Ethylene oligomerization catalyst and use thereof
By using a chromium-based catalyst with perfluorophenyl boron salt ligands, the problems of large catalyst usage and polymer byproducts in existing technologies have been solved, achieving efficient production of 1-octene, reducing production costs and improving the stability of the equipment operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WANHUA CHEM GRP CO LTD
- Filing Date
- 2023-10-10
- Publication Date
- 2026-05-19
AI Technical Summary
In the existing process of selective tetramerization of ethylene to produce 1-octene, the co-catalyst methylaluminoxane is used in large quantities and is expensive, which increases the production cost and causes ethylene polymer to clog the equipment, affecting the operation of the plant.
A chromium-based catalyst containing perfluorophenyl boron salt ligand is used. By co-coupling with a chromium source to form a highly active cation-anion pair, the amount of co-catalyst required is reduced. Inexpensive alkyl aluminum is used as a co-catalyst to reduce polymer byproducts.
It significantly reduced the amount of co-catalyst used, increased the yield of 1-octene, reduced polymer production, lowered production costs, and prevented equipment blockage.
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Figure CN117563670B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of olefin polymerization, specifically relating to an ethylene oligomerization catalyst and its application. Background Technology
[0002] 1-Octene is mainly used in the production of high-end PE and POE, as well as as a raw material in the production of plasticizers, detergent alcohols, and lubricant additives. It is an important organic raw material and chemical intermediate. Currently, selective oligomerization of ethylene is one of the main methods for the industrial preparation of linear 1-octene. Patent CN100548946C uses a catalytic system composed of PNP ligands, a chromium source, and methylaluminoxane to achieve selective tetramerization of ethylene, with a 1-octene selectivity of 70% in the product, realizing the industrial production of 1-octene.
[0003] However, in existing technologies, the selective tetramerization of ethylene to produce 1-octene requires the extensive use of methylaluminoxane as a co-catalyst, typically with an Al / Cr ratio of 200:1 to 1000:1. Methylaluminoxane is expensive, costing thousands of yuan per ton of 1-octene, thus reducing the profitability of 1-octene. Furthermore, the production process generates small amounts of ethylene polymers, which can cause blockages in equipment and instruments, necessitating periodic shutdowns for cleaning and increasing the operating costs of the plant.
[0004] To overcome the shortcomings of existing production processes, developing a new ethylene oligomerization catalyst, its preparation method, and its application, and reducing the amount of co-catalyst and polymer by-products, is of great significance. Summary of the Invention
[0005] The purpose of this invention is to provide an ethylene oligomerization catalyst and its application. This ligand can be combined with metallic chromium to obtain a chromium-based catalyst, enabling ethylene to undergo tetramerization with high selectivity to prepare 1-octene. This significantly reduces the amount of co-catalyst used, resulting in a high yield of 1-octene and a low content of by-products.
[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:
[0007] An ethylene oligomerization catalyst includes a chromium source, a co-catalyst, and a ligand, wherein the ligand is a perfluorophenylboron salt having the following structure:
[0008]
[0009] Where n is 1 to 4;
[0010] In this invention, the ligand is prepared by reacting a ligand precursor with lithium tetra(pentafluorophenyl)borate and an acid. The structure of the ligand precursor is as follows or is its hydrochloride salt:
[0011] , where n is 1 to 4.
[0012] The acid is selected from one or more of hydrochloric acid, sulfuric acid, and hydrobromic acid.
[0013] Its synthetic route is as follows:
[0014]
[0015] Preferably, the ligand precursor reacts with lithium tetra(pentafluorophenyl)borate and H in the acid. + The molar ratio is 1:1:1 to 1:1.05:1.05, and the reaction can be carried out at room temperature and pressure. Further, the ligand precursor is prepared by reacting the amine of Formula I with diphenylphosphine chloride in the presence of an acid-binding agent, wherein the structural formula of the amine of Formula I is... Where n is 1 to 4.
[0016] Preferably, the acid-binding agent is triethylamine.
[0017] Its synthetic route is as follows:
[0018]
[0019] Preferably, the molar ratio of the amine shown in Formula I to diphenylphosphine chloride is 1:1.95 to 1:2.05, the amount of acid-binding agent is 4 to 6 times the molar amount of diphenylphosphine chloride, the reaction temperature is 0 to 5°C, and the reaction pressure is atmospheric pressure.
[0020] In this invention, the chromium source is selected from one or more of chromium acetylacetonate, chromium trichloride, tri(tetrahydrofuran)chromium trichloride, chromium octoate (III), and chromium hexacarbonyl; preferably chromium acetylacetonate or chromium octoate.
[0021] In this invention, the co-catalyst is an alkylaluminum or an aluminum oxane, preferably an alkylaluminum, which is selected from one or more of trimethylaluminum, triethylaluminum, or triisobutylaluminum.
[0022] In the oligomerization of ethylene catalyzed by chromium-based catalysts, the roles of co-catalysts such as alkylaluminum or aluminoxanes are generally considered to be as follows: ① capturing anions from the chromium source to form cationic active centers; ② stabilizing cationic active centers as anions; ③ removing trace amounts of water and oxygen impurities from the reaction system. Theoretically, not a large amount of co-catalyst is needed to achieve these three functions, but in practice, a co-catalyst in excess of several hundred times is required to achieve relatively ideal catalytic activity. The catalyst and co-catalyst form anionic-cation pairs, and the distance between these pairs must be appropriate to generate catalytic activity. If the distance is too close, it is not conducive to ethylene coordination, resulting in low activity; if the distance is too far, the catalyst cations are unstable and easily deactivated. A sufficient amount of co-catalyst is necessary to ensure the formation of a sufficient number of highly active anionic-cation pairs.
[0023] In this invention, by introducing tetra(pentafluorophenyl)boron salt into the ligand, after the ligand coordinates with metallic chromium, the active center chromium atom and tetra(pentafluorophenyl)boron salt maintain a suitable distance, which just forms a highly active anion-cation pair active center, and can effectively reduce the generation of ethylene polymers.
[0024] In this invention, the molar ratio of ligand to Cr is 1:1-5:1; preferably 3:1-4:1.
[0025] In this invention, the molar ratio of Al to Cr in the co-catalyst is 5:1:-20:1; preferably 10:1-15:1. The additional co-catalyst mainly serves to remove trace amounts of water, oxygen and other impurities in the system. Therefore, inexpensive trialkylaluminum can be used, and expensive methylaluminoxane or modified methylaluminoxane is not required.
[0026] The present invention also provides the application of the catalyst in the selective oligomerization reaction of ethylene.
[0027] Furthermore, the polymerization can be carried out in a stainless steel reactor. Before the reaction, the reactor is heated to 110-130°C, evacuated, and purged with nitrogen during the process, and then cooled to room temperature.
[0028] Under an inert atmosphere, a dehydrating and deoxygenating reaction solvent and a co-catalyst are added, and the mixture is stirred until the temperature stabilizes. Then, the ligand and chromium source described in this invention are added, and hydrogen gas is introduced to a pressure of 0.1-0.8 MPa. Ethylene is then continuously introduced, maintaining a reactor pressure of 3-6 MPaG. The reaction is carried out at 30-60°C for 10-40 minutes. Afterward, the ethylene inlet valve is closed, and the mixture is rapidly cooled using a low-temperature circulating water bath. The pressure is slowly released, and the reactor is unloaded to obtain the ethylene oligomer.
[0029] Preferably, the molar concentration of chromium in the system is 0.25-0.85 mmol / L, based on the molar amount of Cr.
[0030] Furthermore, the reaction solvent is one or more of cyclopentane, methylcyclopentane, n-hexane, cyclohexane, methylcyclohexane, and n-heptane.
[0031] Compared with existing processes, the method of this invention can use inexpensive alkylaluminum as the co-catalyst, reducing production costs, and the amount of co-catalyst can be reduced to an Al / Cr ratio of 5:1-20:1, with catalytic activity ≥1×10⁻⁶. 6 g product / (molCr·h), ethylene polymer ≤0.02%. Detailed Implementation
[0032] The method of the present invention will be further illustrated below through specific embodiments, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.
[0033] Gas chromatography (GC): Model: Agilent WAX:1701.42249; Carrier gas: high-purity nitrogen; Injection mode: autosampler; Nitrogen flow rate: 64.5 ml / min; Vaporization chamber temperature: 280℃; Split injection: split ratio: 1:40; Injection volume: 0.2 μl; Column flow rate: 1.5 ml / min; Column temperature: first-order programmed temperature ramp: initial temperature 50℃, hold for 2 minutes, then ramp to 200℃ at a rate of 10℃ / min, hold for 15 minutes; Detector temperature: 300℃; External standard method was used for quantification of 1-octene, 1-hexene, and other oligomeric short-chain products.
[0034] Raw material source: N,N-dimethyl-1,2-ethylenediamine (CAS108-00-9), Shanghai Maclean Biochemical Technology Co., Ltd.
[0035] N,N-Dimethyl-1,3-propanediamine (CAS109-55-7), Shanghai Maclean Biochemical Technology Co., Ltd.
[0036] N,N-Dimethyl-1,4-Butanediamine Hydrochloride (CAS 65592-37-2), Shanghai Jizhi Biochemical Technology Co., Ltd.
[0037] N,N-Dimethyl-1,5-pentanediamine (CAS 3209-46-9), Shanghai Jizhi Biochemical Technology Co., Ltd.
[0038] N,N-Dimethylphenylamine tetra(pentafluorophenyl)borate (CAS118612-00-3) Suzhou Cangmu New Materials Co., Ltd.
[0039] Lithium tetra(pentafluorophenyl)borate (CAS2797-28-6) Suzhou Cangmu New Materials Co., Ltd.
[0040] Preparation of ligands:
[0041] Preparation of ligand 1 precursor: Under nitrogen protection, N,N-dimethyl-1,2-ethylenediamine (0.2 mol) was added to 500 mL of dichloromethane, stirred, and cooled to 0 °C. Excess triethylamine (2 mol) was added, and the mixture was stirred for 5 minutes to ensure homogeneity. Diphenylphosphine chloride (0.4 mol) was added dropwise to the mixture, maintaining the reaction temperature below 5 °C during the addition. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 12 h. After the reaction was complete, the mixture was filtered, and the solvent was removed from the filtrate to obtain the crude product solid. The crude product was purified by column chromatography (eluent was a mixture of methanol and ethyl acetate at a volume ratio of 1:30) to obtain ligand 1 precursor in 53% yield. 1H-NMR (400MHz, CDCl3, 25℃): δ=7.42-7.24ppm (m, 20H), 3.43 (m, 2H), 1.96 (m, 8H). 31 P-NMR (162MHz, CDCl3, 25℃): δ = 63.7ppm (s).
[0042] Preparation of ligand 2 precursor: Following the preparation method of ligand 1 precursor, N,N-dimethyl-1,2-ethylenediamine was replaced with N,N-dimethyl-1,3-propanediamine to obtain ligand 2 precursor, with a yield of 70%. 1 H-NMR (400MHz, CDCl3, 25℃): δ = 7.40-7.21ppm (m, 20H), 3.29 (m, 2H), 1.84 (s, 6H), 1.82 (t, 2H, 3 J HH =2.0Hz), 1.26(m,2H). 31 P-NMR (162MHz, CDCl3, 25℃): δ = 63.0ppm (s).
[0043] Preparation of ligand 3 precursor: Following the preparation method of ligand 1 precursor, N,N-dimethyl-1,2-ethylenediamine was replaced with N,N-dimethyl-1,4-butanediamine hydrochloride to obtain ligand 3 precursor, with a yield of 78%. 1 H-NMR (400MHz, CDCl3, 25℃): δ = 7.40-7.20ppm (m, 20H), 3.28 (m, 2H), 2.04 (s, 6H), 1.84 (m, 2H), 1.09 (m, 4H). 31 P-NMR (162MHz, CDCl3, 25℃): δ=62.5ppm(s).
[0044] Preparation of ligand 4 precursor: Following the preparation method of ligand 1 precursor, N,N-dimethyl-1,2-ethylenediamine was replaced with N,N-dimethyl-1,5-pentanediamine to obtain ligand 4 precursor, with a yield of 77%. 1 H-NMR (400MHz, CDCl3, 25℃): δ = 7.40-7.20ppm (m, 20H), 3.26 (m, 2H), 2.68 (m, 2H), 2.22 (s, 6H), 1.88 (m, 2H), 1.04 (m, 4H). 31 P-NMR (162MHz, CDCl3, 25℃): δ = 62.3ppm (s).
[0045] Preparation of Ligand 1: Under nitrogen protection, 0.1 mol of HCl ethyl acetate solution was added dropwise to a 600 mL solution of 0.1 mol of ligand 1 precursor in dichloromethane at room temperature. After the addition was complete, the mixture was stirred for 10 min. This reaction solution was then added dropwise to a 400 mL solution of 0.1 mol of lithium tetra(pentafluorophenyl)borate in dichloromethane. After the addition was complete, the reaction was allowed to proceed for 2 h. After the reaction was complete, the mixture was filtered, and the solid was washed with 200 mL of dichloromethane. The filtrate and washings were combined and concentrated to 400 mL. 400 mL of n-hexane was added to the concentrate, and the residual dichloromethane was removed by distillation. Solid precipitated during the process. After distillation, the solid was filtered, and dried under vacuum at 100 °C overnight to obtain ligand 1 in 85% yield.
[0046] Preparation of ligand 2: Following the preparation method of ligand 1, the precursor of ligand 1 was replaced with the precursor of ligand 2 to obtain ligand 2.
[0047] Preparation of ligand 3: Following the preparation method of ligand 1, the precursor of ligand 1 was replaced with the precursor of ligand 3 to obtain ligand 3.
[0048] Preparation of ligand 4: Following the preparation method of ligand 1, the precursor of ligand 1 was replaced with the precursor of ligand 4 to obtain ligand 4.
[0049] Example 1
[0050] Ethylene oligomerization: Before the reaction, the reactor was heated to 120°C and evacuated for 3 hours, during which nitrogen was purged three times. After cooling to room temperature, 200 mL of dehydrated and deoxygenated methylcyclohexane and a measured amount of alkyl aluminum were added. The mixture was stirred, and after the temperature stabilized, ligand 1 and chromium octoate were added. Hydrogen gas was introduced to 0.4 MPa, and then ethylene was continuously introduced to maintain the reactor pressure at 4.5 MPaG. The reaction was carried out at 45°C for 60 minutes. Then, the ethylene inlet valve was closed, and the reactor was rapidly cooled using a low-temperature circulating water bath. The pressure was slowly released, and the reactor was unloaded to obtain the reaction product. The amounts of ligand 1 and chromium octoate added are shown in Table 1.
[0051] Examples 2-7
[0052] According to Example 1, different ligands were added and oligomerization reactions were carried out under different conditions, as shown in Table 1.
[0053] Comparative Example 1
[0054] Oligopolymerization was carried out using ligand 1 precursor.
[0055] Ethylene oligomerization: Before the reaction, the reactor was heated to 120°C and evacuated for 3 hours, during which nitrogen was purged three times. After cooling to room temperature, 200 mL of dehydrated and deoxygenated methylcyclohexane and a measured amount of alkyl aluminum were added. The mixture was stirred, and after the temperature stabilized, ligand 1 precursor and chromium octoate were added. Hydrogen gas was introduced to 0.4 MPa, and then ethylene was continuously introduced to maintain the reactor pressure at 4.5 MPaG. The reaction was carried out at 45°C for 60 minutes. Then, the ethylene inlet valve was closed, and the reactor was rapidly cooled using a low-temperature circulating water bath. The pressure was slowly released, and the reactor was unloaded to obtain the reaction product.
[0056] Comparative Example 2
[0057] Oligand 1 precursor and N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate were used for oligomerization.
[0058] Ethylene oligomerization: Before the reaction, the reactor was heated to 120°C and evacuated for 3 hours, during which nitrogen was purged three times. After cooling to room temperature, 200 mL of dehydrated and deoxygenated methylcyclohexane and a measured amount of alkyl aluminum were added. The mixture was stirred, and after the temperature stabilized, ligand 1 precursor, N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate, and chromium octoate were added. Hydrogen gas was introduced to 0.4 MPa, and then ethylene was continuously introduced to maintain the reactor pressure at 4.5 MPaG. The reaction was carried out at 45°C for 30 minutes. Then, the ethylene inlet valve was closed, and the reactor was rapidly cooled using a low-temperature circulating water bath. The pressure was slowly released, and the reactor was unloaded to obtain the reaction product.
[0059] Table 1 Reaction conditions of Examples 2-8 and Comparative Examples 1-2
[0060]
[0061] Table 2 Comparison of reaction results of Examples 1-7 and Comparative Examples 1-2
[0062]
[0063] 1-C6 represents 1-hexene, Other C6 represents alkanes / olefins with 6 carbon atoms excluding 1-C6, 1-C8 represents 1-octene, C4+C10+ represents alkanes / olefins with 4 or more carbon atoms, and PE represents polymers.
[0064] Any modifications or equivalent substitutions to the technical solution of this invention that do not depart from the scope of the technical solution of this invention shall be covered within the protection scope of this invention.
Claims
1. An ethylene oligomerization catalyst, characterized in that, It includes a chromium source, a co-catalyst, and a ligand, wherein the ligand is a perfluorophenyl boron salt having the following structure: Where n is 1 to 4.
2. The catalyst according to claim 1, characterized in that, The ligand is prepared by reacting a ligand precursor with lithium tetra(pentafluorophenyl)borate and an acid. The structure of the ligand precursor is as follows or its hydrochloride salt: Where n is 1 to 4.
3. The catalyst according to claim 2, characterized in that, The acid is selected from one or more of hydrochloric acid, sulfuric acid, and hydrobromic acid.
4. The catalyst according to claim 2, characterized in that, Ligand precursor, lithium tetra(pentafluorophenyl)borate and H in the acid + The molar ratio is 1:1:1 to 1:1.05:1.
05.
5. The catalyst according to claim 2, characterized in that, The ligand precursor is prepared by reacting an amine of Formula I with diphenylphosphine chloride in the presence of an acid-binding agent, wherein the structural formula of the amine of Formula I is: Where n is 1 to 4.
6. The catalyst according to claim 5, characterized in that, The acid-binding agent is triethylamine.
7. The catalyst according to claim 5, characterized in that, The molar ratio of the amine to diphenylphosphine chloride shown in Formula I is 1:1.95 to 1:2.
05.
8. The catalyst according to claim 5, characterized in that, The amount of acid-binding agent used is 4 to 6 times the molar amount of diphenylphosphine chloride.
9. The catalyst according to claim 5, characterized in that, The reaction temperature of the amine represented by Formula I with diphenylphosphine chloride is 0–5 °C, and the reaction pressure is atmospheric pressure.
10. The catalyst according to claim 1, characterized in that, The chromium source is selected from one or more of chromium acetylacetone, chromium trichloride, tri(tetrahydrofuran)chromium trichloride, chromium(III) octoate, and chromium hexacarbonyl.
11. The catalyst according to claim 10, characterized in that, The chromium source is chromium acetylacetone or chromium octanoate.
12. The catalyst according to claim 1, characterized in that, The co-catalyst is an alkylaluminum or an aluminum oxane.
13. The catalyst according to claim 12, characterized in that, The co-catalyst is alkylaluminum.
14. The catalyst according to claim 12 or 13, characterized in that, Alkyl aluminum is selected from one or more of trimethylaluminum, triethylaluminum, or triisobutylaluminum.
15. The catalyst according to claim 1, characterized in that, The molar ratio of ligand to chromium is 1:1 to 5:
1.
16. The catalyst according to claim 15, characterized in that, The molar ratio of ligand to chromium is 3:1-4:
1.
17. The catalyst according to claim 12, characterized in that, The molar ratio of Al to chromium in the co-catalyst is 5:1:-20:
1.
18. The catalyst according to claim 17, characterized in that, The molar ratio of Al to chromium in the co-catalyst is 10:1-15:
1.
19. The use of the catalyst according to any one of claims 1-18 in the selective oligomerization reaction of ethylene.
20. The application according to claim 19, characterized in that, Includes the following steps: Under an inert atmosphere, add the dehydrating and deoxygenating reaction solvent and co-catalyst, stir, then add the ligand and chromium source according to any one of claims 1-18, introduce hydrogen gas to 0.1-0.8 MPa, then continuously introduce ethylene, maintain the reactor pressure at 3-6 MPa, and react at 30-60°C for 10-40 minutes.
21. The application according to claim 20, characterized in that, The molar concentration of chromium in the system is 0.25-0.85 mmol / L, based on the molar amount of Cr.
22. The application according to claim 20, characterized in that, The reaction solvent is one or more of cyclopentane, methylcyclopentane, n-hexane, cyclohexane, methylcyclohexane, and n-heptane.