Ethylene non-selective oligomerization catalyst, its preparation method and application

Abstract

The application provides an ethylene non-selective oligomerization catalyst. The catalyst can be matched with an alkyl aluminum, an alkoxy aluminum and other cocatalysts commonly used in oligomerization to form a catalyst system, which catalyzes the oligomerization of ethylene. Due to the special steric hindrance effect of the tetrahedral center structure of the catalyst molecule, the stability of the active center can be protected during the non-selective oligomerization of ethylene, and the catalyst life and activity are improved. More importantly, the space structure can effectively limit the growth of active ethylene chains, so as to control the repeating units of the active ethylene chains within a certain range, avoid the formation of long carbon chains, and effectively reduce the generation of oligomeric waxy components, improve the content of short-chain alpha-olefins and prevent the generation of high molecular weight PE. The catalyst with high activity, high selectivity and no polymer generation has high industrial application value in the field of non-selective oligomerization of ethylene.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalyst technology, and particularly relates to an ethylene non-selective oligomerization catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] Linear alpha-olefins are important organic chemical raw materials and intermediates, C4-C8 alpha-olefins can be used as a comonomer for producing high-performance linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and polyolefin elastomer (POE), and C8-C24 alpha-olefins can be used as a raw material for producing high-end lubricating oil, plasticizer, surfactant and other fine chemicals. According to different processes, commercial linear alpha-olefin production technologies can be divided into wax cracking method, mixed C4 separation process, ethylene non-selective oligomerization process, ethylene selective oligomerization process, Fischer-Tropsch synthesis method (F-T) and vegetable oil method, etc. At present, more than 80% of linear alpha-olefins in the world are produced by ethylene selective oligomerization and non-selective oligomerization process, followed by Fischer-Tropsch synthesis method, except for the mixed C4 separation 1-butene process. The catalysts and oligomerization processes for ethylene selective oligomerization and non-selective oligomerization have become a research hotspot in recent years, and numerous patents and technical literatures have been reported, which will not be described here.

[0003] However, from the perspective of industrial application, regardless of which oligomerization process, high molecular weight PE polymers are inevitably produced in the long-period continuous industrial production process, which seriously affects the operation cycle and stability of the device, and also reduces the yield of the target product.

[0004] Therefore, it is necessary to develop a catalyst which, by molecular structure design, reduces or does not produce polymer by-products in the oligomerization process from the source of the oligomerization reaction mechanism, while also having high activity and high alpha-olefin selectivity, which is a problem to be solved in the research and development of alpha-olefins. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide an ethylene non-selective oligomerization catalyst as well as a preparation method and application thereof. The catalyst provided by the present application does not produce high polymer by-products in the catalytic ethylene non-selective oligomerization reaction, while also having high activity and high selectivity.

[0006] The present application provides an ethylene non-selective oligomerization catalyst, which has a structure shown in formula I:

[0007] Formula (I)

[0008] In formula (I), R1 is at least one of hydrogen and methyl;

[0009] R2 is at least one of ethyl, isopropyl, phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl, 4-trifluoromethylphenyl.

[0010] Preferably, R2 is at least one of 2-methylphenyl, 5-fluoro-2-methylphenyl, 4-tert-butylphenyl.

[0011] The application also provides a preparation method of the above catalyst, comprising the following steps:

[0012] A) heating and reacting tetraamine and bisacylpyridine in the presence of a catalyst to obtain a precursor;

[0013] B) heating and reacting the precursor with an organic amine in the presence of a catalyst to obtain a ligand;

[0014] C) mixing the ligand with anhydrous ferrous chloride under a protective atmosphere to obtain an ethylene non-selective oligomerization catalyst.

[0015] Preferably, in step A), the tetraamine is tetra(4-aminophenyl)methane;

[0016] The bisacylpyridine is at least one of 2,6-diacetylpyridine and 2,6-diformylpyridine;

[0017] The molar ratio of the tetraamine to the bisacylpyridine is 1:4-1:4.5;

[0018] The precursor has a structure shown in formula II:

[0019] Formula (II).

[0020] Preferably, in step A), the catalyst is selected from p-toluenesulfonic acid;

[0021] The mixing is performed in a solvent selected from toluene;

[0022] The heating reaction is a reflux reaction, and the heating reaction time is 8-24 h.

[0023] Preferably, in step B), the organic amine is ethylamine, isopropylamine, aniline, 2-methylaniline, 4-methylaniline, 2,4-dimethylaniline, 2,4,6-trimethylaniline, 2-ethyl aniline, 4-ethyl aniline, 2-isopropylaniline, 4-isopropylaniline, 4-tert-butylaniline, 2-fluoroaniline, 4-fluoroaniline, 2,4-difluoroaniline, 4-fluoro-2-methylaniline, 5-fluoro-2-methylaniline, 4-trifluoromethylaniline;

[0024] The molar ratio of the precursor to the organic amine is 1:4-1:4.5;

[0025] The ligand has a structure shown in formula (III):

[0026] Formula (III);

[0027] In formula (III), R1 is at least one of hydrogen and methyl;

[0028] R2 is at least one of ethyl, isopropyl, phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl, 4-trifluoromethylphenyl.

[0029] Preferably, in step B), the catalyst is selected from p-toluenesulfonic acid;

[0030] The mixing is performed in a solvent selected from toluene;

[0031] The heating reaction is a reflux reaction, and the heating reaction time is 12-36 h.

[0032] Preferably, in step C), the molar ratio of the ligand to anhydrous ferrous chloride is 1:4-1:4.2;

[0033] The protective atmosphere is selected from a nitrogen atmosphere;

[0034] The mixing is performed in a solvent selected from tetrahydrofuran;

[0035] The mixing time is 12-72 h.

[0036] The application also provides a use of the above-mentioned ethylene non-selective oligomerization catalyst in an ethylene non-selective oligomerization reaction.

[0037] Preferably, the ethylene non-selective oligomerization reaction comprises the following steps:

[0038] After the catalyst is dissolved in the solvent, a catalytic system is formed with the cocatalyst, and ethylene is non-selectively oligomerized to obtain an oligomerization liquid with a high content of alpha-olefins;

[0039] The catalyst and the cocatalyst are mixed in a molar ratio of Fe / Al=1:100-1:1000;

[0040] The cocatalyst is at least one selected from methylaluminoxane, modified methylaluminoxane, diethylaluminum chloride, ethylaluminum sesquichloride and triethylaluminum.

[0041] The oligomerization is carried out at a reaction pressure of 1-5 MPa, a temperature of 40-90 DEG C, a time of 30-90 minutes and a catalytic concentration Fe=1-10 μmol / L.

[0042] Compared with the prior art, the application provides an ethylene non-selective oligomerization catalyst. The catalyst is a four-nucleus bis-imine-iron complex with a space tetrahedral type, and four metal active centers are respectively located at four distal ends of the tetrahedral space structure. The catalyst can be matched with commonly used alkyl aluminum, alkoxy aluminum and other cocatalysts to form a catalyst system, and catalyze ethylene to carry out oligomerization reaction. Due to the special space steric hindrance effect of the tetrahedral type center structure of the catalyst molecule, the stability of the active center can be protected during the non-selective oligomerization of ethylene, and the catalyst life and activity are improved. More importantly, the space structure can effectively limit the growth of active ethylene chains, so as to control the repeating units of the active ethylene chains in a certain range, avoid the formation of long carbon chains, and effectively increase the content of short-chain alpha-olefins, and prevent the generation of high molecular weight PE. The catalyst with high activity, high selectivity and no polymer generation has high industrial application value in the field of ethylene non-selective oligomerization. DETAILED DESCRIPTION

[0043] The application provides an ethylene non-selective oligomerization catalyst with a structure shown in formula I.

[0044] Formula (I)

[0045] In formula (I), R1 is at least one of hydrogen and methyl;

[0046] R2 is at least one of ethyl, isopropyl, phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl and 4-trifluoromethylphenyl.

[0047] In some embodiments of the present application, R2 is at least one of 2-methylphenyl, 5-fluoro-2-methylphenyl, 4-tert-butylphenyl.

[0048] In some embodiments of the present application, the ethylene non-selective oligomerization catalyst is selected from

[0049] 、 or .

[0050] The present application also provides a preparation method of the above catalyst, comprising the following steps:

[0051] A) heating and reacting tetraamine and bisacylpyridine in the presence of a catalyst to obtain a precursor;

[0052] B) heating and reacting the precursor with an organic amine in the presence of a catalyst to obtain a ligand;

[0053] C) mixing the ligand with anhydrous ferrous chloride under a protective atmosphere to obtain an ethylene non-selective oligomerization catalyst.

[0054] Specifically, the present application first heats and reacts tetraamine and bisacylpyridine. The tetraamine is tetra(4-aminophenyl)methane;

[0055] The bisacylpyridine is at least one of 2,6-diacetylpyridine and 2,6-diformylpyridine;

[0056] The molar ratio of the tetraamine to the bisacylpyridine is 1:4-1:4.5, which can be 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, or any value between 1:4 and 1:4.5.

[0057] The precursor has the structure shown in formula II:

[0058] Formula (II).

[0059] The catalyst is selected from p-toluenesulfonic acid;

[0060] The mixing is carried out in a solvent, and the solvent is selected from toluene;

[0061] The heating reaction is a reflux reaction, and the heating reaction time is 8-24 h, which can be 8, 12, 16, 20, 24, or any value between 8 and 24 h.

[0062] After the heating reaction is completed, the solvent is removed, and then the precursor is obtained by methanol precipitation, washing, filtration, and drying.

[0063] After the precursor is obtained, the precursor is mixed with an organic amine and heated in the presence of a catalyst.

[0064] The organic amine is ethylamine, isopropylamine, aniline, 2-methylaniline, 4-methylaniline, 2,4-dimethylaniline, 2,4,6-trimethylaniline, 2-ethyl aniline, 4-ethyl aniline, 2-isopropylaniline, 4-isopropylaniline, 4-tert-butylaniline, 2-fluoroaniline, 4-fluoroaniline, 2,4-difluoroaniline, 4-fluoro-2-methylaniline, 5-fluoro-2-methylaniline, 4-trifluoromethylaniline.

[0065] The molar ratio of the precursor to the organic amine is 1:4 to 1:4.5, which can be 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, or any value between 1:4 and 1:4.5.

[0066] The ligand has a structure represented by formula (III):

[0067] Formula (III);

[0068] In formula (III), R1 is at least one of hydrogen and methyl;

[0069] R2 is at least one of ethyl, isopropyl, phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl, 4-trifluoromethylphenyl.

[0070] The catalyst is selected from p-toluenesulfonic acid;

[0071] The mixing is carried out in a solvent selected from toluene;

[0072] The heating reaction is a reflux reaction, and the heating reaction time is 12 to 36 hours, which can be 12, 18, 24, 30, 36, or any value between 12 and 36 hours.

[0073] After the heating reaction is completed, the solvent is removed, and then the ligand is precipitated, washed, filtered, and dried to obtain the ligand.

[0074] After the ligand is obtained, the ligand is mixed with anhydrous ferrous chloride under a protective atmosphere to obtain an ethylene non-selective oligomerization catalyst.

[0075] The molar ratio of the ligand to anhydrous ferrous chloride is 1:4-1:4.2, which can be 1:4, 1:4.1, 1:4.2, or any value between 1:4 and 1:4.2.

[0076] The protective atmosphere is selected from a nitrogen atmosphere.

[0077] In the present application, the mixing process is carried out under stirring, and the mixing is carried out in a solvent selected from tetrahydrofuran.

[0078] The mixing time is 12-72 hours, which can be 12, 24, 36, 48, 60, 72, or any value between 12 and 72 hours. The mixing temperature is a normal temperature condition, and in the present application, the normal temperature is defined as 25±5℃.

[0079] After the mixing and stirring are completed, filtration and negative pressure drying are carried out to obtain a tetranuclear bis-imine-iron complex, i.e. the ethylene non-selective oligomerization catalyst of the present application.

[0080] The present application also provides a use of the above-mentioned ethylene non-selective oligomerization catalyst in an ethylene non-selective oligomerization reaction.

[0081] The ethylene non-selective oligomerization reaction comprises the following steps:

[0082] After the catalyst is dissolved in the solvent, a catalytic system is formed with the cocatalyst, and the ethylene non-selective oligomerization is catalyzed to obtain an oligomerization liquid with a high content of α-olefin;

[0083] The catalyst and the cocatalyst are mixed at a molar ratio of Fe / Al=1:100-1:1000, preferably, the molar ratio of Fe / Al in the catalyst and the cocatalyst can be 1:100, 1:200, 1:300, 1:400, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, or any value between 1:100 and 1:1000.

[0084] The cocatalyst is selected from at least one of methylaluminoxane, modified methylaluminoxane, diethylaluminum chloride, ethylaluminum sesquichloride, and triethylaluminum; preferably, at least one of methylaluminoxane and modified methylaluminoxane.

[0085] The oligomerization reaction pressure is 1-5 MPa, which can be 1, 2, 3, 4, 5, or any value between 1-5 MPa, the temperature is 40-90℃, which can be 40, 50, 60, 70, 80, 90, or any value between 40-90℃, the time is 30-90 minutes, which can be 30, 40, 50, 60, 70, 80, 90, or any value between 30-90 minutes, the catalytic concentration Fe = 1-10 μmol / L, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 1-10 μmol / L.

[0086] The application provides an ethylene non-selective oligomerization catalyst. The catalyst is a tetranuclear bis-imine-iron complex with a space tetrahedral type, and four metal active centers are respectively located at four distal ends of the tetrahedral space structure. The catalyst can be matched with an alkyl aluminum or an alkoxy aluminum commonly used in oligomerization to form a catalyst system, and catalyzes ethylene to perform oligomerization. Due to the special space steric hindrance effect of the tetrahedral type center structure of the catalyst molecule, the stability of the active center can be protected during the ethylene non-selective oligomerization, and the catalyst life and activity are improved. More importantly, the space structure can effectively limit the growth of the active ethylene chain, so that the repeating units of the active ethylene chain are controlled within a certain range, the formation of long carbon chains is avoided, the effective gain effect is that the generation of oligomeric wax components is reduced, the content of short-chain alpha-olefin is increased, and the generation of high molecular weight PE is prevented. The catalyst with high activity, high selectivity and no polymer generation has high industrial application value in the field of ethylene non-selective oligomerization.

[0087] In order to further understand the application, the ethylene non-selective oligomerization catalyst provided by the application, the preparation method and application thereof are described below in combination with examples, and the protection scope of the application is not limited by the following examples.

[0088] Example 1

[0089] The complex catalyst tetranuclear bis-imine-iron S1 is prepared, and the synthesis route is as follows:

[0090]

[0091] (1) Synthesis of precursor-tetrahedral mono-imine S1-1. Tetra (4-aminophenyl) methane 7.61 g (20 mmol), 2,6-dimethylpyridine 11.08 g (82 mmol), and 0.1 g of p-toluenesulfonic acid are added to 50 ml of toluene, and refluxed for 10 h. The plate shows that tetra (4-aminophenyl) methane is completely reacted. Most of the toluene is removed by rotary evaporation, 200 ml of methanol is added, a large amount of yellow solid is precipitated, the solid is filtered and washed with methanol, and after vacuum drying, 12.11 g of yellow solid powder of S1-1 is obtained, with a yield of 71.32%.

[0092] (2) Synthesis of ligand-tetrahedral bisimine S1-2. The precursor S1-1 synthesized above 8.49 g (10 mmol), 2,4-dimethylaniline 5.09 g (42 mmol), and 0.1 g p-toluenesulfonic acid were added to 50 ml of toluene, and refluxed for 14 h. Spotting plate showed that the reaction of S1-1 was substantially complete. Most of the toluene was removed by rotary evaporation, 200 ml of methanol was added, a large amount of yellow solid was precipitated, the solid was filtered and washed with methanol, and dried under negative pressure to obtain S1-2 yellow solid powder 8.37 g, yield 66.34%.

[0093] S1-2 nuclear magnetic characterization analysis 1 HNMR (CDC13, 400 MHz): δ = 2.27 ~ 2.28 (s, 24H, CH3Ph); 6.93 ~ 7.06 (m, 12H, CH3Ph); 7.18 ~ 7.21 (m, 16H, C(Ph)4); 8.09 ~ 8.10 (m, 12H, C5H3N); 8.50 (s, 8H, CH=N).

[0094] (3) Synthesis of complex-tetranuclear bisimine-iron S1. In the glove box, the ligand S1-2 synthesized above 6.31 g (5 mmol) and anhydrous ferrous chloride 2.54 g (20 mmol) were added to 50 ml of tetrahydrofuran, and stirred at room temperature for 48 h. After filtration and drying under negative pressure, a dark blue tetranuclear bisimine-iron complex powder 8.43 g was obtained, yield 95.25%, which was the complex catalyst S1 of the embodiment.

[0095] Example 2

[0096] The complex catalyst tetranuclear bisimine-iron S2 was prepared, and the synthesis route was as follows:

[0097]

[0098] (1) Synthesis of precursor-tetrahedral monobisimine S2-1. Tetra (4-aminophenyl) methane 7.61 g (20 mmol), 2,6-diacetylpyridine 14.03 g (86 mmol), and 0.12 g p-toluenesulfonic acid were added to 50 ml of toluene, and refluxed for 12 h. Spotting plate showed that the reaction of tetra (4-aminophenyl) methane was substantially complete. Most of the toluene was removed by rotary evaporation, 200 ml of methanol was added, a large amount of yellow solid was precipitated, the solid was filtered and washed with methanol, and dried under negative pressure to obtain S2-1 yellow solid powder 16.35 g, yield 85.07%.

[0099] (2) Synthesis of ligand-tetrahedral bisimine S2-2. The S2-1 precursor synthesized above 9.61 g (10 mmol), 5-fluoro-2-methylaniline 5.38 g (43 mmol), and 0.1 g p-toluenesulfonic acid were added to 50 ml of toluene, and refluxed for 24 h. Spotting plate showed that the reaction of S2-1 was substantially complete. Most of the toluene was removed by rotary evaporation, 200 ml of methanol was added, a large amount of yellow solid was precipitated, the solid was filtered and washed with methanol, and dried under negative pressure to obtain 11.22 g of S2-2 yellow solid powder, with a yield of 80.72%.

[0100] NMR characterization analysis of S2-2 1 HNMR (CDC13, 400 MHz): δ = 1.81 (s, 24H, CH3C=N); 2.31 (s, 12H, CH3Ph); 6.82~7.14 (m, 12H, FPh); 7.18~7.21 (m, 16H, C(Ph)4); 8.11~8.20 (m, 12H, C5H3N).

[0101] (3) Synthesis of complex-tetranuclear bisimine-iron S2. In the glove box, the S2-2 ligand synthesized above 6.95 g (5 mmol) and anhydrous ferrous chloride 2.54 g (20 mmol) were added to 50 ml of tetrahydrofuran, and stirred at room temperature for 60 h. After filtration and drying under negative pressure, 9.31 g of dark blue tetranuclear bisimine-iron complex powder was obtained, with a yield of 98.17%, which was the complex catalyst S2 of the present embodiment.

[0102] Example 3

[0103] The complex catalyst tetranuclear bisimine-iron S3 was prepared, and the synthesis route was as follows:

[0104]

[0105] (1) Synthesis of ligand-tetrahedral bisimine S3-2. The S2-1 precursor synthesized in Example 2 9.61 g (10 mmol), p-tert-butylaniline 6.12 g (41 mmol), and 0.1 g p-toluenesulfonic acid were added to 50 ml of toluene, and refluxed for 30 h. Spotting plate showed that there was no S2-1 left. Most of the toluene was removed by rotary evaporation, 200 ml of methanol was added, a large amount of light yellow solid was precipitated, the solid was filtered and washed with methanol, and dried under negative pressure to obtain 10.89 g of S3-2 yellow solid powder, with a yield of 73.28%.

[0106] NMR characterization analysis of S3-2 1HNMR (CDC13, 400 MHz): δ = 1.33 (s, 36H, C(CH3)3); 1.81 (s, 24H, CH3C=N); 7.14, 7.31 (m, 16H, (CH3)3CPh), 7.18, 7.21 (m, 16H, C(Ph)4), 8.11 ~ 8.20 (m, 12H, C5H3N).

[0107] (2) Synthesis of complex - tetranuclear diimine-iron S3. In the glove box, the S3-2 ligand synthesized above 7.43 g (5 mmol), anhydrous ferrous chloride 2.54 g (20 mmol) were added to 50 ml of tetrahydrofuran, after stirring at room temperature for 60 h, filtration and negative pressure drying, the dark blue tetranuclear diimine-iron complex powder 8.71 g was obtained, the yield was 87.41%, namely the complex catalyst S3 of the embodiment.

[0108] Example 4

[0109] The complex S1, S2, S3 prepared in the above examples 1-3 were prepared into catalyst solutions, and ethylene non-selective oligomerization reaction was carried out, and the specific content was as follows:

[0110] (1) Preparation of catalyst solution:

[0111] In the glove box, the complex S1, S2, S3 prepared in the above examples 1-3 were prepared into catalyst suspensions with Fe concentration of 2 μmol / ml, which were used as main catalysts for ethylene non-selective oligomerization reaction, and were placed in the glove box for standby.

[0112] (2) Continuous ethylene non-selective oligomerization experiment process:

[0113] Continuous ethylene non-selective oligomerization experiments were carried out on the ethylene non-selective oligomerization catalysts S1, S2, S3 prepared in the above examples 1-3, and the reaction parameters, co-catalysts, raw materials and the like were the same except for the different catalysts. Purified cyclohexane (water and oxygen content <5 ppm) was used as the solvent, and modified methylaluminoxane (MMAO-3A, Akzo Nobel Middle East FZE) was used as the co-catalyst. The solvent, the diluted main catalyst and the co-catalyst were continuously injected into the reaction kettle through the metering pump; the feeding amount of the solvent and the catalyst was controlled through the metering pump, so that the catalyst concentration (the mass of the main catalyst Fe per hour fed into the kettle / the liquid volume fed into the kettle) maintained 5 μmol / L, the aluminum-iron ratio = 800, and the residence time was 1 h; the feeding amount of ethylene was controlled through the gas flow meter, so that the pressure in the kettle maintained 3.0 MPa; the temperature of the reaction kettle was controlled through the kettle jacket and the kettle pipe, and the reaction was maintained at 55-60 ℃.

[0114] The non-selective oligomerization of ethylene occurs in the reactor, the reaction liquid continuously flows into the buffer tank through the overflow pipe at the upper part of the reactor, the metered quenching agent is continuously pumped into the buffer tank to quench the catalyst in the reaction liquid, the oligomerization reaction is stopped, and the reaction liquid is automatically discharged to the flash tank through the bottom valve to maintain the liquid level of the buffer tank; the reaction liquid is discharged into the receiving tank after the dissolved ethylene is flashed out in the flash tank. Each catalyst is subjected to continuous oligomerization for 12 hours.

[0115] After the reaction is completed, the main catalyst is metered into the device; the liquid weight gain (excluding the mass of the quenching agent) is metered into the device; all the PE polymers generated in the reaction, including the PE filtered out of the reaction liquid and the attached PE polymers cleaned from the reactor, are metered; the gas flashed out of the flash tank and the reaction liquid are subjected to gas chromatography analysis, respectively; the catalyst activity, the distribution of different carbon number olefins generated in the reaction, and the proportion of PE polymers are calculated. The experimental results are shown in Table 1.

[0116] Comparative example

[0117] The corresponding single-core catalysts B1, B2 and B3 are prepared respectively corresponding to S1, S2 and S3, and the structural formulae are as follows:

[0118]

[0119] The procedure of Example 4 is repeated, and the single-core catalysts B1, B2 and B3 are subjected to continuous non-selective oligomerization of ethylene, and the experimental results are shown in Table 1.

[0120] Table 1

[0121]

[0122] From the above continuous non-selective oligomerization results, under the same process conditions, the tetrahedral four-core catalysts prepared in Examples 1-3 and the single-core catalysts prepared in the comparative example have greatly improved activity, no PE polymer is generated, the carbon number of the product is widely distributed, the distribution of each carbon number remains basically unchanged, and the selectivity of α-olefin is slightly improved. This shows that the special steric hindrance of the tetrahedral center structure of the catalyst prepared in the present application can protect the stability of the active center in the non-selective oligomerization of ethylene, prolong the service life of the catalyst, and thus improve the activity. A particularly outstanding point is that this spatial structure effectively limits the growth of active ethylene chains, thereby controlling the repeating units of the active ethylene chain within a certain range, avoiding the formation of long carbon chains, reducing the generation of oligomeric wax components, improving the content of short-chain α-olefins, and preventing the generation of high molecular weight PE polymers, which has great practical significance for continuous industrial production.

[0123] From the above examples, the application provides an ethylene non-selective oligomerization catalyst and its preparation method and application. The catalyst is a tetranuclear imine-iron complex, and four active centers are respectively located at four distal ends of a tetrahedral spatial structure. The catalyst can be matched with common alkyl aluminum, alkoxy aluminum and other cocatalysts to catalyze the oligomerization of ethylene. The unique spatial structure of the catalyst molecule is microcosmic, so that it has the characteristics of high activity, high selectivity and no polymer by-product, and the catalytic activity of ethylene non-selective oligomerization is >7500 kg / gFe.h, the alpha-olefin selectivity is >97%, the carbon number of the oligomerization product is wide distribution, and the PE polymer by-product is 0. The catalyst of the application has high industrial application value.

[0124] The above only describes the preferred embodiments of the application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. An ethylene non-selective oligomerization catalyst characterized in that, having the structure of formula I: Formula (I) In formula (I), R1 is at least one of hydrogen and methyl; R2 is at least one of phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl, and 4-trifluoromethylphenyl.

2. The catalyst according to claim 1, characterized in that, R2 is at least one of 2-methylphenyl, 5-fluoro-2-methylphenyl, and 4-tert-butylphenyl.

3. A process for the preparation of a catalyst as claimed in claim 1 or 2, characterized in that, comprising the following steps: A) heating a quaternary amine and a bisacylpyridine in the presence of a catalyst to obtain a precursor, wherein the catalyst is selected from p-toluenesulfonic acid, the quaternary amine is tetra(4-aminophenyl)methane, and the bisacylpyridine is at least one of 2,6-diacetylpyridine and 2,6-diformylpyridine; B) heating the precursor and an organic amine in the presence of a catalyst to obtain a ligand; The precursor has the structure of formula II: Formula (II); C) mixing the ligand and anhydrous ferrous chloride under a protective atmosphere to obtain an ethylene non-selective oligomerization catalyst.

4. The production method according to claim 3, characterized by, In step A), the molar ratio of the quaternary amine to the bisacylpyridine is 1:4 to 1:4.

5.

5. The preparation method according to claim 3, characterized in that, In step A), the mixing is performed in a solvent selected from toluene. The heating is a reflux reaction, and the heating time is 8 to 24 hours.

6. The preparation method according to claim 3, characterized in that, In step B), the organic amine is at least one of aniline, 2-methylaniline, 4-methylaniline, 2,4-dimethylaniline, 2,4,6-trimethylaniline, 2-ethylaniline, 4-ethylaniline, 2-isopropylaniline, 4-isopropylaniline, 4-tert-butylaniline, 2-fluoroaniline, 4-fluoroaniline, 2,4-difluoroaniline, 4-fluoro-2-methylaniline, 5-fluoro-2-methylaniline, and 4-trifluoromethylaniline. The molar ratio of the precursor to the organic amine is 1:4 to 1:4.

5. The ligand has the structure of formula (III): Formula (III); In formula (III), R1 is at least one of hydrogen and methyl; R2 is at least one of phenyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,4,6-trimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl, 2-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 4-fluoro-2-methylphenyl, 5-fluoro-2-methylphenyl, and 4-trifluoromethylphenyl.

7. The preparation method according to claim 3, characterized in that, In step B), the catalyst is selected from p-toluenesulfonic acid. The mixing is performed in a solvent selected from toluene. The heating is a reflux reaction, and the heating time is 12 to 36 hours.

8. The preparation method according to claim 3, characterized in that, In step C), the molar ratio of the ligand to the anhydrous ferrous chloride is 1:4 to 1:4.

2. The protective atmosphere is selected from a nitrogen atmosphere. The mixing is performed in a solvent selected from tetrahydrofuran. The mixing time is 12 to 72 hours.

9. Use of the non-selective ethylene oligomerization catalyst according to claim 1 or 2 in non-selective ethylene oligomerization reaction.

10. Use according to claim 9, characterized in that, The non-selective ethylene oligomerization reaction comprises the following steps: After the catalyst is dissolved in the solvent, the catalyst and the cocatalyst are mixed to form a catalytic system, and the non-selective ethylene oligomerization is catalyzed to obtain an oligomerization liquid with a high content of α-olefin; The catalyst and the cocatalyst are mixed at a molar ratio of Fe / Al = 1:100-1:1000; The cocatalyst is at least one selected from methylaluminoxane, modified methylaluminoxane, diethylaluminum chloride, ethylaluminum sesquichloride and triethylaluminum; The reaction pressure of the oligomerization is 1-5 MPa, the temperature is 40-90°C, the time is 30-90 minutes, and the catalytic concentration Fe is 1-10 μmol / L.

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