Cerium dioxide in-situ composite manganese oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a cerium dioxide in-situ composite manganese oxide catalyst and a preparation method and application thereof, and belongs to the technical field of waste gas treatment engineering.The preparation method comprises the following steps that potassium permanganate is loaded on the surface of a carrier cerium dioxide and then subjected to a reduction reaction, and then an obtained cerium-manganese catalyst precursor is subjected to calcination treatment to obtain the cerium dioxide in-situ composite manganese oxide catalyst. The cerium dioxide in-situ composite manganese oxide catalyst is obtained. The oxygen activity between interfaces is improved through in-situ compounding of cerium dioxide and manganese oxide, excellent catalytic activity is shown, the catalyst is suitable for improvement of the catalytic performance of cerium dioxide prepared through different synthesis methods, the treatment method is simple and convenient, the catalytic combustion performance of the catalyst on VOCs is remarkably improved, and the water resistance is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste gas treatment engineering, and in particular relates to a ceria in-situ composite manganese oxide catalyst, a preparation method and an application thereof. Background Art

[0002] In recent years, volatile organic compounds (VOCs) have become key precursors to atmospheric pollution, with their emissions contributing to photochemical smog, PM2.5, and ozone pollution. Catalytic combustion offers the advantages of complete catalytic oxidation and pollution-free combustion products for VOC waste gas treatment. As a highly efficient organic waste gas treatment technology, catalytic combustion remains one of the primary technologies for VOC treatment. Researching and improving high-performance catalysts for the catalytic oxidation of VOCs is key in the field of catalytic combustion.

[0003] Cerium dioxide catalysts offer excellent thermal and structural stability, while manganese oxides possess excellent low-temperature catalytic activity. Prior art single-use ceria catalysts typically exhibit low catalytic activity at low temperatures, while manganese oxides are susceptible to deactivation at elevated temperatures, making them incapable of meeting industrial application requirements. The catalytic activity of cerium-manganese composite catalysts depends on the strength of the interaction between the two oxides, yet existing composite methods still fail to achieve an ideal interaction.

[0004] Therefore, how to provide a method for significantly improving the catalytic oxidation performance of the cerium-manganese composite oxide catalyst and enhancing the interaction between cerium dioxide and manganese oxide is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a ceria in-situ composite manganese oxide catalyst and its preparation method and application.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps: loading potassium permanganate on the surface of a ceria carrier and performing a reduction reaction; and then calcining the obtained cerium-manganese catalyst precursor to obtain the ceria in-situ composite manganese oxide catalyst.

[0008] Preferably, the potassium permanganate is loaded onto the surface of the ceria carrier by dissolving the ceria carrier and potassium permanganate in water to form a mixed solution, and then drying the mixed solution. This method facilitates the potassium permanganate to first enter the pores of the ceria and, after being reduced, to form a strongly interacting manganese oxide-ceria interface.

[0009] Preferably, the manganese element in the potassium permanganate is 5-30% of the mass of the carrier cerium dioxide.

[0010] Preferably, the carrier cerium dioxide is prepared using cerium nitrate as a cerium source, and the preparation method includes one of a sol-gel method, a hydrothermal method, and a precipitation method.

[0011] Preferably, the reducing agent used in the reduction reaction is hydrogen peroxide.

[0012] Preferably, the reduction reaction temperature is 10-15° C. and the time is 2-4 h.

[0013] Preferably, the calcination temperature is 400-600° C. and the calcination time is 2 hours.

[0014] A ceria in-situ composite manganese oxide catalyst prepared by the above preparation method.

[0015] Application of a ceria in-situ composite manganese oxide catalyst in the catalytic combustion of VOCs.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The preparation method provided by the present invention uses simple reaction equipment, short reaction time, and is easy to operate; the raw materials are readily available, and the raw material and reaction costs are low, which is conducive to large-scale production. During the entire reaction process, the present invention does not use or produce any toxic or harmful substances, and fully meets the requirements of a green catalyst. In addition, the present invention enhances interfacial oxygen activity by in-situ composite manganese oxide with ceria, exhibiting excellent catalytic activity, and is suitable for improving the catalytic performance of ceria prepared by different synthetic methods. The processing method is simple, the catalyst significantly improves the catalytic combustion performance of VOCs, and has good water resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0019] Figure 1 This is a comparison chart of the performance of catalytic oxidation of ethyl acetate by the catalysts before and after the in-situ composite of ceria with manganese oxide in Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0020] Figure 2 1 is a performance diagram of catalytic oxidation of ethyl acetate by catalysts with different manganese contents in Examples 1, 2, 3 and 4 of the present invention;

[0021] Figure 3 Graph showing the performance of catalytic oxidation of ethyl acetate by catalysts with different hydrogen peroxide reduction times in Examples 3, 5, and 6 of the present invention;

[0022] Figure 4 This is a comparison chart of the performance of catalytic oxidation of ethyl acetate by catalysts calcined at different temperatures in Examples 7, 8 and 3 of the present invention;

[0023] Figure 5 The catalytic performance diagram of the in-situ composite manganese oxide of the ceria support prepared by different methods in Example 3, Example 9, Example 10, Comparative Example 1, Comparative Example 4 and Comparative Example 5 of the present invention;

[0024] Figure 6 Performance diagram of the catalysts of ceria in situ composite manganese oxide, manganese oxide in situ composite palladium and ceria in situ composite palladium of Example 3, Comparative Example 6 and Comparative Example 7 of the present invention;

[0025] Figure 7 The catalytic performance diagram of the ceria in-situ composite manganese oxide prepared with different reducing agents in Example 3 of the present invention and Comparative Example 8;

[0026] Figure 8 This is a comparison chart of the catalytic oxidation performance of ethyl acetate by the catalysts before and after calcination of the stabilized manganese oxide in Example 3 of the present invention and Comparative Example 9;

[0027] Figure 9 Example 3 (20% MnO x @CeO2) performance stability temperature diagram of the catalyst for catalytic oxidation of ethyl acetate;

[0028] Figure 10 Example 3 (20% MnO x Comparative Example 1 (CeO2) and Comparative Example 1 (CeO2) catalysts in water atmosphere for ethyl acetate carbon dioxide yield performance comparison;

[0029] Figure 11 Example 3 (20% MnO x @CeO2) and comparative example 1 (CeO2) catalyst catalytic performance diagram for toluene;

[0030] Figure 12 This is a scanning electron microscope image of the catalyst before and after the in-situ composite of ceria with manganese oxide in Example 3 of the present invention;

[0031] Figure 13 This is a scanning electron microscope image of the catalyst before and after the in-situ composite of ceria with manganese oxide in Comparative Example 1 of the present invention;

[0032] Figure 14 This is a scanning electron microscope image of the catalyst before and after the in-situ composite of ceria with manganese oxide in Comparative Example 3 of the present invention;

[0033] Figure 15The nitrogen adsorption and desorption curves of the catalysts before and after the in-situ composite of ceria with manganese oxide in Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention are shown;

[0034] Figure 16 The Raman spectra of the catalysts before and after the in-situ composite of ceria with manganese oxide in Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention are shown. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources;

[0038] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0039] The mass space velocity in the embodiments of the present invention is defined as the standard volume flow rate of the reaction gas entering the reaction system per hour divided by the mass of the catalyst. It is expressed as WHSV, and the unit is mL·g -1 ·h -1 .

[0040] The VOCs conversion rate in the embodiment of the present invention is defined as the volume percentage of VOCs entering the reactor that are converted, that is, the difference in the volume percentage of VOCs in the inlet and outlet gases relative to the volume percentage of VOCs in the inlet gas, in units of %.

[0041] Example 1

[0042] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0043] (1) Add 0.01 mol of cerium nitrate and 0.02 mol of citric acid to a beaker, then add 20 mL of deionized water to dissolve, add 1 mL of ethylene glycol after complete dissolution, stir for 30 min, and then react in an oil bath at 80°C for 12 h. After the reaction is completed, dry the sample in the oil bath in an oven at 60°C overnight to obtain a carrier precursor;

[0044] The supported catalyst precursor was placed in a muffle furnace, heated to 500°C at a heating rate of 5°C / min and calcined for 2 hours. After calcination, the powder was pressed into tablets and ground into particles of 40-60 mesh. The obtained catalyst was recorded as CeO2.

[0045] (2) 1 g of the cerium dioxide (CeO2) carrier prepared by the sol-gel method in step (1) and 0.05 g of potassium permanganate containing manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60°C overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0046] (3) The precursor was placed in a muffle furnace and heated to 500°C at a rate of 5°C / min for 2 h. After calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 5% MnO x @CeO2.

[0047] Example 2

[0048] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0049] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.1 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0050] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 10% MnO x @CeO2.

[0051] Example 3

[0052] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0053] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0054] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2.

[0055] Example 4

[0056] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0057] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.3 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0058] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 30% MnO x @CeO2.

[0059] Example 5

[0060] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0061] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 2 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0062] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-2h.

[0063] Example 6

[0064] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0065] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 4 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0066] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 4 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-4h.

[0067] Example 7

[0068] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0069] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0070] (2) The precursor was placed in a muffle furnace and calcined at 400°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-400.

[0071] Example 8

[0072] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0073] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a manganese-cerium catalyst precursor was obtained.

[0074] (2) The precursor was placed in a muffle furnace and calcined at 600°C for 2 h at a heating rate of 5°C / min. After calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-600.

[0075] Example 9

[0076] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0077] (1) Preparation of carrier cerium dioxide by co-precipitation method: 0.01 mol of cerium nitrate was dissolved in 30 mL of deionized water by stirring for 30 min to obtain a cerium nitrate solution; 0.03 mol of sodium hydroxide was dissolved in 10 mL of deionized water by stirring for 30 min to obtain a sodium hydroxide solution; the sodium hydroxide solution was slowly added dropwise to the cerium nitrate solution. After the addition was completed, the mixture was stirred and reacted for 2 h, washed, dried, and left overnight. The catalyst precursor was placed in a muffle furnace and calcined at 500 ° C for 2 h at a heating rate of 5 ° C / min to prepare cerium dioxide by co-precipitation method, which was recorded as CeO2-P.

[0078] (2) Take 1g of the carrier cerium dioxide (CeO2-P) prepared by the co-precipitation method and potassium permanganate with a manganese element mass of 0.2g in a beaker; then add 20mL of deionized water to dissolve, stir for 30min, and dry the beaker in a 60℃ oven overnight to obtain a solid mixture. After complete drying, grind the solid mixture into powder, add 30mL of 30wt% H2O2 solution dropwise under ice bath conditions, and reduce it for 3h; after washing and drying overnight, a manganese-cerium catalyst precursor is obtained.

[0079] (3) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-P.

[0080] Example 10

[0081] A method for preparing a ceria in-situ composite manganese oxide catalyst comprises the following steps:

[0082] (1) According to the hydrothermal method in the literature (Effect of CeO2 morphologies ontoluene catalytic combustion), CeO2-H with cubic morphology was prepared by hydrothermal method. The specific experimental method is as follows:

[0083] 2g of Ce(NO₃)₃·6H₂O was placed in beaker A and dissolved in 2mL of deionized water, designated Solution A. Simultaneously, 36g of NaOH was weighed and placed in beaker B, where it was dissolved in 60mL of deionized water, designated Solution B. After the solution in beaker B cooled, Solution B was slowly added dropwise to Solution A. After stirring for 30 minutes, the mixture was transferred to a 100mL autoclave and incubated in an oven at 150°C for 48 hours to obtain CeO₂-H with a cubic morphology.

[0084] (2) Take 1g of the carrier cerium dioxide (CeO2-H) prepared by the hydrothermal method and potassium permanganate with a manganese element mass of 0.2g in a beaker; then add 20mL of deionized water to dissolve, stir for 30min, and dry the beaker in a 60℃ oven overnight to obtain a solid mixture. After complete drying, grind the solid mixture into powder, add 30mL of 30wt% H2O2 solution dropwise under ice bath conditions, and reduce it for 3h; after washing and drying overnight, a manganese-cerium catalyst precursor is obtained.

[0085] (3) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into 40-60 mesh particles to obtain a cerium-manganese composite oxide catalyst, which was recorded as 20% MnO x @CeO2-H.

[0086] Comparative Example 1

[0087] Cerium dioxide prepared by a sol-gel method, similar to step (1) of Example 1, specifically comprises the following steps:

[0088] Add 0.01 mol of cerium nitrate and 0.02 mol of citric acid to a beaker, then add 20 mL of deionized water to dissolve. After complete dissolution, add 1 mL of ethylene glycol and stir for 30 minutes. Then, react in an oil bath at 80°C for 12 hours. After the reaction, dry the sample in the oil bath in an oven at 60°C overnight to obtain a catalyst precursor.

[0089] The catalyst precursor was placed in a muffle furnace, heated to 500°C at a heating rate of 5°C / min and calcined for 2 hours. After calcination, the powder was pressed into tablets and ground into particles of 40-60 mesh. The obtained catalyst was recorded as CeO2.

[0090] Comparative Example 2

[0091] A method for preparing a manganese oxide catalyst comprises the following steps:

[0092] Potassium permanganate (0.2 g) of manganese element was added to a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 minutes. 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 hours. After the reaction, the mixture was washed and dried overnight to obtain a manganese catalyst precursor. The precursor was placed in a muffle furnace and calcined at 500°C for 2 hours at a heating rate of 5°C / min to prepare an uncompounded manganese oxide; the powder was pressed into tablets and ground into 40-60 mesh particles. The obtained catalyst was recorded as MnO x .

[0093] Comparative Example 3

[0094] A method for preparing a ceria composite manganese oxide catalyst comprises the following steps:

[0095] 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.2 g of potassium permanganate of the manganese element were placed in a beaker, and 20 mL of deionized water was added to dissolve them. 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After the reaction was completed, the mixture was washed and dried overnight to obtain a manganese-cerium catalyst precursor. The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min to prepare a cerium-manganese composite oxide catalyst. The powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as 20% MnOx / CeO2.

[0096] Comparative Example 4

[0097] A method for preparing cerium dioxide by coprecipitation, similar to step (1) of Example 9, comprises the following steps:

[0098] The ceria carrier was prepared by coprecipitation: 0.01 mol of cerium nitrate was dissolved in 30 mL of deionized water by stirring for 30 minutes to obtain a cerium nitrate solution. 0.03 mol of sodium hydroxide was dissolved in 10 mL of deionized water by stirring for 30 minutes to obtain a sodium hydroxide solution. The sodium hydroxide solution was slowly added dropwise to the cerium nitrate solution. After the addition was complete, the mixture was stirred and reacted for 2 hours. The mixture was then washed, dried, and left overnight. The catalyst precursor was placed in a muffle furnace and calcined at 500°C for 2 hours at a heating rate of 5°C / min to prepare the ceria by coprecipitation, designated CeO2-P.

[0099] Comparative Example 5

[0100] A hydrothermal method is used to prepare cerium dioxide. The same as step (1) of Example 10 is used, and CeO2-H having a cubic morphology is prepared by the hydrothermal method according to the hydrothermal method in the literature (Effect of CeO2morphologies on toluene catalytic combustion).

[0101] Comparative Example 6

[0102] A method for preparing a palladium in-situ composite manganese oxide catalyst, which differs from Example 1 only in that the raw material carrier cerium dioxide is replaced by sodium chloropalladate, specifically comprising the following steps:

[0103] (1) 0.016 g of sodium chloropalladate and 0.2 g of potassium permanganate (containing manganese) were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise in an ice bath for 3 h. After washing and drying overnight, a palladium-manganese catalyst precursor was obtained.

[0104] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder was pressed into tablets and ground into particles of 40-60 mesh to obtain a palladium-manganese composite oxide catalyst, which was recorded as Pd / MnO x .

[0105] Comparative Example 7

[0106] A method for preparing a palladium in-situ composite ceria catalyst, which differs from Example 1 only in that the raw material potassium permanganate is replaced by sodium chloropalladate, specifically comprising the following steps:

[0107] (1) 1 g of the cerium dioxide support prepared by the sol-gel method in step (1) of Example 1 and 0.05 g of sodium chloropalladate were placed in a beaker; 20 mL of deionized water was added to dissolve the mixture, and the mixture was stirred for 30 min. The beaker was dried in an oven at 60° C. overnight to obtain a solid mixture. After complete drying, the solid mixture was ground into powder, and 30 mL of a 30 wt% H2O2 solution was added dropwise. The reduction time was 3 h; after washing and drying overnight, a palladium-cerium catalyst precursor was obtained.

[0108] (2) The precursor is placed in a muffle furnace and calcined at 500°C for 2 h at a heating rate of 5°C / min. After the calcination, the obtained powder is pressed into tablets and ground into particles of 40 to 60 mesh to obtain a cerium-palladium composite oxide catalyst, which is recorded as Pd / CeO2.

[0109] Comparative Example 8

[0110] A method for preparing a ceria in-situ composite manganese oxide catalyst is different from Example 1 only in that the reducing agent (30 mL of a 30 wt% H2O2 solution) is replaced with 30 mL of a 10 mol / L ascorbic acid solution. The other process steps and parameters are the same as those in Example 1, recorded as 20% MnO x @CeO2-AA.

[0111] Comparative Example 9

[0112] A method for preparing a cerium dioxide in-situ composite manganese oxide catalyst is different from Example 1 only in that the calcination process in step (3) is not included to obtain a manganese cerium catalyst precursor. The other process steps and parameters are the same as those in Example 1, recorded as 20% MnO x @CeO2-Un.

[0113] Technical effects:

[0114] 1. Catalytic oxidation performance

[0115] The catalytic combustion performance of the catalysts obtained in Examples 1-10 and Comparative Examples 1-5 on ethyl acetate was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, the ethyl acetate concentration was 1000 ppm, synthetic air was used as the balance gas, and the flow rate was 100 mL min -1 , mass space velocity (WHSV) = 60000 mL·g -1 ·h -1 .

[0116] 1.1. The catalytic combustion effect of ethyl acetate is shown in Table 1.

[0117] Table 1 Ethyl acetate catalytic combustion performance of catalyst

[0118]

[0119]

[0120] As shown in Table 1, the catalytic oxidation performance of VOCs of the catalyst composited with manganese oxide on the surface of ceria in the present invention is significantly improved. In the activity evaluation of the catalyst provided by the present invention, its catalytic activity is greatly improved. 90 (temperature at which the conversion rate is 90%) compared to the non-in-situ composite 20% MnO x / CeO2 decreased by 10 ° C, while the untreated CeO2 catalyst decreased by up to 48 ° C. It can also be seen from Comparative Examples 1 and 2 that the catalytic oxidation performance of VOCs after treatment with the cerium dioxide surface composite manganese oxide catalyst is significantly higher than that after treatment with a single cerium dioxide or manganese oxide catalyst.

[0121] 1.2. Figure 1 The catalytic performance comparison of manganese oxide composite on the surface of cerium dioxide in Example 3 of the present invention and Comparative Examples 1-3 is shown in FIG. Figure 1 It can be seen that the catalytic oxidation performance of VOCs after the catalyst composited with manganese oxide on the surface of ceria is significantly higher than that of the uncomposite catalyst. 90 (the temperature at which the conversion rate reaches 90%) also decreases, and the catalytic oxidation performance improves accordingly;

[0122] 1.3. The performance comparison of different composite amounts of manganese oxide before and after composite of cerium dioxide surface in Examples 1-4 of the present invention is shown in FIG. Figure 2 ,Depend on Figure 2 It can be seen that the catalytic oxidation performance of VOCs of the cerium-manganese composite oxide catalyst after being compounded with manganese oxide is significantly higher than that of the uncompounded catalyst. However, when the mass of manganese element increases to 30%, T 90 (The temperature at which the conversion rate is 90%) begins to increase slightly, indicating that the more manganese oxide is added, the better. The best performance is achieved at 20%.

[0123] 1.4. The performance comparison of the composite manganese oxide on the surface of cerium dioxide before and after hydrogen peroxide reduction at different times in Examples 3 and 5-6 of the present invention is shown in FIG. Figure 3 ,Depend on Figure 3 It can be seen that the catalytic oxidation performance of VOCs of the cerium-manganese composite oxide catalysts after being compounded with manganese oxide is not significantly different, but they are all inferior to the cerium-manganese composite oxide catalysts after hydrogen peroxide reduction for 3h.

[0124] 1.5. The performance comparison of the composite manganese oxide on the surface of cerium dioxide before and after calcination at different temperatures in Examples 3 and 7-8 of the present invention is shown in FIG. Figure 4 ,Depend on Figure 4 It can be seen that the performance of the cerium-manganese composite oxide catalyst after being composited with manganese oxide increases with the calcination temperature, but when the calcination temperature increases to 600℃, T 90 (the temperature at which the conversion rate is 90%) begins to increase significantly, indicating that the higher the calcination temperature is, the better it is. The best temperature is 500℃.

[0125] 1.6. The performance comparison of the composite loading of manganese oxide on the surface of ceria in different synthesis methods in Examples 3, 9-10 of the present invention and Comparative Examples 1, 4-5 is shown in FIG. Figure 5 ,Depend on Figure 5 It can be seen that the performance of cerium-manganese composite oxide catalysts after being composited with manganese oxides was significantly improved, but the support cerium dioxide prepared by the sol-gel method performed the best;

[0126] 1.7. The performance comparison of cerium dioxide in situ composite manganese oxide, palladium in situ composite manganese oxide and palladium in situ composite cerium dioxide catalyst in Example 3 of the present invention and Comparative Examples 6-7 is shown in FIG. Figure 6 ,Depend on Figure 6 It can be seen that the performance of palladium in situ composite manganese oxide catalyst is better than that of palladium in situ composite ceria catalyst, but the performance of cerium-manganese composite oxide catalyst after composite manganese oxide is still the best.

[0127] 1.8. Comparison of the catalytic performance of ceria in situ composite manganese oxide prepared with different reducing agents in Example 3 of the present invention and Comparative Example 8 Figure 7 ,Depend on Figure 7 It can be seen that hydrogen peroxide has the best performance as a reducing agent, while ascorbic acid has a poor performance as a reducing agent. Manganese oxide is excessively reduced, indicating that stronger reducing ability is not necessarily better, and hydrogen peroxide performs better.

[0128] 1.9. The performance comparison of the catalysts for catalytic oxidation of ethyl acetate before and after calcination of stabilized manganese oxide in Example 3 of the present invention and Comparative Example 9 is shown in FIG. Figure 8 ,Depend on Figure 8 It can be seen that the performance of the catalyst after calcination is poor, which shows that calcination can promote the activity of the catalyst.

[0129] 1.10. 20% MnO in Example 3 of the present invention x @CeO2 catalytic performance stability temperature diagram see Figure 9 ,Depend on Figure 9 It can be seen that the catalytic degradation performance of ethyl acetate by cerium-manganese composite oxide decreased slightly after 48 hours, indicating that it has excellent stability in catalytic degradation of ethyl acetate.

[0130] 1.11. 20% MnO obtained in Example 3 of the present invention x The performance comparison of ethyl acetate carbon dioxide yield of CeO2 and CeO2 obtained in comparative example 1 under water atmosphere is shown in the figure Figure 10 ,Depend on Figure 10 It can be seen that the carbon dioxide yield tested at the same conversion rate is 20% MnO x @CeO2 remained basically unchanged, while the CeO2 selectivity of the uncomposite manganese oxide was low and showed a significant decrease, which demonstrated the excellent water resistance and ethyl acetate carbon dioxide yield of the cerium-manganese composite oxide catalyst;

[0131] 2. The catalytic combustion performance of the catalysts obtained in Comparative Example 1 and Example 3 on different VOCs (ethyl acetate and toluene) was evaluated under the same evaluation conditions as the evaluation of the catalytic combustion performance of the catalyst on ethyl acetate in Item 1. The results are shown in Table 2:

[0132] Table 2

[0133]

[0134]

[0135] Figure 11 Table 2 shows the 20% MnO obtained in Example 3. x The catalytic performance of CeO2 obtained from @CeO2 and Comparative Example 1 on toluene and ethyl acetate is compared. Figure 11 As shown in Table 2, the catalytic activity of the cerium-manganese composite oxide catalyst was significantly improved after being compounded with manganese oxide. 90Compared with ceria, the temperature was reduced by 76°C, indicating that the cerium-manganese composite oxide catalyst has excellent ability to catalyze the degradation of toluene and ethyl acetate.

[0136] 3. Figure 12-14 The 20% MnO obtained in Example 3 is x @CeO2, CeO2 obtained in Comparative Example 1, and 20% MnO obtained in Comparative Example 3 x The scanning electron microscopy of / CeO2 shows that the powder structure is mainly derived from CeO2 species, while the rod-like structure is derived from manganese oxide. x @CeO2 Figure 12 It can be clearly seen that there are many nanorod-shaped manganese oxides generated directly on the surface of CeO2, among which MnO x There are more structures embedded in CeO2 on the surface of @CeO2 catalyst. x @MnO in CeO2 x It has better dispersibility and is more tightly bound to the carrier CeO2. Figure 13 and Figure 14 , by comparison, 20% MnO x The manganese oxides on the surface of / CeO2 agglomerated together, and the dispersion was even worse.

[0137] 4. Figure 15 20% MnO obtained in Example 3 x @CeO2, CeO2 obtained in Comparative Example 1 and MnO obtained in Comparative Example 2 x and 20% MnO obtained in Comparative Example 3 x / CeO2 nitrogen adsorption and desorption curves. Figure 15 In the two-step treatment, 20% MnO x @CeO2 still exhibits a large hysteresis loop in nitrogen adsorption / desorption tests, which is due to the loading of manganese oxide within the ceria mesoporous structure. This indicates that after modification, a large portion of the ceria mesopores are occupied by manganese oxide, which inhibits the destruction of the mesoporous structure and particle agglomeration during calcination.

[0138] 5. Figure 16 20% MnO obtained in Example 3 x @CeO2, CeO2 obtained in Comparative Example 1 and MnO obtained in Comparative Example 2 x and 20% MnO obtained in Comparative Example 3 x / CeO2 Raman spectrum, by Figure 16 It can be seen that 20% MnO x @CeO2 appears stronger Ce-O bond stretching and Mn 4+The shortening of the -O bond indicates that there is a strong interaction in the cerium-manganese composite structure.

[0139] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a ceria in-situ composite manganese oxide catalyst, characterized in that: The following steps are involved: Potassium permanganate is loaded on the surface of the carrier cerium dioxide and then subjected to a reduction reaction to obtain a cerium manganese catalyst precursor. The cerium manganese catalyst precursor is calcined to obtain the cerium dioxide in-situ composite manganese oxide catalyst.

2. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The method for loading potassium permanganate on the surface of the carrier cerium dioxide comprises: dissolving the carrier cerium dioxide and potassium permanganate in water to form a mixed solution, and drying the mixed solution.

3. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The manganese element in the potassium permanganate accounts for 5-30% of the mass of the carrier cerium dioxide.

4. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The carrier cerium dioxide is prepared by using cerium nitrate as a cerium source, and the preparation method includes one of a sol-gel method, a hydrothermal method, and a precipitation method.

5. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The reducing agent used in the reduction reaction is hydrogen peroxide.

6. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The reduction reaction temperature is 10-15° C. and the time is 2-4 hours.

7. The method for preparing a ceria in-situ composite manganese oxide catalyst according to claim 1, characterized in that: The calcination temperature is 400-600° C. and the calcination time is 2 hours.

8. The ceria in-situ composite manganese oxide catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the ceria in-situ composite manganese oxide catalyst according to claim 8 in the catalytic combustion of VOCs.

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