A method for preparing monolithic catalysts that improve the loading of active components and intrinsic activity

Abstract

This invention provides a method for preparing a monolithic catalyst with improved loading of active components and intrinsic activity, comprising the following steps: S1, the monolithic metal matrix is ​​sequentially cleaned in ethanol, acetone, and 1 mol / L hydrochloric acid for 5 min each under ultrasonic conditions to remove surface organic matter and metal oxides. Then, the cleaned monolithic metal matrix is ​​immersed in a 0.001-5 mol / L metal cyanide solution and reacted at 25-50℃ for 0.1-5 h. Hydrochloric acid is then added to adjust the pH of the solution to 0-6, and the reaction continues for 0.1-60 min. The product after reaction is washed with ethanol and water, and dried to obtain the PBA / monolithic metal matrix. S2, the PBA / monolithic metal matrix from S1 is immersed in a 0.0001-4 mol / L potassium permanganate solution and reacted at 80-200℃ for 0.5-24 h. The product after reaction is washed with ethanol or water and dried to obtain the manganese-based monolithic catalyst. The preparation method of the present invention can simultaneously improve the loading of active components and intrinsic activity of manganese-based monolithic catalysts, which has great advantages in the field of low-temperature catalytic oxidation of VOCs and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, specifically relating to a method for preparing an integral catalyst that improves the loading of active components and intrinsic activity. Background Technology

[0002] VOCs (volatile organic compounds) are widely derived from industries such as paint spraying, shoemaking, pharmaceuticals, motor vehicle and shipbuilding, and kitchen fumes. They are toxic, have a foul odor, and are flammable and explosive. They are also important precursors to O3 and PM2.5, making them one of the major sources of air pollution. Therefore, the government has issued numerous regulations to control VOC emissions. Effective control of VOCs is therefore crucial for complying with increasingly stringent environmental policies, promoting sustainable development in various industries, and protecting public health. VOCs treatment technologies mainly include direct combustion, regenerative thermal combustion, and catalytic oxidation. While direct combustion and regenerative thermal combustion are relatively effective at treating VOCs, they suffer from high energy consumption, significant safety risks, and the potential for generating secondary pollutants, greatly limiting their industrial application. Catalytic oxidation, on the other hand, is promising due to its simplicity, high efficiency, safety, energy saving, and lack of secondary pollution.

[0003] The core of catalytic oxidation processes lies in developing catalysts with excellent performance. These materials mainly include supported noble metal catalysts and transition metal oxide catalysts. Among them, manganese-based catalysts stand out due to their low cost, variable valence state, and excellent thermal stability. Furthermore, to meet the low voltage resistance requirements in industrial applications, manganese-based active components are typically immobilized onto a matrix to construct monolithic catalysts. However, current methods for constructing manganese-based monolithic catalysts suitable for low-temperature catalytic oxidation of VOCs face the following challenges:

[0004] 1) Compared with noble metal-based active components, manganese-based catalysts have poor oxygen activation ability, resulting in poor low-temperature activity;

[0005] 2) In the process of constructing manganese-based monolithic catalysts by traditional coating or impregnation methods, the active components are prone to aggregation, and the catalyst is prone to detachment during the reaction, which leads to a sharp decline in catalytic performance;

[0006] 3) Traditional in-situ growth methods result in low loading of active components due to the large differences in physicochemical properties between the matrix and the active components, and also fail to regulate the intrinsic activity of the active components. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preparing an integral catalyst that improves the loading of active components and intrinsic activity.

[0008] The technical solution of this invention is: a method for preparing an integral catalyst that improves the loading of active components and intrinsic activity, mainly comprising the following steps:

[0009] S1. The monolithic metal matrix is ​​cleaned sequentially under ultrasonic conditions in ethanol, acetone, and 1 mol / L hydrochloric acid for 5 min each to remove surface organic matter and metal oxides. Then, the cleaned monolithic metal matrix is ​​immersed in a 0.001-5 mol / L metal cyanide solution until submerged. The reaction is carried out at 25-50℃ for 0.1-5 h. Then, hydrochloric acid is added to adjust the pH of the solution to 0-6, and the reaction is continued for 0.1-60 min. The product after the reaction is washed with ethanol and water, and dried to obtain PBA / monolithic metal matrix.

[0010] S2. Immerse the PBA / monolithic metal matrix in S1 into a 0.0001-4 mol / L potassium permanganate solution until submerged, and then react at 80-200℃ for 0.5-24 h. After the reaction, wash the product with ethanol or water and dry it to obtain the manganese-based monolithic catalyst.

[0011] Furthermore, the integral metal matrix is ​​one or more of the following: copper foam, iron foam, nickel foam, iron sheet, tin foil, and zinc plate.

[0012] Note: The metal matrix has good ductility, which is beneficial for installing monolithic catalysts into different reactors. At the same time, the metal matrix also has excellent thermal conductivity, which is beneficial for heat exchange in low-temperature catalytic oxidation processes.

[0013] Furthermore, the metal cyanide is one or more of K3Co(CN)6, K3Fe(CN)6, K4Fe(CN)6·6H2O, Na3Co(CN)6, Na3Fe(CN)6, and Na4Fe(CN)6·6H2O.

[0014] Note: The metal ions of the above-mentioned metal cyanide species have oxidizing properties that drive the interfacial redox reaction of the metal matrix with reducing properties, thereby growing PBA in situ on the surface of the metal matrix.

[0015] Furthermore, in step S1, the ultrasonic power is 100-800W.

[0016] Furthermore, in step S1, hydrochloric acid with a concentration of 0.1–12 mol / L is added to adjust the pH of the solution.

[0017] Furthermore, in step S1, the drying conditions are: vacuum drying at 60°C overnight.

[0018] Furthermore, in step S1, the drying conditions are: vacuum drying at 60°C overnight.

[0019] The present invention also provides the application of the monolithic catalyst prepared by the above method, which improves the loading of active components and intrinsic activity, and applies the catalyst to the low-temperature catalytic oxidation of VOCs.

[0020] Note: Applying the catalyst prepared in this invention to low-temperature catalytic oxidation of VOCs can not only reduce the volume of the catalytic reactor, but also significantly reduce the catalytic oxidation reaction temperature and reduce the energy consumption required for the reaction.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention cleverly utilizes the potential difference between the monolithic metal matrix and the metal cyanide to drive the redox interface reaction, and grows PBA (Prussian blue analogue, a large class in the MOF family) in situ on the surface of the monolithic metal matrix. Then, the PBA grown on the surface is used as a reducing agent, template and dopant to drive the redox reaction with the oxidizing KMnO4, thereby realizing the in situ growth of manganese-based active components in the monolithic metal matrix, and thus successfully preparing a manganese-based monolithic catalyst.

[0023] (2) This invention utilizes the redox interface reaction between the monolithic metal matrix and the metal cyanide to grow PBA, which enhances the interaction between PBA and the monolithic metal matrix, effectively avoids the detachment of PBA from the monolithic matrix, and increases the loading and dispersibility of PBA, solving the problem of the need to use binders and the aggregation of active components in the traditional monolithic catalyst preparation process.

[0024] (3) This invention utilizes the porous structure of PBA as a template for the growth of manganese-based catalysts, which can effectively improve the loading of active components and effectively solve the problem of low loading of active components caused by the large difference between the physical and chemical properties of the matrix and the active components in the traditional in-situ growth method. At the same time, the highly ordered metal clusters in PBA act as doping sources to achieve uniform doping of manganese-based active components, which solves the problem that the traditional monolithic catalyst preparation method cannot meet the intrinsic activity of active components.

[0025] (4) The manganese-based monolithic catalyst prepared by the present invention has significantly improved active component loading and intrinsic activity, and shows good application prospects in low-temperature catalytic oxidation of VOCs. Attached Figure Description

[0026] Figure 1 MnO2-O is a monolithic catalyst based on copper foam (CF) and manganese. v XRD patterns of -0.04 / CF and manganese-based monolithic catalyst MnO2 / CF;

[0027] Figure 2 Manganese-based monolithic catalyst MnO2-O vEPR diagrams of -0.04 / CF and manganese-based monolithic catalyst MnO2 / CF. Detailed Implementation

[0028] To facilitate understanding of the technical solution of this invention, the following description is provided in conjunction with the appendix. Figure 1 The present invention will be further explained and illustrated with specific embodiments, which do not constitute a limitation on the scope of protection of the invention.

[0029] Example 1: Manganese-based monolithic catalyst MnO2-O was prepared according to the following steps. v -0.04 / CF

[0030] (1) 1.5cm×1cm copper foam was washed in ethanol, acetone and 1mol / L hydrochloric acid for 5min each under 100W ultrasonic conditions to remove surface organic matter and metal oxides. Then the washed copper foam was immersed in 30mL of 0.04mol / L K3Fe(CN)6 solution until submerged. The reaction was carried out at 30℃ for 3h. Then 0.1mol / L hydrochloric acid was added to adjust the pH of the solution to 1 and the reaction was continued for 10min. The product after the reaction was washed with ethanol and water and vacuum dried at 60℃ overnight to obtain PBA / monolithic metal matrix.

[0031] S2: Immerse the PBA / monolithic metal matrix from S1 in 35 mL of 0.0007 mol / L potassium permanganate solution, ensuring complete submersion. Then react at 180 °C for 8 h. After washing the product with ethanol and vacuum drying at 60 °C overnight, the manganese-based monolithic catalyst MnO2-O is obtained. v -0.04 / CF.

[0032] Comparative Example 1: The synthesis method is the same as in Example 1, except that the synthesis process does not involve in-situ growth of PBA. The specific steps are as follows:

[0033] A 1.5cm × 1cm copper foam was sequentially washed for 5 minutes each in ethanol, acetone, and 1 mol / L hydrochloric acid under 200W ultrasonic conditions to remove surface organic matter and metal oxides. The washed copper foam was then immersed in 35 mL of 0.0007 mol / L potassium permanganate solution until submerged. The reaction was then carried out at 180℃ for 8 hours. The product was centrifuged, washed, and dried to obtain the manganese-based monolithic catalyst MnO2 / CF.

[0034] Depend on Figure 1 It can be seen that MnO2-O v The crystal structures of -0.04 / CF and MnO2 / CF are similar and perfectly match those of δ-MnO2 (PDF#80-1098), indicating that δ-MnO2 was grown on copper foam. ICP-OES results show that MnO2-Ov The manganese content in -0.04 / CF is 12.19%, significantly higher than the 2.15% in MnO2 / CF, indicating that the synthesis method of this invention can significantly improve the loading of active components. Figure 2 It can be seen that MnO2-O v The signal of -0.04 / CF at g = 2.003 is stronger than that of MnO2 / CF, indicating that MnO2-O v -0.04 / CF has more oxygen vacancies, which explains why the synthesis method of the present invention can significantly improve the intrinsic activity of the active component.

[0035] Example 2: Preparation of manganese-based monolithic catalyst MnO2-O according to the following steps v -0.08 / CF

[0036] (1) 1.5cm×1cm copper foam was washed in ethanol, acetone and 1mol / L hydrochloric acid for 5min each under 300W ultrasonic conditions to remove surface organic matter and metal oxides. Then the washed copper foam was immersed in 30mL of 0.08mol / L K3Fe(CN)6 solution until submerged. The reaction was carried out at 30℃ for 3h. Then 6mol / L hydrochloric acid was added to adjust the pH of the solution to 1 and the reaction was continued for 10min. The product after the reaction was washed with ethanol and water and vacuum dried at 60℃ overnight to obtain PBA / monolithic metal matrix.

[0037] S2: Immerse the PBA / monolithic metal matrix from S1 in 35 mL of 0.0007 mol / L potassium permanganate solution, ensuring complete submersion. Then react at 180 °C for 8 h. After washing the product with ethanol and vacuum drying at 60 °C overnight, the manganese-based monolithic catalyst MnO2-O is obtained. v -0.04 / CF.

[0038] Example 3: Manganese-based monolithic catalyst MnO2-O was prepared according to the following steps. v -0.04 / NF.

[0039] (1) 1.5cm×1cm nickel foam was washed in ethanol, acetone and 1mol / L hydrochloric acid for 5min each under 800W ultrasonic conditions to remove surface organic matter and metal oxides. After immersion, the washed copper foam was immersed in 30mL of 0.04mol / L K3Fe(CN)6 solution and reacted at 30℃ for 3h. Then, 12mol / L hydrochloric acid was added to adjust the pH of the solution to 1 and the reaction was continued for 10min. The product after reaction was washed with ethanol and water and vacuum dried at 60℃ overnight to obtain PBA / monolithic metal matrix.

[0040] S2: Immerse the PBA / monolithic metal matrix from S1 in 35 mL of 0.0007 mol / L potassium permanganate solution, ensuring complete submersion. Then react at 180℃ for 8 hours. After washing with water and drying, the manganese-based monolithic catalyst MnO2-O is obtained. v -0.04 / NF.

[0041] Catalyst performance evaluation: The catalysts synthesized in the examples and comparative examples were evaluated using a fixed-bed catalyst evaluation device coupled with online gas chromatography. The specific steps are as follows: 10 circular catalyst pieces with a diameter of slightly less than 5 mm were accurately weighed and placed into a 5 mm quartz tube, which was then placed in a reactor. At an initial toluene concentration of 1000 ppm, the outlet toluene concentration was measured at different temperatures. The temperature at which the toluene conversion rate reached 90% was used as the standard for evaluating catalyst activity. The results are shown in Table 1.

[0042] Table 1. Toluene concentration at outlet temperature at different temperatures

[0043] Serial Number <![CDATA[T 90％ (℃)]]> Experimental Example 1 215 Experiment Example 2 240 Experimental Example 3 235 Comparative Example 1 315

[0044] As shown in Table 1, the T90% of the experimental example is significantly lower than that of the comparative example. This indicates that the manganese-based monolithic catalyst prepared by the preparation method of the present invention can significantly improve the loading of active components and intrinsic activity, thereby significantly improving the energy consumption required for low-temperature catalytic oxidation of VOCs, which has considerable advantages in practical applications.

Claims

1. An application of in-situ growth of PBA on a metal matrix, characterized in that, The preparation of a monolithic catalyst for the low-temperature catalytic oxidation of VOCs includes the following steps: S1. The copper foam matrix was cleaned sequentially in ethanol, acetone and 1 mol / L hydrochloric acid for 5 min each under ultrasonic conditions to remove surface organic matter and metal oxides. Then, the cleaned copper foam matrix was immersed in 0.04 mol / L K3Fe(CN)6 solution until submerged and reacted at 30℃ for 3 h. Then, hydrochloric acid was added to adjust the pH of the solution to 1 and the reaction was continued for 10 min. The product after reaction was washed with ethanol and water and dried to obtain PBA / monolithic metal matrix. S2. Immerse the PBA / monolithic metal matrix in S1 into a 0.0007 mol / L potassium permanganate solution until submerged, then react at 180℃ for 8 h. After washing and drying the product, the manganese-based monolithic catalyst is obtained.

2. The application of in-situ growth of PBA on a metal matrix according to claim 1, characterized in that, In step S1, the ultrasonic power is 100 W.

3. The application of in-situ growth of PBA on a metal matrix according to claim 1, characterized in that, In step S1, hydrochloric acid with a concentration of 0.1-12 mol / L is added to adjust the pH of the solution.

4. The application of in-situ growth of PBA on a metal matrix according to claim 1, characterized in that, In step S1, the drying conditions are: vacuum drying at 60°C overnight.

5. The application of in-situ growth of PBA on a metal matrix according to claim 1, characterized in that, In step S2, the drying conditions are: vacuum drying at 60°C overnight.

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