Catalytic system for selective oligomerization of ethylene and application thereof

Abstract

The application discloses a catalytic system for ethylene selective oligomerization and application, belongs to the field of high linear alpha-olefin catalysts prepared by ethylene oligomerization, and is mainly used for preparing 1-hexene and 1-octene by ethylene trimerization and tetramerization. The catalytic system comprises four parts of a chromium-based main catalyst, an organic boron assistant, an alkyl aluminum cocatalyst and a promoter. The chromium-based main catalyst is a complex with trivalent chromium as a central ion and a bidentate phosphine as a ligand. The organic boron assistant is selected from one or more of organic boranes, borate esters and organic boron salts. The promoter is a chloro-substituted alkane and / or a chloro-substituted arene. The catalytic system can greatly reduce the generation of high polymers without changing the activity and selectivity of the catalyst, and can replace the existing MAO or MMAO catalytic system, thereby greatly reducing the production cost.

Description

Technical Field

[0001] This invention relates to the field of catalytic preparation of polyolefins, and more particularly to the field of catalysts for the preparation of highly linear α-olefins by ethylene oligomerization. These catalysts are mainly used for the preparation of 1-hexene and 1-octene by ethylene trimerization and tetramerization. In particular, this invention relates to a catalytic system and its application for selective oligomerization of ethylene. Background Technology

[0002] Linear α-olefins are a class of important chemical raw materials with huge demand. Among them, C4-C24 linear α-olefins are widely used in the preparation of low-density polyethylene, high-density polyethylene, high-grade detergents, high-grade lubricants, surfactants, polyolefin elastomers (POE), and higher linear alcohols. With the continuous development of the global economy, people's requirements for high-performance polyolefin materials and lubricant base oils are increasing. The application of higher linear α-olefins such as 1-hexene, 1-octene, 1-decene, and 1-dodecene in high-performance polyolefins and high-end synthetic lubricants is constantly increasing, and their demand continues to grow.

[0003] Ethylene oligomerization is one of the main methods for producing high-purity 1-hexene, 1-octene, 1-decene, and 1-dodecene, among other higher linear α-olefins. It generally includes non-selective and selective ethylene oligomerization, with most of the current research in China focusing on selective catalytic oligomerization. For the preparation of 1-hexene from ethylene trimerization, there are two main approaches: one is to use a modified Philips-Chevron catalytic system, which has low production costs and a 1-hexene selectivity of over 92%, but its catalytic activity is relatively low, only 150–350 kg / g(Cr)h. The other is to use a highly active P-Cr(III)-P framework catalytic system, which has an activity of 1500–5000 kg / g(Cr)h, but tetramerization occurs simultaneously with ethylene trimerization, resulting in low 1-hexene selectivity. Furthermore, most of these catalytic systems use methylaluminoxane (MAO) or MMAO as aids, thus typically leading to higher production costs.

[0004] In the field of ethylene tetramerization to prepare 1-octene, most domestic and international researchers currently employ highly active P-Cr(III)-P catalytic systems. By continuously modifying the phosphine ligand, the coordination angle between phosphine and the metal is adjusted to improve the selectivity of 1-octene. This direction is a hot research area in China, and some progress has been made; therefore, it will not be elaborated upon here.

[0005] In summary, this catalytic system still relies heavily on MAO or MMAO. Due to their high cost and the fact that most MMAO is imported, the progress of domestic industrialization is severely hampered. Therefore, the question of whether a new catalytic system can be developed that combines the low cost of the Phillips catalytic system with the high activity of P-Cr(III)-P catalytic systems has become a key consideration for researchers. Summary of the Invention

[0006] In view of this, the present invention provides a catalytic system for selective oligomerization of ethylene and its application. The present invention provides a new catalytic system that is low in cost and has high activity, while also significantly reducing the formation of polymers, providing a good approach for industrial applications.

[0007] This invention provides a catalytic system for selective oligomerization of ethylene, comprising: a chromium-based main catalyst, an organoboron compound, an alkylaluminum compound, and a promoter;

[0008] The chromium-based main catalyst is a complex with trivalent chromium as the central ion and bidentate phosphine as the ligand; the organoboron compound is selected from one or more organoboranes, borate esters and organoboron salts; the promoter is a chlorinated alkane and / or a chlorinated aromatic hydrocarbon.

[0009] The catalytic system of the present invention can significantly reduce the formation of polymers without changing the catalyst activity and selectivity, and can replace the existing MAO or MMAO catalytic system, thereby achieving a significant reduction in production costs.

[0010] The catalytic system of this invention comprises: A: a chromium-based main catalyst; B: an organoboron auxiliary agent; C: an alkylaluminum co-catalyst; and D: a promoter. For ease of differentiation of the four components, the catalytic system includes four parts: a chromium-based complex main catalyst A, a boron auxiliary agent B, a metallic aluminum co-catalyst C, and a promoter D.

[0011] The main catalyst A is a complex prepared from a trivalent chromium compound and a previously reported bidentate phosphine (PNP) ligand. The chromium-based main catalyst A is a trivalent chromium catalyst with trivalent chromium (Cr(III)) as the central ion of the complex. The trivalent chromium compound used in its preparation can include one or more of chromium naphthenate, chromium 2,2,6,6-tetramethylheptanedionate, chromium neopentanoate, chromium acetylacetonate, chromium isooctanoate, and chromium trichloride trihydrofuran, preferably chromium acetylacetonate, chromium isooctanoate, and chromium trichloride trihydrofuran.

[0012] In some embodiments, the preparation method of part A is described as follows:

[0013] The ligand and trivalent chromium compound are added to a reaction flask in a specific molar ratio, a solvent is added, and the mixture is stirred overnight at room temperature. The mixture is then filtered to obtain a blue solid precipitate, which is dried to obtain the chromium-based complex main catalyst A. In the preparation method of A in the catalytic system, the molar ratio of the ligand to the trivalent chromium compound can be 1.01–1.5. The solvent used can be one or more of n-hexane, n-heptane, cyclohexane, toluene, methylcyclopentane, dichloromethane, chloroform, and chlorobenzene; the main catalyst A is specifically used in solution form.

[0014] Furthermore, the bidentate phosphine ligand in Part A is a previously reported NPNPN ligand, such as the catalyst ligand structure described in patent application number 2023111934057. The ligand has the general formula I, wherein R1, R2, R3, R4, and R5 can be the same or different, and are independently selected from alkyl or aryl groups; Ph is phenyl.

[0015]

[0016] In some embodiments of Formula I, the alkyl group has 1 to 10 carbon atoms, preferably methyl (CH3), ethyl (CH2CH3), isopropyl, isobutyl, cyclopentyl, or cyclohexyl. In other embodiments of Formula I, the aryl group has 6 to 18 carbon atoms, preferably phenyl or substituted phenyl. In Formula I, R1, R2, R3, R4, and R5 can be the same or different, preferably independently selected from alkyl, aryl, haloalkyl, or haloaryl groups, more preferably C1 to 18 chemical groups; further specific ligand structures and preparation methods are not listed here, but can be found in the aforementioned patent literature.

[0017] In this embodiment of the invention, organoboron compound B is used as a catalyst (which may be referred to as organoboron catalytic agent B, etc.). The B part is composed of organoborane, borate ester, or organoboron salt, and commercially available organoborides can be used. Preferably, organoboron catalytic agent B is a fluorinated phenyl borate ester.

[0018] In some embodiments, the organoboron compounds in part B include (3,5,6-tetrafluorophenyl)borates, tetra(2,3,4,5-tetrafluorophenyl)borates, tetra(3,4,5-trifluorophenyl)borates, tetra(2,2,4-trifluorophenyl)borates, phenylbis(pentafluorophenyl)borates, tetra(3,5-bistrifluoromethylphenyl)borates, ferrocene tetra(pentafluorophenyl)borates, 1,1'-dimethylferrocene tetra(pentafluorophenyl)borates, tetra(pentafluorophenyl)borates, triphenylmethyl tetra(pentafluorophenyl)borates, triphenylmethyl tetra(3,5-bistrifluoromethylphenyl)borates, triethylammonium tetra(pentafluorophenyl)borates, triethylaluminum tetra(pentafluorophenyl)borates, triisobutylaluminum tetra(pentafluorophenyl)borates, and tripropylammonium tetra(pentafluorophenyl)borates. One or more of the following: tri(n-butyl)ammonium tetra(pentafluorophenyl)borate, tri(n-butyl)ammonium tetra(3,5-bis(trifluoromethylphenyl)borate, N,N-dimethylaniline tetra(pentafluorophenyl)borate, N,N-diethylaniline tetra(pentafluorophenyl)borate, N,N-2,4,6-pentamethylaniline tetra(pentafluorophenyl)borate, triphenyltetra(pentafluorophenyl)borate, tri(methylphenyl)tetra(pentafluorophenyl)borate, and tri(dimethylphenyl)tetra(pentafluorophenyl)borate, preferably one or more of triphenylmethyltetra(pentafluorophenyl)borate, triethylaluminum tetra(pentafluorophenyl)borate, triisobutylaluminum tetra(pentafluorophenyl)borate, N,N-dimethylaniline tetra(pentafluorophenyl)borate, and tri(pentafluorophenyl)borane.

[0019] Triphenylmethyltetra(pentafluorophenyl)boronic acid ester is also known as triphenylmethyltetra(pentafluorophenyl)borate. Tri(pentafluorophenyl)borane has the CAS number 1109-15-5 and the molecular formula (C6F5)3B. It is also known as perfluorotriphenylborane and has the ability to readily accept anionic ligands that bond with metals, thus forming borates and borate esters.

[0020] Meanwhile, in this embodiment of the invention, alkylaluminum compound C is used as a co-catalyst in the catalytic system, which is a metal co-catalyst. Preferably, the alkyl carbon number in the alkylaluminum co-catalyst is 1 to 10. In some embodiments, the alkylaluminum compound in part C includes one or more of trimethylaluminum, diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, tri-n-hexylaluminum, tri-n-heptylaluminum, and tri-n-octylaluminum, preferably one or more of triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, triisopropylaluminum, and tri-n-propylaluminum.

[0021] This invention introduces a promoter D to address the activity reduction issue caused by component B in the catalytic system, making it suitable for existing PNP ligand systems. It also eliminates the need for pre-preparation of the B-Cr complex, allowing direct addition to the reaction system for catalysis. The promoter D is a chlorinated organic compound, primarily chlorinated alkanes and / or chlorinated aromatics; including one or more of dichloromethane, dichloroethane, hexachloroethane, tetrachloromethane, tetrachloroethane, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, dichlorotoluene, monochloroethylbenzene, dichloroethylbenzene, chloroxylene, monochlorobiphenyl, polychlorinated biphenyl, monochloronaphthalene, and polychlorinated naphthalene, preferably one or more of monochlorobenzene, chlorotoluene, dichloroethane, and chloroethylbenzene. In this invention, component D can be used as both a promoter and a solvent for oligomerization.

[0022] In embodiments of the present invention, the preferred molar ratio of the chromium-based main catalyst A, organoboron promoter B, and alkylaluminum co-catalyst C is 1:1 to 5:500 to 5000. Furthermore, the molar ratio of the chromium-based main catalyst A to promoter D is 1:40000 to 400000. In some embodiments, the catalytic system is prepared under a nitrogen atmosphere. A mixed solution of A and D can be prepared with a concentration of 1 to 10 μmol / ml.

[0023] The present invention also provides the application of the above-mentioned catalytic system in the selective oligomerization of ethylene, specifically providing a method for selective oligomerization of ethylene, comprising: using the catalytic system as a catalyst to carry out an oligomerization reaction of ethylene; wherein the oligomerization reaction is mainly a tetramerization reaction.

[0024] In the method described in the embodiments of the present invention, the reaction temperature is 50–65°C, and the pressure is 3.0 MPa–5.5 MPa; the reaction is carried out under a nitrogen atmosphere and in a chlorinated hydrocarbon solvent. In some embodiments, the solvent for the reaction is component D or a combination of D with one or more of n-hexane, n-heptane, cyclohexane, toluene, xylene, and methylcyclopentane; both component D and the solvent are dried using sodium or molecular sieves.

[0025] In summary, this invention has developed a new catalytic system through continuous innovation and improvement. Using trivalent chromium complexes as the main catalyst and employing organoboron compounds, alkylaluminum compounds, and promoters, it can replace MAO or MMAO in the selective tetramerization catalytic system of ethylene. Besides effectively reducing costs and solids content to 0-0.1%, this catalytic system also boasts advantages such as simple operation, broad ligand compatibility, and no impact on the catalytic activity and selectivity of the original ligand catalytic system. These significant advantages provide a promising route for the industrialization of α-olefins in China. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0027] The ligand compounds mentioned in the examples are cited from the patent "A Catalyst Ligand for Selective Oligomerization of Ethylene, Its Preparation Method and Catalyst for Selective Oligomerization of Ethylene", application number: 202311193405.7. The following specific examples further illustrate the above-mentioned content of the present invention in detail, but should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0028] Example 1

[0029] Preparation of the main catalyst complex solution of component A: Under a nitrogen atmosphere, ligands (L-1 to L-6, structures shown in Table 1) and 3THF·CrCl3 were weighed at a ratio of 1.05 moles, dichloromethane was added, and the mixture was stirred overnight at room temperature. The mixture was then concentrated and filtered to obtain a solid precipitate, which was dried in a vacuum oven at 50°C to obtain a blue solid powder. The blue powder was then weighed and added to chlorobenzene to prepare a 2 μmol / ml main catalyst chlorobenzene solution.

[0030]

[0031] Preparation of component B: Weigh 0.92 g of triphenylmethyltetra(pentafluorophenyl)borate and place it in a reaction flask. Add 50 ml of chlorobenzene and stir until dissolved to obtain a chlorobenzene solution with a concentration of 2 μmol / ml.

[0032] Component C: Triethylaluminum was used as a co-catalyst in a commercially available 1 mol / L hexane solution.

[0033] Both component D and the solvent used are chlorobenzene.

[0034] The material ratios of different main catalysts in the catalytic system are as follows.

[0035]

[0036] D: Total amount of chlorobenzene component.

[0037] Example 2

[0038] In a sealed 500ml autoclave, nitrogen was purged three times. 200ml of chlorobenzene solvent was then introduced under negative pressure, followed by the introduction of ethylene. The mixture was heated to 50°C. Using a syringe, 1ml of component A, 2ml of component B, and 2ml of component C were injected into the reactor in the order of components C, B, and A under a slight positive pressure of ethylene. Ethylene was then introduced to 5MPa, and the temperature was controlled at 50–65°C for 1 hour. After the reaction, the mixture was cooled and the gas was released. The reaction solution was weighed, and the reaction activity was calculated based on the weight gain. Gas phase tracking was used for the reaction solution; the data are as follows.

[0039]

[0040]

[0041] Comparative Example 1

[0042] Compound L and 3THF·CrCl3 were placed in a sealed autoclave. The autoclave was purged with nitrogen three times. 200 ml of dry cyclohexane was introduced under negative pressure, and the mixture was stirred at room temperature for 4 hours. Then, hydrogen gas was introduced, and MMAO was injected into the autoclave under slight positive pressure using a syringe. The pressure was then increased to 0.5 MPa, and finally, ethylene was introduced to 5.0 MPa. The reaction temperature was controlled at 55–65 °C, and the reaction was maintained at this temperature and pressure for 1 hour. After the reaction was complete, the temperature was lowered to 20 °C to release the gas. The reaction solution was weighed, and the reaction activity was calculated based on the weight gain.

[0043] The reaction solution was subjected to gas phase tracking, and the relevant data were obtained as follows.

[0044]

[0045]

[0046]

[0047] Comparative Example 2

[0048]

[0049] The most commonly used ligand in the literature, L-PNP, was used for comparison. The operation steps were the same as those in Comparative Example 1 above. The analysis data are presented below.

[0050]

[0051] Example 3

[0052] The reaction data are as follows: Component D in Example 1 was replaced with a mixed solution of chlorobenzene and cyclohexane, while other conditions remained unchanged.

[0053]

[0054]

[0055] Example 4

[0056] The reaction data are as follows: Component D in Example 1 was replaced with a trichlorobenzene solution, while other conditions remained unchanged.

[0057]

[0058]

[0059] As can be seen from the above embodiments, the embodiments of the present invention do not use MAO or MMAO, effectively reducing costs. Simultaneously, the catalytic system described has high activity and oligomerization selectivity, reducing the solid content to below 0.1%. Furthermore, this catalytic system is simple to apply, has broad ligand compatibility, and is beneficial for the selective oligomerization of ethylene.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A catalytic system for selective oligomerization of ethylene, characterized in that, include: The catalyst comprises a chromium-based main catalyst, an organoboron auxiliary agent, an alkylaluminum co-catalyst, and an accelerator; the molar ratio of the chromium-based main catalyst, organoboron auxiliary agent, and alkylaluminum co-catalyst is 1:1~5:500~5000; the molar ratio of the chromium-based main catalyst to the accelerator is 1:40000~400000; the alkylaluminum co-catalyst includes one or more of trimethylaluminum, diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, tri-n-hexylaluminum, tri-n-heptylaluminum, and tri-n-octylaluminum. The chromium-based main catalyst is a complex with trivalent chromium as the central ion and bidentate phosphine as the ligand; the organoboron accelerator is selected from one or more of organoboranes, fluorinated phenyl boronic acid esters, and organoboron salts; the promoter is a chlorinated substituted alkane and / or a chlorinated substituted aromatic hydrocarbon; the bidentate phosphine ligand in the chromium-based main catalyst has the general formula I, wherein R1, R2, R3, R4, and R5 are each independently selected from alkyl groups having 1 to 10 carbon atoms or aryl groups having 6 to 18 carbon atoms; Equation I.

2. The catalytic system for selective oligomerization of ethylene according to claim 1, characterized in that, In Formula I, the alkyl group is methyl, ethyl, isopropyl, isobutyl, cyclopentyl, or cyclohexyl; the aryl group is phenyl or a substituted phenyl group.

3. The catalytic system for selective oligomerization of ethylene according to any one of claims 1-2, characterized in that, The organoboron additive is a fluorophenyl borate ester, including (3,5,6-tetrafluorophenyl)borate, tetra(2,3,4,5-tetrafluorophenyl)borate, tetra(3,4,5-trifluorophenyl)borate, tetra(2,2,4-trifluorophenyl)borate, phenylbis(pentafluorophenyl)borate, tetra(3,5-bistrifluoromethylphenyl)borate, ferrocene tetra(pentafluorophenyl)borate, 1,1'-dimethylferrocene tetra(pentafluorophenyl)borate, tetra(pentafluorophenyl)borate, triphenylmethyl tetra(pentafluorophenyl)borate, triphenylmethyl tetra(3,5-bistrifluoromethylphenyl)borate, triethylammonium tetra(pentafluorophenyl)borate, triethylaluminum tetra(pentafluorophenyl)borate, triisobutylaluminum tetra(pentafluorophenyl)borate, tripropylammonium tetra(pentafluorophenyl)borate, and tri(n-butylammonium tetra(pentafluorophenyl)borate. One or more of the following: tri(n-butyl)ammonium tetra(3,5-bis(trifluoromethylphenyl)borate), N,N-dimethylaniline tetra(pentafluorophenyl)borate, N,N-diethylaniline tetra(pentafluorophenyl)borate, N,N-2,4,6-pentamethylaniline tetra(pentafluorophenyl)borate, triphenyltetra(pentafluorophenyl)borate, tri(methylphenyl)tetra(pentafluorophenyl)borate, and tri(dimethylphenyl)tetra(pentafluorophenyl)borate.

4. The catalytic system for selective oligomerization of ethylene according to claim 3, characterized in that, The organoboron additive is one or more of triphenylmethyltetra(pentafluorophenyl)borate, triethylaluminumtetra(pentafluorophenyl)borate, triisobutylaluminumtetra(pentafluorophenyl)borate, N,N-dimethylanilinetetra(pentafluorophenyl)borate, and tri(pentafluorophenyl)borane.

5. The catalytic system for selective oligomerization of ethylene according to any one of claims 1-2, characterized in that, The alkylaluminum cocatalyst is one or more of triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, triisopropylaluminum, and tri-n-propylaluminum.

6. The catalytic system for selective oligomerization of ethylene according to any one of claims 1-2, characterized in that, The accelerator includes one or more of dichloromethane, dichloroethane, hexachloroethane, tetrachloromethane, tetrachloroethane, monochlorobenzene, dichlorobenzene, trichlorobenzene, chlorotoluene, dichlorotoluene, monochloroethylbenzene, dichloroethylbenzene, chloroxylene, monochlorobiphenyl, polychlorinated biphenyl, monochloronaphthalene, and polychlorinated naphthalene.

7. The catalytic system for selective oligomerization of ethylene according to claim 6, characterized in that, The accelerator is one or more of monochlorobenzene, chlorotoluene, dichloroethane, and chloroethylbenzene.

8. A method for selective oligomerization of ethylene, characterized in that, include: Using the catalytic system according to any one of claims 1-7 as a catalyst, ethylene is subjected to oligomerization; the oligomerization is mainly a tetramerization reaction.

9. The method according to claim 8, characterized in that, The reaction is carried out at a temperature of 50-65°C and a pressure of 3-5.5 MPa under a nitrogen atmosphere and in a chlorinated hydrocarbon solvent.

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