Superparamagnetic supported ethylene oligomerization catalyst and preparation and fluidized bed reaction system thereof

Abstract

The present invention relates to a superparamagnetic supported ethylene oligomerization catalyst, which comprises a superparamagnetic carrier and an oligomerization catalytic active component, the mass percentage of the superparamagnetic carrier is 98-99.8%, and the mass percentage of the oligomerization catalytic active component is 0.2-2%, based on the total mass of the catalyst. The invention further relates to preparation of the catalyst and a fluidized bed reaction system using the catalyst. The system can realize efficient oligomerization of ethylene, greatly improve the yield and selectivity of alpha olefin, and effectively solve the problems of low catalyst recovery and reaction efficiency in the prior art.

Description

Technical Field

[0001] The invention belongs to the field of olefin polymerization catalysis and relates to a superparamagnetic supported ethylene polymerization catalyst. The invention further relates to the preparation of the catalyst and a fluidized bed reaction system. Background Art

[0002] Low-carbon olefins are widely used in the fields of chemical industry, plastic manufacturing, lubricant additives, etc. Among them, linear α-olefins are important basic chemical raw materials, mainly used as high-grade polyethylene comonomers, and are also the basic raw materials for high-value-added products such as high-carbon alcohols, plasticizer alcohols, surfactants, synthetic lubricants, lubricant additives, and oilfield chemicals. They are widely used in the fields of oil refining, chemical industry, oilfield chemistry, and fine chemistry. Among them, C4~C18 straight-chain α-olefins are widely used, and the most widely used are C4, C6 and C8 components. At present, about 83% of α-olefins are used as polyolefin comonomers, 9% are used to produce α-olefin sulfonates / surfactants, and about 3% are used to produce polyα-olefins. In the next few years, the global production and demand of α-olefins will rise sharply, and it is expected to exceed 8 million tons in 2027.

[0003] Ethylene oligomerization is an important industrial process for producing low-carbon olefins. Traditional ethylene oligomerization usually uses fixed bed or continuous flow reactors. These methods have low catalyst activity, low product selectivity, and low heat and mass transfer efficiency. After the oligomerization catalyst is loaded, it is beneficial to control the kinetics of the polymerization process, improve the heat resistance of the catalyst, and improve the selectivity of α-olefins, which is suitable for industrial applications. After the homogeneous catalyst is loaded, the use of a small amount of co-catalyst can greatly improve the catalytic activity and reduce the production cost. However, the homogeneous ethylene oligomerization catalyst performs ethylene oligomerization at low temperature, the product distribution is wide, and separation is inconvenient.

[0004] CN101376113A provides a molecular sieve-supported ethylene polymerization catalyst and its preparation and application. The catalyst uses MCM-41 or SBA-15 molecular sieve as a carrier and is prepared by constant temperature stirring adsorption to obtain a supported ethylene polymerization catalyst. However, there are problems such as difficulty in catalyst recovery and loss of active components.

[0005] CN106492880B relates to a catalyst for ethylene oligomerization and a preparation method thereof, wherein the main catalyst is carried out on a molecular sieve, chemically bonded with a silanol group on the surface of the molecular sieve and a bis(diphenylphosphine)amine ligand containing a silanol group, and then complexed with a chromium active component to obtain an ethylene oligomerization catalyst. However, the catalyst has problems such as loss of active components and difficulty in catalyst separation.

[0006] CN117181311A discloses a method for preparing linear alpha-olefins by ethylene polymerization, wherein a transition metal is loaded on a molecular sieve by ion exchange, and the transition metal in a first valence state is reduced to a transition metal salt in a second valence state by an active metal additive, wherein the second valence state is lower than the first valence state, to obtain a catalyst. The catalyst needs to be used in a fixed bed, has a high operating pressure, and has poor mass transfer performance of reactants and products on the catalyst surface.

[0007] In view of the problems existing in the prior art, the present invention provides a superparamagnetic supported ethylene oligomerization catalyst. The addition of an organic nitrogen-containing ligand as an electron donor and steric hindrance control can improve the chain length selectivity of α-olefins, and at the same time, a chelate coordination can be formed to enhance the catalytic stability. The catalyst has high activity, high selectivity and good recyclability in the ethylene oligomerization reaction. The fluidized bed reaction system using the catalyst realizes efficient dispersion and fluidization of the catalyst by controlling the magnetic field, and significantly improves the yield and selectivity of light olefins. Summary of the invention

[0008] The present invention aims to provide a superparamagnetic supported ethylene polymerization catalyst, which has high activity, high selectivity and good recyclability in ethylene polymerization reaction and significantly improves the yield and selectivity of light olefins.

[0009] A superparamagnetic supported ethylene polymerization catalyst comprises a superparamagnetic carrier and a polymerization catalytic active component, wherein the mass percentage of the superparamagnetic carrier is 80-99.5%, and the mass percentage of the polymerization catalytic active component is 0.5-20%, based on the total mass of the catalyst.

[0010] The superparamagnetic carrier can be selected from superparamagnetic organic microspheres, superparamagnetic molecular sieves or superparamagnetic metal oxides. These materials have good magnetic properties and specific surface areas and can provide sufficient catalytic reaction active sites.

[0011] The superparamagnetic organic microspheres include polystyrene microspheres, polyacrylonitrile microspheres, and iron oxide / silicon oxide composite magnetic microspheres. The superparamagnetic molecular sieves may be selected from, for example, superparamagnetic Y molecular sieves and superparamagnetic MCM-41 molecular sieves. The superparamagnetic metal oxides include, for example, superparamagnetic aluminum oxides.

[0012] The oligomerization catalytic active component is an organic nitrogen ligand, which can be selected from one or more of diphenylphosphine amine, 1,2,3-triazole, 1,2,4-triazole and terpyridine (2,2':6',2"-terpyridine).

[0013] The superparamagnetic catalyst has a magnetization intensity ranging from 5 to 90 emu / g, preferably ranging from 20 to 80 emu / g.

[0014] The present invention further relates to a method for preparing the superparamagnetic supported ethylene oligomerization catalyst, which comprises the following steps:

[0015] (1) Under nitrogen protection, the superparamagnetic carrier is vacuum dried to remove surface moisture and other impurities;

[0016] (2) Under nitrogen protection, the vacuum-dried superparamagnetic carrier is reacted with an organic nitrogen ligand in an organic solvent, and the organic nitrogen ligand is uniformly grafted onto the surface of the superparamagnetic carrier through chemical bonding to obtain a supported superparamagnetic ethylene oligomerization catalyst;

[0017] In step (2), the reaction is carried out under reflux at a temperature of 80° C. to 120° C. for 2 to 8 hours. By controlling the reaction time and temperature, the loading amount of the ligand can be adjusted and the surface chemical properties of the catalyst can be optimized.

[0018] The organic solvent may be selected from benzene or toluene.

[0019] The mass percentage of the superparamagnetic carrier is 80-99.5%, and the mass percentage of the oligomerization catalytic active component is 0.5-20%, based on the total mass of the catalyst.

[0020] (3) Applying an external magnetic field for separation, washing with an appropriate amount of toluene three times to obtain a superparamagnetic supported catalyst precursor, wherein the external magnetic field strength of the external magnetic field device is 10 to 2000 kA / m.

[0021] (4) Under nitrogen protection, the chromium chloride and the obtained catalyst precursor are added to toluene, reacted at 50° C.-120° C. for 12 hours, subjected to magnetic separation, washed with toluene three times and vacuum dried to obtain a superparamagnetic supported catalyst.

[0022] Wherein, in this step (4), the organic solvent is benzene or toluene.

[0023] The mass ratio of the chromium-containing chloride to the catalyst precursor is 1:100 to 1:5.

[0024] The chromium chloride may be selected from at least one of chromium trichloride, chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride and di(tetrahydrofuran)chromium dichloride.

[0025] The present invention further relates to the application of the superparamagnetic supported ethylene oligomerization catalyst in ethylene oligomerization reaction. Using the superparamagnetic supported ethylene oligomerization catalyst according to the present invention, the content of α-olefins prepared can reach more than 90%.

[0026] The present invention further relates to a fluidized bed reaction system, characterized in that: the system comprises a fluidized bed reactor, an external magnetic field device, a reaction condition control system and a catalyst recovery device, wherein the fluidized bed reactor is equipped with an ethylene gas inlet and a product outlet, a fluidized bed layer is arranged inside the reactor, and the fluidized bed layer is loaded with the superparamagnetic catalyst of the present invention.

[0027] The external magnetic field device, reaction condition control system and catalyst recovery device are respectively connected to the fluidized bed reactor.

[0028] The fluidized bed reactor can be selected from a suitable type of fluidized bed reactor as required.

[0029] Preferably, in the fluidized bed, the superparamagnetic supported ethylene oligomerization catalyst is used as a main catalyst and is used in combination with an alkyl aluminum co-catalyst.

[0030] The mass ratio of the co-catalyst to the main catalyst is 20:1 to 80:1.

[0031] The co-catalyst is an alkyl aluminum, preferably one or a mixture of trimethyl aluminum, triethyl aluminum, trichloromethyl chloride, and trichloroethyl aluminum.

[0032] The external magnetic field device has an external magnetic field strength of 10 to 2000 kA / m. By adjusting the strength and direction of the magnetic field, the distribution and fluidization state of the catalyst in the reactor can be controlled to achieve fluidization of the reaction system. The dynamic regulation of the magnetic field makes the catalyst evenly dispersed in the fluidized bed and ensures sufficient contact between the catalyst and the ethylene gas, thereby improving the reaction efficiency. After the reaction is completed, the catalyst can be quickly separated and recovered by the external magnetic field for reuse.

[0033] The reaction condition control system includes a temperature control system, a pressure control system and a reaction space velocity control system, wherein the reaction temperature is usually controlled at 70°C-130°C, the pressure is controlled at 0.1MPa-5MPa, and the reaction space velocity is controlled at 0.2h -1 ~8h -1 .

[0034] The fluidized bed reactor can achieve continuous operation.

[0035] The superparamagnetic supported catalyst of the present invention can be used again for reaction after simple treatment, thereby greatly improving the economy and sustainability of the fluidized bed reaction system.

[0036] The superparamagnetic supported catalyst of the present invention has high activity, high selectivity and good recyclability in ethylene oligomerization reaction, can significantly improve the yield of light olefins, and reduce the amount of by-products generated. At the same time, the fluidized bed reaction system using the catalyst controls the fluidization state of the catalyst through a magnetic field, effectively improving the mass transfer and heat transfer efficiency of the reaction. The fluidized bed reaction system can also realize the recycling of the catalyst, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a flow chart for preparing the superparamagnetic ethylene polymerization catalyst.

[0038] Figure 2 This is the hysteresis curve of the magnetic aluminum oxide of Example 1.

[0039] Figure 3 This is a scanning electron microscope photograph of the superparamagnetic carrier of Example 1.

[0040] Figure 4 is a scanning electron microscope photograph of the superparamagnetic catalyst of Example 3, wherein Figure a is a scanning electron microscope photograph of the entire superparamagnetic catalyst, Figure 4 b is a scanning electron microscope photograph of a single particle of the superparamagnetic catalyst of Example 3.

[0041] Figure 5 It is the effect of reaction temperature on the distribution of oligomerization products. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific embodiments. The embodiments are merely illustrative and do not constitute any limitation to the present invention. Various modifications may be made within the technical concept of the present invention. According to the teachings of the present invention, all changes or modifications obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1: Preparation of superparamagnetic alumina-supported chromium-based catalyst and ethylene oligomerization reaction

[0044] (1) Preparation of catalyst:

[0045] 1.0 g of superparamagnetic alumina carrier was added to 50 mL of toluene, and then 0.05 g of diphenylphosphine ligand was added, and the mixture was refluxed at 90° C. for 4 hours under nitrogen protection. After the reaction, the carrier was separated by magnetic separation, washed with toluene 3 times, and vacuum dried at 120° C. for 6 hours to obtain a treated carrier.

[0046] 0.1 g of chromium trichloride was dissolved in 10 mL of toluene, and the treated carrier was added, and the reaction was continued at 50° C. for 12 hours. Then, a magnetic field with an intensity of 500 kA / m was applied for magnetic separation, washing and vacuum drying to obtain a superparamagnetic alumina-supported chromium-based catalyst.

[0047] (2) Ethylene polymerization reaction:

[0048] 1.0 g of the above-prepared catalyst was added to the fluidized bed reactor of the fluidized bed reaction system of the present application as the main catalyst, trimethylaluminum was used as the co-catalyst, the mass ratio of the co-catalyst to the main catalyst was 30:1, ethylene gas was introduced through the ethylene gas inlet, and the reaction temperature was controlled to be 80° C., the pressure was 1.0 MPa, and the space velocity was 1.0 h / min by the temperature control system, the pressure control system, and the reaction space velocity control system. -1 After 4 hours of reaction, the light olefin products were collected through the product outlet, and a magnetic field with a strength of 500 kA / m was applied by an external magnetic field device to separate and recover the catalyst, and collect the polymerization products. Product analysis showed that the α-olefin content was 92%. The catalyst recovery rate was not less than 99%.

[0049] Example 2: Preparation of superparamagnetic molecular sieve supported nickel-based catalyst and ethylene oligomerization reaction

[0050] (1) Preparation of catalyst:

[0051] The superparamagnetic Y molecular sieve was vacuum dried at 120°C for 2 hours, 0.05g of 1,2,3-triazole ligand was added, and stirred for 6 hours under nitrogen protection. Then it was immersed in 5ml of 0.1mol / L chromium trichloride solution and stirred at 60°C for 12 hours. The impregnated molecular sieve was removed and calcined at 120°C for 5 hours under nitrogen protection to obtain a superparamagnetic molecular sieve supported nickel-based catalyst.

[0052] (2) Ethylene polymerization reaction:

[0053] In the fluidized bed reactor of the fluidized bed reaction system of the present application, 0.5 g of the above catalyst as the main catalyst and 30 g of triethylaluminum as the co-catalyst were added, the mass ratio of the co-catalyst to the main catalyst was 50:1, ethylene gas was introduced, the reaction temperature was controlled at 100 ° C, the pressure was 2.0 MPa, and the space velocity was 2.0 h 1 The reaction lasted for 3 hours, and a magnetic field with a strength of 800 kA / m was applied to quickly separate and recover the catalyst, and the polymerization product was collected. Product analysis showed that the α-olefin content was 91%. The catalyst recovery rate was not less than 99%.

[0054] Example 3: Preparation of superparamagnetic organic microspheres supported on titanium-based catalyst and ethylene oligomerization reaction

[0055] (1) Preparation of catalyst:

[0056] 10g of superparamagnetic polystyrene organic microspheres were dispersed in 50ml of toluene solution containing terpyridine, the weight ratio of superparamagnetic organic microspheres to terpyridine was 10:100, and refluxed at 80°C for 6 hours under vacuum. After the reaction, the treated carrier was obtained by magnetic separation, and then reacted with 50ml of chromium isooctanoate aqueous solution with a mass concentration of 5% in a nitrogen environment at 80°C for 8 hours. A 600kA / m magnetic field was applied for magnetic separation, washing and drying to obtain a superparamagnetic supported titanium-based catalyst.

[0057] (2) Ethylene polymerization reaction:

[0058] The above magnetic ethylene polymerization catalyst was added into the fluidized bed reactor as the main catalyst, triethylaluminum as the co-catalyst, the ratio of the co-catalyst to the main catalyst was 30:1, the reaction temperature was set at 90 °C, the pressure was 1.5 MPa, and the space velocity was 1.5 h -1 The reaction was carried out for 5 hours, and an external magnetic field with a strength of 600 kA / m was applied to separate and recover the catalyst and collect the polymerization product, the α-olefin content in the product reached 95%. The catalyst recovery rate was above 98%.

[0059] Example 4: Preparation of superparamagnetic alumina-supported iron-based catalyst and ethylene oligomerization reaction

[0060] (1) Preparation of catalyst:

[0061] 5g of superparamagnetic alumina was vacuum dried and reacted with 0.5g of 1,2,4-triazole ligand dissolved in 20ml of toluene at 80°C for 6 hours. After the reaction was completed, magnetic separation and washing were performed to obtain the treated carrier, which was then reacted with 20ml of 10% chromium trichloride aqueous solution at 60°C for 12 hours. The superparamagnetic alumina-supported iron-based catalyst was obtained by magnetic separation, toluene washing and vacuum drying at 80°C for 6 hours.

[0062] (2) Ethylene polymerization reaction:

[0063] 0.8 g of the above catalyst was added to the fluidized bed reactor, trichloromethyl chloride was used as a co-catalyst, the mass ratio of the co-catalyst to the main catalyst was 50:1, and ethylene gas was introduced. The reaction temperature was set to 110 ° C, the pressure was 3.0 MPa, and the space velocity was 0.5 h -1 After the reaction was carried out for 4 hours, a magnetic field with an intensity of 1000 kA / m was applied to separate and recover the catalyst, and the polymerization product was collected. Product analysis showed that the α-olefin content was 90% and the catalyst recovery rate was more than 99%.

[0064] The results of the examples show that the superparamagnetic supported catalyst of the present invention can significantly improve the yield and selectivity of light olefins in the ethylene polymerization reaction. The selectivity results for the product components above C4, C6, C8 and C10 in the ethylene polymerization reaction of each example are shown in Table 1.

[0065] Table 1

[0066] .

Claims

1. A superparamagnetic supported ethylene polymerization catalyst, comprising a superparamagnetic carrier and a polymerization catalytic active component, wherein the mass percentage of the superparamagnetic carrier is 80-99.5%, and the mass percentage of the polymerization catalytic active component is 0.5-20%, based on the total mass of the catalyst.

2. The superparamagnetic supported ethylene oligomerization catalyst according to claim 1, characterized in that: The superparamagnetic carrier is selected from superparamagnetic organic microspheres, superparamagnetic molecular sieves or superparamagnetic metal oxides, and the oligomerization catalytic active component is an organic nitrogen ligand.

3. The superparamagnetic supported ethylene oligomerization catalyst according to claim 2, characterized in that: The organic nitrogen ligand is selected from one or more of diphenylphosphine amine, 1,2,3-triazole, 1,2,4-triazole and terpyridine.

4. A method for preparing a superparamagnetic supported ethylene oligomerization catalyst according to any one of claims 1 to 3, comprising the steps of: (1) Under nitrogen protection, the superparamagnetic carrier is vacuum dried to remove surface moisture and other impurities; (2) Under nitrogen protection, the vacuum-dried superparamagnetic carrier of step (1) is reacted with an organic nitrogen ligand in an organic solvent, and the organic nitrogen ligand is uniformly grafted onto the surface of the superparamagnetic carrier by chemical bonding to obtain a supported superparamagnetic ethylene oligomerization catalyst; (3) applying an external magnetic field for separation, washing with toluene, and obtaining a superparamagnetic supported ethylene oligomerization catalyst precursor; (4) Under nitrogen protection, add the chromium chloride and the catalyst precursor obtained in step (3) into an organic solvent, react at 50° C.-120° C. for 12 hours, perform magnetic separation, wash and vacuum dry to obtain a superparamagnetic supported ethylene polymerization catalyst.

5. The method according to claim 4, characterized in that: In step (2), the weight ratio of the organic nitrogen ligand to the superparamagnetic carrier is 0.5:100 to 20:100; the reaction is refluxed at a temperature of 80°C to 120°C for 2 to 8 hours; in step (4), the mass ratio of the chromium-containing chloride to the catalyst precursor is 1:100 to 1:

5.

6. The method according to claim 4, characterized in that: In step (4), the chromium-containing chloride is selected from at least one of chromium trichloride, chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride or di(tetrahydrofuran)chromium dichloride.

7. Use of the superparamagnetic supported ethylene oligomerization catalyst according to any one of claims 1 to 3 in ethylene oligomerization reaction.

8. A fluidized bed reaction system, characterized in that: The fluidized bed reaction system comprises a fluidized bed reactor, an external magnetic field device, a reaction condition control system and a catalyst recovery device; wherein the fluidized bed reactor is equipped with an ethylene gas inlet and a product outlet, a fluidized bed layer is arranged inside the reactor, and the fluidized bed layer is equipped with the superparamagnetic supported ethylene polymerization catalyst according to any one of claims 1 to 3; the reaction condition control system comprises a temperature control system, a pressure control system and a reaction space velocity control system.

9. The fluidized bed reaction system according to claim 8, characterized in that: In the fluidized bed, the superparamagnetic supported ethylene polymerization catalyst is used in combination with an alkyl aluminum co-catalyst; the mass ratio of the alkyl aluminum co-catalyst to the superparamagnetic supported ethylene polymerization catalyst is 20:1 to 80:

1.

10. The fluidized bed reaction system according to claim 9, characterized in that: The alkyl aluminum co-catalyst is one or a mixture of trimethyl aluminum, triethyl aluminum, trichloromethyl chloride, and trichloroethyl aluminum.

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