Maleate compound, preparation method thereof and application of maleate compound in olefin catalytic polymerization

Abstract

The invention provides a maleate compound and a preparation method and application thereof in olefin catalytic polymerization, an olefin polymerization catalytic component in the application comprises a magnesium source, a titanium source, halogen and an internal electron donor, and the internal electron donor is the maleate compound with a bicyclic structure as shown in a general formula I. Due to the unique space and electron effects of the maleate compound, the catalyst containing the maleate has better activity, stereospecificity and hydrogen regulation sensitivity in propylene (co) polymerization, and the molecular weight distribution of the polymer is wide. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of preparation of Ziegler-Natta catalysts, and relates to a maleate compound, a preparation method thereof and application in olefin catalytic polymerization, including an olefin polymerization catalytic component and a catalyst thereof, and particularly relates to a catalytic component and a catalyst for propylene (co)polymerization. Background Art

[0002] Supported Ziegler-Natta catalyst is a solid titanium catalyst with magnesium, titanium, halogen and electron donor as basic components. It is particularly suitable for the polymerization of α-olefins with 3 or more carbon atoms. The obtained olefin polymer has a high yield and stereoregularity. Electron donor is one of the essential components of supported Ziegler-Natta catalyst, which can effectively improve the activity and isotacticity of the catalyst. Since the discovery of Ziegler-Natta catalyst, polyolefin catalysts have been constantly updated with the development of electron donor compounds.

[0003] A variety of electron donor compounds have been reported in the literature, such as mono- or poly-carboxylic acid esters, anhydrides, ketones, mono- or poly-ethers, amines and their derivatives. At present, di-aromatic carboxylic acid ester compounds, such as di-n-butyl phthalate or diisobutyl phthalate, are more commonly used in industry (PM Trivedi, et al. J. Polym. Res., 2021, 28, Article number: 45). The supported Ziegler-Natta catalyst with 1,3-diether compounds as electron donors is a new generation of electron donor compounds with high activity and isotacticity, such as 9,9-di(methoxymethyl)fluorene disclosed in some patent documents. The Ziegler-Natta catalysts obtained after these internal electron donors are loaded have high catalytic activity and isotacticity for propylene polymerization. However, whether it is 1,3-diether or diol lipid compounds, the synthesis is difficult and costly, and there has been no industrial report of its use as an internal electron donor alone.

[0004] Maleate compounds are common bulk chemicals. Due to their unique structure, researchers have long used them as internal electron donors for olefin polymerization catalysts. However, the catalytic activity of unmodified maleate-supported Ziegler-Natta catalysts is often low. For example, Chinese patent document CN 101824108 A designed and synthesized 2,3-disubstituted maleate with a condensed ring structure as an internal electron donor, and the supported Ziegler-Natta catalyst showed higher activity and isotacticity than unsubstituted maleate. However, the activity of existing modified maleate-based internal electron donors needs to be further improved. Summary of the invention

[0005] In view of this, the present invention provides a maleate compound, a preparation method thereof and application in olefin catalytic polymerization. The maleate compound provided by the present invention can be effectively used as an internal electron donor component of an olefin polymerization catalyst, and the synthesis method of the compound is simple and easy, which is convenient for promotion and application.

[0006] The present invention provides a maleate compound having a general structural formula I:

[0007]

[0008] Where n ≥ 2 and is a positive integer;

[0009] The groups R1 and R2 are identical or different and are independently selected from C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms;

[0010] The groups R3 to R6 are the same or different from each other and are selected from hydrogen, C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; or two or more groups in the groups R3 to R6 are bonded to each other to form one or more condensed ring structures.

[0011] The maleate compound shown in the above formula I has a bicyclic structure and serves as an internal electron donor component. Its unique electronic geometry effect is conducive to obtaining an olefin polymerization catalyst with excellent comprehensive performance. In the formula I, n is preferably 2, 3 or 4. C1-20 means that the group has a certain carbon chain length, and the number of carbon atoms is an integer between 1 and 20. The substituted or unsubstituted chain alkyl includes a linear or branched alkyl, such as an unsubstituted methane group is CH3, and the substituent on the substituted chain alkyl can be an aryl group.

[0012] In some embodiments, the groups R1 and R2 are respectively selected from C1-C10 alkyl, cycloalkyl or aryl alkyl; further, the groups R1 and R2 are respectively preferably C1-C10 alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or neopentyl; in particular, the groups R1 and R2 are respectively preferably ethyl, isopropyl, n-butyl, isobutyl or neopentyl.

[0013] In some embodiments, at least one of the groups R3 and R4, R5 and R6 is hydrogen (H); more preferably, all of the groups R3 to R6 are hydrogen.

[0014] In some specific embodiments, the maleate compound is dimethyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diethyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diisopropyl 7-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, dibutyl 7-methoxy-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diisobutyl 1-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate. , 1,4-dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester, 5,6-dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid neopentyl alcohol ester, 1,4,5,6-tetramethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester, bicyclo[3.2.2.]non-6-ene-6,7-dicarboxylic acid diisobutyl ester or bicyclo[4.2.2.]dec-7-ene-7,8-dicarboxylic acid dineopentyl alcohol ester.

[0015] The present invention provides a method for preparing the maleate compound as described above, comprising the following steps: subjecting the precursor represented by formula II to a selective hydrogenation reaction to obtain a maleate compound having a general formula of formula I;

[0016]

[0017] Where n ≥ 2 and is a positive integer;

[0018] The groups R1 and R2 are identical or different and are independently selected from C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms;

[0019] The groups R3 to R6 are the same or different from each other and are selected from hydrogen, C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; or two or more groups in the groups R3 to R6 are bonded to each other to form one or more condensed ring structures.

[0020] The precursor shown in the above formula II can be obtained by esterification and Diels-Alder reaction. Taking butynedioic acid and 1,3-cyclohexadiene as an example, the specific synthesis includes:

[0021] Dibutyl butynedioate is obtained by esterification reaction, and then 1,3-cyclohexadiene and dibutyl butynedioate are mixed, stirred and refluxed overnight, and separated by column chromatography to obtain a colorless, transparent liquid product, dibutyl bicyclo[2.2.2]octa-2,5-diene-2,3-dicarboxylate (product of Formula II, as shown in a. esterification and b. D-A reaction in the following reaction formula).

[0022] The precursor and commercial Pd / C catalyst are placed in a high-pressure reactor, the air in the reactor is replaced with hydrogen, and finally 1.0 MPa of hydrogen is injected to react at a certain temperature to obtain Formula I (as shown in c. hydrogenation in the following reaction formula);

[0023]

[0024] The present invention provides an olefin polymerization catalyst component, comprising a magnesium source, a titanium source, a halogen and an internal electron donor, wherein the internal electron donor is the maleate compound described above;

[0025] In terms of weight percentage, the olefin polymerization catalyst component preferably comprises 10% to 25% of a magnesium source, 1% to 10% of a titanium source, 40% to 60% of a halogen and 1% to 30% of an internal electron donor.

[0026] In some embodiments, the particle size distribution of the magnesium source in the olefin polymerization catalyst component is 20 to 250 μm, and the general formula is Mg(OR'): m X1 (2-m) ·tROH is provided by a magnesium halide alcoholate, wherein R' is a C1-C20 alkyl group, an arylalkyl group or an aryl group; X1 is a halogen element; m is an integer of 0 to 2, t is a decimal or an integer of 0 to 6; and R is a C1-C20 alkyl group or an arylalkyl group.

[0027] In some specific embodiments, the magnesium halide in the magnesium halide alcoholate is one of magnesium dichloride, magnesium dibromide, chloromethoxymagnesium, and chloroethoxymagnesium; the alcohol in the magnesium halide alcoholate is one of ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Further, the magnesium halide in the magnesium halide alcoholate is magnesium dichloride, and the alcohol is ethanol.

[0028] The magnesium halide alcoholate is obtained by a method in which magnesium halide and alcohol are thermally dissolved and then solidified into microsphere particles. The magnesium halide alcoholate is spherical particles. The specific synthesis method is as follows: under inert gas protection, 20g of dry magnesium halide and a certain proportion of alcohol are added to a stainless steel reactor, the reactor is heated to 30-80°C and the two are fully mixed; then a certain amount of silicone oil (10 times the amount of magnesium halide) is added to the reactor, the reactor is heated to 100-150°C and stirred vigorously; after stirring for 3-8h, the reactor is quickly cooled to -80--20°C and kept at low temperature for 1h. Finally, the generated spherical magnesium halide alcoholate particles are collected and cleaned, with a particle size of 20-250μm and a specific surface area of ​​200-400m 2 / g.

[0029] In some embodiments, the titanium source in the olefin polymerization catalyst component is of the general formula TiX2 z (OR”) 4-zA titanium-containing compound is provided, wherein R" is a C1-C20 hydrocarbon group; X2 is a halogen element; and z=1-4.

[0030] In some specific embodiments, the titanium source in the olefin polymerization catalyst component is provided by titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, titanium tetrabutoxide, titanium tetraethoxide, titanium triethoxide monochloride, titanium diethoxide dichloride or titanium triethoxide monochloride. Further, the titanium source is provided by titanium tetrachloride.

[0031] In addition, the halogen includes fluorine, chlorine, bromine and iodine.

[0032] The preparation method of the olefin polymerization catalyst component described in the embodiment of the present invention comprises: (1) adding a spherical magnesium halide alcoholate to a titanium-containing compound at -40 to 10° C. and reacting for 1 to 4 hours, wherein the molar ratio of magnesium to titanium can be 1:5 to 1:50; (2) heating the temperature to 30 to 80° C. and adding a maleic acid ester compound of formula I as an internal electron donor, wherein the molar ratio of magnesium to the internal electron donor can be 2:1 to 15:1; (3) heating the temperature to 100 to 150° C. and reacting for 1 to 4 hours; (4) filtering and then adding the same amount of titanium-containing compound as in step (1), reacting at 110 to 130° C. for 1 to 4 hours, and filtering, washing and drying to obtain a catalyst component comprising 10 to 25 wt% of a magnesium source, 1 to 10 wt% of a titanium source, 40 to 60 wt% of a halogen and 1 to 30 wt% of an internal electron donor.

[0033] The above catalytic components are the main components. The present invention can further provide a catalyst for olefin polymerization; that is, the present invention provides an olefin polymerization catalyst, comprising:

[0034] The olefin polymerization catalyst component described above;

[0035] Alkyl aluminum compounds;

[0036] Optionally, an external electron donor component;

[0037] The usage of each component is preferably 1:5-1000:0-500 based on the molar ratio of titanium:aluminum:external electron donor component.

[0038] In some embodiments, the alkyl aluminum compound can play an auxiliary catalytic role; further, the alkyl aluminum compound is triethyl aluminum, triisobutyl aluminum, tri-n-butyl aluminum, tri-n-hexylaluminum, tri-n-octylaluminum, a mixture of trialkyl aluminum and alkyl aluminum halide or alkyl aluminum hydride, or alkyl aluminumoxane.

[0039] In addition, an external electron donor (an electron donor that is added directly to the polymerization medium during the polymerization reaction, as opposed to an internal electron donor) can be selectively added as needed. For polymers that require high stereoregularity (e.g., when propylene polymerization requires isotacticity to exceed 99%), it is recommended to add an external electron donor.

[0040] In some embodiments, the external electron donor component is an organosilicon compound having the general formula R 0y Si(OR”') 4-y , wherein y is an integer between 0 and 3, R0 and R'' are the same or different alkyl, cycloalkyl or aryl groups, optionally containing heteroatoms; R0 can also be a halogen or a hydrogen atom. Specifically, the external electron donor component is diphenyldimethoxysilane.

[0041] As the external electron donor component, specific organosilicon compounds such as: trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, cyclohexylmethyldimethoxysilane, methyl-tert-butyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, di-n-butyldimethoxysilane, dicyclopentyldimethoxysilane or di(cyclobutylmethyl)dimethoxysilane, preferably diphenyldimethoxysilane.

[0042] Calculated by the molar ratio of titanium:aluminum:external electron donor components, the usage ratio of the components in the olefin polymerization catalyst is preferably 1:(250-100):(25-300).

[0043] In addition, an embodiment of the present invention provides use of the above-mentioned olefin polymerization catalyst in olefin catalytic polymerization.

[0044] The olefin polymerization catalyst of the present invention can be used for olefin polymerization, especially homopolymerization of propylene or copolymerization of propylene with other olefins, to obtain a polymer with a very high isotactic index. At the same time, it is not excluded that the catalyst is suitable for producing polyethylene and copolymerization of ethylene with α-olefins such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene or 1-octene.

[0045] When used for propylene polymerization, various methods in the prior art can be used, and it can be carried out in liquid phase or gas phase, or in a combination of liquid phase and gas phase polymerization stages. The polymerization is usually carried out at 0-150°C, preferably 40-90°C; the polymerization pressure is 0.01-10MPa. In the embodiments of the present invention, the ability of the catalyst to bond hydrogen to the active chain of the polymer during the polymerization process (the hydrogen sensitivity of the catalyst) can be used to control the molecular weight of the polymer. Different internal electron donors have very different effects on the hydrogen sensitivity of the catalyst.

[0046] The inventors have found through research that the present invention uses a maleic acid ester compound with a bicyclic structure as shown in Formula I as an internal electron donor component, and its unique electronic geometric effect makes the olefin polymerization catalyst have excellent comprehensive performance, and when used for propylene (co)polymerization, a satisfactory polymerization yield can be obtained; and the stereospecificity of the polymer is high. At the same time, the olefin polymerization catalyst based on the internal electron donor component is also very sensitive to hydrogen regulation, and the molecular weight distribution of the obtained polymer is relatively wide, which is conducive to the development of different grades of polymers. DETAILED DESCRIPTION

[0047] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the technical scheme of the present invention is now described in detail below in conjunction with specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0048] In order to further understand the present invention, the ionomer material, preparation method and application provided by the present invention are described in detail below in conjunction with the examples, and the protection scope of the present invention is not limited by the following examples. In the examples, all raw reagents and materials can be obtained commercially, and the experimental methods without specifying specific experimental conditions are conventional methods and conditions well known in the art.

[0049] Example 1

[0050] 1. Synthesis of bicyclic maleate compounds with special structures

[0051] Taking the synthesis of dibutyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate as an example, the specific method is as follows:

[0052] 20.0 g of 1,3-cyclohexadiene and 28.3 g of dibutyl butynedioate were added to a 150 mL flask, and the mixture was stirred and refluxed overnight. Column chromatography was performed to obtain 38.3 g of dibutyl bicyclo[2.2.2]octa-2,5-diene-2,3-dicarboxylate, a colorless and transparent liquid product, with a yield of 99%. 1 H NMR (TMS, CDCl3, 400MHz) analysis results: δ6.37-6.36 (m, 2H); δ4.15-4.14 (t, 4H); δ4.01 (s, 2H); δ1.65-1.61 (m, 4H); δ1.48-1.47 (t, 2H); δ1.39-1.36 (m, 6H); δ0.94-0.92 (t, 6H).

[0053] 38.3 g of dibutyl bicyclo[2.2.2]oct-2,5-diene-2,3-dicarboxylate and 200 mg of commercial Pd / C catalyst were placed in a high-pressure reactor, the air in the reactor was replaced with hydrogen, and finally 1.0 MPa of hydrogen was injected. The reaction was carried out at 50°C for 2 hours to obtain 38.5 g of oily colorless liquid dibutyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate with a yield of 99%. 1 H NMR (TMS, CDCl3, 400 MHz) analysis results: δ4.16-4.14 (t, 4H); δ2.99 (s, 2H); δ1.66-1.59 (m, 8H); δ1.40-1.36 (m, 8H); δ0.94-0.92 (t, 6H).

[0054] 2. Preparation of Catalytic Component A

[0055] TiCl4 was added to a dry, nitrogen-protected glass reactor and cooled to -20°C. A microspherical magnesium chloride alcoholate (magnesium alcohol ratio of 2.9:1) carrier was added under stirring. The mixing ratio of the carrier to TiCl4 was 1g:20mL. The reaction mixture was uniformly heated from -20°C to 0°C, and then to 70°C. The internal electron donor was added to the reactor, and the reaction mixture was heated to 110°C and continued to react for 2h. Filtered with suction, re-added with an equal amount of fresh TiCl4, heated to 120°C and continued to react for 2h, filtered with suction, washed the filter cake with hexane, and dried in vacuo to obtain a catalyst component.

[0056] The loading amount of internal electron donor was determined by Angent 8890A gas chromatograph; the loading amount of titanium was determined by spectrophotometer.

[0057] 3. Propylene polymerization

[0058] 0.1 mL of external electron donor diphenyldimethoxysilane, 4.0 mL of a hexane solution of a co-catalyst triethylaluminum with a concentration of 1 mol / L, and 0.005 mmol (calculated as titanium) of the catalyst component a prepared by the present invention were added to a 5 L autoclave in sequence, 2.5 L of liquid propylene and 0.2 MPa of hydrogen were introduced, stirred and mixed uniformly at room temperature, heated to 70° C., stirred for reaction for 2 h, the autoclave was opened to take out the polypropylene, the polymer was cooled to room temperature, and the propylene was completely volatilized before weighing, the activity of the catalyst was calculated, and the obtained polypropylene was measured by insoluble matter in boiling n-heptane; the bulk density was measured by a natural stacking method; the melt index was measured by a melt index instrument FR-1811A; and the molecular weight distribution was measured by a high temperature gel chromatograph PL-GOC-220.

[0059] Embodiment 2-10

[0060] The synthesized products were diethyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (99%), diisopropyl 7-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (98%), dibutyl 7-methoxy-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (90%), diisobutyl 1-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (89%), and dibutyl 1,4-dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (91%). 1,4,5,6-tetramethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester (75%), 5,6-dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid neopentyl alcohol ester (90%), 1,4,5,6-tetramethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester (70%), bicyclo[3.2.2.]non-6-ene-6,7-dicarboxylic acid diisobutyl ester (83%), bicyclo[4.2.2.]dec-7-ene-7,8-dicarboxylic acid dineopentyl alcohol ester (88%). The structures of the above internal electron donors are shown in Table 1. 1 The results were determined by H NMR (TMS, CDCl3, 400 MHz). The values ​​in brackets are the yields of the corresponding internal electron donors.

[0061] The contents of the catalytic component a and the propylene polymerization are the same as those in Example 1.

[0062] Comparative Example 1-2

[0063] Di-n-butyl phthalate and di-n-butyl maleate were used as internal electron donors for comparison with the examples. The test results are as follows:

[0064] Table 1. Aggregation results

[0065]

[0066]

[0067] From the above results, it can be seen that the activity and isotacticity of the synthesized catalyst with maleate compounds as internal electron donors are significantly better than those of the commercial di-n-butyl phthalate and di-n-butyl maleate supported catalysts.

[0068] Examples 11-12

[0069] In order to further illustrate the excellent polymerization performance of the ZN catalyst synthesized by the bicyclic maleate of formula I, bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid dibutyl ester and bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester and the corresponding precursor (formula II) were used as internal electron donors to prepare ZN catalysts and the polymerization performance was compared. The polymerization results are shown in Table 2. Among them, bicyclo[2.2.2]oct-2,5-diene-2,3-dicarboxylic acid dibutyl ester and bicyclo[2.2.2]oct-2,5-diene-2,3-dicarboxylic acid diisobutyl ester are of formula II. The synthesis of the internal electron donor, the catalytic component a and the propylene polymerization are the same as those in Example 1.

[0070] Table 2. Comparison of propylene polymerization results

[0071]

[0072]

[0073] From the above results, it can be seen that the synthesized catalyst with the structure of formula I as an internal electron donor has significantly better activity and isotacticity than the catalyst with the corresponding precursor (formula II) as an internal electron donor.

[0074] As can be seen from the above embodiments, the present invention uses the maleic acid ester compound of the bicyclic structure shown in Formula I as the internal electron donor component, and its unique electronic geometric effect makes the comprehensive performance of the olefin polymerization catalyst excellent. When used for propylene (co)polymerization, the polymerization yield is good; and the stereospecificity of the polymer is high. At the same time, the olefin polymerization catalyst based on the internal electron donor component is also very sensitive to hydrogen regulation, and the molecular weight distribution of the obtained polymer is relatively wide, which is conducive to the development of different grades of polymers.

[0075] The above examples are only used to illustrate the technical features and implementation process of the present invention, rather than to limit the technical solution of the present invention. It should be pointed out that for ordinary technicians in this field, the present invention can still be modified or replaced by equivalents, and modifications or replacements that do not deviate from the principles of the present invention are all covered by the protection of the present invention.

Claims

1. A maleate compound, characterized in that It has the general structural formula I: Where n ≥ 2 and is a positive integer; The groups R1 and R2 are identical or different and are independently selected from C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; The groups R3 to R6 are the same or different from each other and are selected from hydrogen, C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; or two or more groups in the groups R3 to R6 are bonded to each other to form one or more condensed ring structures.

2. The maleate compound according to claim 1, characterized in that The groups R1 and R2 are independently selected from C1-C10 alkyl, cycloalkyl or arylalkyl, preferably C1-C10 alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or neopentyl, particularly preferably ethyl, isopropyl, n-butyl, isobutyl or neopentyl.

3. The maleate compound according to claim 1, characterized in that At least one of the groups R3 and R4, R5 and R6 is hydrogen, and preferably all of R3 to R6 are hydrogen.

4. The maleate compound according to claim 1, characterized in that The maleic acid ester compounds are dimethyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diethyl bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diisopropyl 7-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, dibutyl 7-methoxy-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diisobutyl 1-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, dibutyl 1-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diethyl 1-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, diisopropyl 7-methyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate, dibutyl 1 ... -dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester, 5,6-dimethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid neopentyl alcohol ester, 1,4,5,6-tetramethyl-bicyclo[2.2.2]oct-2-ene-2,3-dicarboxylic acid diisobutyl ester, bicyclo[3.2.2.]non-6-ene-6,7-dicarboxylic acid diisobutyl ester or bicyclo[4.2.2.]dec-7-ene-7,8-dicarboxylic acid dineopentyl alcohol ester.

5. The method for preparing a maleic acid ester compound according to any one of claims 1 to 4, comprising the following steps: The precursor represented by formula II is subjected to a selective hydrogenation reaction to obtain a maleate compound having the general formula of formula I; Where n ≥ 2 and is a positive integer; The groups R1 and R2 are identical or different and are independently selected from C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; The groups R3 to R6 are the same or different from each other and are selected from hydrogen, C1-C20 substituted or unsubstituted alkyl, alkenyl, cycloalkyl or aryl groups, optionally containing heteroatoms; or two or more groups in the groups R3 to R6 are bonded to each other to form one or more condensed ring structures.

6. An olefin polymerization catalyst component, comprising a magnesium source, a titanium source, a halogen and an internal electron donor, wherein the internal electron donor is the maleate compound according to any one of claims 1 to 5; In terms of weight percentage, the olefin polymerization catalyst component preferably comprises 10% to 25% of a magnesium source, 1% to 10% of a titanium source, 40% to 60% of a halogen and 1% to 30% of an internal electron donor.

7. The olefin polymerization catalyst component according to claim 6, characterized in that The magnesium source is of the general formula Mg(OR') m X1 (2-m) ·tROH is provided by a magnesium halide alcoholate, wherein R' is a C1-C20 alkyl group, an arylalkyl group or an aryl group; X1 is a halogen element; m is an integer of 0 to 2, t is a decimal or an integer of 0 to 6; R is a C1-C20 alkyl group or an arylalkyl group; The titanium source is of the general formula TiX2 z (OR”) 4-z A titanium-containing compound is provided, wherein R" is a C1-C20 hydrocarbon group; X2 is a halogen element; and z=1-4.

8. An olefin polymerization catalyst, characterized in that include: The olefin polymerization catalyst component according to claim 6 or 7, an alkyl aluminum compound and optionally an external electron donor component; Calculated by the molar ratio of titanium:aluminum:external electron donor component, the amount of each component used is preferably 1:(5-1000):(0-1200).

9. The olefin polymerization catalyst according to claim 8, characterized in that The alkyl aluminum compound is a trialkyl aluminum compound, and the external electron donor component is an organic silicon compound.

10. Use of the olefin polymerization catalyst according to claim 8 or 9 in olefin catalytic polymerization.

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