A method for preparing high carbon number α-olefins

Abstract

This invention discloses a method for preparing high-carbon-number α-olefins. The method utilizes the iron-based complex shown in formula (I) to catalyze the polymerization of ethylene in a solvent under the activation of a co-catalyst, yielding a broadly distributed ethylene oligomer; after separation, a solid high-carbon-number α-olefin is obtained. 20+ α-olefin; the C 20+ The content of α-olefins in the total product is not less than 50 wt%; in formula (I), R1 is a C1-C3 alkyl or halogen, and R2 is a phenyl or C1-C6 alkyl. This invention uses the designed and synthesized iron-based complex to catalyze ethylene polymerization. By changing the steric hindrance and electronic environment of the catalyst's active center, the molecular weight and distribution of the product are controlled, resulting in a narrowly distributed C1-C6 alkyl group. 20 The above are target products of long-chain linear α-olefins.

Description

Technical Field

[0001] This invention relates to the field of ethylene oligomerization into long-chain linear α-olefins, and specifically to a method for preparing high-carbon-number α-olefins. Background Technology

[0002] Catalysts and preparation methods for the oligomerization of ethylene into a series of α-olefins can produce linear α-olefins with high selectivity, including over 98% α-olefin selectivity and 100% linear selectivity. However, the resulting oligomers typically follow a Schulz-Flory distribution (i.e., the oligomer content decreases with increasing carbon number from C4 onwards). While distillation can yield C... 20 The above are long-chain linear α-olefins, but C 20 The yields of the above long-chain linear α-olefins are particularly low. Therefore, while ensuring high α-olefin selectivity and linear selectivity, it is necessary to further improve the carbon number selectivity, especially the C2000. 20 The above-mentioned selective and high-yield preparation of C64-carbon chains exhibits high efficiency. 20 The above long-chain linear α-olefins are of great significance.

[0003] CN 112920227 A discloses a metallocene compound containing an indene-indole structure, its preparation method, applications, and a method for preparing α-olefins. The provided metallocene compound containing an indene-indole structure can be used as a catalyst for the catalytic synthesis of α-olefins, and can synthesize high-carbon-number α-olefins with high activity and high selectivity. The main components of the product are 1-octene, 1-decene, and 1-dodecene, and it contains little or no α-olefins with higher carbon numbers (C...). 20 (The above long-chain linear α-olefins).

[0004] CN 105797773 A discloses a novel linear α-olefin catalyst, its preparation process, and its applications. The catalyst composition comprises a main catalyst and a co-catalyst, wherein the main catalyst is an iron-based imine coordination compound, and the co-catalyst is methylaluminoxane, triisobutylaluminum, borane, and GaCl3. This catalyst composition is used to catalyze the oligomerization of ethylene to prepare linear α-olefins, with a selectivity greater than 96% and a carbon number distribution between C4 and C6. 28 C6-C 20 Greater than 75%.

[0005] CN101927187A discloses a catalyst for ethylene oligomerization and polymerization, using 2-(6'-iminepyridyl)benzothiazole Fe 2+ Co 2+ Ni 2+ Cr 3+The halides are used as the main catalyst. With the aid of different co-catalysts modified with methylaluminoxane or diethylaluminum chloride, this catalyst exhibits good catalytic performance for ethylene oligomerization and / or polymerization. Among them, the iron(II) complex shows very high oligomerization and polymerization activity for ethylene, reaching 10. 7 g / mol Fe -1 h -1 The products are a series of α-olefins, with a selectivity of up to 99%. However, the main components of the products from this technology are low-carbon α-olefins such as C4, C6, and C8.

[0006] CN101205243A discloses a 2-(6'-iminopyridyl)benzimidazole metal complex, its preparation method, and its applications. The chlorinated 2-(6'-iminopyridyl)benzimidazole metal complex provided by this invention exhibits good catalytic performance for ethylene oligomerization and polymerization under the action of the co-catalyst methylaluminoxane, and can achieve catalytic oligomerization and polymerization of ethylene; however, the main components of the product are low-carbon α-olefins such as C4 and C6.

[0007] CN101440090A discloses 2-(6'-iminepyridyl)benzoxazole metal complexes, their preparation methods, and applications. The catalysts provided by this invention are used as ethylene oligomerization and polymerization catalysts, exhibiting excellent catalytic activity. The iron(II) complex, in particular, demonstrates high oligomerization and polymerization activity towards ethylene, reaching 10-. 7 g mol -1 (Fe)h -1 The selectivity for α-olefins is as high as 99% or more; the catalyst also exhibits high polymerization activity; however, the main components of the product are low-carbon α-olefins such as C4, C6, and C8. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing high-carbon-number α-olefins, using an iron-based complex designed and synthesized according to this invention as a catalyst, which greatly increases the C content of the product. 20 The above describes the selectivity of long-chain linear α-olefins.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing high-carbon-number α-olefins involves using an iron-based complex as shown in formula (I) to catalyze the polymerization of ethylene in a solvent under the activation of a co-catalyst, yielding a broadly distributed ethylene oligomer; followed by separation to obtain a solid high-carbon-number α-olefin. 20+ α-olefin; C 20+ The content of α-olefins (containing 20 or more carbon atoms) in the total product is not less than 50 wt%, more preferably not less than 60 wt%, and even more preferably 64 wt% to 88 wt%.

[0011]

[0012] In formula (I), R1 is a C1-C3 alkyl or halogen, and R2 is a phenyl or C1-C6 alkyl.

[0013] In the iron-based complex of the present invention, preferably, R1 is one of methyl, ethyl, propyl, fluorine, chlorine, bromine, and iodine. More preferably, R1 is one of methyl, ethyl, n-propyl, chlorine, and bromine.

[0014] In the iron-based complex of the present invention, preferably, R2 is one of methyl, ethyl, n-propyl, isopropyl, n-pentyl, isopentyl, n-hexyl, cyclohexyl, and phenyl. More preferably, R2 is one of methyl, ethyl, n-propyl, isopropyl, cyclohexyl, and phenyl.

[0015] In the iron-based complex of the present invention, preferably, R1 is one of methyl, ethyl, n-propyl, chlorine, and bromine, and R2 is one of methyl, ethyl, n-propyl, isopropyl, cyclohexyl, and phenyl.

[0016] In the iron-based complex of the present invention, preferably, the structural formula of the iron-based complex is:

[0017]

[0018] In the method for preparing high-carbon-number α-olefins of the present invention, preferably, the co-catalyst is an aluminum oxane or an alkyl aluminum compound. More preferably, the co-catalyst is methylaluminoxane, modified methylaluminoxane, triethylaluminum, or diethylaluminum chloride; for example, methylaluminoxane or a toluene solution thereof is used.

[0019] In the method for preparing high carbon number α-olefins of the present invention, preferably, the ratio of the iron-based complex (main catalyst) to the co-catalyst is an Al / Fe molar ratio of (100-2000):1.

[0020] In the method for preparing high carbon number α-olefins of the present invention, preferably, the solvent is an alkane containing only C and H elements, and the water content does not exceed 20 ppm, and it is a liquid at 15-35°C; more preferably, the alkane is selected from at least one of n-pentane, n-hexane, cyclohexane, n-heptane, and n-octane.

[0021] In the method for preparing high-carbon-number α-olefins of the present invention, preferably, the ethylene polymerization pressure is 0.1 MPa to 3 MPa, the polymerization temperature is -20°C to 120°C, and the polymerization time is no more than 4 hours, more preferably 0.5 to 4 hours.

[0022] In the method for preparing high-carbon-number α-olefins of the present invention, preferably, the separation is achieved by filtration to obtain solid high-carbon-number C 20+α-olefins.

[0023] In the method for preparing high carbon number α-olefins of the present invention, preferably, the filtered liquid phase is separated by distillation to obtain liquid α-olefins.

[0024] In the method for preparing high-carbon-number α-olefins of the present invention, preferably, C 20+ The content of α-olefins in the total product is not less than 60 wt%.

[0025] In the method for preparing high-carbon-number α-olefins of the present invention, preferably, C 20+ The content of α-olefins in the total product is 64 wt% to 88 wt%.

[0026] The iron-based complex used in this invention is prepared through the following steps:

[0027]

[0028] 1) Compound 2 was prepared by reacting 2-acetyl-6-bromopyridine (compound 1 in equation 1) with 2-R1-aniline under acid catalysis conditions;

[0029] 2) Compound 2 and N-R2-imidazole react upon heating to obtain compound 3;

[0030] 3) After adding KN(SiMe3)2 to the solution of compound 3 and reacting for a certain period of time, ferrous chloride is added to obtain the iron-based complex.

[0031] In the preparation of the iron-based complex, regarding step 1): 2-acetyl-6-bromopyridine (compound 1 in equation 1) is reacted with 2-R1-aniline under acid catalyst conditions to prepare compound 2.

[0032] Preferably, in the molar ratio of 2-acetyl-6-bromopyridine to 2-R1-aniline, 2-R1-aniline is in appropriate excess, preferably 1:(1.05-1.5), more preferably 1:1.2.

[0033] Preferably, the acid catalyst is selected from at least one of sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid; more preferably, it is p-toluenesulfonic acid.

[0034] The amount of acid catalyst used is the catalytic amount, preferably 1 mol% to 10 mol% of 2-acetyl-6-bromopyridine.

[0035] Preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R1-aniline is carried out in a solvent, wherein the solvent is toluene or ethanol; more preferably, toluene.

[0036] Preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R1-aniline is carried out under reflux for 4 to 24 hours, more preferably 12 hours.

[0037] Preferably, after the reaction of 2-acetyl-6-bromopyridine with 2-R1-aniline is completed, the product is separated and purified by column chromatography, for example, using a silica gel column and an ethyl acetate / petroleum ether solvent system.

[0038] In the preparation of the iron-based complex, regarding step 2): compound 2 and N-R2-imidazole reacted under heat to obtain compound 3.

[0039] Preferably, the molar ratio of compound 2 to N-R2-imidazole is 1:(1.05-1.5), with N-R2-imidazole in slight excess, and more preferably 1:1.08.

[0040] Preferably, the reaction between compound 2 and N-R2-imidazole is carried out in a solvent, wherein the solvent is chloroform or dichloromethane; more preferably, chloroform.

[0041] Preferably, the reaction between compound 2 and N-R2-imidazole is carried out under reflux conditions for 2 to 12 hours, more preferably 6 hours.

[0042] Preferably, after the reaction of compound 2 and N-R2-imidazole is completed, diethyl ether is added to produce a precipitate, which is then filtered to obtain solid compound 3.

[0043] In the preparation of the iron-based complex, regarding step 3): KN(SiMe3)2 is added to the solution of compound 3 and reacted for a certain period of time, and then ferrous chloride is added to obtain the iron-based complex.

[0044] Preferably, in the solution of compound 3, the solvent is tetrahydrofuran or tetrahydropyran; more preferably, it is tetrahydrofuran.

[0045] Preferably, under a protective atmosphere, the solution of compound 3 is cooled to -10°C to -30°C (e.g., -20°C), KN(SiMe3)2 is added and reacted for 0.1 to 1 h (e.g., 0.5 h), followed by the addition of ferrous chloride and the reaction continuing for 2 to 12 h (e.g., 4 h); after the reaction is completed, pentane or heptane is added to precipitate a solid product.

[0046] Preferably, the molar ratio of compound 3 to KN(SiMe3)2 is 1:(1-3), more preferably 1:2.

[0047] Preferably, the molar ratio of compound 3 to ferrous chloride is (0.8-1.2):1, more preferably 1:1.

[0048] Preferably, the precipitated solid product is then purified by recrystallization. More preferably, tetrahydrofuran and pentane are used as solvents for recrystallization.

[0049] Preferably, the protective atmosphere is nitrogen, argon, or the like.

[0050] This invention utilizes a designed and synthesized iron-based complex to catalyze ethylene polymerization. By altering the steric hindrance and electronic environment of the catalyst's active sites, the molecular weight and distribution of the products are controlled, resulting in narrowly distributed C466. 20 The above are target products of long-chain linear α-olefins. Detailed Implementation

[0051] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0052] Experimental methods in the following examples, where specific conditions are not specified, are generally performed under conventional conditions in the art or as recommended by the manufacturer; raw materials and reagents used, unless otherwise specified, are commercially available from conventional markets. All numerical specifications in this invention (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that can be changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about".

[0053] I. Preparation of iron-based ethylene oligomerization catalysts:

[0054] Example 1

[0055] This embodiment prepares an iron-based complex 1, including the following steps:

[0056]

[0057] ① Weigh 0.1 mol of 2-acetyl-6-bromopyridine (compound 1) and 0.12 mol of 2-methylaniline, add them to a three-necked flask, then add 150 mL of toluene and 0.2 g of p-toluenesulfonic acid, and reflux for 12 h. Separate by silica gel column chromatography (ethyl acetate / petroleum ether = 1:10, v / v) to obtain compound 2, totaling 0.075 mol, yield 75%.

[0058] The product was analyzed by NMR. 1H NMR (CDCl3, 200MHz): δ1.81(d,3H,CH3), δ2.31(d,3H,CH3), δ7.01-7.24(m,4H,Ph-H), δ7.76(m,1H,Py-CH), δ8.07-8.15(m,2H,Py-CH).

[0059] ② Weigh 0.06 mol of compound 2 and 0.065 mol of N-methylimidazole, add them to a three-necked flask, then add 150 mL of chloroform, and reflux for 6 h; after cooling, add 100 mL of diethyl ether, filter, and obtain solid compound 3, totaling 0.05 mol, with a yield of 83%.

[0060] The product was analyzed by NMR. 1 H NMR (CDCl3, 200MHz): δ1.81(d,3H,CH3), δ2.31(d,3H,CH3), δ3.72(d,3H,CH3), δ 7.01-7.24(m,4H,Ph-H), δ7.90-8.15(m,3H,Py-CH), δ7.27-7.83(m,3H,Im-CH).

[0061] ③ Weigh 0.04 mol of compound 3, add 100 mL of tetrahydrofuran, place in a three-necked flask, and under nitrogen protection, cool to -20 °C. Add 0.08 mol of KN(SiMe3)2 and react for 0.5 h. Add 0.04 mol of ferrous chloride and continue the reaction for 2 h. Slowly raise the temperature to room temperature and continue the reaction for 2 h. Add 30 mL of pentane, and a blue solid powder precipitates. Dissolve the precipitate in 100 mL of tetrahydrofuran, add another 30 mL of pentane, and purify once to obtain iron-based complex 1, with a yield of 0.025 mol.

[0062] The product was analyzed by NMR. 1 H NMR (CDCl3, 200MHz): δ1.81(d,3H,CH3), δ2.31(d,3H,CH3), δ3.06(d,3H,CH3), δ7.01-7.24(m,4H,Ph-H), δ7.25-8.10(m,3H,Py-CH), δ5.06-5.3(m,2H,Im-CH).

[0063] Example 2

[0064] In Example 1, step ① was changed to 2-ethylaniline, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 2).

[0065] Example 3

[0066] In Example 1, step ①, 2-methylaniline was replaced with 2-n-propylaniline, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 3).

[0067] Example 4

[0068] In Example 1, step ①, 2-methylaniline was replaced with 2-chloroaniline, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 4).

[0069] Example 5

[0070] In Example 1, step ①, 2-methylaniline was replaced with 2-bromoaniline, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 5).

[0071] Example 6

[0072] In step ② of Example 1, N-methylimidazole was replaced with N-ethylimidazole, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 6).

[0073] Example 7

[0074] In step ② of Example 1, N-methylimidazole was replaced with N-isopropylimidazole, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 7).

[0075] Example 8

[0076] In step ② of Example 1, N-methylimidazole was replaced with N-phenylimidazole, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 8).

[0077] Example 9

[0078] In step ② of Example 1, N-methylimidazole was replaced with N-cyclohexylimidazole, and the rest of the synthesis steps were the same. The structure of the synthesized product is shown below (Example 9).

[0079] Example 10

[0080] In Example 1, 2-methylaniline in step ① was replaced with 2-n-propylaniline, and N-methylimidazole in step ② was replaced with N-isopropylimidazole. The remaining synthesis steps were the same, and the structure of the synthesized product is shown below (Example 10).

[0081]

[0082] Table 1 Summary of Catalyst Synthesis Examples

[0083]

[0084]

[0085] Note: The proportions of compounds, reaction temperatures, pressures, and times are consistent in Examples 1-10.

[0086] II. Evaluation of Iron-Based Ethylene Oligomerization Catalysts:

[0087] Example 11

[0088] The ethylene oligomerization reaction was carried out using the catalysts prepared in Examples 1-10, including the following processes:

[0089] After repeatedly evacuating and purging with ethylene three times in a 2-liter reactor, ethylene was introduced to atmospheric pressure. Then, 1000 mL of n-pentane and 10 mL of methylaluminoxane (MAO) (10 wt% toluene solution) were added sequentially, and the mixture was stirred for 5 minutes. Next, 5 mg of the catalyst from Example 1 was added, and the pressure was rapidly increased to 0.3 MPa. The reaction was carried out at 70°C for 1 hour. After cooling, the product was filtered to obtain solid C. 20+ α-olefins; gas chromatography analysis of the liquid phase products showed that 96% were linear α-olefins with a carbon number distribution between C6 and C6. 20 Between. The catalytic activity, calculated based on the amount of ethylene consumed, is 3 × 10⁻⁶. 6 g olefin / mol catalyst / atmospheric pressure, C 20+ α-olefins account for 70 wt% of the product.

[0090] The catalysts of other Examples 2-10 were evaluated using the same ethylene polymerization process and conditions as described above, and the results are shown in Table 2.

[0091] Table 2 Summary of Evaluation Results of Ethylene Oligomerization Examples

[0092]

[0093]

[0094] Note: The reaction pressure in Example 11 was 0.3 MPa, the reaction temperature was 70°C, and the reaction time was 1 h.

[0095] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing high-carbon-number α-olefins, wherein, The preparation method uses the iron-based complex shown in formula (I) to catalyze the polymerization of ethylene in a solvent under the activation of a co-catalyst, obtaining a broadly distributed ethylene oligomer; after separation, a solid with a high carbon number (C) is obtained. 20+ α-olefins; The C 20+ The content of α-olefins in the total product is not less than 50 wt%; Formula (I) In formula (I), R1 is a C1-C3 alkyl or halogen, and R2 is a phenyl or C1-C6 alkyl. The cocatalyst is an aluminum oxane or an alkyl aluminum compound; The Al / Fe molar ratio in the iron-based complex and the co-catalyst is (100~2000):1; The ethylene polymerization is carried out at a pressure of 0.1 MPa to 3 MPa, a polymerization temperature of -20°C to 120°C, and a polymerization time of 0.5 to 4 hours.

2. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, R1 is one of methyl, ethyl, propyl, fluorine, chlorine, bromine, or iodine.

3. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, R2 is one of methyl, ethyl, n-propyl, isopropyl, n-pentyl, isopentyl, n-hexyl, cyclohexyl, or phenyl.

4. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, The structural formula of the iron-based complex is: or .

5. The method for preparing high-carbon-number α-olefins according to claim 4, wherein, The cocatalyst is methylaluminoxane, modified methylaluminoxane, triethylaluminum, or diethylaluminum chloride.

6. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, The solvent is an alkane that is liquid at 15~35℃ and has a water content of no more than 20 ppm.

7. The method for preparing high-carbon-number α-olefins according to claim 6, wherein, The alkane is selected from at least one of n-pentane, n-hexane, cyclohexane, n-heptane, and n-octane.

8. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, The separation is achieved through filtration, yielding solids with high carbon number (C). 20+ α-olefins.

9. The method for preparing high-carbon-number α-olefins according to claim 8, wherein, The filtered liquid phase was separated by distillation to obtain liquid α-olefins.

10. The method for preparing high-carbon-number α-olefins according to claim 1, wherein, C 20+ The content of α-olefins in the total product is not less than 60 wt%.

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