Absorbents for capturing carbon dioxide and methods of capturing carbon dioxide

Abstract

This invention provides an absorbent for capturing carbon dioxide and a method for capturing carbon dioxide. By volume percentage, the absorbent comprises 20-60% glycine salt aqueous solution, 10-50% triethylene glycol monomethyl ether, 5-10% ethylene glycol, and the balance being water. This absorbent combines the advantages of glycine salt systems, such as low volatility, non-toxicity, safety, and better antioxidant degradation resistance, while avoiding the risk of solid precipitates forming after absorption by the glycine salt system, which could cause pipeline blockage.

Description

Technical Field

[0001] This invention relates to the field of gas purification and separation, and specifically to an absorbent for capturing carbon dioxide and a method for capturing carbon dioxide. Background Technology

[0002] Industrially, 3–5 mol / L ethanolamine (MEA) solutions are commonly used to absorb CO2 from flue gas. However, this method suffers from problems such as high volatility, easy oxidation and decomposition, strong corrosivity, and high regeneration energy consumption (typically 3.8–4.0 GJ / ton CO2), resulting in poor economic efficiency. Given the shortcomings of typical MEA absorption processes, the energy consumption problem of chemical absorption methods for CO2 capture urgently needs to be addressed, necessitating the development of novel, low-energy-consumption absorbents.

[0003] Phase change absorbents have attracted considerable attention as a novel type of absorbent material. These absorbents typically undergo a phase change during CO2 absorption or upon temperature change after absorption, forming a CO2-rich phase and a CO2-poor phase. Only the rich phase needs to be desorbed, and then directly mixed with the lean solution to achieve solvent regeneration and recycling, effectively reducing the throughput of the regeneration process and thus achieving energy reduction.

[0004] Currently developed phase change absorbents mainly include mixed amine systems, ionic liquid systems, and organic solvent composite systems. While these systems demonstrate good performance in CO2 absorption capacity and enrichment rate, high-concentration mixed amine systems, systems incorporating organic solvents, and ionic liquid systems typically suffer from a sharp increase in solution viscosity and poor flowability after CO2 loading. For example, in a typical ethanolamine-organic solvent composite system, the viscosity of the enriched solution reaches 141.6 mPa·s after absorption. This increased viscosity negatively impacts mass transfer and phase separation processes. Therefore, it is necessary to provide a new absorbent for capturing carbon dioxide to address these issues. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the present invention aims to provide an absorbent for capturing carbon dioxide and a method for capturing carbon dioxide. The absorbent has advantages such as stability and non-volatility, good absorption performance, low system viscosity, and good CO2 enrichment effect.

[0006] To achieve the above objectives, the present invention provides an absorbent for capturing carbon dioxide, comprising, by volume percentage, 20-60% of an aqueous solution of glycine salt, 10-50% of triethylene glycol monomethyl ether, 5-10% of ethylene glycol, and the balance being water.

[0007] Glycine salts react rapidly with CO2 to produce carbamates and other products, achieving efficient CO2 absorption. Triethylene glycol monomethyl ether has a hydroxyl end group, exhibiting strong electronegativity and basicity, which further enhances its ability to absorb carbon dioxide, significantly improving the absorption rate and adsorption capacity of the absorbent. Ethylene glycol possesses advantages such as high polarity and low specific heat capacity, and is miscible with water, especially glycine salts. This effectively reduces the water content in the post-absorption rich phase, avoiding the problem of high regeneration energy consumption caused by the large latent heat of vaporization of water during subsequent thermal desorption. Simultaneously, the polarity differences between the components allow for a liquid-liquid phase transition after CO2 absorption and the generation of corresponding carbamates and other electrolyte products, under the salting-out effect. The viscosity of the CO2-rich liquid phase after phase separation is low, enabling complete liquid-liquid phase separation within a very short time after absorption, thereby reducing the throughput of the regeneration process and lowering regeneration energy consumption. The absorbent of the present invention combines the advantages of glycinate system, such as non-volatile nature, non-toxicity and safety, and better antioxidant degradation ability, while avoiding the risk of pipeline blockage caused by the formation of solid precipitates after absorption by glycinate system.

[0008] According to a specific embodiment of the present invention, preferably, the concentration of glycine salt in the absorbent is 1-4 mol / L, more preferably 2-3 mol / L.

[0009] According to a specific embodiment of the present invention, preferably, the absorbent comprises, by volume percentage, 35-45% of an aqueous solution of glycine salt, 20-30% of triethylene glycol monomethyl ether, 5-10% of ethylene glycol, and the balance being water.

[0010] According to a specific embodiment of the present invention, preferably, the concentration of glycine salt in the glycine salt aqueous solution is 4-5 mol / L.

[0011] In one optional embodiment, the glycine salt solution is obtained by a chemical reaction of glycine, a strong base, and water; the strong base is potassium hydroxide and / or sodium hydroxide. The role of the strong base is to neutralize the carboxyl group in the amino acid, causing the amino acid to form a weakly basic and stable salt, which also has good solubility in water, preventing the formation of solid products after absorbing CO2. Further, the glycine salt aqueous solution is selected from potassium glycine salt aqueous solution and / or sodium glycine salt aqueous solution.

[0012] The present invention also provides a method for capturing carbon dioxide, comprising: absorbing CO2 in the material to be treated using the aforementioned absorbent for capturing carbon dioxide.

[0013] According to a specific embodiment of the present invention, preferably, the absorption temperature is 30-50°C and the pressure is atmospheric pressure.

[0014] In one optional embodiment, the volume fraction of CO2 in the material to be treated is 10-15%.

[0015] Furthermore, after absorption, the absorbent undergoes a liquid-liquid phase transition, forming a CO2-poor phase and a CO2-rich phase. The CO2-poor phase includes triethylene glycol monomethyl ether and water, while the CO2-rich phase includes water, ethylene glycol, and the product formed by the reaction of glycine salt with CO2. Attached Figure Description

[0016] Figure 1 The diagram shows the time test results for phase separation in embodiments 1-6 of the present invention;

[0017] Figure 2 The absorption performance test graphs of the absorbents in Comparative Example 1 and Examples 1-6 of the present invention are shown;

[0018] Figure 3 The following are test graphs showing the CO2 load and the proportion of CO2 load in the CO2-rich phase after absorption in Comparative Example 1 and Examples 1-6 of the present invention;

[0019] Figure 4 The viscosity test results of the CO2-rich phase liquid after absorption are shown in Examples 1-6 of the present invention. Detailed Implementation

[0020] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0021] Example 1

[0022] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0023] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 20% vol., the volume ratio of ethylene glycol is 5% vol., and the remainder is supplemented by deionized water.

[0024] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0025] Example 2

[0026] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0027] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 20% vol., the volume ratio of ethylene glycol is 10% vol., and the remainder is supplemented by deionized water.

[0028] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0029] Example 3

[0030] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0031] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 25% vol., the volume ratio of ethylene glycol is 5% vol., and the remainder is supplemented by deionized water.

[0032] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0033] Example 4

[0034] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0035] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 25% vol., the volume ratio of ethylene glycol is 10% vol., and the remainder is supplemented by deionized water.

[0036] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0037] Example 5

[0038] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0039] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 30% vol., the volume ratio of ethylene glycol is 5% vol., and the remainder is supplemented by deionized water.

[0040] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0041] Example 6

[0042] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0043] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of triethylene glycol monomethyl ether is 30% vol., the volume ratio of ethylene glycol is 10% vol., and the remainder is supplemented by deionized water.

[0044] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time, CO2 loading in the lean / rich CO2 phases, and viscosity of the rich CO2 phase were measured.

[0045] Figure 1 The diagram shows the time test charts for phase separation in Examples 1-6 of the present invention. After absorption is completed, the absorbent of the present invention can undergo a rapid liquid-liquid phase change and achieve complete liquid-liquid phase separation within 3 minutes. Figure 4 The following are viscosity test graphs of the CO2-rich phase liquid after absorption in Examples 1-6 of the present invention. Figure 4 It can be seen that the viscosity of the CO2-rich phase obtained by the above absorbent in this invention is only 2 to 5 mPa·s.

[0046] Comparative Example 1

[0047] Prepare a 5 mol / L potassium glycinate solution: Dissolve 5 mol each of glycine and potassium hydroxide in deionized water to a final volume of 1 L.

[0048] Preparation of the absorbent: The concentration of potassium glycinate in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium glycinate aqueous solution is 40% vol., the volume ratio of polyethylene glycol dimethyl ether is 25% vol., and the remainder is supplemented by deionized water.

[0049] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and absorption experiments were conducted at 40°C. After absorption saturation, the phase separation time and CO2 loading in the lean / rich CO2 phases were measured.

[0050] Figure 2 The diagram shows the absorption performance test graphs of the absorbents in Comparative Example 1 and Examples 1-6 of the present invention. Figure 2 It can be seen that, compared with Comparative Example 1, the absorbents in Examples 1-6 have a higher absorption rate for CO2 and can achieve CO2 loading in a shorter time. Figure 3 This diagram shows the CO2 load and the load percentage in the CO2-rich phase after absorption in Comparative Example 1 and Examples 1-6 of the present invention. Figure 3 It can be seen that, compared with Comparative Example 1, the CO2 loading of the absorbent in Examples 1-6 is higher, and the CO2 loading in the CO2-rich phase accounts for 91% to 95% of the total.

[0051] Comparative Example 2

[0052] Prepare a 5 mol / L potassium alanine solution: Dissolve 5 mol of alanine and 5 mol of potassium hydroxide in deionized water to a final volume of 1 L.

[0053] Preparation of the absorbent: The potassium alanine concentration in the absorbent is 2 mol / L, that is, the volume ratio of 5 mol / L potassium alanine aqueous solution is 40% vol., the volume ratio of polyethylene glycol dimethyl ether is 30% vol., and the remainder is supplemented by deionized water.

[0054] The absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12.5%, and the absorption experiment was conducted at 40°C. Comparative Example 2 produced a solid after absorption, failing to achieve liquid-liquid phase separation.

Claims

1. An absorbent for capturing carbon dioxide, wherein, The absorbent comprises, by volume percentage, 20-60% of an aqueous solution of glycine salt, 10-50% of triethylene glycol monomethyl ether, 5-10% of ethylene glycol, and the balance being water.

2. The absorbent for capturing carbon dioxide according to claim 1, wherein, The concentration of glycine salt in the absorbent is 1–4 mol / L.

3. The absorbent for capturing carbon dioxide according to claim 1, wherein, The concentration of glycine salt in the absorbent is 2–3 mol / L.

4. The absorbent for capturing carbon dioxide according to claim 1, wherein, The concentration of glycine salt in the aqueous solution is 4–5 mol / L.

5. The absorbent for capturing carbon dioxide according to claim 1, wherein, The absorbent comprises, by volume percentage, 35-45% of the glycine salt aqueous solution, 20-30% of the triethylene glycol monomethyl ether, 5-10% of the ethylene glycol, and the balance being water.

6. The absorbent for capturing carbon dioxide according to claim 1, wherein, The glycine salt aqueous solution is selected from potassium glycine salt aqueous solution and / or sodium glycine salt aqueous solution.

7. A method for capturing carbon dioxide, wherein, include: The CO2 in the material to be treated is absorbed by the absorbent for capturing carbon dioxide as described in any one of claims 1 to 6.

8. The method for capturing carbon dioxide according to claim 7, wherein, The absorption temperature is 30–50°C.

9. The method for capturing carbon dioxide according to claim 7, wherein, The volume fraction of CO2 in the material to be treated is 10-15%.

10. The method for capturing carbon dioxide according to claim 7, wherein, After absorption, the absorbent undergoes a liquid-liquid phase transition, forming a CO2-poor phase and a CO2-rich phase. The CO2-poor phase includes triethylene glycol monomethyl ether and water, while the CO2-rich phase includes water, ethylene glycol, and the product formed by the reaction of glycine salt with CO2.

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