Use of carboxylate compounds as absorbents for capturing carbon dioxide

Abstract

The application discloses application of a carboxylate compound as an absorbent for capturing carbon dioxide. The application provides application of the carboxylate compound as an absorbent for capturing carbon dioxide and / or in preparation of the absorbent for capturing carbon dioxide; in the carboxylate compound, a carboxylic acid anion is a carboxylic acid radical with a carbon chain with a carbon atom number greater than 3 or a branched carboxylic acid radical greater than 6, and a cation is a substituted quaternary ammonium ion, a quaternary phosphorus ion, a pyridine ion, a pyrrole ion, a piperidine ion, an imidazole ion or a metal ion. The application adopts the carboxylate compound to efficiently and energy-savingly capture carbon dioxide which is stable to water, and the method comprises the following steps: placing an aqueous solution of the carboxylate compound in a carbon dioxide atmosphere to absorb the carbon dioxide, and obtaining a combination of the carboxylate compound and the carbon dioxide which is separated from water. The application can obtain a higher carbon dioxide capturing capacity under high temperature, low pressure and high pressure of the carbon dioxide partial pressure; the combination of the carboxylate compound and the carbon dioxide is stable to water; and the carboxylate compound can be regenerated.

Description

Technical Field

[0001] The present invention relates to the application of carboxylate compounds, and in particular to the application of carboxylate compounds as absorbents for capturing carbon dioxide and / or in the preparation of absorbents for capturing carbon dioxide, belonging to the technical field of carbon dioxide capture and carbon emission reduction. Background Art

[0002] With the advent of the Industrial Revolution, humanity has been using fossil fuels extensively for energy, emitting significant amounts of carbon dioxide. The rate of carbon dioxide emissions has far outstripped nature's ability to absorb and utilize it, leading to a continuous rise in atmospheric carbon dioxide concentrations. Carbon dioxide is a greenhouse gas, and its large-scale emissions have led to increased global temperatures, climate anomalies, and extreme weather events. Therefore, capturing and storing human-generated carbon dioxide (CCS) has become a social consensus.

[0003] Nowadays, the alcohol amine aqueous solution absorption method is mainly used in industry.Although the alcohol amine aqueous solution has a large absorption capacity and low viscosity, it 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, with many unique properties, such as low volatility, strong solubility, wide electrochemical window, and many advantages such as 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 physical adsorption of carbon dioxide, and the absorption required 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 to achieve chemical adsorption of carbon dioxide (Bates, ED, Mayton, RD, Ntai, I. & Davis, JH Jr., J. Am. Chem. Soc. 2002, 124, 926). Many researchers at home and abroad have used various alkaline ionic liquids to achieve chemical absorption of carbon dioxide (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). In addition to a few imidazolium acetate ionic liquids that have clear evidence of forming new C-C bonds when absorbing carbon dioxide (Holbrey, JD, et al, Chem. Commun. 2003, 28), other researchers have also claimed that carbamic acid or formamide is formed. However, Jairton Dupont et al. believe that due to the inevitable presence of water in ionic liquids, bicarbonate and carbonate are formed in most absorption processes, and use nuclear magnetic resonance data from these works as evidence (Zanatta, M., Simon, NM & Dupont, J., ChemSusChem 2020, 13, 3101). Ionic liquids have a high viscosity under solvent-free conditions, which makes absorption difficult. Superbase ionic liquids interact strongly with carbon dioxide, and desorption requires high energy consumption.Therefore, finding more suitable carbon dioxide absorbers remains one of the challenges facing scientists.

[0004] Quaternary ammonium / phosphonium carboxylates have also been used to absorb carbon dioxide. Quinn et al. used quaternary ammonium acetates, propionates, and malonates to achieve high absorption rates under equimolar water conditions (Quinn, R., Appleby, J. Band Pez, GP, J. Am. Chem. Soc. 1995, 117, 329; Quinn, R., Synth. React. Inorg. Met.-Org. Chem. 2001, 31(3), 359). However, the carbon dioxide absorption rate decreases significantly with increasing water content. For example, for tetraethylammonium propionate, at a molar ratio of tetraethylammonium propionate to water of 1:4, the carbon dioxide absorption rate was only 0.155 mol / mol of carboxylate. Zhang Zhibing et al. from Nanjing University studied the absorption of carbon dioxide by triethylbutylammonium acetate. The results showed that the best effect was achieved when the brine molar ratio was 1:1. At room temperature and 1 atmosphere, the mole fraction of carbon dioxide reached 0.386 (Wang, GN, et al., J. Chem. Eng. Data 2011, 56, 1125). However, the absorption rate decreased sharply with increasing water content. When the brine molar ratio was 1:5, the mole fraction of carbon dioxide was only 0.054 under the same conditions. Anderson et al. studied the absorption of carbon dioxide by various quaternary ammonium / quaternary phosphonium carboxylates at 5 atmospheres, with the monohydrates of these salts showing the highest absorption capacity (Anderson, K., et al. Green Chem., 2015, 17, 4340). They also studied the effect of water content on the absorption of carbon dioxide by tetrabutylphosphonium carboxylate at 5 atmospheres. The results showed that the absorption rate decreased significantly when the brine molar ratio exceeded 1:1. Yasaka et al. studied tetrabutylphosphonoformate, and the results showed that its monohydrate can effectively absorb carbon dioxide, and the absorption amount decreases sharply with the increase of 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., ChemPhysChem 2018, 19, 1674). Their work primarily focused on formates, acetates, and propionates. Anderson et al. studied a variety of carboxylates, most of which were linear (the only branched one was trihexyltetradecylphosphine 2-methylpropionate). Their primary focus was on the absorption of carbon dioxide by their monohydrates at 5 atmospheres, with only tetrabutylphosphonium formate and the hydrophobic trihexyltetradecylphosphonium formate examining the effects of water on carbon dioxide absorption at 5 atmospheres. These studies achieved promising results, but the effect of water on carbon dioxide absorption was not addressed, leaving room for improvement in their practical application.There is still a gap in the field of carbon dioxide absorption in the presence of a large amount of water, or even in aqueous solution, while keeping the desorption process low in temperature, fast in speed and low in energy consumption.

[0005] Invention Disclosure

[0006] The present invention aims to provide the use of carboxylate compounds as absorbents for capturing carbon dioxide. This invention offers advantages such as readily available, inexpensive absorbent raw materials, simple synthesis, high capture capacity, water-stable capture capacity, low desorption temperature, high desorption speed, and low energy consumption, and has promising application prospects.

[0007] Use of the carboxylate 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;

[0008] The carboxylate anion in the carboxylate compound is a carboxylate radical having a carbon chain with a carbon number greater than 3, and the cation is a substituted quaternary ammonium ion and / or a quaternary phosphonium ion.

[0009] In the above application, the carboxylate compound has appropriate hydrophilicity, is soluble in water at room temperature, and can be precipitated from water after absorbing carbon dioxide; the carboxylate compound can form a water-stable complex after absorbing carbon dioxide.

[0010] In the above application, the carboxylate radical having a carbon chain with more than 3 carbon atoms is a branched carboxylate radical.

[0011] In the above application, the carboxylic acid having a carbon chain with more than 3 carbon atoms may have 4 to 20 carbon atoms.

[0012] In the above application, 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.

[0013] In the above application, the carboxylate having a carbon chain with a carbon number greater than 3 is specifically at least one of 2,2-dimethylbutyrate, 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, cyclohexylcarboxylate and n-octanoate.

[0014] In the above application, the structural formulas of the substituted quaternary ammonium ion and quaternary phosphonium ion are shown in the following formulas I and II:

[0015]

[0016] In formula I and II, n is 2 to 4, m is 4 to 16, and the substituents in formula I and II are the same or different.

[0017] In the present invention, in Formulas I and II, n is 2 or 4, and m is 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; in the quaternary phosphine ion represented by Formula II, n is 4, and m is 4, 6, 8, 10, 12, 14 or 16.

[0018] In the above application, the substituted quaternary ammonium ion is selected from at least one of triethylbutylammonium, tetrabutylammonium and tributylhexylammonium;

[0019] The substituted quaternary phosphonium ion is at least one selected from tetrabutylphosphine, tributylhexylphosphine, tributyloctylphosphine, tributyldecanylphosphine, tributyldodecylphosphine, tributyltetradecylphosphine and tributylhexadecylphosphine.

[0020] The present invention also provides an absorbent for capturing carbon dioxide, which is made of the carboxylate compound or contains the carboxylate compound.

[0021] The present invention further provides a method for capturing carbon dioxide with high efficiency and energy saving by using carboxylate compounds that are stable to water, comprising the following steps: placing an aqueous solution of the carboxylate compound in a carbon dioxide atmosphere to absorb carbon dioxide and obtain a combination of the carboxylate precipitated from the water and the carbon dioxide.

[0022] 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.

[0023] In the above method, the conditions for absorbing carbon dioxide are as follows: the carbon dioxide partial pressure can be 0.01-2 MPa, specifically 0.01 MPa, 0.1 MPa, 2 MPa; the temperature can be 25-80°C, specifically 25°C, 80°C.

[0024] In the above method, the carbon dioxide absorption capacity of each mole of the carboxylate compound may be 0.1 to 1.2 moles, specifically 0.12 to 1.1 moles.

[0025] In the above method, the method further comprises the step of regenerating the carboxylate compound after the absorption of carbon dioxide is completed.

[0026] In the above method, the regeneration process is as follows: under reduced pressure conditions, the pressure can be 0.01 to 1 atmosphere, the temperature can be 10 to 120°C (i.e., room temperature to 120°C, where room temperature is common knowledge in the art, specifically 10 to 30°C); the time can be 1 min to 10h, specifically 3 min, 30 min, 1 h, 3 h, 3 min to 3 h, or 1 min to 5 h. The temperature can be specifically room temperature to 80°C, specifically 25 to 80°C.

[0027] The present invention also provides another carboxylate compound for use as an absorbent for capturing carbon dioxide and / or in the preparation of an absorbent for capturing carbon dioxide;

[0028] The carboxylate compound comprises a carboxylate anion having a branched carboxylate radical with a total carbon atom count greater than 6, and a cation having a substituted quaternary ammonium ion, a quaternary phosphonium ion, a pyridinium ion, a pyrrolidine ion, a piperidinium ion, an imidazolium ion, and a metal ion;

[0029] The structural formulas of the substituted quaternary ammonium ion and quaternary phosphonium ion are shown in the following formulas I-1 and II-1:

[0030]

[0031] In Formula I-1 and Formula II-1, n is 1 to 4, m is 1 to 16, and the substituents in Formula I-1 and Formula II-1 are the same or different.

[0032] In the above-mentioned use, the number of carbon atoms in the branched carboxylate radical having a total carbon atom count greater than 6 may be 7 to 20.

[0033] In the above-mentioned use, the number of carbon atoms in the branched carboxylate radical having a total carbon atom count greater than 6 may be 8 to 16.

[0034] In the above-mentioned use, the branched carboxylate having a total carbon atom count greater than 6 is selected from at least one of 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, 2-propylnonanoate, 2-butyloctanoate and 2-hexyldecanoate.

[0035] In the above-mentioned use, the substituted quaternary ammonium ion is selected from at least one of tetramethylammonium, tetraethylammonium and tributylmethylammonium;

[0036] The substituted quaternary phosphine ion is selected from at least one of tetramethylphosphine, tetraethylphosphine and tributylmethylphosphine.

[0037] In the above-mentioned use, the pyridinium ion is an N-substituted pyridinium cation, and its structural formula is shown in the following formula III;

[0038] The pyrrolidinium ion is an N-substituted pyrrole cation, and its structural formula is shown in Formula IV below;

[0039] The piperidinium ion is an N-substituted piperidinium cation, and its structural formula is shown in the following formula V;

[0040] The imidazolium ion is a disubstituted or / and trisubstituted imidazolium cation, and its structural formula is shown in the following formula VI;

[0041] The metal ion is selected from at least one of lithium, sodium, potassium and cesium;

[0042]

[0043] In formula III, IV, V, and VI, R1 and R2 are both straight fatty chains with carbon atoms greater than or equal to 1, R3 is H or CH3, and R1 and R2 are the same or different.

[0044] In the above-mentioned uses, in the formulae III, IV, V and VI, R1 and R2 can be specifically linear aliphatic chains having 1 to 10 carbon atoms.

[0045] The present invention also provides an absorbent for capturing carbon dioxide, the active ingredient of which is the carboxylate compound.

[0046] The present invention further provides a method for capturing carbon dioxide by stabilizing water using carboxylate compounds, comprising the following steps: placing an aqueous solution of the carboxylate compounds in a carbon dioxide atmosphere to absorb carbon dioxide and obtain a combination of carboxylate and carbon dioxide precipitated from the water.

[0047] 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.

[0048] In the above method, the conditions for absorbing carbon dioxide are as follows: the carbon dioxide partial pressure can be 0.00004~0.5MPa, specifically 0.01MPa, 0.1MPa, 0.5Mpa, 0.01~0.1MPa, 0.1~0.5MPa and captured from the atmosphere (carbon dioxide partial pressure is about 0.00004MPa); the temperature can be 5~80℃, specifically 5℃, 25℃, 80℃, 5~25℃, 25~80℃.

[0049] In the above method, the carbon dioxide absorption capacity of each 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.

[0050] In the above method, the method further comprises the step of regenerating the carboxylate compound after the absorption of carbon dioxide is completed.

[0051] In the above method, the regeneration process is as follows: under reduced pressure conditions, the pressure can be 0.01 to 1 atmosphere, the temperature can be 10 to 120°C (i.e., room temperature to 120°C, the room temperature is common knowledge known in the art, specifically 10 to 30°C), specifically 25°C, 120°C or 25 to 120°C; the time can be 1 min to 10 h, specifically 1 h, 3 h or 1 to 3 h.

[0052] Best Mode for Carrying Out the Invention

[0053] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0054] The carboxylates in the following examples were synthesized by established techniques (Suarez, PAZ; Dullius, JEL; Einloft, S.; DE Souza RF and Dupont, J., Poly, Hedron, 1996, 15, 1217-1219).

[0055] The following examples are used to illustrate the present invention, but are by no means intended to limit the scope of use of the present invention.

[0056] Example 1

[0057] 2 mmol of tributylhexylphosphine 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 to the solution to expose it to 1 atmosphere of carbon dioxide. The solution was stirred at 25°C for 12 hours, and the system separated into an organic phase and an aqueous phase. The balloon was removed, and the carbon dioxide gas in the upper part of the solution in the bottle was replaced with air. The solution was then titrated with sodium hydroxide solution (0.2 w %) using phenolphthalein as an indicator, and the amount of carbon dioxide absorbed was found to be 0.98 mmol.

[0058] Under the same conditions, tributylhexylphosphine 2-ethylhexanoate was replaced by the following reagents, and the following reagents were used to determine tetrabutylphosphine 2-ethylhexanoate, tributyloctylphosphine 2-ethylhexanoate, tributyldecanylphosphine 2-ethylhexanoate, tributyldodecylphosphine 2-ethylhexanoate, tributyltetradecylphosphine 2-ethylhexanoate, tributylhexadecylphosphine 2-ethylhexanoate, tetrabutylammonium 2-ethylhexanoate, triethylbutylammonium 2-ethylhexanoate, tributylhexylammonium 2-ethylhexanoate, tributylhexylphosphine 2,2-dimethylbutyrate, tributylhexylphosphine 2-propylvalerate, and tributyloctylphosphine 2-ethylhexanoate. The absorption of carbon dioxide by 2 mmol each of butylhexylphosphine 2,2-dimethylhexanoate, tributylhexylphosphine 2-propylhexanoate, tributylhexylphosphine 2-ethylheptanoate, tributylhexylphosphine cyclohexylcarboxylate, and tributylhexylphosphine n-octanoate (40 mmol of water were added to each) resulted in the formation of new liquid or solid phases after absorbing carbon dioxide, 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.

[0059] Example 2

[0060] Essentially the same as Example 1 of the present invention, except for the addition of 2 mmol of tributylhexylphosphine 2-ethylhexanoate (0.86 g) and 1 mmol of water, the carbon dioxide absorption was 1.0 mmol. This indicates that the carbon dioxide absorption of the carboxylate salt at a molar ratio of 1:0.5 is stable in the presence of water compared to Example 1.

[0061] Example 3

[0062] The reaction was essentially the same as in Example 2 of the present invention, except that 2 mmol of water was added. The carbon dioxide absorption was 1.0 mmol. This indicates that the carbon dioxide absorption at a 1:1 molar ratio of the carboxylate to water is stable compared to that in Example 1 and does not change with the addition of water.

[0063] Example 4

[0064] Essentially the same as in Example 1 of the present invention, tributylhexylphosphine 2-ethylhexanoate was used, except for the temperature being 80°C. After carbon dioxide absorption, a new organic phase was formed, and the carbon dioxide absorption capacity was 0.62 mmol. This indicates that the carbon dioxide absorption capacity of the carboxylate aqueous solution at different temperatures is higher than that of Example 1 of the present invention, even at high temperatures.

[0065] Example 5

[0066] Essentially the same as in Example 1 of the present invention, for tributylhexylphosphine 2-ethylhexanoate, except for the atmosphere being at a carbon dioxide partial pressure of 0.01 MPa and a nitrogen atmosphere of 0.09 MPa, all other conditions were the same as in Example 1, resulting in a carbon dioxide absorption capacity of 0.40 mmol. This indicates that the carboxylate aqueous solution can absorb a relatively high carbon dioxide capture capacity at low carbon dioxide partial pressures, compared to Example 1 of the present invention.

[0067] Example 6

[0068] 2 mmol of tributyloctylphosphine 2-ethylhexanoate (0.92 g) was added to 40 mmol of water (0.72 g) in an autoclave, and 2 MPa of carbon dioxide was introduced. The mixture was stirred at 25°C for 12 hours. After decompression, the carbon dioxide gas in the upper portion of the solution in the autoclave was replaced with air. The solution was then titrated with sodium hydroxide solution (0.2 w %) using phenolphthalein as an indicator, yielding a carbon dioxide absorption of 1.2 mmol. This indicates that the carboxylate aqueous solution can absorb carbon dioxide at high pressures, demonstrating a higher carbon dioxide capture capacity even at high carbon dioxide partial pressures, compared to Example 1 of the present invention.

[0069] Example 7

[0070] Essentially the same as Example 1 of the present invention, for tributylhexylphosphine 2-ethylhexanoate, except that the carbon dioxide atmosphere was changed to carbon dioxide bubbling (20 ml / min) and the absorption was carried out for 30 minutes, the remaining conditions were exactly the same as Example 1, resulting in a carbon dioxide absorption capacity of 0.98 mmol. A comparison of Examples 1 and 7 shows that different absorption modes have little effect on carbon dioxide absorption, indicating that the carbon dioxide absorption capacity of the present invention is not affected by the absorption mode.

[0071] Example 8

[0072] For tributylhexylphosphine 2-ethylhexanoate, the carbon dioxide absorption portion was identical to that of Example 1. After completion of the absorption, the solution was exposed to air and stirred continuously for 3 hours at room temperature (25°C). It was determined that the carbon dioxide was completely released. This indicates that the carboxylate aqueous solution can be regenerated after absorbing carbon dioxide.

[0073] Example 9

[0074] The method is basically the same as Example 8 of the present invention, except that the released portion is stirred at 80°C for 30 minutes. The carbon dioxide is completely released. Comparison between Examples 8 and 9 of the present invention shows that the carboxylate compound can be regenerated at different temperatures.

[0075] Example 10

[0076] The method is essentially the same as Example 8 of the present invention, except that the release portion is changed to a water pump under reduced pressure (0.01 atmosphere) and stirring is continued for 1 hour. The rest is exactly the same as Example 8. It is determined that the carbon dioxide is completely released. A comparison of Examples 8 and 10 shows that the carboxylate compound can be regenerated at different pressures.

[0077] Example 11

[0078] 1 millimole tributyl hexadecylphosphine 2-ethylhexanoate (57 milligrams) adds in 5.4 gram water (0.3 mole), after the dissolving, blasts into carbon dioxide bubble (20 ml / minute) under the room temperature after three minutes, and solution becomes muddy, shows that carboxylate can effectively absorb carbon dioxide under this concentration, and separates out after absorption.Stop feeding carbon dioxide, solution is exposed in the air, continues stirring under room temperature (25 ℃), and after 3 minutes, solution clarification shows that this solution can release carbon dioxide quickly.By the embodiment of the present invention 1 and 11 contrasts, different concentrations, different absorption modes can realize carboxylate compounds absorption and regeneration.

[0079] Example 12

[0080] 2 mmol of tetramethylammonium 2-ethylhexanoate (0.434 g) was added to 2 mmol of water (0.036 g) in a glass bottle. A carbon dioxide balloon was connected to the solution to place it under a 0.1 MPa carbon dioxide atmosphere and stirred at 25°C for 12 hours. The balloon was removed, and the carbon dioxide gas at the top of the solution in the bottle was replaced with air. The solution was then titrated with sodium hydroxide solution (0.2 w%) using phenolphthalein as an indicator to obtain a carbon dioxide absorption amount of 1.0 mmol.

[0081] Under the same conditions, tetramethylammonium 2-ethylhexanoate was replaced by the following reagents, and the following reagents were used to determine the concentrations of tetraethylammonium 2-ethylhexanoate, tributylmethylammonium 2-ethylhexanoate, tetramethylphosphine 2-ethylhexanoate, tetraethylphosphine 2-ethylhexanoate, tributylmethylphosphine 2-ethylhexanoate, tributylmethylammonium 2,2-dimethylhexanoate, tributylmethylammonium 2-ethylheptanoate, tributylmethylammonium 2-propylvalerate, tributylmethylammonium 2-propylhexanoate, tetramethylammonium 2-propylnonanoate, tetramethylammonium 2-butyloctanoate, tetramethylammonium 2-hexyldecanoate, sodium 2-ethylhexanoate, potassium 2,2-dimethylhexanoate, lithium 2-ethylheptanoate, cesium 2-propylvalerate, N-butyl The absorption of carbon dioxide by 2 mmol of each of 1-butylpyridine 2-ethylhexanoate, N-butyl-N-methylpyrrolidine 2-ethylhexanoate, N-butyl-N-methylpiperidinium 2-ethylhexanoate (2 mmol of water was added respectively) was 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. All absorptions were within the range of 0.95 to 1.05 mmol.

[0082] This shows that all substances can effectively absorb carbon dioxide.

[0083] Example 13

[0084] Essentially the same as Example 12 of the present invention, except for the addition of 2 mmol of tributylmethylammonium 2-ethylhexanoate (0.86 g) and 1 mmol of water (0.018 g), the carbon dioxide absorption capacity was 1.0 mmol. This indicates that the carbon dioxide absorption capacity of the above carboxylate salt at a molar ratio of 1:0.5 is stable to water within a certain range compared to Example 12.

[0085] Example 14

[0086] Essentially the same as Example 12 of the present invention, except that 2 mmol of sodium 2-hexyldecanoate (0.56 g) was added to 200 mmol (3.6 g of water), the carbon dioxide absorption was 2.05 mmol, indicating that the carbon dioxide absorption of the carboxylate salt is stable in water over a wide range.

[0087] After absorption, the solution was heated at 120°C for 3 hours, and the carbon dioxide was completely released, indicating that the carboxylate aqueous solution can be regenerated after absorbing carbon dioxide.

[0088] Example 15

[0089] The carbon dioxide absorption capacity was 2.0 mmol, which was substantially the same as in Example 14 of the present invention, except that the absorption temperature was 80°C. The carbon dioxide absorption capacity of the carboxylate was stable over a wide temperature range compared to Example 14.

[0090] Example 16

[0091] 2 mmol of tributylmethylammonium 2-ethylhexanoate (0.69 g) was added to 0.7 g of water in a glass bottle. A carbon dioxide balloon was connected to the solution, and the solution was exposed to 1 atmosphere of carbon dioxide. The solution was stirred at 5°C for 12 hours. The balloon was removed, and the carbon dioxide gas in the upper part of the solution was replaced with air. The solution was then titrated with sodium hydroxide solution (0.2 w %) using phenolphthalein as an indicator. The amount of carbon dioxide absorbed was 1.2 mmol. Compared with Example 12, this indicates that lowering the absorption temperature is beneficial to increasing the absorption amount.

[0092] After the absorption was completed, the solution was exposed to air and stirred for 3 hours at room temperature (25°C). It was determined that the carbon dioxide was completely released, indicating that the carboxylate aqueous solution can be regenerated after absorbing carbon dioxide.

[0093] Example 17

[0094] Basically the same as Example 12 of the present invention, for tributylmethylammonium 2-ethylhexanoate, except that the atmosphere is a carbon dioxide partial pressure of 0.01 MPa and a nitrogen partial pressure of 0.09 MPa, the rest is exactly the same as Example 12, and the carbon dioxide absorption amount is 0.98 mmol.

[0095] 0.278 g of sodium 2-hexyldecanoate (1 mmol) was dissolved in 1 g of water and bubbling was performed using an air pump (the atmospheric carbon dioxide partial pressure was approximately 0.00004 MPa) at an air flow rate of 10 ml / min. After 12 hours, the solution was titrated with sodium hydroxide solution (0.2 w %) until clear, yielding a carbon dioxide absorption of 0.10 mmol.

[0096] This shows the amount of carbon dioxide absorbed by the above-mentioned carboxylate aqueous solution at low carbon dioxide partial pressure. Compared with Example 12 of the present invention, a higher carbon dioxide capture capacity can still be obtained at low carbon dioxide partial pressure, and even a certain amount of carbon dioxide can be absorbed from the atmosphere.

[0097] Example 18

[0098] 2 mmol of tributylmethylammonium 2-ethylhexanoate (0.69 g) was added to 2 mmol of water (0.036 g) in an autoclave, and 0.5 MPa of carbon dioxide was introduced, followed by stirring at 25°C for 12 hours. After decompression, the gaseous carbon dioxide in the upper portion of the solution in the autoclave was replaced with air, and the carbon dioxide absorbed was measured according to the method of Example 12, yielding a carbon dioxide absorption capacity of 1.5 mmol. This indicates that the carboxylate aqueous solution absorbs carbon dioxide at high carbon dioxide pressures, and compared to Example 12 of the present invention, a higher carbon dioxide capture capacity can be achieved at high carbon dioxide partial pressures.

[0099] From the above results, we can see that:

[0100] 1) The halide salts of the organic cations in the present invention are bulk chemicals, with a price of several thousand yuan per ton; while the current market price of the halides of tributylhexylphosphine and tributyloctylphosphine in the comparative example is several thousand yuan per kilogram, it is obvious that the raw material price of the present invention is lower;

[0101] 2) In Examples 1, 3, and 4 of the present invention, sodium 2-ethylhexanoate, potassium 2,2-dimethylhexanoate, lithium 2-ethylheptanoate, cesium 2-propylpentanoate, and sodium 2-hexyldecanoate were used to conduct carbon dioxide absorption experiments. The inorganic salt metal ions of lithium, sodium, potassium, and cesium used have higher stability;

[0102] 3) The present invention can achieve a higher carbon dioxide absorption capacity (relative to the mass of the absorbent) at an appropriate water content. For example, per mole of tetramethylammonium 2-ethylhexanoate (molecular weight 217.3) or trimethylhexylphosphine 2-ethylhexanoate (molecular weight 430.7), at a salt-to-water molar ratio of 1:1 and one atmosphere of carbon dioxide pressure, the absorbent can absorb 2.12 and 1.11 moles of carbon dioxide per kilogram, respectively.

[0103] Industrial Applications

[0104] 1. The present invention is used to solve the problems of the existing system such as corrosiveness, volatility, high energy consumption, etc., and it can obtain a higher carbon dioxide capture capacity at high temperature, low carbon dioxide partial pressure and high pressure.

[0105] 2. When the selected carboxylate aqueous solution absorbs carbon dioxide, its combination with carbon dioxide will precipitate from the water in liquid or solid form, indicating that the combination of the selected carboxylate and carbon dioxide is stable to water.

[0106] 3. Carboxylates can be regenerated by reducing pressure at room temperature. Depending on the conditions, the absorption time can range from a few minutes to several hours. After the carbon dioxide is released, the carboxylates become miscible with water. Increasing the temperature accelerates the regeneration rate.

[0107] 4. The present invention uses carboxylate compounds in which cations are substituted quaternary ammonium ions, substituted quaternary phosphonium ions, pyridinium ions, pyrrole ions, piperidinium ions, imidazolium ions or metal ions. Compared with the more expensive tetraalkyl-substituted phosphonium / ammonium onium ions, the onium ions are inexpensive, thereby significantly reducing the cost of capturing carbon dioxide.

Claims

1. An application of a carboxylate compound, characterized in that: The carboxylate compound is used as an absorbent for capturing carbon dioxide, or the carboxylate compound is used to prepare an absorbent for capturing carbon dioxide; 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 anion in the carboxylate compound is at least one of 2,2-dimethylbutyrate, 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, and cyclohexylcarboxylate; The substituted quaternary ammonium ion is selected from at least one of triethylbutylammonium, tetrabutylammonium and tributylhexylammonium; The substituted quaternary phosphonium ion is at least one selected from tetrabutylphosphonium, tributylhexylphosphonium, tributyloctylphosphonium, tributyldecanylphosphonium, tributyldodecylphosphonium, tributyltetradecylphosphonium, and tributylhexadecylphosphonium.

2. An application of a carboxylate compound, characterized in that: The carboxylate compound is used as an absorbent for capturing carbon dioxide, or the carboxylate compound is used to prepare an absorbent for capturing carbon dioxide; The carboxylate compound comprises a carboxylate anion which is a branched carboxylate having a total carbon atom count greater than 6, and a cation which is at least one of a substituted quaternary ammonium ion, a quaternary phosphonium ion, a pyridinium ion, a pyrrolidine ion, a piperidinium ion, an imidazolium ion, and a metal ion; Wherein, the metal ion is selected from at least one of lithium ion, sodium ion, potassium ion and cesium ion; Wherein, the structural formulas of the substituted quaternary ammonium ion and quaternary phosphonium ion are shown in the following formula I-1 and formula II-1: In formula I-1 and formula II-1, n is 1-4, m is 1 to 16, and the substituents in formula I-1 and formula II-1 are the same or different, and the number of carbon atoms in the branched carboxylate group having a total carbon atom count greater than 6 is 7 to 20.

3. The use according to claim 2, characterized in that: The branched carboxylate radical having a total carbon atom count greater than 6 has a carbon atom count of 8 to 16.

4. The use according to claim 2 or 3, characterized in that: The branched carboxylate having a total carbon atom count greater than 6 is selected from at least one of 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, 2-propylnonanoate, 2-butyloctanoate and 2-hexyldecanoate.

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

6. The use according to claim 2 or 3, characterized in that: The pyridinium ion is an N-substituted pyridinium cation, and its structural formula is shown in Formula III below; The pyrrolidinium ion is an N-substituted pyrrole cation, and its structural formula is shown in Formula IV below; The piperidinium ion is an N-substituted piperidinium cation, and its structural formula is shown in the following formula V; The imidazolium ion is a disubstituted or / and trisubstituted imidazolium cation, and its structural formula is shown in the following formula VI; In formula III, IV, V, and VI, R1 and R2 are both straight fatty chains with carbon atoms greater than or equal to 1, R3 is H or CH3, and R1 and R2 are the same or different.

7. The use according to claim 6, characterized in that: In the formulae III, IV, V and VI, R1 and R2 are both straight fatty chains having 1 to 10 carbon atoms.

8. A method for capturing carbon dioxide with high efficiency and energy conservation using a carboxylate compound that is stable to water, comprising the following steps: placing an aqueous solution of a first carboxylate compound or an aqueous solution of a second carboxylate compound in a carbon dioxide atmosphere to absorb the carbon dioxide; in, The carboxylate anion in the first carboxylate compound is a carboxylate radical having a carbon chain with more than 3 carbon atoms, and the cation in the first carboxylate compound is a substituted quaternary ammonium ion and / or a quaternary phosphonium ion. The carboxylate anion in the first carboxylate compound is at least one of 2,2-dimethylbutyrate, 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, and cyclohexylcarboxylate; The substituted quaternary ammonium ion in the first carboxylate compound is selected from at least one of triethylbutylammonium, tetrabutylammonium and tributylhexylammonium; The substituted quaternary phosphonium ion in the first carboxylate compound is at least one selected from tetrabutylphosphonium, tributylhexylphosphonium, tributyloctylphosphonium, tributyldecanylphosphonium, tributyldodecylphosphonium, tributyltetradecylphosphonium, and tributylhexadecylphosphonium, The carboxylate anion in the second carboxylate compound is a branched carboxylate having a total carbon atom count greater than 6, and the cation in the second carboxylate compound is at least one of a substituted quaternary ammonium ion, a quaternary phosphonium ion, a pyridinium ion, a pyrrolidium ion, a piperidinium ion, an imidazolium ion, and a metal ion; Wherein, the metal ion is selected from at least one of lithium ion, sodium ion, potassium ion and cesium ion; Wherein, the structural formulas of the substituted quaternary ammonium ion and quaternary phosphonium ion in the second carboxylate compound are shown in Formula I-1 and Formula II-1: In formula I-1 and formula II-1, n is 1-4, m is 1 to 16, and the substituents in formula I-1 and formula II-1 are the same or different, and the number of carbon atoms in the branched carboxylate group having a total carbon atom count greater than 6 is 7 to 20.

9. The method according to claim 8, characterized in that: The branched carboxylate radical having a total carbon atom count greater than 6 has a carbon atom count of 8 to 16.

10. The method according to claim 8 or 9, characterized in that: The branched carboxylate having a total carbon atom count greater than 6 is selected from at least one of 2,2-dimethylhexanoate, 2-ethylhexanoate, 2-ethylheptanoate, 2-propylpentanoate, 2-propylhexanoate, 2-propylnonanoate, 2-butyloctanoate and 2-hexyldecanoate.

11. The method according to claim 8 or 9, characterized in that: The substituted quaternary ammonium ion in the second carboxylate compound is selected from at least one of tetramethylammonium, tetraethylammonium and tributylmethylammonium; The substituted quaternary phosphonium ion in the second carboxylate compound is selected from at least one of tetramethylphosphonium, tetraethylphosphonium, and tributylmethylphosphonium.

12. The method according to claim 8 or 9, characterized in that: The pyridinium ion is an N-substituted pyridinium cation, and its structural formula is shown in Formula III below; The pyrrolidinium ion is an N-substituted pyrrole cation, and its structural formula is shown in Formula IV below; The piperidinium ion is an N-substituted piperidinium cation, and its structural formula is shown in the following formula V; The imidazolium ion is a disubstituted or / and trisubstituted imidazolium cation, and its structural formula is shown in the following formula VI; In formula III, IV, V, and VI, R1 and R2 are both straight fatty chains with carbon atoms greater than or equal to 1, R3 is H or CH3, and R1 and R2 are the same or different.

13. The method according to claim 12, wherein: In the formulae III, IV, V and VI, R1 and R2 are both straight fatty chains having 1 to 10 carbon atoms.

14. The method according to claim 8, wherein: The molar ratio of the first carboxylate compound to water is 1:0.5-300; The conditions for absorbing carbon dioxide are as follows: carbon dioxide partial pressure is 0.01-2 MPa; temperature is 25-80°C.

15. The method according to claim 8, wherein: The molar ratio of the second carboxylate compound to water is 1:0.5-100; The conditions for absorbing carbon dioxide are as follows: carbon dioxide partial pressure is 0.00004-0.5 MPa; temperature is 5-80°C.

16. The method according to claim 8 or 14, characterized in that: The carbon dioxide absorption capacity of each mole of the first carboxylate compound is 0.1-1.2 moles.

17. The method according to claim 8 or 15, characterized in that: The carbon dioxide absorption capacity of each mole of the second carboxylate compound is 0.1-1.1 moles.

18. The method according to claim 8, wherein: The method further comprises the step of regenerating the first carboxylate compound or the second carboxylate compound after the absorption of carbon dioxide is completed.

19. The method according to claim 18, wherein: The regeneration process is as follows: under reduced pressure conditions, the pressure is 0.01-1 atmosphere, the temperature is 10-120° C., and the time is 1 min-10 h.

Images