A supported nickel catalyst and a process for catalyzing the polymerization of ethylene

Abstract

The application discloses a supported nickel catalyst and a method for catalyzing ethylene polymerization, and belongs to the technical field of ethylene polymerization. The supported nickel catalyst is prepared by mixing and reacting alkyl magnesium, chlorinated alkyl aluminum and a nickel complex shown in formula 1; wherein R and R' are independently selected from C1-C 10 alkyl, C6-C 18 aryl, C6-C 18 heteroaryl, C1-C 30 alkoxy, C2-C 30 alkylamino, C6-C 30 aryloxy, C6-C 30 arlamino, C 10 -C 30 aralkyl, C3-C 30 siloxy, halogen, nitro, one or more of which. The supported nickel catalyst has excellent stability and high catalytic activity, and can be mass-produced and applied. The supported nickel catalyst can be used for catalyzing ethylene polymerization to obtain ultrahigh molecular weight polyethylene which is low in branching degree, narrow in molecular weight distribution, good in mechanical property, easy to process and free of sticky kettle phenomenon.

Description

Technical Field

[0001] This invention relates to the field of ethylene polymerization technology, and more particularly to a supported nickel catalyst and a method for catalyzing ethylene polymerization. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) generally refers to polyethylene with a molecular weight exceeding one million. Due to its excellent wear resistance, self-lubricating properties, chemical resistance, and biocompatibility, it holds significant value in many high-end applications. In the preparation of UHMWPE, the choice of catalyst has a crucial impact on the polymer's molecular weight and distribution, branching degree, and even determines the polymer's processing and mechanical properties.

[0003] Pre-transition metals refer to transition metals with fewer d electrons (generally no more than 5), such as scandium (Sc), vanadium (V), titanium (Ti), zirconium (Zr), and chromium (Cr); while post-transition metals are those transition metals with more d electrons, such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).

[0004] Among pre-transition metal catalysts, the Ziegler-Natta (ZN) catalyst, composed of triethylaluminum and titanium tetrachloride, is an excellent directional polymerization catalyst. Currently, commercially available UHMWPE is typically prepared using Ziegler-Natta (ZN) catalysts. These catalysts are widely used due to their long development history, low cost, and efficient catalytic polymerization of ethylene to UHMWPE. However, UHMWPE prepared by ZN catalysts has a wide molecular weight distribution, which, while beneficial for processing, can lead to inconsistencies in material properties, affecting its performance in certain high-end applications. Other pre-transition metal catalysts can also catalyze the preparation of UHMWPE materials, but they often suffer from a lack of branching, leading to processing difficulties. Furthermore, pre-transition metal catalysts generally exhibit poor stability and sensitivity to water and oxygen, which is detrimental to industrial production.

[0005] In recent years, post-transition metal catalysts such as α-diimine nickel have become a hot topic in catalytic ethylene polymerization research, as they can produce UHMWPE with a narrow molecular weight distribution. However, a drawback is that the resulting polymers often have a high degree of branching, which may affect the crystallinity and mechanical strength of polyethylene. Furthermore, in the process of preparing UHMWPE using homogeneous α-diimine nickel catalysis, the polymer tends to adhere to the reactor wall, hindering mass transfer, leading to material loss and difficulties in equipment cleaning, severely reducing the efficiency of the catalytic polymerization reaction. This limits its application in industrial production.

[0006] Therefore, it is of great significance to research and develop a catalyst for the preparation of UHMWPE products. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a supported nickel catalyst and a method for catalyzing ethylene polymerization. The catalyst has excellent stability and is suitable for large-scale production and application. Using it to catalyze ethylene polymerization can produce ultra-high molecular weight polyethylene with low branching, narrow molecular weight distribution, excellent mechanical strength, and easy processing, while significantly reducing the sticking phenomenon.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This invention provides a supported nickel catalyst, which is prepared by mixing and reacting alkylmagnesium, alkylaluminum chloride and a nickel complex shown in Formula 1;

[0010]

[0011] Among them, R and R' are independently selected from C1-C 10 Alkyl, C6-C 18 Aryl, C6-C 18 heteroaryl, C1-C 30 Alkoxy, C2-C 30 Alkylamino, C6-C 30 Aryloxy group, C6-C 30 Aromatic amino, C 10 -C 30 Aryl alkyl, C3-C 30 One or more of silanoxy, halogen, and nitro groups.

[0012] The C1-C 10 Alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.

[0013] The C6-C 18 Aryl groups include, but are not limited to, phenyl, naphthyl, benzyl, biphenyl, linear terphenyl, anthracene, phenanthryl, pyrene, fluorene, etc.

[0014] The above reaction is simple and can be completed by dispersing the alkylmagnesium, alkylaluminum chloride and the nickel complex shown in Formula 1 in a solvent.

[0015] In the above reaction, the alkyl magnesium and alkyl aluminum chloride are used to generate magnesium chloride support in situ.

[0016] The alkylaluminum chloride and the nickel complex shown in Formula 1 generate cationic nickel active species in situ.

[0017] The cationic nickel active species are loaded onto an in-situ generated magnesium chloride support.

[0018] The present invention does not impose any special limitation on the above-mentioned loading method, including but not limited to embedding on the surface and / or inside of the magnesium chloride carrier generated in situ.

[0019] This invention improves the performance of the supported nickel catalyst by adjusting the ratio of aluminum, magnesium, and nickel elements in the raw materials for its preparation.

[0020] Preferably, in the alkylaluminum chloride and nickel complex shown in Formula 1, the molar ratio of aluminum to nickel is (200-1000):1; more preferably, it is (300-1000):1.

[0021] Preferably, in the alkyl magnesium and nickel complex of Formula 1, the molar ratio of magnesium to nickel is (10-500):1; more preferably (50-500):1; and even more preferably (200-500):1.

[0022] Preferably, the molar ratio of aluminum to magnesium in the alkylaluminum chloride and alkylmagnesium chloride is (1-10):1; more preferably (1-5):1; and even more preferably 2:1.

[0023] Preferably, the alkylaluminum chloride is selected from one or more of diethylaluminum chloride, dimethylaluminum chloride, ethylaluminum chloride, dibutylaluminum chloride, methylaluminum chloride, and sesquiethylaluminum chloride; more preferably, it is diethylaluminum chloride, dimethylaluminum chloride, or sesquiethylaluminum chloride; and even more preferably, it is diethylaluminum chloride.

[0024] Preferably, the alkyl magnesium is selected from dibutyl magnesium or diethyl magnesium; more preferably, it is dibutyl magnesium.

[0025] The solvent for the above reaction is preferably one or more of dichloromethane, n-hexane, n-pentane, n-heptane, and toluene; more preferably a mixture of dichloromethane and n-hexane.

[0026] Preferably, in this invention, R and R' are independently selected from C1-C5 alkyl groups and C6-C4 alkyl groups. 12 Aryl, C6-C 12 heteroaryl, C1-C 10 Alkoxy, C2-C6 alkylamino, C6-C 30 Aryloxy group, C6-C 20 Aromatic amino, C 13 -C 20 Aryl alkyl, C3-C 20 One or more of silanoxy, halogen, and nitro groups.

[0027] The C1-C5 alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, etc.

[0028] The C6-C12 Aryl groups include, but are not limited to, phenyl, naphthyl, benzyl, and biphenyl.

[0029] The C6-C 12 Heteroaryl groups include, but are not limited to, carbazolyl and indolel.

[0030] The C2-C6 alkylamino groups include, but are not limited to, dimethylamino, diethylamino, and diisopropylamino.

[0031] The C 13 -C 20 Aryl groups include, but are not limited to, diphenylmethyl, triphenylmethyl, etc.

[0032] The C6-C 20 Aromatic amino groups include, but are not limited to, diphenylamino, dinaphthylamino, and di(p-methylphenyl)amino.

[0033] Preferably, the nickel complex of Formula 1 of the present invention has any of the following structures:

[0034]

[0035] In some specific embodiments of the present invention, the nickel complex shown in Formula 1 has any of the following structures:

[0036]

[0037] The present invention also provides a method for catalytic polymerization of ethylene, wherein the above-mentioned supported nickel catalyst is used to catalyze the polymerization reaction of ethylene.

[0038] Preferably, the polymerization reaction temperature is ≤50℃; more preferably, it is ≤15℃.

[0039] The pressure of the polymerization reaction is ≥10 bar; more preferably ≥20 bar.

[0040] Because the supported nickel catalyst described in this invention has good stability, it is possible to place the supported nickel catalyst in the ethylene polymerization equipment for a period of time before introducing ethylene. This solves the problem of poor stability of active catalysts, which cannot be stored for a long time and must react with the monomers in a timely manner.

[0041] Using the above-mentioned catalytic ethylene polymerization method, the ultra-high molecular weight polyethylene obtained has a branching degree of less than 5 branches per 1,000 carbon atoms.

[0042] The molecular weight distribution of the ultra-high molecular weight polyethylene is less than 3.5; more preferably less than 3.0.

[0043] In some specific embodiments of the present invention, the weight-average molecular weight of the ultra-high molecular weight polyethylene is 4.02 million, 3.98 million, 3.8 million, 3.6 million, 3.45 million, or 2.88 million.

[0044] Compared with the prior art, the present invention provides a supported nickel catalyst prepared by a mixed reaction of alkylmagnesium, alkylaluminum chloride and a nickel complex of Formula 1; wherein R and R' are independently selected from C1-C1. 10 Alkyl, C6-C 18 Aryl, C1-C 30 Alkoxy, C2-C 30 Alkylamino, C6-C 30 Aryloxy group, C6-C 30 Aromatic amino, C 10 -C 30 Aryl alkyl, C3-C 30 One or more of silanoxy, halogen, and nitro groups. The supported nickel catalyst exhibits excellent stability and high catalytic activity, enabling large-scale production and application. Using the supported nickel catalyst described in this invention to catalyze ethylene production yields ultra-high molecular weight polyethylene with low branching, narrow molecular weight distribution, good mechanical properties, and easy processing, without residue sticking. Attached Figure Description

[0045] Figure 1 The high-temperature (110°C) proton NMR spectrum of the polymer prepared in Example 1 is shown below. 1 HNMR);

[0046] Figure 2 The high-temperature (150°C) gel permeation chromatography (GPC) spectrum of the polymer prepared in Example 1 is shown.

[0047] Figure 3 The image shows the differential scanning calorimetry (DSC) spectrum of the polymer prepared in Example 1. Detailed Implementation

[0048] To further illustrate the present invention, the supported nickel catalyst and the method for catalytic ethylene polymerization provided by the present invention will be described in detail below with reference to embodiments.

[0049] The polymerization reactor can be a 200mL or 20L Swiss Buchi reactor or a 1L Beijing Century Senlang AC1000ml fully automatic reactor.

[0050] The polymerization solvents used are selected from n-hexane or toluene, both of which are from Braun's solvent handling system.

[0051] Example 1

[0052] (1) Preparation of nickel complexes

[0053] The nickel complex structure (R = -CH₂Ph, R' = Me) is as follows:

[0054]

[0055] The preparation process of the above nickel complex is as follows:

[0056] 4-Methyl-2,6-dibromoaniline and pinacol diboronic acid ester were coupled under palladium catalysis to prepare 4-methyl-2,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)aniline. 4-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborane)aniline was then coupled with 1-benzyl-4-iodobenzene under tetra(triphenylphosphine)palladium catalysis (in a toluene / ethanol / water mixed solvent, reacted at 90°C for 24 hours) to yield 4-methyl-2,6-bis(p-benzylphenyl)aniline.

[0057] The aniline and 2,3-butanedione were reacted in toluene at 80°C for 24 hours under the catalysis of p-toluenesulfonic acid. The reaction was then carried out by reflux with a water separator for 3 days. The solvent was removed by concentration and the mixture was washed several times with methanol to obtain the target α-diimine ligand.

[0058] The ligand was reacted with an equimolar amount of nickel dibromide (ethylene glycol dimethyl ether) in dichloromethane for 3 days. The solvent was removed by concentration, and the target nickel complex was obtained by recrystallization in a dichloromethane / n-hexane mixed solvent.

[0059] (2) Ethylene polymerization reaction

[0060] First, the jacket temperature of the 20L reactor was set to 120℃ and the reactor was vacuum-dried. The temperature inside the reactor was then lowered to 15℃ using a circulating oil bath and maintained. Then, 4.9L of hexane was added to the reactor.

[0061] Under a nitrogen atmosphere, diethylaluminum chloride (500 equivalents, 34 mL), dibutylmagnesium (250 equivalents, 17 mL), and the above-mentioned nickel complex (68 μmol, 78 mg) previously dissolved in dichloromethane, along with 100 mL of n-hexane, were mixed and stirred until homogeneous to complete the in-situ loading process and obtain a supported nickel catalyst, which was then loaded into an ampoule.

[0062] Under vacuum, the supported nickel catalyst in the ampoule was added to a 20L reactor, followed by the introduction of ethylene, and the polymerization reaction was carried out at a pressure of 25 bar and a temperature of 15°C for 60 minutes.

[0063] After polymerization, the polymerization vessel was inverted, and the reacted polymer was poured out. Ethanol was added, and the mixture was stirred with a 1 mol / L hydrochloric acid solution for 120 minutes. The polymer was filtered and then dried in a vacuum oven to obtain 353 g of polymer in granular form, without any sticking to the vessel.

[0064] Through high temperature 1 ¹H NMR analysis (Bruker AV400 NMR spectrometer, using deuterated tetrachloroethane as solvent) yielded a calculated polymer branching degree of approximately 1.7 brs / 1000°C. Figure 1 The Mw was determined by high-temperature GPC analysis using a PL-GPC 220 gel permeation chromatography system at 150℃ with 1,2,4-trichlorobenzene as the mobile phase. The results showed an Mw of approximately 4.02 million and a PDI of 2.22. Figure 2 The polymer melting point was tested using a DSC3 or Q2000 differential scanning calorimeter at a scan rate of 10℃ / min and a scan range of 50℃-180℃. Specifically, the melting point after the second heating was measured to be 131.5℃ using DSC. Figure 3 The unnotched impact strength of the polymer, measured using a JJ-20 memory impact testing machine from Changchun Intelligent Instrument Equipment Co., Ltd., was 63.83 kJ / m. 2 The impact strength of the cantilever beam, measured using a cantilever beam impact testing machine manufactured by Chengde Testing Machine Factory, was 64 KJ / M. 2 Its density, measured by a true density meter, is approximately 0.9177 g / cm³. 3 .

[0065] Stability verification experiment:

[0066] Similar to step (2) above, the difference is that after the in-situ loading process is completed, the supported nickel catalyst is added to a 20L reactor at 15°C and stirred for 1 hour in the absence of ethylene. Then, ethylene is introduced to carry out the polymerization reaction, and 332g of polymer is obtained. It is in granular state and there is no sticking to the reactor.

[0067] Because mixing the diethylaluminum chloride, dibutylmagnesium chloride, and nickel complex described in this invention generates a supported nickel catalyst containing active centers. Normally, in the absence of ethylene, the active centers of this supported nickel catalyst are unstable, and leaving the catalyst for a period of time leads to a significant decrease in activity. However, the above verification experiments show that the supported nickel catalyst described in this invention has strong stability, and its activity decreases very little after 1 hour of storage.

[0068] Example 2

[0069] Same as Example 1, except that the nickel complex structure is as follows:

[0070]

[0071] The synthesis of the above nickel complex follows the same route as the nickel complex in Example 1, except that 1-benzyl-4-iodobenzene is replaced with 1-diphenylmethyl-4-iodobenzene.

[0072] The difference in the ethylene polymerization reaction is that it is carried out at 30°C, and 367g of polymer is finally obtained. The polymer is in granular state and there is no problem of sticking to the reactor.

[0073] Through high temperature 1 ¹H NMR analysis yielded a polymer branching degree of approximately 3.0 brs / 1000°C; high-temperature GPC analysis determined a polymer Mw of approximately 3.45 million and a PDI of 2.40; DSC analysis revealed a melting point of 130.5°C. The unnotched impact strength of the simply supported beam is 63.00 kJ / m². 2 The impact strength of the cantilever beam with double notches is 61 kJ / m. 2 .

[0074] The stability verification experiment was the same as in Example 1, and the result was 358g of polymer, which was in granular state and did not stick to the reactor.

[0075] Example 3

[0076] Same as Example 1, except that the nickel complex structure is as follows:

[0077]

[0078] The synthesis of the above nickel complex follows the same route as the nickel complex in Example 1, except that p-methylaniline is replaced with p-fluoroaniline.

[0079] The difference in the ethylene polymerization reaction is that it is carried out at 25°C, and 380g of polymer is finally obtained. The polymer is in granular state and there is no problem of sticking to the reactor.

[0080] Through high temperature 1 ¹H NMR analysis yielded a polymer branching degree of approximately 2.8 brs / 1000°C; high-temperature GPC analysis determined a polymer Mw of approximately 2.88 million and a PDI of 2.50; DSC analysis revealed a melting point of 131.2°C. The unnotched impact strength of the simply supported beam is 61.00 kJ / m. 2 The impact strength of the cantilever beam with double notches is 58 kJ / m. 2 .

[0081] The stability verification experiment was the same as in Example 1, and the result was 333g of polymer, which was in granular state and did not stick to the reactor.

[0082] Example 4

[0083] Same as Example 1, except that the nickel complex structure is as follows:

[0084]

[0085] The synthesis of the above nickel complex follows the same route as the nickel complex in Example 1, except that p-methylaniline is replaced with p-methoxyaniline.

[0086] The difference in the ethylene polymerization reaction is that it is carried out at 45°C, and 360g of polymer is finally obtained. The polymer is in granular state and there is no problem of sticking to the reactor.

[0087] Through high temperature 1 ¹H NMR analysis yielded a polymer branching degree of approximately 5.0 brs / 1000°C; high-temperature GPC analysis determined a polymer Mw of approximately 3.98 million and a PDI of 2.70; DSC analysis revealed a melting point of 129.8°C. The unnotched impact strength of the simply supported beam was 58.00 kJ / m. 2 The impact strength of the cantilever beam with double notches is 59 KJ / M. 2 .

[0088] The stability verification experiment was the same as in Example 1, and the result was 355g of polymer, which was in granular state and did not stick to the reactor.

[0089] Example 5

[0090] Same as Example 1, except that the nickel complex structure is as follows:

[0091]

[0092] The synthesis of the above nickel complex follows the same route as the nickel complex in Example 1, except that 1-benzyl-4-iodobenzene is replaced with 1-(9-anthrayl)-4-bromobenzene.

[0093] The difference in the ethylene polymerization reaction is that it is carried out at 50°C, and 340g of polymer is finally obtained. The polymer is in granular state and there is no problem of sticking to the reactor.

[0094] Through high temperature 1 ¹H NMR analysis yielded a polymer branching degree of approximately 4.8 brs / 1000°C; high-temperature GPC analysis determined a polymer Mw of approximately 3.8 million and a PDI of 2.30; DSC analysis revealed a melting point of 131.8°C. The unnotched impact strength of the simply supported beam is 55.00 kJ / m. 2 The impact strength of the cantilever beam with double notches is 52 kJ / m. 2 .

[0095] The stability verification experiment was the same as in Example 1, and the result was 337g of polymer, which was in granular form and did not stick to the reactor.

[0096] Example 6

[0097] Same as Example 1, except that the nickel complex structure is as follows:

[0098]

[0099] The synthesis of the above nickel complex was carried out according to CN 113045453 A and the method of Example 1. The sterically hindered aromatic amine was prepared by coupling 4-(9H-carbazole-9-yl)phenylboronic acid with 2,6-dibromo-4-methylaniline under palladium catalysis. The remaining steps were carried out according to the route of Example 1.

[0100] The ethylene polymerization reaction was distinguished by being carried out at 25°C, ultimately yielding 240g of polymer, which was in particulate form, thus mitigating the problem of sticking to the reactor compared to homogeneous polymerization.

[0101] Through high temperature 1 ¹H NMR analysis yielded a polymer branching degree of approximately 3.8 brs / 1000°C; high-temperature GPC analysis determined a polymer Mw of approximately 3.6 million and a PDI of 2.44; DSC analysis revealed a melting point of 130.0°C. The unnotched impact strength of the simply supported beam was 47.00 kJ / m. 2 The impact strength of the cantilever beam with double notches is 56 kJ / m. 2 .

[0102] The stability verification experiment was the same as in Example 1, and the result was 200g of polymer, which was in granular form and did not stick to the reactor.

[0103] In summary, the supported nickel catalyst of this invention exhibits excellent stability and high catalytic activity. The prepared UHMWPE is granular, with significantly reduced adhesion to the reactor and good processing performance.

[0104] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A supported nickel catalyst characterized in that, Prepared by mixing reaction of alkyl magnesium, alkyl aluminum chloride and nickel complex of formula 1; Formula 1; wherein R and R' are independently selected from C1-C 10 alkyl, C6-C 18 aryl, C6-C 18 heteroaryl, C1-C 30 alkoxy, C2-C 30 alkylamino, C6-C 30 aryloxy, C6-C 30 aralkyl, C3-C 10 -C 30 aryl, C6-C 30 siloxy, halogen, nitro; The above reaction is a reaction of dispersing the alkyl magnesium, alkyl aluminum chloride and nickel complex of formula 1 in a solvent; In the above reaction, the alkyl magnesium and alkyl aluminum chloride generate in situ a magnesium chloride carrier; The alkyl aluminum chloride and nickel complex of formula 1 generate in situ a cationic nickel active species; The cationic nickel active species is supported on the in-situ generated magnesium chloride carrier.

2. The supported nickel catalyst according to claim 1, characterized in that, The molar ratio of aluminum element and nickel element in the alkyl aluminum chloride and nickel complex of formula 1 is (200-1000):

1.

3. The supported nickel catalyst of claim 1, wherein the support is selected from the group consisting of silica, alumina, titania, zirconia, ceria, magnesia, calcium oxide, baria, strontia, and mixtures thereof. The molar ratio of magnesium element and nickel element in the alkyl magnesium and nickel complex of formula 1 is (10-500):

1.

4. The supported nickel catalyst of claim 1, wherein the support is selected from the group consisting of silica, alumina, titania, zirconia, ceria, magnesia, calcium oxide, baria, strontia, and mixtures thereof. The molar ratio of aluminum element and magnesium element in the alkyl aluminum chloride and alkyl magnesium is (1-10):

1.

5. The supported nickel catalyst according to any one of claims 1 to 4, characterized in that, The alkyl aluminum chloride is selected from one or more of diethyl aluminum chloride, dimethyl aluminum chloride, ethyl aluminum dichloride, dibutyl aluminum chloride, methyl aluminum dichloride, and sesquiethyl aluminum chloride.

6. The supported nickel catalyst of claim 1, wherein, The alkyl magnesium is selected from dibutyl magnesium or diethyl magnesium.

7. The supported nickel catalyst of claim 1, wherein, R and R' are independently selected from C1-C5alkyl, C6-C 12 aryl, C6-C 12 heteroaryl, C1-C 10 alkoxy, C2-C6alkylamino, C6-C 30 aryloxy, C6-C 20 armino, C 13 -C 20 aralkyl, C3-C 20 siloxy, halogen, nitro.

8. The supported nickel catalyst of claim 1, wherein, The nickel complex of formula 1 has any one of the following structures: 。 9. A process for catalyzing the polymerization of ethylene, characterized in that, The supported nickel catalyst of any one of claims 1-8 is used to catalyze the polymerization of ethylene.

10. The method of claim 9, wherein, The temperature of the polymerization reaction is ≤ 50°C; The pressure of the polymerization reaction is ≥ 10 bar.

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