A noble metal confined ozone decomposition catalyst and its preparation method and application

Abstract

The present invention discloses a noble metal confined ozone decomposition catalyst and its preparation method and application, which belongs to the technical field of ozone removal. The ozone decomposition catalyst uses a bimetallic oxide as a carrier, and the carrier is loaded with Pd 2+ and / or Ag + ; the Pd 2+ The loading amount of Ag is 0.01% to 10% of the weight of the ozone decomposition catalyst; + The loading amount accounts for 0.1% to 20% of the weight of the ozone decomposition catalyst. The catalyst has excellent ozone decomposition activity and stability under dry and wet conditions and can meet the ozone removal requirements of near-ground and airborne environmental control systems.

Description

Technical Field

[0001] The present invention relates to a noble metal confined ozone decomposition catalyst and a preparation method and application thereof, belonging to the technical field of ozone catalytic removal. Background Art

[0002] In recent years, ground-level ozone pollution has become a major atmospheric pollutant. While ozone pollution is gaining increasing attention, its causes are complex, with distinct seasonal and regional characteristics. my country's ozone pollution control efforts are still in their infancy. In certain microenvironments or relatively confined spaces, such as those with office equipment and aircraft cabins, ozone concentrations can accumulate, posing a serious health hazard. Ozone in offices primarily comes from static electricity generated by copying and printing, while cabin ozone originates from air drawn from the stratosphere by the engine's exhaust system. Studies have shown that long-term exposure to ozone concentrations above 0.1 ppm can cause serious health problems and even increase the risk of death. Consequently, the World Health Organization (WHO, 2000) issued its "Air Quality Guidelines," which mandate an eight-hour average ozone concentration of no more than 50 ppb. The US Environmental Protection Agency (EPA) standard is an eight-hour average ozone concentration of no more than 70 ppb. The EU standard is 60 ppb. my country's 2012 revised Ambient Air Quality Standards also added ozone control standards: a maximum eight-hour average daily level of 50 ppb for Level 1 and 80 ppb for Level 2. To reduce ozone pollution, ozone needs to be decomposed and converted into oxygen.

[0003] Research on ozone decomposition began as early as the 1970s. Currently, the most commonly used ozone treatment methods include thermal decomposition, activated carbon adsorption, liquid chemical absorption, and catalytic decomposition. Each of these methods has its own advantages and disadvantages. Thermal decomposition often requires heating to above 400°C to rapidly decompose ozone. While simple, this method is energy-intensive. Activated carbon adsorption utilizes the strong adsorption properties of activated carbon to remove ozone. Activated carbon has a large specific surface area and can rapidly adsorb ozone. However, due to its limited adsorption capacity, activated carbon requires frequent regeneration after reaching saturation, resulting in high costs. Liquid chemical absorption utilizes solutions such as sodium thiosulfate or sodium nitrite to absorb ozone, but the problem is that the wastewater is difficult to dispose of. Catalytic decomposition is currently the most ideal and promising method. Using a catalyst to decompose ozone allows for ozone decomposition at lower temperatures and eliminates wastewater disposal issues.

[0004] Ground-level ozone, particularly cabin ozone, requires catalytic decomposition at low temperatures, high air velocities, and in a water vapor atmosphere, placing high demands on ozone decomposition catalysts. While extensive research has been conducted on ozone decomposition catalysts and their mechanisms, the stability of ozone decomposition catalysts, particularly in water vapor atmospheres, remains to be further improved. Summary of the Invention

[0005] This invention addresses the problems of existing ozone decomposition catalysts, such as poor low-temperature stability and, in particular, insufficient ozone decomposition efficiency in aqueous atmospheres, by providing a highly efficient noble metal ozone decomposition catalyst and preparation method. The catalyst utilizes a hydrotalcite (e.g., NiMn-LDH, CuMn-LDH, NiFe-LDH, or CuCo-LDH) as a carrier. Precious metals Pd and Ag are highly dispersed and confined within the hydrotalcite layered structure to form a sandwich structure. This structure is then calcined at high temperature to produce a mesoporous metal oxide-supported noble metal catalyst with excellent ozone removal performance.

[0006] According to one aspect of the present invention, a noble metal confined ozone decomposition catalyst is provided, wherein the ozone decomposition catalyst is supported by a bimetallic oxide, and the support is loaded with a confined domain of Pd 2+ and / or Ag + ;

[0007] The Pd 2+ The loading amount of Ag is 0.01% to 10% of the weight of the ozone decomposition catalyst; + The loading amount accounts for 0.1% to 20% of the weight of the ozone decomposition catalyst.

[0008] Optionally, Pd 2+ The loading amount of Ag accounts for 0.05% to 1.0% of the weight of the ozone decomposition catalyst; + The loading amount accounts for 1.0% to 5.0% of the weight of the ozone decomposition catalyst.

[0009] Optionally, the ozone decomposition catalyst has pores, and the pores are mesoporous structures with a diameter of 2 to 50 nm.

[0010] Optionally, the bimetallic oxide contains divalent metal cations and trivalent metal cations, and the divalent metal cations and trivalent metal cations are both derived from transition metal elements.

[0011] Optionally, the divalent metal cation is selected from Ni 2+ 、Fe 2+ 、Cu 2+ 、Mn 2+ 、Co 2+ At least one of; the trivalent metal cation is selected from Fe 3+ 、Mn 3+ 、Co 3+ At least one of .

[0012] According to one aspect of the present invention, there is provided a method for preparing the ozone decomposition catalyst as claimed in any one of claims 1 to 2, wherein the noble metal Pd is intercalated between the carrier precursor layers.2+ and / or Ag + , preparing a noble metal confined catalyst precursor, and calcining it to obtain the ozone decomposition catalyst;

[0013] The support precursor is layered double hydroxide (LDH).

[0014] The noble metal confined catalyst precursor is calcined under an oxidizing, reducing or inactive atmosphere.

[0015] Optionally, the carrier precursor is dried before intercalation but not calcined.

[0016] Optionally, the following steps are included:

[0017] (1) obtaining a layered double hydroxide, i.e., a support precursor;

[0018] (2) dispersing the carrier precursor into an aqueous solution containing a noble metal precursor, adjusting the pH value of the solution to 5-6.5, stirring, filtering, washing, drying, and calcining to obtain a noble metal confined ozone decomposition catalyst.

[0019] The layered double metal hydroxide can be prepared by a co-precipitation method or a hydrothermal method to obtain a carrier precursor precipitate containing divalent and trivalent cations and having a hydrotalcite structure, and then filtered, washed and dried.

[0020] Optionally, in step (1), the drying temperature is 60 to 100° C., and the drying time is 2 to 10 hours.

[0021] Optionally, in step (2), the stirring time is 10 to 40 hours, the stirring temperature is 70 to 80°C, and the stirring rate is 50 to 200 rpm; the drying temperature is 60 to 100°C, and the drying time is 4 to 24 hours; the roasting temperature is 200 to 500°C, and the roasting time is 2 to 8 hours.

[0022] Optionally, the noble metal precursor is selected from at least one of palladium salt, silver salt, palladium chloride, and silver chloride.

[0023] Optionally, the noble metal precursor is selected from PdCl2, Na2PdCl4, (NH3)4PdCl2, Pd dissolved in aqua regia, 2+ Solution, silver nitrate, [Ag(NH3)2] + At least one of the complexing ion salts.

[0024] The concentration of the aqueous solution containing the noble metal precursor is determined according to the water absorption rate and the amount of the noble metal.

[0025] According to one aspect of the present invention, a monolithic ozone decomposition catalyst is provided. The monolithic ozone decomposition catalyst or the ozone decomposition catalyst prepared by the above preparation method is prepared by ball milling to prepare a slurry which is then coated on the surface of a honeycomb carrier to obtain the monolithic ozone decomposition catalyst.

[0026] The honeycomb carrier is a ceramic honeycomb carrier or a metal honeycomb carrier.

[0027] According to one aspect of the present invention, there is provided an ozone decomposition catalyst, an ozone decomposition catalyst prepared by the above preparation method, and an ozone decomposition catalyst having an overall structure. The ozone decomposition catalyst is prepared by the above preparation method and the above preparation method. The ozone decomposition catalyst is prepared by the above preparation method and the above preparation method. -1 , the reaction temperature is from room temperature to 250 ° C, and it is used in ozone decomposition;

[0028] The ozone conversion rate of the ozone decomposition catalyst is 100%.

[0029] As an embodiment of the present application, a method for preparing a noble metal confined ozone decomposition catalyst is carried out according to the following steps:

[0030] (1) Weigh a certain ratio of divalent and trivalent cation nitrates, hydrochlorides or carbonates and dissolve them in deionized water to prepare solution A; then add the solution to 100 ml of sodium hydroxide and sodium carbonate aqueous solution under vigorous stirring, and adjust the pH value to about 10.0; then, age the solution at 30-95° C. for 2-24 hours; filter the obtained precipitate, wash it with water until the pH value reaches about 7.0, and then dry it at 60-100° C. for 2-10 hours to obtain a hydrotalcite carrier precursor;

[0031] The hydrotalcite precursor can also be synthesized by a hydrothermal method. An organic amine such as hexamethylenetetramine or ethylenediamine is added to the above-prepared solution A, and the solution is treated for 0.5 to 2 hours under strong stirring and nitrogen bubbling conditions. The solution is then placed in a reactor at 120 to 180° C. and hydrothermally treated for 2 to 24 hours. The obtained precipitate is then filtered, washed, and dried in the same manner as above to obtain a hydrotalcite carrier precursor.

[0032] (2) dispersing the hydrotalcite carrier precursor prepared in (1) into a certain concentration of H2PdCl4 and / or AgNO3 aqueous solution, adding 0.1M dilute nitric acid to adjust the pH value of the solution to between 5 and 6.5, and then treating at 70 to 80°C with strong stirring for 10 to 40 hours, preferably 15 to 20 hours;

[0033] (3) Filter and wash the sample obtained in (2) until the pH value is about 7.0, and dry at 60-100°C for 4-24 hours;

[0034] (4) The sample prepared in (3) is calcined at 200-500° C. for 2-8 hours to obtain a noble metal confined ozone decomposition catalyst.

[0035] The ozone decomposition catalyst provided by the present invention can also be made into a slurry by ball milling, and then coated on the surface of a ceramic or metal honeycomb carrier, or other porous carrier to obtain a structured ozone decomposition catalyst.

[0036] The ozone decomposition catalyst provided by the present invention can be used for catalytic removal of ozone indoors, in aircraft cabins, and in catalytic wet ozone oxidation tail gas, and has excellent catalytic decomposition performance.

[0037] The present invention includes the following advantages:

[0038] 1. The ozone decomposition catalyst provided by the present invention has high ozone removal activity and stability under high space velocity and water-containing atmosphere.

[0039] 2. The ozone decomposition catalyst provided by the present invention has high catalytic ozone removal activity and can achieve complete ozone removal at room temperature.

[0040] 3. The ozone decomposition catalyst provided by the present invention has a high degree of dispersion of the noble metal and is evenly dispersed on the surface of the mesoporous metal oxide after CO chemical titration and transmission electron microscopy characterization.

[0041] 4. The ozone decomposition catalyst provided by the present invention, the noble metal and the metal oxide have a specific spatially confined structure. DETAILED DESCRIPTION

[0042] The present invention is described in detail below. The following are only preferred embodiments of the present invention and are not intended to limit the scope of the present invention. That is, all equivalent changes and modifications made within the scope of the present invention should fall within the scope of the present invention.

[0043] Example 1

[0044] Dissolve 10.905g (0.0375mol) Ni(NO3)2·6H2O and 4.47ml (0.0125mol) 50% manganese nitrate solution in deionized water to prepare 50ml aqueous solution A; then, dissolve 3.2g (0.08mol) NaOH and 1.325g (0.025mol) Na2CO3 in deionized water to prepare 50ml solution B. Then, under the condition of a 30℃ water bath, add solution A dropwise to solution B. After reacting for 24 hours, filter, wash with water until neutral, and dry at 60℃ for 18h to obtain Ni3Mn-LDH. Then, disperse the obtained hydrotalcite carrier in 10mg / ml Pd 2+0.1 M dilute nitric acid was added to the H2PdCl4 aqueous solution to adjust the pH value of the solution to 5.0, and then the solution was treated at 80°C and 150 rpm for 10 hours, filtered, washed, dried at 100°C for 10 hours, and calcined at 400°C for 4 hours to obtain a 1.0 wt% Pd / Ni3MnOx catalyst.

[0045] Example 2

[0046] Dissolve 10.905g (0.0375mol) Ni(NO3)2·6H2O and 4.47ml (0.0125mol) 50% manganese nitrate solution in deionized water to prepare 50ml aqueous solution A; then, dissolve 3.2g (0.08mol) NaOH and 1.325g (0.025mol) Na2CO3 in deionized water to prepare 50ml solution B. Then, under 60℃ water bath conditions, add solution A dropwise to solution B. After reacting for 24 hours, filter, wash with water until neutral, and dry at 60℃ for 18h to obtain Ni3Mn-LDH. Then, disperse the obtained hydrotalcite carrier into 20mg / ml Ag + 0.1 M dilute nitric acid was added to the AgNO3 aqueous solution to adjust the pH value of the solution to 6.0, and then the solution was treated at 80°C with strong stirring for 10 hours, filtered, washed, dried at 100°C for 10 hours, and calcined at 400°C for 4 hours to obtain a 2.0 wt% Ag / Ni3MnOx catalyst.

[0047] Example 3

[0048] Dissolve 9.058g (0.0375mol) of Cu(NO3)2·3H2O and 4.47ml (0.0125mol) of 50% manganese nitrate solution in deionized water to prepare 50ml of aqueous solution A. Then, dissolve 3.2g (0.08mol) of NaOH and 1.325g (0.025mol) of Na2CO3 in deionized water to prepare 50ml of solution B. Then, under the condition of a 30℃ water bath, solution A was added dropwise to solution B. After reacting for 48 hours, the mixture was filtered, washed with water until neutral, and dried at 60℃ for 18h to obtain Cu3Mn-LDH. Then, the obtained hydrotalcite carrier was dispersed in 10mg / ml Pd 2+ 0.1 M dilute nitric acid was added to the H2PdCl4 aqueous solution to adjust the pH value of the solution to 6.5, and then the solution was treated at 70°C with strong stirring for 20 hours, filtered, washed, dried at 100°C for 10 hours, and calcined at 400°C for 2 hours to obtain a 1.0 wt% Pd / Cu3MnOx catalyst.

[0049] Example 4

[0050] Dissolve 10.905g (0.0375mol) Ni(NO3)2·6H2O and 5.05g (0.0125mol) ferric nitrate nonahydrate in deionized water to prepare 50ml of aqueous solution A; then, dissolve 3.2g (0.08mol) NaOH and 1.325g (0.025mol) Na2CO3 in deionized water to prepare 50ml of solution B. Then, under the condition of 80℃ water bath, add solution A dropwise to solution B. After reacting for 48 hours, filter, wash with water until neutral, and dry at 80℃ for 24h to obtain Ni3Fe-LDH. Then, disperse the obtained hydrotalcite carrier in 10mg / ml Pd 2+ 0.1 M dilute nitric acid was added to the H2PdCl4 aqueous solution to adjust the pH value of the solution to 6.0, and then the solution was treated at 80°C with strong stirring for 24 hours, filtered, washed, dried at 100°C for 10 hours, and calcined at 400°C for 3 hours to obtain a 1.0 wt% Pd / Ni3FeOx catalyst.

[0051] Example 5

[0052] 3.019g (0.0125mol) Cu(NO3)2·3H2O and 4.988ml (0.0125mol) Co(NO3)2·6H2O were dissolved in deionized water to prepare 50ml of aqueous solution A; then, 3.2g (0.08mol) NaOH and 1.325g (0.025mol) Na2CO3 were dissolved in deionized water to prepare 50ml of solution B. Then, solution A was added dropwise to solution B in a 30℃ water bath. After reacting for 48 hours, the mixture was filtered, washed with water until neutral, and dried at 60℃ for 18h to obtain CuCo-LDH. Then, the obtained hydrotalcite carrier was dispersed in 10mg / ml Pd 2+ 0.1 M dilute nitric acid was added to the H2PdCl4 aqueous solution to adjust the pH value of the solution to 6.0, and then the solution was treated at 80°C with strong stirring for 20 hours, filtered, washed, dried at 100°C for 20 hours, and calcined at 450°C for 2 hours to obtain a 1.0 wt% Pd / CuCoOx catalyst.

[0053] Comparative Example 1

[0054] Dissolve 10.905g (0.0375mol) Ni(NO3)2·6H2O and 5.05g (0.0125mol) ferric nitrate nonahydrate in deionized water to prepare 50ml aqueous solution A; then, dissolve 3.2g (0.08mol) NaOH and 1.325g (0.025mol) Na2CO3 in deionized water to prepare 50ml solution B. Then, under 80℃ water bath conditions, add solution A dropwise to solution B. After reacting for 48 hours, filter, wash with water until neutral, and dry at 80℃ for 24h to obtain Ni3Fe-LDH. Then, impregnate 10mg / ml Pd on Ni3Fe-LDH by equal volume impregnation method. 2+ The H2PdCl4 aqueous solution was dried at 100℃ for 10 hours and then calcined at 400℃ for 3 hours to prepare a 1.0wt% Pd / Ni3FeOx-JZ catalyst.

[0055] Comparative Example 2

[0056] 10.905g (0.0375mol) of Ni(NO3)2·6H2O and 4.47ml (0.0125mol) of 50% manganese nitrate solution were dissolved in deionized water to prepare 50ml of solution A. Then, 3.2g (0.08mol) of NaOH and 1.325g (0.025mol) of Na2CO3 were dissolved in deionized water to prepare 50ml of solution B. Solution A was then added dropwise to solution B in a 30°C waterbath. After reacting for 24 hours, the mixture was filtered, washed with water until neutral, and dried at 60°C for 18 hours to produce Ni3Mn-LDH. The Ni3Mn-LDH was calcined at 400°C for 4 hours to produce Ni3MnOx, which was then impregnated with 1% Pd via an equal volume impregnation method to produce a 1.0wt% Pd / Ni3MnOx-JZ catalyst.

[0057] Test Case

[0058] Examples 1 to 5 and Comparative Examples 1 to 2 were placed in an ozone environment and reacted for 100 hours, and the ozone decomposition efficiency was calculated.

[0059] Ozone decomposition efficiency % = (inlet ozone concentration - outlet ozone concentration) / inlet ozone concentration

[0060] Catalyst evaluation conditions: The reaction gas is air as the balance gas, with an ozone concentration of 15±1ppm; in a dry atmosphere, the temperature is 30°C, the relative humidity is <5% RH, and the air velocity is 600Lg -1 h -1 , catalyst dosage 0.15g; in humid atmosphere, temperature 30℃, relative humidity>90%RH, space velocity 600Lg -1 h -1 , catalyst dosage 0.15g.

[0061] Table 1. Comparison of ozone decomposition performance of different examples and comparative examples

[0062]

[0063]

[0064] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A noble metal confined ozone decomposition catalyst, characterized in that: The ozone decomposition catalyst uses a bimetallic oxide as a carrier, and the carrier carries a limited domain of Pd 2+ and / or Ag + ; The Pd 2+ The loading amount accounts for 0.01% to 10% of the weight of the ozone decomposition catalyst; the Ag + The loading amount accounts for 0.1% to 20% of the weight of the ozone decomposition catalyst; The ozone decomposition catalyst has a pore, and the pore is a mesoporous structure of 2 to 50 nm; The bimetallic oxide comprises divalent metal cations and trivalent metal cations; The divalent metal cation is selected from Ni 2+ 、Fe 2+ 、Cu 2+ 、Mn 2+ 、Co 2+ At least one of; the trivalent metal cation is selected from Fe 3+ 、Mn 3+ 、Co 3+ At least one of .

2. A method for preparing the ozone decomposition catalyst according to claim 1, characterized in that: By intercalating the precious metal Pd between the support precursor layers 2+ and / or Ag + , preparing a noble metal confined catalyst precursor, and calcining it to obtain the ozone decomposition catalyst; The carrier precursor is layered double hydroxide (LDH).

3. The preparation method according to claim 2, characterized in that The following steps are involved: (1) Obtaining a layered double hydroxide, i.e., a support precursor; (2) Dispersing the carrier precursor into an aqueous solution containing a noble metal precursor, adjusting the solution pH to 5-6.5, stirring, filtering, washing, drying, and calcining to obtain a noble metal confined ozone decomposition catalyst.

4. The preparation method according to claim 3, characterized in that The carrier precursor is dried before intercalation but not calcined.

5. The preparation method according to claim 3, characterized in that In step (1), the drying temperature is 60~100 o C, drying time is 2 to 10 hours.

6. The preparation method according to claim 3, characterized in that In step (2), the stirring time is 10 to 40 hours, and the stirring temperature is 70 to 80 o C, the stirring rate is 50~200 rpm; the drying temperature is 60~100 o C, the drying time is 4 to 24 hours; the calcination temperature is 200 to 500 o C, the roasting time is 2 to 8 hours.

7. The preparation method according to claim 3, characterized in that The noble metal precursor is selected from at least one of palladium salt and silver salt.

8. An integral structure ozone decomposition catalyst, characterized in that: The ozone decomposition catalyst according to claim 1 or the ozone decomposition catalyst prepared by the preparation method according to any one of claims 2 to 7 is ball-milled to prepare a slurry which is then coated on the surface of a honeycomb carrier to obtain the monolithic ozone decomposition catalyst.

9. The ozone decomposition catalyst according to claim 1, the ozone decomposition catalyst prepared by the preparation method according to any one of claims 2 to 7, and the monolithic ozone decomposition catalyst according to claim 8 are capable of performing the following steps: -1 The reaction temperature is from room temperature to 250 o C, application in ozone decomposition.

10. The use according to claim 9, characterized in that The ozone conversion rate of the ozone decomposition catalyst is 100%.

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