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CN-121974340-A - High-efficiency waste-liquid-free expanded graphite prepared in one step by microwaves and preparation method

CN121974340ACN 121974340 ACN121974340 ACN 121974340ACN-121974340-A

Abstract

The invention provides high-efficiency waste liquid-free expanded graphite prepared by one step of microwaves and a preparation method, wherein the method comprises the steps of mixing crystalline flake graphite with nitric acid according to the ratio of 0.2-3 mL/g to form a mixture, placing the mixture in a pressure-resistant quartz reaction vessel, carrying out pulse irradiation for 10-120 s under the power of 100-1200W, synchronously finishing intercalation, decomposition and expansion of the nitric acid, and directly obtaining worm-shaped expanded graphite, wherein peroxyurea accounting for 0.01-0.6 g/g of the mass of graphite is added to realize in-situ conversion of waste gas. The preparation process of the expanded graphite does not need washing in the whole process, shortens the reaction time to the second level, and has the outstanding advantages of zero waste liquid discharge, extremely low energy consumption, high expansion volume of products and the like. The prepared expanded graphite is in a worm-shaped porous shape, the length of the expanded graphite is 0.5 mm-5 mm, the width of the expanded graphite is not more than 1mm, and the expansion volume of the expanded graphite is 100-400 mL/g.

Inventors

  • LIU BO
  • TANG XU
  • SUN HONGJUAN
  • ZHANG TAO
  • XIE JINGXIU

Assignees

  • 西南科技大学

Dates

Publication Date
20260505
Application Date
20260127

Claims (10)

  1. 1. A method for preparing expanded graphite by high-efficiency waste liquid-free microwave in one step, which is characterized by comprising the following steps: (1) Uniformly mixing graphite and nitric acid in proportion to form a mixture; (2) And placing the mixture into a microwave reactor, and reacting under microwave irradiation to obtain the expanded graphite.
  2. 2. The method for preparing expanded graphite in one step by using high-efficiency waste liquid-free microwaves, as claimed in claim 1, wherein in the step (1), the ratio is a liquid-solid ratio of the nitric acid to the graphite, and the liquid-solid ratio is 0.2-3 mL/g.
  3. 3. The method for preparing the expanded graphite by using the efficient waste liquid-free microwaves in one step according to claim 1, wherein the mass fraction of the nitric acid in the step (1) is 68% -98%.
  4. 4. The method for preparing expanded graphite by using high-efficiency waste liquid-free microwaves in one step according to claim 1, wherein the step (1) further comprises adding urea peroxide, and the adding amount of the urea peroxide is 0.01-0.6 g/g of the mass of the graphite.
  5. 5. The method for preparing the expanded graphite by using the high-efficiency waste liquid-free microwaves in one step according to claim 1, wherein the graphite comprises flake graphite, the flake diameter of the flake graphite is-50 meshes to +150 meshes, and the carbon content of the flake graphite is more than 90%.
  6. 6. The method for preparing expanded graphite by using high-efficiency waste liquid-free microwaves in one step according to claim 5, wherein the method further comprises the step of pre-treating the crystalline flake graphite before the step (1), and the pre-treating is that the crystalline flake graphite is placed in a 40-105 ℃ oven to be dried for 2-48 hours.
  7. 7. The method for preparing expanded graphite by using high-efficiency waste liquid-free microwaves in one step according to claim 1, wherein the power of microwave radiation in the step (2) is 100-1200W, and the time is 10 s-120 s.
  8. 8. The method for preparing expanded graphite in one step by using high-efficiency waste liquid-free microwaves according to claim 1, wherein in the step (2), the reaction is performed by placing the mixture in a pressure-resistant quartz reaction vessel and then placing the mixture in a microwave reactor.
  9. 9. The method for preparing the expanded graphite by the high-efficiency waste liquid-free microwave in one step, which is characterized in that the microwave irradiation adopts a pulse mode, and the pulse duty ratio is 25% -100%.
  10. 10. An expanded graphite, characterized in that the expanded graphite is prepared by the method for preparing the expanded graphite by one step by high-efficiency waste liquid-free microwaves according to any one of claims 1 to 9; The expanded graphite is worm-shaped and porous, the length of the expanded graphite is 0.5 mm-5 mm, the width of the expanded graphite is not more than 1mm, and the expansion volume of the expanded graphite is 100-400 mL/g.

Description

High-efficiency waste-liquid-free expanded graphite prepared in one step by microwaves and preparation method Technical Field The invention relates to the field of preparation of graphite functional materials, in particular to an expanded graphite prepared by high-efficiency waste liquid-free microwaves in one step and a preparation method thereof. Background The expanded graphite has been paid attention to and intensively studied in the fields of sealing materials, greasy dirt adsorption, catalyst carriers, energy storage devices and the like because of its unique interlayer porous structure, high specific surface area, excellent electric and heat conductivity and chemical stability. Currently, the industrial mass production mainly adopts a chemical intercalation-thermal expansion two-step method. The process comprises (1) intercalation stage, namely mixing graphite with strong oxidizing intercalating agent (such as concentrated sulfuric acid, nitric acid, etc.), reacting to obtain graphite intercalation compound, and (2) post-treatment stage, namely washing and drying intercalation product, and performing high-temperature or microwave treatment to realize expansion. For example, in the scheme disclosed in the Chinese patent No. CN114890415A, graphite and sulfuric acid are mixed and reacted for 3 hours according to the mass ratio of 1:15 to generate an intercalation compound, and the research of Tang et al (Diamond AND RELATED materials.2025,158, 112601) shows that the intercalation product needs to be washed with water according to the liquid-solid ratio of 160mL/g, and then dried for 48 hours, and finally the intercalation product with the expansion volume of 220mL/g is obtained by microwave expansion. The mainstream technology has the obvious defects that (1) the process flow is complex. Intercalation reaction, water washing purification, drying and expansion are carried out step by step, the operation chain is long, and (2) the energy consumption of production is high. The intercalation reaction takes several hours, the energy efficiency is low due to the superposition of ultra-long drying period, and (3) the environmental pollution is serious. The discharge amount of the acid waste liquid is large, and the treatment cost is high. In order to solve the problems, the invention discloses a high-efficiency expanded graphite preparation method which synchronously drives intercalation reaction and an expansion process through microwave energy, reduces waste gas emission and realizes zero waste liquid emission. Disclosure of Invention The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, one of the purposes of the invention is to provide a method for preparing expanded graphite by microwave without waste liquid in one step, and the other purpose of the invention is to provide expanded graphite. In order to achieve the above object, in one aspect, the present invention provides a method for preparing expanded graphite by microwave in one step with high efficiency and without waste liquid, the method comprising: (1) Uniformly mixing graphite and nitric acid in proportion to form a mixture; (2) And placing the mixture into a microwave reactor, and reacting under microwave irradiation to obtain the expanded graphite. Optionally, in the step (1), the ratio is a liquid-solid ratio of the nitric acid to the graphite, and the liquid-solid ratio is 0.2-3 mL/g. Optionally, the mass fraction of the nitric acid in the step (1) is 68% -98%. Optionally, the step (1) further includes adding urea peroxide (CO (NH 2)2·H2O2), where the adding amount of urea peroxide is 0.01-0.6 g/g of the mass of the graphite. Optionally, the graphite comprises flake graphite, the flake diameter of the flake graphite is-50 meshes to +150 meshes, and the carbon content of the flake graphite is more than 90%. Optionally, the step (1) is preceded by a pretreatment of the crystalline flake graphite, wherein the pretreatment is to dry the crystalline flake graphite in an oven at 40-105 ℃ for 2-48 hours. Optionally, the power of the microwave radiation in the step (2) is 100-1200 w, and the time is 10 s-120 s. Optionally, in the step (2), the mixture is placed in a pressure-resistant quartz reaction vessel and then placed in a microwave reactor for reaction, wherein the microwave irradiation adopts a pulse mode, and the pulse duty ratio is 25% -100%. In another aspect, the invention provides an expanded graphite, which can be prepared by the method for preparing the expanded graphite by one-step microwave with high efficiency and no waste liquid. Optionally, the expanded graphite is in a worm-shaped porous shape, the length of the expanded graphite is 0.5 mm-5 mm, the width of the expanded graphite is not more than 1mm, and the expansion volume of the expanded graphite is 100-400 mL/g. Compared with the prior art, the invention has the beneficial effects that at least one of the follow