Graphite spheres and methods for making the same

Abstract

The application relates to the field of non-metal elements, in particular to a graphite ball and a preparation method thereof, which is made of a modified asphalt binder and graphite powder; the modified asphalt binder is made of coal pitch and a furfuryl-based phenolic resin with a mass ratio of 1:0.08-0.12, and the furfuryl-based phenolic resin contains a tert-butyl group in the structure; the graphite ball prepared by the application is excellent in two key indexes of compression strength and drop strength, and can fully meet the performance requirement of the steel and iron metallurgical industry on the graphite carburant.

Description

Technical Field

[0001] This invention relates to the field of non-metallic elements, specifically to a graphite sphere and its preparation method. Background Technology

[0002] In the iron and steel metallurgy and casting industries, carbon is one of the key elements for regulating the composition of molten steel and controlling its properties. Carbon additives, represented by recarburizers, introduce carbon components into molten steel during tapping, refining, or casting, precisely adjusting the carbon content, compensating for carbon loss during smelting, and promoting deoxidation reactions. Traditional recarburizers are mainly divided into two categories: graphitized and non-graphitized recarburizers, and their forms include granules, powders, and compressed pellets. Among these, pelletized recarburizers are increasingly widely used due to their advantages such as low splash loss, high carbon recovery rate, and ease of automated addition.

[0003] Currently, graphite balls used in metallurgy are mostly made from natural or artificial graphite powder as aggregate and asphalt or organic resin as binder, through mixing, molding, and heat treatment. Asphalt, as the most common binder, has the advantages of high carbonization yield, wide availability, and low cost. However, its molecular structure is mainly composed of polycyclic aromatic hydrocarbons. After high-temperature carbonization, the resulting coke skeleton is brittle and has poor mechanical strength. During transportation and addition, it is prone to breakage and pulverization, causing carbon powder to fly around. This not only significantly reduces the carbon yield but also makes it difficult to remove slag from the molten steel surface and causes environmental pollution. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a graphite sphere and its preparation method.

[0005] The technical solution adopted is as follows: A graphite ball made of modified bitumen binder and graphite powder; The modified asphalt binder is made of coal tar pitch and furfural-based phenolic resin in a mass ratio of 1:0.08-0.12, wherein the furfural-based phenolic resin contains tert-butyl groups in its structure.

[0006] Furthermore, the mass ratio of the modified asphalt binder to the graphite powder is 0.15-0.25:1.

[0007] Furthermore, the furfural-based phenolic resin is made from phenol, p-tert-butylphenol, 37% formaldehyde aqueous solution, furfural, and a catalyst.

[0008] Furthermore, the mass ratio of phenol, p-tert-butylphenol, 37% formaldehyde aqueous solution, and furfural is 1:0.25-0.45:0.55-0.65:0.2-0.3.

[0009] Furthermore, the catalyst is at least one selected from oxalic acid, hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid.

[0010] Furthermore, the preparation method of the furfural-based phenolic resin is as follows: Phenol and p-tert-butylphenol are heated and melted in a certain ratio. Then, 37% formaldehyde aqueous solution and furfural are added. After stirring evenly, a catalyst is added. The mixture is stirred and reacted at 95-105℃ for 2-4 hours. After the reaction is completed, an alkaline solution is added to neutralize the pH to 6.5-7.5. Finally, the mixture is dehydrated under vacuum.

[0011] Furthermore, the graphite powder undergoes acyl chloride modification treatment.

[0012] Furthermore, the graphite powder is prepared as follows: Carboxylated graphite is obtained by oxidizing graphite with a mixed acid solution made of concentrated sulfuric acid and concentrated nitric acid after pulverizing it. Then, the carboxylated graphite is reacted with an acyl chloride reagent in an organic medium.

[0013] Furthermore, the acyl chloride reagent is any one of thionyl chloride, acetyl chloride, benzoyl chloride, oxalyl chloride, chloroacetyl chloride, and trichloroacetyl chloride.

[0014] Furthermore, the organic solvent is at least one selected from dichloromethane, chloroform, carbon tetrachloride, and toluene. The organic solvent has undergone drying treatment to ensure it is anhydrous.

[0015] This invention also provides a method for preparing graphite spheres, comprising the following steps: (1) Heat coal tar pitch to 160-180℃ to melt it, add furfural-based phenolic resin while stirring, and stir for 30-60 minutes to obtain modified asphalt binder. (2) Under an inert atmosphere, graphite powder is added and kneaded at 160-180℃ for 30-60 minutes to obtain spherical material; (3) Press the ball material into shape, first heat it to 200-300℃ in air atmosphere for pre-oxidation for 1-5h, then heat it to 1000-1200℃ in inert atmosphere for carbonization treatment for 2-4h, and then obtain graphite balls after cooling.

[0016] The beneficial effects of the technical solution of the present invention are as follows: This invention modifies coal tar pitch using a self-made furfural-based phenolic resin. Furfural, as a comonomer, introduces a furan heterocyclic structure into the phenolic resin backbone. This structure facilitates the formation of a denser carbon microcrystalline structure during high-temperature carbonization, improving the density and strength of the carbonized product and effectively compensating for the high brittleness and adhesion of carbonized pitch. Simultaneously, the introduction of tert-butylphenol monomer, on the one hand, moderately adjusts the crosslinking density of the resin through steric hindrance, improving toughness while maintaining structural thermal stability; on the other hand, it significantly improves the compatibility between the phenolic resin and coal tar pitch, enabling highly uniform micro-dispersion during the melt mixing stage, avoiding local defects caused by macroscopic phase separation. Ultimately, the overall toughness and strength of the resulting carbonized skeleton are fundamentally improved.

[0017] This invention involves a two-step surface chemical modification of graphite powder: mixed acid oxidation and acylation. Mixed acid oxidation introduces oxygen-containing functional groups such as carboxyl groups onto the graphite surface, increasing the number of reactive sites. The subsequent acylation treatment converts the carboxyl groups into acylation groups, significantly enhancing the reactivity of the graphite surface. During the kneading stage, the acylated graphite surface can interact with phenolic hydroxyl groups in the modified asphalt binder and active hydrogen in the asphalt molecules. This enhanced interfacial interaction significantly improves the wetting and coating effect of the modified asphalt binder on the graphite, reducing interfacial voids and defects common in traditional physical mixing. In the pre-oxidation stage, the three-dimensional cross-linked network formed by the modified asphalt binder on the graphite particle surface shrinks and solidifies uniformly with the graphite particles as the framework, providing a good structural basis for the final carbon skeleton construction. In the subsequent high-temperature carbonization stage, the organic segments grafted onto the graphite surface undergo simultaneous in-situ carbonization, forming a transitional carbon layer between the graphite and the binder coke. The transitional carbon layer is similar in material and carbonization process to the continuous carbon skeleton formed by the carbonization of modified asphalt binder. At high temperature, carbon atoms diffuse and microcrystals rearrange in the interface region to form a tightly bonded carbon network structure, thereby transforming the loose physical coating in traditional graphite spheres into a more robust integrated structure. This facilitates the efficient transfer of load between the graphite matrix and the carbon skeleton, improving the compressive strength and impact resistance of the graphite spheres.

[0018] During the pre-oxidation process in an air atmosphere, the coal tar pitch component in the modified asphalt binder undergoes oxidative dehydrogenation and oxygen-bridge cross-linking, transforming from a thermoplastic to a thermosetting state and forming a stable three-dimensional cross-linked network. This pre-oxidized network effectively shapes and enhances the shape retention of the green pellets. During subsequent high-temperature carbonization in an inert atmosphere, the pre-oxidized cross-linked network transforms into a continuous and dense carbon skeleton, avoiding the problems of pellet melting, deformation, and cracking caused by direct carbonization in traditional processes. This helps improve the yield and structural integrity of the graphite pellet products.

[0019] The graphite balls prepared by this invention exhibit excellent performance in both compressive strength and drop strength, which fully meet the performance requirements of the iron and steel metallurgical industry for graphite carburizers. Detailed Implementation

[0020] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0021] Example 1: A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, a 37% formaldehyde aqueous solution and furfural were added in one batch. The mass ratio of phenol, p-tert-butylphenol, 37% formaldehyde aqueous solution (mass percentage concentration of 37%, the same below), and furfural was 1:0.3:0.6:0.25. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, with the amount of oxalic acid being 1% of the mass of phenol. The temperature was slowly raised to 100℃, and the reaction was stirred for 3 hours. After the reaction was completed, 30wt% sodium hydroxide solution was added to neutralize to a pH of 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120℃ under a vacuum of -0.09 MPa to dehydrate until no distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0022] Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0023] Medium-temperature coal tar pitch and furfural-based phenolic resin in a mass ratio of 1:0.1 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to obtain a modified asphalt binder. Acyl chloride graphite powder was added under argon protection, with a mass ratio of modified asphalt binder to acyl chloride graphite powder of 0.2:1. The mixture was stirred at 170°C for 45 minutes to obtain a paste-like pellet. The hot pellet was fed into a roller briquetting machine with a roller pressure set to 25 MPa to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 250°C for 2.5 hours in air atmosphere, followed by purging with argon and then carbonization at 1100°C for 3 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0024] Example 2: A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, 37% formaldehyde aqueous solution and furfural were added in a single batch, with a mass ratio of phenol:p-tert-butylphenol:37% formaldehyde aqueous solution:furfural of 1:0.45:0.55:0.3. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, at a concentration of 1% of the phenol mass. The temperature was slowly raised to 95°C, and the reaction was stirred for 4 hours. After the reaction was complete, 30wt% sodium hydroxide solution was added to neutralize the pH to 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120°C under a vacuum of -0.09 MPa to dehydrate the product until no more distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0025] Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0026] Medium-temperature coal tar pitch and furfural-based phenolic resin at a mass ratio of 1:0.08 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to obtain a modified asphalt binder. Acyl chloride graphite powder was added under argon protection, with a mass ratio of modified asphalt binder to acyl chloride graphite powder of 0.25:1. The mixture was kept at 170°C and stirred for 60 minutes to obtain a paste-like pellet. The pellet was fed into a double-roller briquetting machine while hot, with the roller pressure set to 25 MPa, to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 200°C for 5 hours in air atmosphere, followed by purging with argon and then carbonization at 1000°C for 4 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0027] Example 3: A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, 37% formaldehyde aqueous solution and furfural were added in a single batch, with a mass ratio of phenol:p-tert-butylphenol:37% formaldehyde aqueous solution:furfural of 1:0.25:0.65:0.2. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, at a concentration of 1% of the phenol mass. The temperature was slowly raised to 105°C, and the reaction was stirred for 2 hours. After the reaction was complete, 30wt% sodium hydroxide solution was added to neutralize the pH to 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120°C under a vacuum of -0.09 MPa to dehydrate the product until no more distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0028] Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0029] Medium-temperature coal tar pitch and furfural-based phenolic resin at a mass ratio of 1:0.12 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to obtain a modified asphalt binder. Acyl chloride graphite powder was added under argon protection, with a mass ratio of modified asphalt binder to acyl chloride graphite powder of 0.15:1. The mixture was kept at 170°C and stirred for 30 minutes to obtain a paste-like pellet. The pellet was fed into a double-roller briquetting machine while hot, with the roller pressure set to 25 MPa, to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 300°C for 1 hour in air atmosphere, followed by purging with argon and then carbonization at 1200°C for 2 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0030] Example 4: A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, 37% formaldehyde aqueous solution and furfural were added in a single batch, with a mass ratio of phenol:p-tert-butylphenol:37% formaldehyde aqueous solution:furfural of 1:0.45:0.65:0.3. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, at a concentration of 1% of the phenol mass. The temperature was slowly raised to 105℃, and the reaction was stirred for 4 hours. After the reaction was complete, 30wt% sodium hydroxide solution was added to neutralize the pH to 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120℃ under a vacuum of -0.09 MPa to dehydrate the product until no more distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0031] Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0032] Medium-temperature coal tar pitch and furfural-based phenolic resin at a mass ratio of 1:0.12 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to obtain a modified asphalt binder. Acyl chloride graphite powder was added under argon protection, with a mass ratio of modified asphalt binder to acyl chloride graphite powder of 0.25:1. The mixture was kept at 170°C and stirred for 60 minutes to obtain a paste-like pellet. The pellet was fed into a double-roller briquetting machine while hot, with the roller pressure set to 25 MPa, to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 300°C for 5 hours in air atmosphere, followed by purging with argon and then carbonization at 1200°C for 4 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0033] Example 5: A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, 37% formaldehyde aqueous solution and furfural were added in a single batch, with a mass ratio of phenol:p-tert-butylphenol:37% formaldehyde aqueous solution:furfural of 1:0.25:0.55:0.2. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, at a concentration of 1% of the phenol mass. The temperature was slowly raised to 95°C, and the reaction was stirred for 2 hours. After the reaction was complete, 30wt% sodium hydroxide solution was added to neutralize the pH to 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120°C under a vacuum of -0.09 MPa to dehydrate the product until no more distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0034] Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0035] Medium-temperature coal tar pitch and furfural-based phenolic resin at a mass ratio of 1:0.08 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to obtain a modified asphalt binder. Acyl chloride graphite powder was added under argon protection, with a mass ratio of modified asphalt binder to acyl chloride graphite powder of 0.15:1. The mixture was kept at 170°C and stirred for 30 minutes to obtain a paste-like pellet. The hot pellet was fed into a double-roller briquetting machine with a roller pressure set to 25 MPa to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 200°C for 1 hour in air atmosphere, followed by purging with argon and then carbonization at 1000°C for 2 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0036] Comparative Example 1: This comparative example is basically the same as Example 1, except that furfural-based phenolic resin is not added and the graphite powder is not subjected to acyl chloride modification treatment.

[0037] A method for preparing graphite spheres: Commercially available natural flake graphite was pulverized using a pulverizer until it passed through a 200-mesh sieve to obtain fine graphite powder. Medium-temperature coal tar pitch was added to a kneader and heated to 170°C until completely melted. Then, the fine graphite powder was added, with a mass ratio of medium-temperature coal tar pitch to fine graphite powder of 0.2:1. The mixture was stirred at 170°C for 45 minutes to obtain a paste-like pellet. The hot pellet was fed into a roller briquetting machine with a roller pressure set to 25 MPa to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. They were first pre-oxidized at 250°C for 2.5 hours in an air atmosphere, then the air was replaced with argon, and the temperature was further increased to 1100°C for carbonization treatment for 3 hours in an argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0038] Comparative Example 2: This comparative example is basically the same as Example 1, except that the graphite powder is not subjected to acyl chloride modification treatment.

[0039] A method for preparing graphite spheres: Phenol and p-tert-butylphenol were added to a reactor equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping device. The mixture was heated until completely melted and stirred for 10 minutes. Then, 37% formaldehyde aqueous solution and furfural were added in a single batch, with a mass ratio of phenol:p-tert-butylphenol:37% formaldehyde aqueous solution:furfural of 1:0.3:0.6:0.25. The mixture was stirred again for 10 minutes. Oxalic acid was added as a catalyst, at a concentration of 1% of the phenol mass. The temperature was slowly raised to 100°C, and the reaction was stirred for 3 hours. After the reaction was complete, 30wt% sodium hydroxide solution was added to neutralize the pH to 6.8-7.2. The mixture was then switched to a vacuum distillation apparatus and heated to 120°C under a vacuum of -0.09 MPa to dehydrate the product until no more distillate dripped out. The product was discharged onto a tray, cooled, and then pulverized to obtain furfural-based phenolic resin.

[0040] Medium-temperature coal tar pitch and furfural-based phenolic resin in a mass ratio of 1:0.1 were added to a kneader and heated to 170°C to completely melt them. The mixture was stirred for 45 minutes to ensure thorough mixing and obtain a modified asphalt binder. Commercially available natural flake graphite was then pulverized to pass through a 200-mesh sieve to obtain fine graphite powder, with a mass ratio of modified asphalt binder to fine graphite powder of 0.2:1. The mixture was stirred at 170°C for 45 minutes to obtain a paste-like pellet material. The hot pellet material was fed into a double-roll briquetting machine with a roller pressure set to 25 MPa to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. They were first pre-oxidized at 250°C for 2.5 hours in an air atmosphere, then the air was replaced with argon, and the mixture was carbonized at 1100°C for 3 hours in an argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0041] Comparative Example 3: This comparative example is basically the same as Example 1, except that furfural-based phenolic resin is not added.

[0042] A method for preparing graphite spheres: Commercially available natural flake graphite was pulverized to pass through a 200-mesh sieve to obtain fine powder. Under ice-water bath cooling and stirring, 100g of the pulverized graphite was slowly added to 1L of a pre-prepared mixed acid solution (concentrated sulfuric acid to concentrated nitric acid, volume ratio 3:1). After the addition was complete, the ice bath was removed, and the mixture was ultrasonically stirred at 40℃ for 4 hours. After the reaction was complete, the precipitate was collected and repeatedly washed with deionized water until the supernatant was neutral, yielding carboxylated graphite. The carboxylated graphite filter cake was transferred to a reaction flask equipped with a drying tube, and 1L of anhydrous dichloromethane was added. The mixture was ultrasonically dispersed for 30 minutes. Under argon protection, 500mL of thionyl chloride and 1mL of anhydrous N,N-dimethylformamide were slowly added dropwise. After the addition was complete, the mixture was heated to reflux and reacted for 24 hours. After the reaction was complete, small molecules were removed by vacuum distillation. The resulting product was washed with anhydrous dichloromethane and vacuum dried to constant weight to obtain acyl-chlorographite powder.

[0043] Medium-temperature coal tar pitch was added to a kneader and heated to 170°C until completely melted. Acyl chloride graphite powder was then added under argon protection, with a mass ratio of medium-temperature coal tar pitch to acyl chloride graphite powder of 0.2:1. The mixture was stirred at 170°C for 45 minutes to obtain a paste-like pellet. The hot pellet was fed into a double-roll briquetting machine with a roller pressure set to 25 MPa to obtain green pellet blanks. The green pellets were placed in a crucible and placed in an atmosphere furnace. Pre-oxidation was performed at 250°C for 2.5 hours in air, followed by purging with argon and then carbonization at 1100°C for 3 hours in argon atmosphere. After cooling, graphite pellets with a diameter of approximately 10 mm were obtained.

[0044] Comparative Example 4: This comparative example is basically the same as Example 1, except that the same mass of phenol is used instead of p-tert-butylphenol.

[0045] Comparative Example 5: This comparative example is basically the same as Example 1, except that formaldehyde is used instead of furfural in the same mass.

[0046] Comparative Example 6: This comparative example is basically the same as Example 1, except that commercially available 2124 phenolic resin (Sawada Chemical) is used instead of the self-made furfural-based phenolic resin.

[0047] Performance testing: The graphite spheres prepared in Examples 1-5 and Comparative Examples 1-6 were used as samples for performance testing.

[0048] Compressive strength: The compressive strength of the specimens was tested using a universal testing machine with an indenter movement rate of 0.05 mm / min. Five graphite spheres were selected for testing in each group, and the average value was taken. The formula for calculating the compressive strength is as follows: σ=2P / πdh In the formula: σ is the compressive strength, MPa; P is the crushing load, N; d and h are the diameter and height, respectively, mm.

[0049] Drop strength: Weigh a sample with a mass of m0, place it at a height of 2m and drop it freely onto a 10mm thick steel plate. Repeat this drop 5 times, then sieve it using a standard sieve and collect particles larger than 1mm, weighing them as m1. The drop strength is calculated using the formula (m1 / m0) × 100%. The higher the drop strength, the stronger the drop resistance of the sample.

[0050] The test results are shown in Table 1 below.

[0051] Table 1:

[0052] The graphite balls prepared in Examples 1-5 of this invention have high levels of both compressive strength and drop strength, which are key indicators. The compressive strength is in the range of 27.9-38.2 MPa, and the drop strength is over 93%, with the highest reaching 96.8%. These properties can meet the mechanical performance requirements of graphite carburizers in the iron and steel metallurgical industry.

[0053] In Comparative Example 1, the mechanical properties of the graphite spheres decreased significantly, making them prone to crushing during actual transportation and application. This indicates that the traditional direct asphalt-graphite mixing system suffers from poor mechanical reliability due to insufficient density and strength of the binder coke after coal tar pitch carbonization, and the lack of effective interfacial interaction between graphite and asphalt, making it difficult to form a tightly bonded integral structure.

[0054] Comparative Example 2 introduced a self-made furfural-based phenolic resin to modify coal tar pitch, but the graphite powder was not subjected to acyl chloride treatment, and its mechanical properties were improved compared to Comparative Example 1. This proves that the addition of furfural-based phenolic resin does indeed help improve the mechanical properties of graphite spheres by increasing the density and strength of the carbonization products and improving compatibility with coal tar pitch.

[0055] Comparative Example 3 retained the acyl chloride treatment of graphite but did not use furfural-based phenolic resin modification, using only medium-temperature coal tar pitch as a binder. Compared to Comparative Example 1, its performance was improved to some extent. This is because the acyl chloride treatment introduced active groups on the graphite surface, enhancing the interfacial interaction between graphite and pitch, improving wetting and coating effects, and forming a transitional carbon layer during carbonization, thus strengthening the interfacial bonding strength.

[0056] Comparative Example 4 completely replaced p-tert-butylphenol with ordinary phenol. The tert-butyl side group of p-tert-butylphenol can moderately adjust the crosslinking density of the resin through steric hindrance, while significantly improving the compatibility of phenolic resin with coal tar pitch. Without this component, the compatibility of phenolic resin with pitch decreases, it is difficult to achieve highly uniform micro-dispersion during melt mixing, and local defects and stress concentration are easily generated after carbonization, leading to a decrease in strength.

[0057] Comparative Example 5 completely replaced furfural with formaldehyde. The furan heterocyclic structure introduced by furfural helps to form a denser carbon microcrystalline structure during high-temperature carbonization, which significantly contributes to improving the density and strength of the bonded coke skeleton, while the carbonization products of phenolic resin with ordinary methylene bridging structure are relatively weak in strength.

[0058] Comparative Example 6 uses commercially available ordinary phenolic resin instead of the self-made furfural-based phenolic resin. Commercially available phenolic resin does not contain furan heterocyclic structures, nor does it have any tunable tert-butyl substituted phenolic segments. Its compatibility with coal tar pitch is not ideal, and it cannot effectively achieve highly uniform micro-dispersion and interface bonding optimization. Therefore, its performance is significantly lower than that of the technical solution of this invention.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphite sphere, characterized in that, Made from modified bitumen binder and graphite powder; The modified asphalt binder is made of coal tar pitch and furfural-based phenolic resin in a mass ratio of 1:0.08-0.12, wherein the furfural-based phenolic resin contains tert-butyl groups in its structure.

2. The graphite sphere as described in claim 1, characterized in that, The mass ratio of the modified asphalt binder to the graphite powder is 0.15-0.25:

1.

3. The graphite sphere as described in claim 1, characterized in that, The furfural-based phenolic resin is made from phenol, p-tert-butylphenol, 37% formaldehyde aqueous solution, furfural, and a catalyst.

4. The graphite sphere as described in claim 3, characterized in that, The mass ratio of phenol, p-tert-butylphenol, 37% formaldehyde aqueous solution, and furfural is 1:0.25-0.45:0.55-0.65:0.2-0.

3.

5. The graphite sphere as described in claim 3, characterized in that, The catalyst is at least one of oxalic acid, hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid.

6. The graphite sphere as described in claim 3, characterized in that, The preparation method of the furfural-based phenolic resin is as follows: Phenol and p-tert-butylphenol are heated and melted in a certain ratio. Then, 37% formaldehyde aqueous solution and furfural are added. After stirring evenly, a catalyst is added. The mixture is stirred and reacted at 95-105℃ for 2-4 hours. After the reaction is completed, an alkaline solution is added to neutralize the pH to 6.5-7.

5. Finally, the mixture is dehydrated under vacuum.

7. The graphite sphere as described in claim 1, characterized in that, The graphite powder was modified by acyl chloride treatment.

8. The graphite sphere as described in claim 7, characterized in that, The graphite powder is prepared as follows: Carboxylated graphite is obtained by oxidizing graphite with a mixed acid solution made of concentrated sulfuric acid and concentrated nitric acid after pulverizing it. Then, the carboxylated graphite is reacted with an acyl chloride reagent in an organic medium.

9. The graphite sphere as described in claim 8, characterized in that, The acyl chloride reagent is any one of thionyl chloride, acetyl chloride, benzoyl chloride, oxalyl chloride, chloroacetyl chloride, and trichloroacetyl chloride.

10. A method for preparing graphite spheres as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) Heat coal tar pitch to 160-180℃ to melt it, add furfural-based phenolic resin while stirring, and stir for 30-60 minutes to obtain modified asphalt binder. (2) Under an inert atmosphere, graphite powder is added and kneaded at 160-180℃ for 30-60 minutes to obtain spherical material; (3) Press the ball material into shape, first heat it to 200-300℃ in air atmosphere for pre-oxidation for 1-5h, then heat it to 1000-1200℃ in inert atmosphere for carbonization treatment for 2-4h, and then obtain graphite balls after cooling.

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