Low-viscosity rich-liquid-phase carbon dioxide liquid-liquid phase change absorbent and preparation method thereof

Abstract

The invention discloses a low-viscosity rich-liquid-phase carbon dioxide liquid-liquid phase change absorbent and a preparation method, and belongs to the technical field of gas separation. The low-viscosity rich-liquid-phase carbon dioxide liquid-liquid phase change absorbent comprises the following components in percentage by mass: 25-30% of a main agent, 10-30% of a phase splitting agent and the balance of water, the main agent is one of 2-methylaminoethanol or diglycolamine; and the phase-splitting agent is benzyl alcohol. The invention further discloses a preparation method of the low-viscosity liquid-phase-rich carbon dioxide liquid-liquid phase change absorbent. The viscosity of a carbon dioxide rich liquid phase obtained after the absorbent absorbs carbon dioxide and is split is lower than 5 mPa.s, and the mass transfer efficiency of the rich liquid phase in the desorption process is improved. Liquid-liquid phase splitting can still be achieved after carbon dioxide is absorbed when the phase splitting content in the absorbent is as low as 10%, the purpose of reducing energy consumption in the carbon dioxide desorption process is achieved, and the absorbent has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of gas separation technology, specifically relating to a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent and its preparation method. Background Technology

[0002] With rapid industrialization, the concentration of carbon dioxide (CO2) in the atmosphere has continued to rise, currently exceeding 417 ppm, and its emissions are still increasing year by year. As a major greenhouse gas, CO2 has a significant impact on global climate change. Developing and promoting efficient carbon dioxide capture technologies is of great importance.

[0003] Chemical absorption is one of the most widely used CO2 capture technologies, among which traditional organic amine absorbents (such as monoethanolamine MEA) have been extensively studied due to their high absorption efficiency. However, the regeneration process of these absorbents requires heating the entire solvent system, resulting in significant energy consumption and high operating costs, which severely limits their large-scale industrial application.

[0004] To reduce regeneration energy consumption, researchers have focused on developing novel, highly efficient absorbents in recent years, with liquid-liquid phase change absorbents being a promising technological approach. These absorbents are homogeneous solutions before absorbing CO2, but undergo liquid-liquid phase separation after absorption, forming a CO2-rich phase and a CO2-depleted phase. Only the CO2-rich phase is sent to the desorption unit for regeneration, significantly reducing the volume of liquid to be processed and the heat energy consumption, thereby substantially lowering operating costs.

[0005] Although liquid-liquid phase change absorbents exhibit good energy-saving potential, this technology is still under development, and several patents have proposed related systems. For example, Chinese patent application 202411004248.5 discloses a phase change absorbent composed of hydroxyethyl ethylenediamine, pentamethyldiethylenetriamine, and diethylene glycol dimethyl ether for the capture and purification of CO2 in waste gas; another application 202410840585.1 proposes a ternary biphase absorbent system using diethylenetriamine as a promoter, N,N-dimethylcyclohexylamine as the main absorbent, and polyethylene glycol dimethyl ether as a phase-separating agent, achieving liquid-liquid phase separation after absorption saturation. In addition, an earlier application 201610035154.3 also reported a composite absorbent based on MDEA, an organic solvent immiscible with water, and water, which can undergo phase separation after absorbing CO2.

[0006] However, the aforementioned absorbent systems generally suffer from high viscosity in the enriched phase, leading to decreased mass transfer performance, increased pumping energy consumption, and impacting overall system efficiency. On the other hand, high-concentration amine composite systems such as DIPAE / MAPA and DIPAE / DAB, as reported in Chinese Patent 201280031688.9, while capable of phase separation, suffer from drawbacks such as high viscosity, high raw material costs, and complex synthesis, limiting their industrial application.

[0007] Therefore, developing a phase change absorbent that is low in viscosity, easily regenerable, cost-effective, and exhibits good phase separation behavior has become a pressing technical problem in this field. Summary of the Invention

[0008] One objective of this invention is to provide a low-viscosity, liquid-liquid phase change absorbent for carbon dioxide. Before absorbing carbon dioxide, this absorbent is in a homogeneous liquid phase. After absorbing a certain amount of carbon dioxide, it spontaneously forms a two-phase system: one phase is a low-carbon dioxide-content liquid phase, and the other is a carbon dioxide-rich liquid phase. This phase change behavior significantly reduces the total amount of liquid phase entering the desorption unit, thereby reducing the energy consumption of the carbon dioxide desorption process. Simultaneously, the low viscosity of the rich liquid phase is beneficial to the mass transfer efficiency during the desorption process.

[0009] The second objective of this invention is to provide a method for preparing the low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent, wherein the absorbent, by mass fraction of 100%, comprises 25-30% main agent, 10-30% phase-separating agent, and the remainder is water; The main agent is one of 2-methylaminoethanol or diethylene glycolamine; The phase-separating agent is benzyl alcohol.

[0011] The mass content of the main agent is any value between 25% and 30%, such as 25%, 26%, 27%, 28%, 29%, and 30%.

[0012] The mass content of the phase separation agent is any value between 10% and 30%, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0013] In some embodiments of the present invention, the absorbent, by mass fraction of 100%, comprises: 30% main agent, 10% benzyl alcohol, and the remainder being water.

[0014] In some embodiments of the present invention, the absorbent, with a mass fraction of 100%, comprises: 30% main agent, 20% benzyl alcohol, and the remainder being water.

[0015] In some embodiments of the present invention, the absorbent, with a mass fraction of 100%, comprises: 30% main agent, 30% benzyl alcohol, and the remainder being water.

[0016] In some embodiments of the present invention, the absorbent, by mass fraction of 100%, comprises: 25% main agent, 25% benzyl alcohol, and the remainder being water.

[0017] In some embodiments of the present invention, the volume of the carbon dioxide-rich liquid phase after the absorbent absorbs carbon dioxide and separates is 70-95%.

[0018] In some embodiments of the present invention, the viscosity of the carbon dioxide-rich liquid phase after the absorbent absorbs carbon dioxide and separates into phases is 3.0~5.0 mPa·s.

[0019] In some embodiments of the present invention, the viscosity of the carbon dioxide-rich liquid phase after the absorbent absorbs carbon dioxide and separates into phases is preferably 3.3~4.6 mPa·s.

[0020] The second aspect of the present invention discloses a method for preparing the above-mentioned low-viscosity liquid-liquid phase change absorbent rich in liquid phase, comprising: preparing a main agent, a phase separating agent and water in proportion, mixing them evenly to obtain the low-viscosity liquid-liquid phase change absorbent rich in liquid phase.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention is scientifically designed and ingeniously conceived. The absorbent of this invention can efficiently capture carbon dioxide from the gas source and undergo liquid-liquid phase separation after absorption. The resulting rich liquid phase has a high carbon dioxide loading, and only this rich liquid phase enters the desorption unit, significantly reducing the total amount of liquid to be processed. This effectively reduces the sensible heat required to heat the absorbent and the latent heat required for water evaporation during desorption, thereby significantly reducing energy consumption in the carbon dioxide desorption stage and improving overall energy efficiency.

[0022] The absorbent of this invention exhibits excellent phase separation performance; even when the proportion of the phase-separating agent is as low as 10%, it can still separate into liquid and liquid phases after absorbing carbon dioxide. The absorbent of this invention significantly reduces dependence on the amount of phase-separating agent used, thereby lowering material costs.

[0023] The absorbent of this invention forms a liquid-liquid two-phase structure after absorbing carbon dioxide. The viscosity of the liquid-rich phase is 3.307~4.68 mPa·s, all below 5 mPa·s. The lower viscosity helps improve the mass transfer conditions during desorption, accelerates the release of carbon dioxide, improves desorption efficiency, and further enhances the energy-saving and consumption-reducing effect.

[0024] In summary, the absorbent of the present invention has outstanding advantages in reducing desorption energy consumption, saving chemical agents, and enhancing mass transfer performance. It is suitable for large-scale carbon dioxide capture processes and has good prospects for industrial application. Detailed Implementation

[0025] The following describes specific embodiments of the present invention to facilitate understanding by those skilled in the art. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various modifications are readily apparent as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims. All inventions utilizing the concept of this invention are protected.

[0026] In the embodiments and comparative examples of the present invention, the absorbent was subjected to a constant temperature water bath at 40°C, through which a mixture of 15% CO2 and 85% N2 by volume was introduced until saturation, and the phase separation was observed after standing.

[0027] Example 1 This embodiment discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent of the present invention.

[0028] The absorbent configured in this embodiment, based on a 100% mass percentage, contains 30% of the main agent 2-methylaminoethanol, 10% of the phase-separating agent benzyl alcohol, and 60% water. After absorbing carbon dioxide, it forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 95%. The viscosity of the carbon dioxide-rich liquid phase is 3.417 mPa·s.

[0029] Example 2 This embodiment discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent of the present invention.

[0030] The absorbent configured in this embodiment, based on a 100% mass percentage, contains 30% of the main agent 2-methylaminoethanol, 20% of the phase-separating agent benzyl alcohol, and 50% water. After absorbing carbon dioxide, it forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 84%. The viscosity of the carbon dioxide-rich liquid phase is 3.920 mPa·s.

[0031] Example 3 This embodiment discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent of the present invention.

[0032] The absorbent configured in this embodiment, based on a 100% mass percentage, contains 30% of the main agent 2-methylaminoethanol, 30% of the phase-separating agent benzyl alcohol, and 40% water. After absorbing carbon dioxide, it forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 71%. The viscosity of the carbon dioxide-rich liquid phase is 4.680 mPa·s.

[0033] Example 4 This embodiment discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent of the present invention.

[0034] The absorbent configured in this embodiment, based on a 100% mass percentage, contains 25% of the main agent 2-methylaminoethanol, 25% of the phase-separating agent benzyl alcohol, and 50% water. After absorbing carbon dioxide, it forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 75%. The viscosity of the carbon dioxide-rich liquid phase is 3.307 mPa·s.

[0035] Example 5 This embodiment discloses a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent of the present invention.

[0036] The absorbent configured in this embodiment, based on a 100% mass percentage, contains 30% diethylene glycol amine (the main agent), 20% benzyl alcohol (the phase-separating agent), and 50% water. After absorbing carbon dioxide, it forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 85%. The viscosity of the carbon dioxide-rich liquid phase is 3.739 mPa·s.

[0037] Comparative Example 1 The absorbent prepared in Comparative Example 1, by mass percentage, contains 30% N-methyldiethanolamine (the main agent), 20% benzyl alcohol (the phase-separating agent), and 50% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0038] Comparative Example 2 The absorbent prepared in Comparative Example 2, by mass percentage, contains 30% of the main agent 2-methylaminoethanol, 8% of the phase-separating agent benzyl alcohol, and 62% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0039] Comparative Example 3 The absorbent prepared in Comparative Example 3, by mass percentage, contains 30% of the main agent 2-methylaminoethanol, 35% of the phase-separating agent benzyl alcohol, and 35% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0040] Comparative Example 4 The absorbent prepared in Comparative Example 4, by mass percentage, contains 30% 2-methylaminoethanol (the main agent), 20% ethylene glycol dimethyl ether (the phase-separating agent), and 50% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0041] Comparative Example 5 The absorbent prepared in Comparative Example 5, by mass percentage, contains 30% of the main agent 2-methylaminoethanol, 20% of the phase-separating agent n-propanol, and 50% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0042] Comparative Example 6 The absorbent prepared in Comparative Example 6, by mass percentage, contains 30% of the main agent 2-methylaminoethanol, 20% of the phase-separating agent sulfolane, and 50% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0043] Comparative Example 7 The absorbent prepared in Comparative Example 7, by mass percentage, contains 30% ethanolamine (the main agent), 10% sulfolane (the phase-separating agent), and 60% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0044] Comparative Example 8 The absorbent prepared in Comparative Example 8, by mass percentage, contains 30% ethanolamine (the main agent), 30% sulfolane (the phase-separating agent), and 40% water. After absorbing carbon dioxide, the absorbent in this comparative example forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 87%, and the viscosity of the carbon dioxide-rich liquid phase is 5.833 mPa·s.

[0045] Comparative Example 9 The absorbent prepared in Comparative Example 9, by mass percentage, contains 30% ethanolamine (the main agent), 30% n-propanol (the phase-separating agent), and 40% water. After absorbing carbon dioxide, the absorbent in this comparative example forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 74%, and the viscosity of the carbon dioxide-rich liquid phase is 5.995 mPa·s.

[0046] Comparative Example 10 The absorbent prepared in Comparative Example 10, by weight percentage, contains 30% hydroxyethyl ethylenediamine (the main agent), 10% polyethylene glycol 600 (the phase-separating agent), and 60% water. The absorbent in this comparative example does not undergo phase separation after absorbing carbon dioxide.

[0047] Comparative Example 11 The absorbent prepared in Comparative Example 11, by mass percentage, contains 30% hydroxyethyl ethylenediamine (the main agent), 20% polyethylene glycol 600 (the phase-separating agent), and 50% water. After absorbing carbon dioxide, the absorbent in this comparative example forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 76%, and the viscosity of the carbon dioxide-rich liquid phase is 12.240 mPa·s.

[0048] Comparative Example 12 The absorbent prepared in Comparative Example 12, by mass percentage, contains 30% hydroxyethyl ethylenediamine (the main agent), 20% benzyl alcohol (the phase-separating agent), and 50% water. After absorbing carbon dioxide, the absorbent in this comparative example forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 78%, and the viscosity of the carbon dioxide-rich liquid phase is 6.710 mPa·s.

[0049] Comparative Example 13 The absorbent prepared in Comparative Example 13, by mass percentage, contains 30% diethylenetriamine (the main agent), 30% diethylene glycol dimethyl ether (the phase-separating agent), and 40% water. After absorbing carbon dioxide, the absorbent in this comparative example forms a liquid-liquid two-phase system. The volume percentage of the carbon dioxide-rich liquid phase is 68%, and the viscosity of the carbon dioxide-rich liquid phase is 34.650 mPa·s.

[0050] The composition of the absorbents in Examples 1-5 and Comparative Examples 1-13, as well as their effects after absorbing carbon dioxide, are shown in Table 1.

[0051] Table 1

[0052] As can be seen from the table above, the occurrence of phase separation after the phase-separating agent absorbs carbon dioxide is closely related to the type and content of the phase-separating agent. When the content of the phase-separating agent is too low or too high, or when the main agent or phase-separating agent is replaced with other components, most formulations cannot achieve phase separation, indicating that phase separation of the absorbent requires a specific combination and a specific range of phase-separating agent content.

[0053] In systems capable of phase separation, as the content of the phase-separating agent increases, the viscosity of the rich liquid phase generally increases, while the volume ratio of the rich liquid phase decreases. This indicates that the phase-separating agent promotes phase separation but also increases the viscosity of the rich liquid phase.

[0054] Although comparative examples 8, 9, and 11-13 achieved phase separation, their rich liquid phase viscosity was generally higher, ranging from 5.833 to 34.650 mPa·s, which was significantly higher than the 3.307 to 4.680 mPa·s of the examples. This demonstrates that the absorbent of the present invention can achieve lower viscosity based on phase separation and has greater application potential.

[0055] In Comparative Examples 7 and 10, the content of the phase-separating agent was 10%, but liquid-liquid phase separation after carbon dioxide absorption was not achieved. In Example 1 of this invention, the content of the phase-separating agent was also 10%, yet liquid-liquid phase separation after carbon dioxide absorption was achieved. This proves that the absorbent of this invention can achieve phase separation with only a small amount of phase-separating agent, saving the amount of phase-separating agent used and reducing material costs. The above description is merely a preferred embodiment of this invention and is illustrative only, not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of this invention by those skilled in the art without departing from the spirit of this invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent, characterized in that, The absorbent, by mass fraction of 100%, contains 25-30% main agent, 10-30% phase separation agent, and the remainder is water; The main agent is one of 2-methylaminoethanol or diethylene glycolamine; The phase-separating agent is benzyl alcohol.

2. The low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to claim 1, characterized in that, The absorbent, by mass fraction of 100%, consists of: 30% main agent, 10% benzyl alcohol, and the remainder is water.

3. The low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to claim 1, characterized in that, The absorbent, by mass fraction of 100%, consists of: 30% main agent, 20% benzyl alcohol, and the remainder is water.

4. The low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to claim 1, characterized in that, The absorbent, by mass fraction of 100%, consists of: 30% main agent, 30% benzyl alcohol, and the remainder is water.

5. The low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to claim 1, characterized in that, The absorbent, by mass fraction of 100%, consists of: 25% main agent, 25% benzyl alcohol, and the remainder is water.

6. A low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to any one of claims 1-5, characterized in that, The volume of the carbon dioxide-rich liquid phase after the absorbent absorbs and separates carbon dioxide is 70-95%.

7. A low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to any one of claims 1-5, characterized in that, The viscosity of the carbon dioxide-rich liquid phase after the absorbent absorbs and separates carbon dioxide is 3.0~5.0 mPa·s.

8. A low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to any one of claims 1-5, characterized in that, The viscosity of the carbon dioxide-rich liquid phase after the absorbent absorbs and separates carbon dioxide is preferably 3.3~4.6 mPa·s.

9. A method for preparing a low-viscosity, liquid-rich carbon dioxide liquid-liquid phase change absorbent according to any one of claims 1-8, characterized in that, Prepare the main agent, phase-separating agent, and water in proportion, mix them evenly, and you will get a low-viscosity, liquid-liquid phase change absorbent for carbon dioxide.

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