Preparation and Application of a Deep Eutectic Solvent for Efficient CO2 Capture

Abstract

The invention discloses the preparation and application of a deep eutectic solvent for efficiently capturing CO2, belonging to the technical field of high-temperature and efficient CO2 capture. The deep eutectic solvent of the invention is prepared from cyclodextrin and amines. The DES prepared by the invention can endow volatile amines with high stability; the DES system has a high absorption capacity for CO2 at high temperatures, low solvent volatility, small loss, good thermal stability, good recycling effect, and can achieve the advantages of efficient and reversible absorption of CO2. This is because hydrogen bonding occurs between cyclodextrin and the hydroxyl groups of ethanolamine, while the amino groups that have an adsorption effect on CO2 are retained. At the same time, due to the hydrogen bonding effect, the volatility of ethanolamine is greatly reduced. Hydrogen bonding occurs between cyclodextrin and the amino groups in enamines such as triethylenetetramine, which also has the effect of reducing its volatility, while retaining other amino groups for CO2 absorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of CO2 capture, and specifically relates to a preparation method of cyclodextrin-based deep eutectic solvents and their application in CO2 capture. Background Art

[0002] With the development of society, the emission of CO2 gas has intensified, and the resulting environmental problems have become increasingly serious. How to effectively reduce CO2 emissions, or even achieve "zero emissions", has attracted extensive attention worldwide. CO2 capture is not only beneficial to coping with and alleviating climate change, but also can be used as a high-quality raw material for C1 resources and high-value-added chemical products. Currently, the main CO2 capture methods include absorption method, membrane separation method, cryogenic distillation method, adsorption method, etc. Among them, the chemical absorption method with aqueous alkanolamine solution has the widest application range in industry. However, its further development is restricted due to the easy volatilization of the absorbent, low absorption temperature, high regeneration energy consumption, and corrosion of equipment.

[0003] Deep eutectic solvents (DESs) are multicomponent mixtures formed by hydrogen bond donors and hydrogen bond acceptors through hydrogen bond interactions, with a melting point lower than that of any component. They are also known as ionic liquid-like solvents. As a new type of solvent, DESs not only inherit the advantages of low vapor pressure and adjustable physicochemical properties of ionic liquids, but also have the characteristics of simple preparation process, high purity, high atomic utilization rate, and biodegradability. They have been preliminarily applied in the field of gas capture and shown good capture ability. Patent (CN114768479A) prepared DESs using imidazole and ethanolamine as raw materials at 70-90 °C for CO2 absorption. After 5 cycles at 30 °C, the absorption capacity did not change significantly. In addition, other DESs used as absorbents include DESs prepared from quaternary ammonium salts and / or quaternary phosphonium salts and ethylene glycol (CN108993098A), DESs composed of double negatively charged anion-functionalized ionic liquids as hydrogen bond acceptors and polyols as hydrogen bond donors (CN109908707A), mixtures of alkanolamine compounds and DESs (CN111603894A, CN111603895A), binary or ternary DESs composed of calcium chloride and ethanolamine, etc. (CN108993125A, CN109200760A). Currently, when using DESs as absorbents for CO2 capture, due to the limited types and amounts of hydrogen bond ligands, the CO2 absorption capacity per unit mass of the deep eutectic solvent is limited, and the absorption amount is small.

[0004] Cyclodextrin is a degradation product of starch and has good biocompatibility. Due to its special molecular structure of "hydrophobic inside and hydrophilic outside", it can not only form inclusion compounds with a variety of organic small molecules, but also activate reactants through non-covalent bond forces to promote the progress of the reaction. Although a variety of different types of DESs have been synthesized, there are few studies and reports on cyclodextrin-based DESs. Patent CN111234733B prepared an adhesive using cyclodextrin, malic acid, tartaric acid, etc. as raw materials, and its relatively high viscosity limits its application in fields such as extraction and separation. Patent CN114196431B prepared acidic DESs using cyclodextrin and small molecule organic acids as raw materials for oxidative desulfurization of fuel, but the acidic DESs have poor absorption effects on acidic gases such as CO2. Cyclodextrin contains a large number of hydroxyl groups, and these hydroxyl groups can form functional groups with CO2 (Acta Chimica Sinica, 2013, 29(8), 1645-1648). Summary of the Invention

[0005] A class of liquid alkaline cyclodextrin-based DESs is synthesized by using cyclodextrin and ethanolamine through hydrogen bonding, and a preparation method and application of a CO2 absorption liquid based on DESs are provided through special hydrogen bonding and amino adsorption sites, so as to solve the disadvantages of small CO2 absorption amount and high loss caused by easy volatilization of the solvent in the current existing technologies.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a deep eutectic solvent for efficiently capturing CO2, comprising the following steps:

[0008] Step 1, mixing cyclodextrin and a hydrogen bond donor and stirring to obtain a cyclodextrin-based deep eutectic solvent;

[0009] Step 2, introducing CO2 into the cyclodextrin-based deep eutectic solvent for absorption. When the weight no longer changes, it indicates that the adsorption equilibrium is reached, and the adsorption amount is obtained; then switch CO2 to N2 for regeneration.

[0010] Further, the cyclodextrin is any one or a mixture of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0011] Further, the hydrogen bond donor is any one or a mixture of ethanolamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc.

[0012] Further, the molar ratio of cyclodextrin to the hydrogen bond donor is 1:2 to 1:4.

[0013] Further, the stirring temperature in Step 1 is 30°C to 80°C.

[0014] Further, the stirring time in Step 1 is 10 to 30 min.

[0015] Further, in step 2, CO2 is introduced into the cyclodextrin-based deep eutectic solvent for absorption, and the absorption temperature is 30°C to 110°C.

[0016] Further, in step 2, N2 is switched to for regeneration, and the temperature of the regeneration process is 80°C to 110°C.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The DES prepared by the present invention can make volatile amines have high stability.

[0019] 2. The DES system of the present invention has a high absorption capacity for CO2 at high temperatures, low solvent volatility, small loss, good thermal stability, good recycling effect, and can achieve efficient and reversible absorption of CO2. Description of the Drawings

[0020] Figure 1 It is the infrared spectrum of DES prepared from β-cyclodextrin, ethanolamine, and their different ratios.

[0021] Figure 2 It is the nuclear magnetic spectrum of DES prepared from β-cyclodextrin, ethanolamine, and their different ratios.

[0022] Figure 3 It is the recycling performance of β-cyclodextrin-based DES at 80°C. Detailed Embodiments

[0023] The present invention is illustrated by the following examples, but the present invention is not limited to the following examples. Without departing from the scope of the above-mentioned purpose, various changes and implementations are included in the technical scope of the present invention.

[0024] Example 1

[0025] The hydrogen bond acceptor α-cyclodextrin and the hydrogen bond donor ethanolamine are added to a round-bottom flask in a molar ratio of 1:3, heated and stirred at 30°C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES is taken into an absorption tube, and CO2 is introduced at 80°C. After absorption reaches equilibrium, the absorption amount mass ratio is 28.3%.

[0026] Example 2

[0027] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine are added to a round-bottom flask in a molar ratio of 1:3, heated and stirred at 30°C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES is taken into an absorption tube, and CO2 is introduced at 80°C. After absorption reaches equilibrium, the absorption amount mass ratio is 28.7%.

[0028] Example 3

[0029] The hydrogen bond acceptor γ-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 28.1%.

[0030] Example 4

[0031] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:2, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 25.7%.

[0032] Example 5

[0033] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:4, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 30.3%.

[0034] Example 6

[0035] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor tetraethylenepentamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 80 °C for 30 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 15.4%.

[0036] Example 7

[0037] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor pentaethylenehexamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 80 °C for 20 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 13.7%.

[0038] Example 8

[0039] The hydrogen bond acceptor α-cyclodextrin and the hydrogen bond donor triethylenetetramine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 50 °C for 20 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After absorption reached equilibrium, the mass ratio of the absorption amount was 23.8%.

[0040] Example 9

[0041] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 110 °C. After the absorption reached equilibrium, the mass ratio of the absorption amount was 20.6%.

[0042] Example 10

[0043] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 30 °C. After the absorption reached equilibrium, the mass ratio of the absorption amount was 30.1%.

[0044] Example 11

[0045] The hydrogen bond acceptor β-cyclodextrin and the hydrogen bond donor ethanolamine were added to a round-bottom flask in a molar ratio of 1:3, and heated and stirred at 30 °C for 10 minutes to obtain a deep eutectic solvent. A certain amount of DES was taken into an absorption tube, and CO2 was introduced at 80 °C. After the absorption reached equilibrium, desorption was carried out. CO2 was switched to N2, and the temperature was raised to 110 °C for desorption. After being reused 10 times, the DES still maintained 96% of the initial absorption amount.

[0046] Figure 1 This is the infrared and nuclear magnetic spectra of β-cyclodextrin, ethanolamine, and DES prepared with different ratios involved in the present invention. It can be seen from the figure that hydrogen bonds are formed between the raw materials.

[0047] Figure 2 This is the recycling performance of β-cyclodextrin-based DES at 80 °C. It can be seen from the figure that the DES still maintained 91.5% of the absorption amount after being recycled 23 times.

[0048] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. Although the illustrative specific embodiments of the present invention are described above for the convenience of those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A preparation method of a deep eutectic solvent for efficient CO2 capture, characterized in that: It includes the following steps: Step 1: Mix cyclodextrin and hydrogen bond donor and stir to obtain cyclodextrin-based eutectic solvent; Step 2: Introduce CO2 into the cyclodextrin-based eutectic solvent for absorption. When the weight no longer changes, it indicates that the adsorption equilibrium is reached to obtain the adsorption capacity; switch CO2 to N2 for regeneration; The hydrogen bond donor is any one or a mixture of more than one of ethanolamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

2. The preparation method of a deep eutectic solvent for efficiently capturing CO2 according to claim 1, wherein: The cyclodextrin is any one or a mixture of more than one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

3. The preparation method of a deep eutectic solvent for efficiently capturing CO2 according to claim 1, characterized in that: The molar ratio of cyclodextrin to hydrogen bond donor is 1:2 to 1:

4.

4. The preparation method of a deep eutectic solvent for efficiently capturing CO2 according to claim 1, wherein: In Step 1, the stirring temperature is 30°C to 80°C.

5. The preparation method of a deep eutectic solvent for efficiently capturing CO2 according to claim 1, characterized in that: In Step 1, the stirring time is 10 to 30 min.

6. The preparation method of a deep eutectic solvent for efficiently capturing CO2 according to claim 1, characterized in that: In Step 2, introduce CO2 into the cyclodextrin-based eutectic solvent for absorption, and the absorption temperature is 30°C to 110°C.

7. The preparation method of the deep eutectic solvent for efficiently capturing CO2 according to claim 1, wherein in step 2, N2 is switched to for regeneration, and it is characterized in that: The temperature of the regeneration process is 80°C to 110°C.

8. Application of the eutectic solvent prepared by the preparation method according to claim 1 in highly efficient CO2 capture.

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