Denitration catalyst with K gain and water and sulfur composite poisoning resistance as well as preparation method and application

Abstract

The invention relates to a denitration catalyst with K gain and water and sulfur composite poisoning resistance as well as a preparation method and application thereof, and belongs to the field of environment-friendly catalytic materials and air pollution control. An organic solvent is used as a template agent, cerium oxide, manganese oxide, tungsten oxide and titanium oxide are used as active components, and a cerium-manganese-tungsten-titanium composite oxide active component with a porous structure and strong acidity is prepared by an evaporation-induced self-assembly method. The catalyst component is environment-friendly, low in cost and simple in preparation method, and is particularly suitable for stable and efficient purification of NOx in complex flue gas in the cement industry.

Description

Technical Field

[0001] The present invention relates to an SCR denitration catalyst with K gain at medium and low temperatures and resistance to combined poisoning by water and sulfur, and a preparation method and application thereof, belonging to the fields of environmental catalytic materials and air pollution control. Technical Background

[0002] Nitrogen oxides (NO x ) are the main pollutants released by human activities. A large amount of emissions can cause smog, acid rain, ozone holes and photochemical smog, which will cause serious harm to the environment and human health. The control of NO x emissions has been widely studied. The selective catalytic reduction (SCR) denitration technology has the advantages of high denitration efficiency, mature technology and no harmful products, and is the most widely used denitration technology.

[0003] In the actual application process, alkali metals (such as K, Na, Ca, Mg) in the flue gas of various process sections of the cement industry will poison the SCR catalyst, resulting in catalyst deactivation and deterioration of the SCR purification system. The deactivation of the SCR catalyst by alkali metals mainly includes physical deactivation and chemical deactivation. Physical deactivation is mainly manifested as the deposition of alkali metals (such as K, Ca, Mg), which will block the catalyst pores, resulting in a decrease in the specific surface area and pore volume of the catalyst. Chemical poisoning mainly leads to the redox performance and surface acidity of the catalyst, thereby affecting the adsorption of NH3 and reducing the denitration performance. For vanadium-based and manganese-based catalysts, alkali metals will destroy their B acid centers, inhibit the adsorption of NH3 on the catalyst, and reduce the surface adsorption of oxygen on the catalyst, thereby inhibiting the denitration activity of the SCR catalyst. For copper-based catalysts, isolated Cu 2+ is often the main active component of the copper-based catalyst. However, the presence of alkali metals will cause the free Cu 2+ to be converted into other copper species, reducing the active components of the catalyst, thereby reducing the activity of the catalyst. For cerium-based catalysts, the content of chemically adsorbed oxygen, Ce 3+ / (Ce 3+ +Ce 4+)The decrease in the ratio and NH3 adsorption capacity is the main reason for the poisoning and deactivation of the catalyst. For iron-based catalysts, the destruction of Brønsted acid sites by alkali metals and the inhibition of oxygen adsorption capacity are the main reasons for catalyst poisoning. Generally speaking, alkali metals reduce the surface acidity and reducibility of the catalyst sharply by occupying active sites, thereby reducing the denitrification activity. Among the related technologies of anti-alkali poisoning denitrification catalysts reported at home and abroad, (CN118719048A) prepares a niobium-modified sulfur- and alkali-metal-resistant low-temperature denitrification catalyst by impregnation after preparing manganese-titanium metal oxide by the sol-gel method. Its denitrification activity is higher than 80% at 100-300 °C, and the activity decreases rapidly after alkali poisoning. (CN116637614B) prepares a denitrification catalyst with cerium-manganese composite oxide as the active component and silica as the carrier. Its denitrification activity is higher than 80% at 225-350 °C. After loading Na by the impregnation method, the activity decreases, and the denitrification activity decreases by more than 10% in the whole temperature range. (CN114433195B) prepares a γ-Fe2O3 / HZSM-5 denitrification catalyst with high low-temperature catalytic activity. Its denitrification activity is higher than 80% at 300-400 °C, and the activity decreases after loading Na. At the same time, under actual working conditions, the presence of H2O and SO2 will also poison the catalyst and thus reduce the denitrification performance.

[0004] In the research on SCR denitrification catalysts, it is necessary not only to improve the single anti-alkali metal, anti-water, and anti-sulfur poisoning stability of the catalyst, but also to significantly improve its anti-compound poisoning stability under the coexistence of alkali metals, water, and sulfur. Therefore, it is of great significance to develop a highly efficient denitrification catalyst with excellent anti-sulfur, anti-water, and anti-alkali metal compound poisoning under actual working conditions. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of poor anti-compound poisoning stability of denitrification catalysts in the cement industry, and to provide a highly efficient denitrification catalyst that can achieve K gain at medium and low temperatures and has water and sulfur resistance; another purpose of the present invention is to provide a preparation method of the above denitrification catalyst.

[0006] A denitrification catalyst with K gain and resistance to water and sulfur compound poisoning, which uses F127 as a template agent, potassium nitrate as an alkali metal precursor, and cerium oxide, manganese oxide, tungsten oxide, and titanium oxide as denitrification active components.

[0007] In the above catalyst, the molar ratio of the four elements Ce, Mn, W, and Ti is 1:(0.02-0.8):(0.02-0.30):(0.1-0.6). Preferably, the molar ratio of the four elements Ce, Mn, W, and Ti is 1:(0.2-0.6):(0.1-0.30):(0.1-0.6).

[0008] A preparation method of the above catalyst is as follows:

[0009] (1) Preparation of the template agent

[0010] Add F127 to distilled water and stir in an oil bath until completely dissolved to obtain solution A;

[0011] (2) Preparation of the cerium-manganese-tungsten-titanium composite oxide catalyst

[0012] Add the cerium-manganese-tungsten-titanium oxide precursor to solution A and stir evenly; then place the above sample in an oven to dry, and finally calcine it to obtain the cerium-manganese-tungsten-titanium composite oxide catalyst;

[0013] (3) Preparation of the alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0014] Add the alkali metal precursor to distilled water and stir until completely dissolved, then add the cerium-manganese-tungsten-titanium catalyst to the above solution and continue to stir. Subsequently, place the sample in an oven to dry, and finally transfer it to a muffle furnace for calcination.

[0015] In the above preparation method, the temperature of the oil bath in step (1) is 30 - 50 °C.

[0016] In the above preparation method, the cerium-manganese-tungsten-titanium oxide precursor in step (2) is cerium nitrate, manganese nitrate, ammonium metatungstate, and tetrabutyl titanate.

[0017] In the above preparation method, the mass ratio of the cerium-manganese-tungsten-titanium oxide precursor to F127 in step (2) is 12 - 17:1 - 6.

[0018] In the above preparation method, the drying temperature of the sample in step (2) is 80 - 100 °C, and the drying time is 36 - 60 h; the calcination temperature is 400 - 700 °C, the calcination time is 1 - 5 h, and the calcination is a programmed temperature rise with a heating rate of 3 - 8 °C / min.

[0019] In the above preparation method, the alkali metal precursor in step (3) is potassium nitrate; the mass ratio of the cerium-manganese-tungsten-titanium composite oxide catalyst to the alkali metal precursor is 100:0.5 - 3.

[0020] In the above preparation method, the drying temperature in step (3) is 70 - 110 °C, and the drying time is 10 - 24 h; the calcination temperature is 400 - 700 °C, the calcination time is 1 - 5 h, and the calcination is a programmed temperature rise with a heating rate of 3 - 8 °C / min.

[0021] In the technical solution of the present invention, the application of the catalyst in denitrification.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The catalyst of the present invention has excellent denitrification activity and anti-compound poisoning stability under the coexistence conditions of 100-325 °C, alkali metal, water, and sulfur. The denitrification efficiency of the CMWT catalyst is >80% at 150-325 °C, while the denitrification efficiency of the CMWT-K catalyst after loading 1 wt.% K is >80% at 100-325 °C and >90% at 100-300 °C. It shows that the CMWT catalyst prepared by the evaporation-induced self-assembly method has an increase in medium and low-temperature activity after being poisoned by K, indicating that K has a certain beneficial effect on this catalyst. This is mainly because K dynamically regulates the valence state and surface chemical state of the active components. K + donates electrons to Ce, Mn, and Ti, inducing partial reduction of some metals (Ce 4+ →Ce 3+ , Mn 4+ →Mn 3+ , Ti 4+ →Ti 3+ ), accompanied by the generation of oxygen vacancies. The oxygen vacancies act as active sites to adsorb and activate NO, reduce the low-temperature reaction energy barrier, and enhance the low-temperature redox activity. At the same time, the activity is maintained above 90% for 12 h under the conditions of 200 °C, 1 wt.% K, 5% H2O, and 300 ppm SO2.

[0024] (2) The present invention uses an organic solvent as a template agent, which can introduce pore structures, accelerate the decomposition of ABS, and improve the water and sulfur resistance performance. At the same time, the doping of titanium dioxide causes the carboxyl group to lose protons, thereby providing more Brønsted acid sites, increasing the surface acid amount of the catalyst, and thus improving the ability of the catalyst to resist poisoning by alkali metals, water, and sulfur. In the case of loading 1 wt.% K, the denitrification efficiency of the catalyst is >90% under the conditions of 200 °C, 5 vol.% H2O, and 300 ppm SO2, and its denitrification efficiency is stable above 90% after 12 h.

[0025] (3) The preparation method of the present invention is simple, low in cost, requires low synthesis equipment, and has the advantages of being resistant to water and sulfur poisoning in the presence of K at medium and low temperatures. It is suitable for flue gas denitrification containing alkali / alkaline earth metal fly ash and SO2, such as in the fields of waste incinerators, cement kilns, biomass fuel boilers, and glass furnaces, and can greatly extend the service life of the catalyst in flue gas denitrification. Brief Description of the Drawings

[0026] Figure 1 is the NH3-SCR removal of NO x stability diagram of the present invention's Example 2 and Comparative Example 1 against water, sulfur, and combined poisoning by alkali and water and sulfur at 200 °C. Detailed Embodiments

[0027] The following further illustrates the present invention with reference to embodiments, but the protection scope of the present invention is not limited thereto.

[0028] The method for evaluating the denitration performance of the catalyst of the present invention is as follows: Simulate the composition of gas turbine exhaust gas, with an NO inlet concentration of 1000 ppm, an NH3 inlet concentration of 1000 ppm, an O2 content of 10%, an SO2 concentration of 300 ppm (added during use), an H2O content of 5 vol.% (added during use), and N2 as the carrier gas. Set the catalyst dosage to 1.2 ml, and set the reaction space velocity (GHSV) to 30000 h -1 , set the reaction temperature range to 50 - 400 °C, and use a flue gas analyzer to on-line monitor the concentration change of NO x before and after the reaction.

[0029] Example 1

[0030] (1) Preparation of the template agent

[0031] Add 3 g of F127 to 100 ml of distilled water, stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0032] (2) Preparation of the cerium-manganese-tungsten-titanium composite oxide catalyst

[0033] According to the molar ratio of Ce, Mn, W, and Ti elements of 1:0.4:0.14:0.4, weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 2.72 g of tetrabutyl titanate and add them to solution A, and stir evenly; then place the above sample in an oven at 90 °C for drying for 48 h, and after drying, put it into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the catalyst named M-CMWT-1.

[0034] (3) Preparation of the alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0035] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of the cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h, then place the sample in an oven at 80 °C for drying for 24 h, and after drying, put the sample into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the catalyst K-M-CMWT-1 after alkali metal poisoning.

[0036] (4) Testing of the denitration performance of the catalyst

[0037] The denitration efficiency of the fresh catalyst is > 90% at 175 - 275 °C. In the case of loading 1 wt.% K, the denitration efficiency is > 90% at 125 - 275 °C. It shows that the catalyst loaded with 1 wt.% K shows a gain phenomenon at low temperatures.

[0038] Example 2

[0039] (1) Preparation of the template agent

[0040] Add 4 g of F127 to 100 ml of distilled water, and stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0041] (2) Preparation of cerium-manganese-tungsten-titanium composite oxide catalyst

[0042] According to the molar ratio of the four elements Ce, Mn, W, and Ti of 1:0.4:0.14:0.4, weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 2.72 g of tetrabutyl titanate and add them to solution A, and stir evenly; then place the above sample in an oven at 90 °C for drying for 48 h, and after drying, put it into a muffle furnace and heat it up to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst named M-CMWT-2.

[0043] (3) Preparation of alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0044] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h, then place the sample in an oven at 80 °C for drying for 24 h, and put the dried sample into a muffle furnace and heat it up to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst poisoned by alkali metal, K-M-CMWT-2.

[0045] (4) Denitrification performance test of catalyst

[0046] The denitrification efficiency of the fresh catalyst is >90% at 175 - 300 °C. When 1 wt.% K is loaded, the denitrification efficiency is >90% at 100 - 300 °C. It shows that the catalyst loaded with 1 wt.% K shows a gain phenomenon at low temperature. The denitrification efficiency of the cerium-manganese-tungsten-titanium composite oxide catalyst loaded with 1 wt.% K is 100% under the conditions of 200 °C, 5 vol.% H2O, and 300 ppm SO2, and its denitrification efficiency remains stable above 100% after 12 h.

[0047] Example 3

[0048] (1) Preparation of template agent

[0049] Add 5 g of F127 to 100 ml of distilled water, and stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0050] (2) Preparation of cerium-manganese-tungsten-titanium composite oxide catalyst

[0051] Weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 2.72 g of tetrabutyl titanate according to the molar ratio of Ce, Mn, W, and Ti elements being 1:0.4:0.14:0.4, and add them to solution A, stirring evenly; then place the above sample in an oven at 90 °C for drying for 48 h, and after drying, put it into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst named M-CMWT-3.

[0052] (3) Preparation of alkali metal-loaded cerium manganese tungsten titanium catalyst

[0053] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium manganese tungsten titanium composite oxide catalyst and stir for 2 h. Subsequently, place the sample in an oven at 80 °C for drying for 24 h, and after drying, put the sample into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the alkali metal-poisoned catalyst K-M-CMWT-3.

[0054] (4) Denitrification performance test of the catalyst

[0055] The denitrification efficiency of the fresh catalyst is >90% at 175 - 275 °C. When 1 wt.% K is loaded, the denitrification efficiency is >90% at 125 - 275 °C. It shows that the catalyst loaded with 1 wt.% K exhibits a gain phenomenon at low temperatures.

[0056] Example 4

[0057] (1) Preparation of the template agent

[0058] Add 4 g of F127 to 100 ml of distilled water, and stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0059] (2) Preparation of cerium manganese tungsten titanium composite oxide catalyst

[0060] Weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 1.36 g of tetrabutyl titanate according to the molar ratio of Ce, Mn, W, and Ti elements being 1:0.4:0.14:0.2, and add them to solution A, stirring evenly; then place the above sample in an oven at 90 °C for drying for 48 h, and after drying, put it into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst named M-CMWT-4.

[0061] (3) Preparation of alkali metal-loaded cerium manganese tungsten titanium catalyst

[0062] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h. Subsequently, place the sample in an oven at 80 °C and dry for 24 h. Put the dried sample into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the catalyst K-M-CMWT-4 poisoned by alkali metal.

[0063] (4) Catalyst denitrification performance test

[0064] The denitrification efficiency of the fresh catalyst is >90% at 150 - 275 °C. When 1 wt.% K is loaded, the denitrification efficiency is >90% at 125 - 275 °C. It shows that the catalyst loaded with 1 wt.% K exhibits a gain phenomenon at low temperatures.

[0065] Example 5

[0066] (1) Preparation of template agent

[0067] Add 4 g of F127 to 100 ml of distilled water, stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0068] (2) Preparation of cerium-manganese-tungsten-titanium composite oxide catalyst

[0069] According to the molar ratio of Ce, Mn, W, and Ti elements of 1:0.4:0.14:0.3, weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 2.04 g of tetrabutyl titanate and add them to solution A, and stir evenly; then place the above sample in an oven at 90 °C and dry for 48 h. After drying, put it into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the catalyst named M-CMWT-5.

[0070] (3) Preparation of alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0071] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h. Subsequently, place the sample in an oven at 80 °C and dry for 24 h. Put the dried sample into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain the catalyst K-M-CMWT-5 poisoned by alkali metal.

[0072] (4) Catalyst denitrification performance test

[0073] The denitrification efficiency of the fresh catalyst is >90% at 200 - 300 °C. When 1 wt.% K is loaded, the denitrification efficiency is >90% at 150 - 300 °C. It shows that the catalyst loaded with 1 wt.% K exhibits a gain phenomenon at low temperatures.

[0074] Example 6

[0075] (1) Preparation of template agent

[0076] Add 4 g of F127 into 100 ml of distilled water, stir in an oil bath at 40 °C until completely dissolved to obtain a clear solution A;

[0077] (2) Preparation of cerium-manganese-tungsten-titanium composite oxide catalyst

[0078] According to the molar ratio of Ce, Mn, W, and Ti elements of 1:0.4:0.14:0.5, weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 3.4 g of tetrabutyl titanate and add them to solution A, stir evenly; then place the above sample in an oven at 90 °C for drying for 48 h, and after drying, put it into a muffle furnace and heat it up to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst named M-CMWT-6.

[0079] (3) Preparation of alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0080] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h. Subsequently, place the sample in an oven at 80 °C for drying for 24 h, and put the dried sample into a muffle furnace and heat it up to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst poisoned by alkali metal, K-M-CMWT-6.

[0081] (4) Testing of catalyst denitrification performance

[0082] The denitrification efficiency of the fresh catalyst is >90% at 200 - 300 °C. Under the condition of loading 1 wt.% K, the denitrification efficiency is >90% at 150 - 300 °C. It shows that the catalyst loaded with 1 wt.% K has a gain phenomenon at low temperature.

[0083] Comparative Example 1

[0084] (1) Preparation of cerium-manganese-tungsten-titanium composite oxide catalyst

[0085] According to the molar ratio of Ce, Mn, W, and Ti elements of 1:0.4:0.14:0.4, weigh 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate, 0.6942 g of ammonium metatungstate, and 3.4 g of tetrabutyl titanate and add them to distilled water, stir evenly; then add ammonia water to adjust the pH to 10. Subsequently, let the above sample stand for aging for 24 h, then wash and filter until neutral, place the sample in an oven at 80 °C for drying for 24 h, and after drying, put it into a muffle furnace and heat it up to 600 °C at a rate of 5 °C / min for calcination for 3 h to obtain a catalyst named CMWT-2.

[0086] (2) Preparation of alkali metal-loaded cerium-manganese-tungsten-titanium catalyst

[0087] Disperse 0.1 g of potassium nitrate in 20 ml of distilled water, then add 1 g of cerium-manganese-tungsten-titanium composite oxide catalyst and stir for 2 h. Subsequently, place the sample in an oven and dry it at 80 °C for 24 h. Put the dried sample into a muffle furnace and heat it to 600 °C at a rate of 5 °C / min and calcine it for 3 h to obtain the catalyst K-CMWT-2 poisoned by alkali metal.

[0088] (3) Denitrification performance test of the catalyst

[0089] The denitrification efficiency of the fresh catalyst is >90% at 150 - 300 °C. Under the condition of loading 1 wt.% K, the denitrification efficiency is >90% at 200 - 250 °C. No gain phenomenon is found in the catalyst loaded with 1 wt.% K at low temperature. The denitrification efficiency of the catalyst loaded with 1 wt.% K is 98% under the conditions of 200 °C, 5 vol.% H2O, and 300 ppm SO2, and its denitrification efficiency remains stable above 50% after 12 h.

[0090] Table 1 shows the denitrification activity of the catalyst prepared by the present invention

[0091]

Claims

1. A denitration catalyst with K gain and resistance to combined poisoning by water and sulfur, characterized in that, The catalyst uses F127 as the template agent, potassium nitrate as the alkali metal precursor, and cerium oxide, manganese oxide, tungsten oxide, and titanium oxide as the denitrification active components.

2. The denitration catalyst with K gain and resistance to combined poisoning by water and sulfur according to claim 1, characterized in that, The molar ratio of the four elements Ce, Mn, W, and Ti is 1:(0.02 - 0.8):(0.02 - 0.30):(0.1 - 0.6); Preferably, the molar ratio of the four elements Ce, Mn, W, and Ti is 1:(0.2 - 0.6):(0.1 - 0.30):(0.1 - 0.6).

3. A method for preparing the catalyst according to claim 2, characterized in that, The specific steps are as follows: (1) Preparation of the template agent Add F127 to distilled water and stir in an oil bath until completely dissolved to obtain solution A; (2) Preparation of the cerium-manganese-tungsten-titanium composite oxide catalyst Add the cerium-manganese-tungsten-titanium oxide precursor to solution A and stir evenly; then place the above sample in an oven to dry, and finally perform calcination to obtain the cerium-manganese-tungsten-titanium composite oxide catalyst; (3) Preparation of the alkali metal-loaded cerium-manganese-tungsten-titanium catalyst Add the alkali metal precursor to distilled water and stir until completely dissolved, then add the cerium-manganese-tungsten-titanium catalyst to the above solution and continue stirring, then place the sample in an oven to dry, and finally transfer it to a muffle furnace for calcination.

4. The preparation method according to claim 3, characterized in that, In step (1), the temperature of the oil bath is 30 - 50 °C.

5. The preparation method according to claim 3, characterized in that, In step (2), the cerium-manganese-tungsten-titanium oxide precursor is cerium nitrate, manganese nitrate, ammonium metatungstate, and tetrabutyl titanate.

6. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio between the cerium-manganese-tungsten-titanium oxide precursor and F127 is 12 - 17:1 - 6.

7. The preparation method according to claim 3, wherein In step (2), the drying temperature of the sample is 80 - 100 °C, and the drying time is 36 - 60 h; the calcination temperature is 400 - 700 °C, the calcination time is 1 - 5 h, and the calcination is a programmed temperature rise with a heating rate of 3 - 8 °C / min.

8. The preparation method according to claim 3, wherein In step (3), the alkali metal precursor is potassium nitrate; the mass ratio of the cerium-manganese-tungsten-titanium composite oxide catalyst to the alkali metal precursor is 100:0.5 - 3.

9. The preparation method according to claim 3, characterized in that, In step (3), the drying temperature is 70 - 110 °C, and the drying time is 10 - 24 h; the calcination temperature is 400 - 700 °C, the calcination time is 1 - 5 h, and the calcination is a programmed temperature rise with a heating rate of 3 - 8 °C / min.

10. Application of the catalyst according to claim 1 in denitrification.

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