A method for producing alpha-olefins

Abstract

The present invention discloses a method for producing alpha-olefins, and relates to the technical field of alpha-olefin synthesis, in order to solve the problem that the polymer produced when producing alpha-olefins remains in the reactor and pipeline, affects the heat transfer of the reactor and the alpha-olefins are difficult to separate. The preparation method of the alpha-olefin includes: adding a solvent and a co-catalyst to a reactor containing ethylene, then adding a catalyst, carrying out an ethylene polymerization reaction, and obtaining alpha-olefins, wherein the alpha-olefins include 1-octene and 1-hexene. The preparation method of the alpha-olefin provided by the present invention is used for the production of alpha-olefins, and under the condition of not increasing the reaction temperature, the amount of polymer generated in the polymerization reaction can be minimized. At the same time, under the condition of not removing the solvent, 1-hexene and 1-octene can be directly separated and purified, which not only reduces the equipment investment, but also improves the yield of 1-hexene and 1-octene, and reduces the separation cost. In addition, after the polymerization reaction ends, the solvent does not need to be distilled and can be directly reused, which ensures the continuous operation of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of alpha-olefin synthesis, and in particular to a method for producing alpha-olefin. Background Art

[0002] α-olefin is an important terminal olefin product, which has a wide range of uses in the fields of polyolefin comonomers, plasticizers, surfactant synthesis intermediates, synthetic advanced lubricant base oils and lubricant additives. In recent years, the demand for α-olefins has grown rapidly and the import volume has increased significantly. Among them, 1-octene is an important comonomer for the production of high-performance high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), and is also an important raw material for the production of fine chemicals such as fragrances, dyes, plasticizers, surfactants, fatty alcohols, etc.

[0003] At present, the main process for producing high-grade α-olefins such as 1-hexene and 1-octene is ethylene polymerization. The copolymer (PE) of ethylene and a small amount of α-olefin generated by the polymerization reaction needs to be cleaned up manually. When the residual PE is cleaned up manually, the reaction temperature needs to be increased to above 80°C or even higher. However, in the prior art, ethylene tetramerization catalyst is generally used. In order to avoid high-temperature deactivation of ethylene tetramerization catalyst and improve reaction efficiency, the reaction temperature is often set below 65°C, resulting in PE remaining in the reactor and pipeline, thereby blocking the pipeline, affecting the heat transfer of the reactor, and reducing the reaction efficiency.

[0004] Moreover, in the prior art process of preparing 1-octene by ethylene polymerization, when methylcyclohexane is used as solvent, many oligomers adhere to the equipment during the polymerization process, and the proportion of α-olefin is 30-50%, and the rest is basically solvent, which is a large proportion. Since the boiling point of methylcyclohexane is 101° C., and the boiling point of 1-octene is 123° C. To obtain 1-octene by distillation, methylcyclohexane needs to be distilled off first, and then 1-octene or 1-hexene needs to be separated, and the separation process is complicated. Summary of the invention

[0005] The object of the present invention is to provide a method for producing alpha-olefins, which does not require increasing the reaction temperature or removing the solvent, and at the same time, the solvent can be directly reused, thereby ensuring the continuous operation of the device.

[0006] The present invention provides a method for preparing α-olefins, comprising:

[0007] Add a solvent and a co-catalyst to a reactor containing ethylene, then add a catalyst, perform an ethylene polymerization reaction, and obtain α-olefins, wherein the α-olefins include 1-octene and 1-hexene, the selectivity of 1-octene is >70%, and the byproduct PE (copolymer of ethylene and a small amount of α-olefins) is less than 0.2wt%. The boiling point of the solvent is greater than the boiling point of 1-hexene and the boiling point of 1-octene, and the solvent is selected from at least one of n-octane, n-nonane, n-decane, n-dodecane, and n-tetradecane. After the ethylene polymerization reaction, 1-hexene and 1-octene are separated by distillation, and the remaining solvent and olefins with a carbon number greater than 10 are directly recycled, and the mass fraction of olefins with a carbon number greater than 10 in the recycled solvent is monitored;

[0008] When the solvent is recycled for multiple times and the olefin components with carbon atoms greater than 10 in the solvent accumulate to more than 50 wt %, the solvent is used as a raw material for poly-α-olefin synthetic oil.

[0009] Compared with the prior art, the above technical solution has the following technical effects:

[0010] The embodiment of the present invention adopts a specific high boiling point solvent, especially n-nonane and n-heptane, which can dissolve the side reaction product PE relatively quickly, avoid PE adhering to the inner wall of the reactor and the stirring blade, and then avoid the repolymerization of the adhering PE part, thereby significantly reducing the amount of polymer PE generated, and almost no polymer can be seen in the kettle; in addition, the use of these solvents with boiling points significantly higher than the boiling points of 1-hexene and 1-octene can more easily achieve the separation of 1-hexene and 1-octene, and the reaction solvent can be directly recycled after separating 1-hexene and 1-octene, which increases the continuous operation time of the device, greatly improves the production efficiency, and has high economic added value. When the solvent is recycled for many times, when the olefin component with a carbon number greater than 10 accumulates to more than 50%, it can be directly used as a PAO (poly alpha olefin synthetic oil) raw material to directly complete the utilization of by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0012] Figure 1 A flow chart for preparing the catalyst ligand provided by the present invention;

[0013] Figure 2 A flow chart for preparing the second intermediate product provided by the present invention;

[0014] Figure 3 A process flow chart for producing 1-octene and 1-hexene by ethylene polymerization provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0017] 1-Hexene and 1-octene are important comonomers for producing high-performance high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), and are also important raw materials for producing fine chemicals such as fragrances, dyes, plasticizers, surfactants, fatty alcohols, etc. At present, the main process for producing high-grade α-olefins such as 1-hexene and 1-octene is ethylene polymerization. However, the biggest difficulty affecting the industrial application of ethylene polymerization is the accumulation of polymers, which affects the continuous operation time of the device. The copolymer (PE) of ethylene and a small amount of α-olefins generated by the polymerization reaction will remain in the reactor and pipeline, affecting the heat transfer of the reactor, or blocking the pipeline, affecting the heat transfer of the reactor, and reducing the reaction efficiency. It is necessary to manually clean up the residual PE.

[0018] In addition, in the ethylene polymerization reaction, low-boiling point solvents (such as cyclohexane and methylcyclohexane) are usually used, and the solvent accounts for a large proportion. To obtain high-purity higher α-olefins such as 1-hexene and 1-octene, the solvent must be evaporated first, which greatly increases the separation cost.

[0019] In view of the above problems, an embodiment of the present invention provides a method for producing α-olefins, which includes an ethylene oligomerization method. In order to solve the problem that the PE produced when using the ethylene oligomerization method to produce α-olefins in the prior art is easy to remain in the reactor and pipeline, affecting the heat transfer of the reactor, and the separation cost is high. By using the catalyst and solvent of the present application, when producing α-olefins, not only the generation of PE is reduced and the reaction heat transfer efficiency is improved, but also 1-hexene and 1-octene can be directly separated, reducing the separation cost.

[0020] In an achievable manner, the method for producing α-olefins provided by an embodiment of the present invention comprises: adding a solvent and a co-catalyst to a reactor containing ethylene, and then adding a catalyst to carry out an ethylene polymerization reaction to obtain α-olefins, wherein the α-olefins include 1-octene and 1-hexene, the selectivity of 1-octene is >70%, and the by-product PE is less than 0.2wt%; preferably, the selectivity of 1-octene is >75%, and the by-product PE is less than 0.15wt%. The boiling point of the solvent is greater than the boiling point of 1-hexene and the boiling point of 1-octene, and the solvent is selected from at least one of n-octane, n-nonane, n-decane, n-dodecane, and n-tetradecane. The solvent is preferably n-nonane or n-decane; and n-decane is most preferred.

[0021] In an optional manner, after the ethylene polymerization reaction in the embodiment of the present invention, 1-hexene and 1-octene are separated by distillation, and the remaining solvent in the reactor and the olefins with carbon atoms greater than 10 are directly recycled, and the mass fraction of olefins with carbon atoms greater than 10 in the recycled solvent is monitored; when the solvent is recycled for multiple times and the olefin components with carbon atoms greater than 10 accumulate to more than 50wt%, the solvent is used as a raw material for poly-alpha-olefin synthetic oil. The solvent is preferably n-nonane or n-decane; and n-decane is most preferred.

[0022] The embodiment of the present invention adopts a specific high boiling point solvent, especially n-nonane and n-heptane, which can dissolve the side reaction product PE relatively quickly, avoid PE adhering to the inner wall of the reactor and the stirring blade, and then avoid the repolymerization of the adhering PE part, thereby significantly reducing the amount of polymer PE generated, and almost no polymer can be seen in the kettle; in addition, the use of these solvents with boiling points significantly higher than the boiling points of 1-hexene and 1-octene can more easily achieve the separation of 1-hexene and 1-octene, and the reaction solvent can be directly recycled after separating 1-hexene and 1-octene, which increases the continuous operation time of the device, greatly improves the production efficiency, and has high economic added value. When the solvent is recycled for many times, when the olefin component with a carbon number greater than 10 accumulates to more than 50%, it can be directly used as a PAO (poly alpha olefin synthetic oil) raw material to directly complete the utilization of by-products.

[0023] In addition, the special solvent and catalyst used in the α-olefin production method of the present invention can reduce the adhesion of PE on the reactor, stirring blades and pipelines, and can also reduce the production of PE as a whole. By detecting the adhesion of PE in the solution and the reactor, the data shows that most of the generated PE is dissolved and dispersed in the solvent. The PE in the solution of the embodiment of the present invention can be removed by cooling and precipitation and then filtering to avoid affecting the next step of α-olefin separation and solvent recycling.

[0024] In addition, after the polymerization reaction is completed, only 1-hexene and 1-octene need to be separated. The solvent does not need to be distilled and can be directly reused. Alpha-olefins with more than 10 carbon atoms do not affect the polymerization reaction, and the activity and selectivity are almost unaffected, thus ensuring the continuous operation of the device.

[0025] For example, the catalyst used in the above method can be a late transition metal ethylene polymerization catalyst, such as Shell's SHOP catalyst, diimine nickel polymerization catalyst, or an early transition metal ethylene polymerization catalyst, such as Cp 2 ZrCl 2 etc. It can also be a complex catalyst formed by a complex reaction between a transition metal compound and a catalyst ligand such as a phosphorus-containing ligand.

[0026] Exemplarily, the above-mentioned continuous process for producing α-olefins by ethylene polymerization specifically comprises the following steps:

[0027] Heat the reactor to 120°C, evacuate for 2 hours, and then replace with high-purity inert gas and ethylene three times respectively, and maintain an ethylene environment. After the temperature drops to a certain temperature, inject the solvent and co-catalyst into the reactor in a certain proportion, and then add the main catalyst. The solvent, co-catalyst, and co-catalyst can also be added at the same time; then introduce a certain pressure of hydrogen and ethylene into the reactor in turn, and carry out ethylene polymerization under a certain pressure and temperature. After the reaction is completed, the reaction liquid first enters the buffer tank, and then passes through the quenching-filtration tower, flash tower, C6 tower, and C8 tower for separation to separate 1-hexene and 1-octene. The recovered ethylene and hydrogen are directly reused, and the solvent does not need to be distilled and can be used with C10 + The components are directly reused together to ensure the continuous operation of the device. + When the olefin component accumulation reaches more than 50%, it can be directly used as the raw material of PAO.

[0028] A small amount of organic phase was taken from the buffer tank, filtered and analyzed by gas chromatography. The solids from the quenching-filtration tower were collected, dried under constant temperature and vacuum, and weighed.

[0029] The method for producing α-olefins in the embodiment of the present invention is to add a solvent, n-nonane or decane, a co-catalyst and an inlet catalyst into a reactor containing ethylene to carry out an ethylene polymerization reaction.

[0030] Among them, the boiling point of n-nonane or decane is higher than that of 1-octene and 1-hexene. The use of such high boiling point solvents not only does not affect the catalytic activity and α-olefin selectivity, but also can significantly reduce the amount of oligomers produced. In addition, the use of high boiling point solvents improves the separation process, and only 1-hexene and 1-octene can be separated without removing the solvent first. The solvent does not need to be distilled and can be directly recycled, saving production costs.

[0031] Exemplarily, the ethylene polymerization reaction is carried out in a solvent after dehydration and deoxygenation, and the reaction temperature of the ethylene polymerization reaction is 30°C to 120°C, preferably 45°C to 70°C, and more preferably 50°C to 65°C; the reaction pressure is 1MPa to 10MPa, preferably 2MPa to 8MPa, and more preferably 5.5MPa; the reaction time is 5min to 240min, preferably 5min to 120min, and more preferably 10-60min. It should be understood that the solvent is selected from a solvent having a boiling point greater than 1-octene (122°C), such as at least one of n-octane, n-nonane or n-decane, preferably at least one of n-nonane or n-decane, and more preferably n-decane. The amount of solvent used is 30ml to 500ml of an inert solvent per μmol of metal ions, and preferably, 50ml to 300ml of an inert solvent is added per μmol of metal ions.

[0032] For the complex catalyst, the embodiment of the present invention also provides a method for preparing a catalyst ligand. Figure 1 The preparation flow chart of the catalyst ligand provided by the present invention is shown as follows: Figure 1 As shown, the preparation method of the catalyst ligand comprises:

[0033] Step 100: Under the action of a lithium reagent, a first reactant and a second reactant undergo a substitution reaction to generate a first intermediate product. The first reactant is a pyridine compound, and the second reactant has a general chemical structure of Among them, X 1 , X 1 ' and X 2 All are halogen.

[0034] For example: under -80℃, inert gas protection, stirring conditions, add n-butyl lithium (2.4M n-hexane solution), add ether solution of pyridine compounds drop by drop, and keep the temperature below -70℃ during the addition process. After the addition is completed, react at -80℃ for 2h. Then, add the ether solution of the second reactant drop by drop to the above reaction solution, and keep the temperature below -70℃ during the addition process. After the addition is completed, react at -80℃ for 4h, and then slowly heat the reaction system to 30℃ for 2h. The reaction system is extracted twice with 1M dilute sulfuric acid, the aqueous phase is combined, and the saturated sodium hydroxide aqueous solution is adjusted to neutral, a yellow solid is precipitated, filtered, and dried to obtain the first intermediate product. Among them, the reason for adding drop by drop is that the reaction is a violent exothermic reaction. The reaction at a low temperature can absorb the heat released by the reaction, so that the reaction temperature is not too high during the reaction process, ensuring that the structure of the reactants and the first intermediate product is not destroyed by high temperature, and improving the reaction efficiency.

[0035] Since the phosphorus atom of the above-mentioned catalyst ligand has a lone electron pair (i.e., a negative electron), when one of the phosphorus atoms of the catalyst ligand is connected to a benzene ring and pyridine or a pyridine containing a substituent, the phosphorus atom can form a p-π conjugation with the benzene ring connected thereto, and can also form a p-π conjugation with the pyridine or the pyridine containing a substituent connected thereto, thereby making the electron cloud density of the p-π conjugation stronger through the delocalization of electrons inside the molecule, reducing the energy of the molecule, and further increasing the stability of the molecule, thereby avoiding the decomposition of the catalyst ligand at high temperature, and having strong thermal stability.

[0036] Step 200: Under the action of the Grignard reagent, the first intermediate product and the third reactant undergo a substitution reaction to generate a second intermediate product. The third reactant has the general chemical structure of Among them, X 2 and X 2 ' are all halogen, R 2 Selected from alkyl, alkoxy, aryl, amino, mercapto or hydrogen atom.

[0037] Figure 2 The preparation flow chart of the second intermediate product provided by the present invention is shown, such as Figure 2 As shown, the preparation method of the second intermediate product comprises:

[0038] Step 201: Add a Grignard reagent to the first intermediate product to form an active intermediate.

[0039] For example: at -80°C, under inert gas protection and stirring conditions, add a tetrahydrofuran solution of the first intermediate product, then add the Grignard reagent dropwise, react for 1 hour, and then react for another 2 hours at 30°C to obtain an active intermediate.

[0040] Exemplary, the above-mentioned Grignard reagent includes an alkyl metal halide or a phenyl metal halide, the halide contained in the alkyl metal halide includes a magnesium halide or a complex formed by a magnesium halide and a lithium halide, and the alkyl contained in the alkyl metal halide includes an isopropyl group, a methyl group or an ethyl group. Wherein, when the halide contained in the alkyl metal halide is a magnesium halide, the magnesium halide includes at least one of isopropyl magnesium chloride, isopropyl magnesium bromide, ethyl magnesium chloride, ethyl magnesium bromide, methyl magnesium chloride, methyl magnesium bromide and propyl magnesium chloride. When the halide contained in the alkyl metal halide is a complex formed by a magnesium halide and a lithium halide, the alkyl metal halide is an isopropyl magnesium chloride lithium chloride complex. The alkyl metal halide is preferably an isopropyl magnesium chloride lithium chloride complex.

[0041] Step 202: Add the active intermediate dropwise to the third reactant to generate a second intermediate product.

[0042] For example: at -80°C, under inert gas protection and stirring conditions, first add a tetrahydrofuran solution of the third reactant, then add the active intermediate dropwise, react for 1 hour, then remove the solvent in vacuo, add ether to the residue to obtain a precipitate, filter, remove the solvent in vacuo from the supernatant, and dry to obtain the second intermediate product.

[0043] Step 300: Under the action of the lithium reagent, the second intermediate product and the fourth reactant undergo a substitution reaction to generate a third intermediate product, and the fourth reactant is a primary amine compound.

[0044] For example, at -80°C, under inert gas protection and stirring conditions, the second intermediate product is dissolved in ether, and n-butyl lithium (2.4M n-hexane solution) is added dropwise, and the temperature is kept below -70°C during the addition process. After the addition is completed, the reaction is carried out at -80°C for 2 hours. Then, the primary amine compound is added dropwise, and the reaction is carried out for 6 hours. The reaction solution is post-treated and dried to obtain the third intermediate product.

[0045] Step 400: Under the action of the lithium reagent, the third intermediate product and the fifth reactant undergo a substitution reaction to obtain a catalyst ligand. The chemical structure of the fifth reactant is Among them, X 4 is halogen, R 4 and R 4 ' is selected from alkyl, alkoxy, aryl, amino, thiol or hydrogen atom, and the chemical structural formula of the catalyst ligand is:

[0046]

[0047] For example: at -80°C, under inert gas protection and stirring conditions, the third intermediate product is dissolved in ether, and n-butyl lithium (2.4M n-hexane solution) is added dropwise, and the temperature is kept below -70°C during the addition process. After the addition is completed, the reaction is carried out at -80°C for 2 hours. Then the fifth reactant is added dropwise, and the reaction is carried out for 6 hours. The reaction liquid is purified by column chromatography, and the eluent is a mixed solvent of n-hexane and ethyl acetate (volume ratio is 1:1). After drying, a white solid is obtained, which is the catalyst ligand. Then, a nuclear magnetic detector is used to measure the hydrogen spectrum of the catalyst ligand.

[0048] The carbon atoms, phosphorus atoms and nitrogen atoms in the catalyst ligands of the embodiments of the present invention all have lone electron pairs, and the benzene ring and pyridine or pyridine containing substituents can form large π bonds. When phosphorus atoms and nitrogen atoms are present, due to the presence of lone electron pairs, the catalyst ligands can form delocalized large π bonds, thereby making the various delocalized electrons of the catalyst ligands more abundant. Therefore, the energy of the entire catalyst ligand is reduced and the stability is improved.

[0049] Exemplarily, the molar ratio of the first reactant and the second reactant in the embodiment of the present invention is 2:1, the molar ratio of the first intermediate product and the third reactant is 1:1, the molar ratio of the second intermediate product and the fourth reactant is 1:1, and the molar ratio of the third intermediate product and the fifth reactant is 1:1. Among them, by controlling the molar ratio of the first reactant and the second reactant at 2:1, the halogens at two positions on the second reactant can be completely replaced, so that the reaction is more complete, thereby obtaining the desired first intermediate product. By controlling the molar ratio of the first intermediate product and the third reactant at 1:1, one of the halogens on the third reactant can be replaced, and the other halogen is not replaced, to obtain the second intermediate product, so that the other halogen can be subjected to the next step of reaction. By controlling the molar ratio of the second intermediate product and the fourth reactant at 1:1, and the molar ratio of the third intermediate product and the fifth reactant at 1:1, the reaction can be more complete, thereby obtaining the desired product.

[0050] The chemical structural formula of the catalyst ligand provided in the embodiment of the present invention is:

[0051]

[0052] In general formula 1, R 1 and R 1 ' are selected from alkyl, alkoxy, aryl, amino, mercapto, hydrogen atom or halogen-containing substituents. 2 , R 3 , R 4 and R 4 ' are selected from alkyl, alkoxy, aryl, amino, mercapto or hydrogen atoms.

[0053] The catalyst ligand provided by the embodiment of the present invention comprises a benzene ring and pyridine or pyridine containing a substituent. Among them, each of the six carbon atoms on the benzene ring has a 2p orbital that does not participate in hybridization, and a closed π bond can be formed. The carbon atoms and nitrogen atoms on the pyridine ring or the pyridine ring containing a substituent overlap with each other with sp2 hybrid orbitals to form a σ bond, forming a planar six-membered ring, each atom has a p orbital perpendicular to the ring plane, each p orbital has an electron, and these p orbitals overlap laterally to form a large π bond. Since the formation of a large π bond can make the electron cloud density of the π bond stronger, the stability of the benzene ring and pyridine or pyridine containing a substituent is better. At the same time, since the phosphorus atom has a lone pair of electrons (i.e., negative electrons), when one of the phosphorus atoms of the catalyst ligand is connected to a benzene ring and pyridine or pyridine containing a substituent, the phosphorus atom can form a p-π conjugation with the benzene ring connected thereto, or can form a p-π conjugation with the pyridine or pyridine containing a substituent connected thereto, thereby making the electron cloud density of the p-π conjugation stronger through the delocalization of electrons inside the molecule, reducing the energy of the molecule, and further increasing the stability of the molecule, thereby avoiding the decomposition of the catalyst ligand at high temperatures, and having strong thermal stability.

[0054] On this basis, the carbon atom, phosphorus atom and nitrogen atom in the catalyst ligand of the embodiment of the present invention all have lone electron pairs, and benzene ring and pyridine or pyridine containing substituents can form large π bonds, and when phosphorus atom and nitrogen atom exist, due to the presence of lone electron pairs, the catalyst ligand can be made to form a delocalized large π bond, so that the various delocalized electrons of the catalyst ligand are more abundant. Therefore, the energy of the entire catalyst ligand is reduced, and stability is improved. When the catalyst ligand is applied in ethylene polymerization to prepare alpha-olefins, when reacting under high temperature conditions, although the catalyst ligand absorbs thermal energy to make the movement of electrons more active, the delocalized large π bond formed by the catalyst ligand can provide sufficient space for the movement of electrons, and the destruction of the catalyst ligand structure will not be caused. Therefore, the catalyst of the embodiment of the present invention has good temperature resistance, good stability under high temperature conditions, and the PE remaining in the reactor and pipeline can be dissolved when preparing alpha-olefins under high temperature conditions, and the clogging of the pipeline is avoided, and the reactor heat transfer and reaction efficiency are improved.

[0055] At the same time, since the catalyst ligand of the embodiment of the present invention can greatly slow down the speed of generating ethylene and a small amount of α-olefin copolymer (PE), when the reaction temperature is below 65°C, the residual PE in the reactor pipeline can be reduced, avoiding pipeline blockage.

[0056] In addition, the catalyst ligand provided in the embodiment of the present invention is more likely to form a complex with the active metal ion because the catalyst ligand is rich in various delocalized electrons and the phosphorus atom and the nitrogen atom both have lone electron pairs. The lone electron pairs can accept electrons fed back from the metal center through the empty d orbital of the phosphorus atom.

[0057] In one achievable manner, the alkyl group contained in the catalyst ligand of the embodiment of the present invention includes an alkyl group with 1 to 6 carbon atoms. It should be understood that the alkyl group with 1 to 6 carbon atoms can be a straight-chain alkyl group, or a branched alkyl group or a cycloalkyl group. For example: a straight-chain alkyl group with 1 to 6 carbon atoms can be a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group. A branched-chain alkyl group with 1 to 6 carbon atoms can be an isopropyl group, a tert-butyl group, an n-butyl group, or an n-hexyl group, or other branched-chain alkyl groups, which are not limited here. A cycloalkyl group with 1 to 6 carbon atoms can be a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group.

[0058] Exemplarily, the aryl group contained in the catalyst ligand of the embodiment of the present invention includes a phenyl substituent, a condensed ring group or a biphenyl group. When the phenyl group contains a substituent, the substituent includes at least one of a silane group, a halogen, an alkyl group, and a haloalkyl group, and the alkyl group is tri-tert-butylsilicon or methyl.

[0059] For example: when the substituent contained in the above-mentioned phenyl group is tri-tert-butylsilyl, the aryl group can be 2-tri-tert-butylsilylphenyl, 4-tri-tert-butylsilylphenyl. When the substituent contained in the phenyl group is a silyl group, the aryl group can be 4-tri-tert-butylsilylphenyl, 3-tri-tert-butylsilylphenyl, 2-tri-tert-butylsilylphenyl or 4-triisopropylsilylphenyl. When the substituent contained in the phenyl group is a halogen, the aryl group can be 2-fluorophenyl, 4-fluorophenyl, 3-fluorophenyl, 4-chlorophenyl or 3-chlorophenyl. When the substituent contained in the phenyl group is a haloalkyl, the aryl group can be 2-trifluoromethylphenyl, 4-trifluoromethylphenyl, 3-trifluoromethylphenyl, 4-trichloromethylphenyl. When the aryl group is a condensed ring group, the aryl group can be a naphthyl or anthracenyl.

[0060] In one example, the above R 1 and R 1 'Preferably methyl, isopropyl or tert-butyl, R 2 Preferably phenyl, ethyl, R 3 Preferred are isopropyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl, 4-methylphenyl, R 4 and R 4 'Preferred are phenyl, 2-fluorophenyl and naphthyl.

[0061] In an achievable manner, an embodiment of the present invention further provides a catalyst, which includes a complex with a transition metal ion as a central ion and a catalyst ligand provided in an embodiment of the present invention as an active ligand. Wherein, the transition metal ion is provided by a metal compound, and the transition metal ion is selected from one or more of chromium ions, molybdenum ions, tungsten ions, cobalt ions, rhodium ions, titanium ions, vanadium ions, zirconium ions, iron ions, nickel ions or palladium ions, preferably chromium ions, zirconium ions, nickel ions and titanium ions. The catalyst provided in an embodiment of the present invention has a relatively rich variety of delocalized electrons in the catalyst ligand, and both the phosphorus atom and the nitrogen atom have lone electron pairs, which can accept electrons fed back from the metal center through the empty d orbital of the phosphorus atom. Therefore, the catalyst ligand is more likely to form a complex with the active metal ion to obtain the required catalyst.

[0062] The present invention uses a chromium or titanium catalyst capable of forming ethylene tetramerization, an alkylaluminoxane or modified alkylaluminoxane or alkylaluminum-borate cocatalyst and corresponding catalyst system conditions, and performs a polymerization reaction in a high-boiling point specific solvent after dehydration and deoxygenation to obtain α-olefins. Preferably, the present invention uses a chromium catalyst coordinated by a phosphine-containing ligand.

[0063] Preferably, relative to the chromium catalyst, the amount of the solvent is 30 to 500 ml per μmol of chromium, more preferably, 50 to 400 ml per μmol of chromium.

[0064] The present invention adopts a chromium or titanium catalyst capable of forming ethylene tetramerization, adopts an alkylaluminoxane or modified alkylaluminoxane or alkylaluminum-borate co-catalyst and corresponding catalytic system conditions, and carries out a polymerization reaction in a high-boiling point specific solvent after dehydration and deoxygenation. The sum of the selectivity of 1-hexene and 1-octene can reach more than 95%.

[0065] In an optional manner, an embodiment of the present invention further provides a method for preparing a catalyst, comprising: performing a complex reaction on a metal compound and a catalyst ligand to form a catalyst, wherein the catalyst ligand is a catalyst ligand provided by an embodiment of the present invention. Wherein, the metal compound comprises at least one of a transition metal inorganic salt, a transition metal organic salt, an organic metal complex and a transition metal coordination compound. Preferably, it is one or more of chromium acetylacetonate, chromium chloride, tetrahydrofuran trichloride, chromium isooctanoate, chromium octanoate, chromium hexacarbonyl, (benzene) tricarbonyl chromium, chromium naphthenate, chromium acetate, and chromium 2,2,6,6-tetramethylheptanedione.

[0066] For example, when α-olefins are prepared by ethylene oligomerization, when the reaction system contains the catalyst ligand provided by the embodiment of the present invention, the molar ratio of the transition metal compound to the catalyst ligand is (1-5):1, preferably (2-3):1, and more preferably 2:1. The molar number of the metal is selected from 1 to 20 μmol, preferably 1 to 5 μmol, and more preferably 1 μmol.

[0067] In another optional manner, the cocatalyst of the embodiment of the present invention includes one or more of alkylaluminoxane, modified alkylaluminoxane, other organoaluminum compounds and boron-containing compounds, preferably methylaluminoxane and / or modified methylaluminoxane; more preferably MMAO-3A. ​​When alpha-olefins are prepared by ethylene polymerization, when the reaction system contains the catalyst composition provided by the embodiment of the present invention, the molar ratio of the cocatalyst to the transition metal compound is (100-2000):1, preferably (200-1000):1, and more preferably 500:1.

[0068] It can be seen that the production method of α-olefins provided in the embodiment of the present invention uses n-nonane or decane as a solvent. The boiling point of n-nonane or decane is higher than that of 1-octene and 1-hexene. The use of such a high boiling point solvent not only does not affect the catalytic activity and the selectivity of α-olefins, but also can greatly reduce the amount of oligomers produced. In addition, the use of a high boiling point solvent improves the separation process, and the solvent can be removed first, and only 1-hexene and 1-octene can be separated. The solvent does not need to be distilled and can be directly recycled with olefins having a carbon number greater than 10, saving production costs.

[0069] In order to verify the effect of the method for producing α-olefins provided in the examples of the present invention, the present invention uses the example to compare with the comparative example to demonstrate.

[0070] Embodiment 1

[0071] Embodiment 1 of the present invention provides a ligand 1 and a catalyst 1, wherein the structural formula of the ligand 1 is

[0072]

[0073] Embodiment 1 of the present invention provides a method for preparing the ligand 1, comprising the following steps:

[0074] In the first step, the reaction bottle was replaced with nitrogen three times at -80 °C and N 2Under protection and stirring conditions, 8.5 ml of n-butyl lithium (2.4 M n-hexane solution) was added, and then 20 mmol of 2-bromo-4-methylpyridine ether solution was added dropwise, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 2 hours. Then, 10 mmol of dichloro (2-benzylbromo)phosphine ether solution was added dropwise to the reaction solution, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 4 hours, and then the reaction system was slowly heated to 30 ° C for 2 hours. The reaction system was extracted twice with 40 ml of dilute sulfuric acid (1 M), the aqueous phase was combined, and then the pH was adjusted to neutral with a saturated sodium hydroxide aqueous solution. A yellow solid was precipitated, filtered, and dried to obtain the first intermediate product with a yield of 60%.

[0075] In the second step, the reaction flask was nitrogen replaced three times at -80 °C and N 2 Under protection and stirring conditions, a tetrahydrofuran solution (10 mmol) of the first intermediate product was added, and then a tetrahydrofuran solution (10 mmol) of isopropylmagnesium chloride and lithium chloride complex was added dropwise, and the reaction was continued for 1 h, and then at 30 ° C for another 2 h to obtain solution 1. The reaction flask was replaced with nitrogen three times and heated at -80 ° C, N 2 Under protection and stirring conditions, a solution of phenylphosphine dichloride (10 mmol) in tetrahydrofuran (60 mL) was first added, and then solution 1 was added dropwise for 1 h. The solvent was then removed in vacuo, and ether (100 mL) was added to the residue to obtain a precipitate, which was filtered, and the supernatant was removed in vacuo to obtain the solvent, and the second intermediate product was obtained after drying with a yield of 60%.

[0076] The third step is to replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2 Under protection and stirring conditions, the second intermediate product (8 mmol) was dissolved in ether, and 3.4 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then, isopropylamine (8 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was post-treated and dried to obtain the third intermediate product with a yield of 84%.

[0077] Step 4: Replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2Under protection and stirring conditions, the third intermediate product (5 mmol) was dissolved in ether, and 2.1 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then di(2-fluorophenyl)phosphine chloride (5 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was purified by column chromatography, and the eluent was a mixed solvent of n-hexane and ethyl acetate (volume ratio of 1:1). After drying, a white solid (i.e., catalyst ligand 1) was obtained, with a yield of 70%. The results of nuclear magnetic hydrogen spectrum were measured: 1H-NMR (400 MHz, CDCl3): δ7~8.6 (m, 23H), 2.8~3 (m, 1H), 2~2.7 (m, 8H), 1~1.2 (m, 6H).

[0078] Embodiment 1 of the present invention also provides a method for preparing the catalyst 1, comprising:

[0079] The reaction flask was nitrogen replaced 3 times. 2 Under protective conditions, catalyst ligand 1 (50 mmol) and metal compound chromium trichloride (100 mmol, 37.5 g) were added, and dehydrated and deoxygenated dichloromethane (50 mL) was added, and stirred at room temperature for 24 hours. After filtration, the solid was washed with n-hexane (5 mL × 3 times), and dried to obtain a blue powder (i.e., catalyst 1), with a yield of 90%.

[0080] Embodiment 1 of the present invention also provides a method for continuously producing α-olefins using the catalyst 1, comprising:

[0081] A 500 ml high-pressure reactor was used for ethylene polymerization. The reactor was heated to 120°C and vacuumed for 2 hours. The reactor was then replaced with high-purity nitrogen and ethylene three times, respectively, and the ethylene environment was maintained. When the temperature dropped to 55°C, 200 ml of dehydrated and deoxygenated solvent decane, 2 μmol Cr main catalyst (catalyst 1), and co-catalyst modified methylaluminoxane (MMAO-3A, ​​Al / Cr=500) were continuously injected into the reactor in proportion, and then 0.1 MPa of H 2 , and then supplemented with ethylene to 5MPa, and ethylene polymerization reaction was carried out for 30 minutes. The reaction liquid after the reaction first entered the buffer tank, and then passed through the quenching-filtration tower, flash tower, C6 tower, and C8 tower for separation to separate 1-hexene and 1-octene. The recovered ethylene and hydrogen were directly reused, and the solvent discharged from the bottom of the tower and the olefin components with a carbon number greater than 10 were directly reused together. A small amount of organic phase was taken from the buffer tank, filtered and analyzed by gas chromatography. The solids from the quenching-filtration tower were collected, vacuum dried at 60°C for 8 hours and weighed. The results are shown in Table 1.

[0082] Embodiment 2

[0083] Embodiment 2 of the present invention provides a ligand 2 and a catalyst 2, wherein the structural formula of the ligand 2 is:

[0084]

[0085] Embodiment 2 of the present invention provides a method for preparing the ligand 2, comprising the following steps:

[0086] In the first step, the reaction bottle was replaced with nitrogen three times at -80 °C and N 2 Under protection and stirring conditions, 8.5 ml of n-butyl lithium (2.4 M n-hexane solution) was added, and then 20 mmol of 2-bromo-4-methylpyridine ether solution was added dropwise, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 2 hours. Then, 10 mmol of dichloro (2-benzylbromo)phosphine ether solution was added dropwise to the reaction solution, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 4 hours, and then the reaction system was slowly heated to 30 ° C for 2 hours. The reaction system was extracted twice with 40 ml of dilute sulfuric acid (1 M), the aqueous phase was combined, and then the pH was adjusted to neutral with a saturated sodium hydroxide aqueous solution. A yellow solid was precipitated, filtered, and dried to obtain the first intermediate product with a yield of 62%.

[0087] In the second step, the reaction flask was nitrogen replaced three times at -80 °C and N 2 Under protection and stirring conditions, a tetrahydrofuran solution (10 mmol) of the first intermediate product was added, and then a tetrahydrofuran solution (10 mmol) of isopropylmagnesium chloride and lithium chloride complex was added dropwise, and the reaction was continued for 1 h, and then at 30 ° C for another 2 h to obtain solution 1. The reaction flask was replaced with nitrogen three times and heated at -80 ° C, N 2 Under protection and stirring conditions, a solution of phenylphosphine dichloride (10 mmol) in tetrahydrofuran (60 mL) was first added, and then solution 1 was added dropwise for 1 h. The solvent was then removed in vacuo, and ether (100 mL) was added to the residue to obtain a precipitate, which was filtered, and the supernatant was removed in vacuo to obtain the solvent, and the second intermediate product was obtained after drying with a yield of 58%.

[0088] The third step is to replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2 Under protection and stirring conditions, the second intermediate product (8 mmol) was dissolved in ether, and 3.4 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then cyclopentylamine (8 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was post-treated and dried to obtain the third intermediate product with a yield of 80%.

[0089] Step 4: Replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2Under protection and stirring conditions, the third intermediate product (5 mmol) was dissolved in ether, and 2.1 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then diethylphosphine chloride (5 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was purified by column chromatography, and the eluent was a mixed solvent of n-hexane and ethyl acetate (volume ratio of 1:1). After drying, a white solid (i.e., catalyst ligand 2) was obtained, and the yield was 72%. The results of nuclear magnetic hydrogen spectrum were measured: 1H-NMR (400 MHz, CDCl3): δ7~8.6 (m, 15H), 2~3 (m, 9H), 1~1.8 (m, 18H).

[0090] Embodiment 2 of the present invention also provides a method for preparing the catalyst 2, comprising:

[0091] The reaction flask was nitrogen replaced 3 times. 2 Under protective conditions, catalyst ligand 2 (50 mmol) and metal compound chromium acetylacetonate (100 mmol) were added, and dehydrated and deoxygenated dichloromethane (50 mL) was added, and stirred at room temperature for 24 hours. After filtration, the solid was washed with n-hexane (5 mL × 3 times), and dried to obtain a blue powder (i.e., catalyst 2), with a yield of 85%.

[0092] The second embodiment of the present invention also provides a method for continuously producing α-olefins using the catalyst 2, wherein the reaction process is the same as that of the first embodiment, except that the solvent decane is replaced by n-nonane and the reaction temperature is 53° C. The results are shown in Table 1.

[0093] Embodiment 3

[0094] Embodiment 3 of the present invention provides a ligand 3 and a catalyst 3, wherein the structural formula of the ligand 3 is:

[0095] Embodiment 3 of the present invention provides a method for preparing the ligand 3, comprising the following steps:

[0096] In the first step, the reaction bottle was replaced with nitrogen three times at -80 °C and N 2Under protection and stirring conditions, 8.5 ml of n-butyl lithium (2.4 M n-hexane solution) was added, and then 20 mmol of 2-bromo-4-isopropylpyridine ether solution was added dropwise, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 2 hours. Then, 10 mmol of dichloro (2-benzylbromo)phosphine ether solution was added dropwise to the reaction solution, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 4 hours, and then the reaction system was slowly heated to 30 ° C for 2 hours. The reaction system was extracted twice with 40 ml of dilute sulfuric acid (1 M), the aqueous phase was combined, and then the pH was adjusted to neutral with a saturated sodium hydroxide aqueous solution. A yellow solid was precipitated, filtered, and dried to obtain the first intermediate product with a yield of 58%.

[0097] In the second step, the reaction flask was nitrogen replaced three times at -80 °C and N 2 Under protection and stirring conditions, a tetrahydrofuran solution (10 mmol) of the first intermediate product was added, and then a tetrahydrofuran solution (10 mmol) of isopropylmagnesium chloride and lithium chloride complex was added dropwise, and the reaction was continued for 1 h, and then at 30 ° C for another 2 h to obtain solution 1. The reaction flask was replaced with nitrogen three times and heated at -80 ° C, N 2 Under protection and stirring conditions, a solution of ethylphosphine dichloride (10 mmol) in tetrahydrofuran (60 mL) was first added, and then solution 1 was added dropwise for 1 h. The solvent was then removed in vacuo, and ether (100 mL) was added to the residue to obtain a precipitate, which was filtered, and the supernatant was removed in vacuo to obtain the solvent, and the second intermediate product was obtained after drying with a yield of 59%.

[0098] The third step is to replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2 Under protection and stirring conditions, the second intermediate product (8 mmol) was dissolved in ether, and 3.4 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then aniline (8 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was post-treated and dried to obtain the third intermediate product with a yield of 82%.

[0099] Step 4: Replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2Under protection and stirring conditions, the third intermediate product (5mmol) was dissolved in ether, and 2.1ml of n-butyl lithium (2.4M n-hexane solution) was added dropwise, and the temperature was kept below -70℃ during the addition process. After the addition was completed, the reaction was carried out at -80℃ for 2h. Then diphenylphosphine chloride (5mmol) was added dropwise, and the reaction was carried out for 6h. The reaction solution was purified by column chromatography, and the eluent was a mixed solvent of n-hexane and ethyl acetate (volume ratio of 1:1). After drying, a white solid (i.e., catalyst ligand 1) was obtained with a yield of 70%. The results of nuclear magnetic hydrogen spectrum were measured: 1H-NMR (400MHz, CDCl3): δ7~8.6 (m, 22H), 6~6.8 (m, 3H), 2~3.5 (m, 4H), 1~1.8 (m, 17H).

[0100] Embodiment 3 of the present invention further provides a method for preparing the catalyst 3, comprising:

[0101] The reaction flask was nitrogen replaced 3 times. 2 Under protective conditions, catalyst ligand 3 (50 mmol) and metal compound tetrahydrofuran chromium trichloride (100 mmol) were added, and dehydrated and deoxygenated dichloromethane (50 mL) was added, and stirred at room temperature for 24 hours. After filtration, the solid was washed with n-hexane (5 mL × 3 times), and dried to obtain a blue powder (i.e., catalyst 1), with a yield of 87%.

[0102] The third embodiment of the present invention also provides a method for continuously producing α-olefins using the catalyst 3, wherein the reaction process is the same as that of the first embodiment, except that the reaction time is 20 min and the reaction temperature is 50° C. The results are shown in Table 1.

[0103] Embodiment 4

[0104] Embodiment 4 of the present invention provides a ligand 4 and a catalyst 4, wherein the structural formula of the ligand 4 is:

[0105]

[0106] Embodiment 4 of the present invention provides a method for preparing the ligand 4, comprising the following steps:

[0107] In the first step, the reaction bottle was replaced with nitrogen three times at -80 °C and N 2Under protection and stirring conditions, 8.5 ml of n-butyl lithium (2.4 M n-hexane solution) was added, and then 20 mmol of 2-bromo-4-isopropylpyridine ether solution was added dropwise, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 2 hours. Then, 10 mmol of dichloro (2-benzylbromo)phosphine ether solution was added dropwise to the reaction solution, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 4 hours, and then the reaction system was slowly heated to 30 ° C for 2 hours. The reaction system was extracted twice with 40 ml of dilute sulfuric acid (1 M), the aqueous phase was combined, and then the pH was adjusted to neutral with a saturated sodium hydroxide aqueous solution. A yellow solid was precipitated, filtered, and dried to obtain the first intermediate product with a yield of 63%.

[0108] In the second step, the reaction flask was nitrogen replaced three times at -80 °C and N 2 Under protection and stirring conditions, a tetrahydrofuran solution (10 mmol) of the first intermediate product was added, and then a tetrahydrofuran solution (10 mmol) of isopropylmagnesium chloride and lithium chloride complex was added dropwise, and the reaction was continued for 1 h, and then at 30 ° C for another 2 h to obtain solution 1. The reaction flask was replaced with nitrogen three times and heated at -80 ° C, N 2 Under protection and stirring conditions, a solution of dichlorophenylphosphine (10 mmol) in tetrahydrofuran (60 mL) was first added, and then solution 1 was added dropwise for 1 h. The solvent was then removed in vacuo, and ether (100 mL) was added to the residue to obtain a precipitate, which was filtered, and the supernatant was removed in vacuo to obtain the solvent, and the second intermediate product was obtained after drying with a yield of 61%.

[0109] The third step is to replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2 Under protection and stirring conditions, the second intermediate product (8 mmol) was dissolved in ether, and 3.4 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then, isopropylamine (8 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was post-treated and dried to obtain the third intermediate product with a yield of 81%.

[0110] Step 4: Replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2Under protection and stirring conditions, the third intermediate product (5 mmol) was dissolved in ether, and 2.1 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then diethylphosphine chloride (5 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was purified by column chromatography, and the eluent was a mixed solvent of n-hexane and ethyl acetate (volume ratio of 1:1). After drying, a white solid (i.e., catalyst ligand 4) was obtained, with a yield of 70%. The results of the nuclear magnetic hydrogen spectrum were measured: 1H-NMR (400 MHz, CDCl3): δ7~8.6 (m, 15H), 2~3 (m, 5H), 1~1.8 (m, 28H).

[0111] Embodiment 4 of the present invention further provides a method for preparing the catalyst 4, comprising:

[0112] The reaction flask was nitrogen replaced 3 times. 2 Under protective conditions, catalyst ligand 4 (50 mmol) and metal compound chromium octanoate (100 mmol) were added, and dehydrated and deoxygenated dichloromethane (50 mL) was added, and stirred at room temperature for 24 hours. After filtration, the solid was washed with n-hexane (5 mL × 3 times), and dried to obtain a blue powder (i.e., catalyst 4), with a yield of 83%.

[0113] The fourth embodiment of the present invention also provides a method for continuously producing α-olefins using the catalyst 4, wherein the reaction process is the same as that of the first embodiment, except that the solvent decane is replaced by n-nonane, the reaction time is 40 min, and the reaction temperature is 60° C. The results are shown in Table 1.

[0114] Embodiment 5

[0115] Embodiment 6 of the present invention provides a ligand 5 and a catalyst 5, wherein the structural formula of the ligand 5 is:

[0116]

[0117] Embodiment 5 of the present invention provides a method for preparing the ligand 5, comprising the following steps:

[0118] In the first step, the reaction bottle was replaced with nitrogen three times at -80 °C and N 2Under protection and stirring conditions, 8.5 ml of n-butyl lithium (2.4 M n-hexane solution) was added, and then 20 mmol of 2-bromo-4-tert-butylpyridine in ether solution was added dropwise, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 2 hours. Then, 10 mmol of dichloro (2-benzylbromo)phosphine in ether solution was added dropwise to the reaction solution, and the temperature was kept below -70 ° C during the addition process. After the addition was completed, the reaction was carried out at -80 ° C for 4 hours, and then the reaction system was slowly heated to 30 ° C for 2 hours. The reaction system was extracted twice with 40 ml of dilute sulfuric acid (1 M), the aqueous phase was combined, and then the pH was adjusted to neutral with a saturated sodium hydroxide aqueous solution. A yellow solid was precipitated, filtered, and dried to obtain the first intermediate product with a yield of 65%.

[0119] In the second step, the reaction flask was nitrogen replaced three times at -80 °C and N 2 Under protection and stirring conditions, a tetrahydrofuran solution (10 mmol) of the first intermediate product was added, and then a tetrahydrofuran solution (10 mmol) of isopropylmagnesium chloride and lithium chloride complex was added dropwise, and the reaction was continued for 1 h, and then at 30 ° C for another 2 h to obtain solution 1. The reaction flask was replaced with nitrogen three times and heated at -80 ° C, N 2 Under protection and stirring conditions, a solution of phenylphosphine dichloride (10 mmol) in tetrahydrofuran (60 mL) was first added, and then solution 1 was added dropwise for 1 h. The solvent was then removed in vacuo, and ether (100 mL) was added to the residue to obtain a precipitate, which was filtered, and the supernatant was removed in vacuo to obtain the solvent, and the second intermediate product was obtained after drying with a yield of 64%.

[0120] The third step is to replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2 Under protection and stirring conditions, the second intermediate product (8 mmol) was dissolved in ether, and 3.4 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then cyclopentylamine (8 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was post-treated and dried to obtain the third intermediate product with a yield of 85%.

[0121] Step 4: Replace the nitrogen atmosphere in the reaction flask three times at -80 °C and N 2Under protection and stirring conditions, the third intermediate product (5 mmol) was dissolved in ether, and 2.1 ml of n-butyl lithium (2.4 M n-hexane solution) was added dropwise, and the temperature was kept below -70°C during the addition process. After the addition was completed, the reaction was carried out at -80°C for 2 hours. Then diethylphosphine chloride (5 mmol) was added dropwise, and the reaction was carried out for 6 hours. The reaction solution was purified by column chromatography, and the eluent was a mixed solvent of n-hexane and ethyl acetate (volume ratio of 1:1). After drying, a white solid (i.e., catalyst ligand 6) was obtained, with a yield of 74%. The results of nuclear magnetic hydrogen spectrum were measured: 1H-NMR (400 MHz, CDCl3): δ7~8.6 (m, 15H), 2~3 (m, 3H), 1~1.9 (m, 36H).

[0122] Embodiment 5 of the present invention further provides a method for preparing the catalyst 5, comprising:

[0123] The reaction flask was nitrogen replaced 3 times. 2 Under protective conditions, catalyst ligand 1 (50 mmol) and metal compound tetrahydrofuran chromium trichloride (100 mmol) were added, and dehydrated and deoxygenated dichloromethane (50 mL) was added, and stirred at room temperature for 24 hours. After filtration, the solid was washed with n-hexane (5 mL × 3 times), and dried to obtain a blue powder (i.e., catalyst 6), with a yield of 88%.

[0124] The fifth embodiment of the present invention also provides a method for continuously producing α-olefins using the catalyst 5, wherein the reaction process is the same as that of the first embodiment, except that the reaction time is 45 min and the reaction temperature is 50° C. The results are shown in Table 1.

[0125] Embodiment 6

[0126] The catalyst 1 and reaction process conditions of Example 1 were used, except that the solvent decane was replaced with decane containing about 5% C10 and C12, and the reaction time was 50 min. The results are shown in Table 1.

[0127] Comparative Example 1

[0128] The catalyst 1 and reaction process conditions were the same as those in Example 1, except that the solvent decane was replaced with methylcyclohexane. The results are shown in Table 1.

[0129] Comparative Example 2

[0130] The catalyst 2 and reaction process conditions are the same as those of Example 2, except that the solvent nonane is replaced with n-hexane. The results are shown in Table 1.

[0131] Comparative Example 3

[0132] The reaction process conditions were the same as those in Example 1, except that ligand 1 was replaced with (diphenyl)phosphine nitrogen (cyclohexyl)phosphine (diphenyl) ligand to prepare the corresponding catalyst for the experiment. The results are shown in Table 1.

[0133] Comparative Example 4

[0134] The catalyst 1 and reaction process conditions are the same as those in Example 1, except that the solvent decane is replaced with C10 + The olefin content of the recycled decane is about 50%. The results are shown in Table 1.

[0135] Table 1 Ethylene oligomerization performance results

[0136]

[0137] PE content (wt%) refers to the mass percentage of polymer PE in the reaction product, generally including PE in the solution and PE adhering to the stirring blade and the wall of the reactor.

[0138] The PE distribution of each embodiment and comparative example is shown in Table 2

[0139] Table 2 PE distribution

[0140]

[0141] From the data in Tables 1 and 2, it can be found that the PE content produced by the present invention is much lower than that of existing solvents and other ligand catalysts, and the PE is low molecular weight PE that can be dissolved in the solution, and the PE adhering to the stirring paddle is less, and the total amount of PE on the reactor wall and the stirring paddle is less than 35%, and most of it exists in the solution, which is greatly beneficial to continuous production. However, if a low boiling point solvent is used, the dissolution efficiency of PE is poor, and the PE that is not dissolved in time will adhere to the reactor wall and the stirring paddle. These adhered PE surfaces are prone to continue polymerization and adhesion, resulting in the production of more PE.

[0142] As can be seen from the above table, the catalyst ligand and catalyst of the present application are used in Examples 1 to 6, Comparative Examples 1 and 2 of the present invention, and the catalyst of the present application is not used in Comparative Example 3. The PE residues in Examples 1 to 6 are much smaller than those in Comparative Examples 1, 2 and 3. Comparative Example 4 uses the C10 + Even with a solvent having an olefin content of about 50%, the PE content produced by the reaction is still lower than that of other comparative examples. Therefore, the special solvent used in the embodiment of the present invention not only ensures the catalytic activity and α-olefin selectivity, but also can significantly reduce the amount of oligomers generated.

[0143] At the same time, in Examples 1 to 6 of the present invention, n-nonane or decane is used as the solvent, and the residual PE content thereof is much smaller than that in Comparative Examples 1, 2 and 3. Since the boiling point of n-nonane or decane is higher than that of 1-hexene and 1-octene, after the reaction is completed, ethylene and hydrogen are directly recycled without removing the solvent. After directly separating 1-hexene and 1-octene, the solvent does not need to be distilled and can be used with C10 + Direct recycling saves production costs and ensures the continuous operation of the device. + When the above components accumulate to more than 50%, they can be directly used as PAO raw materials with high economic added value.

[0144] Furthermore, since the embodiment of the present invention uses a high boiling point solvent, the amount of polymer generated is significantly reduced, the continuous operation time of the device is increased, and the economic benefit is high.

[0145] The above is only a specific embodiment of the present invention. Obviously, various modifications and combinations can be made without departing from the spirit and scope of the present invention. Accordingly, this specification and the drawings are only exemplary illustrations of the present invention as defined by the attached claims, and are deemed to have covered any and all modifications, changes, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and variations. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope of protection of the claims.

Claims

1. A method for producing α-olefins, characterized in that: include: The transition metal compound and the catalyst ligand are subjected to a complex reaction to form a catalyst; Adding a solvent and a co-catalyst to a reactor containing ethylene, and then adding a catalyst to carry out an ethylene polymerization reaction to obtain α-olefins; The α-olefins include 1-octene and 1-hexene, and the selectivity of 1-octene is greater than 70%, and the by-product PE is less than 0.2wt%; The transition metal compound is a chromium-based transition metal compound, and the transition metal compound includes at least one of a transition metal inorganic salt, a transition metal organic salt, an organic metal complex, and a transition metal coordination compound; The boiling point of the solvent is greater than the boiling points of 1-hexene and 1-octene, the solvent is selected from at least one of n-nonane, n-decane, n-dodecane and n-tetradecane, and the cocatalyst is a modified alkylaluminoxane; The reaction temperature of the ethylene polymerization reaction is 30°C to 120°C, the reaction pressure of the ethylene polymerization reaction is 1MPa to 10MPa, and the reaction time of the ethylene polymerization reaction is 5min to 240min; The chemical structural formula of the catalyst ligand is: , where R1 and R1 ' is selected from a C1-C6 alkyl group, R2 is selected from a C1-C6 alkyl group or a phenyl group, R3 is selected from a C1-C6 alkyl group, a cyclopentyl group or a phenyl group, R4 and R4 ' Selected from C1~C6 alkyl, phenyl or difluorophenyl.

2. The method for producing α-olefins according to claim 1, characterized in that: After the ethylene oligomerization reaction, 1-hexene and 1-octene are separated by distillation, the remaining solvent and olefins with carbon atoms greater than 10 are directly recycled, and the mass fraction of olefins with carbon atoms greater than 10 in the recycled solvent is monitored; When the solvent is recycled for multiple times and the olefin components with carbon atoms greater than 10 accumulate to more than 50 wt %, the solvent is used as a raw material for poly-α-olefin synthetic oil.

3. The method for producing α-olefins according to claim 1, characterized in that: Before the transition metal compound and the catalyst ligand are subjected to complex reaction to form the catalyst, the method further comprises: Under the action of the lithium reagent, the first reactant and the second reactant undergo a substitution reaction to generate a first intermediate product, wherein the first reactant is a pyridine compound, and the chemical structure of the second reactant is generally expressed as follows: , wherein X1, X1' and X2 are all halogen; Under the action of the Grignard reagent, the first intermediate product and the third reactant undergo a substitution reaction to generate a second intermediate product. The chemical structure of the third reactant is generally as follows: , wherein X2 and X2' are both halogen; Under the action of the lithium reagent, the second intermediate product and the fourth reactant undergo a substitution reaction to generate a third intermediate product, wherein the fourth reactant is a primary amine compound; Under the action of the lithium reagent, the third intermediate product and the fifth reactant undergo a substitution reaction to obtain a catalyst ligand, and the chemical structure of the fifth reactant is generally expressed as follows: , wherein X4 is a halogen; the chemical structural formula of the catalyst ligand is: , where R1 and R1 ' is selected from a C1-C6 alkyl group, R2 is selected from a C1-C6 alkyl group or a phenyl group, R3 is selected from a C1-C6 alkyl group, a cyclopentyl group or a phenyl group, R4 and R4 ' Selected from C1~C6 alkyl, phenyl or difluorophenyl.

4. The method for producing α-olefins according to claim 3, characterized in that: The first intermediate product and the third reactant undergo a substitution reaction under the action of a Grignard reagent to generate a second intermediate product, comprising: adding a Grignard reagent to the first intermediate product to form an active intermediate; The active intermediate is added dropwise to the third reactant to generate a second intermediate product.

5. The method for producing α-olefins according to claim 3, characterized in that: The molar ratio of the first reactant to the second reactant is 2:1, the molar ratio of the first intermediate product to the third reactant is 1:1, the molar ratio of the second intermediate product to the fourth reactant is 1:1, and the molar ratio of the third intermediate product to the fifth reactant is 1:

1.

6. The method for producing α-olefins according to any one of claims 3 to 5, characterized in that: The Grignard reagent includes an alkyl metal halide or a phenyl metal halide, the halide contained in the alkyl metal halide includes magnesium halide or a complex formed by magnesium halide and lithium halide, and the alkyl contained in the alkyl metal halide includes isopropyl, methyl or ethyl.

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