Core-shell structured scr catalysts, methods of making and using the same

Abstract

The application discloses a core-shell structure SCR catalyst and a preparation method and application thereof, and belongs to the field of SCR catalysts. The core-shell structure SCR catalyst is of a core-shell structure, wherein the core phase is spherical MnCeOx, and the shell layer is SbCeOx or PrCeOx. The special core-shell structure enhances the interaction between the active components, and has a large specific surface area and rich acid sites. The shell layer wrapping the core phase effectively widens the temperature window of the core-shell structure SCR catalyst for catalyzing reactions, further inhibits the diffusion of SO2 and H2O to the core phase, protects the core phase denitration active site, reduces the deposition of sulfates, and greatly enhances the sulfur and water resistance of the catalyst. The preparation method of the core-shell structure SCR catalyst is realized by adopting an alcohol heating method and a chemical precipitation method, and the method is simple and easy to operate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of denitration catalysts, and in particular relates to a core-shell structure SCR catalyst and a preparation method and application thereof. BACKGROUND

[0002] At present, pollutants in the steel, building materials, non-ferrous, thermal power, boiler, coking and other industries implement ultra-low emission standards. For example, the nitrogen oxide emission of the boiler must be reduced from the current standard of ≤200mg / m 3 to ≤80mg / m 3 , and the nitrogen oxide emission of the newly built boiler must be reduced from the current standard of ≤80mg / m 3 to ≤30mg / m 3 . The improvement of the standard has formed a certain pressure on the existing environmental protection technology.

[0003] Selective catalytic reduction (SCR) technology is one of the main technologies for flue gas NOx removal. SCR technology uses catalysts to reduce NO to N2 by NH3 at 300-400℃, with high de-NOx efficiency (>80%) and is widely used. However, unlike the flue gas characteristics of the power industry, the flue gas emitted by the steel, cement, glass and other non-electricity industries has low temperature (<300℃), high NOx concentration, SO2 and water vapor, etc., which leads to the poor de-NOx activity of traditional medium-temperature vanadium-based catalysts, and the low-temperature manganese-based catalysts and copper-based catalysts with better activity are prone to sulfur poisoning. Domestic and foreign researchers have also carried out research on low-temperature catalysts, including catalyst formulation, catalyst structure, etc. Among them, the core-shell structure is a typical new structure of de-NOx catalyst. For the application of core-shell structure in SCR, researchers mostly use single-component oxides as the outer shell to protect the active center of the catalyst. For example, patent number CN104190408A invention patent proposes a kind of titanium-based core-shell structure low-temperature SCR de-NOx catalyst and its preparation method. The process uses MnOx-CeO2 as the core and TiO2 as the shell of the titanium-based core-shell structure low-temperature SCR de-NOx catalyst, uses TiO2 shell to protect the active center of the catalyst, reduces the probability of contact between the active center and SO2 in the flue gas, and thus avoids irreversible poisoning of the active center by SO2. The catalyst mainly uses a single metal oxide shell as a sacrificial site to protect the active center to improve the sulfur poisoning resistance of the catalyst. In addition, the preparation of the shell process uses the reverse microemulsion method, which requires selecting the appropriate surfactant to form a strong interfacial film strength in the microemulsion system. The interfacial film strength is an important factor affecting the nucleation and size of nanoparticles. If the strength of the interfacial film is too low, the nanometer micro-water nucleus is easy to break during collision, leading to coagulation of the two, thus making it difficult to control the size of the nanoparticles. If the strength of the interfacial film is too high, it is difficult to make the micro-water nucleus exchange substances, so the reaction cannot proceed normally. Therefore, the method for preparing the core-shell structure has low controllability. For example, patent number CN104190409A invention patent proposes a kind of low-temperature SCR sulfur-resistant catalyst with graphene supported titanium-based core-shell structure and its preparation method, which constructs a graphene supported titanium-based core-shell structure catalyst to further use the graphene carrier to reduce the accumulation of ammonium sulfate salt, thereby enhancing the sulfur resistance of the low-temperature de-NOx catalyst. The catalyst uses graphene as a carrier, increasing the cost of preparation. There are also studies on the construction of multi-shell structure (two or more) catalysts, but the synthesis process is too complicated and the cost is relatively high. For example, patent number CN108906074A invention patent proposes a kind of low-temperature SCR catalyst with carbon sphere as template and its preparation method. The process first prepares carbon sphere templates with glucose as carbon source, then prepares carbon-transition metal core-shell microspheres with the carbon sphere templates, finally immerses the carbon-transition metal core-shell microspheres in a Mn-containing solution, and finally calcines to obtain a Mn-based double-shell hollow sphere low-temperature SCR catalyst. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a core-shell structure SCR catalyst, which has a core phase of MnCeOx and a shell layer of SbCeOx or PrCeOx, the core phase provides main denitration active sites for efficient removal of NOx, and the shell layer is used to protect the MnCeOx core phase from direct contact with SO2 or H2O, the special core-shell structure combines the properties of the inner and outer materials, and exhibits excellent NH3-SCR catalytic activity and sulfur and water resistance in a wide working temperature window, and endows the core-shell structure SCR catalyst with uniformly distributed active sites and abundant acid sites.

[0005] Another object of the present application is to provide a preparation method of the above-mentioned core-shell structure SCR catalyst.

[0006] Another object of the present application is to provide an application of the above-mentioned core-shell structure SCR catalyst in denitration.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] The core-shell structure SCR catalyst has a core-shell structure, the core phase is spherical MnCeOx, and the shell layer is SbCeOx or PrCeOx.

[0009] In the above technical solution, the thickness of the shell layer is 30-45 nm, and the particle size of the core-shell structure SCR catalyst is 160-200 nm.

[0010] The preparation method of the above-mentioned core-shell structure SCR catalyst comprises the following steps:

[0011] Step 1: A solution and a B solution are added dropwise to a MnCeOx solution to obtain a C solution, wherein the A solution is a mixture of a precipitating agent and water; the B solution is a mixture of a metal source, a cerium source and water, the metal element in the metal source is antimony or praseodymium, the ratio of the metal element in the metal source to the cerium element in the B solution is (1-3):3 in terms of the amount of substance, the MnCeOx solution is a mixture of MnCeOx and anhydrous ethanol, the ratio of the amount of substance of the precipitating agent, the amount of substance of the metal element in the metal source and the mass fraction of MnCeOx in the MnCeOx solution is 1:(1-3):0.4, the unit of the mass fraction is g, and the unit of the amount of substance is mmol;

[0012] In step 1, the concentration of the metal element in the B solution is 0.1 mol / L.

[0013] In step 1, the MnCeOx solution is uniformly mixed with anhydrous ethanol to obtain.

[0014] In the above technical solution, the concentration of MnCeOx in the MnCeOx solution is 0.005 g / mL, and the concentration of the precipitant in the A solution is 0.1 mol / L.

[0015] In the above technical solution, the particle size of the MnCeOx is 100-130 nm.

[0016] In the above technical solution, the precipitant is hexamethylenetetramine.

[0017] In step 2, the C solution is heated at 60-80℃ for 2 h and then cooled to room temperature to obtain a second precipitate, the second precipitate is washed and dried, and then calcined at 450℃ for 2-3 h to obtain the core-shell structure SCR catalyst.

[0018] In step 2, the drying is performed at 60-80℃ for 10-12 h.

[0019] In step 2, the heating rate of the calcination after drying is 1-2℃ / min.

[0020] The method for preparing MnCeOx comprises: mixing a cerium salt, a manganese nitrate solution and ethylene glycol, alcohol-heating at 180℃ for 24 h, cooling, centrifuging to obtain a first precipitate, washing and drying the first precipitate, and calcining at 450℃ for 3.5-4.5 h to obtain MnCeOx, wherein the molar fraction of the cerium salt, the molar fraction of manganese in the manganese nitrate solution and the volume fraction of ethylene glycol are in a ratio of (1-2):1:120, the unit of the molar fraction is mmol, and the unit of the volume fraction is mL.

[0021] In the above technical solution, the drying is performed at 60℃ for 10-12 h.

[0022] In the above technical solution, the washing is performed with water and anhydrous ethanol.

[0023] The above core-shell structure SCR catalyst is applied in flue gas denitration.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application utilizes a special core-shell structure, enhances the interaction between each active component, and has a large specific surface area and rich acid sites. The shell (SbCeOx or PrCeOx) wraps the core phase, effectively widening the temperature window of the core-shell structure SCR catalyst catalytic reaction, and further inhibiting the diffusion of SO2 and H2O to the core phase, protecting the core phase denitration active site, reducing the deposition of sulfates, and greatly enhancing the sulfur and water resistance of the catalyst.

[0026] The preparation method of the core-shell structure SCR catalyst is realized by using an alcohol heating method and a chemical precipitation method, which is simple and easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 TEM image of MnCeOx in Example 1;

[0028] Figure 2 TEM image of the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2;

[0029] Figure 3 TEM image of the supported MnCeOx / PrCeOx catalyst prepared in Comparative Example 3;

[0030] Figure 4 DeNOx performance diagram of MnCeOx, the core-shell structure SCR catalyst (MnCeOx@SbCeOx) prepared in Example 1, the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2, the core-shell structure SCR catalyst (MnCeOx@CoCeOx) prepared in Comparative Example 1, the supported SCR catalyst (MnCeOx / SbCeOx) prepared in Comparative Example 2, and the supported SCR catalyst (MnCeOx / PrCeOx) prepared in Comparative Example 3;

[0031] Figure 5 Sulfur resistance performance diagram of MnCeOx, the core-shell structure SCR catalyst (MnCeOx@SbCeOx) prepared in Example 1, and the supported SCR catalyst (MnCeOx / SbCeOx) prepared in Comparative Example 2;

[0032] Figure 6 Sulfur and water resistance performance diagram of the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2 and the supported SCR catalyst (MnCeOx / PrCeOx) prepared in Comparative Example 3. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be further described below in combination with specific embodiments.

[0034] The raw materials and their manufacturers involved in the following examples are as follows:

[0035]

[0036] The instruments and their model numbers involved in the following examples are as follows:

[0037]

[0038]

[0039] The water in the following examples is deionized water.

[0040] Example 1

[0041] A method for preparing a core-shell structure SCR catalyst, comprising the following steps:

[0042] Step 1, under the condition of magnetic stirring, slowly drop A solution and B solution into MnCeOx solution to obtain C solution, wherein, B solution is a mixture of antimony acetate, cerium nitrate hexahydrate and water, the ratio of antimony element in antimony acetate in B solution and cerium element in B solution is 1:1 in terms of mole fraction; A solution is a mixture of precipitant and water, and the precipitant is hexamethylene tetramine; MnCeOx solution is a mixture obtained by mixing MnCeOx (particle size is 100-130 nm) and anhydrous ethanol and then ultrasonicating for 30 min; the ratio of the mole fraction of precipitant, the mole fraction of antimony element in antimony acetate and the mass fraction of MnCeOx in MnCeOx solution is 1:1:0.4, the unit of mass fraction is g, the unit of mole fraction is mmol, the concentration of antimony element in B solution is 0.1 mol / L, the concentration of MnCeOx in MnCeOx solution is 0.005 g / mL, and the concentration of precipitant in A solution is 0.1 mol / L;

[0043] Step 2, heat C solution in a 70℃ water bath for 2h and then cool to room temperature 20-25℃ to obtain a second precipitate, wash the obtained second precipitate with water and anhydrous ethanol for 3 times, dry at 60℃ for 12h, then heat to 450℃ at a heating rate of 1℃ / min and calcine at 450℃ for 2h to obtain a core-shell structure SCR catalyst (MnCeOx@SbCeOx).

[0044] The method for preparing the MnCeOx includes: mixing a cerium nitrate hexahydrate, a manganese nitrate solution and ethylene glycol to be uniform, transferring to a polytetrafluoroethylene-lined stainless steel autoclave, alcohol heating at 180℃ for 24h, naturally cooling to room temperature, centrifuging to obtain a first precipitate, washing the first precipitate with water and anhydrous ethanol, drying at 60℃ for 12h, and calcining at 450℃ for 4h to obtain the MnCeOx, wherein the ratio of the number of moles of the cerium nitrate hexahydrate, the number of moles of manganese in the manganese nitrate solution and the volume fraction of the ethylene glycol is 1:1:120, the unit of the number of moles is mmol, and the unit of the volume fraction is mL, and the mass fraction of the manganese nitrate in the manganese nitrate solution is 50wt%.

[0045] Example 2

[0046] A method for preparing a core-shell structure SCR catalyst (MnCeOx@PrCeOx) is basically the same as the method for preparing the core-shell structure SCR catalyst in Example 1, and the only difference is that the "antimony acetate" is replaced by "praseodymium nitrate hexahydrate", the B solution is a mixture of praseodymium nitrate hexahydrate, cerium nitrate hexahydrate and water, the ratio of the praseodymium element in the praseodymium nitrate hexahydrate in the B solution and the cerium element in the B solution is 1:1 in terms of the number of moles; the ratio of the number of moles of the precipitant, the number of moles of the praseodymium element in the praseodymium nitrate hexahydrate and the mass fraction of the MnCeOx in the MnCeOx solution is 1:1:0.4, the unit of the mass fraction is g, the unit of the number of moles is mmol, and the concentration of the praseodymium element in the B solution is 0.1mol / L.

[0047] The TEM of the MnCeOx is shown in FIG. 1, and the TEM of the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in this example is shown in FIG. 2. Figure 1 The TEM of the MnCeOx is shown in FIG. 1, and the TEM of the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in this example is shown in FIG. 2. Figure 2 After the shell layer coats the MnCeOx, the particle size of the MnCeOx@PrCeOx increases, the MnCeOx maintains its spherical structure, and has a clear shell structure;

[0048] The thickness of the shell layer in the core-shell structure SCR catalyst prepared in this example is about 35nm, and the particle size of the core-shell structure SCR catalyst is 160nm-200nm.

[0049] Comparative Example 1

[0050] A preparation method of a core-shell structure SCR catalyst (MnCeOx@CoCeOx) is basically the same as the preparation method of the core-shell structure SCR catalyst in Example 1, and the only difference is that "antimony acetate" is replaced by "cobalt nitrate hexahydrate", the B solution is a mixture of cobalt nitrate hexahydrate, cerium nitrate hexahydrate and water, and the ratio of cobalt element in the cobalt nitrate hexahydrate in the B solution to cerium element in the B solution is 1:1 in terms of the number of moles; the ratio of the number of moles of the precipitant, the number of moles of cobalt element in the cobalt nitrate hexahydrate and the number of moles of MnCeOx in the MnCeOx solution is 1:1:0.4, the unit of the number of moles is mmol, and the concentration of cobalt element in the B solution is 0.1 mol / L.

[0051] The core-shell structure SCR catalyst prepared in the present comparative example is a core-shell structure, and the ratio of Co element to Ce element in the shell layer is 1:1 in terms of the number of moles.

[0052] The SCR catalyst prepared in the present comparative example is a catalyst with cobalt-cerium composite oxide as the shell layer.

[0053] Comparative Example 2

[0054] A preparation method of a supported SCR catalyst (MnCeOx / SbCeOx) includes the following steps:

[0055] Step 1, 0.4g of MnCeOx (the method for preparing MnCeOx is the same as that in Example 1) is ultrasonically dispersed in 60ml of deionized water to obtain a first solution, 0.299g of antimony acetate and 0.434g of cerium nitrate hexahydrate are dissolved in 20ml of deionized water to obtain a second solution, and the second solution and the first solution are mixed to obtain a mixed solution;

[0056] Step 2, the mixed solution is magnetically stirred for 1h and then left to stand for 12h, washed, centrifuged, dried to obtain a third precipitate, and the third precipitate is placed in a muffle furnace and heated to 450℃ at a heating rate of 5℃ / min, and calcined at 450℃ for 2 hours to obtain a supported SCR catalyst (MnCeOx / SbCeOx).

[0057] Comparative Example 3

[0058] A preparation method of a supported SCR catalyst (MnCeOx / PrCeOx) is basically the same as the preparation method of the supported SCR catalyst in Comparative Example 2, and the only difference is that "0.299g of antimony acetate" is replaced by "0.435g of praseodymium nitrate hexahydrate".

[0059] The TEM of MnCeOx / PrCeOx is as shown in Figure 3As shown, compared with the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2, the surface of the MnCeOx / PrCeOx nanospheres became irregular, which might be due to the uneven dispersion of the PrCeOx particles on the surface of the catalyst prepared by the impregnation method.

[0060] The denitration activity test and the water and sulfur resistance test of the catalysts are as follows:

[0061] Test 1:

[0062] The denitration tests were respectively conducted on MnCeOx, the core-shell structure SCR catalyst (MnCeOx@SbCeOx) prepared in Example 1, the core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2, the core-shell structure SCR catalyst (MnCeOx@CoCeOx) prepared in Comparative Example 1, the supported SCR catalyst (MnCeOx / SbCeOx) prepared in Comparative Example 2 and the supported SCR catalyst (MnCeOx / PrCeOx) prepared in Comparative Example 3. The conditions of the simulated flue gas were as follows: the reaction temperature was 90-270°C, N2was used as the carrier gas, O2(5 vol.%), NO (500 ppm) and NH3(500 ppm) were introduced, the total gas flow was 200 mL / min, and the space velocity was 30,000 h-1. -1 .

[0063] The test results are shown in Table 1. Figure 4 As shown in Table 1, the core-shell structure SCR catalysts prepared in Examples 1-2 are the catalysts with antimony cerium oxide or praseodymium cerium oxide as the shell layer, and the denitration performance has a significant advantage. Among them, the denitration activity of the catalyst with praseodymium cerium oxide as the shell layer (MnCeOx@PrCeOx) is all above 90% in the whole temperature range (90-270°C) of the test. The denitration activity of the catalyst with cobalt cerium oxide as the shell layer is poor.

[0064] Test 2:

[0065] The sulfur resistance tests were respectively conducted on MnCeOx, the core-shell structure SCR catalyst (MnCeOx@SbCeOx) prepared in Example 1 and the supported SCR catalyst (MnCeOx / SbCeOx) prepared in Comparative Example 2. The conditions of the simulated flue gas were as follows: the reaction temperature was 180°C, N2was used as the carrier gas, O2(5 vol.%), NO (500 ppm), NH3(500 ppm) and SO2(0, 100 ppm and 200 ppm) were introduced, the total gas flow was 200 mL / min, and the space velocity was 30,000 h-1. -1 .

[0066] As shown in Table 2, Figure 5As shown, first, the MnCeOx was subjected to sulfur resistance performance test under simulated flue gas conditions. When no SO2 was introduced, the denitration rate of MnCeOx at 180°C was 88%, when 100 ppm of SO2 was introduced, the denitration rate of MnCeOx decreased to 75%, and when the SO2 concentration increased to 200 ppm, the denitration rate of MnCeOx decreased to about 61%. Under the same conditions, the core-shell structure SCR catalyst prepared in Example 1 was subjected to sulfur resistance test under simulated flue gas conditions. When no SO2 was introduced, the activity of MnCeOx@SbCeOx at 180°C was 93%, when 100 ppm of SO2 was introduced, the MnCeOx@SbCeOx showed excellent catalytic performance, and the NOx removal rate was not affected. When the temperature was kept at 180°C, and the SO2 concentration increased to 200 ppm SO2, the denitration rate only decreased by about 3%, indicating that the core-shell structure SCR catalyst (MnCeOx@SbCeOx) had good SO2 resistance. When no SO2 was introduced, the denitration rate of MnCeOx / SbCeOx was 89%, when 100 ppm of SO2 was introduced, the denitration rate decreased from 89% to about 79.2%, and when the SO2 concentration increased to 200 ppm, the denitration rate decreased to about 68.2%. Compared with the core-shell structure MnCeOx@SbCeOx, the MnCeOx / SbCeOx had poor sulfur resistance.

[0067] Test 3:

[0068] The core-shell structure SCR catalyst (MnCeOx@PrCeOx) prepared in Example 2 and the supported SCR catalyst (MnCeOx / PrCeOx) prepared in Comparative Example 3 were subjected to denitration test, respectively. The simulated flue gas conditions were as follows: the reaction temperature was 120°C, N2 was the carrier gas, 5 vol.% of O2, 500 ppm of NO, 500 ppm of NH3, 0 and 200 ppm of SO2, 0 and 8 vol.% of H2O were introduced, the total gas flow was 200 mL / min, the space velocity was 30,000 h-1, and the denitration rate was calculated. -1 .

[0069] The test results are shown in Table 3. Figure 6As shown in the figure, when no SO2 is introduced, the denitration rate of MnCeOx@PrCeOx is about 94%, and when the temperature continues to be kept at 120°C, while 200 ppm of SO2 and 8 vol.% of H2O are introduced, the denitration rate of MnCeOx@PrCeOx still remains above 80%, indicating that the MnCeOx@PrCeOx with core-shell structure has good SO2 and water resistance. However, when 200 ppm of SO2 and 8 vol.% of H2O are introduced at the same time, the denitration rate of the supported SCR catalyst prepared in Comparative Example 3 decreases to about 61.4%. Compared with the MnCeOx@PrCeOx with core-shell structure, the traditional MnCeOx / PrCeOx has poor SO2 and water resistance.

[0070] Table 1: BET specific surface area and pore structure properties of the core-shell structure SCR catalyst prepared in Example 1, the supported SCR catalyst (MnCeOx / SbCeOx) prepared in Comparative Example 2 and MnCeOx

[0071]

[0072] As can be seen from Table 1, the core-shell structure SCR catalyst has stronger adsorption capacity for NH3, indicating that it has more abundant acid sites.

[0073] The above has exemplarily described the present application, and it should be indicated that any simple modification, change or other equivalent replacement which can not cost creative labor of those skilled in the art without departing from the core of the present application falls into the protection scope of the present application.

Claims

1. The use of a core-shell structured SCR catalyst to improve the resistance to sulfur and water in flue gas denitrification, characterized in that, The core-shell structure SCR catalyst has a core-shell structure, the core is a spherical MnCeO x , the shell is SbCeO x or PrCeO x , the thickness of the shell is 30-45 nm, the particle size of the core-shell structure SCR catalyst is 160-200 nm, and the preparation method of the core-shell structure SCR catalyst comprises the following steps: Step 1, drop A solution and B solution into MnCeO solution to obtain C solution, wherein the A solution is a mixture of precipitant and water; the B solution is a mixture of metal source, cerium source and water, the metal element in the metal source is antimony or praseodymium, the ratio of the metal element in the metal source to the cerium element in the B solution is (1-3):3 in terms of the number of moles; the MnCeO solution is a mixture of MnCeO, water and anhydrous ethanol. x x The MnCeO solution is a mixture of MnCeO, water and anhydrous ethanol. x ​​ the mass fraction of the precipitant, the mass fraction of the metal element in the metal source and the mass fraction of the MnCeO x in the solution are in the ratio of 1:(1~3):0.4, the unit of the mass fraction is g, the unit of the amount of substance is mmol, and the precipitant is hexamethylenetetramine; x in the solution are in the ratio of 1:(1~3):0.4, the unit of the mass fraction is g, the unit of the amount of substance is mmol, and the precipitant is hexamethylenetetramine; Preparation of MnCeO x The method includes: mixing cerium salt, manganese nitrate solution, and ethylene glycol, reacting them at 180°C for 24 hours using an alcoholic heat treatment method, cooling, centrifuging to obtain a first precipitate, washing and drying the first precipitate, and calcining it at 450°C for 3.5–4.5 hours to obtain MnCeO. x The ratio of the molar amount of cerium salt, the molar amount of manganese in the manganese nitrate solution, and the volume fraction of ethylene glycol is (1-2):1:

120. The molar amount is expressed in mmol, and the volume fraction is expressed in mL. Step 2: The C solution is heated at 60-80°C for 2h and then cooled to room temperature to obtain a second precipitate, which is washed, dried, and then calcined at 450°C for 2-3h to obtain a core-shell structured SCR catalyst.

2. Use according to claim 1, characterized in that, In step 1, the concentration of the metal element in solution B is 0.1 mol / L, and the MnCeO x MnCeO in solution x The concentration of the precipitant is 0.005 g / mL, and the concentration of the precipitant in solution A is 0.1 mol / L.

3. Use according to claim 1, characterized in that, The MnCeO x The solution is MnCeO x and absolute ethanol are mixed homogeneously to obtain.

4. Use according to claim 1 or 3, characterized in that, The MnCeO x has a particle size of 100-130 nm.

5. Use according to claim 4, characterized in that, In Step 2, the drying is performed at 60-80°C for 10-12h; in Step 2, the calcination after drying is performed at a temperature increasing rate of 1-2°C / min.

6. Use according to claim 5, characterized in that, In the process for preparing MnCeO x the temperature of drying is 60°C, the time of drying is 10-12h, and the washing is carried out with water and anhydrous ethanol.

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