Corrosion-resistant graphite material for rectifying column and preparation method thereof

Abstract

The application relates to the technical field of corrosion-resistant chemical materials, and particularly discloses a kind of corrosion-resistant graphite materials for rectifying column and a preparation method thereof, the material is composed of modified graphite powder, high-performance ceramic powder, activated carbon fiber, composite binder and dispersant;The modified graphite powder is modified by a three-step method of "silane coupling agent grafting-in-situ deposition of inorganic nanoparticles-polymerization of fluorine-containing monomer", and a double protection structure is constructed on the surface thereof;The high-performance ceramic powder and the activated carbon fiber are both surface-functionalized by a specific process;The graphite material is prepared through material mixing, mould pressing and gradient temperature carbonization process;The raw material modification and process synergy of the application improve the compactness, mechanical strength, strong corrosion medium penetration resistance and high-temperature structural stability of the graphite material, solve the medium penetration and internal corrosion problems caused by the pores of traditional graphite materials, and are suitable for rectifying column internal components under harsh corrosion conditions.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant chemical materials technology, specifically to a corrosion-resistant graphite material for distillation columns and its preparation method. Background Technology

[0002] In the separation and purification processes of chemical, pharmaceutical, pesticide and hydrometallurgical industries, distillation columns are core and critical equipment. Their internal components, such as trays and packing, must withstand harsh conditions of high temperature, high pressure and complex and highly corrosive media for a long time. They are often in contact with corrosive substances such as mixed inorganic acids, halogens, organic solvents and high-concentration salt solutions, which places comprehensive and stringent requirements on the corrosion resistance, impermeability, thermal conductivity and structural strength of the materials.

[0003] Traditional artificial graphite materials are widely used in the manufacture of corrosion-resistant distillation column internals due to their excellent thermal conductivity, self-lubrication, thermal stability and good machinability.

[0004] However, traditional graphite materials develop numerous open micropores during production, which pose a fundamental defect in corrosive environments. When corrosive fluids (such as mixed acids, halogens, and organic solvents) come into contact with the material surface, they rapidly penetrate into the pores through capillary action. This penetration not only causes media loss and contamination, but more importantly, the corrosive media remains within the material for a long time, continuously acting on the graphite matrix and initiating progressive erosion from the inside out, significantly weakening the material's overall mechanical properties. Simultaneously, the internal pores can become stress concentration points under temperature and pressure fluctuations, accelerating fatigue damage.

[0005] Based on the above statements, this application provides a corrosion-resistant graphite material for distillation columns and a method for preparing the same. Summary of the Invention

[0006] To address the problems of corrosive media penetration and internal erosion caused by the inherent microporous structure of traditional graphite materials, as well as the resulting technical bottlenecks such as reduced structural strength, shortened service life, and insufficient operational reliability of distillation columns, this application provides a corrosion-resistant graphite material for distillation columns and its preparation method.

[0007] In a first aspect, this application provides a corrosion-resistant graphite material for distillation columns, employing the following technical solution:

[0008] A corrosion-resistant graphite material for distillation columns comprises the following raw materials in parts by weight: 65-75 parts modified graphite powder, 10-20 parts high-performance ceramic micro powder, 3-8 parts activated carbon fiber, 8-15 parts composite binder, and 0.5-1.5 parts dispersant.

[0009] Preferably, the modified graphite powder is prepared by the following steps:

[0010] A1. Grafting with silane coupling agent: Graphite powder is added to anhydrous ethanol and ultrasonically dispersed. Silane coupling agent is added, stirred, filtered, washed, and dried to obtain graphite powder intermediate A.

[0011] A2. In-situ deposition of inorganic nanoparticles: Add inorganic nanoparticle precursor and deionized water to graphite powder intermediate A, adjust the pH of the system to 8-9, stir, filter, wash, and dry to obtain graphite powder intermediate B.

[0012] A3. Polymerization of compound fluorinated monomers: Add compound fluorinated monomers, initiators and ethyl acetate to graphite powder intermediate B, disperse by ultrasonication to form a uniform suspension; heat the suspension to 68-75℃ under nitrogen protection, react for 3-5 hours, wash and dry to obtain modified graphite powder.

[0013] Preferably, in step A1, the mass ratio of graphite powder, anhydrous ethanol, and silane coupling agent is 100:150-180:3-6; the particle size of the graphite powder is 30-50 μm, and the purity is ≥99.5%; the silane coupling agent is KH-570 or KH-571.

[0014] Preferably, in step A2, the inorganic nanoparticle precursor is composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 6-8:3; the mass ratio of the graphite powder intermediate A, the inorganic nanoparticle precursor, and deionized water is 100:6-10:120-150.

[0015] Preferably, in step A3, the compound fluorinated monomer is composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:1-3; the initiator is azobisisobutyronitrile; and the mass ratio of graphite powder intermediate B, compound fluorinated monomer, initiator and ethyl acetate is 100:4-8:0.2-0.5:200-300.

[0016] In the A1 reaction described above, anhydrous ethanol is used as the dispersion medium, and ultrasonic dispersion is used to break up graphite powder agglomerates, allowing them to be uniformly dispersed and expanding the reaction interface. The alkoxy groups in the silane coupling agent molecules hydrolyze to generate hydroxyl groups, which undergo a dehydration condensation reaction with the hydroxyl groups on the graphite powder surface, achieving chemical grafting of the coupling agent onto the graphite powder surface; at the same time, active functional groups are introduced, improving the interfacial compatibility between graphite powder and subsequent components, and providing anchoring sites for subsequent reactions; after washing and drying to remove free coupling agent and residual solvent, pure graphite powder intermediate A is obtained.

[0017] In the A2 reaction process described above, the pH of the system is adjusted to an alkaline environment of 8-9, providing suitable conditions for the hydrolysis-condensation reaction of the inorganic nanoparticle precursor. Under this environment, the precursor gradually hydrolyzes to generate nanoparticles, which combine with the active functional groups on the surface of graphite powder intermediate A, depositing in situ and firmly loading onto the surface. The formed inorganic nanolayer provides anchoring sites for subsequent polymerization reactions and enhances the mechanical properties of graphite powder through nano-reinforcement effects, while also initially constructing a dense protective substrate. The washing and drying steps remove reaction impurities, ensuring the purity and reactivity of intermediate B.

[0018] In the A3 reaction process described above, ethyl acetate serves as the solvent to construct a stable suspension system, and ultrasonic dispersion ensures uniform mixing of the compounded fluorinated monomers, initiator, and graphite powder intermediate B. Nitrogen protection isolates oxygen, preventing monomer oxidation and quenching of free radicals generated by initiator decomposition. The initiator decomposes at 68-75℃ to generate free radicals, initiating the polymerization reaction of the compounded fluorinated monomers. The polymer chains are chemically bonded to the hydroxyl and silane functional groups of the inorganic nanoparticles on the surface of intermediate B, firmly grafting to form a dual protective layer of "inorganic nanoparticles + fluorinated polymer." The fluorinated groups endow the material with excellent corrosion resistance and hydrophobicity, while the inorganic particles fill coating defects. After washing and drying, a synergistic improvement in corrosion resistance and mechanical properties is achieved.

[0019] Preferably, the high-performance ceramic micro powder is prepared by the following steps:

[0020] Boron nitride powder and nano-silicon carbide powder were mixed to obtain a mixed powder. Tris-HCl and dopamine were added and stirred to deposit the mixture. The mixture was then centrifuged, washed, and spray-dried to obtain composite ceramic micro powder. The composite ceramic micro powder was added to anhydrous ethanol and ultrasonically dispersed to obtain a ceramic micro powder dispersion. Hexamethyldisilazane was added dropwise to the ceramic micro powder dispersion, and the mixture was stirred, filtered, washed, and dried to obtain high-performance ceramic micro powder.

[0021] Preferably, the high-performance ceramic micro powder is prepared by the following steps:

[0022] Boron nitride powder and nano-silicon carbide powder were mixed at a mass ratio of 3-5:1 to obtain a mixed powder. Tris-HCl (pH 8.0-9.0) and dopamine were added to the mixed powder at a mass ratio of 1:20-30:0.01-0.02. The mixture was stirred and deposited at 30-40℃ for 2-3 hours, centrifuged at 8000-10000 rpm for 15-20 minutes, washed 2-4 times with deionized water, and spray-dried for 25-35 minutes (inlet air temperature 110-140℃, outlet air temperature 70-90℃) to obtain a composite ceramic. Ceramic micro powder; composite ceramic micro powder is added to anhydrous ethanol at a mass ratio of 1:8-15, and ultrasonically dispersed at a power of 200-300W and a frequency of 40-50kHz for 30-60 minutes to obtain a ceramic micro powder dispersion; hexamethyldisilazane is added dropwise to the ceramic micro powder dispersion at a mass ratio of 100:3-5, with a dropping rate of 1-2mL / s, and stirred at 40-50℃ for 1-2 hours, filtered through a 200-300 mesh filter cloth, washed 2-3 times with anhydrous ethanol, and dried at 60-80℃ for 2-3 hours to obtain high-performance ceramic micro powder.

[0023] Preferably, the activated carbon fiber is prepared by the following steps: placing the carbon fiber in a mixed aqueous solution of hydrogen peroxide and sulfuric acid, oxidizing it, filtering it, washing it until neutral, and drying it to obtain the activated carbon fiber.

[0024] Preferably, the activated carbon fiber is prepared by the following steps:

[0025] Carbon fibers are placed in a mixed aqueous solution of hydrogen peroxide and sulfuric acid (the concentration of sulfuric acid is 0.3-0.5 mol / L, and the mass fraction of hydrogen peroxide is 3-5%), with a mass-to-volume ratio of carbon fibers to the mixed aqueous solution of hydrogen peroxide and sulfuric acid of 1:10-15. The carbon fibers are oxidized at 40-50℃ for 1-2 hours, filtered through a 200-300 mesh filter cloth, and then washed with deionized water until the pH of the washing solution is 6.5-7.5. The carbon fibers are then dried at 60-80℃ for 2-3 hours to obtain activated carbon fibers.

[0026] Preferably, the composite adhesive is prepared by compounding silane coupling agent and zinc borate in a mass ratio of 6-7:3-4.

[0027] Preferably, the dispersant is polyethylene glycol 2000 or polyethylene glycol 4000.

[0028] Secondly, this application provides a method for preparing corrosion-resistant graphite material for distillation columns, employing the following technical solution:

[0029] A method for preparing a corrosion-resistant graphite material for a distillation column includes the following steps:

[0030] S1. Mix the modified graphite powder, high-performance ceramic micro powder, activated carbon fiber, dispersant and composite binder evenly to obtain a homogeneous mixture;

[0031] S2. The homogeneous mixture is molded under a pressure of 60-100MPa and a temperature of 80-150℃ and held under pressure for 1.5-2.5h to obtain a green body;

[0032] S3. The billet is preheated and carbonized once and then cooled to obtain corrosion-resistant graphite material for distillation towers.

[0033] Preferably, in step S1, the stirring speed is 400-600 rpm and the stirring time is 20-25 min.

[0034] Preferably, in step S3, the first heating pre-firing specifically involves heating to 200-300℃ at a heating rate of 3-5℃ / min and holding for 3-4 hours to remove residual dispersant, unreacted small molecules, and moisture from the green body; the second heating carbonization specifically involves heating to 800-1200℃ at a heating rate of 2-4℃ / min after pre-firing and holding for 4-6 hours, with nitrogen gas introduced as a protective atmosphere during carbonization to prevent oxidation of the green body; the cooling specifically involves cooling to room temperature at a cooling rate of 5-8℃ / min after carbonization to avoid rapid cooling that could cause thermal stress inside the material.

[0035] In summary, this application has the following beneficial effects:

[0036] (1) Significantly improved corrosion resistance, solving the problem of media penetration and erosion: This application constructs a dual protective structure of "inorganic nanoparticle filling layer + fluorinated polymer dense coating" on the surface of graphite powder through triple synergistic modification of graphite powder by "silane coupling agent grafting - in-situ deposition of inorganic nanoparticles - compound fluorinated monomer polymerization". Among them, the fluorinated groups of the fluorinated polymer coating have low surface energy characteristics, which can directly block the contact between corrosive media and graphite matrix; inorganic nanoparticles (such as silicon dioxide, titanium dioxide, etc.) can not only fill the pores of the fluorinated polymer coating, but also block the inherent micropores of graphite, thereby reducing porosity. Compared with traditional unmodified graphite materials, the resistance to strong acid and strong alkali corrosion is significantly enhanced, effectively avoiding the internal erosion problem caused by media penetration. At the same time, inorganic nanoparticles have both high corrosion resistance and mechanical enhancement properties. The synergistic effect formed by inorganic nanoparticles with compound fluorinated polymers and silane coupling agents further improves the overall corrosion resistance and structural stability of graphite materials, which can stably adapt to the complex corrosion conditions of distillation columns.

[0037] (2) Synergistic optimization of mechanical strength and structural stability to extend service life: Traditional graphite materials are brittle and have poor crack resistance. During the operation of the distillation column, they are prone to structural strength decline due to pressure fluctuations and temperature changes. This application achieves performance enhancement through triple design: ① Carbon fiber is mildly oxidized by a mixed aqueous solution of hydrogen peroxide and sulfuric acid, and carboxyl-based active functional groups are generated on the surface, which effectively improves the interfacial bonding ability with the matrix and auxiliary materials. The fiber is uniformly dispersed in the system to construct a reinforcing skeleton, which significantly improves the tensile strength and fracture toughness of the material; ② The composite binder (silane coupling agent + zinc borate) has both adhesive and flame retardant properties. It can not only enhance the interfacial compatibility of each component and reduce agglomeration defects, but also improve the high temperature stability of the graphite material; ③ The compression molding and segmented carbonization process precisely control the densification process of the blank to avoid defects such as pores and cracks. Finally, the compressive strength and flexural strength of the material are improved. There is no obvious cracking or strength decay under low temperature to high temperature cycling, and the service life is extended.

[0038] (3) Strong synergistic compatibility of each component, high process controllability, and suitable for industrial-scale production: The raw material modification process and preparation method of this application form a closed-loop design: ① The surface functional groups (including silicon functional groups, carboxyl groups, hydroxyl groups, etc.) of modified graphite powder, high-performance ceramic micro powder, and activated carbon fiber can react chemically with the composite binder to achieve the dual effect of "chemical bonding + physical filling". The material has a high degree of homogenization and no risk of component stripping; ② The parameters of all modification steps and preparation processes are clearly quantified, such as ultrasonic dispersion power, molding pressure, carbonization heating rate, etc. No special customized equipment is required. Conventional chemical production equipment can be used to achieve large-scale production, reducing the threshold for industrial application; ③ The selection of dispersant (polyethylene glycol 2000 / 4000) can further optimize the dispersion uniformity of the mixture, reduce the agglomeration problem in the molding process, and improve the product qualification rate.

[0039] (4) It combines green environmental protection with practicality and has a wide range of applications: The raw materials used in this application are all commonly used industrial chemicals, without any dangerous components such as highly toxic or explosive substances. There are no harmful gas emissions during the preparation process, and the washing wastewater can be discharged in compliance with environmental protection requirements after simple treatment. At the same time, the material has excellent corrosion resistance, high temperature resistance, mechanical strength and thermal conductivity. It is not only suitable for core components such as the tower body, tower plate and heat exchanger of distillation tower, but can also be extended to other equipment in corrosive environments such as chemical reaction vessels and pipeline linings. It has a wide range of applications and strong practicality.

[0040] (5) Excellent cost control and outstanding cost performance: Compared with existing high-end corrosion-resistant graphite materials, this application reduces raw material costs and preparation energy consumption while ensuring performance improvement through raw material optimization and process simplification. It has both technological advancement and economic feasibility, and is easier to promote industrialization. Attached Figure Description

[0041] Figure 1 The image shows the microstructure of the corrosion-resistant graphite material for the distillation column prepared in Example 2.

[0042] Figure 2 This is a microscopic morphology image of the corrosion-resistant graphite material for distillation columns prepared in Example 2, viewed from another field of view.

[0043] Figure 3 This is a diagram showing the pore size of the corrosion-resistant graphite material used in the distillation column prepared in Example 2.

[0044] Figure 4 This is a three-dimensional profile measurement image of the corrosion-resistant graphite material for the distillation column prepared in Example 2. Detailed Implementation

[0045] The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0046] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0047] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0048] The graphite powder was purchased from Qingdao Tianyuan Graphite Co., Ltd., with a particle size of 50μm and a purity of 99.5%.

[0049] Both silane coupling agents KH-550 and KH-570 were purchased from Shandong Qingbang Chemical Technology Co., Ltd.

[0050] Boron nitride powder was purchased from Qingzhou Fangzhou New Materials Co., Ltd., with a density of 2.27 g / cm³. 3 The particle size is 8μm.

[0051] The nano-silicon carbide powder was purchased from Shanghai Pantian Powder Materials Co., Ltd., item number: PT-SiC-50nm, with a density of 3.2 g / cm³. 3 The particle size is 50nm.

[0052] Hexamethyldisilazane was purchased from Shandong Yihong Chemical Co., Ltd.

[0053] The carbon fiber was purchased from Wuhan Jiyesheng Chemical Co., Ltd., and its density is 1.75 g / cm³. 3 The particle size is 7μm.

[0054] The silica sol was purchased from Hubei Zhenghe Technology Co., Ltd., product model: ZS-20, density: 1.12 g / cm³. 3 The particle size is 20nm.

[0055] Example 1

[0056] A corrosion-resistant graphite material for distillation columns comprises the following raw materials in parts by weight: 65 parts modified graphite powder, 10 parts high-performance ceramic micro powder, 3 parts activated carbon fiber, 8 parts composite binder, and 0.5 parts polyethylene glycol 2000.

[0057] A method for preparing a corrosion-resistant graphite material for a distillation column includes the following steps:

[0058] S1. Modified graphite powder, high-performance ceramic micro powder, activated carbon fiber, polyethylene glycol 2000 and composite binder are stirred and mixed at 400 rpm for 20 min to obtain a homogeneous mixture.

[0059] S2. The homogeneous mixture is molded under a pressure of 60 MPa and a temperature of 80°C and held under pressure for 1.5 hours to obtain a blank.

[0060] S3. The billet is heated to 200℃ at a heating rate of 3℃ / min and held for 3 hours for a first heating pre-firing. After the pre-firing, under nitrogen protection, the billet is heated to 800℃ at a heating rate of 2℃ / min and held for 4 hours for a second heating carbonization. After carbonization, the billet is cooled to room temperature at a cooling rate of 5℃ / min to obtain corrosion-resistant graphite material for distillation columns.

[0061] Modified graphite powder is prepared by the following steps:

[0062] A1. Grafting with silane coupling agent: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:150:3. The mixture was stirred at 55℃ and 200rpm for 2h, filtered through a 200-mesh filter cloth, washed twice with deionized water, and dried at 100℃ for 2h to obtain graphite powder intermediate A.

[0063] A2. In-situ deposition of inorganic nanoparticles: Inorganic nanoparticle precursor (composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 6:3) and deionized water were added to graphite powder intermediate A at a mass ratio of 100:6:120. 5 wt% ammonia was added to adjust the pH of the system to 8. The mixture was stirred at 55℃ and 200 rpm for 2 h, filtered through a 200-mesh filter cloth, washed twice with deionized water, and dried at 100℃ for 2 h to obtain graphite powder intermediate B.

[0064] A3. Polymerization of compound fluorinated monomers: Compound fluorinated monomers (composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:1), azobisisobutyronitrile, and ethyl acetate were added to graphite powder intermediate B at a mass ratio of 100:4:0.2:200. The mixture was ultrasonically dispersed at 250W for 8 minutes to form a uniform suspension. The suspension was heated to 68℃ under nitrogen protection and reacted for 3 hours. The mixture was first washed twice with ethyl acetate to remove unpolymerized monomers and residual initiators, then washed twice with deionized water, and dried at 100℃ for 2 hours to obtain modified graphite powder.

[0065] High-performance ceramic micro powder is prepared by the following steps:

[0066] Boron nitride powder and nano-silicon carbide powder were mixed at a mass ratio of 3:1 to obtain a mixed powder. Tris-HCl (pH 8.0) and dopamine were added to the mixed powder at a mass ratio of 1:20:0.01. The mixture was stirred and deposited at 30℃ for 2 hours, centrifuged at 8000 rpm for 15 minutes, washed twice with deionized water, and spray-dried for 25 minutes (inlet air temperature 110℃, outlet air temperature 70℃) to obtain composite ceramic micro powder. The composite ceramic micro powder was added to anhydrous ethanol at a mass ratio of 1:8 and ultrasonically dispersed at 200W power and 40kHz frequency for 30 minutes to obtain a ceramic micro powder dispersion. Hexamethyldisilazane was added dropwise to the ceramic micro powder dispersion at a mass ratio of 100:3 at a dropping rate of 1 mL / s. The mixture was stirred and reacted at 40℃ for 1 hour, filtered through a 200-mesh filter cloth, washed twice with anhydrous ethanol, and dried at 60℃ for 2 hours to obtain high-performance ceramic micro powder.

[0067] Activated carbon fibers are prepared through the following steps:

[0068] Carbon fibers were placed in a mixed aqueous solution of hydrogen peroxide and sulfuric acid (the concentration of sulfuric acid was 0.3 mol / L and the mass fraction of hydrogen peroxide was 3%), with a mass-volume ratio of carbon fibers to the mixed aqueous solution of hydrogen peroxide and sulfuric acid of 1:10. The solution was oxidized at 40°C for 1 hour, filtered through a 200-mesh filter cloth, and then washed with deionized water until the pH of the washing solution reached 6.5. The solution was then dried at 60°C for 2 hours to obtain activated carbon fibers.

[0069] The composite adhesive is made by compounding silane coupling agent KH-550 and zinc borate in a mass ratio of 6:3.

[0070] Example 2

[0071] A corrosion-resistant graphite material for distillation columns comprises the following raw materials in parts by weight: 70 parts modified graphite powder, 15 parts high-performance ceramic micro powder, 5 parts activated carbon fiber, 12 parts composite binder, and 1 part polyethylene glycol 2000.

[0072] A method for preparing a corrosion-resistant graphite material for a distillation column includes the following steps:

[0073] S1. Modified graphite powder, high-performance ceramic micro powder, activated carbon fiber, polyethylene glycol 2000 and composite binder are stirred and mixed at 500 rpm for 22 min to obtain a homogeneous mixture.

[0074] S2. The homogeneous mixture is molded under a pressure of 80 MPa and a temperature of 120°C and held under pressure for 2 hours to obtain a blank.

[0075] S3. The billet is heated to 250℃ at a heating rate of 4℃ / min and held for 3.5h for a first heating pre-firing. After the pre-firing, under nitrogen protection, the billet is heated to 1000℃ at a heating rate of 3℃ / min and held for 5h for a second heating carbonization. After carbonization, the billet is cooled to room temperature at a cooling rate of 6℃ / min to obtain corrosion-resistant graphite material for distillation columns.

[0076] Modified graphite powder is prepared by the following steps:

[0077] A1. Grafting with silane coupling agent: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:165:4.5. The mixture was stirred at 60℃ and 300rpm for 2.5h, filtered through a 250-mesh filter cloth, washed three times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate A.

[0078] A2. In-situ deposition of inorganic nanoparticles: Inorganic nanoparticle precursor (composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 7:3) and deionized water were added to graphite powder intermediate A at a mass ratio of 100:8:135. 7.5wt% ammonia water was added to adjust the pH of the system to 8.5. The mixture was stirred at 60℃ and 300rpm for 3h, filtered through a 250-mesh filter cloth, washed 3 times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate B.

[0079] A3. Polymerization of compound fluorinated monomers: Compound fluorinated monomers (composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:2), azobisisobutyronitrile, and ethyl acetate were added to graphite powder intermediate B at a mass ratio of 100:6:0.35:250. The mixture was ultrasonically dispersed at 300W for 10 min to form a uniform suspension. The suspension was heated to 72℃ under nitrogen protection and reacted for 4 h. The mixture was first washed three times with ethyl acetate to remove unpolymerized monomers and residual initiators, then washed three times with deionized water, and dried at 100-120℃ for 3 h to obtain modified graphite powder.

[0080] High-performance ceramic micro powder is prepared by the following steps:

[0081] Boron nitride powder and nano-silicon carbide powder were mixed at a mass ratio of 4:1 to obtain a mixed powder. Tris-HCl (pH 8.5) and dopamine were added to the mixed powder at a mass ratio of 1:25:0.015. The mixture was stirred and deposited at 35℃ for 2.5 h, centrifuged at 9000 rpm for 18 min, washed three times with deionized water, and spray-dried for 30 min (inlet air temperature 130℃, outlet air temperature 80℃) to obtain composite ceramic micro powder. The composite ceramic micro powder was added to anhydrous ethanol at a mass ratio of 1:12 and ultrasonically dispersed at 250 W and 45 kHz for 45 min to obtain a ceramic micro powder dispersion. Hexamethyldisilazane was added dropwise to the ceramic micro powder dispersion at a mass ratio of 100:4 at a dropping rate of 1.5 mL / s. The mixture was stirred and reacted at 45℃ for 1.5 h, filtered through a 250-mesh filter cloth, washed three times with anhydrous ethanol, and dried at 70℃ for 2.5 h to obtain high-performance ceramic micro powder.

[0082] Activated carbon fibers are prepared through the following steps:

[0083] Carbon fibers were placed in a mixed aqueous solution of hydrogen peroxide and sulfuric acid (the concentration of sulfuric acid was 0.4 mol / L and the mass fraction of hydrogen peroxide was 4%), with a mass-volume ratio of carbon fibers to the mixed aqueous solution of hydrogen peroxide and sulfuric acid of 1:12. The solution was oxidized at 45°C for 1.5 h, filtered through a 250-mesh filter cloth, and then washed with deionized water until the pH of the washing solution reached 7. The solution was then dried at 70°C for 2.5 h to obtain activated carbon fibers.

[0084] The composite adhesive is made by compounding silane coupling agent KH-550 and zinc borate in a mass ratio of 6.5:3.5.

[0085] Example 3

[0086] A corrosion-resistant graphite material for distillation columns comprises the following raw materials in parts by weight: 75 parts modified graphite powder, 20 parts high-performance ceramic micro powder, 8 parts activated carbon fiber, 15 parts composite binder, and 1.5 parts polyethylene glycol 2000.

[0087] A method for preparing a corrosion-resistant graphite material for a distillation column includes the following steps:

[0088] S1. Modified graphite powder, high-performance ceramic micro powder, activated carbon fiber, polyethylene glycol 2000 and composite binder are stirred and mixed at 600 rpm for 25 min to obtain a homogeneous mixture.

[0089] S2. The homogeneous mixture is molded under a pressure of 100 MPa and a temperature of 150°C and held under pressure for 2.5 hours to obtain a blank.

[0090] S3. The billet is heated to 300℃ at a heating rate of 5℃ / min and held for 4 hours for a first heating pre-firing. After the pre-firing, under nitrogen protection, the billet is heated to 1200℃ at a heating rate of 4℃ / min and held for 6 hours for a second heating carbonization. After carbonization, the billet is cooled to room temperature at a cooling rate of 8℃ / min to obtain corrosion-resistant graphite material for distillation columns.

[0091] Modified graphite powder is prepared by the following steps:

[0092] A1. Grafting with silane coupling agent: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:180:6. The mixture was stirred at 65℃ and 400rpm for 3h, filtered through a 300-mesh filter cloth, washed 4 times with deionized water, and dried at 120℃ for 4h to obtain graphite powder intermediate A.

[0093] A2. In-situ deposition of inorganic nanoparticles: Inorganic nanoparticle precursor (composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 8:3) and deionized water were added to graphite powder intermediate A at a mass ratio of 100:10:150. 10wt% ammonia was added to adjust the pH of the system to 9. The mixture was stirred at 65℃ and 400rpm for 4h, filtered through a 300-mesh filter cloth, washed 4 times with deionized water, and dried at 120℃ for 4h to obtain graphite powder intermediate B.

[0094] A3. Polymerization of compound fluorinated monomers: Compound fluorinated monomers (composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:3), azobisisobutyronitrile, and ethyl acetate were added to graphite powder intermediate B at a mass ratio of 100:8:0.5:300. The mixture was ultrasonically dispersed at 350W for 12 minutes to form a uniform suspension. The suspension was heated to 75℃ under nitrogen protection and reacted for 5 hours. The mixture was first washed 4 times with ethyl acetate to remove unpolymerized monomers and residual initiators, then washed 4 times with deionized water, and dried at 120℃ for 4 hours to obtain modified graphite powder.

[0095] High-performance ceramic micro powder is prepared by the following steps:

[0096] Boron nitride powder and nano-silicon carbide powder were mixed at a mass ratio of 5:1 to obtain a mixed powder. Tris-HCl (pH 9.0) and dopamine were added to the mixed powder at a mass ratio of 1:30:0.02. The mixture was stirred and deposited at 40℃ for 3 hours, centrifuged at 10000 rpm for 20 minutes, washed four times with deionized water, and spray-dried for 35 minutes (inlet air temperature 140℃, outlet air temperature 90℃) to obtain composite ceramic micro powder. The composite ceramic micro powder was added to anhydrous ethanol at a mass ratio of 1:15 and ultrasonically dispersed at 300W and 50kHz for 60 minutes to obtain a ceramic micro powder dispersion. Hexamethyldisilazane was added dropwise to the ceramic micro powder dispersion at a mass ratio of 100:5 at a dropping rate of 2 mL / s. The mixture was stirred and reacted at 50℃ for 2 hours, filtered through a 300-mesh filter cloth, washed three times with anhydrous ethanol, and dried at 80℃ for 3 hours to obtain high-performance ceramic micro powder.

[0097] Activated carbon fibers are prepared through the following steps:

[0098] Carbon fibers were placed in a mixed aqueous solution of hydrogen peroxide and sulfuric acid (the concentration of sulfuric acid was 0.5 mol / L and the mass fraction of hydrogen peroxide was 5%), with a mass-volume ratio of carbon fibers to the mixed aqueous solution of hydrogen peroxide and sulfuric acid of 1:15. The solution was oxidized at 50°C for 2 hours, filtered through a 300-mesh filter cloth, and then washed with deionized water until the pH of the washing solution reached 7.5. The solution was then dried at 80°C for 3 hours to obtain activated carbon fibers.

[0099] The composite adhesive is made by compounding silane coupling agent KH-550 and zinc borate in a mass ratio of 7:4.

[0100] Comparative Example 1

[0101] The only difference between this comparative example and Example 2 is that graphite powder (50 μm particle size, 99.5% purity) was used instead of modified graphite powder. All other component compositions, preparation methods, and parameters remained consistent with Example 2.

[0102] Comparative Example 2

[0103] The only difference between this comparative example and Example 2 is that ceramic micropowder was used instead of high-performance ceramic micropowder. All other component compositions, preparation methods, and parameters remain consistent with Example 2.

[0104] The ceramic micro powder is prepared by the following steps: mixing boron nitride powder and nano silicon carbide powder at a mass ratio of 4:1 to obtain ceramic micro powder.

[0105] Comparative Example 3

[0106] The only difference between this comparative example and Example 2 is that carbon fiber (density 1.75 g / cm³) was used. 3The activated carbon fibers were replaced with those with a particle size of 7 μm. All other components, preparation methods, and parameters remained consistent with those in Example 2.

[0107] Comparative Example 4

[0108] The only difference between this comparative example and Example 2 is the specific preparation steps of the modified graphite powder; only the silane coupling agent grafting in step A1 is performed. All other component compositions, preparation methods, and parameters remain consistent with Example 2.

[0109] Modified graphite powder is prepared by the following steps:

[0110] Silane coupling agent grafting: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:165:4.5. The mixture was stirred at 60℃ and 300rpm for 2.5h, filtered through a 250-mesh filter cloth, washed three times with deionized water, and dried at 110℃ for 3h to obtain modified graphite powder.

[0111] Comparative Example 5

[0112] The only difference between this comparative example and Example 2 is the specific preparation steps of the modified graphite powder. In step A2, the inorganic nanoparticle precursor consists only of tetraethyl orthosilicate. All other component compositions, preparation methods, and parameters remain consistent with Example 2.

[0113] Modified graphite powder is prepared by the following steps:

[0114] A1. Grafting with silane coupling agent: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:165:4.5. The mixture was stirred at 60℃ and 300rpm for 2.5h, filtered through a 250-mesh filter cloth, washed three times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate A.

[0115] A2. In-situ deposition of inorganic nanoparticles: Tetraethyl orthosilicate and deionized water were added to graphite powder intermediate A at a mass ratio of 100:8:135. The pH of the system was adjusted to 8.5 by adding 7.5wt% ammonia. The mixture was stirred at 60℃ and 300rpm for 3h, filtered through a 250-mesh filter cloth, washed 3 times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate B.

[0116] A3. Polymerization of compound fluorinated monomers: Compound fluorinated monomers (composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:2), azobisisobutyronitrile, and ethyl acetate were added to graphite powder intermediate B at a mass ratio of 100:6:0.35:250. The mixture was ultrasonically dispersed at 300W for 10 min to form a uniform suspension. The suspension was heated to 72℃ under nitrogen protection and reacted for 4 h. The mixture was first washed three times with ethyl acetate to remove unpolymerized monomers and residual initiators, then washed three times with deionized water, and dried at 100-120℃ for 3 h to obtain modified graphite powder.

[0117] Comparative Example 6

[0118] The only difference between this comparative example and Example 2 is the specific preparation steps of the modified graphite powder. In step A3, a fluorinated monomer (trifluoroethyl methacrylate) is used instead of the compounded fluorinated monomer. All other component compositions, preparation methods, and parameters remain consistent with Example 2.

[0119] Modified graphite powder is prepared by the following steps:

[0120] A1. Grafting with silane coupling agent: Graphite powder was ultrasonically dispersed in anhydrous ethanol, and silane coupling agent KH-570 was added. The mass ratio of graphite powder, anhydrous ethanol and silane coupling agent KH-570 was 100:165:4.5. The mixture was stirred at 60℃ and 300rpm for 2.5h, filtered through a 250-mesh filter cloth, washed three times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate A.

[0121] A2. In-situ deposition of inorganic nanoparticles: Inorganic nanoparticle precursor (composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 7:3) and deionized water were added to graphite powder intermediate A at a mass ratio of 100:8:135. 7.5wt% ammonia water was added to adjust the pH of the system to 8.5. The mixture was stirred at 60℃ and 300rpm for 3h, filtered through a 250-mesh filter cloth, washed 3 times with deionized water, and dried at 110℃ for 3h to obtain graphite powder intermediate B.

[0122] A3. Polymerization of fluorinated monomers: Trifluoroethyl methacrylate, azobisisobutyronitrile and ethyl acetate were added to graphite intermediate B at a mass ratio of 100:6:0.35:250. The mixture was ultrasonically dispersed at 300W for 10 min to form a uniform suspension. The suspension was heated to 72℃ under nitrogen protection and reacted for 4 h. The mixture was first washed three times with ethyl acetate to remove unpolymerized monomers and residual initiators, then washed three times with deionized water, and dried at 100-120℃ for 3 h to obtain modified graphite powder.

[0123] Performance testing

[0124] This experiment tested the performance of the corrosion-resistant graphite materials for distillation columns prepared in Examples 1-3 and Comparative Examples 1-6. Four key indicators were selected: density, mechanical properties, corrosion resistance, and high-temperature stability. Testing methods were developed in accordance with chemical materials industry standards and technical requirements, as detailed below:

[0125] ① Bulk density: determined by Archimedes' water displacement method.

[0126] ② Open porosity: Derived and calculated based on density data, the specific method is as follows:

[0127] The theoretical density of pure graphite is 2.26 g / cm³. 3 The theoretical density of the corrosion-resistant graphite material in this application is calculated based on the weighted average of the raw material proportions.

[0128] The measured density of the material was obtained using Archimedes' displacement method, and the bulk density was calculated.

[0129] Because the closed-cell porosity of this material is extremely low (<0.1%) after composite modification, and the open-cell porosity is approximately equal to the total porosity, the calculation formula is as follows:

[0130] ③ Flexural strength / compressive strength: Tested using a universal testing machine according to GB / T 3074.1-2013 "Method for Determination of Flexural Strength of Graphite Electrodes". Compressive strength: Tested using a universal testing machine according to GB / T 1431-2019 "Method for Determination of Compressive Strength of Carbon Materials".

[0131] ④ Corrosion resistance: The sample was immersed in a mixed acid solution of 20% hydrochloric acid, 5% hydrofluoric acid and 10% nitric acid for 1000 hours, and its mass loss rate was measured.

[0132] ⑤ High temperature stability: After being kept at 500℃ for 1000h, the flexural strength retention rate was tested after cooling.

[0133] To further illustrate the microstructure and surface morphology of the corrosion-resistant graphite material used in distillation columns, the sample prepared in Example 2 was used as a representative for microscopic morphology observation and three-dimensional profile testing. The results are as follows: Figures 1-4 As shown.

[0134] in, Figure 1 The microstructure of the corrosion-resistant graphite material used in distillation columns is shown to illustrate the overall morphological characteristics and structural density of the material surface. Figure 2 The microstructure of the corrosion-resistant graphite material used in distillation columns is shown in another field of view to further illustrate the surface microstructure and local structural features of the material. Figure 3 This diagram illustrates the pore size of corrosion-resistant graphite materials used in distillation columns, serving to help explain the size and distribution of pores in the material. Figure 4 The results of three-dimensional profile measurement of corrosion-resistant graphite material used in distillation columns are shown, which can reflect the profile undulation and dimensional characteristics of the material surface.

[0135] Combination Figures 1-4 It can be seen that the overall microstructure of the corrosion-resistant graphite material used in distillation columns is relatively dense, the surface morphology is relatively continuous, and there are few local pores and irregular areas, indicating that the material has good structural stability and surface density.

[0136] The performance test data results are shown in Table 1.

[0137] Table 1 Performance test data results

[0138] Group Bulk density (%) Open porosity (%) Flexural strength (MPa) Compressive strength (MPa) Mass loss rate (%) after soaking in mixed acid for 1000 hours Flexural strength retention rate (%) after heat treatment at 500℃ for 1000h Example 1 99.3 0.7 69.2 138.5 0.78 96.8 Example 2 99.5 0.5 71.5 142.3 0.67 97.2 Example 3 99.4 0.6 70.3 140.1 0.79 96.5 Comparative Example 1 97.1 2.9 44.6 88.9 2.32 82.1 Comparative Example 2 97.5 2.5 51.8 104.5 2.15 85.3 Comparative Example 3 97.9 2.1 57.3 113.8 1.18 89.6 Comparative Example 4 98.3 1.7 59.5 118.6 0.85 91.2 Comparative Example 5 98.2 1.8 62.3 121.7 0.58 90.3 Comparative Example 6 97.7 2.3 46.9 93.5 2.17 81.5

[0139] As can be seen from the data in Table 1, the corrosion-resistant graphite materials for distillation columns prepared in Examples 1-3 have good density, mechanical properties, corrosion resistance and high-temperature stability.

[0140] In Comparative Example 1, replacing modified graphite powder with unmodified graphite powder resulted in a decrease in the density, mechanical properties, and corrosion resistance of the obtained graphite material. This result indicates that synergistic modification of graphite powder through silane coupling agent grafting, in-situ deposition of inorganic nanoparticles, and polymerization of compound fluorinated monomers is beneficial for improving the dispersibility, interfacial compatibility, and surface protection capabilities of graphite powder, thereby enhancing the overall performance of the material.

[0141] In Comparative Example 2, replacing the high-performance ceramic powder with ceramic micropowder resulted in a decrease in the compressive strength and corrosion resistance of the obtained graphite material. This result indicates that high-performance ceramic micropowder modified with dopamine polymerization and hexamethyldisilazane can improve the interfacial bonding with the matrix and enhance the material's density and corrosion resistance.

[0142] In Comparative Example 3, replacing activated carbon fibers with carbon fibers resulted in a decrease in the flexural strength and structural stability of the resulting graphite material. This result indicates that surface oxidation activation of carbon fibers can improve their bonding ability with the matrix and enhance the fiber reinforcement effect, thereby contributing to improved mechanical properties and structural stability of the material.

[0143] In Comparative Example 4, the graphite material obtained after grafting with only silane coupling agent showed high porosity and poor corrosion resistance. This result indicates that surface grafting alone is insufficient to simultaneously achieve pore sealing and effective protection, while inorganic nanoparticle deposition and fluorinated monomer polymerization play a crucial role in improving the material's density and corrosion resistance.

[0144] In Comparative Example 5, when only tetraethyl orthosilicate was used as the inorganic nanoparticle precursor, the resulting graphite material exhibited decreased density, increased open-pore porosity, and inferior corrosion resistance, mechanical properties, and high-temperature stability compared to the examples. These results indicate that the combination of tetraethyl orthosilicate and tetraisopropyl titanate is more conducive to forming a dense and stable inorganic deposition layer, thereby improving the overall performance of the material.

[0145] In Comparative Example 6, replacing the compounded fluorinated monomers with trifluoroethyl methacrylate resulted in a decrease in the density and an increase in the open porosity of the obtained graphite material, along with a reduction in corrosion resistance, mechanical properties, and high-temperature stability. These results indicate that the compounded fluorinated monomer system is more conducive to forming a dense and stable organic protective layer, thereby improving the overall performance of the material.

[0146] The above specific embodiments are merely explanations of this application and are not intended to limit this application. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A corrosion-resistant graphite material for distillation columns, characterized in that, The raw materials include the following parts by weight: 65-75 parts modified graphite powder, 10-20 parts high-performance ceramic micro powder, 3-8 parts activated carbon fiber, 8-15 parts composite binder, and 0.5-1.5 parts dispersant.

2. The corrosion-resistant graphite material for distillation columns according to claim 1, characterized in that, The modified graphite powder is prepared by the following steps: A1. Grafting with silane coupling agent: Graphite powder is added to anhydrous ethanol and ultrasonically dispersed. Silane coupling agent is added, stirred, filtered, washed, and dried to obtain graphite powder intermediate A. A2. In-situ deposition of inorganic nanoparticles: Add inorganic nanoparticle precursor and deionized water to graphite powder intermediate A, adjust the pH of the system to 8-9, stir, filter, wash, and dry to obtain graphite powder intermediate B. A3. Polymerization of compound fluorinated monomers: Add compound fluorinated monomers, initiators and ethyl acetate to graphite powder intermediate B, and disperse by ultrasonication to form a uniform suspension; The suspension was heated to 68-75℃ under nitrogen protection and reacted for 3-5 hours. After washing and drying, modified graphite powder was obtained.

3. The corrosion-resistant graphite material for distillation columns according to claim 2, characterized in that, In step A1, the mass ratio of graphite powder, anhydrous ethanol, and silane coupling agent is 100:150-180:3-6.

4. The corrosion-resistant graphite material for distillation columns according to claim 2, characterized in that, In step A2, the inorganic nanoparticle precursor is composed of tetraethyl orthosilicate and tetraisopropyl titanate in a mass ratio of 6-8:3; the mass ratio of the graphite powder intermediate A, the inorganic nanoparticle precursor, and deionized water is 100:6-10:120-150.

5. The corrosion-resistant graphite material for distillation columns according to claim 2, characterized in that, In step A3, the compound fluorinated monomer is composed of trifluoroethyl methacrylate and hexafluorobutyl methacrylate in a mass ratio of 1:1-3; the initiator is azobisisobutyronitrile; the mass ratio of graphite powder intermediate B, compound fluorinated monomer, initiator and ethyl acetate is 100:4-8:0.2-0.5:200-300.

6. The corrosion-resistant graphite material for distillation columns according to claim 1, characterized in that, The high-performance ceramic micro powder is prepared by the following steps: Boron nitride powder and nano-silicon carbide powder were mixed to obtain a mixed powder. Tris-HCl and dopamine were added and stirred to deposit the mixture. The mixture was then centrifuged, washed, and spray-dried to obtain composite ceramic micro powder. The composite ceramic micro powder was added to anhydrous ethanol and ultrasonically dispersed to obtain a ceramic micro powder dispersion. Hexamethyldisilazane was added dropwise to the ceramic micro powder dispersion, and the mixture was stirred, filtered, washed, and dried to obtain high-performance ceramic micro powder.

7. The corrosion-resistant graphite material for distillation columns according to claim 1, characterized in that, The activated carbon fiber is prepared by the following steps: placing the carbon fiber in a mixed aqueous solution of hydrogen peroxide and sulfuric acid, oxidizing it, filtering it, washing it until neutral, and drying it to obtain the activated carbon fiber.

8. The corrosion-resistant graphite material for distillation columns according to claim 1, characterized in that, The composite adhesive is prepared by compounding silane coupling agent and zinc borate in a mass ratio of 6-7:3-4.

9. The corrosion-resistant graphite material for distillation columns according to claim 1, characterized in that, The dispersant is polyethylene glycol 2000 or polyethylene glycol 4000.

10. A method for preparing a corrosion-resistant graphite material for a distillation column according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the modified graphite powder, high-performance ceramic micro powder, activated carbon fiber, dispersant and composite binder evenly to obtain a homogeneous mixture; S2. The homogeneous mixture is molded under a pressure of 60-100MPa and a temperature of 80-150℃ and held under pressure for 1.5-2.5h to obtain a green body; S3. The billet is preheated and carbonized once and then cooled to obtain corrosion-resistant graphite material for distillation towers.

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