Method for preparing low-carbon-number olefin through ethylene oligomerization

Abstract

The invention provides a method for preparing low-carbon-number olefin through ethylene oligomerization. The method comprises the following steps: adding a solvent, a cocatalyst and an iron-based complex into a reactor, reacting for 15-60 minutes under the conditions that the ethylene pressure is 1-3 MPa and the reaction temperature is 60-80 DEG C, and cooling to obtain an ethylene oligomerization product, in the formula I, R1 and R1'are the same or different and are respectively and independently selected from H, C1-C4 alkyl and derivatives thereof, R2, R3, R4, R2 ', R3' and R4 'are the same or different and are respectively and independently selected from H, C1-C2 alkyl and derivatives thereof, and M is halogen. The method can be used for selectively preparing C4-C8 olefin.

Description

Technical Field

[0001] This invention belongs to the field of ethylene oligomerization to linear α-olefins, specifically relating to a method for preparing low-carbon-number olefins by ethylene oligomerization. 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] CN113943201A discloses the application of a nickel-organic metal framework catalyst in the production of 1-butene from ethylene dimerization. The nickel-organic metal framework catalyst includes 1D Ni-MIL-77 and 3D Ni-MIL-77, which can be obtained through a one-step hydrothermal synthesis method, resulting in low cost. The hydrothermally synthesized 1D Ni-MIL-77 and 3D Ni-MIL-77 do not require post-modification and can be directly used as catalysts. With the aid of a co-catalyst, they catalyze the ethylene oligomerization reaction, achieving high ethylene oligomerization activity and 1-butene selectivity. This catalyst can be recycled and reused. The butene selectivity is above 99%, and the 1-C4 selectivity reaches above 85.0%. However, the main component of the product is 1-butene.

[0004] CN105797773A 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 carbon number distribution of C4-C6. 28 C6-C 20 Greater than 75%. This catalyst has a stable structure, can be used for ethylene oligomerization, has high catalytic efficiency, and its preparation method is simple, yielding high output, using readily available raw materials, with low cost and minimal environmental pollution, making it easy for industrial production. However, its products are concentrated in the C6-C range. 20 . Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for preparing low-carbon-number olefins through ethylene oligomerization. This method can selectively prepare C4-C8 olefins.

[0006] To achieve the above objectives, the present invention provides a method for preparing linear α-olefins by ethylene oligomerization, comprising the following steps: adding a solvent, a co-catalyst, and an iron-based complex to a reactor; reacting for 15-60 minutes under ethylene pressure of 1-3 MPa and reaction temperature of 60-80°C; and cooling to obtain the ethylene oligomer product; wherein the iron-based complex 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; R2, R3, R4, R2', R3', and R4' may be the same or different, and each is independently selected from H, C1-C2 alkyl groups and their derivatives; M is a halogen.

[0009] According to a specific embodiment of the present invention, preferably, in the above method for preparing linear α-olefins by ethylene oligomerization, the reaction temperature is 65-80℃ (more preferably 70℃).

[0010] According to a specific embodiment of the present invention, preferably, in the above method for preparing linear α-olefins by ethylene oligomerization, the reaction time is 25-40 min (more preferably 30 min).

[0011] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different, and each is independently selected from H, C1-C4 alkyl groups; R2, R3, R4, R2', R3', and R4' are the same or different, and each is independently selected from H, C1-C2 alkyl groups.

[0012] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same and selected from H, methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl; R2, R3, R4, R2', R3', and R4' are the same and selected from H, methyl, and ethyl.

[0013] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different, and each is independently selected from H or methyl; R2, R3, R4, R2', R3', and R4' are the same or different, and each is independently selected from H or methyl.

[0014] According to a specific embodiment of the present invention, preferably, in Formula I, R1 and R1' are the same or different, and each is independently selected from methyl; R2, R3, R4, R2', R3', and R4' are the same or different, and each is independently selected from methyl.

[0015] According to a specific embodiment of the present invention, preferably, in Formula I, M is selected from fluorine, chlorine, bromine, and iodine.

[0016] According to a specific embodiment of the present invention, preferably, the preparation method of the iron-based complex includes the following steps:

[0017] (1) The compound shown in Formula IV was prepared by reacting 2,6-diacylpyridine as shown in Formula II with the compound shown in Formula III under the conditions of catalyst A and solvent A.

[0018]

[0019] (2) The compound of formula IV obtained in step (1) was subjected to a coordination reaction under the conditions of iron halide and solvent B to obtain the compound of formula I.

[0020]

[0021] R1, R1', R2, R3, R4, R2', R3', and R4' in Formulas I to IV have the same definition as any of the above; Catalyst A includes one or more combinations of sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid.

[0022] According to a specific embodiment of the present invention, preferably, in step (1), the solvent A includes one or more of toluene, ethanol, and cyclohexane.

[0023] According to a specific embodiment of the present invention, preferably, in step (1), the reaction temperature is 80-140℃, the reaction time is 10-30h, and the reaction pressure is ≤0.1MPa.

[0024] According to a specific embodiment of the present invention, preferably, in step (2), the iron halide includes ferrous chloride and / or ferrous bromide.

[0025] According to a specific embodiment of the present invention, preferably, in step (2), the solvent B includes one or more of dichloromethane, toluene, cyclohexane, and methylcyclohexane.

[0026] According to a specific embodiment of the present invention, preferably, in step (2), the reaction temperature is 20-60℃, the reaction time is 60-240min, and the reaction pressure is ≤0.1MPa.

[0027] According to a specific embodiment of the present invention, preferably, the cocatalyst comprises an aluminum oxane compound.

[0028] According to a specific embodiment of the present invention, preferably, in the process of preparing linear α-olefins by ethylene oligomerization, the solvent includes one or more of n-hexane, cyclohexane, n-heptane, toluene, dichloromethane, and methylcyclohexane.

[0029] 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 1:200-3000.

[0030] According to a specific embodiment of the present invention, preferably, the mass percentage of C4-C8 olefins in the ethylene oligomer is ≥90%.

[0031] The method for preparing low-carbon-number olefins by ethylene oligomerization of the present invention controls the molecular weight and distribution of the product by changing the steric hindrance and electronic environment of the active center of the iron-based complex, and can selectively prepare C4-C8 olefins. The olefin carbon number in the product is mainly distributed between C4 and C8, and narrowly distributed C4-C8 linear α-olefins can be obtained. Low-carbon-number olefins (C4, C6, C8) can be selectively prepared with a selectivity greater than 90%. These low-carbon-number olefins are the main comonomers of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). Detailed Implementation

[0032] 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.

[0033] 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.

[0034] I. Preparation of Iron-Based Ethylene Oligomerization Catalysts

[0035] Example 1

[0036] This embodiment provides an iron-based complex, which is prepared by the following steps:

[0037] (a) Weigh 4.99 g of 2,6-diacetylpyridine (compound A1) and 9.20 g of 4-tert-butylcyclohexylamine (compound B2), 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 25 h. Recrystallize from ethanol to obtain compound C2, totaling 2.03 g, yield 12%.

[0038] Elemental analysis (C 29 H 47 Theoretical values ​​(N3,%): C, 79.63; H, 10.76; N, 9.61. Measured values: C, 79.47; H, 10.65; N, 9.88.

[0039] (b) Weigh 0.085 g of compound C2 and 0.075 g of ferrous chloride into a three-necked flask, then add 50 mL of dichloromethane and 50 mL of toluene. Stir at 25 °C for 60 min under a nitrogen atmosphere to obtain a "dichloromethane + toluene" solution of compound D2, which is then set aside for use. The reaction route is as follows:

[0040]

[0041] II. Evaluation of Ethylene Oligomerization

[0042] The selectivity of C4-C8 olefins is calculated using the following formula:

[0043] Selectivity for C4-C8 olefins = (mass of C4-C8 olefins in the product) / total product mass.

[0044] Example 2

[0045] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure (0.1 MPa). Then, 100 ml of toluene and 100 ml of dichloromethane, along with 1.5 ml of MMAO-3A (7% wt, purchased from Norinco), were added sequentially. The mixture was stirred for 10 minutes, and then 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 1250; then the pressure was rapidly increased to 1.0 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The olefins in the product were mainly distributed between C4 and C8, with a selectivity of 90.03% for C4-C8 olefins. The catalytic activity was calculated to be 0.78 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0046] Example 3

[0047] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially. The mixture was stirred for 10 minutes, and then 2 ml of a solution of the product obtained in Example 1 (compound D2 + dichloromethane + toluene) was added. In this solution: Fe 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 1.5 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The olefin carbon number in the product was mainly distributed between C4 and C8, with a selectivity of 95.22% for C4-C8 olefins. The catalytic activity was calculated to be 1.04 × 10⁻⁴ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0048] Example 4

[0049] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially. The mixture was stirred for 10 minutes, and then 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; 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 olefin carbon number in the product was mainly distributed between C4 and C8, with a selectivity of 95.56% for C4-C8 olefins. The catalytic activity was calculated to be 1.26 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0050] Example 5

[0051] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially. The mixture was stirred for 10 minutes, and then 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.5 MPa, and the reaction was carried out at 70 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The olefins in the product were mainly distributed between C4 and C8, with a selectivity of 92.51% for C4-C8 olefins. The catalytic activity was calculated to be 1.15 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0052] Example 6

[0053] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially. The mixture was stirred for 10 minutes, and then 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 50 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography, and the selectivity for C4-C8 olefins was 49.92%. The catalytic activity was calculated to be 0.35 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0054] Example 7

[0055] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially, and the mixture was stirred for 10 minutes. Next, 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 60 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography, and the selectivity for C4-C8 olefins was 67.82%. The catalytic activity was calculated to be 0.77 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0056] Example 8

[0057] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially, and the mixture was stirred for 10 minutes. Next, 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 80 °C for 30 min. After cooling, the liquid product was analyzed by gas chromatography. The olefin carbon number in the product was mainly distributed between C4 and C8, and the selectivity for C4-C8 olefins was 85.86%. The catalytic activity was calculated to be 0.89 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0058] Example 9

[0059] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially, and the mixture was stirred for 10 minutes. Next, 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 60 min. After cooling, the liquid product was analyzed by gas chromatography. The olefin carbon number in the product was mainly distributed between C4 and C8, and the selectivity for C4-C8 olefins was 87.55%. The catalytic activity was calculated to be 1.06 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0060] Example 10

[0061] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially, and the mixture was stirred for 10 minutes. Next, 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 90 min. After cooling, the liquid product was analyzed by gas chromatography. The olefin carbon number in the product was mainly distributed between C4 and C8, with a selectivity of 80.36% for C4-C8 olefins. The catalytic activity was calculated to be 0.75 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0062] Example 11

[0063] After repeatedly evacuating and purging with ethylene three times in a 1-liter reactor, ethylene was introduced to atmospheric pressure. Then, 100 ml of toluene and 100 ml of dichloromethane, along with 3.0 ml of MMAO-3A (7% wt), were added sequentially, and the mixture was stirred for 10 minutes. Next, 2 ml of the product obtained in Example 1 (a solution of compound D2 + dichloromethane + toluene, in which Fe...) was added. 2+ The concentration was 2 μmol / ml; the Al / Fe molar ratio was 2500; then the pressure was rapidly increased to 2.0 MPa, and the reaction was carried out at 70 °C for 120 min. After cooling, the liquid product was analyzed by gas chromatography, and the selectivity for C4-C8 olefins was 58.45%. The catalytic activity was calculated to be 0.59 × 10⁻⁶ based on the amount of ethylene consumed. 5 g / mol Fe·h.

[0064] As can be seen from the above, the method of the present invention can selectively prepare C4-C8 olefins.

Claims

1. A method for preparing low-carbon-number olefins by ethylene oligomerization, comprising the following steps: Solvent, co-catalyst, and iron-based complex are added to the reactor, and the reaction is carried out for 15-60 minutes under the conditions of ethylene pressure of 1-3 MPa and reaction temperature of 60-80℃. After cooling, ethylene oligomerization product is obtained. The iron-based complex has 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; R2, R3, R4, R2', R3', and R4' may be the same or different, and each is independently selected from H, C1-C2 alkyl groups and their derivatives; M is a halogen.

2. The method according to claim 1, wherein, In Formula I, R1 and R1' may be the same or different, and each is independently selected from H, C1-C4 alkyl groups; R2, R3, R4, R2', R3', and R4' may be the same or different, and each is independently selected from H, C1-C2 alkyl groups.

3. The method according to claim 1, wherein, In Formula I, R1 and R1' are the same and are selected from H, methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl; R2, R3, R4, R2', R3', and R4' are the same and are selected from H, methyl, and ethyl.

4. The method according to claim 1, wherein, In Formula I, R1 and R1' may be the same or different, and each is independently selected from H or methyl; R2, R3, R4, R2', R3', and R4' may be the same or different, and each is independently selected from H or methyl.

5. The method according to claim 1, wherein, The preparation method of the iron-based complex includes the following steps: (1) The compound shown in Formula IV was prepared by reacting 2,6-diacylpyridine as shown in Formula II with the compound shown in Formula III under the conditions of catalyst A and solvent A. (2) The compound of formula IV obtained in step (1) was subjected to a coordination reaction under the conditions of iron halide and solvent B to obtain the compound of formula I. R1, R1', R2, R3, R4, R2', R3', and R4' in Formulas I to IV have the definitions corresponding to any one of claims 1 to 4; Catalyst A includes one or more of sulfuric acid, benzenesulfonic acid, and p-toluenesulfonic acid.

6. The method according to claim 5, wherein, In step (1), solvent A includes one or more of toluene, ethanol, and cyclohexane; And / or, in step (1), the reaction temperature is 80-140℃, the reaction time is 10-30h, and the reaction pressure is ≤0.1MPa.

7. The method according to claim 5, wherein, In step (2), the iron halide includes ferrous chloride and / or ferrous bromide; And / or, in step (2), the solvent B includes one or more of dichloromethane, toluene, cyclohexane, and methylcyclohexane; And / or, in step (2), the reaction temperature is 20-60℃, the reaction time is 60-240min, and the reaction pressure is ≤0.1MPa.

8. The method according to claim 1, wherein, The cocatalyst includes aluminum oxoalkane compounds; And / or, the solvent includes one or more of n-hexane, cyclohexane, n-heptane, toluene, dichloromethane, and methylcyclohexane.

9. The method according to claim 8, wherein, The molar ratio of Fe in the iron-based complex to Al in the co-catalyst is 1:200-3000.

10. The method according to claim 1, wherein, The mass percentage of C4-C8 olefins in the ethylene oligomer is ≥90%.

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