Rare-earth-based high-temperature denitration catalyst as well as preparation method and application thereof

Abstract

The invention discloses a rare-earth-based high-temperature denitration catalyst as well as a preparation method and application thereof. The rare earth-based high-temperature denitration catalyst comprises an attapulgite mixed titanium dioxide carrier, a rare earth oxide and a polyoxoate, the catalyst comprises the following components in percentage by mass: 0.1%-30% of rare earth oxide, 0.1%-20% of polyoxoate and the balance of an attapulgite mixed titanium dioxide carrier, wherein the rare earth oxide is one or a mixture of cerium dioxide, lanthanum oxide and neodymium oxide; the polyoxoate is a metal-oxygen cluster compound with terminal oxygen and bridge oxygen on the surface. The rare-earth-based high-temperature denitration catalyst can effectively inhibit phase change of anatase, and the high-temperature structural stability and sintering resistance of the catalyst can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a rare earth-based high-temperature denitration catalyst and a preparation method and application thereof. BACKGROUND

[0002] Nitrogen oxides (NOx) are one of the main atmospheric pollutants, and its emission will cause a series of environmental problems such as photochemical smog, acid rain, haze, etc. Selective catalytic reduction (SCR) technology is the most widely used and effective fixed source NOx emission control technology for power plant boilers, industrial kilns, etc. in the world. Commercial vanadium-based catalysts (such as V2O5-WO3(MoO3) / TiO2) have excellent denitration activity and selectivity in the medium temperature range of 300-400℃, but they still have some inherent defects: (1) The active temperature window is narrow, and the adaptability to high-temperature flue gas higher than 400℃ is poor. V2O5 is easy to volatilize at high temperature and will accelerate the conversion of SO2 to SO3, causing equipment corrosion and secondary pollution; (2) High biological toxicity, and the abandoned catalyst is a hazardous waste, which has high disposal cost and great environmental risk.

[0003] CN 120571596 A discloses a high-temperature denitration catalyst used in a waste incinerator and a preparation process thereof. A large amount of nickel powder is added to the vanadium-tungsten-titanium catalyst for mixing, so that the catalyst drives nickel and oxides to react with water vapor under high-temperature conditions, reduces the presence of water in the catalyst environment, improves the reaction of SO2 and NH3, increases the conversion rate of NO, and improves the denitration performance of the catalyst.

[0004] Rare earth elements (such as Ce, La, Pr, etc.) have great potential in the field of catalysis due to their unique 4f electron layer structure and excellent oxygen storage / release capacity. Rare earth oxides represented by CeO2 are good SCR catalytic active components or additives. However, pure rare earth-based catalysts, especially when TiO2 (anatase phase) is used as the carrier, face severe challenges under high temperature (>500℃) and complex flue gas conditions:

[0005] 1. High-temperature structural instability and sintering: The active components and TiO2 carrier particles of the catalyst are prone to migration, aggregation and sintering at high temperature, resulting in a sharp decrease in specific surface area, a decrease in active sites, and catalyst deactivation.

[0006] 2. Phase transition of anatase: The TiO2 carrier will transform from the high-activity anatase phase to the low-activity rutile phase at high temperature (usually >550℃), which is accompanied by a sharp decrease in specific surface area and collapse of pore structure, seriously damaging the structure of the catalyst.

[0007] 3. Water vapor and SO2 poisoning: High concentrations of water vapor (H2O) and SO2 in the flue gas can compete with the active sites for adsorption or reaction, forming sulfate species that cover or block the active sites, leading to temporary or permanent deactivation of the catalyst.

[0008] Therefore, it is of great significance to develop a non-vanadium-based high-temperature denitration catalyst that can maintain structural stability at high temperatures, resist sintering, inhibit anatase phase transition, and has excellent water and sulfur resistance, in order to broaden the application range of SCR technology and meet more stringent environmental protection requirements. SUMMARY

[0009] To solve the above technical problems, the present application provides a rare earth-based high-temperature denitration catalyst, its preparation method and application. The rare earth-based high-temperature denitration catalyst introduces a specific type of polyoxometallate to modify the rare earth-based catalyst supported by the attapulgite mixed titanium white powder. The strong interaction between the polyoxometallate and the attapulgite mixed titanium white powder carrier and the rare earth active component significantly improves the high-temperature structural stability of the catalyst, inhibits the sintering of the active component and the transition of TiO2 anatase to rutile, and endows the catalyst with excellent water and sulfur resistance.

[0010] To achieve the above purpose, the present application adopts the following technical solutions:

[0011] A rare earth-based high-temperature denitration catalyst, comprising an attapulgite mixed titanium white powder carrier, a rare earth oxide and a polyoxometallate; the content of the rare earth oxide is 0.1%~30%, the content of the polyoxometallate is 0.1%~20%, and the balance is the attapulgite mixed titanium white powder carrier;

[0012] The rare earth oxide is one or a mixture of several of cerium dioxide, lanthanum oxide and neodymium oxide; the polyoxometallate is a metal-oxygen cluster compound with terminal oxygen and bridging oxygen on the surface; the mass ratio of attapulgite in the attapulgite mixed titanium white powder carrier is 1%~20%.

[0013] The polyoxometallate is one or several of phosphotungstic acid, silicotungstic acid and phosphomolybdic acid.

[0014] The polyoxometallate is a mixture of metal-oxygen cluster compounds with terminal oxygen and bridging oxygen on the surface, and the rare earth oxide is a mixture.

[0015] The content of the rare earth oxide in the rare earth-based high-temperature denitration catalyst is 5%~30%, and the content of the polyoxometallate is 5%~10%.

[0016] The mass ratio of attapulgite in the attapulgite mixed titanium white powder carrier is 1%~20%.

[0017] The preparation method of the rare earth-based high-temperature denitration catalyst comprises the following steps:

[0018] S1: A calculated amount of rare earth oxide precursor metal salt solution is loaded on the attapulgite mixed titanium white powder carrier by an equal volume impregnation method, and is subjected to aging, drying and first calcination to obtain a rare earth oxide / TiO2 basic catalyst with different contents; the first calcination temperature is 400-600 DEG C, and the time is 3-6 hours;

[0019] S2: A calculated amount of polyoxometalate solution is loaded on the rare earth oxide / attapulgite mixed titanium white powder basic catalyst obtained in step S1 by a preliminary wet impregnation method, and is subjected to drying and second calcination to obtain the rare earth-based high-temperature denitration catalyst; the second calcination temperature is 250-350 DEG C, and the time is 2-4 hours.

[0020] In step S2 and step S3, the drying temperature is 80-120 DEG C, and the time is 6-12 hours.

[0021] The rare earth oxide precursor solution is obtained by dissolving a rare earth oxide precursor in water, and the polyoxometalate solution is obtained by dissolving a calculated amount of polyoxometalate in water, ethanol or a mixed solution of water and ethanol (the volume ratio of water to alcohol is 1:1).

[0022] Before step S1, step S0 is further included:

[0023] S0: Attapulgite and titanium white are mechanically ball-milled and uniformly mixed according to a certain mass ratio, and are subjected to 400 DEG C thermal activation pretreatment for 2-4 hours to obtain an attapulgite mixed titanium white powder carrier.

[0024] The rare earth-based high-temperature denitration catalyst is applied in the denitration field at 420-550 DEG C.

[0025] The beneficial effects of the present application are as follows:

[0026] (1) The rare earth-based high-temperature denitration catalyst can significantly improve the high-temperature structural stability and sintering resistance of the catalyst: the polyoxometalate molecules can produce strong chemical anchoring with the attapulgite mixed titanium white powder carrier and the rare earth oxide (such as CeO2) surface through the end oxygen and bridge oxygen on the surface, which is like a "mortise and tenon structure", effectively inhibiting the migration and growth of TiO2 crystal grains and rare earth oxide particles at high temperatures, preventing sintering and growth, and thus maintaining the high specific surface area and rich pore structure of the catalyst.

[0027] (2) The rare earth-based high-temperature denitration catalyst of the present application can effectively inhibit the anatase phase transition: the attapulgite mixed with titanium dioxide powder carrier utilizes the interlayer confinement of attapulgite to realize the stable distribution of TiO2 rich support sites, and the WO3 or MoO3 species possibly formed after the thermal decomposition of polyoxometalate can form a physical barrier on the surface or grain boundary of TiO2 particles, hindering the direct contact of anatase grains at high temperatures and the bulk diffusion of O 2- ions, thereby significantly increasing the activation energy of the TiO2 phase transition from anatase to rutile, increasing the phase transition temperature to 650 DEG C or even higher, and ensuring the stability of the catalyst carrier at high temperatures.

[0028] (3) The rare earth-based high-temperature denitration catalyst of the present application has excellent water and sulfur resistance: ① In terms of water resistance, polyoxometalate itself has strong acidity, and the number and strength of the acid sites on the surface of the modified catalyst are increased. The adsorption capacity of these strong acid sites for NH3 is much stronger than that of H2O, thereby effectively reducing the competitive adsorption of water vapor on the active sites and alleviating the activity decline caused by water vapor; ② In terms of sulfur resistance, attapulgite with a large adsorption capacity in the carrier can serve as a buffer site to provide a temporary foothold for SO2 in the flue gas, to a certain extent, "protecting" the internal rare earth active center. At the same time, polyoxometalate and its decomposition products (such as WO3) can inhibit the excessive deposition and accumulation of SO2 into sulfates, reducing the generation of by-products such as ammonium sulfate / ammonium bisulfate and the blockage of the pores. Even if a small amount of sulfates are generated, they are more likely to decompose under the strong surface acidity of the catalyst and suitable reaction temperature, allowing the active sites to be regenerated.

[0029] (4) The rare earth-based high-temperature denitration catalyst of the present application has a synergistic catalytic effect: polyoxometalate itself has reversible redox properties (such as W 6+ / W 5+ , Mo 6+ / Mo 5+ ), which can form a synergistic redox pair with rare earth oxides (such as Ce 4+ / Ce 3+ ) to promote the NH3-SCR reaction cycle and play a positive role in widening the active temperature window.

[0030] (5) The rare earth-based high-temperature denitration catalyst of the present application is environmentally friendly and has high temperature adaptability: the catalyst of the present application does not contain vanadium, avoiding the biological toxicity and high-temperature volatilization problems of vanadium, and is an environmentally friendly catalyst; its design target is applicable to high-temperature flue gas environments of 420-550 DEG C, filling the gap in the application of commercial vanadium-based catalysts at high temperatures. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1XRD patterns of the PW-15CeO2 / ATP-TiO2 catalyst prepared in Example 1 of the present application and the 15CeO2 / TiO2 catalyst without polyoxometalate modification prepared in Comparative Example 1 after high-temperature and high-humidity aging treatment in a 700℃, 10% water vapor / air atmosphere for 12 hours.

[0032] Figure 2 NOx conversion rate-time curves of the catalyst PW-15CeO2 / ATP-TiO2 prepared in Example 1 of the present application and the commercial VWTi catalyst of Comparative Example 3 in a 500℃ flue gas containing H2O (10 vol%) and SO2 (100 ppm) for water and sulfur resistance performance test. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1

[0035] The present embodiment provides a rare earth-based high-temperature denitration catalyst, and a preparation method thereof includes the following steps:

[0036] (1) Preparation of ATP-TiO2 mixed with attapulgite and titanium white powder: a certain amount of attapulgite and titanium white powder were weighed, the mass ratio of attapulgite in the carrier was controlled to be 1%-20%, and mechanical ball milling was performed for 0.5-3 hours to mix uniformly. Heat activation pretreatment was completed by calcining at 400℃ for 2-4 hours to obtain an attapulgite mixed with titanium white powder carrier. 8.5g of 1% attapulgite mixed with titanium white powder carrier (ATP-TiO2) was taken.

[0037] (2) 4.34 g of Ce(NO3)3·6H2O was dissolved in 10 mL of deionized water to prepare a Ce precursor solution.

[0038] (3) The above Ce precursor solution was slowly added to the carrier B by equal volume impregnation method, and stirring was performed during the addition. After impregnation, the sample was aged at room temperature for 6 hours.

[0039] (4) The aged sample was dried in a 110℃ oven for 10 hours, and then transferred to a muffle furnace and calcined at 500℃ in an air atmosphere for 4 hours to obtain a CeO2 / ATP-TiO2 basic catalyst (CeO2 loading amount is about 15 wt%).

[0040] (5) 0.5 g of phosphotungstic acid (H3PW 12 O 40 ) was dissolved in 5 mL of a mixed solvent of ethanol and water (V / V = 1:1).

[0041] (6) The phosphotungstic acid solution was slowly and uniformly impregnated onto the CeO2 / ATP-TiO2 base catalyst obtained in step 4 by using an equal volume impregnation method, avoiding vigorous stirring. After impregnation, it was left to stand at room temperature for 2 hours.

[0042] (7) The sample was dried at 80°C for 8 hours and then calcined at 300°C for 3 hours to obtain the final catalyst, which was recorded as PW-15CeO2 / ATP-TiO2 (phosphotungstic acid loading was about 5 wt%).

[0043] Example 2

[0044] The preparation method of this example was the same as that of Example 1, but the amount of Ce(NO3)3·6H2O was reduced to 0.03 g, so that the loading of CeO2 was about 0.1 wt%. The final catalyst obtained was recorded as PW-0.1CeO2 / ATP-TiO2.

[0045] Example 3

[0046] The preparation method of this example was the same as that of Example 1, but the amount of Ce(NO3)3·6H2O was increased to 10.41 g, so that the loading of CeO2 was about 30 wt%. The final catalyst obtained was recorded as PW-30CeO2 / ATP-TiO2.

[0047] Example 4

[0048] The preparation method of this example was the same as that of Example 1, and 2.89 g of Ce(NO3)3·6H2O and 1.63 g of La(NO3)3·6H2O were used as precursors in this example, so that the loadings of CeO2 and La2O3 were ~10 wt% and ~5 wt%, respectively. The final catalyst obtained was recorded as PW-10CeO2-5La2O3 / ATP-TiO2.

[0049] Example 5

[0050] The preparation method of this example was the same as that of Example 1, and 1.64 g of Nd(NO3)3·6H2O was used as a precursor in this example, so that the loading of Nd2O3 was ~5 wt%. The final catalyst obtained was recorded as PW-5Nd2O3 / ATP-TiO2.

[0051] Example 6

[0052] The preparation method of this example was the same as that of Example 1, and the phosphotungstic acid was replaced by an equal molar amount (about 0.51 g) of silicotungstic acid (H4SiW12 O 40 ), the final catalyst is noted as SiW-15CeO2 / ATP-TiO2.

[0053] Example 7

[0054] The preparation method of this example is the same as Example 1, but the amount of phosphotungstic acid is reduced to 10 mg, making its loading about 0.1 wt%, the final catalyst is noted as 0.1PW-15CeO2 / ATP-TiO2. 12 O 40 ), the final catalyst is noted as PMo-15CeO2 / ATP-TiO2.

[0055] Example 8

[0056] The preparation method of this example is the same as Example 1, but the amount of phosphotungstic acid is reduced to 10 mg, making its loading about 0.1 wt%, the final catalyst is noted as 0.1PW-15CeO2 / ATP-TiO2.

[0057] Example 9

[0058] The preparation method of this example is the same as Example 1, but the amount of phosphotungstic acid is increased to 2 g, making its loading about 20 wt%, the final catalyst is noted as 20PW-15CeO2 / ATP-TiO2.

[0059] Example 10

[0060] The preparation method of this example is the same as Example 1, but the amount of phosphotungstic acid is reduced to 10 mg, making its loading about 0.1 wt%, the final catalyst is noted as 0.1PW-15CeO2 / ATP-TiO2.

[0061] Example 11

[0062] The preparation method of this example is the same as Example 1, but the support uses a 10% attapulgite mixed with titanium white powder support (10ATP-TiO2) A (unpretreated TiO2), the final catalyst is noted as PW-15CeO2 / 10ATP-TiO2.

[0063] Example 12

[0064] The preparation method of this example is the same as Example 1, but the support uses a 20% attapulgite mixed with titanium white powder support (20ATP-TiO2), the final catalyst is noted as PW-15CeO2 / 20ATP-TiO2.

[0065] Example 13

[0066] The preparation method in this embodiment is the same as in Example 1, but the calcination temperature of the rare earth oxide in step (4) is increased to 600℃. The final catalyst obtained is denoted as PW-15CeO2 / ATP-TiO2(H). Comparative Example 1 (Titanium dioxide supported on CeO2 active component)

[0067] Using pure titanium dioxide as a support (TiO2), only steps (2) to (4) of Example 1 were performed, without the polyoxoate modification step. The final catalyst was denoted as 15CeO2 / TiO2.

[0068] Comparative Example 1 (without attapulgite or polyoxophosphate modification)

[0069] Only steps (1) to (4) in Example 1 were performed, without the polyoxoate modification step, and pure titanium dioxide support (TiO2) was used as the support to obtain the final catalyst, denoted as 15CeO2 / TiO2.

[0070] Comparative Example 2 (without polyoxophosphate modification)

[0071] Only steps (1) to (4) of Example 1 were performed, without the polyoxoate modification step. The final catalyst was denoted as 15CeO2 / ATP-TiO2.

[0072] Comparative Example 3 (without rare earth active components)

[0073] Phosphotungstic acid (0.5 g) was directly loaded onto support B, and the sample was obtained by drying at 80 °C and calcining at 300 °C and denoted as PW / ATP-TiO2.

[0074] Comparative Example 4 (without attapulgite admixture)

[0075] The preparation method is the same as in Example 1, but pure titanium dioxide (TiO2) is used as the support, and the final catalyst is denoted as PW-15CeO2 / TiO2.

[0076] Comparative Example 5 (carrier not subjected to thermal activation treatment)

[0077] The preparation method is the same as in Example 1, but the support used is attapulgite mixed with titanium dioxide ATP-TiO2(F) without thermal activation treatment, and the final catalyst is denoted as PW-15CeO2 / ATP-TiO2(F).

[0078] Comparative Example 6 (Commercial VWTi Reference)

[0079] (1) Weigh 10 g of titanium dioxide as a carrier.

[0080] (2) Dissolve 0.137 g ammonium metavanadate and 0.565 g ammonium metatungstate in 10 mL of deionized water to prepare an active component precursor solution.

[0081] (3) Using equal volume impregnation method, slowly drop the above active component precursor solution onto the carrier titanium white powder, stirring while dropping. After impregnation, stand at room temperature for 6 hours.

[0082] (4) After aging, the sample is placed in a 110°C oven for 10 hours, then transferred to a muffle furnace, calcined at 500°C in air atmosphere for 4 hours, to obtain V2O5-WO3 / TiO2 catalyst (V2O5 ~ 1%, WO3 ~ 5%).

[0083] Performance test

[0084] All catalysts obtained from Example 1 to Example 12, Comparative Example 1 to Comparative Example 3 are pressed into tablets, and 40-60 mesh particles are screened for activity evaluation.

[0085] Fresh state test: Directly test the activity of the catalyst.

[0086] Hydrothermal aging: The catalyst is treated at 700°C, 10% water vapor / air atmosphere for 12 hours to simulate high temperature and high humidity aging.

[0087] Activity test conditions: Simulated flue gas: [NO] = [NH3] = 500 ppm, [O2] = 5%, [H2O] = 10%, [SO2] = 100 ppm, N2 balance, space velocity GHSV = 50,000 h -1 Record the steady-state NOx conversion rate at 450°C and 500°C.

[0088] Test results are summarized in the following table:

[0089] Table 1: Catalyst performance comparison table (NOx conversion rate / %)

[0090]

[0091] Results and conclusions

[0092] I. Synergistic effect of polyoxometalate modification and mixing with attapulgite (Example 1 vs. Comparative Examples 1, 2, and 4):

[0093] Example 1 showed significantly better activity than Comparative Example 1 in its fresh state, indicating that polyoxoate modification and attapulgite blending have a significant positive effect on catalytic activity. After harsh hydrothermal aging, the activity of Comparative Example 1 (without attapulgite blending and polyoxoate modification) dropped sharply to 55-68%, while Example 1 remained above 90%, showing a significant advantage over Comparative Example 2 (without polyoxoate modification) and Comparative Example 4 (without attapulgite blending). This directly demonstrates the core role of polyoxoate modification synergistically with attapulgite blending in improving the catalyst's high-temperature structural stability and resistance to hydrothermal sintering.

[0094] Figure 1 This is a comparison of the X-ray diffraction (XRD) patterns of the PW-15CeO2 / ATP-TiO2 catalyst prepared in Example 1 of this invention and the 15CeO2 / TiO2 catalyst prepared in Comparative Example 1 without attapulgite doping and polyoxoate modification, after undergoing a high-temperature and high-humidity aging treatment at 700°C and in a 10% water vapor / air atmosphere for 12 hours. Figure 1 It can be observed that after 12 hours of high-temperature and high-humidity aging treatment at 700℃ and in a 10% water vapor / air atmosphere, the XRD pattern of the 15CeO2 / TiO2 catalyst prepared in Comparative Example 1 showed obvious rutile phase characteristic peaks. However, the PW-15CeO2 / ATP-TiO2 catalyst prepared in Example 1 of this invention did not show rutile phase after high-temperature and high-humidity aging treatment. This further confirms that polyoxophosphate modification and synergistic attapulgite mixing make an important contribution to inhibiting the sintering of active components and the transformation of TiO2 anatase phase to rutile phase.

[0095] II. Role and Content Optimization of Rare Earth Components (Examples 1-5):

[0096] Comparative Example 3 (without rare earth elements) showed extremely low activity, confirming that rare earth oxides are indispensable active centers. Example 2 (0.1% CeO2) exhibited the lowest activity, indicating insufficient active sites. Therefore, a rare earth oxide loading of 5%–30% (optimal 15%) showed the best balance between activity and stability in this system.

[0097] III. Advantages of Composite Rare Earth Formulation (Example 4 vs. Example 1):

[0098] Example 4 (Ce-La) showed slightly better or equivalent performance than the single Ce-based catalyst (Example 1) both before and after aging. This indicates that the introduction of a second rare earth component (La, Nd, etc.) may further enhance the overall stability of the catalyst by forming a more stable solid solution or generating electronic synergistic effects.

[0099] IV. Effects of Polyoxoacid Types and Contents (Examples 6-10 vs. Example 1):

[0100] Example 6 (silicotungstic acid) has comparable or even slightly better performance than phosphotungstic acid, both are preferred species.

[0101] Example 7 (molybdophosphoric acid) has significantly worse performance, possibly because molybdenum-based polyoxometalates have relatively low thermal stability and are prone to decomposition at high temperatures.

[0102] Example 8 (low content of polyoxometalate, 0.1%) has comparable activity to Example 1 and Comparative Example 1 in fresh state, but after severe hydrothermal aging, the performance of Example 8 is significantly improved compared to Comparative Example 1, but far inferior to Example 1, indicating that the content of polyoxometalate is too low and the catalyst performance has not been optimized. Example 9 (high content of polyoxometalate, 20%) does not linearly improve with increasing content, but is slightly lower than Example 1 (5%), indicating that there is an optimal modification amount, and excessive amount may block the pores of the carrier. Therefore, the content of polyoxometalate is preferably in the range of 5% to 10%.

[0103] Example 10 (multiple polyoxometalates, phosphotungstic acid + silicotungstic acid) has slightly better performance than Example 1 (phosphotungstic acid) and Example 6 (silicotungstic acid), indicating that the heteroatoms in polyoxometalates may also have a positive impact on the catalytic performance of the catalyst to some extent.

[0104] V. Importance of carrier and calcination temperature (Example 11, 12, 13 vs. Example 1):

[0105] Example 11 (attapulgite content 10%) has basically the same fresh state activity and performance after aging as Example 1, while Example 12 (attapulgite content 20%) has significantly decreased catalytic performance, indicating that the mixed amount of attapulgite should not be too high, and the preferred mixed amount is in the range of 1% to 10%. The fresh state activity and performance after aging of Comparative Example 5 (attapulgite mixed with titanium white powder carrier without heat activation pretreatment) are both inferior to Example 1, indicating that moderate heat activation pretreatment of the carrier helps to stabilize the TiO2 structure and provides a more stable substrate for subsequent loading.

[0106] Example 13 (high calcination temperature) has a significant loss of catalytic performance, proving that excessively high calcination temperature (600°C for the first time) can cause partial sintering and phase change of the carrier and active components during the preparation stage, damaging the intrinsic activity and aging resistance potential of the catalyst.

[0107] VI. Comparison with commercial catalysts (all examples vs. Comparative Example 6):

[0108] The commercial VWTi catalyst has excellent activity at 450°C in fresh state, but its 500°C activity has already started to decline, showing medium-temperature characteristics.

[0109] After hydrothermal aging, the activity of the catalyst at 500℃ drops to 58%, while the activity of most preferred embodiments of the present application (such as 1, 4, 5, and 6) remains stable at more than 90% after aging at 500℃. This fully demonstrates that the catalyst of the present application has much better performance than the conventional commercial catalyst in the high temperature zone, especially after aging, and perfectly solves the problem of deactivation at high temperature.

[0110] Figure 2 Figure 8 is a graph showing the change in NOx conversion rate with time for the anti-water and anti-sulfur performance test of the catalyst PW-15CeO2 / TiO2 (B) prepared in Example 1 of the present application and the commercial VWTi catalyst of Comparative Example 6 in a 500℃ flue gas containing H2O (10 vol%) and SO2 (100 ppm). From the graph, it can be seen that the catalyst PW-15CeO2 / TiO2 (B) prepared in Example 1 of the present application has very good stability in the 500℃ H2O and SO2 containing condition, while the NOx conversion rate of the commercial VWTi catalyst of Comparative Example 3 has a clear downward trend with time, which fully embodies the advantages of the rare earth-based high-temperature denitration catalyst described in the present application in terms of water resistance and sulfur resistance. Figure 2

[0111] In summary, through systematic design of examples and comparative examples and performance comparison, it is fully verified that the catalyst prepared by modifying a specific content (5%~30%) of rare earth oxides (preferably Ce-based composite oxides) with polyoxometalate (preferably phosphotungstic acid, silicotungstic acid, or a combination of the two) and loading the same on a heat-activated pretreated attapulgite mixed titanium dioxide carrier has excellent high-temperature denitration activity, extraordinary hydrothermal aging resistance, and strong sulfur and water resistance, fully achieving the technical goal of the present application.

[0112] Those skilled in the art will readily understand that the above description is only of the preferred embodiments of the present application and is not intended to limit the present application, and any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0113] Some parts of the present application not described in detail are provided by the known technology in the art. The above examples are only for the purpose of describing the present application and are not intended to limit the scope of the present application. The scope of the present application is defined by the appended claims. Any equivalent replacements and modifications made without departing from the spirit and principles of the present application shall be included in the scope of the present application.​

Claims

1. A rare earth-based high-temperature denitration catalyst, characterized in that, The rare earth-based high-temperature denitrification catalyst comprises attapulgite-mixed titanium dioxide carrier, rare earth oxides, and polyoxoacid salts; by mass percentage: the content of rare earth oxides is 0.1%~30%, the content of polyoxoacid salts is 0.1%~20%, and the balance is attapulgite-mixed titanium dioxide carrier. The rare earth oxide is one or a mixture of several of cerium dioxide, lanthanum oxide, and neodymium oxide; the polyoxygenate is a metal-oxygen cluster compound with terminal oxygen and bridging oxygen on its surface.

2. The rare earth-based high-temperature denitration catalyst according to claim 1, characterized in that, The polyoxygenate is one or more of phosphotungstic acid, silicotungstic acid, and phosphomolybdic acid.

3. The rare earth-based high-temperature denitration catalyst according to claim 1, characterized in that, The polyoxoacid salt is a mixture of metal-oxygen cluster compounds with terminal oxygen and bridging oxygen on the surface, and the rare earth oxide is a mixture.

4. The rare earth-based high-temperature denitration catalyst according to claim 1, characterized in that, The rare earth-based high-temperature denitrification catalyst contains 5% to 30% rare earth oxides and 5% to 10% polyoxophosphates.

5. The rare earth-based high-temperature denitrification catalyst according to any one of claims 1 to 4, characterized in that, The attapulgite mass percentage of the titanium dioxide carrier is 1% to 20%.

6. The method for preparing the rare earth-based high-temperature denitration catalyst according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: The calculated amount of rare earth oxide precursor metal salt solution is loaded onto an attapulgite-mixed titanium dioxide support by an equal volume impregnation method. After aging, drying and first calcination, basic catalysts with different contents of rare earth oxide / TiO2 are obtained. The temperature of the first calcination is 400-600℃ and the time is 3-6 hours. S2: The calculated amount of polyoxo acid salt solution is loaded onto the rare earth oxide / attapulgite mixed titanium dioxide basic catalyst obtained in step S1 by initial wet impregnation method, and after drying and second calcination, the rare earth-based high-temperature denitrification catalyst is obtained; the second calcination temperature is 250-350℃ and the time is 2-4 hours.

7. The preparation method of the rare earth-based high-temperature denitration catalyst according to claim 5, characterized in that, The drying temperature in steps S2 and S3 is 80-120℃, and the drying time is 6-12 hours.

8. The preparation method of the rare earth-based high-temperature denitration catalyst according to claim 5, characterized in that, The rare earth oxide precursor solution is obtained by dissolving the rare earth oxide precursor in water, and the polyoxygenate solution is obtained by dissolving a calculated amount of polyoxygenate in water, ethanol, or a mixture of water and ethanol.

9. The preparation method of the rare earth-based high-temperature denitration catalyst according to claim 5, characterized in that, Step S0 is included before step S1: S0: Attapulgite and titanium dioxide are mechanically ball-milled and mixed evenly according to a certain mass ratio, and then pretreated with thermal activation at 400℃ for 2-4 hours to obtain an attapulgite-mixed titanium dioxide carrier.

10. The application of the rare earth-based high-temperature denitrification catalyst according to any one of claims 1 to 4 in the field of denitrification at 420-550℃.

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