Mechanism, Regulation Law and Engineering Value of High Efficiency Capture of CO _ 2 by Choline Chloride-Monoethanolamine Eutectic Solvent (ChCl-MEA DES) Deep Analysis of Mechanism, Regulation Law and Engineering Value of High Efficiency Capture of CO _ 2 by Choline Chloride-Monoethanolamine Eutectic Solvent (ChCl-MEA DES) Deep Analysis
1. Research positioning and scientific breakthrough: jumping out of the traditional amine solution and low temperature physical solvent third green capture route 1. Research positioning and scientific breakthrough: jumping out of the traditional amine solution and low temperature physical solvent third green capture route
In industrial scenarios such as synthesis gas refining, flue gas decarbonization, and natural gas purification, CO 2 capture is a core unit operation to ensure the synthesis of high-end chemicals and achieve low carbon emissions. Although traditional alcohol amine aqueous solutions (such as MEA and MDEA) have fast absorption rate and high selectivity, they exist in industrial scenarios such as synthesis gas refining, flue gas decarbonization, and natural gas purification. CO 2 capture is a core unit operation to ensure the synthesis of high-end chemicals and achieve low carbon emissions. Although traditional alcohol amine aqueous solutions (such as MEA and MDEA) have fast absorption rate and high selectivity, they have fatal defects such as large amine volatilization loss, high regeneration energy consumption (about 120 ° C), serious equipment corrosion, large degradation by-product polyamine volatilization loss, high regeneration energy consumption (about 120 ° C), serious equipment corrosion, and many degradation by-products, etc., which are difficult to meet the industrial needs of low-carbon, energy-saving, and long-cycle operation; while physical absorption processes such as polyethylene glycol dimethyl ether (Selexol) and low-temperature methanol (Rectisol) have no chemical degradation and low regeneration energy consumption, they must operate under ultra-low temperature and high pressure at ** -60 ° C. The equipment investment is huge and the refrigeration energy consumption is extremely high. It is only suitable for high-pressure scenarios rich in CO2 The universality is extremely poor. And other fatal flaws, it is difficult to meet the industrial needs of low-carbon, energy-saving, and long-cycle operation; while polyethylene glycol dimethyl ether (Selexol), low-temperature methanol (Rectisol) and other physical absorption processes, although no chemical degradation, low energy consumption for regeneration, but must be operated at ultra-low temperature and high pressure at ** -60 ° C, with huge equipment investment and extremely high refrigeration energy consumption. It is only suitable for high-pressure scenarios rich in CO 2, and the universality is extremely poor.
As a new green separation medium, the eutectic solvent (DES) is formed by the self-assembly of hydrogen bond supply receptors, and the eutectic solvent (DES) is used as a new green separation medium. It is formed by the self-assembly of hydrogen bond supply receptors. It has the advantages of simple synthesis, cheap raw materials, adjustable structure, biodegradable, simple synthesis with extremely low vapor pressure, cheap raw materials, adjustable structure, biodegradable, and extremely low vapor pressure. It is regarded as the core direction of the next generation of carbon capture materials. However, the common advantages of conventional DES are regarded as the core direction of the next generation of carbon capture materials. However, conventional DES generally has the problems of high viscosity, high mass transfer resistance, low CO2 absorption capacity, high viscosity, high mass transfer resistance, and low CO2 absorption capacity, which seriously restricts industrial application. problem, seriously restricting industrial application.This study takes choline chloride-monoethanolamine (ChCl-MEA) choline chloride-monoethanolamine (ChCl-MEA) eutectic solvent as the object of this study, and for the first time systematically reveals that the eutectic solvent is the object. For the first time, the coupling effect law of temperature, pressure, water content temperature, pressure, water content on its CO2 absorption behavior is systematically revealed. It is clear that the coupling effect law of temperature, pressure, water content on its CO2 absorption behavior is clear. The mechanism of action of physical absorption is mainly physical absorption , and the mechanism of action is confirmed. It is confirmed that water modification and water modification can be modified without changing the absorption mechanism At the same time, it breaks through the three bottlenecks of viscosity, capacity and rate, and provides a new scientific paradigm and engineering path for the development of mild conditions, low energy consumption, high capacity mild conditions, low energy consumption and high capacity new carbon capture solvents. The new carbon capture solvent provides a new scientific paradigm and engineering path.
II. Microscopic mechanism of action: hydrogen bond regulation and mass transfer enhancement under the dominance of physical absorption II. Microscopic mechanism of action: hydrogen bond regulation and mass transfer enhancement under the dominance of physical absorption
1. Qualitative absorption mechanism: clear physical absorption-based, different from traditional amine liquefaction 1. Qualitative absorption mechanism: clear physical absorption-based, different from traditional amine liquefactionThe absorption of CO2 by ChCl-MEA DES is absolutely dominated by physical dissolution physical dissolution
, and no significant chemical reaction occurs. This conclusion can be strictly supported by three macroscopic laws: for absolute dominance, no significant chemical reaction occurs. This conclusion can be strictly supported by three macroscopic laws:Absorption capacity Absorption capacity increases linearly with pressure increase, decreases significantly with temperature increase Linearly increases with pressure increase, decreases significantly with temperature increase , fully conforms to the physical dissolution characteristics described by Henry's Law;, fully conforms to the physical dissolution characteristics described by Henry's Law;
Absorption behavior is not limited by the metering ratio of amine-based chemical reaction, and the capacity continues to increase with the partial pressure, without chemical saturation point; absorption behavior is not limited by the metering ratio of amine-based chemical reaction, and the capacity continues to increase with the partial pressure, without chemical saturation point;
Adding water to 50 vol% did not trigger chemical reactions such as carbamate formation, and the mechanism remained stable and consistent. Adding water to 50 vol% did not trigger chemical reactions such as carbamate formation, and the mechanism remained stable and consistent.
In sharp contrast to this, traditional MEA aqueous solutions rely on CO2 to chemically react with amino groups to generate ammonium carbamate. CO ³ chemically reacts with amino groups to generate ammonium carbamate. The absorption capacity is rapidly saturated at low pressure, and the increase in temperature promotes the reaction. The mechanism is completely opposite to physical absorption. This non-reactive physical absorption gives ChCl-MEA DES two innate advantages: the absorption capacity is rapidly saturated at low pressure, and the increase in temperature promotes the reaction. The mechanism is completely opposite to physical absorption. This non-reactive physical absorption gives ChCl-MEA DES two innate advantages: no degradation loss of the absorbent, mild regeneration conditions (desorption at low pressure/temperature), no degradation loss of the absorbent, and mild regeneration conditions (desorption at low pressure/temperature) , which avoids the chemical attenuation problem of amine solution from the root., avoids the chemical attenuation problem of amine solution from the root.
2. The forward regulation mechanism of water: triple synergy of reducing viscosity, increasing solubility and promoting mass transfer 2. The forward regulation mechanism of water: triple synergy of reducing viscosity, increasing solubility and promoting mass transfer
Pure DES due to pure DES due to hydrogen bond network density, strong intermolecular force Hydrogen bond network density, strong intermolecular force , great viscosity, resulting in high CO2 diffusion resistance, slow absorption rate, and low effective utilization rate. Appropriate amount of water (≤ 50 vol%) can achieve triple mechanism synergistic strengthening, and the viscosity is very large, resulting in high CO2 diffusion resistance, slow absorption rate, and low effective utilization rate. Appropriate amount of water (≤ 50 vol%) can achieve triple mechanism synergistic strengthening, and does not damage the DES structure, does not change the physical absorption mechanism, does not damage the DES structure, and does not change the physical absorption mechanism :
Hydrogen Bond Breaking and Viscosity Reduction Hydrogen Bond Breaking and Viscosity Reduction : Water molecules are inserted between ChCl and MEA, weakening the ion-hydrogen bond network, resulting in a significant increase in fluid fluidity and an exponential increase in CO2 diffusion coefficient;: Water molecules are inserted between ChCl and MEA, weakening the ion-hydrogen bond network, resulting in a significant increase in fluid fluidity and an exponential increase in CO2 diffusion coefficient;
Increased dissolution check points Increased dissolution check points : Water forms a multi-component hydrogen bond system with MEA and ChCl, providing more physical dissolution check points for CO 2, doubling the effective utilization rate of DES per mole;: Water forms a multi-component hydrogen bond system with MEA and ChCl, providing more physical dissolution check points for CO 2, doubling the effective utilization rate of DES per mole;
Interfacial Mass Transfer Enhancement Interfacial Mass Transfer Enhancement : The interfacial tension of the aqueous solution is lower, the gas-liquid contact is more sufficient, and the pressure-driven mass transfer efficiency is significantly improved.: The interfacial tension of the aqueous solution is lower, the gas-liquid contact is more sufficient, and the pressure-driven mass transfer efficiency is significantly improved.
Research confirms: DES containing 50 vol% water, research confirms: DES containing 50 vol% water, unit molar DES absorption capacity reaches nearly 2 times that of pure DES, unit molar DES absorption capacity reaches nearly 2 times that of pure DES , the absorption rate is increased by about 1 times, and the modification goal of "water-assisted solution and water-accelerated" is achieved., the absorption rate is increased by about 1 times, and the modification goal of "water-assisted solution and water-accelerated" is achieved.
3. Multi-factor coupling law and optimal operation window (quantitative analysis based on response surface method RSM) 3. Multi-factor coupling law and optimal operation window (quantitative analysis based on response surface method RSM)
This study uses Box-Behnken design and response surface method to achieve the interactive decoupling of temperature (40-80 ° C), pressure (5-10 bar), and water content (0-50 vol%), resulting in accurate and scalable operation laws: This study uses Box-Behnken design and response surface method to achieve the interactive decoupling of temperature (40-80 ° C), pressure (5-10 bar), and water content (0-50 vol%), resulting in accurate and scalable operation laws:
1. Single factor main effect ranking 1. Single factor main effect ranking
Pressure Pressure : For both absorption capacity and rate: for both absorption capacity and rate Strong positive effect Strong positive effect , increasing pressure can linearly increase the solubility of CO 2, which is the most effective means to strengthen absorption;, increasing pressure can linearly increase the solubility of CO 2, which is the most effective means to strengthen absorption;
Water content Water content : Positive effect Significant positive effect Significant positive effect , 0 → 50 vol% range content and rate increase simultaneously, and no mechanism change;, 0 → 50 vol% range content and rate increase simultaneously, and no mechanism change;
Temperature Temperature : Strong Negative Effect Strong Negative Effect , the increase in temperature leads to a rapid decrease in the physical solubility of CO2, and 40 ° C is the optimal absorption temperature., The increase in temperature leads to a rapid decrease in the physical solubility of CO2, and 40 ° C is the optimal absorption temperature.
2. Optimal operating conditions and performance extremes 2. Optimal operating conditions and performance extremes
Under the conditions of 10 bar, 40 ° C, 50 vol% water 10 bar, 40 ° C, 50 vol% water , under the implementation conditions of ChCl-MEA DES, the ChCl-MEA DES achieves the maximum CO2 absorption capacity of 0.379 mol-CO2/mol-DES , while maintaining the maximum absorption rate, providing a clear parameter anchor point for the optimization of industrial conditions., while maintaining the maximum absorption rate, providing a clear parameter anchor point for the optimization of industrial conditions.
3. Key Cognition Corrections: Volume Vs Molar Capacity 3. Key Cognition Corrections: Volume Vs Molar Capacity
Study clarifies a highly confusing engineering concept: Study clarifies a highly confusing engineering concept:
Molar capacity Molar capacity : After adding water: After adding water Unit molar DES Unit molar DES The absorbed CO 2 is significantly increased (Technologies doubled), reflecting the maximization of DES molecular efficiency; the absorbed CO 2 is significantly increased (Technologies doubled), reflecting the maximization of DES molecular efficiency;
Volumetric capacity Volumetric capacity : Under equal volume and equal volume The total CO 2O dissolution of pure DES is still higher than that of the water-added system, which is suitable for the scenario where the equipment volume is strictly limited. The total CO 2O dissolution of pure DES is still higher than that of the water-added system, which is suitable for the scenario where the equipment volume is strictly limited.
This conclusion provides a scientific basis for the formulation selection of different industrial scenarios: Pursue solvent utilization rate to choose high water ratio, pursue equipment volume efficiency to choose low water/pure DES Pursue solvent utilization rate to choose high water ratio, pursue equipment volume efficiency to choose low water/pure DES ...
IV. Differentiating advantages and industrialization potential with mainstream carbon capture technologies IV. Differentiating advantages and industrialization potential with mainstream carbon capture technologies
1. Contrast traditional alcohol amine solution (MEA) 1. Contrast traditional alcohol amine solution (MEA)
Advantages: Advantages: No degradation, no volatile loss, low regeneration energy consumption, no corrosion of equipment, high stability No degradation, no volatile loss, low regeneration energy consumption, no corrosion of equipment, high stability ;
Short board: The capacity under low pressure is lower than chemical absorption, more suitable for short board: The capacity under low pressure is lower than chemical absorption, more suitable for medium and high pressure syngas refining medium and high pressure syngas refining scene.
2. Comparison of low temperature physical solvents (Selexol/Rectisol) 2. Comparison of low temperature physical solvents (Selexol/Rectisol)
Advantages: Advantages: Substantial increase in operating temperature (40 ° C vs -60 ° C) Substantial increase in operating temperature (40 ° C vs -60 ° C) , no need for ultra-low temperature refrigeration system, equipment investment and energy consumption are greatly reduced;, no ultra-low temperature refrigeration system is required, equipment investment and energy consumption are greatly reduced;
Features: Stable operation at room temperature and pressure, suitable for more low-pressure and low-grade gas sources. Features: Stable operation at room temperature and pressure, suitable for more low-pressure and low-grade gas sources.
3. Contrast conventional eutectic solvents 3. Contrast conventional eutectic solvents
Breakthrough: Breakthrough: Add water modification to achieve high capacity and high rate Add water modification to achieve high capacity and high rate , completely solve the pain points of high viscosity and poor quality transfer of pure DES;, completely solve the pain points of high viscosity and poor quality transfer of pure DES;
Innovation: Innovation: mechanism unchanged, structural stability mechanism unchanged, structural stability , to avoid side reactions and solvent failure caused by modification., to avoid side reactions and solvent failure caused by modification.
5. Research on core innovation and industry value (without repeating the high-level condensation of the original text) 5. Research on core innovation and industry value (without repeating the high-level condensation of the original text)
Mechanism originality Mechanism originality : It is confirmed for the first time that ChCl-MEA DES is: It is confirmed for the first time that ChCl-MEA DES is Physically dominated absorption Physically dominated absorption , and elucidates the "non-reactive strengthening" mechanism of water, filling the cognitive gap of amine DES carbon capture mechanism;, and elucidates the "non-reactive strengthening" mechanism of water, filling the cognitive gap of amine DES carbon capture mechanism;
Method Scientific Method Scientific : Use Response Surface Method (RSM) to achieve multi-factor interaction analysis, break through the one-sidedness of single-factor variables, and obtain coupling laws that can be directly used in engineering amplification;: Use Response Surface Method (RSM) to achieve multi-factor interaction analysis, break through the one-sidedness of single-factor variables, and obtain coupling laws that can be directly used in engineering amplification;
Application Breakthrough Application Breakthrough : Proposed ** "Add water to reduce viscosity and improve effect" ** Simple and easy strategy, no complex synthesis, no high temperature and high pressure, provides a low-cost implementation plan for DES industrial application;: Proposed ** "Add water to reduce viscosity and improve effect" ** Simple and easy strategy, no complex synthesis, no high temperature and high pressure, provides a low-cost implementation plan for DES industrial application;
Scene accuracy Scene accuracy : Special adaptation: Special adaptation Syngas decarbonization, natural gas dehydration and decarbonization, medium and high pressure flue gas capture Syngas decarbonization, natural gas dehydration and decarbonization, medium and high pressure flue gas capture , is an efficient green alternative to traditional processes., is an efficient green alternative to traditional processes.
VI. Limitations and Future Research Directions (Professional Depth Extension) VI. Limitations and Future Research Directions (Professional Depth Extension)
Long-term cycle stability: Long-term cycle stability needs to be further verified: After multiple rounds of absorption-regeneration , the structural integrity and capacity retention rate of DES added with water; After that, the structural integrity and capacity retention rate of DES added with water;
Selective evaluation: Study the separation selectivity of CO _ 2/CH _ 1 and CO _ 2/H _ 2 to expand the natural gas and synthesis gas refining scenarios; Selective evaluation: Study the separation selectivity of CO _ 2/CH _ 1 and CO _ 2/H _ 2 to expand the natural gas and synthesis gas refining scenarios;
Ternary modification: introduction of third components such as polyols and ionic liquids to further enhance low pressure capacity and rate; Ternary modification: introduction of third components such as polyols and ionic liquids to further enhance low pressure capacity and rate;
Process integration: Coupled phase change, membrane separation and other technologies, build process integration: Coupled phase change, membrane separation and other technologies, build low energy consumption, continuous low energy consumption, continuous new carbon capture. new carbon capture process.
VII. SUMMARY VII. SUMMARY
From the four dimensions of mechanism, law, method and application, this study constructs the complete theoretical system of choline chloride-monoethanolamine eutectic solvent choline chloride-monoethanolamine eutectic solvent high efficiency, stability and low energy consumption to capture CO 2. Its greatest value lies in: a complete theoretical system of high efficiency, stability and low energy consumption to capture CO 2. Its greatest value lies in: with the simplest water modification, to achieve the most critical performance breakthrough with the simplest water modification, to achieve the most critical performance breakthrough , without changing the physical absorption mechanism, without introducing complex chemical processes, while improving the capacity and rate, providing a path for industrial decarbonization, without changing the physical absorption mechanism, without introducing complex chemical processes, while improving the capacity and rate, providing a mild conditions for industrial decarbonization, green environmental protection, low cost, scalable mild conditions, green environmental protection, low cost, scalable The new technical route has important scientific significance and engineering value for promoting the upgrading of carbon capture solvents to high efficiency, energy saving and long life. The new technical route of carbon capture solvent has important scientific significance and engineering value for promoting the upgrading of carbon capture solvent to high efficiency, energy saving and long life.
