Method for preparing coal-based activated carbon by microwave heating assisted water vapor one-step activation

A coal-based activated carbon and microwave heating technology, which is applied in the field of activated carbon, can solve the problems of uneven heating of particles, reduce the performance of activated carbon, and easy wear and tear, and achieve the effect of uniform heating and increased strength

Inactive Publication Date: 2019-11-15
TIANJIN CHENGJIAN UNIV
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  • Abstract
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Problems solved by technology

[0006] (1) The carbonization and activation process requires a lot of heat energy. When using conventional heating methods, such as convective heat exchange (hot flue gas scouring), heat conduction (heat transfer from outside to inside of particles), it has low heat transfer rate, long heating time, Disadvantages such as high energy consumption, and it is easy to cause uneven heating of particles and reduce the performance of activated carbon
[0007] (2) The carbonization process is usually carried out at 600-750°C, and the strengthening of the microcrystalline carbon structure (strong condensation to form graphite-like crystallites) usually has an obvious effect above 1000°C, so it cannot be effectively improved at relatively low temperatures. The strength of activated carbon, especially for low-rank coal with low microcrystalline carbon content, the activated carbon usually has low strength and is easy to wear
[0008] (3) If the carbonization temperature is increased to above 1000 °C, the graphite-like microcrystalline structure will increase, and the reactive sites will decrease, which will increase the water vapor and CO in the next activation process. 2 The difficulty of reacting with the carbon structure, which in turn affects the formation of the pore structure
[0010] (5) The existing microwave heating method is used to prepare activated carbon, mostly for raw materials with rich graphite-like microcrystalline structures such as petroleum coke and pitch, and microwave heating alone cannot produce a large number of micropores and mesoporous structures
Adding KOH and other chemicals can generate a large number of micropores, but the mesopores are underdeveloped, and a large amount of chemicals (the mass ratio of KOH to coal is generally higher than 1:1) is likely to cause equipment corrosion and environmental pollution

Method used

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  • Method for preparing coal-based activated carbon by microwave heating assisted water vapor one-step activation
  • Method for preparing coal-based activated carbon by microwave heating assisted water vapor one-step activation
  • Method for preparing coal-based activated carbon by microwave heating assisted water vapor one-step activation

Examples

Experimental program
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Effect test

Embodiment 1

[0047] Using FeCl hexahydrate 3 Added to raw coal and pulverized coal, mixed uniformly by ball milling method, wherein Fe element accounted for 8% of the mass ratio of pulverized coal, the speed of ball mill was 1500rad / min, and the ball milling time was 100min to obtain the pulverized coal mixture. Under the condition of microwave irradiation, the pulverized coal mixture is activated by water vapor, the microwave output power is 450W, the water vapor volume concentration (volume percentage) is 50%, and other gases are nitrogen, and the mixture of water vapor and nitrogen per 10g of the mixture is The gas flow rate is 400mL / min, and the activation time is 60min. The activated mixture was soaked in hydrochloric acid to remove the Fe element. The concentration of hydrochloric acid was 1mol / L. The amount of hydrochloric acid required per 10g of the mixture was 120mL. The soaking time was 2h, and then the product was washed with deionized water until no chloride ions were detected...

Embodiment 2

[0049] Using the same process parameters as in Example 1, adjusting the mass ratio of iron to pulverized coal to 4%, 6% and 10%, respectively preparing activated carbons with different iron additions, and investigating the relationship between mesopore volume and iron additions . In order to increase the strength of activated carbon, a small amount of Fe-based catalyst (i.e. iron element) is doped into low-rank coal. Because Fe has good wave-absorbing ability, it can generate local high temperature above 1000 °C, and Fe has the effect of catalyzing graphitization. , so a large amount of graphite-like crystallite structure can be formed around Fe to improve the strength of activated carbon. By controlling the content of Fe-based catalyst, the content of graphite-like crystallite can be adjusted. figure 2 The transmission electron microscope image shows short-range ordered graphite-like crystallite groups. The graphite-like crystallite structure can improve the strength of acti...

Embodiment 3

[0051] Using the same process parameters as in Example 1, the activation time was adjusted to 40 and 80 min, and activated carbons with different activation times were prepared respectively, and the relationship between micropore volume and activation time was investigated. In the process of microwave heating and water vapor activation to prepare coal-based activated carbon, water vapor reacts on the active sites of the carbon structure, mainly forming a microporous structure. By adjusting the concentration of water vapor and activation time, the micropore volume can be adjusted, making the microporous Pore ​​volume not less than 0.2cm 3 / g—Only change the water vapor activation time, when the activation time increases from 40min to 80min, the micropore volume changes from 0.21cm 3 / g increased to 0.27cm 3 / g.

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Abstract

The invention discloses a method for preparing coal-based activated carbon by microwave heating assisted water vapor one-step activation. The method comprises the following steps: adding an iron source into coal powder, carrying out microwave irradiation, introducing water vapor for activation, removing iron elements in an activated mixture by using hydrochloric acid, and carrying out drying. According to the invention, a microwave irradiation method is adopted to provide heat energy for preparing activated carbon from low-rank coal, a small amount of Fe-based catalyst is doped into the coal powder for increasing strength of the activated carbon, and the content of graphite-like microcrystals is adjusted. Fe is removed after acid washing, and thus an obvious mesoporous structure is formed.In the process of preparing coal-based active carbon by combining microwave heating and water vapor activation, the defect of a carbon structure is increased by microwave irradiation, and reaction active sites are increased, so that the reaction rate of the water vapor and the carbon structure is promoted. The increase of carbon structure defects also promotes formation of activated carbon surface functional groups, so that the number of oxygen-containing functional groups is not less than 9.5 mmol / g, which is much higher than the number of oxygen-containing functional groups generated by activation of water vapor alone.

Description

technical field [0001] The invention belongs to the technical field of activated carbon, and more specifically relates to a method for preparing coal-based activated carbon through one-step activation of water vapor assisted by microwave heating and a product thereof. Background technique [0002] At present, the gas activation method is mainly used to prepare coal-based activated carbon. Compared with the chemical activation method, there is no need to add a large amount of chemicals, which not only has low production costs, but also avoids equipment corrosion and environmental pollution. The gas activation method is to use the activated gas to activate the carbonized material at a certain temperature after the raw coal is carbonized, and finally form a well-developed pore structure with certain surface chemical characteristics. The carbonization process is usually carried out under an inert atmosphere at 600-750°C to decompose the irregular carbon in coal and strengthen th...

Claims

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Application Information

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IPC IPC(8): C01B32/33C01B32/336
Inventor 朱玉雯郝云飞韩广程高婷婷刘汉桥杨俊兰
Owner TIANJIN CHENGJIAN UNIV
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