Ethylene oligomerization catalyst as well as preparation method and application thereof

Abstract

The invention provides a complex as shown in a formula (I) which is used as an ethylene oligomerization catalyst for preparing alpha-olefin, and the complex has higher catalytic activity and linear alpha-olefin selectivity.

Description

An ethylene oligomerization catalyst, its preparation method and application Technical Field

[0001] This invention belongs to the field of catalysts for ethylene oligomerization, and relates to an ethylene oligomerization catalyst, its preparation method, and its application. Background Technology

[0002] Linear α-olefins are straight-chain olefins with C4 or more double bonds at the molecule's ends. They have wide applications in polyethylene comonomers, surfactant synthesis intermediates, plasticizer alcohols, synthetic lubricants, and oil additives. In recent years, with the continuous development of the polyolefin industry, the global demand for linear α-olefins has grown rapidly.

[0003] Industrially, the main methods for producing linear α-olefins include wax cracking, ethylene oligomerization, extraction separation, fatty alcohol dehydrogenation, internal olefin isomerization, and the Alfene process. Among these, wax cracking and fatty alcohol dehydrogenation are largely obsolete. Internal olefin isomerization, the Alfene process, and Exxon's ethylene oligomerization method have not been industrialized due to technical and economic reasons, and extraction separation is rarely used. Currently, almost all α-olefin production in China (except for 1-butene from the C4 fraction) uses wax cracking. This method utilizes inexpensive wax-containing feedstocks such as soft wax and underwax oil to produce a certain quantity of α-olefins, but the yield is low and the quality is poor, only meeting the requirements for a portion of low-grade synthetic lubricants and additives. Statistics from 1997 show that ethylene oligomerization accounted for 94.1% of total α-olefin production. Therefore, ethylene oligomerization is a very important method for producing α-olefins.

[0004] The development of ethylene oligomerization catalysts represents the most advanced level in the production of α-olefins from ethylene oligomerization and has always been a focus of attention in academia and industry. In recent years, the development of catalysts for the ethylene oligomerization process to α-olefins abroad has mainly focused on zirconium-based and chromium-based catalysts in the early transition metals, and nickel-based, iron-based, and cobalt-based catalysts in the later transition metals. Existing catalysts all suffer from low selectivity for the target products 1-octene and 1-hexene; similarly, some catalysts exhibit relatively high selectivity but relatively low activity. For these reasons, it is necessary to develop new ethylene oligomerization catalysts. Summary of the Invention

[0005] To improve the above-mentioned technical problems, the present invention provides a complex of formula (I):

[0006]

[0007] Where X is selected from halogens, such as Cl, Br, and I;

[0008] Each R1 is either identical or different, and is independently selected from H and C. 1-10 Alkyl, C 1-10 Alkoxy, C 3-10 cycloalkyl;

[0009] Each R2 is either identical or different, and is selected independently from H and C. 1-10 Alkyl, C 3-10 cycloalkyl;

[0010] Each R is identical or different and independently selected from the following groups, either unsubstituted or optionally substituted by one, two or more Ra: C 6-14 Aryl groups; each Ra may be identical or different, and each is independently selected from C. 1-10 Alkyl, C 1-10 Alkyl group.

[0011] According to an embodiment of the present invention, R1 is selected from H and C. 1-6 alkyl;

[0012] According to an embodiment of the present invention, R1 is selected from H, methyl, ethyl, isopropyl, and tert-butyl.

[0013] According to an embodiment of the present invention, R2 is selected from H and C. 1-6 Alkyl, C 3-6 cycloalkyl;

[0014] According to an embodiment of the present invention, R2 is selected from H, methyl, ethyl, isopropyl, tert-butyl, and cyclohexyl.

[0015] According to embodiments of the present invention, R is selected from the following groups that are unsubstituted or optionally substituted by one, two or more Ra groups: C 6-12 Aryl.

[0016] According to embodiments of the present invention, R is selected from the following groups that are unsubstituted or optionally substituted by one, two or more Ra: phenyl, naphthyl.

[0017] According to an embodiment of the invention, each Ra may be the same or different, and is independently selected from C. 1-6 Alkyl, C 1-6 Alkyl group.

[0018] According to embodiments of the present invention, each Ra may be the same or different, and is independently selected from methyl, ethyl, isopropyl, tert-butyl, and methoxy.

[0019] According to an embodiment of the present invention, the complex represented by formula (I) has the following structure:

[0020]

[0021] The present invention also provides a ligand compound represented by formula (II):

[0022]

[0023] Among them, R1, R2, and R have the definitions described above independently.

[0024] The present invention also provides a method for preparing the complex shown in formula (I), comprising reacting the ligand compound shown in formula (II) with a chromium salt to obtain the complex shown in formula (I);

[0025]

[0026] Among them, R1, R2, R, and X independently have the definitions described above.

[0027] According to an embodiment of the present invention, the chromium salt may be selected from chromium halide salts, such as chromium trichloride hexahydrate.

[0028] The present invention also provides the application of the complex shown in formula (I) above in the catalytic oligomerization of ethylene.

[0029] The present invention also provides a catalyst for ethylene oligomerization, the catalyst comprising the complex shown in formula (I) above.

[0030] The present invention also provides a catalytic system comprising the complex shown in formula (I) above or comprising the above-described catalyst for ethylene oligomerization.

[0031] According to an embodiment of the present invention, the catalytic system further includes a co-catalyst selected from at least one of the hydrolysis products of alkyl aluminum compounds.

[0032] According to an embodiment of the present invention, the alkylaluminum compound is selected from at least one of trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum chloride, and ethylaluminum dichloride; preferably triethylaluminum.

[0033] According to an embodiment of the present invention, in the catalytic system, the molar ratio of the complex shown in formula (I) to the Cr / Al in the co-catalyst is 1:200-1000, for example, 1:400, 1:600, 1:800, or 1:1000.

[0034] According to an embodiment of the present invention, the catalytic system may include a solvent. Specifically, the solvent may be selected from alkanes, cycloalkanes, or aromatics, such as at least one selected from n-pentane, cyclopentane, n-hexane, cyclohexane, toluene, etc.

[0035] The present invention also provides a method for preparing α-olefins, the method comprising polymerizing ethylene in the presence of the above-described catalytic system to obtain the α-olefins.

[0036] According to an embodiment of the present invention, the α-olefin is selected from at least one of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene.

[0037] According to an embodiment of the present invention, the temperature of the polymerization reaction is 40°C-100°C, exemplarily 50-80°C, for example 60°C or 70°C.

[0038] According to an embodiment of the present invention, the pressure of the polymerization reaction is 0.1 MPa-5 MPa, for example 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa or 4.5 MPa.

[0039] According to an embodiment of the present invention, in the α-olefin, C6-C 10 The content of linear α-olefins is not less than 40%, preferably not less than 45%; and can also be as high as 55%.

[0040] Beneficial effects

[0041] This invention provides a complex of formula (I) as an ethylene oligomerization catalyst, exhibiting high catalytic activity for the preparation of C6-C 10 Linear α-olefins exhibit high selectivity.

[0042] Terminology Definitions and Explanations

[0043] Unless otherwise stated, the definitions of groups and terms recorded in this application specification and claims, including definitions as examples, exemplary definitions, preferred definitions, definitions recorded in tables, and definitions of specific compounds in the examples, can be arbitrarily combined and combined with each other. Such combinations and combinations of group definitions and compound structures should be understood as being within the scope of this application specification and / or claims.

[0044] Unless otherwise stated, the numerical ranges described in this specification and claims are equivalent to describing at least each specific integer value therein. For example, the numerical range "1-10" is equivalent to describing each integer value, namely 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0045] The term "halogen" refers to fluorine, chlorine, bromine, and iodine.

[0046] Term "C" 1-10"Alkyl" should be understood as representing a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 10 carbon atoms. For example, "C 1-6 "Alkyl" refers to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, or 6 carbon atoms. "C" 1-4 "Alkyl" means a straight-chain or branched alkyl group having 1, 2, 3, or 4 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers.

[0047] Term "C" 1-10 "Alkoxy" should be understood as "C 1-10 Alkyl-O-”, where C 1-10 Alkyl groups have the definition described in this invention.

[0048] Term "C" 3-10 "Cycloalkyl" should be understood to refer to a saturated monovalent monocyclic, bicyclic (e.g., bridged, spirocyclic) hydrocarbon ring or tricyclic alkane having 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, preferably "C". 3-8 "Cycloalkyl" or "C" 3-6 "Cycloalkyl". 3-10 Cycloalkyl groups can be monocyclic hydrocarbon groups, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, or cyclodecyl; or bicyclic hydrocarbon groups, such as borneolyl, indolyl, hexahydroindolyl, tetrahydronaphthyl, decahydronaphthyl, bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.1]heptenyl, 6,6-dimethylbicyclo[3.1.1]heptyl, 2,6,6-trimethylbicyclo[3.1.1]heptyl, bicyclo[2.2.2]octyl, 2,7-diazaspiro[3,5]nonyl, 2,6-diazaspiro[3,4]octyl; or tricyclic hydrocarbon groups, such as adamantyl.

[0049] Term "C" 6-14 "Aryl" refers to a 6- to 14-membered all-carbon monocyclic or fused polycyclic (i.e., a ring sharing adjacent carbon atom pairs) group with a conjugated electronic system, preferably a 6- to 10-membered ring, such as phenyl and naphthyl. Detailed Implementation Methods

[0050] The technical solutions of this disclosure will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of this disclosure and should not be construed as limiting the scope of protection of this disclosure. All technologies implemented based on the above content of this disclosure are covered within the scope of protection intended by this disclosure.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Preparation Example 1

[0053]

[0054] Under nitrogen protection, CuI (435 mg, 2.28 mmol), diphenylphosphine (8.5 g, 45.7 mmol), N,N-dimethylethylenediamine (1.5 mL), and anhydrous toluene (80 mL) were added to a three-necked flask. After stirring for 10 minutes, 2-iodoaniline (10 g, 45.7 mmol) and Cs₂CO₃ (17.85 g, 54.8 mmol) were added. The reaction mixture was heated at 110 °C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, diluted with water (50 mL), and extracted with ethyl acetate (100 mL × 3). The combined organic extracts were concentrated under vacuum and purified by column chromatography to give 8.2 g of compound 1b.

[0055] Compound 1b (6 g, 21.6 mmol) and methanol (60 mL) were added to a three-necked flask, followed by 2,3-butanedione (0.93 g, 10.82 mmol). After stirring for 10 minutes, acetic acid (2 mL) was added, and the reaction was continued at room temperature for 3 hours. After the reaction was complete, water was added to dilute the mixture, and the methanol was removed. The mixture was then extracted with ethyl acetate (100 mL × 3). The combined organic extracts were concentrated under vacuum to give 5.8 g of compound 1c. ESIMS: m / z 605.8 ([M+H) + ). 1 H NMR (400MHz, CDCl3-d)δ:7.52-7.40(m,16H),7.22-7.10(m,12H),2.08-2.02(s,6H). 31 P NMR(162MHz, CDCl3-d)δ:52.4(s).

[0056] Compound 1c (5 g, 8.27 mmol) and tetrahydrofuran (50 mL) were added to a three-necked flask, followed by the addition of a tetrahydrofuran suspension (10 mL) of chromium trichloride hexahydrate (1.96 g, 8.24 mmol) at room temperature. The reaction mixture was stirred at room temperature for 3 hours, and the mixture was filtered to obtain 4.6 g of compound 1.1 H NMR (400MHz, CDCl3-d) δ: 7.56-7.42 (m, 16H), 7.24-7.12 (m, 12H), 2.09-2.04 (s, 6H).

[0057] Preparation Example 2

[0058] Complexes 2-3 were prepared according to the method of Preparation Example 1, as detailed in Table 1.

[0059] Table 1. Structural formulas and characterization data of coordination compounds 2-3

[0060]

[0061] Example

[0062] Preparation of co-catalyst: Triethylaluminum was dissolved in cyclohexane, and 1 equivalent of water was added dropwise. The mixture was stirred for 10 min to obtain an ethylaluminoxane solution with a concentration of 1 mmol / mL.

[0063] Ethylene oligomerization: After replacing ethylene in a 500 mL reactor that has been dried at high temperature, 1 mL of ethylaluminoxane solution, the complex prepared in this invention, and cyclohexane are added. The total volume of all components is 50 mL, and the Al / Cr ratio is 200-1000:1. Then, ethylene is introduced at 2 MPa, and the reaction is carried out at 60 °C for 1 h. After the reaction is complete, samples are taken for gas phase analysis, and the results are summarized in the table below.

[0064]

[0065] It is evident that the complexes of this invention, as ethylene oligomerization catalysts, can effectively catalyze the polymerization of ethylene to obtain linear α-olefins, and possess high reactivity, particularly for C6-C... 10 It exhibits high selectivity for α-olefins.

[0066] The above description provides an exemplary illustration of the implementation scheme of the technical solution disclosed herein. It should be understood that the scope of protection of this disclosure is not limited to the above-described implementation scheme. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of this disclosure should be included within the scope of protection of the claims of this application.

Claims

1. A complex of formula (I): in, X is selected from halogens, such as Cl, Br, I; each R1 is selected from H, C, or other halogens, either identically or differently. 1-10 Alkyl, C 1-10 Alkoxy, C 3-10 Cycloalkyl; each R2 may be the same or different and is independently selected from H, C 1-10 Alkyl, C 3-10 Cycloalkyl; each R is the same or different, and independently selected from the following groups that are unsubstituted or optionally substituted by one, two or more Ra: C 6-14 Aryl groups; each Ra may be identical or different, and each is independently selected from C. 1-10 Alkyl, C 1-10 Alkyl group.

2. The complex according to claim 1, characterized in that, R1 is selected from H and C. 1-6 Alkyl group; preferably, R1 is selected from H, methyl, ethyl, isopropyl, tert-butyl; preferably, R2 is selected from H, C 1-6 Alkyl, C 3-6 Cycloalkyl; preferably, R2 is selected from H, methyl, ethyl, isopropyl, tert-butyl, cyclohexyl; preferably, R is selected from the following groups that are unsubstituted or optionally substituted by one, two or more Ra: C 6-12 Aryl; preferably, R is selected from the following groups that are unsubstituted or optionally substituted by one, two or more Ra: phenyl, naphthyl.

3. The complex according to claim 1 or 2, characterized in that, Each Ra is identical or different, and is selected independently from C. 1-6 Alkyl, C 1-6 Alkoxy; preferably, each Ra is the same or different, and is independently selected from methyl, ethyl, isopropyl, tert-butyl, and methoxy.

4. The complex according to any one of claims 1-3, characterized in that, The complex shown in formula (I) has the following structure:

5. A method for preparing the complex according to any one of claims 1-4, comprising reacting the ligand compound of formula (II) with a chromium salt to obtain the complex of formula (I); in, R1, R2, R, and X independently have the definitions described in any one of claims 1-4.

6. A ligand compound represented by formula (II): in, R1, R2, and R independently have the definitions described in any one of claims 1-4.

7. The use of the complex according to any one of claims 1-4 in the catalytic oligomerization of ethylene.

8. A catalyst for ethylene oligomerization, said catalyst comprising the complex according to any one of claims 1-4.

9. A catalytic system comprising the complex according to any one of claims 1-4 or the catalyst for ethylene oligomerization according to claim 8.

10. A method for preparing an α-olefin, the method comprising polymerizing ethylene in the presence of the catalytic system of claim 9 to obtain the α-olefin.

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