Amino mesoporous silica supported copper catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer material synthesis and heterogeneous catalysis, and particularly discloses an amino mesoporous silica supported copper catalyst as well as a preparation method and application thereof. The catalyst is prepared by a direct co-condensation method which comprises the following steps: in the presence of a structure-directing agent, copolymerizing a silicon source and amino silane to form a mesoporous silica carrier which has a regular mesoporous structure and is modified by amino in a skeleton; then loading cuprous through a solid-state ion exchange method in an inert atmosphere, and stably endowing highly dispersed cuprous (Cu < + >) with an active center through low-temperature heat treatment; the catalyst can be used for efficiently catalyzing oxidative coupling of phenol, and is particularly suitable for synthesizing polyphenyl ether with controllable number-average molecular weight and terminal functionality, the synthesized product is high in purity and narrow in molecular weight distribution, and the catalyst is particularly suitable for high-performance copper-clad plates, semiconductor packaging and other electronic chemicals.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material synthesis and heterogeneous catalysis, and particularly relates to a mesoporous silica supported copper catalyst, a preparation method and application thereof. BACKGROUND

[0002] Polyphenylene ether prepared by oxidative coupling of phenol is a high-performance engineering plastic with excellent dielectric properties, heat resistance and dimensional stability, and is widely used in high-frequency high-speed communication, integrated circuit packaging and other high-end electronic fields. In order to improve its processing performance and obtain cross-linkable prepolymer, it is necessary to synthesize low molecular weight polyphenylene ether with active functional groups (such as hydroxyl or epoxy) at the end in industry.

[0003] At present, the "A monomer method" of self-polymerization of monophenol oxidation or the "AB monomer method" of copolymerization with monophenol and diphenol are generally used in industry to prepare hydroxyl-terminated polyphenylene ether. The core of these methods is to use copper-amine complex as a homogeneous catalyst to catalyze the coupling reaction of phenol oxygen free radicals in the presence of oxygen. However, the traditional process has the following inherent defects: (1) the homogeneous catalyst is difficult to effectively separate and recover from the high-viscosity polymer solution, resulting in complex subsequent purification steps, and the residual copper ions may affect the long-term reliability of the final product in harsh electronic applications; (2) a large amount of organic solvent and organic amine ligand is required for the reaction, which exists environmental and cost pressure; (3) the precise control of polymer molecular weight and end group functionality cannot be achieved.

[0004] In order to solve the problem of catalyst separation, researchers try to load copper species on silica, molecular sieve and other carriers to prepare heterogeneous catalysts. However, these methods often have problems such as uneven dispersion of copper species, easy leaching or agglomeration during the reaction, and difficulty in maintaining the high activity of monovalent copper (Cu + ) state. Cu + is considered to be the key active center of the oxidative coupling reaction, but its stabilization on the heterogeneous carrier is a major technical difficulty.

[0005] CN104741140B discloses an amine-functionalized mesoporous silica microsphere supported heterogeneous catalyst, which uses an acidic solution and an anionic surfactant (sodium N-lauroyl glutamate) as a template, and grows metal ions in situ into nanometer metal oxide clusters by hydrothermal method, and finally is used for oxidative degradation of organic dyes by hydrogen peroxide. This technology has three major limitations: ① the amine group is easily protonated under acidic conditions, resulting in low loading and uneven distribution of the amine group on the carrier; ② the active center of the metal oxide cluster formed by the hydrothermal method (rather than a single valence state metal ion) is ambiguous; ③ its application scenario is limited to dye degradation, and it is not involved in oxidative coupling and high molecular weight polymerization, and it does not consider the stringent requirements of low molecular weight polyphenylene ether synthesis on the valence state, dispersity and metal residue of the active center of the catalyst.

[0006] Therefore, it is of great significance for the green upgrading and high-endization of the chemical industry to develop a heterogeneous copper catalyst with high activity, high stability, easy recovery and precise regulation of the structure of the polymerization product. SUMMARY

[0007] The primary purpose of the present application is to overcome the problems of existing copper-amine homogeneous catalysts, such as difficult separation and recovery, easy metal residue, and existing heterogeneous copper catalysts, such as low activity and poor stability, and to provide a preparation method of mesoporous silica supported copper catalyst (Cu + MSN-N) by a direct co-condensation method to prepare amine-functionalized mesoporous silica and stabilize the monovalent copper active center of the catalyst.

[0008] The second purpose of the present application is to provide an amine-functionalized mesoporous silica supported copper catalyst (Cu + MSN-N) prepared by the above method, which has a single valence Cu + MSN-N) as the active center, and the catalyst preparation process is simple, easy to recover, and can be recycled.

[0009] The third purpose of the present application is to provide a method for efficiently and greenly synthesizing a structure-controllable bifunctional low molecular weight polyphenyl ether using the above catalyst.

[0010] To achieve the above purposes, the present application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a preparation method of amine-functionalized mesoporous silica supported copper catalyst (Cu + MSN-N), which core is to construct the carrier by a one-step direct co-condensation strategy, and to stabilize the active center by combining solid-state ion exchange and inert atmosphere heat treatment, and specifically includes the following steps:

[0012] S1, synthesis of amine-functionalized mesoporous silica: in an alkaline aqueous solution, under stirring at 60-90°C, a mixed solution of tetraethyl orthosilicate (TEOS) and amino silane is quickly injected as a structure-directing agent, the molar ratio of the amino silane to TEOS is 1:20 to 1:5, the reaction is continued for 2-6 hours, the obtained product is centrifuged and washed, and then refluxed with an acidic ethanol solution to remove the structure-directing agent, and finally dried to obtain the amine-functionalized mesoporous silica;

[0013] S2. Synthesis of Amine-functionalized Mesoporous Silica-Supported Copper Heterogeneous Catalyst: Under an inert atmosphere, the amino-functionalized mesoporous silica obtained in step S1 was ground and mixed with a monovalent copper salt precursor at a mass ratio of copper to amino-functionalized mesoporous silica of 0.5%-5%. The mixture was then heat-treated at 200-400°C for 2-6 hours in an inert or reducing atmosphere. After cooling, the amino-functionalized mesoporous silica-supported monovalent copper catalyst (Cu) was obtained. + @MSN-N).

[0014] Preferably, the structure-directing agent mentioned in step S1 is selected from cationic surfactants, specifically those containing C 10 —C 22 Long-chain alkyl quaternary ammonium salts, such as at least one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, or octadecyltrimethylammonium bromide.

[0015] Preferably, the aminosilane mentioned in step S1 is selected from silane coupling agents containing amino groups, specifically organosilane compounds containing at least one primary amino group, such as at least one of 3-aminopropyltriethoxysilane (APTES), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (AEAPTMS), or N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0016] Preferably, the acidic ethanol solution used to remove the structure-directing agent in step S1 is an ethanol solution containing 1-5 wt% concentrated hydrochloric acid, with a reflux temperature of 70-85°C and a reflux time of 6-24 hours.

[0017] Preferably, the monovalent copper salt precursor in step S2 is at least one of cuprous chloride (CuCl), cuprous iodide (CuI), or cuprous bromide (CuBr).

[0018] Preferably, the heat treatment atmosphere in step S2 is any one of high-purity nitrogen, argon, or a mixture of 5% hydrogen and 95% nitrogen by volume.

[0019] In this invention, a cationic surfactant is used as a template to induce a co-hydrolysis condensation reaction between TEOS and aminosilane under alkaline conditions. The aminosilane directly participates in the framework construction, resulting in uniform and firm bonding of amino groups to the pore surface of mesoporous silica. After removing the template with an acidic ethanol solution, an amino-functionalized support (MSN-NH2) with high specific surface area and regular pore structure is obtained. Under anhydrous and oxygen-free conditions, MSN-NH2 is mixed with a monovalent copper salt through solid-state grinding. Subsequently, heat treatment is performed in an inert atmosphere to allow Cu to... +It migrates and coordinates with the amine groups and skeletal oxygen on the support, thereby being stably anchored within the pores to form highly dispersed Cu. + The active center effectively prevents oxidation and aggregation.

[0020] Secondly, the present invention provides a mesoporous silica-supported copper catalyst (Cu) prepared by the above-mentioned preparation method. + @MSN-N).

[0021] Thirdly, the present invention provides the above-mentioned mesoporous silica-supported copper catalyst (Cu + @MSN-N) is used in oxidative coupling, especially in the synthesis of bifunctional low molecular weight polyphenylene ethers.

[0022] Taking the polymerization of bisphenol A and 2,6-dimethylphenol as an example, bisphenol A, 2,6-dimethylphenol and Cu... + The @MSN-N catalyst is dispersed in an organic solvent and undergoes oxidative coupling polymerization under mild heating and oxygenation conditions. After the reaction, the catalyst can be separated from the polymer solution by simple filtration, and the catalyst can be recycled after washing and drying. By adjusting the monomer feed ratio, catalyst dosage, and reaction time, the molecular weight of the obtained polyphenylene ether can be precisely controlled between 2000 and 5000, ensuring that it has a bifunctionality close to the theoretical value.

[0023] Reaction mechanism:

[0024] (1) Carrier synthesis mechanism: In alkaline aqueous solution, cationic surfactants (such as DTAC) form ordered micelle templates. When TEOS undergoes co-hydrolysis and condensation with aminosilane, the amino groups do not undergo protonation and can be uniformly bonded to the surface of the mesoporous framework, providing stable sites for subsequent metal ion anchoring; (2) Active center stabilization mechanism: Solid-state ion exchange method (grinding and mixing + inert atmosphere heat treatment) makes Cu + It forms a synergistic coordination with the carrier amine group and the framework oxygen, avoiding Cu + Oxidized to Cu 2+ Or agglomerate, ensuring the singleness and high dispersion of the active center; (3) Catalytic polymerization mechanism: Cu + The active center efficiently initiates phenoxy radical coupling, while the carrier amine group simultaneously plays a "co-catalytic" role, promoting the directional polymerization of free radicals and achieving precise control of molecular weight and end-group functionality.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] The catalyst is ingeniously designed, combining both activity and stability: the amine groups in the support not only act as ligands to stabilize Cu during the preparation process. + And with Cu +Constructing highly efficient catalytic active centers. The support structure prepared by the one-step co-condensation method is stable and has open pores, which is beneficial for reaction mass transfer.

[0027] The process is green and easy to scale up: the catalyst preparation method is simple, reproducible, and requires no complex post-modification process, making it easy for industrial production. The catalyst can be quantitatively recovered by filtration after the polymerization reaction, greatly reducing the burden of metal waste and product purification.

[0028] High product purity and controllable structure: The heterogeneous catalytic properties fundamentally avoid the residue of heavy metals in the polymer, making it suitable for the production of low molecular weight polyphenylene ethers, a high-end electronic-grade chemical. Based on the bifunctional initiation properties of bisphenol A, prepolymers with dihydroxyl-terminated ends can be precisely synthesized, with controllable molecular weight and distribution.

[0029] With broad application prospects, the obtained bifunctional low molecular weight polyphenylene ether can be used as a high-performance prepolymer, directly used as a modifier for preparing thermosetting materials such as epoxy resin and cyanate ester resin, or used to manufacture copper-clad laminates with low dielectric loss, meeting the stringent material requirements of cutting-edge fields such as 5G / 6G communication and high-performance computing. Attached Figure Description

[0030] Examples are illustrated in the accompanying drawings to enhance understanding of the concepts presented herein.

[0031] Figure 1 The Cu prepared in Example 1 of this invention + Nitrogen adsorption-desorption curves of the @MSN-N catalyst.

[0032] Figure 2 The Cu prepared in Example 1 of this invention + BJH (adsorption) pore volume distribution curve of @MSN-N catalyst.

[0033] Figure 3 In Embodiment 2 of the present invention, Cu is used. + GPC diagram of bifunctional low molecular weight polyphenylene ether prepared by @MSN-N catalyst.

[0034] Figure 4 This is the GPC diagram of the bifunctional low molecular weight polyphenylene ether prepared using Cu / SiO2 catalyst in Comparative Example 2 of this invention.

[0035] Figure 5 This is a graph showing the residual amount of copper in the bifunctional low molecular weight polyphenylene ether prepared in Example 2 and Comparative Example 2 of this invention.

[0036] Figure 6 This is a cycle stability diagram of the bifunctional low molecular weight polyphenylene ether prepared in Example 2 of the present invention. Detailed Implementation

[0037] To make the objectives, features, and advantages of this invention clearer, a detailed description is provided below in conjunction with specific embodiments. Specific details are provided in the description for understanding purposes, but the embodiments of this invention are not limited thereto. Those skilled in the art can make various modifications or variations without departing from the spirit of this invention, which is not limited to the specific forms disclosed.

[0038] Unless otherwise stated, the technical terms used herein have their common meaning in the technical field to which this invention pertains. The terminology in this specification is used only to describe specific embodiments and is not intended to limit the invention. Unless otherwise specified, conventional conditions or manufacturer's recommendations shall apply. Reagents or instruments used, unless otherwise specified, are commercially available conventional products.

[0039] Example 1: Catalyst Cu + Preparation of @MSN-N

[0040] In a 1L three-necked flask equipped with a stirrer and condenser, 480g of deionized water, 0.68g of NaOH (to make the NaOH concentration approximately 0.028 M), and 20.0g of dodecyltrimethylammonium chloride (DTAC) were added sequentially. The mixture was vigorously stirred in an 80°C water bath until the solution became clear. Maintaining the temperature and stirring, a premixed solution of 40.8g (196 mmol) of TEOS and 2.2g (10 mmol) of 3-aminopropyltriethoxysilane (APTES) was rapidly injected into the above solution using a syringe. The molar ratio of APTES to TEOS was approximately 1:19.6. The system immediately became turbid after injection. The reaction was continued at 80°C with stirring for 2 hours.

[0041] After the reaction was complete, the mixture was cooled, and the white precipitate was collected by centrifugation. The precipitate was washed three times each with deionized water and ethanol. The washed solid was dispersed in 500 mL of an ethanol solution containing 3.6 wt% concentrated hydrochloric acid and refluxed at 80°C for 12 hours to remove the DTAC template. This acid washing process was repeated once. Finally, the solid was washed with ethanol and dried under vacuum at 100°C for 12 hours to obtain a white powdery MSN-NH2 support.

[0042] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh 5.0 g of dry MSN-NH2 support and 0.1 g of cuprous chloride (CuCl) (2 wt% copper loading). Grind and mix thoroughly in a mortar for 30 minutes to ensure uniform mixing.

[0043] The mixture was transferred to a quartz boat and placed in a tube furnace. Under continuous purging with high-purity nitrogen (99.999%), the temperature was increased to 300°C at a rate of 2°C / min and held at this temperature for 4 hours. It was then allowed to cool naturally to room temperature, yielding a pale blue-gray Cu. +@MSN-N catalyst powder, stored in a glove box for later use.

[0044] Characterization data:

[0045] BET testing showed that the specific surface area of ​​MSN-NH2 was 1112.88 m². 2 / g, with an average pore size of approximately 3nm ( Figure 1 and Figure 2 )

[0046] Comparative Example 1: Preparation of amine-free supported copper catalyst (Cu / SiO2)

[0047] Except for the absence of APTES during the synthesis of the support, the remaining steps were exactly the same as in Example 1. That is, pure silica support was used, which was ground with CuCl and then heat-treated at 300°C in nitrogen to obtain the Cu / SiO2 catalyst.

[0048] Example 2: Using Cu + @MSN-N Catalytic Synthesis of Bifunctional Polyphenylene Ethers

[0049] In a 500 mL three-necked flask equipped with a magnetic stirrer, an oxygen bubbler, and a condenser, the following procedure was performed:

[0050] Add the following in sequence: bisphenol A (2.28 g, 10.0 mmol), 2,6-dimethylphenol (14.7 g, 120.0 mmol), 150 mL toluene, and 50 mL methanol. Stir at room temperature until the solid is completely dissolved.

[0051] Cu prepared in Example 1 was added to the above homogeneous solution. + @MSN-N catalyst 1.0 g (approximately 5.9% of the total monomer mass). The reaction system was heated to 40°C, and oxygen was continuously introduced at a flow rate of 100 mL / min to initiate the polymerization reaction. The viscosity of the system gradually increased during the reaction.

[0052] The reaction was stopped after 4 hours. The reaction solution was filtered while hot, and the filter cake (catalyst) was washed with hot toluene. The recovered catalyst was dried and could be recycled. The filtrate and washings were combined and concentrated to about half of the original volume, then added dropwise to 1 L of methanol under vigorous stirring. The precipitated white fibrous solid was collected by vacuum filtration and washed with methanol. The final product was dried under vacuum at 60°C for 24 hours to obtain 15.5 g of white solid polyphenylene ether.

[0053] Product characterization: such as Figure 3As shown, the product's number-average molecular weight (Mn) was 5000 and its molecular weight distribution (PDI) was 1.72, as determined by gel permeation chromatography (GPC). Hydroxyl titration showed its functionality to be approximately 1.98, close to the theoretical bifunctionality. Yield: 91%.

[0054] Comparative Example 2

[0055] The operation steps are the same as in Example 2, with Cu... + The @MSN-N catalyst was replaced with the Cu / SiO2 catalyst prepared in Comparative Example 2, and 1 ml of tetramethylpropanediamine was added as an amine ligand, finally yielding 14.6 g of grayish-white fibrous solid product.

[0056] Product characterization: such as Figure 4 As shown, the product's number-average molecular weight (Mn) was 3,042, and its molecular weight distribution (PDI) was 1.80, as determined by gel permeation chromatography (GPC). Hydroxyl titration determined its functionality to be approximately 1.91, close to the theoretical bifunctionality. Yield: 88%.

[0057] Effect Comparison

[0058] like Figure 5 As shown, the residual copper content in the products of Example 2 and Comparative Example 2 was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The residual copper ion content in Example 2 was 0.005 ppm, while the residual copper content in the product of Comparative Example 2 was 1.492 ppm, indicating the successful preparation of PPO.

[0059] Cu + Cyclic stability of @MSN-N catalyst

[0060] like Figure 6 As shown, the catalyst exhibits excellent cycling stability in the synthesis of polyphenylene ether. After 10 consecutive catalytic cycles, the product yield only slightly decreased from about 91% to about 88%, which fully demonstrates its excellent resistance to deactivation and its potential for industrial application.

[0061] The polymers obtained in Example 2 and Comparative Example 2 were blended with an equivalent amount of polyphenylmethane polyisocyanate (MDI) to prepare varnishes, which were then coated onto glass cloth and molded by hot pressing to obtain copper-clad laminate samples. Subsequently, the dielectric constant (Dk), dielectric loss (Df), and glass transition temperature (Tg) of the samples were tested at a frequency of 10 GHz.

[0062] The results are shown in the table below:

[0063]

[0064] As shown in the table, the amine-based mesoporous silica-supported copper catalyst prepared in this invention exhibits excellent performance in the synthesis of bifunctional low molecular weight polyphenylene ethers. The superior dielectric properties demonstrate the great potential of the high-purity polyphenylene ether, free of metal residues, prepared by this patented method, in high-end electronic applications.

[0065] Comparative Example 3 (Preparation of catalyst using a simulated CN104741140B method)

[0066] (1) Catalyst preparation: According to the ratio of Example 1, in hydrochloric acid solution (pH=2), anionic surfactant N-lauroyl sarcosinate sodium was added as a template, and TEOS and APTES were co-condensed to prepare MSN-NH2; the support was mixed with CuCl2 aqueous solution, and hydrothermally reacted at 120℃ for 10h, and dried to obtain Cu@MSN-N catalyst; (2) Polyphenylene ether synthesis: According to the conditions of Example 2, the catalyst was used to catalyze polymerization, and 13.8g of product was obtained with a yield of 81%; (3) Product characterization: Mn=2860, PDI=1.95, functionality=1.83; copper residue=1.52ppm; dielectric constant (10GHz)=2.61, dielectric loss=0.0021. Effect comparison: The catalyst of Example 2 of this invention (Cu + @MSN-N showed significantly better yield (91% vs 81%), product uniformity (PDI 1.72 vs 1.95), metal residue (0.005ppm vs 1.52ppm), and dielectric properties (Dk 2.40 vs 2.61) than Comparative Example 3, confirming the non-obviousness of the preparation method and catalyst of this invention.

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an amino-based mesoporous silica-supported copper catalyst, characterized in that, Includes the following steps: S1. Synthesis of amino-functionalized mesoporous silica: In an alkaline aqueous solution at 60-90°C with stirring, a mixed solution of TEOS and aminosilane was rapidly injected using a cationic surfactant as a structure directing agent. The molar ratio of aminosilane to TEOS was 1:20 to 1:

5. The reaction was continued for 2-6 hours. The resulting product was centrifuged, washed, and then refluxed with an acidic ethanol solution to remove the structure directing agent. Finally, it was dried to obtain amino-functionalized mesoporous silica. S2. Synthesis of copper catalyst supported on amino-functionalized mesoporous silica: Under an inert atmosphere, the amino-functionalized mesoporous silica obtained in step S1 is ground and mixed with a monovalent copper salt precursor at a mass ratio of copper to amino-functionalized mesoporous silica of 0.5%-5%; then the mixture is heat-treated at 200-400°C for 2-6 hours in an inert or reducing atmosphere, and after cooling, the amino-functionalized mesoporous silica-supported monovalent copper catalyst is obtained.

2. The preparation method according to claim 1, characterized in that, The cationic surfactant mentioned in step S1 contains C 10 —C 22 Long-chain alkyl quaternary ammonium salts.

3. The preparation method according to claim 2, characterized in that, The ammonium salt compound is selected from at least one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, or octadecyltrimethylammonium bromide.

4. The preparation method according to claim 1, characterized in that, The aminosilane mentioned in step S1 is an organosilane compound containing at least one primary amino group.

5. The preparation method according to claim 4, characterized in that, The organosilane compound is selected from at least one of APTES, AEAPTMS, or N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

6. The preparation method according to claim 1, characterized in that, The acidic ethanol solution used to remove the structure-directing agent in step S1 is an ethanol solution containing 1-5 wt% concentrated hydrochloric acid, with a reflux temperature of 70-85°C and a reflux time of 6-24 hours.

7. The preparation method according to claim 1, characterized in that, The monovalent copper salt precursor mentioned in step S2 is at least one of cuprous chloride, cuprous iodide, or cuprous bromide.

8. The preparation method according to claim 1, characterized in that, The heat treatment atmosphere described in step S2 is any one of high-purity nitrogen, argon, or a mixture of 5% hydrogen and 95% nitrogen by volume.

9. The mesoporous silica-supported copper catalyst prepared by the preparation method according to any one of claims 1-8.

10. The application of the mesoporous silica-supported copper catalyst of claim 9 as a catalyst in the synthesis of phenol oxidative coupling narrow molecular weight distribution polyphenylene ether.

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