Preparation method of expandable graphite

A technology of expanded graphite and graphite, which is applied in the field of chemical preparation of graphite, can solve problems such as complex equipment, uneven product expansion rate, and insufficient contact, and achieve the effects of reducing production costs, controllable product quality, and reducing consumption

Active Publication Date: 2012-03-21
湖北联投恒达石墨有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Disadvantages: The production cost is 2,000 yuan / T higher than the hydrogen peroxide production method, and the sulfur content is as high as 3,000ppm. It cannot be used in the nuclear industry and aerospace industry, and the export of heavy metal salts cannot meet the standards, which seriously pollutes the environment.
As described in the method of Chinese patent 200410090866 using sulfuric acid hydrogen peroxide to produce low-sulfur expandable graphite, and control the temperature of the reactor to increase the expansion rate, but in actual operation, it is difficult to control, because the water content of hydrogen peroxide reaches more than 70%. Concentrated sulfuric acid releases a large amount of heat instantly, but it is difficult to control the temperature below 50°C with cost-effective methods such as vacuuming and water cooling. Technical requirements for flexibility and tensile properties of products
[0006] Chinese patent 200410090866 uses sulfuric acid hydrogen peroxide to manufacture the method described in the method for low-sulfur expandable graphite when adopting high-purity graphite and high-carbon graphite as raw material effect is better, but the hydrogen peroxide of this method is easy to react with sulfuric acid before contacting with material and thus Decomposition, insufficient contact with the material, resulting in uneven oxidation of the material, uneven expansion rate of the final product, difficult quality control, and high consumption of hydrogen peroxide
[0007] Chinese patent 200710191191.4 provides a chemical treatment method for preparing high-quality expandable graphite. The expansion rate of the final product can be improved by vacuum stirring, but there are also problems of uneven expansion rate and large consumption of hydrogen peroxide, and the equipment is relatively complicated. The acid mist generated during the reaction has great corrosion on the equipment, especially the vacuum pump, and the production cost is high

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] 1) Add 50g of medium-carbon flake graphite into the reaction kettle through a vacuum feeder, and start stirring and sealing for 2 minutes.

[0027] 2) Inject 6g of 40%wt hydrogen peroxide into the graphite material with a metering pump, turn on the air flow and mechanically stir for 5 minutes.

[0028] 3) Open the 98%wt concentrated sulfuric acid valve with accurate metering, quickly inject 120g of concentrated sulfuric acid to react and stir for 15min, and increase the air volume.

[0029] 4) Add 7.5g of mixed acid and then react and stir for 180min. The mixed acid is 30wt% hydrochloric acid: 40wt% hydrofluoric acid; 98wt% nitric acid = 1:6:0.5.

[0030] 5) After deacidification and water washing to PH ≥ 5, after dehydration treatment, it is dried in a steam dryer at a temperature of 100 ℃ ~ 120 ℃ until the moisture content is ≤ 0.5%, and the product expansion rate is 250ml / g, and the volatile content is 11. %, the sulfur content is 1300ppm, and the fixed carbon is 4...

Embodiment 2

[0034] 1) Use a vacuum feeder to transport 50g of medium-carbon flake graphite to a dry reaction kettle, seal the reaction kettle and stir for 2 minutes.

[0035] 2) Use a metering pump to inject 7g of 35wt%~40wt% hydrogen peroxide into the reactor material, turn on the air flow and react with mechanical stirring for 5 minutes.

[0036] 3) Open the 98wt% concentrated sulfuric acid valve and inject 110g of concentrated sulfuric acid without stopping the stirring, and react for 15 minutes.

[0037] 4) After the reaction is completed, inject 10g of mixed acid and stir for 180min.

[0038] 5) After the reaction is over, transfer the material to a washing tower for washing until pH ≥ 5, and then put it into a dehydrator for dehydration.

[0039] 6) The dehydrated material is sent to a 100-120°C steam dryer for drying.

[0040] After the above reaction, an expandable graphite with an expansion rate of 240ml / g, a volatile content of 12%, a sulfur content of 1800ppm, a residual sulf...

Embodiment 3

[0044] 1. Take 450kg+50 mesh carbon flake graphite, and put the sieve ≥ 82% into the reaction kettle.

[0045] 2. Add 45 kg35wt% hydrogen peroxide to the container and stir evenly;

[0046] 3. Add 900kg98wt% sulfuric acid to the above mixture, cool and stir, and react for 15min;

[0047] 4. Add 67.5kg of mixed acid to the above mixture and react for 160-180min;

[0048] 5. Rinse the material until the pH value is ≥ 5, dehydrate and dry the package, and the water content is ≤ 1.5wt%;

[0049] After the above reaction, an expandable graphite with an expansion rate of 245ml / g, a volatile content of 12.5%, a sulfur content of 1800ppm, a residual sulfur of 800ppm after expansion at 950°C for 30s, and a fixed carbon increase of 4.5% was obtained.

[0050] The optimized scheme is to control the temperature in the container to be 40°C during the reaction.

[0051] The stirring method is to use spiral blade stirring. Different from the existing flat-blade mechanical agitator, the h...

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Abstract

The invention discloses a preparation method of expandable graphite, comprising the following steps of: A. adding 35-40wt% of hydrogen peroxide with 10-14% of graphite by taking crystalline flake graphite as the raw material, cooling and stirring for 3-5min or enabling the hydrogen peroxide to be uniformly attached on the surface of a material; B. adding 98wt% of sulfuric acid which is 2-2.5timesof the weight of the graphite into the mixture, cooling, stirring, and reacting for 10-16min; C. adding mixed acids which is 13-20% of the weight of the graphite into the mixture, and reacting for 160-180min; D. washing the material to the pH value not less than 5, dehydrating and drying to obtain the expandable graphite. By using the method provided by the invention, the expansion ratio of a final product can be stabilized, and the cost can be reduced.

Description

technical field [0001] The invention relates to a chemical preparation method of graphite, in particular to a method for preparing expandable graphite with low sulfur and high expansion rate by using sulfuric acid, hydrogen peroxide and mixed acid. Background technique [0002] Expandable graphite is a widely used inorganic non-metallic material that has appeared in recent years. It has been extended from the previous common use in flanges, chemicals, and power machinery to nuclear industry, aerospace industry, fireproof sealing, and geothermal materials. It shows great potential. The market prospect of it is irreplaceable by other materials for sealing flame retardant and fire prevention. The sulfur content of the expandable graphite prepared by the traditional method is as high as 2500ppm, which is extremely harmful to the metal material. At the same time, the expansion rate of the traditional method is low, and it cannot be fully flame-retardant when it is sealed in a fir...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B31/04
Inventor 张宏兵沈兵李云峰王凤军
Owner 湖北联投恒达石墨有限公司
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