Cerium-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of gas waste treatment, provides a cerium-based catalyst as well as a preparation method and application thereof, and solves the problem of poor catalytic activity of a cerium-based catalyst in the prior art. The cerium-based catalyst comprises a carrier and an active component, the carrier is Ni-Fe layered bimetallic oxide, and the active component is CeO2. The cerium-based catalyst provided by the invention has the advantages that the catalytic activity is obviously improved, and the denitration performance is obviously improved. Meanwhile, the cerium-based catalyst provided by the invention can be suitable for a wide-temperature flue gas working condition, and is green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas waste treatment, in particular to a cerium-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Nitrogen oxide (NO x ) is one of the main atmospheric pollutants, which has great harm to human health and ecological environment, and its emission mainly comes from coal-fired boilers, kilns and motor vehicle exhausts, etc. Selective catalytic reduction (SCR) technology is an effective means for reducing NO x pollution at present, which can generate N2 and H2O by catalyzing the reaction of NO x with a reducing agent. The denitration catalyst is the core of the SCR technology, and its performance directly determines the denitration efficiency and applicable working conditions. The traditional SCR catalyst mainly uses a vanadium-based system (such as V2O5-WO3 / TiO2), and the denitration efficiency can reach more than 90% in the temperature window of 300℃-420℃. However, on the one hand, the active component vanadium pentoxide (V2O5) has biological toxicity, and long-term use may cause ecological environment pollution and harm to human health; on the other hand, the high-temperature working window of the vanadium-based catalyst cannot adapt to the wide temperature flue gas conditions of 150℃-350℃ in non-electricity industries (such as cement kilns).

[0003] In order to meet the green denitration demand of non-electricity industries, vanadium-free wide-temperature catalysts have become the research focus. The cerium-based (CeO2) catalyst has become a very potential alternative scheme due to its unique Ce 3+ / Ce 4+ redox cycle and oxygen storage capacity. However, the existing cerium-based catalyst has the problem of poor catalytic activity. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defect of poor catalytic activity of the existing cerium-based catalyst, so as to provide a cerium-based catalyst and a preparation method and application thereof.

[0005] To this end, the present application provides the following technical solutions:

[0006] In a first aspect, the present application provides a cerium-based catalyst, comprising a carrier and an active component.

[0007] The carrier is a Ni-Fe layered double metal oxide, and the active component comprises CeO2; the mass ratio of the carrier and the active component is (0.1-0.8):1.

[0008] In an optional embodiment, the active component is a nanoparticle.

[0009] In a second aspect, the present application further provides a preparation method of the cerium-based catalyst, comprising the following steps:

[0010] S1. obtaining a Ni-Fe layered double hydroxide;

[0011] S2. mixing the Ni-Fe layered double hydroxide and the cerium salt solution, sequentially heating and calcining to obtain the cerium-based catalyst.

[0012] In an alternative embodiment, the process of obtaining the Ni-Fe layered double hydroxide in S1 comprises mixing a nickel salt, an iron salt, an ammonium salt, a precipitant, and water, and performing a hydrothermal reaction to obtain the Ni-Fe layered double hydroxide.

[0013] In an alternative embodiment, the hydrothermal reaction has a temperature of 140-160°C and a time of 0.5-1.5h.

[0014] In an alternative embodiment, the nickel salt comprises one or more of nickel chloride, nickel nitrate.

[0015] In an alternative embodiment, the iron salt comprises one or more of iron nitrate, iron chloride.

[0016] In an alternative embodiment, the ammonium salt comprises one or more of ammonium fluoride, ammonium chloride.

[0017] In an alternative embodiment, the precipitant comprises one or more of urea, carbamide.

[0018] In an alternative embodiment, the molar ratio of the nickel salt to the iron salt is (8-12):(2.4-3.6).

[0019] In an alternative embodiment, the molar ratio of the nickel salt to the ammonium salt is (8-12):(80-120).

[0020] In an alternative embodiment, the molar ratio of the nickel salt to the precipitant is (8-12):(40-60).

[0021] In an alternative embodiment, the molar ratio of the nickel salt to water is 1:(100-120).

[0022] In an alternative embodiment, the process of mixing the Ni-Fe layered double hydroxide and the cerium salt solution in S2 comprises mixing the Ni-Fe layered double hydroxide with ethanol to obtain a dispersion, and then mixing the dispersion with the cerium salt solution.

[0023] In an alternative embodiment, the ratio of the mass of the Ni-Fe layered double hydroxide to the volume of ethanol is (3-7)g:(90-110)mL.

[0024] In an alternative embodiment, the cerium salt comprises one or more of cerium nitrate hexahydrate, cerium oxalate.

[0025] In an alternative embodiment, the concentration of the cerium salt solution is 0.05 mol / L-0.15 mol / L.

[0026] In an alternative embodiment, the mass ratio of the Ni-Fe layered double hydroxide and the cerium salt is (0.1-100):100.

[0027] In an alternative embodiment, the temperature of the heating in S2 is 50℃-70℃.

[0028] In an alternative embodiment, the temperature of the calcination in S2 is 250℃-400℃, and the time is 1h-3h.

[0029] In an alternative embodiment, the time for mixing the nickel salt, the iron salt, the ammonium salt, the precipitant and the water is 0.8h-1.5h.

[0030] In an alternative embodiment, after the hydrothermal reaction, the system is naturally cooled to 20℃-30℃, and the precipitate is taken for washing and drying to obtain the Ni-Fe layered double hydroxide.

[0031] In an alternative embodiment, the washing comprises ethanol washing and water washing in sequence, and the number of times of the ethanol washing and the water washing is ≥2 times respectively; the temperature of the drying is 70℃-90℃.

[0032] In an alternative embodiment, after the Ni-Fe layered double hydroxide is ground into powder, the powder is mixed with ethanol, stirred uniformly, then ultrasonic is performed, and finally stirred again to obtain a dispersion liquid.

[0033] In an alternative embodiment, the frequency of the ultrasonic is 500W-700W, and the time is 20min-40min.

[0034] In an alternative embodiment, the heating is performed to evaporate the liquid in the system to obtain a solid sample, and then calcination is performed.

[0035] In an alternative embodiment, after the calcination is completed, the system is naturally cooled to 20℃-30℃.

[0036] In an alternative embodiment, the method comprises the following steps: a cerium-based catalyst with a particle size of 40 mesh-60 mesh is filled into a fixed bed reactor, then a mixed flue gas comprising NH3, NO x and O2 is introduced to perform a denitration reaction.

[0037] In an optional embodiment, the amount of cerium-based catalyst added is 0.08g-0.15g, the concentration of NH3 in the mixed flue gas is 400ppm-1000ppm, and the NO content is... x The concentration of the flue gas is 400ppm-1000ppm, and the volume fraction of O2 is 4%-6%; the gas flow rate of the mixed flue gas is 200mL / min-300mL / min.

[0038] In one optional embodiment, the denitrification reaction is carried out at a temperature of 150°C-350°C, a pressure of 101.325 kPa, and a time of 30 min.

[0039] In a third aspect, the present invention provides the application of the above-described cerium-based catalyst or the cerium-based catalyst prepared according to the above preparation method in a denitrification reaction.

[0040] The technical solution of this invention has the following advantages:

[0041] 1. This invention provides a cerium-based catalyst, comprising a support and an active component; the support is a Ni-Fe layered bimetallic oxide (LDO), and the active component is CeO2.

[0042] The cerium-based catalyst provided by this invention uses LDO as a support to load CeO2 active components, which facilitates the highly dispersed embedding of the active components between the LDO layers, resulting in excellent dispersibility and stability. Simultaneously, the LDO is obtained through high-temperature calcination of Ni-Fe layered bimetallic hydroxide (Ni-Fe LDH), effectively removing water molecules and anions between the layers, which promotes high dispersion of CeO2 within its structure and improves the diffusion efficiency of reactants and products, thereby enhancing catalytic efficiency. The cerium-based catalyst provided by this invention effectively solves the problems of poor dispersibility (easy agglomeration) and unclear exposure of active sites in traditional CeO2 catalysts. Furthermore, the cerium-based catalyst provided by this invention is suitable for wide-temperature flue gas conditions of 150℃-350℃ in non-electric industries (such as cement kilns), and is vanadium-free, making it environmentally friendly.

[0043] 2. This invention first designs and synthesizes Ni-Fe layered bimetallic hydroxides using a simple co-precipitation method, then highly disperses Ce ions on the Ni-Fe layered bimetallic hydroxides using an impregnation method. Finally, it is calcined to transform into LDO@CeO2. The Ni-Fe layered bimetallic hydroxides possess a unique two-dimensional layered structure; during calcination, OH... - and CO3 2-The escape of the structure and the recombination of the structure will not destroy its original layered structure. The obtained LDO@CeO2 can maintain a high specific surface area, thereby further improving the dispersion and exposure of the active sites on the catalyst; at the same time, a large number of basic sites can be effectively converted into Lewis acidic sites. In the denitration process by using the selective catalytic reduction technology, not only is it beneficial to balance the adsorption and conversion of NH3 and NO x , but also it is beneficial to expose more active sites, thereby effectively improving the low surface acidity problem in pure CeO2.

[0044] 3. The preparation process has the advantages of easy availability of raw materials, low energy consumption and simplified process, greatly reduces the production cost, and provides a new technical path with environmental friendliness and economic feasibility for efficient treatment of nitrogen oxides.

[0045] 4. Ni-Fe LDH and LDO can be converted in a simple method, so there is a significant advantage in the multiple use of cerium-based catalysts, greatly reducing the use cost of the overall denitration process, and having strong market competitiveness. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0047] Figure 1 is the XRD characterization diagram of Ni-Fe LDH and LDO in Example 1;

[0048] Figure 2 is the XRD characterization diagram of the catalyst and LDO prepared in Example 1-Example 3, Comparative Example 1;

[0049] Figure 3 is the SEM characterization diagram of the catalyst prepared in Example 1-Example 3, Comparative Example 1, and Ni-Fe LDH and LDO in Example 1;

[0050] Figure 4 is the actual picture of the catalyst and LDO prepared in Example 1-Example 3, Comparative Example 1;

[0051] Figure 5 is the N2 adsorption-desorption diagram of the catalyst and LDO prepared in Example 1-Example 3, Comparative Example 1;

[0052] Figure 6 Figure 1 is a pore size distribution graph of the catalysts and LDO prepared in Example 1-3 and Comparative Example 1;

[0053] Figure 7 Figure 2 is a denitration performance graph of the catalysts prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0054] The following examples are provided to better enable those skilled in the art to further understand and practice the application, and are not intended to limit the scope of the application. Any product, input, or process, which is similar to the products, inputs, or processes described in the examples, and which is not expressly identified in the claims, is intended to fall within the scope of the present application.

[0055] Unless otherwise indicated, conventional methods of laboratory preparation, molecular biology, chemistry, and biochemistry, which are well within the purview of the skilled artisan, are employed in the examples. Unless otherwise indicated, all reagents and instruments are commercially available conventional products.

[0056] Example 1

[0057] The present example provides a method for preparing a cerium-based catalyst, comprising the following steps:

[0058] Nickel chloride, iron nitrate, ammonium fluoride, urea, and water (molar ratio of nickel chloride, iron nitrate, ammonium fluoride, and urea is 10:3:100:50, molar ratio of nickel chloride and water is 1:110) were mixed and stirred for 1 h, and then placed in a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction at 150°C for 1 h. After the hydrothermal reaction was completed, the mixture was naturally cooled to 25°C. The precipitate was washed with ethanol for 3 times and then washed with water for 3 times. Finally, the mixture was dried at 80°C to obtain a Ni-Fe layered double hydroxide (labeled as Ni-Fe LDH).

[0059] After 5 g of the Ni-Fe LDH was ground into a powder, it was added to 100 mL of ethanol and stirred until uniform. Then, the mixture was ultrasonically treated at 600 W for 30 min. After the ultrasonic treatment was completed, the mixture was stirred again to obtain a dispersion. The dispersion was mixed with a cerium nitrate hexahydrate solution having a concentration of 0.1 mol / L (mass ratio of the Ni-Fe LDH in the dispersion to the cerium nitrate hexahydrate in the cerium nitrate hexahydrate solution is 20:100). The mixture was heated at 60°C until the liquid in the system evaporated. The obtained solid sample was calcined at 300°C for 2 h. After the calcination was completed, the mixture was naturally cooled to 25°C to obtain a cerium-based catalyst (labeled as 20wt% LDO@CeO2).

[0060] Example 2

[0061] The embodiment provides a preparation method of a cerium-based catalyst, which is basically the same as that in Embodiment 1, except that the mass ratio of Ni-Fe LDH in the dispersion liquid and cerium nitrate hexahydrate in the cerium nitrate hexahydrate solution is 40:100 (marked as 40wt% LDO@CeO2).

[0062] Embodiment 3

[0063] The embodiment provides a preparation method of a cerium-based catalyst, which is basically the same as that in Embodiment 1, except that the mass ratio of Ni-Fe LDH in the dispersion liquid and cerium nitrate hexahydrate in the cerium nitrate hexahydrate solution is 60:100 (marked as 60wt% LDO@CeO2).

[0064] Embodiment 4

[0065] Nickel chloride, iron nitrate, ammonium fluoride, urea and water (the molar ratio of nickel chloride, iron nitrate, ammonium fluoride and urea is 12:2.4:100:50, and the molar ratio of nickel chloride and water is 1:110) are mixed and stirred for 1h, and then placed in a polytetrafluoroethylene hydrothermal reaction kettle for hydrothermal reaction at 150℃ for 1h. After the hydrothermal reaction is completed, the mixture is naturally cooled to 25℃. The precipitate is washed with ethanol for 3 times, and then washed with water for 3 times. Finally, drying is performed at 80℃ to obtain Ni-Fe layered double hydroxide (marked as Ni-Fe LDH).

[0066] After 5g of the Ni-Fe layered double hydroxide is ground into powder, the powder is added into 90mL of ethanol, and then stirred uniformly. Then, ultrasonic treatment is performed at 600W for 30min. After the ultrasonic treatment is completed, the mixture is stirred again to obtain a dispersion liquid. The dispersion liquid and a cerium nitrate hexahydrate solution with a concentration of 0.1mol / L are mixed (the mass ratio of Ni-Fe LDH in the dispersion liquid and cerium nitrate hexahydrate in the cerium nitrate hexahydrate solution is 20:100). The mixture is heated at 60℃ until the liquid in the system is evaporated. The obtained solid sample is calcined at 300℃ for 2h. After the calcination is completed, the mixture is naturally cooled to 25℃ to obtain a cerium-based catalyst.

[0067] Embodiment 5

[0068] Nickel chloride, iron nitrate, ammonium fluoride, urea and water (the molar ratio of nickel chloride, iron nitrate, ammonium fluoride and urea is 8:3.6:100:50, and the molar ratio of nickel chloride and water is 1:110) are mixed and stirred for 1h, and then placed in a polytetrafluoroethylene hydrothermal reaction kettle for hydrothermal reaction at 150℃ for 1h. After the hydrothermal reaction is completed, the mixture is naturally cooled to 25℃. The precipitate is washed with ethanol for 3 times, and then washed with water for 3 times. Finally, drying is performed at 80℃ to obtain Ni-Fe layered double hydroxide (marked as Ni-Fe LDH).

[0069] After 5 g of the Ni-Fe layered double hydroxide powder obtained by grinding was weighed into 110 mL of ethanol, the mixture was stirred uniformly, and then ultrasonic treatment was performed for 30 min at 600 W. After the ultrasonic treatment, the mixture was stirred again to obtain a dispersion liquid. The dispersion liquid was mixed with a cerium nitrate hexahydrate solution with a concentration of 0.1 mol / L (the mass ratio of the Ni-Fe LDH in the dispersion liquid to the cerium nitrate hexahydrate in the cerium nitrate hexahydrate solution was 20:100), and the liquid in the system was evaporated by heating at 60°C. The obtained solid sample was calcined at 300°C for 2 h, and then naturally cooled to 25°C to obtain a cerium-based catalyst.

[0070] Comparative Example 1

[0071] The present comparative example provides a preparation method of a CeO2catalyst, which comprises the following steps:

[0072] A cerium nitrate hexahydrate solution with a concentration of 0.1 mol / L was heated at 60°C until the liquid in the system was evaporated. The obtained solid sample was calcined at 300°C for 2 h, and then naturally cooled to 25°C to obtain a CeO2catalyst (labeled as CeO2).

[0073] Test Example 1

[0074] After 0.4 g of the Ni-Fe layered double hydroxide obtained in Example 1 was weighed into a powder, the obtained uniform powder was calcined at 300°C for 2 h, and then naturally cooled to 25°C to obtain a Ni-Fe layered double oxide (labeled as LDO).

[0075] The Ni-Fe LDH obtained in Example 1 and the LDO obtained by calcining the Ni-Fe LDH were subjected to XRD characterization, and the XRD characterization graph is shown in Figure 1 .

[0076] In combination Figure 1 It can be seen that the diffraction peaks of the LDH are relatively narrow and strong in intensity, which proves that the LDH synthesized by the coprecipitation method has good crystallinity, and the diffraction peaks of the LDH gradually change into the peaks of the LDO after calcination at a certain temperature. Compared with the diffraction peaks of the original Ni-Fe LDH, the peaks of the LDO are relatively wide and slightly weaker in intensity, which indicates that the size of the crystal grains gradually decreases when the Ni-Fe LDH forms the LDO. This may be caused by the fact that the OH - ions and the interlayer H2O molecules are removed during the calcination process, and the internal metal ions and oxygen ions are recombined.

[0077] The catalysts obtained in Example 1 to Example 3 and Comparative Example 1, and the LDO were subjected to XRD characterization, and the XRD characterization graphs of different catalysts are shown in Figure 2 .

[0078] from Figure 2 As can be seen, the diffraction peak positions of the cerium-based catalysts in Examples 1-3 and Comparative Example 1 can all match the peak positions of the standard card (PDF 03-065-5923) of CeO2. As the proportion of Ce in the cerium-based catalyst continues to increase, the diffraction peak of LDO can never be shown, which is due to the high crystallinity of CeO2.

[0079] Test Example 2

[0080] The catalysts prepared in Examples 1-3 and Comparative Example 1, as well as the Ni-Fe LDH and LDO obtained by calcining Ni-Fe LDH in Example 1, were characterized by SEM and physical analysis. SEM images of the different catalysts were obtained, as shown below. Figure 3 As shown. From Figure 3 As can be seen, before and after LDH is transformed into LDO, its morphology consists of large microspheres formed by interspersed nanosheets, with the size of the microspheres being around 4 μm. With the continuous loading of CeO2, the number of nanoparticles on the surface of LDO nanosheets gradually increases. These nanoparticles are about 50 nm in size and are evenly distributed, indicating the successful composite of the two materials.

[0081] Images of the catalysts prepared in Examples 1-3 and Comparative Example 1, and of the LDO obtained by calcining Ni-Fe LDH in Example 1, are shown below. Figure 4 As shown. From Figure 4 As can be seen, the color of the sample changes with the continuous change of the ratio of Ni-Fe LDH to CeO2, which proves the successful composite of LDO@CeO2 material.

[0082] Test Example 3

[0083] The catalysts prepared in Examples 1-3 and Comparative Example 1, as well as LDO, were subjected to N2 adsorption-desorption experiments under the conditions of an adsorption temperature of liquid nitrogen (-196℃ / 77K) and a relative pressure (P / P0, where P is the actual partial pressure of N2 and P0 is the saturated vapor pressure of N2 at liquid nitrogen temperature) of 0.05-0.99. The N2 adsorption-desorption figures for the catalysts prepared in Examples 1-3 and Comparative Example 1, as well as LDO, are shown in the attached figures. Figure 5 As shown. Simultaneously, the pore size distribution of different catalysts was analyzed, yielding pore size distribution diagrams of the catalysts prepared in Examples 1-3, Comparative Example 1, and LDO, as shown. Figure 6 As shown in Table 1, the pore size distribution data for different catalysts are as follows.

[0084] Table 1 Pore size distribution data for different catalysts

[0085] Catalyst name Specific surface area (m 2 / g) Pore size (nm) Pore volume (cm 3 / g) Example 1 20 wt% LDO @ CeO2 80.2 8.4 0.17 Example 2 40 wt% LDO @ CeO2 70.0 9.0 0.16 Example 3 60 wt% LDO @ CeO2 79.7 8.3 0.16 Comparative Example 1 CeO2 57.6 8.7 0.13 LDO 122.5 7.3 0.22

[0086] In combination Figure 5 - Figure 6 and Table 1, all catalysts have a mesoporous structure, and the specific surface area of the cerium-based catalyst prepared in the application is greatly improved relative to single CeO2. The specific surface area of 20wt% LDO@CeO2 can reach 80.2m 2 / g. High specific surface area and mesoporous structure are conducive to the diffusion and transmission of reaction gas in the catalyst and contact reaction with active sites. At the same time, the pore volume also changes with the change of the specific surface area. The above data prove that the addition of LDO can effectively improve the physical and chemical properties of the catalyst.

[0087] Test Example 4

[0088] The cerium-based catalysts obtained in Example 1 and Comparative Example 1 were respectively subjected to denitration experiment test, which specifically included the following steps:

[0089] 0.12g of cerium-based catalyst with a particle size of 50 mesh was filled into a fixed bed reactor, and then a mixed flue gas including NH3, NO x and O2was introduced, wherein the volume concentration of NH3 in the mixed flue gas was 500ppm, the volume concentration of NO x was 500ppm, and the volume fraction of O2was 5%. The gas flow rate of the mixed flue gas was set to 300mL / min, the reaction pressure was 101.325kPa, and the denitration reaction was carried out at temperatures of 150, 200, 250 and 300℃ respectively, and the reaction time at each temperature was 30min. The denitration performance diagram of the catalyst prepared in Example 1 and Comparative Example 1 was obtained, as shown in Figure 7 .

[0090] As can be seen from Figure 7 , under the condition that the space velocity of the mixed flue gas is 150000h -1 , the pure CeO2has almost no denitration performance at a reaction temperature below 300℃, while the denitration performance of the cerium-based catalyst prepared in the application is obviously improved, and the catalyst of the application is suitable for wide-temperature flue gas denitration.

[0091] Obviously, the above examples are only examples for clearly illustrating, and not limit the embodiments. For those skilled in the art, on the basis of the above description, other different forms of changes or variations can also be made. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A cerium-based catalyst, characterized in that, comprising a carrier and an active component; the carrier is a Ni-Fe layered double metal oxide, and the active component comprises CeO2; and the mass ratio of the carrier to the active component is (0.1-0.8):

1.

2. The method of producing a cerium-based catalyst as claimed in claim 1, characterized by, comprising the following steps: S1. obtaining a Ni-Fe layered double metal hydroxide; S2. mixing the Ni-Fe layered double metal hydroxide and a cerium salt solution, and sequentially heating and calcining to obtain the cerium-based catalyst.

3. The method of claim 2, wherein the cerium-based catalyst is prepared by the steps of: The process of obtaining the Ni-Fe layered double metal hydroxide in S1 comprises mixing a nickel salt, an iron salt, an ammonium salt, a precipitant and water, and performing a hydrothermal reaction to obtain the Ni-Fe layered double metal hydroxide.

4. The method of claim 3, wherein the cerium-based catalyst is prepared by the steps of: The temperature of the hydrothermal reaction is 140-160℃, and the time is 0.5-1.5h.

5. The method of claim 3, wherein the cerium-based catalyst is prepared by the steps of: At least one of the following conditions is met: (1) the nickel salt comprises one or more of nickel chloride and nickel nitrate; (2) the iron salt comprises one or more of iron nitrate and iron chloride; (3) the ammonium salt comprises one or more of ammonium fluoride and ammonium chloride; (4) the precipitant comprises one or more of urea and carbimide; (5) the molar ratio of the nickel salt to the iron salt is (8-12):(2.4-3.6); (6) the molar ratio of the nickel salt to the ammonium salt is (8-12):(80-120); (7) the molar ratio of the nickel salt to the precipitant is (8-12):(40-60); (8) the molar ratio of the nickel salt to water is 1:(100-120).

6. The process for the preparation of a cerium-based catalyst according to any one of claims 2 to 5, characterized in that, The process of mixing the Ni-Fe layered double metal hydroxide and the cerium salt solution in S2 comprises mixing the Ni-Fe layered double metal hydroxide with ethanol to obtain a dispersion, and then mixing the dispersion with the cerium salt solution.

7. The method of claim 6, wherein the cerium-based catalyst is prepared by the steps of: At least one of the following conditions is met: (1) the mass of the Ni-Fe layered double metal hydroxide to the volume of ethanol is (3-7)g:(90-110)mL; (2) the cerium salt comprises one or more of cerium nitrate hexahydrate and cerous oxalate; (3) the concentration of the cerium salt solution is 0.05-0.15mol / L; (4) the mass ratio of the Ni-Fe layered double metal hydroxide to the cerium salt is (0.1-100):

100.

8. The process for the preparation of a cerium-based catalyst according to any one of claims 2 to 5, characterized in that, The temperature of the heating in S2 is 50-70℃.

9. The process for the preparation of a cerium-based catalyst according to any one of claims 2 to 5, characterized in that, The temperature of the calcining in S2 is 250-400℃, and the time is 1-3h.

10. The cerium-based catalyst of claim 1 or the cerium-based catalyst prepared by the method of any one of claims 2-9 in a denitration reaction.

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