Iron-based complex, ethylene oligomerization catalyst composition and preparation method thereof

Abstract

The invention discloses an iron-based complex, an ethylene oligomerization catalyst composition and a preparation method thereof. The structural formula of the iron-based complex is imgabs0 #, R1 is C1-C3 alkyl or halogen, and R2 is phenyl and C1-C6 alkyl. The novel ethylene oligomerization catalyst is designed and synthesized, the steric hindrance and electronic environment of the active center of the catalyst are changed, the molecular weight and distribution of a polymerization product are controlled, and a narrow-distribution long-chain linear alpha-olefin target product of C20 or above is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene oligomerization to grow long-chain linear α-olefins, and particularly relates to an iron-based complex, an ethylene oligomerization catalyst composition and a preparation method thereof. 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 an α-olefin selectivity of more than 98% and a 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 C 20 and above long-chain linear α-olefins can be obtained by rectification, the yield of C 20 and above long-chain linear α-olefins 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 C 20 and above long-chain carbons, and preparing C 20 and above long-chain linear α-olefins with high yield is of great significance.

[0003] CN 112920227 A discloses a metallocene compound containing an indenoindole structure, a preparation method and application thereof, and a preparation method of α-olefins. The metallocene compound containing an indenoindole structure provided therein can be used as a catalyst for catalytic synthesis of α-olefins, and can synthesize α-olefins with high carbon numbers 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 α-olefins with higher carbon numbers (C 20 and above long-chain linear α-olefins).

[0004] CN 105797773 A discloses a novel linear α-olefin catalyst, a preparation process and uses thereof. The catalyst composition is composed of a main catalyst and a co-catalyst. 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. The linear α-olefin selectivity is greater than 96%, and the carbon number distribution is in C 4 -C 28 , wherein 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+ 、Ni2+ , Cr 3+ 's halide as the main catalyst, under the action of different cocatalysts modified methylaluminoxane or diethylaluminum chloride, this catalyst has good ethylene oligomerization and / or polymerization catalytic performance. Among them, the iron(II) complex shows high oligomerization and polymerization activity 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 low-carbon number α-olefins.

[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 ethylene oligomerization and polymerization catalytic performance under the action of the cocatalyst methylaluminoxane, and can realize the oligomerization and polymerization catalysis of ethylene; however, the main components in the product are C 4 , C 6 and other low-carbon number α-olefins.

[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 activity for ethylene, reaching 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 low-carbon number α-olefins. SUMMARY OF THE INVENTION

[0008] The purpose of the present invention is to provide an iron-based complex, an ethylene oligomerization catalyst composition and its preparation method.

[0009] The present invention designs and synthesizes an iron-based complex and uses it as an ethylene oligomerization catalyst, which can greatly improve the selectivity of C 20 and above long-chain linear α-olefins in the product.

[0010] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0011] The first aspect of the present invention provides an iron-based complex, and its structural formula is as follows:

[0012]

[0013] In formula (I), R 1 is C 1 -C 3 alkyl or halogen, and R 2 is phenyl, C 1 -C 6 alkyl.

[0014] For the iron-based complex according to the present invention, preferably, R 1 is one of methyl, ethyl, propyl, fluorine, chlorine, bromine, iodine. More preferably, R 1 is one of methyl, ethyl, n-propyl, chlorine, bromine.

[0015] For the iron-based complex according to the present invention, preferably, R 2 is one of methyl, ethyl, n-propyl, isopropyl, n-pentyl, isopentyl, n-hexyl, cyclohexyl, phenyl. More preferably, R 2 is one of methyl, ethyl, n-propyl, isopropyl, cyclohexyl, phenyl.

[0016] For the iron-based complex according to the present invention, preferably, R 1 is one of methyl, ethyl, n-propyl, chlorine, bromine, and R 2 is one of methyl, ethyl, n-propyl, isopropyl, cyclohexyl, phenyl.

[0017] For the iron-based complex according to the present invention, preferably, the structural formula of the iron-based complex is:

[0018]

[0019] The second aspect of the present invention provides a preparation method of any one of the above iron-based complexes, wherein the preparation method includes the following steps:

[0020]

[0021] 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;

[0022] 2) Heat and react compound 2 with N-R 2 -imidazole to obtain compound 3;

[0023] 3) Add KN(SiMe 3 ) 2After reacting for a certain period of time, ferrous chloride is added to obtain the iron-based complex.

[0024] Regarding step 1): 2-acetyl-6-bromopyridine (compound 1 in Equation 1) reacts with 2-R 1 -aniline under the condition of an acid catalyst to prepare compound 2.

[0025] According to the preparation method of the present invention, preferably, the molar ratio of 2-acetyl-6-bromopyridine to 2-R 1 -aniline is such that 2-R 1 -aniline is appropriately in excess, preferably 1:(1.05 - 1.5), more preferably 1:1.2.

[0026] According to the preparation method of the present invention, preferably, the acid catalyst is selected from at least one of sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid; more preferably p-toluenesulfonic acid.

[0027] According to the preparation method of the present invention, the amount of the acid catalyst used is a catalytic amount. Preferably, the amount of the acid catalyst used is 1 mol% - 10 mol% of 2-acetyl-6-bromopyridine.

[0028] According to the preparation method of the present invention, preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R 1 -aniline is carried out in solvent A, and the solvent A is toluene or ethanol; more preferably toluene.

[0029] According to the preparation method of the present invention, preferably, the reaction of 2-acetyl-6-bromopyridine with 2-R 1 -aniline is carried out under reflux conditions for 4 - 24 h, more preferably 12 h.

[0030] According to the preparation method of the present invention, 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.

[0031] Regarding step 2): Compound 2 and N-R 2 -imidazole are heated to react to obtain compound 3.

[0032] According to the preparation method of the present invention, preferably, the molar ratio of compound 2 to N-R 2 -imidazole is 1:(1.05 - 1.5), and N-R 2 -imidazole is slightly in excess, more preferably 1:1.08.

[0033] According to the preparation method of the present invention, preferably, compound 2 and N-R 2The reaction of -imidazole is carried out in solvent B, and the solvent B is chloroform or dichloromethane; more preferably chloroform.

[0034] According to the preparation method of the present invention, preferably, the reaction of compound 2 and N-R 2 -imidazole is carried out under reflux conditions for 2 to 12 h, more preferably 6 h.

[0035] According to the preparation method of the present invention, preferably, after the reaction of compound 2 and N-R 2 -imidazole is completed, ether is added to produce a precipitate, and the solid compound 3 is obtained by filtration.

[0036] Regarding step 3): KN(SiMe 3 ) 2 is added to the solution of compound 3. After reacting for a certain time, ferrous chloride is added to obtain the iron-based complex.

[0037] According to the preparation method of the present invention, preferably, the solution of compound 3 includes compound 3 and solvent C, and the solvent C is tetrahydrofuran or tetrahydropyran; more preferably tetrahydrofuran.

[0038] According to the preparation method of the present invention, preferably, under a protective atmosphere, the solution of compound 3 is cooled to -10°C to -30°C (such as -20°C), and KN(SiMe 3 ) 2 is added. After reacting for 0.1 to 1 h (such as 0.5 h), ferrous chloride is added and the reaction continues for 2 to 12 h (such as 4 h); after the reaction is completed, pentane or heptane is added to precipitate a solid product.

[0039] According to the preparation method of the present invention, preferably, the molar ratio of compound 3 to KN(SiMe 3 ) 2 is 1:(1 - 3), more preferably 1:2.

[0040] According to the preparation method of the present invention, preferably, the molar ratio of compound 3 to ferrous chloride is (0.8 - 1.2):1, more preferably 1:1.

[0041] According to the preparation method of the present invention, preferably, after the solid product is precipitated, it is recrystallized and purified. More preferably, the solvents for recrystallization are tetrahydrofuran and pentane.

[0042] According to the preparation method of the present invention, preferably, the protective atmosphere is nitrogen, argon, etc.

[0043] The third aspect of the present invention provides an ethylene oligomerization catalyst composition, which includes a main catalyst and a cocatalyst; the main catalyst is any of the iron-based complexes provided in the first aspect above.

[0044] For the ethylene oligomerization catalyst according to the present invention, preferably, the cocatalyst is aluminoxane or an alkylaluminum compound; more preferably methylaluminoxane, modified methylaluminoxane, triethylaluminum or diethylaluminum chloride.

[0045] For the ethylene oligomerization catalyst according to the present invention, preferably, the molar ratio of Al / Fe in the main catalyst and the cocatalyst is (100 - 2000):1.

[0046] The present invention designs and synthesizes a novel ethylene oligomerization catalyst to change the steric hindrance and electronic environment of the catalyst active center, so as to control the molecular weight and distribution of the polymerization product and obtain a narrow - distribution C 20 The above long - chain linear α - olefin target product; in the obtained polymerization product, C 20 The selectivity of the above long - chain linear α - olefins reaches more than 50%. Detailed implementation manners

[0047] To illustrate the present invention more clearly, the following further describes the present invention in conjunction with 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.

[0048] For the experimental methods without specific conditions in the following examples, they are generally 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, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. All numerical designations in the present invention (such as 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 as having the term "about" in front.

[0049] I. Preparation of iron - based ethylene oligomerization catalyst:

[0050] Example 1

[0051] This example prepares an iron - based complex 1, including the following steps:

[0052]

[0053] 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 (ethyl acetate / petroleum ether = 1:10, v / v) to obtain Compound 2, a total of 0.075 mol, with a yield of 75%.

[0054] The product is subjected to NMR measurement. 1¹H NMR(CDCl 3 , 200 MHz): δ 1.81 (d, 3H, CH 3 ), δ 2.31 (d, 3H, CH 3 ), δ 7.01 - 7.24 (m, 4H, Ph - H), δ 7.76 (m, 1H, Py - CH), δ 8.07 - 8.15 (m, 2H, Py - CH).

[0055] 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%.

[0056] The product was subjected to NMR measurement. 1 ¹H NMR(CDCl 3 , 200 MHz): δ 1.81 (d, 3H, CH 3 ), δ 2.31 (d, 3H, CH 3 ), δ 3.72 (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).

[0057] ③ Weigh 0.04 mol of compound 3, add 100 mL of tetrahydrofuran, add it to a three - necked flask, under nitrogen protection, cool to - 20 °C, 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 for purification once to obtain iron - based complex 1, with a yield of 0.025 mol.

[0058] The product was subjected to NMR measurement. 1 ¹H 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).

[0059] Example 2

[0060] Replace 2-methylaniline in step ① of Example 1 with 2-ethylaniline, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 2).

[0061] Example 3

[0062] Replace 2-methylaniline in step ① of Example 1 with 2-n-propylaniline, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 3).

[0063] Example 4

[0064] Replace 2-methylaniline in step ① of Example 1 with 2-chloroaniline, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 4).

[0065] Example 5

[0066] Replace 2-methylaniline in step ① of Example 1 with 2-bromoaniline, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 5).

[0067] Example 6

[0068] Replace N-methylimidazole in step ② 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).

[0069] Example 7

[0070] Replace N-methylimidazole in step ② 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).

[0071] Example 8

[0072] Replace N-methylimidazole in step ② 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).

[0073] Example 9

[0074] Replace N-methylimidazole in step ② 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).

[0075] Example 10

[0076] Replace 2-methylaniline in step ① of Example 1 with 2-n-propylaniline, and replace N-methylimidazole in step ② with N-isopropylimidazole, and keep the rest of the synthesis steps the same. The structure of the synthesized product is as shown below (Example 10).

[0077]

[0078]

[0079] Example 10

[0080] Table 1 Summary Table of Catalyst Synthesis Examples

[0081]

[0082] Note: The compound ratios, reaction temperatures, pressures, and times described in Examples 1 to 10 are the same. II. Evaluation of Iron-based Ethylene Oligomerization Catalysts:

[0083] Example 11

[0084] The catalysts prepared in Examples 1 - 10 were used for ethylene oligomerization reaction, including the following process:

[0085] After evacuating and filling with ethylene three times in a 2-liter reaction kettle, 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. Then, 5 mg of the catalyst of Example 1 was added, and the pressure was quickly increased to 0.3 MPa, and the reaction was carried out at 70 °C for 1 h. After the product was cooled, solid C was obtained by filtration and separation 20+ α-olefin; The liquid-phase product was analyzed by gas chromatography, and the linear α-olefin was 96%, and the carbon number distribution was between C 6 -C 20 . The catalytic activity was calculated to be 3×10 6 g olefin / mol catalyst / atmosphere according to the consumed ethylene amount, and the C 20+ α-olefin accounted for 70% of the product weight.

[0086] 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.

[0087] Table 2 Summary Table of Ethylene Oligomerization Evaluation Example Results

[0088]

[0089]

[0090] Note: The reaction pressure described in Example 11 is 0.3 MPa, the reaction temperature is 70 °C, and the reaction time is 1 h.

[0091] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners 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 enumerate all the implementation manners 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. An iron-based complex, wherein The structural formula of the iron-based complex is as follows: 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 iron-based complex according to claim 1, wherein R1 is one of methyl, ethyl, propyl, fluorine, chlorine, bromine and iodine.

3. The iron-based complex according to claim 1, wherein R2 is one of methyl, ethyl, n-propyl, isopropyl, n-pentyl, isopentyl, n-hexyl, cyclohexyl and phenyl.

4. The iron-based complex according to claim 1, wherein The structural formula of the iron-based complex is:

5. A method for preparing the iron-based complex according to any one of claims 1 to 4, wherein: The preparation method comprises the following steps: 1) 2-acetyl-6-bromopyridine is reacted with 2-R1-aniline under acid catalyst conditions to prepare compound 2; 2) Compound 2 and N-R2-imidazole are heated to react to obtain compound 3; 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.

6. The preparation method according to claim 5, wherein: The molar ratio of the 2-acetyl-6-bromopyridine to the 2-R1-aniline is 1:(1.05-1.5).

7. The preparation method according to claim 5, wherein: The acid catalyst is selected from at least one of sulfuric acid, benzenesulfonic acid and p-toluenesulfonic acid; The amount of the acid catalyst used is 1 mol% to 10 mol% of 2-acetyl-6-bromopyridine.

8. The preparation method according to claim 5, wherein The reaction of 2-acetyl-6-bromopyridine and 2-R1-aniline is carried out in solvent A, and the solvent A is toluene or ethanol; The reaction of 2-acetyl-6-bromopyridine and 2-R1-aniline is carried out under reflux conditions for 4 to 24 hours; After the reaction of 2-acetyl-6-bromopyridine and 2-R1-aniline is completed, column chromatography is used to separate and purify the product.

9. The preparation method according to claim 5, wherein: The molar ratio of the compound 2 to N-R2-imidazole is 1:(1.05-1.5).

10. The preparation method according to claim 5, wherein: The reaction of the compound 2 and N-R2-imidazole is carried out in solvent B, and the solvent B is chloroform or dichloromethane; The reaction of the compound 2 and N-R2-imidazole is carried out under reflux conditions for 2 to 12 hours; After the reaction of the compound 2 and N-R2-imidazole is completed, ether is added to produce a precipitate, which is filtered to obtain a solid compound 3.

11. The preparation method according to claim 5, wherein: The compound 3 solution comprises compound 3 and solvent C, wherein the solvent C is tetrahydrofuran or tetrahydropyran; Under a protective atmosphere, the solution of compound 3 is cooled to -10°C to -30°C, KN(SiMe3)2 is added to react for 0.1 to 1 h, and then ferrous chloride is added to continue the reaction for 2 to 12 h; after the reaction is completed, pentane or heptane is added to precipitate a solid product.

12. The preparation method according to claim 11, wherein The molar ratio of the compound 3 to KN(SiMe3)2 is 1:(1-3); The molar ratio of the compound 3 to ferrous chloride is (0.8-1.2):

1.

13. An ethylene oligomerization catalyst composition, wherein: The ethylene oligomerization catalyst composition comprises a main catalyst and a co-catalyst; the main catalyst is the iron-based complex according to any one of claims 1-4.

14. The ethylene oligomerization catalyst composition according to claim 13, wherein The cocatalyst is aluminoxane or an alkyl aluminum compound.

15. The ethylene oligomerization catalyst composition according to claim 14, wherein The co-catalyst is methylaluminoxane, modified methylaluminoxane, triethylaluminum or diethylaluminum chloride.

16. The ethylene oligomerization catalyst composition according to claim 13, wherein The Al / Fe molar ratio in the main catalyst and the co-catalyst is (100-2000):1.

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