Preparation method of late transition metal catalyst for synthesizing hyperbranched polyethylene

Abstract

The invention relates to the technical field of high-molecular compounds, and particularly discloses a preparation method of a late transition metal catalyst for synthesizing hyperbranched polyethylene. The preparation method comprises the following steps: under the protection of inert gas, dissolving p-phenylenediamine into anhydrous alcohol, adding pyridine-2-formaldehyde into a mixed solution, and heating to react to obtain a ligand A; the method comprises the following steps: under the protection of inert gas, dropwise adding an alcoholic solution of a metal precursor into a chlorinated alkane solution dissolved with a ligand A, and then fully reacting at room temperature; and after the reaction is finished, purifying the product to obtain the late transition metal catalyst. The metal precursor is a bivalent Fe salt, a bivalent Co salt and a bivalent Ni salt. According to the synthetic catalyst, the polymerization activity of the late transition metal catalyst can be enhanced, and the synthesis of hyperbranched polyethylene is facilitated. The molecular weight of the hyperbranched polyethylene catalyzed by the catalyst is 1.1-2.6 kg / mol, the molecular weight distribution PDI is less than 2, and the branching degree is more than 100.

Description

Technical Field

[0001] The invention relates to the technical field of polymer compounds, and particularly discloses a method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene. Background Art

[0002] During the rapid development of the polyolefin industry, polyolefin catalysts have undergone three major phases: Ziegler-Natta catalysts, metallocene catalysts, and late transition metal catalysts. While Ziegler-Natta and metallocene catalysts are currently the most widely used catalysts, traditional Ziegler-Natta and metallocene catalysts primarily produce branched polyethylene through the copolymerization of ethylene and long-chain α-olefins. Late transition metal catalysts can synthesize branched or hyperbranched polyethylene using ethylene as the sole monomer, representing a breakthrough in production methods that are simpler and faster than traditional processes.

[0003] Late transition metals are single-site catalytic systems, with complexes containing Group VIIIB metal atoms such as Fe, Co, Ni, Pd, and Ru as the active center, used to catalyze olefin polymerization. Transition metals coordinate with amino alcohols, phosphites, nitrogen heterocyclic carbenes, and Schiff bases to form corresponding catalysts. Compared with transition metal catalysts containing other ligands, Schiff base transition metal catalysts have attracted widespread attention due to their advantages such as simple synthesis, higher catalytic activity, adjustable catalytic products through group modification, and good functional group tolerance.

[0004] At the same time, different metals as active centers affect the activity and selectivity of the catalyst. Therefore, it is of great significance to study Schiff base transition metal catalysts with different metal active centers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to prepare a late transition metal catalyst for synthesizing hyperbranched polyethylene by using different metals as active centers, thereby improving the activity and selectivity of the catalyst.

[0006] The technical solution adopted in the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene, comprising the following steps:

[0008] S1. Preparation of ligand: Under inert gas, p-phenylenediamine is dissolved in anhydrous alcohol at a concentration of 2-4 mol / L. Pyridine-2-carboxaldehyde is added to the mixed solution at room temperature to a concentration of 4-9 mol / L. The solution is then heated to 60-90°C. After the reaction is complete and the reaction solution is cooled to room temperature, the product is purified to obtain ligand A.

[0009] S2. Preparation of the Metal Complex: Under inert gas, an alcohol solution of the metal precursor is added dropwise to a chlorinated alkane solution containing ligand A, followed by a complete reaction at room temperature. After completion of the reaction, the product is purified to obtain a late transition metal catalyst.

[0010] The metal precursor is a divalent Fe, Co, or Ni salt;

[0011] The molar ratio of the metal precursor to the ligand A is 5:1 to 5:2.

[0012] Preferably, the metal precursor is FeCl2·4H2O, CoCl2·6H2O or NiCl2·6H2O.

[0013] Preferably, in step S1, p-phenylenediamine is dissolved in anhydrous ethanol; in step S2, the metal precursor is dissolved in methanol, and the ligand is dissolved in dichloromethane.

[0014] Preferably, in step S1, pyridine-2-carboxaldehyde is added dropwise to the mixed solution; after the addition is completed, the solution is heated to 80° C. and refluxed for 6 hours.

[0015] Furthermore, in step S1, the product purification operation is: filtering, washing with methanol three times, and recrystallizing to obtain ligand A.

[0016] Preferably, in step S2, the product purification operation is: filtering and washing with methanol three times. The obtained product is recrystallized in a mixed solution of dichloromethane and n-hexane.

[0017] In a second aspect, the present invention provides a late transition metal catalyst for synthesizing hyperbranched polyethylene, which is prepared by the method described in the first aspect.

[0018] In a third aspect, the present invention provides an application of the late transition metal catalyst described in the second aspect for synthesizing hyperbranched polyethylene.

[0019] Preferably, after the catalyst is dissolved in a solvent, ethylene gas and a co-catalyst are added, and the polymerization reaction is carried out at a pressure of not less than 2 MPa.

[0020] Furthermore, the hyperbranched polyethylene has a molecular weight of 1.1 to 2.6 kg / mol, a molecular weight distribution PDI of less than 2, and a branching degree of more than 100.

[0021] The beneficial effects achieved by the present invention are:

[0022] The present invention uses different metals as active center catalysts to enhance the polymerization activity of late transition metal catalysts, facilitating the synthesis of hyperbranched polyethylene. The hyperbranched polyethylene produced by the catalytic institute has a molecular weight of 1.1 to 2.6 kg / mol, a molecular weight distribution (PDI) of less than 2, and a degree of branching exceeding 100. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear and distinct, the present invention is further described in detail with reference to the following examples. It should be noted that the present invention is not limited to the following examples.

[0024] Example 1

[0025] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex a.

[0026] Under nitrogen, a 10 mmol solution of NiCl2·6H2O in methanol was added dropwise to a 3 mmol solution of the ligand in dichloromethane. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex a.

[0027] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing metal complex a were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 2.6 kg / mol, a molecular weight distribution (PDI) of 1.5, and a degree of branching of 150.

[0028] Example 2

[0029] Under nitrogen, 15 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex b.

[0030] Under nitrogen, a 10 mmol solution of NiCl2·6H2O in methanol was added dropwise to a 3 mmol solution of the ligand in dichloromethane. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex b.

[0031] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180ml of n-hexane solvent, 0.2ml of the co-catalyst TIBa, and 20ml of the reaction solvent n-hexane containing the metal complex b were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.6kg / mol, a molecular weight distribution (PDI) of 1.9, and a degree of branching of 110.

[0032] Example 3

[0033] Under nitrogen, 25 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex c.

[0034] Under nitrogen, a 10 mmol solution of NiCl2·6H2O in methanol was added dropwise to a 3 mmol solution of the ligand in dichloromethane. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex c.

[0035] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180ml of n-hexane solvent, 0.2ml of the co-catalyst TIBa, and 20ml of the reaction solvent n-hexane containing the metal complex C were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.4kg / mol, a molecular weight distribution (PDI) of 1.7, and a degree of branching of 105.

[0036] Example 4

[0037] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 35 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex d.

[0038] Under nitrogen, a 10 mmol solution of NiCl2·6H2O in methanol was added dropwise to a 3 mmol solution of the ligand in dichloromethane. The mixture was allowed to react at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex d.

[0039] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing the metal complex d were added to the reactor via a feed tank. The pressure in the reactor was raised to 3 MPa, and the polymerization reaction began. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.6 kg / mol, a molecular weight distribution (PDI) of 1.9, and a degree of branching of 110.

[0040] Example 5

[0041] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 50 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex e.

[0042] Under nitrogen protection, 10mmolNiC l2 A methanol solution of 6H₂O was added dropwise to a dichloromethane solution containing 3 mmol of the ligand. The mixture was allowed to react at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex e.

[0043] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180ml of n-hexane solvent, 0.2ml of the co-catalyst TIBa, and 20ml of the reaction solvent n-hexane containing the metal complex e were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.7kg / mol, a molecular weight distribution (PDI) of 1.7, and a degree of branching of 115.

[0044] Example 6

[0045] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex a.

[0046] Under nitrogen, a 10 mmol solution of FeCl2·4H2O in methanol was added dropwise to a 3 mmol solution of the ligand in dichloromethane. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex f.

[0047] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing the metal complex f were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 2.0 kg / mol, a molecular weight distribution (PDI) of 1.5, and a degree of branching of 105.

[0048] Example 7

[0049] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex a.

[0050] Under nitrogen, a 10 mmol methanol solution of CoCl2·6H2O was added dropwise to a 3 mmol ligand solution in dichloromethane. The mixture was allowed to react at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex g.

[0051] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing the metal complex g were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.4 kg / mol, a molecular weight distribution (PDI) of 1.9, and a degree of branching of 120.

[0052] Example 8

[0053] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex a.

[0054] Under nitrogen, a 10 mmol methanol solution of NiCl2·6H2O was added dropwise to a 2 mmol ligand solution in dichloromethane. The mixture was allowed to react at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex h.

[0055] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing the metal complex h were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.7 kg / mol, a molecular weight distribution (PDI) of 1.9, and a degree of branching of 120.

[0056] Example 9

[0057] Under nitrogen, 20 mmol of p-phenylenediamine was dissolved in 70 mL of anhydrous ethanol. At room temperature, 45 mmol of pyridine-2-carboxaldehyde was added dropwise to the mixed solution. After the addition was complete, the solution was heated to 80°C and refluxed for 6 hours. After the reaction was complete and the temperature of the reaction solution cooled to room temperature, the product was filtered and washed three times with methanol. Recrystallization afforded a yellow solid powder, complex a.

[0058] Under nitrogen protection, a 10 mmol solution of FeCl2·4H2O in methanol was added dropwise to a 4 mmol solution of the ligand in dichloromethane. The reaction was allowed to proceed at room temperature for 24 hours. After the reaction, the product was filtered and washed three times with methanol. The resulting product was recrystallized from a mixture of dichloromethane and n-hexane (volume ratio 2:1) to obtain a solid powder, namely, metal complex i.

[0059] The reactor was first heated to 100°C and held for 30 minutes. The temperature was then lowered to the set point using a built-in condenser, and the air in the reactor was replaced three times with ethylene gas. Under magnetic stirring, 180 ml of n-hexane solvent, 0.2 ml of the co-catalyst TIBa, and 20 ml of the reaction solvent n-hexane containing the metal complex i were added to the reactor via a feed tank. Simultaneously, the ethylene valve was quickly opened, raising the pressure in the reactor to 3 MPa to initiate the polymerization reaction. After the reaction was complete, the reactor temperature was lowered to room temperature, the pressure was vented, and the product was collected for performance evaluation. The resulting hyperbranched polyethylene product had a molecular weight of 1.9 kg / mol, a molecular weight distribution (PDI) of 1.8, and a degree of branching of 130.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene, characterized in that: The steps include: S1. Preparation of ligand: Under inert gas, p-phenylenediamine is dissolved in anhydrous alcohol at a concentration of 2-4 mol / L. Pyridine-2-carboxaldehyde is added to the mixed solution at room temperature to a concentration of 4-9 mol / L. The solution is then heated to 60-90°C. After the reaction is complete and the reaction solution is cooled to room temperature, the product is purified to obtain ligand A. S2. Preparation of the Metal Complex: Under inert gas, an alcohol solution of the metal precursor is added dropwise to a chlorinated alkane solution containing ligand A, followed by a complete reaction at room temperature. After completion of the reaction, the product is purified to obtain a late transition metal catalyst. The metal precursor is a divalent Fe, Co, or Ni salt; The molar ratio of the metal precursor to the ligand A is 5:1 to 5:

2.

2. The method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene according to claim 1, wherein The metal precursor is FeCl2·4H2O, CoCl2·6H2O or NiCl2·6H2O.

3. The preparation method of the late transition metal catalyst for synthesizing hyperbranched polyethylene according to claim 1, wherein In step S1, p-phenylenediamine is dissolved in anhydrous ethanol; in step S2, the metal precursor is dissolved in methanol, and the ligand is dissolved in dichloromethane.

4. The method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene according to claim 1, wherein In step S1, pyridine-2-carboxaldehyde is added dropwise to the mixed solution; after the addition is completed, the solution is heated to 80° C. and refluxed for 6 hours.

5. The method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene according to claim 4, wherein In step S1, the product purification operation is: filtering, washing with methanol three times, and recrystallizing to obtain ligand A.

6. The method for preparing a late transition metal catalyst for synthesizing hyperbranched polyethylene according to claim 1, wherein In step S2, the product is purified by filtering and washing with methanol three times, and the obtained product is recrystallized in a mixed solution of dichloromethane and n-hexane.

7. A late transition metal catalyst for synthesizing hyperbranched polyethylene, prepared by the method according to any one of claims 1 to 6.

8. Use of the late transition metal catalyst according to claim 7 for synthesizing hyperbranched polyethylene.

9. The use of the late transition metal catalyst according to claim 8 for synthesizing hyperbranched polyethylene, characterized in that: After the catalyst is dissolved in the solvent, ethylene gas and a co-catalyst are added, and a polymerization reaction is carried out at a pressure not less than 2 MPa.

10. Use of the late transition metal catalyst according to claim 9 for synthesizing hyperbranched polyethylene, characterized in that: The hyperbranched polyethylene has a molecular weight of 1.1 to 2.6 kg / mol, a molecular weight distribution PDI of less than 2, and a branching degree of more than 100.