A mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material

Abstract

The application discloses a kind of mesoporous aluminium oxide-based multifunctional air purification and flue gas desulfurization composite material, belong to atmospheric pollution control catalytic adsorption material technical field, adopt multistage through mesoporous gamma-alumina as main carrier, compound composite metal desulfurization and denitrification active component, TiO2-based noble metal photocatalytic component and skeleton stabilizing auxiliary agent, combined with ultrasonic auxiliary layering impregnation and high-temperature activation forming process to obtain multifunctional composite material.The application is loaded by hierarchical pore structure design and functional component partition, so that the material has a large number of stable adsorption catalytic sites inside, which can achieve simultaneous removal of sulfur dioxide and nitrogen oxides under industrial low-temperature flue gas conditions, and can also degrade formaldehyde, benzene series, TVOC and adsorb dust particles under normal temperature and light conditions.The application realizes regeneration and recycling by low-temperature thermal purging, has strong structural stability, high purification efficiency, wide adaptation conditions, wide application scenarios, and good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalytic adsorption materials for air pollution control, specifically a mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material. Background Technology

[0002] At present, atmospheric environment purification materials are divided into two major independent systems: industrial flue gas desulfurization and denitrification materials and indoor normal temperature air purification filter materials. The two types of materials have separate functions and are incompatible with each other under different operating conditions, resulting in obvious technical defects.

[0003] Current industrial flue gas desulfurization mainly employs calcium-based wet desulfurization processes, which consume consumables only once, generating large amounts of wastewater and desulfurization gypsum residue, resulting in significant secondary pollution and high water consumption. Furthermore, these processes can only remove sulfur dioxide and cannot simultaneously remove nitrogen oxides, VOCs, and dust. Conventional alumina-based dry desulfurization materials have disordered and singular carrier pore structures, low specific surface areas, poor pore connectivity, and high airflow resistance. Under high-temperature and high-humidity flue gas environments, they are prone to crystal transformation, mesoporous structure collapse, and poor carrier skeleton stability. Simultaneously, traditional preparation processes often employ conventional impregnation methods, resulting in uneven dispersion and severe agglomeration of active components, low utilization of active sites, limited sulfur capacity, rapid degradation of regeneration performance, short service life, and only single flue gas desulfurization and denitrification functions, lacking the ability to degrade organic pollutants at room temperature.

[0004] Existing indoor air purification materials are mostly activated carbon and single titanium dioxide photocatalytic filters, which are only suitable for purifying low-concentration pollutants at room temperature. These materials have poor high-temperature resistance and cannot withstand the conditions of high-temperature industrial flue gas. They also lack the ability to adsorb and remove acidic gases, making them unsuitable for industrial flue gas treatment. Furthermore, activated carbon is easily saturated and prone to microbial growth, while pure photocatalytic materials have low adsorption capacity, resulting in limited purification effects when used alone.

[0005] While existing modified alumina catalytic materials can achieve synergistic removal of sulfur and nitrate from flue gas, they generally lack hierarchical interconnected channels, resulting in low mass transfer efficiency and large bed pressure drop. They also lack photocatalytic purification systems, making it impossible to treat pollutants such as VOCs and formaldehyde at room temperature. Furthermore, their functional components are arranged in a single way without a layered loading design, making it easy for the various functional systems to interfere with each other, resulting in poor overall versatility of the materials.

[0006] In summary, existing purification materials generally suffer from problems such as limited functionality, narrow adaptability to different operating conditions, poor structural stability, weak regeneration performance, and inability to simultaneously address industrial flue gas treatment and indoor air purification. There is an urgent need to develop a multifunctional alumina-based composite purification material that is structurally stable, can synergistically remove multiple pollutants, is applicable to both high and low temperature conditions, and is recyclable. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material, wherein the composite material is prepared by using multi-level interconnected mesoporous γ-alumina as the main carrier, combined with composite metal desulfurization and denitrification active components, photocatalytic air purification components, structural stabilizing agents and organic molding binders; The proportions of each component are as follows: 75%~85% multi-level interconnected mesoporous γ-alumina, 10%~18% composite metal oxide, 2%~5% photocatalytic functional component, 1%~3% structural stabilizing agent, and the remainder is organic molding binder. The multi-level interconnected mesoporous γ-alumina was prepared using a sol-gel combined hydrothermal method, and its internal structure comprises a hierarchical pore structure with interconnected mesopores and macropores. The mesopore diameter is 5~12 nm, and the specific surface area is 320~450 m². 3 / g, pore volume not less than 1.4cm 3 / g; The composite material is loaded with functional components in layers using an ultrasonic-assisted equal-volume impregnation process. The inner wall of the pores is loaded with desulfurization and denitrification active sites, and the outer surface of the material is loaded with photocatalytic degradation sites. Under industrial high-temperature flue gas conditions, SO2 and NO are removed through mesoporous physical adsorption combined with catalytic oxidation of metal oxides. x In the process of removing pollutants under normal temperature and light conditions, the photocatalytic components excite electron-hole pairs to degrade volatile pollutants, achieving pollutant purification under both high and low temperature conditions.

[0009] Preferably, the multi-level interconnected mesoporous γ-alumina is prepared using aluminum isopropoxide as the aluminum source and P123 triblock copolymer as the mesoporous template agent; During the preparation process, anhydrous ethanol and deionized water mixture is used as solvent, and the pH value of the system is adjusted to 9.5~10.5 with nitric acid. After continuous stirring, hydrothermal aging, drying and calcination to remove the template agent, the product is formed. The multi-stage through-pore γ-alumina sieve has a particle size of 40~60 mesh and possesses stable high-temperature anti-collapse performance and gas conduction performance.

[0010] Preferably, the composite metal oxide is a multi-component composite system of CuO, MnO2, Fe2O3, and CeO2; Each metal oxide component is uniformly dispersed on the inner wall of the mesoporous alumina channels, with no obvious agglomerated particles; The composite metal oxide relies on the oxygen in the flue gas to achieve low-temperature catalytic oxidation of SO2 and NO. x Synergistic oxidation and adsorption, suitable for medium and low temperature industrial flue gas conditions of 200~450℃.

[0011] Preferably, the structural stabilizing agent is a composite doped phase of La2O3 and SiO2; the structural stabilizing agent is doped inside the mesoporous alumina framework to suppress the crystal transformation of γ-Al2O3 to α-Al2O3 under high-temperature flue gas and high-humidity conditions, fix the carrier pore structure, and improve the hydrothermal stability and mechanical strength of the material.

[0012] Preferably, the photocatalytic functional component is composed of nano-anatase TiO2 and trace amounts of precious metals Pt / Pd; the photocatalytic functional component is uniformly coated on the outer surface of the composite material without clogging the mesopores inside the carrier; under normal temperature and light conditions, formaldehyde, benzene series compounds, and TVOC volatile organic compounds are completely decomposed into carbon dioxide and water through photocatalytic reaction, while physically adsorbing and intercepting fine dust particles.

[0013] Preferably, the organic molding binder is a mixture of guar gum powder and carboxymethyl cellulose; the organic molding binder is only used for material molding and curing, and can be completely decomposed without residue by high-temperature calcination process, and the decomposition process can assist the carrier in secondary pore formation to maintain the smooth flow of the pores.

[0014] Preferably, the ultrasonic-assisted equal-volume impregnation process parameters are: ultrasonic impregnation power 240W, impregnation time 3h, and room temperature standing aging for 8h; the ultrasonic vibration breaks up the metal salt agglomeration system, so that the active components are uniformly anchored in nano-sized particles on the inner wall of the alumina pores, thereby improving the utilization rate of active sites.

[0015] Preferably, the curing and activation process of the composite material is as follows: drying at a constant temperature of 95°C for 6 hours to remove free moisture, and calcining at 620°C for 4 hours in an air atmosphere in a tube furnace; during the calcination process, the metal nitrates are completely decomposed into the active phase of metal oxides, and the noble metal components are simultaneously reduced to the nano-elemental state, thus completing the material activation and molding.

[0016] Preferably, the composite material has thermal regeneration and recycling performance; after the material is saturated with adsorption, pollutants are desorbed by 300°C hot air purging, SO2 is enriched and purified for resource recovery, and the material's pore structure and active sites are not significantly damaged after regeneration, so it can be repeatedly recycled.

[0017] Preferably, the composite material is adaptable to multiple purification operation modes; one application is in the treatment of industrial flue gas from thermal power plants, metallurgical plants, and brick and tile kilns, simultaneously removing SO2 and NO. x Firstly, it is used for the purification of flue gas and dust; secondly, it is used for the purification of factory exhaust gas, kitchen fumes, VOCs, and odors; thirdly, it is compatible with fresh air systems and air purifiers, and can remove indoor formaldehyde, benzene series compounds, and exhaust pollutants in enclosed spaces at room temperature.

[0018] Compared with the prior art, the present invention provides a mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material, which has the following beneficial effects: 1. A multi-level interconnected mesoporous γ-alumina support structure was constructed, forming a synergistic structure of mesoporous adsorption catalytic sites and macroporous flow channels. Compared with ordinary single-channel alumina, the specific surface area of ​​the support in this invention can reach 320~450 m² / g, and the pore volume is not less than 1.4 cm³ / g. This results in higher gas mass transfer efficiency, lower bed airflow resistance, and a significant increase in sulfur adsorption and storage capacity. It effectively solves the defects of traditional supports, such as disordered pores, small pore volume, low adsorption capacity, and large airflow pressure loss.

[0019] 2. The alumina framework modified with lanthanum and silicon composite doping effectively suppresses alumina crystal transformation and pore collapse under high temperature and high humidity conditions. This significantly improves the material's hydrothermal stability, high-temperature structural stability, and mechanical strength, slows down activity decay, and significantly extends the material's service life and cycle life, overcoming the problems of traditional desulfurization materials being prone to high-temperature failure and having poor regeneration stability.

[0020] 3. The inner wall of the pores is loaded with multi-metal composite desulfurization and denitrification active components, while the outer surface of the material is loaded with a TiO2-noble metal photocatalytic system. The two functional regions are independent of each other and do not interfere with each other, simultaneously achieving the synergistic removal of sulfur and nitrate from high-temperature flue gas and the degradation of VOCs, formaldehyde, and benzene compounds at room temperature, breaking through the technical bottleneck of traditional materials that can only be used in a single working condition and have fragmented functions.

[0021] 4. This allows the active metal components to be uniformly dispersed at the nanoscale within the pores, preventing agglomeration and pore blockage. The utilization rate of active sites is significantly improved, resulting in superior low-temperature catalytic performance and significantly enhanced resistance to sulfur poisoning and moisture interference.

[0022] 5. After adsorption saturation, desorption and regeneration can be achieved by purging with 300℃ hot air, and the enriched sulfur dioxide can be recycled and reused. After regeneration, the material has an intact pore structure and high activity retention rate, and can be recycled multiple times, avoiding the problems of large solid waste production, one-time consumption, and serious secondary pollution of traditional wet desulfurization. It is green and environmentally friendly with lower operation and maintenance costs.

[0023] 6. It can be simultaneously adapted to multiple scenarios such as low-temperature flue gas desulfurization and denitrification in industry, odor treatment of industrial waste gas, indoor air purification, and exhaust gas purification in confined spaces. One set of materials can achieve multi-functionality and multi-condition replacement, significantly reducing the cost of replacing consumables and operating and maintenance investment in environmental protection equipment, and has high industrial application value. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] A mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material is disclosed. Aluminum isopropoxide is used as the aluminum source, P123 triblock copolymer as the mesoporous template agent, and anhydrous ethanol and deionized water as a mixed solvent. The pH of the system is adjusted to 9.5–10.5 with nitric acid, and the mixture is continuously stirred for 14 hours to form a homogeneous aluminum sol. The sol is then transferred to a hydrothermal reactor and aged at 140°C for 36 hours. The gel precursor is removed, thoroughly dried at 85°C, and calcined at 550°C for 5 hours to remove the template agent, yielding multi-level interconnected mesoporous γ-alumina. The resulting 40–60 mesh particles are obtained for later use. The resulting carrier has a mesoporous pore size of 5–12 nm and a specific surface area of ​​320–450 m². 2 / g, pore volume ≥1.4 cm 3 / g.

[0026] A mixed impregnation solution containing copper nitrate, manganese nitrate, iron nitrate, cerium nitrate, and lanthanum nitrate was prepared. The solution was then impregnated with an equal volume for 3 hours using 240W ultrasonic assistance, followed by sealed aging at room temperature for 8 hours, so that the multi-metal precursors were uniformly dispersed on the inner wall of the alumina pores.

[0027] Nano-anatase TiO2 sol is compounded with a trace amount of dilute chloroplatinic acid solution and then impregnated onto the outer surface of the material to form a surface photocatalytic functional layer.

[0028] Free water is removed by drying at 95℃ for 6 hours; the metal nitrate is then calcined at 620℃ for 4 hours in air atmosphere to decompose the metal nitrate into an active oxide phase and reduce the noble metal into nano-elemental substances, while the organic binder is completely decomposed to create pores; after cooling, the product is washed with water to remove impurities and dried at low temperature to obtain the finished composite material.

[0029] The composite material comprises, by mass percentage: 75%~85% multi-level interconnected mesoporous γ-alumina, 10%~18% composite metal oxide, 2%~5% photocatalytic functional components, 1%~3% structural stabilizing agents, and the balance being a composite organic binder of guar gum powder and carboxymethyl cellulose.

[0030] Among them, the composite metal oxide is a multi-component system of CuO, MnO2, Fe2O3, and CeO2, which is responsible for desulfurization and denitrification of medium and low temperature flue gas; The structural stabilizing agent is a composite phase of La2O3 and SiO2, which is used to stabilize the alumina skeleton, resist high-temperature crystal transformation, and prevent pore collapse. The photocatalytic component is anatase TiO2 loaded with trace amounts of Pt / Pd noble metals, which is responsible for the degradation of VOCs, formaldehyde, and benzene compounds and dust adsorption at room temperature; the organic binder leaves no residue at high temperature and has both shaping and pore-forming functions. Example 1

[0031] The mass percentages of each component are as follows: 80% multi-level interconnected mesoporous γ-alumina, 15% composite metal oxide, 3% photocatalytic functional component, and 2% structural stabilizing agent; among which, the mass ratio of CuO, MnO2, Fe2O3, and CeO2 in the composite metal oxide is 3:2:2:1; the mass ratio of La2O3 and SiO2 in the structural stabilizing agent is 1:1; the photocatalytic component is mainly TiO2 with trace amounts of Pt / Pd doping; it is prepared using the aforementioned general process, with ultrasonic power of 240W, impregnation for 3 hours, aging for 8 hours, and calcination at 620℃ for 4 hours.

[0032] The material has a complete pore structure and no aggregation of active components. It has high efficiency in the synergistic removal of sulfur and nitrate under high temperature conditions, excellent photocatalytic degradation performance at room temperature, and the best thermal regeneration stability. Example 2

[0033] The mass percentages of each component are as follows: 85% multi-level interconnected mesoporous γ-alumina, 10% composite metal oxide, 2% photocatalytic functional component, and 3% structural stabilizing agent; the proportions of the remaining components and the preparation process parameters are the same as in Example 1. This example has a higher content of additives, resulting in better high-temperature hydrothermal stability and mechanical strength of the material, making it suitable for high-humidity, high-temperature, and strong-scouring industrial flue gas conditions. Example 3

[0034] The mass percentages of each component are as follows: 75% multi-level interconnected mesoporous γ-alumina, 18% composite metal oxide, 5% photocatalytic functional component, and 2% structural stabilizing agent; the proportions of the remaining components and the preparation process parameters are the same as in Example 1. This example has a higher content of active and photocatalytic components, making it suitable for low-concentration waste gas and deep indoor air purification scenarios, with stronger effects on organic matter degradation and odor removal.

[0035] Comparative Example Comparative Example 1: Ordinary commercial single mesoporous γ-alumina desulfurizer, without hierarchical pore structure, without rare earth doping, without photocatalytic components, conventional static impregnation with a single CuO active component.

[0036] Comparative Example 2: Commercial TiO2 photocatalytic filter screen, without alumina porous carrier, without desulfurization and denitrification metal active components, only has the function of adsorbing and degrading organic waste gas at room temperature, and is not resistant to high temperature flue gas.

[0037] Comparative Example 3: Conventional unmodified alumina-based bifunctional desulfurization and denitrification material, without layered loading structure, without composite precious metal photocatalytic system, and without high-temperature stabilizing additives.

[0038] After high-temperature flue gas enters the material bed, the multi-stage interconnected large pores rapidly guide the airflow, reducing bed resistance; the mesoporous channels rapidly physical adsorb SO2 and fine dust; the Cu-Mn-Fe-Ce composite metal oxide within the channels utilizes the flue gas's own oxygen to catalytically oxidize SO2 to SO3 at low temperature, and stabilize it by binding with the alkaline sites of the support, while simultaneously synergistically oxidizing and adsorbing NO. x This achieves integrated removal of sulfur and nitrate.

[0039] Under normal indoor temperature and light conditions, the TiO2-Pt / Pd photocatalytic system on the surface of the material generates electron-hole pairs, which completely mineralize organic pollutants such as formaldehyde, benzene series compounds, and TVOC into carbon dioxide and water; the porous structure simultaneously physically adsorbs odors and fine particulate matter, thus purifying the air in human dwellings.

[0040] After the material is saturated with adsorption, it is purged with 300℃ hot air to desorb and enrich high concentrations of SO2, and sulfur can be recovered as a resource. After regeneration, the material's pore structure does not collapse and the active components are not lost in large quantities, so it can be recycled multiple times, solving the problems of traditional consumables being consumed once and causing serious secondary pollution.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material, characterized in that: The composite material is prepared by using multi-level interconnected mesoporous γ-alumina as the main carrier, combined with composite metal desulfurization and denitrification active components, photocatalytic air purification components, structural stabilizing agents and organic molding binders. The proportions of each component are as follows: 75%~85% multi-level interconnected mesoporous γ-alumina, 10%~18% composite metal oxide, 2%~5% photocatalytic functional component, 1%~3% structural stabilizing agent, and the remainder is organic molding binder. The multi-level interconnected mesoporous γ-alumina was prepared using a sol-gel combined hydrothermal method, and its internal structure comprises a hierarchical pore structure with interconnected mesopores and macropores. The mesopore diameter is 5~12 nm, and the specific surface area is 320~450 m². 2 / g, pore volume not less than 1.4cm 3 / g; The composite material is loaded with functional components in layers using an ultrasonic-assisted equal-volume impregnation process. The inner wall of the pores is loaded with desulfurization and denitrification active sites, and the outer surface of the material is loaded with photocatalytic degradation sites. Under industrial high-temperature flue gas conditions, SO2 and NO are removed through mesoporous physical adsorption combined with catalytic oxidation of metal oxides. x In the process of removing pollutants under normal temperature and light conditions, the photocatalytic components excite electron-hole pairs to degrade volatile pollutants, achieving pollutant purification under both high and low temperature conditions.

2. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The multi-level interconnected mesoporous γ-alumina was prepared using aluminum isopropoxide as the aluminum source and P123 triblock copolymer as the mesoporous template agent. During the preparation process, anhydrous ethanol and deionized water mixture is used as solvent, and the pH value of the system is adjusted to 9.5~10.5 with nitric acid. After continuous stirring, hydrothermal aging, drying and calcination to remove the template agent, the product is formed. The multi-stage through-pore γ-alumina sieve has a particle size of 40~60 mesh and possesses stable high-temperature anti-collapse performance and gas conduction performance.

3. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The composite metal oxide is a multi-component composite system of CuO, MnO2, Fe2O3, and CeO2; Each metal oxide component is uniformly dispersed on the inner wall of the mesoporous alumina channels, with no obvious agglomerated particles; The composite metal oxide relies on the oxygen in the flue gas to achieve low-temperature catalytic oxidation of SO2 and NO. x Synergistic oxidation and adsorption, suitable for medium and low temperature industrial flue gas conditions of 200~450℃.

4. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The structural stabilizing agent is a composite doped phase of La2O3 and SiO2. The structural stabilizing agent is doped into the mesoporous alumina framework to suppress the crystal transformation of γ-Al2O3 to α-Al2O3 under high temperature flue gas and high humidity conditions, fix the carrier pore structure, and improve the hydrothermal stability and mechanical strength of the material.

5. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The photocatalytic functional component is composed of nano-anatase TiO2 and trace amounts of precious metals Pt / Pd. The photocatalytic functional component is uniformly coated on the outer surface of the composite material without blocking the mesopores inside the carrier. Under normal temperature and light conditions, formaldehyde, benzene series compounds, and TVOC volatile organic compounds are completely decomposed into carbon dioxide and water through photocatalytic reaction, while physically adsorbing and intercepting fine dust particles.

6. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The organic molding binder is a mixture of guar gum powder and carboxymethyl cellulose; the organic molding binder is only used for material molding and curing, and can be completely decomposed without residue by high-temperature calcination process, and the decomposition process can assist the carrier in secondary pore formation to maintain the smooth flow of the pores.

7. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The ultrasonic-assisted equal-volume impregnation process parameters are: ultrasonic impregnation power 240W, impregnation time 3h, and room temperature standing aging for 8h; the ultrasonic vibration breaks up the metal salt agglomeration system, so that the active components are uniformly anchored in nano-sized particles on the inner wall of the alumina channels, thereby improving the utilization rate of active sites.

8. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The curing and activation process of the composite material is as follows: drying at a constant temperature of 95℃ for 6 hours to remove free moisture, and calcining at 620℃ for 4 hours in an air atmosphere in a tube furnace; during the calcination process, the metal nitrates are completely decomposed into the active phase of metal oxides, and the noble metal components are simultaneously reduced to the nano-elemental state, thus completing the material activation and molding.

9. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The composite material has thermal regeneration and recycling performance; after the material is saturated with adsorption, pollutants are desorbed by 300°C hot air purging, SO2 is enriched and purified for resource recovery, and the material's pore structure and active sites are not significantly damaged after regeneration, so it can be repeatedly recycled.

10. The mesoporous alumina-based multifunctional air purification and flue gas desulfurization composite material according to claim 1, characterized in that: The composite material is adaptable to multiple purification operation modes; firstly, it can be used for industrial flue gas treatment in thermal power, metallurgy, and brick and tile kilns, simultaneously removing SO2 and NO. x Firstly, it is used for the purification of flue gas and dust; secondly, it is used for the purification of factory exhaust gas, kitchen fumes, VOCs, and odors; thirdly, it is compatible with fresh air systems and air purifiers, and can remove indoor formaldehyde, benzene series compounds, and exhaust pollutants in enclosed spaces at room temperature.

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