A method of predicting the adsorption capacity of a gas in an activated carbon material

Abstract

The application discloses a method for predicting the adsorption capacity of gas in activated carbon material, and belongs to the technical field of gas separation. The method is based on the construction of a quantitative prediction model of gas physical property parameters, activated carbon pore distribution characteristics and activated carbon surface chemical properties, and can quickly predict and evaluate the equilibrium adsorption capacity of target gas in activated carbon material by only inputting activated carbon microstructure and surface property parameters. The method is realized by constructing a quantitative relationship model of gas molecular parameters, activated carbon pore distribution, surface oxygen content and gas adsorption capacity, and only needs to obtain the pore distribution and surface oxygen content of activated carbon, so that the quick prediction and evaluation of gas adsorption performance from the microstructure and surface chemical properties of activated carbon are realized, and the process is simple and has high accuracy.

Description

Technical Field

[0001] This invention belongs to the field of gas separation technology, specifically relating to a method for predicting the adsorption capacity of gas in activated carbon materials. Background Technology

[0002] Activated carbon, as an important gas adsorption material, possesses advantages such as high stability, large specific surface area, wide pore size distribution, and abundant surface functional groups. Gas adsorption capacity, as a core indicator for activated carbon materials in gas purification, typically requires cumbersome experimental determination. Therefore, establishing a method to predict the adsorption capacity of different gases in activated carbon materials will significantly reduce the difficulty of screening activated carbon materials for different gas purification processes.

[0003] Typically, the amount of gas adsorbed in activated carbon materials is determined by the gas's physical properties, the pore distribution of the activated carbon material, and its surface functional groups. To date, there is a lack of quantitative relationship models between the amount of gas adsorbed in activated carbon materials and the pore distribution and surface functional groups of the activated carbon material. Conversely, establishing a quantitative relationship model between the pore distribution and surface functional groups of activated carbon materials and the amount of gas adsorbed in activated carbon materials can be used to quickly screen and evaluate the gas adsorption performance of activated carbon materials, thereby optimizing the screening and structural control of activated carbon materials. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for predicting the adsorption capacity of gas in activated carbon materials. This method can quickly screen and evaluate the performance of activated carbon materials for gas purification by constructing a quantitative relationship model between the physical properties of gas, the pore distribution of activated carbon materials and oxygen-containing functional groups on the surface of activated carbon materials and the amount of gas adsorbed in activated carbon materials.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for predicting the adsorption capacity of a gas in activated carbon material is proposed. Based on the gas physical properties, the pore distribution characteristics of activated carbon, and the surface chemical properties of activated carbon, a quantitative prediction model is constructed. Only the microstructure and surface property parameters of activated carbon are input, and the equilibrium adsorption capacity of the target gas in the activated carbon material can be quickly predicted and evaluated.

[0007] Furthermore, the pore distribution characteristics of the activated carbon are characterized by characteristic pore size; the surface chemical properties of the activated carbon are characterized by the oxygen-to-carbon ratio of the activated carbon surface.

[0008] Furthermore, the gas is carbon dioxide, methane, or carbon monoxide.

[0009] Furthermore, the method for preparing the activated carbon is as follows: bamboo charcoal is mixed with potassium hydroxide powder, the mixture is placed in a tube furnace for activation, cooled, and then washed alternately with hydrochloric acid solution and deionized water until neutral, and dried to obtain bamboo activated carbon material.

[0010] Furthermore, the mass ratio of bamboo charcoal to potassium hydroxide powder is 0.5~4:1.

[0011] Furthermore, the activation temperature is 800℃ and the activation time is 2 hours.

[0012] Furthermore, the surface oxygen-to-carbon ratio of the activated carbon is 0.16-1.25.

[0013] Furthermore, the activated carbon material has a characteristic pore size of 0.6-1.0 nm for carbon dioxide, a characteristic pore size of 0.7-1.1 nm for methane, and a characteristic pore size of 0.65-1.0 nm for carbon monoxide.

[0014] Furthermore, the equilibrium adsorption capacity of the quantitative prediction model ( The calculation formula is:

[0015] ;

[0016] In the formula, This represents the characteristic pore volume corresponding to different gases in activated carbon. α represents the geometric mean of the energy parameters of the gas and carbon; α represents the polarity of the adsorbed gas; O / C represents the oxygen-to-carbon ratio on the surface of the activated carbon; and P represents the adsorption pressure.

[0017] Furthermore, the basic relationship for saturated adsorption capacity in the model is as follows: In the formula, This refers to the surface saturation adsorption capacity of the activated carbon material. This represents the characteristic pore volume corresponding to different gases in activated carbon.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) This invention constructs a quantitative relationship model between the physical properties of gas, the pore distribution of activated carbon material and the amount of gas adsorbed in activated carbon material by using the polarity and energy parameters of gas, the characteristic pore volume of activated carbon and the surface oxygen-carbon ratio as input values, thereby realizing accurate prediction of the amount of gas adsorbed in activated carbon material.

[0020] (2) The quantitative relationship model proposed in this invention predicts that the adsorption amount of carbon dioxide, methane and carbon monoxide in activated carbon has an error of only 13.8% compared with the experimental results. Attached Figure Description

[0021] Figure 1 The nitrogen adsorption isotherms (a) and pore size distribution (b) of the five types of bamboo activated carbon in Example 1 of this application are shown.

[0022] Figure 2 In Example 2 of this application, carbon dioxide (a), methane (b), and carbon monoxide (c) are reacted in activated carbon material BAC. 0.5:1 BAC 1:1 BAC 3:1 BAC 4:1 Figure showing the results of gas adsorption measurement and model fitting;

[0023] Figure 3 Example 3 of this application shows the trend of adsorption capacity of carbon dioxide, methane and carbon monoxide under different activated carbon pore sizes;

[0024] Figure 4 This is a quantitative relationship diagram between the theoretical saturated adsorption capacity and the characteristic pore volume of the activated carbon material in Example 4 of this application;

[0025] Figure 5 This is a comparison chart of the adsorption amounts of carbon dioxide, methane, and carbon monoxide in bamboo-based activated carbon materials in Example 5 of this application. Detailed Implementation

[0026] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0027] Example 1

[0028] Using bamboo charcoal as raw material, potassium hydroxide powder in different proportions (mass ratios of 0.5:1, 1:1, 2:1, 3:1, and 4:1) was mixed evenly. The mixtures were then placed in a tube furnace and activated at 800℃ for 2 hours. After cooling, the mixtures were alternately washed with 1.0 mol / L hydrochloric acid solution and deionized water until neutral, and then dried in an oven to obtain bamboo activated carbon materials. Samples 1-5 of the bamboo activated carbon materials were prepared using this method and are denoted as BAC. 0.5:1 BAC 1:1 BAC 2:1 BAC 3:1 BAC 4:1 .

[0029] The pore structure distribution of activated carbon was measured and analyzed using a Micromeritics ASAP 2460 surface area analyzer and non-local density functional theory, and the oxygen-to-carbon ratio on the surface of bamboo activated carbon was analyzed using X-ray photoelectron spectroscopy. The results are shown in Table 1 and... Figure 1 .

[0030] Table 1. Oxygen-to-carbon ratio on the surface of bamboo activated carbon materials

[0031]

[0032] From Table 1 and Figure 1 It can be seen that the activated carbon material obtained by the above preparation method is mainly microporous. With the increase of potassium hydroxide dosage, the pore distribution of the activated carbon material shows a trend of first increasing and then decreasing. Among them, BAC 1:1 and BAC 2:1 It exhibits the most developed pore distribution. Meanwhile, with the increase of potassium hydroxide dosage, the surface oxygen content of the activated carbon material shows a trend of first increasing and then decreasing. The surface functional groups are mainly oxygen-containing functional groups such as carbonyl and carboxyl groups. 3:1 It has the highest surface oxygen-to-carbon ratio.

[0033] Example 2

[0034] Take the bamboo activated carbon material BAC prepared in Example 1 0.5:1 BAC 1:1 BAC 3:1 BAC 4:1 0.1 g of each was used to determine the gas adsorption amounts of carbon dioxide, methane, and carbon monoxide at 308.15 K and 0–1.0 bar using an ASAP 2020 analyzer. The gas adsorption amounts were fitted using the Langmuir model to obtain the adsorption values ​​of different gases at BAC. 0.5:1 BAC 1:1 BAC 3:1 BAC 4:1 The theoretical saturated adsorption capacity and Langmuir affinity parameter are shown in the figure. Figure 2 .

[0035] The Langmuir model expression is:

[0036] Where, q e To balance the adsorption capacity, q m K represents the surface saturation adsorption capacity. L Here, P represents the Langmuir affinity parameter, and P represents the adsorption pressure.

[0037] Figure 2 For carbon dioxide, methane and carbon monoxide in activated carbon material BAC 0.5:1 BAC 1:1 BAC 3:1 BAC 4:1 The results of the gas adsorption amount determination and the fitting of the Langmuir model were compared. The Langmuir model can fit different gas adsorption amounts well. The relative average deviations between the model fitting and the experimental determination were 3.3%, 1.2% and 1.0%, respectively.

[0038] Example 3

[0039] The adsorption capacities of carbon dioxide, methane, and carbon monoxide under different activated carbon pore sizes were calculated using perturbation chain statistical associative fluid theory coupled with classical density functional theory (PC-SAFT-DFT, commercially available). Results are shown below. Figure 3 .

[0040] Figure 3 The adsorption trends of carbon dioxide, methane, and carbon monoxide by activated carbon materials with different pore sizes were shown (based on calculations using perturbation chain statistical associative fluid theory coupled with classical density functional theory). The optimal characteristic pore sizes of activated carbon materials for adsorption of carbon dioxide, methane, and carbon monoxide were 0.6-1.0 nm, 0.7-1.1 nm, and 0.65-1.0 nm, respectively.

[0041] Example 4

[0042] Based on the different gases obtained in Example 2, in BAC 0.5:1 BAC 1:1 BAC 3:1 BAC 4:1 Based on the theoretical saturated adsorption capacity obtained in Example 3 for different gases, a theoretical saturated adsorption capacity and the characteristic pore volume of the activated carbon material (according to...) were constructed. Figure 1 The quantitative relationship model yields the following expression: ; This refers to the surface saturation adsorption capacity of the activated carbon material. The characteristic pore volumes correspond to different gases in the activated carbon. Results are shown below. Figure 4 .

[0043] Figure 4 The quantitative relationship between theoretical saturated adsorption capacity and characteristic pore volume of activated carbon material is shown, with a relative average deviation of 18.4%, indicating a good linear correlation.

[0044] Example 5

[0045] Based on the Langmuir affinity parameters obtained in Example 2, and coupled with the quantitative relationship model between the theoretical saturated adsorption capacity and the characteristic pore volume of the activated carbon material in Example 4, a gas adsorption capacity prediction model based on gas properties (polarity and energy parameters), pore distribution of the activated carbon material (characteristic pore volume), and surface oxygen-to-carbon ratio is further obtained, yielding the expression: ; where q e This represents the equilibrium adsorption capacity of the gas. This represents the characteristic pore volume corresponding to different gases in activated carbon. The values ​​represent the geometric mean of the energy parameters of the gas and carbon; α represents the polarity of the adsorbed gas; O / C represents the oxygen-to-carbon ratio at the surface of the activated carbon; and P represents the adsorption pressure. Results are shown in […]. Figure 5 And Table 2.

[0046] Table 2 Comparison of gas adsorption amounts at different pressures as measured experimentally and predicted by the model (temperature: 308.2 K)

[0047]

[0048] Depend on Figure 5 Table 2 compares the adsorption amounts of carbon dioxide, methane, and carbon monoxide in bamboo-based activated carbon materials (model prediction vs. experimental determination). The average deviation between model prediction and experimental determination is 13.8%, indicating high prediction accuracy.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for predicting the adsorption capacity of a gas in activated carbon material, characterized in that, A quantitative prediction model is constructed based on gas physical properties, activated carbon pore distribution characteristics, and activated carbon surface chemical properties. By simply inputting the microstructure and surface property parameters of activated carbon, the equilibrium adsorption capacity of the target gas in the activated carbon material can be quickly predicted and evaluated.

2. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 1, characterized in that: The pore distribution characteristics of the activated carbon are defined as characteristic pore size; the surface chemical properties of the activated carbon are defined as the oxygen-to-carbon ratio of the activated carbon surface.

3. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 1, characterized in that: The gas is carbon dioxide, methane, or carbon monoxide.

4. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 1, characterized in that: The method for preparing activated carbon is as follows: bamboo charcoal is mixed with potassium hydroxide powder, the mixture is placed in a tube furnace for activation, cooled and then washed alternately with hydrochloric acid solution and deionized water until neutral, and dried to obtain bamboo activated carbon material.

5. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 4, characterized in that: The mass ratio of bamboo charcoal to potassium hydroxide powder is 0.5~4:

1.

6. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 4, characterized in that: The activation temperature is 800℃ and the activation time is 2 hours.

7. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 2, characterized in that: The surface oxygen-to-carbon ratio of the activated carbon is 0.16-1.

25.

8. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 1, characterized in that: The activated carbon material has a characteristic pore size of 0.6-1.0 nm for carbon dioxide, 0.7-1.1 nm for methane, and 0.65-1.0 nm for carbon monoxide.

9. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 1, characterized in that: The equilibrium adsorption capacity of the quantitative prediction model ( The calculation formula is: ； In the formula, This represents the characteristic pore volume corresponding to different gases in activated carbon. α represents the geometric mean of the energy parameters of the gas and carbon; α represents the polarity of the adsorbed gas; O / C represents the oxygen-to-carbon ratio on the surface of the activated carbon; and P represents the adsorption pressure.

10. The method for predicting the adsorption capacity of a gas in activated carbon material according to claim 9, characterized in that: The basic relationship of saturated adsorption capacity in the model is as follows: In the formula, This refers to the surface saturation adsorption capacity of the activated carbon material. This represents the characteristic pore volume corresponding to different gases in activated carbon.

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