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CN-121988311-A - Low-temperature SCR denitration catalyst capable of preventing ammonia from escaping and preparation method thereof

CN121988311ACN 121988311 ACN121988311 ACN 121988311ACN-121988311-A

Abstract

The invention relates to a low-temperature SCR denitration catalyst capable of preventing ammonia from escaping and a preparation method thereof, and belongs to the technical field of catalysts. The catalyst takes niobium-cerium composite oxide as an active component (25-45%), titanium-zirconium composite oxide as a carrier (50-70%), lignin-derived carbon microsphere modified bismuth molybdate as an auxiliary agent (3-7%), graphene quantum dots as a structure enhancer (0.5-2% and particle size of 2-5 nm), and sesbania powder as a binder (1.5-2%). The auxiliary agent is prepared by reacting alkali lignin with formaldehyde and phenol to prepare microspheres, carbonizing, treating with nitric acid and compositing with bismuth molybdate. During preparation, the active component, the carrier and the graphene quantum dots are prepared respectively, then mixed according to a proportion, added with the binder, granulated and molded, and calcined to obtain the catalyst. The catalyst has high specific surface area and specific pore size distribution, can effectively improve the low-temperature denitration efficiency and prevent ammonia from escaping, and is suitable for industrial low-temperature flue gas denitration treatment.

Inventors

  • LIU QINYU
  • LIU SHAOGUANG
  • CHEN CHENGWU
  • LIU SHAOMING

Assignees

  • 上海瀚昱环保材料有限公司
  • 上海瀚昱环保科技有限公司

Dates

Publication Date
20260508
Application Date
20260130

Claims (10)

  1. 1.A low-temperature SCR denitration catalyst for preventing ammonia from escaping is characterized by comprising the following components, The active component is niobium-cerium composite oxide 25-45%, wherein the molar ratio of Nb to Ce is 1 (0.3-0.8); The carrier is 50-70% of titanium-zirconium composite oxide, wherein the molar ratio of Ti to Zr is 1 (0.1-0.3); 3-7% of auxiliary agent lignin derived carbon microsphere modified bismuth molybdate; The structural reinforcing agent is graphene quantum dots with the particle size of 2-5 nm and 0.5-2%; 1.5-2% of adhesive, namely sesbania powder.
  2. 2. The low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 1, wherein the preparation process of the auxiliary lignin-derived carbon microsphere modified bismuth molybdate is as follows, S1, dissolving alkali lignin in a sodium hydroxide solution with the mass fraction of 5-10%, filtering, adding formaldehyde and phenol, and reacting for 2-4 hours at 60-80 ℃ in an acidic environment with the pH value of 2-3 to obtain microspheres A; s2, heating the microsphere A to 700-900 ℃ from room temperature at 5-10 ℃ per min under nitrogen atmosphere, and carbonizing for 1-2 hours to obtain a carbon microsphere B; S3, soaking the carbon microspheres B in a nitric acid solution with the mass fraction of 10-15% for 2-3 hours to obtain lignin-derived carbon microspheres; S4, dissolving bismuth nitrate and ammonium molybdate in a mixed solvent of glycol and water, and controlling the molar ratio of Bi/Mo to be 2:1 to obtain a mixed solution C; S5, adding the lignin-derived carbon microspheres prepared in the step S3 into the mixed solution C, and performing ultrasonic dispersion to form a uniform suspension; s6, transferring the suspension into a high-pressure reaction kettle, performing hydrothermal reaction for 12-24 hours at 120-160 ℃, cooling, and performing centrifugal separation to obtain a precursor D; And S7, calcining the precursor D at the temperature of 500-600 ℃ for 2-4 hours to obtain the auxiliary lignin-derived carbon microsphere modified bismuth molybdate.
  3. 3. The low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 1 or 2, wherein the specific surface area of the prepared auxiliary lignin-derived carbon microsphere modified bismuth molybdate is more than or equal to 50m 2 /g.
  4. 4. A low temperature SCR denitration catalyst for preventing ammonia slip as defined in claim 2, wherein the molar ratio of formaldehyde to phenol in S1 is 1:1.
  5. 5. The low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 2, wherein the volume ratio of glycol to water in S4 is 1 (1-2).
  6. 6. The low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 2, wherein the mass ratio of the carbon microspheres in S5 to the mixed solution C is 1 (2-3).
  7. 7. A method for preparing a low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 1-6, which is characterized by comprising the following specific steps of, A1, mixing ammonium niobium oxalate and cerium nitrate solution according to the molar ratio of Nb to Ce, adding ammonia water to adjust the pH value to 9-10, washing with deionized water after coprecipitation, drying at 80-110 ℃ for 12-24 hours, and calcining at 400-600 ℃ for 2-4 hours to obtain a niobium-cerium composite oxide; A2, mixing tetrabutyl titanate and zirconium nitrate according to the molar ratio of Ti to Zr, dissolving in absolute ethyl alcohol, dropwise adding acetic acid to adjust the pH value to 3-4, standing and aging for 12-24 hours after stirring to form sol, drying for 12-16 hours at 105 ℃, and calcining for 3-5 hours at 550-650 ℃ after drying to obtain a titanium-zirconium composite oxide; A3, dispersing graphene oxide in deionized water, adding sodium citrate as a reducing agent, performing hydrothermal reaction at 180-200 ℃ for 6-8 hours, and performing centrifugal purification to obtain graphene quantum dots with particle diameters of 2-5 nm, wherein the dispersity is more than or equal to 90%; and A4, mixing the niobium-cerium composite oxide, the titanium-zirconium composite oxide, the lignin-derived carbon microsphere modified bismuth molybdate and the graphene quantum dots according to mass percent, adding sesbania powder as a binder, and calcining at 300-400 ℃ for 1-2 hours after granulating and forming to obtain the low-temperature SCR denitration catalyst for preventing ammonia from escaping.
  8. 8. The method for preparing a low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 7, wherein the specific surface area of the niobium-cerium composite oxide prepared in A1 is not less than 80 m 2 /g.
  9. 9. The method for preparing the low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 7, wherein the pore size distribution of the titanium-zirconium composite oxide in A2 is 2-10 nm.
  10. 10. The preparation method of the low-temperature SCR denitration catalyst for preventing ammonia slip according to claim 7, wherein the mass ratio of graphene oxide to deionized water in A3 is 1 (50-100), and the mass ratio of graphene oxide to sodium citrate is 1 (3-5).

Description

Low-temperature SCR denitration catalyst capable of preventing ammonia from escaping and preparation method thereof Technical Field The invention belongs to the technical field of catalysts, and relates to a low-temperature SCR denitration catalyst capable of preventing ammonia from escaping and a preparation method thereof. Background Nitrogen oxides (NO x) are key pollutants causing environmental problems such as acid rain, photochemical smog and the like, and the high-efficiency treatment of the nitrogen oxides is significant for improving the quality of the atmosphere. Selective Catalytic Reduction (SCR) technology is the current mainstream means of denitration, but traditional SCR catalysts are mostly suitable for medium-high temperature (300-400 ℃) environments. With the industrial development, the denitration requirement of low-temperature flue gas (150-300 ℃) is increasingly remarkable, and the existing low-temperature SCR catalyst has various problems, such as insufficient activity caused by easy agglomeration of active components, poisoning deactivation caused by poor sulfur and water resistance of a carrier, serious ammonia escape phenomenon, secondary pollution and resource waste. At present, there are studies on improving catalyst performance by optimizing active components, carriers and additives, but the effect is limited. Therefore, development of an SCR denitration catalyst which has high denitration activity and strong poisoning resistance at low temperature and can effectively inhibit ammonia slip is a key problem to be solved urgently in the field. Disclosure of Invention The invention aims to provide a low-temperature SCR denitration catalyst for preventing ammonia from escaping and a preparation method thereof, and the catalyst has the characteristic of effectively inhibiting ammonia from escaping. The aim of the invention can be achieved by the following technical scheme: A low-temperature SCR denitration catalyst for preventing ammonia from escaping comprises the following components, The active component is niobium-cerium composite oxide 25-45%, wherein the molar ratio of Nb to Ce is 1 (0.3-0.8); The carrier is 50-70% of titanium-zirconium composite oxide, wherein the molar ratio of Ti to Zr is 1 (0.1-0.3); 3-7% of auxiliary agent lignin derived carbon microsphere modified bismuth molybdate; The structural reinforcing agent is graphene quantum dots with the particle size of 2-5 nm and 0.5-2%; 1.5-2% of adhesive, namely sesbania powder. Further, the preparation process of the auxiliary lignin derived carbon microsphere modified bismuth molybdate is as follows, S1, dissolving alkali lignin in a sodium hydroxide solution with the mass fraction of 5-10%, filtering, adding formaldehyde and phenol, and reacting for 2-4 hours at 60-80 ℃ in an acidic environment with the pH value of 2-3 to obtain microspheres A; s2, heating the microsphere A to 700-900 ℃ from room temperature at 5-10 ℃ per min under nitrogen atmosphere, and carbonizing for 1-2 hours to obtain a carbon microsphere B; S3, soaking the carbon microspheres B in a nitric acid solution with the mass fraction of 10-15% for 2-3 hours to obtain lignin-derived carbon microspheres; S4, dissolving bismuth nitrate and ammonium molybdate in a mixed solvent of glycol and water, and controlling the molar ratio of Bi/Mo to be 2:1 to obtain a mixed solution C; S5, adding the lignin-derived carbon microspheres prepared in the step S3 into the mixed solution C, and performing ultrasonic dispersion to form a uniform suspension; s6, transferring the suspension into a high-pressure reaction kettle, performing hydrothermal reaction for 12-24 hours at 120-160 ℃, cooling, and performing centrifugal separation to obtain a precursor D; And S7, calcining the precursor D at the temperature of 500-600 ℃ for 2-4 hours to obtain the auxiliary lignin-derived carbon microsphere modified bismuth molybdate. Furthermore, the specific surface area of the prepared auxiliary lignin derived carbon microsphere modified bismuth molybdate is more than or equal to 50m 2/g. Further, the molar ratio of formaldehyde to phenol in S1 is 1:1. Further, the volume ratio of the glycol to the water in the S4 is 1 (1-2). Further, the solid-liquid mass ratio of the carbon microsphere in the step S5 to the mixed solution C is 1 (2-3). A preparation method of a low-temperature SCR denitration catalyst for preventing ammonia from escaping comprises the following specific procedures, A1, mixing ammonium niobium oxalate and cerium nitrate solution according to the molar ratio of Nb to Ce, adding ammonia water to adjust the pH value to 9-10, washing with deionized water after coprecipitation, drying at 80-110 ℃ for 12-24 hours, and calcining at 400-600 ℃ for 2-4 hours to obtain a niobium-cerium composite oxide; A2, mixing tetrabutyl titanate and zirconium nitrate according to the molar ratio of Ti to Zr, dissolving in absolute ethyl alcohol, dropwise adding acetic acid to adjust the pH v