Absorbent for capturing acid gases and method of preparation and use thereof.

Abstract

The present application relates to the field of the absorption and regeneration of acid gases, and specifically relates to an absorbent for capturing acid gases, and a preparation method therefor and the use thereof. A compound for capturing acid gases provided by the present application has a structure as represented by formula (I), wherein R1 is an alkyl group having five or more carbon atoms, M is at least one of a proton-bound organic amine group and a proton-bound heterocyclic group containing a nitrogen atom, and n is an integer from 1 to 4. The compound for capturing acid gases provided by the present application has a relatively weak alkalinity and a relatively small acting force towards acid gases; moreover, the generation of a solid can be avoided during the absorption of acid gases with the compound, and therefore difficulties in the regeneration of the acid gases are reduced, and the regeneration process is relatively easy. The compound provided by the present application has a higher absorption rate for acid gases in the case of a relatively high water content.

Description

1 / 22 Absorbent for capturing acid gases and method of preparation and use thereof. CROSS-REFERENCE TO RELATED REQUESTS

[001] The present application claims priority to Chinese Patent Application No. 2023118110382, filed on December 26, 2023 with the National Intellectual Property Administration of China, entitled “ABSORBENT FOR CAPTURING ACID GASES, AND PREPARATION METHOD THEREFOR AND USE THEREFOR”, the full content of which is incorporated into the present invention by reference. TECHNICAL FIELD

[002] The present application relates to the field of absorption and regeneration of acid gases, specifically to an absorbent for capturing acid gases and its method of preparation and use. BACKGROUND

[003] The large-scale emission of acidic gases, such as sulfur dioxide and carbon dioxide, not only affects the environment and human health but also results in resource waste. Therefore, the absorption and regeneration of acidic gases has become an important approach for resource recovery and utilization. Acidic gas capture can be achieved through techniques such as chemical absorption, pressure swing adsorption, and membrane separation, among which chemical absorption is the most widely used method, mainly employing alkanolamine absorbents for acidic gas absorption. However, alkanolamines react strongly with carbon dioxide, resulting in high reaction and regeneration temperatures between 105 and 120°C, leading to high energy consumption for regeneration and increased energy loss during acidic gas regeneration. Currently, researchers have been exploring the use of Petition 870250074222, dated 08 / 21 / 2025, pp. 88 / 109 2 / 22 Carboxylate salts and carboxylate-based ionic liquids are used for the absorption of acid gases, but these materials have high viscosity. Although increasing the water concentration can reduce the viscosity of the system, increasing the water content also leads to a decrease in the rate of acid gas absorption.

[004] Existing technology has revealed the application of carboxylate salt-based compounds as absorbents to capture carbon dioxide, where quaternary ammonium or phosphonium ions serve as cations of the carboxylate salts to improve the CO2 absorption rate. However, these materials tend to form solids during the absorption process of acidic gases, such as CO2, making the separation process inconvenient. SUMMARY OF THE INVENTION

[005] Therefore, the present application aims to address the issue of the tendency for solids to be produced during the absorption of acid gases by carboxylate salts in existing technology, thus providing an absorbent to capture acid gases, as well as its method of preparation and application to improve the absorption rate of acid gases and reduce the difficulty of acid gas regeneration.

[006] On the one hand, the present application provides a compound for capturing acid gases, wherein the compound has a structure shown in Formula (I), Formula (I) wherein, Ri is an alkyl group with the number of carbon atoms greater than or equal to 5, M is at least one of protonated organic amine groups and protonated nitrogen-containing heterocyclic groups, en is an integer from 1 to 4.

[007] In one embodiment, Ri is a branched alkyl group.

[008] Optionally, the number of carbon atoms in Ri is 6 to 20. Petition 870250074222, dated 08 / 21 / 2025, pages 89 / 109 3 / 22

[009] In one embodiment, the organic amine is at least one of a fatty amine and an alcoholic amine.

[010] Optionally, the organic amine is at least one of a monoamine, diamine, or polyamine.

[011] In one embodiment, the nitrogen-containing heterocycle is at least one of , where R2, R3, R4, Rs, Re are any one of the following: alkyl, substituted alkyl, or hydrogen atoms.

[012] In one embodiment, the compound for capturing acidic gases has any of the following structures: Petition 870250074222, dated 08 / 21 / 2025, pages 90 / 109 4 / 22

[013] The present application also provides an absorbent for capturing acid gases, which includes the compound for capturing acid gases as described above.

[014] On the other hand, the present application provides a method for preparing the absorbent to capture acid gases, which includes the following steps: mixing a carboxylic acid and a weak organic base to obtain the absorbent, wherein the carboxylic acid has a molecular formula R1COOH, and Ri is an alkyl group with the number of carbon atoms greater than or equal to 5.

[015] In one embodiment, the absorbent also includes water.

[016] In one embodiment, the carboxylic acid is a fatty acid. Optionally, the carboxylic acid is at least one of: 2,2-dimethylhexanoic acid, 2-ethylhexanoic acid, 2-ethylheptanoic acid, 2-propylvaleric acid, 2-propylhexanoic acid, 2-propylnonanoic acid, 2-butyloctanoic acid, and 2-hexyldecanoic acid.

[017] In one embodiment, the organic weak base is at least one of an organic amine compound and a nitrogen-containing heterocyclic compound.

[018] Optionally, the organic amine compound is at least one of triethylamine, tripropylamine, monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, N,Ndiethylethanolamine, hydroxyethylethylenediamine, 2-amino-2-methyl-1-propanol, Nmethyl-1,3-propanediamine, 1,4-butanediamine, N,N,N',N'tetramethylhexanediamine, diethylenetriamine and triethylenetetramine. Petition 870250074222, dated 08 / 21 / 2025, pp. 91 / 109 5 / 22

[019] Optionally, the nitrogen-containing heterocyclic compound is at least one of a pyridine ring-containing compound, an imidazole ring-containing compound, a pyrrole ring-containing compound, and piperazine.

[020] In one embodiment, the molar ratio of the carboxylic acid, the weak organic base, and water is 1:(0.25-1):(0-20).

[021] The present application also provides the use of compounds for capturing acid gases, absorbents for capturing acid gases or absorbents prepared by the method for preparing absorbents for capturing acid gases in the absorption and regeneration of acid gases, wherein the acid gas is at least one of carbon dioxide, sulfur dioxide or hydrogen sulfide.

[022] The absorption of acid gases includes steps of placing the absorbent in contact with the acid gases to be absorbed at a partial pressure of acid gas of 0.003 MPa to 1.0 MPa and a temperature of 0 to 50 °C and carrying out the absorption.

[023] Acid gas regeneration includes a desorption step of the absorbent after absorption of the acid gases under agitation for 0.1 to 2 hours at 80 to 100 °C, or acid gas regeneration comprises a desorption step of the absorbent after absorption of the acid gases under agitation for 0.1 to 1 hour at 10 to 80 °C under vacuum conditions.

[024] The technical solutions provided by this application offer the following advantages: 1. The compound for capturing acid gases provided by the present application has a structure represented by Formula (I), where Ri is an alkyl group with a number of carbon atoms greater than or equal to 5, M is at least one of protonated organic amine groups and a protonated nitrogen-containing heterocyclic group, and en is an integer from 1 to 4. On the one hand, the compound Petition 870250074222, dated 08 / 21 / 2025, pp. 92 / 109 The compound 6 / 22 for capturing acid gases provided in this application has weaker basicity and therefore has a lower interaction strength with acid gases. This compound can prevent the formation of solids during the absorption of acid gases and reduce the difficulty of regenerating acid gases, thus making the regeneration process relatively easier. On the other hand, under higher water content, the compound provided in this application has a higher absorption rate for acid gases. 2. In the acid gas capture compound provided by the present application, Ri is a branched alkyl group. As the carbon chain increases, it can improve the absorption rate of the compound for acid gases. At the same time, a branched alkyl group has a weaker interaction force with water; therefore, after carbon dioxide absorption, the organic phase and the aqueous phase formed are more stable. 3. The absorbent for capturing acid gases provided by this application includes the aforementioned compound for capturing acid gases. The absorbent provided by this application is a salt of a weak acid and a weak base. Under higher water content, the absorbent can absorb a greater amount of acid gases and does not generate solids during the absorption of acid gases, thus not increasing the difficulty of regenerating acid gases and improving the rate of acid gas regeneration. 4. The method for preparing the absorbent for capturing acidic gases provided by the present application involves mixing a carboxylic acid, a weak organic base, and water to obtain the absorbent, where the carboxylic acid has a molecular formula of R1COOH, and R1 is an alkyl group with a number of carbon atoms greater than or equal to 5. The present application requires only one mixing step of the carboxylic acid and the weak organic base to create the weak acid and weak base salt, making the synthesis method simple. Petition 870250074222, dated 08 / 21 / 2025, pp. 93 / 109 7 / 22 5. The compound, absorbent, and absorbent prepared by the aforementioned method described above and provided in this application can absorb and regenerate acid gases. The regeneration steps include heating the absorbent after absorbing acid gases to 100 °C or agitating the absorbent after absorbing acid gases under vacuum conditions for a certain period of time to complete the regeneration. The compound, absorbent, and absorbent prepared by the aforementioned method described above and provided in this application can desorb the absorbed acid gases at 100 °C or by using negative pressure at room temperature, significantly reducing the energy consumption for the regeneration of acid gases. ILLUSTRATION OF THE DRAWINGS

[025] To illustrate more clearly the specific embodiments of the present application or the technical solutions of existing technologies, a brief introduction to the drawings required in the description of specific embodiments or existing technologies will be provided below. It is obvious that the drawings described below are some implementations of the present application. In the absence of creative work, those skilled in the art may obtain other drawings based on these drawings.

[026] Figure 1 is a schematic diagram of the amount of carbon dioxide absorbed by the absorbents made in Examples 1, 28 to 32 of the present application. DETAILED DESCRIPTION

[027] The following examples are provided for a better understanding of this application and are not limited to the best mode of implementation. They do not constitute a limitation on the content and scope of protection of this application. Any product that is identical or similar to this application, whether derived from the information in this application or by combining the attributes of this application, may be used for any product that is identical or similar to this application, whether derived from the information in this application or by combining the attributes of this application. Petition 870250074222, dated 08 / 21 / 2025, pp. 94 / 109 8 / 22 The present application, with the attributes of other existing technologies, is within the scope of protection of the present application.

[028] If specific experimental steps or conditions are not specified in the examples, the operations or conditions may be performed in accordance with conventional experimental steps described in the literature in the field. If the manufacturer of the reagents or instruments used is not specified, they are all conventional reagents and products that can be purchased commercially.

[029] During the research and development process, it was discovered that the water-to-salt ratio of existing acid gas carboxylate salt-based absorbents significantly affects the absorption rate of acid gases. The higher the water-to-salt ratio, the lower the amount of acid gases absorbed by the absorbent. Furthermore, with increased absorption of acid gases, solids can form in the absorption system. The solids formed not only cause inconveniences in subsequent operations, such as pipe clogging and equipment damage, but also add additional procedures for solids removal, hindering the regeneration of acid gases and reducing their regeneration rate.

[030] Therefore, the inventor developed a method for generating weak base and weak acid salts by reacting carboxylic acids with weak organic bases. For example, the weak base and weak acid salt obtained by reacting 2-butyl octanoic acid with monoethanolamine, as shown in Formula ( Π), can effectively address the above problems. Petition 870250074222, dated 08 / 21 / 2025, pages 95 / 109 9 / 22 Formula (II)

[031] The onium carboxylate salt in Comparative Examples 5 to 9 of the present application was synthesized using mature technologies, with the synthesis method referenced in the literature: Suarez, PAZ; Dullius, JEL; Einloft, S.; DE Souza RF and Dupont, J., Polyhedron, 1996, 15, 1217-1219. Examples 1 to 27

[032] Examples 1 to 27 provide methods for preparing absorbents to capture acid gases, with the specific steps and parameters as follows: Based on the names and quantities of carboxylic acid, weak organic base, and water listed in Table 1, various raw materials were mixed and stirred to obtain the absorbents. Table 1. Information on absorbent preparation and structural formulas. Group No. Carboxylic Acid Name / Quantity (g) Base Name / Quantity (g) Amount of Water (g) Absorbing Structural Formula Example 1 2-Butyloctanoic Acid / 20.0 Monoethanolamine (MEA) / 6.1 23.9 ' 1 + / \ / OH 1 h3n (rV Example 2 2,2-Dimethylhexanoic Acid / 14.4 MEA / 6.1 23.9 / OH |\ h3n O^>)“ Example 3 2-Ethylhexanoic Acid / 14.4 MEA / 6.1 23.9 / / X / X / X + / OH h3n Example 4 2-Ethylheptanoic Acid / 15.8 MEA / 6.1 23.9 / 011 1 h3n Example 5 2-Propylvaleric Acid / 14.4 MEA / 6.1 23.9 / OH 1 h3n Example 6 2-Propylhexanoic acid / 1 5.8 MEA / 6.1 23.9 / OH 1 h3n — O'X^O~ Example 7 2-Propylnonanoic acid / 2 0.0 MEA / 6.1 23.9 / OH h3n Example 8 2- MEA / 6.1 23.9 / OH \ HjN (r\ Petition 870250074222, dated 08 / 21 / 2025, pp. 96 / 109 10 / 22 Group No. Carboxylic Acid Name / Quantity (g) Base Name / Quantity (g) Amount of Water (g) Structural Formula absorbing hexyldecanoic acid / 25.6 Example 9 2-Butyloctanoic acid / 20.0 Triethylamine / 10.1 23.9 O^\)- - c HN Example 10 2-Butyloctanoic acid / 20.0 Tripropylamine / 14.3 23.9 O^?o- Example 11 2-Butyloctanoic acid / 20.0 Diethanolamine / 10.5 23.9 / —_ / °H h2n Example 12 2-Butyloctanoic acid / 20.0 Triethanolamine / 14.9 23.9 O^>)- / OH <\ + / \ / OH HN \^^ / OH Example 13 2-Butyloctanoic acid / 20.0 N-methyldiethanolamine / 1 1.9 23.9 O^^o- . \ ♦ / -\ / OH HN ___ / OH Example 14 2Butyloctanoic acid / 20.0 N,N- dimethylethanolamine / 8 .9 23.9 / / ^\ / °H HN +\ Example 15 2Butyloctanoic acid / 20.0 N,Ndiethylethanolamine / 11.7 23.9 (ΧΊΟ- / -0H HX\ Example 16 2Butyloctanoic acid / 20.0 Hydroxyethylethylene diamine / 5.2 23.9 fy o~ H3N+ / \ * / \ / OH NX / Hj Example 17 2Butyloctanoic acid / 20.0 2-amino-2-methyl-1propanol / 8.9 23.9 crj)' HjN..Example 18 2-Butyloctanoic acid / 20.0 N-methyl-1,3propanediamine / 4.4 23.9 O^'o + Hj 2 Example 19 2-Butyloctanoic acid / 20.0 1,4-butanediamine / 4.4 23.9 o” Example 20 2-Butyloctanoic acid / 20.0 N,N-dimethylethylenediamine / 4.4 23.9 2 Example 21 2-Butyloctanoic acid / 20.0 N,N,N',N'-tetramethyl1,6hexanediamine / 8.6 23.9 +NH 2 Example 22 2-Butyloctanoic acid / 20.0 Diethylenetriamine / 3.4 23.9 O' o- _ 3 HaNÍ / - / * / \ -- / - N - / - 3 Ha Example 23 2Butyloctanoic acid / 20.0 Triethylene tetramine / 3.7 23.9 4 Hj / - * / \ ,N. / \ + Ha '. Petition 870250074222, dated 08 / 21 / 2025, pages 97 / 109 11 / 22 Group No. Carboxylic acid name / quantity (g) Base name / quantity (g) Amount of water (g) Absorbing structural formula Example 24 2-Butyloctanoic acid / 20.0 Piperazine / 4.5 23.9 H2O Example 25 2-Butyloctanoic acid / 20.0 Imidazole / 6.8 23.9 © y g+ Q £ Example 26 2-Butyloctanoic acid / 20.0 Pyridine / 7.9 23.9 o ) °i / Example 27 2-Butyloctanoic acid / 20.0 Pyrrole / 6.7 23.9 0 o Example 28 2-Butyloctanoic acid / 20.0 MEA / 6.1 0 \ ^0H 1 HjN —<r\> Example 29 2-Butyloctanoic acid / 20.0 MEA / 6.1 1.8 ' + / -\ / OH 1 h3n — Example 30 2-Butyloctanoic acid / 20.0 MEA / 6.1 5 / OH J H3N ο;ίΧχο Example 31 2-Butyloctanoic acid / 20.0 MEA / 6.1 10 ,OH 1 h3n (rV Example 32 2-Butyloctanoic acid / 20.0 MEA / 6.1 36 ' + / --\ / OH 1 h3n rr'''·® Example 33 2-Butyloctanoic acid / 20.0 Triethylenetetramine / 3.7 18.0 Hj 3 4 Comparative Example 1 2-Butyloctanoic acid / 20.0 23.9 Example Comparative 2 MEA / 6.1 23.9 .OH h2n Example Comparative 3 Potassium Acetate / 8.9 23.9 O 11 k+ Comparative Example 4 Acetic Acid / 6.0 MEA / 6.1 23.9 0 II + / °H / ^\ _ h3n Comparative Example 5 Triethylbutylammonium Isobutyrate / 24.5 23.9 θ \ γK-. Petition 870250074222, dated 08 / 21 / 2025, pages 98 / 109 12 / 22 Group No. Carboxylic acid name / quantity (g) Base name / quantity (g) Amount of water (g) Absorbing structural formula Example Comparison 6 Tributylhexylphosphonium acetate / 34.6 23.9 o 0 +\ Examples 28 to 32

[033] Examples 28 to 32 provide methods for preparing absorbents for capturing acid gases, with the specific steps and parameters as follows: 2-Butyloctanoic acid, monoethanolamine, and deionized water were mixed in molar ratios of 1:1:0, 1:1:1, 1:1:2.8, 1:1:5.6, and 1:1:20 and stirred uniformly to obtain the absorbents. Example 33

[034] This example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 2-Butyloctanoic acid, triethylenetetramine, and deionized water were mixed in a molar ratio of 1:0.25:10 and stirred uniformly to obtain the absorbent. Comparative Example 1

[035] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of 2-butyloctanoic acid and 1.33 mol of water were mixed directly and stirred to obtain the absorbent. Comparative Example 2

[036] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: Petition 870250074222, dated 08 / 21 / 2025, pp. 99 / 109 13 / 22 0.1 mol of monoethanolamine (MEA) and 1.33 mol of water were mixed directly and stirred to obtain the absorbent. Comparative Example 3

[037] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of potassium acetate and 1.33 mol of water were mixed to obtain the absorbent. Comparative Example 4

[038] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of acetic acid, 0.1 mol of MEA, and 1.33 mol of water were mixed to obtain the absorbent. Comparative Example 5

[039] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of triethylbutylammonium isobutyrate and 1.33 mol of water were mixed to obtain the absorbent. Comparative Example 6

[040] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of tributylhexylphosphonium acetate and 1.33 mol of water were mixed to obtain the absorbent. Comparative Example 7 Petition 870250074222, dated 08 / 21 / 2025, pages 100 / 109 14 / 22

[041] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of tributylhexylphosphonium 2-ethylhexanoate and 10 g of water were mixed to obtain the absorbent. Comparative Example 8

[042] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of trimethylbutylammonium 2-butyloctanoate and 10 g of water were mixed to obtain the absorbent. Comparative Example 9

[043] This comparative example provided a method for preparing an absorbent to capture acid gases, with the specific steps and parameters as follows: 0.1 mol of potassium 2-butyloctanoate and 10 g of water were mixed to obtain the absorbent. Example Application 1

[044] The absorbents prepared by Examples 1 to 33 and Comparative Examples 1 to 6, each with 50 g, were injected into glass bottles, respectively. The bottles were connected to CO2 balloons and the absorbent solution was immersed in CO2 at an atmospheric pressure of 20°C under agitation for 3 hours. The weight of the bottles is recorded before and after CO2 absorption, and the amount of CO2 absorbed is calculated from the weight gain of the system. The results of the amount of CO2 absorbed by the absorbents prepared by Examples 1 to 33 and Comparative Examples 1 to 6 are shown in Table 2. Petition 870250074222, dated 08 / 21 / 2025, pages 101 / 109 15 / 22 Table 2: Results of CO2 Absorption Amount and Rate Absorption Group No. CO2 Absorption Amount (g) CO2 Absorption Rate (%) Group No. CO2 Absorption Amount (g) CO2 Absorption Rate (%) Group No. CO2 Absorption Amount (g) CO2 Absorption Rate (%) Example 1 2.13 4.3 Example 14 1.80 3.6 Example 27 1.59 3.2 Example 2 1.14 2.3 Example 15 1.76 3.5 Example 28 1.25 2.6 Example 3 1.16 2.3 Example 16 1.78 3.6 Example 29 1.60 3.2 Example 4 1.34 2.7 Example 17 1.93 3.9 Example 30 1.96 3.9 Example 5 1.18 2.4 Example 18 1.93 3.9 Example 31 Example 6 2.08 4.2 Example 19 1.42 2.8 Example 20 1.82 3.6 Example 32 2.10 4.2 Example 7 1.82 3.6 Example 20 1.62 3.2 Example 33 1.61 3.2 Example 8 2.04 4.1 Example 21 1.62 3.2 Example Comparative 1 0.15 0.3 Example 9 2.62 5.2 Example 22 1.70 3.4 Example Comparative 2 4.13 8.2 Example 10 2.40 4.8 Example 23 1.66 3.3 Example Comparative 3 0.56 1.1 Example 11 1.81 3.6 Example 24 1.93 3.9 Example Comparative 4 0.39 Example 12: 0.8 Example 25: 1.72 Example 3:4 Comparative Example 5: 0.49 Example 13: 1.050 3.0 Example 26 1.61 3.2 Comparative Example 6 0.47 0.9

[045] The CO2 absorption rate is defined as the amount of CO2 absorbed divided by the mass of the absorbent.

[046] According to Table 2, it can be observed that the absorbents prepared by the present application by mixing carboxylic acid and weak organic base were effective in absorbing CO2, with absorption rates ranging from 2.3% to 5.2%. Comparative Example 1 shows a low amount of Petition 870250074222, dated 08 / 21 / 2025, pages 102 / 109 Comparative Example 16 / 22 shows CO2 absorption using only carboxylic acid, while Comparative Example 3 uses carboxylate salts formed by using short-chain aliphatic alkyl carboxylic acids and strong bases, Comparative Example 4 uses an absorbent prepared by short-chain aliphatic alkyl carboxylic acids and weak organic bases, Comparative Example 5 uses quaternary ammonium salts of short-chain aliphatic alkyl carboxylic acids, and Comparative Example 6 uses quaternary phosphonium salts of short-chain aliphatic alkyl carboxylic acids, respectively. Comparative Examples 3, 4, 5, and 6 showed CO2 absorption rates of only 0.8% to 1.1%.

[047] As shown in Figure 1, the molar ratios of water to salt in Example 28, Example 29, Example 30, Example 31, Example 1 and Example 32 were 0.1:1, 2.8:1, 5.6:1, 13.3:1 and 20:1, respectively. It can be observed in Figure 1 that increasing the molar ratio of water to salt in the absorbents can increase the amount of CO2 absorption by the absorbents. Application Example 2

[048] The glass bottles containing the absorbents from Example 1 and Comparative Example 2, after absorbing CO2 as described in Application Example 1, were agitated at 100°C in an oil bath, while the glass bottle containing the absorbent from Example 14, after absorbing CO2, was agitated at 80°C in an oil bath. The outlet of each of the glass bottles was connected to a spiral stainless steel tube submerged in ice water to retain moisture in the gas. After different regeneration times, the amount of CO2 desorption was determined according to the change in total weight of the glass bottles and stainless steel tubes. The results are shown in Table 3. Table 3. Comparison of Thermal Regeneration Performance of Petition 870250074222, dated 08 / 21 / 2025, pp. 103 / 109 17 / 22 Sanitary pads Group No. CO2 Absorption Amount / g Regeneration Oil Bath Temperature / °C Regeneration Time / h CO2 Desorption Amount / g Desorption Rate / % Example 1 2.13 100 1 2.02 95 Example 1 2.13 100 0.1 0.81 38 Example 14 1.80 80 2 1.45 80 Comparative Example 2 4.13 100 1 0.32 8

[049] It can be observed in Table 3 that the absorbents obtained in the present application showed a good desorption effect for absorbed carbon dioxide. At 80°C, the desorption rate can reach 80%, and at 100°C, the desorption rate can reach 95%. In Comparative Example 2, the weak organic base was used as an absorbent, although the amount of carbon dioxide absorption was relatively large, the carbon dioxide desorption rate by thermal regeneration was only 8%.

[050] It can be observed in Table 2 and Table 3, in Comparative Example 1, where the carboxylic acid was used as the absorbent, that there was only a small amount of physical absorption of carbon dioxide. In Comparative Example 2, where the weak organic base was used as the absorbent, the rate of carbon dioxide desorption below 100°C was extremely low. This suggested that the absorption and regeneration effects for carbon dioxide by the weak acid and weak base salt absorbents obtained in the present application were achieved by the product function of the reaction between carboxylic acid and weak base, and not due to the effects of the carboxylic acid or the weak base individually.

[051] Under normal temperature conditions, the glass bottle containing the absorbents of Example 1, after absorbing CO2 as described in Application Example 1, was connected to a water pump, the glass bottle was vacuumed to maintain a state of negative pressure and the glass bottle was Petition 870250074222, dated 08 / 21 / 2025, pp. 104 / 109 18 / 22 placed in a shaker and agitated for 1 hour. There was ample bubbling, and the system transitioned from two phases to a homogeneous phase.

[052] Under normal temperature conditions, the glass bottle containing the absorbents of Example 14, after absorbing CO2 as described in Application Example 1, was connected to a water pump, the glass bottle was aspirated to maintain a negative pressure state, and the glass bottle was placed in a shaker and agitated for 0.1 hour. There was ample bubbling, and the system transitioned from two phases to a homogeneous phase.

[053] Under normal temperature conditions, the glass bottle containing the absorbent of Example 14, after absorbing CO2 as described in Application Example 1, was connected to a water pump. The glass bottle was aspirated to maintain a negative pressure state and the glass bottle was placed in a shaker and agitated for 0.5 hours. There was a large amount of bubbling, and the system transitioned from two phases to a homogeneous phase. The above indicates that the absorbents produced in the present application can desorb most of the carbon dioxide under normal temperature and negative pressure conditions, achieving carbon dioxide regeneration. Application Example 3

[054] The absorbents obtained in Examples 1 to 33 and Comparative Examples 7 to 9 were placed in glass bottles under a carbon dioxide atmosphere and shaken for 3 hours at 20°C, and changes in phase state were observed.

[055] It can be observed that Comparative Examples 7 to 9, which used strong base salts of carboxylic acids as absorbents, produced solids Petition 870250074222, dated 08 / 21 / 2025, pages 105 / 109 19 / 22 after absorbing carbon dioxide. The absorbents obtained in Examples 1 to 33 of the present application did not produce solids after absorbing carbon dioxide. This was due to the poor asymmetric structure and weak interaction between cations and anions in the absorbents produced in the present application, making it less likely that weak acid and weak base salts of carboxylic acids will produce solid products after absorbing carbon dioxide. Application Example 4

[056] 50 grams of the absorbent obtained in Example 1 were injected into a glass bottle, and the glass bottle was connected to a carbon dioxide balloon to place the absorbent solution under carbon dioxide pressure. Stirring was carried out for 3 hours at temperatures of 0°C, 10°C, 40°C, and 50°C, respectively, and the weights of the glass bottles were recorded before and after carbon dioxide absorption. Based on the weight gain of the system, the amount of carbon dioxide absorption was obtained. The results of the amount of carbon dioxide absorption of the absorbent obtained from Example 1 at different temperatures are shown in Table 4. Table 4: Results of carbon dioxide absorption by the absorbent at different temperatures Absorption Temperature Amount of CO2 absorbed / g CO2 absorption rate / % 0 °C 2.44 4.9 10 °C 2.26 4.5 20 °C 2.13 4.3 40 °C 1.97 3.9 50 °C 1.67 3.4

[057] It can be observed that the absorbents produced in the present application can achieve good CO2 absorption effects within the temperature range of 0 C to 50 C. Application Example 5

[058] For absorption under partial pressure of carbon dioxide equal to or Petition 870250074222, dated 08 / 21 / 2025, pages 106 / 109 20 / 22 less than 0.1 MPa, 50 grams of the absorbent obtained from Example 1 were injected into a glass bottle, which was then connected to flasks containing different concentrations of carbon dioxide and nitrogen mixtures, respectively, and agitation was carried out at 20°C for 3 hours. Based on the weight gain of the system, the amount of carbon dioxide absorption was obtained. The carbon dioxide concentrations in the flasks were measured.

[059] For absorption under a partial pressure of carbon dioxide higher than 0.1 MPa, an acid gas partial pressure of 0.5 MPa was used as an example. At 20°C, 10 grams of the absorbent obtained from Example 1 were injected into a stainless steel pressure vessel with a valve. The magnon remained stationary. The air inside the vessel was evacuated using a water pump. The vessel was filled with 0.5 MPa of carbon dioxide. The valve was immediately closed and the piping was disconnected. The stainless steel pressure vessel was weighed and the weight was recorded as the initial weight. Magnetic stirring was then activated to ensure adequate contact between the absorption liquid and the carbon dioxide. The piping was reconnected and the valve was opened to continuously introduce carbon dioxide, maintaining a carbon dioxide pressure of 0.5 MPa in the system.After 3 hours, the valve was closed and the piping disconnected, and the stainless steel tank was weighed and recorded. The weight difference before and after the absorption process yielded a carbon dioxide absorption quantity of 0.5 MPa.

[060] The results of the amount of carbon dioxide absorption of the absorbent obtained from Example 1 at different partial pressures of carbon dioxide were shown in Table 5. Table 5: Amount of CO2 absorption by absorbent at different partial pressures Petition 870250074222, dated 08 / 21 / 2025, pages 107 / 109 21 / 22 Partial pressure of CO2 in a CO2 balloon Amount of CO2 absorbed / g CO2 absorption rate / % 0.014 MPa 0.75 1.5 0.036 MPa 1.0 2.0 0.1 MPa 2.13 4.3 0.5 MPa 0.60 6.0 1.0 MPa 0.79 7.9

[061] Based on Table 5, it can be observed that the absorbents produced in the present application can absorb carbon dioxide within the partial pressure range of carbon dioxide from 0.01 MPa to 1.0 MPa and have better absorption capacity for higher concentrations of carbon dioxide. Application Example 6

[062] 10 grams of the absorbent obtained from Example 1 were injected into a glass bottle, connected to a flask containing a certain concentration of sulfur dioxide and nitrogen mixture at 20°C and stirred for 3 hours. The weights of the glass bottle before and after sulfur dioxide absorption were recorded and, based on the weight gain of the system, the amount of sulfur dioxide absorption (concentration of 3%) at a partial pressure of 0.003 MPa was obtained.

[063] 10 grams of the absorbent obtained from Example 1 were injected into a glass bottle and connected to a balloon containing hydrogen sulfide, stirred for 3 hours at 20°C, and the weights of the glass bottle before and after the absorption of hydrogen sulfide were recorded, and the amount of hydrogen sulfide absorption was obtained based on the weight gain of the system.

[064] The amount of acid gas absorption of the absorbent obtained from Example 1 at 20°C was shown in Table 6. Table 6: The amount of acid gas absorbed by the absorbent. Petition 870250074222, dated 08 / 21 / 2025, pp. 108 / 109 22 / 22 Acid gas Amount of acid gas absorption / g Acid gas absorption rate / % Sulfur dioxide 1.17 11.7 Hydrogen sulfate 0.33 3.3

[065] It can be seen from Table 6 that the absorbent produced in the present application can effectively absorb sulfur dioxide and hydrogen sulfide.

[066] Obviously, the above examples are merely examples provided for clear illustration and are not intended to limit methods of implementation. For those skilled in the art, other variations or modifications in different forms may be made based on the above description. It is neither necessary nor feasible to exhaust all methods of implementation here. Obvious variations or modifications derived from this are still within the scope of protection of the present invention. Petition 870250074222, dated 08 / 21 / 2025, page 109 / 109

Claims

1 / 4 CLAIMS 1. Compound for capturing acid gases, characterized in that the compound has a structure shown in Formula (I), Formula (I) wherein, Ri is an alkyl group with the number of carbon atoms greater than or equal to 5, M is at least one of protonated organic amine groups and protonated nitrogen-containing heterocyclic groups, en is an integer from 1 to 4.

2. Compound for capturing acidic gases, according to claim 1, characterized in that Ri is a branched alkyl group; and / or, the organic amine is at least one of a fatty amine and an alcoholic amine; and / or, the nitrogen-containing heterocycle is at least one of which R2, Rs, FU, Rs, Re are any one of an alkyl, substituted alkyl or hydrogen atom.

3. Compound for capturing acidic gases, according to claim 2, characterized in that the number of carbon atoms of Ri is from 6 to 20; and / or, the organic amine is at least one of monoamine, diamine and polyamine.

4. Compound for capturing acid gases, according to claim 1, characterized in that the compound has any of the following structures:

5. Absorbent for capturing acid gases, characterized in that Petition 870250074222, dated 08 / 21 / 2025, page 83 / 109 3 / 4 the absorbent comprises the compound for capturing acid gases defined in any one of claims 1 to 4.

6. Method for preparing an absorbent to capture acid gases, defined in claim 5, characterized in that the method comprises the following steps: mixing a carboxylic acid and a weak organic base to obtain the absorbent, wherein the carboxylic acid has the molecular formula R1COOH, and R1 is an alkyl group with a number of carbon atoms greater than or equal to 5.

7. Method according to claim 6, characterized in that the absorbent also comprises water; and / or, the carboxylic acid is a fatty acid; and / or, the weak organic base is at least one of an organic amine compound and a nitrogen-containing heterocyclic compound.

8. Method according to claim 7, characterized in that the carboxylic acid is at least one of 2,2-dimethylhexanoic acid, 2-ethylhexanoic acid, 2-ethylheptanoic acid, 2-propylvaleric acid, 2-propylhexanoic acid, 2-propylnonanoic acid, 2-butyloctanoic acid and 2-hexyldecanoic acid; and / or, the organic amine compound is at least one of triethylamine, tripropilamine, monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, hydroxyethylethylenediamine, 2-amino-2-methyl-1-propanol, N-methyl-1,3-propanediamine, 1,4-butanediamine, N,N,N',N'-tetramethylhexanediamine, diethylenetriamine and triethylenetetramine; and / or, the nitrogen-containing heterocyclic compound is at least one of a pyridine ring-containing compound, an imidazole ring-containing compound, a pyrrole ring-containing compound, and a piperazine compound; and / or, Petition 870250074222, dated 08 / 21 / 2025, page.84 / 109 4 / 4 a molar ratio of the carboxylic acid, the weak organic base, and water is 1:(0.25-1):(0.20).

9. Use of the compound for capturing acid gases defined in any one of claims 1 to 4, of the absorbent for capturing acid gases defined in claim 5 and of the absorbent for capturing acid gases prepared by the method defined in any one of claims 6 to 8, characterized in that it is for the absorption and regeneration of acid gases, wherein the acid gases are at least one of carbon dioxide, sulfur dioxide or hydrogen sulfide.

10. Use according to claim 9, characterized in that absorbing acid gases comprises steps of bringing the absorbent into contact with the acid gases to be absorbed at a partial pressure of acid gas of 0.003 MPa to 1.0 MPa and a temperature of 0 to 50°C and performing the absorption; and / or, regenerating acid gases comprises a step of desorption of the absorbent after absorbing the acid gases under agitation for 0.1 to 2 hours at 80 to 100°C, or regenerating acid gases comprises a step of desorption of the absorbent after absorbing the acid gases under agitation for 0.1 to 1 hour at 10 to 80°C under vacuum conditions. Petition 870250074222, dated 21 / 08 / 2025, pp. 85 / 109

Images