Preparation method of high-carbon-number alpha-olefin

Abstract

The invention discloses a preparation method of high-carbon-number alpha-olefin. According to the preparation method, an iron-based complex as shown in a formula (I) is adopted to catalyze ethylene polymerization in a solvent under the activation of a cocatalyst, and the wide-distribution ethylene oligomer is obtained, separating to obtain solid C20 + alpha-olefin with high carbon number; the content of the C20 + alpha-olefin in the total product is not less than 50wt%; in the formula (I), R1 is C1-C3 alkyl or halogen, and R2 is phenyl and C1-C6 alkyl. The designed and synthesized iron-based complex is used for catalyzing ethylene polymerization, the molecular weight and distribution of the product are controlled by changing the steric hindrance and the electronic environment of the active center of the catalyst, and the narrow-distribution long-chain linear alpha-olefin target product of C20 or above is obtained. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene co-polymerization to grow long-chain linear α-olefins, and specifically relates to a method for preparing higher-carbon-number α-olefins. Background Art

[0002] Although the catalysts and preparation methods for ethylene oligomerization to synthesize a series of α-olefins can prepare linear α-olefins with high selectivity, including α-olefin selectivity above 98% and 100% linear selectivity, the obtained oligomerization products usually follow the Schulz-Flory distribution (that is, starting from C 4 onwards, as the carbon number increases, the content of the oligomerization products decreases). Although long-chain linear α-olefins with C 20 or above can be obtained by rectification, the yield of long-chain linear α-olefins with C 20 or above is extremely low. Therefore, on the basis of ensuring high α-olefin selectivity and linear selectivity, further improving the selectivity of carbon numbers, especially the selectivity of long-chain carbons with C 20 or above, and preparing long-chain linear α-olefins with C 20 or above in high yield is of great significance.

[0003] CN 112920227 A discloses a metallocene compound containing an indenoindole structure, its preparation method, application, and a method for preparing α-olefins. The provided metallocene compound containing an indenoindole structure can be used as a catalyst for catalytic synthesis of α-olefins, and can synthesize higher-carbon-number α-olefins with high activity and high selectivity. The main components in the product are 1-octene, 1-decene, and 1-dodecene, and do not contain or contain less higher-carbon-number α-olefins (long-chain linear α-olefins with C 20 or above).

[0004] CN 105797773 A discloses a novel linear α-olefin catalyst, its preparation process, and uses. The catalyst composition consists of a main catalyst and a co-catalyst, where the main catalyst is an iron-based imido coordination compound, and the co-catalyst is methylaluminoxane, triisobutylaluminum, borane, and GaCl 3 . This catalyst composition is used for catalytic ethylene oligomerization to prepare linear α-olefins, with a linear α-olefin selectivity greater than 96%, and the carbon number distribution is in C 4 -C 28 , where C 6 -C 20 is greater than 75%.

[0005] CN101927187A discloses a catalyst for ethylene oligomerization and polymerization, which is Fe 2+ of 2-(6'-iminopyridyl)benzothiazole, Co 2+ , Ni 2+, Cr 3+ The halide of 3+ is used as the main catalyst. Under the action of different cocatalysts to modify methylaluminoxane or diethylaluminum chloride, this catalyst has good catalytic performance for ethylene oligomerization and / or polymerization. Among them, the iron(II) complex shows high oligomerization and polymerization activities for ethylene, reaching 10 7 g / mol Fe -1 h -1 . The product is a series of α-olefins, and the selectivity of α-olefins is as high as 99%. However, the main components in the product of this technology are C 4 , C 6 , C 8 and other α-olefins with low carbon numbers.

[0006] CN101205243A discloses a 2-(6'-iminopyridyl)benzimidazole metal complex and its preparation method and application. The 2-(6'-iminopyridyl)benzimidazole metal chloride complex provided by the present invention has good catalytic performance for ethylene oligomerization and polymerization under the action of the cocatalyst methylaluminoxane, and can realize the catalytic oligomerization and polymerization of ethylene; however, the main components in the product are C 4 , C 6 and other α-olefins with low carbon numbers.

[0007] CN101440090A discloses a 2-(6'-iminopyridyl)benzoxazole metal complex and its preparation method and application. The catalyst provided by this invention is used as an ethylene oligomerization and polymerization catalyst and has good catalytic activity. Among them, the iron(II) complex shows high oligomerization and polymerization activities for ethylene, which can reach 10 7 g mol -1 (Fe)h -1 , and the selectivity of α-olefins is more than 99%; this catalyst also shows relatively high polymerization activity; however, the main components in the product are C 4 , C 6 , C 8 and other α-olefins with low carbon numbers. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing high-carbon-number α-olefins. Using the iron-based complex designed and synthesized by the present invention as a catalyst, the selectivity of C 20 and above long-chain linear α-olefins in the product is greatly improved.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] A method for preparing high-carbon-number α-olefins. Using the iron-based complex shown in formula (I), under the activation of a cocatalyst, in a solvent, ethylene is catalytically polymerized to obtain a wide-distribution ethylene oligomer; then through separation, solid high-carbon-number C20+ α-olefin; C 20+ (α-olefins containing 20 or more carbon atoms) The content of α-olefins in the total product is not less than 50 wt%, more preferably not less than 60 wt%, and further preferably 64 wt% - 88 wt%;

[0011]

[0012] In formula (I), R 1 is C 1 -C 3 alkyl or halogen, and R 2 is phenyl, C 1 -C 6 alkyl.

[0013] In the iron-based complex of the present invention, preferably, R 1 is one of methyl, ethyl, propyl, fluorine, chlorine, bromine, and iodine. More preferably, R 1 is one of methyl, ethyl, n-propyl, chlorine, and bromine.

[0014] In the iron-based complex of the present invention, preferably, R 2 is one of methyl, ethyl, n-propyl, isopropyl, n-pentyl, isopentyl, n-hexyl, cyclohexyl, and phenyl. More preferably, R 2 is one of methyl, ethyl, n-propyl, isopropyl, cyclohexyl, and phenyl.

[0015] In the iron-based complex of the present invention, preferably, R 1 is one of methyl, ethyl, n-propyl, chlorine, and bromine, and R 2 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 cocatalyst is aluminoxane or an alkylaluminum compound. More preferably, the cocatalyst is methylaluminoxane, modified methylaluminoxane, triethylaluminum, or diethylaluminum chloride; for example, methylaluminoxane or its toluene solution 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 cocatalyst is such that the Al / Fe molar ratio is (100 - 2000):1.

[0020] In the method for preparing higher-carbon-number α-olefins of the present invention, preferably, the solvent is an alkane containing only C and H elements, with a water content not exceeding 20 ppm and being 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 higher-carbon-number α-olefins of the present invention, preferably, the pressure for ethylene polymerization is 0.1 MPa to 3 MPa, the polymerization temperature is -20 °C to 120 °C, and the polymerization time is not more than 4 h, more preferably 0.5 - 4 h.

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

[0023] In the method for preparing higher-carbon-number α-olefins of the present invention, preferably, the liquid phase after filtration is separated by rectification to obtain liquid α-olefins.

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

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

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

[0027]

[0028] 1) React 2-acetyl-6-bromopyridine (compound 1 in Equation 1) with 2-R 1 -aniline under the condition of an acid catalyst to prepare compound 2;

[0029] 2) Heat and react compound 2 with N-R 2 -imidazole to obtain compound 3;

[0030] 3) Add KN(SiMe 3 ) 2 to the solution of compound 3, and after reacting for a certain time, add ferrous chloride to obtain the iron-based complex.

[0031] In the preparation process of the iron-based complex, regarding step 1): React 2-acetyl-6-bromopyridine (compound 1 in Equation 1) with 2-R 1 -aniline under the condition of an acid catalyst to prepare compound 2.

[0032] Preferably, the molar ratio of 2-acetyl-6-bromopyridine to 2-R 1 -aniline only requires a slight excess of 2-R 1 -aniline, preferably 1:(1.05 to 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 p-toluenesulfonic acid.

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

[0035] Preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R 1 -aniline is carried out in a solvent, and the solvent is toluene or ethanol; more preferably toluene.

[0036] Preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R 1 -aniline is carried out under reflux conditions for 4 to 24 h, more preferably 12 h.

[0037] Preferably, after the reaction of 2-acetyl-6-bromopyridine with 2-R 1 -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 for separation and purification.

[0038] In the preparation process of the iron-based complex, regarding step 2): Compound 2 and N-R 2 -imidazole are heated and reacted to obtain Compound 3.

[0039] Preferably, the molar ratio of Compound 2 to N-R 2 -imidazole is 1:(1.05 to 1.5), and a slight excess of N-R 2 -imidazole is sufficient, more preferably 1:1.08.

[0040] Preferably, the reaction of Compound 2 with N-R 2 -imidazole is carried out in a solvent, and the solvent is chloroform or dichloromethane; more preferably chloroform.

[0041] Preferably, the reaction of Compound 2 with N-R 2 -imidazole is carried out under reflux conditions for 2 to 12 h, more preferably 6 h.

[0042] Preferably, after the reaction of Compound 2 with N-R 2 -imidazole is completed, diethyl ether is added to produce a precipitate, and the solid Compound 3 is obtained by filtration.

[0043] During the preparation of the iron-based complex, regarding step 3): Add KN(SiMe 3 ) 2 to the solution of compound 3. After reacting for a certain period of time, add ferrous chloride to obtain the iron-based complex.

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

[0045] Preferably, under a protective atmosphere, cool the solution of compound 3 to -10°C to -30°C (e.g., -20°C), add KN(SiMe 3 ) 2 React for 0.1 - 1 h (e.g., 0.5 h), then add ferrous chloride and continue to react for 2 - 12 h (e.g., 4 h); after the reaction is completed, add pentane or heptane to precipitate the solid product.

[0046] Preferably, the molar ratio of compound 3 to KN(SiMe 3 ) 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, after the solid product is precipitated, it is purified by recrystallization. More preferably, the solvents for recrystallization are tetrahydrofuran and pentane.

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

[0050] The present invention uses the designed and synthesized iron-based complex to catalyze ethylene polymerization. By changing the steric hindrance and electronic environment of the catalyst active center, the molecular weight and distribution of the product are controlled to obtain the above-mentioned long-chain linear α-olefin target product with a narrow distribution. 20 C Specific Embodiments

[0051] To illustrate the present invention more clearly, the following describes the present invention in further detail with reference to preferred embodiments. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0052] In the following examples, experimental methods without specific conditions are usually carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used are, unless otherwise specified, raw materials and reagents that can be obtained from commercial channels such as the conventional market. All numerical designations in the present invention (e.g., temperature, time, concentration, weight, etc., including the range of each of them) can generally be approximate values that can be appropriately changed (+) or (-) in increments of 0.1 or 1.0. All numerical designations can be understood to be preceded by the term "about".

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

[0054] Example 1

[0055] In this example, an iron-based complex 1 is prepared, which includes 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, add 0.2 g of p-toluenesulfonic acid, and reflux for 12 h. Separate by silica gel column (ethyl acetate / petroleum ether = 1:10, v / v) to obtain Compound 2, a total of 0.075 mol, with a yield of 75%.

[0058] The product is subjected to NMR measurement, 1 H NMR(CDCl 3 , 200 MHz): δ1.81(d, 3H, CH 3 ), δ2.31(d, 3H, CH 3 ), 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 ether, filter to obtain solid Compound 3, a total of 0.05 mol, with a yield of 83%.

[0060] The product is subjected to NMR measurement, 1 H NMR(CDCl 3 , 200 MHz): δ1.81(d, 3H, CH 3 ), δ2.31(d, 3H, CH 3 ), δ3.72(d, 3H, CH 3), δ 7.01 - 7.24 (m, 4H, Ph-H), δ 7.90 - 8.15 (m, 3H, Py-CH), δ 7.27 - 7.83 (m, 3H, Im-CH).

[0061] ③ Weigh 0.04 mol of compound 3, add 100 mL of tetrahydrofuran, and add it to a three-necked flask. Under nitrogen protection, cool it down to -20 °C, and add 0.08 mol of KN(SiMe 3 ) 2 React for 0.5 h, add 0.04 mol of ferrous chloride, continue to react for 2 h, slowly warm up to room temperature, and continue to react for 2 h. Add 30 mL of pentane to precipitate a blue solid powder. Then dissolve it with 100 mL of tetrahydrofuran, and add 30 mL of pentane to precipitate again. Purify once to obtain iron-based complex 1 with a yield of 0.025 mol.

[0062] The product is subjected to NMR measurement. 1 H NMR(CDCl 3 , 200 MHz): δ 1.81 (d, 3H, CH 3 ), δ 2.31 (d, 3H, CH 3 ), δ 3.06 (d, 3H, CH 3 ), δ 7.01 - 7.24 (m, 4H, Ph-H), δ 7.25 - 8.10 (m, 3H, Py-CH), δ 5.06 - 5.3 (m, 2H, Im-CH).

[0063] Example 2

[0064] Replace 2-methylaniline in step ① of Example 1 with 2-ethylaniline, and the remaining synthesis steps are the same. The structure of the synthesized product is as shown below (Example 2).

[0065] Example 3

[0066] Replace 2-methylaniline in step ① of Example 1 with 2-n-propylaniline, and the remaining synthesis steps are the same. The structure of the synthesized product is as shown below (Example 3).

[0067] Example 4

[0068] Replace 2-methylaniline in step ① of Example 1 with 2-chloroaniline, and the remaining synthesis steps are the same. The structure of the synthesized product is as shown below (Example 4).

[0069] Example 5

[0070] Replace 2-methylaniline in step ① of Example 1 with 2-bromoaniline, and the remaining synthesis steps are the same. The structure of the synthesized product is as shown below (Example 5).

[0071] Example 6

[0072] Replace N-methylimidazole in the second step of Example 1 with N-ethylimidazole, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 6).

[0073] Example 7

[0074] Replace N-methylimidazole in the second step of Example 1 with N-isopropylimidazole, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 7).

[0075] Example 8

[0076] Replace N-methylimidazole in the second step of Example 1 with N-phenylimidazole, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 8).

[0077] Example 9

[0078] Replace N-methylimidazole in the second step of Example 1 with N-cyclohexylimidazole, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 9).

[0079] Example 10

[0080] Replace 2-methylaniline in the first step of Example 1 with 2-n-propylaniline, and replace N-methylimidazole in the second step with N-isopropylimidazole. Keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 10).

[0081]

[0082] Table 1 Summary Table of Catalyst Synthesis Examples

[0083]

[0084]

[0085] Note: The compound ratios, reaction temperature, pressure, and time in Examples 1 - 10 are the same.

[0086] II. Evaluation of Iron-based Ethylene Oligomerization Catalyst:

[0087] Example 11

[0088] Use the catalysts prepared in Examples 1 - 10 for ethylene oligomerization reaction, including the following process:

[0089] After evacuating and filling with ethylene three times repeatedly in a 2-L reactor, ethylene was filled to atmospheric pressure. Then, 1000 mL of n-pentane and 10 mL of methylaluminoxane MAO (10 wt% toluene solution) were added in sequence and stirred for 5 minutes. Subsequently, 5 mg of the catalyst of Example 1 was added, and the pressure was rapidly increased to 0.3 MPa, followed by reacting at 70 °C for 1 h. After the product was cooled, it was filtered to obtain solid C. 20+ α-olefins; The liquid-phase product was analyzed by gas chromatography, and the linear α-olefins were 96%, and the carbon number distribution was in C 6 -C 20 Between. The catalytic activity was calculated to be 3×10 6 g olefins / mol catalyst / atmosphere, and the C 20+ α-olefins accounted for 70 wt% of the product weight.

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

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

[0092]

[0093]

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

[0095] Obviously, the above examples of the present invention are merely illustrations for clearly explaining the present invention, rather than limitations on the implementation modes of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation modes here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing high carbon number α-olefins, wherein: The preparation method adopts the iron-based complex shown in formula (I) to catalyze ethylene polymerization in a solvent under the activation of a co-catalyst to obtain a broad distribution ethylene oligomer; and then separates and obtains a solid high carbon number C 20+ α-olefins; The C 20+ The content of α-olefin in the total product is not less than 50wt%; In formula (I), R1 is a C1-C3 alkyl group or a halogen, and R2 is a phenyl group or a C1-C6 alkyl group.

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 and 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 and 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:

5. The method for preparing high carbon number α-olefins according to claim 1, wherein: The cocatalyst is aluminoxane or an alkyl aluminum compound.

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

7. The method for preparing high carbon number α-olefins according to claim 1, wherein: The Al / Fe molar ratio in the iron-based complex and the promoter is (100-2000):

1.

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

9. The method for preparing high carbon number α-olefins according to claim 8, wherein: The alkane is selected from at least one of n-pentane, n-hexane, cyclohexane, n-heptane and n-octane.

10. The method for preparing high carbon number α-olefins according to claim 1, wherein: 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 0.5 to 4 hours.

11. The method for preparing high carbon number α-olefins according to claim 1, wherein: The separation is achieved by filtration to obtain a solid high carbon number C 20+ α-Olefins.

12. The method for preparing high carbon number α-olefins according to claim 11, wherein: The filtered liquid phase is separated by distillation to obtain liquid α-olefins.

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

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