A high-efficiency catalyst ligand for selective trimerization of ethylene and its preparation method, catalyst system and application

Abstract

The present invention provides a catalyst ligand for preparing 1-hexene by trimerization of ethylene, wherein the catalyst ligand contains a chlorinated tripyrrole functional group; the catalyst ligand has a structural formula shown in formula A and / or B. The chlorinated tripyrrole ligand compound provided by the present invention has both the function of a ligand and the function of a promoter. Based on the ligand, the trimerization catalytic system is improved, and the original four-component system of main catalyst, auxiliary catalyst, ligand and promoter is simplified to a three-component system, so that the preparation of the catalytic system is simpler, and the catalytic activity of trimerization is also significantly improved, up to 760kg / g(Cr).h. The high activity and high selectivity of the catalytic system at high temperature enable the reaction to run for a long period of time, have obvious advantages in the industrial process, and are more suitable for the promotion and application of industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts for selective ethylene trimerization, and relates to a catalyst ligand for ethylene trimerization to produce 1-hexene, and a preparation method thereof, a catalyst system, and an application thereof, and a preparation method for ethylene trimerization to produce 1-hexene, and in particular to a high-efficiency catalyst ligand for ethylene selective trimerization, and a preparation method thereof, a catalyst system, and an application thereof. Background Art

[0002] Linear α-olefins are an important chemical raw material with huge demand, among which C4-C 10 Linear α-olefins are widely used in the preparation of low-density polyethylene, high-density polyethylene, high-grade detergents, high-grade lubricants, surfactants, POE and high-grade straight-chain alcohols. 1-Hexene is a high-quality comonomer for the production of high-grade polyolefin resins. Although there are several domestic companies that can industrially produce 1-hexene, they still cannot meet the demand and still rely heavily on imports, which directly affects the development of new domestic polyolefin grades.

[0003] With the rapid development of the polyethylene industry, the demand for advanced α-olefins such as 1-hexene and 1-octene is increasing, and the application market prospects are broad, especially in terms of removing the bottlenecks in the development of polyethylene comonomers and advanced lubricants in my country. Compared with linear low-density polyethylene resins copolymerized with 1-butene, linear low-density polyethylene resins copolymerized with 1-hexene have obvious advantages in tensile strength, impact strength, tear resistance and durability. The impact strength, tear strength and stability of agricultural covering films such as LLDPE ground films, greenhouse films, packaging films, and greenhouses produced using 1-hexene as a comonomer also have obvious advantages.

[0004] In recent years, the research on ethylene trimerization to produce 1-hexene has received widespread attention. Since UCC published the patent for ethylene trimerization to produce 1-hexene with chromium metal as the active center in the early 1990s, major oil companies in the world have also quickly carried out follow-up research and continuously published patents. Among them, the Philips-Chevron catalytic system is the first catalytic system to achieve industrial production. Since 2003, the device has produced 47,000 tons of 1-hexene per year. The catalytic system is a mixture of chromium isooctanoate, 2,5-dimethylpyrrole, triethylaluminum and diethylaluminum monochloride in a molar ratio of 1:3.3:10.8:7.8 to generate an ethylene trimerization catalyst in situ, with a 1-hexene selectivity of 93% and a reaction activity of more than 8.146kg / (mmolCr.h). Later, Mitsubishi Corporation improved the above system. Chromium isooctanoate, 2,5-dimethylpyrrole, hexachloroethane and triethylaluminum are directly mixed in a reactor at a molar ratio of 1:6:4:40 to obtain a trimerization catalyst in situ, and by adjusting the molar ratio of 1-hexene / ethylene to less than 0.5:1, the 1-hexene selectivity of the system can reach 95%, and the reaction activity can exceed 196.56kg / (mmolCr.h), which is more than 20 times higher than the original system. Tosoh Company reacted a series of oriented coordination tripyrazolyl methane with tritetrahydrofuran chromium trichloride in tetrahydrofuran to obtain a highly selective trimerization catalyst. After activation with 360 times the equivalent of methylaluminoxane, the 1-hexene selectivity can reach 99.1%, and the reaction activity is 2.085kg / (mmolCr.h). Later, Hor et al. conducted supplementary research on it. By introducing sulfur-containing or oxygen-containing electron donors into the ligand, a Cr-NON complex containing hexyl group was synthesized. After activation with the main catalyst, the selectivity of 1-hexene can reach 98.5%, and the activity is 842g / (mmolCr.h). Amoco developed the first catalytic system containing a radially coordinated tridentate ligand. After activation with 214 equivalents of butylaluminoxane (BAO), the chromium complex of the asymmetric triphosphine tridentate ligand can catalyze ethylene to obtain 96.5% of 1-hexene, and the reaction activity is 1.764kg / (mmolCr.h). British Petroleum has developed an ethylene selective trimerization catalyst composed of tritetrahydrofuran chromium trichloride and bidentate PNP ligand, in which the phosphine functional group of the PNP ligand contains a cresol substituent. After activation with methylaluminoxane, the selectivity of 1-hexene reaches more than 90%, and the reaction activity is 53.726kg / (mmolCr.h). Later, McGuinness, Wasserscheid and others obtained a new PNP tridentate ligand by adding CH2 bridge between P and N of PNP ligand. The ligand was mixed with methylaluminoxane and chromium precursor, and the catalytic selectivity of 1-hexene reached 97%, and the reaction activity was 1.942kg / (mmolCr.h). The phosphine functional group was replaced by the sulfide functional group to synthesize the Cr-SNS system with better catalytic performance.The improved catalyst system can catalyze ethylene selectivity of up to 98%, and the reaction activity is 8.364kg / (mmolCr.h). Rosenthal et al. synthesized a chromium catalyst containing PNPNH auxiliary ligands. The 1-hexene selectivity of the system exceeded 90%, and the reaction activity was 1.404kg / (mmolCr.h). The reaction conditions are: toluene as the reaction solvent, 65°C, and 30bar ethylene pressure. The system uses 70 equivalents of alkyl aluminum to replace the expensive alkyl aluminoxane. The polyethylene content in the product is the highest, the C6 content is high, and the 1-hexene content in C6 can reach 99.3%. And the catalyst life is long. Other Cr-PN systems, including chromium complexes containing bis(methylphosphine)amine bidentate ligand PCNCP, can catalyze ethylene to produce 99% 1-hexene after activation with methyl aluminoxane, with a reaction activity of 0.509kg / (mmolCr.h). By changing the steric hindrance of the substituents on the phosphine functional group, the selectivity of the system to olefins can be regulated. The introduction of a cyclohexyl group with large steric hindrance makes the system have a high selectivity for 1-hexene, while the introduction of a n-butyl group with smaller steric hindrance causes part of the 1-hexene selectivity to shift to 1-octene. At the same time, the Lewis basicity of the phosphine functional group and the substituents on the N atom of the ligand also have a certain influence on the selectivity of the system to 1-hexene and 1-octene. Others include some chromium complexes containing orthophosphorane amidine ligands, which are activated by modified methylaluminoxane. The system has a 1-hexene selectivity of more than 93% and a reaction activity of up to 57.7kg / (mmolCr.h). In addition, some titanium-based and tantalum-based ethylene trimerization catalytic systems have also been developed, but they are not mainstream and will not be discussed in detail.

[0005] In summary, the existing ethylene selective trimerization catalytic systems at home and abroad are mainly Cr-N-Al-Cl and Cr-PNP-Al. The former is mostly based on the Philips catalytic system with various improvements. Although the amount of auxiliary catalyst used is small and the selectivity for 1-hexene is high, the main catalyst has low activity, large dosage and high cost. The latter is a catalytic system based on PNP-type modified ligands. Its advantage is high activity, but the selectivity for 1-hexene is low. Generally, 1-octene is co-produced. The auxiliary catalyst generally uses MMAO, which is used in a high amount and the auxiliary catalyst cost is much higher.

[0006] Therefore, how to find a more suitable catalyst for the selective trimerization of ethylene to solve the problems existing in the above-mentioned existing technical solutions has become one of the focuses of widespread attention of many front-line researchers and R&D companies in the industry. Summary of the invention

[0007] The technical problem solved by the present invention is to provide a catalyst ligand for ethylene trimerization to produce 1-hexene and its preparation method, catalyst system, application and ethylene trimerization to produce 1-hexene preparation method, especially a catalyst ligand for ethylene selective trimerization. The pyrrole-based modified ligand provided by the present invention has bifunctionality, and the Phillips trimerization catalytic system is improved by combining the modified ligand, and the original four-component system of main catalyst, auxiliary catalyst, ligand and promoter is simplified to a three-component system, making the preparation of the catalytic system simpler, and the catalytic activity of trimerization is also significantly improved.

[0008] The present invention provides a catalyst ligand for preparing 1-hexene by ethylene trimerization, wherein the catalyst ligand contains a chlorotripyrrole functional group;

[0009] The catalyst ligand has the structural formula shown in formula A and / or B:

[0010]

[0011] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl;

[0012] R2 is selected from methyl and / or ethyl.

[0013] The present invention provides a method for preparing a catalyst ligand for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0014] a) reacting 2,4-dichlorobenzaldehyde, pyrrole and 2-R1-pyrrole, then adding trifluoroacetic acid and continuing the reaction to obtain a catalyst ligand having a structure shown in formula A;

[0015]

[0016] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl;

[0017] 1) under the action of protective gas, the raw materials and the solvent are mixed, an initiator is added, and then N-bromosuccinimide is added to react to obtain an intermediate terminal bromine-substituted oxidized tripyrrole compound;

[0018] The raw material is a compound with a structure shown in formula A when R1 is H;

[0019] 2) The intermediate obtained in the above step is protected with a tert-butyloxycarbonyl protecting group, then alkylated with R2-MgCl, and then the Boc group is removed with an acid solution to obtain a catalyst ligand having a structure shown in formula B;

[0020]

[0021] Wherein, R2 is selected from methyl and / or ethyl.

[0022] Preferably, the molar ratio of 2,4-dichlorobenzaldehyde to pyrrole is (1.5-2.5):1;

[0023] The molar ratio of pyrrole to 2-R1-pyrrole is 1:(1.5-2.5);

[0024] In the step a), the reaction temperature is -15 to 50°C;

[0025] In the step a), the reaction time is 15 to 60 minutes;

[0026] In the step a), the temperature for continuing the reaction is 5 to 40°C;

[0027] In the step a), the reaction time is 20 to 30 minutes;

[0028] After the continued reaction, the step of using an amine compound to quench the reaction is also included;

[0029] The amine compound includes one or more of triethylamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, di-n-propylamine and diisopropylamine.

[0030] Preferably, in step 1), the solvent comprises one or more of dichloromethane, carbon tetrachloride, tetrahydrofuran and dioxane;

[0031] The initiator includes azobisisobutyronitrile;

[0032] The mass ratio of the initiator to the raw material is 1% to 10%;

[0033] The molar ratio of the N-bromosuccinimide to the raw material is (0.8-1.5):1.

[0034] Preferably, the reaction temperature in step 1) is -50 to -10°C;

[0035] In the step 1), after the reaction, one or more steps of layer extraction, solvent removal and recrystallization are further included;

[0036] The acid solution includes one or more of formic acid, acetic acid, trifluoroacetic acid, hydrochloric acid and propionic acid;

[0037] In the step 2), after removing the Boc group, one or more steps of washing, extraction, solvent removal and recrystallization are further included;

[0038] The solvent used for the recrystallization includes one or more of methanol, ethanol, n-propanol, isopropanol and n-butanol.

[0039] The present invention provides a catalyst system for preparing 1-hexene by ethylene trimerization, comprising a main catalyst and a co-catalyst;

[0040] The main catalyst comprises a trivalent chromium compound and a ligand;

[0041] The ligand includes the catalyst ligand described in the above technical solution or the catalyst ligand prepared by the preparation method described in any one of the above technical solutions.

[0042] Preferably, the trivalent chromium compound includes one or more of chromium naphthenate, chromium 2,2,6,6-tetramethylheptanedione, chromium pivalate, chromium acetylacetonate, chromium isooctanoate and chromium trichloride in tetrahydrofuran;

[0043] The molar ratio between the trivalent chromium compound and the ligand is 1:(1-10);

[0044] The co-catalyst comprises alkyl aluminum and / or alkoxy aluminum;

[0045] The molar ratio of the main catalyst to the main catalyst is 1: (30-200).

[0046] The present invention provides the use of the catalyst ligand described in the above technical scheme, the catalyst ligand prepared by the preparation method described in any one of the above technical schemes, or the catalyst system described in any one of the above technical schemes in ethylene trimerization to produce 1-hexene.

[0047] The present invention also provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0048] (1) under the action of protective gas, a trivalent chromium compound, a ligand and a preparation solvent are mixed to obtain a main catalyst solution;

[0049] The ligand includes the catalyst ligand described in the above technical solution, and the catalyst ligand prepared by the preparation method described in any one of the above technical solutions;

[0050] (2) Under vacuum conditions, the main catalyst solution, co-catalyst and reaction solvent obtained in the above steps are sent to a reaction device, ethylene is introduced, and a polymerization reaction is carried out to obtain 1-hexene.

[0051] Preferably, the preparation solvent includes one or more of toluene, n-heptane, cyclohexane and n-hexane;

[0052] The mixing time is 0.5 to 24 hours;

[0053] The reaction solvent includes one or more of cyclohexane, n-heptane, methylcyclohexane, 1-hexene and toluene;

[0054] The pressure of the ethylene is 4-6Mpa;

[0055] The polymerization temperature is 100-150°C

[0056] The polymerization reaction time is 15 to 100 minutes.

[0057] The present invention provides a catalyst ligand for preparing 1-hexene by trimerization of ethylene, wherein the catalyst ligand contains a chlorinated tripyrrole functional group; the catalyst ligand has a structural formula shown in formula A and / or B. Compared with the prior art, the present invention provides a chlorinated tripyrrole ligand compound with a specific structure and composition, and the ligand has both the function of a ligand and the function of a promoter. The present invention also improves the trimerization catalytic system based on the ligand, and simplifies the original four-component system of main catalyst, auxiliary catalyst, ligand and promoter into a three-component system, so that the preparation of the catalytic system is simpler.

[0058] Compared with the reports in the existing literature, the catalyst system for preparing high linear 1-hexene by ethylene polymerization provided by the present invention adopts triethylaluminum with lower economic cost as a co-catalyst, and the catalytic activity of trimerization can reach up to 760kg / g(Cr).h, and the selectivity of 1-hexene can reach up to 96.76%. The high activity and high selectivity of the catalytic system at high temperature enable the reaction to run for a long period of time, so that the catalytic system has obvious advantages in the industrial process and is more suitable for the promotion and application of industrial production. DETAILED DESCRIPTION

[0059] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0060] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0061] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials of conventional purity used in the field of catalyst preparation for selective trimerization of ethylene.

[0062] All noun expressions, abbreviations and trademarks in the present invention are conventional noun expressions, abbreviations and trademarks in the field. Each noun expression, abbreviation and trademark is clear and unambiguous in its relevant application field, and those skilled in the art can clearly, accurately and uniquely understand it based on the noun expressions, abbreviations and trademarks.

[0063] The present invention provides a catalyst ligand for preparing 1-hexene by ethylene trimerization, wherein the catalyst ligand contains a chlorotripyrrole functional group;

[0064] The catalyst ligand has the structural formula shown in formula A and / or B:

[0065]

[0066] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl;

[0067] R2 is selected from methyl and / or ethyl.

[0068] In the present invention, the catalyst ligand has a structural formula shown in formula A and / or B, and can be a structural formula shown in formula A or B:

[0069]

[0070] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl, and can be hydrogen, methyl or ethyl.

[0071] R2 is selected from methyl and / or ethyl, and can be methyl or ethyl.

[0072] The present invention provides a method for preparing a catalyst ligand for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0073] a) reacting 2,4-dichlorobenzaldehyde, pyrrole and 2-R1-pyrrole, then adding trifluoroacetic acid and continuing the reaction to obtain a catalyst ligand having a structure shown in formula A;

[0074]

[0075] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl;

[0076] 1) under the action of protective gas, the raw materials and the solvent are mixed, an initiator is added, and then N-bromosuccinimide is added to react to obtain an intermediate terminal bromine-substituted oxidized tripyrrole compound;

[0077] The raw material is a compound with a structure shown in formula A when R1 is H;

[0078] 2) The intermediate obtained in the above step is protected with a tert-butyloxycarbonyl protecting group, then alkylated with R2-MgCl, and then the Boc group is removed with an acid solution to obtain a catalyst ligand having a structure shown in formula B;

[0079]

[0080] Wherein, R2 is selected from methyl and / or ethyl.

[0081] The present invention reacts 2,4-dichlorobenzaldehyde, pyrrole and 2-R1-pyrrole, then adds trifluoroacetic acid and continues the reaction to obtain a catalyst ligand having a structure shown in formula A;

[0082] Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl.

[0083] In the present invention, R1 is preferably selected from one or more of hydrogen, methyl and ethyl, more preferably hydrogen, methyl or ethyl.

[0084] In the present invention, the molar ratio of 2,4-dichlorobenzaldehyde to pyrrole is preferably (1.5-2.5):1, more preferably (1.7-2.3):1, and more preferably (1.9-2.1):1.

[0085] In the present invention, the molar ratio of pyrrole to 2-R1-pyrrole is preferably 1:(1.5-2.5), more preferably 1:(1.7-2.3), and more preferably 1:(1.9-2.1).

[0086] In the present invention, in the step a), the reaction temperature is preferably -15 to 50°C, more preferably -5 to 40°C, more preferably 5 to 30°C, more preferably 15 to 20°C.

[0087] In the present invention, in the step a), the reaction time is preferably 15 to 60 min, more preferably 25 to 50 min, and more preferably 35 to 40 min.

[0088] In the present invention, in the step a), the temperature for continuing the reaction is preferably 5 to 40°C, more preferably 10 to 35°C, more preferably 15 to 30°C, more preferably 20 to 25°C.

[0089] In the present invention, in the step a), the reaction time is preferably 20 to 30 minutes, more preferably 22 to 28 minutes, and more preferably 24 to 26 minutes.

[0090] In the present invention, after the continued reaction, it is preferred to further include a step of quenching the reaction with an amine compound.

[0091] In the present invention, the amine compound preferably includes one or more of triethylamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, di-n-propylamine and diisopropylamine, more preferably triethylamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, di-n-propylamine or diisopropylamine.

[0092] The present invention firstly mixes raw materials and solvents under the action of protective gas, then adds an initiator, and then adds N-bromosuccinimide, and reacts to obtain an intermediate terminal bromine-substituted oxidized tripyrrole compound;

[0093] The raw material is a compound of the structure shown in formula A when R1 is H, that is, a compound of the structure shown in formula A when R1 is H.

[0094] In the present invention, in the step 1), the solvent preferably includes one or more of dichloromethane, carbon tetrachloride, tetrahydrofuran and dioxane, and more preferably dichloromethane, carbon tetrachloride, tetrahydrofuran or dioxane.

[0095] In the present invention, the initiator preferably includes azobisisobutyronitrile.

[0096] In the present invention, the mass ratio of the initiator to the raw material is preferably 1% to 10%, more preferably 3% to 8%, and more preferably 5% to 6%.

[0097] In the present invention, the molar ratio of the N-bromosuccinimide to the raw material is preferably (0.8-1.5):1, more preferably (0.9-1.4):1, and more preferably (1.0-1.3):1.

[0098] In the present invention, the reaction temperature in step 1) is preferably -50 to -10°C, more preferably -42 to -18°C, and more preferably -34 to -26°C.

[0099] In the present invention, in the step 1), after the reaction, preferably one or more steps of layered extraction, solvent removal and recrystallization are further included, and more preferably multiple steps of layered extraction, solvent removal and recrystallization are included.

[0100] In the present invention, the acid solution preferably includes one or more of formic acid, acetic acid, trifluoroacetic acid, hydrochloric acid and propionic acid, and more preferably formic acid, acetic acid, trifluoroacetic acid, hydrochloric acid or propionic acid.

[0101] The present invention further uses a tert-butyloxycarbonyl protecting group to protect the intermediate obtained in the above step, then uses R2-MgCl to perform alkylation, and then uses an acid solution to remove the Boc group to obtain a catalyst ligand having a structure shown in formula B;

[0102] Wherein, R2 is selected from methyl and / or ethyl.

[0103] In the present invention, R2 is preferably selected from methyl and / or ethyl, more preferably methyl or ethyl.

[0104] In the present invention, the tert-butyloxycarbonyl type protecting group preferably includes (Boc)2O (di-tert-butyl dicarbonate, BOC anhydride).

[0105] In the present invention, in step 2), after removing the Boc group, it is preferred that one or more steps of water washing, extraction, solvent removal and recrystallization are further included, and more preferably, multiple steps of water washing, extraction, solvent removal and recrystallization are included.

[0106] In the present invention, the solvent used for the recrystallization preferably includes one or more of methanol, ethanol, n-propanol, isopropanol and n-butanol, more preferably methanol, ethanol, n-propanol, isopropanol or n-butanol.

[0107] The present invention is to complete and refine the overall technical solution, better ensure the structure and composition of the catalyst ligand for ethylene trimerization to 1-hexene, further improve the catalytic activity, selectivity and practicality of the catalyst ligand and the catalyst system, and the preparation method for ethylene trimerization to 1-hexene and its catalyst ligand may specifically include the following contents:

[0108] A catalyst ligand for selective trimerization of ethylene and a preparation method thereof, wherein the catalyst ligand contains a chlorotripyrrole functional group and has the following structural formula:

[0109]

[0110] Among them, R1 is one of hydrogen, methyl and ethyl, and R2 is one of methyl and ethyl.

[0111] The preparation method, preparation route and specific steps of the ethylene selective trimerization catalyst ligand are described as follows:

[0112] (1) Synthesis of compound A, the reaction formula is as follows:

[0113]

[0114] A certain amount of 2,4-dichlorobenzaldehyde and a certain proportion of pyrrole and 2-R1-pyrrole are reacted at a certain temperature for a certain time, and then trifluoroacetic acid is added, and the reaction is continued at room temperature for a certain time. After the reaction is completed, an amine compound is used to quench the reaction, and the reaction liquid is filtered through a sand core. After the reaction liquid is rotary evaporated, compound A is obtained by separation through a chromatography column.

[0115] (2) Synthesis of compound B, the reaction formula is as follows:

[0116]

[0117] Under the protection of inert gas, compound A (when R1 is H) is used as a raw material, dissolved in a solvent, a small amount of initiator is added, and then the reaction system is placed in a low temperature tank, and NBS (N-bromosuccinimide) is added to the reaction system in batches, and the reaction is kept warm. After the reaction is completed, a saturated sodium thiosulfate aqueous solution is added, and then the layers are extracted, the organic phases are combined, and the solvent is evaporated and the crude product is recrystallized using methanol to obtain a terminal bromine-substituted oxidized tripyrrole compound B-1.

[0118] Then, tert-butyloxycarbonyl is used to protect compound B-1 to obtain compound B-2, and then Grignard reagent R2-MgCl is used for alkylation to obtain compound B-2, and then acid solution is used to remove the Boc group to obtain a mother liquor containing compound B. Pure compound B is obtained by washing with water, extracting, removing solvent, recrystallizing, etc.

[0119] Specifically, in the synthesis of the catalyst ligand A, the reaction temperature is -15 to 50°C, preferably -5 to 0°C.

[0120] Specifically, in the synthesis of the catalyst ligand A, the first stage reaction time is 15 to 60 minutes, and the second stage room temperature reaction time is 20 to 30 minutes.

[0121] Specifically, in the synthesis of the catalyst ligand A, the amine quencher is one or more of triethylamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, di-n-propylamine, and diisopropylamine, preferably triethylamine.

[0122] Specifically, in the synthesis of the catalyst ligand A, the molar ratio of 2,4-dichlorobenzaldehyde, pyrrole, and 2-R1-pyrrole is 2:1:2.

[0123] Specifically, in the synthesis of the catalyst ligand B, the reaction solvent is dichloromethane, carbon tetrachloride, tetrahydrofuran, dioxane, etc., preferably dichloromethane or carbon tetrachloride.

[0124] Specifically, in the synthesis of the catalyst ligand B, the molar amount of the Grignard reagent is twice that of the compound B-1.

[0125] Specifically, in the synthesis of the catalyst ligand B, the molar amount of (Boc)2O is the same as that of B-1.

[0126] Specifically, in the synthesis of the catalyst ligand B, the initiator is azobisisobutyronitrile, and its usage is 5% of the mass of the raw material.

[0127] Specifically, in the synthesis of the catalyst ligand B, the reaction temperature is -50 to -10°C, preferably -35 to -25°C.

[0128] Specifically, in the synthesis of the catalyst ligand B, the solvent used for the recrystallization of the compounds B-1 and B-2 is one of methanol, ethanol, n-propanol, isopropanol, and n-butanol, preferably methanol or ethanol.

[0129] Specifically, in the synthesis of the catalyst ligand B, the acid used for the de-Boc is one of formic acid, acetic acid, trifluoroacetic acid, hydrochloric acid, and propionic acid, preferably formic acid or trifluoroacetic acid.

[0130] The present invention provides a catalyst system for preparing 1-hexene by ethylene trimerization, comprising a main catalyst and a co-catalyst;

[0131] The main catalyst comprises a trivalent chromium compound and a ligand;

[0132] The ligand includes the catalyst ligand described in the above technical solution or the catalyst ligand prepared by the preparation method described in any one of the above technical solutions.

[0133] In the present invention, the trivalent chromium compound preferably includes one or more of chromium naphthenate, chromium 2,2,6,6-tetramethylheptanedionate, chromium pivalate, chromium acetylacetonate, chromium isooctanoate and tri-tetrahydrofuran chromium trichloride, and more preferably chromium naphthenate, chromium 2,2,6,6-tetramethylheptanedionate, chromium pivalate, chromium acetylacetonate, chromium isooctanoate or tri-tetrahydrofuran chromium trichloride.

[0134] In the present invention, the molar ratio between the trivalent chromium compound and the ligand is preferably 1:(1-10), more preferably 1:(3-8), and more preferably 1:(5-6).

[0135] In the present invention, the co-catalyst preferably comprises alkyl aluminum and / or alkoxy aluminum, more preferably alkyl aluminum or alkoxy aluminum.

[0136] In the present invention, the molar ratio of the main catalyst to the main catalyst is preferably 1: (30-200), more preferably 1: (70-160), and more preferably 1: (110-120).

[0137] The present invention provides the use of the catalyst ligand described in the above technical scheme, the catalyst ligand prepared by the preparation method described in any one of the above technical schemes, or the catalyst system described in any one of the above technical schemes in ethylene trimerization to produce 1-hexene.

[0138] The present invention provides a method for preparing 1-hexene by ethylene trimerization, comprising the following steps:

[0139] (1) under the action of protective gas, a trivalent chromium compound, a ligand and a preparation solvent are mixed to obtain a main catalyst solution;

[0140] The ligand includes the catalyst ligand described in the above technical solution, and the catalyst ligand prepared by the preparation method described in any one of the above technical solutions;

[0141] (2) Under vacuum conditions, the main catalyst solution, co-catalyst and reaction solvent obtained in the above steps are sent to a reaction device, ethylene is introduced, and a polymerization reaction is carried out to obtain 1-hexene.

[0142] The present invention firstly mixes trivalent chromium compounds, ligands and a preparation solvent under the action of protective gas to obtain a main catalyst solution;

[0143] The ligand includes the catalyst ligand described in the above technical solution and the catalyst ligand prepared by the preparation method described in any one of the above technical solutions.

[0144] In the present invention, the formulation solvent preferably includes one or more of toluene, n-heptane, cyclohexane and n-hexane, and more preferably toluene, n-heptane, cyclohexane or n-hexane.

[0145] In the present invention, the mixing time is preferably 0.5 to 24 hours, more preferably 5 to 20 hours, and more preferably 10 to 15 hours.

[0146] In the present invention, the reaction solvent preferably includes one or more of cyclohexane, n-heptane, methylcyclohexane, 1-hexene and toluene, and more preferably cyclohexane, n-heptane, methylcyclohexane, 1-hexene or toluene.

[0147] In the present invention, the main catalyst solution, the co-catalyst and the reaction solvent obtained in the above steps are sent to a reaction device under vacuum conditions, ethylene is introduced, and a polymerization reaction is carried out to obtain 1-hexene.

[0148] In the present invention, the pressure of ethylene is preferably 4-6 MPa, more preferably 4.4-5.6 MPa, and more preferably 4.8-5.2 MPa.

[0149] In the present invention, the polymerization reaction temperature is preferably 100 to 150°C, more preferably 110 to 140°C, and even more preferably 120 to 130°C.

[0150] In the present invention, the polymerization reaction time is preferably 15 to 100 min, more preferably 20 to 80 min, more preferably 25 to 60 min, and more preferably 30 to 40 min.

[0151] The present invention is a complete and detailed overall technical solution, which further improves the catalytic activity, selectivity and practicality in the process of preparing 1-hexene by ethylene trimerization. The above-mentioned catalyst system for preparing 1-hexene by ethylene trimerization and the preparation method for preparing 1-hexene by ethylene trimerization can specifically include the following contents:

[0152] The preparation method of ethylene selective trimerization catalyst ligand, the catalytic system is described as follows:

[0153] (1) Preparation of the main catalyst: Under the protection of inert gas, weigh the Cr(III) compound and ligand A or B in a certain proportion and dissolve them in a solvent to prepare a main catalyst of a certain concentration, and stir at room temperature for a period of time until all the catalysts are dissolved. Then use a sampling tank to take a certain amount of the main catalyst and the co-catalyst.

[0154] (2) The reactor is heated to a certain temperature, and then the sampling tank is connected to the reactor. Under vacuum, the reaction solvent and the catalyst are sucked into the reactor, and ethylene is introduced to 4-6 MPa to control the reaction temperature. After a period of reaction, the temperature is lowered, the pressure is released, and the material is discharged.

[0155] Specifically, the Cr(III) compound is one of chromium cyclohexaneate, chromium 2,2,6,6-tetramethylheptanedione, chromium pivalate, chromium acetylacetonate, chromium isooctanoate, and chromium trichloride in tetrahydrofuran.

[0156] Specifically, the prepared solvent is one of toluene, n-heptane, cyclohexane and n-hexane.

[0157] Specifically, the molar ratio between the Cr(III) and the ligand is 1:1-10, preferably 1:1-5.

[0158] Specifically, the molar ratio between the main catalyst and the auxiliary catalyst is 1:30-200, preferably 1:50-100.

[0159] Specifically, the preparation time is 0.5 to 24 hours.

[0160] Specifically, the reaction temperature is 100-150° C., and the reaction time is 30 minutes.

[0161] Specifically, the reaction solvent is one of cyclohexane, n-heptane, methylcyclohexane, 1-hexene and toluene.

[0162] Specifically, the co-catalyst is alkyl aluminum and alkoxy aluminum, preferably triethyl aluminum, tributyl aluminum, aluminum sesquioxide, and methylaluminoxane.

[0163] Specifically, the reaction solution is weighed, and the reaction activity is calculated according to the weight gain.

[0164] The technical solution described in the present invention is only one of the methods for synthesizing partially modified ligands. All ligand compounds based on chlorine-containing tripyrrole derivatives are within the protection scope of the present invention.

[0165] The above content of the present invention provides a high-efficiency catalyst ligand for selective trimerization of ethylene and its preparation method, catalyst system, application and preparation method of 1-hexene from trimerization of ethylene. The chlorine-containing tripyrrole ligand compound with a specific structure and composition provided by the present invention has both the function of a ligand and the function of a promoter. The present invention also improves the trimerization catalytic system based on the ligand, and simplifies the original four-component system of main catalyst, auxiliary catalyst, ligand and promoter into a three-component system, making the preparation of the catalytic system simpler. Compared with the reports in the existing literature, the catalyst system for preparing high linear 1-hexene from ethylene oligomerization provided by the present invention adopts triethylaluminum with lower economic cost as a co-catalyst, and the catalytic activity of trimerization can reach up to 760kg / g(Cr).h, and the selectivity of 1-hexene can reach up to 96.76%. The high activity and high selectivity of the catalytic system at high temperature enable the reaction to run for a long period of time, so that the catalytic system has obvious advantages in the industrialization process and is more suitable for the promotion and application of industrial production.

[0166] To further illustrate the present invention, a catalyst ligand for preparing 1-hexene by ethylene trimerization, a preparation method thereof, a catalyst system, an application thereof, and a preparation method for preparing 1-hexene by ethylene trimerization provided by the present invention are described in detail below in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following embodiments.

[0167] Example 1

[0168] Synthesis of Compound AI:

[0169]

[0170] Weigh 17.5g of 2,4-dichlorobenzaldehyde into a 100ml round-bottom flask, stir magnetically, place in an ice-salt bath, maintain -5 to 0°C, then weigh 10.06g of pyrrole into a constant pressure dropping funnel, slowly drip into the reaction system under nitrogen protection. After the addition is complete, keep warm for 30 minutes, then warm to room temperature, weigh 11.4g of trifluoroacetic acid and add it to the reaction system, react for 30 minutes, then add 12g of triethylamine to quench the reaction.

[0171] The reaction solution was filtered using a sand core funnel, and the filtrate was evaporated to remove the solvent to obtain an orange-red oily liquid, which was then separated using a chromatography column. Toluene was used as the eluent to collect the penultimate component, and the solvent was evaporated to remove the solvent, and finally 6.13 g of compound AI was obtained. It was characterized by H NMR spectrum:

[0172] 1H-NMR (400MHz, CDCl3, δ, ppm): 11.83~11.86(2H,s,NH); 9.28~9.35(1H,s,NH); 7.69~7.73(2H,s,benzene-H); 7.18~7.25(2H,d,benzene-H ); 7.04~7.10(2H,d,benzene-H); 6.60~6.65(2H,t,NCH); 5.86~5.89(2H,t,NCCH); 5.70~5.75(2H,s,NCCH); 5.32~5.35(2H,s,benzene-CH).

[0173] Example 2

[0174] Synthesis of compound A-II:

[0175]

[0176] Weigh 17.5g of 2,4-dichlorobenzaldehyde into a 100ml round-bottom flask, stir magnetically, place in an ice-salt bath, maintain -5 to 0°C, then weigh 6.71g of pyrrole and 4.05g of 2-methylpyrrole, mix evenly, and slowly drip into the reaction system in a constant pressure dropping funnel under nitrogen protection. After the addition is complete, keep the temperature for 30 minutes, then warm to room temperature, weigh 11.4g of trifluoroacetic acid and add it to the reaction system. After 30 minutes of reaction, add 12g of triethylamine to quench the reaction.

[0177] The reaction solution was filtered using a sand core funnel, and the filtrate was evaporated to remove the solvent to obtain an orange-red oily liquid, which was then separated using a chromatography column. Toluene was used as the eluent to collect the penultimate component, and the solvent was evaporated to remove the solvent, and finally 5.51 g of compound A-II was obtained. It was characterized by H NMR spectrum:

[0178] 1 H-NMR (400MHz, CDCl3, δ, ppm): 11.83~11.86(2H,s,NH); 9.26~9.33(3H,s,NH); 7.67~7.70(2H,s,benzene-H); 7.05~7.20(4H,d , benzene-H); 6.60~6.65(2H,t,NCH); 5.69~5.73(6H,s,NCCH); 5.31~5.34(2H,s,benzene-CH); 2.13~2.16(6H,s,pyrrole-CH).

[0179] Example 3

[0180] Synthesis of compound A-III:

[0181]

[0182] Weigh 17.5g of 2,4-dichlorobenzaldehyde into a 100ml round-bottom flask, stir magnetically, place in an ice-salt bath, maintain -5 to 0°C, then weigh 6.71g of pyrrole and 4.05g of 2-ethylpyrrole, mix evenly, and slowly drip into the reaction system in a constant pressure dropping funnel under nitrogen protection. After the addition is complete, keep the temperature for 30 minutes, then warm to room temperature, weigh 11.4g of trifluoroacetic acid and add it to the reaction system. After 30 minutes of reaction, add 12g of triethylamine to quench the reaction.

[0183] The reaction solution was filtered using a sand core funnel, and the filtrate was evaporated to remove the solvent to obtain an orange-red oily liquid, which was then separated using a chromatography column. Toluene was used as the eluent to collect the penultimate component, and the solvent was evaporated to remove the solvent, and finally 4.92 g of compound A-III was obtained. It was characterized by H NMR spectrum:

[0184] 1 H-NMR (400MHz, CDCl3, δ, ppm): 11.83 ~ 11.86 (2H, s, NH); 9.26 ~ 9.33 (3H, s, NH); 7.67 ~ 7.70 (2H, s, benzene-H); 7.05 ~ 7.19 (4H, d, benzene-H); 6. 60~6.65(2H,t,NCH); 5.69~5.73(6H,s,NCCH); 5.31~5.34(2H,s,benzene-CH); 3.10~3.15(4H,m,pyrrole-CH); 1.28~1.31(6H,t,pyrrole-CCH).

[0185] Example 4

[0186] Synthesis of compound BI:

[0187] Under the protection of inert gas, weigh 5.15g of compound AI and 0.05g in a 100ml round-bottom flask, add 50ml of dichloromethane, stir to dissolve, then place the reaction system in a low temperature tank, maintain -25°C, then add NBS to the reaction system in batches, add it in 1 hour, and continue to keep warm for 6 hours. After the reaction is completed, add saturated sodium thiosulfate aqueous solution, then extract by layer, combine the organic phases, evaporate the solvent, and recrystallize the crude product using methanol to obtain 5.25g of bromine-substituted oxidized tripyrrole compound B-1.

[0188]

[0189] Weigh 5.25g of compound B-1 in a 100ml reaction bottle, add 50ml of dichloromethane and stir to dissolve, then add 1.5g (Boc) 2O, keep warm at 50℃ for 2h, and the reaction is complete. The reaction solvent is removed by rotary evaporation to obtain a crude compound B-2. Dissolve compound B-2 in 50ml of tetrahydrofuran, keep the reaction system at -20℃, then measure 8ml of 2.0mol / L Grignard reagent methylmagnesium chloride and slowly drop it into the reaction system, keep warm for 2h, and the reaction is complete. After the reaction is completed, do not handle it, slowly add 20ml of formic acid at -25℃, then reflux for 2 hours, and the reaction is complete. The reaction solution is rotary evaporated to remove the solvent, washed with water, extracted with dichloromethane, the organic phase is combined, the solvent is removed, and finally recrystallized with methanol to obtain 0.35g of orange-red solid compound BI.

[0190] The H NMR spectrum was used to characterize it:

[0191] 1 H-NMR (400MHz, CDCl3, δ, ppm): 12.88~12.91(1H,s,NH)7.83~7.86(2H,d,NCCH); 7.46~7.50(2H,s,benzene-H); 7 .20~7.35(4H,d,benzene-H)); 6.36~6.40(2H,d,NCCH); 6.23~6.25(2H,d,NCCH); 2.21~2.25(6H,s,pyrrole-CH).

[0192] Example 5

[0193] Synthesis of compound B-II:

[0194]

[0195] Weigh 5.25g of compound B-1 in a 100ml reaction bottle, add 50ml of dichloromethane and stir to dissolve, then add 1.5g (Boc) 2O, keep warm at 50℃ for 2h, and the reaction is complete. The reaction solvent is removed by rotary evaporation to obtain a crude compound B-2. Dissolve compound B-2 in 50ml of tetrahydrofuran, keep the reaction system at -20℃, then measure 8ml of 2.0mol / L Grignard reagent ethylmagnesium chloride and slowly drop it into the reaction system, keep warm for 2h, and the reaction is complete. After the reaction is completed, do not handle it, slowly add 20ml of formic acid at -25℃, then reflux for 2 hours, and the reaction is complete. The reaction solution is rotary evaporated to remove the solvent, washed with water, extracted with dichloromethane, the organic phase is combined, the solvent is removed, and finally recrystallized with methanol to obtain 0.47g of orange-red solid compound BI.

[0196] The H NMR spectrum was used to characterize it:

[0197] 1 H-NMR (400MHz, CDCl3, δ, ppm): 12.88 ~ 12.90 (1H, s, NH) 7.82 ~ 7.85 (2H, d, NCCH); 7.46 ~ 7.50 (2H, s, benzene-H); 7.20 ~ 7.35 (4H, d, benzene-H)); 6.36~6.40(2H,d,NCCH); 6.23~6.25(2H,d,NCCH); 2.15~2.20(4H,m,pyrrole-CH); 0.80~0.83(6H,t,pyrrole-CCH).

[0198] Example 6

[0199] Under the protection of inert gas, prepare a n-heptane solution of chromium isooctanoate (8% Cr content) and ligand AI in a 1:1 molar ratio, with a concentration of 10 μmol / ml. Stir the materials for 30 minutes after mixing, and use a sampling tank to measure 0.5 ml of the main catalyst and 0.4 ml of triethylaluminum (1 mol / L n-hexane solution) solution for use.

[0200] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, and in a vacuum environment, suck 200ml of cyclohexane together with the catalyst into the reactor, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge the material. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0201] Table 1 is the verification data of Examples 6 to 17 and Comparative Examples 1 to 2.

[0202] Comparative Example 1

[0203] Use the existing Philips catalytic system, a four-component catalytic system. Under the protection of inert gas, prepare chromium isooctanoate (8% Cr content), 2,5-dimethylpyrrole and tetrachloroethane in n-heptane solution at a molar ratio of 1:3:3, and the concentration is still 10μmol / ml. After mixing the materials, stir for 30 minutes, and use a sampling tank to measure 0.5ml of the main catalyst and 0.4ml of triethylaluminum (1mol / L n-hexane solution) solution for use.

[0204] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, suck cyclohexane and the catalyst into the reactor under vacuum, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0205] Example 7

[0206] Under the protection of inert gas, prepare a n-heptane solution of chromium isooctanoate (8% Cr content) and ligand A-II in a 1:1 molar ratio, with a concentration of 10 μmol / ml. Stir the materials for 30 minutes after mixing, and use a sampling tank to measure 0.5 ml of the main catalyst and 0.4 ml of triethylaluminum (1 mol / L n-hexane solution) solution for use.

[0207] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, suck cyclohexane and the catalyst into the reactor under vacuum, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0208] Example 8

[0209] Under the protection of inert gas, prepare a n-heptane solution of chromium isooctanoate (8% Cr content) and ligand A-III in a 1:1 molar ratio, with a concentration of 10 μmol / ml. Stir the materials for 30 minutes after mixing, and use a sampling tank to measure 0.5 ml of the main catalyst and 0.4 ml of triethylaluminum (1 mol / L n-hexane solution) solution for use.

[0210] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, suck cyclohexane and the catalyst into the reactor under vacuum, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0211] Example 9

[0212] Under the protection of inert gas, prepare a n-heptane solution of chromium isooctanoate (8% Cr content) and ligand BI in a 1:1 molar ratio, with a concentration of 10 μmol / ml. Stir the materials for 30 minutes after mixing, and use a sampling tank to measure 0.5 ml of the main catalyst and 0.4 ml of triethylaluminum (1 mol / L n-hexane solution) solution for use.

[0213] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, suck cyclohexane and the catalyst into the reactor under vacuum, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0214] Example 10

[0215] Under the protection of inert gas, prepare a n-heptane solution of chromium isooctanoate (8% Cr content) and ligand B-II in a 1:1 molar ratio, with a concentration of 10 μmol / ml. Stir the materials for 30 minutes after mixing, and use a sampling tank to measure 0.5 ml of the main catalyst and 0.4 ml of triethylaluminum (1 mol / L n-hexane solution) solution for use.

[0216] Heat the 1L reactor to 120°C, then connect the sampling tank to the reactor, suck cyclohexane and the catalyst into the reactor under vacuum, introduce ethylene to 5Mpa, control the reaction temperature to 120-130°C, react for 30 minutes, cool down, release the pressure, and discharge. Track the reaction liquid by gas chromatography, weigh the reaction liquid, and calculate the reaction activity according to the weight gain. The experimental data are summarized in Table 1 below.

[0217] Embodiment 11

[0218] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand AI in a molar ratio of 1:2. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0219] Comparative Example 2

[0220] The main catalyst solution was prepared according to a molar ratio of 1:6:6: the n-heptane solution of chromium isooctanoate (8% Cr content), 2,5-dimethylpyrrole and tetrachloroethane, and the n-heptane solution of chromium isooctanoate (8% Cr content) and ligand AI. The other conditions were the same as in Example 6. The experimental data are summarized in Table 1 below.

[0221] Example 12

[0222] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand A-II in a molar ratio of 1:2. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0223] Embodiment 13

[0224] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand A-III in a molar ratio of 1:2. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0225] Embodiment 14

[0226] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand BI in a molar ratio of 1:2. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0227] Embodiment 15

[0228] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand B-II in a molar ratio of 1:2. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0229] Example 16

[0230] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand AI in a molar ratio of 1:2. n-heptane was also used as the reaction solvent. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0231] Embodiment 17

[0232] The main catalyst solution was prepared with chromium isooctanoate (8% Cr content) and n-heptane solution of ligand BI in a molar ratio of 1:2. n-heptane was also used as the reaction solvent. Other conditions were the same as those in Example 6. The experimental data are summarized in Table 1 below.

[0233] Table 1

[0234]

[0235]

[0236] The above is a detailed introduction to a high-efficiency catalyst ligand for selective trimerization of ethylene and its preparation method, catalyst system, application and preparation method of 1-hexene by trimerization of ethylene provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation method of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the text of the claims, or if they include equivalent structural elements that are not substantially different from the text of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. Use of a catalyst ligand represented by formula A and / or B in the preparation of 1-hexene by ethylene trimerization; The catalyst ligand contains chlorotripyrrole functional groups; The structural formula shown in formula A and / or B is: in, R1 is selected from one or more of hydrogen, methyl and ethyl; R2 is selected from methyl and / or ethyl.

2. A method for preparing a catalyst ligand for ethylene trimerization to 1-hexene, characterized in that: The following steps are involved: a) reacting 2,4-dichlorobenzaldehyde, pyrrole and 2-R1-pyrrole, then adding trifluoroacetic acid and continuing the reaction to obtain a catalyst ligand having a structure shown in formula A; Wherein, R1 is selected from one or more of hydrogen, methyl and ethyl; 1) under the action of protective gas, the raw materials and the solvent are mixed, an initiator is added, and then N-bromosuccinimide is added to react to obtain an intermediate terminal bromine-substituted oxidized tripyrrole compound; The raw material is a compound with a structure shown in formula A when R1 is H; 2) The intermediate obtained in the above step is protected with a tert-butyloxycarbonyl protecting group, then alkylated with R2-MgCl, and then the Boc group is removed with an acid solution to obtain a catalyst ligand having a structure shown in formula B; Wherein, R2 is selected from methyl and / or ethyl.

3. The preparation method according to claim 2, characterized in that: The molar ratio of 2,4-dichlorobenzaldehyde to pyrrole is (1.5-2.5):1; The molar ratio of pyrrole to 2-R1-pyrrole is 1:(1.5-2.5); In the step a), the reaction temperature is -15 to 50°C; In the step a), the reaction time is 15 to 60 minutes; In the step a), the temperature for continuing the reaction is 5 to 40°C; In the step a), the reaction time is 20 to 30 minutes; After the continued reaction, the step of using an amine compound to quench the reaction is also included; The amine compound includes one or more of triethylamine, dimethylamine, diethylamine, n-propylamine, isopropylamine, di-n-propylamine and diisopropylamine.

4. The preparation method according to claim 2, characterized in that: In the step 1), the solvent includes one or more of dichloromethane, carbon tetrachloride, tetrahydrofuran and dioxane; The initiator includes azobisisobutyronitrile; The mass ratio of the initiator to the raw material is 1% to 10%; The molar ratio of the N-bromosuccinimide to the raw material is (0.8-1.5):

1.

5. The preparation method according to claim 2, characterized in that: The reaction temperature in step 1) is -50 to -10°C; In the step 1), after the reaction, one or more steps of layer extraction, solvent removal and recrystallization are further included; The acid solution includes one or more of formic acid, acetic acid, trifluoroacetic acid, hydrochloric acid and propionic acid; In the step 2), after removing the Boc group, one or more steps of washing, extraction, solvent removal and recrystallization are further included; The solvent used for the recrystallization includes one or more of methanol, ethanol, n-propanol, isopropanol and n-butanol.

6. A catalyst system for preparing 1-hexene by trimerization of ethylene, characterized in that: Including main catalyst and co-catalyst; The main catalyst comprises a trivalent chromium compound and a ligand; The ligand includes the catalyst ligand according to claim 1 or the catalyst ligand prepared by the preparation method according to any one of claims 2 to 5.

7. The catalyst system according to claim 6, characterized in that The trivalent chromium compound includes one or more of chromium naphthenate, chromium 2,2,6,6-tetramethylheptanedione, chromium pivalate, chromium acetylacetonate, chromium isooctanoate and chromium trichloride tritetrahydrofuran; The molar ratio between the trivalent chromium compound and the ligand is 1:(1-10); The co-catalyst comprises alkyl aluminum and / or alkoxy aluminum; The molar ratio of the main catalyst to the co-catalyst is 1:(30-200).

8. Use of the catalyst ligand prepared by the preparation method according to any one of claims 2 to 5 or the catalyst system according to any one of claims 6 to 7 in the preparation of 1-hexene by ethylene trimerization.

9. A method for preparing 1-hexene by ethylene trimerization, characterized in that: The following steps are involved: (1) under the action of protective gas, a trivalent chromium compound, a ligand and a preparation solvent are mixed to obtain a main catalyst solution; The ligand includes the catalyst ligand according to claim 1, or the catalyst ligand prepared by the preparation method according to any one of claims 2 to 5; (2) Under vacuum conditions, the main catalyst solution, co-catalyst and reaction solvent obtained in the above steps are sent to a reaction device, ethylene is introduced, and a polymerization reaction is carried out to obtain 1-hexene.

10. The preparation method according to claim 9, characterized in that: The preparation solvent includes one or more of toluene, n-heptane, cyclohexane and n-hexane; The mixing time is 0.5 to 24 hours; The reaction solvent includes one or more of cyclohexane, n-heptane, methylcyclohexane, 1-hexene and toluene; The pressure of the ethylene is 4-6 MPa; The polymerization reaction temperature is 100-150° C.; the polymerization reaction time is 15-100 min.

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