Disclosure of Invention
The invention aims to provide a novel nickel catalyst or a supported nickel catalyst, which is used for C2-C6The homopolymerization reaction of the low-carbon olefin has higher thermal stability and catalytic activity, and the obtained polymer has higher molecular weight. The invention also aims to provide a ligand compound of the nickel catalyst, a preparation method and application thereof.
The application provides a bulky, sterically hindered nickel ketimine complex of formula (I):
wherein
R1Is selected from C1-C6Alkyl, phenyl or substituted phenyl, said substituted phenyl being substituted by one or more groups selected from OH, halogen, nitro, C1-C6Alkyl and C1-C6Substituent in alkoxy;
ar represents a group of formula (101):
in the formula (101), R
2、R
3And R
8Independently of one another, from hydrogen, C
1-C
6Alkyl, halogen, nitro, methoxy or phenyl; and R is
4、R
5、R
6And R
7Independently of one another, from phenyl, substituted phenyl, naphthyl or substituted naphthyl, said substituted phenyl or substituted naphthyl being substituted by one or more groups selected from OH, halogen, nitro, C
1-C
6Alkyl and C
1-C
6Substituent in alkoxy; symbol
Represents the point of attachment of the group of formula (101) to the N atom in formula (I);
BAF-represents a tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate anion, and
(symbol)
represents an allyl group bonded to a Ni atom.
In a preferred embodiment, R4、R5、R6And R7Independently of one another, from phenyl or naphthyl; preferably, R2、R3And R8Independently of one another, from hydrogen or C1-C6An alkyl group.
In another aspect, the present invention provides a supported, highly hindered nickel catalyst comprising: the nickel complex of the large steric hindrance ketimine is loaded on a carrier by an impregnation method. Preferably, the carrier is one or more selected from the group consisting of silica, anhydrous magnesium chloride and alumina.
In another aspect, the present invention provides a ketimine ligand compound of formula (II):
wherein R is1And Ar is as defined above.
In another aspect, the present invention provides a process for preparing the above sterically hindered ketimine nickel complex, the process comprising: reacting the ketimine ligand compound of the above formula (II) with an allyl nickel salt and tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate in an organic solvent, wherein the organic solvent is one or more selected from the group consisting of tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, 1, 4-dioxane, and 1, 2-dichloroethane.
In another aspect, the present invention provides a method of preparing the ketimine ligand compound of formula (II) described above, the method comprising:
in the presence of an organic acid catalyst, at the temperature of 60-150 ℃, leading Ar-NH to be in a formula
2With an arylamine compound of formula
The diketone compound of (A) is reacted in an organic solvent for 12-72 h, wherein R
1And Ar is as defined above.
In a preferred embodiment, the organic acid catalyst is selected from formic acid, acetic acid, p-toluenesulfonic acid, or camphorsulfonic acid; the organic solvent is one or more selected from tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, 1, 4-dioxane and 1, 2-dichloroethane.
In another aspect, the present invention provides a method of preparing a polyolefin compound, the method comprising: the sterically hindered nickel ketimine complex described above was used as catalyst pair C2-C6And carrying out catalytic polymerization on the low-carbon olefin.
In another aspect, the present invention provides a method of preparing a polyolefin compound, the method comprising: using the above-mentioned supported highly hindered nickel catalyst pair C2-C6And carrying out catalytic polymerization on the low-carbon olefin.
In a preferred embodiment, the polymerization is carried out at a temperature of 20 to 100 ℃.
The application provides a novel ketimine nickel complex and a supported nickel catalyst supported on a carrier, wherein an Ar substituent group connected with an N atom of imine in a ligand of the novel ketimine nickel complex is specially designed to have a significantly larger steric hindrance structure, so that large steric hindrance is provided on one side of a metal nickel atom. The large steric hindrance structure can effectively protect a Ni metal center in the polymerization reaction of catalyzing low-carbon olefin, thereby improving the thermal stability and chemical activity of the nickel complex as a catalyst.
In addition, since the carbonyl group of the ketimine is designed to be linked with a p-hydroxyphenyl group, the resulting nickel complex is easily adsorbed and supported on a carrier such as silica, resulting in a supported catalyst having high activity and thermal stability, while also eliminating the need for a co-catalyst that is generally necessary.
In addition, the supported nickel catalyst is used for catalyzing ethylene polymerization, and the obtained polyethylene has relatively higher number average molecular weight, so that the supported nickel catalyst can be used for preparing ultrahigh molecular weight polyethylene. Moreover, the polyethylene prepared by the supported nickel catalyst is granular, so the prepared polyethylene polymer does not have the problem of kettle sticking caused by cluster aggregation of common polyethylene products, and the supported nickel catalyst is more suitable for large-scale industrial production.
Detailed Description
In view of the problems of the prior art that the activity of the nickel ketimine catalyst in the ethylene polymerization reaction is very low and the molecular weight of the obtained polyethylene product is not high, the inventors of the present invention have conducted intensive and extensive studies, and unexpectedly discovered that, through a new structural design, an aryl substituent structure having a larger steric hindrance is designed on the aromatic substituent connected to the N atom of imine in the ketimine ligand compound, thereby providing a substantially larger steric hindrance structure that is approximately half-surrounded around the active metal nickel atom, such a large steric hindrance structure can effectively protect the Ni metal center in the polymerization reaction of catalytic ethylene, and at the same time, a p-hydroxyphenyl group is designed to be connected to the carbonyl group of ketimine, thereby being capable of improving the thermal stability and chemical activity of the nickel complex as a catalyst, and simultaneously, using such a large steric hindrance ketimine nickel complex as a catalyst, the ethylene homopolymer obtained may have a higher molecular weight.
In addition, the invention also unexpectedly discovers in the research that the nickel complex of the large-steric-hindrance ketimine with the hydroxyl functional group can be easily supported on a carrier such as silicon dioxide by utilizing the nickel complex of the large-steric-hindrance ketimine designed by the invention, thereby forming a supported heterogeneous nickel catalyst with high activity. In addition, the supported catalyst provided by the invention can avoid the use of a cocatalyst.
Based on this finding, the present invention has been devised and provided, first, a ketimine ligand compound of the following formula (II):
wherein
R1Is selected from C1-C6Alkyl, phenyl or substituted phenyl, said substituted phenyl being substituted by one or more groups selected from OH, halogen, nitro, C1-C6Alkyl and C1-C6Substituent in alkoxy;
ar represents a group of formula (101):
in the formula (101), R
2、R
3And R
8Independently of one another, from hydrogen, C
1-C
6Alkyl, halogen, nitro, methoxy or phenyl; preferably, R
2、R
3And R
8Independently of one another, from hydrogen or C
1-C
6An alkyl group; r
4、R
5、R
6And R
7Independently of one another, from phenyl, substituted phenyl, naphthyl or substituted naphthyl, said substituted phenyl or substituted naphthyl being substituted by one or more groups selected from OH, halogen, nitro, C
1-C
6Alkyl and C
1-C
6Substituent in alkoxy; preferably, R
4、R
5、R
6And R
7Independently of one another, from phenyl or naphthyl; and symbol
Represents the point of attachment of the group of formula (101) to the N atom in formula (I).
As used herein, C1-C6The alkyl group represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and examples thereof are a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and isomeric forms thereof, and preferably a methyl group, an ethyl group, or a tert-butyl group.
As used herein, C1-C6Alkoxy represents the above-mentioned C bonded through an oxygen atom (O)1-C6Examples of the alkyl group are methoxy, ethoxy, propoxy, tert-butoxy and the like.
As used herein, halogen includes fluorine, chlorine, bromine and iodine, preferably chlorine or bromine.
In the present invention, the substituent R of the ketimine ligand compound of the formula (II) is substituted by1And Ar, in particular substituents Ar, in which at least four bulky steric hindrance groups R independently selected from phenyl, substituted phenyl, naphthyl or substituted naphthyl are introduced into the specific structural formula (101) represented by the formula4、R5、R6And R7Thereby allowing the ligand compound to form an approximately semi-closed cage structure. This enables formation of a large steric hindrance on the active metal Ni atom side when the ligand compound is complexed with the active metal Ni atom to form a complex, thereby enabling effective protection of the Ni metal center when such a complex is applied as a catalyst in catalyzing the polymerization reaction of ethylene, thereby enabling improvement in thermal stability and chemical activity of the resulting nickel complex as a catalyst. Furthermore, since the carbonyl group of ketimine is designed to be bonded with a p-hydroxyphenyl group, the resulting nickel complex is easily adsorbed and supported on a carrier such as silica, and a supported catalyst having high activity and thermal stability is conveniently formedCatalysts, while also eliminating the need for the co-catalysts that are normally necessary.
The method for preparing the ketimine ligand compound of formula (II) provided by the present invention is not particularly limited, and can be prepared, for example, by the following method: in the presence of an organic acid catalyst, at a temperature of 60-150 ℃, preferably 80-100 ℃, reacting Ar-NH
2With an arylamine compound of formula
Reacting the diketone compound or the ketoaldehyde compound in an organic solvent for 12-72 h, wherein R
1And Ar is as defined above. Preferably, the reaction is carried out under reflux at elevated temperature. Preferably, the organic acid catalyst used may be selected from formic acid, acetic acid, p-toluenesulfonic acid or camphorsulfonic acid. Preferably, the organic solvent used may be selected from one or more of tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, 1, 4-dioxane and 1, 2-dichloroethane, for example toluene. Preferably, in the reaction, water produced by the reaction may be removed using, for example, anhydrous magnesium sulfate. Preferably, the molar ratio of the amine to the aldehyde is 1: (0.1-10); in a specific embodiment, formula Ar-NH
2With an arylamine compound of formula
The molar ratio of the diketone compound or the ketone-aldehyde compound (b) is 1: 0.1 to 10, and more preferably 1: 1 to 5.
As used herein, among the above arylamine compounds, the Ar substituent representing the structure of formula (101) can be easily obtained from the most basic raw material such as a substituted or unsubstituted benzene or naphthalene compound using a conventional technique well known in the art to obtain the corresponding structure and bonded to the N atom of the amine to obtain the corresponding arylamine compound, for example. Further, the above diketone compound can be obtained by a conventional reaction well known in the art using a corresponding diketone and a para-substituted phenol compound commercially available in the art as raw materials.
In the present invention, it is preferableThe ketimine ligand compound of the above formula (II) may be, for example, the following formula (II)1) The compound of (1):
wherein Ph represents phenyl (i.e. group C)6H5-)。
Based on the ketimine ligand compound of the above formula (II), the present invention provides a bulky steric hindrance ketimine nickel complex of the formula (I):
wherein, the substituent R
1And Ar has the same meaning as defined above, BAF
-Represents a tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate anion and is given the symbol
Represents an allyl group (CH) bonded to the Ni atom
2=CH-CH
2-)。
Such sterically hindered ketimine nickel complexes can be prepared, for example, by the following method: the ketimine ligand compound of the above formula (II) is reacted with an allylnickel salt such as allylnickel chloride and tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate such as tetrakis (3, 5-bis (trifluoromethyl) phenyl) sodium borate in an organic solvent, wherein the organic solvent may be one or more selected from tetrahydrofuran, petroleum ether, toluene, benzene, dichloromethane, tetrachloromethane, 1, 4-dioxane and 1, 2-dichloroethane, for example, dichloromethane. Preferably, in the reaction, the ligand compound of formula (II) and the allyl nickel salt and tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate may be reacted in a molar ratio of, for example, but not limited to, 1: 1. Such a reaction can be carried out at room temperature, for example, and the reaction time can be 10 to 20 hours, for example.
In the present invention, preferably, the bulky hindered ketimine nickel complex of the above formula (I) may have, for example, the followingFormula (I)1) The structure of (1);
wherein BAF
-And
as defined above, and Ph represents phenyl (i.e. group C)
6H
5-)。
Based on the bulky sterically hindered ketimine nickel complex of formula (I) above, the present invention also provides a supported bulky sterically hindered nickel catalyst, which can be obtained by, for example, supporting or adsorbing the bulky sterically hindered ketimine nickel complex onto a support by an impregnation method common in the art. For example, the supported nickel catalyst can be obtained by stirring the bulky hindered ketimine nickel complex with a support in an organic solvent such as toluene to mix uniformly, followed by filtration and drying. Preferably, the carrier used may be one or more selected from the group consisting of silica, anhydrous magnesium chloride and alumina. Since the bulky hindered ketimine nickel complexes of the present invention have free hydroxyl groups, they can be readily adsorbed onto supports such as silica.
In one embodiment, the supported nickel catalyst (Ni-OH @ SiO) obtained according to the invention2) Can be expressed as follows:
the nickel complex of the ketone imine with great steric hindrance can be used as a catalyst or the supported nickel catalyst with great steric hindrance can be used for preparing C2-C6Homopolymers of lower olefins such as ethylene. Preferably, the polymerization reaction is carried out at a temperature of 20 to 100 ℃.
Examples
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to illustrate further features and advantages of the invention, rather than to limit the scope of the invention.
The synthesis of the complex and the polymerization process in the following examples were carried out in the absence of water and oxygen, all sensitive substances were stored in a glove box, all solvents were strictly dried to remove water, and the ethylene gas was purified by a water and oxygen removal column. All raw materials are purchased and used without specific mention.
Silica gel with 200-mesh and 300-mesh is used for silica gel column separation; the nuclear magnetism detection is performed by a Bruker 400MHz nuclear magnetism instrument; the element analysis is determined by the physicochemical center of Chinese science and technology university; molecular weight and molecular weight distribution were determined by high temperature GPC; mass spectra were determined using Thermo LTQ Orbitrap XL (ESI +) or P-SIMS-Gly of Bruker Daltonics Inc (EI +).
Example 1: 2- ((2, 6-bis (di-p-tolylmethyl) -4-methylphenyl) imino) -1- (4-hydroxyphenyl) propan-1-one (II)1) Preparation of
A solution of 2, 6-bis (diphenylmethyl) -4-methylaniline (1758 mg, 4 mmol), 1- (4-hydroxyphenyl) propane-1, 2-dione (328 mg, 2 mmol) and p-toluenesulfonic acid (20 mg) in toluene (20 ml) was stirred at 80 ℃ for 12 hours under nitrogen in a 250 ml round bottom flask equipped with reflux condenser, magnetic stirrer and oil bath and the reaction was monitored by Thin Layer Chromatography (TLC). The reaction was terminated when a major product spot was indicated on the thin layer chromatography plate. The reaction was cooled to room temperature, a yellow solid precipitated and was isolated by filtration to give a yellow solid (585 mg, 50% yield). The product obtained was subjected to detection analysis, and as a result, it was confirmed to be the title compound.
1H NMR(400MHz,CDCl3) Δ 7.52(br, 2H), 7.35-6.75(m, 20H), 6.66(br, 2H), 6.45(br, 2H), 5.29(s, 2H, CHPh2), 2.13(s, 3H, aryl-CH)3),1.15(s,3H,N=CMe)。
13C NMR(100MHz,[D6]DMSO)δ189.82(s,COCH3),170.44(s),162.52(s),144.26(s),143.07(s),142.63(s),133.24(s),131.76(s),131.03(s),129.52(s),129.21(s),128.75(s),128.53(s),128.35(s),126.49(s),126.38(s),125.45(s),115.11(s),51.17(s,CHPh2),21.02(s),17.40(s)。
HRMS (m/z): theoretical value C42H36O2N:[M+H]+586.2741, respectively; measured value: 5702742.
example 2: preparation of 2- ((2, 6-bis (di-p-tolylmethyl) -4-methylphenyl) imino) -1- (4-hydroxyphenyl) propan-1-one nickel complex (catalyst Ni-OH)
In a glove box, a solution of a mixture of 2- ((2, 6-bis (di-p-tolylmethyl) -4-methylphenyl) imino) -1- (4-hydroxyphenyl) propan-1-one (293 mg, 0.5 mmol), allylnickel chloride (67.5 mg, 0.5 mmol) and sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate (443 mg, 0.5 mmol) in a 20 ml glass vial was stirred at room temperature for 12 hours. The resulting mixture was filtered through celite and evaporated to give a black red solid (619 mg, 80% yield). The product obtained was subjected to detection analysis, and as a result, it was confirmed to be the title compound.
1H NMR(400MHz,CDCl3) δ 7.78-7.50(m, 10H), 7.37(s, 4H), 7.24(t, J ═ 7.3Hz, 4H), 7.18(d, J ═ 6.7Hz, 2H), 7.08(s, 6H), 6.94(s, 4H), 6.87(s, 3H), 6.76(s, 2H), 6.67(d, J ═ 8.6Hz, 2H), 5.68(s, 1H), 5.40-4.95(m, 3H), 2.12(s, 3H, aryl-CH), and pharmaceutically acceptable salts thereof3),1.02(s,3H,N=CMe)。
13C NMR(100MHz,CDCl3) δ 195.40(s), 176.51(s), 165.68(s), 142.02(s), 140.56(s), 140.41(s), 138.44(s), 135.55(s), 133.76(s), 129.87(s), 129.50(s), 129.44(s), 129.34(s), 127.84(s), 127.64(s), 125.02(s), 119.46(s, allyl group) 117.45(s), 53.17(s), 21.50(s, aryl-CH)3),20.50(s,N=CMe)。
1H-13C HSQC Association (CDCl)3): 119.46(s, allyl)/5.40-4.95 (m, 3H), 21.50(s, aryl-CH)3) 2.12(s, 3H, aryl-CH)3),20.50(s,N=CMe)/1.02(s,3H,N=CMe)。
Elemental analysis: theoretical value C77H52BF24NNiO2: c, 59.72; h, 3.38; measured value: c, 59.86; h, 3.25.
Example 3: supported nickel catalyst (Ni-OH @ SiO)2) Preparation of
Silica (available from Grace-Devison, model 955) as a carrier is calcined at 600 ℃ for 6 hours in a muffle furnace and stored in a glove box for use.
In a glove box in a 20 ml glass bottle under nitrogen protection, 100 mg of the above prepared carrier silica and 1. mu. mol of the catalyst Ni-OH prepared in example 2 were dissolved in 1 ml of toluene and stirred at room temperature for 6 hours. The solid product was then obtained by filtration and washed twice with toluene (15 ml) and finally dried under vacuum to give the desired supported nickel catalyst.
Application examples 1 to 11: complex catalyst (Ni-OH) and supported catalyst (Ni-OH @ SiO)2) Use of catalysts for ethylene polymerization
In a glove box, 28 ml of toluene or 30 ml of n-heptane were added under nitrogen to a 350 ml autoclave (with magnetic stirring, oil bath heating and thermometer). The reactor was connected to a high pressure line and the piping was evacuated, and the reactor was heated to the temperature shown in Table 1 below (20 ℃, 50 ℃, 80 ℃ or 100 ℃) using an oil bath and kept for 15 minutes. Then adding complex catalyst (Ni-OH) or supported catalyst (Ni-OH @) dissolved in 2 ml of dichloromethaneSiO2) (1 micromole), close the valve. After adjusting the ethylene pressure to atmospheric pressure shown in table 1 below, the reaction was carried out for 3 minutes; the reaction was stopped. The reaction vessel was opened, ethanol (50 ml) was added thereto to precipitate a solid, which was filtered under reduced pressure and dried in a vacuum oven (50 ℃ C.) to obtain a white solid. The results are shown in Table 1.
Table 1: nickel catalyst catalyzed ethylene homopolymerizationaAs a result of (A)
aEthylene homopolymerization conditions: catalyst 1 micromole; toluene (28 ml), dichloromethane (2 ml), ethylene (8 atm) for 3 min;
bactivity 10 ═ 107g·mol-1·h-1(ii) a As is known in the art, it is obtained by dividing the mass of polyethylene by the mass of catalyst and then by the reaction time;
cthe molecular weight was measured by GPC using polystyrene as a solvent for trichlorobenzene at 150 ℃; (ii) a
dThe degree of branching per 1000 carbons was determined by nuclear magnetic resonance hydrogen spectroscopy;
ethe melting point is measured by a differential scanning calorimeter;
fthe time is 30 minutes;
g30 ml of n-heptane and 30 minutes.
From the above, it can be seen that by using the nickel ketoimine complex with large steric hindrance as a catalyst, the nickel ketoimine complex has high thermal stability and activity for homopolymerization polymerization of ethylene, and can obtain high molecular weight polyethylene with a certain branching degree. For example, in the case of a single complex as catalyst, the activity thereof may beUp to 1.6X 107g·mol-1·h-1(ii) a The polyethylene product has a number average molecular weight of up to 1.04X 106g/mol; and the melting point can reach 124.6 ℃. In the case of supported catalysts, the activity can reach 8.0X 106g·mol-1·h-1(ii) a The polyethylene product has a number average molecular weight of up to 1.59X 106g/mol; the melting point can reach 131.9 ℃.
In addition, it is noted that although the supported nickel catalyst has relatively low activity compared to the unsupported nickel catalyst, the supported nickel catalyst of the present invention is more suitable for large-scale industrial production because the polyethylene polymer prepared by using the supported nickel catalyst does not have the problem of sticking to the kettle of the polymer product; moreover, the molecular weight of the polyethylene obtained by catalyzing ethylene polymerization by using the supported nickel catalyst is relatively higher.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.