A rare earth-modified sulfur- and alkali-resistant metal low-temperature denitrification catalyst, its preparation method, and flue gas denitrification method

Abstract

This invention provides a rare-earth-modified sulfur- and alkali-metal-resistant low-temperature denitrification catalyst, its preparation method, and a flue gas denitrification method. The preparation method includes: directly using manganese salt, titanium source, and rare-earth precursor as main raw materials to prepare the rare-earth-modified sulfur- and alkali-metal-resistant low-temperature denitrification catalyst via a sol-gel method; or, the preparation method includes: first using manganese salt and titanium source as main raw materials to prepare a metal oxide catalyst via a precipitation-filtration method; then impregnating the rare-earth precursor onto the metal oxide catalyst to obtain the rare-earth-modified sulfur- and alkali-metal-resistant low-temperature denitrification catalyst. The denitrification catalyst prepared by this invention is suitable for lower denitrification temperatures, exhibits high NH3-SCR reactivity in the low-temperature range, and also possesses resistance to sulfur and alkali metal poisoning.

Description

Technical Field

[0001] This invention relates to the field of SCR denitrification reaction, specifically to a rare earth modified sulfur- and alkali metal low-temperature denitrification catalyst, its preparation method, and a flue gas denitrification method. Background Technology

[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants, and among them, sintering flue gas from iron and steel is a major contributor to NO pollution. x A major source of emissions. Currently, Selective Catalytic Reduction (SCR) is the main means of solving the problem of flue gas pollution. SCR refers to selectively removing NO from the atmosphere by adding an additional reducing agent to the reaction system under the condition of excess O2. x It is reduced to non-toxic and harmless N2. Selective catalytic reduction (SCR) is currently the most effective and widely used method for NO reduction under oxygen-enriched conditions. x Removal technologies. Depending on the reducing agent added, SCR technology mainly includes hydrocarbon selective catalytic reduction (HC-SCR) and ammonia selective catalytic reduction (NH3-SCR). Among them, NH3-SCR is the most effective method for flue gas denitrification.

[0003] NH3-SCR technology has been industrialized and applied to NO3-containing stationary sources such as flue gas from coal-fired power plants. x The removal of NO2. Under humid, oxygen-rich, and sulfur-containing conditions, the catalyst using this technology still maintains high activity and a long service life. This technology is used for the removal of NO2 from diesel vehicle exhaust under oxygen-rich conditions. x Ammonia removal can lead to problems such as ammonia leakage and difficulties in storage and transportation. Therefore, urea hydrolysis is commonly used to generate ammonia. Generally, the following reaction occurs on the catalyst surface.

[0004] 4NO + 4NH3 + O2 → 4N2 + 6H2O (1.1)

[0005] 2NO₂ + 4NH₃ + O₂ → 3N₂ + 6H₂O (1.2)

[0006] 2NO+2NO2+4NH3→4N2+6H2O (1.3)

[0007] Equation (1.1) is the equation for the "standard SCR" reaction, in which NH3 and NO have the same stoichiometric coefficients. Equation (1.3) is the reaction process for the "fast SCR", which has a reaction rate more than 10 times that of the "standard SCR" above 200℃.

[0008] The core of NH3-SCR technology is the catalyst. Over the years, researchers have conducted in-depth and extensive research and have developed a variety of NH3-SCR catalysts. These catalysts can be divided into three main categories: vanadium-based oxide catalysts, non-vanadium-based metal oxide catalysts, and molecular sieve catalysts supported on transition metals.

[0009] Among them, the optimal reaction window temperature for the most widely used vanadium-based NH3-SCR denitrification technology is between 250-450℃, while the sintering flue gas temperature is relatively low (110-200℃). For example, the V2O5-WO3(MoO3) / TiO2 catalyst can be applied to flue gas denitrification reactions and has become the most widely used NH3-SCR catalyst in industry. The main active center of V2O5-WO3(MoO3) / TiO2 is V2O5, the support is TiO2, and the promoter is WO3 or MoO3. This catalyst has high surface acidity, catalytic activity, and stability, and exhibits good NO reduction performance in the mid-temperature range (250-400℃). x While it exhibits good denitrification performance and resistance to sulfur, in practical applications, such as the steel industry, the sintering flue gas temperature is relatively low (120-180℃), making it difficult for the V2O5-WO3(MoO3) / TiO2 catalyst to meet denitrification requirements within this temperature range. This typically necessitates the addition of supplementary heating devices to raise the sintering flue gas temperature to above 260℃, which increases costs and wastes resources and energy. Furthermore, vanadium is biotoxic and volatilizes at high temperatures, which is detrimental to nitrogen oxide removal and further damages the ecological environment. Therefore, it is necessary to develop other types of catalysts.

[0010] In response to this situation, non-vanadium-based metal oxide NH3-SCR catalysts have become a research hotspot. In recent years, various transition metal oxides (MnO4, NH3, and NH3-SCR catalysts) have been studied. x FeO x CeO x Due to their excellent low-temperature NH3-SCR catalytic performance, ce-based catalysts have attracted the attention of researchers, and some of them have already achieved industrial application, but their preparation cost is high. It is worth noting that stationary source flue gas contains a significant amount of dust, water, and SO2. However, manganese-based metal oxides have poor sulfur resistance; in the presence of trace amounts of sulfur, the catalysts deactivate rapidly (Li J, Chang H, Ma L, et al. Low-temperature selective catalytic reduction of NO). xWith NH3 over metal oxide and zeolite catalysts - A review [J]. Catalysis Today, 2011, 175: 147-156.). Therefore, flue gas usually undergoes dust removal and desulfurization processes before NH3-SCR denitrification, but this makes the process more complicated and increases industrial costs.

[0011] In addition, since sintering fly ash contains a large amount of KCl and K2SO4, alkali metal salts tend to adhere to the surface of the denitrification catalyst in sintering flue gas with low temperature and high water content. This not only blocks the catalyst pores and causes physical poisoning of the catalyst, but also reacts chemically with the active acid sites on the catalyst surface, causing chemical deactivation of the catalyst.

[0012] Therefore, developing an environmentally friendly low-temperature NH3-SCR catalyst that also possesses certain resistance to sulfur and alkali metal poisoning is currently a research challenge. Summary of the Invention

[0013] To address the aforementioned technical problems, the present invention aims to provide a rare-earth-modified sulfur- and alkali-metal-resistant low-temperature denitrification catalyst, its preparation method, and a flue gas denitrification method. Through rare-earth modification, the catalyst achieves sulfur and alkali-metal resistance and can be used for denitrification reactions at low temperatures.

[0014] To achieve the above objectives, the present invention provides a method for preparing a rare earth-modified sulfur- and alkali metal-resistant low-temperature denitration catalyst, wherein the preparation method includes:

[0015] A rare earth-modified low-temperature denitration catalyst resistant to sulfur and alkali metals was prepared directly from manganese salt, titanium source, and rare earth precursor as main raw materials via a sol-gel method. The molar ratio of manganese salt to rare earth precursor is 1:(0.1-0.5), the molar ratio of manganese salt to titanium source is (0.1-0.5):1, the molar amount of manganese salt is calculated as manganese ions, the molar amount of rare earth precursor is calculated as rare earth ions, and the molar amount of titanium source is calculated as TiO2.

[0016] Alternatively, the preparation method includes:

[0017] First, a metal oxide catalyst is prepared by precipitation and filtration using manganese salt and titanium source as the main raw materials. Then, a rare earth precursor is impregnated onto the metal oxide catalyst to obtain a rare earth modified sulfur- and alkali-resistant metal low-temperature denitration catalyst. The rare earth element loading in the rare earth precursor is 1%-10% based on the mass of the metal oxide catalyst as 100%. The molar ratio of manganese salt to titanium source is (2-5):10, and the molar amount of manganese salt is calculated as manganese ions, while the molar amount of titanium source is calculated as TiO2.

[0018] According to a specific embodiment of the present invention, preferably, the preparation method includes the following steps:

[0019] (1-1) Manganese salt, rare earth precursor, ethylenediaminetetraacetic acid and citric acid are dissolved in water, the pH is adjusted to 2-6, and after a first heating and stirring, a sol of metallic manganese oxide is obtained; wherein, the molar ratio of manganese salt, rare earth precursor, ethylenediaminetetraacetic acid and citric acid is 1:(0.1-0.5):(1-1.5):(1-1.5);

[0020] (1-2) The titanium source was dissolved in anhydrous ethanol, and after a second heating and stirring until transparent and uniform, a titanium oxide sol was obtained.

[0021] (1-3) The oxide sol of manganese metal and the oxide sol of titanium metal are mixed evenly, and the mixture is continuously heated and stirred for the third time while maintaining the pH value of the solution at 4-7 to obtain a gel; the gel is then dried and calcined to obtain a solid powder.

[0022] (1-4) The solid powder is further heated and then cooled to room temperature to obtain a rare earth modified sulfur-resistant and alkali metal low-temperature denitrification catalyst.

[0023] Alternatively, the preparation method includes the following steps:

[0024] (2-1) Dissolve manganese salt and titanium source in water, adjust the pH to 8-11, stir and allow to precipitate fully to obtain a mixture;

[0025] (2-2) The mixture is filtered, dried and calcined to obtain a metal oxide catalyst;

[0026] (2-3) The rare earth precursor is dispersed in a solvent, then impregnated on a metal oxide catalyst, and subjected to degassing, drying and calcination to obtain a solid powder.

[0027] (2-4) The solid powder is further heated and then cooled to room temperature to obtain a rare earth modified sulfur-resistant and alkali-resistant metal low-temperature denitrification catalyst.

[0028] The inventors of this invention have discovered that adjusting the pH during the preparation of metal oxide sols can affect the sol formation rate, thereby resulting in more uniform Mn dispersion. Furthermore, controlling the pH value can inhibit the hydrolysis of metal salts, preventing a decrease in denitrification efficiency due to metal salt hydrolysis.

[0029] According to a specific embodiment of the present invention, preferably, the manganese salt includes one or a combination of two or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

[0030] According to a specific embodiment of the present invention, preferably, the rare earth precursor includes one or more of yttrium nitrate, cerium nitrate, and samarium nitrate.

[0031] According to a specific embodiment of the present invention, preferably, the titanium source includes one or a combination of two or more of tetraethyl titanate, tetrabutyl titanate, and titanium isopropoxide.

[0032] According to a specific embodiment of the present invention, preferably, in steps (1-3) and (2-3), the calcination temperature is 200-500°C, and the calcination time is 8-28 hours. The calcination operation removes bound water from the gel and burns the complexing agent (e.g., ethylenediaminetetraacetic acid, citric acid).

[0033] According to a specific embodiment of the present invention, preferably, in steps (1-4) and (2-4), the heating temperature of the heating treatment is 500-800°C, and the temperature is maintained for 4-12 hours. Performing the heating treatment again helps to decompose the organic matter in the sol, while also making the various components more uniformly dispersed.

[0034] According to a specific embodiment of the present invention, preferably, in step (2-2), the calcination temperature is 400-600℃ and the calcination time is 4-24h.

[0035] According to a specific embodiment of the present invention, preferably, in step (1-2), the volume ratio of the anhydrous ethanol to the water in step (1-1) is 1:(5-10).

[0036] In the above preparation method, preferably, in steps (2-2) and (2-3), the drying temperature is 80-200℃ and the drying time is 12-24h.

[0037] In the above preparation method, preferably, in step (2-1), the stirring temperature is 15-35℃ and the stirring time is 3-15h.

[0038] In the above preparation method, preferably, in step (2-3), the evacuation operation is carried out by evacuating in a vacuum oven at 80-200°C to reduce the gas pressure to 100-2000Pa.

[0039] According to a specific embodiment of the present invention, preferably, the first heating and stirring operation is performed at 30-90°C with ultrasonic-assisted stirring at 20000-50000Hz for 4-12 hours. Dispersion using ultrasound can make the distribution of Mn and rare earth metals in the sol more uniform.

[0040] According to a specific embodiment of the present invention, preferably, the second heating and stirring operation is to heat to 20-50°C and stir for 4-12 hours.

[0041] According to a specific embodiment of the present invention, preferably, the third heating and stirring operation is to heat to 60-90°C and continuously stir to evaporate the solution until a gel is obtained.

[0042] In the above preparation method, preferably, the preparation method of rare earth modified sulfur- and alkali metal-resistant low-temperature denitration catalyst can also adopt the following steps:

[0043] (1-1) Dissolve ethylenediaminetetraacetic acid (EDTA) in water, adjust the pH to 2-6 with ammonia, then add manganese salt, rare earth precursor and citric acid (CA), stir, adjust the pH to 2-6 again with ammonia, stir at 30-90℃ in an ultrasonic environment of 20000-50000Hz for 4-12 hours to obtain a metallic manganese oxide sol; the molar ratio of manganese salt, rare earth precursor, EDTA and CA is 1:(0.1-0.5):(1-1.5):(1-1.5);

[0044] (1-2) Dissolve the titanium source in anhydrous ethanol, heat to 20-50℃, stir for 4-12h until transparent and uniform, and obtain a titanium oxide sol; wherein, the molar ratio of manganese to titanium is (0.1-0.5):1; the volume ratio of the anhydrous ethanol to the water in step (2-1) is 1:(5-10).

[0045] (1-3) Mix the metal manganese oxide sol and the metal titanium oxide sol evenly, heat to 60-90℃, and evaporate by continuous stirring. During this process, adjust the solution value by adding ammonia solution dropwise to keep it at 4-7 to obtain a gel. Then dry the gel in an oven at 80-200℃ for 8-28 hours, and calcine it in a muffle furnace at 200-500℃ for 8-28 hours.

[0046] (1-4) The obtained solid powder is heated to 500-800℃ at a rate of 2-10℃ / min in a tube furnace with an air atmosphere (gas flow rate of 20-80ml / min) and held at the temperature for 4-12h. Then it is naturally cooled to room temperature in an air atmosphere to obtain a rare earth modified sulfur-resistant and alkali metal low-temperature denitrification catalyst.

[0047] Alternatively, the following steps can be used:

[0048] (2-1) Dissolve manganese salt and titanium source in deionized water at a molar ratio of (2-5):10, adjust the pH value to 8-11 with ammonia, stir at 15-35℃ for 3-15h to allow it to fully precipitate and obtain a mixture;

[0049] (2-2) The mixture is filtered, and the resulting solid is dried in an oven at 80-200℃ for 12-24h. Then it is calcined in a muffle furnace at 400-600℃ for 4-24h to obtain a metal oxide catalyst.

[0050] (2-3) Dissolve the rare earth precursor in a solvent (water and / or ethanol), impregnate it onto the metal oxide obtained in step (2-2), then place it in a vacuum oven at 80-200℃, evacuate the air, reduce the air pressure to 100-2000Pa, dry it in the oven for 12-24h, and then calcine it in a muffle furnace at 200-500℃ for 8-28h; wherein, based on the mass of the metal oxide catalyst as 100%, the loading of the rare earth precursor (based on rare earth elements) is 1%-10%.

[0051] (2-4) The obtained solid powder is heated to 500-800℃ at a rate of 2-10℃ / min in a tube furnace with an air atmosphere (gas flow rate of 20-80ml / min) and held at the temperature for 4-12h. Then it is naturally cooled to room temperature in an air atmosphere to obtain a rare earth modified sulfur-resistant and alkali metal low-temperature denitrification catalyst.

[0052] The present invention also provides a rare earth modified sulfur- and alkali metal low-temperature denitrification catalyst, which is obtained by the above preparation method.

[0053] The present invention also provides a flue gas denitrification method, which uses the above-mentioned rare earth modified sulfur- and alkali-resistant metal low-temperature denitrification catalyst to denitrify the flue gas, wherein the flue gas contains nitrogen oxides, such as NO and NO2.

[0054] In some specific implementations, preferably, a pretreatment process is included before the denitrification treatment of the rare earth modified sulfur- and alkali-resistant metal low-temperature denitrification catalyst. The pretreatment temperature is 150-400℃, the pretreatment time is 2-8h, and the heating rate is 5-15℃ / min.

[0055] In some specific implementations, preferably, the pretreatment atmosphere is one or a combination of two or more of argon, nitrogen, helium, and air.

[0056] According to a specific embodiment of the present invention, preferably, the reaction temperature of the denitrification treatment is 50-450℃, more preferably 100-300℃, and even more preferably 100-200℃.

[0057] In some specific embodiments, preferably, the reaction space velocity of the denitrification treatment is 10,000-160,000 h⁻¹ -1 More preferably 10,000-50,000h -1 .

[0058] In some specific embodiments, preferably, the reaction pressure of the denitrification treatment is 0.1-0.6 MPa, more preferably 0.1-0.3 MPa.

[0059] According to a specific embodiment of the present invention, preferably, the ratio of NO to catalyst in the reaction gas component of the denitrification treatment is 1 mol:(0.5-2) g; and the ratio of NH3 to catalyst in the reaction gas component of the denitrification treatment is (1-1.2) mol:(0.5-2) g.

[0060] According to a specific embodiment of the present invention, preferably, the volume fraction of SO2 is 0-200 ppm, based on the total volume of the reaction gas components in the denitrification treatment being 100%.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] (1) The rare earth modified sulfur-resistant and alkali-resistant metal low-temperature denitrification catalyst prepared by the present invention has good NH3-SCR low-temperature reaction activity and shows good NO removal rate in the simulated sintering flue gas tail gas denitrification experiment, realizing efficient catalytic reduction of nitrogen oxides into harmless nitrogen gas at a low temperature.

[0063] (2) The rare earth modified sulfur-resistant and alkali metal-resistant low-temperature denitrification catalyst provided by the present invention has both sulfur-resistant and alkali metal-resistant properties. The preparation method is simple, easy to operate, and low in cost. It has good application prospects and effectively solves the problem of insufficient sulfur-resistant and alkali metal-resistant properties of catalysts in existing technical solutions on the market. Attached Figure Description

[0064] Figure 1 The NO conversion curves of the catalysts prepared in Examples 1-5 and Comparative Example 1 at low temperatures are shown.

[0065] Figure 2 The NO conversion curves are for the catalysts prepared in Examples 1-5 and Comparative Example 1 after K poisoning.

[0066] Figure 3 The results show the sulfur resistance performance test results of the catalysts prepared in Examples 1-5 and Comparative Example 1.

[0067] Figure 4 The NO conversion curves of the catalysts prepared for comparative examples 1-3 at low temperatures. Detailed Implementation

[0068] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0069] Examples 1-5 and Comparative Examples 1-3 below provide methods for preparing denitration catalysts, and the obtained denitration catalysts are subjected to alkali metal poisoning treatment. In the alkali metal poisoning treatment, the mass fraction of the alkali metal is 1-4% based on 100% of the mass of the denitration catalyst, and the alkali metal source is potassium nitrate and / or sodium nitrate.

[0070] Example 1

[0071] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate, 0.521g of yttrium nitrate hexahydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A2.

[0072] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B2.

[0073] Solutions A2 and B2 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample is designated ex-2-Y. 0.05 Mn 0.4 TiO x .

[0074] Alkali metal poisoning treatment: Weigh 0.026g potassium nitrate, dissolve in 0.75ml deionized water, and immerse in 0.5g ex-2-Y. 0.05 Mn 0.4 TiO x Up, get ex-2-KY 0.05 Mn 0.4 TiO x .

[0075] Example 2

[0076] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate, 0.598g of cerium nitrate hexahydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A3.

[0077] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B3.

[0078] Solutions A3 and B3 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated ex-3-Ce. 0.05 Mn 0.4 TiO x .

[0079] Alkali metal poisoning treatment: Weigh 0.026 g potassium nitrate, dissolve it in 0.75 ml deionized water, and immerse it in 0.5 g ex-3-Ce. 0.05 Mn 0.4 TiO x Above, we obtain ex-3-K-Ce 0.05 Mn 0.4 TiO x .

[0080] Example 3

[0081] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate, 0.611g of samarium nitrate hexahydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A4.

[0082] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B4.

[0083] Solutions A4 and B4 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated ex-4-Sm. 0.05 Mn 0.4 TiO x .

[0084] Alkali metal poisoning treatment: Weigh 0.026 g potassium nitrate, dissolve it in 0.75 ml deionized water, and immerse it in 0.5 g ex-4-Sm 0.05 Mn 0.4 TiO x Above, we obtain ex-4-K-Sm 0.05 Mn 0.4 TiO x .

[0085] Example 4

[0086] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate, 0.306g of samarium nitrate hexahydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A5.

[0087] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B5.

[0088] Solutions A5 and B5 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated ex-5-Sm. 0.025 Mn 0.4TiO x .

[0089] Alkali metal poisoning treatment: Weigh 0.026 g potassium nitrate, dissolve it in 0.75 ml deionized water, and immerse it in 0.5 g ex-5-Sm 0.025 Mn 0.4 TiO x Above, we obtain ex-5-K-Sm 0.025 Mn 0.4 TiO x .

[0090] Example 5

[0091] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate, 1.211g of samarium nitrate hexahydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A6.

[0092] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B6.

[0093] Solutions A6 and B6 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated ex-6-Sm. 0.1 Mn 0.4 TiO x .

[0094] Alkali metal poisoning treatment: Weigh 0.026 g potassium nitrate, dissolve it in 0.75 ml deionized water, and immerse it in 0.5 g ex-6-Sm 0.1 Mn 0.4 TiO x Above, we obtain ex-6-K-Sm 0.1 Mn 0.4 TiO x .

[0095] Comparative Example 1

[0096] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A1.

[0097] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B1.

[0098] Solutions A1 and B1 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated ex-1-Mn. 0.4 TiO x .

[0099] Alkali metal poisoning treatment: Weigh 0.026g of potassium nitrate, dissolve it in 0.75ml of deionized water, and immerse it in 0.5g of ex-1-Mn. 0.4 TiO x Above, we obtain ex-1-K-Mn 0.4 TiO x .

[0100] Comparative Example 2

[0101] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate and 3.168g of CA. Stir, add ammonia to adjust the pH to 5, and stir for 8 hours to prepare solution A7.

[0102] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B7.

[0103] Solutions A7 and B7 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was placed in a muffle furnace and calcined in air at 350°C to remove bound water from the gel, and the complexing agent was burned to obtain a solid powder. The obtained solid powder was heated to 750°C at a programmed rate of 5°C / min in a tube furnace with an air atmosphere (gas flow rate of 50 ml / min) and held at that temperature for 5 h, then naturally cooled to room temperature in air. The obtained sample was designated as sa-1-Mn. 0.4 TiO x .

[0104] Comparative Example 3

[0105] Weigh 4.82g of EDTA and add it to 100ml of deionized water. Add ammonia dropwise to adjust the pH to 5. Then add 1.862g of manganese sulfate monohydrate and 3.168g of CA. Stir and add ammonia to adjust the pH to 5. Stir at 50℃ with ultrasonic assistance at 40000Hz for 8 hours to prepare solution A8.

[0106] Weigh 9.365 ml of tetrabutyl titanate, dissolve it in 10 ml of ethanol, heat to 30°C, stir for 8 hours until transparent and homogeneous, and prepare solution B8.

[0107] Solutions A8 and B8 were mixed and stirred continuously, then heated to 80°C. During this process, the pH of the solution was adjusted by adding ammonia solution dropwise to maintain it at 6. After prolonged stirring and evaporation, a viscous sol was formed. The obtained sol was dried at 180°C to form a gel-like catalyst precursor. This precursor was then calcined in a muffle furnace at 750°C in air for 5 hours and then cooled to room temperature. The resulting sample was designated as sa-2-Mn. 0.4 TiO x .

[0108] The samples from Examples 1-5 and Comparative Examples 1-3 were subjected to ammonia selective catalytic reduction reactions. All reactions were conducted in a micro fixed-bed reactor at atmospheric pressure, equipped with a gas distribution system and an online nitrogen oxide analyzer. Nitrogen oxide concentration analysis was performed using a German Sick S710 and a Swiss ECO analyzer. Furthermore, resistance to alkali metal poisoning and SO2 resistance were tested.

[0109] Test Example 1

[0110] The ex-2-Y prepared in Example 1 0.05 Mn 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0111] In an atmospheric pressure fixed-bed reactor, weigh 0.5 g of ex-2-Y 0.05 Mn 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0112] Resistance to alkali metal poisoning test:

[0113] Weigh 0.5g of ex-2-KY 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0114] SO2 resistance performance test:

[0115] Weigh 0.5g of ex-2-Y 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3 As shown.

[0116] Test Example 2

[0117] The ex-3-Ce prepared in Example 2 0.05 Mn 0.4 TiO xThe catalytic evaluation experiment was conducted, and the specific process is as follows:

[0118] In an atmospheric pressure fixed-bed reactor, 0.5 g of ex-3-Ce was weighed. 0.05 Mn 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0119] Resistance to alkali metal poisoning test:

[0120] Weigh 0.5g ex-3-K-Ce 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0121] SO2 resistance performance test:

[0122] Weigh 0.5g ex-3-Ce 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3 As shown.

[0123] Test Example 3

[0124] The ex-4-Sm prepared in Example 2 0.05 Mn0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0125] In an atmospheric pressure fixed-bed reactor, 0.5 g of ex-4-Sm was weighed. 0.05 Mn 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0126] Resistance to alkali metal poisoning test:

[0127] Weigh 0.5g ex-4-K-Sm 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0128] SO2 resistance performance test:

[0129] Weigh 0.5g ex-4-Sm 0.05 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3 As shown.

[0130] Test Example 4

[0131] The ex-5-Sm prepared in Example 4 0.025 Mn 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0132] In an atmospheric pressure fixed-bed reactor, 0.5 g of ex-5-Sm was weighed. 0.025 Mn 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0133] Resistance to alkali metal poisoning test:

[0134] Weigh 0.5g ex-5-K-Sm 0.025 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0135] SO2 resistance performance test:

[0136] Weigh 0.5g ex-5-Sm 0.025 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3 As shown.

[0137] Test Example 5

[0138] The ex-6-Sm prepared in Example 5 0.1 Mn 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0139] The ex-6-Sm prepared in Example 5 0.1 Mn 0.4 TiO x The catalytic evaluation experiment was conducted in a fixed-bed reactor at atmospheric pressure. 0.5 g of catalyst was weighed, heated to 300 °C with N2 at 2 °C / min, and purged for 2 h. After cooling to room temperature, a reaction gas (based on a total volume of 100%, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0140] Resistance to alkali metal poisoning test:

[0141] Weigh 0.5g ex-6-K-Sm 0.1 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0142] SO2 resistance performance test:

[0143] Weigh 0.5g ex-6-Sm 0.1 Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3As shown.

[0144] Test Example 6

[0145] The ex-1-Mn prepared in Comparative Example 1 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0146] In an atmospheric pressure fixed-bed reactor, 0.5 g of ex-1-Mn was weighed. 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 1 As shown.

[0147] Resistance to alkali metal poisoning test:

[0148] Weigh 0.5g ex-1-K-Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at a rate of 2° / min and purged for 2 hours. After cooling to room temperature, a reaction gas (based on a total volume of 100% reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 2 As shown.

[0149] SO2 resistance performance test:

[0150] Weigh 0.5g ex-1-Mn 0.4 TiO x The catalyst was heated to 300℃ in N2 at 2° / min and purged for 2 h, then cooled to room temperature. A reaction gas (based on 100% of the total reaction gas volume, consisting of 500 ppm each of NO and NH3, 10% oxygen, 5% H2O, 10% CO2, 100 ppm SO2, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 3 As shown.

[0151] Test Example 7

[0152] The sa-1-Mn prepared in Comparative Example 2 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0153] In an atmospheric pressure fixed-bed reactor, 0.5 g of sa-1-Mn was weighed. 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 4 As shown.

[0154] Test Example 8

[0155] The sa-2-Mn prepared in Comparative Example 3 0.4 TiO x The catalytic evaluation experiment was conducted, and the specific process is as follows:

[0156] In an atmospheric pressure fixed-bed reactor, 0.5 g of sa-2-Mn was weighed. 0.4 TiO x The catalyst was purged with N2 at 2° / min to 300°C for 2 hours, then cooled to room temperature. A reaction gas (based on 100% of the total volume of the reaction gas, consisting of 500 ppm each of NO and NH3, 10% O2, 5% H2O, and the remainder N2) was introduced. The reaction pressure was 0.15 MPa, and the reaction space velocity was 30,000 h⁻¹. -1 The temperature was raised to 150-300℃ for the reaction. All collected NO was analyzed, and the results are as follows: Figure 4 As shown.

[0157] from Figure 1 As can be seen, the rare earth-modified sulfur- and alkali metal-resistant low-temperature denitration catalyst prepared in this invention exhibits a NO conversion rate greater than 80% within a wide temperature window range of 100-350℃, achieving good NH3-SCR catalytic activity in the low-temperature range. Furthermore, for temperatures below 100℃, the NO conversion rates of Examples 1-5 are also higher than those of the unmodified comparative examples.

[0158] from Figure 2 As can be seen from this, ex-1-Mn 0.4 TiO xAfter being impregnated with 2% K for poisoning, the NO conversion rate of the catalyst at 150°C decreased from 100% to about 80%, while the NO conversion rate of the rare earth-modified manganese-titanium catalyst (Examples 1-5) at the same temperature was all above 85%. This indicates that modifying the catalyst with rare earth metals can improve its resistance to alkali metal poisoning.

[0159] from Figure 3 As can be seen from this, ex-1-Mn 0.4 TiO x After poisoning the catalyst with 150 ppm SO2 at 150℃ for 20 h, the NO conversion rate decreased from 100% to about 65%, while the NO conversion rate of the rare earth-modified manganese-titanium catalyst remained above 72%. This indicates that modifying the catalyst with rare earth metals can improve its resistance to SO2 poisoning.

[0160] from Figure 4 It can be seen that the catalyst sa-1-Mn without pre-ultrasonic treatment 0.4 TiO x The activity of the catalyst Sa-2-Mn significantly decreased at low temperatures, which may be due to uneven dispersion of the metal components during the sol-gel process; while the catalyst treated by the conventional calcination method with only one heating was significantly reduced. 0.4 TiO x The activity decreases significantly at high temperatures, which may be due to the uneven dispersion of active species on the catalyst prepared by conventional calcination methods, leading to severe ammonia oxidation. This demonstrates that ultrasonic treatment and secondary heating are effective heat treatment methods that comprehensively improve the reactivity of the denitrification catalyst throughout the entire temperature window.

[0161] Taking into account the reactivity throughout the entire temperature window ( Figure 1 , Figure 4 ) and resistance to alkali metal poisoning and sulfur resistance ( Figure 2 , Figure 3 It can be seen that ex-4-Sm 0.05 Mn 0.4 TiO x It has the best catalytic performance.

[0162] Therefore, the rare earth-modified sulfur- and alkali metal-resistant low-temperature denitrification catalyst prepared in this invention has high NH3-SCR activity in the low-temperature range, and has good resistance to SO2 and alkali metal poisoning. It can simultaneously achieve resistance to sulfur and alkali metal poisoning during low-temperature denitrification, and is expected to replace the existing catalytic system, showing good application prospects.

Claims

1. A process for the preparation of a rare earth modified sulfur and alkali metal resistant low temperature deNOx catalyst, wherein, The preparation method includes: (1-1) Manganese salt, rare earth precursor, ethylenediaminetetraacetic acid and citric acid are dissolved in water, the pH is adjusted to 2-6, and after a first heating and stirring, a metal manganese oxide sol is prepared; wherein, the first heating and stirring operation is carried out at 30-90℃ with ultrasonic-assisted stirring at 20000-50000 Hz for 4-12 hours. (1-2) The titanium source is dissolved in anhydrous ethanol, and after a second heating and stirring until it becomes transparent and uniform, a titanium oxide sol is obtained; wherein, the second heating and stirring operation is to heat to 20-50℃ and stir for 4-12 h; (1-3) The oxide sol of manganese metal and the oxide sol of titanium metal are mixed evenly, and the third heating and stirring are continuously carried out while maintaining the pH value of the solution at 4-7 to obtain a gel; the gel is then dried and calcined to obtain a solid powder; wherein, the third heating and stirring operation is to heat to 60-90℃ and stir continuously to evaporate the solution until a gel is obtained. (1-4) The solid powder is further heated and then cooled to room temperature to obtain a rare earth modified sulfur- and alkali metal low-temperature denitrification catalyst. The molar ratio of the manganese salt, rare earth precursor, ethylenediaminetetraacetic acid, and citric acid is 1 : (0.1-0.5) : (1-1.5) : (1-1.5); the molar ratio of the manganese salt and titanium source is (0.1-0.5) :

1. The molar amount of the manganese salt is calculated as manganese ions, the molar amount of the rare earth precursor is calculated as rare earth ions, and the molar amount of the titanium source is calculated as TiO2. In steps (1-3), the calcination temperature is 200-500℃ and the calcination time is 8-28 h; in steps (1-4), the heating temperature of the heating treatment is 500-800℃ and the temperature is kept constant for 4-12 h. The rare earth precursors include one or more of yttrium nitrate, cerium nitrate, and samarium nitrate.

2. The production method according to claim 1, wherein, The manganese salt includes one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

3. The production method according to claim 1, wherein The titanium source includes one or more of tetraethyl titanate, tetrabutyl titanate, and titanium isopropoxide.

4. The production method according to claim 1, wherein In step (1-2), the volume ratio of the anhydrous ethanol to the water in step (1-1) is 1: (5-10).

5. A rare earth-modified sulfur- and alkali-resistant metal low-temperature denitrification catalyst, which is obtained by the preparation method described in any one of claims 1-4.

6. A method for flue gas denitration, which is a denitration treatment of flue gas using the rare earth modified sulfur-resistant alkali metal-resistant low-temperature denitration catalyst according to claim 5, wherein, The flue gas contains nitrogen oxides.

7. The method of claim 6, wherein, The reaction temperature for the denitrification treatment is 100-200℃.

8. The method according to claim 6, wherein, The ratio of NO to catalyst in the reaction gas component of the denitrification treatment is 1 mol : (0.5-2) g; the ratio of NH3 to catalyst in the reaction gas component of the denitrification treatment is (1-1.2) mol : (0.5-2) g.

9. The method according to claim 6, wherein, Based on the total volume of the reaction gas components in the denitrification treatment being 100%, the volume fraction of SO2 is 0-200 ppm.

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