阅读说明：本技术 一类叠加大位阻α-二亚胺配体、镍催化剂及其制备方法和应用 (Overlapped steric hindrance-enhanced alpha-diimine ligand, nickel catalyst, preparation method and application thereof ) 是由 简忠保 夏健 张燚鑫 于 2020-05-21 设计创作，主要内容包括：本发明提供一类叠加大位阻α-二亚胺配体、镍催化剂及其制备方法和应用。属于催化剂领域。该配体的结构如式(I)所示。本发明还提供一类叠加大位阻α-二亚胺配体的制备方法。本发明还提供一种镍催化剂,结构如式(II)所示。本发明还提供一种镍催化剂的制备方法。该类镍催化剂在一定条件下,催化乙烯聚合活性可高达1026.0×10<Sup>6</Sup>g mol<Sup>-1</Sup>h<Sup>-1</Sup>,且可得到超高分子量,支化度可调的聚乙烯。此外,在110～150℃高温下,该类催化剂仍然具有相当高的催化活性。其中,超高分子量低支化度聚乙烯具有良好的工业应用前景,在一定程度上可考虑作为超高分子量聚乙烯纤维使用。(The invention provides a cascade steric hindrance-increased α -diimine ligand, a nickel catalyst, a preparation method and application thereof, belongs to the field of catalysts, and has a structure shown in a formula (I). the invention also provides a preparation method of the cascade steric hindrance-increased α -diimine ligand, a nickel catalyst with a structure shown in a formula (II) and a preparation method of the nickel catalyst, wherein the activity of catalyzing ethylene polymerization can reach 1026.0 × 10 under certain conditions 6 g mol ‑1 h ‑1 And the polyethylene with ultrahigh molecular weight and adjustable branching degree can be obtained. In addition, the catalyst still has quite high catalytic activity at the high temperature of 110-150 ℃. The ultrahigh molecular weight low-branching polyethylene has good industrial application prospect, and can be considered as the ultrahigh molecular weight polyethylene fiber to a certain extent.)

1. A cascade steric hindrance-enhanced alpha-diimine ligand is characterized in that the structure is shown as the formula (I):

in the formula (I), R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

2. A stack sterically hindered α -diimine ligand as set forth in claim 1 having the formula:

3. the method for preparing a sterically hindered α -diimine ligand of claim 1 which comprises:

the method comprises the following steps: dissolving aniline with a general formula (b) and diketone with a general formula (a) in a solvent, adding a catalyst, and reacting at 25-80 ℃ to obtain a monoimine product with a structural formula (c);

step two: dissolving a monoimine product with a structural formula shown as (c) and aniline with a general formula shown as (b) in a solvent, adding a catalyst, and carrying out reflux reaction on a reaction mixture to obtain a cascade-enlarged steric hindrance alpha-diimine ligand with a structure shown as a formula (I);

4. the method for preparing a sterically hindered α -diimine ligand of claim 3, wherein in step two, the molar ratio of the monoimine product of formula (c) to the aniline of formula (b) is 1: 1.

5. a nickel catalyst is characterized by having a structure shown in a formula (II):

in the formula (II), R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

6. The nickel catalyst of claim 5, having the formula:

7. the method for preparing a nickel catalyst according to claim 5, comprising:

the structure of the compound is shown as the formula (I) and the steric hindrance of α -diimine ligand and NiBr are increased₂(DME) (DME ═ 1, 2-dimethoxyethane) is dissolved in dichloromethane or chloroform solvent to react to obtain the nickel catalyst with the structure shown in the formula (II);

8. the method of claim 7, wherein the structure of the sterically bulky α -diimine ligand and NiBr is represented by formula (I)₂(DME) in a molar ratio of 1: 1.

9. use of a nickel catalyst according to claim 5 for the catalysis of polyethylene polymerization.

10. The use of a nickel catalyst according to claim 9 for catalyzing the polymerization of polyethylene, wherein said nickel catalyst catalyzes the polymerization of polyethylene by:

connecting a reactor with a high-pressure gas line, adjusting the temperature of the reactor to 0-150 ℃, adding a solvent and a cocatalyst into the reactor under an inert atmosphere, then injecting a dichloromethane or chloroform solution of a nickel catalyst into the reactor, introducing ethylene while stirring and keeping the pressure at 4-40atm, and reacting for 1-6min to obtain the polyethylene.

Technical Field

The invention belongs to the field of catalysts, and particularly relates to a superposed large-steric-hindrance alpha-diimine ligand, a nickel catalyst, and a preparation method and application thereof.

Background

Since 1995, α -nickel diimine catalyst (J.Am. chem. Soc.1995,117,6414) has been developed to be a very useful class of ethylene polymerization catalyst due to a unique chain-walking mechanism, however, in order to better satisfy the industrial demand, the catalytic activity of the catalyst is still to be improved (currently, α -nickel diimine catalyst catalyzes ethylene polymerization with the highest activity of 1.0 × 10⁸g mol^-1h^-1Macromolecules 2000,33,7, 2320). In order to increase the catalytic activity of the catalyst and to obtain (ultra) high molecular weight polymers at the same time, it is currently common practice to adjust the axial steric hindrance of the catalyst or to regulate the electronic effect of the ligand.

Although the alpha-nickel diimine catalyst can obtain (ultra) high molecular weight (millions) of polymers by regulating the steric effect and the electronic effect of the ligand in the aspect of catalyzing ethylene polymerization, the catalytic activity is still to be improved. Meanwhile, the existing alpha-diimine nickel catalyst is difficult to combine the characteristics of high thermal stability, high activity and high molecular weight, so that the industrial application is limited to a certain extent.

Disclosure of Invention

The invention aims to provide a cascade enlarged steric hindrance alpha-diimine ligand, a nickel catalyst, a preparation method and application thereof, wherein the nickel catalyst has the characteristics of high thermal stability, high activity and high molecular weight.

The invention firstly provides a cascade enlarged steric hindrance alpha-diimine ligand, the structure of which is shown as the formula (I):

in the formula (I), R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

Preferably, the class of sterically hindered α -diimine ligands has the following structural formula:

the invention also provides a preparation method of the cascade enlarged steric hindrance alpha-diimine ligand, which comprises the following steps:

the method comprises the following steps: dissolving aniline with a general formula (b) and diketone with a general formula (a) in a solvent, adding a catalyst, and reacting at 25-80 ℃ to obtain a monoimine product with a structural formula (c);

step two: dissolving a monoimine product with a structural formula shown as (c) and aniline with a general formula shown as (b) in a solvent, adding a catalyst, and carrying out reflux reaction on a reaction mixture to obtain a cascade-enlarged steric hindrance alpha-diimine ligand with a structure shown as a formula (I);

preferably, in the second step, the molar ratio of the monoimine product of formula (c) to the aniline of formula (b) is 1: 1.

the invention also provides a nickel catalyst, which has a structure shown in the formula (II):

in the formula (II), R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

Preferably, the nickel catalyst has the following structural formula:

the invention also provides a preparation method of the nickel catalyst, which comprises the following steps:

the structure of the compound is shown as the formula (I) and the steric hindrance of α -diimine ligand and NiBr are increased₂(DME) (DME ═ 1, 2-dimethoxyethane) is dissolved in dichloromethane or chloroform solvent to react to obtain the nickel catalyst with the structure shown in the formula (II);

preferably, the structure is represented by formula (I), i.e., a class of stacked sterically bulky α -diimine ligands and NiBr₂(DME) in a molar ratio of 1: 1.

the invention also provides the application of the nickel catalyst in catalyzing polyethylene polymerization.

The invention also provides a method for catalyzing polyethylene by using the nickel catalyst, which comprises the following steps:

connecting a reactor with a high-pressure gas line, adjusting the temperature of the reactor to 0-150 ℃, adding a solvent and a cocatalyst into the reactor under an inert atmosphere, then injecting a dichloromethane or chloroform solution of a nickel catalyst into the reactor, introducing ethylene while stirring and keeping the pressure at 4-40atm, and reacting for 1-6min to obtain the polyethylene.

Principle of the invention

The invention provides a superposed and sterically-enhanced alpha-diimine ligand, a nickel catalyst and a preparation method thereof, wherein the superposed and sterically-enhanced principle is shown in figure 1, namely double-layer steric hindrance is introduced at 2, 6-positions of an N-aromatic ring: the first layer of steric hindrance plays a role in steric hindrance at the axial position of the metal center, and simultaneously provides enough space around the metal center, so that the coordination insertion of olefin is facilitated, the chain growth is accelerated, and the polymerization activity is improved; the second layer of steric hindrance further provides steric hindrance at the axial position of the metal center while forming a key spatial cross-locking closure; the formation of the blocking and closing effect hinders chain transfer reaction caused by olefin synergistic replacement, not only can improve the molecular weight of the polymer and regulate the branching degree of the polymer, but also can open the first layer of steric hindrance through the repulsion effect formed by space staggering, and increase the space around the metal center, thereby improving the polymerization activity again. The core of the strategy is that a space staggered blocking effect is formed while large axial steric hindrance is kept through smart superposition of double-layer steric hindrance.

The invention has the advantages of

The invention provides a cascade enlarged steric hindrance α -diimine ligand, a nickel catalyst and a preparation method thereofThe nickel catalyst can catalyze the polymerization of ethylene to 1026.0 × 10⁶g mol^-1h^-1And the polyethylene with ultrahigh molecular weight (Mw of 3.1-500.4 ten thousand) and adjustable branching degree (branching degree of 3-32/1000C) can be obtained, and in addition, the catalyst still has quite high catalytic activity (2.1 × 10)⁶～2.1×10⁷g mol^-1h^-1). The ultrahigh molecular weight low-branching polyethylene has good industrial application prospect, and can be considered as the ultrahigh molecular weight polyethylene fiber to a certain extent. Ultra-high molecular weight polyethylene fibers have internationally become a high-tech material which is developed vigorously in the 21 st century. Ropes, textile fabrics and composite materials made of ultra-high molecular weight polyethylene fibers are widely used in various fields such as national defense and military industry, aerospace, marine industry, sports equipment, medical treatment and health, building industry and the like, and play a very important role. And the ultrahigh polymerization activity of the catalyst can greatly reduce the production cost of the catalyst and meet the potential requirements of industrial production.

Drawings

FIG. 1 is a schematic view of the principle of the superimposed large steric hindrance of the present invention;

FIG. 2 is a single crystal diffractogram of an alpha-diimine nickel catalyst prepared in example 4 of this invention;

FIG. 3 is a NMR chart of an alpha-diimine nickel catalyst prepared in example 4 of this invention;

FIG. 4 is a mass spectrum (MALDI-TOF-MS) of an alpha-diimine nickel catalyst prepared in example 4 of this invention;

FIG. 5 shows the NMR spectra of the polymer prepared in example 6 of the present invention (entry 15 in Table 5).

Detailed Description

The invention firstly provides a cascade enlarged steric hindrance alpha-diimine ligand, the structure of which is shown as the formula (I):

formula (I)In, R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

Preferably, the class of sterically hindered α -diimine ligands has the following structural formula:

the invention also provides a preparation method of the cascade enlarged steric hindrance alpha-diimine ligand, which comprises the following steps:

the method comprises the following steps: dissolving aniline represented by the general formula (b) and diketone represented by the general formula (a) in a solvent, wherein the molar ratio of the aniline represented by the general formula (b) to the diketone represented by the general formula (a) is 1: N, wherein N is more than or equal to 1, the reaction time is shorter as N is larger, and the product conversion rate can be improved, the molar ratio is preferably 1 (1-10), and more preferably 1: 5, preferably selecting the solvent as toluene, xylene, chlorobenzene, dichloromethane, chloroform or acetonitrile, then adding a catalyst, reacting at 25-80 ℃, preferably selecting the reaction time to be more than 6 hours, more preferably selecting the reaction time to be 12-48 hours, after the reaction is finished, preferably cooling to room temperature, performing rotary evaporation on the solvent until yellow solid appears, adding excessive methanol or ethanol to precipitate a product, filtering and separating the yellow solid, washing with methanol or ethanol for three times, and drying under vacuum to obtain a monoimine product with the structural formula (c); the catalyst is preferably p-toluenesulfonic acid, formic acid or acetic acid, and the molar ratio of the catalyst to the aniline of the formula (b) is preferably 0.001: 1;

step two: dissolving a monoimine product with a structural formula shown as (c) and aniline with a general formula (b) in a solvent, preferably toluene, adding a catalyst, preferably p-toluenesulfonic acid monohydrate, carrying out reflux reaction on the reaction mixture, preferably at a temperature of more than 110 ℃, more preferably at a temperature of 120-180 ℃, preferably at a temperature of more than 48h, more preferably for 3-4 days, cooling to room temperature after the reaction is finished, carrying out rotary evaporation on the solvent until yellow solid appears, adding excessive methanol or ethanol to precipitate the product, filtering and separating the yellow solid, washing with methanol or ethanol for three times, and drying under vacuum to obtain a cascade steric-hindrance-increased alpha-diimine ligand with a structure shown as a formula (I); the molar ratio of the monoimine product of formula (c), aniline of formula (b) and catalyst is preferably 1: 1: 0.001.

the invention also provides a nickel catalyst, which has a structure shown in the formula (II):

in the formula (II), R¹An alkyl group represented by H, C1 to C20 or

R²Representation H, CH₃、^tBu (tert-butyl), Cl, OCH₃、CF₃、NO₂X represents N, P, CH.

Preferably, the nickel catalyst has the following structural formula:

the invention also provides a preparation method of the nickel catalyst, which comprises the following steps:

the structure of the compound is shown as the formula (I) and the steric hindrance of α -diimine ligand and NiBr are increased₂(DME) is dissolved in dichloromethane or chloroform solvent for reaction, the reaction temperature is preferably 20-50 ℃, the reaction time is more than 24 hours, more preferably 24-48 hours, then the solvent is evaporated by rotary evaporation, n-hexane or ether and dichloromethane or chloroform are used for recrystallization, solid is filtered and separated, hexane or ether is used for washing for three times, and the nickel catalyst with the structure shown in formula (II) is obtained by drying in vacuum, wherein the structure shown in formula (I) is a class of overlapped and enlarged steric hindrance α -diimine ligand and NiBr₂The molar ratio of (DME) is preferably 1: 1, the solvent is preferably dichloromethane or chloroform.

The invention also provides the application of the nickel catalyst in catalyzing polyethylene polymerization.

The invention also provides a method for catalyzing polyethylene by using the nickel catalyst, which comprises the following steps:

drying the reactor preferably at 90 deg.C for more than 1h, connecting with high pressure gas line, adjusting the temperature of the reactor to 0-150 deg.C, preferably 30 deg.C, adding solvent preferably toluene, hexane or chlorobenzene and cocatalyst preferably MAO (methylaluminoxane), MMAO (modified methylaluminoxane), EASC (trichlorotriethylaluminum) or AlEt (aluminum trichloride) under inert atmosphere₂Cl (diethylaluminum chloride), then dissolving the nickel catalyst in a solvent to obtain a catalyst solution, wherein the solvent is preferably dichloromethane or chloroform, then injecting the catalyst solution into a reactor through a syringe, stirring the catalyst solution at a stirring speed of preferably more than 750 turns, introducing ethylene and keeping the pressure of 4-40atm, preferably 8atm, and after reacting for 1-6min, preferably reactingAdding a large amount of acidic methanol (or ethanol) (hydrochloric acid alcohol solution with concentration of more than 5%) to quench the polymerization reaction for 1min, filtering the polymer, and drying in a vacuum oven to obtain the polyethylene. The concentration of the nickel catalyst is preferably 0.1-1. mu. mol, preferably 0.1-0.25. mu. mol, and the concentration of the promoter is preferably 500. mu. mol.

The present invention is described in further detail below with reference to specific examples, in which the starting materials are all commercially available.