Method for ultrasonic-assisted preparation of attapulgite composite monolithic catalyst and application of attapulgite composite monolithic catalyst in degradation of VOCs (volatile organic compounds)

Abstract

The invention discloses an ultrasonic-assisted attapulgite composite monolithic catalyst preparation method and VOCs degradation application thereof, and the method comprises the following steps: (1) dissolving cobalt nitrate, attapulgite and oxalic acid in water, and uniformly stirring to obtain a mixed solution; (2) carrying out auxiliary ultrasonic treatment on the mixed solution in the precipitation process, centrifuging, drying, and calcining to obtain a U-Co3O4 / ATP powder catalytic material; and (3) adding the prepared U-Co3O4 / ATP powder catalytic material and a binder into water, mixing to obtain slurry, coating the acid-treated cordierite honeycomb with the slurry, and calcining to obtain the U-Co3O4 / ATP / cordierite honeycomb catalyst. According to the method disclosed by the invention, the high-bonding-strength monolithic catalyst is prepared by adopting an ultrasonic-assisted synthesis and honeycomb coating process, and the catalyst can realize efficient low-temperature catalytic oxidation degradation of toluene VOCs (Volatile Organic Compounds).

Description

Technical Field

[0001] This invention belongs to the field of environmental protection, specifically relating to a method for preparing an ultrasonic-assisted attapulgite composite monolithic catalyst and its application in the catalytic oxidation and degradation of VOCs. Background Technology

[0002] In recent years, with the increasing awareness of environmental protection and the government's emphasis on environmental protection, VOCs treatment has become an important issue in the industrial sector. Among various methods for removing VOCs, catalytic oxidation is considered one of the most promising options due to its advantages such as economic feasibility, high efficiency, and almost no harmful byproducts.

[0003] Supported noble metal and transition metal oxide catalysts are two basic types of catalysts in the catalytic oxidation of VOCs. Supported noble metal catalysts, including Pd, Pt, Au, and Ag, exhibit excellent catalytic activity for VOC degradation. However, these catalysts are typically expensive, resource-scarce, and prone to sintering, hindering their further application in VOC removal. Therefore, developing abundant, inexpensive, and thermally stable transition metal oxide catalysts to replace noble metal catalysts has become a mainstream trend in this field. A suitable support material not only serves as a physical support to disperse the active components and interact with the metal oxide, but also influences the catalyst's activity and durability. Catalytic performance is mainly determined by the number of active sites and the inherent activity of each site; the interaction between the metal oxide and the support can simultaneously improve both factors, which is crucial for the catalytic process. Ultrasonic technology is considered a simple method to induce local physical and chemical processes through acoustic cavitation for the synthesis of stable, efficient, and multi-functional novel nanomaterials. Cavitation bubbles, under the influence of ultrasound, reach temperatures as high as 5000℃, pressures exceeding 1000 atm, lifespans shorter than one microsecond, and heating and cooling rates as high as 10 billion℃ / second. The introduction of ultrasound can effectively modulate the carrier structure, promoting the formation of oxides rich in oxygen vacancies, thereby facilitating the formation of metal oxide-carrier interactions.

[0004] Monolithic catalysts consist of a support and an active component coating. Cordierite, as a honeycomb ceramic support, is widely used in various operating conditions due to its high geometrical surface area, low coefficient of thermal expansion, high porosity, excellent thermal shock resistance, and low exhaust resistance. There are two main methods for preparing its coating: indirect coating involves preparing oxides, zeolite molecular sieves, or carbon materials as a second support on a pretreated support to increase the adhesion area of ​​the active component, followed by loading the active component; direct coating involves preparing the catalyst powder or active component precursor into a slurry, controlling the performance by adjusting the solid content, pH, and binder dosage, then immersing the support in the slurry and drying and calcining it to produce a monolithic catalyst. Attapulgite (ATP) is a naturally occurring nano-clay mineral fiber with good adsorption properties and a unique pore structure. In catalytic processes, ATP can serve as a highly efficient support, especially performing excellently in treating VOCs pollutants such as toluene.

[0005] Chinese patent CN117797829A discloses a manganese-cobalt spinel / attapulgite composite catalytic material, its preparation method, and its application in VOCs degradation. The technical solution involves dissolving a cobalt source and a manganese source in deionized water, then adding attapulgite and citric acid, stirring until a mixed solution is obtained; transferring the mixed solution to an ultrasonic reactor for intermittent ultrasonic-assisted treatment; stirring the ultrasonicated solution until it forms a sol, drying it overnight in an oven until it becomes a sponge-like dry gel, and then calcining and grinding it to obtain MnCo2O. 4.5 / ATP photothermal catalytic composite material. Although this technology introduces ultrasound, the role of ultrasound in this technology is to reduce particle size and achieve uniform distribution through cavitation and mechanical effects. Moreover, the spinel phase obtained by this process mainly exhibits a photothermal effect, and the role of attapulgite as a second support layer in the monolithic catalyst is not taken into consideration.

[0006] Chinese patent CN115445599B discloses a method for preparing a honeycomb catalyst using ultrasonic dual atomization and its application in the catalytic oxidation and degradation of VOCs. The technical solution involves: first, pretreating the original honeycomb substrate and then surface-modifying it; using ammonia as a precipitant; placing the reaction solution and precipitant solution separately in an ultrasonic atomization device for atomization; and then introducing the atomized gas into a closed reactor containing a surface-treated honeycomb substrate. The micro-droplets collide in the air and react with each other on the surface of the honeycomb substrate, generating hydroxide precursors on the honeycomb surface. After drying and calcination, a honeycomb-supported transition metal oxide monolithic catalyst is obtained. While this technology reduces the agglomeration of the active components to some extent and improves their dispersibility, it does not fundamentally improve the interfacial bonding strength between the active components and the cordierite honeycomb matrix, and technical problems such as easy wear and detachment still exist.

[0007] Chinese patent CN106513053A discloses a catalyst using cordierite honeycomb ceramic as a support. This catalyst comprises the following raw materials: cordierite honeycomb ceramic, MoO2, Cr2O3, MnO2, SnO2, ZrO2, a lubricant, and a heteropoly acid. The preparation method involves impregnating the cordierite honeycomb ceramic in an electrolyte solution, aging it, and then transferring it to a hydrothermal reactor for reaction to obtain the support. MoO2, Cr2O3, MnO2, SnO2, ZrO2, and the heteropoly acid are mixed, added to the support, and impregnated to obtain the catalyst. However, the supported catalyst in this invention patent suffers from poor catalytic performance.

[0008] There are currently no reports on the preparation of ultrasonic-assisted attapulgite composite honeycomb monolithic catalysts and their use for VOCs degradation. Summary of the Invention

[0009] To address the problems of high cost of precious metal catalysts and low low-temperature catalytic activity and low bonding strength of non-precious metal catalysts, this invention provides an ultrasonic-assisted precipitation method for preparing attapulgite composite monolithic catalysts and their applications. This method employs ultrasonic-assisted synthesis and a honeycomb coating process. By precisely controlling key parameters such as raw material ratios, ultrasonic processes, and heat treatment, the efficient preparation of Co3O4 / ATP powder catalytic materials is achieved. Furthermore, the prepared Co3O4 / ATP powder and binder are coated onto cordierite honeycomb to prepare a monolithic catalyst with high bonding strength, enabling efficient low-temperature catalytic oxidation and degradation of toluene VOCs.

[0010] To achieve the objective of this invention, the ultrasonic-assisted preparation method for attapulgite composite monolithic catalyst includes the following steps:

[0011] (1) Dissolve cobalt nitrate, attapulgite and oxalic acid in water and stir until homogeneous to obtain a mixed solution;

[0012] (2) During the precipitation process of the mixed solution, ultrasonic treatment was assisted, followed by centrifugation, drying and calcination to obtain U-Co3O4 / ATP powder catalytic material;

[0013] (3) The prepared U-Co3O4 / ATP powder catalyst and binder are added to water and mixed to obtain a slurry. The slurry is coated onto an acid-treated cordierite honeycomb and calcined to obtain a U-Co3O4 / ATP / cordierite honeycomb catalyst.

[0014] Further, preferably, in step (1), the mass ratio of cobalt nitrate to attapulgite is 1:2 to 8; and the molar ratio of oxalic acid to cobalt nitrate is 1.2 to 2:1.

[0015] Further, preferably, in step (2), the ultrasonic power of the ultrasonic treatment is 200-400W; the frequency of the ultrasonic treatment is set to 3-50 seconds every 20 seconds, lasting 1-4 hours.

[0016] Further, preferably, in step (2), the drying conditions are: drying in an oven at 50-120°C for 10-18 hours; the calcination conditions are: calcination at 250-500°C for 2-6 hours.

[0017] Further, preferably, in step (3), the preparation process of the acid-treated cordierite honeycomb includes: placing the cordierite honeycomb ceramic in a 10-30wt% oxalic acid solution, treating it in a water bath at 60-90℃ for 1-4 hours, washing, drying, and calcining to obtain the acid-treated cordierite honeycomb.

[0018] Further, preferably, in step (3), the binder is polyvinyl alcohol; the mass ratio of polyvinyl alcohol to U-Co3O4 / ATP powder catalyst is 1 to 5:10; and the mass ratio of polyvinyl alcohol to water is 0.5 to 1.8:100.

[0019] Furthermore, preferably, the coating rate of U-Co3O4 / ATP on the cordierite honeycomb monolithic catalyst is 10-20%.

[0020] Further, preferably, the specific steps of applying the slurry to the acid-treated cordierite honeycomb include: adding U-Co3O4 / ATP powder catalyst material to water, then adding binder to it, stirring the mixed slurry thoroughly, immersing the acid-treated cordierite honeycomb in the slurry, then removing it to dry, and then immersing it in the slurry again, repeating this process three times.

[0021] Further, preferably, in step (3), the calcination conditions are calcination at 300-500℃ for 2-6 hours. The purpose of calcination in step (3) is to carbonize the polyvinyl alcohol binder to form a rich porous structure, while removing excess polymeric impurities. At the same time, the long polyvinyl alcohol polymer chains provide steric hindrance to disperse Co3O4 / ATP powder particles and prevent particle agglomeration.

[0022] According to another aspect of the present invention, the present invention also provides the application of the prepared attapulgite composite monolithic catalyst in the catalytic oxidation of VOCs.

[0023] In the preparation method of this invention, the abundant Si-OH groups on the surface of attapulgite play a crucial role in anchoring Co. The instantaneous high-energy input of ultrasound promotes the formation of Si-O-Co bonds in Co3O4 / ATP. Simultaneously, the interaction between Co3O4 and ATP promotes the breaking of Co-O bonds in Co3O4, thereby initiating a large amount of lattice deformation and oxygen vacancies in U-Co3O4 / ATP, reducing the activation energy of toluene oxidation. Furthermore, ultrasonic treatment effectively achieves efficient and non-destructive dissociation of attapulgite rod-shaped crystal bundles, increasing their specific surface area and thus increasing their surface hydroxyl groups. This facilitates the combination of attapulgite with the hydroxyl groups of the binder polyvinyl alcohol to form ether bonds, thereby enhancing the bonding strength between attapulgite and the cordierite honeycomb surface. This significantly improves the catalytic oxidation and low-temperature degradation performance of the monolithic catalyst for toluene and its stability over long-term use. Attached Figure Description

[0024] Figure 1 XRD patterns of ATP, Co3O4, Co3O4 / ATP, and U-Co3O4 / ATP.

[0025] Figure 2 FT-IR plots of ATP, Co3O4, Co3O4 / ATP, and U-Co3O4 / ATP.

[0026] Figure 3 The image shows the XRD pattern of the U-Co3O4 / ATP / cordierite honeycomb catalyst prepared in Example 1.

[0027] Figure 4 SEM image of the U-Co3O4 / ATP / cordierite honeycomb catalyst prepared in Example 1. Detailed Implementation

[0028] The present invention will be further described below through specific embodiments and comparative examples. The present invention is not limited to the following embodiments. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional reagents, which can be purchased commercially or synthesized according to conventional methods in the art; the experimental methods, unless otherwise specified, are all conventional methods.

[0029] Example 1

[0030] 0.948 g Co(NO3)2·6H2O, 0.45 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:4, and the molar ratio of oxalic acid to cobalt nitrate was 1.5:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 300 W, a frequency of 20 s, with 10 s intervals, repeated for 2 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 50 °C oven for 12 h. The dried sample was then calcined in a muffle furnace at 400 °C for 4 h to obtain U-Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in an 80 °C water bath for 2 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0031] 2g of U-Co3O4 / ATP powder catalyst was dissolved in 20mL of deionized water, and then 0.2g of polyvinyl alcohol was added to the mixed solution. The resulting slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1:100). The acid-treated cordierite honeycomb was immersed in the slurry for 10min, then dried in an oven for 1h, and then immersed in the slurry again. This process was repeated 3 times, with a coating rate of 10%. The dried cordierite honeycomb catalyst precursor was placed in a muffle furnace and calcined at 400℃ for 4h to obtain the U-Co3O4 / ATP cordierite honeycomb catalyst.

[0032] Figure 1 XRD patterns of ATP, Co3O4, Co3O4 / ATP, and U-Co3O4 / ATP catalytic materials are shown. The (311) characteristic peak of Co3O4 in the U-Co3O4 / ATP sample is wider and shifts to a lower angle at 2θ = 36.91° compared to Co3O4 / ATP. The introduction of ultrasound has a significant impact on the position and width of the diffraction peak, indicating that lattice expansion of Co3O4 is induced, suggesting a strong interaction between Co3O4 and ATP in the catalyst synthesized by ultrasound precipitation.

[0033] Figure 2 FT-IR spectra of ATP, Co3O4, Co3O4 / ATP, and U-Co3O4 / ATP. Antisymmetric stretching vibrations of surface Si-OH groups and stretching and bending vibrations of Si-O-Si bonds are observed in the range of 950–1100 cm⁻¹. -1The Si-OH group appears at the site of Co3O4 anchorage, promoting the formation of Si-O-Co bonds. The peak intensity of Si-O-Si bonds in U-Co3O4 / ATP is significantly lower than that in ATP and Co3O4 / ATP, indicating that more Co3O4 is anchored to form Si-O-Co bonds in U-Co3O4 / ATP, verifying that the introduction of ultrasound enhances the interaction between Si-O-Co bonds and oxide-support.

[0034] Figure 3 The image shows the XRD pattern of the U-Co3O4 / ATP cordierite honeycomb catalyst prepared in this embodiment. The characteristic peaks of cordierite honeycomb appear at 2θ = 10.35, 10.45, 21.694 and 28.275, corresponding to crystal planes (200), (110), (202) and (222), respectively, which is consistent with cordierite (PDF#85-1541). A weak ATP characteristic peak was observed at 2θ = 8.49.

[0035] Figure 4 This is a SEM image of the U-Co3O4 / ATP cordierite honeycomb catalyst prepared in this embodiment. Polyvinyl alcohol is used as a binder; after calcination, a carbon layer forms on the ATP surface from polyvinyl alcohol, increasing its surface roughness and exhibiting uniform distribution characteristics and abundant porous structure. This greatly increases the contact area between the catalyst and toluene, thus enhancing its toluene adsorption capacity.

[0036] The U-Co3O4 / ATP cordierite honeycomb catalyst of this embodiment is used for the catalytic oxidation of VOCs. The specific steps are as follows:

[0037] The U-Co3O4 / ATP / cordierite honeycomb catalyst was placed in the quartz tube of the evaluation device. Toluene was bubbled with N2, with air used as a balance gas, and simultaneously introduced into the reaction device. The initial toluene concentration was 1500 ppm. The reactor was then heated, and the real-time concentration was recorded. The degradation rate of toluene was calculated. Generally, the temperature at which the degradation rate reaches 99% is used to evaluate the ability to degrade toluene, i.e., T. 99 .

[0038] The Tg of the U-Co3O4 / ATP cordierite honeycomb catalyst for toluene degradation was tested using the above method. 99 The temperature is 302℃.

[0039] Example 2

[0040] 0.474 g Co(NO3)2·6H2O, 0.18 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:8, and the molar ratio of oxalic acid to cobalt nitrate was 1.2:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 200 W, a frequency of 20 s, an interval of 3 s, and repeated for 4 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 90 °C oven for 12 h. The dried sample was then calcined in a muffle furnace at 250 °C for 6 h to obtain U-Co3O4 / ATP powder catalytic material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 30 wt% oxalic acid solution and treated in a 90 °C water bath for 1 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0041] 0.5 g of U-Co3O4 / ATP powder catalyst material was dissolved in 20 mL of deionized water. Then, 0.1 g of polyvinyl alcohol was added to the mixed solution, and the resulting slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 0.5:100). Acid-treated cordierite honeycomb was immersed in the slurry for 10 min, then dried in an oven for 3 h. This process was repeated four times, achieving a coating rate of 15%. The dried cordierite honeycomb catalyst precursor was then placed in a muffle furnace and calcined at 300 °C for 6 h to obtain the U-Co3O4 / ATP / cordierite honeycomb catalyst.

[0042] The U-Co3O4 / ATP cordierite honeycomb catalyst of this embodiment was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0043] The Tg of toluene degradation by the U-Co3O4 / ATP / cordierite honeycomb catalyst was tested using the above method. 99 The temperature is 305℃.

[0044] Example 3

[0045] 1.896 g Co(NO3)2·6H2O, 1.19 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:2, and the molar ratio of oxalic acid to cobalt nitrate was 2:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 400 W, a frequency of 20 s, an interval of 50 s, and repeated for 1 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 120 °C oven for 10 h. The dried sample was then calcined in a muffle furnace at 500 °C for 2 h to obtain U-Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in an 80 °C water bath for 2 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0046] 0.72 g of U-Co3O4 / ATP powder catalyst material was dissolved in 20 mL of deionized water. Then, 0.36 g of polyvinyl alcohol was added to the mixed solution, and the resulting slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1.8:100). Acid-treated cordierite honeycomb was immersed in the slurry for 10 min, then dried in an oven for 4 h. This process was repeated four times, achieving a coating rate of 18%. The dried cordierite honeycomb catalyst precursor was then placed in a muffle furnace and calcined at 500 °C for 2 h to obtain the U-Co3O4 / ATP / cordierite honeycomb catalyst.

[0047] The U-Co3O4 / ATP cordierite honeycomb catalyst of this embodiment was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0048] The Tg of toluene degradation by the U-Co3O4 / ATP / cordierite honeycomb catalyst was tested using the above method. 99 The temperature is 303℃.

[0049] Example 4

[0050] 0.948 g Co(NO3)2·6H2O, 0.53 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:4, and the molar ratio of oxalic acid to cobalt nitrate was 1.8:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 250 W, a frequency of 20 s, an interval of 30 s, and repeated for 1.5 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 50 °C oven for 18 h. The dried sample was then calcined in a muffle furnace at 500 °C for 4 h to obtain U-Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in a 60 °C water bath for 4 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0051] 1 g of U-Co3O4 / ATP powder catalyst was dissolved in 20 mL of deionized water. Then, 0.3 g of polyvinyl alcohol was added to the mixed solution, and the resulting slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1.5:100). Acid-treated cordierite honeycomb was immersed in the slurry for 10 min, then dried in an oven for 5 h. This process was repeated 5 times, achieving a coating rate of 20%. The dried cordierite honeycomb catalyst precursor was then placed in a muffle furnace and calcined at 300 °C for 6 h to obtain the U-Co3O4 / ATP / cordierite honeycomb catalyst.

[0052] The U-Co3O4 / ATP cordierite honeycomb catalyst of this embodiment was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0053] The Tg of toluene degradation by the U-Co3O4 / ATP / cordierite honeycomb catalyst was tested using the above method. 99 It is 310℃.

[0054] Example 5

[0055] 0.948 g Co(NO3)2·6H2O, 0.39 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:4, and the molar ratio of oxalic acid to cobalt nitrate was 1.3:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 350 W, a frequency of 20 s, an interval of 40 s, and repeated for 3.5 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 100 °C oven for 15 h. The dried sample was then calcined in a muffle furnace at 500 °C for 2 h to obtain U-Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 10 wt% oxalic acid solution and treated in a 70 °C water bath for 3 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0056] 2g of U-Co3O4 / ATP powder catalyst was dissolved in 20mL of deionized water, and then 0.34g of polyvinyl alcohol was added to the mixed solution. The resulting slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1.7:100). The acid-treated cordierite honeycomb was immersed in the slurry for 10min, then dried in an oven for 2h, and then immersed in the slurry again. This process was repeated 3 times, with a coating rate of 13%. The dried cordierite honeycomb catalyst precursor was placed in a muffle furnace and calcined at 500℃ for 2h to obtain the U-Co3O4 / ATP cordierite honeycomb catalyst.

[0057] The U-Co3O4 / ATP cordierite honeycomb catalyst of this embodiment was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0058] The Tg of toluene degradation by the U-Co3O4 / ATP / cordierite honeycomb catalyst was tested using the above method. 99 It is 309℃.

[0059] Comparative Example 1

[0060] To compare the effect of ultrasound on the interaction between metal oxides and attapulgite support, the ultrasound step was removed in this comparative example to prepare a Co3O4 / ATP cordierite honeycomb catalyst.

[0061] 0.948 g Co(NO3)2·6H2O, 0.45 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:4, and the molar ratio of oxalic acid to cobalt nitrate was 1.5:1). The mixed solution was allowed to stand for 2 h. After centrifugation and filtration, the mixed solution was dried in a 50 °C oven for 12 h. The dried sample was then calcined in a muffle furnace at 400 °C for 4 h to obtain Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in an 80 °C water bath for 2 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0062] 2g of Co3O4 / ATP powder catalyst material was dissolved in 20mL of deionized water, and then 0.2g of polyvinyl alcohol was added to the mixed solution. The mixed slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1:100). The acid-treated cordierite honeycomb was immersed in the slurry for 10min, then dried in an oven for 1h, and then immersed in the slurry again. This process was repeated 3 times, with a coating rate of 10%. The dried cordierite honeycomb catalyst precursor was placed in a muffle furnace and calcined at 400℃ for 4h to obtain the Co3O4 / ATP / cordierite honeycomb catalyst.

[0063] The Co3O4 / ATP / cordierite honeycomb catalyst of this comparative example was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0064] The Tg of the Co3O4 / ATP / cordierite honeycomb catalyst for toluene degradation was tested using the above method. 99 The temperature is 353℃.

[0065] Comparative Example 2

[0066] To compare the interaction between the metal oxide and the attapulgite support and the key influence of ATP as a second coating, this comparative example removed the addition of ATP to prepare a U-Co3O4 / cordierite honeycomb catalyst.

[0067] 0.948 g of Co(NO3)2·6H2O and 0.45 g of oxalic acid were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (molar ratio of oxalic acid to cobalt nitrate was 1.5:1). The mixed solution was then transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 300 W, a frequency of 20 s, with 10 s intervals, repeated for 2 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 50 °C oven for 12 h. The dried sample was then calcined in a muffle furnace at 400 °C for 4 h to obtain U-Co3O4 powdered catalyst material. Cordierite honeycomb ceramic (cylinder with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in an 80 °C water bath for 2 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0068] 2g of U-Co3O4 powder catalyst was dissolved in 20mL of deionized water, and then 0.2g of polyvinyl alcohol was added to the mixed solution. The mixed slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1:100). The acid-treated cordierite honeycomb was immersed in the slurry for 10min, then dried in an oven for 1h, and then immersed in the slurry again. This process was repeated 3 times, with a coating rate of 10%. The dried cordierite honeycomb catalyst precursor was placed in a muffle furnace and calcined at 400℃ for 4h to obtain the U-Co3O4 / cordierite honeycomb catalyst.

[0069] The U-Co3O4 / cordierite honeycomb catalyst of this comparative example was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0070] The Tg of toluene degradation by the U-Co3O4 / cordierite honeycomb catalyst was tested using the above method. 99 It is 364℃.

[0071] Comparative Example 3

[0072] To compare the key effects of appropriate temperature on U-Co3O4 / ATP / cordierite honeycomb catalysts, this comparative example calcined the coated honeycomb catalyst at 700°C to prepare a monolithic cordierite honeycomb catalyst.

[0073] 0.948 g Co(NO3)2·6H2O, 0.45 g oxalic acid, and 3.9 g ATP were placed in a 50 mL beaker and stirred for 30 min to obtain a mixed solution (the mass ratio of cobalt nitrate to attapulgite was 1:4, and the molar ratio of oxalic acid to cobalt nitrate was 1.5:1). The mixed solution was transferred to an ultrasonic reactor, and ultrasonication was performed at a power of 300 W, a frequency of 20 s, with 10 s intervals, repeated for 2 h. After ultrasonication, the mixed solution was centrifuged, filtered, and dried in a 50 °C oven for 12 h. The dried sample was then calcined in a muffle furnace at 400 °C for 4 h to obtain U-Co3O4 / ATP powdered catalyst material. Cordierite honeycomb ceramic (cylinders with a diameter of 30 mm and a height of 10 mm) was placed in a 20 wt% oxalic acid solution and treated in an 80 °C water bath for 2 h. The cordierite honeycomb ceramic treated with oxalic acid was washed several times with deionized water. After washing, the cordierite honeycomb ceramic was dried. The dried cordierite honeycomb ceramic was placed in a muffle furnace and calcined at 300°C for 3 hours to obtain acid-treated cordierite honeycomb.

[0074] 2g of U-Co3O4 / ATP powder catalyst material was dissolved in 20mL of deionized water, and then 0.2g of polyvinyl alcohol was added to the mixed solution. The mixed slurry was stirred thoroughly (the mass ratio of polyvinyl alcohol to deionized water was 1:100). The acid-treated cordierite honeycomb was immersed in the slurry for 10min, then dried in an oven for 1h, and then immersed in the slurry again. This process was repeated 3 times, with a coating rate of 10%. The dried cordierite honeycomb catalyst precursor was placed in a muffle furnace and calcined at 700℃ for 4h to obtain the U-Co3O4 / ATP / cordierite honeycomb catalyst.

[0075] The U-Co3O4 / ATP / cordierite honeycomb catalyst of this comparative example was used for the catalytic oxidation of VOCs, and the specific steps were the same as in Example 1.

[0076] The cordierite honeycomb catalyst prepared by the above method showed severe surface coating peeling and destruction of the ATP structure. The Tg of the cordierite honeycomb catalyst for toluene degradation was tested. 99 It is 371℃.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultrasonic-assisted monolithic attapulgite composite catalyst, characterized in that, Includes the following steps: (1) Dissolve cobalt nitrate, attapulgite and oxalic acid in water and stir until homogeneous to obtain a mixed solution; (2) During the precipitation process of the mixed solution, ultrasonic treatment was assisted, followed by centrifugation, drying and calcination to obtain U-Co3O4 / ATP powder catalytic material; (3) The prepared U-Co3O4 / ATP powder catalyst and binder are added to water and mixed to obtain a slurry. The slurry is coated onto an acid-treated cordierite honeycomb and calcined to obtain a U-Co3O4 / ATP / cordierite honeycomb catalyst.

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of cobalt nitrate to attapulgite is 1:2 to 8; the molar ratio of oxalic acid to cobalt nitrate is 1.2 to 2:

1.

3. The method according to claim 1, characterized in that, In step (2), the ultrasonic power of the ultrasonic treatment is 200-400W; the frequency of the ultrasonic treatment is set to 3-50 seconds every 20 seconds, lasting 1-4 hours.

4. The method according to claim 1, characterized in that, In step (2), the drying conditions are: drying in an oven at 50-120°C for 10-18 hours; the calcination conditions are: calcination at 250-500°C for 2-6 hours.

5. The method according to claim 1, characterized in that, In step (3), the preparation process of the acid-treated cordierite honeycomb includes: placing the cordierite honeycomb ceramic in a 10-30wt% oxalic acid solution, treating it in a water bath at 60-90℃ for 1-4 hours, washing, drying, and calcining to obtain the acid-treated cordierite honeycomb.

6. The method according to claim 1, characterized in that, In step (3), the binder is polyvinyl alcohol; the mass ratio of polyvinyl alcohol to U-Co3O4 / ATP powder catalyst is 1 to 5:10; and the mass ratio of polyvinyl alcohol to water is 0.5 to 1.8:

100.

7. The method according to claim 1, characterized in that, The coating rate of U-Co3O4 / ATP on cordierite honeycomb monolithic catalysts is 10-20%.

8. The method according to claim 1, characterized in that, The specific steps for applying the slurry to the acid-treated cordierite honeycomb include: adding U-Co3O4 / ATP powder catalyst material to water, then adding binder to it, stirring the mixed slurry thoroughly, immersing the acid-treated cordierite honeycomb in the slurry, then removing it to dry, and then immersing it in the slurry again, repeating this process three times.

9. The method according to claim 1, characterized in that, In step (3), the calcination conditions are calcination at 300-500℃ for 2-6 hours.

10. The application of an attapulgite composite monolithic catalyst prepared by the method according to any one of claims 1-9 in the catalytic oxidation of VOCs.

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