Use of carboxylate compounds as absorbents for carbon dioxide capture

Abstract

The present invention discloses the use of a carboxylate compound as an absorbent for capturing carbon dioxide. In the use of a carboxylate compound according to the present invention as an absorbent for capturing carbon dioxide and / or in preparing an absorbent for capturing carbon dioxide, the carboxylate anion in the carboxylate compound is a carboxylate radical having a carbon chain of more than three carbon atoms or a branched carboxylate radical having more than six carbon atoms, and the cation is a substituted quaternary ammonium ion, quaternary phosphonium ion, pyridine ion, pyrrole ion, piperidine ion, imidazole ion, or metal ion. The present invention provides a method for capturing carbon dioxide using a carboxylate compound in a water-stable, efficient, and energy-saving manner, comprising the steps of placing an aqueous solution of the carboxylate compound in a carbon dioxide atmosphere to absorb carbon dioxide and obtaining a complex of the carboxylate salt and carbon dioxide precipitated from the water. The present invention provides a high carbon dioxide capture capacity at high temperatures and at both low and high carbon dioxide partial pressures, and the complex of the carboxylate salt and carbon dioxide is stable in water, allowing the carboxylate salt to be regenerated.

Description

[Technical field]

[0001] The present invention relates to the use of carboxylate-based compounds, in particular to the use of carboxylate-based compounds as and / or in the preparation of absorbents for carbon dioxide capture, in the field of carbon dioxide capture and carbon emission reduction. [Background technology]

[0002] Since the advent of the Industrial Revolution, human beings have used large amounts of fossil fuels to supply energy while emitting large amounts of carbon dioxide. The rate at which carbon dioxide is emitted has far exceeded the natural world's ability to absorb and use it, resulting in a steady rise in the concentration of carbon dioxide in the atmosphere. Meanwhile, carbon dioxide is a greenhouse gas, and its massive emissions have caused the average global temperature to rise and led to an increase in abnormal and extreme weather. As a result, society has come to share the understanding that carbon dioxide captured and confined by human beings (CCS) is a means of preventing the release of carbon dioxide.

[0003] At present, industry mainly adopts the alcohol amine aqueous solution absorption method. Alcohol amine aqueous solution has a large absorption capacity and low viscosity, but has problems such as amine decomposition, volatilization, corrosion, and large regeneration energy consumption (Riemer, PW, Ormerod, WG Energy Convers. Manag. 1995, 36, 813-818). Room temperature ionic liquids are liquids composed entirely of ions at room temperature and have many unique properties, such as low volatility, strong dissolving ability, wide electrochemical window, and designability (Wilkes, JS & Zaworotko, MJ, J. Chem. Soc., Chem. Commun. 1992, 965;Wang, YL, Chem. Rev. 2020, 120, 5798). Brennecke et al. used ionic liquids for the physical adsorption of carbon dioxide, which must be carried out under high pressure and anhydrous conditions (Blanchard, LA, Hancu, D., Beckman, EJ & Brennecke, JF, Nature 1999, 399, 28). Davis et al. attached amino groups to the cations of ionic liquids and realized the chemical adsorption of carbon dioxide (Bates, ED, Mayton, RD, Ntai, I. & Davis, JH Jr., J. Am. Chem. Soc. 2002, 124, 926). Many researchers in China and abroad have realized the chemical absorption of carbon dioxide using various alkaline ionic liquids (Zhang, JM, et al, Chem. Eur. J., 2006, 12, 4021; Huang, Y., et al, Angew. Chem. Int. Ed., 2017, 56, 13293; Aghaie, M., Rezaei, N. & Zendehboudi, S., Renewable and Sustainable Energy Reviews 2018, 96, 502).There is evidence that a few imidazole acetate-based ionic liquids absorb carbon dioxide and form new C-C bonds (Holbrey, JD, et al, Chem. Commun. 2003, 28), while others claim that they form carbamates or carboxamides. However, Jairton Dupont et al. claim that most absorptions involve the formation of bicarbonate and carbonate radicals due to the unavoidable presence of water in ionic liquids, and they cite nuclear magnetic data as evidence for these actions (Zanatta, M., Simon, NM & Dupont, J., Chem Sus Chem 2020, 13, 3101). Ionic liquids have high viscosity under solvent-free conditions, which makes absorption difficult. Super-strong alkaline ionic liquids have strong interactions with carbon dioxide and require high energy consumption for desorption. Therefore, the search for more suitable carbon dioxide absorbents remains one of the challenges faced by scientists.

[0004] Quaternary ammonium / phosphonium carboxylates are also used for carbon dioxide absorption. Quinn et al. obtained high absorption rates under equimolar water conditions using acetates, propionates, and malonates of quaternary amines (Quinn, R., Appleby, JB and Pez, GP, J. Am. Chem. Soc. 1995, 117, 329; Quinn, R., Synth. React. Inorg. Met. - Org. Chem. 2001, 31(3), 359). However, the amount of carbon dioxide absorbed decreased significantly with increasing water content. For example, in the case of tetraethylammonium propionate, when the molar ratio of water to water was 1:4, the amount of carbon dioxide absorbed was only 0.155 mol / mol of the carboxylate. Zhang Zhibing et al. of Nanjing University studied the carbon dioxide absorption of triethylbutylammonium acetate and found that a salt-to-water molar ratio of 1:1 was the most effective, with the carbon dioxide molar percentage reaching 0.386 at room temperature and 1 atm (Wang, GN, et al, J. Chem. Eng. Data 2011, 56, 1125). However, the absorption rate dropped sharply with increasing water content, and when the salt-to-water molar ratio was 1:5, the carbon dioxide molar percentage was only 0.054 under the same conditions. Anderson et al. investigated the carbon dioxide absorption of several quaternary ammonium / quaternary phosphonium carboxylates at 5 atm, and the monohydrates of these salts showed relatively large absorption rates (Anderson, K., et al. Green Chem., 2015, 17, 4340). They studied the effect of water content on the carbon dioxide absorption of tetrabutyl formate at 5 atm and found that the absorption rate dropped significantly when the salt-to-water molar ratio exceeded 1:1.Yasaka et al. have studied tetrabutylphosphonium formate and found that its monohydrate efficiently absorbs carbon dioxide, but the absorption rate decreases rapidly with increasing water content (Yasaka, Y., Ueno, M. & Kimura, Y., Chem. Lett. 2014, 43, 626; Yasaka, Y. & Kimura, Y., J. Chem. Eng. Data 2016, 61, 837; Yasaka, Y., Saito, Y. & Kimura, Y., Chem Phys Chem 2018, 19, 1674). These studies have mainly focused on the formate, acetate, and propionate salts. Anderson et al. have studied many carboxylates, but most of these carboxylates are linear carboxylates (only trihexyltetradecylphosphonium 2-methylpropionate is branched), and mainly examined the absorption of carbon dioxide by monohydrates of these carboxylates at 5 atmospheres, and only tetrabutylphosphonium formate and hydrophobic trihexyltetradecylphosphonium formate were examined for their effect on the absorption of water in carbon dioxide at 5 atmospheres. Although these studies have achieved relatively good results, the reduction effect of water on carbon dioxide absorption has not been resolved, and its practicality needs to be improved. Carbon dioxide absorption that absorbs carbon dioxide even in an aqueous solution under conditions where a large amount of water is present, while ensuring that the temperature, speed, and energy consumption of the desorption process are low, has not yet been examined. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a method for the use of a carboxylate compound as an absorbent for capturing carbon dioxide. The present invention has the advantages that the raw materials of the absorbent are easily available at low cost, the absorbent is easy to synthesize, the absorbent has a high absorption capacity, the absorbent is stable in water, the temperature required for desorption is low, the desorption speed is fast, and the energy consumption is low, and the application of the present invention is promising. [Means for solving the problem]

[0006] Use of the carboxylate-based compound provided by the present invention as an absorbent for capturing carbon dioxide and / or in the preparation of an absorbent for capturing carbon dioxide, comprising: The carboxylate anion in the carboxylate compound is a carboxylate radical having a carbon chain with more than 3 carbon atoms, and the cation is a substituted quaternary ammonium ion and / or quaternary phosphonium ion.

[0007] In the above use, the carboxylate compound has suitable hydrophilicity, is soluble in water at room temperature, and can precipitate from water after absorbing carbon dioxide, and when the carboxylate compound absorbs carbon dioxide, a stable bond can be formed in water.

[0008] In the above uses, said carboxylate radical having a carbon chain length of more than 3 carbons is a branched carboxylate radical.

[0009] In the above use, the carboxylic acid having a carbon chain with more than 3 carbon atoms may have 4 to 20 carbon atoms.

[0010] In the above uses, the carboxylic acid having a carbon chain with more than 3 carbon atoms may have 4 to 10 carbon atoms, more specifically 6 to 9 carbon atoms.

[0011] In the above use, the carboxylate radical having a carbon chain of more than 3 carbon atoms is specifically at least one of a 2,2-dimethylbutyrate radical, a 2,2-dimethylhexanoate radical, a 2-ethylhexanoate radical, a 2-ethylheptanoate radical, a 2-propylpentanoate radical, a 2-propylhexanoate radical, a cyclohexylformate radical, and an n-octanoate radical.

[0012] In the above-mentioned use, the structural formula of the substituted quaternary ammonium ion and quaternary phosphonium ion is represented by the following formula I and formula II. TIFF0007644534000001.tif42146 (In formula I and formula II, n is always 2 to 4, m is always 4 to 16, and the substituents are the same or different.)

[0013] In the present invention, in formula I and formula II, n is always 2 or 4, and m is always 4, 6, 8, 10, 12, 14, or 16. More specifically, in the substituted quaternary ammonium ion represented by formula I, n is 2 or 4, and m is 4 or 6, and in the quaternary phosphonium ion represented by formula II, n is 4, and m is 4, 6, 8, 10, 12, 14, or 16.

[0014] In the above use, the substituted quaternary ammonium ion is at least one selected from triethylbutylammonium, tetrabutylammonium, and tributylhexylammonium; The substituted quaternary phosphonium ion is at least one selected from tetrabutylphosphonium, tributylhexylphosphonium, tributyloctylphosphonium, tributyldecylphosphonium, tributyldodecylphosphonium, tributyltetradecylphosphonium, and tributylhexadecylphosphonium.

[0015] The present invention also provides an absorbent for capturing carbon dioxide, which is the above-mentioned carboxylate compound or contains the above-mentioned carboxylate compound.

[0016] The present invention further provides a method for capturing carbon dioxide stably, efficiently, and energy-savingly in water using a carboxylate compound, the method comprising the steps of placing an aqueous solution of the carboxylate compound in a carbon dioxide atmosphere to absorb carbon dioxide, and obtaining a combination of the carboxylate and carbon dioxide precipitated from the water.

[0017] In the above method, the molar ratio of the carboxylate compound to water may be 1:0.5-300, specifically, 1:0.5, 1:1, 1:10, 1:20, 1:300, 1:0.5-20, 1:0.5-100, or 1:1-200.

[0018] In the above method, the conditions for absorbing carbon dioxide may be a carbon dioxide partial pressure of 0.01 to 2 MPa, specifically, 0.01 MPa, 0.1 MPa, or 2 MPa, and a temperature of 25 to 80°C, specifically, 25°C or 80°C.

[0019] In the above method, the amount of carbon dioxide absorbed per mole of the carboxylate compound may be 0.1 to 1.2 moles, specifically, 0.12 to 1.1 moles.

[0020] In the above method, the method further includes a step of regenerating the carboxylate compound after carbon dioxide absorption is completed.

[0021] In the above method, the regeneration may be performed under reduced pressure conditions, with a pressure of 0.01 to 1 atm, a temperature of 10 to 120°C (i.e., room temperature to 120°C, the room temperature being common knowledge in the art, specifically 10 to 30°C), and a time of 1 min to 10 h, specifically 3 min, 30 min, 1 h, 3 h, 3 min to 3 h, or 1 min to 5 h. The temperature may be room temperature to 80°C, specifically 25 to 80°C.

[0022] The present invention also relates to the use of another carboxylate-based compound as an absorbent for carbon dioxide capture and / or in the preparation of an absorbent for carbon dioxide capture, comprising: The carboxylate anion in the carboxylate compound is a branched carboxylate radical having a total carbon number of more than 6, and the cation is at least one of a substituted quaternary ammonium ion, a quaternary phosphonium ion, a pyridine ion, a pyrrolidine ion, a piperidine ion, an imidazole ion, and a metal ion; The structural formula of the substituted quaternary ammonium ion and quaternary phosphonium ion is represented by the following formula I-1 and formula II-1. TIFF0007644534000002.tif39146 (In formula I-1 and formula II-1, n is always 1 to 4, m is always 1 to 16, and the substituents are the same or different.)

[0023] In the above use, the branched carboxylate radical having a total carbon number of more than 6 may have 7 to 20 carbon atoms.

[0024] In the above use, the branched carboxylate radical having a total carbon number of more than 6 may have 8 to 16 carbon atoms.

[0025] In the above use, the branched carboxylate radical having a total carbon number of more than 6 is at least one selected from a 2,2-dimethylhexanoate radical, a 2-ethylhexanoate radical, a 2-ethylheptanoate radical, a 2-propylpentanoate radical, a 2-propylhexanoate radical, a 2-propylnonaate radical, a 2-butyloctanoate radical, and a 2-hexyldecanoate radical.

[0026] In the above use, the substituted quaternary ammonium ion is at least one selected from tetramethylammonium, tetraethylammonium, and tributylmethylammonium; The substituted quaternary phosphonium ion is at least one selected from tetramethylphosphonium, tetraethylphosphonium, and tributylmethylphosphonium.

[0027] In the above use, the pyridine ion is an N-substituted pyridine cation having the structural formula III: The pyrrolidine ion is an N-substituted pyrrole cation having the structural formula represented by the following formula IV: The piperidine ion is an N-substituted piperidine cation having the structural formula V: The imidazole ion is a di- and / or tri-substituted imidazole cation having the structural formula represented by the following formula VI: The metal ion is at least one selected from lithium, sodium, potassium and cesium ions. TIFF0007644534000003.tif42146 (In formula III, formula IV, formula V, and formula VI, R1 and R2 are each a linear aliphatic chain having one or more carbon atoms, R3 is H or CH3, and R1 and R2 are the same or different.)

[0028] In the above uses, in the formula III, formula IV, formula V, and formula VI, R1 and R2 may each specifically be a linear aliphatic chain having 1 to 10 carbon atoms.

[0029] The present invention also provides an absorbent for capturing carbon dioxide, which contains the carboxylate compound as an active ingredient.

[0030] The present invention further provides a method for capturing carbon dioxide stably, efficiently, and energy-savingly in water using a carboxylate compound, the method comprising the steps of placing an aqueous solution of the carboxylate compound in a carbon dioxide atmosphere to absorb carbon dioxide, and obtaining a combination of the carboxylate and carbon dioxide precipitated from the water.

[0031] In the above method, the molar ratio of the carboxylate compound to water may be 1:0.5-100, specifically, 1:0.5, 1:1, 1:20, 1:100, 1:1-100, 1:20-100, or 1:0.5-20.

[0032] In the above method, the conditions for absorbing carbon dioxide may be such that the carbon dioxide partial pressure is 0.00004 to 0.5 MPa, specifically, 0.01 MPa, 0.1 MPa, 0.5 MPa, 0.01 to 0.1 MPa, or 0.1 to 0.5 MPa, and that carbon dioxide is captured from the atmosphere (the carbon dioxide partial pressure is approximately 0.00004 MPa), and the temperature is 5 to 80°C, specifically, 5°C, 25°C, 80°C, 5 to 25°C, or 25 to 80°C.

[0033] In the above method, the amount of carbon dioxide absorbed per mole of the carboxylate compound may be 0.4 to 1.1 moles, specifically, 0.49, 0.5, 0.6, 1.0, 1.05 moles, 0.49 to 0.525 moles, or 0.49 to 1.05 moles.

[0034] In the above method, the method further includes a step of regenerating the carboxylate compound after carbon dioxide absorption is completed.

[0035] In the above method, the regeneration may be performed under reduced pressure conditions, with the pressure being 0.01 to 1 atm, the temperature being 10 to 120°C (i.e., room temperature to 120°C, the room temperature being common knowledge in this field, specifically, 10 to 30°C), specifically, 25°C, 120°C or 25 to 120°C, and the time being 1 min to 10 h, specifically, 1 h, 3 h or 1 to 3 h. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] All experimental methods in the following examples are conventional methods unless otherwise specified.

[0037] In the examples below, carboxylates are synthesized according to established techniques (Suarez, PAZ; Dullius, JEL; Einloft, S.; DE Souza RF and Dupont, J., Polyhedron, 1996, 15, 1217-1219).

[0038] The following examples are intended to illustrate the present invention and are not intended to limit the scope of use of the present invention.

[0039] Example 1 2 mmol of tributylhexylphosphonium 2-ethylhexanoate (0.86 g) was added to 40 mmol of water (0.72 g) in a glass bottle, a carbon dioxide balloon was connected so that the solution was at 1 atm of carbon dioxide, and the solution was stirred at 25°C for 12 hours, separating the system into an organic phase and an aqueous phase. After removing the balloon and replacing the carbon dioxide gas at the top of the solution in the bottle with air, the solution was titrated with sodium hydroxide solution (0.2 w%) and, using phenolphthalein as an indicator, the amount of carbon dioxide absorbed was 0.98 mmol.

[0040] Under the same conditions, tributylhexylphosphonium 2-ethylhexanoate was replaced with the following reagents: tetrabutylphosphonium 2-ethylhexanoate, tributyloctylphosphonium 2-ethylhexanoate, tributyldecylphosphonium 2-ethylhexanoate, tributyldodecylphosphonium 2-ethylhexanoate, tributyltetradecylphosphonium 2-ethylhexanoate, tributylhexadecylphosphonium 2-ethylhexanoate, tetrabutylammonium 2-ethylhexanoate, triethylbutylammonium 2-ethylhexanoate, tributylhexylammonium 2-ethylhexanoate, tributylhexylphosphonium 2,2-dimethylbutyrate ... The carbon dioxide absorption of 2 mmol of each of tributylhexyl 2-propyl valerate, tributylhexyl phosphonium 2,2-dimethylhexanoate, tributylhexyl phosphonium 2-propyl hexanoate, tributylhexyl phosphonium 2-ethylheptanoate, tributylhexyl phosphonium cyclohexylcarboxylate, and tributylhexyl phosphonium n-octanoate was measured. When carbon dioxide was absorbed, new liquid or solid phases were formed, and the absorption amounts were 0.87, 2.2, 1.8, 1.6, 1.6, 1.7, 0.86, 0.24, 0.96, 0.22, 1.02, 0.53, 1.0, 0.99, 0.71, and 0.36 mmol, respectively.

[0041] Example 2 The same procedure as in Example 1 of the present invention was followed except that 1 mmol of water was added to 2 mmol (0.86 g) of tributylhexylphosphonium 2-ethylhexanoate, and the carbon dioxide absorption amount was 1.0 mmol. This clearly shows that when the molar ratio of the carboxylate to water was 1:0.5, the carbon dioxide absorption amount was stable in water compared to Example 1.

[0042] Example 3 Except for adding 2 mmol of water, the remaining procedure was the same as in Example 2, and the carbon dioxide absorption amount was 1.0 mmol. This clearly shows that when the molar ratio of the carboxylate to water was 1:1, the carbon dioxide absorption amount was stable in water compared to Example 1, and did not change with an increase in water.

[0043] Example 4 In the case of tributylhexylphosphonium 2-ethylhexanoate, the remaining procedures were the same as in Example 1 except that the temperature was 80° C. When carbon dioxide was absorbed, a new organic phase was formed, and the amount of carbon dioxide absorbed was 0.62 mmol. From this, it is clear that the carbon dioxide capture capacity was higher even at high temperatures in terms of the amount absorbed by the aqueous carboxylate solution at each temperature, compared to Example 1 of the present invention.

[0044] Example 5 In the case of tributylhexylphosphonium 2-ethylhexanoate, the atmosphere was a carbon dioxide partial pressure of 0.01 MPa and nitrogen gas of 0.09 MPa, and the rest of the experiment was performed in the same manner as in Example 1, resulting in an amount of carbon dioxide absorbed of 0.40 mmol. This clearly shows that, in the case of the aqueous carboxylate solution having a low carbon dioxide partial pressure, the carbon dioxide capture capacity was higher than that in Example 1 of the present invention, even when the carbon dioxide partial pressure was low.

[0045] Example 6 2 mmol (0.92 g) of tributyloctylphosphonium 2-ethylhexanoate was added to 40 mmol (0.72 g) of water and placed in a pressure cooker, and 2 MPa of carbon dioxide was introduced and stirred at 25°C for 12 hours. After reducing the pressure, the carbon dioxide gas above the solution in the cooker was replaced with air, and then titration was performed with sodium hydroxide solution (0.2 w%) using phenolphthalein as an indicator, and the carbon dioxide absorption amount was 1.2 mmol. From this, it is clear that the carbon dioxide capture capacity was higher in the case of the absorption amount in the case of high carbon dioxide pressure of the above carboxylate aqueous solution than in Example 1 of the present invention, even when the carbon dioxide partial pressure was high.

[0046] Example 7 In the case of tributylhexylphosphonium 2-ethylhexanoate, the carbon dioxide atmosphere was changed to carbon dioxide bubbling (20 mL / min) and absorption was performed for 30 minutes, but the rest was the same as in Example 1. As a result, the amount of carbon dioxide absorbed was 0.98 mmol. Comparison between Examples 1 and 7 showed that the absorption method has a small effect on carbon dioxide absorption, and the amount of carbon dioxide absorbed in the present invention is not affected by the absorption method.

[0047] Example 8 In the case of tributylhexylphosphonium 2-ethylhexanoate, the absorption of carbon dioxide was the same as in Example 1 of the present invention, and after the absorption was completed, the solution was exposed to air and stirred continuously for 3 hours at room temperature (25°C), and the carbon dioxide was completely released. This shows that the aqueous carboxylate solution was regenerative after absorbing carbon dioxide.

[0048] Example 9 In the release, the remaining steps were the same as in Example 8, except that the stirring was performed at 80°C for 30 minutes, and the measurement results showed that carbon dioxide was released completely. Comparison of Examples 8 and 9 of the present invention showed that the carboxylate compound could be regenerated at any temperature.

[0049] Example 10 In the release, the mixture was stirred continuously for 1 hour under reduced pressure (0.01 atm) using a water pump, and the rest of the procedure was the same as in Example 8. The measurement results showed that carbon dioxide was completely released. Comparison between Examples 8 and 10 showed that the carboxylate compound could be regenerated at any pressure.

[0050] Example 11 1 mmol (57 mg) of tributylhexadecylphosphonium 2-ethylhexanoate was dissolved in 5.4 g (0.3 mol) of water, and then carbon dioxide bubbles were bubbled into the solution at room temperature (20 mL / min). After 3 minutes, the solution became cloudy, indicating that the carboxylate could effectively absorb carbon dioxide at this concentration and precipitate after absorption. The introduction of carbon dioxide was stopped, the solution was exposed to air, and stirred continuously at room temperature (25°C). After 3 minutes, the solution became clear, indicating that the solution could rapidly release carbon dioxide. Comparison of Examples 1 and 11 of the present invention showed that the absorption and regeneration of carboxylate compounds was possible regardless of the concentration or absorption method.

[0051] Example 12 2 mmol (0.434 g) of tetramethylammonium 2-ethylhexanoate was added to 2 mmol (0.036 g) of water and placed in a glass bottle, a carbon dioxide balloon was connected, the solution was placed in a 0.1 MPa carbon dioxide atmosphere, and the mixture was stirred at 25°C for 12 hours. After removing the balloon and replacing the carbon dioxide gas above the solution in the bottle with air, the mixture was titrated with a sodium hydroxide solution (0.2 w%) and, using phenolphthalein as an indicator, the amount of carbon dioxide absorbed was found to be 1.0 mmol.

[0052] Under the same conditions, tetramethylammonium 2-ethylhexanoate was replaced with the following reagents: tetraethylammonium 2-ethylhexanoate, tributylmethylammonium 2-ethylhexanoate, tetramethylphosphonium 2-ethylhexanoate, tetraethylphosphonium 2-ethylhexanoate, tributylmethylphosphonium 2-ethylhexanoate, tributylmethylammonium 2,2-dimethylhexanoate, tributylmethylammonium 2-ethylheptanoate, tributylmethylammonium 2-propyl valerate, tributylmethylammonium 2-propyl hexanoate, tetramethylammonium 2-propylnonanoate, tetramethylammonium 2-butyloctanoate, tetramethylammonium 2-hexyldecanoate, 2-ethylhexanoic acid naphthalene. The absorption of 2 mmol of each of the following compounds (adding 2 mmol of water to each compound) against carbon dioxide was measured: potassium 2,2-dimethylhexanoate, lithium 2-ethylheptanoate, cesium 2-propylvalerate, N-butylpyridine 2-ethylhexanoate, N-butyl-N-methylpyrrolidine 2-ethylhexanoate, N-butyl-N-methylpiperidine 2-ethylhexanoate, and 1-butyl-2,3 dimethylimidazole 2-ethylhexanoate. The absorptions were 1.03, 0.99, 1.02, 0.98, 1.03, 1.01, 0.99, 1.00, 1.01, 1.01, 1.03, 1.05, 0.99, 0.97, 0.98, 0.95, 1.00, 1.02, 0.99, and 1.02 mmol, respectively, and all absorptions were within the range of 0.95 to 1.05 mmol.

[0053] This clearly shows that each of the above materials can effectively absorb carbon dioxide.

[0054] Example 13 Except for adding 1 mmol (0.018 g) of water to 2 mmol (0.86 g) of tributylmethylammonium 2-ethylhexanoate, the remaining steps were carried out in the same manner as in Example 12, and the carbon dioxide absorption amount was 1.0 mmol. This clearly shows that when the molar ratio of the carboxylate to water was 1:0.5, the carbon dioxide absorption amount was stable in water within a specified range compared to Example 12.

[0055] Example 14 The same procedure as in Example 12 was repeated except that 200 mmol (3.6 g of water) was added to 2 mmol (0.56 g) of sodium 2-hexyldecanoate, and the carbon dioxide absorption was 2.05 mmol. This clearly shows that the carbon dioxide absorption of the above carboxylate was stable in water within a wide range.

[0056] After absorption, the solution was heated at 120°C for 3 hours and the measurement showed that carbon dioxide was completely released, which clearly showed that the carboxylate solution was regenerative after absorbing carbon dioxide.

[0057] Example 15 The remaining procedure was the same as in Example 3 except that the absorption temperature was 80° C., and the carbon dioxide absorption amount was 2.0 mmol. Compared with Example 14, it was shown that the carbon dioxide absorption amount of the above carboxylate is stable over a wide range of temperatures.

[0058] Example 16 2 mmol (0.69 g) of tributylmethylammonium 2-ethylhexanoate was added to 0.7 g of water and placed in a glass bottle, a carbon dioxide balloon was connected so that the solution was at 1 atm of carbon dioxide, and the mixture was stirred at 5°C for 12 hours. After removing the balloon and replacing the carbon dioxide gas above the solution in the bottle with air, the mixture was titrated with sodium hydroxide solution (0.2 w%) and phenolphthalein was used as an indicator, resulting in a carbon dioxide absorption of 1.2 mmol. Compared to Example 12, it was shown that lowering the absorption temperature is advantageous for improving the absorption amount.

[0059] After the absorption was completed, the solution was exposed to air and stirred continuously for 3 hours at room temperature (25°C), and the carbon dioxide was completely released. The carboxylate solution was shown to be regenerative after absorbing carbon dioxide.

[0060] Example 17 In the case of tributylmethylammonium 2-ethylhexanoate, the procedure was the same as in Example 12 except that the atmosphere had a carbon dioxide partial pressure of 0.01 MPa and nitrogen gas of 0.09 MPa. As a result, the amount of carbon dioxide absorbed was 0.98 mmol. 0.278 g (1 mmol) of sodium 2-hexyldecanoate was dissolved in 1 g of water, and air was supplied using an air pump to bubble the solution (the partial pressure of carbon dioxide in the atmosphere was approximately 0.00004 MPa). The air flow rate was set to 10 milliliters per minute, and after 12 hours, the solution was titrated with sodium hydroxide solution (0.2 w%) until it became clear. The amount of carbon dioxide absorbed was 0.10 mmol.

[0061] From this, it is clear that, in terms of the absorption amount in the case of a low carbon dioxide partial pressure of the above-mentioned carboxylate aqueous solution, compared with Example 12 of the present invention, even when the carbon dioxide partial pressure was low, the carbon dioxide capture capacity was high and a certain amount of carbon dioxide could be absorbed from the atmosphere.

[0062] Example 18 2 mmol (0.69 g) of tributylmethylammonium 2-ethylhexanoate was added to 2 mmol (0.036 g) of water and placed in a pressure cooker, and 0.5 MPa of carbon dioxide was introduced and stirred at 25° C. for 12 hours. After reducing the pressure, the carbon dioxide gas above the solution in the cooker was replaced with air, and the carbon dioxide absorption amount was measured by the method of Example 12, and was found to be 1.5 mmol. As is clear from this, the carbon dioxide capture capacity was higher in the case of the absorption amount in the case of high carbon dioxide pressure of the above carboxylate aqueous solution than in Example 12 of the present invention, even when the carbon dioxide partial pressure was high.

[0063] The above results revealed the following:

[0064] 1) In the present invention, the halogen salts of each organic cation are bulk chemicals, and the price is several thousand RMB per ton, whereas in the comparative example, the current market price of tributylhexylphosphonium and tributyloctylphosphonium halides is (several thousand RMB per kilogram). Obviously, the price of the raw materials in the present invention is low.

[0065] 2) In Examples 1, 3, and 4 of the present invention, carbon dioxide absorption experiments were carried out using sodium 2-ethylhexanoate, potassium 2,2-dimethylhexanoate, lithium 2-ethylheptanoate, cesium 2-propylvalerate, and sodium 2-hexyldecanoate, and the inorganic salts used, that is, the metal ions lithium, sodium, potassium, and cesium, have higher stability.

[0066] 3) In the present invention, when the water content is appropriate, a higher carbon dioxide absorption amount (relative to the mass of the absorbent) can be obtained. For example, when the molar ratio of salt to water is 1:1 for 1 mole of tetramethylammonium 2-ethylhexanoate (molecular weight 217.3) or trimethylhexylphosphonium 2-ethylhexanoate (molecular weight 430.7), the amounts of carbon dioxide that the absorbent can absorb per kilogram at 1 atmosphere of carbon dioxide are 2.12 and 1.11 moles, respectively. [Industrial Applicability]

[0067] 1. The present invention solves the problems of conventional systems such as corrosiveness, volatility, and high energy consumption, and has a high carbon dioxide capture capacity at high temperatures and both low and high carbon dioxide partial pressures.

[0068] 2. When the aqueous solution of the carboxylate used absorbs carbon dioxide, a complex between the aqueous solution of the carboxylate and carbon dioxide is precipitated from the water in the form of a liquid or solid, which indicates that the complex between the carboxylate used and carbon dioxide is stable in water.

[0069] 3. The carboxylate can be regenerated by reducing pressure at room temperature. The absorption time ranges from a few minutes to a few hours depending on the conditions. The carboxylate with released carbon dioxide is soluble in water. The regeneration speed can be increased by increasing the temperature.

[0070] 4. In the carboxylate compounds used in the present invention, the cations are substituted quaternary ammonium ions, substituted quaternary phosphonium ions, pyridine ions, pyrrole ions, piperidine ions, imidazole ions or metal ions, which have lower valence than the costly tetraalkyl-substituted phosphonium / ammonium onium ions, thereby significantly reducing the cost of capturing carbon dioxide.

Claims

1. Use of a carboxylate-based compound as an absorbent for capturing carbon dioxide and / or in the preparation of an absorbent for capturing carbon dioxide, comprising: the carboxylate anion in the carboxylate compound is a carboxylate radical having a carbon chain with more than 3 carbon atoms, and the cation is a substituted quaternary ammonium ion and / or a quaternary phosphonium ion; The carboxylate radical having a carbon chain with more than 3 carbon atoms is at least one of a 2,2-dimethylbutyrate radical, a 2,2-dimethylhexanoate radical, a 2-ethylhexanoate radical, a 2-ethylheptanoate radical, a 2-propylpentanoate radical, a 2-propylhexanoate radical, a cyclohexylformate radical, and an n-octanoate radical; The substituted quaternary ammonium ion is at least one selected from triethylbutylammonium, tetrabutylammonium, and tributylhexylammonium, The substituted quaternary phosphonium ion is at least one selected from tetrabutylphosphonium, tributylhexylphosphonium, tributyloctylphosphonium, tributyldecylphosphonium, tributyldodecylphosphonium, tributyltetradecylphosphonium, and tributylhexadecylphosphonium.

2. Use of a carboxylate-based compound as an absorbent for capturing carbon dioxide and / or in the preparation of an absorbent for capturing carbon dioxide, comprising: the carboxylate anion in the carboxylate compound is a branched carboxylate radical having a total of 7 to 20 carbon atoms, and the cation is at least one of a substituted quaternary ammonium ion, a quaternary phosphonium ion, a pyridine ion, a pyrrolidine ion, a piperidine ion, an imidazole ion, and a metal ion; The structural formulas of the substituted quaternary ammonium ion and quaternary phosphonium ion are represented by the following formula I-1 and formula II-1, (In formula I-1 and formula II-1, n is always 1 to 4, m is always 1 to 16, and the substituents are the same or different.) The metal ion is selected from at least one of lithium ions, sodium ions, potassium ions and cesium ions.

3. The use according to claim 2, characterized in that the branched carboxylate radical has from 8 to 16 carbon atoms.

4. 4. The use according to claim 2 or 3, characterized in that the branched carboxylate radical is at least one selected from the group consisting of 2,2-dimethylhexanoate radical, 2-ethylhexanoate radical, 2-ethylheptanoate radical, 2-propylpentanoate radical, 2-propylhexanoate radical, 2-propylnonanoate radical, 2-butyloctanoate radical and 2-hexyldecanoate radical.

5. The substituted quaternary ammonium ion is at least one selected from tetramethylammonium, tetraethylammonium, and tributylmethylammonium, 4. The use according to claim 2 or 3, characterized in that the substituted quaternary phosphonium ion is at least one selected from tetramethylphosphonium, tetraethylphosphonium, and tributylmethylphosphonium.

6. The pyridine ion is an N-substituted pyridine cation having a structural formula represented by the following formula III: The pyrrolidine ion is an N-substituted pyrrolidine cation, and has the structural formula represented by the following formula IV: The piperidine ion is an N-substituted piperidine cation, and has the structural formula V: The use according to claim 2 or 3, characterized in that the imidazole ion is a di- and / or tri-substituted imidazole cation, the structural formula of which is represented by the following formula VI: (In formula III, formula IV, formula V, and formula VI, R 1 , R 2 are linear aliphatic chains having one or more carbon atoms, and R 3 is H or CH 3 And R 1 and R 2 are the same or different.)

7. In the above formula III, formula IV, formula V, and formula VI, R 1 , R 2 The use according to claim 6, characterized in that each of them is a linear aliphatic chain having 1 to 10 carbon atoms.

8. A method for capturing carbon dioxide in a water-stable, efficient and energy-saving manner using a carboxylate compound, comprising: A method comprising the step of placing an aqueous solution of the carboxylate compound according to claim 1 or an aqueous solution of the carboxylate compound according to any one of claims 2 to 7 in a carbon dioxide atmosphere to absorb carbon dioxide.

9. The molar ratio of the carboxylate compound according to claim 1 to water is 1:0.5 to 300; The method according to claim 8, characterized in that the conditions for absorbing carbon dioxide are a carbon dioxide partial pressure of 0.01 to 2 MPa and a temperature of 25 to 80°C.

10. The molar ratio of the carboxylate compound according to any one of claims 2 to 7 to water is 1:0.5 to 100, The method according to claim 8, wherein the conditions for absorbing carbon dioxide are a carbon dioxide partial pressure of 0.00004 to 0.5 MPa and a temperature of 5 to 80°C.

11. 10. The method according to claim 9, wherein the amount of carbon dioxide absorbed per mole of the carboxylate compound according to claim 1 is 0.1 to 1.2 moles.

12. The method according to claim 10, wherein the amount of carbon dioxide absorbed per mole of the carboxylate compound according to any one of claims 2 to 7 is 0.1 to 1.1 moles.

13. 9. The method of claim 8, further comprising the step of regenerating the carboxylate compound after the absorption of carbon dioxide is completed.

14. The method according to claim 13, wherein the regeneration process is carried out under reduced pressure conditions, the pressure is 0.01-1 atm, the temperature is 10-120° C., and the time is 1 min-10 h.

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