Ligand and preparation method thereof, catalyst and preparation method and application of catalyst

Abstract

The invention relates to the field of catalysts, in particular to a ligand and a preparation method thereof, a catalyst and a preparation method and application of the catalyst. The ligand has a structure represented by formula (1), # imgabs 0 # imgabs 1 #, wherein R1 to R7 are each independently selected from hydrogen, an alkyl group, a substituted alkyl group, a cycloalkyl group, a substituted cycloalkyl group, an aryl group, or a substituted aryl group. The catalyst prepared from the ligand is simple and has excellent activity and selectivity when being applied to ethylene selective tetramerization catalysis, and the high polymers in the finally obtained product are few.

Description

Technical Field

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

[0002] Linear α-olefins (LAOs) are an important class of chemical raw materials, and are widely used in the synthesis, processing and production of chemical intermediates, epoxy compounds, plasticizers, synthetic carboxylic acids, lubricants, surfactants and rubber processing chemicals. At the same time, butene-1, hexene-1 and octene-1 in LAOs can be used as comonomers in the production of polyolefin products, which is one of the most important applications of LAOs. In particular, hexene-1 and octene-1 are used in the production of high-quality polyethylene, which can significantly improve the mechanical properties, optical properties, tear strength and impact strength of polyethylene.

[0003] In recent years, with the rapid development of the polyolefin industry, the consumption of LAOs has increased rapidly worldwide, especially the demand for hexene-1 and octene-1, which are comonomers of high-end polyolefin products.

[0004] At present, the main production method of LAOs is ethylene oligomerization. The carbon number of the product obtained by this method follows the Schulz-Flory distribution. In addition to high-value-added hexene-1 and octene-1, a large amount of butene-1 and other high-carbon linear α-olefins are also generated. Obviously, the production of LAOs by ethylene oligomerization with Schulz-Flory distribution is less economical than the direct preparation of hexene-1 and octene-1 by ethylene selective oligomerization. Selective ethylene oligomerization has the advantages of high product purity, easy separation, and high raw material utilization.

[0005] For the selective oligomerization of ethylene to prepare linear α-olefins, also known as the selective oligomerization of ethylene, the catalytic activity of the catalyst system and the selectivity of the target product are the key to evaluating the advancement of the technology. The change of the ligand structure in the catalyst has a decisive influence on the activity of the selective oligomerization reaction of ethylene and the selectivity of the product.

[0006] US5523507 discloses the use of a chromium / pyrrole system to catalyze the polymerization of ethylene, with a 1-hexene selectivity of 93%.

[0007] WO2004056478 discloses an ethylene tetramerization catalyst system, which uses a PNP-type ligand and can produce 1-octene, a tetramerization product of ethylene, with a selectivity of up to 70%.

[0008] CN111094308A, CN109476779A and CN104169003A disclose chiral PCCP ligands, Cr and MAO to form a catalyst system for ethylene tetramerization, and the catalyst has high catalytic activity and long-term stability. However, the by-product content in the catalytic system is high, and the selectivity of C6 and C8 linear α-olefins is low. Summary of the invention

[0009] The purpose of the present invention is to overcome the problem that the catalyst in the prior art cannot have both activity and selectivity, and to provide a ligand and a preparation method thereof, a catalyst and a preparation method and application thereof. The catalyst has a simple structure and has excellent activity and selectivity for the selective tetramerization of ethylene.

[0010] In order to achieve the above object, the present invention provides a ligand in a first aspect, wherein the ligand has a structure shown in formula (1),

[0011]

[0012] Among them, R 1 To R 7 Each is independently selected from hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl or substituted aryl.

[0013] The second aspect of the present invention provides a method for preparing a catalyst, wherein the preparation method comprises: subjecting a ligand, a transition metal compound and a co-catalyst to an in-situ reaction to obtain the catalyst;

[0014] Wherein, the ligand is the aforementioned ligand.

[0015] The third aspect of the present invention provides a catalyst prepared by the above preparation method.

[0016] A fourth aspect of the present invention provides a use of the aforementioned catalyst in the selective tetramerization of ethylene.

[0017] Through the above technical solution, the beneficial effects of the present invention are as follows:

[0018] The invention provides a novel ligand. The catalyst prepared by the ligand is simple. When the ligand is applied to ethylene selective tetramerization catalysis, the catalyst has excellent activity and selectivity, and the final product contains less polymers. Description of the drawings:

[0019] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the ligand L1 prepared in Preparation Example 1. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The first aspect of the present invention provides a ligand, wherein the ligand has a structure shown in formula (1),

[0022]

[0023] Among them, R 1 To R 7 Each is independently selected from hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl or substituted aryl.

[0024] In the present invention, the structure of formula (1) prepared can be detected by hydrogen nuclear magnetic resonance spectrum.

[0025] In the present invention, the ligand has a simple and novel structure, is easy to synthesize, and is highly modifiable. It can meet the different requirements for the metal center electronic effect and steric hindrance required by different catalytic reactions by changing the skeleton substituents.

[0026] According to the present invention, the R 1 To R 7 are independently selected from hydrogen, C 1 -C 20 Alkyl, C 1 -C 20 Substituted alkyl, C 5 -C 20 Cycloalkyl, C 6 -C 20 Aryl or C 6 -C 20 Substituted aryl; wherein the substituent when substituted is selected from halogen, C 1 -C 20 Alkyl, C 5 -C 20 Cycloalkyl and C 6 -C 20 At least one of the aromatic groups; preferably selected from halogen, C 1 -C 6 Alkyl, C 5 -C 10 Cycloalkyl and C 6 -C 10 At least one of the aromatic groups.

[0027] In the present invention, R 1To R 7 When the above range is satisfied, the metal center electronic effect and the size of the steric hindrance can be effectively regulated.

[0028] Furthermore, the R 1 To R 4 are independently selected from hydrogen, C 1 -C 6 Alkyl, C 1 -C 6 Substituted alkyl, phenyl or C 6 -C 12 Substituted aryl, wherein the substituent when substituted is selected from C 1 -C 20 Alkyl, C 5 -C 20 Cycloalkyl and C 6 -C 20 At least one of the aromatic groups; preferably selected from C 1 -C 6 Alkyl, C 5 -C 10 Cycloalkyl and C 6 -C 10 At least one of the aromatic groups.

[0029] Furthermore, the R 5 At least one selected from hydrogen, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isopropyl, isobutyl, tert-butyl, isopentyl, tert-pentyl, cyclopentyl, cyclohexyl, 2,6-dimethylcyclohexyl, methoxy, benzyl, phenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 3-isopropylphenyl, 4-isopropylphenyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthracenyl, biphenyl, p-fluorophenyl, o-fluorophenyl and m-fluorophenyl.

[0030] Furthermore, the R 6 and R 7 Each is independently selected from at least one of methyl, ethyl, n-propyl, isopropyl, tert-butyl, cyclopentyl and cyclohexyl.

[0031] According to the present invention, the ligand is selected from

[0032]

[0033]

[0034] At least one of, preferably selected from

[0035]

[0036] At least one of .

[0037] The preparation method of the ligand in the present invention is a conventional organic synthesis method in the art. In a preferred embodiment, the preparation method of the ligand is as follows: in a nitrogen atmosphere, 10 mmol of phospholane is added to 50 mL of tetrahydrofuran, cooled to 0° C., 4-5 mL of n-butyl lithium solution (2.5 M n-hexane solution) is added dropwise thereto, and the addition is completed within 10-15 min, the temperature is raised to 25° C., and the stirring is carried out for 1 h; the stirred solution is cooled to 0° C., and the cooled solution is added dropwise to the solution. Add 12 mmol of trimethylsilyl chloride, add dropwise within 5-8 minutes, heat to 25°C, stir for 1.5-2 hours; remove the solvent under vacuum to obtain trimethylphospholylsilane; add 15-20 mL of dichloromethane to all the trimethylphospholylsilane, add 8-10 mmol of hexachloroethane thereto, heat under reflux to react, the reaction temperature is 10-50°C, the reaction time is 10-12 hours, and remove the solvent to obtain chlorophospholane;

[0038] Add 8-10 mmol of isopropylamine to 10-15 mL of tetrahydrofuran, and add 3-4 mL of n-butyl lithium solution dropwise at 0°C within 8-10 min. Heat to 25°C and stir for 1.5-2 h. Remove the solvent under vacuum to obtain isopropyl lithium amide.

[0039] Add all the isopropylamide lithium to 10-15 mL of n-hexane to obtain an isopropylamide lithium n-hexane solution, dissolve 10 mmol of chlorophospholane in 10-15 mL of n-hexane to obtain a chlorophospholane n-hexane solution, dropwise add 8-10 mL of the chlorophospholane n-hexane solution to the isopropylamide lithium n-hexane solution within 8-10 min, stir at 25 ° C for 10-12 h, remove volatile components in vacuo, and distill under reduced pressure to obtain phospholyl-isopropylamine;

[0040] Among them, "n-hexane recrystallization" can also be used instead of "reduced pressure distillation";

[0041] Under a nitrogen atmosphere, add all the obtained phosphotylidene-isopropylamine to 8-10 mL of n-hexane, cool the solution to 0°C, add 4-5 mL of n-butyllithium thereto, and complete the addition within 5-8 min, then raise the temperature to 25°C and react for 1.5-2 h to obtain phosphotylidene-isopropyl-lithium amide;

[0042] Under a nitrogen atmosphere, add 10 mmol of (diphenylphosphino)methylene-dimethylchlorosilane to 8-10 mL of n-hexane, cool to -35 ° C, slowly add all the phosphotylidene-isopropyl-lithium amide obtained in the previous step, raise the temperature to 25 ° C, react for 10-12 h to obtain a crude product, filter out the lithium chloride salt, remove the solvent under reduced pressure, wash three times with n-hexane, and recrystallize with n-hexane at -35 ° C to obtain a ligand.

[0043] The second aspect of the present invention provides a method for preparing a catalyst, wherein the preparation method comprises: subjecting a ligand, a transition metal compound and a co-catalyst to an in-situ reaction to obtain the catalyst;

[0044] Wherein, the ligand is the aforementioned ligand.

[0045] According to the present invention, the general formula of the transition metal compound is AR n ;

[0046] wherein A is selected from transition metals, preferably at least one selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten and palladium, more preferably at least one selected from chromium, cobalt, titanium, iron, nickel and palladium, most preferably chromium;

[0047] Among them, R n At least one selected from inorganic anions, organic anions and organic neutral molecules, and n is an integer of 1-6.

[0048] In the present invention, when the catalyst is used in the selective tetramerization of ethylene, the polymerization activity and selectivity are high, and the obtained polymer content is low. In a specific embodiment, the obtained polymer is generally an ethylene trimerization product and a tetramerization product.

[0049] According to the present invention, the co-catalyst is selected from at least one of an alkyl aluminum compound, an alkyl aluminumoxane compound and an organic boron compound.

[0050] According to the present invention, in the catalyst, the molar ratio of the ligand: the co-catalyst: the transition metal in the transition metal compound is 0.01-100:1-100000:1; preferably 0.1-10:1-10000:1.

[0051] According to the present invention, the transition metal compound is selected from at least one of chromium trichloride-tri(tetrahydrofuran) complex, benzene tricarbonyl chromium, chromium octoate, chromium hexacarbonyl, chromium acetylacetonate, chromium naphthenate, chromium 2-ethylhexanoate, chromium acetate, 2,2,6,6-tetramethylheptanedione chromium and chromium chloride, and is preferably at least one of chromium trichloride-tri(tetrahydrofuran) complex, chromium acetylacetonate, chromium 2-ethylhexanoate and di(acetylacetonate)chromium.

[0052] According to the present invention, the alkyl aluminum compound is selected from at least one of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexylaluminum, tri-n-octyl aluminum, aluminum alkyl aluminum halide, alkyl aluminum hydride or alkyl aluminum sesquichloride, preferably diethyl aluminum monochloride and / or triethyl aluminum trichloride.

[0053] According to the present invention, the alkylaluminoxane compound is selected from at least one of linear alkylaluminoxane compounds, cyclic alkylaluminoxane compounds and caged alkylaluminoxane compounds; preferably selected from at least one of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and modified aluminoxane.

[0054] In the present invention, the modified aluminoxane is methylaluminoxane or ethylaluminoxane modified from other alkanes, which is not limited in the present invention and can be commercially obtained.

[0055] According to the present invention, the organic boron compound is at least one selected from boroxine, triethylborane, triphenylborane and tri(pentafluorophenyl)borane, preferably tri(pentafluorophenyl)borane.

[0056] According to the present invention, the conditions of the in-situ reaction include: the temperature of the in-situ reaction is 0-200° C., preferably 20-100° C.; the time of the in-situ reaction is 1-300 min, preferably 1-100 min.

[0057] The third aspect of the present invention provides a catalyst prepared by the aforementioned preparation method.

[0058] According to the present invention, the content of transition metal elements in the catalyst is 0.001wt%-50wt%, preferably 0.01wt%-45wt%.

[0059] In the present invention, the metal elements in the catalyst are tested by elemental analysis XPS.

[0060] A fourth aspect of the present invention provides a use of the aforementioned catalyst in the selective tetramerization of ethylene.

[0061] The use of catalysts for selective tetramerization of ethylene is a conventional treatment method in the art. A particularly preferred method in the present invention includes: adding ethylene and a catalyst to an inert solvent for polymerization reaction to obtain an ethylene selective tetramer polymer.

[0062] According to the present invention, the inert solvent is selected from alkanes, aromatic hydrocarbons, olefins or ionic liquids, preferably selected from at least one of benzene, toluene, xylene, isopropylbenzene, chlorobenzene, dichlorobenzene, fluorobenzene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene and 1-octene, more preferably toluene and / or methylcyclohexane.

[0063] According to the present invention, the conditions of the polymerization reaction include: the polymerization reaction temperature is 0-200°C, preferably 10-120°C, more preferably 20-100°C; the polymerization reaction pressure is 0.1-50MPa, preferably 1-10MPa; the polymerization reaction time is 5-120min, preferably 5-60min.

[0064] According to the present invention, based on the total weight of ethylene and the catalyst, the content of the catalyst is 0.01-10000 μmol metal / L, preferably 1-500 μmol metal / L; wherein the metal is a transition metal in the transition metal compound in the catalyst.

[0065] Here, "L" refers to the volume phase theory for inert solvents.

[0066] The present invention will be described in detail below through examples.

[0067]

[0068] Method for detecting the selectivity of hexene-1: The selectivity can be known by calculating the content of hexene-1 in the liquid product using the gas chromatography internal standard method;

[0069] Method for detecting octene-1 selectivity: Calculate the content of octene-1 in the liquid product using the gas chromatography internal standard method to know its selectivity;

[0070] Method for detecting the selectivity of a polymer: The selectivity of the polymer can be determined by filtering, washing, drying, and weighing the polymer and comparing the mass of the polymer obtained by the tetramerization reaction to the mass of the total product.

[0071] Phosphorolane (purity>97%), tetrahydrofuran, n-hexane, trimethylsilyl chloride, dichloromethane, hexachloroethane, n-butyllithium solution (2.5 M n-hexane solution), hexane, isopropylamine, (diphenylphosphino)methylene-dimethylsilyl chloride, diphenylphosphine chloride, all of which were purchased from commercial sources.

[0072] Preparation Example 1

[0073] In a nitrogen atmosphere, 10 mmol of phospholane was added to 50 mL of tetrahydrofuran, cooled to 0°C, 4.5 mL of n-butyl lithium solution (2.5 M n-hexane solution) was added dropwise thereto, the addition was completed within 10 min, the temperature was raised to 25°C, and the stirring was performed for 1 h; the stirred solution was cooled to 0°C, 12 mmol of trimethylchlorosilane was added dropwise to the cooled solution, the addition was completed within 5 min, the temperature was raised to 25°C, and the stirring was performed for 2 h; the solvent was removed under vacuum to obtain 11 mmol of trimethylphospholane; 11 mmol of trimethylphospholane was added to 20 mL of dichloromethane, 10 mmol of hexachloroethane was added thereto, and the reaction was heated to reflux for reaction, the reaction temperature was 45°C, the reaction time was 12 h, and the solvent was removed to obtain 11 mmol of chlorophospholane;

[0074] Add 10 mmol of isopropylamine to 10 mL of tetrahydrofuran, and at 0°C, add 4 mL of n-butyl lithium solution dropwise within 10 min. Heat to 25°C and stir for 2 h. Remove the solvent under vacuum to obtain 10 mmol of isopropyl lithium amide.

[0075] Add 10 mmol of dried lithium isopropylamide to 10 mL of n-hexane to prepare a lithium isopropylamide n-hexane solution, dissolve 10 mmol of chlorophospholane in 10 mL of n-hexane to obtain a chlorophospholane n-hexane solution, add 10 mL of the chlorophospholane n-hexane solution dropwise to the lithium isopropylamide n-hexane solution within 10 min, stir at 25 ° C for 12 h, remove volatile components in vacuo, and distill under reduced pressure to obtain 10 mmol of phospholyl-isopropylamine;

[0076] Under nitrogen atmosphere, add 10 mmol of phosphotylidene-isopropylamine to 10 mL of n-hexane, cool the solution to 0°C, add 4 mL of n-butyllithium, and add dropwise within 5 min. Then, heat to 25°C and react for 2 h to obtain 10 mmol of phosphotylidene-isopropyl-lithium amide.

[0077] Under nitrogen atmosphere, 10 mmol of (diphenylphosphino)methylene-dimethylchlorosilane was added to 10 mL of n-hexane, cooled to -35 °C, 10 mmol of phosphotyl-isopropyl-lithium amide was slowly added thereto, the temperature was raised to 25 °C, and the reaction was carried out for 12 h to obtain a crude product, the lithium chloride salt was filtered out, the solvent was removed under reduced pressure, and the product was washed three times with n-hexane, and recrystallized with n-hexane at -35 °C to obtain ligand L1. 1 H-NMR measurement, the obtained spectrum is as follows Figure 1As shown, 10 H at 7.5-7.2 are H of phosphorus-phenyl group, 1 H at 2.88-2.78 is H on the secondary carbon atom of isopropyl group, and 6 H at 0.00 are H of silicon methyl group.

[0078] Preparation Example 2

[0079] Ligand L2 was obtained in the manner of Preparation Example 1, except that "(2R,5R)-2,5-dimethylphospholane" was used instead of "phospholane".

[0080] Preparation Example 3

[0081] Ligand L3 was obtained in the manner of Preparation Example 1, except that "(2R,5R)-2,5-diethylphospholane" was used instead of "phospholane".

[0082] Preparation Example 4

[0083] Ligand L4 was obtained in the manner of Preparation Example 1, except that "(2R,5R)-2,5-diisopropylphospholane" was used instead of "phospholane".

[0084] Preparation Example 5

[0085] Ligand L5 was obtained in the same manner as in Preparation Example 2, except that "cyclohexylamine" was used instead of "isopropylamine".

[0086] Preparation Example 6

[0087] Ligand L6 was obtained in the same manner as in Preparation Example 2, except that "2,6-diisopropylaniline" was used instead of "isopropylamine".

[0088] Preparation Example 7

[0089] Ligand L7 was obtained in the same manner as in Preparation Example 2, except that diphenylphosphine chloride was used to replace chlorophospholane.

[0090] Example 1

[0091] Under vacuum, heat a 1L autoclave to 130°C and keep it for 2h, then replace it with nitrogen and cool it to 40°C, and replace it with ethylene three times. Add 300mL of methylcyclohexane, followed by 2.4 m mol of ligand L1,2 m mol of di(acetylacetonate)chromium and 1 mmol of modified methylaluminoxane (calculated based on the amount of aluminum atoms therein), stirred for 1 min, wherein the molar ratio of ligand:cocatalyst:transition metal oxide was 1.2:500:1, to obtain catalyst A1;

[0092] After 1 minute, ethylene was introduced into the reactor containing the catalyst A1 system. The content of the catalyst was 6.67 μmol metal / L based on the total weight of ethylene and the catalyst. The polymerization reaction was carried out under stirring. The polymerization reaction temperature was 40° C., the polymerization reaction pressure was 4 MPa, and the polymerization reaction time was 30 minutes. After the polymerization reaction was completed, the reactor was cooled to 10° C. and the pressure was released. 1 g of nonane with accurate mass measurement was added to the reactor as an internal standard and stirred evenly. 100 mL of 10% aqueous hydrochloric acid solution was added to the above mixture to quench the reaction, and the liquid product was collected for gas chromatography analysis.

[0093] The solid high molecular polymer produced by the reaction was collected by filtration, washed once with 20 mL of a 10% hydrochloric acid aqueous solution, then washed twice with 20 mL of ethanol, dried, and weighed.

[0094] Example 2

[0095] The method of Example 1 is followed, except that "ligand L2" is used to replace "ligand L1" to obtain catalyst A2, and the subsequent steps are followed according to the method of Example 1.

[0096] Example 3

[0097] The method of Example 1 is followed, except that "ligand L3" is used to replace "ligand L1" to obtain catalyst A3, and the subsequent steps are followed according to the method of Example 1.

[0098] Example 4

[0099] The method of Example 1 is followed, except that "ligand L4" is used to replace "ligand L1" to obtain catalyst A4, and the subsequent steps are followed according to the method of Example 1.

[0100] Example 5

[0101] The method of Example 1 is followed, except that "ligand L5" is used to replace "ligand L1" to obtain catalyst A5, and the subsequent steps are followed according to the method of Example 1.

[0102] Example 6

[0103] The method of Example 1 is followed, except that "ligand L6" is used to replace "ligand L1" to obtain catalyst A6, and the subsequent steps are followed according to the method of Example 1.

[0104] Example 7

[0105] The method of Example 2 is followed, except that "the temperature of the polymerization reaction is 60° C." is used instead of "the temperature of the polymerization reaction is 40° C.", and the subsequent steps are followed according to the method of Example 1.

[0106] Example 8

[0107] The method of Example 2 is followed, except that "the temperature of the polymerization reaction is 80° C." is used instead of "the temperature of the polymerization reaction is 40° C.", and the subsequent steps are followed according to the method of Example 1.

[0108] Example 9

[0109] The method of Example 7 is followed, except that "the pressure of the polymerization reaction is 5 MPa" is used instead of "the pressure of the polymerization reaction is 4 MPa", and the subsequent steps are followed according to the method of Example 1.

[0110] Example 10

[0111] The method of Example 7 was followed, except that “300 mL of methylcyclohexane was added thereto, followed by 2.4 μmol of ligand L1, 2 μmol of di(acetylacetonate)chromium and 2 mmol of modified methylaluminoxane (calculated based on the amount of aluminum atoms therein), and stirred for 1 min, wherein the molar ratio of ligand:cocatalyst:transition metal oxide was 1.2:1000:1” was used instead of “300 mL of methylcyclohexane was added thereto, followed by 2.4 μmol of ligand L1, 2 μmol of di(acetylacetonate)chromium and 2 mmol of modified methylaluminoxane (calculated based on the amount of aluminum atoms therein), and stirred for 1 min, wherein the molar ratio of ligand:cocatalyst:transition metal oxide was 1.2:1000:1”. m mol of ligand L1,2 m mol of di(acetylacetonate)chromium and 1 mmol of modified methylaluminoxane (calculated based on the amount of aluminum atoms therein), stirred for 1 min, wherein the molar ratio of ligand:cocatalyst:transition metal oxide is 1.2:500:1", to obtain catalyst A10, and the subsequent steps are carried out in the same manner as in Example 1.

[0112] Comparative Example 1

[0113] The method of Example 1 is followed, except that "ligand L7" is used to replace "ligand L1" to obtain catalyst D1, and the subsequent steps are followed according to the method of Example 1.

[0114] The activity of the prepared catalyst and the final product were tested, and the results are shown in Table 1.

[0115] Table 1

[0116]

[0117] a Catalyst activity 10 6 g·mol(Cr) -1 ·h -1 The unit meaning is: the mass of product generated by unit mole of metallic chromium per unit time.

[0118] It can be seen from the results in Table 1 that the use of the catalyst of the present invention for ethylene selective tetramerization catalysis can effectively change the selectivity of ethylene trimerization and tetramerization by changing the ligand structure in the catalyst.

[0119] Under the optimized catalyst structure and reaction conditions, higher catalytic reaction activity and ethylene trimerization and tetramerization selectivity, and ethylene tetramerization selectivity can be obtained compared with the comparative example. At the same time, the solid polymer obtained by the catalyst has low selectivity, which is conducive to using the catalyst in a continuous production device, reducing problems such as pipeline blockage caused by the large-scale generation of solid polymers, and has high industrial application value.

[0120] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. a ligand, It is characterized in that The ligand has a structure shown in formula (1), Among them, R 1 To R 7 Each is independently selected from hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl or substituted aryl.

2. The ligand according to claim 1, in, The R 1 To R 7 are independently selected from hydrogen, C 1 -C 20 Alkyl, C 1 -C 20 Substituted alkyl, C 5 -C 20 Cycloalkyl, C 6 -C 20 Aryl or C 6 -C 20 Substituted aryl; wherein the substituent when substituted is selected from halogen, C 1 -C 20 Alkyl, C 5 -C 20 Cycloalkyl and C 6 -C 20 At least one of the aromatic groups; preferably selected from halogen, C 1 -C 6 Alkyl, C 5 -C 10 Cycloalkyl and C 6 -C 10 at least one of aromatic groups; Preferably, the R 1 To R 4 are independently selected from hydrogen, C 1 -C 6 Alkyl, C 1 -C 6 Substituted alkyl, phenyl or C 6 -C 12 Substituted aryl; wherein the substituent when substituted is selected from C 1 -C 20 Alkyl, C 5 -C 20 Cycloalkyl and C 6 -C 20 At least one of the aromatic groups; preferably selected from C 1 -C 6 Alkyl, C 5 -C 10 Cycloalkyl and C 6 -C 10 at least one of aromatic groups; Preferably, the R 5 At least one selected from hydrogen, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isopropyl, isobutyl, tert-butyl, isopentyl, tert-pentyl, cyclopentyl, cyclohexyl, 2,6-dimethylcyclohexyl, methoxy, benzyl, phenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 3-isopropylphenyl, 4-isopropylphenyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthracenyl, biphenyl, p-fluorophenyl, o-fluorophenyl and m-fluorophenyl; Preferably, the R 6 and R 7 Each is independently selected from at least one of methyl, ethyl, n-propyl, isopropyl, tert-butyl, cyclopentyl and cyclohexyl.

3. The ligand according to claim 1 or 2, in, The ligand is selected from At least one of, preferably selected from At least one of .

4. A method for preparing a catalyst, It is characterized in that The preparation method comprises: subjecting a ligand, a transition metal compound and a co-catalyst to an in-situ reaction to obtain the catalyst; Wherein, the ligand is the ligand described in any one of claims 1-3.

5. The preparation method according to claim 4, in, The general formula of the transition metal compound is AR n ; wherein A is selected from transition metals, preferably at least one selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten and palladium, more preferably at least one selected from chromium, cobalt, titanium, iron, nickel and palladium, most preferably chromium; Among them, R n At least one selected from inorganic anions, organic anions and organic neutral molecules, wherein n is an integer of 1-6; Preferably, the co-catalyst is selected from at least one of an alkyl aluminum compound, an alkyl aluminoxane compound and an organic boron compound; Preferably, in the catalyst, the molar ratio of the ligand: the co-catalyst: the transition metal in the transition metal compound is 0.01-100:1-100000:1; preferably 0.1-10:1-10000:

1.

6. The preparation method according to claim 4 or 5, in, The transition metal compound is selected from at least one of chromium trichloride-tri(tetrahydrofuran) complex, benzene tricarbonyl chromium, chromium octoate, chromium hexacarbonyl, chromium acetylacetonate, chromium naphthenate, chromium 2-ethylhexanoate, chromium acetate, 2,2,6,6-tetramethylheptanedione chromium and chromium chloride, preferably at least one of chromium trichloride-tri(tetrahydrofuran) complex, chromium acetylacetonate, chromium 2-ethylhexanoate and di(acetylacetonate)chromium; Preferably, the alkyl aluminum compound is selected from at least one of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum, aluminum alkyl aluminum halide, alkyl aluminum hydride or alkyl aluminum sesquichloride, preferably diethyl aluminum monochloride and / or triethyl aluminum trichloride; Preferably, the alkylaluminoxane compound is selected from at least one of a linear alkylaluminoxane compound, a cyclic alkylaluminoxane compound and a caged alkylaluminoxane compound; preferably selected from at least one of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and modified aluminoxane; Preferably, the organic boron compound is selected from at least one of boroxine, triethylborane, triphenylborane and tri(pentafluorophenyl)borane, preferably tri(pentafluorophenyl)borane.

7. The preparation method according to any one of claims 4 to 6, in, The conditions of the in-situ reaction include: the temperature of the in-situ reaction is 0-200° C., preferably 20-100° C.; the time of the in-situ reaction is 1-300 min, preferably 1-100 min.

8. A catalyst prepared by the preparation method according to any one of claims 4 to 7.

9. The catalyst according to claim 8, in, The content of transition metal elements in the catalyst is 0.001 wt%-50 wt%, preferably 0.01 wt%-45 wt%.

10. Use of the catalyst according to claim 9 in the selective tetramerization of ethylene.

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