Green nanofluid absorbent for photo-thermal carbon capture and preparation method thereof

Abstract

The invention discloses a green nanofluid absorbent for photo-thermal carbon capture and a preparation method of the green nanofluid absorbent, and belongs to the technical field of functional materials. The preparation method comprises the following steps: dispersing carboxyl carbon nanotubes in a dispersing agent, adjusting to alkalinity, adding tetraethyl silicate under high-speed stirring of 1000-2000r / min, adjusting the pH value of the system to 7-7.5 after reaction, centrifuging, and washing the precipitate to obtain a black gel substance; drying and grinding the black gelatinous substance to obtain carboxyl carbon nano tube and silicon dioxide compounded nano particles; and jointly dispersing the carboxyl carbon nanotube and silicon dioxide compounded nanoparticles and a surfactant in a deep eutectic solvent to obtain the green nanofluid absorbent for photo-thermal carbon capture. The prepared green nanofluid absorbent for photo-thermal carbon capture has high photo-thermal conversion efficiency, high carbon capture capability and high stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and particularly relates to a green nanofluid absorbent for photothermal carbon capture and a preparation method thereof. Background Art

[0002] Deep eutectic solvents are environmentally friendly and recyclable green solvents, which have great potential in the field of carbon capture and have gradually become a research hotspot in the fields of chemistry, physics, materials, heat transfer, etc. Carbon nanotubes are nanomaterials with a nanoscale diameter, having characteristics such as high thermal conductivity and high photothermal conversion efficiency. Using deep eutectic solvents as the base fluid of nanofluids has always been a research hotspot for nanofluid researchers. However, in the current nanofluid photothermal carbon capture technology, many problems are faced. For example, if the particle content is too small, the mass transfer effect is poor and the increase is not obvious; if there are too many particles, it will lead to obvious aggregation and rapid sedimentation, and then lose the properties of nanofluids; ordinary nanofluids cannot utilize photothermal energy during the photothermal carbon dioxide absorption process; the stability is too poor.

[0003] Carbon nanotubes have good photothermal conversion efficiency, but their stability in deep eutectic solvents is poor. There is no research in this field on how to obtain a stable green nanofluid that can effectively utilize photothermal energy to meet the requirements of carbon capture. Summary of the Invention

[0004] The purpose of the present invention is to provide a green nanofluid absorbent for photothermal carbon capture and a preparation method thereof. By compounding carboxylated carbon nanotubes with silica and then dispersing them in a deep eutectic solvent, a green nanofluid absorbent with high photothermal conversion efficiency, high carbon capture ability, and high stability is obtained.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention: provides a preparation method of a green nanofluid absorbent for photothermal carbon capture, including the following steps:

[0007] Disperse carboxylated carbon nanotubes in a dispersant, adjust to alkaline, and then add tetraethyl orthosilicate under high-speed stirring at 1000 - 2000 r / min. After the reaction, adjust the pH value of the system to 7 - 7.5, centrifuge, and wash the precipitate to obtain a black gel-like substance. After drying and grinding the black gel-like substance, carboxylated carbon nanotubes and silica composite (CNTs@SiO 2 ) nanoparticles are obtained; disperse the carboxylated carbon nanotubes and silica composite nanoparticles and a surfactant in a deep eutectic solvent together to obtain the green nanofluid absorbent for photothermal carbon capture.

[0008] In the present invention, carboxylated carbon nanotubes are uniformly dispersed in a mixed solution of isopropanol and deionized water. By creating an alkaline environment, the hydrolysis and condensation of tetraethyl orthosilicate are accelerated. During this reaction process, tetraethyl orthosilicate first generates silicic acid and siloxane in an alkaline environment. The silicic acids condense with each other, and the oligomers further polymerize to form long chains and extend into a three-dimensional spatial framework structure. At this time, the dispersed carboxylated carbon nanotubes provide attachment sites for the condensation of silicic acid. Under high-speed stirring, the spherical morphology and small particle size of the formed silica can be maintained. Further dispersing in a deep eutectic solvent can obtain a green nanofluid absorbent with high photothermal conversion efficiency, high carbon capture ability, and high stability.

[0009] Preferably, the diameter of the carboxylated carbon nanotubes is 8 - 15 nm, and the length does not exceed 30 μm.

[0010] Preferably, the dispersant is obtained by mixing isopropanol and water.

[0011] Preferably, the dosage ratio of the carboxylated carbon nanotubes to the dispersant is 0.4 - 0.6 g:50 mL.

[0012] Preferably, the mass ratio of tetraethyl orthosilicate to the carboxylated carbon nanotubes is 3 - 5:0.4 - 0.6.

[0013] Preferably, adjusting to alkaline means using ammonia water to adjust the pH value to 11.5 - 12.

[0014] Preferably, the tetraethyl orthosilicate is added in 4 - 5 times, and the addition time for each time is 1 - 2 min.

[0015] Preferably, the reaction temperature is 45 - 55 °C, and the reaction time is 12 - 16 h.

[0016] Preferably, the mass ratio of the nanoparticles of the composite of carboxylated carbon nanotubes and silica to the deep eutectic solvent is 0.25 - 1.25:10000.

[0017] Preferably, the mass ratio of the surfactant to the deep eutectic solvent is 1 - 2:1000.

[0018] Optionally, the surfactant is sodium dodecyl sulfate.

[0019] Preferably, the hydrogen bond acceptor of the deep eutectic solvent is choline chloride, and the hydrogen bond donors are urea and / or ethanolamine.

[0020] The second technical solution of the present invention: Provide a green nanofluid absorbent for photothermal carbon capture prepared by the preparation method of the green nanofluid absorbent for photothermal carbon capture according to the above.

[0021] The third technical solution of the present invention: Provide an application of the above-mentioned green nanofluid absorbent for photothermal carbon capture in photothermal carbon capture.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] By forming regularly shaped silica spheres on the surface of carboxyl carbon nanotubes and further dispersing them in a deep eutectic solvent, the present invention obtains a green nanofluid absorbent for photothermal carbon capture. The provided preparation steps are simple, and the reagents used are green and pollution-free.

[0024] The green nanofluid absorbent for photothermal carbon capture provided by the present invention has high photothermal conversion efficiency, high carbon capture ability, and high stability. Description of the Drawings

[0025] Figure 1 It is the preparation flow chart of CNTs@SiO 2 / DES nanofluid in Example 1 of the present invention.

[0026] Figure 2 It is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Example 1.

[0027] Figure 3 It is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Comparative Example 1 and Comparative Example 2. Among them, (a) is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Comparative Example 1, and (b) is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Comparative Example 2.

[0028] Figure 4 It is the macroscopic image of CNTs@SiO 2 / DES nanofluids with different concentrations prepared according to the method of Example 1 after being placed for 15 days. Among them, (a) is the macroscopic image of the CNTs@SiO 2 / DES nanofluid with a concentration of 0-100 ppm, and (b) is the macroscopic image of the CNTs@SiO 2 / DES nanofluid with a concentration of 100-500 ppm.

[0029] Figure 5 It is the transmittance diagram of CNTs@SiO 2 / DES nanofluids with different concentrations prepared according to the method of Example 1.

[0030] Figure 6 It is the CNTs@SiO of 0 ppm and 150 ppm prepared according to the method of Example 1. 2CO₂ absorption diagram of the / DES nanofluid.

[0031] Figure 7 CNTs@SiO of 0 ppm and 150 ppm prepared by the method of Example 1 2 CO₂ desorption diagram of the / DES nanofluid after absorbing CO₂ under light conditions. Detailed implementation manners

[0032] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be regarded as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention.

[0033] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0035] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0036] Unless otherwise specified, "room temperature" as used in the present invention refers to a temperature of 20 ± 5 °C.

[0037] Unless otherwise specified, the raw materials used in the present invention are all commercially available products well-known to those skilled in the art.

[0038] The diameter of the carboxylated carbon nanotubes used in the examples and comparative examples of the present invention is 8 - 15 nm, and the length does not exceed 30 μm.

[0039] The concentration of ammonia water used in the examples and comparative examples of the present invention is 26 - 28 wt.%.

[0040] The deep eutectic solvent used in the examples and comparative examples of the present invention is obtained by mixing choline chloride and urea in a molar ratio of 1:2 and stirring in a water bath at 85 °C until clear.

[0041] Example 1

[0042] (1) At room temperature, add a mixed solution of 50 mL of isopropanol and deionized water (containing 0.462 mol of isopropanol and 0.82 mol of deionized water) to a 50 mL beaker. Then add 0.5 g of carboxyl carbon nanotubes. After magnetic stirring at room temperature for 10 min, add 3.5 g of ammonia water to the solution to adjust the pH value to 11.67, and then ultrasonicate for 30 min to achieve uniform dispersion.

[0043] (2) Under the condition of a 50 °C water bath and a magnetic stirring speed of 1400 r / min, use a 2.5 mL syringe needle to inject 4 g of tetraethyl orthosilicate into the stirred dispersion in 4 portions, with each injection time being 1 min. After the injection is completed, continue the reaction for 14 h. Add deionized water to make the pH value reach 7.5, then centrifuge for the first time. After centrifugation, add deionized water again and centrifuge, repeat three times, and then centrifuge twice with absolute ethanol. Dry at 75 °C for 24 h, and after grinding, CNTs@SiO 2 nanoparticles can be obtained.

[0044] (3) Add 5 mg of CNTs@SiO 2 nanoparticles and 50 mg of sodium dodecyl sulfate to 50 g of deep eutectic solvent, and ultrasonicate in an ultrasonic cell disruptor with a power of 325 W for 90 min to obtain CNTs@SiO 2 / DES nanofluid.

[0045] The flow chart for preparing CNTs@SiO 2 / DES nanofluid in Example 1 is shown in Figure 1 .

[0046] The SEM image of the CNTs@SiO 2 nanoparticles prepared in Example 1 is shown in Figure 2 , and it can be seen from Figure 2 that most of the prepared silica nanoparticles are regular spherical particles, without fragmentation or large-scale agglomeration.

[0047] Example 2

[0048] Based on Example 1, change the dropping amount of ammonia water.

[0049] (1) At room temperature, add a mixed solution of 50 mL of isopropanol and deionized water (containing 0.462 mol of isopropanol and 0.82 mol of deionized water) to a 50 mL beaker. Then add 0.5 g of carboxyl carbon nanotubes. After magnetic stirring at room temperature for 10 min, add 3.0 g of ammonia water to the solution to adjust the pH value to 11.5, and then ultrasonicate for 30 min to achieve uniform dispersion.

[0050] (2) Under the condition of a 50 °C water bath with a magnetic stirring speed of 1400 r / min, using a 2.5 mL syringe needle, 4 g of tetraethyl orthosilicate was injected into the stirred dispersion in 4 portions, with each injection time being 1 min. After the injection, the reaction continued for 14 h. Deionized water was added to adjust the pH value to 7.5, and then the first centrifugation was carried out. After centrifugation, deionized water was added again for centrifugation, and this was repeated three times. Then, centrifugation was carried out twice with absolute ethanol, and it was dried at 75 °C for 24 h. After grinding, CNTs@SiO 2 nanoparticles can be obtained.

[0051] (3) 5 mg of CNTs@SiO 2 nanoparticles and 50 mg of sodium dodecyl sulfate were added to 50 g of a deep eutectic solvent, and ultrasonic treatment was carried out in an ultrasonic cell disruptor with a power of 325 W for 90 min to obtain CNTs@SiO 2 / DES nanofluid.

[0052] Example 3

[0053] Based on Example 1, the addition amount of the silicon source was changed.

[0054] (1) At room temperature, 50 mL of a mixed solution of isopropanol and deionized water (containing 0.462 mol of isopropanol and 0.82 mol of deionized water) was added to a 50 mL beaker, and then 0.5 g of carboxyl carbon nanotubes was added. After magnetic stirring at room temperature for 10 min, 3.5 g of ammonia water was added dropwise to the solution to adjust the pH value to 11.67, and then ultrasonic treatment was carried out for 30 min to achieve uniform dispersion.

[0055] (2) Under the condition of a 50 °C water bath with a magnetic stirring speed of 1400 r / min, using a 2.5 mL syringe needle, 3 g of tetraethyl orthosilicate was injected into the stirred dispersion in 4 portions, with each injection time being 1 min. After the injection, the reaction continued for 14 h. Deionized water was added to adjust the pH value to 7.5, and then the first centrifugation was carried out. After centrifugation, deionized water was added again for centrifugation, and this was repeated three times. Then, centrifugation was carried out twice with absolute ethanol, and it was dried at 75 °C for 24 h. After grinding, CNTs@SiO 2 nanoparticles can be obtained.

[0056] (3) 5 mg of CNTs@SiO 2 nanoparticles and 50 mg of sodium dodecyl sulfate were added to 50 g of a deep eutectic solvent, and ultrasonic treatment was carried out in an ultrasonic cell disruptor with a power of 325 W for 90 min to obtain CNTs@SiO 2 / DES nanofluid.

[0057] Comparative Example 1

[0058] Compared with Example 1, the only difference is that the dosage of ammonia water in step (1) is adjusted to 2 g, and the final pH value is 11.2.

[0059] Comparative Example 2

[0060] Compared with Example 1, the only difference is that the stirring speed in step (2) is adjusted to 800 r / min.

[0061] The SEM images of the CNTs@SiO2 nanoparticles prepared in Comparative Example 1 and Comparative Example 2 are shown in Figure 3 , where (a) is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Comparative Example 1, and (b) is the SEM image of the CNTs@SiO 2 nanoparticles prepared in Comparative Example 2.

[0062] It can be seen from Figure 3 that although the morphology of the silica nanoparticles attached to the carbon nanotubes is still nearly spherical, small-scale agglomeration has occurred.

[0063] CNTs@SiO 2 / DES nanofluids with different concentrations were prepared according to the method of Example 1. After standing for 15 days, the macroscopic images are shown in Figure 4 , where (a) is the macroscopic image of the CNTs@SiO 2 / DES nanofluids with concentrations of 0-100 ppm (from left to right are 0 ppm, 20 ppm, 40 ppm, 60 ppm, 80 ppm, and 100 ppm), and (b) is the macroscopic image of the CNTs@SiO 2 / DES nanofluids with concentrations of 100-500 ppm (from left to right are 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm).

[0064] It can be seen from Figure 4 that the CNTs@SiO 2 / DES nanofluids prepared in the present invention do not show precipitation after long-term standing and have high stability.

[0065] Furthermore, the transmittance of the prepared CNTs@SiO 2 / DES nanofluids with concentrations of 100-500 ppm was measured, and the results are shown in Figure 5 .

[0066] It can be seen from Figure 5 that for the prepared CNTs@SiO 2 / DES nanofluids, as the concentration of the nanoparticles in them increases, the light transmittance gradually decreases, and when it reaches above 400 ppm, the light transmittance is basically 0.

[0067] Furthermore, the carbon dioxide absorption performance and desorption performance under light illumination conditions of the prepared CNTs@SiO 2 / DES nanofluids were preliminarily tested (the selected concentrations were 0 ppm and 150 ppm).

[0068] Method: The CNTs@SiO 2 / DES nanofluid was added to the reactor, and a mixed gas of carbon dioxide and nitrogen was introduced. The inlet carbon dioxide concentration was 20%, and the reaction duration was about 3 h. The infrared flue gas analyzer (MRU, Germany) was used to record the outlet carbon dioxide concentration, and the total carbon dioxide absorption amount was calculated.

[0069] After absorption, the CNTs@SiO 2 / DES nanofluid saturated absorbent was desorbed under simulated light illumination conditions. Using a xenon lamp (Zhongjiao Jinyuan, China) as the light source, its carbon dioxide desorption rate and desorption amount at a light power density of 1000 mW / cm 2 were measured.

[0070] Figure 6 Carbon dioxide absorption diagrams of CNTs@SiO 2 / DES nanofluids with concentrations of 0 ppm and 150 ppm.

[0071] Figure 7 Carbon dioxide desorption diagrams of CNTs@SiO 2 / DES nanofluids with concentrations of 0 ppm and 150 ppm after absorbing carbon dioxide under light illumination conditions.

[0072] Figure 6 and Figure 7 The results show that whether during the absorption process or the light illumination desorption process, the CNTs@SiO 2 nanoparticles have a positive impact. For the absorption process, within the same time, the CNTs@SiO 2 nanoparticles with 150 ppm added to the CNTs@SiO 2 / DES nanofluid not only increased the absorption rate but also significantly enhanced the total absorption amount; for the desorption process, the 150 ppm CNTs@SiO 2 / DES nanofluid can release carbon dioxide faster under light illumination conditions due to a faster heating rate.

[0073] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a green nanofluid absorbent for photothermal carbon capture, characterized in that: The following steps are involved: The carboxyl carbon nanotubes are dispersed in a dispersant and adjusted to alkalinity, and then tetraethyl silicate is added under high-speed stirring at 1000-2000 r / min. After the reaction, the pH value of the system is adjusted to 7-7.5, centrifuged, and the precipitate is washed to obtain a black gel-like substance. The black gel-like substance is dried and ground to obtain nanoparticles composited with carboxyl carbon nanotubes and silicon dioxide; the nanoparticles composited with carboxyl carbon nanotubes and silicon dioxide and a surfactant are co-dispersed in a deep eutectic solvent to obtain the green nanofluid absorbent for photothermal carbon capture.

2. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The carboxyl carbon nanotubes have a diameter of 8 to 15 nm and a length of no more than 30 μm; and / or, the dispersant is obtained by mixing isopropanol and water.

3. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The dosage ratio of the carboxyl carbon nanotubes to the dispersant is 0.4-0.6 g:50 mL; and / or the mass ratio of the tetraethyl silicate to the carboxyl carbon nanotubes is 3-5:0.4-0.

6.

4. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The adjusting to alkalinity is to use ammonia water to adjust the pH value to 11.5-12.

5. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The tetraethyl silicate is added in 4 to 5 times, and the time of each addition is 1 to 2 minutes.

6. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The reaction temperature is 45-55°C and the reaction time is 12-16 hours.

7. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The mass ratio of the carboxyl carbon nanotube and silicon dioxide composite nanoparticles to the deep eutectic solvent is 0.25-1.25:10000; and / or the mass ratio of the surfactant to the deep eutectic solvent is 1-2:1000.

8. The method for preparing a green nanofluid absorbent for photothermal carbon capture according to claim 1, characterized in that: The hydrogen bond acceptor of the deep eutectic solvent is choline chloride, and the hydrogen bond donor is urea and / or ethanolamine.

9. A green nanofluid absorbent for photothermal carbon capture prepared according to the method for preparing a green nanofluid absorbent for photothermal carbon capture according to any one of claims 1 to 8.

10. Use of the green nanofluid absorber for photothermal carbon capture according to claim 9 in photothermal carbon capture.

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