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

Abstract

The invention provides an iron-based complex, a preparation method thereof and an ethylene oligomerization catalyst. The iron-based complex is formed by coordination of a ligand and an iron compound, the ligand has a structure as shown in a formula I. In the formula I, R1 and R1'are the same or different and are independently selected from H, C1-C4 alkyl and derivatives thereof, and when the iron-based complex and a cocatalyst form an ethylene oligomerization catalyst and are used for ethylene oligomerization, the generation amount of a byproduct polymer can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of ethylene oligomerization into linear α-olefins, specifically relating to an iron-based complex, its preparation method, and an ethylene oligomerization catalyst. Background Technology

[0002] Alpha-olefins, as a distinctive type of terminal olefin, have a wide range of applications. With the rapid growth in demand for alpha-olefins, imports have increased significantly. Therefore, efficient production of alpha-olefins is of great importance.

[0003] CN112920227A discloses a metallocene compound containing an indene-indole structure, its preparation method, applications, and a method for preparing α-olefins. This metallocene compound 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 selectivity. The main components of the product are 1-octene, 1-decene, and 1-dodecene. However, the product contains some polymers, which may cause blockage in the equipment's piping.

[0004] CN114192192A discloses a catalyst composition for ethylene oligomerization, its preparation method, and its application, relating to the field of ethylene oligomerization catalysis. The catalyst composition comprises a self-supported metal complex and an alkylaluminum co-catalyst. The self-supported metal complex is generated through the coordination reaction of a self-supported phosphine-nitrogen ligand with a transition metal, and the self-supported phosphine-nitrogen ligand is obtained by copolymerizing a phosphine-nitrogen ligand monomer containing a terminal double bond with styrene. The CN114192192A also discloses an ethylene oligomerization method using the above catalyst composition, employing a three-reactor series oligomerization process. Appropriate reaction conditions are used to suit the characteristics of different catalytic stages, effectively increasing the catalyst residence time. This catalyst is easily separated from the reaction system, exhibits high temperature tolerance, and maintains high activity for a long period, with a total selectivity of over 90% for 1-hexene and 1-octene. However, the product contains some polymer, which may cause blockage in the equipment's piping. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an iron-based complex, its preparation method, and an ethylene oligomerization catalyst. When used for ethylene oligomerization, this catalyst can reduce the amount of by-product polymers generated.

[0006] To achieve the above objectives, the present invention provides an iron-based complex formed by coordination of a ligand and an iron compound, wherein the ligand has the structure shown in Formula I:

[0007]

[0008] In Formula I, R1 and R1' may be the same or different, and each is independently selected from H, C1-C4 alkyl groups and their derivatives.

[0009] According to a specific embodiment of the present invention, preferably, the iron compound includes iron halides and / or iron acetylacetonate and its derivatives.

[0010] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different, and are each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl.

[0011] According to a specific embodiment of the present invention, preferably, the iron compound includes ferrous halide and / or ferric acetylacetonate.

[0012] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different, and are each independently selected from hydrogen and methyl.

[0013] According to a specific embodiment of the present invention, preferably, the iron compound includes ferrous chloride and / or ferric acetylacetonate.

[0014] The present invention also provides a method for preparing the above-mentioned iron-based complex, which includes the following steps:

[0015] (1) The ligand shown in Formula I was prepared by reacting 2,6-diacetylpyridine (Formula II) with 4-R1-naphthylamine (Formula III) under the conditions of catalyst A and solvent A.

[0016]

[0017] (2) The ligand shown in Formula I undergoes a coordination reaction under the conditions of an iron compound and solvent B to obtain the iron-based complex shown in Formula IV.

[0018]

[0019] In Formula IV, X represents an anion in an iron compound; R1 and R1' in Formulas I to IV have the same definition as any of the above; the catalyst A includes one or more of sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, and glacial acetic acid.

[0020] According to a specific embodiment of the present invention, preferably, in step (1), the solvent A includes one or more of heptane, toluene, ethanol, and cyclohexane.

[0021] According to a specific embodiment of the present invention, preferably, in step (1), the reaction temperature is 60-130℃, the reaction time is 12-48h, and the reaction pressure is ≤0.1MPa.

[0022] According to a specific embodiment of the present invention, preferably, in step (2), the iron compound includes ferrous chloride and / or ferric acetylacetonate.

[0023] According to a specific embodiment of the present invention, preferably, in step (2), the solvent B includes one or more of heptane, dichloromethane, toluene, cyclohexane, and methylcyclohexane.

[0024] According to a specific embodiment of the present invention, preferably, in step (2), the reaction temperature is 25-50℃, the reaction time is 30-240min, and the reaction pressure is ≤0.1MPa.

[0025] The present invention also provides an ethylene oligomerization catalyst, the composition of which includes the above-mentioned iron-based complex and a co-catalyst.

[0026] According to a specific embodiment of the present invention, preferably, the cocatalyst comprises an aluminum oxane compound.

[0027] According to a specific embodiment of the present invention, preferably, the molar ratio of Fe in the iron-based complex to Al in the co-catalyst is 1:200-2000.

[0028] This invention controls the molecular weight and distribution of products by altering the steric hindrance and electronic environment of the catalyst's active center, resulting in a series of linear α-olefin products with virtually no by-product polymers visible to the naked eye. The ethylene oligomerization catalyst of this invention is simple to prepare, uses inexpensive raw materials, and significantly reduces the amount of by-product polymers that may cause pipeline blockage, thereby improving the economic efficiency of the equipment. Detailed Implementation

[0029] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0030] 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. Unless otherwise specified, all raw materials and reagents used are commercially available from conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on this invention are within the scope of protection claimed by this invention.

[0031] I. Preparation of iron-based complexes

[0032] Example 1

[0033] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0034] (1) Weigh 4.99 g of 2,6-diacetylpyridine and 9.20 g of naphthylamine, add them to a three-necked flask, then add 62 mL of cyclohexane and 0.61 g of p-toluenesulfonic acid, and reflux at 90 °C for 30 h. Recrystallize from ethanol to obtain ligand 1, totaling 2.21 g, with a yield of 16%.

[0035] Elemental analysis (C 29 H 23 Theoretical values ​​(N3,%): C, 84.26; H, 5.57; N, 10.17. Measured values: C, 84.08; H, 5.62; N, 10.30.

[0036] (2) Weigh 0.082g of the above ligand 1 and 0.070g of acetylacetone iron, add them to a three-necked flask, add 100ml of toluene, stir at 30℃ under nitrogen atmosphere for 80min to obtain a solution of iron-based complex 1 (toluene), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0037]

[0038] Example 2

[0039] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0040] (1) Weigh 4.99 g of 2,6-diacetylpyridine and 9.20 g of naphthylamine, add them to a three-necked flask, then add 62 mL of heptane and 0.61 g of p-toluenesulfonic acid, and reflux at 100 °C for 12 h. Recrystallize from ethanol to obtain ligand 1, totaling 2.06 g, with a yield of 15%.

[0041] Elemental analysis (C 29 H 23 Theoretical values ​​(N3,%): C, 84.26; H, 5.57; N, 10.17. Measured values: C, 83.99; H, 5.70; N, 10.31.

[0042] (2) Weigh 0.082g of the above ligand 1 and 0.070g of acetylacetone iron, add them to a three-necked flask, then add 100ml of dichloromethane, stir at 25℃ under nitrogen atmosphere for 30min to obtain a solution of iron-based complex 1 (dichloromethane), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0043]

[0044] Example 3

[0045] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0046] (1) Weigh 4.99 g of 2,6-diacetylpyridine and 9.20 g of naphthylamine, add them to a three-necked flask, then add 62 mL of toluene and 0.61 g of p-toluenesulfonic acid, and reflux at 130 °C for 20 h. Recrystallize from ethanol to obtain ligand 1, totaling 2.68 g, with a yield of 19%.

[0047] Elemental analysis (C 29 H 23 Theoretical values ​​(N3,%): C, 84.26; H, 5.57; N, 10.17. Measured values: C, 84.01; H, 5.64; N, 10.35.

[0048] (2) Weigh 0.082g of the above ligand 1 and 0.070g of acetylacetone iron, add them to a three-necked flask, then add 50mL of dichloromethane and 50mL of toluene, stir at 25℃ under nitrogen atmosphere for 60min to obtain a solution of iron-based complex 1 (dichloromethane + toluene), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0049]

[0050] Example 4

[0051] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0052] (1) Weigh 0.12 g of 2,6-diacetylpyridine and 0.25 g of 4-methylnaphthyl-1-amine, add them to a three-necked flask, then add 10 mL of ethanol and 0.02 mL of glacial acetic acid, and reflux at 80 °C for 48 h. After recrystallization from ethanol, ligand 2 was obtained, totaling 0.09 g, with a yield of 26%.

[0053] Elemental analysis (C 31 H 27 Theoretical values ​​(N3,%): C, 84.35; H, 6.12; N, 9.53. Measured values: C, 84.21; H, 6.21; N, 9.58.

[0054] (2) Weigh 0.088g of the above ligand 2 and 0.025g of ferrous chloride, add them to a three-necked flask, then add 50mL of dichloromethane and 50mL of cyclohexane, stir at 40℃ under nitrogen atmosphere for 240min to obtain a solution of iron-based complex 2 (dichloromethane + cyclohexane), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0055]

[0056] Example 5

[0057] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0058] (1) Weigh 0.12 g of 2,6-diacetylpyridine and 0.25 g of 4-methylnaphthyl-1-amine, add them to a three-necked flask, then add 10 ml of cyclohexane and 0.15 g of p-toluenesulfonic acid, and reflux at 90 °C for 36 h. Recrystallize from ethanol to obtain ligand 2, totaling 0.11 g, with a yield of 32%.

[0059] Elemental analysis (C 31 H 27 Theoretical values ​​(N3,%): C, 84.35; H, 6.12; N, 9.53. Measured values: C, 84.41; H, 6.07; N, 9.52.

[0060] (2) Weigh 0.044 g of the above ligand 2 and 0.025 g of ferrous chloride, add them to a three-necked flask, then add 50 mL of dichloromethane and 50 mL of toluene, stir at 25 °C under a nitrogen atmosphere for 60 min to obtain a solution of iron-based complex 2 (dichloromethane + toluene), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0061]

[0062] Example 6

[0063] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0064] (1) Weigh 4.99 g of 2,6-diacetylpyridine and 9.20 g of naphthylamine, add them to a three-necked flask, then add 120 ml of ethanol and 0.8 ml of glacial acetic acid, and react at 60 °C for 48 h. After recrystallization from ethanol, ligand 1 was obtained, totaling 3.49 g, with a yield of 25%.

[0065] Elemental analysis (C 29 H 23 Theoretical values ​​(N3,%): C, 84.26; H, 5.57; N, 10.17. Measured values: C, 84.31; H, 5.02; N, 10.67.

[0066] (2) Weigh 0.082g of the above ligand 1 and 0.023g of ferrous chloride, add them to a three-necked flask, add 100mL of dichloromethane, stir at 50℃ under nitrogen atmosphere for 120min to obtain a solution of ligand 1 (dichloromethane), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0067]

[0068] Example 7

[0069] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0070] (1) Weigh 0.12 g of 2,6-diacetylpyridine and 0.25 g of 4-methylnaphthyl-1-amine, add them to a three-necked flask, then add 10 mL of toluene and 0.15 g of p-toluenesulfonic acid, and reflux at 130 °C for 20 h. Recrystallize from ethanol to obtain ligand 2, totaling 0.10 g, with a yield of 29%.

[0071] Elemental analysis (C 31 H 27 Theoretical values ​​(N3,%): C, 84.35; H, 6.12; N, 9.53. Measured values: C, 84.26; H, 6.30; N, 9.44.

[0072] (2) Weigh 0.088g of the above ligand 2 and 0.070g of acetylacetone iron, add them to a three-necked flask, then add 50mL of dichloromethane and 50mL of toluene, stir at 25℃ under nitrogen atmosphere for 60min to obtain a solution of iron-based complex 2 (dichloromethane + toluene), and set aside for use; the reaction conditions are shown in Table 1, and the reaction route is as follows.

[0073]

[0074] Table 1

[0075]

[0076] II. Evaluation of Ethylene Oligomerization Catalysts

[0077] C 10+ The selectivity of α-olefins is calculated using the following formula:

[0078] C 10+ Selectivity of α-olefins = (C 10+ (mass of α-olefin product / total product mass) × 100%.

[0079] Example 8

[0080] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure (0.1 MPa). Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt, purchased from Norinco) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution (iron-based complex 1 + toluene) obtained in Example 1 was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 2.9 × 10⁻⁶. 5 g / mol Fe h, C 10+α-olefins accounted for 52% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0081] Example 9

[0082] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product obtained in Example 2 (iron-based complex 1 + dichloromethane) solution was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 2.4 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 50% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0083] Example 10

[0084] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution obtained in Example 3 (iron-based complex 1 + dichloromethane + toluene) was added. In this solution: Fe... 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 2.5 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 53% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0085] Example 11

[0086] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution obtained in Example 4 (iron-based complex 2 + dichloromethane + cyclohexane) was added. In this solution: Fe 2+The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 1.6 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 42% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0087] Example 12

[0088] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution obtained in Example 5 (iron-based complex 2 + dichloromethane + toluene) was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 1.4 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 43% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0089] Example 13

[0090] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution (iron-based complex 1 + dichloromethane) obtained in Example 6 was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 1.9 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 49% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0091] Example 14

[0092] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 200 ml of cyclohexane and 2.5 ml of MMAO-3A (7% wt) were added sequentially, and the mixture was stirred for 5 minutes. Next, 2 ml of the product solution obtained in Example 7 (iron-based complex 2 + dichloromethane + toluene) was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The carbon number distribution of the α-olefin in the product was C4-C6. 32 Between these values, the catalytic activity is 2.1 × 10⁻⁶. 5 g / mol Fe h, C 10+ α-olefins accounted for 53% of the product weight, and no obvious by-product polymers were generated. The results are shown in Table 2.

[0093] Table 2 Evaluation results of ethylene oligomerization

[0094]

[0095]

[0096] As can be seen from the above, the ethylene oligomerization catalyst composed of the iron-based complex and the co-catalyst of the present invention can reduce the amount of by-product polymer generated.

Claims

1. An iron-based complex formed by coordination of a ligand and an iron compound, said ligand having the structure shown in Formula I: In formula I, R1 and R1' may be the same or different, and each is independently selected from H, C1-C4 alkyl groups and their derivatives.

2. The iron-based complex according to claim 1, wherein, The iron compounds include iron halides and / or iron acetylacetonate and its derivatives.

3. The iron-based complex according to claim 1, wherein, In Formula I, R1 and R1' may be the same or different, and each is independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl. And / or, the iron compounds include ferrous halides and / or ferric acetylacetonate.

4. The iron-based complex according to claim 1, wherein, In Formula I, R1 and R1' may be the same or different, and each is independently selected from hydrogen or methyl. And / or, the iron compounds include ferrous chloride and / or ferric acetylacetonate.

5. A method for preparing the iron-based complex according to any one of claims 1-4, comprising the following steps: (1) The ligand shown in Formula I was prepared by reacting 2,6-diacetylpyridine (Formula II) with 4-R1-naphthylamine (Formula III) under the conditions of catalyst A and solvent A. (2) The ligand shown in Formula I undergoes a coordination reaction under the conditions of an iron compound and solvent B to obtain the iron-based complex shown in Formula IV. In Formula IV, X represents the anion in the iron compound; R1 and R1' in Formulas I to IV have the definitions corresponding to any one of claims 1-4; Catalyst A comprises one or more of sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, and glacial acetic acid.

6. The preparation method according to claim 5, wherein, In step (1), solvent A includes one or more of heptane, toluene, ethanol, and cyclohexane; And / or, in step (1), the reaction temperature is 60-130℃, the reaction time is 12-48h, and the reaction pressure is ≤0.1MPa.

7. The preparation method according to claim 5, wherein, In step (2), the iron compound includes ferrous chloride and / or ferric acetylacetonate; And / or, in step (2), the solvent B includes one or more of heptane, dichloromethane, toluene, cyclohexane, and methylcyclohexane; And / or, in step (2), the reaction temperature is 25-50℃, the reaction time is 30-240min, and the reaction pressure is ≤0.1MPa.

8. An ethylene oligomerization catalyst, comprising the iron-based complex and co-catalyst as described in any one of claims 1-4.

9. The ethylene oligomerization catalyst according to claim 8, wherein, The cocatalyst includes aluminum oxoalkane compounds.

10. The ethylene oligomerization catalyst according to claim 8, wherein, The molar ratio of Fe in the iron-based complex to Al in the co-catalyst is 1:200-2000.

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