CN106517181A - A kind of preparation method of biomass-based activated carbon with high efficiency adsorption CO2 - Google Patents

Abstract

The invention discloses a preparation method of biomass based activated carbon with high CO2 adsorption efficiency. The method includes the steps of (1) crushing cleaned and dried peanut shells, walnut shells or pecan shells to 20-40-mesh so as to obtain biomass shell powder; (2) mixing the biomass shell powder, potassium oxalate and distilled water evenly according to a certain mass ratio, and then transferring the mixture into a polytetrafluoroethylene lined reaction kettle to be subjected to a hydrothermal reaction to obtain a hydrothermal product; (3) drying the hydrothermal product, then carbonizing the dried product under an N2 atmosphere to obtain a carbonized material; and (4) washing the carbonized material with 0.1mol/L hydrochloric acid and distilled water repeatedly to be neutral, and performing drying to obtain activated carbon. According to the method provided by the invention, carbonization and activation are performed in one step, and the traditional post-activation method is replaced. The required raw materials are widely available and are low in cost, and the preparation process is simple. The prepared activated carbon with high specific surface area has excellent adsorption performance and stable recycling adsorption performance on CO2 under room temperature and atmospheric pressure.

Description

A kind of preparation method of biomass-based activated carbon with high efficiency adsorption CO2

technical field

The invention relates to a preparation method of activated carbon, in particular to a preparation method of biomass-based activated carbon for efficiently adsorbing _CO2 .

Background technique

At present, resource and energy crises and environmental issues are becoming more and more prominent. How to dispose and utilize agricultural waste has become one of the focuses of countries all over the world. Peanut shells, walnut shells, and pecan shells are produced in China. Generally, these agricultural wastes have no value in use and are treated as garbage in waste treatment plants. However, due to the high carbon content of these biomass shells, they are widely available and low in cost. Advantages, can be used as an ideal precursor for the preparation of activated carbon, so the preparation of activated carbon with these biomass shells as precursors can not only reduce the amount of domestic waste, but also develop new uses of these biomass shells, and prepare efficient CO ₂ adsorption materials .

Since the industrial revolution, a large amount of fossil fuels such as coal and oil have been burned to emit a large amount of CO ₂ gas, causing the concentration of greenhouse gases in the atmosphere to increase year by year, seriously destroying the ecological environment, and endangering the survival and development of human beings. Therefore, it is of great theoretical and practical significance to implement the capture and enrichment of _CO2 . At present, the main methods for capturing _CO2 include liquid-phase absorption, solid-state adsorption, and membrane separation. Among them, the liquid phase absorption method is highly corrosive to the equipment, the energy consumption of absorbent regeneration is large, and it is easy to be oxidized and easily degraded; the membrane separation method has problems such as low separation efficiency and high cost, which limit its application. In contrast, the solid adsorption method is relatively simple to operate and less corrosive to equipment, and it is a _CO2 capture and recovery technology with great promotion prospects. Activated carbon for _CO2 adsorption is one of the most promising materials in solid materials for _CO2 capture because of its low cost, high adsorption capacity, high adsorption selectivity, and excellent cycle regeneration performance.

Patent documents CN 103157436 A and CN 103193228 A respectively disclose that pine nut shells and melon seed skins are used as raw materials, and the pine nut shells and melon seed skins are crushed to obtain their powders. The average particle size of the powders is 500-800 microns; Carrying out carbonization treatment to obtain carbonized material; placing the carbonized material in potassium hydroxide solution for impregnation treatment; performing activation treatment on the carbonized material after impregnation treatment, so as to obtain the pine nut shell base that absorbs CO ₂ and melon seed peel-based activated carbon. The _CO2 adsorption capacity of the activated carbon obtained by this method is still good, but the disadvantages are that the energy consumption of carbonization treatment and activation treatment is relatively large, the impregnation treatment process of carbonized material and potassium hydroxide solution is cumbersome, and potassium hydroxide is easy to use as an activator. polluted environment. Patent document CN 104310396 A discloses adding p-aminophenol after reacting melamine and formaldehyde, reflux reaction 4, cooling to room temperature, and then adding methanol solution of F127 or P123, respectively at 100-120, 130-160, 170-190, 210 -230 and 240-260°C were solidified in stages to obtain nitrogen-containing prepolymers, and then carbonized. The carbonized material was mixed with KOH and activated for 0.5-2.0 hours. Finally, it was repeatedly washed with deionized water until neutral, and dried to obtain the product. This method uses a large number of expensive and toxic organic substances as precursors, which are first carbonized and then activated by mixing with KOH. The process is complicated, which is inconsistent with the current concept of green chemistry advocating the use of non-toxic and harmless raw materials.

In summary, the development of a cheap and efficient _CO2 adsorption material has important scientific value and good application prospects.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing activated carbon with cheap raw materials and one-step carbonization and activation. The prepared activated carbon has excellent adsorption performance and stable cycle regeneration adsorption performance for greenhouse gas _CO2 at room temperature.

The present invention solves its technical problem and adopts the following technical solutions:

Efficiently adsorbed _CO provided by the invention The preparation method of the biomass-based activated carbon comprises the following steps:

(1) powder the cleaned and dried biomass shells to 20-40 mesh to obtain biomass shell powder;

(2) Mix the weighed biomass shell powder with a mass ratio of 1:1 to 5:1, the activator and distilled water evenly, and then transfer it to a polytetrafluoroethylene-lined reactor for hydroheating to obtain a hydrothermal product ;

(3) The hydrothermal product is dried at 100-110°C and placed under _N2 atmosphere for carbonization to obtain carbonized material;

(4) The carbonized material was repeatedly washed with 0.1 mol/L hydrochloric acid and distilled water to neutrality, and then dried to obtain activated carbon.

In the above step (1), the biomass shell is obtained after drying at 110° C. for 12 hours.

The biomass shell is peanut shell, walnut shell or pecan shell.

Above-mentioned in step (2), described activator is potassium oxalate.

In the above step (2), the mass ratio of the biomass shell powder to distilled water is 1:10.

In the above step (2), the temperature of the hydrothermal treatment is 200-280° C., and the hydrothermal time is 8-16 hours.

In the above step (3), the carbonization process is as follows: the temperature is 600-800° C., and the time is 1.5-2 hours.

In the above step (4), the drying process is as follows: the drying temperature is 100-110° C., and the drying time is 24-36 hours.

The biomass-based activated carbon material for adsorbing _CO2 prepared by the invention has a specific surface area of ^638-1644m2 /g.

Compared with the prior art, the present invention has the following main advantages:

(1) Biomass shells are used as raw materials, which are cheap and widely sourced, and expensive and toxic organic substances are avoided;

(2) Potassium oxalate is both a carbon source and an activator;

(3) Activated carbon is quickly prepared by one-step carbonization and activation, which saves the conventional process of carbonization first and then activation, greatly reducing energy consumption and reaction time;

(4) The prepared activated carbon absorbs _CO and can be regenerated at a lower temperature (the sample after absorbing _CO is placed on the degasser of a new generation of TriStar II 3020 adsorption analyzer produced by Mike Company of the United States at 200 ° C under vacuum conditions. The regeneration experiment can be completed after degassing for 4 hours), and its cycle regeneration adsorption performance is excellent.

Description of drawings

Fig. ₁ is the adsorption curve of activated carbon prepared in Examples 1-8 and commercial activated carbon (sample A0) to CO at normal temperature and pressure.

Fig. 2 is the cyclic adsorption diagram of activated carbon prepared in Example 2 for _CO2 adsorption at normal temperature and pressure.

Fig. 3 and Fig. 4 are the scanning electron micrographs of the activated carbon prepared in embodiment 2 respectively.

Fig. 5 is the _N2 adsorption-desorption isotherm of activated carbon prepared in Examples 1-8.

detailed description

The present invention will be further described below in conjunction with the examples and accompanying drawings. These examples are only descriptions of the preferred implementation modes of the present invention, but are not limited to the content described below.

Example 1:

First, take the pecan husks washed and dried at 110°C for 12h and powder them to 20-40 meshes to obtain pecan husk powder; then, mix 3g of pecan husk powder, 3g of potassium oxalate (pecan husk The mass ratio of powder to potassium oxalate is 1:1) mixed with 30g of distilled water evenly, then transferred to a polytetrafluoroethylene-lined reactor and heated at 240°C for 12 hours to obtain a hydrothermal product; secondly, the hydrothermal product was heated at 110°C After drying for 24 hours, carbonize at 600°C for 2 hours under _N2 atmosphere (50ml/min) to obtain carbonized material; finally, the carbonized material is repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 638m ² /g, and its CO ₂ adsorption capacity is 3.42mmol/g (see curve A1 in Figure 1).

Example 2:

First, take the pecan husk that has been washed and dried at 110°C for 12 hours and powder it to 20-40 meshes to obtain the pecan husk powder; then, mix 3g of pecan husk powder, 9g of potassium oxalate (pecan husk The mass ratio of powder to potassium oxalate is 1:3) mixed with 30g of distilled water evenly, then transferred to a polytetrafluoroethylene-lined reactor and heated at 240°C for 12 hours to obtain a hydrothermal product; secondly, the hydrothermal product was heated at 110°C After drying for 24 hours, carbonize at 700°C for 2 hours under _N2 atmosphere (50ml/min) to obtain carbonized material; finally, the carbonized material is repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 999m ² /g, and its CO ₂ adsorption capacity is 4.31mmol/g (see curve A2 in Figure 1).

Example 3:

First, take the pecan husks that have been washed and dried at 110°C for 12 hours and powdered to 20-40 meshes to obtain pecan husk powder; then, 3g of pecan husk powder, 15g of potassium oxalate (pecan husk The mass ratio of powder to potassium oxalate is 1:5) mixed with 30g of distilled water evenly, and then transferred to a reaction kettle lined with polytetrafluoroethylene and heated at 240°C for 12 hours to obtain a hydrothermal product; secondly, the hydrothermal product was heated at 110°C After drying for 24 hours, carbonize at 800°C for 2 hours under _N2 atmosphere (50ml/min) to obtain carbonized material; finally, the carbonized material is repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 1485m ² /g, and its CO ₂ adsorption capacity is 3.69mmol/g (see curve A3 in Figure 1).

Example 4:

First, take the peanut shells washed and dried at 110°C for 12 hours and powder them to 20-40 meshes to obtain peanut shell powder; ratio of 1:1) mixed with 30g of distilled water, then transferred to a polytetrafluoroethylene-lined reactor and heated at 240°C for 12 hours to obtain a hydrothermal product; secondly, the hydrothermal product was dried at 110°C for 24 hours and placed in N ₂ Atmosphere (50ml/min) at 700°C for 2 hours to obtain carbonized material; finally, the carbonized material was repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 1913m ² /g, and its CO ₂ adsorption capacity is 3.93mmol/g (see curve A4 in Figure 1).

Embodiment 5:

First, take the walnut shells washed and dried at 110°C for 12 hours and powder them to 20-40 meshes to obtain walnut shell powder; ratio of 1:3) mixed with 30g of distilled water, and then transferred to a polytetrafluoroethylene-lined reactor at 240 ° C for 12 hours to obtain a hydrothermal product; secondly, the hydrothermal product was dried at 110 ° C for 24 hours and placed in N ₂ Atmosphere (50ml/min) at 700°C for 2 hours to obtain carbonized material; finally, the carbonized material was repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 894m ² /g, and its CO ₂ adsorption capacity is 3.84mmol/g (see curve A5 in Figure 1).

Embodiment 6:

First, take the peanut shells washed and dried at 110°C for 12 hours and powder them to 20-40 meshes to obtain peanut shell powder; ratio of 1:3) mixed with 30g of distilled water, and then transferred to a polytetrafluoroethylene-lined reactor at 200 ° C for 8 hours to obtain a hydrothermal product; secondly, the hydrothermal product was dried at 110 ° C for 30 h and placed in N ₂ Atmosphere (50ml/min) at 800°C for 2 hours to obtain carbonized material; finally, the carbonized material was repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 961m ² /g, and its CO ₂ adsorption capacity is 3.23mmol/g (see curve A6 in Figure 1).

Embodiment 7:

First, take the walnut shells washed and dried at 110°C for 12 hours and powder them to 20-40 meshes to obtain walnut shell powder; ratio of 1:3) was mixed with 30g of distilled water, then transferred to a polytetrafluoroethylene-lined reactor and heated at 280°C for 12h to obtain a hydrothermal product; secondly, the hydrothermal product was dried at 110°C for 36h and placed in N ₂ Atmosphere (50ml/min) at 700°C for 2 hours to obtain carbonized material; finally, the carbonized material was repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 1644m ² /g, and its CO ₂ adsorption capacity is 3.61mmol/g (see curve A7 in Figure 1).

Embodiment 8:

First, take the peanut shells washed and dried at 110°C for 12 hours and powder them to 20-40 meshes to obtain peanut shell powder; The ratio is 1:3) mixed with 30g of distilled water, and then transferred to a polytetrafluoroethylene-lined reactor with 280°C hydroheating for 16h to obtain a hydrothermal product; secondly, the hydrothermal product was dried at 110°C for 36h and placed in N ₂ Atmosphere (50ml/min) at 700°C for 2 hours to obtain carbonized material; finally, the carbonized material was repeatedly washed with 0.1mol/L hydrochloric acid and distilled water until neutral, and dried at 110°C for 12 hours to obtain activated carbon. Its specific surface area is 705m ² /g, and its CO ₂ adsorption capacity is 3.68mmol/g (see curve A8 in Figure 1).

The sample after adsorbing CO ₂ was degassed at 200 °C under vacuum conditions for 4 h on the degassing device of the new generation TriStar II 3020 adsorption analyzer produced by American Mike Company. Then, the degassed sample was subjected to cyclic adsorption experiment, and after 10 cycles, the CO ₂ adsorption capacity at room temperature was basically maintained at 4.31mmol/g, showing excellent recycling and regeneration capabilities (see Figure 2).

Claims (9)

1. a kind of efficient adsorption _CO The preparation method of the biomass-based activated carbon is characterized in that comprising the following steps: (1) powder the cleaned and dried biomass shells to 20-40 mesh to obtain biomass shell powder; (2) Mix the weighed biomass shell powder with a mass ratio of 1:1 to 5:1, the activator and distilled water evenly, and then transfer it to a polytetrafluoroethylene-lined reactor for hydroheating to obtain a hydrothermal product ; (3) The hydrothermal product is dried at 100-110°C and placed under _N2 atmosphere for carbonization to obtain carbonized material; (4) The carbonized material was repeatedly washed with 0.1 mol/L hydrochloric acid and distilled water to neutrality, and then dried to obtain activated carbon. 2. The preparation method according to claim 1, characterized in that in step (1), the biomass shell is obtained after drying at 110° C. for 12 hours. 3. The preparation method according to claim 2, characterized in that the biomass shell is peanut shell, walnut shell or pecan shell. 4. preparation method according to claim 1 is characterized in that in step (2), described activator is potassium oxalate. 5. The preparation method according to claim 1, characterized in that in step (2), the mass ratio of the biomass shell powder to distilled water is 1:10. 6. The preparation method according to claim 1, characterized in that in step (2), the temperature of the hydrothermal treatment is 200-280° C., and the hydrothermal time is 8-16 hours. 7. The preparation method according to claim 1, characterized in that in step (3), the carbonization process is as follows: the temperature is 600-800° C., and the time is 1.5-2 hours. 8. The preparation method according to claim 1, characterized in that in step (4), the drying process is as follows: the drying temperature is 100-110° C., and the drying time is 24-36 hours. 9. The biomass-based activated carbon material for adsorbing _CO2 prepared by the method according to any one of claims 1 to 8, characterized in that the specific surface area of the biomass-based activated carbon material is ^638-1644m2 /g.