Carbon dioxide absorption liquid, its application and method for treating carbon dioxide

Abstract

This application belongs to the field of carbon dioxide absorption, and provides a carbon dioxide absorption liquid, its application and a method for treating carbon dioxide. The carbon dioxide absorption liquid contains water, a thermodynamic promoter and a kinetic promoter. Among them, the kinetic promoter includes amine-modified graphene oxide, and the amine-modified graphene oxide is graphene oxide modified with tertiary amine groups. The carbon dioxide absorption liquid has a high hydrate formation rate when reacting with carbon dioxide and can improve the separation efficiency of carbon dioxide.

Description

Technical Field

[0001] This application belongs to the field of gas adsorption. Specifically, a carbon dioxide absorbent solution, its application, and a method for treating carbon dioxide are provided. Background Art

[0002] With the progress of industrialization, climate change and environmental problems exacerbated by the excessive emission of carbon dioxide (CO2) have attracted wide attention. As one of the greenhouse gases, the concentration of carbon dioxide in the atmosphere has increased from 278 ppm at the start of the industrial revolution to over 400 ppm today. To control the temperature rise within 2°C, it is crucial to achieve net-zero carbon dioxide emissions as soon as possible. Currently, various methods have been developed to capture carbon dioxide from industrial flue gases, mainly including: chemical absorption, physical adsorption, membrane separation, cryogenic condensation, etc. Although these methods can alleviate the carbon dioxide emission problem to a certain extent, there are still some serious drawbacks. For example, the amine solution chemical absorption method, which is currently the most mature and widely used in industry, has problems such as high solvent circulation energy consumption, high cost, and equipment corrosion.

[0003] In recent years, gas hydrate technology has become a research hotspot due to its low energy consumption, low cost, simple operation process, environmental friendliness, etc. Carbon dioxide hydrate is an ice-like crystalline substance formed by CO2 gas molecules and water under high pressure and low temperature conditions. By utilizing the large difference in phase equilibrium during hydrate formation, CO2 in flue gas can be effectively separated. For flue gas containing multiple components, CO2 can be captured by water cavities in the form of solid hydrates, while the remaining components that are difficult to hydrate are released. Under changing ambient conditions, CO2 can be released again. Therefore, the carbon dioxide hydration technology is an effective combination of capture, transportation, and storage technologies, which can save a large number of steps and capital consumption in the disposal of CO2.

[0004] To improve the hydration adsorption effect, the research and development of gas promoters are particularly important for improving the gas separation technology using hydrates. Promoters are divided into thermodynamic promoters and kinetic promoters. Common kinetic promoters include surfactants, such as sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS), but most of these kinetic promoters have problems such as environmental pollution; thermodynamic promoters mainly include tetrahydrofuran, tetrabutylammonium fluoride, etc. These promoters can effectively shift the hydrate equilibrium conditions to milder conditions. However, the carbon dioxide separation based on hydrates is still limited by the slow hydrate formation rate and low carbon dioxide separation efficiency, which seriously hinders the development of this type of carbon dioxide separation technology. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to provide a carbon dioxide absorbent, its application, and a method for treating carbon dioxide. The carbon dioxide absorbent has a high hydrate formation rate when reacting with carbon dioxide and can improve the separation efficiency of carbon dioxide.

[0006] In a first aspect, the present application provides a carbon dioxide absorbent, which comprises water, a thermodynamic promoter, and a kinetic promoter. Among them, the kinetic promoter includes amine-modified graphene oxide, and the amine-modified graphene oxide is graphene oxide modified with tertiary amine groups.

[0007] In the carbon dioxide absorbent of the present application, the thermodynamic promoter can promote the hydration phase change equilibrium to move towards high temperature and low pressure. When used in combination with amine-modified graphene oxide as the kinetic promoter, it can further improve the utilization rate of the thermodynamic promoter and form more carbon dioxide hydrates faster. Among them, the amine-modified graphene oxide provides tertiary amine groups, and the tertiary amine groups will introduce more CO2 in the gas phase into the aqueous phase (R3N + H2O + CO2 = R3NH + +HCO 3- , where R represents the graphene oxide part), increasing the CO2 capacity in the liquid phase to better promote the occurrence of the hydration reaction. At the same time, the amine-modified graphene oxide does not affect the property of the graphene oxide part as a hydration kinetic promoter: due to the hydrophobic structure in the middle and hydrophilicity around the graphene oxide, it can connect water molecules at the hydrophilic end and gases at the hydrophobic end, playing a mass transfer role, similar to the role of a surfactant. In addition, since the hydration phase change reaction that occurs between the carbon dioxide absorbent of the present application and CO2 is a physical change, and the introduced amine-modified graphene oxide has no chemical reaction with CO2, the absorbed CO2 is naturally decomposed and released under normal temperature and pressure, greatly saving energy consumption.

[0008] In some embodiments of the present application, the mass content of the amine-modified graphene oxide is 90 - 120 mg / L.

[0009] In some embodiments of the present application, relative to 100 parts by weight of water, the mass of the thermodynamic promoter is 2 - 10 parts by weight.

[0010] In some embodiments of the present application, the amine-modified graphene oxide is prepared by modifying graphene oxide with an amino modifier, and the amino modifier is selected from at least one of alkanolamines and tertiary amine silane coupling agents, where the alkanolamine is diethanolamine and / or triethanolamine.

[0011] In some embodiments of the present application, the tertiary amine silane coupling agent is [3-(diethylamino)propyl]trimethoxysilane.

[0012] In some embodiments of the present application, the amino-modified graphene oxide is prepared by a method comprising the following steps: potassium hydroxide is added to the graphene oxide dispersion to activate the graphene oxide, then the alkanolamine is added, and the temperature is raised to reflux and reacted for 2 to 5 hours. The obtained solid-liquid product is filtered, washed, and dried.

[0013] Further, the concentration of graphene oxide in the graphene oxide dispersion is 1 to 3 mg / mL, the mass ratio of potassium hydroxide to graphene oxide is 1:(0.6 to 1.2), and the volume ratio of the alkanolamine to the graphene oxide dispersion is 1:(12 to 15).

[0014] In some embodiments of the present application, the amino-modified graphene oxide is prepared by a method comprising the following steps: the graphene oxide dispersion, the tertiary amine silane coupling agent, and the alcohol are mixed, stirred at 20 to 40 °C for 20 to 50 minutes, and the temperature is raised to reflux and reacted for 5 to 7 hours. The obtained solid-liquid product is filtered, washed, and dried.

[0015] Further, the concentration of graphene oxide in the graphene oxide dispersion is 1 to 3 mg / mL, the volume ratio of the graphene oxide dispersion to the alcohol is 1:(8 to 12), and the mass ratio of the tertiary amine silane coupling agent to graphene oxide is (10 to 20):1.

[0016] In some embodiments of the present application, the thermodynamic promoter is selected from one or more of tetrabutylammonium fluoride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium nitrate, cyclopentane, tetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, methylcyclopentane, and neohexane.

[0017] Further, the thermodynamic promoter is selected from tetrabutylammonium bromide (TBAB) and tetrahydrofuran (THF). Compared with other thermodynamic promoters, TBAB and THF have a synergistic effect in promoting the hydration phase change. THF enters the cage structure of the TBAB hydrate to displace the TBAB ions, and the displaced TBAB ions can recombine with water molecules to form CO2 hydrate again, thereby further improving the CO2 absorption efficiency.

[0018] In some embodiments of the present application, the kinetic promoter further includes an amino acid. When the hydration adsorption reaction occurs, a large amount of solid hydrate is generated, which covers the gas-liquid surface in large quantities, resulting in poor contact. The amino acid can effectively disperse the hydrate on the wall of the reaction kettle, thereby promoting the full contact of the gas-liquid interface and ensuring the full utilization of the amino-modified graphene oxide.

[0019] Further, in the carbon dioxide absorption liquid, the mass content of the amino acid is 1 to 10 mg / L.

[0020] In a second aspect, the present application provides the use of the carbon dioxide absorbent solution described in the first aspect of the present application in treating the waste gas from a cigarette factory or vehicle exhaust.

[0021] In a third aspect, the present application provides a method for treating carbon dioxide, the method comprising: subjecting a carbon dioxide-containing mixed gas to a hydration reaction with the carbon dioxide absorbent solution described in the first aspect of the present application to form a carbon dioxide hydrate.

[0022] In some embodiments of the present application, in the mixed gas, the volume concentration of carbon dioxide ≥ 10%.

[0023] In some embodiments of the present application, the temperature of the hydration reaction is 0 - 6°C, and the inlet pressure is 1.3 - 2.5 MPa.

[0024] In some embodiments of the present application, the method further comprises: desorbing the carbon dioxide hydrate, and the desorption temperature is 15 - 30°C. In particular, the formed hydrate can effectively release carbon dioxide at room temperature, greatly saving consumption.

[0025] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Detailed Embodiments

[0026] The embodiments of the present application are described in detail below. The described embodiments are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application.

[0027] The "range" disclosed in the present application is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range not explicitly recorded, and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each separately disclosed point or single value itself can be used as a lower limit or an upper limit and combined with any other point or single value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0028] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0029] The formation of hydrates requires the presence of guest gas molecules such as carbon dioxide, nitrogen, methane and other gases. Therefore, one of the key issues in the formation of carbon dioxide hydrates is how to introduce a large amount of carbon dioxide into the liquid phase to increase the effective gas-liquid contact. In traditional methods, carbon dioxide enters the liquid phase mainly relying on the driving force of gas phase pressure and the effect of surfactants to reduce the surface tension of the liquid phase. However, gas phase pressure is extremely costly for industrialization, and surfactants are polluting and cannot be recycled. Therefore, it is very necessary to enable more carbon dioxide to enter the liquid phase from the gas phase. At the same time, the sequestered carbon dioxide needs to be released under mild conditions so that the hydrate promoter can be recycled multiple times to reduce costs.

[0030] For this reason, a first aspect of the present application provides a carbon dioxide adsorption liquid, which comprises water, a thermodynamic promoter and a kinetic promoter, wherein the kinetic promoter comprises amine-modified graphene oxide.

[0031] In the present application, the amine-modified graphene oxide is graphene oxide modified with tertiary amine groups. The tertiary amine groups will introduce more CO2 in the gas phase into the aqueous phase, increasing the liquid phase CO2 capacity to better promote the occurrence of the hydration reaction, increasing the rate of the hydration phase change, and enabling the absorbed CO2 to be naturally decomposed and released at normal temperature and pressure. In particular, this way of promoting absorption and desorption is also different from the traditional method of capturing carbon dioxide with amine solutions. The amine solution method for absorbing carbon dioxide uses the specific chemical reaction between amine groups and carbon dioxide (R-NH2 + CO2 = R-NH 2+ —COO - , where R represents graphene oxide). During this kind of reaction process, the desorption of carbon dioxide requires a temperature of at least 65 °C or higher to release the carbon dioxide again.

[0032] In some embodiments, in the carbon dioxide adsorption liquid, the mass content of amine-modified graphene oxide is 90-120 mg / L, such as 90 mg / L, 95 mg / L, 97 mg / L, 98 mg / L, 100 mg / L, 105 mg / L, 110 mg / L, etc. In this case, while the amine-modified graphene oxide plays a role in promoting the hydration kinetically, it can further reduce the possibility of difficult hydration formation caused by its large-scale capture of gases.

[0033] In the present application, the amine-modified graphene oxide can be prepared by modifying graphene oxide with an amino modifier. By means of grafting reaction between oxygen-containing functional groups (such as epoxy groups) on graphene oxide and the amino modifier, the tertiary amine groups provided by the amino modifier can be introduced into the graphene oxide groups. As some examples, the graphene oxide (GO) can be prepared by the Hummers method or the improved Hummers method.

[0034] In some embodiments, the amino modifier may be selected from at least one of alkanolamines and tertiary amine silane coupling agents.

[0035] In the present application, the alkanolamine is diethanolamine (DEA) and / or triethanolamine (TEA).

[0036] Preferably, the tertiary amine silane coupling agent is [3-(diethylamino)propyl]trimethoxysilane.

[0037] As a specific embodiment, the amino-modified graphene oxide is alkanolamine-modified graphene oxide, and the preparation method of alkanolamine-modified graphene oxide includes:

[0038] (1) In the graphene oxide dispersion, potassium hydroxide is added to activate the graphene oxide;

[0039] (2) The alkanolamine is added, the temperature is raised to reflux and reacted for 2-5 h, and the obtained solid-liquid product is filtered, washed and dried.

[0040] Further, the concentration in the graphene oxide dispersion may be 1-3 mg / mL, the mass ratio of potassium hydroxide to graphene oxide may be 1:(0.6-1.2), and the volume ratio of alkanolamine to the graphene oxide dispersion may be 1:(12-15).

[0041] As another specific embodiment, the amino-modified graphene oxide is tertiary amine silane coupling agent-modified graphene oxide, and its preparation method includes: mixing the graphene oxide dispersion, the tertiary amine silane coupling agent and an alcohol, stirring at 20-40 °C for 20-50 minutes, raising the temperature to reflux and reacting for 5-7 h, and filtering, washing and drying the obtained solid-liquid product.

[0042] Further, the concentration of graphene oxide in the graphene oxide dispersion may be 1-3 mg / mL, the volume ratio of the graphene oxide dispersion to the alcohol (such as ethanol) may be 1:(8-12), and the mass ratio of the tertiary amine silane coupling agent to graphene oxide is (10-20):1.

[0043] In the present application, the thermodynamic promoter is intended to improve the conditions of the hydration phase change, and will shift the phase change towards high temperature and low pressure. The type of the thermodynamic promoter in the present application is not particularly limited, and the existing promoters can be referred to for selection. As some examples, the thermodynamic promoter may be selected from one or more of tetrabutylammonium fluoride, tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride, tetrabutylammonium nitrate, cyclopentane, tetrahydrofuran (THF), 1,3-dioxolane, 1,3-dioxane, methylcyclopentane, and neohexane, etc.

[0044] Preferably, the thermodynamic promoter is selected from tetrabutylammonium bromide and tetrahydrofuran.

[0045] More preferably, the molar ratio of tetrabutylammonium bromide to water is (0.1 - 0.5)∶100, such as 0.2∶100, 0.25∶100, 0.29∶100, 0.3∶100, 0.4∶100, etc.; the volume ratio of tetrahydrofuran to water is (1 - 5)∶100, such as 2∶100, 2.5∶100, 3∶100, 3.2∶100, 4∶100, 5∶100, etc.

[0046] In some embodiments, the kinetic promoter further includes an amino acid. Generally, the hydration adsorption reaction is carried out in a reaction kettle. A large amount of solid hydrate generated by the reaction will cover the gas - liquid surface, resulting in poor contact. However, the amino acid can effectively disperse the hydrate on the wall of the reaction kettle, promote the full contact of the gas - liquid interface, and ensure the full utilization of the amino - modified graphene oxide.

[0047] As some examples, the amino acid can be selected from one or more of L - leucine, methionine, tryptophan, isoleucine, norvaline, and aminoheptanoic acid.

[0048] In some embodiments, in the carbon dioxide absorption liquid, the mass content of the amino acid can be 1 - 10 mg / L, such as 1 mg / L, 2 mg / L, 5 mg / L, 8 mg / L, 10 mg / L, etc.

[0049] Preferably, the kinetic promoter is the amino - modified graphene oxide and the amino acid, and the mass ratio of the two is (8 - 12)∶1, such as 10∶1.

[0050] Optionally, the kinetic promoter further includes graphene oxide. In the carbon dioxide absorption liquid, the mass content of graphene oxide can be 0 - 10 mg / L, such as 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 8 mg / L, 10 mg / L, etc.

[0051] In some embodiments, in the carbon dioxide absorption liquid, the mass ratio of the thermodynamic promoter to the kinetic promoter can be (500 - 1000)∶1, such as 500∶1, 550∶1, 600∶1, 700∶1, 720∶1, 750∶1, 800∶1, etc.

[0052] The preparation method of the carbon dioxide absorption liquid of the present application is not particularly limited as long as various promoters can be evenly distributed in water. As some examples, the carbon dioxide absorption liquid can be prepared by mixing the thermodynamic promoter, kinetic promoter and water and then performing ultrasonic dispersion. The time of ultrasonic dispersion can be, for example, 10 to 50 min, and the ultrasonic dispersion can be carried out at room temperature or heating temperature.

[0053] As described above, the carbon dioxide absorption liquid of the present application increases the amount of CO2 entering the liquid phase from the gas phase, increases the gas-liquid contact. In the compound promoter composed of the thermodynamic promoter and the kinetic promoter, through the specific reaction of the tertiary amine structure with CO2, the problems of too low formation rate and poor formation efficiency of carbon dioxide hydrate are improved. It can significantly shorten the carbon dioxide hydration formation time and significantly increase the hydration formation amount, which is beneficial to the industrial capture of carbon dioxide absorption liquid, and the desorption of CO2 can be realized at room temperature, realizing the recycling of carbon dioxide absorption liquid, thereby reducing energy consumption and disposal costs.

[0054] Therefore, in the second aspect of the present application, there is provided the use of the carbon dioxide absorption liquid in treating the waste gas of a cigarette factory or vehicle exhaust.

[0055] In the third aspect of the present application, there is provided a method for treating carbon dioxide, the method comprising: performing a hydration reaction on a mixed gas of carbon dioxide and the carbon dioxide absorption liquid described in the first aspect of the present application to form carbon dioxide hydrate.

[0056] The method for treating carbon dioxide of the present application is not limited by the gas phase pressure and can effectively reduce the pressure limitation of the carbon dioxide hydration reaction. Usually, the operating pressure required for the hydration reaction needs to be greater than 2.5 MPa to have a high CO2 separation efficiency, and by using this carbon dioxide absorption liquid, the operating pressure can be effectively reduced to below 2.5 MPa.

[0057] In some embodiments, in the mixed gas, the volume concentration of carbon dioxide ≥ 10%, for example, 15% - 20%.

[0058] Optionally, the mixed gas further contains nitrogen, and the volume concentration of nitrogen can be 80% - 85%.

[0059] As some examples, the mixed gas is the waste gas of a cigarette factory.

[0060] In some embodiments, the temperature of the hydration reaction is 0 - 6 °C, and the inlet pressure is 1.3 - 2.5 MPa, for example, 2 MPa. In particular, usually, the operating pressure required for the hydration reaction needs to be greater than 2.5 MPa to have a high CO2 separation efficiency, and by using this carbon dioxide absorption liquid, the operating pressure can be effectively reduced to below 2.5 MPa.

[0061] In order to achieve the recycling of carbon dioxide, according to some embodiments, the method further comprises: desorbing carbon dioxide hydrate, preferably at a temperature of 10 to 30°C.

[0062] The following describes embodiments of the present application. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0063] Preparation Examples 1 to 4 are used to illustrate the preparation methods of graphene oxide and amine-modified graphene oxide used in the examples and comparative examples.

[0064] Preparation Example 1

[0065] Graphene oxide was prepared by a modified Hummers method.

[0066] Mix 3.0g graphite powder and 1.5g NaNO3 in a beaker, place the beaker in an ice bath, then add 69mL concentrated sulfuric acid (concentration is 98wt%) and stir. After the mixture is cooled to 0℃, slowly add 9.0g KMnO4 in 6 batches, control the reaction at a temperature below 20℃ with magnetic stirring for 2h, then raise the temperature of the reaction system to 35℃ and react at a constant temperature for 3h. Then raise the temperature to 98℃ and react at a constant temperature for 1.5h. Cool the resulting reaction product, and when the temperature drops to room temperature, pour the solution into a beaker containing 400mL of ice water and 3mL of 30wt% H2O2. After stirring evenly, filter with a standard sieve of 300μm, then centrifuge (10000r / min) to separate and retain the solids.

[0067] The solid was washed with 200 mL of distilled water, 200 mL of hydrochloric acid (mass concentration 10%) and 200 mL of ethanol, respectively, twice each time. The solid was separated by centrifugation after each washing. After the last centrifugation to separate the solid, the product was vacuum dried at room temperature for 12 h. The brown-black block solid finally obtained was the prepared graphene oxide (GO).

[0068] Preparation Example 2

[0069] Graphene oxide was diluted with water to a graphene oxide dispersion with a concentration of 2 mg / mL. 65 mL of graphene oxide dispersion was placed in a three-necked flask, 0.16 g of potassium hydroxide was added, and ultrasonic treatment was performed for 30 minutes. Then 5 mL of diethanolamine (DEA) was added to the above solution, and refluxed for 3 hours in a water bath at 80°C. After the reaction, a black solution was obtained, and the reaction product was dialyzed to neutrality and freeze-dried to obtain diethanolamine-modified graphene oxide, which was recorded as DEA-GO.

[0070] Preparation Example 3

[0071] The amino-modified graphene oxide was prepared according to the method of Preparation Example 2, except that diethanolamine was replaced with triethanolamine (TEA) to obtain triethanolamine-modified graphene oxide, denoted as TEA-GO.

[0072] Preparation Example 4

[0073] The graphene oxide was diluted with water to a graphene oxide dispersion with a concentration of 2 mg / mL. 15 mL of the graphene oxide aqueous dispersion and 0.5 g of [3-(diethylamino)propyl]trimethoxysilane were slowly added to a three-necked flask containing 150 mL of ethanol, stirred at room temperature for 40 minutes, then heated under reflux and reacted for 6 h. The product obtained from the reaction was subjected to solid-liquid separation, washed with ethanol and deionized water, and freeze-dried to obtain [3-(diethylamino)propyl]trimethoxysilane-modified graphene oxide, denoted as NEt2-GO.

[0074] The following examples are used to illustrate the carbon dioxide absorption liquid and the carbon dioxide treatment method of the present invention.

[0075] Comparative Example 1

[0076] Tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, 100 mg of L-methionine, and water (1 L, 55.6 mol) were mixed and ultrasonically dispersed at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as D1.

[0077] Comparative Example 2

[0078] Tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, 100 mg of graphene oxide, and water (1 L, 55.6 mol) were mixed and ultrasonically dispersed at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as D2.

[0079] Comparative Example 3

[0080] Tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, sodium dodecyl sulfate (SDS, 3 g), and water (1 L, 55.6 mol) were mixed and ultrasonically dispersed at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as D3.

[0081] Example 1

[0082] Tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, 100 mg of amino-modified graphene oxide NEt2-GO, and water (1 L, 55.6 mol) were mixed and ultrasonically dispersed at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as A1.

[0083] Example 2

[0084] Mix tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, 100 mg of amino-modified graphene oxide TEA-GO and water (1 L, 55.6 mol), and disperse them by ultrasonic wave at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as A2.

[0085] Example 3

[0086] Mix tetrabutylammonium bromide (51.6 g, 0.16 mol), 25 mL of tetrahydrofuran, 105 mg of amino-modified graphene oxide DEA-GO and water (1 L, 55.6 mol), and disperse them by ultrasonic wave at room temperature for 30 minutes to obtain a carbon dioxide absorption liquid, denoted as A3.

[0087] Example 4

[0088] Prepare the carbon dioxide absorption liquid according to the method of Example 1, except that 10 mg of L-methionine is additionally added. The prepared carbon dioxide absorption liquid is denoted as B1.

[0089] Example 5

[0090] Prepare the carbon dioxide absorption liquid according to the method of Example 2, except that 100 mg of TEA-GO is replaced by 97 mg of TEA-GO and 3 mg of L-methionine. The prepared carbon dioxide absorption liquid is denoted as B2.

[0091] Example 6

[0092] Prepare the carbon dioxide absorption liquid according to the method of Example 2, except that 100 mg of TEA-GO is replaced by 97 mg of TEA-GO and 3 mg of graphene oxide. The prepared carbon dioxide absorption liquid is denoted as B3.

[0093] The specific compositions of the absorption liquids in the above examples and comparative examples are shown in Table 1.

[0094] Test Example

[0095] 1. Hydration effect test

[0096] Carbon dioxide adsorption: Lower the temperature of the hydration reaction kettle filled with the carbon dioxide absorption liquid by 6 °C, introduce a mixed gas of carbon dioxide and nitrogen (the volume concentration of CO2 is 15%) into the hydration reaction kettle, control the inlet pressure to be 2 MPa, turn on the stirring, and the stirring speed is 900 rpm; when the pressure reduction amplitude slows down, turn off the stirring, and stop the reaction after 2 hours of reaction.

[0097] Carbon dioxide desorption: After the reaction, the temperature of the hydration reactor was raised to 25 °C to start desorption. After 30 minutes of desorption, the gas in the reactor was tested by gas chromatography to calculate the carbon dioxide separation efficiency. The calculation formula for the separation efficiency is:

[0098] Among them,

[0099] S Fr represents the CO2 separation efficiency;

[0100] is the amount of substance of CO2 before the reaction,

[0101] is the amount of substance of CO2 detected at the outlet end after the reaction;

[0102] The test results are shown in Table 1.

[0103] Table 1

[0104]

[0105] 1: The volume ratio of THF is based on the volume of water;

[0106] 2: The molar ratio of TABA is based on the molar mass of water;

[0107] 3: The mass of SDS is based on the mass of water.

[0108] Combined with Table 1, it can be seen that by comparing Examples 1-6 with Comparative Examples 1-3, compared with the commonly used amino acids, GO, and SDS, introducing amino group-modified graphene oxide as a kinetic promoter can improve the formation rate of CO2 hydrate.

[0109] By comparing Examples 4-5 with Examples 1-2 and 6, it can be seen that compared with not adding amino acids and only using amino group-modified graphene oxide (Examples 1-2), or using a combination of amino group-modified graphene oxide and GO (Example 6) as a kinetic promoter, using amino acids and amino group-modified graphene together as a kinetic promoter (Examples 4-5) can significantly improve the CO2 separation efficiency. Although GO is slightly stronger than amino acids in terms of kinetic promotion effect (see Comparative Examples 1 and 2), the combination of amino acids and amino group-modified graphene oxide has a slightly stronger kinetic promotion effect than the combination of GO and amino group-modified graphene oxide, indicating that there is a synergistic promotion effect between amino group-modified graphene oxide and amino acids: Amino acids can effectively disperse the hydrate on the reactor wall, thus ensuring full contact at the gas-liquid interface and ensuring the full utilization of amino group-modified graphene oxide.

[0110] 2. Cyclic stability test

[0111] The adsorption and desorption experiments of carbon dioxide were carried out according to item 1 (hydration effect test). Taking this as a cycle, the adsorption and desorption experiments were carried out cyclically. After each cycle test, the CO2 separation efficiency was measured. The test results of the CO2 separation efficiency of each experiment are shown in Table 2.

[0112] Table 2

[0113] Absorbent liquid number First time Second time Third time Fourth time Fifth time Sixth time D2 62.68％ 61.2％ 60.56％ 58.86％ 58.5％ 58.47％ A1 67.77％ 66.82％ 66.04％ 64.92％ 64.68％ 64.43％ A2 69.64％ 68.75％ 67.48％ 65.43％ 65.26％ 65.18％ B1 71.67％ 69.47％ 68.78％ 66.57％ 66.43％ 66.58％

[0114] Combining Table 1 and Table 2, it can be seen that the CO2 separation efficiencies of A1, A2 and B1 after 5 cycles of use only decreased by about 5% respectively, which is comparable to that of the absorbent (D2) using GO as the kinetic promoter. On the one hand, it shows that the absorbent with graphene oxide modified with tertiary amino groups as the kinetic promoter can achieve the phase change desorption of CO2 at 25°C (if the phase change desorption at room temperature is not achieved, the CO2 separation efficiency of the absorbent will decrease significantly after cyclic use); on the other hand, it also shows that the graphene oxide modified with tertiary amino groups can be recycled and has high cyclic stability.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered by the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A carbon dioxide absorption liquid, characterized in that, It contains water, a thermodynamic promoter and a kinetic promoter. Among them, the kinetic promoter includes amine-modified graphene oxide and an amino acid, and the amine-modified graphene oxide is graphene oxide modified with tertiary amine groups; the thermodynamic promoter is tetrabutylammonium bromide and tetrahydrofuran; the mass content of the amine-modified graphene oxide is 90 - 120 mg / L; relative to 100 parts by weight of water, the mass of the thermodynamic promoter is 2 - 10 parts by weight.

2. The carbon dioxide absorption liquid according to claim 1, wherein The amine-modified graphene oxide is prepared by modifying graphene oxide with an amino modifier, and the amino modifier is selected from at least one of alkanolamines and tertiary amine silane coupling agents, where the alkanolamine is diethanolamine and / or triethanolamine.

3. The carbon dioxide absorption liquid according to claim 2, characterized in that, The tertiary amine silane coupling agent is [3-(diethylamino)propyl]trimethoxysilane.

4. The carbon dioxide absorbent solution according to claim 2, wherein, The amine-modified graphene oxide is prepared by a method comprising the following steps: In a graphene oxide dispersion, potassium hydroxide is added to activate the graphene oxide, then the alkanolamine is added, the temperature is raised to reflux and reacted for 2 - 5 h, and the obtained solid-liquid product is filtered, washed and dried.

5. The carbon dioxide absorbent solution according to claim 4, characterized in that, The concentration of graphene oxide in the graphene oxide dispersion is 1 - 3 mg / mL, the mass ratio of potassium hydroxide to graphene oxide is 1:(0.6 - 1.2), and the volume ratio of the alkanolamine to the graphene oxide dispersion is 1:(12 - 15).

6. The carbon dioxide absorption liquid according to claim 2, wherein The amine-modified graphene oxide is prepared by a method comprising the following steps: The graphene oxide dispersion, the tertiary amine silane coupling agent and an alcohol are mixed, stirred at 20 - 40 °C for 20 - 50 minutes, the temperature is raised to reflux and reacted for 5 - 7 h, and the obtained solid-liquid product is filtered, washed and dried.

7. The carbon dioxide absorption liquid according to claim 6, wherein The concentration of graphene oxide in the graphene oxide dispersion is 1 - 3 mg / mL, the volume ratio of the graphene oxide dispersion to the alcohol is 1:(8 - 12), and the mass ratio of the tertiary amine silane coupling agent to graphene oxide is (10 - 20):

1.

8. The carbon dioxide absorbent according to any one of claims 1-7, characterized in that, The molar ratio of tetrabutylammonium bromide to water is (0.1 - 0.5):100, and the volume ratio of tetrahydrofuran to water is (1 - 5):

100.

9. The carbon dioxide absorption liquid according to claim 1, characterized in that, In the carbon dioxide absorbent, the mass content of the amino acid is 1 - 10 mg / L.

10. The carbon dioxide absorption liquid according to claim 1, characterized in that, The total mass content of the kinetic promoter is 100 - 120 mg / L.

11. Use of the carbon dioxide absorbent according to any one of claims 1 - 10 in treating flue gas from a cigarette factory or vehicle exhaust.

12. A method for treating carbon dioxide, characterized in that, The method includes: Hydrating a mixed gas containing carbon dioxide with the carbon dioxide absorbent according to any one of claims 1 - 10 to form a carbon dioxide hydrate.

13. The method according to claim 12, characterized in that In the mixed gas, the volume concentration of carbon dioxide ≥ 10%.

14. The method according to claim 12, wherein The temperature of the hydration reaction is 0 - 6 °C, and the inlet pressure is 1.3 - 2.5 MPa.

15. The method according to any one of claims 12-14, characterized in that, It also includes: Desorbing the carbon dioxide hydrate, and the desorption temperature is 10 - 30 °C.

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