A modified thermoplastic boron phenolic resin-based material, its preparation method and application

Abstract

This invention relates to the field of carbon materials, and particularly to a modified thermoplastic boron phenolic resin-based material, its preparation method, and its applications. The preparation method involves a co-condensation reaction and carbonization of a modifier, 3-hydroxyphenylboronic acid, and formaldehyde under the action of an acidic catalyst to prepare the modified thermoplastic boron phenolic resin-based material. The carbon material prepared by this invention possesses a rich porous structure, a large specific surface area, and a high boron content. The method is simple and suitable for large-scale preparation. Based on these advantages, using the carbon material of this invention to prepare electrode materials or catalytic materials can significantly improve the electrochemical performance of the materials.

Description

Technical Field

[0001] This invention relates to the field of carbon materials, and in particular to a modified thermoplastic boron phenolic resin-based material, its preparation method, and its application. Background Technology

[0002] Phenolic resin is a material with a long history, serving as a major binder and matrix resin used in the preparation of laminates, coatings, composite materials, refractories, and friction materials. The application of phenolic resin in traditional industrial fields has reached saturation, making the development of new application areas crucial for its further advancement. Phenolic resin is a polymer synthesized from phenols and aldehydes, containing numerous aromatic rings in its structure. It exhibits good thermal stability, high residual carbon content after carbonization, and is easily porous, making it an ideal material for preparing porous carbon materials.

[0003] Porous carbon materials have been widely used in new energy electrodes, catalyst supports, adsorption, and other fields. The composition of porous carbon materials has a significant impact on their performance, especially some doped carbon materials, which show improved electrochemical and catalytic performance. Therefore, how to prepare porous carbon materials with effective doping is a topic of great interest. At present, the main methods for preparing boron-doped carbon materials using phenolic resin as a matrix are: in-situ method and mixing method. For example, patent CN201910449081.6 uses boron-containing monomers as raw materials to prepare polymer resins by condensation with formaldehyde, and then carbonizes them to obtain carbon materials. However, due to the low boron content of the monomers themselves, the boron content in the carbon materials is insufficient (about 1%). The literature (Journal of Materials Chemistry A, 2018, 6(46): 23780-23786) uses 3-hydroxyphenylboronic acid as raw materials to condense with formaldehyde and then carbonizes it to obtain boron-containing carbon microspheres, but its specific surface area is only about 44 m². 2 The boron content in the product is mainly in the form of boron monoxide, which cannot play an effective electrochemical or catalytic role. The hydrothermal method also limits its large-scale preparation and requires ammonia, making it unsuitable for industrial production. Methods involving mixing polymers or carbon materials with boron-containing raw materials and then carbonizing them also result in low boron content and poor doping effects. Therefore, developing a method suitable for large-scale preparation of carbon materials with high specific surface area and boron content remains an unsolved technical problem. Summary of the Invention

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a modified thermoplastic boron phenolic resin-based material with high specific surface area and boron content, a method for preparing the same, and the application of the aforementioned modified thermoplastic boron phenolic resin-based material.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for preparing modified thermoplastic boron phenolic resin-based materials. The modified thermoplastic boron phenolic resin-based materials are prepared by co-condensation reaction and carbonization of modifier, 3-hydroxyphenylboronic acid and formaldehyde under the action of acidic catalyst.

[0006] The modifier is selected from melamine OAT waste residue, melamine, urea, 3-aminophenol, and monomers with structures shown in general formula (1) and general formula (2);

[0007]

[0008] R is selected from one of halogen, alkyl, ester, carboxyl, acyl, -SO3H, -CN, -CCl3, -CF3.

[0009] Further, a modified thermoplastic boron phenolic resin-based material prepared by the aforementioned preparation method is provided, wherein the modified thermoplastic boron phenolic resin-based material has a boron content ≥4% and a BET specific surface area ≥500m². 2 / g.

[0010] Furthermore, the aforementioned modified thermoplastic boron phenolic resin-based materials are provided for use in the preparation of electrode materials, catalytic materials, or composite materials.

[0011] The beneficial effects of this invention are as follows: the modified thermoplastic boron phenolic resin-based material prepared by the method provided by this invention has a rich porous structure, a large specific surface area, and a high boron content. Furthermore, the preparation method is simple and suitable for large-scale production. The prepared modified thermoplastic boron phenolic resin-based material can be used to prepare electrode materials or catalytic materials, and can significantly improve the electrochemical performance of the materials. Attached Figure Description

[0012] Figure 1 The image shown is a SEM image of the modified thermoplastic boron phenolic resin-based material prepared in Example 1 of this invention.

[0013] Figure 2 The image shown is a SEM image of the modified thermoplastic boron phenolic resin-based material prepared in Example 2 of the present invention. Detailed Implementation

[0014] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0015] A method for preparing a modified thermoplastic boron phenolic resin-based material involves co-condensation and carbonization of a modifier, 3-hydroxyphenylboronic acid, and formaldehyde under the action of an acidic catalyst to prepare the modified thermoplastic boron phenolic resin-based material; wherein the modifier is selected from melamine OAT waste residue, melamine, urea, 3-aminophenol, and monomers with structures shown in general formulas (1) and (2);

[0016]

[0017] R is selected from one of halogen, alkyl, ester, carboxyl, acyl, -SO3H, -CN, -CCl3, -CF3.

[0018] In this paper, the halogen is selected from fluorine, chlorine, iodine, and bromine. Due to their high electronegativity, halogens exhibit an electron-withdrawing effect, which passivates the phenolic ring and inhibits its substitution reaction, thereby reducing the crosslinking degree of the phenolic resin. The introduction of the substituent R can also occupy active sites, further reducing the crosslinking degree of the phenolic resin, thus improving the pyrolysis effect and increasing the specific surface area.

[0019] In this paper, the alkyl group is selected from one of methyl, ethyl, propyl, isopropyl, tert-butyl, and sec-butyl. Although alkyl groups have a certain activating ability, the introduction of alkyl groups to occupy active sites has a greater impact, leading to a reduction in the amount of substitution and a decrease in the degree of crosslinking. Therefore, it can also improve the cracking effect.

[0020] In this document, the ester group is -COOCH3 or -CH2COOCH3. The ester group is an electron-withdrawing group and has a passivating effect, similar to that of halogens.

[0021] In this article, melamine OAT waste residue is a type of waste generated during the production of melamine. Its main components are melamine, cyanuric acid, cyanuric acid monoamide, cyanuric acid diamide, etc. (as shown below).

[0022]

[0023] This method involves using a monomer with high boron content (i.e., 3-hydroxyphenylboronic acid) as the boron source, co-condensing it with a modifier, followed by curing, cross-linking, and high-temperature carbonization to prepare modified thermoplastic boron phenolic resin-based materials. Existing technologies have sufficiently demonstrated that directly using 3-hydroxyphenylboronic acid to prepare phenolic resin results in a very low specific surface area after carbonization. Boron mainly exists in its oxide form, failing to improve the product's electrochemical performance and easily clogging pores, further reducing the specific surface area. Therefore, in this invention, modified thermoplastic boron phenolic resin-based materials are prepared by using nitrogen-containing monomers and phenols substituted with weakly activated or passivating groups at the ortho / para positions as cocondensates. On the one hand, the introduction of the second group can effectively disrupt the regularity of the molecular structure, thereby improving the pyrolysis effect of the resin and increasing the pore structure, i.e., increasing the specific surface area. On the other hand, during the carbonization process, the nitrogen atoms of the modified resin prepared with nitrogen-containing groups can form a BN covalent structure with boron atoms, thereby inhibiting the conversion of boron elements to its oxides, further improving the pyrolysis effect of the resin, and avoiding the blockage of pores by boron oxides, thereby improving the specific surface area and enhancing the application performance of the modified thermoplastic boron phenolic resin-based materials.

[0024] Furthermore, phenols whose ortho / para positions are replaced by weakening groups or passivating groups, leaving only two active sites, can reduce the crosslinking degree of the resin product during the copolymerization of 3-hydroxyphenylboronic acid, thereby improving the pyrolysis effect and increasing the specific surface area of ​​the resin product.

[0025] To better maintain the original morphology of the resin and thus improve the carbonization yield, it is preferable to perform a curing and crosslinking reaction on the co-condensation product before carbonization. This involves mixing the product obtained from the co-condensation reaction with a curing agent in a solvent and then thermally curing it to obtain an amorphous carbon material. Although this curing and crosslinking reduces the resin's pyrolysis effect, it can maintain the basic morphology of the resin and achieve a higher yield. Meanwhile, experiments have shown that carbon materials produced without crosslinking and curing may experience pore collapse during carbonization and pyrolysis due to reduced resin stability, directly leading to a decrease in their specific surface area. Therefore, the curing and crosslinking process is necessary for preparing modified thermoplastic boron phenolic resin-based materials. In this embodiment, the degree of crosslinking can be adjusted by the amount of modifier used. Preferably, the amount of modifier is 2-50% of the mass of the 3-hydroxyphenylboronic acid, more preferably 5-20%, and most preferably 5-10%. In this embodiment, increasing the amount of modifier decreases the regularity of the resin molecular structure. Furthermore, increasing the amount of nitrogen-containing modifier introduces more nitrogen, thereby better suppressing the formation of boron oxides. Increasing the amount of other modifiers reduces the total number of active sites, thus improving the specific surface area. However, increasing the amount of modifier reduces the boron content in the modified thermoplastic boron phenolic resin-based material. Especially for modifiers with only two active sites, their dosage should not be too high; otherwise, the overall stability of the resin will significantly decrease, causing the resin to retain its original morphology. This is particularly true for the preparation of spherical carbon materials. Therefore, controlling the amount of modifiers, especially those with only two active sites, is crucial for the formation and maintenance of the morphology of spherical carbon materials.

[0026] In one embodiment, the amount of the acidic catalyst is 0.2 to 2.0% of the sum of the mass of the modifier and 3-hydroxyphenylboronic acid.

[0027] In one embodiment, the acidic catalyst is selected from at least one of oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, phosphonic acid, benzenesulfonic acid, and p-benzenesulfonic acid.

[0028] In one embodiment, the solvent is selected from at least one of water, ethanol, methanol, acetone, tetrahydrofuran, methane, and chloroform.

[0029] In one embodiment, the molar ratio of the formaldehyde and the modifier to 3-hydroxyphenylboronic acid is 0.7 to 0.9.

[0030] In one optional embodiment, the curing and crosslinking reaction is as follows: the product obtained from the co-condensation reaction is mixed with a curing agent in a solvent and then subjected to thermal curing; that is, the curing and crosslinking reaction includes the following steps:

[0031] S1. Mix the surfactant and curing agent in a solvent and adjust the pH of the solution to acidic to obtain solution a;

[0032] S2. Dissolve the product obtained from the co-condensation reaction in an alkaline solution to obtain solution b;

[0033] S3. Add solution b dropwise to solution a, and then heat-cure after the addition is complete;

[0034] S4. Separate and wash the thermosetting precipitate, and obtain spherical products after carbonization.

[0035] Using this method for curing, the cured product is spherical. After carbonizing the cured product, a modified thermoplastic boron phenolic resin-based material with a spherical morphology can be obtained.

[0036] Preferably, the washing process involves washing the thermosetting precipitate with water as the washing solution.

[0037] In another optional embodiment, the curing and crosslinking reaction is: the product obtained from the copolymerization reaction is mixed with a curing agent and then directly subjected to heat curing; that is, the curing and crosslinking reaction includes the following steps:

[0038] S1. The product obtained by the co-condensation reaction is mixed with a curing agent and then heat-cured.

[0039] S2. The thermosetting product is crushed and carbonized to obtain the amorphous carbon material.

[0040] The curing process using this method produces an amorphous product. After further carbonization, a modified thermoplastic boron phenolic resin-based material with an amorphous morphology is obtained.

[0041] Preferably, the pulverization involves pulverizing the thermosetting product to a fineness of 100-1000 mesh.

[0042] In one embodiment, the surfactant is selected from one of the following: polyoxyethylene polyoxypropylene ether block copolymer (F127), polyvinyl alcohol, hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC).

[0043] In one embodiment, the curing agent is selected from hexamethylenetetramine or formaldehyde.

[0044] The modified thermoplastic boron phenolic resin-based material prepared by the aforementioned method has a boron content ≥4% and a BET specific surface area ≥500 m². 2 / g. In this embodiment, the high boron content and high specific surface area are beneficial for the modified thermoplastic boron phenolic resin-based material to exert its excellent electrochemical performance.

[0045] As mentioned above, modified thermoplastic boron phenolic resin-based materials are used in the preparation of electrode materials, catalytic materials, or composite materials.

[0046] Example 1

[0047] A method for preparing a modified thermoplastic boron phenolic resin-based material includes the following steps:

[0048] S1. Melamine, 3-hydroxyphenylboronic acid, and a 37% formaldehyde aqueous solution are reacted at 100°C for 2 hours under the action of oxalic acid catalyst. After dehydration, a modified thermoplastic boron phenolic resin is obtained. The amount of melamine is 10% of the mass of 3-hydroxyphenylboronic acid, the molar ratio of formaldehyde and the sum of melamine and 3-hydroxyphenylboronic acid is 0.7, and the amount of oxalic acid is 0.5% of the total mass of melamine and 3-hydroxyphenylboronic acid.

[0049] S2. Add 0.1g of surfactant CTAB and 0.1g of 37% formaldehyde to 10mL of water, stir to dissolve, and adjust the pH of the solution to 4 to obtain solution A; dissolve 0.2g of modified thermoplastic boron phenolic resin in 20mL of sodium hydroxide aqueous solution with pH 9, and then gradually add this solution dropwise to solution A while stirring continuously; after the addition is complete, heat at 120℃ for 12h to cure; separate the precipitate and wash it.

[0050] S3. The cured resin is carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain carbon material;

[0051] ICP testing showed that the boron content of the carbon material was 6.8%, and the BET specific surface area calculated by nitrogen adsorption-desorption testing was 705 m². 2 / g, its SEM image is as follows Figure 1 As shown.

[0052] Example 2

[0053] A method for preparing a modified thermoplastic boron phenolic resin-based material includes the following steps:

[0054] S1. Melamine, 3-hydroxyphenylboronic acid, and 37% formaldehyde aqueous solution were reacted at 100°C for 2 hours under the action of oxalic acid catalyst, and the modified thermoplastic boron phenolic resin was obtained after dehydration.

[0055] The amount of melamine used is 10% of the mass of 3-hydroxyphenylboronic acid, the molar ratio of formaldehyde to the sum of melamine and 3-hydroxyphenylboronic acid is 0.7, and the amount of oxalic acid used is 0.5% of the total mass of melamine and 3-hydroxyphenylboronic acid.

[0056] S2. After mixing thermoplastic boron phenolic resin and hexamethylenetetramine at a mass ratio of 9:1, cure at 170℃ for 1 hour.

[0057] S3. After the cured resin is crushed, it is carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain carbon material.

[0058] ICP testing showed that the boron content of the carbon material was 6.5%, and the BET specific surface area calculated by nitrogen adsorption-desorption testing was 684 m². 2 / g, its SEM image is as follows Figure 2 As shown. The electrode, prepared as an active material for a supercapacitor, exhibited a capacity of 291 F / g (current density of 1 A / g) in a three-electrode system.

[0059] Example 3

[0060] A method for preparing a modified thermoplastic boron phenolic resin-based material includes the following steps:

[0061] S1. 2-Fluorophenol, 3-hydroxyphenylboronic acid, and 37% formaldehyde aqueous solution were reacted at 100°C for 2 hours under the action of oxalic acid catalyst, and the modified thermoplastic boron phenolic resin was obtained after dehydration.

[0062] The amount of 2-fluorophenol used is 10% of the mass of 3-hydroxyphenylboronic acid, the molar ratio of formaldehyde to the sum of 2-fluorophenol and 3-hydroxyphenylboronic acid is 0.75, and the amount of oxalic acid used is 0.5% of the total mass of 2-fluorophenol and 3-hydroxyphenylboronic acid.

[0063] S2. Add 0.1g of surfactant CTAB and 0.1g of 37% formaldehyde to 10mL of water, stir to dissolve, and adjust the pH of the solution to 4 to obtain solution A; dissolve 0.2g of modified thermoplastic boron phenolic resin in 20mL of sodium hydroxide aqueous solution with pH 9, and then gradually add this solution dropwise to solution A while stirring continuously; after the addition is complete, heat at 120℃ for 12h to cure; separate the precipitate and wash it.

[0064] S3. The cured resin is carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain carbon material;

[0065] ICP testing showed that the boron content of the carbon material was 5.6%, and the BET specific surface area calculated by nitrogen adsorption-desorption testing was 662 m². 2 The electrode, prepared as an active material for supercapacitor electrodes, had a capacity of 262 F / g (current density of 1 A / g) tested in a three-electrode system.

[0066] Comparative Example 1

[0067] A method for preparing a thermoplastic boron phenolic resin-based material includes the following steps:

[0068] S1. 3-hydroxyphenylboronic acid and 37% formaldehyde aqueous solution were reacted at 100°C for 2 hours under the action of oxalic acid catalyst, and dehydrated to obtain boron phenolic resin.

[0069] The molar ratio of formaldehyde to 3-hydroxyphenylboronic acid is 0.7, and the amount of oxalic acid used is 0.5% of the mass of 3-hydroxyphenylboronic acid.

[0070] S2. After mixing boron phenolic resin and hexamethylenetetramine at a mass ratio of 9:1, cure at 170℃ for 1 hour.

[0071] S3. The cured resin is carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain carbon material;

[0072] ICP testing showed that the boron content of the carbon material was 8.1%, and the BET specific surface area calculated by nitrogen adsorption-desorption testing was 59 m². 2 The electrode, prepared as an active material for supercapacitor electrodes, has a capacity of 165 F / g (current density of 1 A / g) tested in a three-electrode system.

[0073] It should be noted that the performance testing method for the above-mentioned supercapacitor is as follows: carbon material, binder, and carbon black are mixed evenly in a mass ratio of 8:1:1, and coated onto the electrode sheet to prepare the working electrode. Constant current charge-discharge tests are performed on a CHI760E electrochemical workstation using 6M KOH electrolyte and a three-electrode system. The three-electrode system includes a reference electrode (Hg / HgO), a counter electrode (Pt sheet), and a self-made working electrode.

[0074] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a modified thermoplastic boron phenolic resin-based material, characterized in that, Modified thermoplastic boron phenolic resin-based materials are prepared by co-condensation reaction and carbonization of a modifier, 3-hydroxyphenylboronic acid, and formaldehyde under the action of an acidic catalyst; the amount of the modifier is 2-50% of the mass of the 3-hydroxyphenylboronic acid. The modifier is selected from melamine OAT waste residue, melamine, urea, 3-aminophenol, and monomers with structures shown by general formula (1) and general formula (2); R is selected from one of halogen, alkyl, ester, carboxyl, acyl, -SO3H, -CN, -CCl3, -CF3.

2. The preparation method according to claim 1, characterized in that, The amount of the acidic catalyst is 0.2 to 2.0% of the sum of the mass of the modifier and 3-hydroxyphenylboronic acid.

3. The preparation method according to claim 1, characterized in that, The molar ratio of formaldehyde and the modifier to 3-hydroxyphenylboronic acid is 0.7 to 0.

9.

4. The preparation method according to claim 1, characterized in that, It also includes a curing and crosslinking reaction between the co-condensation reaction and the carbonization reaction; The curing and crosslinking reaction includes the process of mixing the product obtained by the co-condensation reaction with a curing agent and then performing thermal curing, followed by carbonization to obtain an amorphous carbon material. Alternatively, the curing and crosslinking reaction may include the process of mixing the product obtained from the co-condensation reaction with a curing agent in a solvent and then performing thermal curing, followed by carbonization to obtain a spherical carbon material.

5. The preparation method according to claim 4, characterized in that, The curing and crosslinking reaction includes the following steps: S1. Mix the surfactant and curing agent in a solvent and adjust the pH of the solution to acidic to obtain solution a; S2. Dissolve the product obtained from the co-condensation reaction in an alkaline solution to obtain solution b; S3. Add solution b dropwise to solution a, and then heat-cure after the addition is complete; S4. The thermosetting precipitate product is separated, washed, and carbonized to obtain the spherical carbon material.

6. The preparation method according to claim 4, characterized in that, The curing and crosslinking reaction includes the following steps: S1. The product obtained by the co-condensation reaction is mixed with a curing agent and then heat-cured. S2. The thermosetting product is crushed and carbonized to obtain the amorphous carbon material.

7. The preparation method according to claim 5, characterized in that, The surfactant is selected from one of polyoxyethylene polyoxypropylene ether block copolymer, polyvinyl alcohol, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

8. The modified thermoplastic boron phenolic resin-based material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The modified thermoplastic boron phenolic resin-based material has a boron content ≥4% and a BET specific surface area ≥500 m². 2 / g.

9. The application of the modified thermoplastic boron phenolic resin-based material as described in claim 8 in the preparation of electrode materials, catalytic materials or composite materials.

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