Method for preparing nitrogen-doped porous carbon carbon dioxide adsorbent by utilizing salix psammophila

Abstract

The invention relates to a method for preparing a nitrogen-doped porous carbon dioxide adsorbent by using salix psammophila, which comprises the following steps of: crushing and screening salix psammophila serving as a raw material, performing hydrothermal reaction on powder less than 100 meshes and polyethyleneimine in an aqueous solution, and washing and drying to obtain nitrogen-doped hydrated carbon; the nitrogen-doped hydrated carbon and potassium hydroxide are subjected to high-temperature activation in a tubular furnace, and after a product is cooled, the nitrogen-doped porous carbon is obtained through acidification, water washing and drying processes. The product provided by the invention has a high specific surface area, and the adsorption capacity of the product to CO2 under the conditions of 0 DEG C and 1 bar reaches 6.72 mmol / g. Therefore, the product disclosed by the invention has potential application and popularization values in the field of CO2 removal or enrichment.

Description

Technical Field

[0001] The invention relates to the field of porous carbon carbon dioxide adsorbent preparation, and in particular to a method for preparing nitrogen-doped porous carbon carbon dioxide adsorbent by utilizing Salix psammophila. Background Art

[0002] In recent years, due to the uncontrolled use of fossil energy, a large amount of greenhouse gas carbon dioxide (CO2) has been emitted, leading to problems such as rising global temperatures, melting ice and snow, and rising sea levels. Capturing and storing CO2 is an effective way to control the greenhouse effect.

[0003] Commonly used CO2 capture methods include ammonia scrubbing, membrane separation and solid adsorbents. Compared with traditional adsorption materials, solid adsorption technology has low energy consumption, simple operation and easy regeneration of adsorbents, making it a potential CO2 capture method; currently, solid adsorbents mainly include alkaline metal oxides, metal organic frameworks, zeolites, biomass porous carbon and porous organic polymers.

[0004] Biomass porous carbon adsorbent is considered to be the most promising CO2 adsorption material due to its low cost, simple preparation and renewability. In addition, porous carbon can also improve its performance by activation and regulating the specific surface area and pore structure.

[0005] However, porous carbon without heteroatom doping has few active sites on its surface, weak adsorption affinity for CO2, unstable adsorption and easy desorption; by doping with N heteroatoms, the active sites of porous carbon can be increased, and at the same time, the porous carbon can be induced to produce more pore structures, thereby further improving the adsorption capacity of carbon materials for CO2; in addition, N doping can also effectively improve the selectivity of CO2 / N2; therefore, how to simply and efficiently prepare porous carbon with excellent performance is of great value. Summary of the invention

[0007] In view of the defects of the current technology and products in this field, the present invention has developed a method for preparing nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, which is used to solve the problems of process and product performance in the existing porous carbon preparation methods; the present invention uses Salix psammophila biomass as raw material to obtain a new type of nitrogen-doped porous carbon with low cost, simple preparation method, high specific surface area, high CO2 adsorption capacity and better CO2 selectivity.

[0008] To achieve the above object, the technical solution of the present invention is as follows: The present invention proposes a method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, comprising the following steps: (1) crushing and sieving Salix psammophila to obtain Salix psammophila powder; placing the Salix psammophila powder and polyethyleneimine in a certain mass ratio in a reaction kettle, adding deionized water, stirring for a certain time, performing a hydrothermal reaction at a certain temperature, maintaining for a certain time, filtering, washing and drying the obtained product, and obtaining nitrogen-doped hydrated carbon; (2) mixing nitrogen-doped hydrated carbon and potassium hydroxide in a certain mass ratio, grinding, and then performing high-temperature activation at a certain temperature in a nitrogen atmosphere for a certain period of time. The product is cooled, washed, and dried to obtain nitrogen-doped porous carbon;

[0009] The nitrogen-doped porous carbon prepared by the present invention has a specific surface area of ​​1464 m 2 / g, the average pore diameter is 2.23nm, and the nitrogen content is 1.26wt%.

[0010] Therefore, the nitrogen-doped porous carbon of the present invention is expected to be promoted and applied as a CO2 adsorbent in the field of CO2 removal or enrichment.

[0011] The advantages of the present invention are: The present invention uses Salix psammophila as raw material, adopts simple and easy-to-operate process and conditions, and obtains nitrogen-doped porous carbon CO2 adsorption material with excellent performance. The material has excellent performance and can be reused. Therefore, it has a good application and promotion prospect in the field related to CO2 adsorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 SEM image of nitrogen-doped porous carbon prepared in Example 1; Figure 2 TEM image of nitrogen-doped porous carbon prepared in Example 1; Figure 3 XRD pattern of nitrogen-doped porous carbon prepared in Example 1; Figure 4 CO2 adsorption isotherm of nitrogen-doped porous carbon prepared in Example 1 at 0°C; Figure 5 CO2 and N2 adsorption isotherms at 25 °C for nitrogen-doped porous carbon prepared in Example 1; Figure 6 The selectivity curve of nitrogen-doped porous carbon prepared in Example 1 calculated by ideal adsorption solution theory (IAST) at 25 °C and CO2 / N2 (20:80) mixed gas; Figure 7 CO2 adsorption isotherm of nitrogen-doped porous carbon prepared in Example 1 at 25 °C for 5 consecutive cycles. DETAILED DESCRIPTION Example 1

[0013] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 1:1, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 700°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 700°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.45 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 1464 m 2 / g, total pore volume 0.81cm 3 / g, the average pore size is 2.23nm, the nitrogen content is 1.26wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 6.72mmol / g. Example 2

[0014] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 1:1, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 500°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.62 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 413 m 2 / g, total pore volume 0.24cm 3 / g, the average pore size is 2.34nm, the nitrogen content is 5.07wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 3.77mmol / g. Example 3

[0015] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 1:1, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 600°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 600°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.49 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 835 m 2 / g, total pore volume 0.48cm 3 / g, the average pore size is 2.28nm, the nitrogen content is 2.86wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 6.66mmol / g. Example 4

[0016] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 1:1, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 800°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.31 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 2348 m 2 / g, total pore volume 1.13cm 3 / g, the average pore size is 1.92nm, the nitrogen content is 0.15wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 5.58mmol / g. Example 5

[0017] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 1:2, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 700°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 700°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.34 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 1476 m 2 / g, total pore volume 0.83cm 3 / g, the average pore size is 2.24nm, the nitrogen content is 0.54wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 6.34mmol / g. Example 6

[0018] The dried Salix psammophila was crushed and sieved with a grinder to obtain Salix psammophila powder with a particle size less than 100 mesh. 3g Salix psammophila powder and 0.3g polyethyleneimine were weighed separately and placed in a 100mL polytetrafluoroethylene hydrothermal reactor, 55mL deionized water was added, and stirred at room temperature for 2h. The reactor was placed in a constant temperature forced air drying oven. When the temperature was raised to 220°C, the hydrothermal reaction was carried out under this temperature condition for 24h. The sample was taken out from the hydrothermal reactor that was naturally cooled to room temperature, and washed with 20ml of deionized water each time for a total of 3 times, and then washed once with 20ml of anhydrous ethanol. After natural drying for 2 hours, it was dried at 100°C for 3 hours to obtain nitrogen-doped hydrated carbon; The nitrogen-doped hydrated carbon and potassium hydroxide were mixed in a mass ratio of 2:1, ground and placed in a magnetic boat, which was placed in a tube furnace and heated to 700°C at a heating rate of 5°C / min under a N2 atmosphere, maintained at 700°C for 2 hours, and naturally cooled to room temperature before taking out the sample, soaking it in a 1 mol / L hydrochloric acid solution for 1 hour, filtering and recovering the hydrochloric acid solution, and then washing it with deionized water until it was neutral, and drying it at 100°C for 6 hours to obtain 0.46 g of nitrogen-doped porous carbon; The specific surface area of ​​the nitrogen-doped porous carbon prepared in this example is 1237 m 2 / g, total pore volume 0.74cm 3 / g, the average pore size is 2.39nm, the nitrogen content is 1.63wt%, and the CO2 adsorption capacity at 0℃ and 1bar is 6.70mmol / g.

[0019] Operation method of CO2 adsorption performance test experiment: The carbon dioxide adsorption isotherm of the embodiment at 0°C was measured by the volumetric method. The CO2 / N2 selective adsorption was calculated at 25°C, using the ideal adsorption solution theory (IAST), assuming that a mixture of 20% CO2 and 80% N2 was adsorbed; CO2 adsorption and desorption were repeated five times at 25°C, and the CO2 adsorption stability was calculated; Comparison test results: The preparation of the comparative sample differs from that of Example 1 only in that no activator, potassium hydroxide, is added during activation. The specific surface area of ​​the nitrogen-doped porous carbon of the comparative sample is 187 m 2 / g, total pore volume 0.14cm 3 / g, average pore size is 3.02nm, nitrogen content is 1.73wt%. CO2 adsorption capacity at 0℃ and 1bar is 2.25mmol / g; Compared with Example 1, the nitrogen-doped porous carbon in the comparative sample has a lower specific surface area, less pore structure, and poor CO2 adsorption effect.

Claims

1. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: When preparing nitrogen-doped hydrated carbon, the mass ratio of polyethyleneimine to Salix psammophila powder was 1:

10.

2. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: When preparing nitrogen-doped porous carbon, the mass ratio of nitrogen-doped hydrated carbon to potassium hydroxide is 1:

1.

3. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: The conditions for preparing nitrogen-doped hydrated carbon are: hydrothermal reaction time at 220° C. for 24 hours.

4. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: The conditions for preparing nitrogen-doped porous carbon are: from 25°C to 700°C, the heating rate is 5°C / min, and activation is carried out at 700°C in a nitrogen atmosphere for 2 hours.

5. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: The prepared nitrogen-doped porous carbon has a specific surface area of ​​1464m2 / g, an average pore size of 2.23nm, a nitrogen content of 1.26wt%, and a CO2 adsorption capacity of 6.72mmol / g at 0℃ and 1bar.

6. A method for preparing a nitrogen-doped porous carbon carbon dioxide adsorbent using Salix psammophila, characterized in that: The nitrogen-doped porous carbon prepared by the present invention is used as a carbon dioxide adsorbent.

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