High dust resistance and erosion resistance strong sulfur resistance rare earth composite denitration catalyst and preparation method thereof

Abstract

The application relates to the technical field of atmospheric pollution control, and relates to a high-dust-resistance, erosion-resistance, strong-sulfur-resistance rare earth composite denitration catalyst and a preparation method thereof. 11 The catalyst takes a ternary composite oxide of TiO2, SiO2 and Al2O3 as a carrier, takes V2O5 and MoO3 as double active components, takes CeO2 and Pr6O 11 1.0% to 2.5% as double rare earth additives; the mass percentage of SiO2 in the carrier is 6% to 13%, the mass percentage of Al2O3 is 3% to 7%, and the balance is anatase TiO2; the loadings of the other components in the total mass of the carrier are as follows: V2O5 1.0% to 1.8%, MoO3 1.5% to 3.0%, CeO2 2.5% to 5.5%, and Pr6O 1.0% to 2.5%. The catalyst has the dust-resistance, erosion-resistance and sulfur-resistance by synergistic regulation of the ternary carrier, the double active components and the double rare earth additives, gradient impregnation and low-temperature gradient sintering.

Description

Technical Field

[0001] This invention relates to the field of air pollution control technology, and is a highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst and its preparation method. Background Technology

[0002] Flue gas from coal-fired power plants contains nitrogen oxides (NOx). x Selective catalytic reduction (SCR) is currently the mainstream denitrification technology, and the denitrification catalyst is the core of the SCR system. Dust concentrations in flue gas from high-dust coal-fired power units can reach 50–120 g / m³. 3 It contains a large number of hard particles, which can easily cause catalyst wear and loss of active components; at the same time, SO2 in the flue gas is easily oxidized to generate ammonium sulfate, which blocks the pores, resulting in decreased catalyst activity and shortened life.

[0003] Currently, most commercially available SCR denitration catalysts are based on the V2O5-TiO2 system, and related patents and industrial products generally suffer from the following technical defects: Chinese patent document CN112495365A discloses a low-temperature vanadium-titanium-based SCR denitration catalyst, comprising a TiO2-SiO2 support, an effective component, and a vanadium donor. The TiO2-SiO2 support is prepared by a heterogeneous precipitation method. The effective component is at least one of transition metal active components or at least one of rare earth element active components. The precursor of the vanadium donor is a soluble vanadium salt, specifically at least one of sodium metavanadate, ammonium metavanadate, and potassium metavanadate. However, it still suffers from problems such as low mechanical strength, poor resistance to dust erosion, high wear rate, weak resistance to sulfur poisoning, rapid activity decay under high sulfur conditions, narrow activity temperature window, and insufficient activity in the low load range (170℃ to 250℃).

[0004] Chinese patent document CN111203208A discloses a low-temperature vanadium-titanium-based SCR denitration catalyst for promoting ABS decomposition and its preparation method. The catalyst uses vanadium oxide (V₂O₅) as the active component and at least one of Ce, Mo, or Nb as the ABS decomposition-promoting component. However, it still uses a single TiO₂ support, resulting in insufficient erosion and abrasion resistance, easy pulverization and pore blockage under high dust conditions, limited improvement in sulfur resistance and structural stability, and a simple pore structure leading to large pressure drop, easy ash blockage, and high operating energy consumption under high dust conditions.

[0005] In summary, existing technologies generally suffer from poor abrasion resistance, weak sulfur poisoning resistance, narrow temperature window, short lifespan, and poor adaptability to high dust conditions, making it difficult to meet the requirements for ultra-low emissions and long-term stable operation of coal-fired power units operating under high dust, high sulfur, and wide load conditions. Therefore, developing a rare earth composite denitrification catalyst with high dust resistance, erosion resistance, strong sulfur resistance, wide temperature range, and long lifespan has significant engineering value. Summary of the Invention

[0006] This invention provides a rare earth composite denitrification catalyst with high dust and erosion resistance and strong sulfur resistance, which overcomes the shortcomings of the prior art. It can effectively solve the problems of poor dust and erosion resistance, weak sulfur poisoning resistance, narrow activity temperature window, and short service life of existing denitrification catalysts, which cannot meet the long-term stable denitrification requirements of high dust, high sulfur, and wide load coal-fired units.

[0007] One of the technical solutions of this invention is achieved through the following measures: a highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst, using TiO2, SiO2, and Al2O3 ternary composite oxides as a support, V2O5 and MoO3 as dual active components, and CeO2 and Pr6O3 as active components. 11 It is a rare earth additive; The carrier contains 6% to 13% SiO2 by mass, 3% to 7% Al2O3 by mass, and the remainder is anatase TiO2; Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.0% to 1.8%, MoO₃ 1.5% to 3.0%, CeO₂ 2.5% to 5.5%, Pr₆O₂ 11 1.0% to 2.5%.

[0008] The following are further optimizations and / or improvements to the above-mentioned technical solution: The specific surface area of ​​the above-mentioned anatase TiO2 is 90 m². 2 / g to 130m 2 / g, with pore size distribution concentrated in the range of 8nm to 28nm.

[0009] The aforementioned high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst has a honeycomb structure with square and circular composite channels and a pore density of 18 pores / cm³. 2 Up to 28 holes / cm 2 The wall thickness ranges from 0.75 mm to 1.15 mm.

[0010] The above-mentioned high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst was prepared according to the following steps: Step 1: Mix the required amounts of tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate, add the reaction solvent, adjust the pH of the system to acidic, stir the reaction, age, and the reaction product is dried and calcined to obtain TiO2-SiO2-Al2O3 support. Step 2: The TiO2-SiO2-Al2O3 support is sequentially immersed in a mixed solution of ammonium metavanadate and citric acid and a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate. The dried reaction products are then subjected to gradient sintering to obtain a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst.

[0011] In step one above, the reaction solvent is isopropanol.

[0012] In step one above, the pH of the system is adjusted to 2.5 to 3.5 using a mixture of citric acid and acetic acid.

[0013] In step one above, the reaction is stirred for 40 to 80 minutes and then allowed to stand and age for 30 to 40 hours.

[0014] In step one above, the roasting is carried out at 580℃ to 650℃ for 4 to 6 hours.

[0015] In step two above, the concentration of ammonium metavanadate in the mixed solution of ammonium metavanadate and citric acid is 0.04 mol / L to 0.07 mol / L, and the concentration of citric acid is 0.5 mol / L to 1.5 mol / L.

[0016] In step two above, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium metavanadate and citric acid at a temperature of 70°C to 80°C for 2 to 3 hours.

[0017] In step two above, the concentration of ammonium molybdate, cerium nitrate, and praseodymium nitrate in the mixed solution is 0.08 mol / L to 0.14 mol / L, the concentration of cerium nitrate is 0.07 mol / L to 0.11 mol / L, and the concentration of praseodymium nitrate is 0.03 mol / L to 0.06 mol / L.

[0018] In step two above, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium molybdate, cerium nitrate, and praseodymium nitrate at a temperature of 70°C to 80°C for 2 to 3 hours.

[0019] In step two above, the gradient sintering is a medium-low temperature gradient sintering. The temperature gradient is to first raise the temperature to 360℃ to 400℃ at a heating rate of 3℃ / min, hold it for 40min to 80min, and then raise it to 450℃ to 470℃ and hold it for 3h to 5h.

[0020] The second technical solution of the present invention is achieved through the following measures: a method for preparing a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst, comprising the following steps: Step 1: Mix the required amounts of tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate, add the reaction solvent, adjust the pH of the system to acidic, stir the reaction, age, and the reaction product is dried and calcined to obtain TiO2-SiO2-Al2O3 support. Step 2: The TiO2-SiO2-Al2O3 support is sequentially immersed in a mixed solution of ammonium metavanadate and citric acid and a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate. The dried reaction products are then subjected to gradient sintering to obtain a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst.

[0021] This invention significantly improves the catalyst's resistance to dust, erosion, and sulfur poisoning through synergistic regulation of a ternary carrier, dual active components, and dual rare earth additives, combined with gradient impregnation and low-temperature gradient sintering processes. The product exhibits high denitrification efficiency, a wide activity temperature window, excellent mechanical strength and thermal stability, low operating resistance, minimal ash blockage, and a significantly extended service life. The overall process is stable and controllable, with moderate cost, and can be directly adapted to existing denitrification systems, making it suitable for large-scale industrial production. Detailed Implementation

[0022] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0023] The present invention will be further described below with reference to embodiments: Example 1: This highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst uses TiO2, SiO2, and Al2O3 ternary composite oxides as supports, V2O5 and MoO3 as dual active components, and CeO2 and Pr6O3 as active components. 11 It is a rare earth additive; The carrier contains 6% to 13% SiO2 by mass, 3% to 7% Al2O3 by mass, and the remainder is anatase TiO2; Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.0% to 1.8%, MoO₃ 1.5% to 3.0%, CeO₂ 2.5% to 5.5%, Pr₆O₂ 11 1.0% to 2.5%.

[0024] Example 2: As an optimization of the above example, the specific surface area of ​​the anatase TiO2 is 90 m². 2 / g to 130m 2 / g, with pore size distribution concentrated in the range of 8nm to 28nm.

[0025] Example 3: As an optimization of the above examples, the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst has a honeycomb structure with square and circular composite channels and a pore density of 18 pores / cm³. 2 Up to 28 holes / cm 2 The wall thickness ranges from 0.75 mm to 1.15 mm.

[0026] Example 4: As an optimization of the above examples, the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst was prepared according to the following steps: Step 1: Mix the required amounts of tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate, add the reaction solvent, adjust the pH of the system to acidic, stir the reaction, age, and the reaction product is dried and calcined to obtain TiO2-SiO2-Al2O3 support. Step 2: The TiO2-SiO2-Al2O3 support is sequentially immersed in a mixed solution of ammonium metavanadate and citric acid and a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate. The dried reaction products are then subjected to gradient sintering to obtain a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst.

[0027] Example 5: As an optimization of the above example, in step one, the reaction solvent is isopropanol.

[0028] Example 6: As an optimization of the above example, in step one, the pH of the system is adjusted to 2.5 to 3.5 using a mixed acid of citric acid and acetic acid.

[0029] Example 7: As an optimization of the above example, in step one, the stirring reaction is carried out for 40 min to 80 min, and then left to stand for aging for 30 h to 40 h.

[0030] Example 8: As an optimization of the above example, in step one, the calcination is carried out at 580°C to 650°C for 4 to 6 hours.

[0031] Example 9: As an optimization of the above example, in step two, the concentration of ammonium metavanadate in the mixed solution of ammonium metavanadate and citric acid is 0.04 mol / L to 0.07 mol / L, and the concentration of citric acid is 0.5 mol / L to 1.5 mol / L.

[0032] Example 10: As an optimization of the above example, in step two, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium metavanadate and citric acid at a temperature of 70°C to 80°C for 2 to 3 hours. After impregnation in the mixed solution of ammonium metavanadate and citric acid, the TiO2-SiO2-Al2O3 support is dried at 120°C for 5 hours and then impregnated in a mixed solution of ammonium molybdate, cerium nitrate, and praseodymium nitrate.

[0033] Example 11: As an optimization of the above example, in step two, the concentration of ammonium molybdate solution in the mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate is 0.08 mol / L to 0.14 mol / L, the concentration of cerium nitrate is 0.07 mol / L to 0.11 mol / L, and the concentration of praseodymium nitrate is 0.03 mol / L to 0.06 mol / L.

[0034] Example 12: As an optimization of the above example, in step two, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium molybdate, cerium nitrate, and praseodymium nitrate at a temperature of 70°C to 80°C for 2 to 3 hours. The TiO2-SiO2-Al2O3 support impregnated in the mixed solution of ammonium molybdate, cerium nitrate, and praseodymium nitrate is then dried at 120°C for 5 hours, followed by the next step of gradient sintering.

[0035] Example 13: As an optimization of the above example, in step two, the gradient sintering is a medium-low temperature gradient sintering, with the temperature gradient being to first raise the temperature to 360°C to 400°C at a heating rate of 3°C / min, hold for 40 min to 80 min, and then raise the temperature to 450°C to 470°C and hold for 3 h to 5 h.

[0036] Example 14: The composition of this highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst is as follows: The carrier contains 8% SiO2 by mass, 4% Al2O3 by mass, and the remainder is anatase TiO2. Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.3%, MoO₃ 2.0%, CeO₂ 3.5%, Pr₆O₂ 1.3%, MoO₃ 2.0%, CeO₂ 3.5%, Pr₆O₃ 1.3%, MoO₃ 2.0%, CeO₂ 3.5%, Pr₆O� 11 1.5%.

[0037] The preparation process is as follows: Step 1: Tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate were mixed in a mass ratio of 16:1.2:0.6, with isopropanol as the solvent. The pH of the system was adjusted to 2.8 with citric acid and acetic acid. The mixture was stirred at room temperature for 60 min, aged for 36 h, and the reaction product was dried at 120 °C for 8 h and then calcined at 600 °C for 5 h to obtain the TiO2-SiO2-Al2O3 support.

[0038] Step 2: The TiO2-SiO2-Al2O3 support was immersed in a mixed solution of ammonium metavanadate (0.05 mol / L) and citric acid at 75°C for 2.5 h, and the immersed support was dried at 120°C for 5 h. After drying, the carrier was again immersed in a mixed solution of ammonium molybdate (0.10 mol / L), cerium nitrate (0.08 mol / L), and praseodymium nitrate (0.04 mol / L) for 2.5 h at 75 °C and then dried at 120 °C for 5 h. The dried reaction products were subjected to gradient sintering, with the sintering gradient being a heating rate of 3℃ / min to 380℃ and holding for 1 hour, followed by a heating rate of 460℃ and holding for 4 hours; after this, a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst was obtained.

[0039] Example 15: The composition of this high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst is as follows: The carrier contains 10% SiO2 by mass, 5% Al2O3 by mass, and the remainder is anatase TiO2. Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.5%, MoO₃ 2.3%, CeO₂ 4.0%, Pr₆O₂ 1.5%, MoO₃ 2.3%, CeO₂ 4.0%, Pr₆O₃ ... 11 1.8%.

[0040] The preparation process is as follows: Step 1: Tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate were mixed in a mass ratio of 17.8:3.5:1. Isopropanol was used as the solvent, and the pH of the system was adjusted to 3.0 with citric acid and acetic acid. The mixture was stirred for 60 min, aged for 36 h, and the reaction product was dried at 120 °C for 8 h and then calcined at 620 °C for 5 h to obtain the TiO2-SiO2-Al2O3 support.

[0041] Step 2: The TiO2-SiO2-Al2O3 support was immersed in a mixed solution of ammonium metavanadate (0.06 mol / L) and citric acid at 75°C for 2.5 h, and the immersed support was dried at 120°C for 5 h. After drying, the carrier was again immersed in a mixed solution of ammonium molybdate (0.12 mol / L), cerium nitrate (0.09 mol / L), and praseodymium nitrate (0.05 mol / L) for 2.5 h at 75 °C and then dried at 120 °C for 5 h. The dried reaction products were subjected to gradient sintering, with the sintering gradient being a heating rate of 3℃ / min to 380℃ and holding for 1 hour, followed by a heating rate of 460℃ and holding for 4 hours; after this, a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst was obtained.

[0042] Example 16: The composition of this highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst is as follows: The carrier contains 12% SiO2 by mass, 6% Al2O3 by mass, and the remainder is anatase TiO2. Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.7%, MoO₃ 2.7%, CeO₂ 5.0%, Pr₆O₂ 1.7%, MoO₃ 2.7%, CeO₂ 5.0%, Pr₆O₃ ... 11 2.2%.

[0043] Step 1: Tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate were mixed in a mass ratio of approximately 16.2:4.2:1. Isopropanol was used as the solvent, and the pH of the system was adjusted to 3.2 with citric acid and acetic acid. The mixture was stirred for 60 min, aged for 36 h, and the reaction product was dried at 120 °C for 8 h and then calcined at 640 °C for 5 h to obtain the TiO2-SiO2-Al2O3 support.

[0044] Step 2: The TiO2-SiO2-Al2O3 support was immersed in a mixed solution of ammonium metavanadate (0.07 mol / L) and citric acid at 75°C for 2.5 h, and the immersed support was dried at 120°C for 5 h. After drying, the carrier was again immersed in a mixed solution of ammonium molybdate (0.13 mol / L), cerium nitrate (0.10 mol / L), and praseodymium nitrate (0.06 mol / L) for 2.5 h at 75 °C and then dried at 120 °C for 5 h. The dried reaction products were subjected to gradient sintering, with the sintering gradient being a heating rate of 3℃ / min to 380℃ and holding for 1 hour, followed by a heating rate of 450℃ and holding for 5 hours; after this, a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst was obtained.

[0045] Comparative Example 1: A conventional commercial V2O5-WO3 / TiO2 catalyst, without SiO2, Al2O3 and rare earth additives.

[0046] Comparative Example 2: The difference from Example 15 is that a mixed solution of ammonium molybdate (0.13 mol / L) and cerium nitrate (0.10 mol / L) was used instead of a mixed solution of ammonium molybdate (0.13 mol / L), cerium nitrate (0.10 mol / L), and praseodymium nitrate (0.06 mol / L) for impregnation. In other words, CeO2 modification was used, without Pr6O. 11 .

[0047] Comparative Example 3: The difference from Example 15 is that gradient sintering was replaced by one-step high-temperature sintering at 550°C for 4 hours.

[0048] Test Example 1: High-efficiency denitrification performance test under high dust conditions At a dust concentration of 60 g / m³ 3 Up to 130g / m 3 NO x Ingestion concentration 500 mg / m 3 Up to 700mg / m 3 6000 h -1 The denitrification efficiency of the catalysts obtained in Examples 14 to 16 was tested under simulated high-dust conditions in a coal-fired power plant. The results are shown in Table 1.

[0049] Test results show that the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst of this invention is effective at 60 g / m³. 3 Up to 130g / m 3 Under high dust conditions, the denitrification efficiency is consistently greater than 91%, which is far superior to the denitrification efficiency of conventional commercial catalysts at 85% to 88% under the same conditions, meeting the ultra-low emission requirements of thermal power plants.

[0050] Test Example 2: Erosion Resistance and Abrasion Resistance Test Referring to GB / T 39712-2020 "Marine Sulfoaluminate Cement for Rapid Construction", the catalysts obtained in Examples 14 to 16 were subjected to a 1000-hour continuous dust scouring test, and the results are shown in Table 2.

[0051] Test results show that the wear rate of the high dust resistance, erosion resistance and sulfur resistance rare earth composite denitrification catalyst of the present invention is less than 0.25% / 1000h, which is far superior to the industry standard of 0.5% / 1000h. The dust erosion resistance is improved by more than 50%, which can effectively solve the problems of catalyst wear and loss of active components under high dust conditions.

[0052] Test Example 3: Strong Resistance to Sulfur Poisoning and Long Service Life Test Under high sulfur and high humidity conditions of 350℃, SO2 concentration of 500ppm, and 10% H2O, the catalysts obtained in Examples 14 to 16 were subjected to a 1000-hour continuous sulfur poisoning resistance test and a full life cycle accelerated aging test. The results are shown in Table 3.

[0053] Test results show that the high dust resistance, erosion resistance, and sulfur resistance of the rare earth composite denitrification catalyst of this invention has a sulfur poisoning resistance that is more than 40% higher than that of the traditional V2O5-TiO2 catalyst, effectively inhibiting the formation and deposition of ammonium bisulfate; the cumulative effective operating time is extended by more than 35% compared with the traditional 8000h design life, which can significantly reduce catalyst replacement costs and unit downtime frequency.

[0054] Test Example 4: Activity Temperature Window Test The denitrification efficiency of the catalysts obtained in Examples 14 to 16 was tested in the full temperature range of 170°C to 420°C, and the results are shown in Table 4.

[0055] Test results show that the active temperature window of the high dust resistance, erosion resistance and sulfur resistance rare earth composite denitrification catalyst of the present invention is widened to 170℃ to 420℃, covering the wide load temperature range of coal-fired units. It can ensure that it does not fail under low load (170℃ to 250℃) and does not sinter under high load (380℃ to 420℃), and is suitable for the flexible peak-shaving needs of the unit.

[0056] Test Example 5: Pore Structure and Specific Surface Area Test The pore structure parameters of the supports and catalysts in Examples 14 to 16 were tested using the N2 adsorption-desorption method (BET), and the results are shown in Table 5.

[0057] Test results show that the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst of this invention has a specific surface area of ​​90 m² on its TiO₂-SiO₂-Al₂O₃ support. 2 / g to 130m 2 / g, compared to conventional pure TiO2 support (70m 2 / g to 90m 2 The perg ratio is increased by more than 20%, providing sufficient dispersion sites for active components; the pore size is concentrated in the mesoporous range of 8nm to 28nm, effectively reducing the mass transfer resistance of high dust flue gas, while inhibiting dust blockage.

[0058] Test Example 6: Compressive Strength Test According to GB / T39711-2020 "Test Method for Compressive Strength of Selective Catalytic Reduction Denitrification Catalysts", the axial and radial compressive strengths of the catalysts obtained in Examples 14 to 16 were tested, and the results are shown in Table 6.

[0059] Test results show that the axial and radial compressive strength of the high dust resistance, erosion resistance and sulfur resistance rare earth composite denitrification catalyst of the present invention are far higher than the industry standard. It has excellent mechanical strength and can withstand the mechanical stress during flue gas erosion and installation and transportation, thus avoiding catalyst breakage and failure.

[0060] Test Example 7: Thermal Aging Performance Test A 1000-hour thermal aging test was conducted at 450℃ to test the activity decay of the catalysts obtained in Examples 14 to 16. The results are shown in Table 7.

[0061] Test results show that the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst of the present invention retains a denitrification efficiency of ≥95% and a specific surface area of ​​≥92% after 1000h of thermal aging. It has excellent thermal stability, can adapt to the temperature shock caused by boiler start-up and shutdown and load fluctuation, and has stable long-term operating performance.

[0062] The comparison between the high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst of the present invention and the comparative example is shown in Table 8.

[0063] The performance comparison results show that Comparative Example 1, which uses a traditional pure TiO2 support without the addition of rare earth additives, Al2O3 reinforcement, and rare earth modification, has a significantly higher wear rate, weaker resistance to sulfur poisoning, and shorter service life. All its performance characteristics are far inferior to those of this invention, fully verifying the superior performance of the TiO2-SiO2-Al2O3 ternary composite support compared to CeO2-Pr6O2. 11The dual rare earth additives play a crucial role in improving the catalyst's wear resistance, sulfur resistance, and long-term stability. Comparative Example 2 only used a single CeO2 rare earth for modification, without introducing Pr6O. 11 While a synergistic effect is achieved, the improvement in sulfur resistance and the extension of service life are limited, clearly demonstrating the effectiveness of CeO2 in synergistic interactions with Pr6O. 11 The synergistic modification of rare earth elements is essential for further enhancing sulfur resistance and extending catalyst life. Comparative Example 3 used a conventional one-step high-temperature sintering process without employing the medium-low temperature gradient sintering process of this invention, resulting in a significant decrease in the specific surface area of ​​the support, poorer dispersion of the active components, and reduced catalytic activity. This strongly demonstrates the importance of the medium-low temperature gradient sintering process in ensuring high dispersion of active components, maintaining the integrity of the support pore structure, and improving the overall structural stability of the catalyst.

[0064] In summary, through the comparison of Examples 14 to 16 and the comparative examples, combined with the process parameters, component ratios, structural design and test results, it can be seen that all the reaction conditions and process parameters defined in this invention, such as the ternary carrier composition, carrier preparation conditions, dual-active and dual-rare earth additive loading, gradient stepwise impregnation process, medium-low temperature gradient sintering regime, and honeycomb composite channel structure, are all indispensable technical means to achieve the comprehensive performance of high dust resistance, erosion resistance, strong sulfur resistance, wide temperature window and long life. The conditions are interrelated and synergistic, and none can be omitted. The specific ratio of the TiO2-SiO2-Al2O3 ternary carrier is fundamental to improving its mechanical strength, increasing specific surface area, optimizing mesopore size distribution, and enhancing its wear resistance. Strictly controlling the SiO2 mass percentage to 6% to 13% and the Al2O3 mass percentage to 3% to 7% ensures the carrier possesses suitable toughness, high structural strength, and sufficient active site loading capacity, preventing insufficient strength, increased brittleness, or a decrease in acidic sites due to component imbalance. The carrier preparation process employs a mixed acid of citric acid and acetic acid to adjust the pH to 2.5 to 3.5, sufficient aging for 36 hours, drying at 120℃, and calcination at 580℃ to 650℃. This is crucial for achieving uniform hydrolysis of the precursor, forming a regular pore structure, and improving the carrier's density and thermal stability. It prevents a sudden drop in specific surface area, pore collapse, and substandard mechanical strength caused by uncontrolled hydrolysis, insufficient aging, or improper calcination temperature. The dual active components V2O5 and MoO3, along with CeO2 and Pr6O... 11The specific loading of dual rare earth additives is key to achieving efficient denitrification over a wide temperature range, enhancing resistance to sulfur poisoning, and inhibiting the formation and deposition of ammonium bisulfate. Precise control of the loading range of each component fully leverages the synergistic effects of vanadium-molybdenum and cerium-praseodymium rare earths, ensuring sufficient activity at low temperatures and preventing sintering at high temperatures, while significantly improving sulfur resistance and operational stability. This avoids agglomeration and deactivation due to excessive component loading or limited performance improvement due to insufficient loading. The gradient stepwise impregnation process and citric acid complexation system are essential for ensuring high dispersion and uniform loading of the active components and rare earth additives on the carrier surface. Impregnating the vanadium component first, followed by the molybdenum-cerium-praseodymium mixed component, combined with constant-temperature impregnation at 70℃ to 80℃ and stepwise drying at 120℃, effectively avoids competitive adsorption, hydrolysis precipitation, and localized enrichment of multiple components, ensuring full exposure of active sites and maximizing catalytic efficiency. The medium-low temperature gradient sintering process, which involves slow heating at 3℃ / min, followed by pre-crystallization at 380℃ for 1 hour and final sintering at 460℃ for 4 hours, is a core process for preventing high-temperature agglomeration of active components, preserving the high specific surface area of ​​the support, eliminating internal thermal stress, and improving the structural stability and lifespan of the catalyst. It avoids problems such as pore blockage, specific surface area loss, rapid activity decay, and short lifespan caused by one-step high-temperature sintering. Furthermore, the composite pore structure reduces pressure drop by 12% to 18% compared to a single square pore structure, with a honeycomb-type square + circular composite pore density of 18 pores / cm³. 2 Up to 28 holes / cm 2 The structural design with a wall thickness of 0.75mm to 1.15mm is an important condition for adapting to low-resistance operation of high-dust flue gas, reducing dust blockage, and improving erosion resistance. It can effectively reduce flue gas pressure drop and extend catalyst service life.

[0065] In summary, this invention provides a high dust- and erosion-resistant, sulfur-resistant rare earth composite denitrification catalyst. It employs a synergistic system of a ternary composite support, dual active components, and dual rare earth additives, combined with gradient impregnation and low-temperature gradient sintering processes. Furthermore, the strict limitation and synergistic coordination of reaction conditions and process parameters form a complete innovative chain from support structure, active system, dispersion method to sintering regime. This high dust- and erosion-resistant, sulfur-resistant rare earth composite denitrification catalyst exhibits outstanding dust and erosion resistance and low wear rate; it maintains stable denitrification efficiency under high dust conditions, demonstrates strong resistance to sulfur poisoning, and significantly extends its service life; it has a wide active temperature window, adaptable to wide-load operation of units; it has a reasonable pore structure, low pressure drop, excellent mechanical and thermal stability, controllable process, and moderate cost, making it suitable for industrial production.

[0066] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A highly dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst, characterized in that... Using TiO2, SiO2, and Al2O3 ternary composite oxides as supports, V2O5 and MoO3 as dual active components, and CeO2 and Pr6O as active components... 11 It is a rare earth additive; The carrier contains 6% to 13% SiO2 by mass, 3% to 7% Al2O3 by mass, and the remainder is anatase TiO2; Based on the total mass of the carrier, the loadings of the remaining components are: V₂O₅ 1.0% to 1.8%, MoO₃ 1.5% to 3.0%, CeO₂ 2.5% to 5.5%, Pr₆O₂ 11 1.0% to 2.5%.

2. The high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst according to claim 1, characterized in that... The specific surface area of ​​anatase TiO2 is 90 m². 2 / g to 130m 2 / g, with pore size distribution concentrated in the range of 8nm to 28nm; Or / and, the high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst has a honeycomb structure with square and circular composite channels, and a pore density of 18 pores / cm³. 2 Up to 28 holes / cm 2 The wall thickness ranges from 0.75 mm to 1.15 mm.

3. The high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst according to claim 1 or 2, characterized in that... It is prepared according to the following steps: Step 1: Mix the required amounts of tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate, add the reaction solvent, adjust the pH of the system to acidic, stir the reaction, age, and the reaction product is dried and calcined to obtain TiO2-SiO2-Al2O3 support. Step 2: The TiO2-SiO2-Al2O3 support is sequentially immersed in a mixed solution of ammonium metavanadate and citric acid and a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate. The dried reaction products are then subjected to gradient sintering to obtain a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst.

4. The high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst according to claim 3, characterized in that... In step one, the reaction solvent is isopropanol; Or / and, in step one, the pH of the system is adjusted to 2.5 to 3.5 using a mixed acid of citric acid and acetic acid.

5. The high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst according to claim 3 or 4, characterized in that... In step one, the reaction is stirred for 40 to 80 minutes and then allowed to stand and age for 30 to 40 hours.

6. The high dust resistance, erosion resistance, and sulfur resistance rare earth composite denitrification catalyst according to any one of claims 3 to 5, characterized in that... In step one, the roasting is carried out at 580℃ to 650℃ for 4 to 6 hours.

7. The high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst according to any one of claims 3 to 6, characterized in that... In step two, the concentration of ammonium metavanadate in the mixed solution of ammonium metavanadate and citric acid is 0.04 mol / L to 0.07 mol / L, and the concentration of citric acid is 0.5 mol / L to 1.5 mol / L. Or / and, in step two, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium metavanadate and citric acid at a temperature of 70°C to 80°C for 2 to 3 hours.

8. The high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst according to any one of claims 3 to 7, characterized in that... In step two, the concentration of ammonium molybdate, cerium nitrate, and praseodymium nitrate in the mixed solution is 0.08 mol / L to 0.14 mol / L, the concentration of cerium nitrate is 0.07 mol / L to 0.11 mol / L, and the concentration of praseodymium nitrate is 0.03 mol / L to 0.06 mol / L. Or / and, in step two, the TiO2-SiO2-Al2O3 support is impregnated in a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate at a temperature of 70°C to 80°C for 2 to 3 hours.

9. The high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst according to any one of claims 1 to 8, characterized in that... In step two, the gradient sintering is a medium-low temperature gradient sintering. The temperature gradient is to first raise the temperature to 360℃ to 400℃ at a heating rate of 3℃ / min, hold it for 40min to 80min, and then raise it to 450℃ to 470℃ and hold it for 3h to 5h.

10. A method for preparing a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst according to any one of claims 1 to 9, characterized in that... Includes the following steps: Step 1: Mix the required amounts of tetraisopropyl titanate, tetraethyl orthosilicate, and aluminum nitrate, add the reaction solvent, adjust the pH of the system to acidic, stir the reaction, age, and the reaction product is dried and calcined to obtain TiO2-SiO2-Al2O3 support. Step 2: The TiO2-SiO2-Al2O3 support is sequentially immersed in a mixed solution of ammonium metavanadate and citric acid and a mixed solution of ammonium molybdate, cerium nitrate and praseodymium nitrate. The dried reaction products are then subjected to gradient sintering to obtain a high dust-resistant, erosion-resistant, and sulfur-resistant rare earth composite denitrification catalyst.

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