A catalyst for catalytic oxidation of vocs and its preparation method and application

Abstract

The application provides a catalyst for catalytic oxidation of VOCs and a preparation method and application thereof. The preparation method comprises the following steps: performing primary roasting on a catalyst carrier to obtain a roasting product, mixing the roasting product, a platinum source and nitric acid, and performing secondary roasting to obtain the catalyst. In the preparation method of the catalyst, nitric acid is added to remove hydroxyl groups on the surface of platinum species, so that the platinum species is converted into hydroxyl-free platinum oxide, which is beneficial to catalytic oxidation of volatile organic compounds. The preparation method has simple process operation, and the prepared catalyst has excellent catalytic efficiency and can efficiently oxidize volatile organic compounds, so that the catalyst can be applied to various fields containing volatile organic compounds and has good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of resource and environmental technology, specifically relating to a catalyst for the catalytic oxidation of VOCs, its preparation method, and its application. Background Technology

[0002] VOCs are a wide variety of substances, mainly including benzene, toluene, and xylene, chlorobenzene, trichloroethylene, and ethyl acetate. Long-term exposure to environments with excessive VOCs can cause chronic poisoning, damaging the liver, kidneys, and nervous system. Furthermore, high concentrations of VOCs under sunlight can form photochemical smog, contributing to global warming. Therefore, strictly controlling VOC emissions is a current hot research topic.

[0003] In existing technologies, catalytic oxidation is highly suitable for purifying mixed waste gas containing multiple VOCs at relatively low temperatures (150-500℃), decomposing VOCs into harmless small molecules such as carbon dioxide and water. However, existing methods suffer from cumbersome preparation steps and high Pt loading requirements.

[0004] Therefore, how to simplify the process operation, reduce the Pt loading, and improve the catalytic efficiency of the catalyst so that it can be applied to various fields containing volatile organic compounds is a technical problem that urgently needs to be studied. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a catalyst for the catalytic oxidation of VOCs, its preparation method, and its applications. In the catalyst preparation method, nitric acid is added to remove the hydroxyl groups on the surface of platinum species, thereby transforming the platinum species into hydroxyl-free platinum oxide, which is beneficial for the catalytic oxidation of volatile organic compounds. This preparation method is simple to operate, with a Pt loading as low as 0.1%, and the prepared catalyst exhibits excellent catalytic efficiency, effectively oxidizing volatile organic compounds. It can be applied in various fields containing volatile organic compounds and has good application prospects. To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a catalyst for the catalytic oxidation of VOCs, the preparation method comprising the following steps:

[0007] The catalyst support is calcined once to obtain a calcined product. Then, the calcined product, platinum source, and nitric acid are mixed and calcined a second time to obtain the catalyst.

[0008] This invention incorporates nitric acid into the catalyst preparation method, which removes the hydroxyl groups on the surface of platinum species, thereby transforming the platinum species into hydroxyl-free platinum oxide, which is beneficial for the catalytic oxidation of volatile organic compounds. This preparation method is simple to operate, and the resulting catalyst exhibits excellent catalytic efficiency, effectively oxidizing volatile organic compounds. It can be applied in various fields containing volatile organic compounds and has promising application prospects.

[0009] In this invention, the purpose of calcining the catalyst support once is to remove impurity components adsorbed on the surface of the support.

[0010] As a preferred embodiment of the present invention, the catalyst support comprises a TiO2 support.

[0011] Preferably, the first firing is carried out in an air atmosphere.

[0012] Preferably, the temperature of the first roasting is 200-700℃, for example, 200℃, 300℃, 400℃, 500℃, 600℃ or 700℃, and the time is 2-5h, for example, 2h, 3h, 4h or 5h.

[0013] In this invention, if the initial calcination temperature is too low, impurities on the surface of the support will affect the loading state of the platinum source, thereby affecting the oxidation activity of the catalyst for volatile organic compounds; if the initial calcination temperature is too high, the crystal structure of the support will change, affecting the loading state of the platinum source, thereby affecting the oxidation activity of the catalyst for volatile organic compounds.

[0014] As a preferred embodiment of the present invention, the platinum source includes platinum tetraamminenitrate.

[0015] Preferably, the volume ratio of the platinum source to nitric acid is (200-1000):(50-500), wherein the platinum source is selected in the range of "200-1000", for example, 200 μL, 500 μL, 600 μL or 1000 μL, etc., and the nitric acid is selected in the range of "50-500", for example, 50 μL, 100 μL, 150 μL, 200 μL, 350 μL or 500 μL, etc., preferably (500-1000):(200-400).

[0016] In this invention, if the volume ratio of platinum source to nitric acid is too small, i.e., the amount of nitric acid used is too large, the platinum species will agglomerate to a large extent, which is not conducive to the effective utilization of active sites; if the volume ratio of platinum source to nitric acid is too large, i.e., the amount of nitric acid used is too small, the hydroxyl groups on the surface of platinum species cannot be effectively removed, which is not conducive to improving the oxidation activity of the catalyst.

[0017] As a preferred technical solution of the present invention, the mixing method includes:

[0018] A platinum source, nitric acid, and solvent are mixed to obtain a mixed solution, which is then blended with the calcined product.

[0019] Preferably, the solvent includes water, such as deionized water or pure water.

[0020] Preferably, the blending process is accompanied by stirring and ultrasound.

[0021] Preferably, the blending time is 5-20 minutes, for example, 5 minutes, 10 minutes, 15 minutes or 20 minutes.

[0022] As a preferred technical solution of the present invention, before the secondary roasting, the product obtained by mixing the roasting product, platinum source and nitric acid is subjected to primary heating and secondary heating treatment.

[0023] In this invention, the purpose of the first-stage heating is to detach the sample and facilitate its removal, while the purpose of the second-stage heating is to dry the sample.

[0024] Preferably, the temperature of the first-stage heating is 50-80℃, for example, it can be 50℃, 60℃, 70℃ or 80℃.

[0025] It should be noted that the present invention does not limit the time of the first-stage heating, as long as it is sufficient to allow the sample to detach.

[0026] Preferably, the temperature of the secondary heating is 60-90℃, for example, 60℃, 70℃, 80℃ or 90℃, and the time is 2-6h, for example, 2h, 3h, 4h, 5h or 6h.

[0027] As a preferred embodiment of the present invention, the secondary calcination is carried out in an air atmosphere.

[0028] Preferably, the temperature of the secondary roasting is 200-700℃, for example, 200℃, 300℃, 400℃, 500℃, 600℃ or 700℃, and the time is 2-3h, for example, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h.

[0029] In this invention, if the secondary calcination temperature is too low, active platinum oxide cannot be formed; if the secondary calcination temperature is too high, the state and properties of the active oxide will change, affecting the oxidation activity of the catalyst.

[0030] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0031] (1) The TiO2 support was calcined at 200-700℃ for 2-5 hours in an air atmosphere to obtain the calcined product;

[0032] (2) Mix the platinum source, nitric acid and water evenly to obtain a mixed solution. Then mix the mixed solution with the calcined product, and stir while sonicating for 5-20 minutes. Then perform a first-stage heating at 50-80℃ and a second-stage heating at 60-90℃ for 2-6 hours to obtain the heated product.

[0033] (3) The heated product is subjected to secondary roasting in an air atmosphere at a temperature of 200-700℃ for 2-3 hours to obtain the secondary roasted product.

[0034] In a second aspect, the present invention provides a catalyst for the catalytic oxidation of VOCs, wherein the catalyst is prepared by the preparation method described in the first aspect;

[0035] The catalyst includes a support and an active component, wherein the active component is an oxide of platinum.

[0036] As a preferred embodiment of the present invention, the loading of the active component is 0.1-0.5%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc.

[0037] Thirdly, the present invention provides the application of a catalyst for the catalytic oxidation of VOCs as described in the second aspect, wherein the catalyst is used for the catalytic oxidation of VOCs.

[0038] It should be noted that the present invention does not limit the types of VOCs catalytically oxidized by the catalyst. For example, they may be benzene, toluene, xylene, chlorobenzene, trichloroethylene, and ethyl acetate.

[0039] Preferably, the method of applying the catalyst to the catalytic oxidation of VOCs includes:

[0040] The catalyst is placed in a reactor in a mixed gas mixture for a fixed-bed reaction.

[0041] Preferably, the mixed gas contains 100-1000 ppm (e.g., 100 ppm, 500 ppm, or 1000 ppm, etc.) of benzene compounds, such as benzene, toluene, xylene, or chlorobenzene.

[0042] Preferably, the reaction temperature of the fixed-bed reaction is 100-250℃, for example, it can be 100℃, 150℃, 200℃ or 250℃.

[0043] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention incorporates nitric acid into the catalyst preparation method, which removes the hydroxyl groups on the surface of platinum species, thereby transforming the platinum species into hydroxyl-free platinum oxide, which is beneficial for the catalytic oxidation of volatile organic compounds. This preparation method is simple to operate, and the resulting catalyst exhibits excellent catalytic efficiency, effectively oxidizing volatile organic compounds. It can be applied in various fields containing volatile organic compounds and has promising application prospects. Attached Figure Description

[0046] Figure 1 The XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 of this invention are compared with those of the TiO2 support.

[0047] Figure 2 This is an electron microscope image of the catalyst prepared in Example 1 of this invention.

[0048] Figure 3 This is an electron microscope image of the catalyst prepared in Comparative Example 1 of this invention. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0050] Example 1

[0051] This embodiment provides a method for preparing a catalyst for the catalytic oxidation of VOCs, the preparation method comprising the following steps:

[0052] (1) The TiO2 support was calcined at 550℃ for 3 hours in an air atmosphere to obtain the calcined product.

[0053] (2) Mix 1000 μL of tetraammine nitrate platinum, 350 μL of nitric acid and 5 mL of water evenly to obtain a mixed solution. Then, add the mixed solution dropwise to the calcined product. After sonicating and stirring for 10 min, perform a first heating at 80 °C and a second heating at 80 °C for 5 h to obtain the heated product.

[0054] The volume ratio of platinum source to nitric acid is 1000:350.

[0055] (3) The heated product is subjected to a second calcination in an air atmosphere at a temperature of 500°C for 2 hours to obtain the catalyst.

[0056] This embodiment also provides a catalyst prepared by the above preparation method. The catalyst includes a support and an active component. The active component is platinum oxide, the support is TiO2, and the loading of the active component is 0.5%.

[0057] Figure 2 The electron microscope image of the catalyst prepared in this embodiment is shown. As can be seen from the figure, Pt is uniformly loaded on the catalyst surface and the Pt species particles are aggregated.

[0058] Example 2

[0059] This embodiment provides a method for preparing a catalyst for the catalytic oxidation of VOCs, the preparation method comprising the following steps:

[0060] (1) The TiO2 support was calcined at 200℃ for 5 hours in an air atmosphere to obtain the calcined product;

[0061] (2) Mix 1000 μL of tetraammine nitrate platinum, 200 μL of nitric acid and 3 mL of water evenly to obtain a mixed solution. Then, add the mixed solution dropwise to the calcined product. After sonicating and stirring for 5 min, perform a first heating at 50 °C and a second heating at 60 °C for 6 h to obtain the heated product.

[0062] The volume ratio of platinum source to nitric acid is 1000:200.

[0063] (3) The heated product is subjected to a second calcination in an air atmosphere at a temperature of 200°C for 3 hours to obtain the catalyst.

[0064] This embodiment also provides a catalyst prepared by the above preparation method. The catalyst includes a support and an active component. The active component is platinum oxide, the support is TiO2, and the loading of the active component is 0.5%.

[0065] Example 3

[0066] This embodiment provides a method for preparing a catalyst for the catalytic oxidation of VOCs, the preparation method comprising the following steps:

[0067] (1) The TiO2 support was calcined at 700℃ for 2 hours in air atmosphere to obtain the calcined product;

[0068] (2) Mix 1000 μL of tetraammine nitrate platinum, 400 μL of nitric acid and 1 mL of water evenly to obtain a mixed solution. Then, add the mixed solution dropwise to the calcined product. After sonicating and stirring for 20 min, perform a first heating at 80 °C and a second heating at 90 °C for 2 h to obtain the heated product.

[0069] The volume ratio of platinum source to nitric acid is 1000:400.

[0070] (3) The heated product is subjected to a second calcination in an air atmosphere at a temperature of 700°C for 2 hours to obtain the catalyst.

[0071] This embodiment also provides a catalyst prepared by the above preparation method. The catalyst includes a support and an active component. The active component is platinum oxide, the support is TiO2, and the loading of the active component is 0.5%.

[0072] Example 4

[0073] The difference between this embodiment and Example 1 is that the amount of tetraammineplatinum nitrate added is adjusted so that the loading of the active component in the prepared catalyst is 0.1%.

[0074] The remaining preparation methods and parameters are consistent with those in Example 1.

[0075] Example 5

[0076] The difference between this embodiment and Example 1 is that the amount of tetraammineplatinum nitrate added is adjusted so that the loading of the active component in the prepared catalyst is 0.2%.

[0077] The remaining preparation methods and parameters are consistent with those in Example 1.

[0078] Example 6

[0079] The difference between this embodiment and Example 1 is that the amount of tetraammineplatinum nitrate added is adjusted so that the loading of the active component in the prepared catalyst is 0.3%.

[0080] The remaining preparation methods and parameters are consistent with those in Example 1.

[0081] Example 7

[0082] The difference between this embodiment and Example 1 is that the amount of tetraammineplatinum nitrate added is adjusted so that the loading of the active component in the prepared catalyst is 0.4%.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Example 8

[0085] The difference between this embodiment and embodiment 1 is that the temperature of the first roasting in step (1) is 350°C.

[0086] The remaining preparation methods and parameters are consistent with those in Example 1.

[0087] Example 9

[0088] The difference between this embodiment and embodiment 1 is that the amount of nitric acid added in step (2) is 50 μL.

[0089] The remaining preparation methods and parameters are consistent with those in Example 1.

[0090] Example 10

[0091] The difference between this embodiment and embodiment 1 is that the amount of nitric acid added in step (2) is 200 μL.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 11

[0094] The difference between this embodiment and embodiment 1 is that the temperature of the first roasting in step (1) is 150°C.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Example 12

[0097] The difference between this embodiment and embodiment 1 is that the temperature of the first roasting in step (1) is 750°C.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Example 13

[0100] The difference between this embodiment and embodiment 1 is that the volume ratio of platinum source to nitric acid in step (2) is 200:1000.

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Example 14

[0103] The difference between this embodiment and embodiment 1 is that the volume ratio of platinum source to nitric acid in step (2) is 1000:20.

[0104] The remaining preparation methods and parameters are consistent with those in Example 1.

[0105] Example 15

[0106] The difference between this embodiment and embodiment 1 is that the temperature of the second roasting in step (3) is 150°C.

[0107] The remaining preparation methods and parameters are consistent with those in Example 1.

[0108] Example 16

[0109] The difference between this embodiment and embodiment 1 is that the temperature of the second roasting in step (3) is 750°C.

[0110] The remaining preparation methods and parameters are consistent with those in Example 1.

[0111] Comparative Example 1

[0112] The difference between this comparative example and Example 1 is that nitric acid is not added in step (2).

[0113] The remaining preparation methods and parameters are consistent with those in Example 1.

[0114] Figure 1 The XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 with the TiO2 support are shown. As can be seen from the figure, the platinum species on the prepared catalysts are highly dispersed on the catalyst surface.

[0115] Figure 3 Electron micrographs of the catalysts prepared in this comparative example are shown. As can be seen from the figure, the platinum species particles on the surface of the catalyst prepared without nitric acid are smaller.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 4 is that nitric acid is not added in step (2).

[0118] The remaining preparation methods and parameters are consistent with those in Example 4.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 5 is that nitric acid is not added in step (2).

[0121] The remaining preparation methods and parameters are consistent with those in Example 5.

[0122] Comparative Example 4

[0123] The difference between this comparative example and Example 6 is that nitric acid is not added in step (2).

[0124] The remaining preparation methods and parameters are consistent with those in Example 6.

[0125] Comparative Example 5

[0126] The difference between this comparative example and Example 7 is that nitric acid is not added in step (2).

[0127] The remaining preparation methods and parameters are consistent with those in Example 7.

[0128] Performance testing

[0129] The catalysts prepared in the above examples and comparative examples were subjected to a fixed-bed reaction. The mixed gas contained 500 ppm toluene, the space velocity was 24000 mL / (g·h), and the reaction was tested at a temperature of 100℃-500℃. The concentrations of VOCs in the gas at the reactor inlet and outlet were measured, and the conversion rate was calculated as (reactor inlet VOCs concentration - reactor outlet VOCs concentration) / (reactor inlet VOCs concentration) × 100%. The temperature required for a VOCs conversion rate of 90% (denoted as T) was used. 90% To evaluate the effect of catalysts on the oxidation of VOCs.

[0130] The test results are shown in Table 1.

[0131] Table 1

[0132]

[0133]

[0134] analyze:

[0135] As shown in the table above, the addition of nitric acid in the catalyst preparation method of this invention removes the hydroxyl groups on the surface of platinum species, thereby forming hydroxyl-free platinum oxide, which is beneficial for the catalytic oxidation of volatile organic compounds. This preparation method is simple to operate, and the resulting catalyst exhibits excellent catalytic efficiency, effectively oxidizing volatile organic compounds. It can be applied in various fields containing volatile organic compounds and has good application prospects.

[0136] The data results from Examples 1 and 11-12 show that if the initial calcination temperature is too low, impurities on the surface of the support cannot be effectively removed, resulting in a decrease in the oxidation activity of the catalyst; if the initial calcination temperature is too high, the crystal structure of the support may change, resulting in a decrease in the oxidation activity of the catalyst.

[0137] The data from Examples 1 and 13-14 show that if the volume ratio of platinum source to nitric acid is too small, i.e., the amount of nitric acid is too large, the platinum species on the catalyst surface will excessively aggregate, resulting in the ineffective utilization of platinum species and a decrease in catalyst oxidation activity. If the volume ratio of platinum source to nitric acid is too large, i.e., the amount of nitric acid is too small, the platinum species cannot be completely converted into effective PtO. x This leads to a decrease in the oxidation activity of the catalyst.

[0138] The data from Examples 1 and 15-16 show that if the secondary calcination temperature is too low, platinum species cannot be converted into effective PtO. x This leads to a decrease in the oxidation activity of the catalyst; if the secondary calcination temperature is too high, the state and properties of the platinum species will change, leading to a decrease in the oxidation activity of the catalyst.

[0139] The data from Examples 1 and 1, 4 and 2, 5 and 3, 6 and 4, and 7 and 5 show that effective PtO cannot be formed without the addition of nitric acid. x This leads to a decrease in the oxidation activity of the catalyst.

[0140] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a catalyst for the catalytic oxidation of VOCs, characterized in that, The preparation method includes the following steps: The catalyst support is calcined once to obtain the calcined product. Then, the calcined product, platinum source and nitric acid are mixed and calcined a second time to obtain the catalyst. The volume ratio of the platinum source to nitric acid is 1000:(200-400); The catalyst comprises a support and an active component, wherein the active component is a platinum oxide and the loading of the active component is 0.1-0.5%. The catalyst support includes a TiO2 support; The first roasting is carried out in an air atmosphere; the temperature of the first roasting is 200-700℃, and the time is 2-5 hours. The platinum source includes platinum tetraamminenitrate; The secondary roasting is carried out in an air atmosphere; the temperature of the secondary roasting is 200-700℃, and the time is 2-3 hours.

2. The preparation method according to claim 1, characterized in that, The mixing methods include: A platinum source, nitric acid, and solvent are mixed to obtain a mixed solution, which is then blended with the calcined product.

3. The preparation method according to claim 2, characterized in that, The blending process is accompanied by stirring and ultrasound.

4. The preparation method according to claim 2, characterized in that, The blending time is 5-20 minutes.

5. The preparation method according to claim 1, characterized in that, Before the secondary roasting, the product obtained by mixing the roasting product, platinum source and nitric acid is subjected to primary heating and secondary heating treatment.

6. The preparation method according to claim 5, characterized in that, The temperature of the first-stage heating is 50-80℃.

7. The preparation method according to claim 5, characterized in that, The secondary heating temperature is 60-90℃, and the time is 2-6 hours.

8. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) The TiO2 support was calcined at 200-700℃ for 2-5 hours in an air atmosphere to obtain the calcined product; (2) Mix the platinum source, nitric acid and water evenly to obtain a mixed solution. Then mix the mixed solution with the calcined product, and stir while sonicating for 5-20 minutes. Then perform a first-stage heating at 50-80℃ and a second-stage heating at 60-90℃ for 2-6 hours to obtain the heated product. (3) The heated product is subjected to secondary roasting in an air atmosphere at a temperature of 200-700℃ for 2-3 hours to obtain the secondary roasted product.

9. A catalyst for the catalytic oxidation of VOCs, characterized in that, The catalyst is prepared using the preparation method according to any one of claims 1-8; The catalyst comprises a support and an active component, wherein the active component is a platinum oxide and the loading of the active component is 0.1-0.5%.

10. The application of the catalyst for the catalytic oxidation of VOCs as described in claim 9, characterized in that, The catalyst is used for the catalytic oxidation of VOCs.

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