Double-acid functionalized ionic liquid and preparation method thereof, and method for desorbing CO2 in organic amine solution

Abstract

The invention belongs to the technical field of low carbon, and particularly relates to a double-acid functionalized ionic liquid and a preparation method thereof and a method for desorbing CO2 in an organic amine solution, the double-acid functionalized ionic liquid comprises two acidic sites, the anion part is metal chloride with Lewis acid sites; when in use, the double-acid functionalized ionic liquid is added into an organic amine solution, and then CO2 in the organic amine solution is desorbed. Compared with the prior art, the problems that in the prior art, when CO2 in organic amine is desorbed through solid acid or a molecular sieve, the acid site is prone to inactivation, metal pollution is prone to occurring, and operation is complex are solved. The ionic liquid provided by the scheme has two acidic sites, so that the CO2 release amount and the desorption rate during desorption can be effectively improved, the regeneration energy consumption of a saturated CO2 amine solution is reduced, and the cost of a carbon capture process is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of low-carbon technologies, and particularly relates to a dual-acid functionalized ionic liquid and a preparation method thereof, and a method for desorbing CO2 in an organic amine solution. Background Art

[0002] The excessive emission of carbon dioxide has led to many climate problems, and it is urgent to develop efficient carbon emission reduction technologies. Carbon dioxide capture, utilization, and storage (CCUS) technology is an important means to achieve carbon emission reduction and carbon neutrality, and has received extensive attention in recent years.

[0003] Currently, monoethanolamine (MEA) is commonly used as an absorbent in the CCUS process. MEA reacts with CO2 during the absorption process to form carbamate. However, the C-N bond energy in carbamate is relatively high, and its decomposition process is a strongly endothermic reaction. The energy consumption for absorbent desorption accounts for more than half of the economic cost in the carbon capture process.

[0004] In recent years, researchers have developed various desorption catalysts, including molecular sieve catalysts and solid acid catalysts. These catalysts have abundant Bronsted acid sites (BAS) and Lewis acid sites (LAS) on their surfaces, such as a method for desorbing CO2 from amine solvents using CuO-KIT-6 disclosed in CN114984725A, a UIO-66-derived carbon material catalyst and its preparation method and application in catalytic carbon dioxide desorption disclosed in CN115869932A, etc. Research shows that acid sites can provide protons for carbamate, making it easier to generate activated intermediate RNH*, thereby promoting the cleavage of the C-N bond and reducing the regeneration heat load of the amine solvent. However, such solid catalysts have problems such as acid site deactivation, heavy metal pollution, and complex solid-liquid separation operations, which limit their practical applications in industry.

[0005] Therefore, developing an efficient and stable liquid-phase desorption catalyst is of great significance for optimizing the carbon capture process. Summary of the Invention

[0006] The purpose of the present invention is to provide a dual-acid functionalized ionic liquid and a preparation method thereof, and a method for desorbing CO2 in an organic amine solution to solve at least one of the above problems, so as to solve the problems of easy acid site deactivation, easy metal pollution, and complex operation in the desorption of CO2 in organic amines using solid acids or molecular sieves in the prior art. This solution proposes a dual-acid functionalized ionic liquid, which has two acidic sites and can effectively increase the CO2 release amount and desorption rate during desorption, reduce the regeneration energy consumption of the saturated CO2 amine solution, and thus reduce the cost of the carbon capture process.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The first aspect of the present invention discloses a dual-acid functionalized ionic liquid, which includes two acidic sites. Among them, the cation part is an organic quaternary ammonium salt with Bronsted acid sites and amphoteric acid-base properties, and the anion part is a metal chloride with Lewis acid sites.

[0009] Preferably, the organic quaternary ammonium salt includes one or more of triethylamine hydrochloride, trimethylamine hydrochloride, and isopropylamine hydrochloride.

[0010] Preferably, the metal chloride includes one or more of aluminum chloride, copper chloride, zinc chloride, and ferrous chloride.

[0011] Preferably, the molar ratio of the organic quaternary ammonium salt to the metal chloride is 1:(0.2 - 10).

[0012] The second aspect of the present invention discloses a preparation method of the dual-acid functionalized ionic liquid as described above, which includes the following steps:

[0013] (1) Under ice bath conditions, prepare an organic quaternary ammonium salt solution;

[0014] (2) Add the metal chloride to the organic quaternary ammonium salt solution in portions, stir and react under water bath conditions, and then stir at room temperature;

[0015] (3) Rotate evaporate the stirred mixture, and then dilute the ionic liquid.

[0016] Preferably, in (2), it includes one or more of the following:

[0017] i) The molar ratio of the organic quaternary ammonium salt to the metal chloride is 1:(0.2 - 10);

[0018] ii) The temperature of the stirring reaction is 60 - 100 °C, and the time of the stirring reaction is 8 - 12 hours;

[0019] iii) The stirring time at room temperature is 10 - 15 hours.

[0020] More preferably, in (2), the temperature of the stirring reaction is 70 - 80 °C.

[0021] Preferably, in (3), it includes one or more of the following:

[0022] i) The rotary evaporation is carried out under vacuum conditions, the temperature of the rotary evaporation is 80 - 100 °C, and the time of the rotary evaporation is 4 - 6 hours;

[0023] ii) The dilution is to dilute the concentration of the organic quaternary ammonium salt in the ionic liquid to 0.8 - 1.2 mol / L.

[0024] The third aspect of the present invention discloses a method for desorbing CO2 from an organic amine solution, which comprises the following steps:

[0025] Add any of the above-mentioned dual-acid-functionalized ionic liquids to the organic amine solution, and then desorb CO2 from the organic amine solution.

[0026] Preferably, the mass concentration of the ionic liquid in the organic amine solution is 0.5-2%.

[0027] Preferably, the desorption temperature is 90-110°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The preparation process of the dual-acid-functionalized ionic liquid desorption catalyst in the present invention is simple. It replaces the traditional solid acid catalyst, avoids the loss of solid acid sites and secondary heavy metal pollution, improves the desorption rate of the CO2-saturated organic amine solution, and reduces the regeneration energy consumption.

[0030] (2) The liquid catalyst provided by the present invention can catalyze the desorption of CO2 in a liquid-liquid homogeneous environment. After the "absorption-desorption" process is completed, the solution can be cooled to room temperature and then enter the next "absorption-desorption" process without separating the desorption catalyst from the absorption liquid, and the operation is simple.

[0031] (3) The present invention uses a Brønsted acid with amphoteric properties as a proton transfer carrier during the regeneration process of the organic amine solution. This Brønsted acid can not only provide protons for the decomposition of MEACOO - and HCO3 - but also obtain protons from MEAH + to be regenerated. Compared with the conventional liquid weak acid catalysts, the catalyst has good regenerability. It can be seen that quaternary ammonium salts with zwitterionic characteristics have application potential in the construction of dual-acid-functionalized ionic liquids. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 、 Figure 2 are the desorption rate and desorption amount curves obtained by adding the dual-acid-functionalized ionic liquid catalyst prepared in Example 1 to the MEA solution;

[0033] Figure 3 、 Figure 4 are the desorption rate and desorption amount curves obtained by adding the dual-acid-functionalized ionic liquid catalyst prepared in Example 2 to the MEA solution. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] In the following description, unless otherwise specified, the reagents used are conventional commercially available products, the methods used are common general knowledge in the art, and other matters not covered may be implemented using existing technologies.

[0036] A dual-acid functionalized ionic liquid, including two acidic sites, wherein the cationic part is an organic quaternary ammonium salt with Bronsted acid sites and amphoteric properties, and the anionic part is a metal chloride with Lewis acid sites.

[0037] Preferably, the organic quaternary ammonium salt includes one or more of triethylamine hydrochloride, trimethylamine hydrochloride, and isopropylamine hydrochloride.

[0038] Preferably, the metal chloride includes one or more of aluminum chloride, copper chloride, zinc chloride, and ferrous chloride.

[0039] A preparation method of a dual-acid functionalized ionic liquid, comprising the following steps:

[0040] (1) Add the organic quaternary ammonium salt as Bronsted acid to a certain volume of deionized water, and stir in an ice bath to obtain a homogeneous solution.

[0041] (2) Gradually and slowly add the metal chloride as Lewis acid to the above-mentioned organic quaternary ammonium salt solution. After all additions, transfer the mixture to a water bath, continue to stir and react at 60 - 100 °C for a period of time, and then stir at room temperature for a period of time.

[0042] (3) After complete stirring and homogenization, transfer the solution to a rotary evaporator for concentration by rotary evaporation.

[0043] (4) After concentration by rotary evaporation, dilute the dual-acid functionalized ionic liquid with deionized water to 0.8 - 1.2 mol / L.

[0044] Preferably, in step (1), the concentration of the Bronsted acid is 0.8 - 1.2 mol / L.

[0045] Preferably, in step (2), the molar ratio between the Bronsted acid and the Lewis acid is 1:(0.2 - 10).

[0046] Preferably, in step (2), the water bath heating temperature is 70 - 80 °C, the stirring time is 9 - 12 hours, and the stirring time at room temperature is 12 - 15 hours.

[0047] Preferably, in step (3), the specific process of concentration by rotary evaporation is: transfer the uniformly mixed dual-acid functionalized ionic liquid to a rotary evaporator, and under vacuum conditions and water bath heating at 80 - 100 °C, perform rotary evaporation for 4 - 6 hours.

[0048] The present invention also provides an application method of the above-mentioned dual-acid-functionalized ionic liquid in promoting the desorption of CO2-saturated amine solution, including the following steps:

[0049] Add an appropriate amount of the dual-acid-functionalized ionic liquid to the organic amine solution. After mixing evenly, the absorbent can be used for the absorption and desorption of CO2.

[0050] Preferably, the concentration of the dual-acid-functionalized ionic liquid in the organic amine solution is 0.5-2 wt%, and the heating desorption temperature is 90-110 °C.

[0051] After the heating desorption is completed, the absorbent is cooled to room temperature and can be reused.

[0052] Example 1

[0053] A preparation method of a dual-acid-functionalized ionic liquid, including the following steps:

[0054] (1) Dissolve 2.753 g of triethylamine hydrochloride in 100 mL of distilled water, and continuously stir under ice bath conditions to make a mixed solution.

[0055] (2) Gradually add 2.667 g of aluminum chloride to the dissolved triethylamine hydrochloride. After all are added, remove the ice bath, and react the uniformly mixed solution under the condition of 70 °C water bath heating for 8 hours, and then stir at room temperature for 12 hours.

[0056] (3) After the reaction is complete, transfer the obtained material to a rotary evaporator and heat to evaporate the solvent at 80 °C for 4 hours.

[0057] (4) Dilute the ionic liquid with deionized water to finally obtain a 1 mol / L ionic liquid [Et3NH][AlCl4].

[0058] Example 2

[0059] This example uses trimethylamine hydrochloride and zinc chloride as ionic liquid precursors to prepare a dual-acid-functionalized ionic liquid.

[0060] (1) Dissolve 1.911 g of trimethylamine hydrochloride in 100 mL of distilled water, and continuously stir under ice bath conditions to make a mixed solution.

[0061] (2) Gradually add 2.726 g of zinc chloride to the dissolved trimethylamine hydrochloride. After all are added, remove the ice bath, and react the uniformly mixed solution under the condition of 70 °C water bath heating for 8 hours, and then stir at room temperature for 12 hours.

[0062] (3) After the reaction is complete, transfer the obtained material to a rotary evaporator and heat to evaporate the solvent at 80 °C for 4 hours.

[0063] (4) Dilute the ionic liquid with deionized water to finally obtain 1 mol / L ionic liquid [Me3NH][ZnCl3].

[0064] Example 3

[0065] This example is basically the same as Example 1, with the main differences being that the organic quaternary ammonium salt used is isopropylamine hydrochloride, the metal chloride used is ferrous chloride, and the molar ratio of the organic quaternary ammonium salt to the metal chloride is controlled at 1:0.2; during the preparation process: the reaction is carried out under a water bath heating condition at 95 °C for 10 hours, and then stirred at room temperature for 15 hours; after the reaction is completed, the solvent is heated and evaporated at 100 °C for 5 hours; finally, it is diluted to obtain 0.8 mol / L ionic liquid.

[0066] Example 4

[0067] This example is basically the same as Example 1, with the main differences being that the organic quaternary ammonium salt used is a mixture of triethylamine hydrochloride and isopropylamine hydrochloride, the metal chloride used is copper chloride, and the molar ratio of the organic quaternary ammonium salt to the metal chloride is controlled at 1:2; during the preparation process: the reaction is carried out under a water bath heating condition at 80 °C for 12 hours, and then stirred at room temperature for 12 hours; after the reaction is completed, the solvent is heated and evaporated at 90 °C for 6 hours; finally, it is diluted to obtain 1.2 mol / L ionic liquid.

[0068] Example 5

[0069] This example is basically the same as Example 1, with the main differences being that the organic quaternary ammonium salt used is a mixture of triethylamine hydrochloride and trimethylamine hydrochloride, the metal chloride used is a mixture of copper chloride and zinc chloride, and the molar ratio of the organic quaternary ammonium salt to the metal chloride is controlled at 1:8; during the preparation process: the reaction is carried out under a water bath heating condition at 60 °C for 12 hours, and then stirred at room temperature for 15 hours; after the reaction is completed, the solvent is heated and evaporated at 80 °C for 6 hours; finally, it is diluted to obtain 1.0 mol / L ionic liquid.

[0070] Test method for the CO2 desorption ability of ionic liquid in organic amine solution:

[0071] Ionic liquid [Et3NH][AlCl4] group: The ionic liquid catalyst [Et3NH][AlCl4] prepared in Example 1 was added to a 20 wt% MEA solution, and the catalyst addition amount was 0.75 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. During the CO2 absorption process, pure CO2 was continuously introduced into the absorbent at a flow rate of 300 mL / min until the absorption reached saturation. The final CO2 loading was approximately 0.55 mol CO2 / mol MEA. After complete absorption saturation, desorption was carried out at a desorption temperature of 100 °C for 60 minutes. The desorption results are shown in Figure 1 , Figure 2 .

[0072] Ionic liquid [Me3NH][ZnCl3] group: The ionic liquid catalyst [Me3NH][ZnCl3] prepared in Example 2 was added to a 20 wt% MEA solution, and the catalyst addition amount was 0.75 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. During the CO2 absorption process, pure CO2 was continuously introduced into the absorbent at a flow rate of 300 mL / min until the absorption reached saturation. The final CO2 loading was approximately 0.55 mol CO2 / mol MEA. After complete absorption saturation, desorption was carried out at a desorption temperature of 100 °C for 60 minutes. The desorption results are shown in Figure 3 , Figure 4 .

[0073] Blank control group: A 20 wt% MEA solution was used, and pure CO2 was continuously introduced at a flow rate of 300 mL / min until the absorption reached saturation. After absorption saturation, desorption was carried out at 100 °C for 60 minutes.

[0074] From Figure 1 , 2 and Figure 3 , 4 The desorption results in it can be seen that the MEA solution added with the ionic liquid of the present invention is significantly superior to the blank control group without the addition of ionic liquid in terms of CO2 desorption rate and desorption amount. Under the condition that the addition amount is only 0.75 wt%, the maximum desorption rate is increased by 43%, and the total desorption amount is increased by 83%. It shows that even at a relatively low addition amount, the dual-acid-functionalized ionic liquid can effectively promote the desorption process of CO2-saturated amine solution, significantly improve the CO2 desorption rate and desorption amount, and at the same time reduce the regeneration temperature and energy consumption of CO2-saturated amine solution. In addition, the absorbent using this ionic liquid can be directly reused for CO2 absorption after desorption without additional separation steps, with simple operation and more efficient use.

[0075] Moreover, the ionic liquid of the present solution does not exhibit metal leaching during the desorption process of the CO2-saturated amine solution, and thus there will be no problems of amine oxidation and decreased stability. Compared with the existing desorption catalysts, it ensures the advantages of long-term high-efficiency recyclability in the organic amine solution and the long-term high-efficiency recyclability of the organic amine solution containing it as a CO2 absorbent.

[0076] Application Example 1

[0077] The ionic liquid catalyst [Et3NH][AlCl4] prepared in Example 1 was added to a 20 wt% MEA solution, and the catalyst addition amount was 0.75 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. After the MEA solution was completely saturated with absorption, desorption was carried out at a desorption temperature of 100 °C and a reaction time of 60 minutes.

[0078] Application Example 2

[0079] The ionic liquid catalyst [Et3NH][AlCl4] prepared in Example 1 was added to a 20 wt% MEA solution, and the catalyst addition amount was 0.5 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. After the MEA solution was completely saturated with absorption, desorption was carried out at a desorption temperature of 110 °C and a reaction time of 60 minutes.

[0080] Application Example 3

[0081] The ionic liquid catalyst [Me3NH][ZnCl3] prepared in Example 2 was added to a 20 wt% MEA solution, and the catalyst addition amount was 1 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. After the MEA solution was completely saturated with absorption, desorption was carried out at a desorption temperature of 95 °C and a reaction time of 60 minutes.

[0082] Application Example 4

[0083] The ionic liquid catalyst [Me3NH][ZnCl3] prepared in Example 2 was added to a 20 wt% MEA solution, and the catalyst addition amount was 2 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. After the MEA solution was completely saturated with absorption, desorption was carried out at a desorption temperature of 90 °C and a reaction time of 60 minutes.

[0084] Application Example 5

[0085] The ionic liquid catalyst prepared in Example 3 was added to a 20 wt% MEA solution, and the catalyst addition amount was 1.25 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. After the MEA solution was completely saturated with absorption, desorption was carried out at a desorption temperature of 95 °C and a reaction time of 60 minutes.

[0086] Application Example 6

[0087] The ionic liquid catalyst prepared in Example 4 was added to a 20 wt% MEA solution, and the catalyst addition amount was 0.75 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. Desorption was carried out after the MEA solution was completely saturated with absorption. The desorption temperature was 105 °C, and the reaction time was 60 minutes.

[0088] Application Example 7

[0089] The ionic liquid catalyst prepared in Example 5 was added to a 20 wt% MEA solution, and the catalyst addition amount was 1 wt%. After mixing evenly, it was used as an absorbent for CO2 absorption. Desorption was carried out after the MEA solution was completely saturated with absorption. The desorption temperature was 110 °C, and the reaction time was 60 minutes.

[0090] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A dual-acid-functionalized ionic liquid, characterized in that, It includes two types of acidic sites, where: the cationic part is an organic quaternary ammonium salt with Bronsted acid sites and amphoteric properties, and the anionic part is a metal chloride with Lewis acid sites.

2. The dual-acid-functionalized ionic liquid according to claim 1, wherein The organic quaternary ammonium salt includes one or more of triethylamine hydrochloride, trimethylamine hydrochloride, and isopropylamine hydrochloride.

3. The dual-acid-functionalized ionic liquid according to claim 1, characterized in that, The metal chloride includes one or more of aluminum chloride, copper chloride, zinc chloride, and ferrous chloride.

4. A dual-acid-functionalized ionic liquid according to claim 1, characterized in that, The molar ratio of the organic quaternary ammonium salt to the metal chloride is 1:(0.2 - 10).

5. A method for preparing a dual-acid-functionalized ionic liquid according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Under ice bath conditions, prepare an organic quaternary ammonium salt solution. (2) Add the metal chloride to the organic quaternary ammonium salt solution in portions, stir and react under water bath conditions, and then stir at room temperature. (3) Rotate evaporate the stirred mixture, and then dilute the ionic liquid.

6. The preparation method of a dual-acid-functionalized ionic liquid according to claim 5, wherein, (2) includes one or more of the following: i) The molar ratio of the organic quaternary ammonium salt to the metal chloride is 1:(0.2 - 10); ii) The temperature of the stirring reaction is 60 - 100 °C, and the time of the stirring reaction is 8 - 12 hours; iii) The stirring time at room temperature is 10 - 15 hours.

7. The preparation method of a dual-acid-functionalized ionic liquid according to claim 5, characterized in that, (3) includes one or more of the following: i) The rotation evaporation is carried out under vacuum conditions, the temperature of the rotation evaporation is 80 - 100 °C, and the time of the rotation evaporation is 4 - 6 hours; ii) The dilution is to dilute the concentration of the organic quaternary ammonium salt in the ionic liquid to 0.8 - 1.2 mol / L.

8. A method for desorbing CO2 in an organic amine solution, characterized in that, It includes the following steps: Add the double - acid functionalized ionic liquid as described in any one of claims 1 - 4 to the organic amine solution, and then carry out the desorption of CO2 in the organic amine solution.

9. The method for desorbing CO2 in an organic amine solution according to claim 8, wherein The mass concentration of the ionic liquid in the organic amine solution is 0.5 - 2%.

10. A method for desorbing CO2 from an organic amine solution according to claim 8, characterized in that, The temperature of the desorption is 90 - 110 °C.

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