CO2 adsorption material and preparation method thereof

Abstract

The invention discloses a CO2 adsorption material and a preparation method thereof.The method comprises the steps that 1, a coal-based raw material and an activating agent are mixed and ground to be uniform, and a mixture is obtained; 2) pre-oxidizing the mixture in an oxygen-containing atmosphere to obtain a pre-oxidized sample; 3) carbonizing and activating the pre-oxidized sample in a protective atmosphere, and then performing secondary activation in a CO2 atmosphere to obtain an activated sample; 4) washing the activated sample in an acid solution, washing in an aqueous solution, and drying to obtain an acid-washed sample; and 5) carrying out hot alkali treatment on the acid-washed sample in a high-temperature alkali solution, washing the sample subjected to hot alkali treatment with water, and drying to obtain the adsorption material. The adsorption material prepared by the method has the advantages of large micropore specific surface area, high CO2 adsorption capacity, high CO2 / N2 selectivity and the like, and the preparation process is simple, low in cost and very suitable for large-scale production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of gas adsorption materials, and particularly relates to a CO2 adsorption material and a preparation method thereof. Background Art

[0002] Carbon-based adsorption materials have a large specific surface area, a developed pore structure, low price, simple preparation, and good stability, and are very suitable for large-scale carbon capture. However, they have always had the fatal problems of low CO2 adsorption capacity and poor selectivity, and it is difficult to meet the application requirements of large-scale carbon capture technology for flue gas with low CO2 concentration.

[0003] CN103771407A discloses a method for preparing super activated carbon using biomass power plant ash as a raw material. In this method, impurities such as ash in the raw material are removed by alkali leaching and acid washing first, and then the residual carbon is heated and activated in an atmosphere of a mixture of water vapor and CO2 to obtain an intermediate product. Then, the intermediate product is mixed with NaOH and heated and activated in an N2 atmosphere. The activated product is washed and dried to obtain super activated carbon. The super activated carbon prepared by this method has characteristics such as high specific surface area, narrow pore size distribution, and low ash content. However, this method uses acid-base treatment multiple times, and physical activation and chemical activation cannot be carried out continuously, and the preparation process is complex. Summary of the Invention

[0004] In view of this, the main object of the present invention is to provide a CO2 adsorption material and a preparation method thereof. The adsorption material prepared by this method has the advantages of a large micro-pore specific surface area, high CO2 adsorption capacity, high CO2 / N2 selectivity, etc., and the preparation process is simple and the cost is low, which is very suitable for large-scale production and application.

[0005] To achieve the above-mentioned invention object, the first aspect of the present invention provides a preparation method of a CO2 adsorption material, including the following steps:

[0006] 1) Mixing a coal-based raw material with an activator and grinding evenly to obtain a mixture;

[0007] 2) Pre-oxidizing the mixture in an oxygen-containing atmosphere to obtain a pre-oxidized sample;

[0008] 3) Carbonizing and activating the pre-oxidized sample in a protective atmosphere first, and then performing secondary activation in a CO2 atmosphere to obtain an activated sample;

[0009] 4) Washing the activated sample in an acid solution, and then washing and drying in an aqueous solution to obtain a pickled sample;

[0010] 5) Performing hot alkali treatment on the pickled sample in a high-temperature alkali solution, and the sample after hot alkali treatment is washed with water and dried to obtain the adsorption material.

[0011] In some embodiments, in step 1), the coal-based raw material is crushed and then mixed with an activator, preferably crushed to a particle size of less than 100 mesh.

[0012] In some embodiments, the coal-based raw material is one or more of coal, coal liquefaction residue, and coal tar pitch.

[0013] In some embodiments, the activator is one or more of potassium hydroxide, sodium hydroxide, potassium nitrate, potassium carbonate, sodium carbonate, zinc chloride, and phosphoric acid.

[0014] In some embodiments, in the mixture, the mass ratio of the coal-based material to the activator is 1:(0.1 - 1).

[0015] In some embodiments, the pre-oxidation conditions include: under oxygen or air conditions, the pre-oxidation temperature is 200 - 400 °C, and the pre-oxidation time is 0.5 - 2 hours.

[0016] The above pre-oxidation conditions are beneficial to the formation of the pore structure of the material, removing some impurities in the raw material, and at the same time can significantly improve the yield of activated carbon.

[0017] In some embodiments, the protective atmosphere is nitrogen, argon, or a vacuum environment.

[0018] In some embodiments, the carbonization and activation conditions include: first, under a protective atmosphere, the temperature is raised from room temperature to 550 - 700 °C at a heating rate of 1 - 10 °C / min, held for 0.5 - 2 hours, and then under a CO2 atmosphere, the temperature is raised to 700 - 900 °C at a heating rate of 1 - 10 °C / min and held for 0.5 - 3 hours.

[0019] The present invention can effectively reduce the amount of activator through the composite activation of the activator - CO2, and at the same time is beneficial to the formation of a high specific surface area and a high microporous structure.

[0020] In some embodiments, the acid solution is one or more of hydrochloric acid, sulfuric acid, and phosphoric acid with a mass fraction of 0.1 - 10 wt%.

[0021] The present invention washes the activated sample in the acid solution mainly to remove the residual potassium / sodium and some mineral impurities after the carbonization and activation reaction, increase the specific surface area of the material, and improve the adsorption performance of the material.

[0022] In some embodiments, the conditions of the hot alkali treatment include: the sample is treated at a constant temperature for 0.5 - 6 hours in a potassium hydroxide or sodium hydroxide alkali solution with a temperature of 50 - 200 °C and a concentration of 1 - 5 mol / L.

[0023] Based on the above hot alkali treatment process of the present invention, without changing the pore structure of the activated carbon material, the content of functional groups such as carboxyl and hydroxyl groups on the surface of the activated carbon sample is increased, the surface polarity of the material is changed, and the CO2 adsorption performance of the material is greatly improved.

[0024] The second aspect of the present invention provides a CO2 adsorption material prepared by the above method.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The present invention proposes a preparation method of a novel adsorbent with high specific surface area, high CO2 adsorption capacity and selectivity. Using coal and its related products as carbon sources, through processes such as pre-oxidation, activator-CO2 composite activation, pickling, and hot alkali treatment, a CO2 adsorption material with excellent adsorption performance is prepared. The pre-oxidation process in this method is beneficial to the formation of the pore structure of the material, removes some impurities in the raw materials, and can also significantly improve the yield of activated carbon; the activator-CO2 composite activation can effectively reduce the dosage of the activator and is beneficial to the formation of a high specific surface area and a high microporous structure; the hot alkali treatment process can further improve the adsorption activity of the carbon material and effectively increase the adsorption capacity of the material. This preparation method has simple process, wide raw material sources and low cost, can greatly reduce the cost of carbon capture, and can also realize the clean and efficient utilization of coal. The adsorption material prepared by this method has a large specific surface area, high microporosity, high adsorption capacity, high CO2 / N2 selectivity, fast adsorption rate, and excellent cycle stability.

[0027] Other features and advantages of the present invention will be described in detail in the following specific embodiments. Specific Embodiments

[0028] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention and are not used to limit the present invention.

[0029] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0030] Unless otherwise specified, the raw materials and reagents in the embodiments of the present invention can be obtained through commercial channels.

[0031] The analysis and testing methods adopted in the embodiments of the present invention are as follows:

[0032] (1) Specific surface area test process: The Micromeritics ASAP 2460 gas sorption analyzer produced by Micromeritics Instrument Corporation of the United States was used to measure the physical adsorption of N2 (77K), and the sample was degassed at 300 °C for 4 hours. According to the recommendations of IUPAC, in the range of relative pressure P / P0 = 0.015 - 0.3, the Brunauer-Emmett-Teller (BET) method was used to calculate the surface area;

[0033] (2) Microporosity test process: Microporous specific surface area of adsorbent / Specific surface area of adsorbent;

[0034] (3) CO2 adsorption capacity test process: The STA 449F3 synchronous thermal analyzer produced by Netzsch of Germany was used to measure the adsorption capacity of the sample. The test conditions were as follows: The sample was pre-treated at a constant temperature of 300 °C in N2 for 30 min to remove any physically adsorbed impurities such as H2O and / or CO2. After the temperature was cooled and stabilized at 40 °C, the adsorption gas was switched, and the adsorption capacity was calculated based on the weight gain;

[0035] (4) CO2 / N2 separation factor test process: The breakthrough curve was measured by competitive adsorption and calculated according to the following formula:

[0036]

[0037] In the formula:

[0038] S: Separation factor of CO2 to N2

[0039] X1 / Y1: Mole fraction of CO2 in the adsorbed phase / Mole fraction of CO2 in the gas phase

[0040] X2 / Y2: Mole fraction of N2 in the adsorbed phase / Mole fraction of N2 in the gas phase.

[0041] The preparation method of the CO2 adsorption material of the present invention will be described in detail below by way of examples.

[0042] Example 1

[0043] The coal liquefaction residue was crushed to a particle size of less than 100 mesh, and the coal liquefaction residue, potassium hydroxide, and potassium nitrate were mixed and ground evenly according to a mass ratio of 1:0.9:0.1;

[0044] The mixture was heated to 300 °C and kept at a constant temperature for 1 hour in an air atmosphere for pre-oxidation to obtain a pre-oxidized sample;

[0045] The pre-oxidized sample was heated to 650 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and kept at a constant temperature for 1 hour for carbonization activation, and then heated to 800 °C at a heating rate of 5 °C / min, and the atmosphere was switched to a CO2 atmosphere and kept at a constant temperature for 2 hours for secondary activation to obtain an activated sample;

[0046] The activated sample was washed in a 5 wt% dilute hydrochloric acid solution until no bubbles emerged, and then washed in an aqueous solution until neutral and dried to obtain an acid-washed sample;

[0047] The acid-washed sample was treated in a 2 mol / L potassium hydroxide solution at 100 °C for 3 hours, and then washed with water and dried to obtain an adsorbent with a high specific surface area, high CO2 adsorption capacity, and selectivity.

[0048] In this example, the specific surface area of the prepared CO2 adsorbent was 2475 m 2 / g, the microporosity was as high as 90.6%, at 40 °C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 was about 9.8 wt%, and the CO2 / N2 separation factor was as high as 82.

[0049] Example 2

[0050] The Xinjiang coal was crushed to a particle size below 100 mesh, and the Xinjiang coal and potassium hydroxide were mixed in a mass ratio of 1:0.6 and ground evenly;

[0051] The mixture was heated to 300 °C and kept at a constant temperature for 1 hour in an air atmosphere for pre-oxidation to obtain a pre-oxidized sample;

[0052] The pre-oxidized sample was heated to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and kept at a constant temperature for 1 hour for carbonization activation, and then kept at a constant temperature in a CO2 atmosphere for 2 hours for secondary activation to obtain an activated sample;

[0053] The activated sample was washed in a 5 wt% dilute hydrochloric acid solution until no bubbles emerged, and then washed in an aqueous solution until neutral and dried to obtain an acid-washed sample;

[0054] The acid-washed sample was treated in a 1 mol / L potassium hydroxide solution at 100 °C for 6 hours, and then washed with water and dried to obtain an adsorbent with a high specific surface area, high CO2 adsorption capacity, and selectivity.

[0055] In this example, the specific surface area of the prepared CO2 adsorbent was 2103 m 2 / g, the microporosity was as high as 91.4%, at 40 °C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 was about 9.2 wt%, and the CO2 / N2 separation factor was as high as 75.

[0056] Example 3

[0057] The coal liquefaction residue was crushed to a particle size below 100 mesh, and the coal liquefaction residue, sodium hydroxide, and phosphoric acid were mixed in a mass ratio of 1:0.9:0.1 and ground evenly;

[0058] The mixture is heated to 400 °C in an air atmosphere and kept at a constant temperature for 0.5 hours for pre-oxidation to obtain a pre-oxidized sample;

[0059] The pre-oxidized sample is heated to 550 °C at a heating rate of 10 °C / min in a nitrogen atmosphere and kept at a constant temperature for 2 hours for carbonization activation, then heated to 900 °C at a heating rate of 10 °C / min, and the atmosphere is switched to a CO2 atmosphere and kept at a constant temperature for 1 hour for secondary activation to obtain an activated sample;

[0060] The activated sample is washed in a 10 wt% dilute hydrochloric acid solution until no bubbles emerge, and then washed in an aqueous solution until neutral and dried to obtain a pickled sample;

[0061] The pickled sample is treated in a 3 mol / L potassium hydroxide solution at 70 °C for 6 hours, and then washed with water and dried to obtain an adsorbent with a high specific surface area, high CO2 adsorption capacity and selectivity.

[0062] In this example, the specific surface area of the prepared CO2 adsorbent is 2214 m 2 / g, the microporosity is as high as 95.3%, at 40 °C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 is about 8.7 wt%, and the CO2 / N2 separation factor is as high as 79.

[0063] Example 4

[0064] The coal tar pitch is crushed to a particle size below 100 mesh, and the coal tar pitch, potassium hydroxide and zinc chloride are mixed in a mass ratio of 1:0.8:0.1 and ground evenly;

[0065] The mixture is heated to 200 °C in an air atmosphere and kept at a constant temperature for 2 hours for pre-oxidation to obtain a pre-oxidized sample;

[0066] The pre-oxidized sample is heated to 550 °C at a heating rate of 1 °C / min in a nitrogen atmosphere and kept at a constant temperature for 2 hours for carbonization activation, then heated to 900 °C at a heating rate of 1 °C / min, and the atmosphere is switched to a CO2 atmosphere and kept at a constant temperature for 0.5 hours for secondary activation to obtain an activated sample;

[0067] The activated sample is washed in a 0.1 wt% dilute hydrochloric acid solution until no bubbles emerge, and then washed in an aqueous solution until neutral and dried to obtain a pickled sample;

[0068] The pickled sample is treated in a 5 mol / L potassium hydroxide solution at 200 °C for 0.5 hours, and then washed with water and dried to obtain an adsorbent with a high specific surface area, high CO2 adsorption capacity and selectivity.

[0069] In this example, the specific surface area of the prepared CO2 adsorbent is 1989 m 2 / g, with a micropore rate as high as 93.1%. At 40°C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 is approximately 8.9 wt%, and the CO2 / N2 separation factor is as high as 85.

[0070] Example 5

[0071] Crush Xinjiang coal to a particle size below 100 mesh, and mix and grind Xinjiang coal and potassium carbonate in a mass ratio of 1:0.2 evenly;

[0072] Heat the mixture to 300°C in an air atmosphere and keep it at a constant temperature for 1 hour for pre-oxidation to obtain a pre-oxidized sample;

[0073] Heat the pre-oxidized sample to 650°C at a heating rate of 5°C / min in a nitrogen atmosphere, keep it at a constant temperature for 2 hours for carbonization activation, then heat it to 800°C at a heating rate of 5°C / min, and keep it at a constant temperature for 3 hours in a CO2 atmosphere for secondary activation to obtain an activated sample;

[0074] Wash the activated sample in a 5 wt% dilute hydrochloric acid solution until no bubbles emerge, then wash it in an aqueous solution until neutral and dry it to obtain a pickled sample;

[0075] Treat the pickled sample in a 4 mol / L potassium hydroxide solution at 70°C for 6 hours, then wash it with water and dry it to obtain an adsorbent with a high specific surface area, high CO2 adsorption capacity and selectivity.

[0076] In this example, the specific surface area of the prepared CO2 adsorbent is 1853 m 2 / g, with a micropore rate as high as 92.9%. At 40°C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 is approximately 8.2 wt%, and the CO2 / N2 separation factor is as high as 101.

[0077] Comparative Example 1

[0078] The activated carbon produced by a certain Xinjiang activated carbon manufacturer has a specific surface area of approximately 1267 m 2 / g, with a micropore rate of 86.6%. At 40°C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 is only 1.8 wt%.

[0079] Comparative Example 2

[0080] Crush the coal liquefaction residue to a particle size below 100 mesh, and mix and grind the coal liquefaction residue, potassium hydroxide, and potassium nitrate in a mass ratio of 1:0.9:0.1 evenly;

[0081] Heat the mixture to 300°C in an air atmosphere and keep it at a constant temperature for 1 hour for pre-oxidation to obtain a pre-oxidized sample;

[0082] The pre-oxidized sample was heated to 500 °C at a heating rate of 5 °C / min under a nitrogen atmosphere and carbonized and activated at a constant temperature for 1 hour. Then, it was heated to 600 °C at a heating rate of 5 °C / min, the atmosphere was switched to CO2, and it was secondarily activated at a constant temperature for 2 hours to obtain an activated sample;

[0083] The activated sample was washed in a 5 wt% dilute hydrochloric acid solution until no bubbles emerged, and then washed in an aqueous solution until neutral and dried to obtain a pickled sample;

[0084] The pickled sample was treated in a 2 mol / L potassium hydroxide solution at 100 °C for 3 hours, and then washed with water and dried to obtain a CO2 adsorbent.

[0085] In this example, the specific surface area of the prepared CO2 adsorbent was 875 m 2 / g, the microporosity was 77.8%, at 40 °C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 was approximately 3.5 wt%, and the CO2 / N2 separation factor was 23.

[0086] Comparative Example 3

[0087] The coal liquefaction residue was crushed to a particle size below 100 mesh, and the coal liquefaction residue, potassium hydroxide, and potassium nitrate were mixed in a mass ratio of 1:0.9:0.1 and ground evenly;

[0088] The mixture was heated to 300 °C in an air atmosphere and held at a constant temperature for 1 hour for pre-oxidation to obtain a pre-oxidized sample;

[0089] The pre-oxidized sample was heated to 900 °C at a heating rate of 5 °C / min under a nitrogen atmosphere and carbonized and activated at a constant temperature for 1 hour, and then secondarily activated at a constant temperature for 2 hours in a CO2 atmosphere to obtain an activated sample;

[0090] The activated sample was washed in a 5 wt% dilute hydrochloric acid solution until no bubbles emerged, and then washed in an aqueous solution until neutral and dried to obtain a pickled sample;

[0091] The pickled sample was treated in a 2 mol / L potassium hydroxide solution at 100 °C for 3 hours, and then washed with water and dried to obtain a CO2 adsorbent.

[0092] In this example, the specific surface area of the prepared CO2 adsorbent was 922 m 2 / g, the microporosity was 63.3%, at 40 °C, the CO2 adsorption capacity in a simulated flue gas atmosphere of 15% CO2 + 85% N2 was approximately 2.1 wt%, and the CO2 / N2 separation factor was 19.

[0093] From the examples and comparative examples, it can be seen that in Comparative Example 1, due to the use of steam activation, the prepared activated carbon material has a lower specific surface area and a larger mesopore ratio, resulting in poor CO2 adsorption performance; in Comparative Example 2, due to the relatively low carbonization and activation temperature, the carbonization and activation are incomplete, resulting in a smaller specific surface area and a lower microporosity of the sample, and poor adsorption performance. In Comparative Example 3, due to the excessively high carbonization and activation temperature, the pore structure of the material collapses, the micropores decrease, the medium and large pores increase, and both the specific surface area and the microporosity are low, resulting in poor adsorption performance.

[0094] Obviously, the above-mentioned examples of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation manners here. All obvious changes or modifications derived from the technical solutions of the present invention are within the spirit scope covered by the present invention.

Claims

1. A preparation method of a CO2 adsorption material, characterized in that, It includes the following steps: 1) Mix the coal-based raw material with the activator and grind evenly to obtain a mixed material; 2) Pre-oxidize the mixed material in an oxygen-containing atmosphere to obtain a pre-oxidized sample; 3) First carbonize and activate the pre-oxidized sample in a protective atmosphere, and then perform secondary activation in a CO2 atmosphere to obtain an activated sample; 4) Wash the activated sample in an acid solution, then wash it in an aqueous solution and dry it to obtain a pickled sample; 5) Perform hot alkali treatment on the pickled sample in a high-temperature alkali solution. After the hot alkali treatment, the sample is washed with water and dried to obtain an adsorption material.

2. The preparation method of the adsorption material according to claim 1, characterized in that, In step 1), the coal-based raw material is crushed and then mixed with the activator, preferably crushed to a particle size of less than 100 mesh.

3. The preparation method of the adsorption material according to claim 1 or 2, characterized in that, The coal-based raw material is one or more of coal, coal liquefaction residue, and coal tar pitch.

4. The preparation method of the adsorption material according to claim 1 or 2, characterized in that, The activator is one or more of potassium hydroxide, sodium hydroxide, potassium nitrate, potassium carbonate, sodium carbonate, zinc chloride, and phosphoric acid.

5. The preparation method of the adsorption material according to any one of claims 1-4, characterized in that, In the mixed material, the mass ratio of the coal-based material to the activator is 1:(0.1 - 1).

6. The preparation method of the adsorption material according to any one of claims 1-5, characterized in that, The pre-oxidation conditions include: under oxygen or air conditions, the pre-oxidation temperature is 200 - 400°C, and the pre-oxidation time is 0.5 - 2 hours.

7. The method for preparing the adsorption material according to any one of claims 1 - 6, wherein The carbonization and activation conditions include: first, in a protective atmosphere, heat from room temperature to 550 - 700°C at a heating rate of 1 - 10°C / min and keep it constant for 0.5 - 2 hours; then, in a CO2 atmosphere, heat to 700 - 900°C at a heating rate of 1 - 10°C / min and keep it constant for 0.5 - 3 hours; The protective atmosphere is nitrogen, argon, or a vacuum environment.

8. The preparation method of the adsorption material according to claim 1, characterized in that The acid solution is one or more of hydrochloric acid, sulfuric acid, and phosphoric acid with a mass fraction of 0.1 - 10 wt%.

9. The preparation method of the adsorption material according to any one of claims 1-8, characterized in that, The conditions for the hot alkali treatment include: keep the sample at a constant temperature for 0.5 - 6 hours in a potassium hydroxide or sodium hydroxide alkali solution with a temperature of 50 - 200°C and a concentration of 1 - 5 mol / L.

10. A CO2 adsorption material prepared by the method according to any one of claims 1 - 9.

Images