Honeycomb type CO2 trapping adsorbent and preparation method thereof

Abstract

The invention discloses a honeycomb type CO2 trapping adsorbent and a preparation method thereof, and relates to the technical field of carbon dioxide trapping. The adsorbent matrix is prepared by doping the silicon carbide nanowires, and the Mg-MOF-74 mesoporous silica gel coating and the MIL-101 (Cr) are respectively sprayed on the inlet section and the outlet section of the adsorbent matrix, so that the adsorption rate and the saturated adsorption capacity of the adsorbent can be greatly improved, and rapid mass transfer, large-capacity storage and long cycle life of the adsorbent are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture, and particularly to a honeycomb CO2 capture adsorbent and a preparation method thereof. Background Art

[0002] Carbon dioxide adsorbents are a class of materials specifically used for adsorbing carbon dioxide (CO2), and are widely used in fields such as carbon capture, air purification, and industrial waste gas treatment. CO2 adsorbents capture carbon dioxide through physical or chemical means, and their high adsorption performance and recyclable characteristics make them key materials for carbon capture, utilization, and storage (CCUS) technology.

[0003] According to the adsorption mechanism and material properties, CO2 adsorbents are mainly divided into the following categories:

[0004] (1) Solid adsorbents

[0005] Metal-organic frameworks (MOFs): MOFs have an ultra-high specific surface area and adjustable pore structure, and achieve efficient adsorption through electrostatic interaction or van der Waals force with CO2 molecules. They have a large adsorption capacity, but are easily affected by humidity and need to be further modified to improve stability.

[0006] Zeolite molecular sieves: Zeolites capture CO2 through physical adsorption, have good adsorption efficiency and regeneration performance, but the regeneration cost is relatively high, and they are suitable for dry environments.

[0007] Amine adsorbents: Amine materials react with CO2 through chemical adsorption to form compounds such as carbamates, and have high selectivity and adsorption capacity, but the regeneration energy consumption is relatively high.

[0008] Alkali metal adsorbents: Such as calcium oxide (CaO), which adsorbs by reacting with CO2 to form calcium carbonate, is suitable for high-temperature environments, but has problems such as high adsorption temperature and easy sintering.

[0009] (2) Liquid adsorbents

[0010] Common amine-based solutions (such as monoethanolamine, diethanolamine) have high adsorption efficiency, but have problems of corrosion and volatility, and the process needs to be optimized to reduce environmental impact.

[0011] Currently, traditional solid adsorbents have the following defects:

[0012] (1) Adsorption kinetics and capacity contradiction: Traditional adsorbents such as powdered MOFs face a contradiction between adsorption kinetics and adsorption capacity during the adsorption process. A single material cannot simultaneously achieve rapid mass transfer and large-capacity storage. On the one hand, to achieve rapid mass transfer, the adsorbent needs to have a large specific surface area and pore size so that the adsorbate can quickly enter the interior of the adsorbent. On the other hand, to achieve large-capacity storage, the adsorbent needs to have more adsorption sites. However, it is often difficult for a single material to meet both of these requirements simultaneously. For example, adsorbents with a large specific surface area and pore size usually have fewer adsorption sites, resulting in limited adsorption capacity; while adsorbents with more adsorption sites often have a smaller specific surface area and pore size, resulting in a slower mass transfer rate. This contradiction limits the performance of traditional adsorbents in practical applications.

[0013] (2) Short cycle life: Traditional adsorbents such as powdered MOFs are prone to problems such as structural collapse and inactivation of active sites during the recycling process, resulting in a gradual decline in adsorption performance. Generally, the cycle life of traditional adsorbents is only about 500 times, which far cannot meet the requirements of continuous industrial operation. In actual industrial applications, the adsorbent needs to be able to operate stably for a long time to reduce operating costs and replacement frequencies. However, due to the short cycle life of traditional adsorbents, the adsorbent needs to be replaced frequently, which not only increases operating costs but also may cause interruptions in the production process and affect production efficiency.

[0014] In summary, developing adsorbents with rapid mass transfer, large-capacity storage, and a longer cycle life is of great significance for meeting the requirements of continuous industrial operation. Summary of the Invention

[0015] The technical problem to be solved by the present invention is: To overcome the deficiencies of the prior art, a honeycomb CO2 capture adsorbent and its preparation method are provided. By doping silicon carbide nanowires to prepare an adsorbent matrix and spraying Mg-MOF-74@mesoporous silica coatings on its inlet section and outlet section respectively and impregnating MIL-101(Cr), the adsorption rate and saturated adsorption capacity of the adsorbent can be greatly improved, thereby achieving rapid mass transfer, large-capacity storage, and a long cycle life of the adsorbent.

[0016] The technical solution of the present invention is as follows:

[0017] On the one hand, the present invention provides a preparation method of a honeycomb CO2 capture adsorbent, including the following steps:

[0018] S1 Preparation of adsorbent matrix: Mix 30-50 wt.% of kaolin, 30-40 wt.% of magnesite, 10-15 wt.% of γ-Al2O3, 5-10 wt.% of MgO, and 5-10 wt.% of silicon carbide nanowires, then carry out wet clay refining, extrude and form with a honeycomb mold, and sinter after drying by embedding graphite powder to ensure the uniformity of the sintering temperature to obtain the adsorbent matrix; among them, the silicon carbide nanowires can maintain the structural integrity of the adsorbent matrix during the sintering process and enhance its mechanical properties through the grain boundary pinning effect;

[0019] S2 Spraying the coating for the inlet section: Spray the composite slurry of Mg-MOF-74 and mesoporous silica gel on the inlet section of the adsorbent matrix, and carry out drying and calcination after spraying to form a coating;

[0020] S3 Impregnating the outlet section: Immerse the outlet section of the adsorbent matrix in the MIL-101(Cr) impregnating solution, and carry out vacuum drying after impregnation to obtain the honeycomb CO2 capture adsorbent.

[0021] Preferably, in step S1, the wet clay refining includes the following steps:

[0022] (1) Raw material mixing: After weighing each raw material, add 15-16 wt.% of water and preliminarily stir into a clay mass in a kneader;

[0023] (2) Vacuum clay refining: Put the clay mass into a vacuum clay refining machine to remove internal air bubbles;

[0024] (3) Aging treatment: Let the air bubble-removed clay material stand for 24-48 h to complete the wet clay refining.

[0025] Preferably, in step S1, the drying includes the following steps:

[0026] 1) Preheating stage: Heat by microwave, the microwave power is 0.5-1.5 kW, the temperature is 40-60 °C, and the time is 10-30 min;

[0027] 2) Main drying stage: Adjust the microwave heating power to 2-3 kW, the temperature is 80-100 °C, and the time is 20-50 min;

[0028] 3) Final drying stage: Adjust the microwave heating power to 3-4 kW, the temperature is 100-120 °C, and the heating time is 2-5 min to make the water content of the extruded and formed adsorbent matrix <1 wt.%.

[0029] Preferably, in step S1, the specific process of sintering with graphite powder buried is as follows: Place the dried adsorbent matrix in a crucible and fill the surrounding with graphite powder; Under a flowing nitrogen atmosphere, first heat it from room temperature to 550 - 650 °C at a rate of 5 - 10 °C / min, then heat it from 550 - 650 °C to 1200 - 1300 °C at a rate of 3 - 5 °C / min, and keep it at this temperature for 2 - 4 h; Cool it naturally in the furnace or cool it to room temperature at a rate of ≤5 °C / min.

[0030] Preferably, in step S2, the inlet section accounts for 30 - 45% of the length of the adsorbent matrix.

[0031] Preferably, in step S2, the preparation method of the composite slurry includes the following steps:

[0032] (a) Preparation of the Mg-MOF-74 precursor solution: Weigh Mg(NO3)2·6H2O and 2,5-dihydroxyterephthalic acid (H4DOBDC), dissolve them in a mixed solvent of DMF, water and ethanol to obtain a solution;

[0033] (b) Adding a dispersant: Add 0.1 - 1 wt.% of the dispersant CTAB to the solution;

[0034] (c) Preparation of the composite powder: Immerse mesoporous silica gel into the Mg-MOF-74 precursor solution, stir to make the Mg-MOF-74 precursor penetrate into the pores of the mesoporous silica gel; Transfer the obtained mixture to a reaction kettle, react at 115 - 125 °C for 18 - 30 h to promote the crystallization and growth of the Mg-MOF-74 precursor on the surface and in the pores of the mesoporous silica gel; After the reaction, wash and dry to obtain the Mg-MOF-74@mesoporous silica gel composite powder;

[0035] (d) Preparation of the composite slurry: Mix the composite powder with deionized water, add a dispersant, and ball mill to obtain the composite slurry.

[0036] Preferably, in step (a), the molar ratio of Mg(NO3)2·6H2O to H4DOBDC is (1.5 - 2):1, the volume ratio of DMF, water and ethanol in the mixed solvent is 7:(1.5 - 2.5):(1 - 2), and the concentration of the solution is 0.1 - 0.2 mol / L; in step (c), the mesoporous silica is pretreated first. The mesoporous silica is soaked in 1 M HCl for 0.5 - 1.5 h, washed to neutrality and then dried, calcined at 200 - 250 °C for 2 - 3 h to completely remove the surface adsorbed water and organic residues, and then ultrasonically treated with ethanol to remove the residual impurities in the pores. The pore diameter of the mesoporous silica > 3 nm; the mass ratio of the mesoporous silica to the MOF in the Mg-MOF-74 precursor solution is 1:(2.5 - 3.5); in step (d), after the composite powder is mixed with deionized water, the solid content is 15 - 25 wt.%, and the dispersant is sodium carboxymethyl cellulose (CMC) or polyvinylpyrrolidone (PVP), with a content of 0.05 - 0.15 wt.%; the ball milling speed is 250 - 350 rpm, and the ball milling time is 1.5 - 3 h.

[0037] Preferably, in step S2, the spraying pressure is 0.3 - 0.5 MPa, and it is sprayed multiple times until the coating thickness is 60 - 100 μm; the drying temperature is 75 - 85 °C, the drying time is 1.5 - 3 h, the calcination temperature is 280 - 320 °C, and the calcination time is 1 - 2 h.

[0038] Preferably, in step S3, the preparation method of the MIL-101(Cr) impregnating solution is: disperse MIL-101(Cr) in a 25 - 35 wt.% ethanol solution, with the concentration of MIL-101(Cr) being 6 - 10 wt.%, and ultrasonically treat to obtain the MIL-101(Cr) impregnating solution; during impregnation, the MIL-101(Cr) adsorbent matrix is vertically impregnated for 10 - 30 min, and then pulled out from the impregnating solution at a pulling speed of 0.5 - 1.2 mm / s to ensure the uniform distribution of the loaded MIL-101(Cr) on the matrix surface. The vacuum drying temperature is 100 - 130 °C, and the vacuum drying time is 3 - 6 h. After repeating the above impregnation and vacuum drying multiple times, the loading amount reaches 8 - 9 mmol / g.

[0039] On the other hand, the present invention provides a honeycomb CO2 capture adsorbent prepared by the above preparation method of the honeycomb CO2 capture adsorbent.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention prepares an adsorbent matrix by doping silicon carbide nanowires, and sprays Mg-MOF-74@mesoporous silica coatings on its inlet section and outlet section respectively, and impregnates MIL-101(Cr). Among them, spraying the Mg-MOF-74@mesoporous silica coating can speed up the adsorption by reducing the diffusion resistance and strengthening the kinetic adsorption, while impregnating MIL-101(Cr) can increase the capacity by relying on the ultra-large pore volume and high-density adsorption sites. The two cooperate in different regions to break through the "rate-capacity" trade-off limit, and finally can greatly improve the adsorption rate and saturated adsorption capacity of the adsorbent, so as to realize the rapid mass transfer and large-capacity storage of the adsorbent. At the same time, the adsorbent of the present invention adsorbs CO2 to saturation at 40°C and then regenerates at 120°C. After 10 cycles per day and continuous operation for 30 days, the attenuation rate of the saturated adsorption capacity of the adsorbent <5%, greatly improving the cycle life of the adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a schematic structural diagram of a small-scale CO2 capture device of the present invention.

[0043] In the figure, 1, mixer; 2, N2 storage tank; 3, CO2 storage tank; 4, flow meter; 5, valve; 6, fixed bed reactor; 7, pre-heater; 8, electric heating wire; 9, thermocouple; 10, on-line flue gas analyzer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0045] Example 1

[0046] The preparation method of the honeycomb CO2 capture adsorbent in this example includes the following steps:

[0047] S1 Preparation of adsorbent matrix

[0048] Mix 40 wt.% kaolin, 35 wt.% magnesite, 12 wt.% γ-Al2O3, 8 wt.% MgO, and 5 wt.% silicon carbide nanowires by ball milling for 6 h, then carry out wet clay refining, and then extrude and form with a honeycomb mold (pore diameter 1.5 mm, wall thickness 0.2 mm), and sinter after drying by embedding graphite powder to obtain the adsorbent matrix.

[0049] Among them, the wet clay refining includes the following steps:

[0050] (1) Raw material mixing: After weighing each raw material, add 15 wt.% of water and preliminarily stir into a clay mass in a kneading machine;

[0051] (2) Vacuum kneading: Put the clay mass into a vacuum kneading machine. Through screw extrusion and air extraction by a vacuum pump (vacuum degree is about -0.1 MPa), internal air bubbles are removed to make the clay material dense and uniform.

[0052] (3) Aging treatment: Let the clay material without air bubbles stand for 30 h to promote the even distribution of moisture and enhance plasticity, thus completing wet clay kneading.

[0053] Drying includes the following steps:

[0054] 1) Preheating stage: Through microwave heating, with a microwave power of 1 kW, a temperature of 50 °C, and a time of 20 min, make the green body evenly heated to avoid surface hardening.

[0055] 2) Main drying stage: Adjust the microwave heating power to 2.5 kW, a temperature of 90 °C, and a time of 40 min to accelerate the internal moisture migration.

[0056] 3) Final drying stage: Adjust the microwave heating power to 3.5 kW, a temperature of 110 °C, and a heating time of 3 min to make the water content of the extruded adsorbent matrix 0.8 wt.%.

[0057] The specific process of sintering with buried graphite powder is as follows: Place the dried adsorbent matrix in a crucible and fill the surrounding with graphite powder; under a flowing nitrogen atmosphere, first heat it at a rate of 8 °C / min to 600 °C, then heat it at a rate of 4 °C / min to 1300 °C, and hold for 4 h to promote the formation of the cordierite crystal phase; cool naturally with the furnace to obtain the adsorbent matrix.

[0058] S2 Spraying the coating on the inlet section

[0059] Spray a composite slurry of Mg-MOF-74 and mesoporous silica gel on the inlet section of the adsorbent matrix (the inlet section accounts for 38% of the length of the adsorbent matrix), with a spraying pressure of 0.4 MPa, and spray multiple times until the coating thickness is 80 μm; after spraying, dry it at 80 °C for 2 h, and then calcine it at 300 °C for 1 h to form the coating.

[0060] Among them, the preparation method of the composite slurry includes the following steps:

[0061] (a) Preparation of the Mg-MOF-74 precursor solution: Weigh Mg(NO3)2·6H2O and H4DOBDC with a molar ratio of 1.5:1, dissolve them in a mixed solvent of DMF, water and ethanol with a volume ratio of 7:2:2 to obtain a solution with a concentration of 0.1 mol / L.

[0062] (b) Adding a dispersant: Add 0.5 wt.% of the dispersant CTAB to the solution and ultrasonically treat it for 10 min to improve the compatibility with mesoporous silica gel in the follow-up.

[0063] (c) Preparation of composite powder:

[0064] First, pretreat the mesoporous silica: Immerse the mesoporous silica in 1M HCl for 1 h, wash it until neutral and then dry it. Calcinate it at 220 °C for 2.5 h, and perform ultrasonic treatment on it with ethanol at 40 kHz for 30 min to remove residual impurities in the pores. The pore diameter of the mesoporous silica is >3 nm;

[0065] According to the mass ratio of mesoporous silica to MOF in the Mg-MOF-74 precursor solution of 1:3, immerse the mesoporous silica in the Mg-MOF-74 precursor solution, stir at 25 °C for 12 h to allow the Mg-MOF-74 precursor to penetrate into the pores of the mesoporous silica; transfer the obtained mixture to a high-pressure reactor lined with polytetrafluoroethylene, react at 120 °C for 24 h to promote the crystallization and growth of the Mg-MOF-74 precursor on the surface and in the pores of the mesoporous silica; after the reaction, wash it by centrifugation with DMF and ethanol alternately for 3 times to remove unreacted substances, and then dry it in vacuum at 60 °C for 12 h to obtain the Mg-MOF-74@mesoporous silica composite powder;

[0066] (d) Preparation of composite slurry: Mix the composite powder and deionized water at a solid content of 18 wt.%, add 0.1 wt.% of the dispersant CMC, and ball-mill it at 300 rpm for 2 h to obtain the composite slurry.

[0067] S3 Impregnation outlet section

[0068] Immerse the outlet section of the adsorbent matrix (the outlet section accounts for 62% of the length of the adsorbent matrix) in the MIL-101(Cr) impregnation solution. During impregnation, the MIL-101(Cr) adsorbent matrix is vertically impregnated for 20 min, then pulled out from the impregnation solution at a pulling speed of 0.8 mm / s, and then dried in vacuum at 120 °C for 4 h. Repeat the above impregnation and vacuum drying 3 times to make the loading amount reach 8.5 mmol / g, thus obtaining the honeycomb CO2 capture adsorbent.

[0069] Among them, the preparation method of the MIL-101(Cr) impregnation solution is: Disperse MIL-101(Cr) in a 30 wt.% ethanol solution, with the concentration of MIL-101(Cr) being 8 wt.%, and perform ultrasonic treatment for 30 min to obtain the MIL-101(Cr) impregnation solution.

[0070] Example 2

[0071] The preparation method of the honeycomb CO2 capture adsorbent in this example includes the following steps:

[0072] S1 Preparation of adsorbent matrix

[0073] Mix 50 wt.% kaolin, 30 wt.% magnesite, 10 wt.% γ-Al2O3, 5 wt.% MgO, and 5 wt.% silicon carbide nanowires by ball milling for 6 h, then carry out wet clay refining, and extrude and form using a honeycomb mold (pore diameter 1.5 mm, wall thickness 0.2 mm). After drying, sinter by embedding graphite powder to obtain the adsorbent matrix.

[0074] Among them, the wet clay refining includes the following steps:

[0075] (1) Raw material mixing: After weighing each raw material, add 16 wt.% water and preliminarily stir into a clay mass in a kneader;

[0076] (2) Vacuum clay refining: Put the clay mass into a vacuum clay refining machine, and through screw extrusion and vacuum pump air extraction (vacuum degree about -0.1 MPa), remove internal air bubbles to make the clay material dense and uniform;

[0077] (3) Aging treatment: Let the clay material with removed air bubbles stand for 48 h to promote the even distribution of water and enhance plasticity, thus completing the wet clay refining.

[0078] Drying includes the following steps:

[0079] 1) Preheating stage: Heat uniformly through microwave heating, with a microwave power of 0.5 kW, a temperature of 40 °C, and a time of 30 min, to avoid surface hardening of the green body;

[0080] 2) Main drying stage: Adjust the microwave heating power to 2 kW, a temperature of 80 °C, and a time of 50 min to accelerate the internal water migration;

[0081] 3) Final drying stage: Adjust the microwave heating power to 3 kW, a temperature of 100 °C, and a heating time of 5 min to make the water content of the extruded and formed adsorbent matrix 0.7 wt.%.

[0082] The specific process of sintering by embedding graphite powder is as follows: Place the dried adsorbent matrix in a crucible and fill the surrounding with graphite powder; Under a flowing nitrogen atmosphere, first heat up to 550 °C at a rate of 5 °C / min, then heat up to 1250 °C at a rate of 5 °C / min, and hold for 4 h to promote the formation of the cordierite crystal phase; Cool naturally with the furnace to obtain the adsorbent matrix.

[0083] S2 Spray the coating on the inlet section

[0084] Spray the composite slurry of Mg-MOF-74 and mesoporous silica gel on the inlet section of the adsorbent matrix (the inlet section accounts for 30% of the length of the adsorbent matrix), with a spraying pressure of 0.3 MPa, and spray multiple times until the coating thickness is 60 μm; After spraying, dry at 75 °C for 3 h, and then calcine at 280 °C for 2 h to form the coating.

[0085] Among them, the preparation method of the composite slurry includes the following steps:

[0086] (a) Preparation of Mg-MOF-74 precursor solution: Weigh Mg(NO3)2·6H2O and H4DOBDC with a molar ratio of 2:1, dissolve them in a mixed solvent of DMF, water and ethanol with a volume ratio of 7:1.5:1 to obtain a solution with a concentration of 0.2 mol / L;

[0087] (b) Adding dispersant: Add 0.1 wt.% of dispersant CTAB to the solution, and ultrasonically treat it for 10 min to improve the compatibility with mesoporous silica in the subsequent process;

[0088] (c) Preparation of composite powder:

[0089] First, pretreat the mesoporous silica: Immerse the mesoporous silica in 1 M HCl for 1.5 h, wash it until neutral and then dry it, calcine it at 200 °C for 3 h, and ultrasonically treat it with ethanol at 40 kHz for 30 min to remove the residual impurities in the pores. The pore diameter of the mesoporous silica > 3 nm;

[0090] According to the mass ratio of mesoporous silica to MOF in the Mg-MOF-74 precursor solution of 1:2.5, immerse the mesoporous silica in the Mg-MOF-74 precursor solution, stir it at 25 °C for 12 h to make the Mg-MOF-74 precursor penetrate into the pores of the mesoporous silica; transfer the obtained mixture to a high-pressure reaction kettle lined with polytetrafluoroethylene, react at 115 °C for 30 h to promote the crystallization growth of the Mg-MOF-74 precursor on the surface and in the pores of the mesoporous silica; after the reaction, wash it by centrifugation with DMF and ethanol alternately for 3 times to remove the unreacted substances, and then vacuum dry it at 60 °C for 12 h to obtain Mg-MOF-74@mesoporous silica composite powder;

[0091] (d) Preparation of composite slurry: Mix the composite powder and deionized water according to a solid content of 15 wt.%, add 0.05 wt.% of dispersant PVP, and ball mill it at 250 rpm for 3 h to obtain the composite slurry.

[0092] S3 Impregnation outlet section

[0093] Immerse the outlet section of the adsorbent matrix (the outlet section accounts for 70% of the length of the adsorbent matrix) in the MIL-101(Cr) impregnation solution. When impregnating, the MIL-101(Cr) adsorbent matrix is vertically impregnated for 10 min, and then pulled out from the impregnation solution at a pulling speed of 0.5 mm / s. Subsequently, vacuum dry it at 100 °C for 6 h. Repeat the above impregnation and vacuum drying 3 times to make the loading amount reach 8 mmol / g, thus obtaining the honeycomb CO2 capture adsorbent.

[0094] Among them, the preparation method of the MIL-101(Cr) impregnating solution is as follows: Disperse MIL-101(Cr) in a 25 wt.% ethanol solution with a MIL-101(Cr) concentration of 6 wt.%, and ultrasonically treat for 30 min to obtain the MIL-101(Cr) impregnating solution.

[0095] Example 3

[0096] The preparation method of the honeycomb CO2 capture adsorbent in this example includes the following steps:

[0097] S1 Prepare the adsorbent matrix

[0098] Mix 30 wt.% kaolin, 40 wt.% magnesite, 15 wt.% γ-Al2O3, 5 wt.% MgO, and 10 wt.% silicon carbide nanowires by ball milling for 6 h, then carry out wet clay refining, and extrude and form with a honeycomb mold (pore diameter 1.5 mm, wall thickness 0.2 mm). After drying, sinter by burying graphite powder to obtain the adsorbent matrix.

[0099] Among them, the wet clay refining includes the following steps:

[0100] (1) Raw material mixing: After weighing each raw material, add 15 wt.% water and preliminarily stir into a clay mass in a kneading machine;

[0101] (2) Vacuum clay refining: Put the clay mass into a vacuum clay refining machine, and through screw extrusion and vacuum pump air extraction (vacuum degree about -0.1 MPa), remove internal air bubbles to make the clay material dense and uniform;

[0102] (3) Aging treatment: Let the clay material after removing air bubbles stand for 24 h to promote the uniform distribution of water and enhance plasticity, that is, complete the wet clay refining.

[0103] Drying includes the following steps:

[0104] 1) Preheating stage: Heat by microwave, with a microwave power of 1.5 kW, a temperature of 60 °C, and a time of 10 min, so that the green body is uniformly heated to avoid surface hardening;

[0105] 2) Main drying stage: Adjust the microwave heating power to 3 kW, the temperature to 100 °C, and the time to 20 min to accelerate the internal water migration;

[0106] 3) Final drying stage: Adjust the microwave heating power to 4 kW, the temperature to 120 °C, and the heating time to 2 min, so that the water content of the extruded adsorbent matrix is 0.8 wt.%.

[0107] The specific process of sintering with graphite powder is as follows: Place the dried adsorbent matrix in a crucible and fill the surrounding with graphite powder. Under a flowing nitrogen atmosphere, first heat it to 620°C at a rate of 10°C / min, then heat it to 1200°C at a rate of 3°C / min, and hold for 2 h to promote the formation of cordierite crystal phase. Cool it naturally with the furnace to obtain the adsorbent matrix.

[0108] S2 Spray the coating on the inlet section

[0109] Spray the composite slurry of Mg-MOF-74 and mesoporous silica gel on the inlet section of the adsorbent matrix (the inlet section accounts for 45% of the length of the adsorbent matrix), the spraying pressure is 0.5 MPa, and spray multiple times until the coating thickness is 100 μm. After spraying, dry it at 85°C for 1.5 h, and then calcine it at 320°C for 1 h to form the coating.

[0110] Among them, the preparation method of the composite slurry includes the following steps:

[0111] (a) Preparation of Mg-MOF-74 precursor solution: Weigh Mg(NO3)2·6H2O and H4DOBDC with a molar ratio of 2:1, dissolve them in a mixed solvent of DMF, water and ethanol with a volume ratio of 7:2.5:2 to obtain a solution with a concentration of 0.1 mol / L.

[0112] (b) Add dispersant: Add 1 wt.% of the dispersant CTAB to the solution and ultrasonically treat it for 10 min to improve the compatibility with mesoporous silica gel in the follow-up.

[0113] (c) Preparation of composite powder:

[0114] First, pre-treat the mesoporous silica gel: Immerse the mesoporous silica gel in 1 M HCl for 0.5 h, wash it until neutral and then dry it, calcine it at 250°C for 2 h, and ultrasonically treat it with ethanol at 40 kHz for 30 min to remove the residual impurities in the pores. The pore diameter of the mesoporous silica gel > 3 nm.

[0115] According to the mass ratio of mesoporous silica gel to MOF in the Mg-MOF-74 precursor solution of 1:3.5, immerse the mesoporous silica gel in the Mg-MOF-74 precursor solution, stir at 25°C for 12 h to make the Mg-MOF-74 precursor penetrate into the pores of the mesoporous silica gel. Transfer the obtained mixture to a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, react at 125°C for 18 h to promote the crystallization and growth of the Mg-MOF-74 precursor on the surface and in the pores of the mesoporous silica gel. After the reaction, wash it by centrifugation with DMF and ethanol alternately for 3 times to remove the unreacted substances, and then dry it in vacuum at 60°C for 12 h to obtain the Mg-MOF-74@mesoporous silica gel composite powder.

[0116] (d) Preparation of the composite slurry: The composite powder was mixed with deionized water at a solid content of 25 wt.%, and 0.15 wt.% of the dispersant CMC was added. It was ball-milled at 350 rpm for 1.5 h to obtain the composite slurry.

[0117] S3 Impregnation outlet section

[0118] The outlet section of the adsorbent matrix (the outlet section accounts for 55% of the length of the adsorbent matrix) was impregnated in the MIL-101(Cr) impregnation solution. During impregnation, the MIL-101(Cr) adsorbent matrix was vertically impregnated for 30 min, and then pulled out from the impregnation solution at a pulling speed of 1.2 mm / s. Subsequently, it was vacuum-dried at 130 °C for 3 h. After repeating the above impregnation and vacuum drying 3 times, the loading reached 9 mmol / g, and the honeycomb CO2 capture adsorbent was obtained.

[0119] Among them, the preparation method of the MIL-101(Cr) impregnation solution was: MIL-101(Cr) was dispersed in a 35 wt.% ethanol solution, and the concentration of MIL-101(Cr) was 10 wt.%. It was ultrasonically treated for 30 min to obtain the MIL-101(Cr) impregnation solution.

[0120] Comparative Example 1

[0121] The difference from Example 1 was that steps S2 and S3 were not carried out.

[0122] Comparative Example 2

[0123] The difference from Example 1 was that step S3 was not carried out, and in step S2, the coating was sprayed on the entire adsorbent matrix.

[0124] Comparative Example 3

[0125] The difference from Example 1 was that step S2 was not carried out, and in step S3, the entire adsorbent matrix was impregnated.

[0126] Comparative Example 4

[0127] The difference from Example 1 was that in step S2, the Mg-MOF-74 precursor solution prepared in step (a) was sprayed on the inlet section of the adsorbent matrix.

[0128] Comparative Example 5

[0129] The difference from Example 1 was that in step S2, the coating was sprayed on the outlet section of the adsorbent matrix, and in step S3, the inlet section of the adsorbent matrix was impregnated.

[0130] The adsorbents prepared in Examples 1-3 and Comparative Examples 1-5 were added to a small-scale CO2 capture device for detection of the adsorption rate, saturation adsorption capacity, and cycle stability. Among them, as Figure 1As shown, the CO2 capture pilot device includes a mixer, which is connected to a N2 storage tank and a CO2 storage tank through pipelines, and a flow meter and a valve are arranged on the pipeline; the mixer is connected to a fixed bed reactor through a pipeline, and a flow meter, a preheater and a valve are arranged on the pipeline, and an electric heating wire and a thermocouple are arranged in the preheater; the fixed bed reactor is filled with an adsorbent and is internally provided with an online flue gas analyzer, an electric heating wire and a thermocouple.

[0131] Working principle:

[0132] An adsorbent with an outer dimension of 25mm×25mm×150mm and a mass of 48g is loaded into a fixed bed reactor, and N2 and CO2 are mixed in a mixer at a volume ratio of 90% and 10%. The mixed gas is preheated to 40°C by a preheater and then passed into the fixed bed reactor. The electric heating wire ensures that the adsorbent adsorbs CO2 in the mixed gas at a temperature of 40°C, and the CO2 concentration in the mixed gas is detected in real time by an online flue gas analyzer.

[0133] The detection methods of adsorption rate, saturated adsorption capacity and cycle stability of the adsorbent are as follows:

[0134] (1) Adsorption rate: The mixed gas is introduced into the fixed bed reactor at one time, and the rate of decrease of CO2 concentration per unit time in the fixed bed reactor is observed by an online flue gas analyzer, which is the adsorption rate of the adsorbent.

[0135] (2) Saturated adsorption capacity: The gas flow rate is controlled by a mass flow meter, and the mixed gas is continuously introduced into the fixed bed reactor. The concentration change of CO2 at the outlet of the fixed bed reactor is observed by an online flue gas analyzer. During the decarbonization process, the total gas flow entering the fixed bed reactor is adjusted by a mass flow meter and recorded as Q, and C c t It represents the outlet CO2 concentration in the fixed bed reactor, expressed as C c 0 represents the inlet CO2 concentration, m sorbent is the sample loading amount, then the CO2 absorption amount of the adsorbent q CO2 [mmol CO2·(g adsorbent)- 1 [Calculation] can be obtained by formula (1) and formula (2):

[0136]

[0137] (3) Cyclic stability: After the adsorbent is saturated at 40°C, it is heated to 120°C by an electric heating wire for regeneration, releasing the adsorbed CO2, and then adsorption is restarted. The above adsorption-regeneration process is repeated 10 times a day for 30 consecutive days. The saturated adsorption capacity of the adsorbent is then detected, and the decay rate of the saturated adsorption capacity of the adsorbent before and after operation is calculated.

[0138] After detection, the detection results of the adsorption rate, saturated adsorption capacity, and cycle stability of the adsorbents prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1:

[0139] Table 1 Detection Results of Adsorption Rate, Saturated Adsorption Capacity, and Cycle Stability of Adsorbents in Examples 1-3 and Comparative Examples 1-5

[0140]

[0141] As can be seen from Table 1, in Comparative Example 1, since the Mg-MOF-74@mesoporous silica coating was not sprayed on the inlet section of the adsorbent matrix, the adsorption rate of the finally prepared adsorbent was greatly reduced. At the same time, since MIL-101(Cr) was not impregnated in the outlet section, the saturated adsorption capacity of the adsorbent was also greatly reduced. In Comparative Example 2, since the Mg-MOF-74@mesoporous silica coating was sprayed on the entire surface of the adsorbent matrix, the adsorption rate of the adsorbent was increased. However, since MIL-101(Cr) was not impregnated, the saturated adsorption capacity of the adsorbent was lower than that in Example 1. In Comparative Example 3, since the entire adsorbent matrix was impregnated with MIL-101(Cr), the saturated adsorption capacity of the adsorbent was not reduced too much. However, since the Mg-MOF-74@mesoporous silica coating was not sprayed, the adsorption rate of the adsorbent was reduced. In Comparative Example 4, when spraying the coating on the inlet section of the adsorbent matrix, mesoporous silica was not added to the composite slurry, resulting in a decrease in the adsorption rate, saturated adsorption capacity, and cycle stability of the adsorbent. This is because mesoporous silica is not just a simple container, but actively participates in and guides the growth of Mg-MOF-74 at specific positions in a specific manner, ultimately forming a composite material with a unique structure and potentially excellent properties. Therefore, the lack of mesoporous silica in Comparative Example 4 causes Mg-MOF-74 to lose the advantages of its nanostructure, resulting in a decline in its adsorption performance. Since the turbulence in the inlet section of the adsorbent is more severe than that in the outlet section and the gas molecule collisions are intense, the adsorption rate needs to be increased in the inlet section to improve the total adsorption amount of the catalyst. When MIL-101(Cr) was impregnated in the inlet section and the Mg-MOF-74@mesoporous silica coating was sprayed in the outlet section in Comparative Example 5, it was contrary to the above-mentioned usage requirements, resulting in a decline in the adsorption performance of the adsorbent.

Claims

1. Preparation method of honeycomb CO2 capture adsorbent, characterized in that, It includes the following steps: S1 Preparation of adsorbent matrix: Mix 30 - 50 wt.% kaolin, 30 - 40 wt.% magnesite, 10 - 15 wt.% γ - Al2O3, 5 - 10 wt.% MgO, and 5 - 10 wt.% silicon carbide nanowires, then carry out wet clay refining, extrude and form with a honeycomb mold, dry and sinter by embedding graphite powder to obtain the adsorbent matrix; S2 Spraying the coating on the inlet section: Spray the composite slurry of Mg - MOF - 74 and mesoporous silica gel on the inlet section of the adsorbent matrix, dry and calcine after spraying to form the coating; S3 Impregnating the outlet section: Immerse the outlet section of the adsorbent matrix in the MIL - 101(Cr) impregnating solution, and vacuum dry after impregnation to obtain the honeycomb - type CO2 capture adsorbent.

2. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, characterized in that, In step S1, the wet clay refining includes the following steps: (1) Raw material mixing: Weigh each raw material, add 15 - 16 wt.% water, and preliminarily stir into a clay mass in a kneader; (2) Vacuum clay refining: Put the clay mass into a vacuum clay refining machine to remove internal air bubbles; (3) Aging treatment: Let the clay material after removing air bubbles stand for 24 - 48 h to complete the wet clay refining.

3. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, characterized in that, In step S1, the drying includes the following steps: 1) Pre - heating stage: Heat by microwave, the microwave power is 0.5 - 1.5 kW, the temperature is 40 - 60 °C, and the time is 10 - 30 min; 2) Main drying stage: Adjust the microwave heating power to 2 - 3 kW, the temperature is 80 - 100 °C, and the time is 20 - 50 min; 3) Final drying stage: Adjust the microwave heating power to 3 - 4 kW, the temperature is 100 - 120 °C, and the heating time is 2 - 5 min to make the water content of the extruded and formed adsorbent matrix < 1 wt.%.

4. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, characterized in that, In step S1, the specific process of sintering by embedding graphite powder is as follows: Place the dried adsorbent matrix in a crucible, and fill the surrounding with graphite powder; Under a flowing nitrogen atmosphere, first heat up at a rate of 5 - 10 °C / min to 550 - 650 °C, then heat up at a rate of 3 - 5 °C / min to 1200 - 1300 °C, and keep the temperature for 2 - 4 h; Cool naturally with the furnace or cool to room temperature at a rate of ≤5 °C / min.

5. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, characterized in that, In step S2, the inlet section accounts for 30 - 45% of the length of the adsorbent matrix.

6. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, wherein In step S2, the preparation method of the composite slurry includes the following steps: (a) Preparation of Mg - MOF - 74 precursor solution: Weigh Mg(NO3)2·6H2O and 2,5 - dihydroxyterephthalic acid, dissolve them in a mixed solvent of DMF, water and ethanol to obtain a solution; (b) Adding a dispersant: Add 0.1 - 1 wt.% dispersant CTAB to the solution; (c) Preparation of composite powder: Immerse mesoporous silica gel into the Mg-MOF-74 precursor solution, and stir to make the Mg-MOF-74 precursor penetrate into the pores of the mesoporous silica gel; transfer the obtained mixture to a reaction kettle, and react at 115-125 °C for 18-30 h to promote the crystallization and growth of the Mg-MOF-74 precursor on the surface and in the pores of the mesoporous silica gel; after the reaction, wash and dry to obtain the Mg-MOF-74@mesoporous silica gel composite powder; (d) Preparation of composite slurry: Mix the composite powder with deionized water, add a dispersant, and ball mill to obtain the composite slurry.

7. The preparation method of the honeycomb CO2 capture adsorbent according to claim 6, wherein In step (a), the molar ratio of Mg(NO3)2·6H2O to 2,5-dihydroxyterephthalic acid is (1.5-2):1, the volume ratio of DMF, water and ethanol in the mixed solvent is 7:(1.5-2.5):(1-2), and the concentration of the solution is 0.1-0.2 mol / L; in step (c), first pretreat the mesoporous silica gel, immerse the mesoporous silica gel in 1M HCl for 0.5-1.5 h, wash to neutrality and then dry, calcine at 200-250 °C for 2-3 h, and then perform ultrasonic treatment on it with ethanol to remove residual impurities in the pores, and the pore diameter of the mesoporous silica gel > 3 nm; the mass ratio of the mesoporous silica gel to the MOF in the Mg-MOF-74 precursor solution is 1:(2.5-3.5); in step (d), after mixing the composite powder with deionized water, the solid content is 15-25 wt.%, the dispersant is sodium carboxymethyl cellulose or polyvinylpyrrolidone, and the content is 0.05-0.15 wt.%; the ball milling speed is 250-350 rpm, and the ball milling time is 1.5-3 h.

8. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, wherein, In step S2, the spraying pressure is 0.3-0.5 MPa, and spray multiple times until the coating thickness is 60-100 μm; the drying temperature is 75-85 °C, the drying time is 1.5-3 h, the calcination temperature is 280-320 °C, and the calcination time is 1-2 h.

9. The preparation method of the honeycomb CO2 capture adsorbent according to claim 1, wherein, In step S3, the preparation method of the MIL-101(Cr) impregnation solution is: disperse MIL-101(Cr) in a 25-35 wt.% ethanol solution, the concentration of MIL-101(Cr) is 6-10 wt.%, and perform ultrasonic treatment to obtain the MIL-101(Cr) impregnation solution; during impregnation, the MIL-101(Cr) adsorbent matrix is vertically impregnated for 10-30 min, and then pulled out from the impregnation solution, the pulling speed is 0.5-1.2 mm / s, the vacuum drying temperature is 100-130 °C, and the vacuum drying time is 3-6 h. Repeat the above impregnation and vacuum drying multiple times to make the loading amount reach 8-9 mmol / g.

10. Honeycomb CO2 capture adsorbent, characterized in that, Prepared by the preparation method of the honeycomb CO2 capture adsorbent according to any one of claims 1-9.

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