Preparation method of coal-based activated carbon

Abstract

The invention relates to the technical field of activated carbon materials, and particularly discloses a preparation method of coal-based activated carbon, which comprises the following steps: selecting biomass straw powder, waste molasses, a long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water as a novel adhesive, grinding, kneading and forming, carbonizing, activating and the like to prepare the coal-based activated carbon. The coal-based activated carbon with large specific surface area and large total pore volume is prepared, the carbonization and activation time of the coal-based activated carbon is shortened, the reaction temperature is reduced, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of activated carbon materials, and more particularly to a preparation method of coal-based activated carbon. BACKGROUND

[0002] Activated carbon is a carbon-based adsorption material produced by various carbon-containing materials as raw materials after proper processing. Activated carbon has a large specific surface area, stable physical and chemical properties, and excellent adsorption performance, and is currently widely used in the fields of electronics, medicine, national defense, etc. Activated carbon can be divided into coal-based activated carbon, wood-based activated carbon and coconut shell activated carbon according to the raw materials.

[0003] The conventional production process of coal-based activated carbon includes the following steps: grinding, kneading and molding, carbonization, activation, etc. In the kneading and molding process, a binder is generally added to the coal powder. The binder is selected from coal tar, but coal tar is a highly complex polymer compound and is a dangerous chemical. In the preparation process of activated carbon, coal tar will volatilize, causing serious air pollution. At the same time, coal tar is easy to produce colloid in the carbonization process, causing the carbonization material to adhere to each other, resulting in the blockage of the pore structure of the carbonization material, affecting the activation and pore formation, and finally reducing the specific surface area and total pore volume of the activated carbon. SUMMARY

[0004] In order to solve the problems of environmental pollution and small specific surface area in the production process of coal-based activated carbon, the present application provides a preparation method of coal-based activated carbon.

[0005] The present application provides a preparation method of coal-based activated carbon, which adopts the following technical scheme: A preparation method of coal-based activated carbon, comprising the following steps: Preparation of the binder: biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water are prepared according to the weight ratio (1.2-3.6):(2.5-4):(0.02-0.1):(0.005-0.01):1. First, the waste molasses, long-chain alkyl quaternary ammonium salt surfactant and potassium hydroxide and water are blended according to the weight ratio, and then the biomass straw powder is added and stirred and blended to obtain the binder; Grinding; Kneading and molding: the binder and the coal powder treated by grinding are kneaded and blended according to the weight ratio (0.78-0.92):1, and the pre-carbonization material is obtained by extrusion; Carbonization: the pre-carbonization material is first heated to 300-450℃ for primary carbonization under the protection of an inert gas atmosphere, and then heated to 550-600℃ for secondary carbonization, and the carbonization material is obtained after 20-30min of heat preservation carbonization; Activation: the carbonized material is activated with a gaseous activator at 700-800℃ for 45-60min, and then acid-washed, dried to obtain the coal-based activated carbon.

[0006] Further, the weight ratio of the biomass straw powder, the waste molasses, the long-chain alkyl quaternary ammonium salt surfactant, the potassium hydroxide and the water is (2.4-3.0):(3.2-3.6):(0.05-0.06):(0.008-0.01):1.

[0007] Further, the particle size of the biomass straw powder is 50-100μm.

[0008] Further, in the grinding step, the particle size of the coal powder obtained by the grinding treatment is 200-500μm.

[0009] Further, in the kneading and molding step, the weight ratio of the binder to the coal powder is 0.85:1.

[0010] Further, in the carbonization step, the pre-carbonized material is heated at a rate of 5-6℃ / min in the first carbonization.

[0011] Further, in the carbonization step, the pre-carbonized material is heated at a rate of 6-10℃ / min in the second carbonization.

[0012] Further, in the activation step, the ratio of the amount of the activator to the weight of the carbonized material is 40-60 (m 3 / h):1000kg.

[0013] The present application has at least the following advantages: First, the present application selects the biomass straw powder, the waste molasses, the long-chain alkyl quaternary ammonium salt surfactant, the potassium hydroxide and the water as the binder, the biomass straw powder itself contains a large number of pore structures, which can absorb the waste molasses, the potassium hydroxide and the water and the like, and the biomass straw powder has a binding effect after absorption. The new binder developed in the present application uses the biomass straw powder and the waste molasses and the like as the main components, instead of the coal tar, and does not produce toxic gas in the carbonization and activation stages, which is safe and environmentally friendly.

[0014] The biomass straw powder contains certain alkali metals, which acts together with potassium hydroxide to promote the formation of a rich microporous network structure of the pre-carbonized material in the low-temperature carbonization stage. The viscosity of the waste molasses is reduced after being diluted by the potassium hydroxide aqueous solution; at the same time, the long-chain alkyl quaternary ammonium salt surfactant is an amphiphilic substance, and the long-chain alkyl quaternary ammonium salt surfactant promotes the dispersion of the binder with strong hydrophilicity in the hydrophobic coal powder, so that the binder and the coal powder are kneaded uniformly. The waste molasses is pyrolyzed in the carbonization stage to produce small molecule gases, which can carry out the biomass volatile matter contained in the biomass straw powder, reducing the possibility of volatile matter blocking the pore channels of the coal-based activated carbon; at the same time, the waste molasses increases the fixed carbon content, and the pyrolysis products are rich in oxygen-containing functional groups, which helps to absorb water vapor, potassium hydroxide and other polar activators in the later stage, so that the mesopore rate of the coal-based activated carbon is improved, and the specific surface area is increased. Due to the supplement of the fixed carbon content, a developed pore structure is formed in the coal-based activated carbon during the activation process, the pore structure inside the coal-based activated carbon is not easy to collapse, the strength of the coal-based activated carbon is improved, the specific surface area is increased, the total pore volume is increased, and the adsorption performance is excellent. In addition, the biomass straw powder, potassium hydroxide and waste molasses act together to assist the activation of the pre-carbonized material, improve the reaction activity of the coal powder, reduce the activation reaction temperature, and shorten the original carbonization and activation time of 4h to within 2h, with high production efficiency.

[0015] Secondly, the present application optimizes the composition ratio of each material in the binder, adjusts the viscosity of the whole binder, and balances the viscosity and fluidity of the binder. The binder can fully infiltrate the coal powder particles without affecting the binding performance, which helps the pre-carbonized material formed by pressing to maintain a relatively complete structure during the carbonization and activation stages. The waste molasses, biomass straw powder and potassium hydroxide and other auxiliary activation substances can fully penetrate into the coal powder, and the coal-based activated carbon has a developed pore structure.

[0016] Thirdly, the present application optimizes the particle size range of the biomass straw powder and the coal powder, so that the biomass straw powder can enter the gap of the coal powder, and the alkali metals contained in the biomass straw powder can assist the activation and pore formation in the later carbonization and activation process.

[0017] Fourthly, the present application adopts a step-by-step carbonization method, which helps to shorten the carbonization time, control the decomposition degree of the waste molasses, and make the thermal decomposition products of the waste molasses partially enter the coal powder, while maintaining the structural strength of the carbonized material, which is helpful for the later activation. DETAILED DESCRIPTION

[0018] Unless otherwise specified, the raw materials involved in the following examples and comparative examples are as follows: Coal: Shanxi anthracite; Biomass straw powder: from Hei Longjiang Hailen City, which is soybean straw. The harvested soybean straw is cleaned, dried and other steps. According to the required particle size range, the crushing parameters are adjusted to obtain biomass straw powder; Waste molasses: recycled from Guangdong sugar factory, the viscosity detection value is 4322Pa·s, and the specific gravity is 1.332g / cm 3 ; Long-chain alkyl quaternary ammonium salt surfactant: octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate, from Jiangsu Bosite Chemical Industry. Embodiment Embodiment 1

[0019] A preparation method of coal-based activated carbon is prepared according to the following steps: Preparation of binder: Prepare biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water, and the weight ratio is as follows: 3.0:3.6:0.06:0.01:1, wherein the particle size of the biomass straw powder is 50-100μm; the waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water are put into the stirrer and stirred at a speed of 100rpm; then the biomass straw powder is added and stirred at a speed of 100rpm for 5min to obtain the binder, which is ready for use; Grinding: put Shanxi anthracite into the grinder, set the grinding speed and time, and after screening, coal powder with a particle size range of 200-500μm is obtained; Kneading and forming: put the binder and the coal powder treated by grinding into the kneader according to the weight ratio of 0.85:1, blend, and extrude into a cylindrical pre-carbonization material with a diameter of 1cm and a height of 2cm under a pressure of 20MPa; Carbonization: put the pre-carbonization material into the rotary carbonization furnace, and introduce nitrogen. Under the nitrogen atmosphere, first carbonize at a heating rate of 5℃ / min to 400℃, and keep the temperature for 30min; then carbonize again at a heating rate of 5℃ / min to 600℃, and keep the temperature for 30min to obtain carbonized material; Activation: water vapor is used as the activator, 50m 3 / h of water vapor is introduced for every 1000kg of carbonized material. The temperature in the activation furnace is raised to 800℃. Under the condition of keeping the temperature, the carbonized material is activated for 45min. After the furnace is cooled to room temperature, the carbonized material is put into the hydrochloric acid washing pool for acid washing, then washed with water, and dried after water washing to obtain coal-based activated carbon.

[0020] Embodiment 2-4 A preparation method of coal-based activated carbon, which is different from embodiment 1 in that the weight ratio of biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water is different, which is as follows: In Example 2, the weight ratio of biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water is 2.4:3.2:0.05:0.008:1; In Example 3, the weight ratio of biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water is 3.6:4:0.1:0.01:1; In Example 4, the weight ratio of biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water is 1.2:2.5:0.02:0.005:1.

[0021] Examples 5-6 A preparation method of coal-based activated carbon, which is different from Example 1 in that the weight ratio of binder to coal powder is different, and the specific embodiments are as follows: In Example 5, the weight ratio of binder to coal powder is 0.78:1; In Example 6, the weight ratio of binder to coal powder is 0.92:1.

[0022] Examples 7-8 A preparation method of coal-based activated carbon, which is different from Example 1 in that the particle size range of coal powder and biomass straw powder is different, and the specific embodiments are as follows: In Example 7, the particle size range of biomass straw powder is 200-500 μm, and the particle size range of coal powder is 200-500 μm; In Example 8, the particle size range of biomass straw powder is 500-1500 μm, and the particle size range of coal powder is 200-500 μm.

[0023] Examples 9-10 A preparation method of coal-based activated carbon, which is different from Example 1 in that the temperature and heating rate of the carbonization step are different, and the specific embodiments are as follows: In the carbonization step of Example 9, the pre-carbonization material is put into a rotary carbonization furnace, nitrogen is introduced, and in the nitrogen atmosphere, the furnace is first heated to 450℃ at a heating rate of 6℃ / min for primary carbonization, and the temperature is maintained for 20 min; then heated to 600℃ at a heating rate of 10℃ / min for secondary carbonization, and the temperature is maintained for 20 min, to obtain carbonized material; In the carbonization step of Example 10, the pre-carbonization material is put into a rotary carbonization furnace, nitrogen is introduced, and in the nitrogen atmosphere, the furnace is first heated to 300℃ at a heating rate of 10℃ / min for primary carbonization, and the temperature is maintained for 30 min; then heated to 600℃ at a heating rate of 15℃ / min for secondary carbonization, and the temperature is maintained for 20 min, to obtain carbonized material.

[0024] Examples 11-12 A preparation method of coal-based activated carbon, the difference from example 1 is that the parameters of the activation step are different, as follows: In the activation step of example 11, water vapor is used as the activation agent, 40 m 3 / h of water vapor is introduced for every 1000 kg of carbonized material, the activation furnace is heated to 700℃, and the carbonized material is activated for 60 min under heat preservation. After cooling to room temperature, the material is placed in a hydrochloric acid washing pool for acid washing, followed by water washing, drying, and obtaining coal-based activated carbon. In the activation step of example 12, water vapor is used as the activation agent, 60 m 3 / h of water vapor is introduced for every 1000 kg of carbonized material, the activation furnace is heated to 750℃, and the carbonized material is activated for 50 min under heat preservation. After cooling to room temperature, the material is placed in a hydrochloric acid washing pool for acid washing, followed by water washing, drying, and obtaining coal-based activated carbon. Comparative example

[0025] Comparative example 1 A preparation method of coal-based activated carbon, the difference from example 1 is that the composition of the binder is different, as follows: The binder is composed of waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide, and water, with a weight ratio of 6.6:0.06:0.01:1.

[0026] Comparative example 2 A preparation method of coal-based activated carbon, the difference from example 1 is that the composition of the binder is different, as follows: The binder is composed of biomass straw powder, waste molasses, potassium hydroxide, and water, with a weight ratio of 3.0:3.6:0.07:1.

[0027] Comparative example 3 A preparation method of coal-based activated carbon, the difference from example 1 is that the carbonization step is one-step carbonization, with the specific carbonization steps as follows: The pre-carbonized material is placed in a rotary carbonization furnace and nitrogen is introduced. Under a nitrogen atmosphere, the furnace is heated to 450℃ at a rate of 10℃ / min for carbonization, and heat preservation carbonization is performed for 60 min to obtain carbonized material.

[0028] Blank control group A coal-based activated carbon, purchased from Kangnuo, with a product number of 0103, is made from coal tar as a binder. Performance testing

[0029] The coal-based activated carbon made from examples 1-12 and comparative examples 1-3, as well as the blank control group, are tested.

[0030] Table 1. Detection data of Examples 1-12, Comparative Examples 1-3 and Blank Control Group Test item Example 1 Example 2 Example 3 Example 4 Specific surface area m2 / g 2276 2098 2047 1880 Total pore volume cm3 / g 0.9333 0.8603 0.8394 0.7710 Iodine value mg / g 1722 1587 1549 1423 Test item Example 5 Example 6 Example 7 Example 8 Specific surface area m2 / g 1916 2175 2217 1964 Total pore volume cm3 / g 0.7857 0.8920 0.9090 0.8055 Iodine value mg / g 1450 1646 1677 1486 Test item Example 9 Example 10 Example 11 Example 12 Specific surface area m2 / g 2196 1877 1790 2021 Total pore volume cm3 / g 0.9005 0.7698 0.7342 0.8287 Iodine value mg / g 1662 1420 1355 1529 Test item Comparative Example 1 Comparative Example 2 Comparative Example 3 Blank control Specific surface area m2 / g 1010 1419 1303 1200 Total pore volume cm3 / g 0.4140 0.5688 0.5345 0.4921 Iodine value mg / g 564 1080 986 908 in conclusion

[0031] The test data shows that: First, Example 1 of this application forms a single comparison with Comparative Examples 1-2. In Comparative Example 1, the binder lacks biomass straw powder, and waste molasses is used instead of biomass straw powder. Due to the increase in the content of waste molasses, the viscosity of the binder increases linearly, resulting in a decrease in its fluidity. It can only partially wet the coal powder, and the coal powder is unevenly distributed during the kneading process. In the later carbonization and activation stages, the binder cannot fully play its auxiliary activation role, and the pore-forming effect of the binder and activator on the coal powder is weakened. At the same time, due to the low decomposition temperature of waste molasses, only a small amount of thermal decomposition products of waste molasses enter the coal powder. The coal powder lacks the replenishment of fixed carbon, and the pore structure of the coal powder is prone to collapse, resulting in a decrease in specific surface area and total pore volume. Finally, the iodine value drops to below 600 mg / g. In Comparative Example 2, the lack of long-chain alkyl quaternary ammonium salt surfactants prevented the binder from entering the coal powder and playing an auxiliary activation role on the surface of the coal powder. The pore structure of the carbonized material was restricted, and the specific surface area and total pore volume of the coal-based activated carbon decreased. Compared with Example 1, the iodine value decreased significantly.

[0032] Secondly, Example 1 of this application forms a single comparison with Comparative Example 3. Comparative Example 3 uses a one-step carbonization method, which prolongs the carbonization time, but the specific surface area and total pore volume of the final product still decrease. The reason is that a large amount of waste molasses decomposes at high temperature, and the thermal decomposition products volatilize along with the volatile matter of biomass straw, resulting in only a small amount of thermal decomposition products being added to the coal powder as fixed carbon. The carbonized material experiences pore collapse during the activation stage. At the same time, Example 1 of this application forms a comparison with the blank control group. The blank control group uses coal tar as a binder, but the specific surface area and total pore volume of the final product are lower than those of Example 1 of this application.

[0033] Third, by comparing Example 1 with Examples 2-12 of this application, it can be seen that the composition ratio of the binder, the particle size of the powder, the carbonization and activation parameters all have a significant impact on the specific surface area and total pore volume of coal-based activated carbon.

[0034] The various technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0035] Furthermore, the above-described embodiments merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing coal-based activated carbon, characterized in that, Includes the following steps: Preparation of binder: Biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water are prepared in a weight ratio of (1.2-3.6):(2.5-4):(0.02-0.1):(0.005-0.01):

1. First, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water are mixed in the same weight ratio. Then, biomass straw powder is added and stirred to obtain binder. Grinding; Kneading and molding: The binder and the pulverized coal powder are kneaded and mixed at a weight ratio of (0.78~0.92):1, and then extruded to obtain the pre-carbonized material; Carbonization; the pre-carbonized material is first heated to 300-450℃ under an inert gas atmosphere for primary carbonization, and held for 20-30 minutes. Then, it is heated to 550-600℃ for secondary carbonization, and held for 20-30 minutes to obtain carbonized material. Activation: The carbonized material and gaseous activator are kept at 700-800℃ for 45-60 minutes for activation. After cooling, the material is acid washed and dried to obtain coal-based activated carbon.

2. The method for preparing coal-based activated carbon as described in claim 1, characterized in that: The weight ratio of the biomass straw powder, waste molasses, long-chain alkyl quaternary ammonium salt surfactant, potassium hydroxide and water is (2.4-3.0):(3.2-3.6):(0.05-0.06):(0.008-0.01):

1.

3. The method for preparing coal-based activated carbon as described in claim 1, characterized in that: The particle size range of the biomass straw powder is 50–100 μm.

4. The method for preparing coal-based activated carbon as described in claim 3, characterized in that: In the grinding step, the particle size range of the coal powder obtained by grinding is 200-500 μm.

5. The method for preparing coal-based activated carbon as described in claim 1, characterized in that: In the kneading and molding step, the weight ratio of binder to coal powder is 0.85:

1.

6. The method for preparing coal-based activated carbon as described in claim 1, characterized in that: In the carbonization step, the heating rate of the pre-carbonized material during the first carbonization is 5-6℃ / min.

7. The method for preparing coal-based activated carbon as described in claim 6, characterized in that: In the carbonization step, the heating rate of the pre-carbonized material during the secondary carbonization is 6-10℃ / min.

8. The method for preparing coal-based activated carbon as described in claim 7, characterized in that: In the activation step, the ratio of the activator amount to the weight of the carbonized material is 40–60 (m). 3 / h):1000kg.