Application of Bronsted-Lewis bifunctional acid ionic liquid in catalyzing alcohol amine solution to desorb CO2

Abstract

The invention discloses an application of a Bronsted-Lewis bifunctional acidic ionic liquid catalyst in catalyzing an alcohol amine solution to desorb CO2. The anion part of the ionic liquid is a transition metal compound, and the cation part is a sulfonic acid functionalized imidazole group. The preparation method of the catalyst comprises the following steps: dissolving an imidazole organic matter in an organic solvent at a certain temperature, continuously stirring, slowly dropwise adding a corresponding amount of sulfonyl compound, and reacting for a period of time to obtain a mixed solution A; decantation separation is conducted on A, and washing and drying are conducted to obtain sulfonic acid functionalized imidazolium salt B; and then, adding a corresponding amount of transition metal compound into B at a certain temperature, stirring for a certain time to obtain a mixture C, and drying the mixture C to obtain the product Bronsted-Lewis bifunctional acidic ionic liquid catalyst. The Bronsted-Lewis bifunctional acidic ionic liquid is used for catalyzing the CO2 desorption process of an alcohol amine-rich solution, and compared with a traditional solid acid catalyst, the catalyst has the advantages of being adjustable in acid strength, high in structure designability, good in catalytic effect and the like, and has important significance in the field of CO2 capture through a high-efficiency and low-energy-consumption alcohol amine method.

Description

[0001] Application of Brönsted–Lewis bifunctional acidic ionic liquids in catalytic CO2 desorption from alcoholamine solutions

[0002] Bronsted–Lewis bifunctional acid ionic liquids and their application in catalytic CO2 desorption from alcoholamine solutions Technical Field

[0003] The invention belongs to the technical field of CO2 capture in coal-fired power plants, and mainly relates to the application of Bronsted-Lewis bifunctional acidic ionic liquid in catalyzing the desorption of CO2 by rich alcohol amine solution. Background Art

[0004] Global climate change is driven by a significant increase in atmospheric CO₂ levels. To address this issue, CO₂ capture, utilization, and storage (CCUS) technologies have been extensively researched and are considered one of the most promising approaches to achieving carbon neutrality. CO₂ capture is the foundation and prerequisite for CCUS. Among existing CO₂ capture methods, post-combustion capture (PCC) is considered a viable strategy for large-scale CO₂ capture due to its low cost and simple equipment requirements. Amine-based chemical CO₂ capture technology is the most economical and effective method for reducing CO₂ emissions from coal-fired flue gas. However, this method also faces significant challenges, including solvent degradation, corrosion, and excessive regeneration heat load. The primary bottleneck currently associated with this method is the high regeneration temperature (120-140°C), which generates a significant heat load, accounting for approximately 50-80% of the total energy consumption of the desorption unit. Therefore, it is imperative to develop new technologies that can effectively reduce the high energy consumption of CO₂ capture processes to achieve green and energy-efficient amine-based CO₂ capture.

[0005] To address the high energy consumption of regenerating CO2-rich amine solutions, Idem, Liang Zhiwu, and others proposed adding solid acid catalysts to reduce regeneration energy consumption. Liang Zhiwu et al. (AIChE Journal, 2016, 62:753-65) demonstrated that adding H-ZSM-5, γ-Al2O3, and a physical mixture of γ-Al2O3 and H-ZSM-5 to 5 M MEA at 105°C reduced regeneration energy consumption by 18.6%, 22.1%, and 23.7%, respectively. Tan et al. (Chemical Engineering Journal, 2023, 453:139801) investigated the catalytic performance of transition metal (Ni, Zr)-modified attapulgite composite catalysts for CO2 desorption. The results demonstrated significantly enhanced CO2 desorption activity and effectively reduced desorption energy consumption. Although solid acid catalysts exhibit excellent catalytic activity for CO2 desorption, many of these catalysts are susceptible to deactivation in industrial applications. Therefore, it is necessary to continue to search for more efficient, stable, safe, and cost-effective MEA regeneration catalysts. In recent years, ionic liquids have attracted widespread attention as catalysts in green chemistry due to their good catalytic performance, high selectivity, and strong stability. Compared with most catalytic systems, they are more economical and environmentally friendly, making them ideal catalysts in industry. Imidazolium ionic liquids play an important role in ionic liquid research and are the most studied and highly active class of ionic liquids. Sun et al. (Chemical Engineering Science, 2023, 283:119380.) studied the catalytic effect of a series of acidic imidazolium ionic liquids on CO2 desorption and analyzed their catalytic performance at 90 °C. The results showed that [Bmim]PF6 catalyst has excellent catalytic activity for CO2 desorption. Xin et al. (Advanced Science, 2022, 10(3):2205352.) used [EMmim][NTf2] to catalyze the CO2 desorption reaction of MEA solution. The results showed that the desorption kinetics of the reaction were significantly improved at lower temperatures and the energy consumption requirements were greatly reduced, indicating that [EMmim][NTF2] is a new catalyst for CO2 capture technology. Therefore, in order to further reduce the regeneration energy consumption of CO2-rich amine solution, thereby reducing the CO2 capture cost and improving the practicality of amine-based CO2 capture, it is of great practical significance to develop and design new and efficient ionic liquid catalysts. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to synthesize an ionic liquid catalyst with excellent performance and use it to catalyze the reduction of the regeneration energy consumption of desorbing CO2 by an alcohol amine solution, thereby reducing the cost of capturing CO2 by the alcohol amine method.

[0007] The technical solution of the present invention is to provide a Bronsted-Lewis bifunctional acid ionic liquid for use in catalyzing the desorption of CO2 from an alcohol-rich amine solution. The ionic liquid catalyst is composed of a sulfonic acid-functionalized imidazole group and a transition metal compound. The preparation method of the ionic liquid comprises the following steps:

[0008] (1) Dissolve the imidazole organic compound in an organic solvent, continue stirring at a certain temperature, and slowly add a corresponding amount of sulfonyl compound dropwise. Continue stirring for a period of time to obtain a mixed solution A;

[0009] (2) A is separated by decantation, washed and dried to obtain sulfonic acid functionalized imidazole salt B;

[0010] (3) Add a corresponding amount of transition metal compound to B, stir at a certain temperature for a certain time to obtain a mixture C, and dry C to obtain the corresponding Bronsted-Lewis bifunctional acidic ionic liquid catalyst.

[0011] Preferably, in step (1), the molar ratio of the imidazole organic compound to the sulfonyl compound is 1:2-1:1.

[0012] Preferably, in step (1), the dropping temperature is 0-25°C, more preferably 0-5°C; the reaction time is 1-4 h, more preferably 1-2 h.

[0013] Preferably, in step (2), the drying temperature is 60-100°C, more preferably 70-90°C; the drying time is 8-24 h, more preferably 10-20 h.

[0014] Preferably, in step (3), the molar ratio of the sulfonic acid functionalized imidazole salt to the transition metal compound is 1:4-1:1.

[0015] Preferably, in step (3), the reaction temperature is 30-80°C, more preferably 40-60°C; the reaction time is 1-4 h, more preferably 1-3 h.

[0016] Preferably, in step (3), the drying temperature is 60-100°C, more preferably 70-90°C; the drying time is 8-24h, more preferably 10-20h.

[0017] Preferably, the sulfonyl compounds described herein include various sulfonyl compounds including chlorosulfonic acid and 1,3-propane sultone.

[0018] Preferably, the imidazole organic compounds mentioned herein include various imidazole substances including imidazole, N-methylimidazole, and alkylimidazole.

[0019] Preferably, the transition metal compounds described herein are various transition metal compounds including FeCl3, CuCl2, CuCl, ZnCl2, NiCl3, MnCl2, FeBr3, and ZnBr2.

[0020] Under certain temperature conditions, an imidazole organic compound is dissolved in an organic solvent, stirred continuously, and a corresponding amount of a sulfonyl compound is slowly added dropwise. After a period of reaction, a mixed solution A is obtained. A is separated by decantation, washed, and dried to obtain a sulfonic acid-functionalized imidazole salt B. Then, a corresponding amount of a transition metal compound is added to B at a certain temperature, stirred for a certain period of time, to obtain a mixture C. Drying the mixture C yields the Bronsted-Lewis bifunctional acidic ionic liquid catalyst.

[0021] This catalyst is primarily used in the regeneration of CO2-rich amine solvents in traditional alcohol amine solvent capture CO2 processes, significantly reducing solvent regeneration energy consumption. This is primarily due to the fact that the desorption process of CO2-rich amine solutions requires a large number of acidic sites, and the ionic liquid itself provides a large number of Bronsted and Lewis acid sites. These two acidic sites exhibit a strong synergistic effect in promoting the two-step reactions of carbamate cleavage and protonated amine deprotonation during the CO2 desorption process, significantly improving the reaction rate.

[0022] Alcohol amine solvents used for CO2 capture include traditional amine solutions such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ), as well as newer amine solutions such as 4-(diethylamino)-2-butanol (DEAB), diethyleneamine hydrochloride (DETA), diethylaminoethyl (DEAE), and various binary or ternary mixed amine solvents such as MEA-DEA and MEA-MDEA. The concentration of the amine aqueous solvent ranges from 1 to 7 mol / L.

[0023] Phase-change solvents used for CO2 capture include: the MPA-NHD-H2O system composed of 3-amino-1-propanol (MPA) and polyethylene glycol dimethyl ether (NHD); the AEEA / EAE / PMDETA / DMSO system composed of aminoethylethanolamine (AEEA), ethylenediamine (EAE), N,N,N',N',N''-pentamethyldiethylenetriamine (PMDETA) and dimethyl sulfoxide (DMSO); the MAE-DGM-H2O system composed of 2-methylaminoethanol (MAE), diethylene glycol dimethyl ether (DGM) and water; the AMP-PMDETA-TEPA system composed of 2-amino-2-methyl-1-propanol (AMP), PMDETA and tetraethylenepentamine (TEPA); and the TETA-DGME-H2O system composed of triethylaminetetramine (TETA), diethylene glycol co-methyl ether (DGME) and water, among other commonly reported phase-change absorbents containing alcohol amines.

[0024] The CO2 desorption system employed in this invention comprises a catalyst and an aqueous alcoholamine solution. The catalyst is added to the CO2-rich alcoholamine solution. During the desorption process, the catalyst promotes proton transfer in the reaction system, allowing CO2 to be desorbed at a lower temperature, thereby reducing the energy consumption of the desorption system. The CO2 captured by the alcoholamine solvent comes from various flue gases, with CO2 concentrations in the mixed gas ranging from 5-30%. The catalyst catalyzes the CO2 desorption process, and the alcoholamine solvent regenerates at a temperature range of 70-120°C.

[0025] The beneficial effects of the present invention are:

[0026] (1) The catalyst preparation process is simple, and the acidity strength and structure are adjustable.

[0027] (2) The catalyst has excellent desorption performance and its catalytic performance is stronger than that of traditional single acidic ionic liquid catalysts.

[0028] (3) The catalyst has little effect on CO2 absorption, has good stability and can be recycled repeatedly.

[0029] (4) The ionic liquid catalyst-amine solution can be regarded as a new absorbent and directly used in the existing CO2 capture device without the need for additional equipment modification costs, which is very suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The Fourier transform infrared spectra of the catalysts in Examples 1, 2 and 3 are shown.

[0031] Figure 2 The pyridine infrared spectra of the catalysts in Examples 1, 2, and 3 are shown.

[0032] Figure 3It represents a laboratory-scale batch desorption device for CO2-rich amine solution.

[0033] Table 1 Comparison of catalyst desorption energy consumption of Examples and Control Examples. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the embodiments.

[0035] Example 1: [MSIM]FeCl4 catalyst

[0036] Chlorosulfonic acid (0.05 mol) was added dropwise to a stirred solution of 1-methylimidazole (0.05 mol) in dry dichloromethane (50 mL) over 5 minutes in an ice bath. The reaction was stirred at room temperature for 1 hour to ensure completion. After the reaction, the CH₂Cl₂ layer was decanted, and the remaining mixture was washed with dry CH₂Cl₂ (3 × 20 mL). The mixture was dried at 80°C to yield 3-methyl-1-sulfonic acid imidazolium chloride [MSIM]Cl as a pale yellow viscous oil. Equimolar amounts of 3-methyl-1-sulfonic acid imidazolium chloride and FeCl₃ were then added in an oil bath at 50°C. The mixture was stirred for 1 hour, and the product was dried under vacuum to obtain [MSIM]FeCl₄.

[0037] As a comparison, the catalytic effect of the product MSIMCl in the synthesis process was also verified in the experiment.

[0038] Example 2:

[0039] The same as Example 1, except that during the catalyst preparation process, the transition metal compound was replaced with ZnCl2, and the obtained catalyst was marked as [MSIM]ZnCl3.

[0040] Example 3:

[0041] The same as Example 1, except that during the catalyst preparation process, the transition metal compound was replaced with CuCl2, and the obtained catalyst was marked as [MSIM]CuCl3.

[0042] Embodiment 4:

[0043] The same as Example 1, except that during the catalyst preparation process, the transition metal compound was replaced with NiCl3, and the obtained catalyst was marked as [MSIM]NiCl4.

[0044] Application Examples

[0045] Regeneration process of catalytic desorption of CO2-rich monoethanolamine solvent

[0046] Desorption experimental apparatus Figure 3As shown, the system consists of a mass flow controller, a three-necked flask, and an infrared CO2 analyzer. The reaction is carried out in the three-necked flask. A thermometer is used to measure the temperature of the reactants during the reaction. A condenser is used to minimize MEA loss and prevent experimental errors caused by changes in the amine solution concentration due to MEA vaporization. To minimize errors, N2 is bubbled through the equipment for a certain period of time before each experiment to remove residual CO2. 100 mL of a rich amine solution with a loading of 0.535 (±0.01) mol CO2 / mol MEA is added to the three-necked flask, and 1.0 g of the above-mentioned catalyst is added at a 1.0% ratio. The three-necked flask is placed in an oil bath and heated to the desired desorption temperature of 90°C. Simultaneously, N2 is introduced at a controlled rate of 250 mL / min. The desorbed CO2 mixes with N2, and the mixed gas is passed through a drying flask filled with concentrated sulfuric acid to remove water. The dried gas is then fed to an infrared CO2 analyzer to measure the CO2 content. To ensure complete desorption of CO₂ from the reaction system, each experiment was set to 70 min. Desorption energy consumption (kJ / mol) is defined as the energy required to desorb 1 mol of CO₂. This energy consumption was calculated using an electric meter, with heat provided by an oil bath.

[0047] The experimental results are shown in Table 1 below:

[0048] Table 1 Comparison of catalyst desorption energy consumption of Examples and Control Examples

[0049] catalyst Energy consumption ratio (%) Energy consumption reduction (%) blank 100 0 Comparative Example 1: MSIMCl 82.1 17.9 <![CDATA[[MSIM]ZnCl3]]> 69.7 30.3 <![CDATA[[MSIM]FeCl4]]> 55.3 44.7 <![CDATA[[MSIM]CuCl3]]> 60.7 39.3 <![CDATA[[MSIM]NiCl4]]> 70.7 29.3

[0050] from Figure 1 and Figure 2 The infrared spectra of the ionic liquid catalyst and the pyridine infrared spectra indicate that a Bronsted-Lewis bifunctional acid ionic liquid catalyst has been successfully synthesized, possessing two types of acid sites. Table 1 above shows that the addition of the Bronsted-Lewis bifunctional acid ionic liquid catalyst significantly reduced the desorption energy consumption of the carbon-rich MEA solution by 29.3-44.7% relative to blank MEA. Furthermore, the catalysts prepared in the Examples performed better than the single acidic ionic liquid catalysts in the comparative examples.

Claims

1. Application of Bronsted-Lewis bifunctional acid ionic liquid in catalyzing CO2 desorption from alcoholamine solution, characterized in that: The catalyst is composed of a sulfonic acid functionalized imidazole group with a Bronsted acid site and a transition metal compound with a Lewis acid site. It has both Bronsted acid and Lewis acid sites and is a bifunctional acidic ionic liquid. The specific preparation method of the catalyst is as follows: (1) dissolving an imidazole organic compound in an organic solvent, stirring continuously at a certain temperature, and slowly adding a corresponding amount of a sulfonyl compound dropwise, and continuing to stir and react for a period of time to obtain a mixed solution A; (2) separating A by decantation, washing, and drying to obtain sulfonic acid functionalized imidazole salt B; (3) Add a corresponding amount of transition metal compound to B, stir at a certain temperature for a certain time to obtain a mixture C, and dry C to obtain the corresponding Bronsted-Lewis bifunctional acidic ionic liquid catalyst.

2. The use according to claim 1, characterized in that In step (1), the molar ratio of the imidazole organic compound to the sulfonyl compound is 1:3-1:

1.

3. The use according to claim 1, characterized in that In step (1), the dropping temperature is 0-25°C, and the reaction time is 1-4 h.

4. The use according to claim 1, characterized in that In step (2), the drying temperature is 60-100°C, and the drying time is 8-24 hours.

5. The use according to claim 1, characterized in that In step (3), the molar ratio of the sulfonic acid functionalized imidazole salt to the transition metal compound is 1:4-1:

1.

6. The use according to claim 1, characterized in that In step (3), the reaction temperature is 30-80°C, and the reaction time is 1-4 h.

7. The use according to claim 1, characterized in that In step (3), the drying temperature is 60-100°C and the drying time is 8-24h.

8. The use according to claim 1, characterized in that The sulfonyl compound includes various sulfonyl compounds including chlorosulfonic acid and 1,3-propane sultone.

9. The use according to claim 1, characterized in that The imidazole organic compounds include various imidazole substances including imidazole, N-methylimidazole and alkylimidazole.

10. The use according to claim 1, characterized in that The transition metal compounds are various transition metal compounds including FeCl3, CuCl2, CuCl, ZnCl2, NiCl3, MnCl2, FeBr3, and ZnBr2.

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