Carbon dioxide trapping adsorbent with moisture resistance and preparation method thereof

Abstract

The invention relates to the technical field of adsorbents, and discloses a moisture-resistant carbon dioxide trapping adsorbent, and a preparation method thereof comprises the following steps: S1, blending oxalic acid or oxalate or squaric acid and a zinc source in a reaction system to obtain a mixture I; s2, dissolving an organic ligand in a solvent to obtain a mixture II; s3, the mixture I and the mixture II are subjected to a reaction and post-treatment, and the adsorbent is obtained. According to the prepared adsorbent, a pore structure is formed in situ in the preparation process, the specific surface area is large, the porosity is large, the structure can be kept stable in the presence of water and steam, and the adsorbent is stable to wet acid gas.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, and in particular to a moisture-resistant carbon dioxide capture adsorbent and a preparation method thereof. Background Art

[0002] The process of human industrialization has led to a surge in global CO2 emissions. The 2050 net zero carbon emission target required by the Paris Agreement needs to rely on the coordination of multiple measures, such as carbon capture, utilization and storage (CCUS) technology, renewable energy and industrial decarbonization technology development. The continued use of fossil energy and industrial processes (cement / steel) has led to rigid CO2 emissions, which increasingly highlights the necessity of CCUS. The use of liquid absorption methods (such as amine-based solvents) is currently a mature technology for carbon dioxide capture, but it has problems such as high energy consumption, equipment corrosion, and solvent degradation. Adsorption using porous adsorbents is another method of capturing CO2 from flue gas, but porous adsorbents (such as zeolite 13X) lose their CO2 adsorption performance under humid conditions due to moisture sensitivity and competitive N adsorption, which affects their actual performance.

[0003] Metal organic framework (MOF) is a new type of porous material. By regulating metal nodes, organic ligands or functional modification, CO2 adsorption sites can be designed to optimize adsorption kinetics and selectivity. The pore density of some MOFs can reach 3000m 2 / g or more (such as Mg-MOF-74), significantly higher than traditional materials (zeolite about 1000m 2 The heat of CO2 adsorption in MOFs is typically less than 10 kJ / mol, making them more energy-efficient than amine-based solvents (≈40 kJ / mol) and suitable for dynamic cycling processes (such as pressure swing adsorption, PSA). Some MOFs, such as UiO-66, significantly improve their moisture resistance by introducing functional groups such as hydroxyl and carboxyl groups, making them suitable for use in applications involving humid flue gas.

[0004] During the renovation of coal-fired power plants, the CO concentration in the flue gas is low (approximately 3%-15%) and the moisture content is high (dew point can reach 50-80°C), requiring the adsorbent to have a wide adsorption capacity window, resistance to hydrolysis, and adsorption performance in wet gases. In addition, the emission sources of small and medium-sized enterprises are small in scale and fluctuate greatly, making the modular design and rapid regeneration characteristics of MOFs (such as vacuum pressure swing adsorption, VPSA) more economical. In addition, direct air capture (DAC) requires materials to have high adsorption capacity at low partial pressures (0.04 bar), and MOFs (such as ZIF-8) show potential.

[0005] The widespread application of MOF materials in engineering is plagued by numerous bottlenecks. For example, MOFs are susceptible to failure during long-term cycling due to structural collapse, hydrolysis of metal nodes, or desorption of organic ligands. Large-scale preparation processes are complex, and some MOF materials (such as MOF-74) cost as much as 1,000 yuan per gram. Summary of the Invention

[0006] The technical solution adopted in the present invention is:

[0007] In a first aspect, the present invention provides a method for preparing a moisture-resistant carbon dioxide capture adsorbent, comprising the following steps:

[0008] S1: mixing oxalic acid or oxalate or squaric acid and zinc source in a reaction system to obtain a mixture I;

[0009] S2 dissolves the organic ligand in a solvent to obtain a mixture II;

[0010] S3 mixture I and mixture II are reacted and post-treated to obtain an adsorbent.

[0011] According to some preferred embodiments, in S1, the oxalate includes at least one of ammonium oxalate, sodium oxalate, potassium oxalate, and zinc oxalate.

[0012] According to some preferred embodiments, in S1, the zinc source includes at least one of zinc acetate, zinc oxalate, zinc carbonate, zinc hydroxide, basic zinc carbonate, zinc oxide, zinc chloride, zinc nitrate, and zinc sulfate.

[0013] According to some preferred embodiments, in S2, the organic ligand includes at least one of 1,2,4-triazole, 3-methyl-1H-1,2,4-triazole, 3-amino-1,2,4-triazole, and 3,5-diamino-1,2,4-triazole. The methyl group sterically hinders the formation of a hydrogen bond network by water molecules and, compared to analogs containing hydrophilic amino groups (such as 3-amino-1,2,4-triazole and 3,5-diamino-1,2,4-triazole), repels water molecules from approaching the framework, further improving CO2 absorption at high relative humidity.

[0014] According to some preferred embodiments, hydrophobic ligands are further added in S1, and the hydrophobic ligands include polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polytetrafluoroethylene, hexadecyltrimethoxysilane (HDTMS), stearic acid (C 17 H 35 In the present invention, the prepared adsorbent already has a certain degree of resistance to humid gases (up to 40% RH, 20°C). However, its CO adsorption performance decreases for gases with higher humidity. Therefore, for high-humidity gas sources, a hydrophobic ligand is added to further improve moisture resistance.

[0015] According to some preferred embodiments, the amount of hydrophobic ligand added is 0.5% to 5% of the mass of the adsorbent. In the present invention, hydrophobic modification forms a stable chemical bond with the adsorbent surface through silanization, coordination, graft polymerization, etc., forming a layer of hydrophobic barrier on the adsorbent surface, reducing the surface energy, thereby significantly inhibiting the competitive adsorption and destruction of water molecules on carbon dioxide adsorption sites. That is, by adding hydrophobic ligands for chemical coating, it is made to have CO2 absorption performance and CO2 / N2 selectivity while further improving the moisture stability of the adsorbent. After modification by hydrophobic ligands, the surface water contact angle is significantly increased (>90°), and the adsorbent powder can be suspended on the water surface.

[0016] According to some preferred embodiments, the mass ratio of oxalic acid or oxalate or squaric acid, organic ligand, and zinc source is 1-2:2-3:2-4, more preferably 1-1.2:2:2.

[0017] According to some preferred embodiments, the solvent used in the reaction system in S1 is the same as the solvent used in S2, which is at least one of water, methanol, ethanol, pyridine, ethanolamine, ethylenediamine, and dichloromethane, and is further preferably a methanol / water mixed solvent, with a volume ratio of methanol / water of 0 / 1 to 1 / 0.

[0018] According to some preferred embodiments, in S3, the reaction temperature is 10-200° C., and the reaction time is 1-48 hours. In some embodiments, the reaction temperature can be as low as 10° C., and the reaction time can be shortened to 1 hour.

[0019] According to some preferred embodiments, in S3, post-treatment: after the reaction, separation by filtration and drying are performed to obtain the product at a drying temperature of 80 to 180°C, preferably 105 to 120°C.

[0020] According to some preferred embodiments, in S3, the liquid separated by filtration can be directly used to synthesize an adsorbent without waste liquid discharge, which is environmentally friendly.

[0021] Second, the present invention provides a carbon dioxide capture adsorbent obtained by the aforementioned preparation method.

[0022] The technical mechanism and beneficial effects adopted by the present invention are:

[0023] (1) The carbon dioxide capture adsorbent provided by the present invention has the advantages of simple synthesis process, pollution-free reaction process, and low energy consumption.

[0024] (2) The carbon dioxide capture adsorbent provided by the present invention requires a low temperature during the preparation process, which can save resources to the greatest extent. At the same time, the raw materials are cheap and easily available, and the cost is controllable.

[0025] (3) The carbon dioxide capture adsorbent provided by the present invention forms a pore structure in situ during the preparation process, has a large specific surface area and porosity, can maintain structural stability in the presence of water and steam, and is stable to wet acidic gases. It is a carbon dioxide adsorption material with practical application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the isothermal adsorption curve of the carbon dioxide capture adsorbent prepared in Example 1. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0028] Example 1

[0029] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0030] 8.78g of oxalic acid dihydrate, 15.26g of zinc acetate dihydrate, and 0.5g of PVDF were placed in a 100mL reactor. 20mL of methanol was added and stirred for 2 hours. 9.63g of 1,2,4-triazole was also added to the reactor, followed by 30mL of methanol. The mixture was stirred evenly and placed in an oven at 180°C for 36 hours. After the reaction, solid-liquid separation was performed, and the resulting solid powder was oven-dried at 180°C.

[0031] The adsorption capacity of nitrogen, carbon dioxide and methane of the adsorbent prepared in Example 1 at 80°C (standard conditions) is shown in Table 1.

[0032] Table 1 Adsorption results

[0033] <![CDATA[N2]]> 1.86mL / g <![CDATA[CH4]]> 5.21mL / g <![CDATA[CO2]]> 45.0mL / g

[0034] Example 2

[0035] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0036] Weigh 8.82g of oxalic acid dihydrate and 5.6g of NaOH to react and form sodium oxalate. Add 140mL of water and 60mL of methanol, then add 30.73g of zinc acetate dihydrate and 1.0g of PVDF. Stir for 30 minutes. Then, add 9.66g of 3-methyl-1H-1,2,4-triazole and stir at room temperature for 30 minutes. Filter and separate the solid. Wash the solid powder with 450mL of water, filter, and dry at 110°C.

[0037] After the adsorbent was immersed in water for one month, the adsorption capacity of nitrogen, carbon dioxide, and methane at 80° C. (in an atmosphere with a relative humidity of 75%, standard conditions) was measured. The results are shown in Table 2.

[0038] Table 2 Adsorption results

[0039] <![CDATA[N2]]> 1.76mL / g <![CDATA[CH4]]> 4.64mL / g <![CDATA[CO2]]> 42.58mL / g

[0040] Example 3

[0041] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0042] Weigh 8.68g of ammonium oxalate and dissolve it in 100mL of a methanol / water mixture (3:7 by volume). Add 30.73g of zinc acetate dihydrate and stir for 10 minutes. Subsequently, add 9.66g of 1,2,4-triazole and stir at room temperature (10°C) for 1 hour. Filter and separate the solid. Wash the solid powder with water and stir, filter, and dry at 150°C.

[0043] The adsorption capacity of nitrogen, carbon dioxide and methane by the adsorbent at 80°C (standard conditions) is shown in Table 3.

[0044] Table 3 Adsorption results

[0045] <![CDATA[N2]]> 1.68mL / g <![CDATA[CH4]]> 4.93mL / g <![CDATA[CO2]]> 44.2mL / g

[0046] Example 4

[0047] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0048] Weigh 16.0g of squaric acid, 9.66g of 1,2,4-triazole, and 21.6g of zinc oxalate into a 200mL hydrothermal reactor. Add 100mL of dichloromethane and 10mL of water and stir thoroughly. Then, place the reactor in an oven at 180°C for 40 hours. After the reaction, perform solid-liquid separation and dry the resulting solid powder in an oven at 100°C.

[0049] The adsorption capacity of nitrogen, carbon dioxide and methane by the adsorbent at 80°C (standard conditions) is shown in Table 4.

[0050] Table 4 Adsorption results

[0051] <![CDATA[N2]]> 1.45mL / g <![CDATA[CH4]]> 4.23mL / g <![CDATA[CO2]]> 35.6mL / g

[0052] Example 5

[0053] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0054] 278.3g of zinc hydroxide, 194g of oxalic acid dihydrate, and 6g of PVDF were placed in a 2L reactor. 1.3L of methanol was added and stirred for 30 minutes. Then, 212.5g of 1,2,4-triazole was added. The reactor was heated to 170°C and reacted for 48 hours. After the reaction, solid-liquid separation was performed, the liquid was recycled, and the resulting solid powder was oven-dried at 100°C. The modified surface exhibited a significantly increased water contact angle (>90°), allowing the adsorbent powder to float on the water surface.

[0055] The difference between the adsorbent 1 without hydrophobic modification and Example 5 is that no PVDF is added.

[0056] The adsorption capacities of nitrogen, carbon dioxide, and methane by the adsorbent and the non-hydrophobically modified adsorbent I at 80° C. and 50% relative humidity (standard conditions) are shown in Table 5.

[0057] Table 5 Adsorption results

[0058] gas Hydrophobic modification Unmodified <![CDATA[N2]]> 1.77mL / g 0.2mL / g <![CDATA[CH4]]> 4.98mL / g 0.45mL / g <![CDATA[CO2]]> 40.34mL / g 21.2mL / g

[0059] Example 6

[0060] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0061] Weigh 278.3g of zinc hydroxide, 194g of oxalic acid dihydrate, and 4g of PVDF into a 2L reactor. Add 1.3L of the recycled methanol obtained from the solid-liquid separation in Example 5 and stir for 30 minutes. Then, add 212.5g of 1,2,4-triazole. Heat the reactor to 190°C and react for 48 hours. After the reaction, perform solid-liquid separation, recycle the liquid, and oven dry the resulting solid powder at 105°C.

[0062] The difference between the adsorbent II without hydrophobic modification and Example 6 is that no PVDF is added.

[0063] The adsorption capacities of nitrogen, carbon dioxide, and methane by the adsorbent and the non-hydrophobically modified adsorbent II at 80° C. and 50% relative humidity (standard conditions) are shown in Table 6.

[0064] Table 6 Adsorption results

[0065] gas Hydrophobic modification Unmodified <![CDATA[N2]]> 1.60mL / g 0.18mL / g <![CDATA[CH4]]> 4.22mL / g 0.33mL / g <![CDATA[CO2]]> 39.2mL / g 19.4mL / g

[0066] Example 7

[0067] This embodiment provides a method for preparing a carbon dioxide capture adsorbent, specifically:

[0068] Weigh 9.55g of zinc chloride and 4.41g of oxalic acid into a 200mL reactor. Add 100mL of methanol, 4.27g of ethanolamine, and 5.18g of 1,2,4-triazole. Stir for 10 minutes. Place in a 150°C oven and react for 36 hours. After the reaction, separate the solid and liquid, and dry the resulting solid powder in a 100°C oven.

[0069] The adsorption capacity of nitrogen, carbon dioxide and methane by the adsorbent at 80°C (standard conditions) is shown in Table 7.

[0070] Table 7 Adsorption results

[0071] <![CDATA[N2]]> 1.66mL / g <![CDATA[CH4]]> 5.05mL / g <![CDATA[CO2]]> 40.3mL / g

[0072] Test example

[0073] The carbon dioxide capture adsorbent prepared in Example 1 was used to measure its adsorption isotherm curve. The results are as follows: Figure 1 shown.

[0074] The carbon dioxide capture adsorbent prepared in Example 1 was used as the test evaluation object. Two raw gases were prepared respectively. One was a CO2 / N2 mixed gas as a dry raw gas without water. The other was a wet raw gas with a certain humidity formed by bubbling the CO2 / N2 mixed gas through a container filled with water into saturated water vapor at 25°C. A 6-tower pressure swing adsorption carbon capture simulation test was carried out using the "6-1-3" operating process. The adsorption temperature was 80°C, the adsorption pressure was 0.20 MPa·G, the desorption pressure was -0.08 MPa·G, and the air intake flow rate was 15 L / min. The specific experimental results are shown in Table 8.

[0075] Table 8 Experimental results

[0076]

[0077] Under other consistent experimental conditions, for both dry and wet feed gases, the carbon dioxide capture adsorbent can concentrate the carbon dioxide content from 10.58% to over 95% through a single-stage pressure swing adsorption separation process, indicating that the adsorbent has excellent moisture resistance and is conducive to practical engineering applications.

[0078] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a moisture-resistant carbon dioxide capture adsorbent, characterized in that: The steps include: S1: mixing oxalic acid or oxalate or squaric acid and zinc source in a reaction system to obtain a mixture I; S2 dissolves the organic ligand in a solvent to obtain a mixture II; S3 mixture I and mixture II are reacted and post-treated to obtain an adsorbent.

2. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: In S1, the oxalate includes at least one of ammonium oxalate, sodium oxalate, potassium oxalate, and zinc oxalate.

3. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: In S1, the zinc source includes at least one of zinc acetate, zinc oxalate, zinc carbonate, zinc hydroxide, basic zinc carbonate, zinc oxide, zinc chloride, zinc nitrate, and zinc sulfate.

4. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: In S1, the organic ligand includes at least one of 1,2,4-triazole, 3-methyl-1H-1,2,4-triazole, 3-amino-1,2,4-triazole, and 3,5-diamino-1,2,4-triazole.

5. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: The mass ratio of oxalic acid or oxalate or squaric acid, organic ligand and zinc source is 1-2:2-3:2-4.

6. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: The solvent used in the reaction system in S1 is the same as the solvent used in S2, which is at least one of water, methanol, ethanol, pyridine, ethanolamine, ethylenediamine, and dichloromethane.

7. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 1, wherein: In S3, the reaction temperature is 10-200° C., and the reaction time is 1-48 h.

8. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to any one of claims 1 to 7, wherein: S1 further includes a hydrophobic ligand, which includes at least one of polyvinylidene fluoride, polydimethylsiloxane, polytetrafluoroethylene, hexadecyltrimethoxysilane, and stearic acid.

9. The method for preparing a moisture-resistant carbon dioxide capture adsorbent according to claim 8, wherein: The amount of the hydrophobic ligand added is 0.5 to 5% of the mass of the adsorbent.

10. A carbon dioxide capture adsorbent obtained by the preparation method according to any one of claims 1 to 9.

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