A water-resistant catalyst and its preparation and application

Abstract

This invention relates to the field of VOCs waste gas treatment technology, specifically to a water-resistant catalyst and its preparation and application. The invention provides a method for preparing a water-resistant catalyst, comprising: hydrothermally mixing manganese salt and template agent A in water to obtain precursor A; hydrothermally mixing precursor A, cobalt salt, and template agent B in water to obtain precursor B; and calcining precursor B to obtain the water-resistant catalyst. The method provided by this invention, which involves first preparing a manganese precursor, then loading a cobalt precursor onto the manganese precursor, and finally calcining to obtain a composite material based on urchin-shaped manganese dioxide and cobalt tetroxide supported on the substrate, has been proven to perform catalytic oxidation treatment of Cl-VOCs under low ozone conditions in a water-containing environment.

Description

Technical Field

[0001] This invention relates to the field of VOCs waste gas treatment technology, specifically to a water-resistant catalyst and its preparation and application. Background Technology

[0002] Currently, there are many methods for treating flue gas and waste gas containing chlorine-containing volatile organic compounds (Cl-VOCs). These include preventative measures to prevent Cl-VOCs leakage, such as changing operating conditions, replacing raw materials, and replacing equipment. They also include mandatory end-of-pipe control measures, including destruction and recovery methods for removing Cl-VOCs. Destruction methods include catalytic oxidation and biofiltration, while recovery methods include absorption, adsorption, condensation, and membrane separation.

[0003] Catalytic oxidation technology can completely convert Cl-VOCs in flue gas / exhaust gas into non-toxic or slightly toxic, easily separated and collected small molecules such as water, hydrogen chloride, and carbon dioxide. Furthermore, it is relatively simple to operate; compared to combustion methods, catalytic oxidation requires temperatures below 400℃, achieving complete conversion of Cl-VOCs with fewer secondary pollutants and higher selectivity. Therefore, it is frequently used for the removal of Cl-VOCs from flue gas and exhaust gas. Existing catalytic oxidation technologies for Cl-VOCs include oxygen catalytic oxidation and ozone catalytic oxidation. Notably, compared to other oxidation technologies requiring high temperature or high pressure conditions, ozone catalytic oxidation technology is more widely used due to its ability to perform Cl-VOCs oxidation reactions at lower temperatures (below 120℃).

[0004] However, in the actual treatment of flue gas and waste gas catalytic oxidation, a common problem arises: the water content in flue gas from municipal solid waste incineration can reach 5% vol, and waste gas from industrial processes also often contains high levels of water vapor. Because water has high adsorption energy, its presence usually leads to competing reactions, resulting in a decrease in overall reaction activity. Specifically, under oxygen catalytic oxidation conditions above 300℃, the reaction activity typically decreases by 5–30%; under ozone catalytic oxidation conditions below 200℃, the reaction activity typically decreases by 10–80%. Aqueous conditions lead to catalyst deactivation, incomplete catalytic reactions, and significant product pollution.

[0005] It can be observed that the treatment of water-containing flue gas and exhaust gas is more challenging. Therefore, a common method for treating water-containing flue gas can be found in Chinese Patent Publication No. CN111632462A, which discloses a method for treating water-containing flue gas from steel slag. This method first uses a wet process to coarsely remove dust and cool the flue gas, removing some of the water vapor and large particulate matter. Then, a secondary fine dust removal is performed using a combination of acoustic treatment, spray treatment, and dehydration treatment. In other words, conventional water-containing flue gas treatment requires pre-dehydration treatment before subsequent steps to avoid the negative effects of increased moisture content. This undoubtedly prolongs the flue gas treatment cycle and increases the treatment costs in actual industrial production. Therefore, finding a catalyst that can maintain the treatment efficiency of flue gas and exhaust gas in a water-containing environment is in line with current development requirements. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of existing Cl-VOCs ozone catalytic oxidation removal technologies, which require large ozone dosages and are deactivated by water. It provides a water-resistant catalyst and its preparation and application to overcome the above-mentioned shortcomings.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a water-resistant catalyst, comprising:

[0009] S1, manganese salt and template agent A are mixed in water and then hydrothermally heated to obtain precursor A;

[0010] Precursor A, cobalt salt, and template agent B obtained from S2 and S1 are mixed in water and then hydrothermally heated to obtain precursor B.

[0011] The precursor B obtained from S3 and S2 was calcined to obtain a water-resistant catalyst.

[0012] This application first prepares a manganese-containing precursor, then loads a cobalt precursor onto the manganese precursor, and calcines it to obtain a water-resistant catalyst. The water-resistant catalyst comprises a sea urchin-shaped manganese dioxide substrate and cobalt tetroxide supported on the manganese dioxide substrate; Co is grown on the surface of the sea urchin-shaped oxide, with manganese oxide as the dominant catalyst activity. The water-resistant catalyst with a special structure prepared by this application has been proven to perform catalytic oxidation treatment of Cl-VOCs under low ozone levels in a water-containing environment. Furthermore, the water-resistant catalyst provided in this application, by combining manganese oxide and cobalt oxide, exhibits water resistance comparable to cobalt oxide and lower ozone levels than manganese oxide, demonstrating significant technological advancement.

[0013] Preferably, in step S1, the hydrothermal temperature is 100–110°C, and the hydrothermal time is 6–12 hours.

[0014] More preferably, in S1, the hydrothermal temperature is 100°C and the hydrothermal time is 10 hours.

[0015] Preferably, in step S2, the hydrothermal temperature is 120–130°C, and the hydrothermal time is 10–16 hours.

[0016] More preferably, in step S2, the hydrothermal temperature is 120°C and the hydrothermal time is 10 hours.

[0017] Preferably, in step S3, the calcination temperature is 300–400°C, the calcination time is 2–3 hours, and the calcination heating rate is 1–5°C / min.

[0018] More preferably, in step S3, the calcination temperature is 350°C, the calcination time is 2 hours, and the calcination heating rate is 1°C / min.

[0019] Preferably, in S1, template agent A is an aqueous solution of sulfuric acid with a concentration ≥98wt%.

[0020] Preferably, in S1, the ratio of manganese in the manganese salt to template agent A is 8 mmol:(1-5) mL.

[0021] More preferably, in S1, the ratio of manganese in the manganese salt to template agent A is 8 mmol:(1-3) mL.

[0022] More preferably, in S1, the ratio of manganese in the manganese salt to template agent A is 8 mmol: 2 mL.

[0023] Preferably, in S2, the template agent B is urea and ammonium fluoride.

[0024] Preferably, the molar ratio of cobalt, ammonium fluoride and urea in the cobalt salt is 1:(5-6):(4-5).

[0025] More preferably, the molar ratio of cobalt, ammonium fluoride, and urea in the cobalt salt is 1:6:5.

[0026] Preferably, the cobalt salt is one or more of cobalt nitrate, cobalt chloride, and cobalt acetate.

[0027] Preferably, the manganese salt is one or more of potassium permanganate, manganese sulfate, and manganese chloride.

[0028] Preferably, the molar ratio between cobalt in the cobalt salt and manganese in the manganese salt is (3-5):8.

[0029] More preferably, the molar ratio between cobalt in the cobalt salt and manganese in the manganese salt is 4:8.

[0030] The present invention also provides a water-resistant catalyst, comprising a sea urchin-shaped manganese dioxide substrate and cobalt tetroxide supported on the manganese dioxide substrate; the loading of the cobalt tetroxide is 7.0 to 19.8 wt% by weight of the water-resistant catalyst.

[0031] The present invention also provides the water-resistant catalyst prepared by the above preparation method or the application of the above water-resistant catalyst in the treatment of Cl-VOCs in water-containing flue gas / waste gas.

[0032] Preferably, the method for treating Cl-VOCs in water-containing flue gas / exhaust gas by the water-resistant catalyst is as follows: the water-resistant catalyst is placed in the water-containing flue gas / exhaust gas for ozone catalytic oxidation reaction to achieve Cl-VOCs conversion, and after deacidification, harmless exhaust gas is obtained.

[0033] Preferably, the water-resistant catalyst can treat Cl-VOCs with a water content of (0, 5% vol) by ozone catalytic oxidation.

[0034] More preferably, the water-resistant catalyst can treat Cl-VOCs with a water content of [3% vol, 5% vol] by ozone catalytic oxidation reaction.

[0035] Preferably, during the ozone catalytic oxidation reaction, the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas is (2.5~12.5):1.

[0036] More preferably, during the ozone catalytic oxidation reaction, the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas is (6-12):1.

[0037] More preferably, during the ozone catalytic oxidation reaction, the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas is (6-8):1.

[0038] Therefore, the present invention has the following beneficial effects:

[0039] (1) The composite material obtained by first preparing a manganese precursor, loading a cobalt precursor on the manganese precursor, and finally calcining, based on sea urchin-shaped manganese dioxide and cobalt tetroxide loaded on the substrate, has been proven to be able to carry out catalytic oxidation treatment of Cl-VOCs under low ozone conditions in a water-containing environment.

[0040] (2) The present invention discovered that the water-resistant catalyst has excellent catalytic activity and good water resistance, and can be directly used in the catalytic ozone oxidation treatment of Cl-VOCs in water-containing flue gas / waste gas without the need for a pre-dehydration treatment step before catalytic ozone oxidation, which greatly improves the treatment efficiency.

[0041] (3) When the water-resistant catalyst provided by the present invention is applied to treat Cl-VOCs, the conversion rate of Cl-VOCs can reach more than 90% when the ozone molar ratio is equal to 6, which effectively reduces the ozone addition cost.

[0042] (4) When the water-resistant catalyst provided by the present invention is applied to Cl-VOCs in water-containing flue gas / waste gas, the water-resistant catalyst exhibits obvious water-promoting effect. It can replace part of the ozone with water under low ozone concentration to generate strong oxidizing free radicals such as hydroxyl groups. It can reduce the ozone addition while completely mineralizing dichloromethane, effectively reducing the catalytic cost and has practical application and promotion value.

[0043] (5) When the water-resistant catalyst provided by the present invention is applied to the treatment of water-containing Cl-VOCs flue gas, it can maintain high activity and long-term stability, and can achieve water resistance at 120°C and below, thus requiring less catalytic equipment.

[0044] (6) The water-resistant catalyst provided by the present invention can enhance the activation effect of water on the catalyst surface, convert water molecules into strong oxidizing free radicals such as hydroxyl groups to participate in the oxidation reaction, thereby hindering the condensation of water in the catalyst channels and the influence on acidic sites, preventing water poisoning of the catalyst; and achieving the promotion of catalytic activity by water at low water content.

[0045] (7) The water-resistant catalyst provided by the present invention combines manganese oxide and cobalt oxide, and its water resistance is on par with that of cobalt oxide, while its ozone content is lower than that of manganese oxide, demonstrating significant technological progress. Attached Figure Description

[0046] Figure 1 The image shows the XRD pattern of the water-resistant catalyst prepared in Example 1.

[0047] Figure 2 The diagram shows the catalytic oxidation effect of the water-resistant catalyst prepared in Example 1 of this invention at different ozone concentrations, where the ozone molar ratio is the molar ratio of ozone to Cl-VOCs in water-containing flue gas / exhaust gas.

[0048] Figure 3 The figures show the catalytic oxidation effect of the water-resistant catalysts prepared in Examples 2-4 of this invention at different ozone concentrations, where the ozone molar ratio is the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas.

[0049] Figure 4 The figures show the catalytic oxidation of dichloromethane by the water-resistant catalysts prepared in Comparative Examples 1-5 of this invention under different ozone concentrations, where the ozone molar ratio is the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas.

[0050] Figure 5The images show the SEM structures of Example 1 and Comparative Example 3 obtained by the present invention.

[0051] Figure 6 The images show a comparison of the dry and wet conditions of the water-resistant catalysts prepared in Examples 1-4 of this invention for the ozone catalytic oxidation of dichloromethane.

[0052] Figure 7 The images show a comparison of the dry and wet conditions of the water-resistant catalysts prepared in Comparative Examples 1-5 of this invention for the ozone catalytic oxidation of dichloromethane.

[0053] Figure 8 The water-promoting effect of the water-resistant catalyst prepared in Example 1 under ozone concentration of 143 ppm is shown in the ozone catalytic oxidation process (the two columns of each stage are the average integrated areas of TCM (left) and CT (right) detected by GC spectroscopy, where TCM is trichloromethane and CT is carbon tetrachloride).

[0054] Figure 9 The graph shows the water-promoting effect of the catalyst prepared in Example 1 under ozone concentration of 240 ppm (the two columns of each stage are the average integrated areas of TCM (left) and CT (right) detected by GC spectroscopy, where TCM is trichloromethane and CT is carbon tetrachloride).

[0055] Figure 10 The graph shows the water-promoting effect of the catalyst prepared in Example 2 under ozone concentration of 240 ppm (the two columns of each stage are the average integrated areas of TCM (left) and CT (right) detected by GC spectroscopy, where TCM is chloroform and CT is carbon tetrachloride).

[0056] Figure 11 The graph shows the long-term dichloromethane conversion effect of Example 1 under the conditions of 600 ppm ozone and 3% vol water vapor (the two columns of each stage are the average integrated areas of TCM (left) and CT (right) detected by GC spectroscopy, where TCM is trichloromethane and CT is carbon tetrachloride).

[0057] Figure 12 The graph shows the long-term dichloromethane conversion effect under ozone concentration of 600 ppm and water vapor of Example 2 (the two columns of each stage are the average integrated areas of TCM (left) and CT (right) detected by GC spectroscopy, where TCM is trichloromethane and CT is carbon tetrachloride). Detailed Implementation

[0058] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0059]

Example

[0060] Example 1

[0061] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0062] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 10 hours.

[0063] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0064] (4) Mix the powdered dry base solid with 1.1641 g (4 mmol) cobalt nitrate hexahydrate, 1.2016 g (20 mmol) urea and 0.888 g (24 mmol) ammonium fluoride into 72 mL of deionized water, stir thoroughly and sonicate for 30 min to obtain a mixture.

[0065] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0066] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0067] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder H-MnO2@Co3O4-4.

[0068] The XRD pattern of the prepared H-MnO2@Co3O4-4 is shown below. Figure 1 As shown; by Figure 1 It can be seen that the Co peak is relatively weak, indicating high dispersibility. The Mn peak is more obvious, indicating outstanding activity.

[0069] Example 2

[0070] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0071] (2) Place the mixture in a 100mL hydrothermal reactor and react it in a 100℃ oven for 6 hours.

[0072] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0073] (4) Mix the powdered dry base solid with 1.1641 g (4 mmol) cobalt nitrate hexahydrate, 1.2016 g (20 mmol) urea and 0.888 g (24 mmol) ammonium fluoride into 72 mL of deionized water, stir thoroughly and sonicate for 30 min to obtain a mixture.

[0074] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0075] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0076] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder S-MnO2@Co3O4-4.

[0077] Example 3

[0078] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0079] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0080] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0081] (4) Mix the powdered dry base solid with 0.8731g (3mmol) cobalt nitrate hexahydrate, 1.2016g (20mmol) urea and 0.888g (24mmol) ammonium fluoride into 72mL of deionized water, stir thoroughly and sonicate for 30min to obtain a mixture.

[0082] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0083] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0084] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder H-MnO2@Co3O4-3.

[0085] Example 4

[0086] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0087] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0088] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0089] (4) Mix the powdered dry base solid with 1.4551g (5mmol) cobalt nitrate hexahydrate, 1.2016g (20mmol) urea and 0.888g (24mmol) ammonium fluoride into 72mL of deionized water, stir thoroughly and sonicate for 30min to obtain a mixture.

[0090] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0091] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0092] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder H-MnO2@Co3O4-5.

[0093] [Comparative Example]

[0094] Comparative Example 1

[0095] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0096] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0097] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0098] (4) Mix the powdered dry base solid with 0.2910 g (3 mmol) cobalt nitrate hexahydrate, 1.2016 g (20 mmol) urea and 0.888 g (24 mmol) ammonium fluoride into 72 mL of deionized water, stir thoroughly and sonicate for 30 min to obtain a mixture.

[0099] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0100] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0101] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder H-MnO2@Co3O4-1.

[0102] Comparative Example 2

[0103] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0104] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0105] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0106] (4) Mix the powdered dry base solid with 0.5821g (2mmol) cobalt nitrate hexahydrate, 1.2016g (20mmol) urea and 0.888g (24mmol) ammonium fluoride into 72mL of deionized water, stir thoroughly and sonicate for 30min to obtain a mixture.

[0107] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0108] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0109] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder H-MnO2@Co3O4-2.

[0110] Comparative Example 3

[0111] (1) 1.1641 g (4 mmol) cobalt nitrate hexahydrate, 1.2016 g (20 mmol) urea and 0.888 g (24 mmol) ammonium fluoride were mixed into 72 mL of deionized water, stirred thoroughly and sonicated for 30 min to obtain a mixture.

[0112] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0113] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0114] (4) Dissolve the powdered dry base solid with 1.2614 g potassium permanganate (8 mmol) and 2 mL 98 wt% concentrated sulfuric acid in 75 mL deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0115] (5) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0116] (6) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 10 hours in a forced-air drying oven to obtain powder dry-based solid.

[0117] (7) The dry-based powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder Co3O4@MnO2.

[0118] Comparative Example 4

[0119] (1) 1.1641 g (4 mmol) cobalt nitrate hexahydrate, 1.2016 g (20 mmol) urea and 0.888 g (24 mmol) ammonium fluoride were mixed into 72 mL of deionized water, stirred thoroughly and sonicated for 30 min to obtain a mixture.

[0120] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 120℃ oven for 10h.

[0121] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0122] (4) The dry powder solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder Co3O4.

[0123] Comparative Example 5

[0124] (1) Dissolve 1.2614 g potassium permanganate (8 mmol) and 2 mL of 98 wt% concentrated sulfuric acid in 75 mL of deionized water, stir thoroughly, and sonicate for 30 min to obtain a mixture.

[0125] (2) Place the mixture in a 100mL hydrothermal reactor and perform hydrothermal reaction in a 100℃ oven for 12 hours.

[0126] (3) After cooling to room temperature, centrifuge and wash to obtain wet-based powder solid, dry at 100°C for 12 hours in a forced-air drying oven to obtain powder dry-based solid.

[0127] (4) The dry-based powdered solid was calcined in a tube furnace under static air atmosphere at a heating rate of 1℃ / min and a final temperature of 350℃ for 2h to obtain catalyst powder MnO2.

[0128] Applications of water-resistant catalysts

[0129] Take 0.05g of the catalyst prepared in Examples 1-4 and Comparative Examples 1-5 (the following application examples all follow this dosage) and conduct subsequent application experiments based on it.

[0130] Using dichloromethane (DCM) as a model compound for Cl-VOCs, the performance of the above catalyst in catalytic oxidation of Cl-VOCs under different ozone concentrations in a low-temperature dry gas phase was explored. The specific steps were as follows: the catalysts prepared in Examples 1-4 and Comparative Examples 1-5 were placed in a dry flue gas environment, and different sampling concentrations were adjusted. The catalysts were used to carry out ozone catalytic oxidation of Cl-VOCs containing 100 ppm dichloromethane. After deacidification, the exhaust gas was obtained.

[0131] Table 1 shows the catalyst bed volume space velocity ratio and temperature corresponding to the catalysts prepared under different schemes.

[0132] Table 1 Catalyst bed parameters and heating temperature when using different catalysts

[0133] product Catalyst bed volume space velocity ratio Catalyst bed temperature <![CDATA[H-MnO2@Co3O4-1]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[H-MnO2@Co3O4-2]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[H-MnO2@Co3O4-3]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[H-MnO2@Co3O4-4]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[H-MnO2@Co3O4-5]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[S-MnO2@Co3O4-4]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[Co3O4@MnO2]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[Co3O4]]> <![CDATA[20000h -1 ]]> 120℃ <![CDATA[MnO2]]> <![CDATA[20000h -1 ]]> 120℃

[0134] After the reaction, the conversion rate of dichloromethane during the ozone catalytic oxidation of dichloromethane was detected by gas chromatography. The results are shown in the figure. Figures 2-4 .

[0135] The results show that the water-resistant catalyst prepared in Example 1 achieves a conversion rate of over 90% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The water-resistant catalyst prepared in Example 2 also achieves a conversion rate of over 90% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Example 3 achieves a conversion rate of over 90% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Example 4 achieves a conversion rate of over 90% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Comparative Example 1 achieves a conversion rate of over 75% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Comparative Example 2 achieves a conversion rate of over 85% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Comparative Example 3 achieves a conversion rate of over 60% for the ozone-catalyzed oxidation of dichloromethane when the ozone molar ratio is 6. The catalyst prepared in Comparative Example 4 achieved an ozone-catalyzed oxidation of dichloromethane conversion rate of over 80% when the ozone molar ratio was 6. The catalyst prepared in Comparative Example 5 also achieved an ozone-catalyzed oxidation of dichloromethane conversion rate of over 80% when the ozone molar ratio was 6. Specifically, when the ozone molar ratio was 6, the conversion efficiency of Example 1 was over 90%; however, the conversion rate of Comparative Example 5 only reached over 90% when the ozone molar ratio was increased to 12. Clearly, Example 1, by combining cobalt oxide and manganese oxide, achieved a better dichloromethane conversion rate with less ozone consumption compared to manganese oxide alone (Comparative Example 5).

[0136] Analysis of the above data shows that Examples 1, 2, and Comparative Example 3 are water-resistant catalysts prepared with an addition of 4 mmol of Co. The scheme of this application involves growing Co on the surface of a sea urchin-like oxide, with manganese oxide as the dominant catalyst activity. Due to the uniform growth of a certain amount of Co on the surface of the manganese oxide, and the influence of secondary hydrothermal treatment, the solid / hollow structure of Mn has little impact on the catalyst activity. Figure 5 It can be seen that Comparative Example 3 suffers from decreased adsorption performance and reduced active sites due to the loss of Mn's excellent sea urchin-like structure, resulting in a lower conversion rate. Examples 3 and 4, and Comparative Examples 1 and 2, are water-resistant catalysts prepared with different amounts of Co added. With increasing Co content, the Co-Mn interaction is enhanced, promoting interfacial effects and ion exchange, thus increasing activity. However, when the Co addition reaches a certain value, Co will coat the Mn surface, thereby usurping Mn's dominant activity and causing a decrease in activity.

[0137] Compared to the simple cobalt oxide and manganese oxide of Comparative Examples 4 and 5, Examples 1 and 2 exhibit higher activity than any single metal catalyst due to their unique electronic interactions and synergistic effects between metals.

[0138] Application Example 2

[0139] As shown in Application Example 1, the water-resistant catalysts prepared in Examples 1-4 all exhibited good dichloromethane conversion rates under dry conditions. Therefore, this application example further explores these results.

[0140] In practical applications, it's often not just dry flue gas that's being processed. To address the complex operating conditions that may arise in real-world applications, this application case studies the impact of water-containing flue gas on the catalytic conversion efficiency of the catalyst. Specifically: Flue gas containing 100 ppm dichloromethane (Cl-VOCs) was introduced into an ozone catalytic oxidation unit equipped with a catalyst bed, where it reacted with 600 ppm ozone. The total gas flow rate was maintained at 100 mL / min, and the gas was deacidified and discharged after the reaction. The reaction was first carried out under dry conditions for three hours, then 3% vol water vapor was introduced to continue the reaction for another three hours. Gas chromatography was used to detect the conversion rate of dichloromethane during the ozone catalytic oxidation of dichloromethane. The results are shown in [Figure number missing]. Figure 6-7 .

[0141] The results showed that Examples 1, 2, 4 and Comparative Example 4 exhibited significant water-promoting effects after water addition, Example 3 showed more water resistance, while the activity of Comparative Examples 1, 2, 3, and 5 was affected to some extent by water addition. Comparative results revealed that Co was the main water-resistant component, and the water-resistant effect of Co was more fully realized with increasing Co content. Therefore, while maintaining a specific morphology, the addition of a certain amount of Co can fully utilize the water resistance of Co metal without affecting the dominant Mn activity, thereby improving the overall water resistance of the catalyst, which can be applied to practical scenarios such as municipal solid waste incineration. Specifically, comparing the data from Example 1 and Comparative Example 4, it was found that the water resistance of Example 1, after combining cobalt oxide and manganese oxide, was still comparable to that of cobalt oxide alone.

[0142] Application Example 3

[0143] The water-promoting effect of the water-resistant catalyst prepared in Example 1 (H-MnO2@Co3O4-4) was investigated: flue gas containing 100 ppm dichloromethane and Cl-VOCs was passed into an ozone catalytic oxidation unit equipped with a catalyst bed, and the catalyst bed volume space velocity was 20000 h⁻¹. -1The gas was mixed with ozone at a concentration of 143 ppm in the catalytic oxidation unit and reacted while maintaining a total gas flow rate of 100 mL / min. After the reaction, the gas was deacidified and discharged. During the experiment, the operating conditions were changed every two hours, in the following time sequence: 120℃, flue gas drying; 120℃, 1% vol water vapor; 120℃, 3% vol water vapor; 120℃, 5% vol water vapor; 150℃, 5% vol water vapor; 150℃, 3% vol water vapor; 150℃, 1% vol water vapor; 150℃, flue gas drying. The test results are shown below. Figure 8 .

[0144] The results showed that the H-MnO2@Co3O4-4 catalyst increased the conversion rate from 50% to 51% under conditions of 120℃, 143ppm ozone concentration, and 1%vol water vapor, and further increased the conversion rate to 54% under conditions of 150℃ and 1%vol water vapor. This indicates that the water-resistant catalyst has high activity and still has strong water resistance under low temperature and low ozone conditions.

[0145] Application Example 4

[0146] Further investigation was conducted on the water-promoting effect of increasing ozone concentration on the H-MnO2@Co3O4-4 catalyst: Flue gas containing 100 ppm dichloromethane and Cl-VOCs was introduced into an ozone catalytic oxidation unit equipped with a catalyst bed, with a catalyst bed volume space velocity of 20000 h⁻¹. -1 The gas was mixed with ozone at a concentration of 240 ppm in the catalytic oxidation unit and reacted while maintaining a total gas flow rate of 100 mL / min. After the reaction, the gas was deacidified and discharged. During the experiment, the operating conditions were changed every two hours, in the following order: 120℃, flue gas drying; 120℃, 1% vol water vapor; 120℃, 3% vol water vapor; 120℃, 5% vol water vapor; 150℃, 5% vol water vapor; 150℃, flue gas drying. The test results are shown below. Figure 9 .

[0147] The results show that increasing the ozone concentration makes the catalyst more sensitive to water activation. At 120℃, with an ozone concentration of 240 ppm and 3% vol water vapor, the dichloromethane conversion rate increased from 74% to 79%. When the temperature was increased to 150℃ and the water vapor concentration to 5% vol, the dichloromethane conversion rate increased to 83%. This indicates that the H-MnO2@Co3O4-4 catalyst, after adding water vapor, can completely mineralize dichloromethane while reducing ozone dosage, effectively lowering catalytic costs.

[0148] Application Example 5

[0149] The water resistance of the S-MnO2@Co3O4-4 catalyst was investigated: Flue gas containing 100 ppm dichloromethane and Cl-VOCs was introduced into an ozone catalytic oxidation unit equipped with a catalyst bed, with a catalyst bed volume space velocity of 20000 h⁻¹. -1 The gas was mixed with ozone at a concentration of 230 ppm in the catalytic oxidation unit and reacted while maintaining a total gas flow rate of 100 mL / min. After the reaction, the gas was deacidified and discharged. During the experiment, the operating conditions were changed every two hours, in the following time sequence: 120℃, flue gas drying; 120℃, 1% vol water vapor; 120℃, 3% vol water vapor; 120℃, 5% vol water vapor; 150℃, 5% vol water vapor; 150℃, 3% vol water vapor; 150℃, 1% vol water vapor; 150℃, flue gas drying. The test results are shown below. Figure 10 .

[0150] The results showed that the conversion rate of the catalyst increased from 71% to 82% under conditions of 120℃, 230ppm ozone concentration, and 3%vol water vapor, and could be increased to 84% under conditions of 150℃ and 3%vol water vapor. This indicates that the catalyst has high activity and strong water resistance under low temperature and low ozone conditions. Furthermore, the addition of water vapor can reduce ozone dosage while completely mineralizing dichloromethane, effectively reducing the catalytic cost.

[0151] This result shows that the water-resistant catalysts prepared under different hydrothermal durations in step (2) of the embodiment have similar performance; it proves that the hydrothermal duration has little effect on the catalyst performance.

[0152] Application Example 6

[0153] The water-resistant catalysts prepared in Examples 1 and 2 were subjected to long-term water resistance tests under ozone catalytic oxidation conditions: Flue gas containing 100 ppm dichloromethane and Cl-VOCs was introduced into an oxygen catalytic oxidation unit equipped with a catalyst bed, and reacted with ozone containing 230 ppm ozone in the catalytic oxidation unit, maintaining a total gas flow rate of 100 mL / min. After the reaction, the gas was deacidified and discharged. The catalyst bed volume space velocity was 20000 h⁻¹. -1 The catalyst bed temperature was 120℃. After one hour, 3% vol water vapor was added to the flue gas. After the reaction, the gas was deacidified and discharged. The test results and specific operating conditions are shown in [link to relevant documentation]. Figure 11-12 .

[0154] The results show that H-MnO2@Co3O4-4 and S-MnO2@Co3O4-4 can maintain high efficiency and stability for a long time under 3% vol water vapor conditions, and exhibit water-promoting effects.

Claims

1. A method for preparing a water-resistant catalyst, characterized in that, include: S1, manganese salt and template agent A are mixed in water and then hydrothermally heated to obtain precursor A. The hydrothermal temperature is 100~110℃ and the hydrothermal time is 6~12 h. Template agent A is an aqueous solution of sulfuric acid with a concentration ≥98 wt%. Precursor A, cobalt salt, and template agent B obtained from S2 and S1 are mixed in water and then hydrothermally heated to obtain precursor B. The hydrothermal temperature is 120~130℃ and the hydrothermal time is 10~16 h. Template agent B is urea and ammonium fluoride. The precursor B obtained from S3 and S2 was calcined to obtain a water-resistant catalyst. The calcination temperature was 300~400℃ and the calcination time was 2~3 h. The molar ratio between cobalt in the cobalt salt and manganese in the manganese salt is (3~5):

8.

2. The preparation method according to claim 1, characterized in that, In S3, the heating rate of calcination is 1~5 ℃ / min.

3. The preparation method according to claim 1, characterized in that, In S1, the ratio of manganese in the manganese salt to template agent A is 8 mmol: (1~5) mL.

4. The water-resistant catalyst prepared by the method according to any one of claims 1 to 3, characterized in that, It includes a sea urchin-shaped manganese dioxide substrate and cobalt tetroxide supported on the manganese dioxide substrate; the loading of cobalt tetroxide is 7.0~19.8 wt% based on the weight of the water-resistant catalyst.

5. The application of the water-resistant catalyst prepared by the preparation method according to any one of claims 1 to 3 or the water-resistant catalyst according to claim 4 in the treatment of Cl-VOCs in water-containing flue gas / waste gas.

6. The application as described in claim 5, characterized in that, The method for treating Cl-VOCs in water-containing flue gas / exhaust gas using the water-resistant catalyst is as follows: the water-resistant catalyst is placed in the water-containing flue gas / exhaust gas for ozone catalytic oxidation reaction to achieve Cl-VOCs conversion, and after deacidification, harmless exhaust gas is obtained.

7. The application as described in claim 5, characterized in that, The water-resistant catalyst can treat Cl-VOCs with a water content of (0,5] vol% by ozone catalytic oxidation reaction.

8. The application as described in claim 6, characterized in that, In the ozone catalytic oxidation process, the molar ratio of ozone to Cl-VOCs in the water-containing flue gas / exhaust gas is (2.5~12.5):1.

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