A method for purifying crystalline graphite
By treating crystalline graphite with the chemical effects of fluoride salts and hydrochloric acid, the problems of high energy consumption and high cost in existing technologies are solved, and high-purity, low-cost graphite purification is achieved, which is suitable for electromagnetic shielding, antistatic, fireproofing and lubricant applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN SHIDAI ENKE NEW ENERGY TECH CO LTD
- Filing Date
- 2023-12-06
- Publication Date
- 2026-05-12
Smart Images
Figure CN117509633B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of graphite purification technology, specifically relating to a method for purifying crystalline graphite. Background Technology
[0002] Natural graphite can be divided into two main categories: crystalline graphite and cryptocrystalline graphite. Crystalline graphite is characterized by its wide distribution, large proportion, and high reserves. However, for its applications in various fields, high carbon content and high purity are fundamental requirements for crystalline graphite. Currently, the main purification methods for crystalline graphite are the hydrofluoric acid method, the alkali-acid method, the chlorination roasting method, and the high-temperature method. These purification methods typically achieve a carbon content of over 99%, meeting the 99% purity requirement, but each method has certain drawbacks.
[0003] The hydrofluoric acid method uses hydrofluoric acid, a highly toxic and corrosive reagent, posing significant risks with large-scale use. Its corrosiveness also imposes extremely stringent requirements on production equipment, and the resulting wastewater is highly corrosive. Therefore, the environmental costs significantly diminish the method's low-cost advantage. The chlorination roasting method also has obvious drawbacks: the chlorine gas used is highly toxic and corrosive, and the exhaust gas requires proper treatment, making large-scale application difficult. High-temperature purification methods can achieve a carbon content of over 99.995% in graphite, but they consume a great deal of energy and require specially designed and constructed high-temperature furnaces, resulting in extremely high costs. They are only used in specialized fields such as military and aerospace. The alkali-acid method is currently the most widely used method in my country, but it suffers from high graphite loss, high energy consumption, and long reaction times, leading to high costs. Furthermore, a major limitation of this method in improving graphite purity is the poor dispersibility of graphite in a liquid environment.
[0004] To address the technical problems of strong corrosion, high energy consumption, and high cost in existing methods for purifying crystalline graphite, there is an urgent need to find a new, low-cost, simple, low-pollution method for purifying crystalline graphite with a carbon content higher than 99% in the finished product, thereby improving production safety and economic efficiency. Summary of the Invention
[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for purifying crystalline graphite, so as to solve the technical problems of strong corrosion, high energy consumption and high cost of existing crystalline graphite purification methods.
[0006] To achieve the above objectives, the present invention employs the following technical solution:
[0007] This invention discloses a method for purifying crystalline graphite, comprising the following steps:
[0008] First, fluoride salt, deionized water and crystalline graphite are mixed and heat-dried. Then, dispersant and sodium chloride are added, and the mixture is ground. After grinding, deionized water is added, and the mixture is sonicated. It is then heat-dried again until it becomes viscous. After heat treatment, water washing and alcohol washing, high-carbon crystalline graphite is obtained.
[0009] Preferably, after heat treatment, deionized water and hydrochloric acid are added, and the mixture is heated and stirred, repeatedly washed with water, filtered, and dried to obtain high-carbon crystalline graphite with a carbon content greater than 99%.
[0010] More preferably, the mass ratio of deionized water: hydrochloric acid: crystalline graphite is 100:(12-60):(3-10.06).
[0011] More preferably, the heating and stirring temperature is 60-80℃.
[0012] More preferably, the heating and stirring time is 4-10 hours.
[0013] Preferably, the mass ratio of fluoride salt to crystalline graphite is (0.0057-0.0285):(0.029-0.043).
[0014] Preferably, the mass of the dispersant is 1.0%-12.7% of the mass of crystalline graphite; the dispersant is an ammonium salt or polyvinyl alcohol.
[0015] Preferably, the mass of sodium chloride is 39%-48.5% of the mass of the fluoride salt.
[0016] Preferably, the heat treatment time is 2.5-5.5 hours.
[0017] Preferably, the heat treatment temperature is 630-837℃; the heat treatment is carried out under an inert atmosphere.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] This invention discloses a method for purifying crystalline graphite. First, fluoride salt, deionized water, and crystalline graphite are mixed. The purification effect of the molten fluoride salt removes metal oxides such as aluminum oxide and calcium oxide from the crystalline graphite. After heat drying, a dispersant and sodium chloride are added, followed by grinding. Deionized water is then added, and the mixture is ultrasonicated and heat-dried again until it reaches a viscous state. After heat treatment, water washing, and alcohol washing, high-carbon crystalline graphite is obtained. Using molten salt as the liquid phase and introducing a small amount of dispersant greatly improves the dispersibility of graphite in the liquid phase, increases the contact between graphite and molten salt, and is more conducive to improving the purification efficiency of molten salt for impurities in crystalline graphite, thus improving the purity of the graphite product obtained in the first step. Furthermore, the introduction of dispersant and molten salt does not cause the formation of byproducts. The high-temperature purification effect of fluoride salt greatly improves the purity of the graphite material. Compared with reagents used in other purification processes and methods, the reagents used in this invention are less corrosive and inexpensive, effectively solving the shortcomings of high energy consumption and high cost in existing crystalline graphite purification methods, and significantly improving economic efficiency.
[0020] Furthermore, by introducing hydrochloric acid through secondary treatment, the chemical effect of hydrochloric acid and fluoride salts is utilized to use the hazardous hydrofluoric acid reagent as an intermediate product in the reaction. This greatly reduces the danger of the production process, fully utilizes the raw materials used for purification, and achieves the goals of cost reduction, efficiency improvement, and quality enhancement. The purity of the obtained graphite product is higher than that of the traditional alkaline-acid method and the hydrofluoric acid method. After adding hydrochloric acid, the hydrochloric acid-fluoride salt chemical effect is used to generate hydrofluoric acid intermediate product for further purification of crystalline graphite. This provides a low-cost, low-pollution, simple process for graphite purification, with a finished product carbon content higher than 99%. Using this purification method, crystalline graphite with a carbon content greater than 82% can be purified to high-carbon graphite with a carbon content of not less than 99%, a moisture content of not more than 0.5%, and an ash content of not more than 0.7%. The use of hydrofluoric acid as a reaction intermediate product reduces the requirements for manual operation, improving production safety. At the same time, this purification process has low energy consumption, low production cost, and relatively low environmental protection investment costs. Attached Figure Description
[0021] Figure 1 This is a SEM image of the raw material crystalline graphite disclosed in this invention;
[0022] Figure 2 This is a SEM image of the high-carbon graphite obtained in Example 2 of the present invention. Detailed Implementation
[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0025] The present invention will now be described in further detail with reference to the accompanying drawings:
[0026] This invention addresses the shortcomings of existing technologies, such as high energy consumption and high cost. It removes metal oxides such as aluminum oxide and calcium oxide from crystalline graphite through the purification effect of fluoride salt melting. After adding hydrochloric acid, the hydrochloric acid-fluoride salt chemical effect is used to generate hydrofluoric acid intermediate to further purify crystalline graphite. This provides a low-cost, simple, low-pollution graphite purification method and process with a finished product carbon content of over 99%.
[0027] This invention discloses a method for purifying crystalline graphite, comprising the following steps:
[0028] 1) Using crystalline graphite powder with a carbon content greater than 82% as raw material, first mix fluoride salt with deionized water to prepare a fluoride salt solution of a certain concentration, add a certain proportion of crystalline graphite to obtain mixed solution 1, and quickly heat dry mixed solution 1 in air atmosphere to obtain mixture 1.
[0029] 2) Add a certain amount of dispersant and a certain amount of sodium chloride to mixture 1 and grind to obtain mixture 2; add the same mass of deionized water as in step 1) to mixture 2, then sonicate for a certain time, and quickly heat dry in air until viscous to obtain mixture 3.
[0030] 3) At a certain temperature, mixture 3 is heat-treated in an inert atmosphere. After the reaction is complete, mixture 4 is obtained.
[0031] 4) Wash the mixture 4 with water and alcohol several times to obtain a high-carbon crystalline graphite with a purity of over 97%; if higher purity is required, the following steps can be performed for further processing.
[0032] 5) Mixture 4 directly with deionized water and hydrochloric acid in a certain proportion in sequence to obtain mixture 5; place mixture 5 in a tetrafluoroethylene container and add a rotor, then heat and stir, repeatedly wash with water, filter, and dry to obtain high carbon crystalline graphite with a carbon content greater than 99%.
[0033] In step 1), the concentration of the fluoride salt solution is 0.0057-0.0285 g / mL; the concentration of crystalline graphite in the solution is 0.029-0.043 g / mL; and the fluoride salt is lithium fluoride or sodium fluoride.
[0034] In step 2), the mass of the dispersant added is 1.0%-12.7% of the mass of the crystalline graphite added in step 1); the dispersant is any one of ammonium salt and polyvinyl alcohol.
[0035] In step 3), the heat treatment time is 2.5-5.5 hours and the heat treatment temperature is 630-837℃.
[0036] In step 5), the mass ratio of deionized water, hydrochloric acid and crystalline graphite added in step 1) is 100:(12-60):(3-10.06); the heating and stirring temperature is 60-80℃, and the heating and stirring time is 4-10h.
[0037] In the above steps, attention must be paid to the order of addition of hydrochloric acid, deionized water, and the mixture of deionized water, fluoride salt, and graphite raw materials, as the order of addition has a certain impact on the purification effect. The complete purification method of this invention can purify crystalline graphite with a carbon content of 82% to high-carbon graphite with a carbon content of not less than 99%, an ash content of not more than 0.7%, and a moisture content of not more than 0.5%. The prepared high-carbon graphite can meet the requirements of most fields, especially in applications such as electromagnetic shielding, antistatic agents, fireproofing, lubricants, and anti-corrosion materials, and this purification method does not change the morphology of the crystalline graphite.
[0038] Example 1
[0039] A method for purifying crystalline graphite includes the following steps:
[0040] 1) Weigh 500mL of deionized water, 3g of sodium fluoride, and 15g of crystalline graphite with a carbon content of 82%, mix them evenly, and dry them in air at 80℃ to obtain a uniformly mixed mixture 1.
[0041] 2) Add 1.2g of sodium chloride and 0.15g of polyvinyl alcohol to the mixture of sodium fluoride and crystalline graphite and grind to obtain mixture 2. Add 500g of deionized water, sonicate for 0.5h, and then dry in air at 80℃ until it becomes viscous to obtain mixture 3.
[0042] 3) After heat treatment of mixture 3 at 837℃ in an inert atmosphere for 2.5h, mixture 4 is obtained. After washing with water and alcohol, crystalline graphite with a carbon content of more than 97% can be obtained.
[0043] 4) Further process mixture 4 by adding 500g of deionized water and 150g of hydrochloric acid to mixture 4 and placing it in a polytetrafluoroethylene container, heating and stirring at 70°C for 8 hours.
[0044] 5) The product is filtered, washed, dried and pulverized to obtain the finished high-carbon graphite powder.
[0045] See Figure 1 This is a SEM image of the raw material crystalline graphite disclosed in this invention; the microstructure of natural crystalline graphite without purification by this invention is relatively rough, which is directly related to the high impurity content in the raw material crystalline graphite.
[0046] See Figure 2 The image shows a SEM image of the high-carbon graphite obtained in Example 2 of this invention. It can be seen that the method of this invention not only maintains the microstructure of the crystalline graphite itself, but also maintains its special two-dimensional layered structure. Furthermore, after being processed by the method provided by this invention, the surface microstructure of the crystalline graphite is smoother.
[0047] Example 2
[0048] A method for purifying crystalline graphite includes the following steps:
[0049] 1) Weigh 500mL of deionized water, 3.5g of lithium fluoride, and 15g of crystalline graphite with a carbon content of 82%, mix them evenly, and dry them in air at 80℃ to obtain a uniformly mixed mixture 1.
[0050] 2) Add 1.4g sodium chloride and 1.905g ammonium chloride to the mixture of lithium fluoride and crystalline graphite and grind to obtain mixture 2. Add 500g deionized water, sonicate for 0.5h and dry in air at 80℃ until viscous to obtain mixture 3.
[0051] 3) After heat treatment of mixture 3 at 630℃ in an inert atmosphere for 5.5h, mixture 4 is obtained. After washing with water and alcohol, crystalline graphite with a carbon content of more than 97% can be obtained.
[0052] 4) Further process mixture 4 by adding 500g of deionized water and 300g of hydrochloric acid to mixture 4 and placing it in a polytetrafluoroethylene container, heating and stirring at 80°C for 10 hours.
[0053] 5) The product is filtered, washed, dried and pulverized to obtain the finished high-carbon graphite powder.
[0054] Example 3
[0055] A method for purifying crystalline graphite includes the following steps:
[0056] 1) Weigh 500mL of deionized water, 3.8g of sodium fluoride, and 15g of crystalline graphite with a carbon content greater than 82%, mix them evenly, and dry them in air at 80℃ to obtain a uniformly mixed mixture 1.
[0057] 2) Add 1.6g of sodium chloride and 0.15g of polyvinyl alcohol to the mixture of sodium fluoride and crystalline graphite and grind to obtain mixture 2. Add 500g of deionized water, sonicate for 0.5h, and then dry in air at 80℃ until it becomes viscous to obtain mixture 3.
[0058] 3) After heat treatment of mixture 3 at 837℃ in an inert atmosphere for 4.5h, mixture 4 is obtained. After washing with water and alcohol, crystalline graphite with a carbon content of more than 97% can be obtained.
[0059] 4) Further process mixture 4 by adding 500g of deionized water and 60g of hydrochloric acid to mixture 4 and placing it in a polytetrafluoroethylene container, heating and stirring at 60°C for 4 hours.
[0060] 5) The product is filtered, washed, dried and pulverized to obtain the finished high-carbon graphite powder.
[0061] Example 4
[0062] A method for purifying crystalline graphite includes the following steps:
[0063] 1) Weigh 500mL of deionized water, 4g of lithium fluoride, and 30.18g of crystalline graphite with a carbon content greater than 82%, mix them evenly, and dry them in air at 80℃ to obtain a uniformly mixed mixture 1.
[0064] 2) Add 1.56g sodium chloride and 0.6g polyvinyl alcohol to the mixture of lithium fluoride and crystalline graphite and grind to obtain mixture 2. Add 500g deionized water, sonicate for 0.5h and dry in air at 80℃ until viscous to obtain mixture 3.
[0065] 3) After heat treatment of mixture 3 at 700℃ in an inert atmosphere for 3.5h, mixture 4 is obtained. After washing with water and alcohol, crystalline graphite with a carbon content of more than 97% can be obtained.
[0066] 4) Further process mixture 4 by adding 500g of deionized water and 200g of hydrochloric acid to mixture 4 and placing it in a polytetrafluoroethylene container, heating and stirring at 65°C for 6 hours.
[0067] 5) The product is filtered, washed, dried and pulverized to obtain the finished high-carbon graphite powder.
[0068] Example 5
[0069] A method for purifying crystalline graphite includes the following steps:
[0070] 1) Weigh 500mL of deionized water, 4g of lithium fluoride, and 15g of crystalline graphite with a carbon content greater than 82%, mix them evenly, and dry them in air at 80℃ to obtain a uniformly mixed mixture 1.
[0071] 2) Add 1.94g of sodium chloride and 1.5g of ammonium chloride to the mixture of lithium fluoride and crystalline graphite and grind to obtain mixture 2. Add 500g of deionized water, sonicate for 0.5h, and then dry in air at 80°C until it becomes viscous to obtain mixture 3.
[0072] 3) After heat-treating mixture 3 at 800℃ in an inert atmosphere for 5 hours, mixture 4 is obtained. After washing with water and alcohol, crystalline graphite with a carbon content of more than 97% can be obtained.
[0073] 4) Further process mixture 4 by adding 500g of deionized water and 260g of hydrochloric acid to mixture 4 and placing it in a polytetrafluoroethylene container, heating and stirring at 75°C for 5 hours.
[0074] 5) The product is filtered, washed, dried and pulverized to obtain the finished high-carbon graphite powder.
[0075] This invention discloses a method for purifying crystalline graphite. The method involves pretreating a mixture of crystalline graphite with a carbon content greater than 82% and a fluoride salt. Sodium chloride, a dispersant, and deionized water are then added to the pretreated mixture, followed by drying to obtain a viscous mixture. This mixture is then heat-treated under an inert atmosphere, and after washing with water, crystalline graphite with a carbon content greater than 97% is obtained. Hydrochloric acid and deionized water are directly added to the heat-treated mixture, and the mixture is heated and stirred. After the reaction is complete, the graphite is filtered out, and the waste liquid is recycled. The separated graphite is repeatedly washed with water, filtered, dried, and pulverized to obtain the high-carbon crystalline graphite product. The high-carbon crystalline graphite obtained by this invention has a carbon content of not less than 99%, a moisture content of not more than 0.5%, and an ash content of not more than 0.7%. The finished product can be used in electromagnetic shielding materials, antistatic materials, conductive materials, corrosion-resistant materials, lubricants, fire-retardant materials, etc.
[0076] This purification process can purify crystalline graphite with a carbon content greater than 82% to high-carbon graphite with a carbon content of not less than 99%, a moisture content of not more than 0.5%, and an ash content of not more than 0.7%. Compared to reagents used in other purification processes and methods, the reagents used in this process are less corrosive. Hydrofluoric acid participates in the reaction as an intermediate product, and the requirements for manual operation are relatively lower, improving production safety. Furthermore, this purification process has lower energy consumption, lower production costs, and relatively lower environmental protection costs, significantly improving economic efficiency.
[0077] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for purifying crystalline graphite, characterized in that, Includes the following steps: First, fluoride salt and deionized water are mixed evenly, then mixed with crystalline graphite, and after heat drying, a dispersant and sodium chloride are added. After grinding, deionized water is added, and the mixture is ultrasonicated and heat dried again until it becomes viscous. After heat treatment, water washing, and alcohol washing, high-carbon crystalline graphite is obtained. The dispersant is ammonium chloride or polyvinyl alcohol. Alternatively, after heat treatment, deionized water and hydrochloric acid are added, heated and stirred, repeatedly washed with water, filtered, and dried to obtain high-carbon crystalline graphite with a carbon content greater than 99%. The mass of sodium chloride is 39%-48.5% of the mass of the fluoride salt; the fluoride salt is lithium fluoride or sodium fluoride; The heat treatment temperature is 630-837℃; the heat treatment is carried out in an inert atmosphere; the heat treatment time is 2.5-5.5h.
2. The method for purifying crystalline graphite according to claim 1, characterized in that, The mass ratio of deionized water: hydrochloric acid: crystalline graphite is 100:(12-60):(3-10.06).
3. The method for purifying crystalline graphite according to claim 1, characterized in that, The heating and stirring temperature is 60-80℃.
4. The method for purifying crystalline graphite according to claim 1, characterized in that, The heating and stirring time is 4-10 hours.
5. The method for purifying crystalline graphite according to claim 1, characterized in that, The mass ratio of the fluoride salt to crystalline graphite is (0.0057-0.0285):(0.029-0.043).
6. The method for purifying crystalline graphite according to claim 1, characterized in that, The mass of the dispersant is 1.0%-12.7% of the mass of crystalline graphite.