Carbon capture absorbent, preparation method and application thereof, and method for generating carbon dioxide hydrate

Abstract

This application relates to the field of carbon dioxide absorption and provides a carbon capture absorbent, its preparation method, its application, and a method for generating carbon dioxide hydrates. The carbon capture absorbent comprises water and a promoter dispersed therein, wherein the promoter comprises reduced graphene oxide and amino-modified graphene oxide. The carbon capture absorbent promotes the reaction of CO2 and water to form hydrates, reducing the high pressure required for the hydration reaction, shortening the hydration reaction process, and improving the CO2 absorption efficiency.

Description

Technical Field

[0001] The present application belongs to the field of gas adsorption, and specifically provides a carbon capture absorbent, a preparation method and application thereof, and a method for generating carbon dioxide hydrate. Background Art

[0002] Traditional methods for capturing CO2 include chemical absorption, physical adsorption, membrane separation, and cryogenic condensation. While these methods can address CO2 emissions to some extent, they generally suffer from significant pollution, high costs, and corrosion. In recent years, the hydrate method has garnered widespread attention due to its low cost, environmental friendliness, and low energy consumption. However, the slow growth rate of hydrates, low CO2 separation efficiency, and low separation factor are key limitations in the development of hydrate-based CO2 capture technology. The development of accelerators is crucial for improving hydrate-based gas separation technology. Current accelerators are categorized as thermodynamic and kinetic. Thermodynamic accelerators can lower the thermodynamic equilibrium conditions by occupying hydrate cage pores. Small organic molecules (e.g., tetrahydrofuran) can act as thermodynamic accelerators in the hydration reaction, but these organic molecules are highly toxic. Kinetic accelerators can influence the hydrate formation rate, gas storage capacity, and induction time, and research primarily focuses on surfactants and nanomaterials.

[0003] The use of surfactants significantly reduces the induction time required for hydrate nucleation, but the gas storage capacity is not improved, and surfactants will produce severe foaming during the hydrate dissociation process, which not only affects the application of carbon dioxide hydrates, but also causes the loss of surfactants; nanomaterials generally include metal components, which are easily affected by guest molecules (CO2) and are not acid-resistant. They are easy to lose, resulting in poor recyclability and affecting adsorption efficiency. Related technologies mention that the use of Al2O3, SiO2, Ag and Cu nanoparticles will have a kinetic effect on CO2-CH4 hydrates, but the required conditions have high energy consumption and the preparation process of nanofluids is complex and costly, which limits its industrialization.

[0004] In addition, the flue gas emitted by thermal power plants and other sources is the main source of industrial carbon emissions. Its CO2 concentration is relatively low (the volume concentration generally does not exceed 20%), which makes it difficult to capture. The formation of hydrates between low-concentration CO2 and water requires low temperature and high pressure conditions above 5MPa, and hydrate induction will not begin until more than 1 hour. The reaction conditions are harsh and the adsorption efficiency is too low. Summary of the Invention

[0005] The present application aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] The present application aims to provide a carbon capture absorbent, its preparation method, and application, as well as a method for generating carbon dioxide hydrates. The carbon capture absorbent can promote the reaction of CO2 and water to form hydrates, reduce the high pressure conditions required for the hydration reaction, shorten the hydration reaction process, and improve the CO2 absorption efficiency.

[0007] In a first aspect, the present application provides a carbon capture absorbent comprising water and a promoter dispersed therein, wherein the promoter comprises reduced graphene oxide and amino-modified graphene oxide.

[0008] The carbon capture absorbent of the present application is an acid-resistant CO2 absorption liquid, which uses a compound of reduced graphene oxide (rGO) and amino-modified graphene oxide as a promoter, which can shorten the reaction process of hydrates, improve reaction conditions, and especially improve the absorption efficiency of CO2 in low-concentration CO2 mixed gas. Specifically, on the one hand, reduced graphene oxide can volatilize its nanoparticle properties, which can promptly remove the heat generated during the formation of carbon dioxide hydrates, form a more suitable temperature field, enhance the thermal conductivity and heat transfer performance of the hydration system, and increase the heterogeneity of the hydrate formation system, thereby providing an environment and nucleation sites for heterogeneous nucleation. On the other hand, the small amount of defect sites on the surface of reduced graphene oxide have more oxygen, which contributes to better stability in water and is not easy to agglomerate; amino-modified graphene oxide has surfactant properties, which can reduce the energy between interfaces, expand the contact area between phases, increase the solubility of gas in the liquid phase, accelerate the growth rate of hydrates, and the larger specific surface area can better bring molecules from the gas phase into the liquid phase to form hydrate crystal nuclei. The amino groups grafted on the surface of graphene oxide are more affinity with CO2 molecules, and can avoid the excessively high desorption temperature caused by the direct reaction of organic amines (such as MEA, MDEA) with CO2.

[0009] In some embodiments of the present application, in the carbon capture absorbent, the concentration of the reduced graphene oxide is 0.1 to 1 g / L.

[0010] In some embodiments of the present application, the reduced graphene oxide has a sheet diameter of 0.02 to 10 μm. Preferably, the reduced graphene oxide has a sheet diameter of 0.02 to 2 μm.

[0011] In some embodiments of the present application, the reduced graphene oxide is prepared by a chemical reduction method.

[0012] Furthermore, the reduced graphene oxide is prepared by a method comprising the following steps: reacting graphene oxide with a reducing agent in the presence of an optional stabilizer at 90-95° C. for 12-25 hours.

[0013] Furthermore, the reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; and the stabilizer is tryptophan.

[0014] Furthermore, the mass ratio of the graphene oxide to the reducing agent is 1:(0.7-1).

[0015] Furthermore, the mass ratio of the reducing agent to the stabilizer is 1:(0-0.8).

[0016] In some embodiments of the present application, the concentration of the amino-modified graphene oxide is 0.5 to 1.5 g / L.

[0017] In some embodiments of the present application, the amino-modified graphene oxide is prepared by grafting an amino-modifying agent with graphene oxide, wherein the amino-modifying agent is an aminosilane coupling agent.

[0018] Furthermore, the aminosilane coupling agent is selected from γ-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane.

[0019] In some embodiments of the present application, the method for aminated modification of the graphene oxide using an aminosilane coupling group comprises the following steps:

[0020] Adding the aminosilane coupling agent to a solvent containing water, and stirring in a constant temperature water bath at 30 to 45° C. for 10 to 60 minutes to pre-hydrolyze the aminosilane coupling agent;

[0021] Graphene oxide is added and the temperature is raised to 50-60° C. and stirred for 3-7 hours to form amino-modified graphene oxide.

[0022] In some embodiments of the present application, in the carbon capture absorbent, the mass ratio of the reduced graphene oxide to the amino-modified graphene oxide is 1:(1-10). In this way, more nucleation sites can be provided for hydrates.

[0023] In a second aspect, the present application provides a method for preparing the carbon capture absorbent described in the first aspect of the present application, the method comprising: uniformly dispersing reduced graphene oxide and amino-modified graphene oxide in water to obtain the carbon capture absorbent.

[0024] In a third aspect, the present application provides the use of the carbon capture absorbent described in the first aspect of the present application in removing CO2 from flue gas from tobacco plants, refrigeration energy-saving equipment, refinery gas, natural gas or synthesis gas.

[0025] In a fourth aspect, the present application provides a method for generating carbon dioxide hydrate, comprising: introducing a mixed gas containing carbon dioxide into a reactor containing the carbon capture absorbent described in the first aspect of the present application to carry out a hydration reaction to generate carbon dioxide hydrate.

[0026] Compared with the organic amine capture method for capturing carbon dioxide, the hydrate formation method of the present application combines the high affinity between organic amines (amino-modified graphene oxide) and carbon dioxide and the large specific surface area of reduced graphene oxide, which can achieve lower regeneration energy consumption and higher adsorption capacity.

[0027] In some embodiments of the present application, the volume fraction of carbon dioxide in the mixed gas is 15% to 20%.

[0028] In some embodiments of the present application, the air inlet pressure of the reactor is not higher than 4 MPa, preferably 1 to 3 MPa.

[0029] In some embodiments of the present application, the hydration reaction is carried out under stirring conditions, with a stirring speed of 400-600 rpm and a reaction temperature of 2-5°C.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0032] Figure 1 This is the reaction mechanism diagram of KH-550 ammoniation modification of graphene oxide. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0034] The "range" disclosed in this application is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range that is not clearly stated, and any lower limit can be combined with other lower limits to form a range that is not clearly stated, and similarly any upper limit can be combined with any other upper limit to form a range that is not clearly stated. In addition, each separately disclosed point or single value itself can be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form a range that is not clearly stated.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0036] As mentioned above, although the addition of various traditional promoters has partially solved the problems of slow hydration rate, low gas storage capacity and poor separation efficiency of the hydrate method, the problems of toxic organic promoters, gas production by surfactants hindering the penetration and dissolution of CO2 at the gas-liquid interface, and the acid resistance of nano-ions still limit the rapid development of hydrate technology. Therefore, it is urgent to develop new green and efficient promoters.

[0037] To this end, a first aspect of the present application provides a carbon capture absorbent, comprising water and a promoter dispersed therein, wherein the promoter includes reduced graphene oxide and amino-modified graphene oxide.

[0038] This application uses amino-modified graphene oxide and composite reduced graphene oxide as promoters for carbon capture absorbents. The combination of the two is used for hydration-based adsorption of carbon dioxide, which not only improves the adsorption efficiency, accelerates the adsorption reaction, and optimizes the reaction conditions, but also makes the carbon capture absorbent green, non-toxic, environmentally friendly, and recyclable.

[0039] In the present application, the reduced graphene oxide (rGO) can accelerate the induction time and promote hydrate nucleation. Compared with traditional nanoparticles, the reduced graphene oxide has fewer surface defects and is not easy to agglomerate and settle.

[0040] In the present application, the reduced graphene oxide can be obtained commercially or prepared by methods well known in the art, for example, reduced graphene oxide can be prepared by chemical reduction or thermal reduction.

[0041] As some preferred embodiments, the step of preparing the reduced graphene oxide by chemical reduction method includes: reacting graphene oxide with a reducing agent in the presence of an optional stabilizer at 90-95° C. for 12-25 hours.

[0042] Furthermore, the reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; and the stabilizer is tryptophan.

[0043] Furthermore, the mass ratio of the graphene oxide to the reducing agent is 1:(0.7-1), for example, 1:0.7, 1:0.8, 1:0.9, 1:1, etc.

[0044] Furthermore, the mass ratio of the reducing agent to the stabilizer is 1:(0-0.8), for example, 1:0.2, 1:0.5, 1:0.6, 1:0.7, etc.

[0045] In this application, the reduced graphene oxide flake diameter can be 0.02 to 10 μm, for example, 20 nm, 50 nm, 100 nm, 300 nm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, etc. Generally, the smaller the reduced graphene oxide particles, the greater the micromotion intensity, and the higher the heat and mass transfer efficiency. Preferably, the reduced graphene oxide flake diameter is 0.02 to 2 μm.

[0046] In the present application, different graphite raw materials can be first oxidized to obtain graphene oxide (GO), and then the graphene oxide can be reduced and homogenized to obtain reduced graphene oxide with different sheet diameters. The graphene oxide can be prepared, for example, by the Hummers method or the improved Hummers method.

[0047] In some embodiments, the concentration of the reduced graphene oxide in the carbon capture absorbent may be 0.1 to 1 g / L, for example, 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, etc. In order to promote hydrate growth and balance the system temperature during the reaction while further reducing the effect of solution concentration and viscosity on heat transfer efficiency, the concentration of the reduced graphene oxide is preferably 0.1 to 0.5 g / L.

[0048] In this application, amino-modified graphene oxide refers to graphene oxide with amino groups obtained by grafting graphene oxide. Amino-grafting modification can impart hydrophilic and hydrophobic regions to graphene oxide, promoting gas volume expansion. Furthermore, the introduction of amino groups can enhance CO2 selectivity and improve CO2 adsorption performance.

[0049] In some embodiments, the amino-modified graphene oxide is prepared by grafting an amino-modifying agent with graphene oxide to introduce amino groups into the graphene oxide, wherein the amino-modifying agent is an aminosilane coupling agent.

[0050] Furthermore, the aminosilane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane (KH-550) and 3-aminopropyltrimethoxysilane (APTMS).

[0051] As some specific embodiments, the method of modifying the graphene oxide by amino modification using an aminosilane coupling agent comprises the following steps:

[0052] Adding the aminosilane coupling agent to a solvent containing water, and stirring in a constant temperature water bath at 30 to 45° C. for 10 to 60 minutes to pre-hydrolyze the aminosilane coupling agent;

[0053] Add graphene oxide and heat to 50-60° C. and stir for 3-7 hours to form amino-modified graphene oxide. The solvent may be a mixture of water and ethanol, with a mass ratio of water to ethanol of 1:(0.8-1.2), for example, 1:1.

[0054] In some embodiments, the concentration of the amino-modified graphene oxide in the carbon capture absorbent can be 0.5 g / L to 1.5 g / L, for example, 0.5 g / L, 0.7 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.5 g / L, etc. If the content of the amino-modified graphene oxide is too low, the rate at which CO2 enters the liquid phase from the gas phase may be reduced; if its content is too high, it may cause agglomeration or increase the viscosity of the system, resulting in a reduction in available active sites, which can affect hydrate nucleation and growth and increase the difficulty of desorption. Preferably, the concentration of the amino-modified graphene oxide is 0.5 g / L to 1 g / L.

[0055] In some embodiments, in the carbon capture absorbent, the mass ratio of the reduced graphene oxide to the amino-modified graphene oxide is 1:(1-10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0056] A second aspect of the present application provides a method for preparing the carbon capture absorbent, which comprises: uniformly dispersing the reduced graphene oxide and the amino-modified graphene oxide in water to obtain the carbon capture absorbent.

[0057] In some embodiments, the method comprises the steps of:

[0058] Dispersing the reduced graphene oxide in water to prepare a reduced graphene oxide dispersion having a concentration of 5 to 12 g / L (e.g., 5 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, etc.);

[0059] The amino-modified graphene oxide and the reduced graphene oxide dispersion are mixed according to the required amount of the accelerator, and water is added to make up the volume and disperse to obtain a carbon capture absorbent.

[0060] According to the present application, the dispersion method of the promoter includes, but is not limited to, ultrasonic treatment.

[0061] The third aspect of the present application provides the use of the carbon capture absorbent in removing CO2 from flue gas from tobacco plants, refrigeration energy-saving devices, refinery gas, natural gas or synthesis gas.

[0062] In some embodiments, the volume concentration of CO2 in the tobacco factory exhaust gas is 15% to 20%.

[0063] As some examples, the carbon capture absorbent is used to treat tobacco factory exhaust gas, and the treatment method includes: under hydration reaction conditions, the tobacco factory exhaust gas is contacted with the carbon capture absorbent to generate hydrates; the hydration reaction conditions include: temperature of 2 to 5°C and intake pressure not higher than 4MPa.

[0064] Optionally, the treatment method further comprises: desorbing the formed hydrate, and the desorption temperature may be 50-65° C. The captured CO 2 can be transported, stored or reused through desorption.

[0065] The fourth aspect of the present application provides a method for generating carbon dioxide hydrate, which comprises: introducing a mixed gas containing carbon dioxide into a reactor containing the carbon capture absorbent described in the first aspect of the present application to perform a hydration reaction to generate carbon dioxide hydrate.

[0066] In some embodiments, the mixed gas is tobacco factory exhaust gas.

[0067] In some embodiments, the mass volume of carbon dioxide in the mixed gas is 15% to 20%. Furthermore, the mixed gas also contains nitrogen with a volume concentration of 80% to 85%.

[0068] The carbon capture absorbent of the present application is particularly suitable for treating mixed gases with low concentrations of carbon dioxide and reducing the reaction pressure required for generating hydrates.

[0069] In some embodiments, the air inlet pressure of the reactor is not higher than 4 MPa, such as 1 MPa, 2 MPa, 2.6 MPa, 3 MPa, 4 MPa, etc. Preferably, the air inlet pressure of the reactor is 1 to 3 MPa.

[0070] In some embodiments, the hydration reaction is carried out under stirring conditions with a stirring speed of 400-600 rpm and a hydration reaction temperature of 2-5°C.

[0071] 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 understood as limiting the present application.

[0072] Preparation Examples 1 to 5 are used to illustrate the graphene oxide, reduced graphene oxide, amino-modified graphene oxide and their preparation methods used in the following examples and comparative examples.

[0073] Preparation Example 1

[0074] This preparation example is used to illustrate the preparation of graphene oxide and reduced graphene oxide.

[0075] 3.0 g of nanosheet graphite and 1.5 g of NaNO3 were mixed evenly in a beaker, placed in an ice bath, and then 69 mL of concentrated sulfuric acid (concentration of 98 wt%) was added and stirred evenly. After the temperature dropped to 0°C, 9.0 g of KMnO4 was added in 6 batches. During the addition process, magnetic stirring was performed and the system temperature was kept below 20°C. After the addition was completed, the temperature was raised to 35°C and magnetic stirring was performed to react for 7 hours. After cooling to room temperature, the resulting reaction product solution was poured into a mixed solution containing 400 mL of ice water and 3 mL of 30 wt% H2O2 and stirred evenly. The mixture was then filtered and washed until neutral, and vacuum dried at room temperature for 12 hours to obtain graphene oxide (GO) as a brown-black solid.

[0076] GO was dispersed in water to obtain a 10 g / L GO dispersion. A 4 L beaker containing the GO dispersion was placed in a water bath, heated to 90°C, and stirred at 500 rpm. 40 g of ascorbic acid and 20 g of tryptophan were added, followed by a 24-hour constant temperature reaction. The resulting solution was allowed to stand for one day before vacuum filtration and repeated washing with water until the pH reached neutral, yielding reduced graphene oxide (rGO). The rGO was then mixed with water to obtain a 2.5 g / L rGO dispersion. This dispersion was homogenized five times with a high-pressure homogenizer to obtain reduced graphene oxide flakes with a diameter of 20 nm.

[0077] Preparation Examples 2-3

[0078] Graphene oxide and reduced graphene oxide were prepared according to the method of Preparation Example 1, except that the nanosheet-sized graphite was replaced with graphite powder (325 mesh), and after being prepared into rGO solution, it was homogenized twice and once by a homogenizer, respectively, to obtain reduced graphene oxide with a sheet size of 2 μm and 10 μm.

[0079] Preparation Example 4

[0080] Deionized water and ethanol (mass ratio of 1:1) were added to a beaker and stirred to obtain 60 mL of a mixed solvent. 4 g of KH-550 was then added and the beaker was sealed with plastic wrap. The flask was placed in a 40°C constant temperature water bath and stirred for 30 minutes to pre-hydrolyze the KH-550 and obtain a pre-hydrolyzed solution.

[0081] Add an aqueous dispersion of graphene oxide (GO concentration is 2 g / L, GO is prepared in Preparation Example 2) to the pre-hydrolyzed solution, control the mass ratio of KH-550 to GO to be 2:1, and disperse uniformly by ultrasonication; transfer the resulting reaction solution after uniform dispersion into a reaction bottle, stir in a 60°C water bath for 5 hours, then cool to room temperature, filter, wash the sample with a mixture of ethanol and water, and dry to obtain KH-550-modified graphene oxide. The reaction mechanism is as follows Figure 1 As shown: KH-550 reacts with the hydroxyl, carboxyl and epoxy groups on GO through hydrolysis, and the amino groups are grafted onto GO.

[0082] Preparation Example 5

[0083] APTMS-modified graphene oxide was prepared according to the method of Preparation Example 4, except that KH-550 was replaced with 4 g APTMS.

[0084] The following examples are used to illustrate the carbon capture absorbent, its preparation method and its application according to the present invention.

[0085] The CO2 adsorption experiment was carried out using the following equipment: a mixed gas cylinder (containing a mixture of CO2 and N2, with a volume fraction of CO2 of 15% and a volume fraction of N2 of 85%), a 1L stainless steel 316L hydration reactor (equipped with temperature and pressure sensors and remote control function), and a cooling and heating integrated machine. Before the experiment, the air tightness of the device was checked, and three cycles of pressurization to 0.3MPa were carried out to exhaust the air in the system.

[0086] The operation method is as follows: cool the hydration reactor until the temperature drops to 4.5°C, introduce the mixed gas into the hydration reactor, control the stirring speed to 400 rpm, observe the pressure data on the computer and the pressure gauge, and when the pressure reaches the preset pressure, close the valve and start stirring; when the pressure drops slowly, turn off the stirring, stop the reaction after 2 hours, collect the remaining gas for GC detection, and obtain the absorption efficiency and induction time; wherein the absorption efficiency is the ratio of the CO2 content in the hydrate to the CO2 content in the mixed gas, and the induction start time is the time when the temperature in the reactor suddenly rises;

[0087] After the gas is collected, close the valve, increase the temperature of the refrigerator, and start desorption. Desorption is completed when the pressure in the kettle no longer increases.

[0088] Example 1

[0089] Add 0.3 g of KH-550-modified graphene oxide to a beaker, then add 6 mL of a 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid (i.e., carbon capture absorbent).

[0090] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 12 minutes after the start of the reaction, and the adsorption efficiency reached 46% after 2 hours.

[0091] Example 2

[0092] Add 0.6 g of KH-550-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0093] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 12 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 49%.

[0094] Example 3

[0095] Add 0.3 g of KH-550-modified graphene oxide to a beaker, then add 30 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0096] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 10 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 47%.

[0097] Example 4

[0098] Add 0.6 g of KH-550-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0099] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 8 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 52%.

[0100] Example 5

[0101] Add 0.6 g of KH-550-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 2 μm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0102] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 18 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 45%.

[0103] Example 6

[0104] Add 0.3 g of APTMS-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0105] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 15 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 46%.

[0106] Example 7

[0107] Add 0.3 g of APTMS-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0108] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 9 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 50%.

[0109] Example 8

[0110] Add 0.3 g of APTMS-modified graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 2 μm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain CO2 absorption liquid.

[0111] The CO2 absorption liquid was added to the hydration reactor to conduct a CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 16 minutes after the start of the reaction; after two hours, the adsorption efficiency reached 47%.

[0112] Example 9

[0113] Add 0.6 g of APTMS-modified graphene oxide to a beaker, then add 30 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0114] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 7 minutes after the start of the reaction, and the adsorption efficiency reached 46% after two hours.

[0115] Example 10

[0116] Add 0.6 g of APTMS-modified graphene oxide to a beaker, then add 30 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter is 10 μm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0117] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2MPa inlet pressure, the induction start time was 20 minutes after the start of the reaction, and the adsorption efficiency reached 41% after two hours.

[0118] Comparative Example 1

[0119] 600 mL of deionized water was added to the hydration reactor to conduct a CO2 adsorption experiment. The reaction was carried out at 2-5°C and 5 MPa inlet pressure. There was no obvious hydration induction phenomenon, and the adsorption efficiency was 31% after two hours.

[0120] Comparative Example 2

[0121] Add 0.3 g of graphene oxide (prepared in Preparation Example 2, the same below) to a beaker, then add 6 mL of a 10 g / L graphene nanosheet dispersion (graphene sheet diameter 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0122] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. The reaction was carried out at 2-5°C and 2.6MPa inlet pressure. There was no obvious hydration induction phenomenon. The adsorption efficiency was 32% after two hours.

[0123] Comparative Example 3

[0124] Add 0.3 g of graphene oxide to a beaker, then add 30 mL of a 10 g / L graphene nanosheet dispersion (graphene sheet diameter 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0125] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 25 minutes after the start of the reaction, and the adsorption efficiency was 35% after two hours.

[0126] Comparative Example 4

[0127] Add 0.6 g of graphene oxide to a beaker, then add 6 mL of a 10 g / L graphene nanosheet dispersion (graphene sheet diameter 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain a CO2 absorption liquid.

[0128] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 4MPa inlet pressure, the induction start time was 23 minutes after the start of the reaction, and the adsorption efficiency was 34% after two hours.

[0129] Comparative Example 5

[0130] Add 0.6 g of graphene oxide to a beaker, then add 6 mL of 10 g / L reduced graphene oxide dispersion (rGO sheet diameter 20 nm), add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate for 20 minutes to obtain CO2 absorption liquid.

[0131] The CO2 absorption liquid was added to the hydration reactor for CO2 adsorption experiment. Under the conditions of 2-5°C and 4MPa inlet pressure, the induction start time was 18 minutes after the start of the reaction, and the adsorption efficiency was 37% after two hours.

[0132] Comparative Example 6

[0133] 0.6 g of graphene oxide and 0.3 g of SDS were added to a beaker, and deionized water was added to make the volume to 600 mL. After stirring evenly, ultrasonication was performed for 20 minutes to obtain a CO2 absorption liquid.

[0134] The CO2 absorption liquid was added to the hydration reactor to carry out the CO2 adsorption experiment. Under the conditions of 2-5°C and 2.6MPa inlet pressure, the induction start time was 20 minutes after the start of the reaction. A large number of bubbles appeared during the experiment, and the adsorption efficiency was 40% after two hours.

[0135] Compared to Comparative Examples 1-5, the CO2 absorption solutions of Examples 1-10 effectively improve hydrate formation efficiency at low pressure (≤2.6 MPa): significant hydration induction occurs within 20 minutes of reaction initiation, and adsorption efficiencies exceed 41% after 2 hours. Although Comparative Example 6 also achieves a high hydrate formation rate, the solubility of SDS in water makes absorption solution recovery difficult, preventing the recycling of the accelerator.

[0136] Furthermore, it can be seen from Examples 1 to 10 that, when the accelerator composition is the same, when the sheet diameter of reduced graphene oxide is controlled at the nanometer level, hydrate formation can be promoted at a lower inlet pressure (2 MPa): obvious hydration induction phenomenon occurs within 15 minutes after the start of the reaction, and the adsorption efficiency after 2 hours is above 46%; if the inlet pressure is increased to 2.6 MPa, the induction time is shortened to less than 10 minutes, and the adsorption efficiency after 2 hours is above 50%.

[0137] In Comparative Example 1, when water was used as the absorption liquid, there was no obvious hydration induction phenomenon, and the hydrate at 20°C was completely desorbed within 40 minutes. In Comparative Examples 2 to 5, since the hydration efficiency was not high, the hydrate at 20°C was completely desorbed within 20 minutes.

[0138] Furthermore, in the desorption experiments of Examples 1-3 and 9-10, the hydrate at 65°C was completely desorbed within 20 minutes (<20 minutes). In the desorption experiments of Examples 4-8, the hydrate at 65°C was also completely desorbed within 25 minutes (between 20 and 25 minutes). This indicates that the desorption of CO2 can be completed within half an hour after heating to 65°C in Examples 1-10. However, the desorption temperature of traditional organic amine carbon capture is above 100°C (typically 150-300°C), which requires a large number of heat exchangers in actual production, resulting in high energy consumption and a desorption time of more than 30 minutes. This means that the CO2 cannot be completely released within 30 minutes.

[0139] In summary, the carbon capture absorbent provided by the present invention has been proven to be effective in capturing and separating CO2 from low-concentration flue gas (based on the hydration method). The easy capture and desorption are both beneficial to the subsequent reuse of CO2. The subsequently released CO2 can be used for hydrogenation to produce methanol, carbon mineralization technology, etc.

[0140] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A carbon capture absorbent, characterized in that: The carbon capture absorbent comprises water and a promoter dispersed therein, wherein the promoter comprises reduced graphene oxide and amino-modified graphene oxide; In the carbon capture absorbent, the concentration of the reduced graphene oxide is 0.1 to 1 g / L, and the concentration of the amino-modified graphene oxide is 0.5 to 1.5 g / L; the reduced graphene oxide is prepared by a method comprising the following steps: reacting graphene oxide with a reducing agent in the presence of an optional stabilizer at 90 to 95° C. for 12 to 25 hours.

2. The carbon capture absorbent according to claim 1, characterized in that The mass ratio of the reduced graphene oxide to the amino-modified graphene oxide is 1:(1-10).

3. The carbon capture absorbent according to claim 1 or 2, characterized in that The reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; and the stabilizing agent is tryptophan.

4. The carbon capture absorbent according to claim 1 or 2, characterized in that The mass ratio of the graphene oxide to the reducing agent is 1:(0.7-1).

5. The carbon capture absorbent according to claim 1 or 2, characterized in that: The mass ratio of the reducing agent to the stabilizer is 1:(0-0.8).

6. The carbon capture absorbent according to claim 1 or 2, characterized in that: The reduced graphene oxide has a sheet diameter of 0.02 to 10 μm.

7. The carbon capture absorbent according to claim 6, characterized in that The reduced graphene oxide has a sheet diameter of 0.02 to 2 μm.

8. The carbon capture absorbent according to claim 1 or 2, characterized in that: The amino-modified graphene oxide is prepared by grafting an amino-modifying agent with graphene oxide, wherein the amino-modifying agent is an aminosilane coupling agent.

9. The carbon capture absorbent according to claim 8, characterized in that The aminosilane coupling agent is selected from γ-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane.

10. The carbon capture absorbent according to claim 8, characterized in that The method for modifying the graphene oxide by amino modification using an aminosilane coupling agent comprises the following steps: Adding the aminosilane coupling agent to a solvent containing water, and stirring in a constant temperature water bath at 30 to 45° C. for 10 to 60 minutes to pre-hydrolyze the aminosilane coupling agent; Graphene oxide is added and the temperature is raised to 50-60° C. and stirred for 3-7 hours to form amino-modified graphene oxide.

11. A method for preparing the carbon capture absorbent according to any one of claims 1 to 10, characterized in that: The method comprises: uniformly dispersing the reduced graphene oxide and the amino-modified graphene oxide in water to obtain a carbon capture absorbent.

12. Use of the carbon capture absorbent according to any one of claims 1 to 10 in removing CO2 from flue gas from tobacco plants, refrigeration energy-saving devices, refinery gas, natural gas or synthesis gas.

13. A method for producing carbon dioxide hydrate, characterized in that: The production method comprises: introducing a mixed gas containing carbon dioxide into a reactor containing the carbon capture absorbent according to any one of claims 1 to 10 to carry out a hydration reaction to produce carbon dioxide hydrate.

14. The generation method according to claim 13, characterized in that: In the mixed gas, the volume fraction of carbon dioxide accounts for 15% to 20%.

15. The generation method according to claim 13, characterized in that: The air inlet pressure of the reactor is not higher than 4 MPa.

16. The generation method according to claim 15, characterized in that The air inlet pressure of the reactor is 1-3 MPa.

17. The generation method according to claim 13, characterized in that: The hydration reaction is carried out under stirring conditions with a stirring speed of 400-600 rpm and a reaction temperature of 2-5°C.

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