Preparation method of TiO2-MnOx-CeOx catalyst for catalytic ozonation

Abstract

The invention discloses a preparation method of a TiO2-MnOx-CeOx catalyst, which comprises the following steps: generating a turbid solution containing a Ce (OH) CO3 solid by using a water-soluble cerium salt and urea, and adding a water-soluble titanium salt into the turbid solution for precipitation reaction to prepare a TiO2 doped solid product; dispersing the solid product in pure water, adding a permanganate solution, and carrying out an oxidation-reduction reaction; wherein residual Ce (OH) CO3 in a reaction system is removed by using a dilute acid solution. The method for preparing the catalyst is simple, raw materials are easy to obtain, doping of multiple metal elements can be achieved, then the catalytic performance of the catalyst is regulated and controlled, and ozone oxidation of volatile organic compounds is efficiently catalyzed.

Description

Technical Field

[0001] The present invention relates to the field of environmental technologies, and particularly to a preparation method of a TiO 2 -MnO x -CeO x catalyst for catalytic ozonation. Background Art

[0002] Volatile organic compounds (VOCs) refer to substances with a boiling point below 260 °C at normal temperature and pressure. Most VOCs are toxic, volatile, and potentially carcinogenic. Once they enter the environment, they will pollute the soil, water bodies, and atmosphere, thereby threatening the balance of the ecosystem and human health. Therefore, reducing VOC emissions is not only a basic requirement for improving air quality and ensuring human health but also an urgent need for the sustainable development of social economy.

[0003] As an advanced oxidation technology, catalytic ozonation technology shows unique advantages in treating refractory organic pollutants. In the presence of a catalyst, ozone decomposes to generate reactive oxygen species, reducing the reaction activation energy and enabling efficient removal of VOCs at low temperatures.

[0004] Currently, non-noble metals (Ti, Mn, and Ce) and their composite oxides have been widely used in catalytic ozonation for VOC removal due to their low cost and good thermal stability. For example, CN113648992A discloses a preparation method of a mesoporous manganese-cerium solid solution catalyst, and the catalyst prepared by this method can significantly improve the removal rate of dichloroethane and CO 2 selectivity. CN112495371B discloses a preparation method of a mesoporous manganese dioxide catalyst for catalytic ozonation of VOCs, which can remove toluene at low temperatures with the assistance of ozone. In addition, CN113101920A and CN115254161A each disclose a catalyst for catalytic ozonation of VOCs and its preparation method, which can achieve efficient degradation of VOCs at low temperatures. In fact, many composite metal oxides show high activity and stability in degrading VOCs due to the formation of a solid solution structure under the synergistic effect of ozone. The present invention uses a simple redox reaction to prepare a TiO 2 -MnO x -CeO x catalyst for catalytic ozonation of VOCs. The advantages are that the preparation method is simple, no calcination is required, it has the potential for industrial production, it can efficiently degrade VOCs at low temperatures, and oxidize them into CO 2 and H 2 O, and ozone can be completely decomposed by the catalyst without causing secondary pollution. Summary of the Invention

[0005] The present invention discloses a preparation method of a TiO 2 -MnO x -CeO x catalyst for catalytic ozonation, aiming to improve the deep oxidation of ozone to VOCs and further degrade VOCs into CO 2 and H 2 O and other harmless substances.

[0006] The preparation method of the TiO 2 -MnO x -CeO x catalyst for catalytic ozonation according to the present invention includes the following steps:

[0007] (1) Dissolve a water-soluble cerium salt and urea in water to form a mixed solution, heat and stir in a water bath at 60 - 90 °C for 5 - 10 h. The cerium salt and the precipitant urea react under heating conditions to gradually form a turbid solution containing the intermediate Ce(OH)CO 3 . The cerium salt is one or more of cerium nitrate, cerium chloride, cerium sulfate and cerium acetate, preferably cerium nitrate. The molar ratio of the cerium salt to urea is 1:4 - 1:8.

[0008] (2) Add a water-soluble titanium salt to the turbid solution prepared in step (1), continue to heat and stir in a water bath at 60 - 90 °C for 15 - 20 h. The titanium salt and urea undergo a precipitation reaction, and the titanium-containing precipitate gradually transforms into TiO 2 under heating conditions. After the reaction is completed, filter and wash with pure water to obtain a filter cake, and prepare a TiO 2 -doped solid product. The soluble titanium salt is one or more of titanium sulfate, titanium oxysulfate and titanium tetrachloride, preferably titanium oxysulfate. The molar ratio of the titanium salt to the cerium salt is 1:5 - 1:20.

[0009] (3) Disperse the filter cake obtained in step (2) in pure water, add a permanganate solution, heat and stir in a water bath at 60 - 90 °C for 10 - 15 h. The permanganate and Ce(OH)CO 3 undergo a redox reaction. After the reaction is completed, a titanium-doped manganese and cerium composite oxide solid is formed. Filter and wash with pure water to obtain a filter cake, and prepare a TiO 2 -MnO x -CeO x precursor. The permanganate is one or both of potassium permanganate and sodium permanganate, preferably potassium permanganate. The molar ratio of the permanganate to the cerium salt is 1:5 - 1:10.

[0010] (4) The TiO 2 -MnO x -CeO xThe precursor is dispersed in pure water, and a 0.5 - 1 mol / L dilute acid solution is used to remove the residual Ce(OH)CO 3 , and after filtration, the filter cake is washed with pure water and dried at 60 - 100 °C for 12 - 20 h to obtain the TiO 2 -MnO x -CeO x catalyst. The dilute acid is one or more of nitric acid, sulfuric acid, acetic acid, and oxalic acid, preferably dilute nitric acid.

[0011] The present invention prepares the TiO 2 -MnO x -CeO x catalyst through a simple redox reaction. Its XRD pattern shows that there is only the cerium dioxide crystal phase in this material, and the transmission electron microscope image shows that this material is a flaky structure. By performing energy spectrum surface scanning analysis on it, it can be found that the Ti element appears uniformly in the entire flaky area, indicating that TiO 2 has been successfully doped into the catalyst. The method provided by the present invention does not require calcination, the raw materials are inexpensive, the prepared catalyst has good mechanical and chemical stability, high catalytic activity for ozone oxidation of VOCs, and the VOCs degradation rate and CO 2 selectivity can both reach over 90%.

[0012] The TiO 2 -MnO x -CeO x catalyst is found through a large number of practices that by adding different contents of water-soluble titanium salts, TiO 2 -MnO x -CeO x catalysts with different catalytic performances can be obtained, and these are used as different implementation schemes. Description of the Drawings

[0013] Figure 1 is the result of XRD characterization analysis of the product prepared in Example 1;

[0014] Figure 2 is the result of TEM characterization analysis of the product prepared in Example 1;

[0015] Figure 3 is the result of energy spectrum surface scanning analysis of the product prepared in Example 1;

[0016] Figure 4 is the test result of catalytic ozone oxidation of VOCs by the product prepared in Example 1;

[0017] Figure 5 is the test result of catalytic ozone oxidation of VOCs by the product prepared in Example 2;

[0018] Figure 6 These are the test results of the product prepared in Example 3 for catalytic ozonation of VOCs. Detailed implementation mode

[0019] The following examples are used to illustrate the present invention, but do not limit the scope of the present invention.

[0020] Example 1

[0021] This example provides a method for synthesizing a TiO 2 -MnO x -CeO x catalyst, specifically as follows:

[0022] (1) Take 7.0 g of cerium nitrate, mix cerium nitrate with urea in a molar ratio of 1:6, add 300 mL of pure water to prepare a mixed solution, and heat and stir in a water bath at 85 °C for 6 h.

[0023] (2) Add titanium oxysulfate to the above mixed solution in a molar ratio of 1:5 to cerium nitrate, and heat and stir in a water bath at 85 °C for 18 h.

[0024] (3) Perform solid-liquid separation and washing on the product obtained in step (2), collect the product, and obtain a solid product doped with TiO 2 .

[0025] (4) Disperse the product obtained in step (3) with pure water, make up the volume to 100 mL, add a 0.06 mol / L potassium permanganate solution, and determine the addition amount of potassium permanganate according to a molar ratio of 1:10 to cerium nitrate. Heat and stir in a water bath at 85 °C until there is no permanganate ion in the solution.

[0026] (5) Perform solid-liquid separation on the product obtained in step (4), disperse the solid product in 50 mL of pure water, add 50 mL of 1 mol / L dilute nitric acid solution to remove the residual Ce(OH)CO 3 .

[0027] (6) Perform solid-liquid separation and washing on the product obtained in step (5), and dry at 60-100 °C for 12-20 h to prepare a TiO 2 -MnO x -CeO x catalyst.

[0028] (7) Load 150 mg of TiO 2 -MnO x -CeO x catalyst into a fixed-bed reactor to test the performance of the catalyst. Set the gas flow rate to 100 mL / min, the inlet concentration of the pollutant dichloroethane to 105 mg / m 3 , and the inlet ozone concentration to 500 ppm. Run for 9 h, and the catalyst performance is stable.

[0029] Figure 1 This is the result of the XRD characterization analysis of the product prepared in Example 1. By analyzing this spectrogram, it can be seen that only cerium dioxide is shown in the phase of the product prepared in Example 1, indicating that TiO 2 and MnO x exist in the catalyst in an amorphous form, which is beneficial to improving the catalytic performance of the catalyst.

[0030] Figure 2 This is the result of the TEM characterization analysis of the product prepared in Example 1. The TEM image shows that the morphology of the target product is flaky and has good dispersion.

[0031] Figure 3 This is the result of the energy spectrum surface scanning analysis of the product prepared in Example 1. It can be found that titanium elements appear uniformly in the entire flaky structure, indicating that titanium has been successfully doped into the catalyst.

[0032] Figure 4 This is the test result of the catalytic ozonation of VOCs by the product prepared in Example 1. The figure shows that TiO 2 -MnO x -CeO x catalyst can completely degrade dichloroethane, and the carbon dioxide selectivity can be stabilized above 90% within 9 h.

[0033] Example 2

[0034] This example provides a synthesis method of TiO 2 -MnO x -CeO x catalyst, specifically as follows:

[0035] 1) Take 7.0 g of cerium nitrate, mix cerium nitrate and urea in a molar ratio of 1:6, add 300 mL of pure water to prepare a mixed solution, and heat and stir in a water bath at 85 °C for 6 h.

[0036] (2) Add titanium oxysulfate to the above mixed solution in a molar ratio of 1:10 to cerium nitrate, and heat and stir in a water bath at 85 °C for 18 h.

[0037] (3) Perform solid-liquid separation and washing on the product obtained in step (2), collect the product, and obtain the solid product doped with TiO 2

[0038] (4) Disperse the product obtained in step (3) with pure water, make the volume constant to 100 mL, add a 0.06 mol / L potassium permanganate solution, and determine the addition amount of potassium permanganate according to the molar ratio of 1:10 to cerium nitrate. Heat and stir in a water bath at 85 °C until there is no permanganate ion in the solution.

[0039] ​(5) Perform solid-liquid separation on the product obtained in step (4), disperse the solid product in 50 mL of pure water, add 50 mL of 1 mol / L dilute nitric acid solution to remove the residual Ce(OH)CO 3 .

[0040] (6) Perform solid-liquid separation and washing on the product obtained in step (5), and dry it at 60 - 100 °C for 12 - 20 h to prepare the TiO 2 -MnO x -CeO x catalyst.

[0041] (7) Load 150 mg of the TiO 2 -MnO x -CeO x catalyst into a fixed-bed reactor to test the performance of the catalyst. Set the gas flow rate to 100 mL / min, the inlet concentration of the pollutant dichloroethane to 105 mg / m 3 , and the inlet ozone concentration to 500 ppm. Run for 9 h, and the performance of the catalyst is stable.

[0042] Figure 5 is the test result of the product prepared in Example 2 for catalytic ozonation of VOCs. The figure shows that the TiO 2 -MnO x -CeO x catalyst can completely degrade dichloroethane, and the carbon dioxide selectivity can be stabilized above 95% within 9 h.

[0043] Example 3

[0044] This example provides a synthesis method of TiO 2 -MnO x -CeO x catalyst, specifically as follows:

[0045] 1) Take 7.0 g of cerium nitrate, mix cerium nitrate with urea in a molar ratio of 1:6, add 300 mL of pure water to prepare a mixed solution, and heat and stir in a water bath at 85 °C for 6 h.

[0046] (2) Add titanyl sulfate to the above mixed solution in a molar ratio of 1:15 to cerium nitrate, and heat and stir in a water bath at 85 °C for 18 h.

[0047] (3) Perform solid-liquid separation and washing on the product obtained in step (2), collect the product, and obtain the solid product doped with TiO 2 .

[0048] (4) Disperse the product obtained in step (3) with pure water, make up the volume to 100 mL, add a potassium permanganate solution with a concentration of 0.06 mol / L. The addition amount of potassium permanganate is determined according to the molar ratio of 1:10 to cerium nitrate. Heat and stir in a water bath at 85 °C until there is no permanganate ion in the solution.

[0049] (5) Perform solid-liquid separation on the product obtained in step (4). Disperse the solid product in 50 mL of pure water, add 50 mL of a dilute nitric acid solution with a concentration of 1 mol / L to remove the residual Ce(OH)CO 3 .

[0050] (6) Perform solid-liquid separation and washing on the product obtained in step (5), and dry it at 60 - 100 °C for 12 - 20 h to obtain the TiO 2 -MnO x -CeO x catalyst.

[0051] (7) Load 150 mg of the TiO 2 -MnO x -CeO x catalyst into a fixed-bed reactor to test the performance of the catalyst. Set the gas flow rate to 100 mL / min, the inlet concentration of the pollutant dichloroethane to 105 mg / m 3 , and the inlet ozone concentration to 500 ppm. Run for 9 h, and the performance of the catalyst is stable.

[0052] Figure 6 is the test result of the product prepared in Example 3 for catalytic ozonation of VOCs. The figure shows that the degradation rate of dichloroethane drops to 94% after 9 h, and the carbon dioxide selectivity can be stably above 84% within 9 h.

Claims

1. A TiO2-MnO catalyst for catalytic ozone oxidation x -CeO x A method for preparing a catalyst, characterized in that: The preparation method of the catalyst comprises the steps of: (1) dissolving a water-soluble cerium salt and urea in water to prepare a mixed solution, heating in a water bath and stirring for 5 to 10 hours to obtain a turbid solution containing Ce(OH)CO3 solid; (2) adding a water-soluble titanium salt to the turbid solution prepared in step (1), continuing to heat and stir in a water bath for 15 to 20 hours, and after the reaction is completed, filtering and washing with pure water to obtain a filter cake to obtain a TiO2-doped solid product; (3) Dispersing the filter cake obtained in step (2) in pure water, adding permanganate, heating in a water bath and stirring for 10 to 15 hours, after the reaction is completed, filtering and washing with pure water to obtain the filter cake, and obtaining TiO2-MnO x -CeO x Precursor; (4) The TiO2-MnO obtained in step (3) x -CeO x The precursor was dispersed in pure water, and the residual Ce(OH)CO3 was removed by dilute acid solution. After filtering, the filter cake was washed with pure water and dried to obtain TiO2-MnO x -CeO x catalyst; Wherein, the molar ratio of the cerium salt to urea in step (1) is 1:4 to 1:8; The permanganate concentration is 0.05-0.10 mol / L, the cerium salt concentration is 0.04-0.08 mol / L, and the urea concentration is 0.1-0.5 mol / L; The water bath temperature is 60-90° C., the drying temperature is 60-100° C., and the drying time is 12-20 hours.

2. The method for preparing the catalyst according to claim 1, characterized in that: In step (1), the water-soluble cerium salt is one or more of cerium nitrate, cerium chloride, cerium sulfate and cerium acetate.

3. The method for preparing the catalyst according to claim 1, characterized in that: In step (2), the water-soluble titanium salt is one or more of titanium sulfate, titanyl sulfate and titanium tetrachloride, and the molar ratio of the titanium salt to the cerium salt is 1:5 to 1:

20.

4. The method for preparing the catalyst according to claim 1, characterized in that: In step (3), the permanganate is one or both of potassium permanganate and sodium permanganate, and the molar ratio of permanganate to cerium salt is 1:5 to 1:

10.

5. The method for preparing the catalyst according to claim 1, wherein the dilute acid in step (4) is one or more of nitric acid, sulfuric acid, acetic acid and oxalic acid, and the concentration is 0.5 to 1 mol / L.

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