An ethylene selective oligomerization catalytic system and its application

Abstract

The present invention discloses an ethylene selective oligomerization catalytic system and its application. The catalyst system comprises a ligand a, a transition metal compound b, and an activator c; wherein the transition metal compound b is a metal compound of Groups IVB to VIII; and the activator c is a compound containing a Group IIIA metal. The general structural formula of ligand a is shown in Formula (I): #imgabs0# wherein R1 and R2 are the same or different and are independently selected from hydrogen, an alkyl group, or an aryl group; or R1 and R2 form a cyclic structure with a P atom. The catalyst system of the present invention has high stability, good temperature resistance, high catalytic activity and target product selectivity, and can flexibly switch between trimerization and tetramerization catalytic performance by controlling process conditions.

Description

Technical Field

[0001] The invention belongs to the field of ethylene oligomerization, and particularly relates to an ethylene selective oligomerization catalytic system and application thereof. Background Art

[0002] As an important organic raw material and intermediate product, α-olefins are widely used in polyethylene comonomers, surfactants, lubricants, plasticizers, polyα-olefins, additives, and fine chemicals. Among them, 1-hexene is mainly used in the production of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). 1-octene, as an important organic raw material and chemical intermediate, is mainly used in the production of high-end PE and POE, as well as a raw material for the production of plasticizers, alcohols for detergents, and lubricant additives. Therefore, as important varieties of high-end α-olefins, 1-hexene and 1-octene have a large market demand, especially in my country, where high-purity 1-octene is completely dependent on imports.

[0003] In recent years, the selective oligomerization of ethylene to produce α-olefins with specific carbon numbers has become a research hotspot. The development of catalysts, particularly ligands, for selective ethylene oligomerization is crucial. A significant number of research results and technologies have emerged in recent years. Representative companies in this field, such as BP, Sasol, and SK Innovation, have developed technologies for the selective trimerization and tetramerization of ethylene to produce 1-hexene and 1-octene. The PNP ligands disclosed in Chinese patents CN1741850A (WO2004 / 056478A1), CN101032695A and US2006 / 0128910A1, and the chiral PCCP-type ligands designed and synthesized by South Korea's SK Energy Company CN201880057196.4, CN201780043063.7, CN201080003564.0, CN200880002464.9, and CN200780100280.1, are used in a catalytic system consisting of Cr and alkylaluminoxane for ethylene tetramerization, and have high catalytic activity.

[0004] While research on ethylene trimerization catalysts and production processes is relatively mature, with industrial production facilities already operating in China, ethylene tetramerization catalysts and their production processes still face numerous challenges. For example, currently developed catalysts exhibit poor stability during ethylene tetramerization, undergoing varying degrees of degradation and conversion during the reaction, generating active ethylene polymerization sites and leading to the production of high-molecular-weight polyethylene (HMWPE). This generated HMWPE can, in turn, clog process pipelines, instrumentation, and valves, impacting the stable operation of the facility. Furthermore, to maintain catalyst stability, ethylene tetramerization is typically conducted at relatively low reaction temperatures. However, the resulting HMWPE exhibits poor solubility at these temperatures, exacerbating clogs in pipelines and other locations. Therefore, developing high-temperature-resistant, stable catalysts is one solution to addressing this clogging issue.

[0005] Existing ethylene selective oligomerization catalytic systems typically target only a single oligomerization reaction, either ethylene trimerization or ethylene tetramerization. When different oligomerization products are needed, the catalyst must be replaced, severely impacting production efficiency. To meet the varying demands for 1-hexene and 1-octene at different stages of the market and by different manufacturers, developing catalyst systems that can flexibly switch between trimerization and tetramerization without changing the catalyst system is an important direction for catalyst development. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a controllable ethylene selective oligomerization catalyst system and its application. By adjusting the process reaction temperature and reaction pressure, the catalyst system can achieve different catalytic performance for trimerization or tetramerization, flexibly adjusting the selectivity for 1-hexene and 1-octene. Furthermore, the catalyst system offers the advantages of high stability, excellent temperature resistance, high catalytic activity, and high selectivity for the target product. This system can address the problems of existing ethylene selective oligomerization catalyst systems, such as poor temperature resistance, high production of high-molecular-weight polyethylene, and pipeline clogging.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] An ethylene selective oligomerization catalyst system comprises a ligand a, a transition metal compound b, and an activator c. The transition metal compound b is a metal compound of Groups IVB to VIII; the activator c is a compound containing a Group IIIA metal; and the general structural formula of the ligand a is shown in Formula (I):

[0009]

[0010] Wherein, R1 and R2 may be the same or different and are independently selected from hydrogen, alkyl or aryl; R1 and R2 may also form a ring structure with the P atom, such as a three-membered ring, a four-membered ring, a five-membered ring or a six-membered ring.

[0011] Furthermore, the alkyl group includes a straight-chain alkyl group, a branched alkyl group or a cycloalkyl group; the carbon number of the alkyl group is not greater than 10, preferably an alkyl group with a carbon number of 1-6; the aryl group is a C6-C20 aryl group and a substituted aryl group, preferably a phenyl group or a substituted phenyl group.

[0012] Furthermore, the preparation method of the ligand is as follows: (1) adding ammonia water and an acid-binding agent to a solvent 1, stirring thoroughly and cooling to 0-5°C, adding 2-(chlorobenzyl)thiophene to the reaction solution, continuing stirring for 0.2-1.0 hours after the addition, heating to room temperature and continuing the reaction for 6-12 hours. After the reaction is completed, filtering the reaction solution, and removing the solvent by rotary evaporation to obtain an intermediate of the ligand; (2) adding the intermediate prepared in step (1), a phosphorus chloride compound, and an acid-binding agent 2 to a reaction solvent 2, heating to 60-100°C and reacting for 3-6 hours. After the reaction is completed, pouring the reaction solution into water, filtering to obtain a crude product of the ligand, and further purifying by column chromatography to obtain a pure product of the ligand.

[0013] Preferably, the acid binding agent is triethylamine.

[0014] Wherein, on a molar basis, ammonia: acid binding agent 1: 2-(chlorobenzyl)thiophene: phosphorus chloride compound: acid binding agent 2 = 1:2-3:2-2.5:1-1.2:1.2-2. The general structural formula of the phosphorus chloride compound is shown in Formula (II), and preferably the phosphorus chloride compound has the structural formula ad:

[0015]

[0016] Wherein, R1 and R2 have the same meanings as above.

[0017] Furthermore, the solvent 1 is selected from one or more of tetrahydrofuran, dioxane, toluene, pentane, hexane, diethyl ether and isopropyl ether, preferably tetrahydrofuran or dioxane.

[0018] Furthermore, the second solvent is selected from one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dioxane, methyl ethyl ketone and acetonitrile, preferably DMF or DMSO.

[0019] Furthermore, the second acid binding agent is selected from one or more of potassium carbonate, sodium carbonate, magnesium carbonate and cesium carbonate, preferably cesium carbonate.

[0020] Furthermore, the transition metal compound b is one or more compounds of chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel or palladium, preferably a compound of chromium or nickel.

[0021] Furthermore, the activator c is one or a mixture of two or more of an alkyl aluminum compound, an alkyl aluminum oxane compound, and an organic boron compound; preferably an alkyl aluminum oxane compound.

[0022] Furthermore, the molar ratio of the ligand to the transition metal compound is 0.1:1-10:1, preferably 0.5:1-2:1; the molar ratio of the metal in the transition metal compound to the aluminum in the activator is 1:1-1:5000, preferably 1:30-1:1000; or the molar ratio of the metal in the transition metal compound to the boron in the activator is 0.1:1-10:1, preferably 0.5:1-2:1

[0023] Furthermore, the ethylene selective oligomerization catalyst system of the present invention can be prepared by pre-mixing the ligand, transition metal compound, and activator; or the ligand, transition metal compound, and activator can be directly added into the reaction system for in-situ synthesis.

[0024] The present invention also provides application of the ethylene selective oligomerization catalytic system in ethylene oligomerization reaction.

[0025] Ethylene polymerization reaction: when the reaction temperature is lower than 70°C and the reaction pressure is lower than 5MPa, preferably lower than 4.5MPa, the catalyst catalyzes the ethylene polymerization mainly to produce a trimerization reaction; when the reaction temperature is higher than 70°C, preferably higher than 80°C, and the reaction pressure is higher than 5MPa, preferably higher than 6MPa, the catalyst catalyzes the ethylene polymerization mainly to produce a tetramerization reaction.

[0026] Preferably, when the reaction temperature is 40-60°C and the reaction pressure is 3-4 MPa, the ethylene polymerization reaction is carried out under the catalyst conditions of the present invention, and mainly produces trimerization products. When the reaction temperature is 90-110°C and the reaction pressure is 7-8.5 MPa, the ethylene polymerization reaction is carried out under the catalyst conditions of the present invention, and mainly produces tetramerization products.

[0027] The selective oligomerization reaction of ethylene is carried out in a third solvent, wherein the third solvent is one or a mixture of two or more of an alkane, an aromatic hydrocarbon, an olefin, or an ionic liquid, and preferably an alkane is the third solvent;

[0028] In the selective oligomerization of ethylene, the concentration of the catalyst is 0.01 μmol metal / L to 500 μmol metal / L, preferably 1 μmol metal / L to 50 μmol metal / L.

[0029] The present invention has the following advantages:

[0030] The present invention provides a ligand with multiple coordination sites containing a thienyl rigid structure. The sulfur atom of the thienyl group and the phosphorus atom of the ligand can form a strong coordination bond with different transition metals. This type of coordination bond has strong stability, is not easily degraded, and is converted into a polymerization active center, which can significantly reduce the production of polyethylene. At the same time, the catalyst has excellent temperature resistance and can play a catalytic role at high temperatures. Less polyethylene production and higher reaction temperature can reduce the blockage of the pipeline by the polymer. Under different reaction pressures and reaction temperatures, the spatial configuration of the transition metal complex is different. The selectivity of the oligomerization reaction can be regulated by regulating the reaction temperature and reaction pressure. Therefore, flexible switching of ethylene trimerization and ethylene tetramerization products can be achieved under the same catalyst system to meet different market needs. In addition, the catalyst system also has the characteristics of high reaction activity and high selectivity of the target product. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0032] Raw material source: 2-(Chlorobenzyl)thiophene, CAS: 148670-11-5, Aldlab Chemicals

[0033] Diphenylphosphine chloride, CAS: 1079-66-9, Sigma-Aldrich

[0034] Dimethylphosphine chloride, CAS: 811-62-1, Huaxia Chemical Company

[0035] Diisopropylphosphine chloride, CAS: 40244-90-4, Aladdin

[0036] Cyclopentylphosphine chloride, CAS: 30292-78-5, Didu Pharmaceuticals

[0037] Example 1:

[0038]

[0039] 1. Preparation of Ligand A:

[0040] The preparation method of the ligand of the present invention is:

[0041] In a 500ml flask, add 200ml of tetrahydrofuran, 3.4g of 25% ammonia water, and 10.2g of triethylamine. After thorough stirring and mixing, cool to 0°C, and add 2-(chlorobenzyl)thiophene (21g of 2-(chlorobenzyl)thiophene dissolved in 100ml of tetrahydrofuran) dropwise to the reaction solution. After the addition, continue stirring at 0°C for 0.5 hours. After warming to room temperature, continue the reaction for 12 hours. After the reaction is completed, filter the reaction solution, and remove the solvent by rotary evaporation to obtain the intermediate A1 of ligand A. Add the obtained A1 to a 500ml reaction bottle, add 250ml of N,N-dimethylformamide (DMF) to dissolve it, and then add 11g of diphenylphosphine chloride and 20g of cesium carbonate. Heat to 80°C and react for 3 hours. After the reaction is completed, pour the reaction solution into 1000ml of water and filter to obtain the crude product of ligand A. Further purification by column chromatography gives the pure product of ligand A ( 1 H NMR (500MHz, Chloroform-d) δ7.46-7.24 (m, 22H), 7.20 (s, 2H), 7.02 (s, 2H), 5.50 (d, J = 0.8Hz, 2H).

[0042] 2. Ethylene oligomerization: (1) Ethylene trimerization: Heat a 500 mL reactor to 120°C, evacuate at 120°C for 60 min, then replace with nitrogen three times at 120°C. Add 200 mL of dried methylcyclohexane under nitrogen atmosphere, then add 0.16 mg of chromium trichloride (5 μmol / L), 0.65 mg of ligand A (6 μmol / L), and 0.58 g of 7% MMAO (Al / Cr=300). Heat to 50°C, introduce ethylene into the reactor to replace nitrogen. After five replacements, stir and react. The reactor pressure is maintained at 4 MPa by controlling the ethylene feed rate. After 30 min of reaction, stop feeding ethylene, cool rapidly, release the pressure slowly, take samples, and analyze the results. Catalyst activity 53.6*10 6 g / molCr·h, 1-C6 selectivity 92.5%, 1-C8 selectivity 5.2%, polyethylene 0.06%.

[0043] (2) Ethylene tetramerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 0.16 mg of chromium trichloride (5 μmol / L), 0.65 mg of ligand A (6 μmol / L), and 0.58 g of 7% MMAO (Al / Cr=300). The temperature was raised to 100°C, and nitrogen was introduced into the reactor to replace ethylene. After five replacements, stirring was started to react. The reactor pressure was maintained at 8 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 68.1*10 6 g / molCr·h, 1-C6 selectivity 10.8%, 1-C8 selectivity 87.3%, polyethylene 0.08%.

[0044] Example 2:

[0045]

[0046] 1. Preparation of ligand B:

[0047] The preparation method of the ligand of the present invention is:

[0048] In a 500ml flask, 200ml of dioxane, 3.4g of 25% ammonia water, and 12.1g of triethylamine were added. After thorough stirring and mixing, the temperature was lowered to 0°C. 2-(chlorobenzyl)thiophene (22g of 2-(chlorobenzyl)thiophene was dissolved in 100ml of dioxane) was added dropwise to the reaction solution. After the addition, stirring was continued at 0°C for 1 hour. After warming to room temperature, the reaction was continued for 6 hours. After the reaction was completed, the reaction solution was filtered and the solvent was removed by rotary evaporation to obtain the intermediate B1 of ligand B. The obtained B1 was added to a 500ml reaction bottle, 250ml of dimethyl sulfoxide (DMSO) was added to dissolve it, and then 5.8g of dimethylphosphine chloride and 24.4g of cesium carbonate were added. The temperature was raised to 100°C and the reaction was carried out for 4 hours. After the reaction was completed, the reaction solution was poured into 1000ml of water and filtered to obtain the crude product of ligand B. The pure product of ligand B ( 1 H NMR (500MHz, Chloroform-d) δ7.39 (s, 2H), 7.38–7.26 (m, 10H), 7.17 (s, 2H), 7.00 (s, 2H), 5.56 (d, J = 0.8Hz, 2H), 1.75 (s, 6H).

[0049] 2. Ethylene oligomerization reaction:

[0050] (1) Ethylene trimerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 0.03 mg of chromium trichloride (1 μmol / L), 0.42 mg of ligand B (2 μmol / L), and 0.38 g of 7% MMAO (Al / Cr=1000). The temperature was raised to 40°C, and nitrogen was introduced into the reactor to replace ethylene. After five replacements, stirring was started to react. The reactor pressure was maintained at 3 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 58.9*10 6 g / molCr·h, 1-C6 selectivity 92.1%, 1-C8 selectivity 5.8%, polyethylene 0.05%.

[0051] (2) Ethylene tetramerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 0.03 mg of chromium trichloride (1 μmol / L), 0.42 mg of ligand B (2 μmol / L), and 0.38 g of 7% MMAO (Al / Cr=1000). The temperature was raised to 90°C, and nitrogen was introduced into the reactor to replace ethylene. After five replacements, stirring was started to react. The reactor pressure was maintained at 7.5 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 71.2*10 6 g / molCr·h, 1-C6 selectivity 9.3%, 1-C8 selectivity 89.1%, polyethylene 0.09%.

[0052] Example 3:

[0053]

[0054] 1. Preparation of Ligand C:

[0055] The preparation method of the ligand of the present invention is:

[0056] In a 500ml flask, 200ml of tetrahydrofuran, 3.4g of 25% ammonia water, and 14.2g of triethylamine were added. After thorough stirring and mixing, the temperature was lowered to 0°C. 2-(chlorobenzyl)thiophene (24g of 2-(chlorobenzyl)thiophene was dissolved in 100ml of tetrahydrofuran) was added dropwise to the reaction solution. After the addition, stirring was continued at 0°C for 0.2 hours. After warming to room temperature, the reaction was continued for 10 hours. After the reaction was completed, the reaction solution was filtered and the solvent was removed by rotary evaporation to obtain the intermediate C1 of ligand C. The obtained B1 was added to a 500ml reaction bottle, 250ml of dimethyl sulfoxide (DMSO) was added to dissolve it, and then 8.4g of diisopropylphosphine chloride and 29.3g of cesium carbonate were added. The temperature was raised to 60°C and the reaction was reacted for 6 hours. After the reaction was completed, the reaction solution was poured into 1000ml of water and filtered to obtain the crude product of ligand C. The pure product of ligand C was obtained after further purification by column chromatography ( 1 H NMR (500MHz, Chloroform-d) δ7.40 (s, 2H), 7.37–7.26 (m, 10H), 7.21 (s, 2H), 7.02 (s, 2H), 5.56 (t, J = 0.9Hz, 2H), 2.57 (s, 2H), 1.12 (s, 6H), 1.07 (s, 6H).

[0057] 2. Ethylene oligomerization reaction:

[0058] (1) Ethylene trimerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 0.8 mg of chromium trichloride (25 μmol / L), 9.5 mg of ligand C (40 μmol / L), and 6.7 g of 7% MMAO (Al / Cr=700). The temperature was raised to 55°C, and nitrogen was introduced into the ethylene replacement reactor. After five replacements, stirring was started to react. The reactor pressure was maintained at 3.5 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 68.3*10 6 g / molCr·h, 1-C6 selectivity 90.4%, 1-C8 selectivity 7.9%, polyethylene 0.08%.

[0059] (2) Ethylene tetramerization: Heat a 500 mL reactor to 120°C, evacuate at 120°C for 60 min, then replace with nitrogen three times at 120°C. Add 200 mL of dried methylcyclohexane under nitrogen atmosphere, then add 0.8 mg of chromium trichloride (25 μmol / L), 9.5 mg of ligand C (40 μmol / L), and 6.7 g of 7% MMAO (Al / Cr=700). Heat to 110°C, introduce nitrogen into the ethylene replacement reactor, replace five times, start stirring and react. By controlling the ethylene feed rate, the reactor pressure is always maintained at 8.5 MPa. After 30 min of reaction, stop feeding ethylene, rapidly cool, slowly release the pressure, take samples, and analyze the results. Catalyst activity 70.5*10 6 g / molCr·h, 1-C6 selectivity 7.3%, 1-C8 selectivity 91.6%, polyethylene 0.05%.

[0060] Example 4:

[0061]

[0062] 1. Preparation of ligand D:

[0063] The preparation method of the ligand of the present invention is:

[0064] In a 500ml flask, 200ml of tetrahydrofuran, 3.4g of 25% ammonia water, and 15.2g of triethylamine were added. After thorough stirring, the mixture was cooled to 0°C. 2-(chlorobenzyl)thiophene (26g of 2-(chlorobenzyl)thiophene was dissolved in 100ml of tetrahydrofuran) was added dropwise to the reaction solution. After the addition, stirring was continued at 0°C for 0.8 hours. After warming to room temperature, the reaction was continued for 8 hours. After the reaction was completed, the reaction solution was filtered, and the solvent was removed by rotary evaporation to obtain the intermediate D1 of ligand D. The obtained B1 was added to a 500ml reaction bottle, 250ml of N,N-dimethylformamide (DMF) was added to dissolve it, and then 6.8g of cyclopentylphosphine chloride and 32.5g of cesium carbonate were added. The temperature was raised to 90°C and the reaction was reacted for 5 hours. After the reaction was completed, the reaction solution was poured into 1000ml of water and filtered to obtain the crude product of ligand D. The pure product of ligand D was obtained after further purification by column chromatography ( 1 H NMR(500MHz,Chloroform-d)δ7.40(s,2H),7.37–7.24(m,10H),7.20(s,2H),7.01(s,2H ), 5.27 (t, J = 0.9Hz, 2H), 2.43 (s, 2H), 2.32 (s, 2H), 1.69 (d, J = 3.8Hz, 4H), 1.62 (s, 2H).

[0065] 2. Ethylene oligomerization reaction:

[0066] (1) Ethylene trimerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 1.6 mg of chromium trichloride (50 μmol / L), 5.7 mg of ligand D (25 μmol / L), and 0.58 g of 7% MMAO (Al / Cr=30). The temperature was raised to 45°C, and nitrogen was introduced into the ethylene replacement reactor. After five replacements, stirring was started to react. The reactor pressure was maintained at 4 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 66.7*10 6 g / molCr·h, 1-C6 selectivity 87.5%, 1-C8 selectivity 10.2%, polyethylene 0.1%.

[0067] (2) Ethylene tetramerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 1.6 mg of chromium trichloride (50 μmol / L), 5.7 mg of ligand D (25 μmol / L), and 0.58 g of 7% MMAO (Al / Cr=30). The temperature was raised to 95°C, and nitrogen was introduced into the ethylene replacement reactor. After five replacements, stirring was started to react. The reactor pressure was maintained at 7 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity: 75.8*10 6 g / molCr·h, 1-C6 selectivity 5.0%, 1-C8 selectivity 93.6%, polyethylene 0.09%.

[0068] Example 5:

[0069]

[0070] 1. Preparation of Ligand C:

[0071] The preparation method of the ligand is the same as that of the ligand in Example 3.

[0072] 2. Ethylene oligomerization reaction:

[0073] (1) Ethylene trimerization: Heat a 500 mL reactor to 120°C, evacuate at 120°C for 60 minutes, then replace with nitrogen three times at 120°C. Add 200 mL of dried methylcyclohexane under nitrogen atmosphere, then add 0.32 mg of chromium trichloride (10 μmol / L), 2.6 mg of ligand C (11 μmol / L), and 1.03 mg of tris(pentafluorophenyl)boron. Heat to 60°C, introduce nitrogen into the ethylene replacement reactor, replace five times, start stirring and react. By controlling the ethylene feed rate, the reactor pressure is always maintained at 3 MPa. After 30 minutes of reaction, stop feeding ethylene, rapidly cool down, slowly release the pressure, take samples, and analyze the results. Catalyst activity 62.5*10 6 g / molCr·h, 1-C6 selectivity 91.5%, 1-C8 selectivity 6.8%, polyethylene 0.11%.

[0074] (2) Ethylene tetramerization: Heat a 500 mL reactor to 120°C, evacuate at 120°C for 60 minutes, then replace with nitrogen three times at 120°C, add 200 mL of dried methylcyclohexane under nitrogen atmosphere, then add 0.32 mg of chromium trichloride (10 μmol / L), 2.6 mg of ligand C (11 μmol / L), and 1.03 mg of tris(pentafluorophenyl)boron, heat to 105°C, introduce nitrogen into the ethylene replacement reactor, replace five times, start stirring to react, and control the ethylene feed rate to keep the reactor pressure at 8 MPa. After 30 minutes of reaction, stop feeding ethylene, rapidly cool down, slowly release the pressure, take samples, and analyze the results. Catalyst activity 67.2*10 6 g / molCr·h, 1-C6 selectivity 7.1%, 1-C8 selectivity 91.5%, polyethylene 0.13%.

[0075] Example 6:

[0076]

[0077] 1. Preparation of Ligand C:

[0078] The preparation method of the ligand is the same as that of the ligand in Example 3.

[0079] 2. Ethylene oligomerization reaction:

[0080] (1) Ethylene trimerization: A 500 mL reactor was heated to 120°C, vacuumed at 120°C for 60 min, and then replaced with nitrogen three times at 120°C. 200 mL of dried methylcyclohexane was added under nitrogen atmosphere, followed by 0.65 mg of nickel chloride (25 μmol / L), 9.5 mg of ligand C (40 μmol / L), and 6.7 g of 7% MMAO (Al / Cr=700). The temperature was raised to 55°C, and nitrogen was introduced into the ethylene replacement reactor. After five replacements, stirring was started to react. The reactor pressure was maintained at 4 MPa by controlling the ethylene feed rate. After 30 min of reaction, the ethylene feed was stopped, the temperature was rapidly lowered, the pressure was slowly released, sampling was performed, and the results were analyzed. Catalyst activity 53.6*10 6 g / molCr·h, 1-C6 selectivity 91.6%, 1-C8 selectivity 5.2%, polyethylene 0.07%.

[0081] (2) Ethylene tetramerization: Heat a 500 mL reactor to 120°C, evacuate at 120°C for 60 min, then replace with nitrogen three times at 120°C. Add 200 mL of dried methylcyclohexane under nitrogen atmosphere, then add 0.65 mg of nickel chloride (25 μmol / L), 9.5 mg of ligand C (40 μmol / L), and 6.7 g of 7% MMAO (Al / Cr=700). Heat to 100°C, introduce nitrogen into the ethylene replacement reactor, replace five times, start stirring and react. By controlling the ethylene feed rate, the reactor pressure is always maintained at 7.5 MPa. After 30 min of reaction, stop feeding ethylene, rapidly cool, slowly release the pressure, take samples, and analyze the results. Catalyst activity 57.2*10 6 g / molCr·h, 1-C6 selectivity 6.8%, 1-C8 selectivity 91.2%, polyethylene 0.06%.

Claims

1. An ethylene selective oligomerization catalyst system, characterized in that: The invention comprises a ligand a, a transition metal compound b and an activator c; wherein the transition metal compound b is a metal compound of Groups IVB to VIII; the activator c is a compound containing a Group IIIA metal; the general structural formula of the ligand a is shown in formula (I): wherein R1 and R2 are the same or different and are independently selected from hydrogen, alkyl or phenyl; or R1 and R2 are selected from alkyl and form a six-membered ring structure with the P atom; The alkyl group includes a straight-chain alkyl group, a branched-chain alkyl group or a cycloalkyl group; the alkyl group is an alkyl group with 1 to 6 carbon atoms.

2. The catalyst system according to claim 1, characterized in that The preparation method of the ligand is as follows: (1) adding ammonia water and an acid-binding agent to a first solvent, stirring the mixture thoroughly, cooling the mixture to 0-5° C., adding 2-(chlorobenzyl)thiophene to the reaction solution, stirring the mixture for 0.2-1.0 hours, heating the mixture to room temperature, and reacting the mixture for 6-12 hours. After the reaction is completed, filtering the reaction solution, and removing the solvent by rotary evaporation to obtain an intermediate of the ligand; (2) adding the intermediate prepared in step (1), a phosphorus chloride compound, and an acid-binding agent to a second reaction solvent, heating the mixture to 60-100° C., and reacting the mixture for 3-6 hours. After the reaction is completed, pouring the reaction solution into water, filtering the reaction solution to obtain a crude ligand product, and further purifying the crude ligand product by column chromatography to obtain a pure ligand product. The general structural formula of the phosphorus chloride compound is shown in formula (II): Wherein, R1 and R2 have the same meaning as in claim 1; The first acid binding agent is triethylamine, and the second acid binding agent is selected from one or more of potassium carbonate, sodium carbonate, magnesium carbonate and cesium carbonate.

3. The catalyst system according to claim 2, characterized in that In terms of molar amount, ammonia: acid binding agent 1: 2-(chlorobenzyl)thiophene: phosphorus chloride compound: acid binding agent 2 = 1:2-3:2-2.5:1-1.2:1.2-2.

4. The catalyst system according to claim 2, characterized in that The structural formula of the phosphorus chloride compound is selected from the phosphorus chloride compounds ad:

5. The catalyst system according to claim 2, characterized in that The solvent is selected from one or more of tetrahydrofuran, dioxane, toluene, pentane, hexane, diethyl ether and isopropyl ether.

6. The catalyst system according to claim 2, characterized in that The second solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, dioxane, methyl ethyl ketone and acetonitrile.

7. The catalyst system according to claim 2, characterized in that The second acid binding agent is cesium carbonate.

8. The catalyst system according to claim 1, characterized in that The transition metal compound b is one or more compounds of chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel or palladium.

9. The catalyst system according to claim 8, characterized in that The transition metal compound b is a chromium or nickel compound.

10. The catalyst system according to claim 1, characterized in that The activator c is one or a mixture of two or more of an alkyl aluminum compound, an alkyl aluminumoxane compound, and an organic boron compound.

11. The catalyst system according to claim 10, characterized in that The activator c is an alkylaluminoxane compound.

12. The catalyst system according to claim 1, characterized in that The molar ratio of the ligand to the transition metal compound is 0.5:1-2:1; the molar ratio of the metal in the transition metal compound to the aluminum in the activator is 1:30-1:1000; or the molar ratio of the metal in the transition metal compound to the boron in the activator is 0.5:1-2:

1.

13. The catalyst system according to claim 1, characterized in that The catalyst system is prepared by premixing a ligand, a transition metal compound and an activator; or the ligand, the transition metal compound and the activator are directly added into a reaction system for in-situ synthesis.

14. Use of the ethylene selective oligomerization catalytic system according to any one of claims 1 to 13 in an ethylene oligomerization reaction.

15. The use according to claim 14, wherein the ethylene oligomerization reaction adopts the catalyst system according to any one of claims 1 to 13, and when the reaction temperature is lower than 70°C and the reaction pressure is lower than 5 MPa, the ethylene oligomerization catalyzed by the catalyst mainly undergoes a trimerization reaction; when the reaction temperature is higher than 70°C and the reaction pressure is higher than 5 MPa, the ethylene oligomerization catalyzed by the catalyst mainly undergoes a tetramerization reaction.

16. The use according to claim 15, wherein the ethylene oligomerization reaction adopts the catalyst system according to any one of claims 1 to 13, and when the reaction temperature is lower than 70°C and the reaction pressure is lower than 4.5 MPa, the ethylene oligomerization catalyzed by the catalyst mainly undergoes a trimerization reaction; when the reaction temperature is higher than 80°C and the reaction pressure is higher than 6 MPa, the ethylene oligomerization catalyzed by the catalyst mainly undergoes a tetramerization reaction.

17. The use according to claim 16, wherein the ethylene oligomerization reaction is carried out under the conditions of the catalyst according to any one of claims 1 to 13 at a reaction temperature of 40-60°C and a reaction pressure of 3-4 MPa to mainly produce a trimerization product; and the ethylene oligomerization reaction is carried out under the conditions of the catalyst according to any one of claims 1 to 13 at a reaction temperature of 90-110°C and a reaction pressure of 7-8.5 MPa to mainly produce a tetramerization product.

18. The use according to claim 14, wherein the ethylene oligomerization reaction is carried out in a third solvent, wherein the third solvent is one or a mixture of two or more of an alkane, an aromatic hydrocarbon, an olefin, or an ionic liquid.

19. The use according to claim 18, wherein the third solvent is an alkane.

20. The use according to claim 14, wherein in the ethylene oligomerization reaction, the concentration of the catalyst is 1 μmol metal / L to 50 μmol metal / L.

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