CN111286022A - Supported catalyst and application thereof in preparation of low-molecular-weight polyphenylene ether - Google Patents

Abstract

The invention discloses a supported catalyst and application thereof in preparing low molecular weight polyphenylene ether, wherein the supported catalyst is a complex of imidazole ligands and metal ions grafted on the surface of a nano-alumina particle subjected to surface modification; the surface-modified nano alumina particles are modified by a silane coupling agent. The catalyst has high catalytic efficiency and good selectivity, can be separated from a reaction system in a centrifugal or filtering mode, and is recycled and recycled. Solves the problem that the existing catalyst is difficult to recycle in the PPO production process. The product has the characteristics of low content of residual metal catalyst, low dielectric constant and dielectric loss, good processability and the like, the preparation process is simple and easy to implement, has wide development space and great market application value, is suitable for industrial production, and meets the requirement of sustainable development.

Description

Supported catalyst and application thereof in preparation of low-molecular-weight polyphenylene ether

Technical Field

The invention relates to the technical field of polymer chemical industry, in particular to a supported catalyst, a preparation method thereof and application of the supported catalyst in preparation of low molecular weight polyphenylene ether in an oil-water two-phase medium.

Background

Polyphenylene Oxide (PPO) is an engineering plastic with excellent comprehensive performance, not only has good mechanical properties, but also has outstanding performances such as low dielectric constant, low dielectric loss, low hygroscopicity, high glass transition temperature, acid and alkali corrosion resistance and the like, thereby having wide application prospects in the fields of automobile parts, electronic devices, office equipment, coatings, additives and the like. However, as a thermoplastic resin, high molecular weight PPO has high melt viscosity, poor processability, and low reactivity when used in additives and composites. The PPO with low molecular weight can overcome the defects, and simultaneously, the electrical property of the PPO with high molecular weight is kept. In recent years, PPO oligomers with number average molecular weights of 1000-.

The traditional PPO synthesis method is carried out in an organic solvent, the PPO synthesized in a homogeneous medium has large molecular weight, the variable regulation and control of the molecular weight are difficult to realize, the content of residual catalyst metal ions in a product is high, and the electrical property of the product is reduced to a certain extent. Low molecular weight PPO is generally obtained by redistribution or depolymerization of high molecular weight PPO with phenolic derivatives under the action of an initiator. Redistribution reactions, however, often suffer from problems such as bimodal distribution of product molecular weight, catalyst residues in the polymer, and difficulty in controlling the molecular structure of the polymer. The continuous regulation and control of molecular weight is still an unsolved technical problem.

The recycling of the catalyst can greatly reduce the production cost, save resources, reduce the discharge of three wastes and have high economic and environmental protection values. At present, catalysts for synthesizing polyphenylene oxide are mainly homogeneous and are not easy to separate, the catalysts are loaded on inert carriers, and the catalysts can be separated by simple filtration or centrifugation means after the reaction is finished, but the catalytic efficiency of the catalysts is greatly reduced, so that the recycling of PPO catalysts still remains to be solved.

Disclosure of Invention

The invention provides a supported catalyst which has high catalytic efficiency and good selectivity and is easy to recycle.

The invention also provides a preparation method of the supported catalyst, which is simple to operate and easy to control, and the composition of the catalyst can be adjusted according to production requirements so as to adjust the performance index of the product.

The invention also provides a process for preparing a crosslinkable polyphenylene ether in a two-phase medium of oil and water with a supported catalyst, in which process the catalyst can be recovered and reused as desired. The technical scheme is as follows:

the invention provides a supported catalyst, wherein the supported catalyst is an alumina nano particle modified by a silane coupling agent, and a complex is grafted on the surface of the alumina nano particle modified by the silane coupling agent; the complex is a complex of an imidazole ligand and metal ions;

the imidazole ligand is a cross-linked copolymer containing an N-vinyl imidazole monomer;

the metal ions are divalent copper ions or divalent manganese ions;

wherein the N-vinyl imidazole monomer is a compound shown in a structural formula (I);

in the formula (I), R₁、R₂And R₃Independently is hydrogen or C₁～C₄Alkyl groups of (a);

the molar ratio of imidazole groups to metal ions in the complex is 0.5-200: 1, and the preferred molar ratio of imidazole groups to metal ions is 2-20: 1, so that the reaction rate is higher, the selectivity is better, and the yield of polyphenylene oxide is higher.

The invention also provides a preparation method of the supported catalyst, which comprises the following steps:

(1) dispersing a silane coupling agent and aluminum oxide nanoparticles into a mixed solution of toluene and methanol, carrying out reflux reaction on the mixed solution at 110 ℃ for 24 hours, and after the reaction is finished, centrifuging, washing and drying to obtain silane coupling agent modified aluminum oxide nanoparticles; the volume ratio of the toluene to the methanol is 2-9: 1; the step (1) can be summarized as follows: carrying out coupling reaction on the alumina nano particles and a silane coupling agent to obtain surface-modified nano alumina;

(2) ultrasonically dispersing imidazole monomers, a cross-linking agent and the silane coupling agent modified aluminum oxide nanoparticles in ethyl acetate, adding an initiator, and adding N₂Reacting for 24 hours at 110 ℃, drying and grinding to obtain the crosslinked polyvinyl imidazole ligand grafted on the surface of the alumina nano particles; the step (2) can be summarized as follows: initiating a crosslinking copolymerization reaction of vinyl imidazole monomers and a crosslinking agent by free radicals in the presence of the surface-modified nano alumina particles;

(3) respectively dissolving and dispersing a metal ion precursor and the crosslinked polyvinyl imidazole ligand grafted on the surface of the alumina nano particle in water, mixing and carrying out ultrasonic treatment for 30 minutes, centrifuging and drying to obtain the supported catalyst; the step (3) can be summarized as that the imidazole group and the metal ion are subjected to coordination reaction to prepare the supported catalyst.

Based on the technical scheme, preferably, when the metal ions are divalent copper ions, the metal ion precursor is at least one of copper chloride, copper bromide, copper sulfate and copper nitrate;

when the metal ions are divalent manganese ions, the metal ion precursor is at least one of manganese chloride, manganese bromide, manganese iodide, manganese carbonate, manganese acetate, manganese nitrate, manganese sulfate and manganese phosphate.

Based on the technical scheme, preferably, the silane coupling agent is one or more of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 4-mercaptobutyltrimethoxysilane and 4-mercaptobutyltriethoxysilane;

based on the technical scheme, the cross-linking agent is preferably divinylbenzene or N, N' -methylene-bis (acrylamide); the initiator, the azodiisoheptonitrile, the potassium persulfate, the sodium persulfate, the ammonium persulfate, the benzoyl peroxide, the dicumyl peroxide, the tert-butyl hydroperoxide and the cumene hydroperoxide.

The invention also provides an application of the supported catalyst, and the catalyst is applied to the oxidative polymerization reaction for preparing the low molecular weight polyphenylene ether in the oil-water two-phase medium and can be used for catalyzing the oxidative polymerization reaction for preparing the crosslinkable polyphenylene ether in the oil-water two-phase medium by taking the phenol monomer and the oxidant as raw materials.

The supported catalyst can be separated and recycled by a filtering or centrifuging method after the oxidative polymerization reaction is finished.

The method for preparing the polyphenyl ether in the oil-water two-phase medium by utilizing the supported catalyst comprises the following steps: dissolving a phenol monomer in an organic solvent, dispersing a supported catalyst in water, mixing oil and water, carrying out oxidative polymerization reaction in the presence of an oxidant, standing for layering after the reaction is finished, separating the supported catalyst from a reaction system by using a filtering or centrifuging method, washing and drying the recovered supported catalyst, and recycling the catalyst for the next reaction. The reaction product adopts methanol as a precipitator, and the low molecular weight polyphenylene ether is obtained by filtration and separation.

The phenol monomer is a compound shown in a formula (II):

R₄and R₅Independently hydrogen, alkyl with 1 to 4 carbon atoms, halogenated alkyl, aminoalkyl or alkoxy;

R₆is hydrogen or halogen;

the weight average molecular weight of the polyphenyl ether is 1200-10000.

Based on the above technical scheme, preferably, the molar ratio of the raw materials in the oxidative copolymerization reaction is as follows:

a phenol monomer 1;

0.0001-1 part of metal ions in the supported catalyst;

0.1-10% of an oxidant;

based on the technical scheme, the preferable temperature of the oxidation copolymerization reaction is 10-80 ℃, preferably 20-60 ℃, the reaction rate is higher and the reaction byproducts are less in the temperature range; the reaction time is 4 to 72 hours; the pressure is 0.1MPa to 5.0MPa, preferably 0.1MPa to 2.0MPa, and the pressure range has higher safety in industrial production operation.

Based on the technical scheme, preferably, the oil phase of the oxidation copolymerization reaction medium is one or more of good solvents of phenol monomers such as benzene, toluene, nitrobenzene, trichloromethane or dichloromethane; the volume ratio of oil to water is 50-10: 1.

Based on the technical scheme, preferably, the oxidant is oxygen, air or mixed gas formed by mixing oxygen and inert gas; in the mixed gas of the oxygen and the inert gas, the volume ratio of the oxygen to the inert gas is 0.05-100: 1; the inert gas is one or a mixture of more of carbon dioxide, nitrogen, helium, neon and argon in any proportion; the oxidizing effect of the mixed gas is oxygen, so that the amount of the oxidant is calculated by the oxygen in the invention.

Advantageous effects

(1) The catalyst combines the characteristics of the nano particles and the metal ion-crosslinked polyvinyl imidazole ligand complex; the nano particles are used as the carrier of the catalyst, have small size and large specific surface area, so that the catalyst is fully contacted with a reaction substrate, have high catalytic efficiency and are beneficial to effective loading and catalysis of the catalyst, and meanwhile, the nano particles are the core of the catalyst, and the catalyst can be recovered in a centrifugal or filtering mode.

(2) The low molecular weight polyphenylene ether product obtained by the invention has the characteristics of low content of residual metal catalyst, low dielectric constant and dielectric loss, good processability and the like.

(3) The preparation method disclosed by the invention is simple and easy to operate, has wide development space and great market application value, is suitable for industrial production, meets the requirements of sustainable development, is easy to control, and is suitable for industrial production.

Drawings

FIG. 1 is a schematic diagram of the structure of a supported catalyst according to the present invention; wherein: the curve of class a represents- (CH-CH)₂) -a crosslinked network formed by copolymerization with a crosslinking agent; the b-type curve represents the omitted cross-linked network.

Detailed Description

Example 1

Preparation of Supported catalysts

(1) Preparation of silane coupling agent modified nano alumina particles: under mechanical stirring, 0.3mL (1.5mmol) of 3-mercaptopropyltrimethoxysilane and nano-alumina (1.9g) are refluxed at 110 ℃ for 24 hours in 100mL of a mixed solution of toluene/methanol 80:20 (volume ratio). After the reaction is finished, washing the product with methanol for 3 times, washing the product with deionized water for 3 times, performing centrifugal separation, and performing vacuum drying on the separated solid for 48 hours to prepare silane coupling agent modified nano alumina particles;

(2) preparing a crosslinked polyvinyl imidazole ligand grafted on the surface of a nano alumina particle: ultrasonically dispersing 2.72mL (30mmol) of N-vinylimidazole subjected to reduced pressure distillation, 0.42mL (3mmol) of divinylbenzene and 2g of silane coupling agent modified nano-alumina particles prepared in the step (1) in 50mL of ethyl acetate, adding azobisisobutyronitrile with the mass fraction of 5% of N-vinylimidazole monomer as an initiator, and adding N into the mixture₂Reacting for 24 hours at 110 ℃, and performing vacuum drying on the mixture for 48 hours and grinding to obtain the crosslinked polyvinyl imidazole ligand grafted on the surface of the nano alumina particle; the nanometer alumina particles coated by polymers with different crosslinking degrees can be prepared by changing the feed ratio of N-vinyl imidazole to divinyl benzene;

(3) the cross-linked polyvinyl imidazole ligand grafted on the surface of the nano alumina particle coordinates with metal ions: adding CuCl₂·2H₂O (0.0086g, 0.05mmol) and the crosslinked polymer coated nano alumina particles (0.18g, wherein the content of imidazole groups is 0.2mmol) are respectively dissolved and dispersed in 5mL of water, mixed and subjected to ultrasonic treatment for 30 minutes to coordinate copper ions and imidazole groups, so that the crosslinked polymer ligand-metal ion complex catalyst loaded on the nano alumina particles is obtained.

FIG. 1 is a schematic diagram of the structure of a supported catalyst according to the present invention; wherein: the curve of class a represents- (CH-CH)₂) -a crosslinked network formed by copolymerization with a crosslinking agent; the b-type curve represents an omitted cross-linked network structure in which the kinds of the cross-linking agent and the silane coupling agent are various and can be changed.

Examples 2 to 4

With the exception of changing the charge ratio of N-vinylimidazole to divinylbenzene, the procedure of example 1 was otherwise followed to prepare a crosslinked polymer supported on nano-alumina particles, wherein the specific parameters are shown in Table 2, and finally the crosslinked polymer ligand-metal ion complex catalyst supported on nano-alumina particles was obtained.

TABLE 2

Example number	N-vinylimidazole/divinylbenzene
		2	2.72mL(30mmol)/0.84mL(6mmol)
3	2.72mL(30mmol)/1.40mL(10mmol)
		4	2.72mL(30mmol)/0.21mL(1.5mmol)

Examples 5 to 6

The preparation method is the same as the example 1 except that 3-mercaptopropyltriethoxysilane and 4-mercaptobutyltrimethoxysilane are adopted to replace the 3-mercaptopropyltrimethoxysilane in the example 1, and the silane coupling agent modified nano alumina particles are prepared to finally obtain the nano alumina particle supported cross-linked polymer ligand-metal ion complex catalyst.

Example 7

Except that N, N' -methylene-bis (acrylamide) is adopted to replace divinylbenzene in the example 1 as a crosslinking agent, the other operations are the same as the example 1, the crosslinked polymer supported by the nano alumina particles is prepared, and finally the crosslinked polymer ligand-metal ion complex catalyst supported by the nano alumina particles is obtained.

Examples 8 to 9

Except for changing the mass ratio of the vinyl imidazole monomer to the silane coupling agent modified nano-alumina, the other operations are the same as in example 1, the specific parameters are shown in table 3, and finally the nano-alumina particle supported cross-linked polymer ligand-metal ion complex catalyst is obtained.

TABLE 3

Examples 10 to 12

Except that the crosslinked polymer supported by the nano alumina particles prepared in examples 2 to 4 was used as a ligand and the kind of the metal compound was changed, the other operations were the same as in example 1, and the crosslinked polymer ligand-metal ion complex catalyst supported by the nano alumina particles was finally obtained, as shown in table 4.

TABLE 4

Example number	Metal compound and its use amount	Ligands
			10	0.04mmol of manganese acetate	Example 2
11	0.03mmol of manganese chloride	Example 3
			12	0.05mmol of copper nitrate	Example 4

Examples 13 to 15

The same operations as in example 1 were carried out except that the molar ratio of the metal ions to the imidazole groups in the polyvinyl imidazole based ligand was changed and the metal compound was changed, to finally obtain a crosslinked polymer ligand-metal ion complex catalyst supported on nano alumina particles, as shown in table 7.

TABLE 5

Example 16

Preparation of crosslinkable polyphenyl ether in oil-water two-phase medium

6.162g of 2, 6-dimethylphenol (DMP, 50mmol) is dissolved in 15mL of toluene in a reaction kettle connected with a thermometer, a stirring paddle, a condensation tube and a gas inlet and outlet, the supported catalyst prepared in example 1 is ultrasonically dispersed in 2mL of water, the two media are mixed and stirred uniformly, then the reaction kettle is heated to 40 ℃, oxygen is introduced, and the reaction is carried out for 6 hours at the stirring speed of 600 revolutions per minute.

After the polymerization reaction, the reaction mixture was allowed to stand, and the catalyst was recovered by filtration, washed with distilled water 5 times, and vacuum-dried at room temperature for 24 hours, with the recovery rate of the catalyst being 97.2%. Adding excessive methanol into the reaction product after the catalyst is recovered for precipitation, filtering, washing and drying to obtain a polymerization product. The obtained polymerization product was extracted with acetonitrile to remove by-product 3,3 ', 5,5 ' -tetramethyl-4, 4 ' -Diphenoquinone (DPQ) to obtain white powder, i.e., PPO, yield 94.2%, weight average molecular weight 4000, molecular weight distribution 2.0.

Example 17

Low molecular weight PPO was prepared in a two-phase oil and water medium as in example 16, except that the catalyst recovered in example 16 was used in place of the original catalyst. The catalyst recovery was 93.8%. The polymerization product was obtained in a yield of 93.0%, PPO weight-average molecular weight of 4200, molecular weight distribution of 2.0.

Examples 18 to 20

Low molecular weight PPO was prepared in an oil-water two-phase medium according to the method of example 16, except that the catalysts prepared in examples 2-4 were used, respectively, and the polymerization results are shown in Table 7.

TABLE 7

Example number	Catalyst and process for preparing same	PPO yield (%)	PPO weight average molecular weight	Mw/Mn
					18	Example 2	80.2	5400	1.9
19	Example 3	75.6	4400	1.7
					20	Example 4	93.8	5600	1.8

Examples 21 to 23

Low molecular weight PPO was prepared in an oil-water two-phase medium according to the method of example 16, except that the catalysts prepared in examples 5 to 7 were used, respectively, and the polymerization results are shown in Table 8.

TABLE 8

Examples 24 to 25

Low molecular weight PPO was prepared in an oil-water two-phase medium according to the method of example 16, except that the catalysts prepared in examples 8 to 9 were used, respectively, and the polymerization results are shown in Table 9.

TABLE 9

Example number	Catalyst and process for preparing same	PPO yield (%)	PPO weight average molecular weight	Mw/Mn
					24	Example 8	91.8	3900	1.9
25	Example 9	87.3	5700	1.7

Examples 26 to 28

Low molecular weight PPO was prepared in an oil-water two-phase medium according to the method of example 16, except that the catalysts prepared in examples 8 to 10 were used, respectively, and the polymerization results are shown in Table 10.

Watch 10

Example number	Catalyst and process for preparing same	PPO yield (%)	PPO weight average molecular weight	Mw/Mn
					26	Example 10	93.8	3800	1.8
27	Example 11	90.3	4900	1.9
					28	Example 12	95.5	6500	1.9

Example 29

Low molecular weight PPO was prepared in an oil-water two-phase medium according to the method of example 16, substituting 2, 6-dimethylphenol (5.316g, 40mmol) for 2, 6-dimethylphenol, giving a yield of 80.28%, a product having a weight-average molecular weight of 6200 and a molecular weight distribution of 2.3.

Example 30

Low molecular weight PPO was prepared in an oil-water two-phase medium as in example 16, except that air was used instead of oxygen, the PPO yield was 87.8%, the PPO weight average molecular weight was 3500, and the molecular weight distribution was 1.7.

Example 31

Low molecular weight PPO was prepared in an oil-water two-phase medium as in example 16, except that the reaction temperature was 25 ℃ and the reaction time was 12 hours, the PPO yield was 83.9%, the PPO weight average molecular weight was 2900 and the molecular weight distribution was 1.9.

Example 32

Low molecular weight PPO was prepared in an oil-water two-phase medium as in example 16, except that the reaction temperature was 60 ℃ and the reaction time was 8 hours, the yield of PPO was 96.7%, the weight average molecular weight of PPO was 8700 and the molecular weight distribution was 2.2.

Claims (10)

1. The supported catalyst is characterized by being alumina nano particles modified by a silane coupling agent, wherein a complex is grafted on the surface of the alumina nano particles modified by the silane coupling agent; the complex is a complex of an imidazole ligand and metal ions;

the imidazole ligand is a cross-linked copolymer containing an N-vinyl imidazole monomer;

the metal ions are divalent copper ions or divalent manganese ions;

the N-vinyl imidazole monomer is a compound shown in a structural formula (I);

in the formula (I), R₁、R₂And R₃Independently is hydrogen or C₁～C₄Alkyl groups of (a);

in the complex, the molar ratio of imidazole groups to metal ions is 0.5-200: 1.

2. A method of preparing a supported catalyst according to claim 1, comprising the steps of:

(1) dispersing a silane coupling agent and aluminum oxide nanoparticles in a mixed solvent of toluene and methanol to obtain a mixed solution, carrying out reflux reaction on the mixed solution at 110 ℃ for 24 hours, and after the reaction is finished, centrifuging, washing and drying to obtain silane coupling agent modified aluminum oxide nanoparticles; in the mixed solvent, the volume ratio of toluene to methanol is 2-9: 1;

(2) ultrasonically dispersing aluminum oxide nano particles modified by N-vinyl imidazole monomer, cross-linking agent and silane coupling agent in ethyl acetate, adding initiator, and adding into N₂Reacting for 24 hours at 110 ℃, drying and grinding to obtain the crosslinked polyvinyl imidazole ligand grafted on the surface of the alumina nano particles;

(3) respectively dissolving and dispersing a metal ion precursor and the crosslinked polyvinyl imidazole ligand grafted on the surface of the alumina nano particle in water, mixing and carrying out ultrasonic treatment for 30 minutes, centrifuging and drying to obtain the supported catalyst.

3. The method for preparing a supported catalyst according to claim 2, wherein when the metal ion is a divalent copper ion, the metal ion precursor is at least one of copper chloride, copper bromide, copper sulfate and copper nitrate;

when the metal ions are divalent manganese ions, the metal ion precursor is at least one of manganese chloride, manganese bromide, manganese iodide, manganese carbonate, manganese acetate, manganese nitrate, manganese sulfate and manganese phosphate.

4. The method for preparing the supported catalyst according to claim 3, wherein the silane coupling agent is one or more of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 4-mercaptobutyltrimethoxysilane and 4-mercaptobutyltriethoxysilane.

5. A process for preparing a supported catalyst according to claim 3 wherein the cross-linking agent is divinylbenzene or N, N' -methylene-bis (acrylamide); the initiator is at least one of azobisisobutyronitrile, azobisisoheptonitrile, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide and cumene hydroperoxide.

6. Use of the supported catalyst of claim 1 in oxidative polymerization reactions for the preparation of low molecular weight polyphenylene ethers; the oxidative polymerization reaction takes a phenol monomer and an oxidant as raw materials, and prepares the low molecular weight polyphenylene ether in an oil-water two-phase medium; the structure of the phenol monomer is shown as a formula (II);

R₄and R₅Independently hydrogen, alkyl, haloalkyl, aminoalkyl or alkoxy having 1 to 4 carbon atoms, R₆Is hydrogen or halogen;

the weight average molecular weight of the low molecular weight polyphenylene ether is 1200-10000.

7. The use according to claim 6, wherein the molar ratio of the phenolic monomer to the metal ion in the supported catalyst to the oxidant in the oxidative copolymerization reaction is 1: 0.0001-1: 0.1-10.

8. The use according to claim 6, wherein the oxidative polymerization is carried out at a temperature of 10 ℃ to 80 ℃, for a time of 4 hours to 72 hours and under a pressure of 0.1MPa to 5.0 MPa.

9. The use according to claim 6, wherein in said oxidative polymerization, in said oil-water two-phase medium, the oil phase is at least one of benzene, toluene, nitrobenzene, chloroform or dichloromethane; the volume ratio of oil to water is 50-10: 1.

10. The use of claim 6, wherein the oxidant is oxygen, air or a mixture of oxygen and an inert gas; in the mixed gas of the oxygen and the inert gas, the volume ratio of the oxygen to the inert gas is 0.05-100: 1; the inert gas is at least one of carbon dioxide, nitrogen, helium, neon and argon.

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