Graphene aerogel, regeneration catalyst and its use, and method for regenerating CO2-rich amine solution

Abstract

This invention discloses a graphene aerogel, a regeneration catalyst and its use, and a method for regenerating a CO2-rich amine solution. The graphene aerogel has a B acid content of 0.001 to 0.05 mmol / g and a specific surface area of ​​40 to 200 m². 2 The graphene aerogel has a volume of 50% or more of pores with a diameter of 20 nm or less in weight, relative to the total pore volume of the graphene aerogel. When used as a regeneration catalyst for CO2-rich amine solutions, this graphene aerogel is advantageous in catalyzing CO2 desorption, lowering the initial and final desorption temperatures, accelerating the desorption rate, shortening the desorption time, reducing energy consumption for desorption, and improving the amount of desorbed CO2.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims the benefits of Chinese Patent Application No. 202311049627.1, filed on 18 August 2023, the contents of which are incorporated herein by reference.

[0002] [Technical Field] This invention relates to the field of desorption and regeneration of CO2-rich amine solutions, and more specifically to graphene aerogels, regeneration catalysts and their use, and methods for regenerating CO2-rich amine solutions. [Background technology]

[0003] Reducing CO2 emissions has become a crucial development strategy for China and the world. The International Energy Agency (IEA) points out that CCUS (carbon capture, utilization, and storage) technology is the only technology that can directly reduce carbon emissions in key sectors while simultaneously lowering existing CO2 concentrations, thereby balancing unavoidable carbon emissions and achieving emission reduction objectives. Large scale, low cost, and commercialization will be the trends for the future development of CCUS projects. Coal is currently the most important energy source for China, and coal-fired power plants are the main source of CO2 emissions in China. Capturing, storing, and utilizing CO2 from the exhaust gases of coal-fired power plants is key to reducing carbon emissions in China and is an important pathway toward the large-scale application of CCUS technology. According to reports, CO2 capture technology is the most important process in the large-scale application of CCUS technology, determining the purity and cost of the gas source. Since the energy consumption of this process accounts for more than 60% of the total energy consumption of a CCUS project, reducing energy consumption is extremely important in CO2 capture from exhaust gases.

[0004] Currently, the main methods for CO2 recovery and purification include chemical absorption, physical absorption and physicochemical absorption, solid adsorption, membrane treatment, and cryogenic separation. However, considering the timing of application, the maturity of the technology, and future potential, chemical absorption is undoubtedly the best option at present. Chemical absorption involves selectively chemically reacting CO2 with an absorbent in a mixed exhaust gas to separate CO2 from other gases, and then using the reverse reaction to regenerate and concentrate high-purity CO2.

[0005] Currently, the main bottlenecks preventing the large-scale application of chemical absorption methods are high energy consumption and high cost. To reduce energy consumption, researchers are focusing on two main areas: the development of highly efficient absorbents and the optimization of recovery system processes. CN109316903A discloses a mesoporous solid acid-base catalyst for use in the desorption of CO2-rich amine solutions. This mesoporous solid acid-base catalyst has Fe2O3 supported on a molecular sieve MCM-41 support. This catalyst is easily separable, has good stability, and is recyclable, but its desorption requires a relatively high temperature of 98°C. CN106984333A discloses a supported catalyst for the regeneration of carbon dioxide-rich amine solutions. This catalyst is a metal oxide-supported sulfate type solid superacid catalyst, and its support is γ-Al2O3. SO4 2- Compared to ZrO2 catalysts and γ-Al2O3 catalysts, this catalyst can reduce the energy consumption for ethanolamine (MEA) desorption, but requires a higher desorption temperature.

[0006] Therefore, finding ways to further lower the desorption temperature of CO2-rich amine solutions and reduce energy consumption is a critical issue that urgently needs to be addressed in order to reduce the use of chemical absorption methods for CO2 recovery and purification. [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to overcome the problems of the prior art, such as the high desorption temperature and high energy consumption of carbon dioxide, and to provide a graphene aerogel, a regenerating catalyst and its use, as well as a method for regenerating a CO2-rich amine solution. When the graphene aerogel is used as a regenerating catalyst, the desorption reaction can be accelerated, the initial reaction temperature can be lowered, and energy consumption can be reduced. [Means for solving the problem]

[0008] To achieve the above objective, a first aspect of the present invention provides a graphene aerogel having a B acid content of 0.001 to 0.05 mmol / g and a specific surface area of ​​40 to 200 m². 2 The volume of pores with a diameter of 20 nm or less accounts for 50% or more of the total pore volume of the graphene aerogel.

[0009] A second aspect of the present invention provides a regenerative catalyst comprising a carrier and a metal component supported on the carrier, wherein the metal component has the properties of Lewis acid, and the carrier is the graphene aerogel described in the first aspect.

[0010] A third aspect of the present invention provides the use of the regeneration catalyst described in the second aspect in the regeneration of a CO2-rich amine solution. A fourth aspect of the present invention involves performing CO2 desorption by contacting a CO2-rich amine solution with a catalyst under regeneration conditions. The catalyst is the regeneration catalyst described in the second embodiment, and provides a method for regenerating a CO2-rich amine solution. [Effects of the Invention]

[0011] The graphene aerogel according to the present invention has an appropriate amount of protonic acid (Brønsted acid), an appropriate number of pores and pore structure. When used as a regeneration catalyst for a CO₂-rich amine solution, it acts synergistically with the metal component to not only provide the protonic acid required for the desorption process, but also provide the basic groups necessary to promote the desorption reaction. This is advantageous for catalyzing CO₂ desorption, lowering the initial and final temperatures of desorption, increasing the desorption rate, shortening the desorption time, reducing the energy consumption for desorption, and improving the desorption amount. Furthermore, because it has relatively high mechanical strength, it extends the cycle life. Preferably, it has a three-dimensional porous network structure formed by stacking two-dimensional sheet-like graphene, and through-holes of different sizes are distributed between the sheets, which not only ensures the passage of the solution but also helps to improve the compressive strength of the graphene aerogel and further improve the stability of the catalyst.

Brief Description of the Drawings

[0012] [Figure 1] SEM image of graphene aerogel A1 prepared in Preparation Example 1. [Figure 2] TEM image of graphene aerogel A1 prepared in Preparation Example 1. [Figure 3] X-ray photoelectron spectroscopy of graphene aerogel A1 prepared in Preparation Example 1. [Figure 4] Spectrum of XPS peak separation of O1s of graphene aerogel A1 prepared in Preparation Example 1. [Figure 5] Pore size distribution curve of graphene aerogel A1 prepared in Preparation Example 1.

Modes for Carrying Out the Invention

[0013] The endpoints and any values disclosed in this specification are not limited to the exact range or value, but should be understood to include values close to these ranges or values. Regarding numerical ranges, by combining between the endpoint values of each range, between the endpoint value of each range and individual dot values, and between individual dot values, one or more new numerical ranges can be obtained, and these numerical ranges are regarded as specifically disclosed in this specification.

[0014] The first aspect of the present invention provides a graphene aerogel, and the graphene aerogel has a B acid content of 0.001 to 0.05 mmol / g, a specific surface area of 40 to 200 m 2 / g, and the proportion of the volume of pores with a pore diameter of 20 nm or less in the total pore volume of the graphene aerogel is 50% or more.

[0015] According to the present invention, since the graphene aerogel has an appropriate amount of protonic acid (B acid), it is advantageous for accelerating the CO2 desorption rate. Preferably, the B acid content of the graphene aerogel is 0.01 to 0.03 mmol / g. Controlling the B acid content of the graphene aerogel within the above preferred range and combining it with an appropriate number of pores and pore structure helps to promote the progress of the CO2 desorption reaction and fundamentally reduce the reaction energy consumption.

[0016] In the present invention, the content of B acid (or L acid) is characterized and evaluated using pyridine infrared spectroscopy. The specific test method is as follows. Press 0.0089 g of the test sample into a self-supporting sheet with a diameter of 1.3 cm and place it in an in-situ cell. Vacuum the sample at 300 °C and cool it to room temperature to measure the background infrared spectrum. Adsorb pyridine saturated vapor until the sample is saturated and record the spectrum. After performing He purge for 1 h, perform vacuum evacuation and increase the temperature programmatically (0 to 350 °C) for desorption. The spectrum is recorded every 20 °C. The standard positions of B acid and L acid in the obtained pyridine infrared spectrum are 1540 cm -1 and 1450 cm -1It is as follows. Integrate the peak at the corresponding position in the spectrum, normalize the peak area of the spectrum, and calculate the acid amount according to the following formula.

Equation

[0017] The graphene aerogel of the present invention has an appropriate number of pores and pore structure. The specific surface area of the graphene aerogel is 50 - 200 m 2 / g, preferably 100 - 1'20 m 2 / g. In the above preferred case, when the graphene aerogel is used as a regeneration catalyst for a CO2-rich amine solution, it has an appropriate contact area with the CO2-rich amine solution, which is advantageous for catalyzing the desorption of CO2, and is also advantageous for improving the mechanical strength of the graphene aerogel.

[0018] In some embodiments of the present invention, the total pore volume of the graphene aerogel is 0.01 - 0.5 mL / g, preferably 0.1 - 0.3 mL / g.

[0019] In some embodiments of the present invention, the proportion of the volume of pores with a diameter of 20 nm or less in the graphene aerogel to the total pore volume of the graphene aerogel is 50% or more, preferably 55-90%, and more preferably 70-80%. By keeping the content of pores with a diameter of 20 nm or less within a certain range, the graphene aerogel according to the present invention, when used as a catalyst support, can improve catalytic efficiency, thereby lowering the desorption temperature, shortening the desorption time, and improving the mechanical strength of the catalyst. This is because, when a metal component is later supported to prepare the catalyst, the metal component is filled into the pores with a diameter of 20 nm or less, and the metal component is fixed to the graphene aerogel, which is advantageous for the activation of the metal component. Furthermore, when combined with an appropriate amount of B acid, catalytic efficiency can be improved, thereby lowering the desorption temperature and shortening the desorption time. In addition, it is thought that this helps to reduce the catalyst loss rate during the regeneration process of the alcoholamine solution and extend the service life of the catalyst.

[0020] In this invention, the specific surface area, pore volume, and pore distribution are measured by the N2 adsorption-desorption isotherm method.

[0021] In some preferred embodiments of the present invention, the chemical composition of graphene aerogel is characterized using X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectroscopy analysis is performed using an ESCALAB 250XI X-ray photoelectron spectrometer manufactured by Thermo Fisher Scientific, Inc. The test conditions are as follows: Al Kα rays are used as the excitation source, and the scanning range is 0 to 1200 eV.

[0022] According to some preferred embodiments of the present invention, the graphene aerogel contains elements C, N, and O. The X-ray photoelectron spectroscopy spectrum of the graphene aerogel of the present invention contains characteristic peaks corresponding to C, N, and O, indicating that the graphene aerogel of the present invention contains elements C, N, and O. In the graphene aerogel, the total amount of element C is determined by the area of ​​the C 1s spectral peak in X-ray photoelectron spectroscopy, the total amount of element O is determined by the area of ​​the O 1s spectral peak, and the total amount of element N is determined by the area of ​​the N 1s spectral peak. Preferably, the molar ratio of the C element, O element, and N element is (1-60):(5-30):(0.5-5), preferably (15-35):(10-20):(1-2), for example, 15:10:1, 15:15:1, 15:20:1, 20:10:1, 25:15:1, 25:20:1, 30:10:1, 30:15:1 These may be typical but non-restrictive molar ratios such as 30:20:1, 35:10:1, 35:15:1, 35:20:1, 15:10:2, 15:15:2, 15:20:2, 20:10:2, 25:15:2, 25:20:2, 30:10:2, 30:15:2, 35:10:2, 35:15:2, and 35:20:2.

[0023] In some preferred embodiments of the present invention, the X-ray photoelectron spectroscopy spectrum of the graphene aerogel of the present invention shows that the O1s spectrum consists of peaks for hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen, demonstrating that the oxygen species in the graphene aerogel include hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen, determined by the peak area obtained by peak separation, is (1-20):(0.1-5):(1-5), preferably (1-5):(0.5-2):(1-2). For example, typical but non-limiting molar ratios such as 1:0.5:1, 1:1:1, 1:1.5:1, 1:2:1, 2:0.5:1, 2:1:1, 2:1.5:1, 2:2:1, 3:0.5:1, 3:1:1, 3:1.5:1, 3:2:1, 4:0.5:1, 4:1:1, 4:1.5:1, 4:2:1, 5:0.5:1, 5:1:1, 5:1.5:1, and 5:2:1 may be used. The above preferred distributions of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen further improve the hydrophilicity of the graphene aerogel, which is advantageous for desorption.

[0024] In some embodiments of the present invention, the graphene aerogel is a three-dimensional porous network structure formed by stacking two-dimensional sheet-like graphene.

[0025] In some preferred embodiments of the present invention, the average sheet thickness of the two-dimensional sheet-like graphene in the graphene aerogel is measured to be 10 to 200 nm, preferably 50 to 100 nm, by scanning electron microscopy (SEM).

[0026] Preferably, the average sheet length of the two-dimensional sheet-like graphene is 0.1 to 10 μm, preferably 1 to 5 μm.

[0027] In this invention, "sheet length" refers to the maximum straight-line distance between two points on the same plane of the sheet, and "sheet thickness" refers to the maximum straight-line distance between two points on a plane perpendicular to the sheet length. For 50 two-dimensional sheet-shaped graphene sheets in graphene aerogel, the sheet length and sheet thickness are statistically analyzed using a scanning electron microscope, and their average values ​​are calculated.

[0028] In this invention, the surface morphology of graphene aerogel is observed using a scanning electron microscope (SEM). Scanning electron microscopy analysis is performed using a Hitachi S-4800 scanning electron microscope, with a test voltage of 1 to 10 kV and a magnification of 0.5 to 50 kV.

[0029] The internal structure of graphene aerogel will be characterized using a transmission electron microscope (TEM). Transmission electron microscopy analysis will be performed using a TECNAI G2 F20 emission transmission electron microscope manufactured by FEI, Inc., USA, at a test voltage of 100-500kV and a magnification of 1-100k.

[0030] Scanning electron microscope (SEM) images reveal that the graphene aerogel has a three-dimensional porous network structure formed by stacking two-dimensional sheet-like graphene. The sheets are relatively uniform in size, have a relatively high stacking density, and the connections between sheets are more dense. Further magnification revealed that abundant pores are distributed between the sheets. The internal structure, characterized by transmission electron microscope (TEM) images, indicates that the graphene aerogel forms a network structure internally, possessing good dispersibility and favorable for the movement of the medium.

[0031] In some embodiments of the present invention, the compressive strength of the graphene aerogel is higher than 30 kPa, reaching 80 kPa, and preferably 40 to 50 kPa. In the present invention, the compressive strength of the graphene aerogel is related to the morphology, number of pores, and pore structure of the graphene aerogel. By keeping the number of pores with a diameter of 20 nm or less within a certain range, it is advantageous to improve the compressive strength of the graphene aerogel while ensuring the passage of the solution. At the above preferred compressive strength, the graphene aerogel is advantageous for recycling and reuse, and losses can be reduced. On the other hand, the compressive strength of graphene aerogels using existing technologies is usually 10 to 30 kPa.

[0032] In this invention, the test conditions for the compressive strength of graphene aerogel are as follows: the graphene aerogel to be tested is pressed into a cylindrical test specimen with a height of 10 mm and a diameter of 10 mm; the prepared test specimen is impregnated in physiological saline solution at 37°C; then heated in a constant temperature water bath for 24 hours; the diameter of each test specimen is accurately measured with an accuracy of 0.02 mm using calipers; a preload of 5 N and vertical pressure at a loading rate of 1 mm / min are applied to the test specimen using an electronic universal testing machine; and the maximum load value at which the test specimen breaks is recorded. Compressive strength P = F / S, where F is the maximum load value (N) at which the test specimen breaks, and S is the bottom area (mm²) of the cylindrical test specimen. 2 The resulting compressive strength is in MPa, which is then converted to kPa.

[0033] In some embodiments of the present invention, the method for preparing the graphene aerogel is as follows: Step (1) involves uniformly mixing a dispersion containing graphene oxide with a reducing agent and carrying out a reduction reaction to obtain a graphene hydrogel, Step (2) removes the solvent from the graphene hydrogel to obtain a graphene aerogel intermediate product, The process includes step (3) contacting the graphene aerogel intermediate product with an acidic solution to carry out an activation reaction.

[0034] According to the present invention, after preparing a graphene aerogel intermediate by oxidation followed by reduction, the graphene aerogel intermediate can be activated with an acidic solution to provide the graphene aerogel with an appropriate amount of protic acid, an appropriate number of pores, and a suitable pore structure. Using graphene aerogel in the desorption process of carbon dioxide-captured complex amines helps to promote CO2 desorption.

[0035] In some embodiments of the present invention, the concentration of the dispersion containing graphene oxide is 0.5 to 10 mg / mL, preferably 1 to 3 mg / mL. The present invention does not have any particular limitations on the source of the graphene oxide, which can be obtained by purchasing a commercially available product or by conventional methods for preparing graphene oxide in the art. For example, the graphene oxide can be prepared by the Hummers method or the modified Hummers method. Methods for preparing graphene oxide by the Hummers method or the modified Hummers method are well known to those skilled in the art and can be carried out by reference to the prior art.

[0036] In some embodiments of the present invention, the mass ratio of the reducing agent to graphene oxide is 0.001 to 2:1. To ensure that the prepared graphene aerogel has both a suitable channel structure and good compressive strength, the mass ratio of the reducing agent to graphene oxide is preferably 0.004 to 1:1.

[0037] All reducing agents known in the field for reducing graphene oxide can be used in the present invention, such as ethylenediamine and ascorbic acid.

[0038] In some embodiments of the present invention, the reducing agent is ethylenediamine. When ethylenediamine is used as a reducing agent, it not only helps to improve the degree of reduction of graphene but can also perform a crosslinking action, and at the same time, as a weak reducing agent, it can give the final product a fluffy structure and an appropriate number and structure of pores, which helps in the progress of the CO2 desorption reaction. Furthermore, the use of ethylenediamine increases the hydrophilicity of the product, eliminating the need to add additional crosslinking agents, and the resulting graphene aerogel has strong hydrophilicity.

[0039] In some embodiments of the present invention, in step (1), the reduction reaction is carried out at a temperature of 60 to 180°C, preferably 80 to 100°C, and for a duration of 6 to 18 hours, preferably 6 to 10 hours.

[0040] In the present invention, the method for mixing the dispersion containing graphene oxide with the reducing agent is not particularly limited. Ultrasonic and / or stirring methods can be used as long as the dispersion and the reducing agent are uniformly mixed.

[0041] In the present invention, the solvent in the graphene hydrogel can be removed using any conventional method in the art, as long as the solvent in the graphene hydrogel can be effectively removed to obtain a graphene aerogel. For example, a method for removing the solvent from the graphene hydrogel includes impregnating the graphene hydrogel in an aqueous solution of alcohol and then drying it.

[0042] In some embodiments of the present invention, the volume content of the alcohol in the aqueous solution of the alcohol is 10 to 50%, preferably 20 to 30%, and the alcohol may be at least one of C1 to C5 monohydric alcohols, such as ethanol, methanol, and isopropanol.

[0043] In the present invention, the amount of aqueous solution of alcohol used is not particularly limited, as long as it is sufficient to completely impregnate the graphene hydrogel.

[0044] According to the present invention, the first drying method is diverse. In some specific embodiments of the present invention, the first drying includes first freezing at -10 to -30°C for 1 to 12 hours, followed by freeze-drying at -40 to -120°C for 24 to 60 hours. In the present invention, by using ethylenediamine as a reducing agent and controlling the temperature gradient of the first drying, it is possible to ensure that the graphene aerogel has an appropriate number of pores and pore structure, as well as to ensure the stability of the internal structure of the graphene aerogel and improve the compressive strength of the graphene aerogel. Preferably, the first drying includes first freezing at -15 to -25°C for 1 to 5 hours, followed by freeze-drying at -50 to -90°C for 24 to 36 hours.

[0045] In this invention, a graphene aerogel intermediate is activated using an acidic solution to incorporate an appropriate amount of protic acid into the graphene aerogel, thereby providing an acidic site for the desorption of an alcohol amine solution that absorbs carbon dioxide. In some specific embodiments of this invention, the acidic solution is provided by an aqueous solution of an acid. This invention offers a relatively broad range of choice for the specific type of acid, and can use organic or inorganic acids commonly used in the art, such as at least one of nitric acid, hydrochloric acid, sulfuric acid, oxalic acid, and acetic acid, preferably the acid is selected from nitric acid and / or hydrochloric acid.

[0046] In some embodiments of the present invention, the concentration of the aqueous solution of the acid is 4 to 10 mol / L, preferably 5 to 8 mol / L.

[0047] In some specific embodiments of the present invention, in order to appropriately control the B acid content in the prepared graphene aerogel, the volume ratio of the acidic solution to the graphene aerogel intermediate product is 1 to 2.5:1, preferably 1 to 2:1, and more preferably 1 to 1.5:1.

[0048] In some embodiments of the present invention, the temperature of the activation reaction is 40 to 90°C, preferably 60 to 80°C, and the duration of the activation reaction is 2 to 8 hours, preferably 2 to 4 hours. Employing these preferred embodiments helps to retain more active sites without destroying the graphene aerogel structure.

[0049] In some preferred embodiments of the present invention, the activation reaction is carried out under stirring conditions in order to promote sufficient contact between the graphene aerogel intermediate and the acidic solution and to accelerate the activation reaction rate.

[0050] In some embodiments of the present invention, the preparation method further includes the steps of washing and second drying the product obtained in the activation reaction. The washing and second drying can be carried out according to conventional operating conditions in the art, as long as residual acidic solutions in the product are removed, and the present invention is not particularly limited thereto. The second drying is performed at a temperature of 60 to 120°C, more preferably 100 to 120°C, and for a time of 8 to 24 hours, more preferably 10 to 15 hours.

[0051] A second aspect of the present invention provides a regenerative catalyst comprising a carrier and a metal component supported on the carrier, wherein the metal component has the properties of Lewis acid, and the carrier is the graphene aerogel described in the first aspect.

[0052] According to the present invention, by supporting a metal component having the properties of a Lewis acid on the graphene aerogel described above, the regenerating catalyst can not only provide the protic acid necessary for the desorption process but also the necessary basic group, thereby promoting the desorption reaction and fundamentally reducing the energy consumption of the reaction. In the present invention, the metal component is bonded to the graphene aerogel via chemical bonds, which improves the interaction between the support and the metal component, converting single-center adsorption and desorption to multi-center adsorption and desorption, and is advantageous for further improving the adsorption and desorption capacity.

[0053] In this invention, the term "Lewis acid" refers to a molecule or ion capable of accepting external electrons. A metal component possessing Lewis acid properties is bonded to the graphene aerogel via chemical bonding and can also provide Lewis acid in the regenerative catalyst.

[0054] In some embodiments of the present invention, the regenerating catalyst contains B acid and L acid, and the content of B acid is 0.0005 to 0.02 mmol / g, more preferably 0.008 to 0.016 mmol / g.

[0055] In some embodiments of the present invention, the ratio of L acid to B acid in the regenerating catalyst can be adjusted by adjusting the amount of metal component supported. To improve the desorption performance of the product, preferably, in the regenerating catalyst, the molar ratio of B acid to L acid is 0.01 to 1:1, preferably 0.1 to 0.5:1, and more preferably 0.1 to 0.2:1. Adjusting the molar ratio of L acid to B acid within the above preferred range is advantageous for improving desorption efficiency and reducing energy consumption.

[0056] In this invention, the B acid, L acid, and their relative content in the regenerated catalyst are measured by pyridine infrared spectroscopy, which is the same as the method described above and will not be repeated here.

[0057] In some embodiments of the present invention, the content of the support is 30 to 70 wt%, preferably 30 to 50 wt%, based on the total mass of the regenerating catalyst, and the content of the metal component is an oxide, preferably 30 to 70 wt%, preferably 50 to 70 wt%. Within the above preferred component content range, the regenerating catalyst is acidic and alkaline, and can provide the protonic acid necessary for the desorption process, as well as the necessary basic groups, which helps to promote the desorption reaction.

[0058] In this invention, the content of each component in the regenerated catalyst is obtained by XPS testing.

[0059] In the present invention, the selection range for the specific type of metal component is relatively broad, and any metal having the properties of a Lewis acid can be used in the present invention. In some embodiments of the present invention, the metal component is at least one selected from transition metal elements and / or Group IIIA elements, preferably Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga, and In. To further enhance the catalytic activity of the regenerating catalyst and accelerate the CO2 desorption rate, preferably the metal component is at least one selected from Al, Fe, Co, Ni, and Ti.

[0060] In this invention, the metal component exists at least partially in the form of an oxide.

[0061] In some embodiments of the present invention, the regenerating catalyst has a suitable specific surface area, preferably the specific surface area of ​​the regenerating catalyst is 30 to 100 m². 2 / g, preferably 45-80mg 2 The value is / g. In the preferred case described above, the regenerated catalyst has excellent dispersion properties, which is advantageous for exposing more active sites and thus accelerates the reaction.

[0062] In some embodiments of the present invention, the total pore volume of the regenerated catalyst is 0.06 to 0.2 mL / g, preferably 0.1 to 0.15 mL / g. The abundant pore distribution within the regenerated catalyst ensures mass transfer efficiency, improves regeneration efficiency, and provides relatively high mechanical strength, thereby extending the service life of the catalyst.

[0063] In some embodiments of the present invention, in the regenerated catalyst, the proportion of the volume of pores with a diameter of 20 nm or less to the total pore volume of the regenerated catalyst is 30% or more, preferably 30-80%, and more preferably 50-60%. Compared to graphene aerogel without a supported metal component, when a catalyst is prepared by supporting a metal component, the proportion of the volume of pores with a diameter of 20 nm or less decreases. This is thought to be because the number of pores decreases as some of the metal component fills the pores with a diameter of 20 nm or less in the graphene aerogel. In this case, the metal component is fixed to the graphene aerogel, which is advantageous for the metal component to exert its activity. By combining it with an appropriate amount of B acid, catalytic efficiency can be improved, the desorption temperature can be lowered, the desorption time can be shortened, and the catalyst loss rate in the regeneration process of the alcoholamine solution can be reduced, which helps to extend the service life of the catalyst.

[0064] In this invention, the specific surface area, pore volume, and pore distribution of the regenerated catalyst are measured by the N2 adsorption-desorption isotherm method.

[0065] According to one preferred embodiment of the present invention, the method for preparing the regenerated catalyst is as follows: Step S1 involves mixing a solution containing a carrier and a soluble compound of a metal component in the presence of ultrasound to obtain a mixed solution. The above mixture is mixed with a precipitating agent to carry out a precipitation reaction, followed by drying and roasting (step S2), and the following steps are included: The carrier comprises the graphene aerogel described in the first embodiment, and the metal component has the properties of Lewis acid.

[0066] According to the present invention, since the metal component can be supported on the support by in-situ deposition using an impregnation-precipitation method, in the prepared regenerative catalyst, the metal component is bound to the graphene aerogel via chemical bonds, and the metal component and the support have a relatively strong interaction, which helps to improve the catalytic activity of the regenerative catalyst and accelerate the CO2 desorption rate.

[0067] In some embodiments of the present invention, in step S1, the volume ratio of the solution containing the soluble compound of the metal component to the carrier is 0.1 to 4:1, preferably 0.5 to 2:1.

[0068] In the present invention, the concentration range of the solution containing the soluble compound of the metal component is relatively wide. To ensure uniform dispersion of the metal oxide and avoid channel blockage, the concentration of the solution containing the soluble compound of the metal component is preferably 0.5 to 2 mol / L, more preferably 1 to 1.5 mol / L.

[0069] In some embodiments of the present invention, the frequency of the ultrasound is 10,000 to 100,000 Hz, preferably 30,000 to 50,000 Hz, and the mixing time is 1 to 3 hours, preferably 1 to 1.5 hours. Employing the above preferred mixing method is advantageous for uniform mixing and sufficient contact between the carrier and the soluble compounds of the metal component, thereby improving the uniformity and dispersibility of the metal component supported on the carrier.

[0070] In the present invention, there are no particular restrictions on the specific type of soluble compound of the metal component, and it may be at least one of conventional soluble organic or inorganic salts in the art containing a metal component, such as nitrates, acetates, sulfates, and chlorides containing a metal component.

[0071] In the present invention, the selection range for the specific type of metal component is relatively broad, and any metal having the properties of a Lewis acid can be used in the present invention. In some embodiments of the present invention, the metal component is at least one selected from transition metal elements and / or Group IIIA elements, preferably Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga, and In. To further improve the catalytic activity of the regenerating catalyst and accelerate the CO2 desorption rate, preferably the metal component is at least one selected from Al, Fe, Co, Ni, and Ti.

[0072] In some embodiments of the present invention, in step S2, the pH of the precipitation reaction is adjusted by adding a precipitating agent, and preferably the pH of the precipitation reaction is 8 to 10, more preferably 8 to 9.

[0073] In some embodiments of the present invention, the rate at which the precipitating agent is added to 1 L of the mixture is 0.1 to 2 mL / min, preferably 0.5 to 1 mL / min. Controlling the rate at which the precipitating agent is added within the aforementioned preferred range is advantageous for forming a more uniform precipitate of metal ions.

[0074] In the present invention, there are no particular restrictions on the specific selection of the precipitating agent; any precipitating agent commonly used in the art can be used in the present invention. For example, the precipitating agent may be aqueous ammonia. In the present invention, the range of selectable concentrations of the aqueous ammonia is relatively wide, and preferably, the concentration of the aqueous ammonia is 22 to 28 wt%.

[0075] In the present invention, the specific method and conditions for drying in step S2 are not particularly limited, as long as the solvent in the precipitate reaction product can be removed. A solid-liquid separation operation may be further included before the drying. The present invention is also not particularly limited in terms of the specific method of the solid-liquid separation, and those skilled in the art can select one according to their actual needs.

[0076] In some embodiments of the present invention, in step S2, the drying temperature is 40 to 150°C, the drying time is 8 to 24 hours, and preferably the drying temperature is 80 to 120°C, and the drying time is 8 to 12 hours.

[0077] In some embodiments of the present invention, in step S2, the roasting temperature is 300 to 1000°C, preferably 300 to 600°C, and the roasting time is 1 to 10 hours, preferably 4 to 8 hours.

[0078] A third aspect of the present invention provides the use of the regeneration catalyst described in the second aspect in the regeneration of a CO2-rich amine solution.

[0079] The regeneration catalyst can be used as a CO2 desorption catalyst in the regeneration of a CO2-rich amine solution. The CO2-rich amine solution refers to an organic amine solution that has absorbed CO2. The organic amine solution may be any of the known organic amines or complex organic amine solutions used for CO2 absorption in the art, and may include, but is not limited to, a combination of one or more monoethanolamine, diethanolamine, methyldiethanolamine, and triethanolamine.

[0080] The graphene aerogel in the aforementioned regeneration catalyst has a B acid content, an appropriate number of pores, and a suitable pore structure. By acting synergistically with the metal component, when used in the regeneration process of a CO2-rich amine solution, it effectively promotes the desorption reaction, catalyzes CO2 desorption, lowers the start and end temperatures of desorption, accelerates the desorption rate, shortens the desorption time, reduces energy consumption, and improves desorption capacity. Furthermore, because the regeneration catalyst has high mechanical strength, it extends the cycle life.

[0081] A fourth aspect of the present invention involves bringing a CO2-rich amine solution into contact with a catalyst under regeneration conditions to perform CO2 desorption. The catalyst is the regeneration catalyst described in the second embodiment, and provides a method for regenerating a CO2-rich amine solution.

[0082] In some embodiments of the present invention, the amount of catalyst used is 1 to 10 wt%, preferably 1 to 3 wt%, based on the total mass of the CO2-rich amine solution.

[0083] When conventional regeneration catalysts in prior art are used to regenerate CO2-rich amine solutions, the preparation cost of the regeneration catalyst is high, the required initial desorption temperature is high, and the reaction time is long, resulting in high energy consumption in the desorption process. The regeneration catalyst according to the present invention uses graphene aerogel as a support and, by acting synergistically with the metal component, allows the desorption reaction to proceed in the forward direction, which is advantageous in significantly reducing the desorption temperature and energy consumption for desorption. Furthermore, because the catalyst loss rate in repeated regeneration processes is relatively low, it is advantageous in improving the economic viability of regenerating CO2-rich amine solutions.

[0084] The reason for this is thought to be that graphene aerogel possesses an appropriate amount of protic acid (B acid), an appropriate number of pores, and an appropriate pore structure. This is advantageous for catalyzing CO2 desorption, lowering the initial and final temperatures of desorption, accelerating the desorption rate, and reducing energy consumption for desorption. Furthermore, by supporting metal components, it provides protic acid and a certain amount of weak base to the carbon dioxide desorption process, thereby promoting the rupture of MEA-COO- and the deprotonation of MEAH+ in CO2-rich amine solutions. In addition, the appropriate number of pores and pore structure of graphene aerogel are advantageous for improving the mechanical strength of the catalyst, helping to fix the metal component during catalyst preparation, thereby reducing catalyst loss, extending the service life of regenerated catalysts, and being advantageous for industrial applications.

[0085] In some preferred embodiments of the present invention, the initial temperature for CO2 desorption is 10 to 70°C, preferably 30 to 50°C. According to the present invention, the cumulative volumetric flow rate of desorbed CO2 during the regeneration process is recorded. When the cumulative volumetric flow rate becomes constant, it indicates the end of regeneration. The initial temperature refers to the temperature at which CO2 desorption begins. The time from the start of desorption to the end of regeneration is recorded as the regeneration time.

[0086] According to the present invention, the regeneration of the CO2-rich amine solution has a relatively low initial temperature and a relatively fast desorption rate, further reducing the energy consumption for the regeneration of the CO2-rich amine solution and also resulting in a low loss rate of the regeneration catalyst, which is advantageous for the industrial application of the chemical absorption method.

[0087] In some preferred embodiments of the present invention, the CO2-rich amine solution is brought into complete contact with the catalyst, and in order to further increase the desorption rate, the contact between the CO2-rich amine solution and the catalyst is carried out under stirring conditions, with a stirring speed preferably of 100 to 200 rpm.

[0088] In this invention, the CO2-rich amine solution refers to an organic amine solution that has absorbed CO2. The organic amine solution may be any known organic amine solution or complex organic amine solution used for CO2 absorption in the art. The range of selection for the organic amine solution has already been explained and will not be repeated here.

[0089] The present invention will be described in detail below through the examples provided.

[0090] The graphene used in the following preparation examples and examples is a commercially available product from Qingdao Huatai Lubrication and Sealing Technology Co., Ltd., and the complex amine solution was purchased from Sinopec Nanjing Chemical Research Institute, with product number MA-2.

[0091] Unless otherwise stated, all raw materials used are commercially purchased.

[0092] The test methods related to the examples are as follows:

[0093] (1) The content of acid B and acid L is tested by pyridine infrared spectroscopy. The specific test method is as follows: 0.0089 g of the test sample is pressed onto a 1.3 cm diameter self-supporting sheet and placed in an in-situ cell. The sample is evacuated to 300°C and cooled to room temperature, and the background infrared spectrum is measured. Pyridine saturated vapor is adsorbed onto the sample until saturated, and the spectrum is recorded. After purging with He for 1 hour, the sample is evacuated, and the temperature is programmed to increase (0 to 350°C) to perform desorption. The spectrum is recorded every 20°C. The standard positions of acid B and acid L in the obtained pyridine infrared spectrum are 1540 cm⁻¹, respectively. -1 and 1450cm -1 The relative acid content is calculated by integrating the peaks at corresponding positions in the spectrum, normalizing the peak area of ​​the spectrum, and then determining the acid content. The acid content is calculated according to the following formula.

number

[0094] (2) Testing of specific surface area, pore volume, and pore size distribution The specific surface area, pore volume, and pore structure distribution are measured using the N2 adsorption-desorption isotherm method.

[0095] (3) X-ray photoelectron spectroscopy (XPS) analysis will be performed using an ESCALAB 250XI X-ray photoelectron spectrometer manufactured by Thermo Fisher Scientific, Inc., USA. The test conditions will be as follows: Al Kα rays will be used as the excitation source, and the scanning range will be 0 to 1200 eV.

[0096] (4) Scanning electron microscope (SEM) examination Scanning electron microscopy analysis is performed using a Hitachi S-4800 scanning electron microscope, with a test voltage of 1 to 10 kV and a magnification of 0.5 to 50 kV.

[0097] (5) Transmission electron microscope (TEM) examination Transmission electron microscopy analysis is performed using a TECNAI G2 F20 emission transmission electron microscope manufactured by FEI, Inc. in the United States, with a test voltage of 100-500kV and a magnification of 1-100k.

[0098] (6) Compression strength test The test involves pressing the graphene aerogel to be tested into a cylindrical specimen with a height of 10 mm and a diameter of 10 mm, impregnating the prepared specimen in physiological saline solution at 37°C, then heating it in a constant temperature water bath for 24 hours, accurately measuring the diameter of each specimen with an accuracy of 0.02 mm using calipers, and applying a preload of 5 N and a vertical pressure at a loading rate of 1 mm / min to the specimen using an electronic universal testing machine, and recording the maximum load value at which the specimen fractures. The compressive strength P = F / S, where F is the maximum load value (N) at which the specimen fractures and S is the base area (mm²) of the cylindrical specimen. 2 The resulting compressive strength is in MPa, which is then converted to kPa.

[0099] The following preparation example illustrates the preparation of graphene aerogel. Preparation Example 1

[0100] (1) Preparation of graphene oxide: 0.6 g of graphene, 3 g of potassium permanganate, 30 mL of concentrated sulfuric acid (98 wt%), and the housing and tetrafluoroethylene liner of the reaction vessel were placed in a refrigerator at 4°C and refrigerated for 8 hours. The refrigerated graphene, potassium permanganate, and concentrated sulfuric acid were poured into the reaction vessel tank, the reaction vessel was quickly covered, and the lid was tightened. The reaction vessel was placed in an ice bath, the temperature was controlled to 4°C, and it was left to stand for 1.5 hours. After reacting in an oven at 80°C for 1.5 hours, it was removed and cooled to room temperature. The reaction product was slowly poured into deionized water and diluted by stirring, with the volume of water being 5 times the volume of concentrated sulfuric acid. 5 mL of hydrogen peroxide solution was added dropwise while stirring until the mixture turned yellowish-brown or golden-yellow. After standing for 24 hours, the supernatant was discarded, and the precipitate at the bottom was centrifuged. The centrifuged products were washed five times each with 5 wt% hydrochloric acid solution and deionized water. Once the pH was > 5, the products were transferred to a centrifuge and centrifuged at 1000 rpm for 15 minutes, and the supernatant was discarded. The middle and lower layer samples were poured into beakers, diluted with water and washed, then centrifuged, and this process was repeated four times until the pH was > 5. After washing, the middle and lower layer slurries were transferred to light-shielded containers and stored in a refrigerator at 4°C. (2) Using a burette, the graphene oxide slurry prepared above was weighed out, diluted with water to obtain a 2 mg / mL GO slurry, and the GO slurry and ethylenediamine were mixed so that the mass ratio of ethylenediamine to graphene oxide was 0.004:1. The mixture was stirred by ultrasound, poured into a glass bottle, and heated at 95°C for 6 hours to chemically reduce it. After cooling to room temperature, the solid was removed from the vessel and given as graphene hydrogel GH. (3) The prepared GH was impregnated with 150 mL of 20% V / V ethanol aqueous solution, transferred to a centrifuge tube, placed in the freezer compartment of a refrigerator, and held at approximately -20°C for 1 hour. The frozen GH was placed in a freeze dryer, the temperature was set to -90°C, and it was held under vacuum for 24 hours. A graphene aerogel intermediate product was obtained. (4) The graphene aerogel intermediate was dissolved in an equal volume of dilute nitric acid solution (concentration 8 mol / L), heated to 80°C, and stirred for 2 hours to allow the reaction to proceed. After the reaction was complete, the graphene was removed, washed with water until neutral, and dried in an oven at 100°C for 12 hours. Graphene aerogel A1 was obtained.

[0101] Observation of the surface morphology of graphene aerogel A1 using a scanning electron microscope (SEM) revealed, as shown in Figure 1, that the graphene aerogel has a three-dimensional porous network structure formed by stacking two-dimensional sheet-like graphene. The sheets were found to be relatively uniform in size, with a relatively high stacking density, tighter connections between sheets, and a rich distribution of pores between the sheets. The average sheet length was 2.5 μm, and the average sheet thickness was 50 nm.

[0102] When the internal structure of graphene aerogel A1 was characterized using a transmission electron microscope (TEM), as shown in Figure 2, it was found that the graphene aerogel has a network-like structure formed inside, exhibiting good dispersibility and being advantageous for the movement of the medium.

[0103] Characterization of the chemical composition of graphene aerogel A1 using X-ray photoelectron spectroscopy (XPS) revealed that the prepared graphene aerogel contained elements C, N, and O, as shown in Figure 3. From the area of ​​the corresponding spectral peaks in the X-ray photoelectron spectroscopy, it was determined that the molar ratio of elements C, O, and N was approximately 25:6:1.

[0104] As shown in Figure 4, the O1s spectrum in the X-ray photoelectron spectroscopy spectrum of the graphene aerogel confirmed that the oxygen species in the graphene aerogel include hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen. From the peak areas obtained by peak separation, it was determined that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen is 4:1.5:1.

[0105] When the specific surface area, total pore volume, and pore size distribution of graphene aerogel A1 were tested using an N2 adsorption-desorption isotherm, it was found that the pore size was concentrated at 20 nm or less, as shown in Figure 5.

[0106] The B acid content of graphene aerogel A1 was measured by pyridine infrared spectroscopy, and the compressive strength of A1 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 2

[0107] (1) Preparation of graphene oxide: 0.6 g of graphene, 4.0 g of potassium permanganate, 40 mL of concentrated sulfuric acid (98 wt%), and the housing and tetrafluoroethylene liner of the reaction vessel were placed in a refrigerator at 4°C and refrigerated for 12 hours. The refrigerated graphene, potassium permanganate, and concentrated sulfuric acid were poured into the reaction vessel tank, the reaction vessel was quickly covered, and the lid was tightened. The reaction vessel was placed in an ice bath, the temperature was controlled to 4°C and left to stand for 3 hours, then it was placed in an oven at 80°C and reacted for 3 hours before being removed and cooled to room temperature. The reaction product was slowly poured into deionized water and diluted by stirring, so that the volume of water was 5 times the volume of concentrated sulfuric acid. 5 mL of hydrogen peroxide solution was added dropwise while stirring until the mixture turned yellowish-brown or golden-yellow. After standing for 24 hours, the supernatant was discarded and the precipitate at the bottom was centrifuged. The centrifuged products were washed five times each with 5% hydrochloric acid solution and deionized water. Once the pH was >5, the products were transferred to a centrifuge and centrifuged at 1000 rpm for 15 minutes, and the supernatant was discarded. The middle and lower layer samples were poured into beakers, diluted with water and washed, then centrifuged, and this process was repeated four times until the pH was >5. After washing, the middle and lower layer slurries were transferred to light-shielded containers and stored in a refrigerator at 4°C. (2) Using a burette, the graphene oxide slurry prepared above was weighed out, diluted with water to obtain a 2 mg / mL GO slurry, and the GO slurry and ethylenediamine were mixed so that the mass ratio of ethylenediamine to graphene oxide was 1:1. The mixture was stirred by ultrasound, poured into a glass bottle, and heated at 90°C for 8 hours to chemically reduce it. After cooling to room temperature, the solid was removed from the vessel and given as graphene hydrogel GH. (3) The prepared GH was impregnated with 150 mL of 20% V / V ethanol aqueous solution, transferred to a centrifuge tube, placed in the freezer compartment of a refrigerator, and held at approximately -25°C for 1 hour. The frozen GH was placed in a freeze dryer, set to -60°C, and held under vacuum for 20 hours. A graphene aerogel intermediate product was obtained. (4) The graphene aerogel intermediate was dissolved in an equal volume of dilute nitric acid solution (concentration 6 mol / L), heated to 70°C, and stirred for 4 hours to allow the reaction to proceed. After the reaction was complete, the graphene was removed, washed with water until neutral, and dried in an oven at 100°C for 12 hours. Graphene aerogel A2 was obtained. When the surface morphology of graphene aerogel A2 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. When the chemical composition of graphene aerogel A2 was characterized using X-ray photoelectron spectroscopy (XPS), the molar ratio of C, O, and N was found to be 15:12:2. Peak area analysis using peak separation of O1s revealed that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was 3:1.5:1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A2 were tested using an N2 adsorption-desorption isotherm. The B acid content of graphene aerogel A2 was measured by the pyridine infrared method, and the compressive strength of A2 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 3

[0108] (1) Graphene oxide was prepared according to the method in Preparation Example 1. (2) Using a burette, the graphene oxide slurry prepared above was weighed out, diluted with water to obtain a 2 mg / mL GO slurry, and the GO slurry and ethylenediamine were mixed so that the mass ratio of ethylenediamine to graphene oxide was 0.01:1. The mixture was stirred by ultrasound, poured into a glass bottle, and heated at 80°C for 10 hours to chemically reduce it. After cooling to room temperature, the solid was removed from the vessel and given as graphene hydrogel GH. (3) The prepared GH was impregnated with 150 mL of 20% V / V ethanol aqueous solution, transferred to a centrifuge tube, placed in the freezer compartment of a refrigerator, and held at approximately -15°C for 1 hour. The frozen GH was placed in a freeze dryer, the temperature was set to -50°C, and it was held under vacuum for 24 hours. A graphene aerogel intermediate product was obtained. (4) The graphene aerogel intermediate was dissolved in an equal volume of dilute hydrochloric acid solution (concentration 5 mol / L), heated to 60°C, and stirred for 2 hours to allow the reaction to proceed. After the reaction was complete, the graphene was removed, washed with water until neutral, and dried in an oven at 120°C for 16 hours. Graphene aerogel A3 was obtained. When the surface morphology of graphene aerogel A3 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. Characterization of the chemical composition of graphene aerogel A3 using X-ray photoelectron spectroscopy (XPS) revealed that the molar ratio of elements C, O, and N was approximately 25:15:2. Peak area analysis by O1s peak separation revealed that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was 3:1:1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A3 were tested using an N2 adsorption-desorption isotherm. The B acid content of graphene aerogel A3 was measured by the pyridine infrared method, and the compressive strength of A3 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 4

[0109] Step (2) followed the method in Preparation Example 1, except that it included the following: Using a burette, the graphene oxide slurry prepared above was weighed out, diluted with water to obtain a 2 mg / mL GO slurry, the GO slurry and ethylenediamine were mixed so that the mass ratio of ethylenediamine to graphene oxide was 0.001:1, stirred by ultrasound, poured into a glass bottle, and heated at 90°C for 6 hours to chemically reduce. After cooling to room temperature, the solid was removed from the vessel and given as graphene hydrogel GH. The prepared graphene aerogel was designated A4. When the surface morphology of graphene aerogel A4 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. Characterization of the chemical composition of graphene aerogel A4 using X-ray photoelectron spectroscopy (XPS) revealed that the molar ratio of elements C, O, and N was 45:5:1. Peak area analysis by O1s peak separation revealed that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was 7.5:1.5:1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A4 were tested using an N2 adsorption-desorption isotherm. The B acid content of graphene aerogel A4 was measured by the pyridine infrared method, and the compressive strength of A4 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 5

[0110] The method described in Preparation Example 1 was followed, except that an equal mass of ascorbic acid was used instead of ethylenediamine. Graphene aerogel A5 was obtained. When the surface morphology of graphene aerogel A5 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. Characterization of the chemical composition of graphene aerogel A5 using X-ray photoelectron spectroscopy (XPS) revealed that the molar ratio of elements C, O, and N was 40:3. Peak area analysis by O1s peak separation revealed that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was 10:2:1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A5 were tested using an N2 adsorption-desorption isotherm. The B acid content of graphene aerogel A5 was measured by the pyridine infrared method, and the compressive strength of A5 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 6

[0111] Step (4) followed the method in Preparation Example 1, except that it included the following: The graphene aerogel intermediate was dissolved in an equal volume of dilute nitric acid solution (concentration 4 mol / L), the temperature was raised to 80°C, and the reaction was stirred for 2 hours. After the reaction was complete, the graphene was removed, washed with water until neutral, and dried in an oven at 100°C for 12 hours. Graphene aerogel A6 was obtained. When the surface morphology of graphene aerogel A6 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. The chemical composition of graphene aerogel A6 was characterized using X-ray photoelectron spectroscopy (XPS), and the molar ratio of elements C, O, and N was found to be 30:5:0.3. From the peak area obtained by peak separation of O1s, it was determined that the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was 6:1.5:1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A6 were tested using N2 adsorption-desorption isotherms, the B acid content of graphene aerogel A6 was measured by pyridine infrared spectroscopy, and the compressive strength of A6 was measured using an electronic universal tester. The test results are shown in Table 1. Preparation Example 7

[0112] Step (4) followed the method in Preparation Example 1, except that it included the following: The graphene aerogel intermediate was dissolved in an equal volume of dilute nitric acid solution (concentration 1 mol / L), the temperature was raised to 60°C, and the mixture was stirred for 2 hours to allow the reaction to proceed. After the reaction was complete, the graphene was removed, washed with water until neutral, and dried in an oven at 100°C for 12 hours. Graphene aerogel A7 was obtained. When the surface morphology of graphene aerogel A7 was observed using a scanning electron microscope (SEM), it was similar to that shown in Figure 1. The chemical composition of graphene aerogel A7 was characterized using X-ray photoelectron spectroscopy (XPS), and the molar ratio of elements C, O, and N was found to be 35:4:0.3. From the peak area obtained by peak separation of O1s, the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was found to be 6.5:1:0.5. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A7 were tested using N2 adsorption-desorption isotherms, the B acid content of graphene aerogel A7 was measured by pyridine infrared spectroscopy, and the compressive strength of A7 was measured using an electronic universal tester. The test results are shown in Table 1. Comparative Preparation Example 1

[0113] In Preparation Example 1, the graphene aerogel intermediate product obtained in step (3) was designated as graphene aerogel DA1. When the surface morphology of graphene aerogel DA1 was observed using a scanning electron microscope (SEM), it was found to be a porous structure composed of graphene sheets. Characterization of the chemical composition of graphene aerogel DA1 using X-ray photoelectron spectroscopy (XPS) revealed that the molar ratio of C, N, and O elements was 25:6:1, and the peak area obtained by O1s peak separation indicated that the graphene aerogel contains only hydroxyl atoms. The specific surface area, total pore volume, and pore size distribution of graphene aerogel DA1 were tested using an N2 adsorption-desorption isotherm. The B acid content of graphene aerogel DA1 was measured by the pyridine infrared method, and the compressive strength of DA1 was measured using an electronic universal tester. The test results are shown in Table 1. Comparative Preparation Example 2

[0114] Step (3) followed the method of Preparation Example 1, except that it included the following: The prepared GH was impregnated with 150 mL of 20% V / V ethanol aqueous solution, transferred to a centrifuge tube, placed in the freezer compartment of a refrigerator, and held at approximately -10°C for 1 hour. The frozen GH was placed in a freeze dryer, the temperature was set to -30°C, and it was held under vacuum for 24 hours. A graphene aerogel intermediate product was obtained. Graphene aerogel DA2 was obtained by acid activation according to the method of Preparation Example 1. The specific surface area, total pore volume, and pore size distribution of graphene aerogel DA2 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel DA2 was measured by pyridine infrared spectroscopy, and the compressive strength of DA2 was measured using an electronic universal tester. The test results are shown in Table 1.

[0115] [Table 1]

[0116] The following examples illustrate the preparation of regenerated catalysts. Example 1

[0117] S1: A predetermined volume of aluminum nitrate solution (prepared to a concentration of 1 mol / L) and graphene aerogel A1 were placed under ultrasound, and the volume ratio of aluminum nitrate solution to graphene aerogel was set to 1:1. The mixture was then ultrasonically treated at 40,000 Hz for 1 hour, and both were thoroughly and uniformly mixed to obtain a mixed solution. S2: 25 wt% aqueous ammonia was added to the above mixture and stirred to adjust the pH to 8-9. The rate at which aqueous ammonia was added per liter of the mixture was 0.5 mL / min. The product was filtered and placed in a drying box, dried at 110°C for 8 hours, and then calcined in a muffle oven at 400°C for 6 hours to obtain regenerated catalyst S1. Based on the total mass of the regenerated catalyst, the support content was 40 wt%. The aluminum oxide content was 60 wt%. When the surface morphology of the regenerated catalyst S1 was observed using a scanning electron microscope (SEM), it was found that the supported catalyst also possessed a three-dimensional porous network structure consisting of stacked two-dimensional sheet-like graphene, and the channel structure was relatively completely maintained on the surface of the graphene sheets. This catalyst maintains a loose state of graphene aerogel, and even after support, the aerogel does not aggregate, exhibiting relatively good dispersibility, which is advantageous for the movement of the medium. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S1 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S1 were measured using the pyridine infrared method. The test results are shown in Table 2. Example 2

[0118] S1: A predetermined volume of iron nitrate solution (prepared to a concentration of 1 mol / L) and graphene aerogel A2 were placed under ultrasound, and the volume ratio of iron nitrate solution to graphene aerogel was set to 1:1. The mixture was then ultrasonically treated at 40,000 Hz for 10 hours, and both were thoroughly and uniformly mixed to obtain a mixed solution. S2:25 wt% aqueous ammonia was added to the above mixture and stirred to adjust the pH to 8-9. The rate at which aqueous ammonia was added per 1 L of the mixture was 1 mL / min. The product was filtered and placed in an oven, dried at 100°C for 12 hours, air-dried at room temperature, and then calcined in a muffle oven at 550°C for 6 hours to obtain regenerated catalyst S2. Based on the total mass of the regenerated catalyst, the content of the support was 31 wt%, and the content of iron(II,III) oxide was 69 wt%. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S2 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S2 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 3

[0119] S1: A predetermined volume of cobalt nitrate solution (prepared to a concentration of 1 mol / L) and graphene aerogel A3 were placed under ultrasound, and the volume ratio of cobalt nitrate solution to graphene aerogel was set to 1:1. The mixture was then ultrasonically treated at 40,000 Hz for 1 hour, and both were thoroughly and uniformly mixed to obtain a mixed solution. S2:25 wt% aqueous ammonia was added to the above mixture and stirred to adjust the pH to 8-9. The rate at which aqueous ammonia was added per 1 L of the mixture was 0.5 mL / min. The product was filtered and placed in an oven, dried at 110°C for 8 hours, air-dried at room temperature, and then calcined in a muffle oven at 400°C for 6 hours to obtain regenerated catalyst S3. Based on the total mass of the regenerated catalyst, the content of the support was 48 wt%, and the content of cobalt oxide was 52 wt%. The specific surface area, total pore volume, and pore size distribution of regenerated catalyst S3 were tested by N2 adsorption-desorption isotherm, and the content of B acid and L acid of regenerated catalyst S3 was measured by pyridine infrared spectroscopy. The test results are shown in Table 2. Example 4

[0120] S1: A predetermined volume of iron nitrate solution (prepared to a concentration of 1.0 mol / L) and graphene aerogel A2 were placed under ultrasound, and the volume ratio of iron nitrate solution to graphene aerogel was set to 1:1. The mixture was then ultrasonically treated at 40,000 Hz for 10 hours, and both were thoroughly and uniformly mixed to obtain a mixed solution. S2: The product was filtered and placed in an oven, dried at 110°C for 12 hours, air-dried at room temperature, and then calcined in a muffle oven at 650°C for 4 hours to obtain regenerated catalyst S4. Based on the total mass of the regenerated catalyst, the content of the support was 31 wt%, and the content of iron(III) oxide was 69 wt%. If a precipitant is not added, a higher calcination temperature is required to ensure the support of the metal oxide, but as a result, the graphene aerogel may aggregate, and the specific surface area and pore volume may decrease. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S4 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S4 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 5

[0121] The method in Example 1 was followed, except that graphene aerogel A4 was used instead of A1. Regenerated catalyst S5 was obtained. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S5 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S5 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 6

[0122] The method in Example 1 was followed, except that graphene aerogel A5 was used instead of A1. Regenerated catalyst S6 was obtained. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S6 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S6 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 7

[0123] The method in Example 1 was followed, except that graphene aerogel A6 was used instead of A1. Regenerated catalyst S7 was obtained. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S7 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S7 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 8

[0124] The method in Example 1 was followed, except that graphene aerogel A7 was used instead of A1. Regenerated catalyst S8 was obtained. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S8 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S8 was measured using the pyridine infrared method. The test results are shown in Table 2. Example 9

[0125] The procedure was the same as in Example 1, except that the aluminum nitrate solution was replaced with an equal concentration and volume of boric acid solution to obtain the regenerated catalyst S9. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S9 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst S9 was measured using the pyridine infrared method. The test results are shown in Table 2. Comparative Example 1

[0126] Commercially available aluminum oxide and graphene aerogel A1 were physically pulverized so that the mass ratio of aluminum oxide to graphene aerogel A1 was 2:3. The mixture was then placed in a muffle furnace and calcined at 400°C for 6 hours to obtain regenerated catalyst DS1. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst DS1 were tested using an N2 adsorption-desorption isotherm, and the content of B acid and L acid in the regenerated catalyst DS1 was measured using the pyridine infrared method. The test results are shown in Table 2. Comparative Example 2

[0127] Regenerated catalyst DS2 was obtained according to the method in Example 1, except that an equal amount of HZSM-5 molecular sieve (commercially available, Nankai University catalyst) was used instead of graphene aerogel A1. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst DS2 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst DS2 was measured using the pyridine infrared method. The test results are shown in Table 2. Comparative Example 3

[0128] Regenerated catalyst DS3 was obtained according to the method in Example 1, except that an equal amount of graphene aerogel DA1 was used instead of A1. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst DS3 were tested using an N2 adsorption-desorption isotherm, and the content of B acid and L acid in the regenerated catalyst DS3 was measured using the pyridine infrared method. The test results are shown in Table 2. Comparative Example 4

[0129] The GO slurry obtained in Preparation Example 1, ethylenediamine, and commercially available aluminum oxide were mixed so that the mass ratio of ethylenediamine to graphene oxide was 0.004:1. After stirring with ultrasound, the mixture was reacted in a drying chamber at 95°C for 12 hours. Subsequently, it was frozen in a refrigerator at -18°C. After complete freezing, the sample was placed in a vacuum freeze-dryer and freeze-dried, and the resulting solid product was designated as DS4. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst DS4 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst DS4 was measured using the pyridine infrared method. The test results are shown in Table 2. Comparative Example 5

[0130] Regenerated catalyst DS5 was obtained according to the method in Example 1, except that an equal amount of graphene aerogel DA2 was used instead of A1. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst DS5 were tested using an N2 adsorption-desorption isotherm, and the B acid and L acid content of the regenerated catalyst DS5 was measured using the pyridine infrared method. The test results are shown in Table 2. Table 2 shows the physicochemical data of the regenerated catalysts prepared in the above examples and comparative examples.

[0131] [Table 2]

[0132] The regeneration catalysts prepared in the above examples and comparative examples were evaluated for regeneration using an alcoholamine solution.

[0133] Preparation of CO2-rich amine solution: N2 / CO2 gas was introduced into the complex amine solution at a volume ratio of 85:15 for 2 hours to obtain a CO2-rich amine solution.

[0134] The above regeneration catalyst was added to a CO2-rich amine solution at a mass ratio of 1% (to the CO2-rich amine solution), and the mixture was continuously stirred at a stirring speed of 200 rpm while gradually increasing the temperature. The cumulative volume flow rate of desorbed CO2 was controlled and recorded using a gas flow meter. The temperature at the start of desorption (initial temperature), the end temperature, and the regeneration time were recorded. A sample of the rich solution was taken every 5 minutes, and the amount of CO2 loaded in the complex amine solution at different desorption times was tested using acid-base titration. The desorption rate, amount of desorbed CO2, and relative energy consumption were calculated, and the results are shown in Table 3. The energy consumption for desorption (H) refers to the energy consumption for desorption per unit mole of CO2 (kJ / mol), and is defined as the ratio of the energy input rate to the CO2 desorption rate, and is calculated using equation (1).

number

[0135] The relative energy consumption (RH) is calculated using equation (2), where Hb (kJ / mol) is the energy consumption for desorption in the regeneration process of the blank control solution, and Hi (kJ / mol) is the energy consumption for desorption in the process in which the regeneration catalyst under test catalyzes CO2 desorption.

number

[0136] The regeneration experiment using an alcoholamine solution was repeated six times for each regenerated catalyst. After the reaction, the regenerated catalyst was dried, its weight was measured, and the catalyst mass loss rate was calculated. Loss rate (%) = (Mass of catalyst immediately after regeneration - Mass of regenerated catalyst after 6 regenerations) / Mass of catalyst immediately after regeneration × 100%.

[0137] [Table 3]

[0138] As can be seen from the results in Tables 1-3, when the regenerated catalyst prepared using the graphene aerogel according to the present invention as a catalyst support is used for the regeneration of an alcoholamine solution, the CO2 desorption effect is effectively improved, the initial desorption temperature is lowered, and the energy consumption of the desorption process can be reduced.

[0139] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, several simple modifications can be made to the technical solution of the present invention, including combining each technical feature in any other suitable manner, and these simple modifications and combinations should also be considered as part of the disclosure of the present invention and all fall within the scope of protection of the present invention.

Claims

1. A graphene aerogel, wherein the graphene aerogel has a B acid content of 0.001 to 0.05 mmol / g and a specific surface area of ​​40 to 200 m². ２ A graphene aerogel characterized by having a volume of 50% or more of pores with a diameter of 20 nm or less per g, relative to the total pore volume of the graphene aerogel.

2. The B acid content of the graphene aerogel is 0.01 to 0.03 mmol / g. Preferably, the specific surface area of ​​the graphene aerogel is 100 to 120 m². ２ The graphene aerogel according to claim 1, wherein the amount is / g.

3. The total pore volume of the graphene aerogel is 0.01 to 0.5 mL / g, preferably 0.1 to 0.3 mL / g. Preferably, in the graphene aerogel, the proportion of the volume of pores with a pore size of 20 nm or less to the total pore volume of the graphene aerogel is 55 to 90%, more preferably 70 to 80%, according to claim 1 or 2.

4. The graphene aerogel contains elements C, O, and N, and the molar ratio of the elements C, O, and N is (1-60):(5-30):(0.5-5), preferably (15-35):(10-20):(1-2). Preferably, when measured by X-ray photoelectron spectroscopy, the oxygen species in the graphene aerogel include hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen, and the molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen is (1-20):(0.1-5):(1-5), preferably (1-5):(0.5-2):(1-2), the graphene aerogel according to any one of claims 1 to 3.

5. The graphene aerogel has a three-dimensional porous network structure formed by stacking two-dimensional sheet-like graphene, Preferably, the average sheet thickness of the two-dimensional sheet graphene is 10 to 200 nm, preferably 50 to 100 nm. Preferably, the average sheet length of the two-dimensional sheet-like graphene is 0.1 to 10 μm, preferably 1 to 5 μm, according to any one of claims 1 to 4.

6. The graphene aerogel according to any one of claims 1 to 5, wherein the compressive strength of the graphene aerogel is higher than 30 kPa, preferably 40 to 50 kPa.

7. A regenerative catalyst, wherein the regenerative catalyst comprises a carrier and a metal component supported on the carrier, the metal component having the properties of Lewis acid, and the carrier is a graphene aerogel according to any one of claims 1 to 6.

8. The B acid content in the regenerating catalyst is 0.0005 to 0.02 mmol / g, more preferably 0.008 to 0.016 mmol / g. Preferably, in the regenerating catalyst, the molar ratio of B acid to L acid is 0.01 to 1:1, preferably 0.1 to 0.5:1, and more preferably 0.1 to 0.2:1, as described in claim 7.

9. The regenerative catalyst according to claim 7 or 8, wherein, based on the total mass of the regenerative catalyst, the content of the support is 30 to 70 wt%, preferably 30 to 50 wt%, and the content of the metal component is an oxide, is 30 to 70 wt%, preferably 50 to 70 wt%.

10. The regenerative catalyst according to any one of claims 7 to 9, wherein the metal component is a transition metal element and / or a group IIIA element, preferably at least one selected from Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga, and In, more preferably at least one selected from Al, Fe, Co, Ni, and Ti.

11. The specific surface area of ​​the aforementioned regenerated catalyst is 30 to 100 m². ２ / g, preferably 45 to 80m ２ / g, Preferably, the total pore volume of the regenerated catalyst is 0.06 to 0.2 mL / g, preferably 0.1 to 0.15 mL / g. Preferably, in the regenerating catalyst, the ratio of the volume of pores with a pore size of 20 nm or less to the total pore volume of the regenerating catalyst is 30% or more, preferably 30 to 80%, and more preferably 50 to 60%, according to any one of claims 7 to 10.

12. CO ２ Use of the regeneration catalyst according to any one of claims 7 to 11 in the regeneration of a rich amine solution.

13. CO ２ A method for regenerating a richamine solution, wherein under regeneration conditions, CO ２ When the rich amine solution is brought into contact with the catalyst, CO ２ Remove and reattach, The catalyst is a regenerative catalyst according to any one of claims 7 to 11. Preferably, the CO ２ Based on the total mass of the rich amine solution, the amount of the catalyst used is 1 to 10 wt%, preferably 1 to 3 wt%, Preferably, the CO ２ The CO2 is characterized in that the initial temperature for attachment and detachment is 10 to 70°C, preferably 30 to 50°C. ２ Method for regenerating Richamine solution.

Images