Ag-Mn catalyst for catalyzing ozonolysis and preparation method thereof

Abstract

The invention discloses an Ag-Mn catalyst for catalyzing ozonolysis and a preparation method thereof, and belongs to the field of catalytic ozonolysis purification. The catalyst is Ag / Mn-BTC, wherein the mass of silver accounts for 1-8% of the total mass of the catalyst. The preparation method of the catalyst comprises the following steps: adding trimesic acid and manganese acetate tetrahydrate into a mixed solution of water and DMF (Dimethyl Formamide), uniformly stirring, transferring into a high-pressure kettle for hydrothermal reaction, and centrifuging and drying after the reaction is finished to obtain solid powder Mn-BTC; then, Mn-BTC is used as a carrier, AgNO3 and Mn-BTC are mixed and stirred, and the xAg / Mn-BTC catalyst is obtained after hydrothermal reaction, drying and air calcination. The prepared catalyst has the advantages that complete catalytic decomposition of ozone can be achieved under the conditions of ozone concentration of 40 ppm, room temperature and low humidity, and 93% of catalytic ozonolysis activity can be achieved under the conditions of room temperature and high humidity (80%). The invention opens up a new way for the development of a novel O3 decomposition catalyst, especially in a high-humidity environment.

Description

Technical Field

[0001] The present invention relates to the field of catalytic ozone decomposition and purification, and in particular to an xAg / Mn-BTC catalyst for decomposing ozone and a preparation method thereof. Background Field

[0002] Ozone is commonly used in wastewater treatment, air purification, drinking water bleaching, and sterilization of medical equipment. However, ozone has also caused new problems. Ozone can damage the eyes, respiratory tract, and cardiovascular system. Printers, ultraviolet equipment, and automobile exhaust (secondary pollution of photochemical smog) also produce large amounts of ozone. Especially in large cities, ozone can form and accumulate, causing great environmental damage. In recent years, ozone has replaced PM2.5. 2.5 Ozone pollution has become a major pollutant, and the situation of ozone pollution control is serious. Therefore, eliminating ozone pollution is of great significance to environmental protection and public health safety. The "Indoor Air Quality Standard" (GB / T18883-2002) sets the one-hour average concentration limit of ozone at 160 μg / m 3 The Ambient Air Quality Standard (GB3095-2012) stipulates that the maximum daily 8-hour average ozone concentration limit is 100 g / m 3 (first grade) and 160 g / m 3 (Level 2).

[0003] Currently, ozone removal technologies primarily include activated carbon adsorption, thermal decomposition, electromagnetic radiation, chemical absorption, and catalytic decomposition. The activated carbon method is commonly used in industrial production. While simple and convenient, it loses its activity over time, requiring frequent replacement or regeneration. It is also suitable only for low-concentration ozone and is significantly affected by factors such as humidity, airflow, pressure, and concentration, resulting in significant limitations. Thermal decomposition involves heating the gas to 400°C during combustion, where it undergoes thermal decomposition or combustion to induce a redox reaction. This method suffers from high costs and energy consumption. Ozone is irradiated with ultraviolet light or near-infrared radiation in the 1200-1300 nm range, where it converts to ground-state O₂. Chemical absorption uses uranium thiosulfate or uranium sulfite for absorption, but this poses the problem of subsequent wastewater disposal. Catalytic decomposition is currently considered the most ideal ozone treatment method due to its high efficiency, cost-effectiveness, and safety.

[0004] The catalysts used for catalytic decomposition of ozone can be divided into two categories: precious metals and transition metal oxides. Precious metal catalysts have high catalytic efficiency and good moisture resistance, but their preparation cost is high; in contrast, transition metal oxide catalysts have lower preparation costs and excellent catalytic activity, and are therefore widely considered to be the most ideal catalytic materials at present. Among transition metal oxides, manganese has become a hot topic of current research due to its high activity, relatively simple preparation, and low cost. These characteristics have made manganese oxides a focus of attention in the field of ozone decomposition. However, oxygen vacancies are easily occupied by water molecules, which has led to subsequent work focusing on improving the hydrophobicity of manganese oxides. To date, manganese oxide catalysts for catalytic decomposition of ozone still have many problems, such as a complex preparation process and the need to further improve hydrophobicity.

[0005] For example, patent CN108212153A discloses a self-supporting noble metal-modified manganese-based composite oxide catalyst, its preparation method, and application. The self-supporting noble metal-modified manganese-based composite oxide catalyst is obtained by first in-situ growing Al2O3 nanosheets on an aluminum substrate to form a catalyst support, and then sequentially loading the manganese-based composite oxide and active noble metal onto the catalyst support. This preparation method is relatively complex, making it unsuitable for large-scale production for industrial applications. Patents CN1259398A, CN17167674A, and CN1357348A all use copper, nickel, and cobalt oxides as active components, loaded onto activated carbon to decompose ozone. While these catalysts achieve good results at room temperature, they are unstable, have a short service life, and exhibit poor moisture resistance. Summary of the Invention

[0006] 1. Technical problem to be solved by the invention The present invention aims to improve the catalyst's ozone decomposition activity under high humidity conditions, overcoming the drawback of existing catalysts, which are susceptible to the effects of water molecules when decomposing ozone under high humidity conditions. The technical solution of the present invention effectively improves the catalyst's resistance to water molecules while maintaining high ozone decomposition activity, resulting in relatively stable performance and promising application prospects. 2. Technical solution

[0007] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides an Ag-Mn catalyst for catalyzing ozone decomposition. The catalyst is Ag / Mn-BTC, wherein the mass of silver accounts for 1-8% of the total mass of the catalyst.

[0008] The present invention also provides a method for preparing the above-mentioned Ag / Mn-BTC catalyst, comprising the following steps: (1) Trimellitic acid and manganese acetate tetrahydrate were added to a mixed solution of water and DMF at a mass ratio of 0.86:1, and after stirring evenly, the mixed solution was transferred into a polytetrafluoroethylene autoclave for hydrothermal reaction; after the reaction was completed, centrifugation, washing, and drying were performed in sequence to obtain a solid material Mn-BTC; (2) Add silver nitrate to the Mn-BTC material prepared in step (1), mix and stir evenly, transfer the mixed solution into a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction, and after the reaction is completed, centrifuge, wash, dry, and calcine in sequence to obtain the Ag / Mn-BTC catalyst.

[0009] Furthermore, the hydrothermal reaction conditions in step (1) are: in a 100 mL stainless steel autoclave, the hydrothermal temperature is 150 °C, and the hydrothermal time is 48 h.

[0010] Furthermore, the washing in step (1) refers to: washing with ionized water and methanol alternately.

[0011] Furthermore, the hydrothermal temperature in step (2) is 120° C., and the hydrothermal time is 12 h.

[0012] Furthermore, the calcination temperature in step (2) is 400°C and the calcination time is 2 h.

[0013] The Ag / Mn-BTC catalyst of the present invention can be used in catalytic decomposition of O3 under high humidity conditions.

[0014] Compared with the prior art, the present invention has the following technical effects: 1. Due to the appropriate calcination temperature to avoid crystal agglomeration, it has greater dispersion and maximum specific surface area to expose more active sites. In addition, the introduction of Ag element makes it have more Mn 3+ The chemical adsorption of oxygen increases the oxygen vacancies of the catalyst, accelerates the transfer of free electrons, improves the reducibility of the catalyst, and promotes the decomposition of ozone. Therefore, the Ag / Mn-BTC catalyst of the present invention exhibits a high ozone conversion rate. Complete catalytic decomposition of ozone can be achieved under conditions of 40 ppm ozone concentration, room temperature, and low humidity. 2. The Ag / Mn-BTC catalyst of the present invention can be used to catalyze the decomposition of O3 under high humidity conditions. It can achieve a catalytic ozone decomposition activity of 93% under room temperature and high humidity (80%) conditions.

[0015] 3. The present invention opens up a new path for the development of new O3 decomposition catalysts, especially in high humidity environments, such as outdoor O3 purification near rivers, lakes and oceans, indoor air purification, and places where O3 treatment processes are used for disinfection, food preservation, water treatment, etc. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a graph showing the test results of the catalytic decomposition of ozone activity of the catalysts prepared in Examples 1-5 of the present invention under dry conditions. Figure 2 This is a graph showing the test results of the catalytic decomposition of ozone activity of the catalysts prepared in Examples 1-5 of the present invention under high humidity conditions. DETAILED DESCRIPTION

[0016] The technical solutions of the present invention are described in detail below. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention. 1. Preparation of Catalyst A method for synthesizing an xAg / Mn-BTC catalyst involves synthesizing and preparing a MOF material, using the MOF material as a carrier and loading it with Ag for modification. The catalyst is prepared by the following method: First, a certain amount of trimesic acid and manganese acetate tetrahydrate are added to a mixed solution of water and DMF, stirred evenly, and then transferred to an autoclave for a hydrothermal reaction. After the reaction, the mixture is centrifuged and dried to obtain a solid powder of Mn-BTC. Subsequently, a certain amount of AgNO3 is mixed and stirred with the Mn-BTC material as a carrier. After a hydrothermal reaction, the mixture is dried and air-calcined to obtain the xAg / Mn-BTC catalyst. Example 1

[0017] (1) Preparation of MOF materials First, 5.51 g of Mn(CH3COO)2·4H2O and 4.72 g of H3BTC were dissolved in 40 mL of deionized water and 40 mL of dimethylformamide (DMF), respectively. The two solutions were then mixed and stirred for 30 minutes, transferred to a 100 mL stainless steel autoclave, and maintained at 150°C for 48 hours. After the reaction, the suspension was alternately washed with deionized water and methanol, and the washed suspension was separated by centrifuge. Finally, Mn-BTC was dried at 150°C for 12 hours to obtain a white solid.

[0018] (2) Preparation of catalyst First, 0.024 g of AgNO₃ was weighed into a 100 mL polytetrafluoroethylene-lined container and added to 60 mL of deionized water. The mixture was stirred in the dark for 15 minutes. Then, 1.5 g of the prepared Mn-BTC material carrier was weighed and added to the mixture. The mixture was stirred in the dark for 5 minutes and then sonicated for 15 minutes. The mixture was then transferred to a 100 mL stainless steel autoclave and subjected to a hydrothermal reaction in a 150°C oven for 10 hours. After the autoclave cooled to room temperature, the precipitate containing the sample was centrifuged and washed alternately with deionized water and methanol. Finally, the resulting sample was dried in an oven at 120°C for 12 hours. The calcined catalyst was ground to obtain a catalyst powder. The sample was designated 1Ag / Mn-BTC. Example 2

[0019] (1) Preparation of MOF materials First, 5.51 g of Mn(CH3COO)2·4H2O and 4.72 g of H3BTC were dissolved in 40 mL of deionized water and 40 mL of dimethylformamide (DMF), respectively. The two solutions were then mixed and stirred for 30 minutes, transferred to a 100 mL stainless steel autoclave, and maintained at 150°C for 48 hours. After the reaction, the suspension was alternately washed with deionized water and methanol, and the washed suspension was separated by centrifuge. Finally, Mn-BTC was dried at 150°C for 12 hours to obtain a white solid.

[0020] (2) Preparation of catalyst First, 0.049 g of AgNO₃ was weighed into a 100 mL polytetrafluoroethylene-lined container and added to 60 mL of deionized water. The mixture was stirred in the dark for 15 minutes. Then, 1.5 g of the prepared Mn-BTC material carrier was weighed and added to the mixture. The mixture was stirred in the dark for 5 minutes and then sonicated for 15 minutes. The mixture was then transferred to a 100 mL stainless steel autoclave and subjected to a hydrothermal reaction in a 150°C oven for 10 hours. After the autoclave cooled to room temperature, the precipitate containing the sample was centrifuged and washed alternately with deionized water and methanol. Finally, the resulting sample was dried in an oven at 120°C for 12 hours. The calcined catalyst was ground to obtain a catalyst powder. The sample was named 2Ag / Mn-BTC. Example 3

[0021] (1) Preparation of MOF materials First, 5.51 g of Mn(CH3COO)2·4H2O and 4.72 g of H3BTC were dissolved in 40 mL of deionized water and 40 mL of dimethylformamide (DMF), respectively. The two solutions were then mixed and stirred for 30 minutes, transferred to a 100 mL stainless steel autoclave, and maintained at 150°C for 48 hours. After the reaction, the suspension was alternately washed with deionized water and methanol, and the washed suspension was separated by centrifuge. Finally, Mn-BTC was dried at 150°C for 12 hours to obtain a white solid.

[0022] (2) Preparation of catalyst First, 0.101 g of AgNO₃ was weighed into a 100 mL polytetrafluoroethylene-lined container and added to 60 mL of deionized water. The mixture was stirred in the dark for 15 minutes. Then, 1.5 g of the prepared Mn-BTC material carrier was weighed and added to the mixture. The mixture was stirred in the dark for 5 minutes and then sonicated for 15 minutes. The mixture was then transferred to a 100 mL stainless steel autoclave and subjected to a hydrothermal reaction in a 150°C oven for 10 hours. After the autoclave cooled to room temperature, the precipitate containing the sample was centrifuged and washed alternately with deionized water and methanol. Finally, the resulting sample was dried in an oven at 120°C for 12 hours. The calcined catalyst was ground to obtain a catalyst powder. The sample was named 4Ag / Mn-BTC. Example 4

[0023] (1) Preparation of MOF materials First, 5.51 g of Mn(CH3COO)2·4H2O and 4.72 g of H3BTC were dissolved in 40 mL of deionized water and 40 mL of dimethylformamide (DMF), respectively. The two solutions were then mixed and stirred for 30 minutes, transferred to a 100 mL stainless steel autoclave, and maintained at 150°C for 48 hours. After the reaction, the suspension was alternately washed with deionized water and methanol, and the washed suspension was separated by centrifuge. Finally, Mn-BTC was dried at 150°C for 12 hours to obtain a white solid.

[0024] (2) Preparation of catalyst First, 0.156 g of AgNO₃ was weighed into a 100 mL polytetrafluoroethylene-lined container and added to 60 mL of deionized water. The mixture was stirred in the dark for 15 minutes. Then, 1.5 g of the prepared Mn-BTC material carrier was weighed and added to the mixture. The mixture was stirred in the dark for 5 minutes and then sonicated for 15 minutes. The mixture was then transferred to a 100 mL stainless steel autoclave and subjected to a hydrothermal reaction in a 150°C oven for 10 hours. After the autoclave cooled to room temperature, the precipitate containing the sample was centrifuged and washed alternately with deionized water and methanol. Finally, the resulting sample was dried in an oven at 120°C for 12 hours. The calcined catalyst was ground to obtain a catalyst powder. The sample was designated 6Ag / Mn-BTC. Example 5

[0025] (1) Preparation of MOF materials First, 5.51 g of Mn(CH3COO)2·4H2O and 4.72 g of H3BTC were dissolved in 40 mL of deionized water and 40 mL of dimethylformamide (DMF), respectively. The two solutions were then mixed and stirred for 30 minutes, transferred to a 100 mL stainless steel autoclave, and maintained at 150°C for 48 hours. After the reaction, the suspension was alternately washed with deionized water and methanol, and the washed suspension was separated by centrifuge. Finally, Mn-BTC was dried at 150°C for 12 hours to obtain a white solid.

[0026] (2) Preparation of catalyst First, 0.216 g of AgNO₃ was weighed into a 100 mL polytetrafluoroethylene-lined container and added to 60 mL of deionized water. The mixture was stirred in the dark for 15 minutes. Then, 1.5 g of the prepared Mn-BTC material carrier was weighed and added to the mixture. The mixture was stirred in the dark for 5 minutes and then sonicated for 15 minutes. The mixture was then transferred to a 100 mL stainless steel autoclave and subjected to a hydrothermal reaction in a 150°C oven for 10 hours. After the autoclave cooled to room temperature, the precipitate containing the sample was centrifuged and washed alternately with deionized water and methanol. Finally, the resulting sample was dried in an oven at 120°C for 12 hours. The calcined catalyst was ground to obtain a catalyst powder. The sample was designated 8Ag / Mn-BTC. 2. Catalyst Performance Test 1. Performance Test 1

[0027] The catalysts prepared in Catalyst Preparation Examples 1-5 were weighed and placed in a fixed bed reactor with an inner diameter of 6 mm to test their catalytic ozone decomposition activity. The lower end of the catalyst was supported by quartz wool. The test conditions were: dry atmosphere, 30 ° C, 280,000 h -1 The air velocity condition is controlled and the inlet O3 concentration is 40 ppm. The results are as follows Figure 1 shown.

[0028] The test results are as follows Figure 1 As shown, the conversion rates of all tested catalysts showed the same trend: activity slowly decreased over time before eventually stabilizing. The 6Ag / Mn-BTC catalyst exhibited the best catalytic activity, maintaining an ozone decomposition conversion rate above 96% for 360 minutes. The conversion rate of the Mn-BTC catalyst decreased to 76% after 360 minutes of reaction in a dry environment. 2. Performance Test 2

[0029] The catalysts prepared in Catalyst Preparation Examples 1-5 were weighed and placed in a fixed bed reactor with an inner diameter of 6 mm to test their catalytic ozone decomposition activity. The lower end of the catalyst was supported by quartz wool. The test conditions were: relative humidity 80%, 30°C, 280,000 h -1 The air velocity condition is controlled and the inlet O3 concentration is 40 ppm. The results are as follows Figure 2 shown.

[0030] The test results are as follows Figure 2 As shown: It can be clearly seen that the 6Ag / Mn-BTC catalyst has the best catalytic activity. The conversion rate is in a slowly decreasing state with the increase of reaction time within 360 minutes. After 360 minutes of reaction, the conversion rate stabilizes and tends to 93%. The conversion rate trends of the other catalysts are the same, and the activity increases significantly within 0-30 minutes. The decrease slowed down after 30 minutes and finally stabilized.

Claims

1. An Ag-Mn catalyst for catalyzing ozone decomposition, characterized in that: The catalyst is Ag / Mn-BTC, wherein the mass of silver accounts for 1-8% of the total mass of the catalyst.

2. The method for preparing an Ag-Mn catalyst for catalyzing ozone decomposition according to claim 1, characterized in that The following steps are involved: (1) Trimellitic acid and manganese acetate tetrahydrate were added to a mixed solution of water and DMF at a mass ratio of 0.86:1, and after stirring evenly, the mixed solution was transferred into a polytetrafluoroethylene autoclave for hydrothermal reaction; after the reaction was completed, centrifugation, washing, and drying were performed in sequence to obtain a solid material Mn-BTC; (2) Add silver nitrate to the Mn-BTC material prepared in step (1), mix and stir evenly, transfer the mixed solution into a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction, and after the reaction is completed, centrifuge, wash, dry, and calcine in sequence to obtain the Ag / Mn-BTC catalyst.

3. The method for preparing an Ag-Mn catalyst for catalyzing ozone decomposition according to claim 2, wherein: The hydrothermal reaction conditions in step (1) are: in a 100 mL stainless steel autoclave, the hydrothermal temperature is 150 ° C, and the hydrothermal time is 48 h.

4. The method for preparing an Ag-Mn catalyst for catalyzing ozone decomposition according to claim 2, wherein: The washing in step (1) refers to washing with ionized water and methanol alternately.

5. The method for preparing an Ag-Mn catalyst for catalyzing ozone decomposition according to claim 2, wherein: The hydrothermal temperature in step (2) is 120°C and the hydrothermal time is 12 h.

6. The method for preparing an Ag-Mn catalyst for catalyzing ozone decomposition according to claim 2, wherein: The calcination temperature in step (2) is 400°C and the calcination time is 2 h.

7. Use of the Ag-Mn catalyst for catalyzing ozone decomposition as claimed in claim 2 in the efficient catalytic decomposition of O3 under high humidity conditions.

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