A low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent and its application

Abstract

The embodiment of the application discloses a kind of low-temperature self-extraction regeneration functionalized ionic liquid CO2 absorbent and its application, and the absorbent includes as main absorbent functionalized ionic liquid into di-n-butylamine imidazole ([DBAH][Im]) and solvent.Due to main absorbent is functionalized ionic liquid, there is group interaction between absorbent anion and cation, so that the desorption free energy of absorption product is lower, and low-temperature regeneration is realized to reduce energy consumption.At the same time, the embodiment also has the "self-extraction" characteristic, that is, in the regeneration process, the desorbed ionic liquid is collected at the top of the solution to form an organic phase, which acts as a self-extraction agent to extract the ionic liquid regenerated subsequently in the aqueous phase.Due to the "self-extraction" effect of functionalized ionic liquid in the desorption process, the absorbent can be quickly separated from the product, thereby promoting the desorption process and improving the desorption rate.The embodiment has the advantages of functionalized ionic liquid and phase change absorbent, with the advantages of low cost, high regeneration efficiency and low regeneration energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture technology, specifically relating to a low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent. Background Technology

[0002] Global warming has become one of the most pressing environmental issues for the international community, and carbon dioxide (CO2), as a major greenhouse gas, is crucial for controlling and reducing its emissions. Carbon capture, utilization, and storage (CCUS) technology is considered the most direct and effective carbon reduction technology currently available. In the carbon capture process, chemical absorption using organic amines as absorbents has advantages such as fast absorption rates and good selectivity, and is widely used in industry, accounting for over 60% of the current carbon capture market. However, current chemical absorbents suffer from drawbacks such as low absorption load, easy oxidation and decomposition, and high regeneration energy consumption, which have become technical bottlenecks for their widespread application. Therefore, developing novel absorbents capable of low-temperature regeneration based on traditional organic amine solvents has become a research hotspot in recent years.

[0003] Phase change absorbents are a new type of absorbent with great energy-saving potential, retaining the high reaction rate of chemical absorption methods while possessing broad energy-saving potential. Phase change absorbents are divided into two categories. Most of the phase change absorbents currently being studied are of the first type, which are homogeneous before absorption and undergo a phase change after CO2 absorption saturation. By reducing the volume and mass of the regenerated liquid, regeneration energy consumption can be effectively reduced. However, the rich phase often has high viscosity, easily leading to equipment blockage and pipeline corrosion. The second type of phase change absorbent is a two-phase system at room temperature before absorption. After CO2 absorption saturation, it becomes a homogeneous system and undergoes a phase change again during thermal regeneration. Due to self-extraction, it can break up the chemical reaction vessel and promote regeneration, thereby reducing the regeneration temperature and saving energy. Type II phase change absorbers can effectively reduce regeneration energy consumption, but there are few reports on them. The absorption performance of the developed Type II phase change absorbers cannot reach the level of the benchmark MEA. Most of them require multiple components to regulate the formation of the extraction phase. The self-extraction speed is very slow and the self-extraction effect is not obvious. At the same time, a large amount of extractant needs to be added and multi-stage extraction needs to be used to achieve "extraction", which increases the cost and operation difficulty. Furthermore, N2 stripping is required during the regeneration process. Summary of the Invention

[0004] The purpose of this invention is to overcome the bottlenecks of current technology and propose a low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent and its application, which solves the problems of high CO2 desorption temperature and high regeneration energy consumption in the above-mentioned background technology.

[0005] This invention provides a low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent, comprising the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im]; the chemical formula of the functionalized ionic liquid [DBAH][Im] is:

[0006]

[0007] Preferably, the mixture also includes a solvent, wherein the concentration of the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im] is 0.5–1 mol / L.

[0008] Preferably, the solvent is water, and the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im] forms a binary system with water.

[0009] Preferably, the binary system is a liquid-liquid two-phase solution before absorbing CO2, becomes a homogeneous system after saturation with CO2, and reverts to a liquid-liquid two-phase solution after thermal desorption.

[0010] Preferably, the saturated solution of the homogeneous system is regenerated by thermal desorption, with a regeneration temperature of 70-90°C, a regeneration time of 90-120 min, and a regeneration efficiency of 75-95%.

[0011] Preferably, during the regeneration process, the regenerated ionic liquid forms an organic phase above the solution and spontaneously extracts the regenerated amine into the upper phase.

[0012] The present invention also discloses the application of the functionalized ionic liquid CO2 absorbent with low-temperature self-extraction and regeneration as described above in CO2 absorption; it is used to absorb pure CO2 or CO2 in a mixed gas with a volume ratio of 5-20%, the absorption temperature is 30-60℃, and the absorption load is 0.65-0.82 mol CO2 / mol ILs.

[0013] The embodiments of the present invention have at least the following advantages:

[0014] 1. The embodiments of the present invention employ functionalized ionic liquid phase change absorbents, which achieve efficient self-extraction and regeneration at low temperatures by adjusting the combination of anions and cations. They have good CO2 capture performance (absorption load of 0.65-0.82 mol CO2 / mol ILs) and regeneration performance (regeneration efficiency of 75-95%).

[0015] 2. Due to the designability of functionalized ionic liquids, the stability of the product carbamate is reduced by adjusting the combination of anions and cations, thus achieving low-temperature regeneration; self-extraction regeneration through thermal desorption effectively avoids the use of N2 purging and heating regeneration, effectively ensuring the purity of the final collected CO2 gas, which is beneficial for the subsequent sealing and storage of CCUS.

[0016] 3. During the regeneration process, the regenerated ionic liquid forms an organic phase on the top of the solution, spontaneously extracting the regenerated ionic liquid into the organic phase (self-extraction), thereby promoting the forward regeneration reaction, achieving low-temperature and high-efficiency regeneration, which can greatly reduce regeneration energy consumption, overcome the shortcomings of traditional organic amines in low-temperature regeneration, and is more conducive to industrial promotion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the CO2 absorption performance of aqueous solutions of ionic liquids at different concentrations provided in an embodiment of the present invention.

[0018] Figure 2 Photographs of samples of 0.5 mol / L ionic liquid aqueous solution, where a - before absorption, b - absorption saturation, c - self-extraction regeneration;

[0019] Figure 3 This is a schematic diagram showing the regeneration efficiency of the thermal desorption method at different regeneration temperatures according to the present invention. Detailed Implementation

[0020] Example 1

[0021] This embodiment provides a low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent, which includes the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im]; the chemical formula of the functionalized ionic liquid [DBAH][Im] is:

[0022]

[0023] In this application, the functionalized ionic liquid di-n-butylamine imidazole is used as the main absorbent, and water as the solvent. Because the main absorbent is a functionalized ionic liquid, there are functional group interactions between its cations and anions, resulting in a lower desorption free energy for the absorbed products, enabling low-temperature regeneration and reducing energy consumption. Simultaneously, the functionalized ionic liquid CO2 absorbent exhibits a "self-extraction" characteristic; during regeneration, the desorbed ionic liquid collects at the top of the solution to form an organic phase. This organic phase acts as a self-extracting agent to extract subsequently regenerated ionic liquid from the aqueous phase. Due to the "self-extraction" effect of the functionalized ionic liquid during desorption, the absorbent can be rapidly separated from the products, thereby promoting desorption and increasing the desorption rate.

[0024] Specifically, in this embodiment, the concentration of the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im] is 0.5–1 mol / L, which can be used to absorb pure CO2 or CO2 in a mixed gas at a volume ratio of 5–20%, with an absorption temperature of 30–60°C. Before absorbing CO2, the absorbent is a liquid-liquid two-phase solution. After CO2 absorption saturation, it becomes a homogeneous system (absorption load of 0.65–0.82 mol CO2 / mol ILs). The saturated solution of the homogeneous system is regenerated by thermal desorption at a regeneration temperature of 70–90°C for 90–120 min, with a regeneration efficiency of 75–95%. During the regeneration process, the regenerated ionic liquid forms an organic phase above the solution and spontaneously extracts the regenerated amine into the upper phase, thereby achieving "self-extraction".

[0025] The following are some practical examples illustrating the application of this invention:

[0026] Comparative Example 1

[0027] This comparative example uses 0.5 mol / L DBA aqueous solution and Im aqueous solution. DBA aqueous solution will produce a phase change phenomenon after absorbing CO2, but the self-extraction effect is poor and the regeneration efficiency is low; Im aqueous solution has no phase separation phenomenon and low absorption load.

[0028] Comparative Example 2

[0029] The difference between this comparative example and Example 1 is that the cation amine ions used to prepare the functionalized ionic liquid are different. [DMCAH][IM] was selected as the control sample to absorb CO2. The results showed that it was a liquid-liquid two-phase before absorption and a homogeneous phase after absorption saturation. However, it could not achieve self-extraction and regeneration under thermal desorption, and no phase separation occurred after regeneration.

[0030] Comparative Example 3

[0031] This comparative example uses a 30wt% MEA aqueous solution. MEA was selected as the control sample for CO2 absorption. Both the absorption and the sample were in liquid phase. The absorption load was only 0.50 mol CO2 / mol ILs. The regeneration temperature was 120℃, and the regeneration energy consumption was as high as 3.8 GJ / tCO2.

[0032] I. Load and phase separation effect detection of CO2 absorption systems in Example 1 and Comparative Examples 1, 2, and 3

[0033] At 40°C, the CO2 absorption performance and phase separation effect of the low-temperature self-extraction and regeneration functionalized ionic liquid CO2 capture system [DBAH][Im]-water binary system of Example 1 were tested, and compared with the CO2 absorption load and energy consumption of the comparative examples 0.5 mol / L DBA aqueous solution and Im aqueous solution.

[0034] Method: Take 25 mL of each of the DBAPA aqueous solution and Im aqueous solution from Example 1 and Comparative Example 1, pour them into separate bubbling absorption bottles, and place them in a 40°C water bath to maintain a constant temperature. Then, introduce CO2 to begin the absorption test until the absorbent is saturated. This experiment allows us to obtain the change in the CO2 absorption rate of different absorbents over time. Integrating the absorption rate versus time yields the CO2 load on the absorbent at different times.

[0035] Result: As Figure 1 As shown, the CO2 absorption capacity of the [DBAH][Im]-water binary system varies significantly with different concentrations. The absorption load gradually decreases with increasing concentration. In the [DBAH][Im]-water binary system, the CO2 absorption load is highest at a concentration of 0.5 mol / L, reaching 0.82 mol CO2 / mol ILs. This binary system, composed of a functionalized ionic liquid, forms a self-extraction CO2 capture system. Before CO2 absorption, it is a liquid-liquid two-phase solution; after CO2 absorption saturation, it becomes a homogeneous, transparent liquid solution; and after regeneration, it reverts to a liquid-liquid two-phase solution.

[0036] In Comparative Example 1, the DBA aqueous solution undergoes a phase change after absorbing CO2, but exhibits poor self-extraction and low regeneration efficiency. The Im aqueous solution shows no phase change or self-extraction, and also has a low absorption load. Comparative Example 2 similarly lacks self-extraction regeneration capability. Comparative Example 3, with its MEA absorption load of only 0.50 mol CO2 / mol ILs, a regeneration temperature of 120℃, and a regeneration energy consumption as high as 3.8 GJ / t CO2, demonstrates a clear advantage.

[0037] Figure 2 The figure shows the phase separation of the [DBAH][Im]-water binary system before and after CO2 absorption and after regeneration at a concentration of 0.5 mol / L. As can be seen from the figure, the fresh solution is divided into two liquid phases. After CO2 absorption saturation, it becomes a clear homogeneous phase. After pyrolysis and self-extraction regeneration at 90℃, the solution reverts to a two-liquid phase, indicating that this phase change system can be regenerated at low temperatures.

[0038] The functionalized ionic liquid absorbent provided in this embodiment, compared with traditional organic amine aqueous solutions, while ensuring CO2 absorption performance, can be regenerated at temperatures below 90°C due to its self-extraction and regeneration characteristics. This avoids a large amount of energy consumption in the heating and vaporization process of the solvent water, effectively reducing the energy consumption of the regeneration process, and has obvious advantages.

[0039] II. Example 1: Regeneration Performance Testing

[0040] Due to the large volume of industrial waste gas, the regeneration and recycling of absorbents is a crucial step, impacting process costs. Common absorbent regeneration methods include thermal desorption, membrane filtration, and pressure swing methods. This experimental example uses thermal desorption as the regeneration method. By comparing the absorption load before and after regeneration, the regeneration capacity of the absorbent is examined.

[0041] Methods: The [DBAH][Im]-water binary system (0.5M) solution from Example 1 was used to absorb CO2 to saturation at 40°C, as described in Experiment 1. The saturated absorbent was then thermally desorbed for 120 min at different regeneration temperatures (70, 80, 90°C). The regenerated absorbent was then subjected to repeated absorption experiments as described in Experiment 1 to investigate the effect of different regeneration temperatures on absorption performance.

[0042] Result: As Figure 3 As shown, the [DBAH][Im]-water binary system (0.5M) solution can be regenerated at temperatures ranging from 70 to 90°C. However, the regeneration efficiency increases with increasing temperature, reaching its maximum at 90°C (95%). The regeneration temperature for traditional organic amine aqueous solutions is generally 120°C. Traditional phase change amine absorbents achieve a regeneration efficiency of only 70-80% at 120°C. In Comparative Example 3, MEA achieved a regeneration efficiency of 92% at 120°C, while its regeneration efficiency at 100°C was only 42%. Therefore, the low-temperature self-extraction regeneration functionalized ionic liquid CO2 absorbent described in this patent, in addition to its high self-extraction regeneration efficiency, effectively overcomes the difficulty of low-temperature regeneration of existing chemical absorbents.

[0043] The present invention also discloses the application of the functionalized ionic liquid CO2 absorbent with low-temperature self-extraction and regeneration as described above in CO2 absorption; it is used to absorb pure CO2 or CO2 in a mixed gas with a volume ratio of 5-20%, the absorption temperature is 30-60℃, and the absorption load is 0.65-0.82 mol CO2 / mol ILs.

[0044] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent, characterized in that: This includes the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im]; the chemical formula of the functionalized ionic liquid [DBAH][Im] is: ， The low-temperature self-extraction regeneration functionalized ionic liquid CO2 absorbent further includes a solvent, namely water. The functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im] forms a binary system with water. The concentration of the functionalized ionic liquid di-n-butylamine imidazole [DBAH][Im] is 0.5–1 mol / L, and its absorption load is 0.65–0.82 mol CO2 / mol ILs. The regeneration temperature of the functionalized ionic liquid CO2 absorbent is 70–90℃.

2. The functionalized ionic liquid CO2 absorbent with low-temperature self-extraction and regeneration according to claim 1, characterized in that: The binary system is a liquid-liquid two-phase solution before absorbing CO2, becomes a homogeneous system after saturation with CO2, and reverts to a liquid-liquid two-phase solution after thermal desorption.

3. The functionalized ionic liquid CO2 absorbent with low-temperature self-extraction and regeneration according to claim 2, characterized in that: The saturated solution of the homogeneous system is regenerated by thermal desorption, with a regeneration time of 90–120 min and a regeneration efficiency of 75–95%.

4. The functionalized ionic liquid CO2 absorbent with low-temperature self-extraction and regeneration according to claim 3, characterized in that: During the regeneration process, the regenerated ionic liquid forms an organic phase above the solution and spontaneously extracts the regenerated amine into the upper phase.

5. The application of a low-temperature self-extraction and regeneration functionalized ionic liquid CO2 absorbent as described in any one of claims 1 to 4 in CO2 absorption; it is used to absorb pure CO2 or CO2 in a mixed gas at a volume ratio of 5 to 20%, and the absorption temperature is 30 to 60°C.

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