Graphene aerogel, regeneration catalyst and application thereof, and regeneration method of CO2-rich amine solution

Abstract

The present invention relates to the field of desorption and regeneration of CO2-rich amine solutions, and discloses a graphene aerogel, a regeneration catalyst, an application thereof, and a regeneration method for a CO2-rich amine solution. The graphene aerogel has a B acid content of 0.001-0.05 mmol / g and a specific surface area of ​​40-200 m 2 / g, and the volume of pores with a pore diameter of less than 20nm accounts for no less than 50% of the total pore volume of the graphene aerogel. The graphene aerogel is used in a regeneration catalyst for a CO2-rich amine solution, facilitating the catalytic desorption of CO2, lowering the initial and final desorption temperatures, increasing the desorption rate, shortening the desorption time, reducing desorption energy consumption, and increasing the desorption capacity.

Description

Technical Field

[0001] The present invention relates to the field of desorption and regeneration of CO2-rich amine solutions, and in particular to a graphene aerogel, a regeneration catalyst and applications thereof, and a regeneration method for CO2-rich amine solutions. Background Art

[0002] Large-scale, low-cost and commercialization will be the future development trend of CCUS projects.

[0003] It is reported that CO2 capture technology is the most critical link in the large-scale application of CCUS technology, which determines the purity and cost of the gas source. The process energy consumption accounts for more than 60% of the total energy consumption of the CCUS project. Therefore, reducing energy consumption is crucial for flue gas CO2 capture.

[0004] Current methods for CO2 capture and purification primarily include chemical absorption, physical absorption and physicochemical absorption, solid adsorption, membrane treatment, and cryogenic separation. However, chemical absorption is undoubtedly the most promising method in terms of time to market, technological maturity, and future prospects. Chemical absorption separates CO2 from other gases by selectively reacting an absorbent with the CO2 in the flue gas mixture. The absorbent is then regenerated through the reverse reaction, releasing high-purity CO2 for enrichment.

[0005] At present, the main bottleneck limiting the large-scale application of chemical absorption is its high energy consumption and high cost. In order to reduce energy consumption, researchers have made efforts in two main aspects: the development of high-efficiency absorbents and the process optimization of the capture system. CN109316903A discloses a mesoporous solid acid-base catalyst for the desorption of CO2-rich amine solution. The mesoporous solid acid-base catalyst is Fe2O3 loaded on a carrier molecular sieve MCM-41. The catalyst is easy to separate, has good stability and can be recycled, but the temperature required for its desorption is 98°C, which is a relatively high desorption temperature. CN106984333A discloses a supported catalyst for the regeneration of carbon dioxide-rich amine solution. The catalyst is a metal oxide-supported sulfate-type solid superacid catalyst, wherein the carrier is γ-Al2O3, which is relatively high relative to SO4 2- / ZrO2 catalyst and γ-Al2O3, which can reduce the desorption energy consumption of ethanolamine (MEA), but the desorption temperature required is also high.

[0006] Therefore, how to further reduce the desorption temperature of CO2-rich amine solution and reduce energy consumption is an important issue that needs to be solved in reducing the capture and purification of CO2 by chemical absorption. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of high carbon dioxide desorption temperature and high energy consumption in the prior art, and to provide a graphene aerogel, a regeneration catalyst and its application, and a regeneration method for a CO2-rich amine solution. The graphene aerogel is used in the regeneration catalyst to promote the desorption reaction, reduce the initial reaction temperature, and reduce energy consumption.

[0008] In order to achieve the above object, the first aspect of the present invention provides a graphene aerogel, wherein the B acid content of the graphene aerogel is 0.001-0.05 mmol / g, the specific surface area is 40-200 m 2 / g, the volume of pores with a pore diameter of less than 20 nm accounts for no less than 50% of the total pore volume of the graphene aerogel.

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

[0010] The third aspect of the present invention provides use of the regeneration catalyst described in the second aspect in the regeneration of a CO2-rich amine solution.

[0011] A fourth aspect of the present invention provides a method for regenerating a CO2-rich amine solution, wherein the CO2-rich amine solution is contacted with a catalyst under regeneration conditions to desorb CO2;

[0012] Wherein, the catalyst is the regenerated catalyst described in the second aspect.

[0013] The graphene aerogel provided by the present invention has an appropriate amount of protonic acid (B acid), a suitable number of pores and a pore structure, and is thus applied to the regeneration catalyst of a CO2-rich amine solution. It synergizes with the metal component, can not only provide the protonic acid necessary for the desorption process, but also provide the necessary basic groups to promote the desorption reaction, which is beneficial for catalyzing CO2 desorption, reducing the desorption initial temperature and the end temperature, increasing the desorption rate, shortening the desorption time, reducing the desorption energy consumption and increasing the desorption amount, and having higher mechanical strength, thereby improving the cycle life. Preferably, it has a three-dimensional porous network structure formed by stacking two-dimensional flaky graphene, with through holes of varying sizes distributed between the layers, which not only ensures the shuttling of the solution, but also helps to improve the compressive strength of the graphene aerogel, further improving the stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a SEM image of graphene aerogel A1 prepared in Preparation Example 1;

[0015] Figure 2 is a TEM image of graphene aerogel A1 prepared in Preparation Example 1;

[0016] Figure 3 is the X-ray photoelectron spectrum of the graphene aerogel A1 prepared in Preparation Example 1;

[0017] Figure 4 is the XPS peak spectrum of O1s of graphene aerogel A1 prepared in Preparation Example 1;

[0018] Figure 5 is the pore size distribution curve of graphene aerogel A1 prepared in Preparation Example 1. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0020] The first aspect of the present invention provides a graphene aerogel, wherein the graphene aerogel has a B acid content of 0.001-0.05 mmol / g and a specific surface area of ​​40-200 m 2 / g, the volume of pores with a pore diameter of less than 20 nm accounts for no less than 50% of the total pore volume of the graphene aerogel.

[0021] According to the present invention, the graphene aerogel contains an appropriate amount of protonic acid (Br) to improve the CO2 desorption rate. Preferably, the graphene aerogel has a Br content of 0.01-0.03 mmol / g. Controlling the Br content in the graphene aerogel within the above-mentioned preferred range, combined with an appropriate pore number and pore structure, helps promote the CO2 desorption reaction and fundamentally reduces reaction energy consumption.

[0022] In the present invention, the content of B acid (or L acid) is characterized by pyridine infrared method. The specific test method is as follows: 0.0089g of the sample to be tested is pressed into a self-supporting sheet with a diameter of 1.3cm, placed in an in-situ cell, the sample is vacuumed at 300℃, cooled to room temperature, and a background infrared spectrum is measured. The saturated vapor of pyridine is adsorbed until the sample is saturated with adsorption, and the spectrum is recorded. After He purge for 1h, the sample is vacuumed and programmed temperature desorption (0-350℃) is performed, and the spectrum is recorded every 20℃. The standard positions of B acid and L acid in the obtained pyridine infrared spectrum are 1540cm -1 and 1450cm -1 , integrate the peaks at the corresponding positions in the figure, normalize the peak areas of the spectrum, and then calculate the acid amount according to the following formula.

[0023]

[0024] Wherein, C is the acid content, unit, mmol / g; K L / B is the absorption coefficient of L acid or B acid, which are 1.42 and 1.88 respectively, that is, K L is the absorption coefficient of L acid, which is 1.42, K B is the absorption coefficient of B acid, which is 1.88, and the unit is mmol / cm; I L / B is the peak area of ​​L acid or B acid, the unit is cm -1 ; R is the tablet diameter, in cm; W is the tablet weight, in g.

[0025] The graphene aerogel of the present invention has a suitable number of pores and pore structure, and the specific surface area of ​​the graphene aerogel is 50-200m 2 / g, preferably 100-120m 2 In the above preferred case, it can ensure that when the graphene aerogel is used in the regeneration catalyst of the CO2-rich amine solution, it has a suitable contact area with the CO2-rich amine solution, which is beneficial to catalyzing CO2 desorption and improving the mechanical strength of the graphene aerogel.

[0026] In some preferred 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.

[0027] In some preferred embodiments of the present invention, the volume of pores with a pore diameter of 20 nm or less in the graphene aerogel accounts for no less than 50% of the total pore volume of the graphene aerogel, preferably 55-90%, and more preferably 70-80%. The graphene aerogel provided by the present invention can improve catalytic efficiency when used as a catalyst carrier by ensuring that the pores with a pore diameter of 20 nm or less are within a certain content range, thereby reducing the desorption temperature and shortening the desorption time, and improving the mechanical strength of the catalyst. The reason for this may be that the pores with a pore diameter of 20 nm or less are filled with metal components when the catalyst is subsequently loaded, thereby anchoring the metal components on the graphene aerogel, which is conducive to exerting the activity of the metal components. When combined with an appropriate amount of B acid, the catalytic efficiency can be improved, thereby reducing the desorption temperature and shortening the desorption time, and helping to reduce the catalyst loss rate during the regeneration process of the alcoholamine solution, thereby extending the service life of the catalyst.

[0028] In the present invention, the specific surface area, pore volume and pore distribution are measured by the N2 adsorption-desorption isotherm method.

[0029] In some preferred embodiments of the present invention, X-ray photoelectron spectroscopy (XPS) is used to characterize the chemical composition of the graphene aerogel. The X-ray photoelectron spectroscopy analysis is tested on an ESCALAB250XI X-ray photoelectron spectrometer produced by Thermo Fisher Scientific, USA. The test conditions include: the excitation source is Al Kα ray, and the scanning range is 0-1200 eV.

[0030] According to some preferred embodiments of the present invention, the graphene aerogel contains C, N and O elements. In the X-ray photoelectron spectrum of the graphene aerogel of the present invention, there are corresponding characteristic peaks of C, N and O, indicating that the graphene aerogel of the present invention contains C, N and O elements. The total amount of C element in the graphene aerogel is determined by the area of ​​the C1s peak in the X-ray photoelectron spectrum, the total amount of O element is determined by the area of ​​the O1s peak, and the total amount of N element is determined by the area of ​​the N1s 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, it can be 15:10:1, 15:15:1, 15:20:1, 20:10:1, 25:15:1, 25:20:1, 30:10:1, 30:15:1 :1, 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 are typical but non-limiting molar ratios.

[0031] In some preferred embodiments of the present invention, the O1s spectrum in the X-ray photoelectron spectroscopy of the graphene aerogel of the present invention is composed 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, as determined by peak area analysis, is (1-20):(0.1-5):(1-5), preferably (1-5):(0.5-2):(1-2). For example, typical but non-limiting molar ratios may be 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, 5:2:1, etc. The preferred distribution of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen groups described above is beneficial for further improving the hydrophilicity of the graphene aerogel and facilitating desorption.

[0032] In some preferred embodiments of the present invention, the graphene aerogel is a three-dimensional porous network structure formed by stacking two-dimensional graphene sheets.

[0033] In some preferred embodiments of the present invention, the average sheet thickness of the two-dimensional flaky graphene in the graphene aerogel is determined by scanning electron microscopy (SEM) to be 10-200 nm, preferably 50-100 nm.

[0034] Preferably, the average sheet length of the two-dimensional flaky graphene is 0.1-10 μm, preferably 1-5 μm.

[0035] In this application, "sheet length" refers to the maximum straight-line distance between two points on the same plane of a sheet, and "sheet thickness" refers to the maximum straight-line distance between two points on a plane perpendicular to the sheet length. The sheet lengths and thicknesses of 50 two-dimensional graphene sheets in the graphene aerogel were measured using scanning electron microscopy, and the average values ​​were calculated.

[0036] In the present invention, the surface morphology of the graphene aerogel is observed by scanning electron microscopy (SEM), and the SEM analysis is performed on an S-4800 scanning electron microscope produced by Hitachi, Japan, with a test voltage of 1-10 kV and a magnification of 0.5-50 k.

[0037] The internal structure of the graphene aerogel was characterized by transmission electron microscopy (TEM). The TEM analysis was performed on a TECNAI G2 F20 transmission electron microscope produced by FEI Company in the United States. The test voltage was 100-500 kV and the magnification was 1-100 k.

[0038] In the scanning electron microscope image (SEM image), the graphene aerogel has a three-dimensional porous network structure formed by stacking two-dimensional flake graphene. The flake sizes are relatively uniform, the stacking is relatively dense, and more connections are formed between the flakes. Further magnification shows that there are abundant pores distributed between the flakes. The internal structure characterized by the transmission electron microscope image (TEM image) shows that a network structure is formed inside the graphene aerogel, which has good dispersibility and is conducive to the transmission of the medium.

[0039] In some preferred embodiments of the present invention, the compressive strength of the graphene aerogel is higher than 30kPa, even reaching 80kPa, preferably 40-50kPa. In the present invention, the compressive strength of the graphene aerogel is related to the morphology, pore number and pore structure of the graphene aerogel. By ensuring that the pores with a pore diameter of less than 20nm are within a certain content range, while ensuring the shuttling of the solution, it helps to improve the compressive strength of the graphene aerogel. Under the above-mentioned preferred compressive strength, it is conducive to the recycling and reuse of the graphene aerogel and reduces losses. The compressive strength of the graphene aerogel in the prior art is generally 10-30kPa.

[0040] In the present invention, the test conditions for the compressive strength of graphene aerogel include: pressing the graphene aerogel to be tested into a cylindrical specimen with a height of 10mm and a diameter of 10mm, immersing the prepared specimen in 37°C physiological saline, and then heating it in a constant temperature water bath for 24 hours, accurately measuring the individual diameter of each specimen with a vernier caliper, accurate to 0.02mm, and vertically pressurizing the specimen with a preload of 5N and a loading speed of 1mm / min on an electronic universal testing machine, and recording the maximum load value when the specimen breaks. Compression strength P = F / S, where F is the maximum load value when the specimen breaks (N), and S is the bottom area of ​​the cylindrical specimen (mm 2 ), the unit of compressive strength is MPa, which is converted to kPa.

[0041] In some preferred embodiments of the present invention, the method for preparing the graphene aerogel comprises:

[0042] (1) uniformly mixing a dispersion containing graphene oxide with a reducing agent, performing a reduction reaction, and obtaining a graphene hydrogel;

[0043] (2) removing the solvent in the graphene hydrogel to obtain a graphene aerogel intermediate product;

[0044] (3) contacting the graphene aerogel intermediate product with an acidic solution to perform an activation reaction.

[0045] According to the present invention, after a graphene aerogel intermediate product is prepared by an oxidation-follow-reduction method, the graphene aerogel intermediate product is activated using an acidic solution, so that the graphene aerogel has an appropriate amount of proton acid, a suitable number of pores and a pore structure. When the prepared graphene aerogel is used in the desorption process after carbon dioxide is captured by complex amine, it helps to accelerate CO2 desorption.

[0046] In some preferred embodiments of the present invention, the concentration of the dispersion containing graphene oxide is 0.5-10 mg / mL, preferably 1-3 mg / mL. The present invention does not particularly limit the source of the graphene oxide; it can be commercially available or prepared using conventional graphene oxide preparation methods in the art. For example, the graphene oxide can be prepared using the Hummers method or a modified Hummers method. The techniques for preparing graphene oxide using the Hummers method or the modified Hummers method are well known to those skilled in the art and can be prepared by reference to existing techniques.

[0047] In some preferred embodiments of the present invention, the mass ratio of the reducing agent to graphene oxide is 0.001-2:1. In order to ensure that the prepared graphene aerogel has both suitable pore structure and good compressive strength, the mass ratio of the reducing agent to graphene oxide is preferably 0.004-1:1.

[0048] Any reducing agent known in the art that can be used for graphene oxide reduction can be applied to the present invention, for example, ethylenediamine, ascorbic acid, etc. can be used.

[0049] In some preferred embodiments of the present invention, the reducing agent is ethylenediamine. Using ethylenediamine as a reducing agent not only helps increase the degree of graphene reduction but also provides crosslinking. As a weak reducing agent, it imparts a fluffy structure and an appropriate number and structure of pores to the final product, thereby promoting the CO2 desorption reaction. Furthermore, the use of ethylenediamine enhances the hydrophilicity of the product, eliminating the need for an additional crosslinking agent. The resulting graphene aerogel exhibits a strong hydrophilicity.

[0050] In some preferred embodiments of the present invention, in step (1), the reduction reaction temperature is 60-180° C., preferably 80-100° C., and the time is 6-18 h, preferably 6-10 h.

[0051] In the present invention, there is no particular limitation on the mixing method of the dispersion containing graphene oxide and the reducing agent. Ultrasonication and / or stirring can be used as long as the dispersion and the reducing agent can be uniformly mixed.

[0052] In the present invention, any conventional method in the art can be used to remove the solvent in the graphene hydrogel, as long as the solvent in the graphene hydrogel can be effectively removed to obtain a graphene aerogel. For example, the method of removing the solvent in the graphene hydrogel includes: soaking the graphene hydrogel in an aqueous solution of alcohol, and then performing a first drying.

[0053] In some preferred embodiments of the present invention, the volume content of alcohol in the alcohol aqueous solution is 10-50%, preferably 20-30%; the alcohol can be a C1-C5 monohydric alcohol, such as at least one of ethanol, methanol, and isopropanol.

[0054] The present invention has no particular limitation on the amount of the alcohol aqueous solution, as long as the graphene hydrogel can be completely immersed.

[0055] According to the present invention, there are various ways to carry out the first drying. In some specific embodiments of the present invention, the first drying includes: first freezing at -10 to -30°C for 1-12 hours, and then freeze-drying at -40 to -120°C for 24-60 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, and to ensure the stability of the internal structure of the graphene aerogel, thereby improving the compressive strength of the graphene aerogel. Preferably, the first drying includes: first freezing at -15 to -25°C for 1-5 hours, and then freeze-drying at -50 to -90°C for 24-36 hours.

[0056] In the present invention, an acidic solution is used to activate the graphene aerogel intermediate product, thereby providing an appropriate amount of proton acid in the graphene aerogel, thereby providing acidic sites for the desorption of the alcoholamine solution that absorbs carbon dioxide. In some specific embodiments of the present invention, the acidic solution is provided by an aqueous acid solution. The present invention allows for a wide range of choices for the specific type of acid, and can use any conventional organic or inorganic acid 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.

[0057] In some preferred embodiments of the present invention, the concentration of the acid aqueous solution is 4-10 mol / L, preferably 5-8 mol / L.

[0058] In some specific embodiments of the present invention, in order to ensure that the prepared graphene aerogel has an appropriate B acid content, the volume ratio of the acidic solution to the graphene aerogel intermediate product is 1-2.5:1, preferably 1-2:1, and more preferably 1-1.5:1.

[0059] In some preferred embodiments of the present invention, the temperature of the activation reaction is 40-90°C, preferably 60-80°C; the time of the activation reaction is 2-8h, preferably 2-4h; the adoption of the above preferred embodiments helps to retain more active sites without destroying the graphene aerogel structure.

[0060] In some preferred embodiments of the present invention, in order to promote sufficient contact between the graphene aerogel intermediate product and the acidic solution and increase the activation reaction rate, the activation reaction is carried out under stirring conditions.

[0061] In some preferred embodiments of the present invention, the preparation method further comprises washing the product obtained from the activation reaction and performing a second drying. The washing and second drying can be performed using conventional operating conditions in the art, as long as the residual acidic solution in the product is removed, and the present invention is not particularly limited thereto. Preferably, the second drying temperature is 60-120°C, preferably 100-120°C, and the drying time is 8-24 hours, preferably 10-15 hours.

[0062] A second aspect of the present invention provides a regeneration catalyst, comprising a carrier and a metal component supported on the carrier; the metal component has Lewis acid properties, and the carrier is the graphene aerogel described in the first aspect.

[0063] According to the present invention, a metal component with Lewis acid properties is loaded onto the graphene aerogel, enabling the regenerated catalyst to provide not only the proton acid necessary for the desorption process but also the necessary basic groups, promoting the desorption reaction and fundamentally reducing the energy consumption of the reaction. In the present invention, the metal component is chemically bonded to the graphene aerogel, which helps enhance the interaction between the support and the metal component, transforming single-center adsorption and desorption into multi-center adsorption and desorption, further improving the adsorption and desorption capacity.

[0064] In the present invention, the term "Lewis acid" refers to a molecule or ion that can accept external electrons. The metal component with Lewis acid properties is chemically bonded to the graphene aerogel and can simultaneously provide Lewis acid in the regenerated catalyst.

[0065] In some preferred embodiments of the present invention, the regenerated catalyst comprises B acid and L acid, and the content of B acid is 0.0005-0.02 mmol / g, more preferably 0.008-0.016 mmol / g.

[0066] In some preferred embodiments of the present invention, the ratio of L-acid to B-acid in the regenerated catalyst can be regulated by controlling the loading of the metal component. To improve product desorption performance, the molar ratio of B-acid to L-acid in the regenerated catalyst is preferably 0.01-1:1, preferably 0.1-0.5:1, and more preferably 0.1-0.2:1. Regulating the molar ratio of L-acid to B-acid within this preferred range is beneficial for improving desorption efficiency and reducing energy consumption.

[0067] In the present invention, the B acid, L acid and their relative contents in the regenerated catalyst are measured by pyridine infrared method, which is the same as the method above and will not be repeated here.

[0068] In some preferred embodiments of the present invention, the carrier comprises 30-70 wt%, preferably 30-50 wt%, of the total mass of the regenerated catalyst; and the metal component comprises 30-70 wt%, preferably 50-70 wt%, of the metal component, calculated as oxide. Within these preferred component content ranges, the regenerated catalyst possesses a pH that not only provides the proton acid necessary for the desorption process but also provides the necessary basic groups, thereby promoting the desorption reaction.

[0069] In the present invention, the content of each component in the regenerated catalyst is obtained by XPS testing.

[0070] The present invention has a wide range of options for the specific type of the metal component, and any metal with Lewis acid properties can be used in the present invention. In some preferred embodiments of the present invention, the metal component is selected from transition metal elements and / or Group IIIA elements, preferably at least one of Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga, and In. In order to further improve the catalytic activity of the regenerated catalyst and increase the CO2 desorption rate, the metal component is preferably selected from at least one of Al, Fe, Co, Ni, and Ti.

[0071] In the present invention, the metal component is at least partially present in the form of an oxide.

[0072] In some preferred embodiments of the present invention, the regenerated catalyst has a suitable specific surface area. Preferably, the specific surface area of ​​the regenerated catalyst is 30-100 m 2 / g, preferably 45-80m 2 In the above preferred case, the regenerated catalyst has a good dispersion effect, which is conducive to the exposure of more active sites and accelerates the reaction.

[0073] In some preferred embodiments of the present invention, the total pore volume of the regenerated catalyst is 0.06-0.2 mL / g, preferably 0.1-0.15 mL / g. The rich pore distribution within the regenerated catalyst not only ensures mass transfer efficiency and improves regeneration efficiency, but also provides high mechanical strength and increases the service life of the catalyst.

[0074] In some preferred embodiments of the present invention, the volume of pores with a pore size of 20 nm or less in the regenerated catalyst accounts for no less than 30%, preferably 30-80%, and more preferably 50-60%, of the total pore volume of the regenerated catalyst. Compared to unloaded graphene aerogel, the volume fraction of pores with a pore size of 20 nm or less is reduced after the catalyst is prepared by loading the metal component. This may be due to the fact that some of the metal component fills the pores with a pore size of 20 nm or less in the graphene aerogel, thereby reducing the number of pores in this area. In this case, the metal component is anchored to the graphene aerogel, which facilitates the activity of the metal component. Combining the metal component with an appropriate amount of Br(II) acid can improve catalytic efficiency, thereby lowering the desorption temperature and shortening the desorption time. This helps reduce the catalyst loss rate during the regeneration process in the alcoholamine solution and prolongs the catalyst's service life.

[0075] In the present invention, the specific surface area, pore volume and pore distribution of the regenerated catalyst are measured by the N2 adsorption-desorption isotherm method.

[0076] According to a preferred embodiment of the present invention, the preparation method of the regenerated catalyst comprises:

[0077] S1. In the presence of ultrasound, mixing a support and a solution of a soluble compound containing a metal component to obtain a mixed solution;

[0078] S2, adding a precipitant to the mixed solution to carry out a precipitation reaction, followed by drying and calcining;

[0079] Wherein, the carrier includes the graphene aerogel described in the first aspect, and the metal component has Lewis acid properties.

[0080] According to the present invention, the metal component can be loaded on the carrier by in-situ deposition through the impregnation-precipitation method, so that in the obtained regenerated catalyst, the metal component is bonded to the graphene aerogel through chemical bonds, and the metal component and the carrier have a strong interaction, which helps to improve the catalytic activity of the regenerated catalyst and increase the CO2 desorption rate.

[0081] In some preferred 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 0.1-4:1, preferably 0.5-2:1.

[0082] In the present invention, the concentration of the solution of the soluble compound containing the metal component has a wide selection range. In order to ensure uniform dispersion of the metal oxide and avoid clogging of the pores, preferably, the concentration of the solution of the soluble compound containing the metal component is 0.5-2 mol / L, more preferably 1-1.5 mol / L.

[0083] In some preferred embodiments of the present invention, the ultrasonic frequency is 10,000-100,000 Hz, preferably 30,000-50,000 Hz; and the mixing time is 1-3 hours, preferably 1-1.5 hours. This preferred mixing method facilitates uniform mixing and sufficient contact between the support and the soluble compound of the metal component, thereby improving the uniformity and dispersion of the metal component loading on the support.

[0084] In the present invention, there is no particular limitation on the specific type of the soluble compound of the metal component, and it can be selected from conventional soluble organic salts or inorganic salts containing metal components in the art, for example, it can be selected from at least one of nitrates, acetates, sulfates and chlorides containing metal components.

[0085] The present invention has a wide range of options for the specific type of the metal component, and any metal with Lewis acid properties can be used in the present invention. In some preferred embodiments of the present invention, the metal component is selected from transition metal elements and / or Group IIIA elements, preferably at least one of Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga, and In. In order to further improve the catalytic activity of the regenerated catalyst and increase the CO2 desorption rate, the metal component is preferably selected from at least one of Al, Fe, Co, Ni, and Ti.

[0086] In some preferred embodiments of the present invention, in step S2, the pH of the precipitation reaction is adjusted by adding a precipitant. Preferably, the pH of the precipitation reaction is 8-10, preferably 8-9.

[0087] In some preferred embodiments of the present invention, the precipitant is added at a rate of 0.1-2 mL / min, preferably 0.5-1 mL / min, relative to 1 L of the mixed solution. Controlling the precipitant addition rate within the above preferred range is conducive to more uniform precipitation of metal ions.

[0088] The present invention does not particularly limit the specific selection of the precipitant. Conventional precipitants in the art can be used in the present invention. For example, the precipitant can be aqueous ammonia. The present invention has a wide range of selection for the concentration of the aqueous ammonia. Preferably, the concentration of the aqueous ammonia is 22-28 wt%.

[0089] In the present invention, there are no particular limitations on the specific methods and conditions for drying in step S2, as long as the solvent in the product of the precipitation reaction can be removed. A solid-liquid separation operation may also be included before drying. The present invention also does not particularly limit the specific method for solid-liquid separation, and those skilled in the art may select a method based on actual needs.

[0090] In some preferred embodiments of the present invention, in step S2, the drying temperature is 40-150° C., and the drying time is 8-24 h; preferably, the drying temperature is 80-120° C., and the drying time is 8-12 h.

[0091] In some preferred embodiments of the present invention, in step S2, the calcination temperature is 300-1000°C, preferably 300-600°C; and the calcination time is 1-10 hours, preferably 4-8 hours.

[0092] The third aspect of the present invention provides use of the regeneration catalyst described in the second aspect in the regeneration of a CO2-rich amine solution.

[0093] The regeneration catalyst can be used as a CO2 desorption catalyst in the regeneration of a CO2-rich amine solution, wherein the CO2-rich amine solution refers to an organic amine solution that has absorbed CO2, and the organic amine solution can be any organic amine or composite organic amine solution known in the art for CO2 absorption, including but not limited to a combination of one or more of monoethanolamine, diethanolamine, methyldiethanolamine, and triethanolamine.

[0094] The graphene aerogel B acid content, suitable pore number and pore structure in the regeneration catalyst, under the synergistic effect of the metal component, can be used in the regeneration process of the CO2-rich amine solution to effectively promote the desorption reaction, which is beneficial to catalyze CO2 desorption, reduce the initial and end temperatures of desorption, increase the desorption rate, shorten the desorption time, reduce the desorption energy consumption and increase the desorption amount. In addition, the regeneration catalyst has high mechanical strength, thereby improving the cycle life.

[0095] A fourth aspect of the present invention provides a method for regenerating a CO2-rich amine solution, wherein the CO2-rich amine solution is contacted with a catalyst under regeneration conditions to desorb CO2;

[0096] Wherein, the catalyst is the regenerated catalyst described in the second aspect.

[0097] In some preferred embodiments of the present invention, the amount of the catalyst is 1-10 wt %, preferably 1-3 wt %, based on the total mass of the CO 2 -rich amine solution.

[0098] Conventional regeneration catalysts used in the prior art for regenerating CO₂-rich amine solutions have high preparation costs, require high initial desorption temperatures, and require long reaction times, resulting in high energy consumption during the desorption process. The regeneration catalyst provided by the present invention utilizes graphene aerogel as a carrier. This, in synergistic action with the metal component, promotes the desorption reaction in a positive direction, significantly reducing the desorption temperature and desorption energy consumption. Furthermore, the catalyst loss rate during repeated regeneration is low, thereby improving the economic efficiency of regenerating CO₂-rich amine solutions.

[0099] The reason may be that graphene aerogel has an appropriate amount of proton acid (B acid), a suitable number of pores and a pore structure, which is beneficial to catalyzing CO2 desorption, reducing the initial and end temperatures of desorption, and increasing the desorption rate, thereby reducing the desorption energy consumption. After further loading metal components, it provides proton acid for the carbon dioxide desorption process and a certain weak base, thereby promoting the breakage of MEA-COO- and the deprotonation process of MEAH+ in the CO2-rich amine solution; at the same time, the appropriate number of pores and pore structure of graphene aerogel are also beneficial to improving the mechanical strength of the catalyst, which helps to anchor the metal components during the catalyst preparation process, thereby reducing the loss of the catalyst and increasing the service life of the regenerated catalyst, which is beneficial to industrial application.

[0100] In some preferred embodiments of the present invention, the initial temperature of the CO2 desorption is 10-70° C., preferably 30-50° C. According to the present invention, the cumulative volume flow of the desorbed CO2 is recorded during the regeneration process. When the cumulative volume flow is constant, it indicates that the regeneration is completed. The initial temperature refers to the temperature at which CO2 begins to be desorbed. The time from the start of desorption to the end of regeneration is recorded and recorded as the regeneration time.

[0101] According to the present invention, the regeneration of the CO2-rich amine solution has a lower initial temperature and a higher desorption rate, which further reduces the regeneration energy consumption of the CO2-rich amine solution and has a low loss rate of the regenerated catalyst, which is conducive to the industrial application of the chemical absorption method.

[0102] In some preferred embodiments of the present invention, in order to ensure sufficient contact between the CO2-rich amine solution and the catalyst and further accelerate the desorption rate, the contact between the CO2-rich amine solution and the catalyst is carried out under stirring conditions, and the stirring rate is preferably 100-200 rpm.

[0103] In the present invention, the CO2-rich amine solution refers to an organic amine solution that has absorbed CO2. The organic amine solution can be any organic amine or composite organic amine solution known in the art for CO2 absorption. The selection range of the organic amine solution has been described in the previous text and will not be repeated here.

[0104] The present invention will be described in detail below through examples.

[0105] The graphene used in the following preparation examples and embodiments is a commercial product of Qingdao Huatai Lubrication and Sealing Technology Co., Ltd., and the complex amine solution is purchased from Sinopec Nanjing Chemical Research Institute, model number MA-2.

[0106] Unless otherwise specified, the raw materials used were purchased from commercial sources.

[0107] The test methods involved in the embodiments are as follows:

[0108] (1) The content of B acid and L acid was determined by pyridine infrared method. The specific test method is as follows: 0.0089g of the sample to be tested was pressed into a self-supporting sheet with a diameter of 1.3cm, placed in an in-situ cell, the sample was vacuumed at 300℃, cooled to room temperature, and the background infrared spectrum was measured. The saturated vapor of pyridine was adsorbed until the sample was saturated with adsorption, and the spectrum was recorded. After He purging for 1h, the sample was vacuumed and programmed temperature desorption (0-350℃), and the spectrum was recorded every 20℃. The standard positions of B acid and L acid in the obtained pyridine infrared spectrum were 1540cm -1 and 1450cm -1 , integrate the peaks at the corresponding positions in the graph and normalize the peak areas to calculate the relative acidity. The acidity is calculated using the following formula.

[0109]

[0110] Wherein, C is the acid content, unit, mmol / g; K L / B is the absorption coefficient of L acid or B acid, which are 1.42 and 1.88 respectively, that is, K L is the absorption coefficient of L acid, which is 1.42, K B is the absorption coefficient of B acid, which is 1.88, and the unit is mmol / cm; I L / B is the peak area of ​​L acid or B acid, the unit is cm -1 ; R is the tablet diameter, in cm; W is the tablet weight, in g.

[0111] (2) Specific surface area, pore volume, and pore size distribution tests

[0112] The specific surface area, pore volume and pore structure distribution were measured by the N2 adsorption-desorption isotherm method.

[0113] (3) X-ray photoelectron spectroscopy (XPS) analysis was performed on an ESCALAB250XI X-ray photoelectron spectrometer produced by Thermo Fisher Scientific Inc., USA. The test conditions included: the excitation source was Al Kα ray, and the scanning range was 0-1200 eV.

[0114] (4) Scanning electron microscope (SEM) test

[0115] Scanning electron microscope analysis was performed on a S-4800 scanning electron microscope produced by Hitachi, Japan, with a test voltage of 1-10 kV and a magnification of 0.5-50 k.

[0116] (5) Transmission electron microscopy (TEM) test

[0117] Transmission electron microscopy analysis was performed on a TECNAI G2 F20 transmission electron microscope (FEI, USA) with a test voltage of 100-500 kV and a magnification of 1-5000 k.

[0118] (6) Compression strength test

[0119] The graphene aerogel to be tested was pressed into a cylindrical specimen with a height of 10 mm and a diameter of 10 mm. The prepared specimen was immersed in 37°C physiological saline and then heated in a constant temperature water bath for 24 hours. The individual diameter of each specimen was accurately measured with a vernier caliper to an accuracy of 0.02 mm. The specimen was vertically pressurized on an electronic universal testing machine with a preload of 5 N and a loading speed of 1 mm / min, and the maximum load value when the specimen broke was recorded. The compressive strength P = F / S, where F is the maximum load value when the specimen broke (N) and S is the bottom area of ​​the cylindrical specimen (mm 2 ), the unit of compressive strength is MPa, which is converted to kPa.

[0120] The following preparation example is used to illustrate the preparation of graphene aerogel.

[0121] Preparation Example 1

[0122] (1) Preparation of graphene oxide: 0.6g of graphene, 3g of potassium permanganate, 30mL of concentrated sulfuric acid (98wt%), the reactor shell and the tetrafluoroethylene liner were placed in a 4℃ refrigerator for 8h. The refrigerated graphite, potassium permanganate and concentrated sulfuric acid were poured into the reactor, the reactor was quickly covered and the lid was tightened. The reactor was placed in an ice bath and the temperature was controlled at 4℃ for 1.5 hours. After 1.5 hours of reaction in an 80℃ oven, it was taken out and cooled to room temperature. The reaction product was slowly poured into deionized water and stirred to dilute. The volume of water was 5 times that of concentrated sulfuric acid. 5mL of hydrogen peroxide was added dropwise while stirring until the mixture turned yellow-brown or golden yellow. After standing for 24 hours, the supernatant was discarded and the bottom precipitate was centrifuged. The centrifuged product was washed 5 times with 5wt% hydrochloric acid solution and deionized water respectively until the pH was greater than 5, and then transferred to a centrifuge and centrifuged at 1000 rpm for 15 minutes. The supernatant was discarded. Pour the middle and lower layer samples into a beaker, dilute with water and wash, then centrifuge, repeat 4 times until the pH is greater than 5. After washing, transfer the middle and lower layer slurry to a light-proof container and store in a refrigerator at 4°C.

[0123] (2) Use a dropper to measure the graphene oxide slurry prepared above and dilute it with water to obtain a 2 mg / mL GO slurry. Mix the GO slurry with ethylenediamine at a mass ratio of ethylenediamine to graphene oxide of 0.004:1, stir ultrasonically, pour into a glass bottle, and heat at 95°C for 6 h for chemical reduction. Cool to room temperature and remove the solid in the kettle to obtain the graphene hydrogel GH.

[0124] (3) The prepared GH was immersed in 150 mL of 20% v / v ethanol-water solution, transferred to a centrifuge tube, and placed in a freezer at approximately -20°C for 1 hour. The frozen GH was placed in a freeze dryer at -90°C, vacuumed, and maintained for 24 hours. This yielded a graphene aerogel intermediate product.

[0125] (4) The graphene aerogel intermediate product was dissolved in an equal volume of dilute nitric acid solution (concentration of 8 mol / L), heated to 80°C, and stirred for 2 h. After the reaction, the graphene was taken out, washed with clean water until neutral, and dried in an oven at 100°C for 12 h. Graphene aerogel A1 was obtained.

[0126] The surface morphology of graphene aerogel A1 was observed by scanning electron microscopy (SEM). Figure 1 As shown, the graphene aerogel is a three-dimensional porous network structure formed by stacking two-dimensional graphene sheets. The sheets are relatively uniform in size, densely stacked, with more connections between the sheets and abundant pores distributed between the sheets. The average sheet length is 2.5μm and the average sheet thickness is 50nm.

[0127] The internal structure of graphene aerogel A1 was characterized by transmission electron microscopy (TEM), as shown in Figure 2 As shown, a network structure is formed inside the graphene aerogel, which has good dispersibility and is conducive to the transmission of the medium.

[0128] X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of graphene aerogel A1, such as Figure 3 As shown, it is proved that the prepared graphene aerogel contains C element, N element and O element. The molar ratio of C element, O element and N element is determined to be approximately 25:6:1 through the area of ​​the corresponding peaks in the X-ray photoelectron spectrum.

[0129] like Figure 4 As shown in the X-ray photoelectron spectroscopy of the graphene aerogel, the O1s spectrum confirms 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 was determined to be 4:1.5:1 based on the peak area of ​​the peak separation.

[0130] The specific surface area, total pore volume and pore size distribution of graphene aerogel A1 were tested by N2 adsorption-desorption isotherms. Figure 5 As shown, it can be seen that its pore size distribution is concentrated below 20 nm.

[0131] The B acid content of graphene aerogel A1 was determined by pyridine infrared method, and the compressive strength of A1 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0132] Preparation Example 2

[0133] (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 reactor shell and tetrafluoroethylene lining were placed in a 4 ° C refrigerator for 12 hours. The refrigerated graphite, potassium permanganate and concentrated sulfuric acid were poured into the reactor, and the reactor was quickly covered and the lid was tightened. The reactor was placed in an ice bath and the temperature was controlled at 4 ° C for 3 hours. After 3 hours of reaction in an 80 ° C oven, it was taken out and cooled to room temperature. The reaction product was slowly poured into deionized water and stirred to dilute. The volume of water was 5 times that of concentrated sulfuric acid. 5 mL of hydrogen peroxide was added dropwise while stirring until the mixture turned yellow-brown or golden yellow. It was allowed to stand for 24 hours, the supernatant was discarded, and the bottom precipitate was centrifuged. The centrifuged product was washed with 5% hydrochloric acid solution and deionized water 5 times each until the pH was greater than 5, and then transferred to a centrifuge and centrifuged at 1000 rpm for 15 minutes. The supernatant was discarded. Pour the middle and lower layer samples into a beaker, dilute with water and wash, then centrifuge, repeat 4 times until the pH is greater than 5. After washing, transfer the middle and lower layer slurry to a light-proof container and store in a refrigerator at 4°C.

[0134] (2) Use a dropper to measure the graphene oxide slurry prepared above and dilute it with water to obtain a 2 mg / mL GO slurry. Mix the GO slurry with ethylenediamine at a mass ratio of ethylenediamine to graphene oxide of 1:1, stir ultrasonically, pour into a glass bottle, and heat at 90°C for 8 h for chemical reduction. Cool to room temperature and remove the solid in the kettle to obtain the graphene hydrogel GH.

[0135] (3) The prepared GH was immersed in 150 mL of 20% v / v ethanol-water solution, transferred to a centrifuge tube, and placed in a freezer at approximately -25°C for 1 hour. The frozen GH was placed in a freeze dryer at -60°C, vacuumed, and maintained for 20 hours. This yielded a graphene aerogel intermediate.

[0136] (4) The graphene aerogel intermediate product was dissolved in an equal volume of dilute nitric acid solution (concentration of 6 mol / L), heated to 70°C, and stirred for 4 h. After the reaction, the graphene was taken out, washed with clean water until neutral, and dried in an oven at 100°C for 12 h. Graphene aerogel A2 was obtained.

[0137] The surface morphology of graphene aerogel A2 was observed by scanning electron microscopy (SEM). Figure 1 similar.

[0138] The chemical composition of the graphene aerogel A2 was characterized by X-ray photoelectron spectroscopy (XPS). The molar ratio of the C element, the O element, and the N element was 15:12:2.

[0139] The molar ratio of hydroxyl oxygen, carbonyl oxygen and carboxyl oxygen was determined to be 3:1.5:1 by the peak area of ​​O1s separation peak.

[0140] The specific surface area, total pore volume and pore size distribution of graphene aerogel A2 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel A2 was determined by pyridine infrared method, and the compressive strength of A2 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0141] Preparation Example 3

[0142] (1) Graphene oxide was prepared according to the method in Preparation Example 1.

[0143] (2) Use a dropper to measure the graphene oxide slurry prepared above and dilute it with water to obtain a 2 mg / mL GO slurry. Mix the GO slurry with ethylenediamine at a mass ratio of ethylenediamine to graphene oxide of 0.01:1, stir ultrasonically, pour into a glass bottle, and heat at 80°C for 10 h for chemical reduction. Cool to room temperature and remove the solid in the kettle to obtain the graphene hydrogel GH.

[0144] (3) The prepared GH was immersed in 150 mL of 20% v / v ethanol-water solution, transferred to a centrifuge tube, and placed in a freezer at approximately -15°C for 1 hour. The frozen GH was placed in a freeze dryer at -50°C, vacuumed, and maintained for 24 hours. This yielded a graphene aerogel intermediate product.

[0145] (4) The graphene aerogel intermediate product was dissolved in an equal volume of dilute hydrochloric acid solution (concentration: 5 mol / L), heated to 60°C, and stirred for 2 h. After the reaction, the graphene was taken out, washed with clean water until neutral, and dried in an oven at 120°C for 16 h. Graphene aerogel A3 was obtained.

[0146] The surface morphology of graphene aerogel A3 was observed by scanning electron microscopy (SEM). Figure 1 similar.

[0147] X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of graphene aerogel A3. The molar ratio of carbon, oxygen, and nitrogen was approximately 25:15:2. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was determined to be 3:1:1 based on the peak area of ​​the O1s peak.

[0148] The specific surface area, total pore volume and pore size distribution of graphene aerogel A3 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel A3 was determined by pyridine infrared method, and the compressive strength of A3 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0149] Preparation Example 4

[0150] The method of Preparation Example 1 was followed, except that step (2) included: measuring the graphene oxide slurry prepared above with a dropper, diluting it with water to obtain a 2 mg / mL GO slurry, mixing the GO slurry with ethylenediamine at a mass ratio of ethylenediamine to graphene oxide of 0.001:1, ultrasonically stirring the mixture, pouring the mixture into a glass bottle, and heating the mixture at 90°C for 6 h for chemical reduction. Cooling the mixture to room temperature, and removing the solid from the kettle to obtain the graphene hydrogel GH.

[0151] The prepared graphene aerogel is recorded as A4.

[0152] The surface morphology of graphene aerogel A4 was observed by scanning electron microscopy (SEM). Figure 1 similar;

[0153] X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of graphene aerogel A4. The molar ratio of carbon, oxygen, and nitrogen was 45:5:1. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was determined to be 7.5:1.5:1 based on the peak area of ​​the O1s peak.

[0154] The specific surface area, total pore volume and pore size distribution of graphene aerogel A4 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel A4 was determined by pyridine infrared method, and the compressive strength of A4 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0155] Preparation Example 5

[0156] The method of Preparation Example 1 was followed, except that an equal amount of ascorbic acid was used instead of ethylenediamine to obtain graphene aerogel A5.

[0157] The surface morphology of graphene aerogel A5 was observed by scanning electron microscopy (SEM). Figure 1 similar;

[0158] The chemical composition of graphene aerogel A5 was characterized by X-ray photoelectron spectroscopy (XPS). The molar ratio of carbon, oxygen, and nitrogen was 40:3. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was determined to be 10:2:1 based on the peak area of ​​the O1s peak.

[0159] The specific surface area, total pore volume and pore size distribution of graphene aerogel A5 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel A5 was determined by pyridine infrared method, and the compressive strength of A5 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0160] Preparation Example 6

[0161] The method of Preparation Example 1 was followed, except that step (4) included dissolving the graphene aerogel intermediate product in an equal volume of dilute nitric acid solution (concentration: 4 mol / L), heating the mixture to 80°C, stirring and reacting for 2 h. After the reaction, the graphene was removed, washed with clean water until neutral, and dried in an oven at 100°C for 12 h. Graphene aerogel A6 was obtained.

[0162] The surface morphology of graphene aerogel A6 was observed by scanning electron microscopy (SEM). Figure 1 similar.

[0163] The chemical composition of graphene aerogel A6 was characterized using X-ray photoelectron spectroscopy (XPS). The molar ratio of C, O, and N was 30:5:0.3. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was determined to be 6:1.5:1 based on the peak area of ​​the O1s peak. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A6 were measured using N2 adsorption-desorption isotherms. The B acid content of graphene aerogel A6 was determined using a pyridine infrared spectrophotometer. The compressive strength of A6 was measured using an electronic universal testing machine. The test results are shown in Table 1.

[0164] Preparation Example 7

[0165] The method of Preparation Example 1 was followed, except that step (4) included dissolving the graphene aerogel intermediate product in an equal volume of dilute nitric acid solution (concentration: 1 mol / L), heating the solution to 60°C, stirring, and reacting for 2 h. After the reaction, the graphene was removed, washed with clean water until neutral, and dried in an oven at 100°C for 12 h. Graphene aerogel A7 was obtained.

[0166] The surface morphology of graphene aerogel A7 was observed by scanning electron microscopy (SEM). Figure 1 similar;

[0167] The chemical composition of graphene aerogel A7 was characterized using X-ray photoelectron spectroscopy (XPS). The molar ratio of C, O, and N was 35:4:0.3. The molar ratio of hydroxyl oxygen, carbonyl oxygen, and carboxyl oxygen was determined to be 6.5:1:0.5 based on the peak area of ​​the O1s peak. The specific surface area, total pore volume, and pore size distribution of graphene aerogel A7 were measured using N2 adsorption-desorption isotherms. The B acid content of graphene aerogel A7 was determined using a pyridine infrared spectrophotometer. The compressive strength of A7 was determined using an electronic universal testing machine. The test results are shown in Table 1.

[0168] Comparative Preparation Example 1

[0169] The graphene aerogel intermediate product obtained in step (3) of Preparation Example 1 is recorded as graphene aerogel DA1.

[0170] Scanning electron microscopy (SEM) observation showed that the surface morphology of graphene aerogel DA1 was a porous structure composed of graphene sheets.

[0171] X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of graphene aerogel DA1, and the molar ratio of C, N and O elements was determined to be 25:6:1. The peak area of ​​the O1s peak was used to determine that the graphene aerogel only contained hydroxyl groups.

[0172] The specific surface area, total pore volume and pore size distribution of graphene aerogel DA1 were tested by N2 adsorption-desorption isotherm, the B acid content of graphene aerogel DA1 was determined by pyridine infrared method, and the compressive strength of DA1 was determined by electronic universal testing machine. The test results are shown in Table 1.

[0173] Comparative Preparation Example 2

[0174] The method of Preparation Example 1 was followed, except that step (3) included soaking the prepared GH in 150 mL of 20% v / v ethanol-water solution, transferring the solution to a centrifuge tube, and placing the solution in a freezer at approximately -10°C for 1 hour. The frozen GH was placed in a freeze dryer at -30°C, vacuumed, and maintained for 24 hours. This yielded a graphene aerogel intermediate product.

[0175] Acid activation was then performed according to the method of Preparation Example 1 to obtain graphene aerogel DA2. The specific surface area, total pore volume, and pore size distribution of graphene aerogel DA2 were measured using N2 adsorption-desorption isotherms. The B acid content of graphene aerogel DA2 was determined using a pyridine infrared spectrophotometer. The compressive strength of DA2 was measured using an electronic universal testing machine. The test results are shown in Table 1.

[0176] Table 1

[0177]

[0178] The following examples illustrate the preparation of regenerated catalysts.

[0179] Example 1

[0180] S1. Place a certain volume of aluminum nitrate solution (prepared with a concentration of 1 mol / L) and graphene aerogel A1 in an ultrasonic bath, with the volume ratio of aluminum nitrate solution to graphene aerogel being 1:1. Ultrasonicate at 40,000 Hz for 1 hour to fully mix the two to obtain a mixed solution.

[0181] S2. Add 25 wt% aqueous ammonia to the above mixture while stirring continuously until the pH reaches 8-9. The rate of addition of aqueous ammonia is 0.5 mL / min per 1 L of the mixture. The product is filtered and dried in a drying oven at 110°C for 8 h. It is then calcined in a muffle furnace at 400°C for 6 h to obtain regenerated catalyst S1. Based on the total mass of the regenerated catalyst, the carrier content is 40 wt%; the aluminum oxide content is 60 wt%.

[0182] Scanning electron microscopy (SEM) observations of the surface morphology of regenerated catalyst S1 revealed that the loaded catalyst still possessed a three-dimensional porous network structure composed of stacked two-dimensional graphene sheets, with the pore structure on the graphene sheet surface remaining relatively intact. The catalyst also retained the looseness of the graphene aerogel, and the aerogel did not agglomerate after loading, demonstrating its good dispersion, which facilitated the transfer of the medium.

[0183] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S1 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S1 were determined by pyridine infrared method. The test results are shown in Table 2.

[0184] Example 2

[0185] S1. Place a certain volume of ferric nitrate solution (prepared with a concentration of 1 mol / L) and graphene aerogel A2 in an ultrasonic bath, with the volume ratio of ferric nitrate solution to graphene aerogel being 1:1, and ultrasonicate at 40,000 Hz for 10 h to fully mix the two to obtain a mixed solution;

[0186] S2. Add 25 wt% aqueous ammonia to the above mixture with continuous stirring until the pH reaches 8-9. The rate of addition of aqueous ammonia is 1 mL / min per 1 L of the mixture. The product is filtered and oven-dried at 100°C for 12 hours, air-dried at room temperature, and then calcined in a muffle furnace at 550°C for 6 hours to obtain regenerated catalyst S2. Based on the total mass of the regenerated catalyst, the content of the carrier is 31 wt%; the content of ferrosoferric oxide is 69 wt%.

[0187] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S2 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S2 were determined by pyridine infrared method. The test results are shown in Table 2.

[0188] Example 3

[0189] S1. Place a certain volume of cobalt nitrate solution (prepared with a concentration of 1 mol / L) and graphene aerogel A3 in an ultrasonic chamber. According to the volume ratio of cobalt nitrate solution to graphene aerogel being 1:1, ultrasonicate at 40,000 Hz for 1 hour to fully mix the two to obtain a mixed solution.

[0190] S2. Add 25 wt% aqueous ammonia to the above-mentioned mixed solution and stir continuously until the pH reaches 8-9. The rate of addition of aqueous ammonia is 0.5 mL / min relative to 1 L of the mixed solution. After filtering the product, place it in an oven at 110°C for 8 hours, dry it at room temperature, and then calcine it in a muffle furnace at 400°C for 6 hours to obtain regenerated catalyst S3. Based on the total mass of the regenerated catalyst, the content of the carrier is 48 wt%; the content of cobalt oxide is 52 wt%. The specific surface area, total pore volume, and pore size distribution of the regenerated catalyst S3 are measured by N2 adsorption-desorption isotherm. The B acid and L acid contents of the regenerated catalyst S3 are measured by pyridine infrared spectroscopy. The test results are shown in Table 2.

[0191] Example 4

[0192] S1. Place a certain volume of ferric nitrate solution (prepared with a concentration of 1.0 mol / L) and graphene aerogel A2 in an ultrasonic chamber, with the volume ratio of ferric nitrate solution to graphene aerogel being 1:1, and ultrasonicate at 40,000 Hz for 10 h to fully mix the two to obtain a mixed solution;

[0193] S2. The product was filtered and then dried in an oven at 110°C for 12 hours, air-dried at room temperature, and then calcined in a muffle furnace at 650°C for 4 hours to obtain regenerated catalyst S4. Based on the total mass of the regenerated catalyst, the carrier content was 31 wt%; the ferric oxide content was 69 wt%. When no precipitant is introduced, a higher calcination temperature is required to ensure metal oxide loading, which may cause graphene aerogel agglomeration and reduce specific surface area and pore volume.

[0194] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S4 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S4 were determined by pyridine infrared method. The test results are shown in Table 2.

[0195] Example 5

[0196] The method of Example 1 was followed, except that graphene aerogel A4 was used instead of A1, to obtain regenerated catalyst S5.

[0197] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S5 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S5 were determined by pyridine infrared method. The test results are shown in Table 2.

[0198] Example 6

[0199] The method of Example 1 was followed, except that graphene aerogel A5 was used instead of A1, to obtain regenerated catalyst S6.

[0200] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S6 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S6 were determined by pyridine infrared method. The test results are shown in Table 2.

[0201] Example 7

[0202] The method of Example 1 was followed, except that graphene aerogel A6 was used instead of A1, to obtain regenerated catalyst S7.

[0203] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S7 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S7 were determined by pyridine infrared method. The test results are shown in Table 2.

[0204] Example 8

[0205] The method of Example 1 was followed, except that graphene aerogel A7 was used instead of A1, to obtain regenerated catalyst S8.

[0206] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S8 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S8 were determined by pyridine infrared method. The test results are shown in Table 2.

[0207] Example 9

[0208] The method of Example 1 was followed, except that the aluminum nitrate solution was replaced with a boric acid solution of equal concentration and volume to obtain regenerated catalyst S9.

[0209] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst S9 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst S9 were determined by pyridine infrared method. The test results are shown in Table 2.

[0210] Comparative Example 1

[0211] According to the mass ratio of aluminum oxide to graphene aerogel A1 of 2:3, commercially available aluminum oxide and graphene aerogel A1 were physically ground and then calcined at 400° C. in a muffle furnace for 6 h to obtain regenerated catalyst DS1.

[0212] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst DS1 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst DS1 were determined by pyridine infrared method. The test results are shown in Table 2.

[0213] Comparative Example 2

[0214] The method of Example 1 was followed, except that an equal amount of HZSM-5 molecular sieve (commercially available, Nankai University Catalyst) was used to replace the graphene aerogel A1 to obtain a regenerated catalyst DS2.

[0215] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst DS2 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst DS2 were determined by pyridine infrared method. The test results are shown in Table 2.

[0216] Comparative Example 3

[0217] The method of Example 1 was followed, except that an equal amount of graphene aerogel DA1 was used to replace A1, to obtain a regenerated catalyst DS3.

[0218] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst DS3 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst DS3 were determined by pyridine infrared method. The test results are shown in Table 2.

[0219] Comparative Example 4

[0220] The GO slurry obtained in Preparation Example 1 was mixed with ethylenediamine and commercially available aluminum oxide at a mass ratio of 0.004:1. The mixture was ultrasonically stirred and then reacted in a 95°C oven for 12 hours. The mixture was then frozen in a freezer at -18°C. After complete freezing, the sample was placed in a vacuum freeze dryer for freeze-drying. The resulting solid product was designated DS4.

[0221] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst DS4 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst DS4 were determined by pyridine infrared method. The test results are shown in Table 2.

[0222] Comparative Example 5

[0223] The method of Example 1 was followed, except that an equal amount of graphene aerogel DA2 was used to replace A1, to obtain regenerated catalyst DS5.

[0224] The specific surface area, total pore volume and pore size distribution of the regenerated catalyst DS5 were tested by N2 adsorption-desorption isotherm, and the B acid and L acid contents of the regenerated catalyst DS5 were determined by pyridine infrared method. The test results are shown in Table 2.

[0225] The physical and chemical data of the regenerated catalysts prepared in the above examples and comparative examples are listed in Table 2.

[0226] Table 2

[0227]

[0228]

[0229] The regenerated catalysts prepared in the above examples and comparative examples were evaluated for regeneration using an alcoholamine solution.

[0230] Preparation of CO2-rich amine solution: 2 / CO2 gas was introduced into the composite amine solution at a volume ratio of 85:15 for 2 h to obtain a CO2-rich amine solution.

[0231] 1% (by mass of the CO₂-rich amine solution) of the above-mentioned regenerated catalyst was added to the CO₂-rich amine solution. The temperature was gradually increased with continuous stirring at 200 rpm. A gas flowmeter was used to record the cumulative volumetric flow of desorbed CO₂. The desorption start temperature (initial temperature), end temperature, and regeneration time were also recorded. The rich solution was sampled every 5 minutes and the CO₂ loading in the composite amine solution at different desorption times was measured using acid-base titration to calculate the desorption rate, desorption capacity, and relative energy consumption. The results are shown in Table 3.

[0232] Desorption energy consumption (H) refers to the desorption energy consumption per unit mole of CO2 (kJ / mol), which is defined as the ratio of the energy input rate to the CO2 desorption rate and is calculated by formula (1):

[0233]

[0234] Here, E refers to the amount of electricity consumed by CO2 desorption within a certain period of time as recorded by the electricity meter. The unit is kW·h and needs to be converted into kJ when used.

[0235] The relative energy consumption (RH) was calculated by formula (2), where Hb (kJ / mol) is the desorption energy consumption of the blank control solution during the regeneration process, and Hi (kJ / mol) is the desorption energy consumption of the CO2 desorption process catalyzed by the regenerated catalyst to be tested.

[0236]

[0237] Repeat the alcohol amine solution regeneration experiment for each regenerated catalyst 6 times, then dry and weigh the regenerated catalyst after the reaction, and calculate the catalyst mass loss rate.

[0238] Loss rate (%) = (mass of freshly regenerated catalyst - mass of regenerated catalyst after 6 regenerations) / mass of freshly regenerated catalyst × 100%.

[0239] Table 3

[0240]

[0241]

[0242] From the results in Tables 1-3, it can be seen that when the regeneration catalyst prepared by using the graphene aerogel provided by the present invention as a catalyst carrier is used to regenerate the alcoholamine solution, the desorption effect of CO2 can be effectively improved, the initial desorption temperature can be lowered, and the energy consumption of the desorption process can be reduced.

[0243] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A graphene aerogel for regenerating a catalyst from a CO2-rich amine solution, characterized in that: The graphene aerogel has a B acid content of 0.001-0.05 mmol / g and a specific surface area of ​​40-200 m 2 / g, the volume of pores with a pore diameter of less than 20 nm accounts for no less than 50% of the total pore volume of the graphene aerogel.

2. The graphene aerogel according to claim 1, wherein The graphene aerogel has a B acid content of 0.01-0.03 mmol / g.

3. The graphene aerogel according to claim 1, wherein The specific surface area of ​​the graphene aerogel is 100-120m 2 / g.

4. The graphene aerogel according to claim 1 or 2, wherein: The total pore volume of the graphene aerogel is 0.01-0.5 mL / g.

5. The graphene aerogel according to claim 4, wherein The total pore volume of the graphene aerogel is 0.1-0.3 mL / g.

6. The graphene aerogel according to claim 1 or 2, wherein: In the graphene aerogel, the volume of pores with a pore diameter of less than 20 nm accounts for 55-90% of the total pore volume of the graphene aerogel.

7. The graphene aerogel according to claim 6, wherein In the graphene aerogel, the volume of pores with a pore diameter of less than 20 nm accounts for 70-80% of the total pore volume of the graphene aerogel.

8. The graphene aerogel according to claim 1 or 2, wherein: The graphene aerogel contains C element, O element and N element, and the molar ratio of the C element, O element and N element is (1-60): (5-30): (0.5-5).

9. The graphene aerogel according to claim 8, wherein The graphene aerogel contains C element, O element and N element, and the molar ratio of the C element, O element and N element is (15-35): (10-20): (1-2).

10. The graphene aerogel according to claim 1 or 2, wherein: X-ray photoelectron spectroscopy shows that 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).

11. The graphene aerogel according to claim 10, wherein X-ray photoelectron spectroscopy shows that 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 (1-5): (0.5-2): (1-2).

12. The graphene aerogel according to claim 1 or 2, wherein: The graphene aerogel has a three-dimensional porous network structure formed by stacking two-dimensional graphene sheets.

13. The graphene aerogel according to claim 12, wherein: The average sheet thickness of the two-dimensional flaky graphene is 10-200 nm.

14. The graphene aerogel according to claim 13, wherein The average sheet thickness of the two-dimensional flaky graphene is 50-100 nm.

15. The graphene aerogel according to claim 12, wherein: The average sheet length of the two-dimensional flaky graphene is 0.1-10 μm.

16. The graphene aerogel according to claim 15, wherein The average sheet length of the two-dimensional graphene sheet is 1-5 μm.

17. The graphene aerogel according to claim 1 or 2, wherein: The compressive strength of the graphene aerogel is higher than 30 kPa.

18. The graphene aerogel according to claim 17, wherein The compressive strength of the graphene aerogel is 40-50 kPa.

19. A regeneration catalyst for regenerating a CO2-rich amine solution, characterized in that: The regeneration catalyst comprises a carrier, and a metal component supported on the carrier; the metal component has Lewis acid properties, and the carrier is the graphene aerogel according to any one of claims 1 to 6; The B acid content in the regenerated catalyst is 0.0005-0.02 mmol / g; The molar ratio of B acid to L acid is 0.01-1:

1.

20. The regenerated catalyst according to claim 19, wherein The content of B acid in the regenerated catalyst is 0.008-0.016 mmol / g.

21. The regenerated catalyst according to claim 19, wherein In the regenerated catalyst, the molar ratio of B acid to L acid is 0.1-0.5:

1.

22. The regenerated catalyst according to claim 21, wherein In the regenerated catalyst, the molar ratio of B acid to L acid is 0.1-0.2:

1.

23. The regenerated catalyst according to any one of claims 19 to 22, wherein Based on the total mass of the regenerated catalyst, the content of the carrier is 30-70 wt %, and the content of the metal component is 30-70 wt % calculated as oxide.

24. The regenerated catalyst according to claim 23, wherein Based on the total mass of the regenerated catalyst, the content of the carrier is 30-50wt%; calculated as oxide, the content of the metal component is 50-70wt%.

25. The regenerated catalyst according to any one of claims 19 to 22, wherein The metal component is selected from transition metal elements and / or Group IIIA elements.

26. The regenerated catalyst according to claim 25, wherein The metal component is selected from at least one of Fe, Mn, Co, Ni, Cu, Zn, La, Ce, Zr, Mo, W, Au, Ag, Ti, Pt, Rh, Ru, Re, Al, Ga and In.

27. The regenerated catalyst according to claim 25, wherein The metal component is selected from at least one of Al, Fe, Co, Ni and Ti.

28. The regenerated catalyst according to any one of claims 19 to 22, wherein The specific surface area of ​​the regenerated catalyst is 30-100m 2 / g.

29. The regenerated catalyst according to claim 28, wherein The specific surface area of ​​the regenerated catalyst is 45-80m 2 / g.

30. The regenerated catalyst according to any one of claims 19 to 22, wherein The total pore volume of the regenerated catalyst is 0.06-0.2 mL / g.

31. The regenerated catalyst according to claim 30, wherein The total pore volume of the regenerated catalyst is 0.1-0.15 mL / g.

32. The regenerated catalyst according to any one of claims 19 to 22, wherein In the regenerated catalyst, the volume of pores with a pore diameter of less than 20 nm accounts for no less than 30% of the total pore volume of the regenerated catalyst.

33. The regenerated catalyst according to claim 32, wherein In the regenerated catalyst, the volume of pores with a pore diameter of less than 20 nm accounts for 30-80% of the total pore volume of the regenerated catalyst.

34. The regenerated catalyst according to claim 33, wherein In the regenerated catalyst, the volume of pores with a pore diameter of less than 20 nm accounts for 50-60% of the total pore volume of the regenerated catalyst.

35. Use of the regeneration catalyst according to any one of claims 19 to 34 in the regeneration of a CO2-rich amine solution.

36. A method for regenerating a CO2-rich amine solution, characterized in that: Under regeneration conditions, a CO2-rich amine solution is brought into contact with the catalyst to desorb CO2; Wherein, the catalyst is the regenerated catalyst described in any one of claims 19-34.

37. The regeneration method according to claim 36, wherein: Based on the total mass of the CO2-rich amine solution, the amount of the catalyst is 1-10 wt%.

38. The regeneration method according to claim 37, wherein: Based on the total mass of the CO2-rich amine solution, the amount of the catalyst is 1-3 wt%.

39. The regeneration method according to claim 36, wherein: The initial temperature of the CO2 desorption is 10-70°C.

40. The regeneration method according to claim 39, wherein The initial temperature of the CO2 desorption is 30-50°C.

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