Wooden activated carbon for organic solvent recovery and preparation method thereof

Abstract

The invention discloses wooden activated carbon for organic solvent recovery and a preparation method thereof, and belongs to the technical field of phosphoric acid method activated carbon. The preparation method provided by the invention comprises the following steps: mixing a biological material and phosphoric acid, and granulating to obtain granules; introducing air to activate the granules, then cooling to room temperature, washing and recovering phosphoric acid, and drying to obtain dry granules; and activating the dry granules in a mixed atmosphere of carbon source gas and nitrogen, and cooling to obtain the wooden activated carbon for recovering the organic solvent.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphoric acid method activated carbon, and particularly relates to a wood-based activated carbon for organic solvent recovery and a preparation method thereof. Background Art

[0002] A large amount of organic solvents are required in the chemical production process. Most organic solvents only exist as solvents and do not participate in reactions. For the purpose of reuse and cleaner production, they need to be recovered after use. Activated carbon is commonly used for the recovery of organic solvents, such as toluene, acetone, ether, butyl ether, chloroform, acetic acid, acrylic acid, etc., due to its highly developed pore structure, large specific surface area, and the characteristics of desorption and reuse. Compared with other recovery methods, the use of activated carbon has the advantages of simple operation, wide practicability, and resource conservation. For example, the Chinese invention patent with the application number CN103466616A discloses a preparation method of a coal-based activated carbon for organic solvent recovery. In this method, pulverized coal is mixed with 35-40% of its weight of coal tar, 2-4% of water, and 2-3% of a catalyst, and then undergoes kneading, forming, carbonization, pre-activation, and activation to obtain columnar activated carbon; the catalyst is an aqueous solution of hydroxide with a mass concentration of 13-17%. By adding a hydroxide catalyst during the kneading process, functional groups are split, the internal pores of the activated carbon are enlarged, the adsorption performance is increased, and inorganic acidic compounds in the pulverized coal are neutralized; then two-stage activation is adopted to completely remove the tar substances and cracking products accumulated in the pore structure during the carbonization process, open some closed pores, and further decompose functional groups under the action of the catalyst to create pores and improve the pore volume and specific surface area of the activated carbon. The prepared activated carbon has a carbon tetrachloride adsorption rate ≥ 80%, an iodine adsorption rate ≥ 1050 mg / g, a bulk density of 400-450 g / L, and a ball plate strength ≥ 91%.

[0003] In addition to the above-mentioned coal-based activated carbon, wood-based activated carbon is also commonly used for organic solvent recovery. The pore structure of wood-based activated carbon is more developed than that of coal-based activated carbon. In addition to having abundant micropores, it also has a certain proportion of mesopores. When activated carbon adsorbs organic solvents, the micropores determine the adsorption capacity, and the mesopores determine the adsorption rate. The more developed the mesopores are, the faster the adsorption rate. However, at the same time, the self-heating phenomenon becomes more obvious with the increase of the adsorption rate, which is likely to cause local overheating of the activated carbon bed and spontaneous combustion, thereby damaging the equipment, affecting the normal operation of production, and even possibly leading to fires and explosions, resulting in casualties and property losses in severe cases. Currently, the commonly used solutions mainly include regularly replacing the activated carbon, installing on-line monitoring equipment for waste gas components, installing temperature sensors in the activated carbon adsorption device, and adding cooling equipment, etc. However, these methods all start from the outside and do not improve the activated carbon itself, so the problem of spontaneous combustion of wood-based activated carbon cannot be avoided at the root. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to prepare a wood-based activated carbon for organic solvent recovery that is not prone to spontaneous combustion and its preparation method.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: a preparation method of a wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix the biological material and phosphoric acid, and then granulate to obtain granulated materials; S2. Pass air to carry out activation treatment on the granulated materials; S3. Cool the granulated materials obtained in S2 to room temperature, wash and recover phosphoric acid, and dry to obtain dried granulated materials; S4. Carry out activation treatment on the dried granulated materials under a mixed atmosphere of a carbon source gas and nitrogen, and cool to obtain a wood-based activated carbon for organic solvent recovery.

[0006] Another technical solution adopted by the present invention is: a wood-based activated carbon for organic solvent recovery prepared by the above preparation method.

[0007] The beneficial effects of the present invention are as follows: the preparation method provided by the present invention can effectively improve the heat generation situation of the wood-based activated carbon during use and avoid its spontaneous combustion by reducing the proportion of mesopores and lowering the adsorption rate. Specific Embodiments

[0008] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following is described in conjunction with the embodiments.

[0009] A preparation method of a wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix the biological material and phosphoric acid, and then granulate to obtain granulated materials; S2. Pass air to carry out activation treatment on the granulated materials; S3. Cool the granulated materials obtained in S2 to room temperature, wash and recover phosphoric acid, and dry to obtain dried granulated materials; S4. Carry out activation treatment on the dried granulated materials under a mixed atmosphere of a carbon source gas and nitrogen, and cool to obtain a wood-based activated carbon for organic solvent recovery.

[0010] As can be seen from the above description, the beneficial effects of the present invention are as follows: through the action of carbon deposition, the carbon source gas is pyrolytically deposited in the pores of the activated carbon, especially in the mesopore pores, to adjust the pore size and thus regulate the proportion of mesopores, so as to control the absorption rate of organic gases; the proportion of micropores of the wood-based activated carbon obtained by this preparation method can reach 75% or more, while the proportion of mesopores is less than 15%.

[0011] Further, the biological material is a carbon-containing biological material commonly used for preparing activated carbon, such as wood powder, wood chips, sawdust, wood shavings, coconut shells, palm shells, fruit shells, etc.

[0012] Further, the mixing temperature is 170 - 240 °C and the time is 1 - 2 h. The mixing is carried out in a kneader, where a certain temperature and time are provided. On the basis of fully mixing the raw materials, the biomass material undergoes a ripening transformation to generate plasticity.

[0013] Further, the washing is carried out with chlorine-free water or by boiling with clean water. Compared with washing with chlorine-free water at normal temperature multiple times, boiling with clean water has a better washing effect, but due to restrictions on conditions such as energy and equipment, washing with chlorine-free water at normal temperature can also be used, and high-performance wood-based activated carbon can still be obtained.

[0014] Further, granulation is obtained by extrusion and cutting with a granulator, or first preparing rod-shaped or strip-shaped materials with a granulator, and then dispersing them into columnar materials after pre-drying treatment. Which method to specifically use depends on the pre-drying treatment temperature of 150 - 200 °C, time of 24 - 36 h, and the moisture content of the granular material after pre-drying treatment is 25 - 35%.

[0015] Further, the mass ratio of the biological material to phosphoric acid in S1 is 1:1 - 1:2.

[0016] Further, during the activation treatment in S2, the temperature is raised from room temperature to 500 - 700 °C, and the heating rate is 3 - 8 °C / min.

[0017] Further, the moisture content of the dried granular material is 5%.

[0018] Further, the volume ratio of the carbon source gas to nitrogen in S4 is 5:95 - 10:90. The ratio of the carbon source gas to nitrogen can be adjusted outside the above preferred range, but the amount of the carbon source gas introduced is less than that of nitrogen; nitrogen mainly plays a protective role and can also promote the formation of some micropores, while the carbon source gas plays a major role in pore size regulation.

[0019] Further, the gas flow rate in S4 is 1 - 5 L / min.

[0020] Further, during the activation treatment in S4, the temperature is raised from room temperature to 750 - 950 °C and held for 1 - 3 h. The heating rate is 5 - 10 °C / min.

[0021] Further, in S4, the activation treatment is ended until the carbon source gas in the detected tail gas exceeds 100 ppm.

[0022] A wood-based activated carbon for organic solvent recovery prepared by any of the above preparation methods.

[0023] Example 1: A preparation method of wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix wood powder and phosphoric acid in a kneader at a ratio of 1:1.2, with a mixing temperature of 170 °C and a time of 1.2 h in the kneader; S2. Use a plunger granulator to form rod-shaped columnar materials with a diameter of 4 mm and a length of 100 - 150 mm; S3. Perform pre-drying treatment on the columnar materials in an oven at a treatment temperature of 200 °C and a time of 24 h; S4. Break up the pre-dried granular materials into granular materials with a length of 3 - 5 mm; S5. Load the granular materials into a rotary kiln and introduce air for activation. The rotary kiln rotates at 20 rpm, slowly heats up to 680 °C, and the heating rate is 7 °C / min; S6. After the activation is completed, cool the obtained granular materials to room temperature, wash and recover phosphoric acid, and dry them in an oven at 150 °C until the moisture content is 4% to obtain dry granular materials; S7. Place the dry granular materials in an atmosphere rotary kiln, and introduce a mixed gas of a carbon source gas and nitrogen; the carbon source gas is acetylene; the ratio of the carbon source gas to nitrogen is 10:90, and the flow rate is 3 L / min; heat up to 800 °C, with a reaction time of 2 h, and a heating rate of 10 °C / min; S8. When the carbon source gas in the tail gas is detected to exceed 100 ppm, the reaction ends, and after cooling, the wood-based activated carbon for organic solvent recovery is obtained.

[0024] Example 2: A preparation method of wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix wood powder and phosphoric acid in a kneader at a ratio of 1:1, with a mixing temperature of 240 °C and a time of 1 h in the kneader; S2. Use a plunger granulator to form rod-shaped columnar materials with a diameter of 3 mm and a length of 100 - 150 mm; S3. Perform pre-drying treatment on the columnar materials in an oven at a treatment temperature of 150 °C and a time of 36 h; S4. Break up the pre-dried granular materials into granular materials with a length of 3 - 5 mm; S5. Load the granular materials into a rotary kiln and introduce air for activation. The rotary kiln rotates at 15 rpm, slowly heats up to 700 °C, and the heating rate is 8 °C / min; S6. After the activation is completed, cool the obtained granular materials to room temperature, wash and recover phosphoric acid, and dry them in an oven at 150 °C until the moisture content is 4% to obtain dry granular materials; S7. Place the dried granulates in an atmosphere rotary furnace, and introduce a mixed gas of a carbon source gas and nitrogen. The carbon source gas is ethane. The ratio of the carbon source gas to nitrogen is 5:95, and the flow rate is 5 L / min. Heat up to 950 °C, with a reaction time of 1 h and a heating rate of 5 °C / min. S8. When the carbon source gas in the tail gas is detected to exceed 100 ppm, the reaction ends. After cooling, the wood-based activated carbon for organic solvent recovery is obtained.

[0025] Example 3: A preparation method of wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix wood powder and phosphoric acid in a kneader at a ratio of 1:1.5, with a mixing temperature of 200 °C and a time of 2 h in the kneader. S2. Use a plunger granulator to form rod-shaped columnar materials with a diameter of 2 mm and a length of 100 - 150 mm. S3. Perform pre-drying treatment on the columnar materials in an oven at a treatment temperature of 180 °C and a time of 30 h. S4. Break up the pre-dried granulates into granulates with a length of 3 - 5 mm. S5. Load the granulates into a rotary furnace and introduce air for activation. The rotation speed of the rotary furnace is 18 rpm. Slowly heat up to 500 °C with a heating rate of 3 °C / min. S6. After the activation ends, cool the obtained granulates to room temperature, wash and recover phosphoric acid, and dry them in an oven at 150 °C until the water content is 3% to obtain dried granulates. S7. Place the dried granulates in an atmosphere rotary furnace, and introduce a mixed gas of a carbon source gas and nitrogen. The carbon source gas is methane and ethane. The ratio of the carbon source gas to nitrogen is 7:93, and the flow rate is 2 L / min. Heat up to 750 °C, with a reaction time of 3 h and a heating rate of 7 °C / min. S8. When the carbon source gas in the tail gas is detected to exceed 100 ppm, the reaction ends. After cooling, the wood-based activated carbon for organic solvent recovery is obtained.

[0026] Example 4: A preparation method of wood-based activated carbon for organic solvent recovery, comprising the following steps: S1. Mix wood powder and phosphoric acid in a kneader at a ratio of 1:2, with a mixing temperature of 220 °C and a time of 1 - 2 h in the kneader. S2. Use a plunger granulator to form rod-shaped columnar materials with a diameter of 2 mm and a length of 100 - 150 mm. S3. Perform pre-drying treatment on the columnar materials in an oven at a treatment temperature of 160 °C and a time of 28 h. S4. Break up the pre-dried granulates into granulates with a length of 3 - 5 mm. S5. Load the pellets into a rotary kiln, introduce air for activation, with the rotary kiln rotating at 20 rpm, slowly heat up to 600 °C at a heating rate of 5 °C / min; S6. After the activation is completed, cool the obtained pellets to room temperature, wash and recover phosphoric acid, and dry them in an oven at 150 °C until the moisture content is 5% to obtain dry pellets; S7. Place the dry pellets in an atmosphere rotary kiln, and introduce a mixed gas of a carbon source gas and nitrogen; the carbon source gas is acetylene; the ratio of the carbon source gas to nitrogen is 8:92, and the flow rate is 4 L / min; heat up to 850 °C, with a reaction time of 1.5 h and a heating rate of 8 °C / min; S8. When the carbon source gas in the tail gas is detected to exceed 100 ppm, the reaction ends, and after cooling, wood-based activated carbon for organic solvent recovery is obtained.

[0027] Example 5: The difference between Example 5 and Example 1 is only that the carbon source gas in S7 is methane.

[0028] Example 6: The difference between Example 6 and Example 1 is only that the carbon source gas in S7 is ethane.

[0029] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is only that the gas introduced in S5 is water vapor.

[0030] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is only that the carbon source gas in S7 is carbon dioxide.

[0031] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is only that a mixed gas of nitrogen and acetylene is introduced in S5, and air is introduced in S7, that is, the gases used in the two activation processes are exchanged.

[0032] Perform performance tests on the activated carbon obtained in Example 1 and Comparative Examples 1 to 3. The test standards are ASTM D5228, GB / T19587-2004, GB / T 12496.8-2015, ASTM D3802, GB / T 12496.3-1999. The results are shown in Table 1.

[0033] Table 1

[0034] In summary, the preparation method provided by the present invention can adjust the proportion of mesopores and micropores by adjusting the activation process after phosphoric acid impregnation, and match a suitable activation process for different activators. At the same time, it can avoid the problem of pore collapse during the preparation process, effectively improve the performance of the activated carbon, make it more suitable for organic solvent recovery, and effectively avoid the problem of spontaneous combustion during use.

[0035] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent transformation made by using the content of the specification of the present invention, or directly or indirectly applied in the related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing wood activated carbon for organic solvent recovery, characterized in that: The following steps are involved: S1, mixing the biomaterial and phosphoric acid, and then granulating to obtain granules; S2, introducing air to activate the pellets; S3, cooling the pellets obtained in S2 to room temperature, washing and recovering phosphoric acid, and drying to obtain dry pellets; S4, activating the dried pellets in a mixed atmosphere of carbon source gas and nitrogen, and obtaining wood activated carbon for organic solvent recovery after cooling.

2. The preparation method according to claim 1, characterized in that: The mixing temperature is 170~240℃ and the mixing time is 1~2h.

3. The preparation method according to claim 1, characterized in that: The mass ratio of biomaterial to phosphoric acid in S1 is 1:1~1:

2.

4. The preparation method according to claim 1, characterized in that: During the activation treatment in S2, the temperature is raised from room temperature to 500~700°C, and the rate of heating is 3~8°C / min.

5. The preparation method according to claim 1, characterized in that: The moisture content of the dried pellets was 5%.

6. The preparation method according to claim 1, characterized in that: The volume ratio of the carbon source gas to nitrogen in S4 is 5:95~10:

90.

7. The preparation method according to claim 1, characterized in that: The gas flow rate in S4 is 1~5L / min.

8. The preparation method according to claim 1, characterized in that: In S4, the activation treatment is heated from room temperature to 750~950℃ and kept warm for 1~3h.

9. The preparation method according to claim 1, characterized in that: In S4, the activation treatment is terminated when the carbon source gas content in the exhaust gas exceeds 100 ppm.

10. A wood activated carbon for organic solvent recovery prepared by the preparation method according to any one of claims 1 to 9.

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