CN113444127B

CN113444127B - Three-tooth type iron complex and heat-resistant stable supported iron catalyst

Info

Publication number: CN113444127B
Application number: CN202110665748.3A
Authority: CN
Inventors: 张丽平; 孙文华; 付少海; 林文华
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2021-06-16
Filing date: 2021-06-16
Publication date: 2022-08-02
Anticipated expiration: 2041-06-16
Also published as: CN113444127A

Abstract

The invention discloses a tridentate iron complex and a heat-resistant stable supported iron catalyst, and belongs to the technical field of polyolefin catalysts. The invention utilizes specific diimine pyridine ligand and iron coordination to obtain the tridentate iron complex, and the tridentate iron complex is loaded on an inorganic carrier, and the regulation and control of a micro molecular structure can be realized by adjusting polymerization conditions, so that the invention has the advantages of high catalytic activity, good heat-resistant stability and the like, and has a wide application prospect in industrial production.

Description

Three-tooth type iron complex and heat-resistant stable supported iron catalyst

Technical Field

The invention belongs to the technical field of polyolefin catalysts, and particularly relates to a tridentate iron complex and a heat-resistant stable supported iron catalyst.

Background

The development of olefin polymerization catalysts was a great creation in the 20 th century, and has directly led to a material revolution, namely the use of plastics. Currently, olefin catalysts have been developed for decades, with ziegler-natta catalysts, philips catalysts, and metallocene catalysts all being used commercially. Late transition metal catalysts, which have been gradually developed in the late 90 s of the last century, are expected to be olefin catalysts for next-generation industrial applications by virtue of their excellent catalytic performance. Among the late transition metal catalysts, iron metal is relatively cheap and easily available, and shows extremely high catalytic activity, so that the high-efficiency catalyst for preparing linear polyethylene is expected to be the catalyst for industrial application of the late transition metal catalyst at the earliest time. However, like other late transition metal catalysts, iron catalysts suffer from high temperature deactivation, which prevents further industrial application. The former analysis of the decrease in the high-temperature activity of the iron catalyst revealed that the decrease in the activity of the iron catalyst may be caused by: 1) at high temperature, the aromatic imine group on the ligand of the iron complex is easy to rotate, and hydrogen on the alpha-position group is easy to be caught by the metal center due to the rotation of the aromatic imine group to form a metal-hydrogen bond, which leads the metal to lose the function of further catalyzing olefin polymerization. 2) The solubility of ethylene at high temperature decreases, thus resulting in a decrease in activity. In addition, it is known that the more active the exothermic reaction of ethylene polymerization, the more heat is instantaneously generated in the center of the metal catalyst, which will undoubtedly further cause the catalyst to be degraded by high temperature and even lose its performance in catalyzing ethylene polymerization. According to the reason that the activity of catalyzing ethylene polymerization at high temperature by using iron metal is reduced, the high temperature resistance of the catalyst is improved mainly by a method for adjusting a ligand structure of the catalyst at present. In addition, if the energy generated by the metal catalytic center can be conducted to the environment in time, the temperature of the catalytic center can be objectively ensured not to be too high, and the effect of protecting the catalytic center can also be achieved. Materials such as boron nitride, graphene and carbon nanotubes have good heat conductivity, so that the material is expected to be applied to an ethylene polymerization catalyst as a carrier, thereby improving the heat-resistant stability of the iron catalyst.

Disclosure of Invention

In order to solve the problem of poor heat stability of the iron catalyst, the invention provides a series of imine pyridine tridentate iron complex catalysts with naphthalene ring structures, and the series of catalysts show good heat stability. On the basis, the invention also provides a method for further improving the heat-resistant stability of the catalyst by utilizing a loading method. On the basis of retaining the characteristics of the iron catalyst for catalyzing ethylene polymerization, the supported iron catalyst shows extremely high ethylene polymerization catalytic activity at high temperature under the condition of proper catalyst combination.

The first object of the present invention is to provide a tridentate iron complex for catalyzing ethylene polymerization, which has the following structure:

wherein R is ¹ 、R ² Identical or different, independently of one another, from hydrogen, chlorine, nitro, methyl, ethyl, propyl, isopropyl, phenyl, phenethyl-CH (R) Ph, benzhydryl; r is hydrogen, C ₁ -C ₄ An alkyl group;

m and n are the same or different and independently may be 1, 2 or 3.

In one embodiment of the invention, R ¹ 、R ² Identical or different, independently of one another, from hydrogen, chlorine, methyl or phenylethyl;

in one embodiment of the invention, m and n are both 2;

in one embodiment of the present invention, the tridentate iron complex of the present invention has the following structure, but is not limited to the following compound (formula ii):

the invention also provides a method for preparing the complex catalyst, which comprises the following steps:

and (3) refluxing the diketone compound shown in the formula III, the naphthylamine derivative shown in the formula VI and the metal ferrous salt in an acidic solvent for reaction to prepare the tridentate iron complex shown in the formula I.

In one embodiment of the present invention, a process for preparing the above complex catalyst of formula II, the process is as follows:

the diketone compound shown in the formula V, the naphthylamine derivative shown in the formula VI and the metallic ferrous salt are refluxed in an acid solvent for preparation.

In one embodiment of the present invention, the metallic ferrous salt is selected from any one or more of the following: FeCl ₂ ， FeCl ₂ ·4H ₂ O; preferably FeCl ₂ ·4H ₂ O。

In one embodiment of the invention, the acidic solvent is acetic acid, or a toluene solution of p-toluenesulfonic acid; acetic acid is preferred.

In one embodiment of the present invention, the reaction may be performed in an air environment or an oxygen-free environment. Preferably under oxygen-free conditions, which means under protection of an inert gas such as nitrogen.

In one embodiment of the present invention, the molar ratio of the diketone compound to the naphthylamine is 1:0.8 to 1: 2.5.

In one embodiment of the present invention, the molar ratio of the ferrous salt to the ketone is 1:1 to 1: 1.5.

In one embodiment of the present invention, the temperature of the reaction is 100-130 ℃. Specifically, it may be 120 ℃.

In one embodiment of the invention, the reaction time is 2 to 6 hours. Preferably 3-5 hours. Further preferably 4 hours.

In one embodiment of the invention, the resulting tridentate iron complex may be further purified. The purification method comprises the following steps:

a) most of the solvent was removed from the reaction solution after the reaction by a vacuum pump, and then the reaction solution was recrystallized from ether.

b) After recrystallization, solid-liquid separation is carried out, and the solid phase is washed by anhydrous ether and dried.

The invention also provides a preparation method of the supported iron catalyst, which comprises the step of mixing the complex catalyst and a carrier, wherein the carrier can be nano boron nitride, a carbon nano tube, graphene and nano silica gel.

In one embodiment of the present invention, the loading amount of the iron catalyst is 0.001% to 5%, preferably 0.01% to 1%, and more preferably 0.05%. Wherein, the loading amount refers to the mass percentage of the iron element in the supported catalyst.

The invention also provides a catalyst composition which comprises a main catalyst and a cocatalyst, wherein the main catalyst is the supported iron catalyst.

In one embodiment of the invention, the cocatalyst is Methylaluminoxane (MAO) and/or triisobutylaluminum Modified Methylaluminoxane (MMAO). MAO is preferred.

In an embodiment of the present invention, when the cocatalyst is Methylaluminoxane (MAO), a molar ratio of metal Al in the Methylaluminoxane (MAO) to central metal Fe of the supported iron complex is (1000 to 3000):1, preferably in a molar ratio of 2000: 1.

In one embodiment of the invention, when the cocatalyst is triisobutylaluminum-Modified Methylaluminoxane (MMAO), the molar ratio of metal Al in the triisobutylaluminum-Modified Methylaluminoxane (MMAO) to the central metal Fe of the supported iron complex is (1500-3000): 1. Preferably the molar ratio is 2000: 1.

The invention also provides a method for catalytically synthesizing polyethylene, which utilizes the catalyst composition to carry out catalytic polymerization.

Has the advantages that:

1. the invention utilizes a tridentate iron complex obtained by coordination of a specific diimine pyridine ligand and iron, and loads the tridentate iron complex on a boron nitride carrier to prepare the boron nitride supported iron catalyst. The catalyst can realize the regulation and control of the molecular weight of the polymer and the micro molecular structure of the polymer by adjusting the catalytic conditions, and has the advantages of high catalytic activity, good heat-resistant stability, stable performance and the like. For example, the activity of the supported iron complex catalyst for catalyzing ethylene polymerization at 70 ℃ is as high as 26.9 x 10 ⁶ g(PE)mol ^-1 h ^-1 The activity at 90 ℃ is as high as 20.3 multiplied by 10 ⁶ g(PE)mol ^-1 h ^-1 。

2. The preparation method of the supported iron complex provided by the invention has the advantages of short flow and simple preparation method.

3. The preparation method of the iron complex provided by the invention has the advantages of mild reaction conditions, short period, simple operation conditions, high yield and the like.

4. The supported iron complex catalyst provided by the invention shows very good catalytic activity and heat-resistant stability when used for catalyzing ethylene polymerization. The prepared polyethylene shows linear characteristics, the molecular weight is 52.4-790.2 kg/mol, the molecular weight distribution is 11.3-91, the melting temperature is about 130 ℃, the regulation and control capability on the molecular weight of the obtained polyethylene is shown, and the polyethylene has great industrial application potential.

5. The method for preparing the polyethylene provided by the invention is simple to operate, mild in reaction conditions, suitable for reaction at an industrial production temperature, and has a wide application prospect.

Drawings

FIG. 1 is a schematic diagram of a crystal structure of a tridentate iron complex.

FIG. 2 is a scanning electron micrograph of a supported iron complex; wherein 1 is 0.01% Fe8@ BN; 2 is 0.1% Fe8@ BN; 3 is 0.5% Fe8@ BN; and a, b and c are SEM images under different magnifications.

FIG. 3 is a scanning electron micrograph of an iron-loaded complex (FIG. 21 b), and a schematic representation of the model thereof (top right); wherein, the yellow-green part is a boron nitride carrier, and the dotted blue spherical part is a loaded iron complex.

FIG. 4 shows the polymer obtained in example 6a) ¹ H NMR and ¹³ c NMR spectrum.

FIG. 5 is a schematic structural view of a supported iron catalyst; wherein the blue flaky part is of a carrier structure, and the yellow spherical part is of an iron complex.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, it should be understood that various changes or modifications can be made by those skilled in the art after reading the description of the present invention, and such equivalents also fall within the scope of the invention.

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The concentrations in the following examples are molar concentrations unless otherwise specified.

The molecular weight and molecular weight distribution of the polymer obtained in the following ethylene polymerization examples were measured by a conventional GPC method, the melting point was measured by a conventional DSC method, and the polymerization activity of the polymer was calculated according to the following formula: polymerization activity ═ polymer yield/(catalyst amount. polymerization time).

The following synthesized compounds were confirmed by nuclear magnetic, infrared and elemental analysis.

As a preferred embodiment, the synthesis of the complex in the following examples is carried out according to the following reaction equation:

example 1

Preparation of α, α' -bis (2-phenylethyl-1-naphthylimine) -2,3:5, 6-bis (pentamethylene) pyridiniumiron:

alpha, alpha' -dicarbonyl-2, 3:5, 6-bis (pentamethylene) pyridine (10mmol), 2-phenethyl-1-aminonaphthalene (22mmol), ferrous chloride tetrahydrate (9.5mmol), 30mL acetic acid was heated under reflux for 4 hours. Acetic acid was removed and the residue was washed with diethyl ether. Yield: 70 percent.

The structure validation data is as follows:

FT-IR(KBr,cm ^-1 ):3674.0(w),3057.5(w),2968.2(s),2932.3(w),2899.2(w),2163.9(w), 2018.1(w),1973.1(w),1603.1(s),1562.2(s),1511.6(s),1254.7(s),1049.6(m),905.9(w),823.1(s), 756.2(s),700.8(s),665.1(m).

elemental analysis: C51H47Cl2FeN3(828.70), theoretical C, 73.92; h, 5.72; n,5.07, experimental value C, 74.28; h, 5.50; and N,4.81.

Example 2

Preparing a boron nitride supported iron complex with a loading of 0.01 percent:

weighing 1g of boron nitride powder in a 250mL beaker, adding 100mL of deionized water, and performing ultrasonic dispersion for 12 hours; the supernatant was removed by centrifugation (three times at 2000r/min for 10 min). And (3) carrying out suction filtration on the upper layer liquid by using a filter membrane with the aperture of 250nm, placing the solid obtained after suction filtration in a vacuum drying oven to be dried to constant weight, and testing the particle size of the solid formed in the step by using a Zata potential and particle size analyzer. Accurately weighing the tridentate iron complex and the prepared nanoscale boron nitride into a 50mL Schlenk tube according to the loading capacity of the iron complex on the boron nitride being 0.01 percent, adding about 5mL of dichloromethane subjected to anhydrous anaerobic treatment to dissolve the tridentate iron complex, stirring at room temperature for 12 hours, and slowly draining the dichloromethane through decompression, wherein the whole operation process is completed in an anhydrous anaerobic environment. The solid obtained is collected and washed 3 times with a mixture of dichloromethane and hexane (10 mL each, 8mL hexane +2mL dichloromethane) after anhydrous and anaerobic treatment, and the washed solid is dried in a vacuum oven to constant weight after putting in an anhydrous and anaerobic environment to volatilize most of the solvent.

Example 3

Preparing a boron nitride supported iron complex with a load of 0.05 percent:

weighing 1g of boron nitride powder in a 250mL beaker, adding 100mL of deionized water, and performing ultrasonic dispersion for 12 hours; the supernatant was removed by centrifugation (three times at 2000r/min for 10 min). And (3) carrying out suction filtration on the upper layer liquid by using a filter membrane with the aperture of 250nm, placing the solid obtained after suction filtration in a vacuum drying oven to be dried to constant weight, and testing the particle size of the solid formed in the step by using a Zata potential and particle size analyzer. Accurately weighing the tridentate iron complex and the prepared nanoscale boron nitride into a 50mL Schlenk tube according to the loading capacity of the iron complex on the boron nitride of 0.05 percent, adding about 5mL of dichloromethane subjected to anhydrous anaerobic treatment to dissolve the tridentate iron complex, stirring at room temperature for 12 hours, and slowly draining the dichloromethane through decompression, wherein the whole operation process is completed in an anhydrous anaerobic environment. The solid obtained is collected and washed 3 times with a mixture of dichloromethane and hexane (10 mL each, 8mL hexane +2mL dichloromethane) after anhydrous and anaerobic treatment, and the washed solid is dried in a vacuum oven to constant weight after putting in an anhydrous and anaerobic environment to volatilize most of the solvent.

Example 4

Preparing a boron nitride supported iron complex with a load of 0.10 percent:

weighing 1g of boron nitride powder in a 250mL beaker, adding 100mL of deionized water, and performing ultrasonic dispersion for 12 hours; the supernatant was removed by centrifugation (three times at 2000r/min for 10 min). And (3) carrying out suction filtration on the upper layer liquid by using a filter membrane with the aperture of 250nm, placing the solid obtained after suction filtration in a vacuum drying oven to be dried to constant weight, and testing the particle size of the solid formed in the step by using a Zata potential and particle size analyzer. Accurately weighing the tridentate iron complex and the prepared nanoscale boron nitride into a 50mL Schlenk tube according to the loading capacity of the iron complex on the boron nitride being 0.10%, adding about 5mL of dichloromethane subjected to anhydrous anaerobic treatment to dissolve the tridentate iron complex, stirring at room temperature for 12 hours, and slowly draining the dichloromethane through decompression, wherein the whole operation process is completed in an anhydrous anaerobic environment. The solid obtained is collected and washed 3 times with a mixture of dichloromethane and hexane (10 mL each, 8mL hexane +2mL dichloromethane) after anhydrous and anaerobic treatment, and the washed solid is dried in a vacuum oven to constant weight after putting in an anhydrous and anaerobic environment to volatilize most of the solvent.

Example 5

Preparing a boron nitride supported iron complex with 0.50% of load:

weighing 1g of boron nitride powder in a 250mL beaker, adding 100mL of deionized water, and performing ultrasonic dispersion for 12 hours; the supernatant was removed by centrifugation (three times at 2000r/min for 10 min). And (3) carrying out suction filtration on the upper layer liquid by using a filter membrane with the aperture of 250nm, placing the solid obtained after suction filtration in a vacuum drying oven to be dried to constant weight, and testing the particle size of the solid formed in the step by using a Zata potential and particle size analyzer. Accurately weighing the tridentate iron complex and the prepared nanoscale boron nitride into a 50mL Schlenk tube according to the loading capacity of the iron complex on the boron nitride being 0.50%, adding about 5mL of dichloromethane subjected to anhydrous anaerobic treatment to dissolve the tridentate iron complex, stirring at room temperature for 12 hours, and slowly draining the dichloromethane through decompression, wherein the whole operation process is completed in an anhydrous anaerobic environment. The solid obtained is collected and washed 3 times with a mixture of dichloromethane and hexane (10 mL each, 8mL hexane +2mL dichloromethane) after anhydrous and anaerobic treatment, and the washed solid is dried in a vacuum oven to constant weight after putting in an anhydrous and anaerobic environment to volatilize most of the solvent.

Example 6

The prepared supported iron complex is used for catalyzing ethylene polymerization:

a) adding 0.1% loading of supported iron catalyst to a high pressure reactor (1 μmol of supported iron); replacing the reaction kettle with high-purity nitrogen for two times and then replacing the reaction kettle with ethylene for one time; adding 50mL of anhydrous, oxygen-free treated toluene to the reaction kettle by using an injector, and heating the device to 70 ℃; adding methylaluminoxane (Al/Fe is 2000) into a reaction kettle, and then adding 50mL of anhydrous and anaerobic treated toluene; the reaction was carried out at 500 rpm while maintaining the polymerization temperature at 70 ℃ for 30 minutes. After the reaction is stopped, the reaction solution is poured into ethanol solution acidified by hydrochloric acid to quench the reaction solution, polymer precipitate is obtained, the polymer precipitate is washed for a plurality of times by ethanol, dried in vacuum to constant weight, and weighed.

Polymerization Activity: 26.9X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 Of a polymer T _m 130.9 ℃. (Tm is the melting temperature of the polymer, obtained by DSC measurement), molecular weight M of the polymer _w ＝467kg·mol ^-1 ，PDI＝26.59(M _w Weight average molecular weight of the polymer, obtained by GPC test). Taking 30mg of the polymer obtained in a), dissolving in 0.5mL of deuterated 1, 1, 2, 2-tetrachloroethane, and testing the polymer at 100 DEG C ¹³ And C, data. According to ¹³ The C NMR spectrum showed only the signal peak sum shifted at 30(ppm) ¹ Only two peaks of methylene and methyl in the H NMR spectrum indicate that the polyethylene prepared is a highly linear polyethylene.

b) Essentially the same as a), except that: the polymerization temperature was maintained at 90 ℃. Polymerization Activity: 11.9X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 129.2 ℃, M _w ＝159kg·mol ^-1 ，PDI＝15.63。

c) Essentially the same as a), except that: the polymerization temperature was maintained at 100 ℃. Polymerization Activity: 8.32X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 131.2 ℃, M _w ＝141.3kg·mol ^-1 ，PDI＝39.09。

d) Substantially as in b), except that: the cocatalyst used was MMAO. Polymerization Activity: 9.00X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 130.4 ℃, M _w ＝183.2kg·mol ^-1 ，PDI＝91.43。

e) Substantially as in b), except that: a supported iron complex catalyst was used with a loading of 0.01%. Polymerization Activity: 9.50X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 129.1 ℃, M _w ＝790.2kg·mol ^-1 ，PDI＝25.08。

f) Substantially as in b), except that: a supported iron complex catalyst was used with a loading of 0.05%. Polymerization Activity: 20.3X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 128.6 ℃, M _w ＝789.8kg·mol ^-1 ，PDI＝27.00。

g) Substantially as in b), except that: a supported iron complex catalyst was used at a loading of 0.5%. Polymerization Activity: 12.1X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 131.8 ℃, M _w ＝52.36kg·mol ^-1 ，PDI＝11.27。

Example 7

Preparation of α, α' -bis (1-naphthylimine) -2,3:5, 6-bis (pentamethylene) pyridiniumiron:

alpha, alpha' -dicarbonyl-2, 3:5, 6-bis (pentamethylene) pyridine (10mmol), 1-aminonaphthalene (22mmol), ferrous chloride tetrahydrate (9.5mmol), 30mL acetic acid was heated under reflux for 4 hours. Acetic acid was removed and the residue was washed with diethyl ether. Yield: 74 percent.

The structure validation data is as follows:

FT-IR(cm ^-1 ):3052.8(w),2937.0(w),1676.2(m),1620.0(m)1574.5(m),1451.1(m),1391.1(m), 1339.6(m),1262.9(m),1179.0(m),1105.4(m),1015.2(m),804.1(s),778.8(s).

elemental analysis C ₃₅ H ₃₁ Cl ₂ FeN ₃ (620.40) theoretical value C, 67.76; h, 5.04; n, 6.77; experimental value C, 67.46; h, 5.22; and N,6.32.

Referring to example 4, the tridentate iron complex was replaced with the iron catalyst obtained in this example and applied with reference to the procedure of example 6a), with the result that: polymerization Activity at a polymerization temperature of 70 ℃: 0.03X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 Of a polymer T _m 122.3 ℃. Molecular weight M of the polymer _w ＝1.84kg·mol ^-1 ，PDI＝1.72.

Comparative example 1

Essentially the same as example 6a), except that: an unsupported iron complex catalyst was used. Polymerization Activity: 11.1X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 126.8 ℃, M _w ＝57.23kg·mol ^-1 ，PDI＝11.68。

Comparative example 2

The comparative iron complex has the following structure:

the preparation process comprises the following steps:

prepared essentially as in example 1 by substituting 2-phenethylnaphthylamine in example 1 for 2.6-diisopropylaniline in 80% yield.

Structural characterization:

FT-IR(KBr,cm ^-1 ):2941(w),2864(w),1605(m),1553(w),1467(s),1377(w),1339(w),1259(m), 1207(m),1166(w),1091(w),1035(w),929(w),779(s).

elemental analysis: c ₃₉ H ₅₁ N ₃ FeCl ₂ (688.59), theoretical value: c, 68.03; h, 6.85; n, 6.64%; experimental values: c, 67.89; h, 7.22; and N, 5.94 percent.

Reactivity for catalyzing ethylene polymerization: polymerization Activity: 9.35X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 The polymer Tm is 130.1 ℃ C, M _w ＝35.9kg·mol ^-1 ，PDI＝16.6。

Claims

1. The method for catalytically synthesizing polyethylene is characterized in that ethylene is catalyzed by using a supported iron catalyst to perform polymerization reaction, wherein the supported iron catalyst consists of a tridentate iron complex and a carrier; the carrier is one of nano boron nitride, a carbon nano tube and graphene; the tridentate iron complex is alpha, alpha' -di (2-phenethyl-1-naphthylimine) -2,3:5, 6-bis (pentamethylene) pyridine iron, and the molecular structural formula is as follows:

the content of the iron element in the supported iron catalyst accounts for 0.1 percent of the mass of the supported catalyst;

the method for catalytically synthesizing the polyethylene comprises the following steps: adding the supported iron catalyst containing 1 mu mol of supported iron into a high-pressure reaction kettle; replacing the reaction kettle with high-purity nitrogen for two times and then replacing the reaction kettle with ethylene for one time; adding 50mL of anhydrous and anaerobic treated toluene into the reaction kettle, and heating to 70 ℃; adding methylaluminoxane Al/Fe (2000) into a reaction kettle, and then adding 50mL of anhydrous and anaerobic treated toluene; keeping 500 r/m, keeping the polymerization temperature to 70 ℃ and reacting for 30 minutes; after the reaction is stopped, pouring the reaction solution into ethanol solution acidified by hydrochloric acid to quench the reaction solution, obtaining polymer precipitate, washing the polymer precipitate for a plurality of times by using ethanol, and drying the polymer precipitate in vacuum until the weight of the polymer precipitate is constant to obtain polymer, namely highly linear polyethylene;

polymerization Activity: 26.9X 10 ⁶ g·mol ^-1 (Fe)·h ^-1 Of a polymer T _m 130.9 ℃ C, the weight-average molecular weight M of the polymer _w ＝467kg·mol ^-1 ，PDI＝26.59。

2. The method of claim 1, wherein the α, α' -bis (2-phenylethyl-1-naphthylimine) -2,3:5, 6-bis (pentamethylene) pyridiniumiron is prepared by a process comprising:

3. the process of claim 2, wherein the molar ratio of α, α' -dicarbonyl-2, 3:5, 6-bis (pentamethylene) pyridine to 2-phenethyl-1-aminonaphthalene is 1: 2.2.

4. The method of claim 2, wherein the molar ratio of the ferrous salt to the α, α' -dicarbonyl-2, 3:5, 6-bis (pentamethylene) pyridine is 0.95: 1.

5. The method as claimed in claim 2, wherein the reaction temperature is 100-130 ℃; the reaction time is 2-6 hours.