Carbon dioxide trapping agent and application thereof in trapping carbon dioxide in flue gas

Abstract

The invention discloses a carbon dioxide trapping agent and application thereof to trapping of carbon dioxide in flue gas, and relates to the technical field of carbon dioxide trapping, the carbon dioxide trapping agent is composed of an absorption component and a solvent, the absorption component is composed of diethylenetriamine and 2, 2 '-diethylenetriamine, and the solvent is composed of diethylenetriamine and 2, 2'-diethylenetriamine. The solvent is composed of 2, 2 '-(cyclohexyl imino) diethanol, and the solvent is composed of cyclohexanol and water. According to the invention, diethylenetriamine and 2, 2, 4-trimethyl-1, 3 2, 2 '-(cyclohexyl imino) diethanol is compounded as an absorption component, and is matched with a solvent consisting of cyclohexanol and water to form a water system liquid-liquid phase change absorbent for capturing carbon dioxide, so that the CO2 absorption load capacity of the single diethylenetriamine absorption component is improved; and the obtained carbon dioxide trapping agent has excellent regeneration performance, the regeneration efficiency of the carbon dioxide trapping agent after 10 times of absorption-thermal desorption regeneration cyclic utilization is greater than 70%, and the defects of an existing water system liquid-liquid phase change absorbent are overcome.

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 application thereof in capturing carbon dioxide in flue gas. Background Art

[0002] As the global industrialization process continues to accelerate, the emission of greenhouse gases such as CO2 has become increasingly prominent and has become one of the main factors leading to climate change. In particular, the content of carbon dioxide in flue gas emissions has continued to increase, causing serious impacts on the environment and exacerbating the trend of global warming. Therefore, how to efficiently and economically capture or separate CO2 from CO2-rich gas mixtures has become a key issue that needs to be urgently addressed in the current 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 because of 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] In order to overcome the shortcomings of existing technologies, researchers have been actively exploring new carbon dioxide capture agents. Among them, liquid-liquid phase change absorbents have attracted much attention due to their unique phase change characteristics. This type of absorbent can achieve phase transition during the absorption and regeneration process, reducing the amount of rich liquid required for regeneration, thereby reducing regeneration energy consumption. However, despite the many advantages of liquid-liquid phase change absorbents, current aqueous liquid-liquid phase change absorbents still have some problems. For example, low regeneration efficiency and poor cycle stability, these problems further limit their promotion 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 consists of an absorption component and a solvent, wherein the absorption component consists of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent consists of cyclohexanol and water.

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

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

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

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

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

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

[0013] Furthermore, before the carbon dioxide capture agent contacts and absorbs the gas containing carbon dioxide, the carbon dioxide capture agent is a homogeneous system; after the carbon dioxide capture agent contacts and absorbs carbon dioxide to a saturated state, the carbon dioxide capture agent is a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase, and the lower liquid accounts for 25-60% of the total volume of the upper and lower liquid phase systems;

[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] Furthermore, the regeneration efficiency of the carbon dioxide capture agent after 10 cycles of carbon dioxide absorption-thermal desorption regeneration is greater than 70%.

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

[0017] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0018] The embodiment of the present invention provides a carbon dioxide capture agent and its application in capturing carbon dioxide in flue gas. The present invention uses diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as absorption components, and simultaneously uses a solvent composed of cyclohexanol and water to form a water system liquid-liquid phase change absorbent for carbon dioxide capture. This not only improves the CO2 absorption load capacity of a single diethylenetriamine absorption component, but also the obtained carbon dioxide capture agent has excellent regeneration performance. Its regeneration efficiency after 10 absorption-thermal desorption regeneration cycles is greater than 70%, which makes up for the shortcomings of existing water system liquid-liquid phase change absorbents. Specifically:

[0019] 1. Selection of absorption components

[0020] Diethylenetriamine (DETA) is a linear polyamine (containing three amino groups) with high reactivity, which can quickly react with CO2 to form carbamate, and its polyamino structure provides abundant reaction sites, significantly improving the initial absorption rate and capacity; at the same time, it is combined with 2,2'-(cyclohexylimino)diethanol, which has a 6-membered ring structure-cyclohexyl and a symmetrical chemical structure, which 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, and improving the total absorption load capacity of CO2. On the other hand, the hydrophobicity and steric hindrance effect of the cyclohexyl group reduce the oxidative degradation of the amine, prolong the life of the absorbent, and can also weaken the binding energy of CO2 and 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 of 2,2'-(cyclohexylimino)diethanol with a 6-membered ring symmetrical structure. The combination of the two achieves a balance between high absorption capacity and high regeneration efficiency, reduces degradation, and maintains cyclic stability, thereby improving the regeneration performance of the resulting carbon dioxide capture agent.

[0021] 2. Choice of solvent

[0022] The present invention introduces an appropriate amount of cyclohexanol to form a mixed solvent based on the existing water system liquid-liquid phase change absorbent using water as solvent. The hydrophobicity of the cyclohexyl group is used to reduce the solubility of the product after CO2 absorption, induce and promote the system to undergo liquid-liquid phase change, obtain a CO2-rich phase and a CO2-poor phase, thereby reducing the regeneration processing amount. The present invention optimizes the balance between the solubility and hydrophobicity of the solvent by compounding cyclohexanol and water, matches the absorption component, can ensure the full dissolution of the amine and the effective phase separation of the absorption product, and is also conducive to reducing solvent volatilization and helping to maintain the stability of the system, thereby achieving an efficient cycle of "absorption homogeneity-regeneration phase separation". BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 This is a comparison chart of the regeneration efficiency of different carbon dioxide capture agents in the test examples of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

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

[0029] An embodiment of the present invention provides a carbon dioxide capture agent. The present invention uses diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as absorption components, and simultaneously uses a solvent consisting of cyclohexanol and water to form a water system liquid-liquid phase change absorbent for carbon dioxide capture. This not only improves the CO2 absorption load capacity of a single diethylenetriamine absorption component, but also the obtained carbon dioxide capture agent has excellent regeneration performance. The regeneration efficiency of the carbon dioxide capture agent after 10 absorption-thermal desorption regeneration cycles is greater than 70%, which makes up for the shortcomings of existing water system liquid-liquid phase change absorbents.

[0030] The CAS registration 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 structure is as follows:

[0033]

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

[0035] In some specific embodiments, the molar concentration of the absorption component is 3-6 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 the diethylenetriamine to the 2,2'-(cyclohexylimino)diethanol is (10-17):(1-3).

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

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

[0040] In some specific embodiments, the volume ratio of the cyclohexanol to the 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 a homogeneous system; after the carbon dioxide capture agent contacts and absorbs carbon dioxide to a saturated state, the carbon dioxide capture agent is a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase, and the lower liquid accounts for 25-60% of the total volume of the upper and lower liquid phase systems;

[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 greater than 70%.

[0044] The regeneration efficiency in the present invention refers to the ability of the carbon dioxide capture agent to restore its original capture capacity 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 regenerated carbon dioxide capture agent 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 a use of the carbon dioxide capture agent described in any one of the first aspects in capturing carbon dioxide in flue gas.

[0046] It should be noted that the carbon dioxide capture agent provided in the embodiments of the present invention and the component raw materials involved in its application in capturing carbon dioxide in flue gas, unless otherwise specified or specified, can be directly commercially available products or homemade using existing public preparation methods; at the same time, the steps and parameters involved, unless otherwise specified or specified, can be carried out according to the preparation process disclosed in the prior art or directly using existing equipment with reference to the instructions for use, and the present invention document will not repeat them one by one.

[0047] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0048] Example 1

[0049] This example 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;

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

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

[0052] Example 2

[0053] This example 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;

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

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

[0056] Example 3

[0057] This example 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;

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

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

[0060] Comparative Example 1

[0061] This example provides a carbon dioxide capture agent, which is different from Example 1 only 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 different from Example 1 only 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 different from Example 1 only in that the molar ratio of the diethylenetriamine and 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, the CO2 absorption load capacity of the carbon dioxide capture agents provided in Examples 1 to 3 and Comparative Examples 1 to 3 was tested according to the test method disclosed in the prior art, and whether the system was phase-separated after absorption saturation was observed.

[0068] Test method: Take 25 mL of the carbon dioxide capture agent provided in Examples 1 to 3 and Comparative Examples 1 to 3 respectively, pour each into a bubbling absorption bottle, place it in a 50°C water bath and keep it warm to a constant temperature before starting the absorption test. Pure carbon dioxide gas (30 mL / min) is introduced into the bubbling absorption bottle, and the timing is started for the absorption experiment. The inlet and outlet gas flow rates are tested using a soap film flowmeter. When the inlet and outlet flow rates are equal, the solution is considered saturated, the absorption experiment is completed, and the CO2 absorption load (based on 1 mol of absorbent, the CO2 molar absorption when the absorption is saturated; unit, mol CO2 / mol absorbent) is obtained, and observe whether the system is phase-separated after absorption saturation. The test results are shown in Table 1.

[0069] Table 1

[0070] Test samples <![CDATA[CO2 absorption load]]> Is there phase separation after adsorption saturation? Example 1 2.0 Two-phase separation is obvious Example 2 1.7 Two-phase separation is obvious Example 3 1.8 Two-phase separation is obvious Comparative Example 1 1.2 No phase separation Comparative Example 2 1.5 No phase separation Comparative Example 3 1.3 Two-phase separation is obvious

[0071] From Table 1, we can see that:

[0072] 1) The carbon dioxide capture agent provided in an embodiment of the present invention is compounded with diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as absorption components, and a solvent composed of cyclohexanol and water is used to form a water system liquid-liquid phase change absorbent for carbon dioxide capture. Before contacting and absorbing the gas containing carbon dioxide, the carbon dioxide capture agent is a homogeneous system; when the carbon dioxide capture agent contacts the gas containing carbon dioxide and absorbs carbon dioxide to a saturated state, the carbon dioxide capture agent is a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase.

[0073] 2) After the components of the carbon dioxide capture agent system were changed in Comparative Examples 1 and 2, although they still had good CO2 absorption capacity, two-phase stratification could not occur after adsorption saturation.

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

[0075] Test Example 2

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

[0077] Test method: Refer to the method in Test Example 1 to absorb carbon dioxide. After the carbon dioxide capture agent absorbs CO2 to saturation, thermal desorption is carried out at 95°C for 60 minutes. The regenerated absorbent is then subjected to repeated carbon dioxide absorption-thermal desorption steps to calculate the regeneration efficiency of the carbon dioxide capture agent after 10 cycles.

[0078] Test results such as Figure 1 As shown, the carbon dioxide capture agent provided by the embodiment of the present invention has excellent regeneration performance, and the regeneration efficiency after 10 cycles of carbon dioxide absorption-thermal desorption regeneration is greater than 70%, and the regeneration efficiency of the carbon dioxide capture agent provided by Example 1 is as high as 83%, which is significantly better than the carbon dioxide capture agent provided by 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. The present invention forms a water system liquid-liquid phase change absorbent for carbon dioxide capture by compounding diethylenetriamine and 2,2'-(cyclohexylimino)diethanol as absorption components and combining them with a solvent consisting of cyclohexanol and water. This not only improves the CO2 absorption load capacity of a single diethylenetriamine absorption component, but also the obtained carbon dioxide capture agent has excellent regeneration performance. The regeneration efficiency is greater than 70% after 10 absorption-thermal desorption regeneration cycles, which makes up for the shortcomings of existing water system liquid-liquid phase change absorbents.

[0080] Various embodiments of the present invention may be presented 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 understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0081] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may 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 the embodiments shown herein, but rather to the widest 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 consists of an absorption component and a solvent, wherein the absorption component consists of diethylenetriamine and 2,2'-(cyclohexylimino)diethanol, and the solvent consists of cyclohexanol and water.

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

4. The carbon dioxide capture agent according to claim 1, characterized in that The molar ratio of the diethylenetriamine to the 2,2'-(cyclohexylimino)diethanol is (10-17):(1-3).

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

2.

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

100.

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

100.

8. The carbon dioxide capture agent according to any one of claims 1 to 7, characterized in that Before the carbon dioxide capture agent contacts and absorbs the gas containing carbon dioxide, the carbon dioxide capture agent is a homogeneous system; after the carbon dioxide capture agent contacts and absorbs carbon dioxide to a saturated state, the carbon dioxide capture agent is a two-layer liquid phase system, and carbon dioxide is enriched in the lower liquid phase, and the lower liquid accounts for 25-60% of the total volume of the upper and lower liquid phase systems; 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.

9. The carbon dioxide capture agent according to claim 8, characterized in that The regeneration efficiency of the carbon dioxide capture agent after 10 cycles of carbon dioxide absorption-thermal desorption regeneration is greater than 70%.

10. Use of the carbon dioxide capture agent according to any one of claims 1 to 9 for capturing carbon dioxide in flue gas.

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