Solid waste source solid amine adsorbent and preparation method thereof

Abstract

The invention relates to the technical field of gas adsorbent preparation, in particular to a solid waste source solid amine adsorbent and a preparation method thereof.The solid amine adsorbent comprises a mesoporous silica-alumina carrier and organic amine, and the surface of the mesoporous silica-alumina carrier is loaded with a compound amine system through a graded amine loading technology. The efficient and stable solid waste source solid amine adsorbent with a desulfurization and decarbonization integrated function is successfully developed by combining a graded amine loading process and a ZnO nano-particle doping strategy, the adsorbent not only realizes high-value utilization of industrial solid waste fly ash and effectively reduces the preparation cost, but also improves the desulfurization and decarbonization efficiency by optimizing spatial distribution of amine molecules on a carrier. The adsorption capacity and the cycling stability are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of gas adsorbent preparation technology, and in particular to a solid amine adsorbent for solid waste sources and its preparation method. Background Technology

[0002] Current technologies for preparing solid amine adsorbents from solid waste still face several bottlenecks that urgently need to be overcome. Regarding carrier synthesis, traditional mesoporous silica-alumina materials typically rely on template agents such as hexadecyltrimethylammonium bromide (CTAB) to construct ordered pores, followed by high-temperature calcination to remove the template agent. For example, patent CN115337900B provides a method for preparing solid amine adsorbents using FCC waste catalysts, but the process of preparing mesoporous molecular sieves must rely on template agents. Furthermore, patent CN117380150B employs a template-free synthesis strategy, but this method requires high crystallinity of the raw materials, making it difficult to achieve precise control of the pore structure, resulting in poor amine loading site compatibility.

[0003] Regarding amine loading, patent CN116603513B employs a single physical impregnation method to load macromolecular organic amines into the three-dimensional cage structure of MOFs. While this single impregnation method achieves high loading capacity, the amine and support are only physically bonded, resulting in a high amine loss rate during high-temperature regeneration. To overcome this limitation, a mixed amine strategy was proposed and its synergistic advantages were verified. Patent CN120790109B further proposed a hierarchical loading strategy of small-molecule and macromolecular amines, utilizing the hydroxyl groups of small-molecule amines to form a hydrogen bond network, enhancing cycle stability. However, some small-molecule amines still pose a risk of detachment during long-term cycling. In terms of operating condition adaptation, acidic gases such as SO2 in actual industrial flue gas can cause irreversible poisoning of amine sites. Patent CN118122286B achieves desulfurization through ZnO doping, but its high-temperature calcination process has high energy consumption.

[0004] In conclusion, developing a solid amine adsorbent for solid waste sources that combines high adsorption capacity with excellent cycle stability is key to overcoming existing technological bottlenecks. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a solid amine adsorbent for solid waste sources and its preparation method. This invention uses fly ash as raw material, prepares a mesoporous silica-alumina carrier through directional recombination of silica and aluminum, and combines graded amine loading and cross-linking solidification to achieve a CO2 adsorption capacity of 2.5-3.0 mmol / g. After 30 cycles, the amine loss rate is ≤4% and the adsorption capacity retention rate is >95%. Simultaneous doping with ZnO nanoparticles achieves integrated desulfurization and decarbonization, which can stably adapt to high-sulfur industrial flue gas conditions. This not only achieves high-value utilization of industrial solid waste, but also significantly reduces the preparation and operation costs of the adsorbent, providing a solution with both environmental value and economic feasibility for flue gas treatment in industries such as petrochemicals and power.

[0006] A method for preparing a solid amine adsorbent from solid waste sources includes the following steps: (1) The pretreated fly ash is first mixed with hydrochloric acid with a concentration of 1.5-2 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ In the sodium silicate solution, the Si / Al ratio is adjusted, and a mesoporous aluminosilicate support is synthesized hydrothermally without a template agent. The Si / Al molar ratio in the mesoporous aluminosilicate support is 15:1-25:1. (3) The mesoporous silica-alumina carrier obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a carrier loaded with graded amines. The low molecular weight amine is an aliphatic polyamine with a molecular weight of 20-300 Da, and the high molecular weight amine is a polyamine compound with a molecular weight of 1000-10000 Da. The mass ratio of low molecular weight amine to high molecular weight amine is 1:1-1:1.8. (4) Add a composite crosslinking agent to the carrier loaded with graded amines obtained in step (3) and react at a controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 350-400℃ to convert the precursor into ZnO nanoparticles. The composite crosslinking agent is a composite system of glutaraldehyde and APTES, and the mass ratio of glutaraldehyde to APTES is 1.8:1-2.2:1. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent, wherein the mass fraction of ZnO nanoparticles in the solid amine adsorbent is 5-8%.

[0007] Preferably, the extraction temperature in step (1) is 60-80℃, the concentration of NaOH is 1-1.5 mol / L, and the dissolution temperature is 80-90℃.

[0008] Preferably, the hydrothermal synthesis conditions for step (2) without template agent are: temperature of 120-160℃ and reaction time of 8-12h.

[0009] Preferably, the specific process for graded amine loading in step (3) is as follows: impregnate low molecular weight amines under vacuum for 1.5-2 h, dry at 80°C for 2 h, and then impregnate high molecular weight amines at atmospheric pressure and 60°C for 1-1.5 h.

[0010] Preferably, the crosslinking temperature in step (4) is 50-60℃ and the reaction time is 3-4 h.

[0011] A solid amine adsorbent for solid waste sources is also provided, wherein the solid amine adsorbent comprises a mesoporous silica-alumina support and an organic amine, and the pore size of the mesoporous silica-alumina support is distributed in the range of 2-5 nm. The organic amine is loaded onto the surface of the mesoporous silica-alumina support through a graded amine loading process. The organic amine is a composite amine system composed of low molecular weight amines and high molecular weight amines. The low molecular weight amine is loaded inside the mesoporous silica-alumina carrier. The high molecular weight amine is loaded on the outer surface and pore inlet of the mesoporous silica-alumina carrier; The ZnO nanoparticles are dispersed within the pores of the mesoporous silica-alumina carrier.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention successfully prepares a mesoporous silica-alumina carrier using fly ash as raw material through silica-alumina directional recombination technology, realizing the high-value utilization of industrial solid waste, effectively reducing the cost of adsorbent preparation, and solving the environmental problems caused by solid waste landfill disposal. Secondly, the application of graded amine loading process allows low molecular weight amines and high molecular weight amines to complement each other on the carrier, which not only improves the adsorption capacity but also enhances the cycle stability. Finally, the design of simultaneous doping with ZnO nanoparticles endows the adsorbent with integrated desulfurization and decarbonization functions, which can stably adapt to high sulfur industrial flue gas conditions, avoid the problem of traditional adsorbents being easily poisoned in high sulfur environments, and broaden the application range of adsorbents. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a SEM image of the mesoporous silica-alumina carrier provided in Embodiment 3 of this application; Figure 2This is a SEM image of the carrier for loading graded amines provided in Example 3 of this application; Figure 3 This is a SEM image of the solid amine adsorbent provided in Example 3 of this application. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This invention provides a solid amine adsorbent for solid waste sources, the solid amine adsorbent comprising a mesoporous silica-alumina support and an organic amine; Fly ash, as one of the main components of industrial solid waste, is mainly composed of SiO2, Al2O3 and a small amount of Fe2O3, CaO and other oxides. The efficient separation and directional recombination of silicon and aluminum elements can be achieved through the acid-alkali dissolution combined treatment process.

[0017] Pretreated fly ash refers to fly ash raw material that has been placed in a muffle furnace and burned at 550-600℃ for 2-3 hours to remove residual carbonaceous and organic volatile impurities. After the furnace temperature has naturally dropped to room temperature, the fly ash is taken out and then screened and magnetically separated to remove impurities.

[0018] Fly ash can be obtained commercially or from industrial sites that produce fly ash, such as thermal power plants. Before use, it needs to be pre-treated to remove impurities and unburned carbon particles.

[0019] In some embodiments of the present invention, the surface of the mesoporous silica-alumina carrier is loaded with a composite amine system using a graded amine loading process.

[0020] The graded amine loading process refers to the process of sequentially loading low molecular weight amines and high molecular weight amines onto the surface and pores of a mesoporous silica-alumina carrier under impregnation conditions combining vacuum and atmospheric pressure in a specific mass ratio. Specifically, the low molecular weight amine is first impregnated in a vacuum environment for 1.5-2 hours to allow the amine molecules to be fully loaded into the mesopores of the carrier and form physical adsorption sites. Then, it is dried at 80°C for 2 hours to fix the loading structure. Next, the high molecular weight amine is impregnated at atmospheric pressure and 60°C for 1-1.5 hours, and the amine molecules are loaded onto the outer surface and pore entrances of the carrier through chemical bonding to form a graded loading structure.

[0021] The composite amine system refers to a mixed amine system composed of low molecular weight amines and high molecular weight amines. This system optimizes the spatial distribution of amine molecules on the support through a graded loading process. Low molecular weight amines, with their small molecular size advantage, penetrate deep into the mesopores to form high-density adsorption sites, while high molecular weight amines, through their long-chain structure, are loaded onto the surface of the support and the pore entrance to build a stable adsorption layer. The synergistic effect of the two not only improves the physical adsorption capacity of the adsorbent for CO2, but also enhances the stability of high-temperature regeneration cycle through chemical bonding, effectively solving the contradiction between the high amine loss rate of the single impregnation method and the low loading capacity of the single grafting method.

[0022] In some embodiments of the present invention, the Si / Al molar ratio in the mesoporous silica-alumina support is 15:1-25:1, and the pore size is distributed in the range of 2-5 nm, such as Si / Al molar ratios of 15:1, 20:1, or 25:1. A suitable Si / Al ratio helps to form a stable mesoporous structure, providing a good support environment for the loading of amine molecules. The pore size is uniform and between 2-5 nm. This pore size is conducive to the diffusion and adsorption of gas molecules, enabling the adsorbent to contact and undergo adsorption reactions more effectively with acidic gases such as CO2.

[0023] In some embodiments of the present invention, the graded amine composite system is composed of low molecular weight amines and high molecular weight amines in a mass ratio of 1:1 to 1:1.8, such as 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, etc. The low molecular weight amines and high molecular weight amines can form a good synergistic effect, which ensures that there are enough low molecular weight amines to penetrate into the mesopores to form high-density adsorption sites and improve the adsorption capacity, while a suitable proportion of high molecular weight amines are loaded on the surface of the carrier and the pore inlet to build a stable adsorption layer and enhance the stability of high-temperature regeneration cycle.

[0024] Among them, low molecular weight amines can be ethylenediamine, diethylenetriamine, triethylenetetramine, etc. These low molecular weight amines have small molecular size and can be more easily loaded into the mesopores of the mesoporous silica-alumina support to form dense adsorption sites, thereby improving the adsorption capacity of the adsorbent for CO2. High molecular weight amines can be polyethyleneimine, polyamide-based amines, etc. They have long molecular chains and can be firmly loaded on the outer surface and pore entrance of the support through chemical bonding to form a stable adsorption layer, effectively preventing the loss of amine molecules during high-temperature regeneration and enhancing the cycle stability of the adsorbent.

[0025] In some embodiments of the present invention, the low molecular weight amine is loaded inside the mesopores of the carrier, and the high molecular weight amine is loaded on the outer surface of the carrier and at the pore inlet.

[0026] The hydroxyl content on the surface of mesoporous silica-alumina carrier can form a dual effect of hydrogen bonding and covalent bonding with the hierarchical amine system. The low molecular weight amine inside the mesopores increases capacity through hydrogen bonding, while the high molecular weight amine on the outer surface is strongly stable through covalent bonding.

[0027] In some embodiments of the present invention, the adsorbent is also doped with 5-8% ZnO nanoparticles by mass, for example, the mass fraction may be 5%, 6%, 7%, 8%, etc.

[0028] In some embodiments of the present invention, the ZnO nanoparticles are dispersed in the pores of the silicon-aluminum carrier, and work synergistically with the graded amine composite system to achieve simultaneous adsorption of SO2 and CO2.

[0029] The doping of ZnO nanoparticles endows the adsorbent with integrated desulfurization and decarbonization functions. The ZnO nanoparticles are dispersed in the pores of the silicon-aluminum support and work synergistically with the graded amine composite system to achieve simultaneous adsorption of SO2 and CO2. Under high-sulfur industrial flue gas conditions, ZnO nanoparticles can react with SO2, avoiding the problem of traditional adsorbents being easily poisoned in high-sulfur environments. This allows the adsorbent to be stably adapted to high-sulfur industrial flue gas conditions and meet the needs of continuous industrial treatment.

[0030] This invention also provides a method for preparing the solid amine adsorbent from solid waste sources described above, comprising the following steps: (1) The pretreated fly ash is first mixed with hydrochloric acid with a concentration of 1.5-2 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ The mesoporous silica-alumina support is synthesized hydrothermally by adjusting the Si / Al ratio in the sodium silicate solution. (3) The mesoporous silica-alumina support obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a support loaded with graded amine. (4) Add a composite crosslinking agent to the carrier loaded with graded amine obtained in step (3) and react at a controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 350-400℃ to convert the precursor into ZnO nanoparticles. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent, wherein the mass fraction of ZnO nanoparticles in the solid amine adsorbent is 5-8%.

[0031] Pretreatment methods may include steps such as water washing, sieving, and magnetic separation to ensure that the purity of fly ash meets the requirements of subsequent preparation. Specifically, the collected fly ash is first washed with water to remove soluble impurities and some unburned carbon. Then, large particulate impurities are removed by sieving, and then iron impurities are further removed by magnetic separation technology to obtain relatively pure fly ash raw materials. The particle size of fly ash raw materials is generally 10-100 micrometers. This particle size range is conducive to the efficient separation of silicon and aluminum elements in the subsequent acid-alkali dissolution process.

[0032] In some embodiments of the present invention, in step (1), the concentration of hydrochloric acid is 1.5-2 mol / L, and the extraction temperature is 60-80℃; the concentration of NaOH is 1-1.5 mol / L, and the dissolution temperature is 80-90℃. For example, the concentration of hydrochloric acid can be 1.5 mol / L, 1.7 mol / L, 2 mol / L, etc., and the extraction temperature can be 60℃, 70℃, 80℃, etc.; the concentration of NaOH can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, etc., and the dissolution temperature can be 80℃, 85℃, 90℃, etc. Hydrochloric acid can efficiently extract Al from fly ash. 3+ This process avoids excessive corrosion of the silicon-based structure in fly ash, while NaOH can effectively dissolve the remaining silicon-based residues to obtain a high-purity sodium silicate solution, providing high-quality raw materials for the subsequent preparation of mesoporous aluminosilicate supports.

[0033] In step (4), adding a compound crosslinking agent and controlling the temperature reaction can enhance the binding force between the graded amine and the support, and improve the stability of the adsorbent. The ZnO precursor can be a soluble zinc salt such as zinc nitrate or zinc acetate. These precursors can be dispersed in the solution and fully impregnated and adsorbed into the pores of the support loaded with graded amine. After high-temperature calcination at 350-400℃, the precursor undergoes a thermal decomposition reaction and is transformed into dispersed ZnO nanoparticles. This process not only realizes the in-situ generation of ZnO nanoparticles on the support, but also further enhances the chemical bonding between the graded amine and the support through high-temperature treatment, thereby improving the overall stability of the adsorbent.

[0034] In some embodiments of the present invention, the hydrothermal synthesis conditions for step (2) without template agent are: temperature 120-160℃, reaction time 8-12 h.

[0035] In some embodiments of the present invention, the specific process of step (3) graded amine loading is as follows: impregnate low molecular weight amines for 1.5-2 h under vacuum (-0.08~-0.09 MPa), dry at 80°C for 2 h, and then impregnate high molecular weight amines at atmospheric pressure and 60°C for 1-1.5 h.

[0036] In some embodiments of the present invention, the crosslinking agent in step (4) is a compound system of glutaraldehyde and APTES with a mass ratio of 1.8:1 to 2.2:1, the crosslinking temperature is 50-60℃, and the reaction time is 3-4 h.

[0037] The glutaraldehyde-APTES complex system has significant advantages as a crosslinking agent in adsorbent preparation. Glutaraldehyde, a commonly used bifunctional crosslinking agent, has two aldehyde groups in its molecular structure that can undergo condensation reactions with amine groups to form stable covalent bonds, thereby firmly fixing the hierarchical amine system on the surface and inside the pores of the mesoporous silica-alumina support. APTES (3-aminopropyltriethoxysilane) is a silane coupling agent. The amino group at one end of its molecule can interact with the hierarchical amine system, while the ethoxysilane group at the other end can undergo hydrolytic condensation reactions with the hydroxyl groups on the support surface to form siloxane bonds, further enhancing the binding force between the hierarchical amine system and the support.

[0038] The present invention does not impose any special restrictions on the source of the raw materials used above, and they can be commercially available.

[0039] This invention utilizes a unique silicon-aluminum directional recombination technology, combined with a graded amine loading process and a ZnO nanoparticle doping strategy, to successfully develop a highly efficient, stable solid amine adsorbent for solid waste sources with integrated desulfurization and decarbonization functions. This adsorbent not only achieves high-value utilization of industrial solid waste fly ash and effectively reduces preparation costs, but also significantly improves adsorption capacity and cycle stability by optimizing the spatial distribution of amine molecules on the carrier. Particularly under high-sulfur industrial flue gas conditions, the introduction of ZnO nanoparticles endows the adsorbent with excellent anti-poisoning properties, enabling it to stably adapt to and efficiently treat sulfur-containing flue gas, thereby broadening the application range of the adsorbent and providing a new solution for industrial flue gas treatment. Furthermore, the preparation method has a clear process flow, mild operating conditions, and is easy to scale up for production, showing broad prospects for industrial applications.

[0040] Example 1 This embodiment provides a solid amine adsorbent for solid waste sources, wherein the solid amine adsorbent comprises a mesoporous silica-alumina carrier and an organic amine.

[0041] The surface of the mesoporous silica-alumina carrier is loaded with a composite amine system using a graded amine loading process.

[0042] The mesoporous silica-alumina carrier has a Si / Al molar ratio of 15:1 and a pore size distribution of 2-3.1 nm.

[0043] The graded amine complex system consists of low molecular weight amines and high molecular weight amines in a mass ratio of 1:1.

[0044] The low molecular weight amine is loaded inside the mesopores of the carrier, and the high molecular weight amine is loaded on the outer surface of the carrier and at the pore inlet.

[0045] The adsorbent is also doped with 5% ZnO nanoparticles by mass.

[0046] The ZnO nanoparticles are dispersed within the pores of the silicon-aluminum carrier, and work synergistically with the graded amine composite system to achieve simultaneous adsorption of SO2 and CO2.

[0047] A method for preparing a solid amine adsorbent from solid waste sources includes the following steps: (1) The pretreated fly ash was first mixed with hydrochloric acid with a concentration of 1.5 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ The mesoporous silica-alumina support is synthesized hydrothermally by adjusting the Si / Al ratio in the sodium silicate solution. (3) The mesoporous silica-alumina support obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a support loaded with graded amine. (4) Add a composite crosslinking agent to the carrier loaded with graded amine obtained in step (3) and react at a controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 350°C to convert the precursor into ZnO nanoparticles. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent.

[0048] In step (1), the extraction temperature is 60℃; the NaOH concentration is 1.0 mol / L, and the dissolution temperature is 80℃.

[0049] The conditions for template-free hydrothermal synthesis in step (2) are: temperature 120℃, reaction time 8 h.

[0050] In step (3), the low molecular weight amine is ethylenediamine, and the high molecular weight amine is polyethyleneimine.

[0051] Step (3) The specific process of graded amine loading is as follows: impregnate low molecular weight amines for 1.5 h under vacuum -0.08 MPa conditions, dry at 80℃ for 2 h, and then impregnate high molecular weight amines for 1 h under normal pressure and 60℃ conditions.

[0052] In step (4), the crosslinking agent is a mixture of glutaraldehyde and APTES in a mass ratio of 1.8:1, the crosslinking temperature is 50℃, the reaction time is 3 h, and the ZnO precursor is zinc nitrate.

[0053] Example 2 This embodiment provides a solid amine adsorbent for solid waste sources, wherein the solid amine adsorbent comprises a mesoporous silica-alumina carrier and an organic amine.

[0054] The surface of the mesoporous silica-alumina carrier is loaded with a composite amine system using a graded amine loading process.

[0055] The mesoporous silica-alumina carrier has a Si / Al molar ratio of 20:1 and a pore size distribution of 2.5-3.8 nm.

[0056] The graded amine complex system consists of low molecular weight amines and high molecular weight amines in a mass ratio of 1:1.4.

[0057] The low molecular weight amine is loaded inside the mesopores of the carrier, and the high molecular weight amine is loaded on the outer surface of the carrier and at the pore inlet.

[0058] The adsorbent is also doped with 6.5% ZnO nanoparticles by mass.

[0059] The ZnO nanoparticles are dispersed within the pores of the silicon-aluminum carrier, and work synergistically with the graded amine composite system to achieve simultaneous adsorption of SO2 and CO2.

[0060] A method for preparing a solid amine adsorbent from solid waste sources includes the following steps: (1) The pretreated fly ash was first mixed with hydrochloric acid with a concentration of 1.75 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ The mesoporous silica-alumina support is synthesized hydrothermally by adjusting the Si / Al ratio in the sodium silicate solution. (3) The mesoporous silica-alumina support obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a support loaded with graded amine. (4) Add a composite crosslinking agent to the carrier loaded with graded amine obtained in step (3) and react at controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 375°C to convert the precursor into ZnO nanoparticles. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent.

[0061] In step (1), the extraction temperature is 75℃; the NaOH concentration is 1.25mol / L, and the dissolution temperature is 85℃.

[0062] The conditions for the template-free hydrothermal synthesis in step (2) are: temperature 140℃ and reaction time 10 h.

[0063] In step (3), the low molecular weight amine is ethylenediamine, and the high molecular weight amine is polyethyleneimine.

[0064] Step (3) The specific process of graded amine loading is as follows: impregnate low molecular weight amines for 1.75 h under vacuum -0.085 MPa conditions, dry at 80℃ for 2 h, and then impregnate high molecular weight amines for 1.25 h under normal pressure and 60℃ conditions.

[0065] In step (4), the crosslinking agent is a mixture of glutaraldehyde and APTES in a mass ratio of 2:1, the crosslinking temperature is 55℃, the reaction time is 3.5 h, and the ZnO precursor is zinc nitrate.

[0066] Example 3 This embodiment provides a solid amine adsorbent for solid waste sources, wherein the solid amine adsorbent comprises a mesoporous silica-alumina carrier and an organic amine.

[0067] The surface of the mesoporous silica-alumina carrier is loaded with a composite amine system using a graded amine loading process.

[0068] The mesoporous silica-alumina carrier has a Si / Al molar ratio of 25:1 and a pore size distribution of 3.5-5 nm.

[0069] The graded amine complex system consists of low molecular weight amines and high molecular weight amines in a mass ratio of 1:1.8.

[0070] The low molecular weight amine is loaded inside the mesopores of the carrier, and the high molecular weight amine is loaded on the outer surface of the carrier and at the pore inlet.

[0071] The adsorbent is also doped with 8% ZnO nanoparticles by mass.

[0072] The ZnO nanoparticles are dispersed within the pores of the silicon-aluminum carrier, and work synergistically with the graded amine composite system to achieve simultaneous adsorption of SO2 and CO2.

[0073] A method for preparing a solid amine adsorbent from solid waste sources includes the following steps: (1) The pretreated fly ash was first mixed with hydrochloric acid with a concentration of 2 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ The mesoporous silica-alumina support is synthesized hydrothermally by adjusting the Si / Al ratio in the sodium silicate solution. (3) The mesoporous silica-alumina support obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a support loaded with graded amine. (4) Add a composite crosslinking agent to the carrier loaded with graded amine obtained in step (3) and react at a controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 400℃ to convert the precursor into ZnO nanoparticles. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent.

[0074] In step (1), the extraction temperature is 80℃; the NaOH concentration is 1.5 mol / L, and the dissolution temperature is 90℃.

[0075] The conditions for template-free hydrothermal synthesis in step (2) are: temperature 160℃ and reaction time 12 h.

[0076] The specific process for step (3) graded amine loading is as follows: impregnate low molecular weight amine under vacuum for 2 h, dry at 80℃ for 2 h, and then impregnate high molecular weight amine under normal pressure and 60℃ for 1.5 h.

[0077] In step (3), the low molecular weight amine is ethylenediamine, and the high molecular weight amine is polyethyleneimine.

[0078] In step (4), the crosslinking agent is a mixture of glutaraldehyde and APTES in a mass ratio of 2.2:1, the crosslinking temperature is 60℃, the reaction time is 4 h, and the ZnO precursor is zinc nitrate.

[0079] Comparative Example 1 The difference from Example 3 is as follows: In step (2) of silicon-aluminum directional recombination, cetyltrimethylammonium bromide (CTAB) is added as a template agent, and the remaining steps and parameters are the same as in Example 3.

[0080] Comparative Example 2 The difference from Example 3 is as follows: During step (2) of the directional recombination of silicon and aluminum, the Al obtained from the extraction in step (1) is not added back. 3+ The sodium silicate solution prepared in step (1) was directly transferred to a hydrothermal reactor for template-free hydrothermal synthesis. The remaining steps and parameters were the same as in Example 3.

[0081] Comparative Example 3 The difference from Example 3 is as follows: Step (3) does not use graded amine loading, but only immerses it in a polyethyleneimine single amine solution under normal pressure and 60°C. The total amount of amine used is the same as in Example 3, and the other steps and parameters remain unchanged.

[0082] Comparative Example 4 The difference from Example 3 is as follows: In step (3), high molecular weight amines are first impregnated under normal pressure, and then low molecular weight amines are impregnated under vacuum. The remaining steps are the same as in Example 3.

[0083] Comparative Example 5 The difference from Example 3 is as follows: In step (4), zinc nitrate solution is not added and ZnO doping is not performed. The remaining steps are the same as in Example 3.

[0084] Comparative Example 6 The difference from Example 3 is as follows: In step (5), the ZnO mass fraction is 3%, and the remaining steps are the same as in Example 3.

[0085] Comparative Example 7 The difference from Example 3 is as follows: In step (4), the mass ratio of the crosslinking agent is 1.5:1, and the remaining steps are the same as in Example 3.

[0086] Comparative Example 8 The difference from Example 3 is as follows: In step (4), only glutaraldehyde is used as a single crosslinking agent, and APTES is not added. The remaining steps are the same as in Example 3.

[0087] Performance testing: 1. Characterization of pore structure The mesoporous silica-alumina support, the support for graded amines, and the solid amine adsorbent obtained in Example 3 were tested using scanning electron microscopy. The test results are as follows: Figures 1-3 As shown.

[0088] like Figure 1 As shown, the mesoporous silica-alumina support exhibits a highly ordered mesopore distribution, with clear and interconnected channels, a relatively smooth surface, and no obvious agglomeration. This regular pore structure provides favorable spatial conditions for the effective loading of subsequent graded amines and the adsorption and diffusion of gas molecules. Figure 2 As can be seen, the amine material is uniformly distributed in the pores and on the surface of the carrier after loading graded amine. The distribution of amine material does not destroy the original mesoporous structure, and the pores remain unobstructed. This indicates that the graded amine loading process can effectively introduce the amine system into the carrier while maintaining the mesoporous characteristics of the carrier. Figure 3 The microstructure of the solid amine adsorbent was shown, revealing that ZnO nanoparticles were dispersed within the pores of the silica-alumina support and between the hierarchical amine composite system, achieving simultaneous and efficient adsorption of SO2 and CO2.

[0089] 2. Pore parameter testing of mesoporous silica-alumina carriers The mesoporous silica-alumina support, the support for graded amines, and the solid amine adsorbent obtained in Example 3 were tested for pore parameters using a nitrogen adsorption-desorption apparatus to comprehensively evaluate their pore structure characteristics. The test results are shown in Table 1.

[0090] Table 1

[0091] Table 1 shows that after step-by-step modification, the BET specific surface area, total pore volume, and BJH pore volume of the mesoporous silica-alumina support all showed a gradual decreasing trend. Specifically, the mesoporous silica-alumina support itself has a high specific surface area and pore volume, which provides it with abundant adsorption sites and good gas diffusion channels. However, after loading graded amines, the specific surface area and pore volume decreased because the amines occupied part of the pore space. Nevertheless, the support loaded with graded amines still maintained a high specific surface area and pore volume, indicating that the graded amine loading process did not cause serious damage to the pore structure of the support. Furthermore, when ZnO nanoparticles were introduced into the solid amine adsorbent, their specific surface area and pore volume decreased again. This is because the ZnO nanoparticles were dispersed in the pores of the silica-alumina support and between the graded amine composite system, further occupying some space.

[0092] 3. Adsorption performance test of solid amine adsorbent A 10 mg sample was placed in a crucible in the thermal analyzer. 10,000 ppm CO2 was introduced into the instrument at 50 mL / min. The sample was first heated to 100 °C at 10 °C / min for degassing for 30 min, and then cooled to 25 °C for adsorption experiments, which lasted for 60 min. During the regeneration experiment, the gas flow was switched to argon, and regeneration was performed at 100 °C for 30 min.

[0093] The SO2 adsorption capacity was demonstrated by introducing 5000 ppm SO2 at a flow rate of 30 mL / min into a crucible containing 10 mg of sample in a thermal analyzer. The sample was first degassed at 100 °C for 30 min at a rate of 10 °C / min, then cooled to 30 °C for SO2 adsorption experiments, with the adsorption time set to 90 min. For SO2 regeneration, the gas flow was replaced with nitrogen, and regeneration was performed at 120 °C for 40 min.

[0094] The samples are Examples 1 to 3 and Comparative Examples 1 to 8. The adsorption properties of the samples are shown in Table 2.

[0095] Table 2

[0096] Table 2 clearly shows that the solid amine adsorbents prepared in Examples 1 to 3 all exhibit superior performance in terms of CO2 and SO2 adsorption capacity. This is attributed to their reasonable Si / Al molar ratio, graded amine loading process, and the synergistic effect of ZnO nanoparticles. Compared with Example 3, although Comparative Example 1 added the template agent CTAB (hexadecyltrimethylammonium bromide), there was no significant difference in CO2 and SO2 adsorption capacity. This indicates that the addition of the template agent was not a key factor in improving the adsorption performance in this study system. Furthermore, Comparative Example 2, due to the absence of back-extraction of the Al obtained from extraction, showed a different performance. 3+ The imbalance in the silicon-aluminum ratio in Comparative Example 3 resulted in an unsatisfactory pore structure in the prepared adsorbent, leading to significantly lower CO2 and SO2 adsorption capacities compared to Example 3. This highlights the importance of precise control of the silicon-aluminum ratio for adsorbent performance. Comparative Example 3 did not employ graded amine loading, using only a single amine solution for impregnation. This resulted in an uneven and unreasonable distribution of the amine on the support, failing to fully utilize the synergistic effect of amines with different molecular weights, thus reducing adsorption capacity. Comparative Example 4 altered the order of graded amine loading, first impregnating high molecular weight amines at atmospheric pressure and then impregnating low molecular weight amines under vacuum. This disrupted the originally reasonable amine distribution structure, affecting the diffusion and adsorption of gas molecules within the pores, leading to poorer adsorption performance. Comparative Example 5 did not involve ZnO doping; although CO2 adsorption increased, SO2 adsorption significantly decreased. The decrease indicates that ZnO nanoparticles play an indispensable role in achieving simultaneous adsorption of SO2 and CO2. Without ZnO, the adsorption capacity of the adsorbent for SO2 is significantly weakened. In Comparative Example 6, the ZnO mass fraction was 3%, lower than the 8% in Example 3. Due to insufficient ZnO content, the synergistic effect with the graded amine composite system was not sufficient, resulting in a decrease in SO2 adsorption. Comparative Examples 7 and 8 changed the mass ratio of the composite crosslinking agent or used only a single crosslinking agent, affecting the crosslinking effect and consequently impacting the pore structure of the adsorbent and the loading stability of the amine, ultimately leading to a decrease in adsorption performance. In summary, the solid waste source solid amine adsorbent prepared in this study achieves efficient simultaneous adsorption of SO2 and CO2 through optimized preparation process and composition.

[0097] 4. Cyclic stability test of solid amine adsorbent During the cyclic adsorption process, the adsorption time for a single adsorption cycle of the sample is 45 min, and the regeneration time is 15 min.

[0098] The samples are Examples 1 to 3 and Comparative Examples 1 to 8. The adsorption properties of the samples are shown in Table 3.

[0099] Table 3

[0100] Table 3 clearly shows that the solid amine adsorbents prepared in Examples 1 to 3 maintained high adsorption capacity and relatively low cycle decay rate after 50 CO2 cycles. This fully demonstrates that the adsorbent has excellent cycle stability. Compared with Example 3, Comparative Example 1, although its overall performance is similar, has a slightly higher cycle decay rate than Example 3, indicating that the addition of the template agent has a certain impact on cycle stability, but it is not the decisive factor. In Comparative Example 2, due to the imbalance of silicon-aluminum ratio, the pore structure of the adsorbent is not ideal, resulting in a significant decrease in adsorption capacity and a significant increase in cycle decay rate during the cycle. This further highlights the importance of precise control of the silicon-aluminum ratio for the cycle stability of the adsorbent. Comparative Example 3 did not use graded amine loading, but only used a single amine solution for impregnation, resulting in an uneven and unreasonable distribution of amine on the support. During the cycle, amine is easily lost, leading to a decrease in adsorption performance and an increase in cycle decay rate. Comparative Example 4 altered the loading order of the graded amines, disrupting the original rational amine distribution structure and affecting the diffusion and adsorption of gas molecules within the pores. This resulted in a rapid decrease in adsorption capacity and a correspondingly lower cycle decay rate during cycling. Comparative Example 5, without ZnO doping, while increasing the initial CO2 adsorption capacity to some extent, suffered from decreased adsorption stability during cycling due to the lack of synergistic effect between ZnO nanoparticles and the graded amine composite system, leading to a cycle decay rate of 18.2%. In Comparative Example 6, the ZnO mass fraction was lower than in Example 3. Insufficient ZnO content resulted in inadequate synergistic effect with the graded amine composite system, leading to a significant decrease in adsorption performance during cycling. Comparative Examples 7 and 8 altered the mass ratio of the composite crosslinking agents or used only a single crosslinking agent, affecting the crosslinking effect and consequently impacting the pore structure and amine loading stability of the adsorbent, resulting in a rapid decrease in adsorption capacity during cycling. In conclusion, the solid amine adsorbent for solid waste sources prepared in this study, through optimized preparation process and composition, has broad application prospects in practical industrial flue gas treatment.

[0101] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a solid amine adsorbent from solid waste sources, characterized in that, Includes the following steps: (1) The pretreated fly ash is first mixed with hydrochloric acid with a concentration of 1.5-2 mol / L to extract and recover Al. 3+ The remaining silicon-based residue is then dissolved in NaOH to obtain a sodium silicate solution. (2) Add back the Al extracted in step (1) 3+ In the sodium silicate solution, the Si / Al ratio is adjusted to synthesize mesoporous aluminosilicate supports hydrothermally without template agents, wherein the Si / Al molar ratio in the mesoporous aluminosilicate supports is 15:1-25:1; (3) The mesoporous silica-alumina carrier obtained in step (2) is first impregnated with low molecular weight amine under vacuum, and then impregnated with high molecular weight amine under normal pressure to obtain a carrier loaded with graded amines. The low molecular weight amine is an aliphatic polyamine with a molecular weight of 20-300 Da, and the high molecular weight amine is a polyamine compound with a molecular weight of 1000-10000 Da. The mass ratio of low molecular weight amine to high molecular weight amine is 1:1-1:1.

8. (4) Add a composite crosslinking agent to the carrier loaded with graded amines obtained in step (3) and react at a controlled temperature. Then add ZnO precursor for full impregnation and adsorption, and then calcine at 350-400℃ to convert the precursor into ZnO nanoparticles. The composite crosslinking agent is a composite system of glutaraldehyde and APTES, and the mass ratio of glutaraldehyde to APTES is 1.8:1-2.2:

1. (5) The graded amine support containing ZnO nanoparticles obtained in step (4) is air-cooled and then dried to obtain a solid amine adsorbent, wherein the mass fraction of ZnO nanoparticles in the solid amine adsorbent is 5-8%.

2. The preparation method according to claim 1, characterized in that, In step (1), the extraction temperature is 60-80℃, the NaOH concentration is 1-1.5 mol / L, and the dissolution temperature is 80-90℃.

3. The preparation method according to claim 1, characterized in that, The hydrothermal synthesis conditions for step (2) without template agent are: temperature 120-160℃, reaction time 8-12 h.

4. The preparation method according to claim 1, characterized in that, The specific process for graded amine loading in step (3) is as follows: impregnate low molecular weight amines under vacuum for 1.5-2 h, dry at 80℃ for 2 h, and then impregnate high molecular weight amines at atmospheric pressure and 60℃ for 1-1.5 h.

5. The preparation method according to claim 1, characterized in that, In step (4), the crosslinking temperature is 50-60℃ and the reaction time is 3-4 h.

6. A solid amine adsorbent for solid waste sources obtained by the preparation method according to any one of claims 1-5, characterized in that, The solid amine adsorbent comprises a mesoporous silica-alumina support and an organic amine, wherein the pore size of the mesoporous silica-alumina support is distributed in the range of 2-5 nm. The organic amine is loaded onto the surface of the mesoporous silica-alumina support through a graded amine loading process. The organic amine is a composite amine system composed of low molecular weight amines and high molecular weight amines. The low molecular weight amine is loaded inside the mesoporous silica-alumina carrier. The high molecular weight amine is loaded on the outer surface and pore inlet of the mesoporous silica-alumina carrier; The ZnO nanoparticles are dispersed within the pores of the mesoporous silica-alumina carrier.

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