2 is 1 mmol: (10-20) ml.

13. A method for preparing a polyolefin, characterized in that, Includes the following steps: The polymerization reaction of polyolefin monomers is catalyzed using the catalyst according to any one of claims 1 to 3 or the catalyst obtained by the preparation method according to claims 4 to 12.

14. The preparation method according to claim 13, characterized in that, The molar ratio of the monomer of the polyolefin to the catalyst is (10000~50000):1.

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