A biomass aerogel solid adsorbent, its preparation method and application

Abstract

The present invention provides a biomass aerogel solid adsorbent, a preparation method thereof and an application. The preparation method of the present invention comprises the steps carried out in the following order: S1: Soaking a woody material in a sodium bicarbonate solution, followed by stirring, ultrasonic oscillation, washing and drying to obtain a biomass modified skeleton; S2: Soaking the biomass modified skeleton in a mixed solution containing tris(hydroxymethyl)aminomethane and a water retaining agent, and draining after soaking; S3: Soaking the biomass modified skeleton in a mixed solution containing acid-soluble chitosan and acetic acid, draining after soaking and drying under vacuum to obtain the biomass aerogel solid adsorbent. The biomass aerogel solid adsorbent of the present invention has a large specific surface area and good air permeability, has low wind resistance, small pressure loss and low energy consumption when adsorbing acidic gases such as carbon dioxide, and has a high capture rate for acidic gases.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and particularly to a biomass aerogel solid adsorbent, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of industrialization, a large amount of greenhouse gases such as carbon dioxide are emitted after the use of fossil fuels. Excessive greenhouse gases intercept the long-wave radiation energy emitted from the earth's surface, forming the greenhouse effect and then causing global warming. Based on this, carbon capture, storage, and utilization technologies are being vigorously developed, and it is of great significance to treat carbon dioxide from thermal power plants at low cost.

[0003] Carbon capture technologies mainly include chemical absorption method, physical absorption method, membrane separation method, etc. The chemical absorption method is to use a chemical absorbent to react with carbon dioxide in flue gas to form unstable salts, and then decompose these salts by heating or reducing pressure to release and collect carbon dioxide. Common absorbents include hot potassium carbonate, ammonia water, alkanolamine, etc. The physical absorption method is to capture carbon dioxide by using temperature swing or pressure swing adsorption. Common physical adsorbents include activated carbon, zeolite molecular sieve, silica gel, etc. The membrane separation method is to use the different gas molecule permeability of the membrane to achieve the purpose of separating and collecting carbon dioxide. However, the existing carbon capture adsorbents have a small specific surface area and poor air permeability, resulting in large wind resistance and energy consumption when adsorbing carbon dioxide, which is not conducive to improving the carbon dioxide capture rate.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a biomass aerogel solid adsorbent, a preparation method thereof, and an application thereof. The biomass aerogel solid adsorbent has a large specific surface area and good air permeability, has low wind resistance, small pressure loss, and low energy consumption when adsorbing acidic gases such as carbon dioxide, and has a high capture rate for acidic gases.

[0006] The present invention provides a preparation method of a biomass aerogel solid adsorbent, which includes the following steps carried out in sequence:

[0007] S1: Immerse the woody material in a sodium bicarbonate solution, and after stirring, ultrasonic oscillation, washing, and drying, obtain a biomass modified skeleton;

[0008] S2: Immerse the biomass modified skeleton in a mixed solution containing tris(hydroxymethyl)aminomethane (abbreviated as TRIS) and a water retaining agent, and drain after immersion;

[0009] S3: Immerse the biomass modified skeleton in a mixed solution containing acid-soluble chitosan and acetic acid, drain after immersion, and perform vacuum drying to obtain a biomass aerogel solid adsorbent.

[0010] In step S1, natural sunken wood is used as the wood material; the mass content of the sodium bicarbonate solution is 2-4%, and the soaking time is 2-4 h; the drying temperature is 160-200 °C, and the drying time is 8-12 h.

[0011] Soaking the wood material with the sodium bicarbonate solution can neutralize the acidic substances in the wood material; in particular, after sodium bicarbonate penetrates into the wood material, carbon dioxide can be released during the subsequent heating and drying process, thereby completely opening the internal vein channels of the wood material, significantly increasing the specific surface area and greatly enhancing the air permeability, which is beneficial to reducing the wind resistance during the process of adsorbing acidic gases such as carbon dioxide, and thus improving the capture rate of acidic gases.

[0012] In step S2, the mass content of tris(hydroxymethyl)aminomethane in the mixed solution is 8-12%, and the mass content of the water retention agent is 1-3%; the water retention agent is selected from at least one of calcium chloride and magnesium chloride; the soaking time is 6-10 h.

[0013] When soaking the biomass modified skeleton with the mixed solution containing tris(hydroxymethyl)aminomethane and the water retention agent, the water retention agent with an appropriate concentration has a certain hygroscopicity, which can keep tris(hydroxymethyl)aminomethane in a liquid-solid intermediate state all the time. In this state, the amino groups in tris(hydroxymethyl)aminomethane are completely activated, and its excellent adsorption capacity is maximally exerted.

[0014] In step S3, the mass content of acid-soluble chitosan in the mixed solution is 1-3%, and the mass content of acetic acid is 0.05-0.15%; the soaking time is 2-6 h; the vacuum drying temperature is 110-130 °C, and the vacuum drying time is 10-14 h.

[0015] Acid-soluble chitosan has good biocompatibility and biodegradability, carries a large number of active amino groups by itself, has good film-forming properties, and can retain the amino components to the greatest extent; at the same time, under the action of a small amount of acetic acid, the amino groups of acid-soluble chitosan are fully protonated, and acidic gases are captured to the greatest extent. In particular, after coating the above-mentioned biomass modified skeleton with acid-soluble chitosan, a viscous film can be formed by simple heating, and then the effective functional groups and functional materials can be firmly locked. In addition, vacuum drying can retain the structure of the biomass modified skeleton to the greatest extent, giving play to its advantages such as being porous, having a large specific surface area, and good air permeability, and having advantages such as low wind resistance, small pressure loss, and low energy consumption when applied to directly capture carbon dioxide in the air.

[0016] The present invention also provides a biomass aerogel solid adsorbent prepared according to the above preparation method.

[0017] The present invention also provides the application of the above-mentioned biomass aerogel solid adsorbent in adsorbing acidic gases; there is no strict limitation on the acidic gas, for example, it can be gases such as carbon dioxide and sulfur dioxide.

[0018] The biomass aerogel solid adsorbent of the present invention has excellent air permeability, can be combined into multiple units for use according to actual needs, is applicable to a wide range of carbon dioxide capture scenarios, and can be heated and recycled at 100 °C for repeated use; at the same time, the biomass aerogel solid adsorbent is a biomass carbon-based material, has flammable properties and calorific value, and can also be directly co-fired in a boiler.

[0019] The implementation of the present invention has at least the following advantages:

[0020] 1. The present invention uses wood materials as raw materials, which are inexpensive, have a large density, no secondary pollution, are environmentally friendly, and are conducive to preparing a solid adsorbent for quickly, efficiently, and sustainably capturing carbon dioxide from the air through subsequent modification;

[0021] 2. The present invention treats the wood materials with a sodium bicarbonate solution, which can completely open the internal vein channels of the wood materials, improve the specific surface area and air permeability of the wood materials, and is conducive to reducing the wind resistance during the adsorption of acidic gases such as carbon dioxide, thereby improving the capture rate of acidic gases;

[0022] 3. The present invention treats the wood materials with a mixed solution containing tris (hydroxymethyl) aminomethane and a water retaining agent, which can completely activate the amino groups in the tris (hydroxymethyl) aminomethane, and then maximize its excellent adsorption capacity;

[0023] 4. The present invention treats the wood materials with a mixed solution containing acid-soluble chitosan and acetic acid. Not only can the amino groups of the acid-soluble chitosan be fully protonated to capture acidic gases to the greatest extent, but it is also conducive to forming a viscous film on the surface of the material to firmly lock the effective functional groups and functional materials, ensuring the adsorption performance of the modified material;

[0024] 5. The preparation method of the present invention is simple. By two-stage drying, the specific surface area of the material is increased, and at the same time, the dredged gas channels are completely retained. The prepared biomass aerogel solid adsorbent has a large specific surface area and good air permeability, low wind resistance, small pressure loss, low energy consumption when adsorbing acidic gases such as carbon dioxide, and a high capture rate of acidic gases;

[0025] 6. The application cost of the biomass aerogel solid adsorbent of the present invention is low, the loss is small, the maintenance cost is low, and the application is not restricted by scenarios. A single biomass aerogel solid adsorbent module can be aggregated into multiple biomass aerogel solid adsorbent modules for use to adapt to various scenarios. The whole process is green and environmentally friendly, pollution-free, and can be applied to gas environments within 120 °C. In addition, it can be heated and recycled at 80 - 100 °C for repeated use, with the advantages of low cost, simple operation, rapid effect, environmental friendliness, and no need for maintenance. Description of the Drawings

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic structural diagram of the carbon dioxide capture device in Test Example 1. Specific embodiments

[0028] It should be noted that the following detailed description is illustrative and aims to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0031] Example 1

[0032] The preparation method of the biomass aerogel solid adsorbent in this embodiment is as follows:

[0033] 1) Prepare the biomass modified framework

[0034] After grinding and cutting the natural sunken wood into sunken wood segments with a diameter of 10.8 cm and a length of 20 cm, soak them in a sodium bicarbonate solution with a mass content of 3% for 3 hours; after the sunken wood segments are infiltrated with sodium bicarbonate, stir and ultrasonically oscillate at a suitable speed, wash the surface impurities, and then put them into a blast drying oven, heat at 180 °C for 10 hours, and then naturally cool to room temperature to obtain the biomass modified framework.

[0035] 2) The first soaking treatment

[0036] Stir and dissolve tris(hydroxymethyl)aminomethane and food-grade magnesium chloride in water to obtain a first mixed solution; control the mass content of tris(hydroxymethyl)aminomethane in the first mixed solution to be 10%, and the mass content of magnesium chloride to be 2%.

[0037] Immerse the biomass modified skeleton in the above-mentioned first mixed solution. After soaking for 8 h, drain it by blowing air.

[0038] 3) Second soaking treatment

[0039] Dissolve acid-soluble chitosan in an acetic acid solution with a mass content of 0.1%, stir well to obtain a second mixed solution; control the mass content of acid-soluble chitosan in the second mixed solution to be 2%.

[0040] Immerse the biomass modified skeleton after the first soaking treatment in step 2) in the above-mentioned second mixed solution, soak for 4 h, drain, and then vacuum dry at 120 °C for 12 h to obtain the biomass aerogel solid adsorbent.

[0041] Example 2

[0042] The preparation method of the biomass aerogel solid adsorbent in this example is as follows:

[0043] 1) Preparation of biomass modified skeleton

[0044] After polishing and cutting natural sunken wood into sunken wood segments with a diameter of 10.8 cm and a length of 20 cm, soak them in a sodium bicarbonate solution with a mass content of 2% for 4 h; after the sunken wood segments are infiltrated with sodium bicarbonate, stir and ultrasonically oscillate at an appropriate speed to wash the surface impurities, and then put them into a blast drying oven, heat at 160 °C for 12 h, and then naturally cool to room temperature to obtain the biomass modified skeleton.

[0045] 2) First soaking treatment

[0046] Stir and dissolve tris(hydroxymethyl)aminomethane and food-grade magnesium chloride in water to obtain a first mixed solution; control the mass content of tris(hydroxymethyl)aminomethane in the first mixed solution to be 8%, and the mass content of magnesium chloride to be 1%.

[0047] Immerse the biomass modified skeleton in the above-mentioned first mixed solution. After soaking for 10 h, drain it by blowing air.

[0048] 3) Second soaking treatment

[0049] Dissolve acid-soluble chitosan in an acetic acid solution with a mass content of 0.05%, stir well to obtain a second mixed solution; control the mass content of acid-soluble chitosan in the second mixed solution to be 1%.

[0050] Immerse the biomass modified framework after the first soaking treatment in step 2) in the above-mentioned second mixed solution for 2 h, drain it, and then dry it in vacuum at 110 °C for 14 h to obtain the biomass aerogel solid adsorbent.

[0051] Example 3

[0052] The preparation method of the biomass aerogel solid adsorbent in this example is as follows:

[0053] 1) Prepare the biomass modified framework

[0054] After polishing and cutting natural sunken wood into sunken wood segments with a diameter of 10.8 cm and a length of 20 cm, immerse them in a sodium bicarbonate solution with a mass content of 4% for 2 h; after the sunken wood segments are infiltrated with sodium bicarbonate, stir and ultrasonically oscillate at an appropriate speed to wash the surface impurities, and then put them into a blast drying oven, heat at 200 °C for 8 h, and then naturally cool to room temperature to obtain the biomass modified framework.

[0055] 2) First soaking treatment

[0056] Fully stir and dissolve tris(hydroxymethyl)aminomethane and calcium chloride in water to prepare the first mixed solution; control the mass content of tris(hydroxymethyl)aminomethane in the first mixed solution to be 12% and the mass content of magnesium chloride to be 3%.

[0057] Immerse the biomass modified framework in step 1) in the above-mentioned first mixed solution for 6 h, and then drain it by blowing air.

[0058] 3) Second soaking treatment

[0059] Dissolve acid-soluble chitosan in an acetic acid solution with a mass content of 0.15%, and stir well to prepare the second mixed solution; control the mass content of acid-soluble chitosan in the second mixed solution to be 3%.

[0060] Immerse the biomass modified framework after the first soaking treatment in step 2) in the above-mentioned second mixed solution for 6 h, drain it, and then dry it in vacuum at 130 °C for 10 h to obtain the biomass aerogel solid adsorbent.

[0061] Control Example 1

[0062] Except that food-grade magnesium chloride is not added when preparing the first mixed solution, the rest is basically the same as in Example 1.

[0063] Control Example 2

[0064] Except that when preparing the second mixed solution, acid-soluble chitosan is dissolved in water, the rest is basically the same as in Example 1.

[0065] Control Example 3

[0066] Except for not performing the first soaking treatment, the rest is basically the same as in Example 1.

[0067] Comparative Example 4

[0068] Except for not performing the second soaking treatment, and after the first soaking, draining by blowing air, and vacuum drying at 120 °C for 12 h, the rest is basically the same as in Example 1.

[0069] Test Example 1

[0070] Combined Figure 1 As shown, the process of capturing carbon dioxide in the air is as follows:

[0071] Cut a 11 cm inner diameter PE hose to about 2 m. Insert one end (A port) into the well-sealed acrylic a chamber. The acrylic a chamber has small holes on all four sides for air permeability (for stable flow). A vacuum pump is equipped in the acrylic a chamber. The external connecting tower head of the vacuum pump is hermetically connected to the A port by extrusion. A carbon dioxide detector (dimension in ppm) is also configured in the acrylic a chamber. The other end (B port) is inserted into a single biomass aerogel solid adsorbent module prepared from the biomass aerogel solid adsorbents of Examples 1-4 and Comparative Examples 1-4, and then inserted into the well-sealed acrylic b chamber. The same carbon dioxide detector as in the acrylic a chamber is configured in the acrylic b chamber. Turn on the vacuum pump, and the gas flow rate is about 7.2 m 3 / h. After the data of the two carbon dioxide detectors are stable, count the data before and after the treatment of capturing carbon dioxide in the air. The results are shown in Table 1.

[0072] The recovery method of the biomass aerogel solid adsorbent is as follows:

[0073] Intuitively feel the adsorption saturation state of the biomass aerogel solid adsorbent through the carbon dioxide detector in the acrylic b chamber. When the data of the carbon dioxide detector rises significantly, stop the test, take out the biomass aerogel solid adsorbent and heat it in a blast heating oven at 100 °C. The outlet of the heating oven can be externally connected to a recovery bag, and a carbon dioxide detector is configured in the pipeline. When the data is stable, it indicates the end of the recovery of the adsorbent, which can be reused, and the captured carbon dioxide can be recovered.

[0074] Test Example 2

[0075] Except that the other end (B port) is inserted into two biomass aerogel solid adsorbent modules prepared from the biomass aerogel solid adsorbent of Example 1, the rest is the same as in Example 1.

[0076] Table 1 shows the concentration changes of the biomass aerogel solid adsorbent module before and after carbon dioxide capture

[0077] Solid adsorbent Number of modules / piece <![CDATA[a cabin CO 2 Concentration / ppm]]> <![CDATA[b cabin CO 2 Concentration / ppm]]> Example 1 1 550 350 Example 2 1 550 367 Example 3 1 549 345 Control Example 1 1 551 436 Control Example 2 1 550 394 Control Example 3 1 549 476 Control Example 4 1 553 408 Example 1 2 554 221

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a biomass aerogel solid adsorbent, characterized in that: The steps include the following steps in order: S1: soaking the wood material in a sodium bicarbonate solution, stirring, ultrasonically oscillating, washing, and drying to obtain a biomass modified skeleton; S2: soaking the biomass modified skeleton in a mixed solution containing tris(hydroxymethyl)aminomethane and a water retaining agent, and draining after soaking; S3: soaking the biomass modified skeleton in a mixed solution containing acid-soluble chitosan and acetic acid, draining and vacuum drying after soaking to obtain a biomass aerogel solid adsorbent.

2. The preparation method according to claim 1, characterized in that: The wood material is natural drifting wood; the mass content of the sodium bicarbonate solution is 2-4%.

3. The preparation method according to claim 1, characterized in that: In step S1, the soaking time is 2-4 hours; the drying temperature is 160-200° C., and the drying time is 8-12 hours.

4. The preparation method according to claim 1, characterized in that: In step S2, the mass content of tris(hydroxymethyl)aminomethane in the mixed solution is 8-12%, and the mass content of the water retaining agent is 1-3%.

5. The preparation method according to claim 1, characterized in that: The water retaining agent is selected from at least one of calcium chloride and magnesium chloride.

6. The preparation method according to claim 1, characterized in that: In step S2, the soaking time is 6-10 hours.

7. The preparation method according to claim 1, characterized in that: In step S3, the mass content of acid-soluble chitosan in the mixed solution is 1-3%, and the mass content of acetic acid is 0.05-0.15%.

8. The preparation method according to claim 1, characterized in that: In step S3, the soaking time is 2-6 hours; the vacuum drying temperature is 110-130° C., and the vacuum drying time is 10-14 hours.

9. A biomass aerogel solid adsorbent, characterized in that: Prepared according to any one of the preparation methods of claims 1-8.

10. Use of the biomass aerogel solid adsorbent according to claim 9 in adsorbing acidic gases.

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