High-performance liquid-liquid phase change carbon dioxide capture absorbent based on adjustable chemical combination as well as preparation and application of high-performance liquid-liquid phase change carbon dioxide capture absorbent

Abstract

The invention provides a high-efficiency liquid-liquid phase change carbon dioxide capture absorbent based on adjustable chemical combination, and the absorbent realizes high-efficiency capture of carbon dioxide through an elaborately designed chemical formula. The method is characterized in that multiple chemical components (including but not limited to preferable absorbents such as diethylenetriamine and the like) in a specific proportion are mixed with a solvent to form a two-phase system which can generate obvious phase change after carbon dioxide is absorbed. The phase change characteristic not only improves the loading capacity of the absorbent on carbon dioxide, but also accelerates the absorption and desorption processes, thereby improving the overall efficiency. Besides, chemical combination is allowed to be adjusted according to specific application requirements, so that the optimal capturing effect is achieved, and the advantage of chemical combination variability is shown. In the preparation aspect, detailed steps and conditions are provided, and high-quality preparation of the absorbent is ensured. Finally, the absorbent has wide application prospects in the fields of carbon capture, industrial waste gas treatment and the like, and powerful technical support is provided for coping with global climate changes.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical absorbents, and specifically relates to a high-efficiency liquid-liquid phase change carbon dioxide capture absorbent based on adjustable chemical combination and its preparation and application. This technical field covers the design, preparation, performance testing of chemical absorbents and their applications in carbon dioxide capture and separation, industrial emission source flue gas purification, etc. Background Art

[0002] With the acceleration of global industrialization, greenhouse gas emissions, especially carbon dioxide (CO2) emissions, have increased dramatically and have become the main driving force of global climate change. In order to meet this severe challenge, carbon dioxide capture, utilization and storage (CCUS) technology, as a key means to reduce greenhouse gas emissions, is receiving widespread attention and in-depth research from the international community. Among CCUS technologies, post-combustion capture technology has become an important way to achieve large-scale CO2 emission reductions due to its small changes to existing industrial facilities and strong adaptability. However, traditional absorbents such as monoethanolamine (MEA) still face many challenges in the application of post-combustion capture technology. First, absorbents such as MEA have the problems of high volatility and easy oxidation and degradation, which not only increases operating costs, but also may cause corrosion to equipment, affecting the stability and reliability of the overall system. Secondly, the regeneration energy consumption of traditional absorbents is high, which limits their economy and sustainability in industrial applications.

[0003] In order to overcome the limitations of traditional absorbents, researchers are committed to developing new absorbents, among which phase change absorbents have attracted much attention due to their unique phase change properties. Phase change absorbents can undergo liquid-liquid or liquid-solid phase changes when absorbing CO2 or undergoing temperature changes, thereby achieving efficient recovery and regeneration of CO2 through simple physical separation. However, existing phase change absorbent technology still faces many challenges:

[0004] 1. Unclear separation mechanism: For example, the Chinese patent application “Self-concentrating absorbent for acid gas separation” (application number 201610256672.8) achieves mechanical separation of the concentrated amine phase and the remaining absorbent after absorption, but does not clearly indicate the solvent that causes phase separation, the precise composition of the absorbent and the concentration of each component, nor does it give the concentration and enrichment ratio after the absorbent phase change, which limits its repeatability and efficiency in practical applications.

[0005] 2. Poor absorbent stability: For example, "A liquid-liquid phase change absorbent for acid gas separation" (application number 201510933372.4) uses a combination of MEA and other water-soluble organic matter. Although the liquid-liquid phase change characteristics are utilized, the volatility and oxidative degradation problems of MEA have not been effectively solved, resulting in high loss costs in industrial applications.

[0006] 3. Low mass transfer efficiency: Some phase change absorbents, such as “A liquid-liquid phase change absorbent with controllable threshold for carbon dioxide capture” (application number 202111059605.4), increase the viscosity of the solution after absorbing CO2, resulting in reduced mass transfer efficiency, which is not conducive to industrial applications.

[0007] 4. Poor cycle performance: For example, in the application “A liquid-liquid phase change absorbent for carbon dioxide capture” (application number 202111058819.X), the relatively high amine concentration in the CO2-lean phase after phase separation affects the efficiency and cycle performance of the absorbent, and the phase change point load of the monoethanolamine-based system is low, resulting in poor mass transfer and heat transfer performance of the absorbent during the absorption process.

[0008] In view of the above analysis, the present invention proposes a new type of liquid-liquid phase change absorbent, which aims to overcome the shortcomings of the prior art through innovative chemical combinations and phase change mechanisms. The absorbent of the present invention is carefully proportioned by primary, secondary amines or polyamines, N,N-dimethylformamide (DMF), water and trace additives. By precisely controlling the proportion and interaction of each component, rapid automatic stratification and efficient enrichment after absorbing CO2 are achieved. This innovation not only significantly improves the capture efficiency and enrichment purity of CO2, but also effectively reduces the energy consumption and operating costs during the regeneration process. At the same time, the absorbent of the present invention also exhibits good chemical stability and cycle performance, providing a more reliable and economical solution for the industrial application of CCUS technology. Summary of the invention

[0009] The present invention aims to provide a high-efficiency liquid-liquid phase change carbon dioxide capture absorbent based on adjustable chemical combinations and its preparation and application. The present invention not only solves the problems of high volatility, easy oxidation degradation, high regeneration energy consumption and low mass transfer efficiency of traditional absorbents in the carbon dioxide capture process in the prior art, but also achieves high-efficiency capture and low-energy regeneration of carbon dioxide by preferably using N,N-dimethylformamide (DMF) as a polar aprotic solvent and combining a specific chemical combination such as diethylenetriamine (DETA) as the main component of organic amine compounds.

[0010] The primary purpose of the present invention is to provide a liquid-liquid phase change absorbent with flexible and changeable chemical composition and superior performance. The absorbent overcomes the shortcomings of traditional absorbents by combining preferred solvents with amines, achieves efficient capture of carbon dioxide under mild conditions, and spontaneously forms a clear liquid-liquid two-phase system after absorption, thereby achieving efficient enrichment and recovery of CO2. At the same time, the present invention is also committed to reducing the regeneration energy consumption of the absorbent, improving its chemical stability and cycle performance, so as to meet the needs of industrial applications.

[0011] The core of the present invention is to develop an absorbent with precise chemical composition and excellent performance. Its key ingredient, diethylenetriamine (DETA), exhibits extremely high reactivity because it contains 3 amino groups (including 2 highly reactive primary amino groups and 1 secondary amino group). This unique molecular structure enables DETA to quickly react chemically with CO2 to form a stable complex, thereby ensuring the high absorption rate and absorption capacity of the phase change absorbent. In addition, the phase separation agent N,N-dimethylformamide (DMF) selected in the present invention has a wide phase separation threshold and can phase separate with more organic amine solvents. Therefore, the phase change absorbent of the present invention can achieve the characteristic of controllable threshold and has a variety of application scenarios.

[0012] The technical solution adopted by the present invention is as follows:

[0013] (1) Composition of the absorbent: The core component of the liquid-liquid phase change absorbent of the present invention is the organic amine compound diethylenetriamine (DETA), whose unique molecular structure contains three amino groups (two primary amino groups and one secondary amino group), giving it high reactivity and enabling it to react quickly with CO2 to form a stable complex. The content range of DETA is optimized to 20% to 40% to ensure sufficient reactivity and absorption capacity. In addition, the absorbent also contains a polar aprotic solvent N,N-dimethylformamide (DMF, content range of 20% to 50%) with a wide phase separation threshold, water (content range of 10% to 60%), and trace additives (such as defoamers, antioxidants and corrosion inhibitors, the total content is limited to not affecting the main properties of the absorbent). These components are precisely formulated in specific proportions and work together to improve the overall performance of the absorbent. This flexibility in chemical composition combined with the wide phase separation threshold characteristics of DMF enables the absorbent to spontaneously form a clear liquid-liquid two-phase system under a wider range of conditions, thereby optimizing the capture and enrichment process of CO2. This flexibility in chemical composition allows the performance of the absorbent to be adjusted according to actual needs to suit different application scenarios.

[0014] (2) Preparation of absorbent: It is prepared by a one-step or multi-step synthesis method by precisely controlling the ratio and interaction of each component. During the preparation process, each component is fully mixed under specific conditions to form a uniform and stable solution system.

[0015] (3) Phase change mechanism of absorbent: When the absorbent of the present invention is in full contact with the CO2-containing gas, organic amine compounds such as DETA, especially the three amino groups it contains (including two highly reactive primary amino groups and one secondary amino group), rapidly react chemically with CO2 to form a stable complex. This high reactivity not only ensures the rapid capture of CO2 by the absorbent, but also promotes the formation of a liquid-liquid two-phase system during the absorption process. As the amount of CO2 absorbed gradually increases, due to the wide phase separation threshold of DMF, the system can reach the phase change point under a wider range of conditions and spontaneously form a clear liquid-liquid two-phase system: a lower phase (rich phase) rich in CO2 and an upper phase (poor phase) mainly composed of water and DMF. In this process, the amino group of DETA not only reacts with CO2, but also affects the phase equilibrium of the system, making the phase change process more efficient and controllable. The CO2 content in the rich phase can be as high as more than 90%, and even more than 98% under certain specific chemical combinations, showing excellent CO2 capture efficiency.

[0016] (4) Regeneration of absorbent: The absorbent of the present invention has a simple and efficient regeneration process. Through simple heating treatment, CO2 in the rich phase can be desorbed and recovered, thereby realizing the recycling of the absorbent. During the regeneration process, due to the synergistic effect of DMF and DETA and the chemical stability and phase change characteristics of the absorbent, the regeneration energy consumption is significantly reduced, and the regenerated absorbent has stable performance and excellent cycle performance.

[0017] (5) Application of absorbent and determination of phase separation point: The liquid-liquid phase change absorbent of the present invention can be widely used in the flue gas purification process of industrial emission sources such as coal-fired power plants, cement plants, steel plants, and any environmentally friendly absorbent application scenario aimed at reducing industrial CO2 emissions. Its high CO2 capture efficiency and low energy consumption regeneration process provide a more reliable and economical solution for the industrial application of CCUS technology. In practical applications, in order to accurately grasp the phase separation behavior of the absorbent under different load conditions, we determined the phase separation point. The specific steps are as follows:

[0018] 1) Prepare the phase change absorbent: First, accurately prepare a certain amount of liquid-liquid phase change absorbent according to the ratio and method described in the present invention. The absorbent should contain appropriate ratios of N,N-dimethylformamide (DMF), diethylenetriamine (DETA), water, and possible other trace additives.

[0019] 2) Saturation load experiment: Place the configured phase change absorbent in the absorption device and introduce a mixed gas containing CO2. By controlling the gas flow rate and contact time, the absorbent reaches a saturated load state, that is, its ability to absorb CO2 reaches its maximum.

[0020] 3) Phase separation point determination: Subsequently, the saturated load solution after absorption and the fresh solution that has not absorbed CO2 are prepared in different volume ratios, and the ratio is selected to be between 1:9 and 9:1. For each volume ratio, after sufficient mixing, observe and record the changes in the solution, especially the occurrence of phase separation. Through this series of preparations and observations, we can determine the phase separation point of the absorbent under different load conditions and calculate the CO2 load value under phase separation. This load value reflects the capture efficiency and enrichment capacity of the absorbent for CO2 under specific phase separation conditions.

[0021] Compared with the prior art, the technical advantages of the present invention are mainly reflected in the following aspects:

[0022] (1) Efficient capture: Through the combination of preferred solvents and amines and a unique phase change mechanism, the absorbent of the present invention can efficiently capture CO2 under mild conditions, and the CO2 content in the rich phase is high, achieving efficient enrichment and recovery of CO2.

[0023] (2) Low energy consumption regeneration: Traditional CO2 absorbents are mostly regenerated by thermal desorption at 120 °C, while the regeneration temperature of the present invention is between 70-90 °C, which greatly reduces the regeneration energy consumption compared to the traditional high-temperature thermal desorption method, thereby improving its economy and sustainability.

[0024] (3) Good chemical stability: The absorbent of the present invention has good chemical stability and can resist the influence of adverse factors such as oxidative degradation, thereby extending the service life and reducing the operating cost.

[0025] (4) Excellent cycle performance: The absorbent of the present invention can maintain stable performance after multiple cycles of use, meeting the high requirements for absorbent cycle performance in industrial applications.

[0026] (5) Rapid phase separation and excellent mass transfer performance: Due to the phase separation characteristics of DMF and the efficient reaction ability of DETA, the phase separation process of this absorbent is rapid and the mass transfer performance is excellent, which further improves the CO2 capture efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Attached Figure 1 The CO2 absorption performance comparison between the phase change absorbent proposed in the present invention and 5M MEA is shown in FIG.

[0028] Attached Figure 2 It is the phase loading point under different absorption capacity in Experimental Example 3.

[0029] Attached Figure 3 It is the two-phase volume ratio diagram of DMF solution of DETA with different mass ratios after phase separation, the total DETA concentration and the upper and lower phase ratio diagram, the lean and rich liquid CO2 absorption load diagram, and the rich liquid load ratio diagram.

[0030] Attached Figure 4 1 is a curve showing the change of desorption rate over time at different desorption temperatures in Example 1. DETAILED DESCRIPTION

[0032] The liquid-liquid phase change absorbent of the present invention and its preparation and application are described in detail by the following examples. These examples are only used to illustrate the implementation methods of the present invention and do not constitute a limitation on the protection scope of the present invention. Other examples that can be easily obtained based on the given examples also belong to the protection scope of the present invention.

[0033] Example 1

[0034] This embodiment provides a liquid-liquid phase change absorbent for carbon dioxide capture, which is composed of: the mass fraction of the main absorbent diethylenetriamine (DETA) is 30%, the mass fraction of the phase separation promoter N,N-dimethylformamide (DMF) is 50%, and the mass fraction of the solvent water is 20%. The absorbent is used to absorb simulated flue gas with a CO2 volume fraction of 15% under the absorption conditions of temperature 40 ℃ and time 60 min. After the absorption reaches saturation, the absorbent spontaneously forms two phases, in which the CO2-rich phase is separated and sent to the desorption device for regeneration. The desorption conditions are set to temperature 80 ℃ and time 180 min.

[0035] Embodiment 2-10

[0036] Examples 2 to 10 provide liquid-liquid phase change absorbents with different mass fraction ratios. The common feature of each example is that the total mass fraction of the main absorbent DETA, the phase separation promoter DMF and the solvent water is 100%, and the basic conditions of absorption and desorption (such as temperature and time) remain unchanged. The main changes are the mass fraction of each component and the volume fraction of CO2 in the simulated flue gas. The specific ratios and conditions of each example are briefly summarized as follows:

[0037] Example 2: DETA 30%, DMF 40%, water 30%

[0038] Example 3: DETA 30%, DMF 30%, water 40%

[0039] Example 4: DETA 30%, DMF 20%, water 50%

[0040] Example 5: DETA 40%, DMF 30%, water 30%

[0041] Example 7: The same ratio as Example 4, but the simulated flue gas CO2 volume fraction is 15%, and the absorption temperature is adjusted to 30 °C

[0042] Example 8: The same ratio as Example 2, but the simulated flue gas CO2 volume fraction is 20%, the absorption time is extended to 100 min, and the regeneration time is extended to 250 min

[0043] Example 9: DETA 40%, DMF 20%, water 40%, simulated flue gas CO2 volume fraction is 30%, absorption temperature is reduced to 25 ℃, absorption and regeneration time are 250 min and 300 min respectively

[0044] Example 10: DETA 40%, DMF 40%, water 20%, simulated flue gas CO2 volume fraction is 30%, absorption temperature is set at 30 °C, absorption and regeneration time are 300 min and 400 min respectively

[0045] These embodiments demonstrate the application effects of the absorbent of the present invention under different proportions and conditions, and prove its flexibility and wide applicability.

[0046] Comparative Example 1

[0047] In order to better evaluate the effect of the present invention, this comparative example provides a traditional absorbent as a comparison, that is, monoethanolamine (MEA) is directly dissolved in water to prepare a 5 mol / L MEA aqueous solution, and CO2 absorption and desorption experiments are carried out under the same conditions as in Example 1. This comparative experiment helps to highlight the advantages of the present invention in terms of capture efficiency, regeneration energy consumption, and chemical stability.

[0048] Experimental Example 1

[0049] The CO2 absorption performance comparison experiment compares the CO2 absorption performance of the DETA-DMF aqueous solution in Example 1 and the 5M MEA solution in Comparative Example 1 under the same conditions. Take 50 ml of the DETA-DMF aqueous solution in Example 1 and the 5M MEA solution in Comparative Example 1, respectively, and add them to two identical bubbling reactors. Under the condition that the gas flow rate is set to 500 ml / min, simulated flue gas containing 15% CO2 is introduced into the two reactors. A condenser and a gas drying tube are set at the outlet of the absorption bottle to ensure that the moisture in the gas is removed to avoid affecting the infrared detector. The infrared detector is used to monitor and record the CO2 concentration at the outlet in real time, record the data every 10 s, and calculate the CO2 content absorbed by the solution every 10 s. The curve of the change of absorption rate over time is integrated to obtain the total CO2 absorption load. After the absorption experiment, the absorbed solution is placed in a measuring cylinder and allowed to stand, and the stratification phenomenon of the solution is observed and recorded, and the rich and poor phases of the upper and lower layers are determined by acid-base titration.

[0050] Results: Figure 1As shown, compared with 5M MEA solution, the DETA-DMF aqueous solution of Example 1 exhibited a higher CO2 absorption load under the same absorption conditions. This result shows that, as expected, the liquid-liquid phase change absorbent of the present invention has a significant improvement in absorption performance compared with traditional absorbents.

[0051] Experimental Example 2

[0052] Loading point and phase separation performance study, study the absorption performance and phase separation phenomenon of the absorbent in Example 3 at different loading ratios. Based on the absorbent in Example 3, a series of samples with different loading ratios were prepared by adding different volume ratios of unloaded solvent to dilute the saturated loaded solution. Observe and record the stratification phenomenon of each sample after standing. Use acid-base titration to determine the rich and poor phases of the upper and lower layers of each sample, and calculate the loading point.

[0053] Results: Figure 2 As shown in the figure, when the load reaches 0.798 mol CO2 / mol amine, the solution can be divided into two layers, and the solution after stratification is transparent, indicating that the solution viscosity is small and the phase separation is rapid. As the load increases further, the phase separation phenomenon becomes more obvious. In contrast, the phase separation load point in Example 1 is higher (1.01 mol CO2 / mol amine), and the rich liquid volume is larger. This shows that by adjusting the content of the phase separation agent, the phase separation load point can be effectively controlled and the performance of the absorbent can be optimized.

[0054] Experimental Example 3

[0055] The two-phase volume ratio and CO2 load distribution of the liquid-liquid phase change absorbent were measured after the absorbent absorbed CO2 and separated the two-phase volume ratio, CO2 equilibrium load, distribution of amine concentration in the two phases, and the percentage of CO2 in the enriched phase in Examples 1-4. The absorption experiment steps were the same as those in Experimental Example 1, but this time the operation was performed on all samples of Examples 1-4. After the absorption experiment, the solution was allowed to stand and separate into layers, the volume ratio of the upper and lower layers was analyzed, and the rich and poor phases and CO2 load of the upper and lower layers were determined by acid-base titration.

[0056] Results: Figure 3 As shown in the figure, with the increase of DMF content, the volume fraction of the lower layer after phase separation gradually decreases, but the CO2 load ratio in the rich phase increases significantly. At the ratio of 3:3:4, the CO2 load ratio of the lower rich phase is as high as more than 98%, indicating that the absorbent at this ratio has excellent mass transfer performance and regeneration stability.

[0057] Experimental Example 4

[0058] Desorption regeneration performance study, evaluate the desorption regeneration performance of the absorbent in Example 1 and Comparative Example 1 after absorbing CO2. Repeat the absorption process in Experimental Example 1, and take the rich solution for further absorption to saturation after the solution is allowed to stand and stratify. The saturated rich solution is placed in the desorption device, and N2 is introduced at the set desorption temperature (70 ℃, 80 ℃, 90 ℃) for desorption experiment, and the desorption time is 180 min. After the desorption is completed, the CO2 load of the lean solution is determined by acid-base titration.

[0059] Results: Figure 4 As shown, at different desorption temperatures, the liquid-liquid phase change absorbent of the present invention can achieve a faster desorption rate in a shorter time. As the desorption temperature increases, the desorption rate is significantly accelerated, and CO2 is released more completely. This result shows that the absorbent of the present invention has good regeneration performance and is suitable for industrial CO2 capture and regeneration cycles.

[0060] The above description is only part of the embodiments of the present invention and is not intended to be the scope of protection of the present invention. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. A liquid-liquid phase change absorbent for efficiently capturing carbon dioxide, characterized in that: The absorbent is precisely formulated from the following components measured in weight percentage: an organic amine compound, with a content ranging from 20% to 40%; a polar aprotic solvent, with a content ranging from 20% to 50%; water, with a content ranging from 10% to 60%; and a trace amount of additives for optimizing the performance of the absorbent, the additives being selected from but not limited to defoamers, antioxidants and corrosion inhibitors, and the total content of which is limited to not affecting the main properties of the absorbent.

2. The absorbent according to claim 1, wherein the organic amine compound specifically comprises primary amine, secondary amine, tertiary amine, polyamine or a mixture thereof in any proportion; the polar aprotic solvent is preferably N,N-dimethylformamide (DMF) or an equivalent solvent thereof; the defoaming agent is selected from organic siloxane, polyether-modified silicone and a mixture thereof; the antioxidant is selected from didodecyl alcohol ester, didetradecyl alcohol ester, dideoctadecyl alcohol ester and a mixture thereof; the corrosion inhibitor is selected from toluene thiourea, propyl sulfide, diamylamine and a mixture thereof.

3. The absorbent according to claim 1 or 2 is characterized in that, after absorbing carbon dioxide, the absorbent can spontaneously form a clear liquid-liquid two-phase system, in which the CO2 content in the CO2-rich lower phase (rich phase) accounts for more than 90%, while the upper phase is a CO2-poor phase, mainly composed of water and organic solvents.

4. The absorbent according to any one of claims 1 to 3, when using a specific chemical combination (such as a system with diethylenetriamine DETA as the main component), the CO2 content in the rich phase can be as high as more than 98%, showing excellent CO2 capture efficiency.

5. The absorbent according to any one of claims 1 to 4 has the advantage of being able to effectively absorb CO2 gas with a volume fraction between 5% and 100% at a mild temperature range of 25°C to 50°C and normal pressure conditions, and its CO2 absorption load is stabilized in the range of 1.2 mol CO2 / mol amine to 1.4 mol CO2 / mol amine after phase change, although this range may vary slightly due to adjustments in chemical composition and operating conditions.

6. The absorbent according to any one of claims 1 to 5 has a simple and efficient regeneration process, and CO2 desorption and recovery can be achieved by simply heating the rich phase to 70°C to 90°C. Compared with traditional thermal desorption methods, its energy consumption is significantly reduced.

7. The absorbent according to any one of claims 1 to 6, whose excellent chemical composition adaptability allows it to automatically form liquid-liquid two-phases under different ratios and conditions, thereby flexibly responding to the changing CO2 capture needs. In addition, the absorbent is suitable for a variety of absorption equipment, including but not limited to microporous bubbling absorption devices, which may form bubbles with a size between 1 nanometer and 10 micrometers during operation, further optimizing the balance between absorption efficiency and operating conditions.

8. The absorbent according to any one of claims 1 to 7 has a wide range of applications and is not limited to a specific type of absorption equipment, but can be widely used in flue gas purification processes of industrial emission sources such as coal-fired power plants, cement plants, steel plants, and any environmentally friendly absorbent application scenarios aimed at reducing industrial CO2 emissions.

9. An efficient method for capturing carbon dioxide using the absorbent described in any one of claims 1 to 8, the method comprising fully contacting the absorbent with a CO2-containing gas to cause it to absorb CO2 and form a liquid-liquid two-phase, and then heat-treating the rich phase to release and recover high-purity CO2, thereby achieving effective capture and resource utilization of CO2.

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