A carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas

Abstract

The present invention discloses a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas, which relates to the technical field of carbon dioxide capture. The carbon dioxide capture agent is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water. By using the compound of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as the absorption component and cooperating with the solvent composed of cyclohexanol and water to form a water-based liquid-liquid phase change absorbent for carbon dioxide capture, the present invention not only improves the absorption load capacity of the single diethylenetriamine absorption component for CO2, but also the obtained carbon dioxide capture agent has excellent regeneration performance, and its regeneration efficiency after 10 absorption-thermal desorption regeneration cycles is >70%, making up for the deficiencies of the existing water-based liquid-liquid phase change absorbents.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture, and in particular to a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas. Background Art

[0002] With the continued acceleration of global industrialization, emissions of greenhouse gases such as CO2 have become increasingly prominent, becoming a major factor in climate change. In particular, the increasing concentration of CO2 in flue gas emissions has had a severe impact on the environment and exacerbated global warming. Therefore, efficiently and economically capturing or separating CO2 from CO2-rich gas mixtures has become a critical issue in the environmental protection field.

[0003] Traditional carbon dioxide capture technologies mainly include chemical absorption, physical absorption, membrane separation and adsorption. Among them, chemical absorption is widely used due to its advantages such as high absorption efficiency and good selectivity. However, existing chemical absorbents mostly use single amine absorbents such as monoethanolamine method (MEA), diethanolamine method (DEA), diisopropanolamine method (DIPA) and methyldiethanolamine method (MDEA). Although these absorbents can achieve certain effects in the process of absorbing CO2, they often have problems such as limited absorption load capacity and high regeneration energy consumption, which increases operating costs and energy consumption.

[0004] To overcome the shortcomings of existing technologies, researchers have been actively exploring new CO2 capture agents. Liquid-liquid phase-change absorbers (LPCAs) have attracted significant attention due to their unique phase-change properties. These absorbents can undergo phase transitions during the absorption and regeneration processes, reducing the amount of rich liquid required for regeneration and, consequently, lowering regeneration energy consumption. However, despite their numerous advantages, current aqueous LLCCAs still present several challenges. These include low regeneration efficiency and poor cyclic stability, which further limit their widespread adoption and use in industrial applications. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas.

[0006] In a first aspect, the present invention provides a carbon dioxide capture agent, which is composed of an absorption component and a solvent, wherein the absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water.

[0007] Furthermore, the molar concentration of the absorption component is 3 to 6 mol / L.

[0008] Further, the molar concentration of the absorption component is 4.5 mol / L.

[0009] Further, the molar ratio of the diethylenetriamine to the 2,2'-(cyclohexylimino)diethanol is (10 - 17):(1 - 3).

[0010] Further, the molar ratio of the diethylenetriamine to the 2,2'-(cyclohexylimino)diethanol is 13:2.

[0011] Further, the volume ratio of the cyclohexanol to the water is (23 - 37):100.

[0012] Further, the volume ratio of the cyclohexanol to the water is 31:100.

[0013] Further, before the carbon dioxide capture agent contacts and absorbs the gas containing carbon dioxide, the carbon dioxide capture agent is in a homogeneous system; when the carbon dioxide capture agent contacts and absorbs carbon dioxide from the gas containing carbon dioxide until it reaches a saturated state, the carbon dioxide capture agent forms a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase, and the lower liquid phase accounts for 25 - 60% of the total volume of the two-layer liquid phase system;

[0014] The absorption temperature of the carbon dioxide capture agent is 40 - 60 °C, and the desorption and regeneration temperature of the carbon dioxide capture agent is 85 - 105 °C.

[0015] Further, the regeneration efficiency of the carbon dioxide capture agent after 10 cycles of carbon dioxide absorption - thermal desorption regeneration is > 70%.

[0016] In a second aspect, based on the same inventive concept, the present invention provides an application of the carbon dioxide capture agent according to any one of the first aspect in capturing carbon dioxide in flue gas.

[0017] The above technical solutions provided by the embodiments of the present invention have at least the following advantages compared with the prior art:

[0018] The embodiments of the present invention provide a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas. By using diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as a compounded absorption component, and at the same time cooperating with a solvent composed of cyclohexanol and water to form a water-based liquid-liquid phase change absorbent for carbon dioxide capture, the present invention not only improves the CO2 absorption load capacity of the single diethylenetriamine absorption component, but also the obtained carbon dioxide capture agent has excellent regeneration performance, and its regeneration efficiency after 10 cycles of absorption - thermal desorption regeneration is > 70%, making up for the deficiencies of the existing water-based liquid-liquid phase change absorbents. Specifically:

[0019] 1. Selection of the absorption component

[0020] As a linear polyamine (containing three amino groups), diethylenetriamine (DETA) has high reactivity and can quickly react with CO2 to form carbamate. Moreover, its multi-amino structure provides abundant reaction sites, significantly enhancing the initial absorption rate and capacity. At the same time, it is combined with 2,2'-(cyclohexylimino)diethanol with a six-membered cyclic structure - cyclohexyl and a symmetric chemical structure. On the one hand, it can also participate in the formation of more stable bicarbonate or promote proton transfer, forming a complementary reaction path with the primary amine of DETA, improving the total CO2 absorption load capacity. On the other hand, the hydrophobicity and steric hindrance effect of cyclohexyl reduce the oxidative degradation of the amine, extend the lifespan of the absorbent, and can also weaken the binding energy between CO2 and the amine, making the thermal desorption process more efficient and reducing the regeneration energy consumption. Therefore, the present invention provides fast absorption kinetics through diethylenetriamine and optimizes the thermodynamic equilibrium with 2,2'-(cyclohexylimino)diethanol with a six-membered cyclic symmetric structure. The combination of the two achieves the balance of high absorption capacity and high regeneration efficiency, reduces degradation, maintains the cycle stability, and thus improves the regeneration performance of the obtained carbon dioxide capture agent.

[0021] 2. Selection of Solvent

[0022] Based on the existing water-based liquid-liquid phase change absorbent with water as the solvent, the present invention introduces an appropriate amount of cyclohexanol to form a mixed solvent. Utilizing the hydrophobicity of cyclohexyl, the solubility of the product is reduced after CO2 absorption, inducing and promoting the liquid-liquid phase change of the system to obtain a CO2-rich phase and a CO2-lean phase, thereby reducing the regeneration treatment amount. Through the compounding of cyclohexanol and water, the present invention not only optimizes the balance between the solubility and hydrophobicity of the solvent, matches with the absorption components, can ensure the full dissolution of the amine and the effective phase separation of the absorption product, but also helps to reduce solvent volatilization and maintain the stability of the system, thus realizing the efficient cycle of "homogeneous absorption - phase separation in regeneration". Brief Description of the Drawings

[0023] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a comparison diagram of the regeneration efficiency of different carbon dioxide capture agents in the test examples of the present invention. Detailed Description of the Invention

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or prepared by existing methods.

[0028] In a first aspect, the present invention provides a carbon dioxide capture agent, which is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water.

[0029] The embodiments of the present invention provide a carbon dioxide capture agent. By compounding diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as the absorption component and simultaneously combining with a solvent composed of cyclohexanol and water to form a water-based liquid-liquid phase change absorbent for carbon dioxide capture, not only is the CO2 absorption load capacity of the single diethylenetriamine absorption component improved, but also the obtained carbon dioxide capture agent has excellent regeneration performance, and its regeneration efficiency after 10 absorption-thermal desorption regeneration cycles is > 70%, making up for the deficiencies of existing water-based liquid-liquid phase change absorbents.

[0030] The CAS registry number of diethylenetriamine in the present invention is 111-40-0, and its chemical structural formula is as follows:

[0031]

[0032] The CAS number of 2,2'-(cyclohexylimino)diethanol in the present invention is 4500-29-2, and its chemical structural formula is as follows:

[0033]

[0034] The carbon dioxide capture agent provided by the embodiments of the present invention is simple to prepare, and the components can be stirred and mixed by referring to the methods disclosed in the prior art.

[0035] In some specific embodiments, the molar concentration of the absorption component is 3 to 6 mol / L.

[0036] In some specific embodiments, the molar concentration of the absorption component is 4.5 mol / L.

[0037] In some specific embodiments, the molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is (10 - 17):(1 - 3).

[0038] In some specific embodiments, the molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is 13:2.

[0039] In some specific embodiments, the volume ratio of cyclohexanol to water is (23 - 37):100.

[0040] In some specific embodiments, the volume ratio of cyclohexanol to water is 31:100.

[0041] In some specific embodiments, before the carbon dioxide capture agent contacts and absorbs the gas containing carbon dioxide, the carbon dioxide capture agent is in a homogeneous system; when the carbon dioxide capture agent contacts and absorbs carbon dioxide in the gas containing carbon dioxide until it reaches a saturated state, the carbon dioxide capture agent forms a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase, and the lower liquid phase accounts for 25 - 60% of the total volume of the two-layer liquid phase system.

[0042] The absorption temperature of the carbon dioxide capture agent is 40 - 60 °C, preferably 50 °C; the desorption and regeneration temperature of the carbon dioxide capture agent is 85 - 105 °C, preferably 95 °C.

[0043] In some specific embodiments, the regeneration efficiency of the carbon dioxide capture agent after 10 cycles of carbon dioxide absorption - thermal desorption regeneration is > 70%.

[0044] In the present invention, the regeneration efficiency refers to the ability of the carbon dioxide capture agent to restore its original carbon dioxide capture ability after thermal desorption regeneration. For example, a regeneration efficiency of 83% means that under the same test conditions, the CO2 absorption load capacity of the carbon dioxide capture agent after regeneration is 83% of the CO2 absorption load capacity of the initial carbon dioxide capture agent.

[0045] In a second aspect, based on the same inventive concept, the present invention provides an application of the carbon dioxide capture agent according to any one of the first aspect in capturing carbon dioxide in flue gas.

[0046] It should be noted that for the component raw materials involved in the carbon dioxide capture agent provided in the embodiments of the present invention and its application in capturing carbon dioxide in flue gas, if there is no special limitation or specific description, commercially available products can be directly used or self-made by using existing publicly disclosed preparation methods; at the same time, for the steps and parameters involved, if there is no special limitation or specific description, they can be carried out according to the preparation processes disclosed in the prior art or directly used with reference to the operating instructions of existing equipment, and the present invention document will not elaborate one by one.

[0047] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0048] Example 1

[0049] In this example, a carbon dioxide capture agent is provided. The carbon dioxide capture agent is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water.

[0050] The molar concentration of the absorption component is 4.5 mol / L, and the molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is 13:2.

[0051] The volume ratio of cyclohexanol to water is 31:100.

[0052] Example 2

[0053] In this example, a carbon dioxide capture agent is provided. The carbon dioxide capture agent is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water.

[0054] The molar concentration of the absorption component is 3 mol / L, and the molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is 10:1.

[0055] The volume ratio of cyclohexanol to water is 23:100.

[0056] Example 3

[0057] In this example, a carbon dioxide capture agent is provided. The carbon dioxide capture agent is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent is composed of cyclohexanol and water.

[0058] The molar concentration of the absorption component is 6 mol / L, and the molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is 17:3.

[0059] The volume ratio of cyclohexanol to water is 37:100.

[0060] Comparative Example 1

[0061] This example provides a carbon dioxide capture agent, which is only different from Example 1 in that 2,2'-(cyclohexylimino)diethanol is adjusted to N-cyclohexylmonoethanolamine (CAS No. 2842-38-8); the remaining steps and parameters are the same.

[0062] Comparative Example 2

[0063] This example provides a carbon dioxide capture agent, which is only different from Example 1 in that cyclohexanol is adjusted to 1-propanol; the remaining steps and parameters are the same.

[0064] Comparative Example 3

[0065] This example provides a carbon dioxide capture agent, which is only different from Example 1 in that the molar ratio of the diethylenetriamine to the 2,2'-(cyclohexylimino)diethanol is adjusted to 4:1; the remaining steps and parameters are the same.

[0066] Test Example 1

[0067] In this example, according to the test methods disclosed in the prior art, the carbon dioxide capture agents provided in Examples 1 to 3 and Comparative Examples 1 to 3 were tested for their CO2 absorption loading capacity, and whether the system phase-separated after absorption saturation was observed.

[0068] Test method: 25 mL of the carbon dioxide capture agents provided in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively taken and poured into a bubbling absorption bottle, and placed in a water bath at 50 °C to be kept at a constant temperature before starting the absorption test. Pure carbon dioxide gas (30 mL / min) was introduced into the bubbling absorption bottle, and the absorption experiment was started by timing. The inlet and outlet gas flows were measured using a soap film flowmeter. When the inlet and outlet flows were equal, the solution was considered saturated and the absorption experiment was ended, and the CO2 absorption loading amount (the CO2 molar absorption amount at absorption saturation per 1 mol of the absorbent; unit, mol CO2 / mol absorbent) was obtained, and whether the system phase-separated after absorption saturation was observed. The test results are shown in Table 1.

[0069] Table 1

[0070] Test sample <![CDATA[CO2 absorption load]]> Whether phase separation occurs after adsorption saturation Example 1 2.0 Two-phase stratification is obvious Example 2 1.7 Two-phase stratification is obvious Example 3 1.8 Two-phase stratification is obvious Comparative example 1 1.2 No phase separation occurs Comparative example 2 1.5 No phase separation occurs Comparative example 3 1.3 Two-phase stratification is obvious

[0071] As can be seen from Table 1:

[0072] 1) The carbon dioxide capture agent provided by the embodiments of the present invention uses a compound of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as the absorption component, and at the same time cooperates with a solvent composed of cyclohexanol and water to form a liquid-liquid phase change absorbent for carbon dioxide capture in an aqueous system. Before contacting and absorbing the gas containing carbon dioxide, the carbon dioxide capture agent is in a homogeneous system; when the carbon dioxide capture agent contacts and absorbs carbon dioxide from the gas containing carbon dioxide until it reaches a saturated state, the carbon dioxide capture agent forms an upper and lower two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase.

[0073] 2) After changing the components of the carbon dioxide capture agent system in Comparative Example 1 and Comparative Example 2, although they still have good CO2 absorption capacity, they cannot undergo two-phase stratification after adsorption saturation.

[0074] 3) Compared with Comparative Examples 1-3, the carbon dioxide capture agent provided by the embodiments of the present invention has better CO2 absorption load capacity, can effectively promote the liquid-liquid phase change in the system, obtain a CO2-rich phase and a CO2-lean phase, reduce the amount of regeneration treatment, lower energy consumption, and better meet the industrial use requirements.

[0075] Test Example 2

[0076] On the basis of the above Test Example 1, this example further tests the regeneration performance of the carbon dioxide capture agents provided in Examples 1-3 and Comparative Example .....

[0077] Test method: Refer to the method in Test Example 1 for carbon dioxide absorption. After the carbon dioxide capture agent absorbs CO2 until saturation, it is thermally desorbed at 95 °C for 60 minutes; then the regenerated absorbent is used to repeat the above carbon dioxide absorption-thermal desorption steps, and the regeneration efficiency of the carbon dioxide capture agent after 10 cycles of recycling is calculated.

[0078] The test results are as Figure 1 shown. The carbon dioxide capture agent provided by the embodiments of the present invention has excellent regeneration performance. The regeneration efficiency after 10 cycles of carbon dioxide absorption-thermal desorption regeneration is > 70%, and the regeneration efficiency of the carbon dioxide capture agent provided in Example 1 is as high as 83%, which is significantly better than the carbon dioxide capture agent provided in Comparative Example 3 (regeneration efficiency is 48%).

[0079] In summary, the embodiments of the present invention provide a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas. In the present invention, diethylenetriamine and 2,2'-(cyclohexylimino)diethanol are compounded as absorption components, and at the same time, a solvent composed of cyclohexanol and water is used to form a water-based liquid-liquid phase change absorbent for carbon dioxide capture, which not only improves the CO2 absorption load capacity of the single diethylenetriamine absorption component, but also the obtained carbon dioxide capture agent has excellent regeneration performance, and its regeneration efficiency after 10 absorption-thermal desorption regeneration cycles is >70%, making up for the deficiencies of the existing water-based liquid-liquid phase change absorbents.

[0080] The various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0081] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A carbon dioxide capture agent, characterized in that, The carbon dioxide capture agent is composed of an absorption component and a solvent. The absorption component is composed of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol. The solvent is composed of cyclohexanol and water. The molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is (10 - 17):(1 - 3).

2. The carbon dioxide capture agent according to claim 1, characterized in that, The molar concentration of the absorption component is 3 - 6 mol / L.

3. The carbon dioxide capturing agent according to claim 1, characterized in that, The molar concentration of the absorption component is 4.5 mol / L.

4. The carbon dioxide capturing agent according to claim 1, characterized in that, The molar ratio of diethylenetriamine to 2,2'-(cyclohexylimino)diethanol is 13:

2.

5. The carbon dioxide capture agent according to claim 1, characterized in that, The volume ratio of cyclohexanol to water is (23 - 37):

100.

6. The carbon dioxide capture agent according to claim 5, characterized in that, The volume ratio of cyclohexanol to water is 31:

100.

7. The carbon dioxide capture agent according to any one of claims 1 to 6, characterized in that, Before the carbon dioxide capture agent contacts and absorbs the gas containing carbon dioxide, the carbon dioxide capture agent is in a homogeneous system; when the carbon dioxide capture agent contacts and absorbs carbon dioxide from the gas containing carbon dioxide until it reaches a saturated state, the carbon dioxide capture agent forms a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase. The lower liquid phase accounts for 25 - 60% of the total volume of the two-layer liquid phase system. The absorption temperature of the carbon dioxide capture agent is 40 - 60 °C, and the desorption and regeneration temperature of the carbon dioxide capture agent is 85 - 105 °C.

8. The carbon dioxide capture agent according to claim 7, wherein The regeneration efficiency of the carbon dioxide capture agent after 10 cycles of carbon dioxide absorption - thermal desorption regeneration is > 70%.

9. Application of the carbon dioxide capture agent according to any one of claims 1 - 8 in capturing carbon dioxide in flue gas.

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