Synergistic enhanced amido absorption liquid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of carbon dioxide capture and electro-catalytic conversion, and discloses a synergistic enhancement type amino absorption liquid as well as a preparation method and application thereof. The synergistic enhancement type amino absorption liquid comprises the following components in percentage by mass: 28-32% of a compound amino component, 10-30% of an amino component, 10-30% of a solvent and the balance of a solvent based on the total mass of the absorption liquid being 100%. 5-10% of an electrolyte salt; 2-3% of a cationic interface modifier; 2-3% of a functional ionic liquid; 4-6% of synergistic amine; and the balance of water. According to the invention, the functional ionic liquid is introduced into a bifunctional amino absorption liquid system, so that the synergistic regulation and control of an electrode interface microenvironment are realized, and the electrode shows comprehensive performance advantages in the integrated application of carbon dioxide capture and in-situ electrocatalytic reduction, and has relatively good practicability and application prospects.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture and electrocatalytic conversion technology, specifically to a synergistically enhanced amine-based absorbent, its preparation method, and its application. Background Technology

[0002] Under the "dual carbon" goal, integrated technologies that couple carbon dioxide capture and electrocatalytic reduction in situ have become an important research direction in the CCU field due to their potential to significantly reduce energy consumption and costs. The core of this technology lies in developing bifunctional electrolyte systems that combine highly efficient CO2 absorption capacity with highly selective electrocatalytic reduction performance.

[0003] Early studies mainly used single amine-based absorbents (such as MEA and DEA) to capture CO2, but they have poor conductivity under electrolysis conditions, and the amine molecules themselves are prone to degradation or side reactions at the electrode interface, making them difficult to use directly for electrocatalytic reduction.

[0004] To overcome the aforementioned problems, current improvement schemes generally focus on constructing an "amine-salt" complex system, that is, adding inorganic electrolyte salts (such as KHCO3, KCl) to a high-concentration amine absorbent to improve the solution conductivity. Although this approach achieves a preliminary coupling between capture and electrolysis to some extent, its limited design dimension exposes the following inherent and insurmountable limitations in practical applications: First, the performance of the "amine-salt" system is heavily dependent on the precise matching of a specific amine and a specific salt. Once the electrolysis conditions (such as potential and current density) or the running time change, the ionic strength, pH and distribution of amine species in the solution will change dynamically, causing the CO2 absorption capacity and electroreduction selectivity (such as CO Faraday efficiency) to fluctuate, making it difficult to maintain long-term stability.

[0005] Second, existing systems primarily influence the interface indirectly through the bulk concentration of amines or salts, lacking the ability to directly, actively, and synergistically regulate the electrode / electrolyte interface. At the cathode surface, proton reduction hydrogen evolution (HER) and CO2 reduction reaction (CO2RR) fiercely compete. Traditional amine-salt electrolytes cannot effectively suppress HER, resulting in generally low selectivity for target products (such as CO) at higher current densities, with a significant amount of electrical energy consumed by side reactions.

[0006] Third, during high current density and long-term continuous operation, the mass transfer, chemical reaction and electric field distribution at the electrode interface are extremely complex. The simple "amine-salt" combination is prone to catalyst deactivation, amine component degradation or salt precipitation due to the unstable interface structure, resulting in a significant performance degradation rate that is difficult to meet the needs of industrial applications.

[0007] Therefore, there is an urgent need in this field for a novel electrolyte design strategy that can actively and synergistically construct and stabilize the electrode interface microenvironment while retaining the efficient CO2 capture capability of amine groups, thereby solving the problem of synergistic improvement of selectivity and stability at the molecular / mesoscopic level. Summary of the Invention

[0008] The present invention aims to solve the problem that existing amine-based electrolyte systems lack synergistic and stable regulation of the electrode interface microenvironment, which makes it difficult to synergistically improve the selectivity (such as CO Faradaic efficiency) and long-term operational stability of in-situ electrocatalytic reduction of carbon dioxide.

[0009] To achieve the above objectives, a first aspect of the present invention provides a synergistically enhanced amine-based absorbent, comprising the following components by mass fraction, based on 100% of the total mass of the absorbent: The compound amine component comprises 28-32%, wherein the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; Electrolyte salts 5-10%; Cationic interface modifiers 2-3%; Functional ionic liquids 2-3%; The synergistic amine is 4-6%; the synergistic amine is selected from at least one of N-methyldiethanolamine, diethanolamine, 1,3-propanediamine, 2-amino-2-methyl-1-propanol and 3-amino-1-propanol; The remainder is water; The functional ionic liquid has an imidazolium-type and / or pyridinium-type organic cation structure.

[0010] A second aspect of the present invention provides a method for preparing the synergistically enhanced amine absorbent liquid described in the first aspect, comprising providing raw materials of corresponding masses according to the proportions of the components in the synergistically enhanced amine absorbent liquid described in the first aspect, and performing the following steps: (1) Dissolve the compound amine component in water to obtain a compound amine solution; the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; (2) The compound amine solution is first mixed with electrolyte salt and synergistic amine to obtain a precursor solution; (3) The precursor solution is subjected to ultrasonic treatment, and then mixed with a cationic interface modifier to obtain mixture I; (4) Mix the mixture I with the functional ionic liquid for a third time to obtain the synergistically enhanced amine absorption liquid.

[0011] The third aspect of this invention provides the application of the synergistically enhanced amine absorbent described in the first aspect above, for the absorption of carbon dioxide and its in-situ electrocatalytic reduction.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention is based on a complex amine platform constructed from triethylenetetramine and N,N-dimethylethanolamine. By introducing an electrolyte salt, a cationic interface modifier, a functional ionic liquid, and a synergistic amine, an integrated bifunctional system is formed. This design enables the absorbent to simultaneously possess highly efficient CO2 chemical absorption capacity (up to 0.49 mol / mol) and excellent electrochemical performance, effectively overcoming the technical contradiction often encountered in traditional systems in capture-electrolysis coupling applications where absorption performance and electrolysis performance are mutually constrained and difficult to optimize synergistically.

[0013] 2. This invention overcomes the limitations of existing technologies that only optimize the bulk composition. It creatively utilizes the synergistic effect of cationic interface modifiers and functional ionic liquids to actively regulate the electrode / electrolyte interface microenvironment. This synergistic mechanism stabilizes CO2 reduction reaction intermediates and effectively suppresses the hydrogen evolution reaction (HER). Under the same conditions, this system increases the Faraday efficiency of CO to 65% while suppressing the HER Faraday efficiency to 11%, demonstrating a significant improvement in selectivity.

[0014] 3. The aforementioned interface synergistic mechanism helps maintain the stability of the electrode interface structure during long-term electrolysis. This absorbent operates at 50 mA / cm². 2 After 100 hours of continuous operation at current density, the CO Faraday efficiency decay rate is only about 7.7%, which is much lower than that of the comparative system without the introduction of this synergistic mechanism (the decay rate of Comparative System 1 is about 21.6%), demonstrating excellent operational durability and being closer to the requirements of industrial applications.

[0015] 4. This invention enhances the functionality of amine absorption technology. The functional ionic liquid used as the key additive is used in low quantities and has a simple preparation method. It does not require complex reactions or major modifications to existing capture-electrolysis devices. It has good process compatibility and technical economy, and is easy to integrate and promote on existing carbon capture and utilization technology platforms. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] As previously stated, the first aspect of the present invention provides a synergistically enhanced amine absorbent, comprising the following components by mass fraction based on 100% of the total mass of the absorbent: The compound amine component comprises 28-32%, wherein the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; Electrolyte salts 5-10%; Cationic interface modifiers 2-3%; Functional ionic liquids 2-3%; The synergistic amine is 4-6%; the synergistic amine is selected from at least one of N-methyldiethanolamine, diethanolamine, 1,3-propanediamine, 2-amino-2-methyl-1-propanol and 3-amino-1-propanol; The remainder is water; The functional ionic liquid has an imidazolium-type and / or pyridinium-type organic cation structure.

[0018] Preferably, the synergistic amine is selected from at least one of N-methyldiethanolamine, diethanolamine, and 1,3-propanediamine.

[0019] In a preferred embodiment, the molar ratio of triethylenetetramine to N,N-dimethylethanolamine in the compound amine component is 1:5-15. This preferred embodiment exhibits higher CO generation selectivity and is more conducive to effectively suppressing the hydrogen evolution side reaction.

[0020] In a preferred embodiment, the electrolyte salt is selected from at least one of sodium bicarbonate, potassium sulfate, tetramethylammonium chloride, and potassium chloride.

[0021] In a preferred embodiment, the cationic interface modifier is selected from at least one of dodecyltrimethylammonium bromide, polyethyleneimine, and hexadecyltrimethylammonium bromide.

[0022] In a preferred embodiment, the functional ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, and N-butylpyridine tetrafluoroborate.

[0023] As previously stated, a second aspect of the present invention provides a method for preparing the synergistically enhanced amine absorbent liquid described in the first aspect, comprising providing raw materials of corresponding masses according to the proportions of the components in the synergistically enhanced amine absorbent liquid described in the first aspect, and performing the following steps: (1) Dissolve the compound amine component in water to obtain a compound amine solution; the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; (2) The compound amine solution is first mixed with electrolyte salt and synergistic amine to obtain a precursor solution; (3) The precursor solution is subjected to ultrasonic treatment, and then mixed with a cationic interface modifier to obtain mixture I; (4) Mix the mixture I with the functional ionic liquid for a third time to obtain the synergistically enhanced amine absorption liquid.

[0024] In a preferred embodiment, in step (1), the molar ratio of triethylenetetramine to N,N-dimethylethanolamine in the compound amine component is 1:5-15.

[0025] Preferably, in step (1), the amount of water is controlled such that the mass fraction of the compound amine component in the compound amine solution is 28-38%.

[0026] In a preferred embodiment, in step (3), the conditions for ultrasonic treatment are at least: a temperature of 40°C, a power of 300-500W, and a time of 1-2 hours. This preferred embodiment promotes the uniform dispersion of electrolyte salts and synergistic amines in the precursor solution, reducing local concentration differences.

[0027] Preferably, the method of the present invention further includes: during the ultrasonic treatment, stirring is performed every 20-30 minutes from the start of the ultrasonic treatment, and each stirring independently satisfies the following: time of 60-80 seconds and rotation speed of 150-250 rpm.

[0028] According to a preferred embodiment, in step (2), the first mixing is carried out under stirring conditions, and at least the following conditions are met: temperature is 20°C, rotation speed is 150-250 rpm, and time is 20-30 min.

[0029] According to a preferred embodiment, in step (3), the second mixing is carried out under stirring conditions, and at least the following conditions are met: temperature is 40°C, rotation speed is 150-250 rpm, and time is 1-2 h.

[0030] In a preferred embodiment, in step (4), the third mixing is carried out under stirring conditions and at least meets the following requirements: temperature of 70°C, rotation speed of 250-350 rpm, and time of 60-80 min.

[0031] As mentioned above, the third aspect of the present invention provides the application of the synergistically enhanced amine absorbent described in the first aspect in the absorption of carbon dioxide and its in-situ electrocatalytic reduction.

[0032] In a preferred embodiment, during the electrocatalytic reduction of carbon dioxide, the functional ionic liquid in the absorbent is synergistically adsorbed onto the cathode surface with the cationic interface modifier to improve the selectivity of the carbon monoxide generation reaction and suppress the hydrogen evolution side reaction.

[0033] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0034] Unless otherwise specified, "room temperature" in this invention refers to a temperature of 25±.

[0035] The compound amine components consist of triethylenetetramine and N,N-dimethylethanolamine in a molar ratio of 1:10.

[0036] Preparation Example 1 This preparation example illustrates how the synergistically enhanced amine absorbent provided by the present invention is obtained by following the steps below: (1) Dissolve the compound amine component in water to obtain a compound amine solution with a mass fraction of 36.6%; (2) At a rotation speed of 200 rpm and a temperature of , the compound amine solution was mixed with an electrolyte salt (sodium bicarbonate) and a co-amine (N-methyldiethanolamine, diethanolamine and 1,3-propanediamine in a molar ratio of 1:1:1) for 30 min to obtain a precursor solution; (3) The precursor solution was sonicated at a power of 400W for 1.5h. From the start of the sonication, stirring was performed every 30min. Each stirring independently met the following conditions: time of 60s and rotation speed of 200rpm. Then, it was mixed with a cationic interface modifier (hexadecyltrimethylammonium bromide) for 1 hour at a speed of 250 rpm and a temperature of 100°C to obtain mixture I; (4) The mixture I was mixed with the functional ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) for a third time at a speed of 300 rpm and a temperature of 60 min to obtain the synergistic enhanced amine absorption liquid, named P1.

[0037] Preparation Example 2 This preparation example was carried out using a method similar to that of Preparation Example 1, except that in step (3), the cationic interface modifier used was polyethyleneimine; Finally, a synergistically enhanced amine absorbent was obtained and named P2.

[0038] Preparation Example 3 This preparation example was carried out using a method similar to that of Preparation Example 1. The difference is that in step (3), the cationic interface modifier used was dodecyltrimethylammonium bromide. Finally, a synergistically enhanced amine absorbent was obtained and named P3.

[0039] Preparation Example 4 This preparation example is carried out using a method similar to that of Preparation Example 1. The difference is that in step (4), the functional ionic liquid used is 1-butyl-3-methylimidazolium hexafluorophosphate. Finally, a synergistically enhanced amine absorbent was obtained and named P4.

[0040] Preparation Example 5 This preparation example is carried out using a method similar to that of Preparation Example 1. The difference is that in step (4), the functional ionic liquid used is N-butylpyridine tetrafluoroborate. Finally, a synergistically enhanced amine absorbent was obtained and named P5.

[0041] Comparative Example 1 This comparative example was prepared using a method similar to that of Preparation Example 1, except that the weight amounts of the cationic interface modifier and the functional ionic liquid were the same. Finally, an amine-based absorbent was obtained and named DP1.

[0042] Comparative Example 2 This comparative example was prepared using a method similar to that of Example 1, except that in step (2), the amount of sodium bicarbonate electrolyte salt used was: Finally, an amine-based absorbent was obtained and named DP2.

[0043] Comparative Example 3 This comparative example was prepared using a method similar to that of Example 1, except that in step (4), the amount of functional ionic liquid used was: Finally, an amine-based absorbent was obtained and named DP3.

[0044] Comparative Example 4 This comparative example was prepared using a method similar to that of Preparation Example 1, except that in step (3), the amount of cationic interface modifier used was: Finally, an amine-based absorbent was obtained and named DP4.

[0045] Comparative Example 5 This comparative example was prepared using a method similar to that of Preparation Example 1. The difference is that in step (2), the amount of sodium bicarbonate electrolyte salt was changed so that the molar ratio of sodium bicarbonate to the compound amine component was 1.5:1. Finally, an amine-based absorbent was obtained and named DP5.

[0046] Test Example 1 The in-situ CO2 capture and electrocatalytic reduction performance of the amine absorbent prepared in the above examples was tested using an H-type reactor and reaction system. The main components include an H-type reactor, a gas mass flow controller, an electrochemical workstation, and a gas chromatograph. The H-type reactor consists of two main parts: an anode and anode chamber, each with a volume of 100 mL. The two chambers are separated by a Nafion 117 proton exchange membrane to prevent product cross-mixing. A three-electrode system was used for testing, with a 1×...2 A platinum sheet electrode was used as the counter electrode, a saturated Ag / AgCl electrode as the reference electrode, and a glassy carbon electrode (supported with a metal catalyst) (1× 2 ) as the working electrode.

[0047] First, CO2-containing waste gas (flow rate 200 sccm) is continuously bubbled into the prepared bifunctional amine electrolyte for 1 hour. Since the absorption of CO2 by the amine solution is an exothermic reaction, the absorption capacity of the solution will decrease after heating. After cooling to room temperature, waste gas is continuously bubbled into it for another half hour. Finally, the collection solution is purged with N2 for 30 minutes to remove dissolved CO2, which is then collected using a gas collection bag.

[0048] Preparation of the nano-silver electrode: A catalyst slurry was prepared using silver nanoparticles, a binder (5 wt% Nafion and Sustaining solution), and anhydrous ethanol. The silver nanoparticles were uniformly dispersed in the slurry by ultrasonication for 30 min and magnetic stirring for 15 min. The catalyst slurry was then uniformly sprayed onto a glassy carbon electrode using a spray gun. The catalyst loading was determined by weighing, and the silver catalyst loading was controlled to be 3 mg / cm³. 2 .

[0049] During the testing process, the H-type reactor was first connected to the electrochemical workstation and gas pipeline. Then, the reaction was started and the gas flow controller switch was turned on (gas flow rate 60 sccm) for airtightness and sealing tests. Product detection was performed offline. N2 released from the high-pressure gas cylinder entered the H-type reactor through the pipeline, purging the gaseous products at the working electrode. The products were collected using a gas collecting bag and then injected into a gas chromatograph for offline concentration detection to calculate the Faraday efficiency of the reaction products. During the reaction, a magnetic stirrer was used to agitate the cathode electrolyte solution to enhance mass transport.

[0050] The test was conducted at room temperature and normal pressure.

[0051] The CO Faradaic efficiency and partial current density were tested in the potential range of -1.2V to 1.6V (vs. Ag / AgCl); the initial CO Faradaic efficiency and the initial H2 Faradaic efficiency were recorded, and the CO Faradaic efficiency was tested and recorded after 100 hours of continuous electrolysis. The results are shown in Table 1. Note: "-" in Table 1 indicates that it was not measured.

[0052] The results above demonstrate that this invention utilizes triethylenetetramine and N,N-dimethylethanolamine to construct a complex amine absorption platform, providing stable carbon dioxide chemical absorption capacity. Based on this, a functional ionic liquid with a specific organic cation structure is introduced as a functional component. This component synergistically interacts with a cationic interface modifier at the electrode interface, participating in the construction of the electric double layer structure on the electrode surface and regulating the local reaction microenvironment. Thus, without altering the main amine structure, a synergistic improvement in the selectivity and system stability of in-situ electrocatalytic reduction of carbon dioxide is achieved. Through the synergistic effect of the functional ionic liquid and the interface modifier, targeted regulation of the electrode interface microenvironment is realized.

[0053] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A synergistically enhanced amine absorbent, characterized in that, The absorbent liquid comprises the following components by mass fraction, based on a total mass of 100%: The compound amine component comprises 28-32%, wherein the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; Electrolyte salts 5-10%; Cationic interface modifiers 2-3%; Functional ionic liquids 2-3%; The synergistic amine is 4-6%; the synergistic amine is selected from at least one of N-methyldiethanolamine, diethanolamine, 1,3-propanediamine, 2-amino-2-methyl-1-propanol and 3-amino-1-propanol; The remainder is water; The functional ionic liquid has an imidazolium-type and / or pyridinium-type organic cation structure.

2. The synergistically enhanced amine absorbent liquid according to claim 1, characterized in that, In the compound amine component, the molar ratio of triethylenetetramine to N,N-dimethylethanolamine is 1:5-15.

3. The synergistically enhanced amine absorbent liquid according to claim 1, characterized in that, The electrolyte salt is selected from at least one of sodium bicarbonate, potassium sulfate, tetramethylammonium chloride, and potassium chloride; and / or The cationic interface modifier is selected from at least one of dodecyltrimethylammonium bromide, polyethyleneimine, and hexadecyltrimethylammonium bromide; and / or The functional ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, and N-butylpyridine tetrafluoroborate.

4. A method for preparing a synergistically enhanced amine absorbent as described in any one of claims 1-3, characterized in that, Provide the raw materials in the proportions of the components in the synergistically enhanced amine absorbent liquid according to any one of claims 1-3, and perform the following operations: (1) Dissolve the compound amine component in water to obtain a compound amine solution; the compound amine component includes triethylenetetramine and N,N-dimethylethanolamine; (2) The compound amine solution is first mixed with electrolyte salt and synergistic amine to obtain a precursor solution; (3) The precursor solution is subjected to ultrasonic treatment, and then mixed with a cationic interface modifier to obtain mixture I; (4) Mix the mixture I with the functional ionic liquid for a third time to obtain the synergistically enhanced amine absorption liquid.

5. The method according to claim 4, characterized in that, In step (1), the molar ratio of triethylenetetramine to N,N-dimethylethanolamine in the compound amine component is 1:5-15.

6. The method according to claim 4, characterized in that, In step (1), the amount of water is controlled so that the mass fraction of the compound amine component in the compound amine solution is 28-38%.

7. The method according to claim 4, characterized in that, In step (3), the conditions for ultrasonic treatment must at least be met: temperature of 40°C, power of 300-500W, and time of 1-2 hours.

8. The method according to claim 4, characterized in that, In step (2), the first mixing is carried out under stirring conditions, and at least meets the following requirements: temperature of 20°C, rotation speed of 150-250 rpm, and time of 20-30 min; and / or In step (3), the second mixing is carried out under stirring conditions, and at least meets the following requirements: temperature of 40°C, rotation speed of 150-250 rpm, and time of 1-2 hours; and / or In step (4), the third mixing is carried out under stirring conditions and at least meets the following requirements: temperature of 70°C, rotation speed of 250-350 rpm, and time of 60-80 min.

9. The application of a synergistically enhanced amine absorbent as described in any one of claims 1-3 in the absorption of carbon dioxide and its in-situ electrocatalytic reduction.

10. The application according to claim 9, characterized in that, In the process of carbon dioxide electrocatalytic reduction, the functional ionic liquid and cationic interface modifier in the absorbent are synergistically adsorbed on the cathode surface to improve the selectivity of carbon monoxide generation reaction and suppress hydrogen evolution side reaction.

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