Silica-based adsorbing material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of carbon dioxide trapping, and particularly relates to a silicon dioxide-based adsorbing material as well as a preparation method and application thereof. The silica-based adsorption material provided by the invention comprises a matrix and polyethyleneimine loaded in the matrix, the matrix comprises silicon dioxide; the structure of the silicon dioxide-based adsorption material is a honeycomb cylindrical body; the silica-based adsorption material has a uniformly distributed pore structure, and the pore volume of the silica-based adsorption material is 0.08-0.36 cm < 3 > / g. The silica-based adsorption material provided by the invention has relatively large pore volume and relatively high amine loading capacity, and is beneficial to adsorption of carbon dioxide; meanwhile, the honeycomb structure is adopted, air can be guided to uniformly flow along the channels, pressure drop is reduced, the contact area with the air is increased, and adsorption of carbon dioxide is facilitated. The mechanical strength of the silicon dioxide-based adsorption material is improved by the uniformly distributed pore structure, and the industrial requirements can be met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon dioxide capture, and particularly relates to a silicon dioxide-based adsorption material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous rise of carbon dioxide (CO2) concentration in the atmosphere, the global faces the realistic challenge of climate warming, and at present, the challenge of climate change caused by high concentration of CO2 in the atmosphere is mainly responded by capturing carbon dioxide.

[0003] In the existing CO2 removal technology, direct air capture technology (DAC) is the most effective, and the direct air capture technology is a technology for capturing low-concentration carbon dioxide directly from air, which can remove CO2 in the atmosphere. Since air carbon capture is not related to emission sources, the air direct carbon capture technology has wide applicability and can capture carbon dioxide at different locations. The carbon dioxide adsorption material used in the current direct air capture technology is mostly in a powder state; however, the close packing of the powder results in a bed pressure drop of 0.1~1psi, which is much higher than the industrial economic operation threshold (0.01psi), greatly increasing the fan energy consumption and operation cost; at the same time, the complex pore structure of the powder state carbon dioxide adsorption material causes uneven heat transfer, low desorption regeneration efficiency, large mass transfer resistance, and slow adsorption kinetics. Therefore, researchers have obtained shaped carbon dioxide adsorption materials through extrusion, 3D printing, coating and other molding technologies, and have made efforts to reduce the bed pressure drop and promote the industrial application of adsorption technology.

[0004] At present, the molding technology of adsorption materials provides a solution path for industrial application, but the shaped bodies generally face the dual challenges of adsorption performance decay and insufficient mechanical strength. On the one hand, the addition of binders, high-temperature treatment and other processes in the molding process easily lead to loss of adsorption active sites or blockage of pores, resulting in significant decrease in adsorption capacity; on the other hand, the traditional molding materials are difficult to meet the requirements of mechanical strength under the severe working conditions such as high pressure and high speed airflow scouring in industrial continuous operation. SUMMARY

[0005] Therefore, the application provides a silicon dioxide-based adsorption material and a preparation method and application thereof. The silicon dioxide-based adsorption material provided by the application has good mechanical properties and an advantageous pore structure, and is suitable for being used as a carbon dioxide adsorbent in direct air capture technology.

[0006] In order to solve the above technical problems, the application provides a silicon dioxide-based adsorption material, which comprises a substrate and polyethyleneimine loaded in the substrate. The base body comprises silica; the structure of the silica-based adsorption material is a honeycomb columnar body; the silica-based adsorption material has a uniformly distributed pore structure, and the pore volume of the silica-based adsorption material is 0.08-0.36 cm 3 / g.

[0007] Preferably, the specific surface area of the silica-based adsorption material is 20.68-58.99 m 2 / g.

[0008] Preferably, the loading amount of polyethyleneimine in the silica-based adsorption material is 16-60%.

[0009] The application also provides a preparation method of the silica-based adsorption material, comprising the following steps: The silica, bentonite, methyl cellulose, activated carbon and water are first mixed to obtain a slurry; The slurry is shaped and then calcined to obtain a base body; The base body is immersed in a polyethyleneimine solution for loading to obtain the silica-based adsorption material; and the loading process is accompanied by ultrasonic and stirring in sequence.

[0010] Preferably, the silica comprises fumed silica; The mass ratio of the bentonite to the methyl cellulose is 2.4-2.6:1; The activated carbon accounts for 5-25% of the total mass of the silica, bentonite, methyl cellulose and activated carbon.

[0011] Preferably, the first mixing comprises the following steps: The bentonite and water are secondly mixed, and then the methyl cellulose, activated carbon and silica are added in sequence to obtain a slurry; The second mixing is performed under stirring, and the stirring time is 4-6 min; After the addition of the methyl cellulose, activated carbon and silica, stirring is performed respectively, the stirring time after the addition of the methyl cellulose is 4-6 min, the stirring time after the addition of the activated carbon is 4-6 min, and the stirring time after the addition of the silica is 28-32 min.

[0012] Preferably, the shaping is performed by injecting the slurry into a honeycomb columnar mold for extrusion, the extrusion pressure is 9-11 MPa, and the pressure holding time of the extrusion is 9-11 min; After the shaping, the shaped product is further dried, the drying temperature is 95-105 DEG C, and the drying time is 1.5-2.5 h.

[0013] Preferably, the temperature of the calcination is 890-910 DEG C, and the time is 4.5-5.5 h.

[0014] Preferably, the power of the ultrasonic is 30-40 W, the temperature is 48-52 DEG C, and the time is 1.8-2.2 h. The stirring is magnetic stirring, and the time of the magnetic stirring is 5-7 h.

[0015] The application further provides application of the silica-based adsorbent material or the silica-based adsorbent material prepared by the preparation method as a carbon dioxide adsorbent.

[0016] The application provides a silica-based adsorbent material, which comprises a substrate and polyethylene imine loaded in the substrate; the substrate comprises silica; the structure of the silica-based adsorbent material is a honeycomb columnar body; the silica-based adsorbent material has a uniform pore structure, and the pore volume of the silica-based adsorbent material is 0.08-0.36 cm 3 / g. The silica-based adsorbent material provided by the application has a uniform pore structure and a large pore volume, and the carbon dioxide adsorption capacity is improved. In the application, the polyethylene imine loaded in the substrate is beneficial to carbon dioxide adsorption; meanwhile, the honeycomb structure can guide air to flow uniformly along the channels, reduce the pressure drop, increase the contact area with air, and be beneficial to carbon dioxide adsorption. In the application, the uniform pore structure forms a support system, and the mechanical strength of the silica-based adsorbent material is improved, which can meet the industrial needs. The silica-based adsorbent material provided by the application has certain advantages in carbon dioxide adsorption capacity, stability and adsorption kinetics, and can be used as a carbon dioxide adsorbent in direct air capture technology.

[0017] In the application, activated carbon is introduced as a pore-forming agent to adjust the pore channel of the adsorbent material, the pore connectivity and pore size distribution are optimized, the mass transfer path is effectively shortened, and the additional pore volume provides a pore structure for amine loading and gas transmission; in the application, the impregnation loading improves the loading amount of polyethylene imine, which is beneficial to improving the carbon dioxide adsorption capacity. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The comparison chart of the pore volume and specific surface area of the adsorbent materials prepared in Example 1 and Comparative Examples 1-4; Figure 2 The result chart of the pore size distribution and nitrogen adsorption isotherm of the adsorbent materials prepared in Example 1 and Comparative Examples 1-4, wherein (b) and (d) are the pore size distribution charts, and (c) and (e) are the nitrogen adsorption isotherms; Figure 3A columnar contrast chart of PEI loadings for SiO2 / 50PEI, SiO2-M / 50PEI-stirring, SiO2-M / 50PEI, SiO2-M / 60PEI and SiO2-M / 70PEI; Figure 4 A result of correlation between PEI loadings and pore volume filling rates; Figure 5 A physical map and a scanning electron microscope detection result map of the adsorption material, wherein (a) is a physical map of 20AC-SiO2-M / 50PEI prepared in Example 1, (b) is an energy dispersive spectroscopy (EDS) image of carbon, nitrogen and silicon of 20AC-SiO2-M / 50PEI prepared in Example 1, (c) is a SEM image of 20AC-SiO2-M at a scale of 1 μm, (d) is a SEM image of fumed silica powder, (e) is a SEM image of SiO2-M, (f) is a SEM image of 20AC-SiO2-M, (g) is a SEM image of SiO2 / 50PEI, (h) is a SEM image of SiO2-M / 50PEI, and (i) is a SEM image of 20AC-SiO2-M / 50PEI; Figure 6 A contrast chart of carbon dioxide adsorption amounts and adsorption rate curves of SiO2-M / 50PEI adsorption materials in Example 1 and Comparative Example 3; Figure 7 A columnar contrast chart of carbon dioxide adsorption amounts of 20AC-SiO2-M / 50PEI under dry and humid environments after 10 cycles of adsorption; Figure 8 A thermogravimetric curve of the adsorption material; Figure 9 Porosities and pressure drop results of different adsorption materials; Figure 10 A curve of compressive stress of 20AC-SiO2-M varying with displacement. DETAILED DESCRIPTION

[0019] The present application provides a silica-based adsorption material, comprising a substrate and polyethyleneimine loaded in the substrate.

[0020] In the present application, the substrate comprises silica and also comprises bentonite; the bentonite functions as a binder.

[0021] In the present application, the structure of the silica-based adsorption material is a honeycomb columnar body; the silica-based adsorption material has a uniformly distributed pore structure, and the pore volume of the silica-based adsorption material is 0.08-0.36 cm 3 / g, which can be specifically 0.08 cm 3 / g, 0.11 cm 3 / g, 0.13 cm 3 / g, 0.23 cm 3 / g or 0.36 cm 3 / g; the specific surface area of the silica-based adsorbent material can be 20.68~58.99 m 2 / g, 20.68 m 2 / g, 23.02 m 2 / g, 28.04 m 2 / g, 38.61 m 2 / g or 58.99 m 2 / g. As a specific embodiment of the present application, the height of the honeycomb columnar body can be 3~5 mm, the diameter can be 10~14 mm, and the diameter of the internal channel of the honeycomb columnar body can be 2~2.5 mm. The honeycomb columnar body silica-based adsorbent material prepared by the embodiment of the present application has a honeycomb columnar height of 5 mm, a diameter of 12 mm, and 7 internal channels with a diameter of 2.5 mm uniformly distributed therein.

[0022] In the present application, the loading amount of polyethyleneimine in the silica-based adsorbent material can be 16~60%, can also be 35~47%, and can further be 40~45%.

[0023] In the present application, the raw materials for preparing the silica-based adsorbent material include silica, bentonite, methyl cellulose (MC), polyethyleneimine (PEI), and activated carbon (AC). In the present application, the silica serves as a base material, has the characteristics of high surface area and high pore volume, and has good stability, is easy to obtain, and is inexpensive. In the present application, the bentonite and methyl cellulose serve as binders, wherein the bentonite forms a hydration film after absorbing water, and through electrostatic attraction and van der Waals force, other material particles are bonded together to form stable agglomerates or integral structures, and at the same time, the plasticity and formability of the system are improved; the methyl cellulose serves as a binder to bond the dispersed powder, so that the base material can maintain its shape during pressing or extrusion molding, and is not easy to collapse. In the present application, the activated carbon serves as a pore-forming agent.

[0024] The present application also provides a preparation method of the silica-based adsorbent material described in the above technical solution, which comprises the following steps: mixing silica, bentonite, methyl cellulose, activated carbon, and water to obtain a slurry; shaping and roasting the slurry to obtain a base material; immersing the base material in a polyethyleneimine solution for loading to obtain the silica-based adsorbent material; and the loading process is accompanied by ultrasonic and stirring processes in sequence.

[0025] The present application first mixes silica, bentonite, methyl cellulose, activated carbon and water to obtain a slurry. As a specific embodiment of the present application, the silica can include fumed silica, and the water can be deionized water; the mass ratio of the bentonite and the methyl cellulose can be 2.4-2.6:1, and can specifically be 2.5:1; the activated carbon can account for 5-25% of the total mass of the silica, the bentonite, the methyl cellulose and the activated carbon, and can specifically be 5%, 10%, 15%, 20% or 25%. The present application does not have a special limitation on the amount of water, as long as it can form a slurry to facilitate molding.

[0026] As a specific embodiment of the present application, the first mixing can include the following steps: secondly mixing the bentonite and the water, and then sequentially adding the methyl cellulose, the activated carbon and the silica to obtain the slurry; the second mixing can be performed under stirring, and the stirring time can be 4-6 min, and can specifically be 5 min; after adding the methyl cellulose, the activated carbon and the silica, the stirring can be performed respectively, the stirring time after adding the methyl cellulose can be 4-6 min, and can specifically be 5 min; the stirring time after adding the activated carbon can be 4-6 min, and can specifically be 5 min; the stirring time after adding the silica can be 28-32 min, and can specifically be 30 min. In the process of preparing the slurry, the present application can add an appropriate amount of deionized water in a timely manner to adjust the rheological property of the slurry so that it reaches a suitable molding slurry, so as to ensure that no cracks occur in the extrusion process.

[0027] After obtaining the slurry, the present application performs molding on the slurry and then performs calcination to obtain a matrix. As a specific embodiment of the present application, the molding can be extrusion by injecting the slurry into a honeycomb columnar mold; the pressure of the extrusion can be 9-11 MPa, and can specifically be 10 MPa; the pressure holding time of the extrusion can be 9-11 min, and can specifically be 10 min.

[0028] As a specific embodiment of the present application, the molding can further include drying the product after molding; the temperature of the drying can be 95-105℃, and can specifically be 100℃; the time of the drying can be 1.5-2.5 h, and can specifically be 2 h. The present application removes the moisture in the product after molding by drying.

[0029] As a specific embodiment of the present application, the temperature of the calcination can be 890-910℃, and can specifically be 900℃; the time of the calcination can be 4.5-5.5 h, and can specifically be 5 h. In the calcination process, the activated carbon is changed into carbon dioxide at high temperature, which provides an additional pore volume and provides an excellent pore structure for loading polyethyleneimine (PEI) later, and further reduces the mass transfer resistance in the adsorption process.

[0030] After obtaining the substrate, the application impregnates the substrate in a polyethyleneimine solution to load, to obtain the silica-based adsorbent material. The application dissolves polyethyleneimine in methanol to obtain the polyethyleneimine solution; the mass percentage of polyethyleneimine in the total mass of polyethyleneimine and the substrate can be 50-70%, and can be specifically 50%, 55%, 60%, 65% or 70%; the dissolving can be carried out under ultrasonic conditions, and the ultrasonic time can be 4-6 min, and can be specifically 5 min; the application does not have special requirements for the power of the ultrasonic, as long as it can be completely dissolved. The application does not have special requirements for the mass concentration of the polyethyleneimine solution, as long as the amount of polyethyleneimine and the substrate can meet the ratio; the application does not have special requirements for the volume of the polyethyleneimine solution, as long as it can immerse the substrate.

[0031] In the application, the loading process is accompanied by ultrasonic and stirring in sequence; the power of the ultrasonic can be 30-40 W, and can be specifically 35 W; the temperature of the ultrasonic can be 48-52℃, and can be specifically 50℃; the time of the ultrasonic can be 1.8-2.2 h, and can be specifically 2 h; the stirring can be magnetic stirring, the time of the magnetic stirring can be 5-7 h, and can be specifically 6 h; the temperature of the magnetic stirring can be room temperature, and the temperature of the room temperature can be 20-35℃, and can also be 25-30℃. The application of the composite loading mode of ultrasonic and magnetic stirring can improve the loading amount of polyethyleneimine.

[0032] As a specific embodiment of the application, after loading, the system after loading can be sequentially subjected to rotary evaporation and drying to obtain the silica-based adsorbent material; the temperature of the rotary evaporation can be 45-55℃, and can be specifically 50℃; the rotation speed of the rotary evaporation can be 25-35 rpm, and can be specifically 30 rpm. The application does not have special requirements for the time of the rotary evaporation, as long as most of the methanol solvent can be removed. As a specific embodiment of the application, the drying can be vacuum drying, the temperature of the vacuum drying can be 45-55℃, and can be specifically 50℃; the time of the vacuum drying can be 12-26 h, and can also be 20-24 h; the application does not have special requirements for the vacuum degree of the vacuum drying, as long as it is under vacuum condition.

[0033] The application also provides the application of the silica-based adsorbent material in the above technical solution or the silica-based adsorbent material prepared by the preparation method in the above technical solution as a carbon dioxide adsorbent. As a specific embodiment of the application, the carbon dioxide adsorbent can be used for carbon dioxide capture in direct air capture technology (DAC); the temperature of the carbon dioxide capture can be 30-40℃, and can be specifically 35℃.

[0034] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0035] Example 1 Preparation of honeycomb structure columnar substrate: 0.25 g of bentonite was added to 20 mL of deionized water, and was fully dispersed by stirring at a speed of 1000 rpm for 5 min with a mechanical stirrer; then, 0.1 g of methyl cellulose was added and stirring was continued for 5 min, different amounts of activated carbon were added to the above mixture, and stirring was continued for 5 min, then 3.25 g of fumed silica was added and stirring was continued for 30 min to obtain a slurry. The slurry was injected into a honeycomb structure mold, which was placed in a hand extruder and was subjected to pressure molding at a pressure of 10 MPa for 10 min. The sample after demolding was first dried in a vacuum drying oven at 100 ℃ for 2 h to remove residual water, and then was transferred to a muffle furnace and was calcined at 900 ℃ for 5 h to obtain a honeycomb structure columnar substrate, which was denoted as nAC-SiO2-M.

[0036] Immersion loading of PEI: different amounts of polyethyleneimine were added to 20 mL of methanol, and were dispersed in an ultrasonic cleaner for 5 min to obtain a polyethyleneimine solution. Then, the honeycomb structure columnar substrate was immersed in the polyethyleneimine solution, and was subjected to ultrasonic treatment at 50 ℃ for 2 h and then was subjected to magnetic stirring at room temperature (30 ℃) for 6 h; then, the methanol solvent was evaporated by using a rotary evaporator at 50 ℃ and 30 rpm, and then the sample was placed in a vacuum drying oven at 50 ℃ for 24 h to obtain a silica-based adsorbent material, which was denoted as nAC-SiO2-M / mPEI, wherein n represents the mass fraction of AC in nAC-SiO2-M, m represents the mass fraction of PEI in the total mass of PEI and the honeycomb structure columnar substrate during the immersion loading process, and M represents the honeycomb columnar.

[0037] The specific amounts of activated carbon and polyethyleneimine added in Example 1 are shown in Table 1.

[0038] Comparative Example 1 Polyethyleneimine was directly loaded on powdered fumed silica as a comparative sample, specifically: different amounts of polyethyleneimine were added to 20 mL of methanol, and were subjected to magnetic stirring in a magnetic stirrer for 5 min to obtain a polyethyleneimine solution. Then, the powdered fumed silica was immersed in the polyethyleneimine solution, and was subjected to ultrasonic treatment at 50 ℃ for 2 h and then was subjected to magnetic stirring at room temperature (30 ℃) for 6 h; then, the methanol solvent was evaporated by using a rotary evaporator at 50 ℃ and 30 rpm, and then the sample was placed in a vacuum drying oven at 50 ℃ for 24 h to obtain a silica-supported polyethyleneimine, which was denoted as SiO2 / mPEI, wherein m represents the mass fraction of PEI in the total mass of PEI and fumed silica during the immersion loading process.

[0039] The specific amount of polyethyleneimine added in Comparative Example 1 is shown in Table 1.

[0040] Comparative Example 2 A honeycomb columnar silica was prepared as a comparative sample as follows: 0.25 g of bentonite was added to 20 mL of deionized water, and stirred at 1000 rpm for 5 min to fully disperse; then 0.1 g of methyl cellulose (MC) was added and stirred for another 5 min. Then 3.25 g of fumed silica was added, and stirring was continued for 30 min to ensure that the components were fully mixed. According to actual needs, an appropriate amount of deionized water was added to adjust the rheological properties of the slurry to a state suitable for molding. The prepared slurry was injected into a honeycomb structure mold, and placed in a manual extruder, and kept at 10 MPa for 10 min. Then the molded body was dried in a vacuum oven at 100°C for 2 h to remove residual water, and then transferred to a muffle furnace and calcined at 900°C for 5 h to obtain a honeycomb columnar silica, denoted as SiO2-M.

[0041] Comparative Example 3 A honeycomb columnar silica loaded with polyethyleneimine was prepared as a comparative sample as follows: the honeycomb columnar silica was prepared according to Comparative Example 2; different amounts of polyethyleneimine were added to 20 mL of methanol, and dispersed in an ultrasonic cleaner for 5 min to obtain a polyethyleneimine solution. Then, the honeycomb columnar silica was immersed in the polyethyleneimine solution, and ultrasonically treated at 50°C for 2 h, and then magnetically stirred at room temperature (30°C) for 6 h; then the methanol solvent was removed by rotary evaporation at 50°C and 30 rpm, and the sample was then placed in a 50°C vacuum drying oven for 24 h to obtain a honeycomb columnar silica loaded with polyethyleneimine, denoted as SiO2-M / mPEI.

[0042] The specific amount of polyethyleneimine added in Comparative Example 3 is shown in Table 1.

[0043] Comparative Example 4 A honeycomb columnar silica prepared by adding activated carbon was prepared as a comparative sample as follows: 0.25 g of bentonite was added to 20 mL of deionized water, and stirred with a mechanical stirrer for 5 min to fully disperse; then 0.1 g of methyl cellulose was added and stirred for another 5 min, and different amounts of activated carbon were added to the above mixture, and stirred for 5 min, and then 3.25 g of fumed silica was added and stirring was continued for 30 min to obtain a slurry. The slurry was injected into a honeycomb structure mold, and placed in a manual extruder, and kept at a pressure of 10 MPa for 10 min to complete molding. The demolded sample was first dried in a 100°C vacuum drying oven for 2 h to remove residual water, and then transferred to a muffle furnace and calcined at 900°C for 5 h to obtain a honeycomb structure columnar matrix, denoted as nAC-SiO2-M.

[0044] The specific amount of activated carbon added in Comparative Example 4 is shown in Table 1.

[0045] The pore volume and specific surface area were detected by BET, and the specific detection process was as follows: after impurity removal by pre-treatment of the sample at 90℃ for 2h, the nitrogen adsorption amount under different partial pressure ratios (P / P0=0.05~0.35) was measured in a liquid nitrogen environment, and the monolayer saturated adsorption volume V m was calculated by substituting the BET equation, and then the specific surface area was obtained; in combination with the adsorption isotherm, the pore volume could be derived. The results of the pore volume and specific surface area of the adsorbent materials prepared in Example 1 and Comparative Examples 1~4 are shown in Table 1; the comparison chart of the pore volume and specific surface area of the obtained adsorbent materials is shown in Figure 1 , Figure 2 Fig. 2, which is the result chart of the pore size distribution and nitrogen adsorption isotherm, wherein (b) and (d) are the pore size distribution charts, and (c) and (e) are the nitrogen adsorption isotherm charts. The loading amount of PEI in the adsorbent materials prepared in Example 1 and Comparative Examples 1 and 3 was detected by thermogravimetry, wherein the heating rate was 10℃ / min, and the calcination temperature was 800℃; the results are shown in Table 1.

[0046] Table 1 Material addition amount and physical properties of the adsorbent materials in Example 1 and Comparative Examples 1~4

[0047] “—” in Table 1 indicates that the substance is not added or the related performance is not detected.

[0048] It can be seen from Table 1 and Figures 1-2 that the specific surface area of the fumed silica is 180.92m²·g -1 , and the pore volume is 0.89cm³·g -1 . Compared with the SiO2 / 40PEI, SiO2 / 50PEI and SiO2 / 60PEI series samples, the specific surface area and pore volume decrease significantly with the increase of the loading amount of PEI, which confirms that PEI can effectively fill the pore channels of silica, resulting in a decrease in the pore structure parameters, and the pore structure parameters of SiO2 / 50PEI decrease most significantly. After the powder is extruded into a monolithic adsorbent, the specific surface area and pore volume further decrease, and the pore volume decreases by 51.69%, indicating that the pore channels of the powder are more developed, and the compression process causes the pore channels to be blocked. After introducing activated carbon as a pore-forming agent, different mass fractions of activated carbon can make the pore volume increase by 5.31~96.26%, and the pore volume of 20AC-SiO2-M is best, reaching 0.84cm³·g -1 ; after loading PEI, the specific surface area and pore volume of the monolithic adsorbent decrease significantly again, which indirectly proves that PEI is successfully loaded into the pore channels of the monolithic adsorbent. Figure 2Figures (b) and (c) show the pore structure results of the monolithic adsorbent using activated carbon as a pore-forming agent, with different morphologies in its N2 adsorption-desorption isotherms. After adding activated carbon, the values ​​in the low-pressure region (0.05-0.3 m² / g) slightly increased, and the specific surface area was greater than that of the monolithic adsorbent without activated carbon (160.26 m² / g). The changes were more pronounced in the high-pressure region, manifested as a sharp increase in pore volume. After calcination, the activated carbon disappeared, providing more pore channels and increasing the average pore size of the monolithic adsorbent. Overall, the addition of activated carbon can effectively regulate the pore structure and adsorption performance of the monolithic adsorbent. Figure 2 (d) and (e) show the changes in pore size and pore volume after PEI loading. A significant decrease in pore size and pore volume can be observed. After PEI loading, the pore volume peak in the small particle size region (1-10 nm) of the original sample is "suppressed", and a new peak appears at around 30 nm. This indicates that PEI preferentially fills the small-sized pores, while the remaining mesopores provide gas channels for subsequent adsorption.

[0049] Investigating the impact of different load patterns on PEI load: The adsorbent material was prepared according to the method of SiO2-M / 50PEI in Comparative Example 3, except that the loading method was changed from ultrasonic combined with magnetic stirring to magnetic stirring alone. Specifically, magnetic stirring was performed at room temperature for 8 hours, and the resulting adsorbent material was denoted as SiO2-M / 50PEI-stirred. The actual PEI loading was measured to be 16%. Table 1 shows a bar chart comparing the PEI loading of SiO2 / 50PEI, SiO2-M / 50PEI-stirred, SiO2-M / 50PEI, SiO2-M / 60PEI, and SiO2-M / 70PEI. Figure 3 As shown, MIX indicates magnetic stirring alone, while US+MIX indicates the combined use of ultrasonic and magnetic stirring. Figure 3 It can be seen that when using conventional magnetic stirring to load 50% PEI, the loading capacity of the monolithic adsorbent decreases significantly, making it difficult to meet the needs of industrial applications and resulting in PEI waste. Introducing ultrasonic-assisted stirring significantly increases the PEI loading capacity compared to magnetic stirring alone. However, as the PEI mass fraction further increases (60%, 70%), the loading capacity does not continue to rise but instead decreases to some extent. This is because at high concentrations, PEI clogs the surface pore structure, preventing the internal pores from achieving PEI loading.

[0050] Figure 4The correlation between PEI loading and pore volume filling rate. Since the powder has a developed pore structure, both its PEI loading and pore volume filling rate are the highest; after being extruded into a monolithic adsorbent, both of them decrease significantly. With the increase of activated carbon mass fraction, the original activated carbon forms additional pores after high-temperature calcination, which makes the PEI loading and pore volume increase, reaching a maximum when the activated carbon mass fraction is 20%, and then decreasing again when the activated carbon mass fraction increases to 25%. Combined with the BET data, it is found that this is due to the blockage of the pores caused by the residual activated carbon.

[0051] Analysis of the scanning electron microscope detection results of the adsorbent: Figure 5 The physical map of the adsorbent and the scanning electron microscope detection results are shown in FIG. 1, wherein (a) is the physical map of 20AC-SiO2-M / 50PEI prepared in Example 1, (b) is the energy dispersive spectroscopy (EDS) image of carbon, nitrogen and silicon of 20AC-SiO2-M / 50PEI prepared in Example 1, (c) is the SEM image of 20AC-SiO2-M at a scale of 1 μm, (d) is the SEM image of fumed silica powder, (e) is the SEM image of SiO2-M, (f) is the SEM image of 20AC-SiO2-M, (g) is the SEM image of SiO2 / 50PEI, (h) is the SEM image of SiO2-M / 50PEI, and (i) is the SEM image of 20AC-SiO2-M / 50PEI.

[0052] From FIG. 1, Figure 5 It can be seen that the extruded monolithic adsorbent has a honeycomb structure and is a hollow cylinder with a diameter of 12 mm and 7 holes with a diameter of 2.5 mm uniformly distributed inside. This rich pore structure can significantly reduce the pressure drop loss in the adsorption process and effectively improve the operating efficiency of the adsorption process. Figure 5 FIG. 1(b) shows the cross-sectional morphology and energy dispersive spectroscopy (EDS) optical image of the extruded monolithic adsorbent. The results show that, by ultrasonic-assisted stirring loading, polyethyleneimine (PEI) can fully diffuse and uniformly distribute in the monolithic adsorbent. Among them, the uniform distribution of nitrogen element provides direct characterization evidence for the successful loading of PEI. The scanning electron microscope (SEM) characterization at a scale of 500 nm Figure 5 FIG. 1(d) and (g) show that the fumed silica powder before loading PEI has a developed porous structure, which provides sufficient specific surface area for the impregnation process and forms ideal CO2 diffusion channels. After loading, the powder shows obvious agglomeration, and part of the pores are closed, which indicates that PEI has been successfully embedded in the pore structure of the monolithic adsorbent. It is worth noting that the unblocked pores can still serve as effective mass transfer paths for CO2 adsorption. By comparing the SEM images of the monolithic adsorbent before and after PEI loading,Figure 5 As can be seen in (e) and (h), compared to powder, the extrusion process causes significant aggregation of material particles, resulting in shrinkage and deformation of the pore structure of the monolithic adsorbent. This structural change directly leads to a significant decrease in the CO2 adsorption capacity of the PEI-loaded monolithic adsorbent. Furthermore, although both the loaded monolithic adsorbent and the powder are blocky, the structure of the monolithic adsorbent is more compact. For 20AC-SiO2-M, SEM images before and after PEI loading (…) Figure 5 As shown in (c), (f), and (i), the addition of activated carbon forms a highly developed pore network in the area it originally occupied. This structure effectively alleviates the pore blockage problem caused by powder agglomeration during extrusion, providing additional diffusion channels for CO2 adsorption. Although agglomeration and partial pore closure still occur after loading PEI, the remaining pore structure can still ensure effective CO2 mass transfer.

[0053] Adsorption performance test results of adsorption materials: The adsorbent material was subjected to carbon dioxide adsorption at 35°C and 0% relative humidity (dry environment), and the adsorption capacity and adsorption rate are listed in Table 2. The carbon dioxide adsorption capacity and adsorption rate curves of the SiO2-M / 50PEI adsorbent material in Example 1 and Comparative Example 3 are shown below. Figure 6 As shown, (a) is the carbon dioxide adsorption curve and (b) is the carbon dioxide adsorption rate curve.

[0054] Table 2. Adsorption performance of the adsorption materials in Example 1 and Comparative Examples 1 and 3.

[0055] Carbon dioxide was adsorbed by 20AC-SiO2-M / 50PEI in a dry environment at 35℃ (relative humidity of 0%) and a humid environment at 35℃ (relative humidity of 50%). After adsorption for 6 hours, desorption was carried out at 100℃ for 2 hours. This cycle of adsorption and desorption was repeated 10 times. The adsorption results are listed in Table 3. Figure 7 This is a columnar comparison chart showing the adsorption cycles after 10 cycles.

[0056] Table 3. Adsorption performance of the adsorbent material 20AC-SiO2-M / 50PEI after 10 cycles of adsorption.

[0057] Thermogravimetric analysis (TGA) was performed on the adsorbent material, and the resulting thermogravimetric curves are shown below. Figure 8 As shown.

[0058] Combine Table 2 and Figure 6It can be seen that the CO2 adsorption capacity of the PEI-loaded monolithic adsorbent with different mass fractions of activated carbon presents a typical trend of first increasing and then decreasing with the addition amount of pore-forming agent. According to the specific surface area (BET) test data and scanning electron microscope (SEM) image analysis, it can be seen that after the high-temperature calcination treatment of activated carbon, not only additional active sites are provided for PEI loading, but also new pore structures are constructed, which provide more paths for the diffusion of CO2 molecules. When the mass fraction of activated carbon is 20%, the CO2 adsorption capacity of the monolithic adsorbent reaches the maximum value of 1.94 mmol / g, while when the mass fraction of activated carbon is 25%, the adsorption capacity decreases significantly, which is mainly due to the negative impact of the residual activated carbon in the calcination process. By comparing the adsorption curves of SiO2 / 50PEI and 20AC-SiO2-M / 50PEI, since the mass fraction of PEI loading is similar, the saturated CO2 adsorption capacities of the two are relatively close. However, due to the existence of mass transfer resistance, the time required for 20AC-SiO2-M / 50PEI to reach adsorption saturation is about 2.5 times that of SiO2 / 50PEI, which fully embodies the significant influence of structure on the CO2 mass transfer process. Figure 6 Figure (b) shows the adsorption rate of the monolithic adsorbent. The maximum adsorption rate of 20AC-SiO2-M / 50PEI at the initial stage of adsorption can reach 0.0395 mmol / g / min, which is 88.1% higher than that of the adsorbent without adding pore-forming agent (0.021 mmol / g / min), which highlights the improvement of activated carbon on the pore structure.

[0059] Figure 7 The cycle performance of 20AC-SiO2-M / 50PEI under dry and humid conditions is presented. Under dry conditions, after 10 cycles, the adsorption attenuation is less than 0.5%, which can be considered as almost negligible. This slight capacity loss can be attributed to the volatilization and oxidative degradation of the amino polymer, and the monolithic adsorbent has excellent cycle stability. Under humid conditions, the adsorption capacity during the 10 cycles is generally higher than that under dry conditions, with an increase of 9.27~16%; this is because in the presence of water vapor, the co-adsorption effect of H2O and CO2 changes the reaction path, thereby improving the amine efficiency. Although humidity cycling increases the adsorption capacity, the cycle instability also increases, which is due to the formation of water film in the pores of the monolithic adsorbent, increasing the mass transfer resistance; or the capillary condensation of water blocks the micropores, and the opening degree of the pore structure is different every time the water vapor is degassed, resulting in fluctuations in the adsorption capacity.

[0060] Figure 8The thermogravimetric loss curves of monolithic adsorbents with different activated carbon mass fractions are shown. As can be seen from the figure, the PEI loading of SiO2-M / 50PEI is 26%. After adding different mass fractions of pore-forming agents, the PEI loading shows a trend of first increasing and then decreasing. The loading of 20AC-SiO2-M / 50PEI is 47%, only 3% lower than that of the powdered form, while the loading of 25AC-SiO2-M / 50PEI is only 16% due to pore blockage.

[0061] Test results of pressure drop loss and structural strength of adsorbent material: Using 20AC-SiO2-M from Comparative Example 4 as the honeycomb detection target, columnar and spherical adsorbent materials were prepared as detection targets according to the following method: 0.25g of bentonite was added to 20mL of deionized water and stirred with a mechanical stirrer for 5min to ensure full dispersion; then, 0.1g of methylcellulose was added and stirred for another 5min; 0.72g of activated carbon was added to the above mixture and stirred for 5min; then 3.25g of fumed silica was added and stirred for another 30min to obtain a slurry.

[0062] Columnar: The slurry is poured into a tablet press and held under 10 MPa pressure for 10 min to obtain columnar adsorbent material as the detection object; Spherical: The slurry is extruded using an extruder to obtain strip-shaped products, which are then ground to obtain spherical adsorbent materials with a diameter of 12mm as the test object; Powder form: Silica powder adsorbent material purchased from Evonik A380 was used as the test object.

[0063] The mechanical properties of the adsorbent material were tested using a universal testing machine at rates of 250 mL / min and 500 mL / min, and the results are listed in Table 4. The porosity was calculated using the water displacement method, specifically derived from the relationship between the total volume, the volume of solid particles, and the pore volume. A cylindrical pipe with a diameter of 15 mm and a height of 10 mm was filled with solid particles. The total volume was the volume of the 15 mm diameter cylindrical pipe with a filling depth of 10 mm. 50 mL of water was added to a large beaker, and then the solid particles from the cylindrical pipe were poured in. The rise in water level was observed, and the increase in volume was calculated as the volume of the solid particles (measured by the water displacement method). The pore volume was the difference between the total volume and the volume of solid particles. The porosity was calculated as the pore volume divided by the total volume multiplied by 100%, and the results are listed in Table 4. Figure 9 The porosity and pressure drop results for different adsorbent materials are shown.

[0064] Table 4 Pressure drop loss and porosity of adsorbent materials

[0065] The porosity calculation results show that the porosities of the powder, spherical and columnar structures are 15%, 26% and 21%, respectively, while the porosity of the honeycomb structure is as high as 54%, which provides an efficient channel for the airflow. The pressure drop loss of the honeycomb structure is 0.002 psi at a low flow rate of 250 mL / min; the pressure drop resistance is 0.006 psi at a flow rate of 500 mL / min, both of which can meet the industrial requirements.

[0066] The 20AC-SiO2-M was detected by using a universal testing machine at a compression speed of 1 mm / min, and a compression stress-displacement curve was obtained, as shown in FIG. 3. Figure 10 Combined with the displacement and the maximum compressive strength data, it was found that the compressive strength of the monolithic catalyst matrix (20AC-SiO2-M) was as high as 1.46 MPa, which was much higher than the industrial application requirement (0.4 MPa).

[0067] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A silica-based adsorbent material, characterized in that, The silica-based adsorbent material comprises a substrate and polyethylene imine loaded in the substrate; The base body comprises silica; the structure of the silica-based adsorbent material is a honeycomb columnar body; the silica-based adsorbent material has a uniformly distributed pore structure, and the pore volume of the silica-based adsorbent material is 0.08-0.36 cm 3 / g.

2. The silica-based adsorbent material of claim 1, wherein The specific surface area of the silica-based adsorbent material is 20.68-58.99 m 2 / g.

3. The silica-based adsorbent material of claim 1, wherein The loading amount of polyethylene imine in the silica-based adsorbent material is 16-60%.

4. A process for the production of the silica-based adsorbent material according to any one of claims 1 to 3, characterized in that, The preparation method comprises the following steps: The silica, bentonite, methyl cellulose, activated carbon and water are first mixed to obtain a slurry; The substrate is obtained by shaping and roasting the slurry; The substrate is loaded by being immersed in a polyethylene imine solution, and the loading process is accompanied by ultrasonic and stirring in sequence.

5. The preparation method according to claim 4, characterized in that, The silica comprises fumed silica; The mass ratio of the bentonite to the methyl cellulose is 2.4-2.6:1; The activated carbon accounts for 5-25% of the total mass of the silica, bentonite, methyl cellulose and activated carbon.

6. The preparation method according to claim 4 or 5, characterized in that, The first mixing comprises the following steps: The bentonite and water are secondly mixed, and then the methyl cellulose, activated carbon and silica are added in sequence to obtain the slurry; The second mixing is performed under stirring, and the stirring time is 4-6 min; After the methyl cellulose, activated carbon and silica are added, stirring is performed respectively, the stirring time after the addition of the methyl cellulose is 4-6 min, the stirring time after the addition of the activated carbon is 4-6 min, and the stirring time after the addition of the silica is 28-32 min.

7. The preparation method according to claim 4, characterized in that, The shaping is performed by injecting the slurry into a honeycomb columnar mold for extrusion, the pressure of the extrusion is 9-11 MPa, and the pressure maintaining time of the extrusion is 9-11 min; After the shaping, the product is further dried, the drying temperature is 95-105℃, and the drying time is 1.5-2.5 h.

8. The preparation method according to claim 4, characterized in that, The roasting temperature is 890-910℃, and the roasting time is 4.5-5.5 h.

9. The preparation method according to claim 4, characterized in that, The ultrasonic power is 30-40 W, the temperature is 48-52℃, and the time is 1.8-2.2 h; The stirring is magnetic stirring, and the magnetic stirring time is 5-7 h.

10. Application of the silica-based adsorbent material of any one of claims 1-3 or the silica-based adsorbent material prepared by the preparation method of any one of claims 4-9 as a carbon dioxide adsorbent.

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