Carbon capture absorbent, preparation method and application thereof, and generation method of carbon dioxide hydrate

Abstract

The invention belongs to the field of carbon dioxide absorption, and provides a carbon capture absorbent, a preparation method and application thereof, and a generation method of a carbon dioxide hydrate. The carbon capture absorbent comprises water and an accelerant dispersed in the water, and the accelerant comprises reduced graphene oxide and aminated modified graphene oxide. The carbon capture absorbent can promote the reaction of CO2 and water to form hydrates, reduce the high pressure condition required by the hydration reaction, shorten the hydration reaction process and improve 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 and a preparation method and application thereof, and a method for generating carbon dioxide hydrate. Background Art

[0002] Traditional methods for capturing carbon dioxide include chemical absorption, physical adsorption, membrane separation, and cryogenic condensation. Although these methods can solve the problem of carbon dioxide emissions to a certain extent, they generally have disadvantages such as serious pollution, high cost, and easy corrosion. In recent years, the hydrate method has attracted widespread attention due to its low cost, environmental friendliness, and low energy consumption. However, the shortcomings of hydrates such as slow growth rate, low CO2 separation efficiency, and low separation factor have become the key to restricting the development of hydrate method CO2 capture technology. The development of promoters is particularly important for improving the hydrate method gas separation technology. The current promoters are divided into thermodynamic promoters and kinetic promoters. Thermodynamic promoters can reduce the thermodynamic phase equilibrium conditions by occupying the cage-type pores of hydrates. Small organic molecules (such as tetrahydrofuran) can participate in the hydration reaction as thermodynamic promoters, but organic matter is highly toxic; kinetic promoters can affect the formation rate, gas storage capacity, and formation induction time of hydrates, and the research mainly 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 foam 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, and are easy to wear and tear, 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%), and it is 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 later. 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 some extent.

[0006] The purpose of the present application is to provide a carbon capture absorbent and its preparation method and application and a method for generating carbon dioxide hydrate. 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 absorption efficiency of CO2.

[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 characteristics, 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, a 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. Aminated modified graphene oxide has the characteristics of a surfactant, which can reduce the energy between interfaces, expand the contact area between phases, increase the solubility of gas in the liquid phase, and accelerate the growth rate of hydrates. 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 excessive 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 to 95° C. for 12 to 25 hours.

[0013] Furthermore, the reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; and the stabilizing agent 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 aminated modified graphene oxide is obtained by grafting an aminated modifier with graphene oxide, wherein the aminated modifier 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] Add graphene oxide and heat to 50-60° C. and stir 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, the hydrate can have more nucleation sites.

[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, the stirring speed is 400-600 rpm, and the reaction temperature is 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 apparent from the description below, or will be learned through the 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 amination modification of graphene oxide by KH-550. DETAILED DESCRIPTION

[0033] The following describes the implementation of the present application in detail. The implementation described below is exemplary and is only used to explain the present application, and cannot be understood as limiting the present application.

[0034] The "range" disclosed in the present 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 end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an unclearly recorded range, and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0035] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed 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 that hinder the penetration and dissolution of CO2 at the gas-liquid interface, and nano-ions that are not acid-resistant 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, which comprises water and a promoter dispersed therein, wherein the promoter includes reduced graphene oxide and amino-modified graphene oxide.

[0038] The present application adopts amino-modified graphene oxide and composite reduced graphene oxide as promoters of carbon capture absorbents. The combination of the two is used for hydration method to adsorb carbon dioxide, which can not only improve the adsorption efficiency, accelerate the adsorption reaction, and optimize the reaction conditions, but also the carbon capture absorbent is 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 precipitate.

[0040] In the present application, the reduced graphene oxide can be obtained commercially or prepared by methods well known in the art, for example, the 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 comprises: reacting graphene oxide with a reducing agent in the presence of an optional stabilizer at 90 to 95° C. for 12 to 25 hours.

[0042] Furthermore, the reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; and the stabilizing agent 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 the present application, the reduced graphene oxide sheet diameter can be 0.02 to 10 μm, such as 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 micro-motion intensity, and the higher the heat transfer efficiency and mass transfer efficiency. Preferably, the reduced graphene oxide sheet 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 is 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, in the carbon capture absorbent, the concentration of the reduced graphene oxide may be 0.1 to 1 g / L, such as 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 further reduce the effect of solution concentration and viscosity on heat transfer efficiency while promoting hydrate growth and balancing the system temperature during the reaction process, preferably, the concentration of the reduced graphene oxide is 0.1 to 0.5 g / L.

[0048] In the present application, the amino-modified graphene oxide refers to graphene oxide with amino groups obtained by grafting graphene oxide. Grafting modification with amino groups can make graphene oxide have hydrophilic and hydrophobic regions, promote gas volume expansion, and the introduction of amino groups can improve the selectivity for CO2 and improve the CO2 adsorption performance.

[0049] In some embodiments, the aminated modified graphene oxide is prepared by using an aminated modifier to carry out a grafting reaction with graphene oxide to introduce amino groups into the graphene oxide. Wherein, the aminated modifier 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 implementation methods, 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, and the mass ratio of water to ethanol is 1:(0.8-1.2), for example, 1:1.

[0054] In some embodiments, in the carbon capture absorbent, the concentration of the amino-modified graphene oxide can be 0.5 g / L to 1.5 g / L, such as 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 speed 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 the number of active sites that can be combined to affect the nucleation growth of hydrates 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] The second aspect of the present application provides a method for preparing the carbon capture absorbent, the method comprising: 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 (such as 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 promoter, and water is added to make up the volume and dispersed 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 flue gas of the tobacco factory 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 may 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 accounts for 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 1-3 MPa.

[0070] In some embodiments, the hydration reaction is carried out under stirring conditions, the stirring speed is 400-600 rpm, and the temperature of the hydration reaction is 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 construed 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 preparation methods thereof 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] 3.0g of nanosheet graphite and 1.5g of NaNO3 were mixed evenly in a beaker, placed in an ice bath, and then 69mL of concentrated sulfuric acid (concentration of 98wt%) was added and stirred evenly. After the temperature dropped to 0℃, 9.0g of KMnO4 was added in 6 batches. During the addition, magnetic stirring was performed and the system temperature was kept below 20℃. After the addition was completed, the temperature was raised to 35℃ and magnetic stirring was performed to react for 7h. The reaction product solution was cooled to room temperature, and the obtained reaction product solution was poured into a mixed solution containing 400mL of ice water and 3mL of 30wt% H2O2 and stirred evenly. The mixture was then filtered and washed until neutral, and vacuum dried at room temperature for 12h to obtain graphene oxide (GO) as a brown-black solid.

[0076] GO was dispersed in water to obtain a GO dispersion with a concentration of 10 g / L. A beaker containing 4 L of GO dispersion was placed in a water bath, heated to 90 ° C and stirred at 500 rpm, and 40 g of ascorbic acid and 20 g of tryptophan were added thereto. The mixture was then kept at a constant temperature for 24 hours. The resulting solution was vacuum filtered after standing for one day and repeatedly washed with water until the pH was neutral to obtain reduced graphene oxide (rGO). rGO and water were mixed into a rGO dispersion with a concentration of 2.5 g / L. The dispersion was homogenized 5 times by a high-pressure homogenizer to obtain reduced graphene oxide with a sheet 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-diameter 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 diameter 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 evenly to obtain 60 mL of a mixed solvent, and then 4 g of KH-550 was added, and the beaker was sealed with a plastic wrap; the flask was placed in a constant temperature water bath at 40° C. and stirred for 30 minutes to pre-hydrolyze KH-550 to obtain a pre-hydrolyzed solution;

[0081] Add the aqueous dispersion of graphene oxide (GO concentration is 2 g / L, GO is prepared in Preparation Example 2) to the pre-hydrolysis solution, control the mass ratio of KH-550 to GO to 2:1, and disperse evenly by ultrasonication; transfer the obtained reaction solution after uniform dispersion into a reaction bottle, stir for 5 hours in a water bath at 60°C, 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 is hydrolyzed to react with the hydroxyl, carboxyl and epoxy groups on GO to graft the amino groups 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 by 4 g APTMS.

[0084] The following examples are used to illustrate the carbon capture absorbent, preparation method and application of 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 the volume fraction of CO2 accounting for 15% and the volume fraction of N2 accounting for 85%), a 1L stainless steel 316L hydration reactor (equipped with temperature and pressure sensors and remote control function), and a refrigeration and heating all-in-one machine. Before the experiment, the air tightness of the equipment 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 down the hydration reactor until the temperature drops to 4.5°C, introduce the mixed gas into the hydration reactor, control the stirring speed to 400rpm, observe the pressure data on the computer and the pressure gauge, wait until the pressure reaches the preset pressure, close the valve, and start stirring; when the pressure decreases slowly, turn off the stirring, stop the reaction after 2 hours of reaction, 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 into 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 (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 into 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 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; after two hours, the adsorption efficiency reached 49%.

[0094] Example 3

[0095] Add 0.3 g of KH-550-modified graphene oxide into 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 into 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 carry out the 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 into 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 carry out the 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 into 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 carry out the 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 into 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 carry out the 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 into 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.

[0111] 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 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 into 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 into 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 for 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) into a beaker, then add 6 mL of 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. After two hours, the adsorption efficiency was 32%.

[0123] Comparative Example 3

[0124] Add 0.3 g of graphene oxide to a beaker, then add 30 mL of 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 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 a 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 a 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] Add 0.6 g of graphene oxide and 0.3 g of SDS into a beaker, add deionized water to make the volume to 600 mL, stir evenly and ultrasonicate 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 with Comparative Examples 1 to 5, the CO2 absorption liquids of Examples 1 to 10 can effectively improve the hydrate formation efficiency under low pressure (≤2.6MPa): obvious hydration induction phenomenon occurs within 20 minutes after the start of the reaction, and the adsorption efficiency after 2 hours is above 41%. Although Comparative Example 6 can also obtain a higher hydrate formation rate, SDS dissolves in water, making it difficult to recover the absorption liquid and unable to achieve the recycling of the promoter.

[0136] Furthermore, it can be seen from Examples 1 to 10 that, when the composition of the promoter is the same, when the sheet diameter of the reduced graphene oxide is controlled at the nanometer level, hydrate formation can be promoted at a lower intake pressure (2 MPa): obvious hydration induction occurs within 15 minutes after the start of the reaction, and the adsorption efficiency after 2 hours is above 46%; if the intake 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] When water was used as the absorption liquid in Comparative Example 1, 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] In addition, in the desorption experiments of Examples 1-3 and 9-10, the hydrate at 65°C can be completely desorbed within 20 minutes (<20min), and in the desorption experiments of Examples 4-8, the hydrate at 65°C can also be completely desorbed within 25 minutes (between 20 and 25 minutes), which means that after heating to 65°C in Examples 1-10, the desorption can be completely completed within half an hour, and CO2 can be completely released. However, the desorption temperature of traditional organic amine carbon capture is above 100°C (usually 150-300°C), and a large number of heat exchange devices are required in actual production, with high energy consumption and a desorption time of more than 30 minutes, that is, CO2 cannot be completely released within 30 minutes.

[0139] In summary, the carbon capture absorbent provided by the present invention is proven to be effective in capturing and separating CO2 in low-concentration flue gas (based on the hydration method). 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 replace some or all of the technical features therein by equivalents; 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 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.

2. The carbon capture absorbent according to claim 1, characterized in that In the carbon capture absorbent, the concentration of the reduced graphene oxide is 0.1 to 1 g / L; Preferably, in the carbon capture absorbent, the concentration of the amino-modified graphene oxide is 0.5 to 1.5 g / L.

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

4. The carbon capture absorbent according to any one of claims 1 to 3, characterized in that: The reduced graphene oxide is prepared by a chemical reduction method; Preferably, 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 h; Preferably, the reducing agent is selected from at least one of hydrazine hydrate, ascorbic acid and sodium borohydride; the stabilizing agent is tryptophan; Preferably, the mass ratio of the graphene oxide to the reducing agent is 1:(0.7-1); Preferably, the mass ratio of the reducing agent to the stabilizer is 1:(0-0.8).

5. The carbon capture absorbent according to any one of claims 1 to 4, characterized in that: The reduced graphene oxide has a sheet diameter of 0.02 to 10 μm, preferably 0.02 to 2 μm.

6. The carbon capture absorbent according to any one of claims 1 to 5, characterized in that: The aminated modified graphene oxide is prepared by grafting an aminated modifier with graphene oxide, wherein the aminated modifier is an aminosilane coupling agent; Preferably, the aminosilane coupling agent is selected from γ-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane; Preferably, the method of 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; Add graphene oxide and heat to 50-60° C. and stir for 3-7 hours to form amino-modified graphene oxide.

7. A method for preparing the carbon capture absorbent according to any one of claims 1 to 6, 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.

8. Use of the carbon capture absorbent according to any one of claims 1 to 6 in removing CO2 from flue gas from tobacco plants, refrigeration energy-saving devices, refinery gas, natural gas or synthesis gas.

9. A method for generating carbon dioxide hydrate, characterized in that: The generation method comprises: introducing a mixed gas containing carbon dioxide into a reaction kettle filled with the carbon capture absorbent according to any one of claims 1 to 6 to carry out a hydration reaction to generate carbon dioxide hydrate.

10. The generation method according to claim 9, characterized in that: In the mixed gas, the volume fraction of carbon dioxide accounts for 15% to 20%; Preferably, the inlet pressure of the reactor is not higher than 4 MPa, more preferably 1 to 3 MPa; Preferably, 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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