A cofs supported iron catalyst, its preparation method and application in conjugated diene polymerization

Abstract

The present application relates to a kind of COFs supported iron catalyst, its preparation method and application in conjugated diene polymerization, belong to the field of heterogeneous catalytic preparation of polymer.The COFs supported iron catalyst is formed by coordination of covalent organic framework compound and ferrous chloride, and the preparation method is as follows: under the condition of anhydrous oxygen-free, after ferrous chloride, reaction solvent and covalent organic framework LYU-COFZ are reacted at 25~100 ℃ setting temperature for 3~48 hours, centrifugal, washing, drying, the COFs supported iron catalyst is obtained.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalytic preparation of polymers, and relates to a COFs supported iron catalyst, its preparation method and its application in conjugated diene polymerization. Background Technology

[0002] Polyisoprene is a polymer of isoprene. Due to its good elasticity, cold resistance, and high tensile strength, it exhibits higher tear resistance than natural rubber under oxidation and repeated deformation conditions. However, its processing properties, such as compounding and calendering, are slightly inferior to natural rubber. It is widely used in the tire manufacturing industry and also in the production of footwear, machinery, pharmaceuticals, sporting goods, and other industrial products. Polyisoprene has four stereoregular structures: trans-1,4-, cis-1,4-, 3,4-, and 1,2-polyisoprene. Due to differences in structural units and unit linkages, different polyisoprene varieties exhibit significant performance differences. For example, cis-1,4-polyisoprene has a microstructure similar to natural rubber and can be used as a substitute for it; 3,4-polyisoprene has larger side groups and is generally used in tire anti-skid modifiers and shock-absorbing materials. Catalysts are the core of the polyisoprene production process, determining the polymerization activity and selectivity of isoprene and the properties of polyisoprene. Iron is one of the most abundant late transition metals in the Earth's crust, and due to its environmental friendliness and economic viability, it has received widespread attention from scientists in recent years. Extensive research has been conducted on iron-catalyzed isoprene polymerization, but problems such as poor polymerization selectivity and lack of control remain. Summary of the Invention

[0003] To address the problems and shortcomings of the existing technologies, this invention provides a COF-supported iron catalyst, its preparation method, and its application as a catalyst in the polymerization of conjugated dienes. This invention utilizes the pore structure of COFs to regulate the polymerization process, achieving highly active and selective iron-catalyzed polymerization of isoprene under relatively mild conditions.

[0004] This invention is achieved through the following technical solution: The structure of the COFs-supported iron catalyst is shown in Formula I. Formula I In Equation I, the wavy line represents a periodic extension structure, and all N-containing sites in Equation I may coordinate with ferrous chloride.

[0005] The preparation method of the COFs-supported iron catalyst is to coordinate a covalent organic framework compound with ferrous chloride. The specific steps are as follows: under anhydrous and oxygen-free conditions, ferrous chloride, reaction solvent and covalent organic framework LYU-COFZ are reacted at a set temperature, centrifuged, washed, and finally vacuum dried to obtain the COFs-supported iron catalyst.

[0006] in, The ratio of ferrous chloride, LYU-COFZ, and reaction solvent in the liquid-to-material mixture is 30:(5-8):20, expressed in mg / mg / mL.

[0007] The covalent organic framework LYU-COFZ is formed by the condensation of 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine.

[0008] Further preferably, the reaction solvent is one of dichloromethane, tetrahydrofuran, toluene, and ethanol, with dichloromethane being the most preferred.

[0009] Further preferably, the temperature is set to 25-100℃, with 25℃ being the most preferred.

[0010] Further preferred, the reaction time is 3-48 hours, preferably 15 hours.

[0011] This invention also provides a method for synthesizing the above-mentioned covalent organic framework LYU-COF. The method includes the following steps: adding two building blocks, namely 1,3,5-tris(4-aminophenyl)benzene and 2,2'-diformyl-5,5'-bipyrimidine, into a reaction tube in a weight ratio of 1:1; adding a reaction solvent and a catalyst; sealing the glass tube under vacuum with a flame under liquid nitrogen freezing; then placing it in an oven to react for a certain period of time to obtain a solid; and obtaining LYU-COFZ by repeated solvent washing and vacuum drying.

[0012] More preferably, the reaction solvent in the above synthesis method is one of dichloromethane, tetrahydrofuran, toluene, and ethanol, with dichloromethane being preferred.

[0013] More preferably, the catalyst is a Lewis acid catalyst.

[0014] More preferably, the oven temperature in the above synthesis method is set to 25-100℃, preferably 25℃.

[0015] More preferably, the reaction time in the above synthesis method is 3-5 days, preferably 3 days.

[0016] The present invention also provides the application of the above-mentioned COFs-supported iron catalyst in the conjugated diene polymerization reaction, that is, the COFs-supported iron catalyst can be used as the main catalyst in the conjugated diene polymerization reaction.

[0017] Furthermore, the conjugated diene polymerization reaction steps are as follows: COFs-supported iron catalyst is suspended in an anhydrous solvent, then conjugated diene monomer is added, then a co-catalyst is added to carry out the polymerization reaction, and after post-treatment, polyconjugated diene is obtained. More preferably, the anhydrous solvent is toluene, n-hexane, cyclohexane, and pentane, with toluene being preferred; More preferably, the volume ratio of the anhydrous solvent to the conjugated diene monomer is (1-10):1, more preferably 2.5:1.

[0018] More preferably, the co-catalyst is one or more of methylaluminoxane, triethylaluminum, triisobutylaluminum, and diethylaluminum chloride; the molar ratio of aluminum in the co-catalyst to iron in the main catalyst is (100-1000):1, preferably 1000:1; More preferably, the molar ratio of the conjugated diene monomer to the iron element in the main catalyst is (1000-5000):1, preferably 1000:1; More preferably, the post-treatment method is to add a quenching agent and an antioxidant to quench the reaction, wash with methanol, and dry. More preferably, the quenching agent is methanol, and the antioxidant is an ethanol solution of 2,6-di-tert-butyl-4-methylphenol, wherein the mass fraction of 2,6-di-tert-butyl-4-methylphenol is 1 wt%.

[0019] More preferably, the polymerization temperature is 25~70℃, preferably 25℃; the polymerization time is 10 minutes to 15 hours, preferably 30 minutes; Specifically, the aforementioned COFs-supported iron catalyst can be used as the main catalyst in the preparation of polyisoprene. The process involves dissolving the COFs-supported iron catalyst in an anhydrous solvent in a reaction flask, then adding isoprene monomer, followed by a co-catalyst for polymerization. After post-treatment, polyisoprene is obtained. The resulting polyisoprene has a number-average molecular weight of 0.9 × 10⁻⁶. 5 -8.9×10 5 The molecular weight distribution was 2.2-2.9 g / mol; the proportion of the obtained polyisoprene cis-1,4 structure ranged from 67-68%, and the proportion of 3,4 structure ranged from 32-33%.

[0020] The present invention has the following beneficial effects: (1) The COFs supported iron catalyst of this application has good stability and catalytic polymerization performance, with a reaction activity of up to 2.0×106 g / (mol·h); and good selectivity regulation, with a selectivity of up to 68% for cis-1,4-polyisoprene.

[0021] (2) The iron-based catalyst of this application can achieve a high number-average molecular weight of 0.9 × 10⁻⁶ for polyisoprene. 5 -8.9×10 5 g / mol, with a narrow molecular weight distribution of 2.2-2.9. Attached Figure Description

[0022] Figure 1 The 1H NMR spectrum of the polyisoprene obtained in Example 11; Figure 2 The carbon NMR spectrum of the polyisoprene obtained in Example 11; Detailed Implementation The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope of protection of the claims of this application.

[0023] Example 1: Synthesis of the covalent organic framework LYU-COFZ 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine were added to a reaction tube in a 1:1 ratio. Tetrahydrofuran and Lewis acid catalysts were added. The glass tube was sealed under vacuum with a flame under liquid nitrogen freezing, and then placed in an oven at 25°C for 3 days to obtain a solid. The solid was washed multiple times with a large amount of ethanol and dried under vacuum to obtain LYU-COFZ.

[0024] Example 2 Synthesis of the covalent organic framework LYU-COFZ 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine were added to a reaction tube in a 1:1 ratio. Dichloromethane and Lewis acid catalyst were added. The glass tube was sealed under vacuum with a flame under liquid nitrogen freezing, and then placed in an oven at 100°C for 3 days to obtain a solid. After washing with a large amount of ethanol multiple times, the solid was dried under vacuum to obtain LYU-COFZ.

[0025] Example 3 Synthesis of the covalent organic framework LYU-COFZ 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine were added to a reaction tube in a 1:1 ratio. Toluene and Lewis acid catalysts were added, and the glass tube was sealed under vacuum with a flame under liquid nitrogen freezing. The tube was then placed in a 50°C oven and reacted for 5 days to obtain a solid. The solid was washed multiple times with a large amount of ethanol and dried under vacuum to obtain LYU-COFZ.

[0026] Example 4 Preparation of COFs-supported iron catalyst Weigh 30 mg of the LYU-COFZ material prepared in Example 1 and 5 mg of ferrous chloride into a reaction flask, add 20 mL of anhydrous dichloromethane, stir and react at 25 °C for 15 h, then filter the product, wash the filter cake with a large amount of ethanol, and dry it under vacuum to obtain the COFs supported iron catalyst.

[0027] ICP-AES analysis: 2.1 wt% Fe.

[0028] Example 5 Weigh 30 mg of the LYU-COFZ material prepared in Example 2 and 8 mg of ferrous chloride into a reaction flask, add 20 mL of anhydrous dichloromethane, stir at 50 °C for 48 h, then filter the product, wash the filter cake with a large amount of ethanol, and dry it under vacuum to obtain the COF supported iron catalyst.

[0029] ICP-AES analysis: 3.8 wt% Fe.

[0030] Example 6 Preparation of COFs-supported iron catalyst Weigh 30 mg of the LYU-COFZ material prepared in Example 3 and 5 mg of ferrous chloride into a reaction flask, add 20 mL of anhydrous dichloromethane, stir and react at 100 °C for 3 h, then filter the product, wash the filter cake with a large amount of ethanol, and dry it under vacuum to obtain the COFs supported iron catalyst.

[0031] ICP-AES analysis: 3.3 wt% Fe.

[0032] Example 7 A 25 ml dry reaction tube was transferred to a glove box, and 27 mg (Fe, 1 equiv.) of the 2.1 wt% Fe-supported iron catalyst in COFs prepared in Example 4 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 3.3 mL of methylaluminoxane (1.50 M, 500 equiv.), and 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 25 °C for 1 hour. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 83% and an activity of 5.6 × 10⁻⁶. 4 g / (mol·h). Number-average molecular weight is 1.3 × 10⁻⁶ g / (mol·h). 5 The molecular weight distribution is 2.2, with cis-1,4 structure accounting for 67% and 3,4 structure accounting for 33%.

[0033] Example 8 A 25 ml dry reaction tube was transferred to a glove box, and 27 mg (Fe, 1 equiv.) of the COFs-supported iron catalyst with 2.1 wt% Fe prepared in Example 4 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 5.0 mL of diethylaluminum chloride (1.0 M, 500 equiv.), and 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 70 °C for 15 hours. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 75% and an activity of 5.1 × 10⁻⁶. 4 g / (mol·h). Number-average molecular weight is 0.9 × 10⁻⁶. 5 The molecular weight distribution is 2.9, with cis-1,4 structure accounting for 68% and 3,4 structure accounting for 32%.

[0034] Example 9 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe COFs-supported iron catalyst prepared in Example 5 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 3.3 mL of methylaluminoxane (1.50 M, 500 equiv.), and then 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 25 °C for 1 hour. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 100% and an activity of 6.8 × 10⁻⁶. 4 g / (mol·h). Number-average molecular weight is 4.8 × 10⁻⁶. 5 The molecular weight distribution is 2.3, with cis-1,4 structure accounting for 68% and 3,4 structure accounting for 32%.

[0035] Example 10 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe-supported iron catalyst in COFs prepared in Example 5 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 3.3 mL of methylaluminoxane (1.50 M, 500 equiv.), and then 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 25 °C for 10 minutes. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 89% and an activity of 3.6 × 10⁻⁶. 5 g / (mol·h). Number-average molecular weight is 2.6 × 10⁻⁶. 5 The molecular weight distribution is 2.4, with cis-1,4 structure accounting for 68% and 3,4 structure accounting for 32%.

[0036] Example 11 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe-supported iron catalyst in COFs prepared in Example 5 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 3.3 mL of methylaluminoxane (1.50 M, 500 equiv.), and then 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 25 °C for 30 minutes. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 100% and an activity of 1.4 × 10⁻⁶. 5 g / (mol·h). Number-average molecular weight is 3.9 × 10⁻⁶ g / (mol·h). 5 The molecular weight distribution is 2.3, with cis-1,4 structure accounting for 68% and 3,4 structure accounting for 32%.

[0037] Example 12 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe COFs-supported iron catalyst prepared in Example 5 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 5 ml of anhydrous toluene, 6.6 mL of methylaluminoxane (1.50 M, 1000 equiv.), and then 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added. The reaction was carried out at 25 °C for 10 minutes. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 100% and an activity of 8.2 × 10⁻⁶. 5 g / (mol·h). Number-average molecular weight is 1.7 × 10⁻⁶ g / (mol·h). 5 The molecular weight distribution is 2.9, with cis-1,4 structure accounting for 68% and 3,4 structure accounting for 32%.

[0038] Example 13 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe-supported COFs iron catalyst prepared in Example 5 was added. The tube was then transferred outside the glove box, and under an argon atmosphere, 25 ml of anhydrous toluene, 6.6 mL of methylaluminoxane (1.50 M, 1000 equiv.), and 5 ml of isoprene monomer (50 mmol, 5000 equiv.) were added. The reaction was carried out at 25 °C for 10 minutes. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). After quenching, a large amount of white solid precipitated, with a yield of 65% and an activity of 2.0 × 10⁶ g / (mol·h). The number average molecular weight was 8.9 × 10⁶ g / (mol·h). 5 The molecular weight distribution is 2.5, with cis-1,4 structure accounting for 67% and 3,4 structure accounting for 33%.

[0039] Comparative Example 1 Take a 25 ml dry reaction tube, transfer it to a glove box, add 27 mg (Fe, 1 equiv.) of COFs-supported iron catalyst with 2.1 wt% Fe prepared in Example 4, transfer it outside the glove box, add 5 ml of anhydrous toluene and 5.0 mL of diethylaluminum monochloro (1.0 M, 500 equiv.) under an argon atmosphere, then add 1 ml of isoprene monomer (10 mmol, 1000 equiv.), and react at 25 °C for 15 hours. Terminate the reaction with methanol-dilute hydrochloric acid solution (1:50, V / V). No solid precipitates, and the yield is 0%.

[0040] Comparative Example 2 A 25 ml dry reaction tube was transferred to a glove box, and 27 mg (Fe, 1 equiv.) of COFs-supported iron catalyst with 2.1 wt% Fe prepared in Example 4 was added. The tube was then transferred outside the glove box, and 5 ml of anhydrous toluene, 5.0 mL of triethylaluminum (1.0 M, 500 equiv.), and 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added under an argon atmosphere. The reaction was carried out at 25 °C for 15 hours. The reaction was terminated with a methanol-dilute hydrochloric acid solution (1:50, V / V). No solid precipitated, and the yield was 0%.

[0041] Comparative Example 3 A 25 ml dry reaction tube was transferred to a glove box, and 27 mg (Fe, 1 equiv.) of COFs-supported iron catalyst with 2.1 wt% Fe prepared in Example 4 was added. The tube was then transferred outside the glove box, and 5 ml of anhydrous toluene, 5.0 mL of triisobutylaluminum (1.0 M, 500 equiv.), and 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added under an argon atmosphere. The reaction was carried out at 25 °C for 15 hours. The reaction was terminated with a methanol-dilute hydrochloric acid solution (1:50, V / V). No solid precipitated, and the yield was 0%.

[0042] Comparative Example 4 A 25 ml dry reaction tube was transferred to a glove box, and 14.9 mg (Fe, 1 equiv.) of the 3.8 wt% Fe-supported iron catalyst in COFs prepared in Example 5 was added. The tube was then transferred outside the glove box, and 5 ml of anhydrous toluene, 0.66 mL of methylaluminoxane (1.50 M, 100 equiv.), and 1 ml of isoprene monomer (10 mmol, 1000 equiv.) were added under an argon atmosphere. The reaction was carried out at 25 °C for 30 minutes. The reaction was quenched with a methanol-hydrochloric acid solution (1:50, V / V) and an ethanol solution of 2,6-di-tert-butyl-4-methylphenol (1 wt.%). No solid precipitated after quenching, and the yield was 0%.

Claims

1. A COFs-supported iron catalyst, characterized in that, The structure of the COFs-supported iron catalyst is shown in Formula I. Formula I In Equation I, the wavy line represents a periodic extension structure, and all N-containing sites in Equation I can coordinate with ferrous chloride.

2. The COFs-supported iron catalyst according to claim 1, characterized in that, The COFs-supported iron catalyst is formed by covalent organic framework compound and ferrous chloride. The preparation method is to react ferrous chloride, reaction solvent and covalent organic framework LYU-COFZ at a set temperature of 25~100℃ for 3~48 hours under anhydrous and oxygen-free conditions, centrifuge, wash and dry to obtain COFs-supported iron catalyst. ； The covalent organic framework LYU-COFZ is formed by the condensation of 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine.

3. The COFs-supported iron catalyst according to claim 2, characterized in that, The reaction solvent in the preparation method is one of dichloromethane, tetrahydrofuran, toluene, and ethanol.

4. The COFs-supported iron catalyst according to claim 2 or 3, characterized in that, The covalent organic framework LYU-COFZ is prepared as follows: 1,3,5-tris(4-aminophenyl)benzene and 2,2'-dicarboxy-5,5'-bipyrimidine are mixed in a weight ratio of 1:1, a catalyst and a reaction solvent are added, the glass tube is sealed under vacuum with a flame under liquid nitrogen freezing, and then placed in an oven at 25~100℃ for 3-5 days to obtain a solid. After washing and drying, LYU-COFZ is obtained. 。 5. The COFs-supported iron catalyst according to claim 4, characterized in that, The reaction solvent in the preparation method of the covalent organic framework LYU-COFZ is one of dichloromethane, tetrahydrofuran, toluene, and ethanol.

6. The application of the COFs-supported iron catalyst according to any one of claims 1-5 in the polymerization of conjugated dienes, characterized in that, The COFs-supported iron catalyst is used as the main catalyst in the conjugated diene polymerization reaction.

7. The application according to claim 6, characterized in that, The conjugated diene polymerization reaction is as follows: COFs-supported iron catalyst is suspended in an anhydrous solvent, then conjugated diene monomer is added, then a co-catalyst is added to carry out the polymerization reaction, and after post-treatment, polyconjugated diene is obtained. in, The anhydrous solvent is one or a combination of two or more of toluene, n-hexane, cyclohexane and pentane; The volume ratio of the anhydrous solvent to the conjugated diene monomer is (1-10):1; The co-catalyst is one or more of methylaluminoxane, triethylaluminum, triisobutylaluminum, and diethylaluminum chloride; and the molar ratio of aluminum in the co-catalyst to iron in the COFs-supported iron catalyst is (100-1000):

1. The molar ratio of the conjugated diene monomer to the iron element in the COFs supported iron catalyst is (1000-5000):1; The post-treatment method involves adding a quenching agent and an antioxidant to quench the reaction, washing with methanol, and drying.

8. The application according to claim 7, characterized in that, In the post-treatment method, the quenching agent is methanol; the antioxidant is an ethanol solution of 2,6-di-tert-butyl-4-methylphenol, and the mass fraction of 2,6-di-tert-butyl-4-methylphenol is 1 wt%.

9. The application according to claim 7, characterized in that, The polymerization reaction is carried out at a temperature of 25-70°C for 10 minutes to 15 hours.

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