SCR denitration catalyst carrier and preparation method thereof

Abstract

The invention relates to an SCR (Selective Catalytic Reduction) denitration catalyst carrier and a preparation method and application thereof, and the preparation method comprises the following steps: (1) crushing a waste FCC (Fluid Catalytic Cracking) catalyst, performing roasting treatment, and performing dry ball milling after roasting to obtain powder; (2) adding the powder into a mixed acid solution for pickling treatment, wherein the mixed acid comprises inorganic acid and organic acid; (3) filtering and washing the material subjected to acid pickling treatment to obtain a solid, and drying and roasting the solid to obtain molecular sieve carrier powder; and (4) mixing the carrier powder with TiO2 by a sol-gel method to prepare a composite carrier, namely the SCR denitration catalyst carrier. The waste FCC catalyst is used as a raw material to prepare the SCR denitration catalyst carrier, and the carrier has the advantages of low heavy metal content, high active component content, good water resistance and the like.

Description

Technical Field

[0001] This invention belongs to the field of denitrification catalyst technology, specifically relating to an SCR denitrification catalyst support and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) are a significant pollutant emitted from chemical industry exhaust gases, posing substantial environmental and health risks. Ammonia selective reduction (NH3-SCR) is currently the most mature and stable process for reducing NOx emissions from industrial exhaust gases, especially VW-TiO2 catalysts, which have become one of the most commercially viable denitrification catalysts due to their highly efficient medium- and high-temperature NOx removal performance. However, the catalyst preparation process using fresh TiO2 supports is costly, and the amount of spent catalyst increases over time.

[0003] Fluid catalytic cracking (FCC) is a major process for converting heavy oil into lighter oil in oil refining, playing a crucial role in the refining process. However, after reaching the end of their service life, FCC catalysts become deactivated and are discarded due to heavy metal contamination and carbon buildup. Currently, most of the replaced waste FCC catalysts are disposed of through landfill, causing significant environmental impact.

[0004] Xu Wei et al. (Experimental Study on NH3 Reduction of NO by FCC Waste Catalysis [J]. Environmental Science and Technology, 2009, 32(7):1-5) directly used waste FCC catalyst as a denitrification catalyst, but its reaction temperature requirement is high (above 400℃), and the highest conversion rate is only 50%. Although the cost is reduced, most of the V species deposited on the FCC catalyst are low-valence (+3, +4) vanadium oxides, and most of the vanadium is mainly deposited in the molecular sieve channels, neither participating in the reaction nor blocking the molecular sieve channels. Therefore, there is currently no effective utilization method.

[0005] CN116637636A discloses a method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst. The method uses waste fluidized bed catalytic cracking catalyst as a support, impregnates the support with an equal volume of divalent manganese salt precursor solution, then adds KMnO4 solution dropwise for reaction. After the reaction is complete, the catalyst is obtained by washing and centrifugation, followed by drying. The divalent manganese salt is one of Mn(NO3)2, Mn(AC)2, MnCl2, and MnSO4. Compared with traditional supported catalyst preparation methods, this method has advantages such as simple process, no secondary pollutant emissions, energy saving, adjustable and controllable structure, good low-temperature SCR denitrification activity, and a wide activity temperature window. However, this method does not remove harmful substances from the waste FCC catalyst, which to some extent limits the support performance and catalytic activity.

[0006] CN109482222A discloses a method for preparing a denitrification catalyst, comprising the following steps: (1) ball milling: crushing waste FCC catalyst to a particle size of less than 50 μm; (2) water washing: washing the crushed FCC catalyst, centrifuging it after washing, and drying the precipitate obtained; (3) acid leaching: ultrasonically impregnating the dried precipitate in acid solution, separating the solid, and obtaining leachate; (4) microwave roasting: microwave roasting the solid separated after acid leaching; (5) secondary acid leaching: mixing the microwave roasted material with titanium dioxide in proportion, and ultrasonically impregnating it in acid solution; (6) mixing: transferring all the material after secondary acid leaching to a mixing machine, adding the leachate from step (3), and supplementing the active component and auxiliary component for mixing; (7) honeycomb molding: the mixed material is pre-extruded, aged, extruded, dried, and roasted to obtain a honeycomb denitrification catalyst. This invention addresses the deactivation characteristics of FCC spent catalysts by employing processes such as ball milling, water washing, acid leaching, microwave roasting, and secondary acid leaching to migrate components like V deposited within the molecular sieve channels to the molecular sieve surface. While this helps improve the utilization rate of vanadium in the spent catalyst, both acid leaching processes use inorganic acids. While dissolving non-reactive low-valence (+3, +4) vanadium oxides and toxic substances like Ni, it also dissolves some catalytically active metal components such as cerium, hindering resource utilization. Furthermore, the energy consumption for converting low-valence vanadium within the carrier channels to V₂O₅ using microwave roasting is relatively high. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an SCR denitrification catalyst support and its preparation method. This invention uses spent FCC catalyst as raw material to prepare the SCR denitrification catalyst support, which possesses advantages such as low heavy metal content, high active component content, and good water resistance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of this invention provides a method for preparing an SCR denitrification catalyst support, comprising the following steps:

[0010] (1) The waste FCC catalyst was crushed and then roasted. After roasting, it was dry ball milled to obtain powder.

[0011] (2) The powder is added to a mixed acid solution for pickling treatment, wherein the mixed acid includes inorganic acid and organic acid;

[0012] (3) After acid washing, the material is filtered and washed to obtain solid matter, which is then dried and calcined to obtain molecular sieve carrier powder.

[0013] (4) The carrier powder and TiO2 are mixed by sol-gel method to obtain a composite carrier, namely the SCR denitrification catalyst carrier.

[0014] In step (1), the spent FCC catalyst is the FCC catalyst that has been replaced after use, mainly containing molecular sieves, supports, and binders. Specifically, the molecular sieve is at least one of ZRP, ZSM-5, and Y molecular sieve, with a mass content of 15% to 50%; the support is specifically diatomaceous earth or kaolin, with a mass content of 20% to 70%; the binder is specifically alumina sol or silica sol, with a mass content of 5% to 30%; the total vanadium content, calculated as V2O5, is 0.1% to 2.0%, of which pentavalent vanadium accounts for 25% to 35%; and the total cerium content, calculated as CeO2, is 1% to 3%.

[0015] In step (1), the waste FCC catalyst is pulverized to a D90 particle size of less than 50 μm.

[0016] In step (1), the calcination temperature is 300-500℃ and the calcination time is 1-4h.

[0017] In step (1), the calcined waste FCC catalyst is dry-ball-milled until the D90 particle size is less than 20 μm. The diameter of the grinding balls loaded in the ball mill is 3-10 mm, preferably 2-3 mm; the ball-to-material ratio is 8-15, preferably 10-12; the ball milling speed is 100-400 r / min, preferably 170-210 r / min; the single ball milling time is 3-15 min, preferably 3-7 min; and the number of ball milling cycles is 1-4, preferably 2-3.

[0018] In step (2), the mass ratio of powder to mixed acid is 1:5 to 1, preferably 1:2 to 1. The acid washing treatment adopts the stirring leaching method, the pH value is below 1, the stirring speed is 20 to 100 r / min, preferably 30 to 70 r / min; the treatment time is 2 to 10 h, preferably 3 to 5 h.

[0019] In step (2), the inorganic acid in the mixed acid is selected from one or more of sulfuric acid, nitric acid, phosphoric acid, etc., with sulfuric acid being preferred; the concentration of the inorganic acid in the mixed acid solution is 0.5–2 mol / L, preferably 0.5–1 mol / L. The organic acid in the mixed acid is selected from one or more of citric acid, oxalic acid, salicylic acid, sulfonic acid, etc., with citric acid and oxalic acid being preferred; the concentration of the organic acid in the mixed acid solution is 0.5–2 mol / L, preferably 0.5–1 mol / L.

[0020] In step (3), the material after acid washing is filtered, such as by suction filtration or pressure filtration. Deionized water is used for washing, and after washing 2-5 times, a solid is obtained.

[0021] In step (3), the drying temperature is 100-130℃, preferably 110-120℃; the drying time is 5-10h, preferably 6-8h. The calcination temperature is 200-600℃, preferably 300-500℃; the calcination time is 2-10h, preferably 4-7h.

[0022] In step (4), the mass ratio of molecular sieve carrier powder to TiO2 is 6–15:1, preferably 9–12:1. The specific steps of the sol-gel method are as follows: the titanium source is slowly added dropwise to anhydrous ethanol, and then stirred to obtain a mixed solution for 20–60 min; the carrier powder is added to the mixed solution, and distilled water and concentrated hydrochloric acid are slowly added dropwise, and stirred until a gel is formed; the gel is dried and calcined to obtain the composite carrier. Among them, the titanium source is one or more of tetrabutyl titanate, titanium tetrachloride, titanium nitrate, etc., preferably tetrabutyl titanate; the mass ratio of titanium source to anhydrous ethanol is 1:2–6; the volume ratio of the sum of the added distilled water and concentrated hydrochloric acid to ethanol is 0.1–0.3:1.

[0023] The second aspect of this invention provides an SCR denitrification catalyst support, which is prepared using the method described above. The SCR denitrification catalyst support is a composite support consisting of a molecular sieve support prepared from waste FCC catalyst and TiO2, wherein the TiO2 is loaded on the surface of the molecular sieve support.

[0024] The specific surface area of ​​the composite carrier is 130–170 m². 2 / g; pore volume is 0.05~0.15cm³ 3 / g; pore size distribution ranges from 6.24 to 10.56 nm, with an average pore size of 8.96 nm; total acid content is 0.35 to 0.50 mmol / g. The carrier particle size is D10 0.5 to 1.5 nm; D50 4.0 to 8.0 nm; D90 15 to 25 nm; V content (based on oxides) is less than 0.5%, and Ce content (based on oxides) is more than 2%.

[0025] The third aspect of this invention provides an SCR denitrification catalyst, which is prepared by loading an active component and an additive onto the composite support prepared in this invention as the support. The active component is V₂O₅, and the additive is WO₃. Based on the mass of the catalyst, the V₂O₅ content is 1%–1.5%, and the WO₃ content is 3%–4%.

[0026] The fourth aspect of this invention provides an SCR denitrification catalyst application that can withstand H2O content of 15% (v / v) and SO2 volume concentration of 1000ppm in the exhaust gas.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) In view of the characteristics of spent FCC catalysts, this invention uses a mixed acid containing organic and inorganic acids for acid washing treatment. This effectively removes undesirable substances (such as low-valence V, heavy metals, etc.) from the spent catalyst, avoiding their adverse effects on the subsequent preparation of SCR catalysts, such as occupying adsorption channels; on the other hand, it avoids the removal of beneficial substances such as Ce, which helps to improve catalytic activity. The prepared molecular sieve support has the advantages of low valence vanadium content and high content of useful components.

[0029] (2) A denitrification catalyst support was prepared by combining molecular sieve support powder obtained from waste FCC catalyst with TiO2. TiO2 was loaded on the surface of the molecular sieve support. This support has abundant surface acid sites, good water and sulfur resistance and thermal stability.

[0030] (3) Using the composite support prepared in this invention as the catalyst support and vanadium and tungsten as active components to prepare SCR denitrification catalyst, it not only has good catalytic activity, but also the catalyst service life is comparable to that of using fresh molecular sieve support.

[0031] (4) The preparation method of the present invention is simple, fast and low cost, and can be mass-produced. It is an excellent way to recycle waste FCC catalysts, greatly reducing the cost of catalyst raw materials, and can be widely used in the preparation of SCR catalysts. Detailed Implementation

[0032] The technical solution and its effects of the present invention will be further described in detail below with reference to specific embodiments. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in Example 1 were purchased from conventional biochemical reagent stores.

[0034] The embodiments of this invention utilize spent FCC catalyst that has been replaced after use. It mainly contains a molecular sieve, a support, and a binder. The molecular sieve is ZSM-5 molecular sieve, with a mass content of 30%; the support is diatomaceous earth, with a mass content of 40%; the binder is alumina sol, with a mass content of 20%; the total vanadium content, calculated as V₂O₅, is 1.5%, of which pentavalent vanadium accounts for 30%; and the total cerium content, calculated as CeO₂, is 2%. Before use, the spent FCC catalyst is pulverized to a D90 particle size of less than 50 μm.

[0035] Example 1

[0036] (1) Take 400g of pulverized waste FCC catalyst powder and place it in a muffle furnace, calcining it at 450℃ for 2h. Place the calcined powder into a ball mill jar, with a grinding ball diameter of 3mm, a ball-to-material ratio of 10, a ball milling speed of 200r / min, a single ball milling time of 5min, and a number of ball milling cycles of 2. After ball milling, ultra-low particle size powder with D90 less than 20μm is obtained.

[0037] (2) The ball-milled powder was subjected to acid washing treatment. The powder and mixed acid were mixed at a mass ratio of 1:1.25, wherein the mixed acid consisted of sulfuric acid and oxalic acid, with a sulfuric acid concentration of 1 mol / L and an oxalic acid concentration of 1 mol / L. The acid washing treatment adopted the stirring leaching method, with a stirring speed of 60 r / min and a treatment time of 4 h.

[0038] (3) The acid-washed material was vacuum filtered, the filter cake was physically crushed, and washed with deionized water. It was then vacuum filtered again until all liquid phase was removed. The washing was repeated 3 times. After washing, the sample was dried at 115℃ for 7 hours, and then calcined at 450℃ for 5 hours to obtain molecular sieve carrier powder.

[0039] (4) The composite carrier was prepared by sol-gel method, specifically as follows: titanium source titanium tetrabutyl ester was slowly added dropwise to anhydrous ethanol, the mass ratio of titanium source to anhydrous ethanol was 1:3, and the mixture was stirred for 40 min to obtain a mixed solution; molecular sieve carrier powder was added to the mixed solution, and distilled water and concentrated hydrochloric acid were slowly added dropwise, the sum of the amount of distilled water and concentrated hydrochloric acid added was 0.1 to the volume ratio of ethanol, and the volume ratio of distilled water and concentrated hydrochloric acid was 3; the mixture was stirred until a gel was formed, dried at 115℃ for 7 h, and calcined at 450℃ for 5 h to obtain composite carrier S1.

[0040] Example 2

[0041] (1) Take 400g of pulverized waste FCC catalyst powder and place it in a muffle furnace, calcining it at 300℃ for 4h. Place the calcined powder into a ball mill jar, with a grinding ball diameter of 5mm, a ball-to-material ratio of 8, a ball milling speed of 150r / min, a single ball milling time of 3min, and a ball milling cycle of 2 times. After ball milling, ultra-low particle size powder with D90 less than 20μm is obtained.

[0042] (2) The ball-milled powder was subjected to acid washing treatment. The powder and mixed acid were mixed at a mass ratio of 1:2, wherein the mixed acid consisted of sulfuric acid and oxalic acid, with a sulfuric acid concentration of 2 mol / L and an oxalic acid concentration of 0.5 mol / L. The acid washing treatment was carried out by stirring leaching method, with a stirring speed of 30 r / min and a treatment time of 5 h.

[0043] (3) The acid-washed material was vacuum filtered, the filter cake was physically crushed, and washed with deionized water. It was then vacuum filtered again until all liquid phase was removed. The washing was repeated 3 times. After washing, the sample was dried at 110℃ for 10 hours, and then calcined at 300℃ for 7 hours to obtain molecular sieve carrier powder.

[0044] (4) The composite carrier was prepared by sol-gel method, specifically as follows: titanium source titanium tetrabutyl ester was slowly added dropwise to anhydrous ethanol, the mass ratio of titanium source to anhydrous ethanol was 1:2, and the mixture was stirred for 30 min to obtain a mixed solution; molecular sieve carrier powder was added to the mixed solution, and distilled water and concentrated hydrochloric acid were slowly added dropwise, the sum of the amount of distilled water and concentrated hydrochloric acid added was 0.2 to the volume ratio of ethanol, and the volume ratio of distilled water and concentrated hydrochloric acid was 3; the mixture was stirred until a gel was formed, dried at 100℃ for 10 h, and calcined at 500℃ for 4 h to obtain composite carrier S2.

[0045] Example 3

[0046] (1) Take 400g of pulverized waste FCC catalyst powder and place it in a muffle furnace, calcining it at 500℃ for 1h. Place the calcined powder into a ball mill jar, with grinding balls of 10mm diameter, a ball-to-material ratio of 15, a ball milling speed of 250r / min, a single ball milling time of 3min, and a total of 3 ball milling cycles. After ball milling, ultra-low particle size powder with D90 less than 20μm is obtained.

[0047] (2) The ball-milled powder was subjected to acid washing treatment. The powder and mixed acid were mixed at a mass ratio of 1:3, wherein the mixed acid consisted of sulfuric acid and oxalic acid, with a sulfuric acid concentration of 0.5 mol / L and an oxalic acid concentration of 2 mol / L. The acid washing treatment adopted the stirring leaching method, with a stirring speed of 70 r / min and a treatment time of 5 h.

[0048] (3) The acid-washed material was vacuum filtered, the filter cake was physically crushed, and washed with deionized water. It was then vacuum filtered again until all liquid phase was removed. The washing was repeated 3 times. After washing, the sample was dried at 120℃ for 6 hours, and then calcined at 500℃ for 4 hours to obtain molecular sieve carrier powder.

[0049] (4) The composite carrier was prepared by sol-gel method, specifically as follows: titanium source titanium tetrabutyl ester was slowly added dropwise to anhydrous ethanol, the mass ratio of titanium source to anhydrous ethanol was 1:5, and the mixture was stirred for 60 min to obtain a mixed solution; molecular sieve carrier powder was added to the mixed solution, and distilled water and concentrated hydrochloric acid were slowly added dropwise, the sum of the amount of distilled water and concentrated hydrochloric acid added was 0.3 to the volume ratio of ethanol, and the volume ratio of distilled water and concentrated hydrochloric acid was 3; the mixture was stirred until a gel was formed, dried at 130℃ for 5 h, and calcined at 400℃ for 8 h to obtain composite carrier S3.

[0050] Example 4

[0051] The basic steps are essentially the same as in Example 1, except that: nitric acid is used as the inorganic acid component in the mixed acid mixture, with a concentration of 1 mol / L, and citric acid is used as the organic acid component, with a concentration of 1 mol / L. All other conditions remain unchanged, and the composite carrier S4 is finally prepared.

[0052] Example 5

[0053] The basic steps are essentially the same as in Example 1, except that: phosphoric acid is used as the inorganic acid component in the mixed acid mixture, with a concentration of 1 mol / L, and salicylic acid is used as the organic acid component, with a concentration of 1 mol / L. All other conditions remain unchanged, and the composite carrier S5 is finally prepared.

[0054] Example 6

[0055] The basic steps are essentially the same as in Example 1, except that the titanium source used is titanium tetrachloride, while the other conditions remain unchanged. The final composite support S6 is thus prepared.

[0056] Comparative Example 1

[0057] The basic steps are essentially the same as in Example 1, except that oxalic acid is used instead of the mixed acid at a concentration of 1 mol / L, while the other conditions remain unchanged. The final composite carrier DS1 is thus prepared.

[0058] Comparative Example 2

[0059] The basic steps are essentially the same as in Example 1, except that sulfuric acid is used instead of the mixed acid at a concentration of 1 mol / L, while the other conditions remain unchanged. The final composite carrier DS2 is thus prepared.

[0060] Comparative Example 3

[0061] The basic steps are basically the same as in Example 1, except that step (1) calcination and dry ball milling were not performed; instead, the powder was directly mixed with a mixed acid solution for acid washing. All other conditions remained unchanged. The carrier DS3 was finally prepared.

[0062] Comparative Example 4

[0063] The basic steps are essentially the same as in Example 1, except that the molecular sieve support is directly mixed with TiO2, and the sol-gel method is not used for preparation. All other conditions remain unchanged. The final prepared support DS4 is obtained.

[0064] Comparative Example 5

[0065] The basic steps are essentially the same as in Example 1, except that alumina is used instead of TiO2. All other conditions remain unchanged. The final prepared support DS4 is obtained.

[0066] Comparative Example 6

[0067] The basic steps are essentially the same as in Example 1, except that fresh molecular sieve support powder is used instead of spent catalyst support powder. All other conditions remain unchanged. The final prepared support DS4 is obtained.

[0068] The properties of the composite carriers obtained in the embodiments and comparative examples of the present invention are shown in Table 1 below:

[0069] Table 1 shows the physicochemical properties of the prepared composite carriers.

[0070]

[0071]

[0072] Using the supports prepared in the examples and comparative examples as composite supports, denitrification catalysts were prepared by loading active components and additives. The method of equal volume impregnation was adopted, specifically including the following steps: (1) Preparation of active component solution: 15g of ammonium metavanadate, 40g of ammonium metatungstate, 30g of oxalic acid and 60g of water were poured into a 250mL beaker to obtain an active component solution. (2) Preparation of catalyst: 10g of composite support was weighed and mixed with the active component solution so that the composite support was just in a saturated absorption state. After impregnation for 12h, it was dried at 120℃ for 20h and calcined at 500℃ for 4h. The specific calcination method in the muffle furnace was as follows: the temperature was first increased from room temperature to 500℃ at 5℃ / min, and then kept at 500℃ for 4h. After calcination, it was slowly reduced to room temperature. Finally, catalyst C1 was obtained. Catalysts C2, C3, C4, C5, C6, DC1, DC2, DC3, DC4, DC5, and DC6 were prepared using S2, S3, S4, S5, S6, DS1, DS2, DS3, DS4, DS5, and DS6, respectively.

[0073] The denitrification catalysts prepared in the examples and comparative examples were evaluated. The evaluation was conducted on a small-scale laboratory apparatus under the following conditions: NO and NH3 volume concentrations of 200 ppm, O2 content of 3% (v / v), H2O content of 15% (v / v), SO2 volume concentration of 1000 ppm, NH3 / NO molar ratio of 1:1, and volume hourly space velocity of 19000–54000 h⁻¹. -1 To eliminate the influence of surface adsorption, data collection and testing were initiated 20-30 minutes after the system had been running stably under ventilation.

[0074] The catalytic activity of the catalyst is reflected by the denitrification activity of NO, which is calculated by the following formula: Denitrification activity = [(C0-C) / C0] × 100%.

[0075] In the formula, C0 is the initial NO concentration, and C is the NO concentration in the treated gas.

[0076] The NOx removal efficiencies of different catalysts at different temperatures are shown in the table below.

[0077] Table 2. Denitrification effect of different catalysts at different temperatures

[0078]

Claims

1. A method for preparing an SCR denitrification catalyst support, characterized in that... Includes the following steps: (1) The waste FCC catalyst was crushed and then roasted. After roasting, it was dry ball milled to obtain powder. (2) The powder is added to a mixed acid solution for pickling treatment, wherein the mixed acid includes inorganic acid and organic acid; (3) After acid washing, the material is filtered and washed to obtain solid matter, which is then dried and calcined to obtain molecular sieve carrier powder; (4) The carrier powder and TiO2 are mixed by sol-gel method to obtain a composite carrier, namely the SCR denitrification catalyst carrier.

2. The method according to claim 1, characterized in that: In step (1), the waste FCC catalyst is the FCC catalyst that has been replaced after use, mainly containing molecular sieves, supports and binders; wherein the molecular sieve is at least one of ZRP, ZSM-5 and Y molecular sieves, with a mass content of 15% to 50%; the support is diatomaceous earth and / or kaolin, with a mass content of 20% to 70%; the binder is alumina sol and / or silica sol, with a mass content of 5% to 30%; the total vanadium content is 0.1% to 2.0% based on V2O5, of which pentavalent vanadium accounts for 25% to 35%; and the total cerium content is 1% to 3% based on CeO2.

3. The method according to claim 1, characterized in that: In step (1), the waste FCC catalyst is crushed to a D90 particle size of less than 50 μm.

4. The method according to claim 1, characterized in that: In step (1), the calcination temperature is 300-500℃ and the calcination time is 1-4h; the calcined waste FCC catalyst is dry ball-milled until the D90 particle size is less than 20μm.

5. The method according to claim 1, characterized in that: In step (2), the mass ratio of powder to mixed acid is 1:5 to 1, preferably 1:2 to 1.

6. The method according to claim 1, characterized in that: In step (2), the pickling treatment adopts the stirring leaching method, the stirring speed is 20-100 r / min, preferably 30-70 r / min; the treatment time is 2-10 h, preferably 3-5 h.

7. The method according to claim 1, characterized in that: In step (2), the inorganic acid in the mixed acid is selected from one or more of sulfuric acid, nitric acid, and phosphoric acid, with sulfuric acid being preferred; the concentration of the inorganic acid in the mixed acid solution is 0.5 to 2 mol / L, preferably 0.5 to 1 mol / L.

8. The method according to claim 1, characterized in that: In step (2), the organic acid in the mixed acid is selected from one or more of citric acid, oxalic acid, salicylic acid and sulfonic acid, preferably citric acid and oxalic acid; the concentration of organic acid in the mixed acid solution is 0.5 to 2 mol / L, preferably 0.5 to 1 mol / L.

9. The method according to claim 1, characterized in that: In step (3), the drying temperature is 100-130℃, preferably 110-120℃; the drying time is 5-10h, preferably 6-8h; the calcination temperature is 200-600℃, preferably 300-500℃; and the calcination time is 2-10h, preferably 4-7h.

10. The method according to claim 1, characterized in that: In step (4), the mass ratio of molecular sieve carrier powder to TiO2 is 6 to 15:1, preferably 9 to 12:

1.

11. The method according to claim 1, characterized in that: In step (4), the specific steps of the sol-gel method are as follows: the titanium source is slowly added dropwise into anhydrous ethanol and then stirred to obtain a mixed solution. The stirring time is 20-60 min. The carrier powder is added to the mixed solution, and distilled water and concentrated hydrochloric acid are slowly added dropwise. The mixture is stirred until a gel is formed. The gel is dried and calcined to obtain the composite carrier.

12. The method according to claim 11, characterized in that: The titanium source is one or more of tetrabutyl titanate, titanium tetrachloride, and titanium nitrate, preferably tetrabutyl titanate; the mass ratio of the titanium source to anhydrous ethanol is 1:2 to 6; the volume ratio of the sum of the amounts of distilled water and concentrated hydrochloric acid added to ethanol is 0.1 to 0.3:

1.

13. A support for an SCR denitrification catalyst, characterized in that... It is prepared using the method described in any one of claims 1-12.

14. The carrier according to claim 13, characterized in that: The specific surface area of ​​the composite carrier is 130–170 m². 2 / g; pore volume is 0.05~0.15cm³ 3 / g; pore size distribution ranges from 6.24 to 10.56 nm, with an average pore size of 8.96 nm; total acid content is 0.35 to 0.50 mmol / g. The carrier particle size is D10 of 0.5 to 1.5 nm; D50 of 4.0 to 8.0 nm; D90 of 15 to 25 nm; V content (based on oxides) is less than 0.5%, and Ce content (based on oxides) is greater than 2%.

15. An SCR denitrification catalyst, characterized in that it is prepared by using a support prepared by any one of claims 1-12 or a composite support as described in claims 13-14 as a support, and loading an active component and an additive; wherein the active component is V2O5, the additive is WO3, and the V2O5 content is 1% to 1.5% and the WO3 content is 3% to 4% by mass of the catalyst.

16. The application of the catalyst according to claim 15, characterized in that: The catalyst can withstand H2O content of 15% (v / v) and SO2 volume concentration of 1000ppm in the exhaust gas.

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