Self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent as well as preparation method and application thereof

Abstract

The invention relates to a self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent as well as a preparation method and application thereof, and belongs to the technical field of carbon dioxide capture. An absorbent system is composed of a secondary amine and tertiary amine compound amine solution in a set ratio, and a water phase is used as a polar medium to regulate phase equilibrium. The absorbent realizes a dynamic phase change behavior through molecular polarity gradient regulation and control: the absorbent presents an organic phase-water phase two-phase separation state in an initial low polarity state; cO2 is converted into a uniform single-phase state after absorption saturation; in the desorption process, a low-polarity double-phase state is reversibly recovered. The organic amine substance in the absorbent system causes a self-extraction-mutual extraction behavior based on polarity change, so that continuous separation from a uniform phase to two phases is realized. Due to the characteristic, the CO2 desorption dynamic performance under the low-temperature condition is obviously enhanced, the regeneration temperature is effectively reduced, and relatively high temperature rise heat and evaporation heat caused by high temperature are avoided.

Description

Technical Field

[0001] The present invention relates to a self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent and a preparation method and application thereof, belonging to the technical field of carbon dioxide capture. Background Art

[0002] Greenhouse gases released by the combustion of fossil energy are the key driving factor of global warming. Carbon dioxide (CO2), as the main greenhouse gas, has a significant cumulative and persistent impact on global climate disturbances. In this context, carbon dioxide capture, utilization and storage (CCUS) has become an indispensable technical approach to addressing climate change and the only means to achieve low-carbon utilization of fossil energy. Among the existing carbon capture methods, the chemical absorption method based on organic amine solution has become one of the current mainstream technologies for carbon capture due to its wide adaptability and mature process. However, its industrial application is still subject to the high energy consumption of the absorbent regeneration process. Therefore, the development of high-efficiency absorbents with low regeneration energy consumption has become the core breakthrough direction for the upgrading of CCUS technology.

[0003] In order to break through the bottleneck of regeneration energy consumption, the academic community has successively proposed new systems such as two-phase absorbents, ionic liquids, and low-water absorbents. Although this type of material reduces the regeneration energy consumption by 30%-50% through phase change regulation or solvent modification, its desorption temperature is still generally maintained in the range of 120-140°C. There is a significant temperature mismatch between this temperature window and the low-grade heat source (50-100°C) in the cascade utilization of industrial waste heat, which makes it difficult to substantially improve the energy efficiency of the system. In addition, the high viscosity of CO2-rich liquid has become a common problem that restricts its industrial application. It is worth noting that catalyst-assisted organic amine absorbent regeneration can reduce the desorption temperature to 80-90°C, but there are problems with easy loss of catalyst active components and poor cycle stability, which makes it difficult to meet the long-term operation requirements of industrial equipment.

[0004] To address these issues, novel absorbent systems based on the self-extraction effect offer an innovative solution for low-temperature regeneration. Initially, these systems exhibit an organic-aqueous biphasic separation characteristic. After CO2 absorption, a homogeneous solution is formed. During regeneration, the absorbed product undergoes spontaneous separation via a reversible phase transition. The core mechanism is the strong polarity difference between the low-polarity aliphatic amine and the aqueous phase, which induces phase separation. During regeneration, the migration of the hydrophobic amine component to the organic phase after carbamate decomposition significantly shifts the reaction equilibrium, thermodynamically driving CO2 desorption. This mechanism can significantly lower the absorbent's regeneration temperature and reduce the heat of warming and evaporation caused by excessive temperatures. However, reports on self-extractable absorbents are limited, and the developed absorbents have low CO2 absorption loadings, low low-temperature self-extraction rates, and limited effectiveness. These factors require the introduction of large amounts of extractant, increasing solvent costs and operational complexity. Summary of the Invention

[0005] The technical problem solved by the present invention is to overcome the technical bottleneck of existing absorbents that are difficult to take into account high CO2 absorption load, low viscosity, low-temperature regeneration and low energy consumption, and propose a self-extraction-mutual extraction synergistic low-temperature regeneration CO2 absorbent and its preparation method and application, so as to break through the problem of difficulty in coordinating the key indicators of the above-mentioned absorbents.

[0006] The technical solution of the present invention is:

[0007] A self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent is disclosed. The absorbent is an aqueous solution, and the solute is an organic amine. The organic amines include secondary fatty amines and tertiary fatty amines, and the oil-water partition coefficient (Log P) of the secondary fatty amines and tertiary fatty amines is in the range of 1.20≤Log P≤3.5. The secondary fatty amine molecules contain secondary amino groups, which react with CO2 to form products such as carbamates, providing the main CO2 absorption capacity and ensuring a high CO2 absorption rate. The tertiary fatty amines react with CO2 to form products such as carbonates and bicarbonates, and can act as proton transfer acceptors for the reaction between A and CO2. During the absorbent regeneration process, both organic amines can achieve self-extraction of the absorption products, and have a more significant mutual extraction effect, promoting the decomposition and transfer of the absorption products, thereby enhancing the low-temperature regeneration performance of the absorbent.

[0008] The total mass concentration of the organic amine in each component of the absorbent is in the range of 10-50%, preferably 10%, 30%, or 50%;

[0009] In each component of the absorbent, the mass concentration of the fatty secondary amine is in the range of 5-45%, preferably 5%, 15%, and 45%;

[0010] In each component of the absorbent, the mass concentration of the fatty tertiary amine is in the range of 5-45%, preferably 5%, 15%, and 5%;

[0011] The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent is captured in a mixed gas containing CO2, and the absorption temperature is 30 to 60°C, preferably 40°C;

[0012] The single homogeneous phase is desorbed by heating to achieve self-extraction regeneration, with a typical regeneration temperature above 50°C, preferably 70-90°C;

[0013] After the absorbent is saturated with CO2, the viscosity of its single homogeneous phase at 25°C is 4.68-15.63 mPa·s.

[0014] Compared with traditional absorbents, the present invention proposes a self-extraction-mutual extraction synergistic low-temperature regeneration CO2 absorbent, which has the following advantages:

[0015] 1. The polarity difference between organic amines and water is utilized to construct a self-extracting absorbent that can be efficiently regenerated under low temperature conditions. It has good CO2 capture performance, a CO2 absorption loading capacity of 0.80-1.50 molCO2 / molamine, and can achieve a regeneration efficiency of 75.8%-98.8% under conditions of 70-90°C.

[0016] 2. After saturated CO2 absorption, the absorbent presents a single homogeneous phase, with CO2 absorption products such as carbamate evenly dispersed throughout the absorbent system. At 25°C, the absorbent viscosity is 4.68-15.63 mPa·s, demonstrating a low CO2 rich liquid viscosity.

[0017] 3. During the regeneration process, the self-extraction-mutual extraction synergistic CO2 absorbent reversibly recovers from a single homogeneous phase to a two-phase state. After the absorption product carbamate decomposes, the fatty amine will spontaneously transfer to the organic layer, driving the CO2 desorption reaction equilibrium toward the direction of absorbent regeneration, thereby achieving efficient regeneration under low temperature conditions and significantly reducing the regeneration temperature, heating heat and evaporation heat of the absorbent.

[0018] 4. The new absorbent has a low regeneration temperature and high regeneration efficiency. It can utilize medium and low temperature waste heat / waste heat to significantly reduce the energy consumption of CO2 capture systems in power plants, steel mills, cement plants, etc.

[0019] A self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent, which is an absorbent system composed of secondary amines, tertiary amines and water. The secondary amines and tertiary amines are both fatty amines with an oil-water partition coefficient (Log P) of not less than 1.2 and not more than 3.5 (1.20≤Log P≤3.50).

[0020] The absorbent is a mixture of secondary and tertiary amines, with no restrictions on the type or quantity of amines. Prior to carbon dioxide absorption, the absorbent maintains low polarity and maintains a two-phase separation between an upper organic amine phase and a lower aqueous phase. Upon reaching saturation carbon dioxide absorption, it presents a single homogeneous phase and reversibly returns to a low-polarity, two-phase state after thermal desorption. During the thermal desorption process, the two organic amines self-extract their absorbed products, achieving a more pronounced mutual extraction effect, significantly promoting the decomposition of the absorbed products.

[0021] The mass concentration of the secondary amine is 5%-50%, the mass concentration of the tertiary amine is 5%-50%, the total mass concentration of the absorbent organic amine is maintained at 10-50%, and its polarity is significantly lower than that of water.

[0022] The absorbent is suitable for mixed gases containing CO2, with an absorption temperature of 30-60°C and a typical CO2 loading of 0.80-1.50 mol CO2 / mol amine, but is not limited to this loading range.

[0023] At 25° C., the typical viscosity of the absorbent after saturation with carbon dioxide absorption is 4.68 to 15.63 mPa·s.

[0024] After the carbon dioxide absorption is saturated, the homogeneous absorbent is regenerated by self-extraction through heating desorption. The typical regeneration temperature is 50 to 120° C., but is not limited to this temperature range.

[0025] An application of a self-extraction-mutual extraction synergistic low-temperature regeneration CO2 absorbent, comprising the following steps:

[0026] The first step is to introduce the mixed gas containing CO2 into a three-necked flask containing an absorbent by bubbling at a temperature of 30-60°C until the absorbent is saturated, and then stop introducing the mixed gas containing CO2;

[0027] In the second step, the three-necked flask containing the absorbent obtained in the first step is transferred to an oil bath pot with a temperature of 50-120° C., and the absorbent is stirred until the absorbent is completely regenerated, and then the heating is stopped.

[0028] The absorption temperature is 30-60°C, the typical regeneration temperature is 50-120°C, the typical absorption load is 0.80-1.50 mol CO2 / mol amine, the typical regeneration efficiency is 75.8%-98.8%, and the typical viscosity after saturation of carbon dioxide absorption is 4.68-15.63 mPa·s.

[0029] The present invention provides a self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent, as well as its preparation method and application. The absorbent system is composed of a complex amine solution of fatty secondary amine and fatty tertiary amine in a specific ratio, wherein the total mass concentration of the organic amine is 10-50%, and the aqueous phase serves as a polar medium to regulate the phase equilibrium. The characteristic is that the absorbent realizes dynamic phase change behavior through molecular polarity gradient regulation: in the initial low-polarity state, it presents an organic phase-aqueous phase separation state; after saturation of CO2 absorption, it transforms into a uniform single-phase state; and during the desorption process, it reversibly recovers to a low-polarity two-phase state. During the absorbent regeneration process, both organic amines can achieve self-extraction of their absorbed products, and have a more significant mutual extraction effect, which promotes the decomposition and transfer of the absorbed products. The organic amine substances in the absorbent system achieve continuous separation from a homogeneous phase to a two-phase phase based on the self-extraction-mutual extraction behavior caused by polarity changes and intermolecular forces. This characteristic significantly enhances its CO2 desorption kinetics under low-temperature conditions. The absorbent of the present invention maintains a CO2 loading of 0.80 to 1.50 mol / mol and can achieve an efficient regeneration of 98.8% at 90°C. In addition, at 80°C and 70°C, the regeneration efficiency of the absorbent can reach 84.9% and 75.8%, respectively, effectively reducing the regeneration temperature and avoiding the high temperature rise heat and evaporation heat caused by high temperature. Compared with traditional absorbents, the self-extraction-mutual extraction synergistic CO2 absorbent provided by the present invention has the advantages of high CO2 loading and low saturation viscosity, and the characteristics of efficient regeneration under low temperature conditions provide a new solution for reducing the energy consumption of absorbent regeneration and matching industrial low-grade heat sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a physical picture of the self-extraction-mutual extraction synergistic CO2 absorbent;

[0031] Figure 2 Schematic diagram of CO2 absorption capacity of self-extraction-mutual extraction synergistic CO2 absorbent under different concentration ratio conditions;

[0032] Figure 3 Schematic diagram of the regeneration efficiency of the self-extraction-mutual extraction synergistic CO2 absorbent under conditions of 70-90°C. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Specifically, in this embodiment, the total mass concentration of organic amines in the self-extraction / interextraction synergistic CO2 absorbent is 10%, 30%, and 50%, respectively, and the mass concentrations of secondary and tertiary fatty amines are in the range of 5-45%, respectively. The configured absorbent is captured in a mixed gas containing CO2 at an absorption temperature of 30-60°C, and the CO2 loading after saturation absorption is 0.80-1.50 mol CO2 / mol amine. At room temperature of 25°C, the viscosity of the saturated absorbent is measured to be 4.68-15.63 mPa·s. The single homogeneous phase is heated in an oil bath to desorb CO2, achieving a regeneration efficiency of 75.8%-98.8% at 70-90°C. The self-extraction properties of the absorbent facilitate the transfer of fatty amines to the organic layer after decomposition of the absorbed carbamate, driving the CO2 desorption reaction equilibrium toward absorbent regeneration, thereby achieving efficient regeneration at low temperatures and significantly reducing the regeneration temperature and energy consumption of the absorbent.

[0035] Example 1

[0036] This example provides a self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent, which is composed of an absorbent system consisting of fatty secondary amines, fatty tertiary amines and water. The total mass concentration of organic amines is 10%, and among the organic amine components, the mass concentrations of fatty secondary amines and fatty tertiary amines are 5% and 5%, respectively.

[0037] Example 2

[0038] This example provides a self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent, which is composed of an absorbent system consisting of fatty secondary amines, fatty tertiary amines and water. The total mass concentration of organic amines is 30%, and among the organic amine components, the mass concentrations of fatty secondary amines and fatty tertiary amines are 15% and 15%, respectively.

[0039] Example 3

[0040] This example provides a self-extraction-mutual extraction synergistic low-temperature regenerative CO2 absorbent, which is composed of an absorbent system consisting of fatty secondary amines, fatty tertiary amines and water. The total mass concentration of organic amines is 50%, and among the organic amine components, the mass concentrations of fatty secondary amines and fatty tertiary amines are 45% and 5%, respectively.

[0041] Comparative Example 1

[0042] In this comparative example, the absorbent is composed of ethanolamine and water, wherein the mass concentration of ethanolamine is 30%. The absorbent is in a homogeneous state before, after and after CO2 absorption. The CO2 absorption capacity is only 0.5 molCO2 / molamine. Under the regeneration condition of 100°C, the regeneration efficiency is only 67.3%.

[0043] Test Example 1

[0044] This test example examined the phase separation effect of the self-extraction-mutual extraction synergistic CO2 absorbents in Examples 1 and 2, their CO2 absorption performance at an absorption temperature of 40°C, and the viscosity of a single homogeneous phase at room temperature of 25°C. Specifically, the following steps were performed: 50 g of the absorbents containing different concentrations of secondary and tertiary fatty amines in Examples 1, 2, and 3 were prepared, respectively, and transferred to a bubbling absorption bottle. The absorption bottle was placed in a constant temperature water bath at 40°C to maintain a constant temperature. The test was initiated in a mixed gas containing CO2 until the absorbent reached saturation. The saturated absorbent was then transferred to an oil bath and regenerated at 90°C.

[0045] Figure 1 A photo of a CO2 absorbent demonstrating synergistic self-extraction and mutual extraction. It can be seen that in the fresh solvent state, absorbents of varying concentrations all exhibit stratification, with the organic amine layer located in the upper layer and the aqueous phase in the lower layer. After saturated CO2 absorption, the absorbents of varying concentrations exhibit a single, homogeneous phase. After regeneration at 90°C, the absorbents of varying concentrations can all reversibly recover to a biphasic state.

[0046] Figure 2 Schematic diagram of the CO2 absorption capacity of the self-extraction-mutual extraction synergistic CO2 absorbent under different mass concentration ratios. It can be seen that when the total mass concentration of the organic amine is 10%, 30%, and 50%, the CO2 absorption capacity of the self-extraction absorbent is 0.80, 0.86, and 0.88 mol CO2 / mol amine, respectively, significantly higher than the CO2 absorption capacity of the absorbent in Comparative Example 1.

[0047] The viscosity of the CO2 absorbent, which exhibits a self-extraction-interextraction synergistic effect, was tested at various concentration ratios at 25°C. The measured single-phase viscosity after saturated CO2 absorption ranged from 4.68 to 15.63 mPa·s. Overall, the absorbent exhibited relatively low viscosity after saturated CO2 absorption.

[0048] Test Example 2: To match the absorbent regeneration temperature with the temperature of low-grade industrial waste heat and improve overall system efficiency, this test tested the regeneration performance of the absorbent from Example 2 at regeneration temperatures between 70°C and 90°C. This test involved the following steps: Three 50g groups of the absorbent from Example 2 were prepared and transferred to bubbling absorption bottles. The bottles were then placed in a 40°C water bath to maintain a constant temperature. Testing began in a CO2-containing gas mixture until the absorbent reached saturation. The saturated absorbent was then transferred to an oil bath and regenerated at 70°C to 90°C. The regeneration efficiency at various temperatures was examined.

[0049] Figure 3Figure 2 shows the regeneration efficiency of a CO2 absorbent using a self-extraction-interextraction synergistic method at 70-90°C. It can be seen that the absorbent in Example 2 can be regenerated at temperatures between 70 and 90°C, and the regeneration efficiency increases significantly with increasing regeneration temperature, reaching a high of 98.8% at 90°C. Conventional ethanolamine absorbents have a regeneration temperature of approximately 120°C. Currently, newer absorbents, such as biphasic absorbents, homogeneous water-reduced absorbents, and ionic liquids, generally have regeneration temperatures between 100 and 120°C, and their regeneration efficiencies are often below 90%.

[0050] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent, characterized by: The absorbent includes a secondary amine, a tertiary amine and water; The secondary amine and the tertiary amine are both fatty amines with an oil-water partition coefficient of not less than 1.2 and not more than 3.

5.

2. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 1, characterized in that: The absorbent maintains low polarity before absorbing carbon dioxide, and maintains a state of separation between the upper organic amine phase and the lower aqueous phase. After reaching saturation of carbon dioxide absorption, it presents a single uniform phase and can be reversed to a low-polarity two-phase state after thermal desorption. During the thermal desorption process, the two organic amines have a self-extraction effect on their absorption products, and can achieve a more significant mutual extraction effect, which significantly promotes the decomposition of the absorption products.

3. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 2, characterized in that: The mass concentration of the secondary amine is 5%-50%; The mass concentration of the tertiary amine is 5%-50%; The total mass concentration of the absorbent organic amine is maintained at 10%-50%, and its polarity is significantly lower than that of water.

4. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 1, characterized in that: The absorbent is suitable for mixed gases containing CO2, the absorption temperature is 30-60°C, and the CO2 loading capacity is 0.80-1.50 mol CO2 / mol amine.

5. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 4, characterized in that: At 25°C, the viscosity of the absorbent after saturation with carbon dioxide is 4.68-15.63 mPa·s.

6. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 1, characterized in that: After the carbon dioxide is absorbed to saturation, the homogeneous absorbent is regenerated by self-extraction through heating desorption, and the regeneration temperature is 50℃-120℃.

7. A method for preparing a self-extraction-mutual extraction synergistic low-temperature regeneration CO2 absorbent, characterized in that: The secondary amine, the tertiary amine and water are mixed and stirred evenly to obtain an absorbent.

8. Application of a self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent, characterized in that: include: The first step is to introduce the mixed gas containing CO2 into a three-necked flask containing an absorbent by bubbling at a temperature of 30-60°C until the absorbent is saturated, and then stop introducing the mixed gas containing CO2; In the second step, the three-necked flask containing the absorbent obtained in the first step is transferred to an oil bath pot with a temperature of 50-120° C., and the absorbent is stirred until the absorbent is completely regenerated, and then the heating is stopped.

9. The self-extraction-mutual extraction synergistic low-temperature regeneration type CO2 absorbent according to claim 8, characterized in that: The absorption temperature is 30-60° C., the regeneration temperature is not lower than 50° C., the absorption load is 0.80-1.50 mol CO2 / mol amine, the regeneration efficiency is 75.8%-98.8%, and the viscosity after saturation of carbon dioxide absorption is 4.68-15.63 mPa·s.

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