A supported metallocene catalyst and its preparation method and application

Abstract

The present invention relates to a supported metallocene catalyst and a preparation method and application thereof. In the preparation method, an Al-based MOFs carrier is first prepared, and then a co-catalyst is loaded on the surface and inside the pores of the MOFs carrier by an impregnation method, and then a main catalyst metallocene compound is loaded on the surface and inside the pores of the MOFs carrier with the co-catalyst by an impregnation method, and finally a highly stable Al-based MOFs-loaded metallocene catalyst is obtained. Compared with the prior art, the Al-based MOFs carrier selected in the present invention has high stability, high specific surface area and uniform structural composition, can achieve orderly dispersion of metallocene and significant improvement of catalytic performance, and can greatly reduce the amount of co-catalyst while maintaining catalytic activity, thereby reducing the preparation cost of the catalyst.

Description

Technical Field

[0001] The invention relates to the field of supported metallocene catalysts, in particular to a supported metallocene catalyst and a preparation method and application thereof. Background Art

[0002] Polyolefin products are closely related to our daily life, and the development of the polyolefin industry also promotes the development and progress of many other fields. In recent years, my country's polyolefin industry has developed rapidly, but its production capacity and performance still cannot meet market demand. Therefore, it is urgent to develop highly active polyolefin catalysts and high-performance polyolefin products.

[0003] Metallocene is one of the main catalysts for synthesizing polyolefins in industry. Compared with traditional Ziegler-Natta catalysts, metallocene catalysts have significant advantages such as uniform active sites, easy control of structural properties, narrow product relative molecular mass distribution, and high monomer selectivity. Metallocene catalysts have developed rapidly in the field of polyolefins in recent decades, and can produce a variety of high-performance homopolymers and copolymers, such as low-density linear polyethylene, isotactic polypropylene, polyolefin elastomers, ethylene propylene diene monomer rubber, etc. Metallocene catalysts were originally developed in a homogeneous form. However, homogeneous metallocene catalysts have problems such as easy deactivation of active centers, excessive use of co-catalysts, poor polymer morphology, and easy blockage of polymerization kettles and devices. Therefore, in actual use, metallocene catalysts are usually loaded to make them heterogeneous to improve the above problems. At present, the most widely used carrier is silicon dioxide. For example, Chinese patents CN1174848A, CN103586081A, CN115279799A and CN105980417A all disclose loaded metallocene catalysts with silicon dioxide as carriers. Silica has a high specific surface area, suitable pore volume and pore diameter, good fluidity and mechanical strength, and is low in cost, which can meet the needs of industrial production equipment. Silica carriers mainly rely on silanol to load metallocenes, but the type and distribution of hydroxyl groups on their surface are unclear, which will affect the uniformity of catalyst activity to a certain extent. In addition, silica itself does not have catalytic activity, and it is also impossible to produce strong interactions with metallocene main catalysts to improve their catalytic activity. In addition, silica carriers also have the disadvantages of uneven particle morphology and poor structural adjustability. Therefore, it is urgent to develop carrier materials with uniform sites, controllable structures, and strong interactions with metallocenes. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a highly stable Al-based MOFs-supported metallocene catalyst, a preparation method and its application. The selected Al-based MOFs carrier has high stability, high specific surface area and uniform structural composition, which can achieve orderly dispersion of metallocene in the carrier, and can significantly improve the loading efficiency of metallocene compounds and co-catalysts. At the same time, the strong interaction between the carrier and the metallocene can improve the stability and catalytic activity of the active sites during the reaction.

[0005] In the process of the present invention:

[0006] Metal-organic frameworks (MOFs) are a class of crystalline porous materials composed of metal ions or metal oxygen clusters and organic ligands. They have regular morphology, ordered pores, and adjustable building blocks, and can therefore be used as catalysts or catalyst supports. As metallocene catalyst supports, MOFs have the following significant advantages over traditional supports: (1) The ordered pore structure and chemical composition of MOFs can promote the uniform dispersion of metallocenes, thereby preparing supported catalysts with uniform activity; (2) MOFs can provide abundant loading, encapsulation, and anchoring sites to fix metallocenes and their co-catalysts, thereby improving the stability of supported catalysts; (3) The adjustable organic and inorganic building blocks in MOFs can produce various interactions with metallocenes, thereby obtaining better catalytic performance and better polymer products.

[0007] It can be seen that among many MOFs materials, Al-based MOFs usually have good stability and rich structural types, so they are expected to be used as carriers of metallocene catalysts.

[0008] By utilizing the ordered pore structure and clear building units of Al-based MOFs carriers, the orderly dispersion of metallocenes in the carrier can be achieved. At the same time, the strong interaction between the carrier and the metallocene can improve the stability of the active sites and the catalytic activity during the reaction. In addition, the inorganic nodes of Al-based MOFs are usually Al-O clusters, which are similar to the co-catalyst methylaluminoxane (MAO) commonly used in metallocene catalysts. Therefore, when Al-based MOFs are used as carriers, it is expected to reduce the amount of MAO used and thus reduce the cost of catalyst production.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A method for preparing a supported metallocene catalyst comprises the following steps:

[0011] S1, mixing the metal precursor, organic ligand, solvent and regulator evenly and adding them into a hydrothermal reactor for reaction to obtain an Al-based MOFs carrier;

[0012] S2, loading the co-catalyst on the surface and inside the pores of the MOFs carrier by impregnation method;

[0013] S3. The main catalyst metallocene compound is loaded on the surface and pores of the MOFs carrier with the co-catalyst by an impregnation method to obtain the final loaded catalyst.

[0014] Furthermore, the Al-based MOFs carrier described in step S1 is any one of MIL-53, MIL-68, MIL-69, MIL-96, MIL-100, MIL-101, MIL-110, CAU-1, CAU-3, CAU-10, CAU-16, DUT-4, DUT-5, MOF-333, MOF-519, NU-2000, and PCN-333.

[0015] Further preferably, considering the structural stability and preparation cost, the Al-based MOFs carrier in step S1 is any one of MIL-53, MIL-96, MIL-100 or MIL-110.

[0016] Furthermore, the metal precursor described in step S1 is one of AlCl3, Al(NO3)3, Al(OH)(AcO)2, and Al2(SO4)3, and the organic ligand is any one of H2BDC, H2BDC-NH2, H2BDC-NO2, H2IPA, H2IPA-CH3, H2IPA-OCH3, H2IPA-NO2, H2IPA-NH2, H2IPA-OH, H3PTC, 2,6-H2NDC, H2BPDC, H3BTC, H3BTB, Me3BTC, H3TATB, and H2BODC.

[0017] Furthermore, the molar ratio of the metal precursor to the organic ligand in step S1 is 0.4-2.

[0018] Furthermore, the solvent described in step S1 is one or more of N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), methanol, ethanol, and water, and the regulator is one of formic acid, acetic acid, benzoic acid, hydrochloric acid, nitric acid, hydrofluoric acid, and trifluoroacetic acid.

[0019] Furthermore, the concentration of the organic ligand in the solvent in step S1 is 0.02-0.3 mol / L.

[0020] Further preferably, the concentration of the organic ligand in the solvent in step S1 is 0.1 to 0.15 mol / L.

[0021] Furthermore, the molar ratio of the regulator to the metal precursor in step S1 is 0-200.

[0022] More preferably, the molar ratio of the regulator to the metal precursor in step S1 is 0-30.

[0023] Furthermore, the synthesis temperature of the Al-based MOFs carrier described in step S1 is 60-250° C., and the time is 0.5-72 h.

[0024] Further preferably, the synthesis temperature of the Al-based MOFs carrier in step S1 is 120-180° C. and the time is 12-36 h.

[0025] Furthermore, after the reaction described in step S1 is completed, the following steps are further included: separating, washing, and activating the solid product. The solvent used for washing the solid product is one or more of DMF, DEF, methanol, ethanol, acetone, toluene, and water, and the activation is carried out by high-temperature vacuuming, the activation temperature is 60 to 300 ° C, and the time is 4 to 24 hours.

[0026] More preferably, the activation temperature is 120-180° C. and the activation time is 8-18 h.

[0027] Furthermore, the co-catalyst described in step S2 is one or more of methylaluminoxane (MAO), modified methylaluminoxane (MMAO), trimethylaluminum (TMA), triethylaluminum (TEA), and triisobutylaluminum (TIBA).

[0028] Furthermore, the solvent used for the impregnation in step S2 can be any inert solvent that does not chemically react with the co-catalyst and the carrier.

[0029] More preferably, the inert solvent is toluene.

[0030] Furthermore, the mass fraction of the promoter in step S2 in the inert solvent is 0% to 20%, and the amount of the inert solvent is 0 to 10 mL / g MOF.

[0031] Furthermore, the immersion temperature in step S2 is 25 to 100° C., and the immersion time is 1 to 24 h.

[0032] More preferably, the immersion temperature in step S2 is 25-60° C. and the immersion time is 1-5 h.

[0033] Further, the metallocene compound described in step S3 is Cp2MCl2, ( n -BuCp)2MCl2,( i -BuCp)2MCl2, CpMCl3, Me2Si(Ind)2MCl2, Et(Ind)2MCl2, rac -Et(Ind)2MCl2, Ind2MCl2, rac -Ph2Si(Ind)2ZrC l2 , TMSCpMCl3, (TMS)2CpMCl3 and iPr(Cp)(Flu)MCl2, wherein M is a metal element selected from Zr, Hf and Ti.

[0034] Furthermore, the metallocene compound described in step S3 can be directly added to the mixture obtained in S2, or can be pre-configured as a solution and then added to the mixture obtained in S2.

[0035] Furthermore, the amount of the metallocene compound in step S3 is 10-200 μmol / g MOF.

[0036] Further preferably, the amount of the metallocene compound in step S3 is 60-200 μmol / g MOF.

[0037] On the other hand, a highly stable Al-based MOFs-supported metallocene catalyst is prepared by the above method.

[0038] On the other hand, the Al-based MOFs-supported metallocene catalyst prepared by the above method is applied to the slurry polymerization reaction of ethylene.

[0039] Furthermore, the polymerization reaction is carried out in a kettle reactor, and the kettle body is first purged and replaced with dry nitrogen for more than 5 times, and n-hexane, comonomer, impurity remover and metallocene catalyst supported by Al-based MOFs are added thereto in sequence. Ethylene is then introduced to make the internal pressure of the reactor reach the set temperature and pressure, and the reaction is terminated after a period of constant temperature and pressure reaction. After the device is cooled to room temperature, the material is discharged and dried to obtain a polyethylene product.

[0040] More preferably, the reaction temperature is 40-90° C., the reaction pressure is 0.5-3 MPa, the reaction time is 0.5-4 h, and the amount of catalyst is 0.01-0.5 g.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The Al-based MOFs carrier selected in the present invention has high stability, high specific surface area and uniform structural composition, which can achieve orderly dispersion of metallocene in the carrier, and can significantly improve the loading efficiency of metallocene compounds and co-catalysts. At the same time, the strong interaction between the carrier and the metallocene can improve the stability and catalytic activity of the active sites during the reaction. In addition, the inorganic nodes of Al-based MOFs are usually Al-O clusters, which are similar to the co-catalyst methylaluminoxane (MAO) commonly used in metallocene catalysts. It can greatly reduce the amount of co-catalyst while maintaining the catalytic activity, thereby reducing the preparation cost of the catalyst.

[0043] (2) The catalytic activity of the supported metallocene catalyst created by the present invention is significantly better than that of the traditional silica gel supported metallocene catalyst, and the mechanical strength of the catalyst particles is far better than that of silica gel, and the particles will not break during the loading process, thereby affecting the product performance.

[0044] (3) The polyethylene product obtained based on the supported metallocene catalyst created by the present invention contains a certain amount of microporous MOFs. These MOFs can effectively improve the porosity and hydrophilicity of polyethylene and are expected to be used in high-end application fields such as battery separators. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structures of four highly stable Al-based MOFs selected in the embodiments of the present invention.

[0046] Figure 2 This is a comparison diagram of the metallocene catalyst supported by silica gel in Comparative Example 1 and the metallocene catalyst supported by MOF in Example 3 of the present invention. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are implemented based on the above technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0048] Any features such as preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution shall be deemed as common technical features disclosed in the prior art.

[0049] Example 1

[0050] This embodiment provides a method for preparing a supported metallocene catalyst and its application, and the specific steps are as follows:

[0051] S1. Add 0.562 g Al(NO3)3·9H2O, 0.252 g Me3BTC and 7.2 mL deionized water into a 50 mL polytetrafluoroethylene hydrothermal reactor. Stir until the mixture is evenly mixed, seal the hydrothermal reactor and place it in a 150 ℃ oven for reaction for 24 hours. After the reaction is completed and cooled to room temperature, the supernatant is filtered out to obtain a white powder sample. The obtained sample is centrifugally washed with DMF and acetone for 3 times and 6 times respectively within three days, with an interval of more than 2 hours between each two washings. Finally, the washed sample is vacuum activated at 150 ℃ for 12 hours, and the obtained sample is MIL-100.

[0052] S2. Weigh 500 mg of activated MIL-100, disperse it in 10 mL of toluene, add 3 mL of 10% MAO toluene solution, stir and react at 40 °C for 3 h, wash it with toluene three times, remove unreacted MAO and disperse it in 10 mL of toluene.

[0053] S3. Weigh 15 mg of Cp2ZrCl2 and disperse it in 5 mL of toluene. Add the Cp2ZrCl2 solution dropwise into the suspension of MIL-100 and stir at 40 °C for 3 h. Then wash it with toluene and n-hexane, and finally vacuum dry it at 40 °C to obtain a supported catalyst.

[0054] Ethylene polymerization test: The kettle of a 2 L polymerization kettle was purged and replaced with dry nitrogen for more than 5 times, and then 700 mL of n-hexane and 2 mL of triethylaluminum were added to the kettle, and the reaction was stirred at 50 °C for 10 min to remove impurities from the reaction system. Then 50 mg of catalyst and 300 mL of n-hexane were added to the kettle, and the temperature was raised to 70 °C and ethylene gas was filled to start the reaction. The reaction pressure was maintained at 1 MPa and the reaction time was 1 h. After the reaction was completed, the temperature was lowered and the pressure was released, and the kettle was purged and replaced with nitrogen for more than 5 times. Then the polymerization product was taken out and dried and weighed. The activity was calculated to be 1440 gPE / gCat based on the mass of the catalyst.

[0055] Example 2

[0056] This embodiment provides a method for preparing a supported metallocene catalyst and its application, and the specific steps are as follows:

[0057] S1. Add 0.562 g Al(NO3)3·9H2O, 0.252 g Me3BTC, 0.12 mL formic acid and 7.2 mL deionized water into a 50 mL polytetrafluoroethylene hydrothermal reactor. Stir until the mixture is evenly mixed, seal the hydrothermal reactor and place it in a 150 ℃ oven for reaction for 24 h. After the reaction is completed and cooled to room temperature, the supernatant is filtered out to obtain a white powder sample. The obtained sample is centrifugally washed with DMF and acetone for 3 times and 6 times respectively within three days, with an interval of more than 2 h between each two washings. Finally, the washed sample is vacuum activated at 150 ℃ for 12 h, and the obtained sample is MIL-110.

[0058] S2. Weigh 500 mg of activated MIL-110, disperse it in 10 mL of toluene, add 3 mL of 10% MAO toluene solution, stir and react at 40 °C for 3 h, wash it with toluene three times, remove unreacted MAO and disperse it in 10 mL of toluene.

[0059] S3. Weigh 15 mg of Cp2ZrCl2 and disperse it in 5 mL of toluene. Add the Cp2ZrCl2 solution dropwise into the suspension of MIL-100 and stir at 40 °C for 3 h. Then wash it with toluene and n-hexane, and finally vacuum dry it at 40 °C to obtain a supported catalyst.

[0060] Ethylene polymerization test: The kettle of a 2 L polymerization kettle was purged and replaced with dry nitrogen for more than 5 times, and then 700 mL of n-hexane and 2 mL of triethylaluminum were added to the kettle, and the reaction was stirred at 50 °C for 10 min to remove impurities from the reaction system. Then 50 mg of catalyst and 300 mL of n-hexane were added to the kettle, and the temperature was raised to 70 °C and ethylene gas was filled to start the reaction. The reaction pressure was maintained at 1 MPa and the reaction time was 1 h. After the reaction was completed, the temperature was lowered and the pressure was released, and the kettle was purged and replaced with nitrogen for more than 5 times. Then the polymerization product was taken out and dried and weighed. The activity was calculated to be 1752 gPE / gCat based on the mass of the catalyst.

[0061] Example 3

[0062] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that 1.7 mL of formic acid was added in step S1. The obtained sample was MIL-96, and the activity was calculated to be 1553 gPE / gCat based on the catalyst mass.

[0063] Example 4

[0064] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that 11.3 mL of formic acid was added in step S1. The obtained sample was MIL-96, and the activity was calculated to be 1720 gPE / gCat based on the catalyst mass.

[0065] Example 5

[0066] This embodiment provides a method for preparing a supported metallocene catalyst and its application, and the specific steps are as follows:

[0067] S1. Add 0.510 g Al(NO3)3·9H2O, 0.514 g Me3BTC and 30 mL DMF into a 50 mL polytetrafluoroethylene hydrothermal reactor, stir until well mixed, seal the hydrothermal reactor and place it in a 150 ℃ oven for 24 h. After the reaction is completed and cooled to room temperature, the supernatant is filtered out to obtain a white powder sample. The obtained sample is centrifugally washed with DMF and acetone for 3 times and 6 times respectively within three days, with an interval of more than 2 h between each two washings. Finally, the washed sample is vacuum activated at 150 ℃ for 12 h, and the obtained sample is MIL-53.

[0068] S2. Weigh 500 mg of activated MIL-53, disperse it in 10 mL of toluene, add 3 mL of 10% MAO toluene solution, stir and react at 40 °C for 3 h, wash it with toluene three times, remove unreacted MAO and disperse it in 10 mL of toluene.

[0069] S3. Weigh 15 mg of Cp2ZrCl2 and disperse it in 5 mL of toluene. Add the Cp2ZrCl2 solution dropwise into the suspension of MIL-100 and stir at 40 °C for 3 h. Then wash it with toluene and n-hexane, and finally vacuum dry it at 40 °C to obtain a supported catalyst.

[0070] Ethylene polymerization test: The kettle of a 2 L polymerization kettle was purged and replaced with dry nitrogen for more than 5 times, and then 700 mL of n-hexane and 2 mL of triethylaluminum were added to the kettle, and the reaction was stirred at 50 °C for 10 min to remove impurities from the reaction system. Then 50 mg of catalyst and 300 mL of n-hexane were added to the kettle, and the temperature was raised to 70 °C and ethylene gas was filled to start the reaction. The reaction pressure was maintained at 1 MPa and the reaction time was 1 h. After the reaction was completed, the temperature was lowered and the pressure was released, and the kettle was purged and replaced with nitrogen for more than 5 times. Then the polymerization product was taken out and dried and weighed. The activity was calculated to be 1004 gPE / gCat based on the mass of the catalyst.

[0071] Example 6

[0072] The catalyst loading and ethylene polymerization test were carried out in the same manner as in Example 2, except that 1 mL of a 10% by mass MAO toluene solution was added in step S2, and the activity was calculated to be 1660 gPE / gCat based on the catalyst mass.

[0073] Example 7

[0074] The catalyst loading and ethylene polymerization test were carried out in the same manner as in Example 2, except that the reaction pressure was maintained at 2 MPa in the ethylene polymerization test. The activity was calculated to be 2850 gPE / gCat based on the catalyst mass.

[0075] Example 8

[0076] The catalyst loading and ethylene polymerization test were carried out in the same manner as in Example 2, except that 18 mg of ( n -BuCp)2ZrCl2 was used as the main catalyst, and the activity was calculated to be 2010 gPE / gCat based on the catalyst mass.

[0077] Example 9

[0078] This embodiment provides a method for preparing a supported metallocene catalyst and its application, and the specific steps are as follows:

[0079] S1. Add 0.562 g Al(NO3)3·9H2O, 0.252 g Me3BTC, 0.12 mL formic acid and 7.2 mL deionized water into a 50 mL polytetrafluoroethylene hydrothermal reactor. Stir until the mixture is evenly mixed, seal the hydrothermal reactor and place it in a 150 ℃ oven for reaction for 24 h. After the reaction is completed and cooled to room temperature, the supernatant is filtered out to obtain a white powder sample. The obtained sample is centrifugally washed with DMF and acetone for 3 times and 6 times respectively within three days, with an interval of more than 2 h between each two washings. Finally, the washed sample is vacuum activated at 150 ℃ for 12 h, and the obtained sample is MIL-110.

[0080] S2. Weigh 500 mg of activated MIL-110, disperse it in 10 mL of toluene, add 6 mL of 10% MAO toluene solution, stir and react at 40 °C for 3 h, wash it with toluene three times, remove unreacted MAO and disperse it in 10 mL of toluene.

[0081] S3, weigh 35 mg of ( n -BuCp)2ZrCl2 was dispersed in 10 mL toluene. n -BuCp)2ZrCl2 solution was added dropwise into the suspension of MIL-110 and stirred at 40 °C for 3 h. It was then washed with toluene and n-hexane and finally dried under vacuum at 40 °C to obtain a supported catalyst.

[0082] Ethylene polymerization test: The kettle of a 2 L polymerization kettle was purged and replaced with dry nitrogen for more than 5 times, and then 700 mL of n-hexane and 2 mL of triethylaluminum were added to the kettle, and the reaction was stirred at 50 °C for 10 min to remove impurities from the reaction system. Then 50 mg of catalyst and 300 mL of n-hexane were added to the kettle, and the temperature was raised to 70 °C and ethylene gas was filled to start the reaction. The reaction pressure was maintained at 1 MPa and the reaction time was 1 h. After the reaction was completed, the temperature was lowered and the pressure was released, and the kettle was purged and replaced with nitrogen for more than 5 times. Then the polymerization product was taken out and dried and weighed. The activity was calculated to be 2744 gPE / gCat based on the mass of the catalyst.

[0083] Example 10

[0084] This embodiment provides a method for preparing a supported metallocene catalyst and its application, and the specific steps are as follows:

[0085] S1. Add 0.562 g Al(NO3)3·9H2O, 0.252 g Me3BTC, 0.12 mL formic acid and 7.2 mL deionized water into a 50 mL polytetrafluoroethylene hydrothermal reactor. Stir until the mixture is evenly mixed, seal the hydrothermal reactor and place it in a 150 ℃ oven for reaction for 24 h. After the reaction is completed and cooled to room temperature, the supernatant is filtered out to obtain a white powder sample. The obtained sample is centrifugally washed with DMF and acetone for 3 times and 6 times respectively within three days, with an interval of more than 2 h between each two washings. Finally, the washed sample is vacuum activated at 150 ℃ for 12 h, and the obtained sample is MIL-110.

[0086] S2. Weigh 500 mg of activated MIL-110, disperse it in 10 mL of toluene, add 3 mL of 10% MAO toluene solution, stir and react at 40 °C for 3 h, wash it with toluene three times, remove unreacted MAO and disperse it in 10 mL of toluene.

[0087] S3, weigh 18 mg of ( n -BuCp)2ZrCl2 was dispersed in 5 mL of toluene, and 2 mL of 1 mmol / mL triisobutylaluminum toluene solution was added thereto, and the mixture was stirred at 40 °C for 3 h. n -BuCp)2ZrCl2 and triisobutylaluminum mixed solution was added dropwise to the suspension of MIL-110 and stirred at 40 °C for 3 h. It was then washed with toluene and n-hexane and finally dried under vacuum at 40 °C to obtain a supported catalyst.

[0088] Ethylene polymerization test: The kettle of a 2 L polymerization kettle was purged and replaced with dry nitrogen for more than 5 times, and then 700 mL of n-hexane and 2 mL of triethylaluminum were added to the kettle, and the reaction was stirred at 50 °C for 10 min to remove impurities from the reaction system. Then 50 mg of catalyst and 300 mL of n-hexane were added to the kettle, and the temperature was raised to 70 °C and ethylene gas was filled to start the reaction. The reaction pressure was maintained at 1 MPa and the reaction time was 1 h. After the reaction was completed, the temperature was lowered and the pressure was released, and the kettle was purged and replaced with nitrogen for more than 5 times. Then the polymerization product was taken out and dried and weighed. The activity was calculated to be 1660 gPE / gCat based on the mass of the catalyst.

[0089] Comparative Example 1

[0090] The catalyst loading and ethylene polymerization test were carried out in the same manner as in Example 1, except that the catalyst carrier was replaced with SYLOPOL 955 silica gel purchased from GRACE Company. The activity was calculated based on the catalyst mass to be 920 gPE / gCat.

[0091] Comparative Example 2

[0092] Catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that the catalyst carrier was replaced with a mixture of SYLOPOL 955 silica gel purchased from GRACE and MIL-110 in a mass ratio of 1:1. The activity was calculated based on the catalyst mass to be 1332 gPE / gCat.

[0093] Comparative Example 3

[0094] The catalyst loading and ethylene polymerization test were carried out in the same manner as in Example 1, except that the catalyst carrier was replaced with alumina powder purchased from Hairui Chemical Company. The activity was calculated based on the catalyst mass to be 619 gPE / gCat.

[0095] Comparative Example 4

[0096] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 2, except that the activation temperature of MIL-110 was lowered from 150° C. to 30° C. The activity was calculated based on the catalyst mass to be 377 gPE / gCat.

[0097] Comparative Example 5

[0098] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that the catalyst support Al-based MOFs was replaced with Fe-based MOFs (MIL-100). The activity was calculated based on the catalyst mass to be 1100 gPE / gCat.

[0099] Comparative Example 6

[0100] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that the catalyst carrier Al-based MOFs was replaced with Zn-based MOFs (MOF-74). The activity was calculated based on the catalyst mass to be 496 gPE / gCat.

[0101] Comparative Example 7

[0102] The catalyst loading and ethylene polymerization tests were carried out in the same manner as in Example 1, except that the catalyst carrier Al-based MOFs was replaced with Zr-based MOFs (UiO-66). The activity was calculated to be 883 gPE / gCat based on the catalyst mass.

[0103] Comparative Example 8

[0104] The MOF synthesis and ethylene polymerization test were carried out in the same manner as in Example 1, but MAO was not added during the catalyst loading process. The activity was calculated based on the catalyst mass to be 710 gPE / gCat.

[0105] Comparative Example 9

[0106] The MOF synthesis and ethylene polymerization test were carried out in the same manner as in Example 1, except that the amount of Cp2ZrCl2 used in the catalyst loading process was reduced to 1.5 mg. The activity was calculated based on the catalyst mass to be 235 gPE / gCat.

[0107] Attached Figure 1 The schematic diagram of the structure of four kinds of Al-based MOFs selected in the embodiment of the present invention are MIL-53, MIL-96, MIL-100 and MIL-110. These four kinds of Al-based MOFs have stable structures and low preparation costs. As can be seen from Table 1, the use of different catalyst carriers in Examples 1-10 and Comparative Examples 1-9 and under different reaction conditions have a greater impact on the activity of the catalyst. The catalytic activity of the supported metallocene catalyst prepared by the present invention is significantly better than that of the traditional silica gel and alumina supported metallocene catalysts. In addition, in the present invention, the loading effect of the MIL-110 (Al) carrier is the best.

[0108] Attached Figure 2 By comparing the metallocene catalyst supported by silica gel in Comparative Example 1 and the metallocene catalyst supported by MOF in Example 3, it can be found that when silica gel is used as a carrier, the final catalyst is broken to a certain extent, while when MOF is used as a carrier, the final catalyst can maintain its original morphology. This shows that the mechanical strength of MOF material is higher than that of silica gel, and the morphology of catalyst particles can be maintained during the loading process, avoiding the reduction of activity due to catalyst breakage.

[0109] Table 1 Activity of catalysts prepared under different conditions in Examples 1-10 and Comparative Examples 1-9 for ethylene polymerization

[0110]

[0111] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a supported metallocene catalyst, characterized in that: The steps include: S1, mixing Al metal precursor, organic ligand and solvent evenly and heating to react to obtain Al-based MOFs carrier; S2, loading the co-catalyst on the surface and inside the pores of the MOFs carrier by impregnation method; S3, loading the main catalyst metallocene compound on the surface and pores of the MOFs carrier with the co-catalyst by an impregnation method to obtain the final supported metallocene catalyst; In S1, the Al-based MOFs carrier is MIL-96 or MIL-110; The solvent is one or more of N,N-dimethylformamide, N,N-diethylformamide, methanol, ethanol, and water; In S1, a regulator is mixed with the Al metal precursor, the organic ligand, and the solvent, wherein the regulator is formic acid, the concentration of the organic ligand in the solvent is 0.02-0.3 mol / L, the molar ratio of the regulator to the metal precursor is 0-200, and the amount of the regulator is not 0; The co-catalyst is one or more of methylaluminoxane, modified methylaluminoxane, trimethylaluminum, triethylaluminum, and triisobutylaluminum; The solvent of the impregnation method is an inert solvent that does not chemically react with the promoter and the carrier, and the mass fraction of the promoter in the inert solvent is 0% to 20%, and the mass fraction is not 0; In S3, the amount of the metallocene compound is 60-200 μmol / g MOF.

2. The method for preparing a supported metallocene catalyst according to claim 1, characterized in that: In S1, the metal precursor is Al(NO3)3, the organic ligand is Me3BTC, and the molar ratio of the metal precursor to the organic ligand is 0.4-2.

3. The method for preparing a supported metallocene catalyst according to claim 1, characterized in that: In S1, the heating reaction temperature of the Al-based MOFs carrier is 150°C and the time is 24 h.

4. The method for preparing a supported metallocene catalyst according to claim 1, characterized in that: In S2, the amount of the inert solvent is 20 mL / g MOF, the immersion temperature is 25-60° C., and the immersion time is 1-24 h.

5. The method for preparing a supported metallocene catalyst according to claim 1, characterized in that: In S3, the metallocene compound is Cp2MCl2, ( n -BuCp)2MCl2, ( i -BuCp)2MCl2, CpMCl3, Me2Si(Ind)2MCl2, Et(Ind)2MCl2, rac -Et(Ind)2MCl2, Ind2MCl2, rac -Ph2Si(Ind)2ZrC l2 , TMSCpMCl3, (TMS)2CpMCl3 and iPr(Cp)(Flu)MCl2, wherein M is a metal element selected from Zr, Hf and Ti.

6. Use of a supported metallocene catalyst prepared by the method according to any one of claims 1 to 5 in ethylene polymerization.

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