SCR (Selective Catalytic Reduction) denitration catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of catalyst preparation, in particular to an SCR denitration catalyst and a preparation method and application thereof. Comprising the following steps: mixing butyl titanate and absolute ethyl alcohol to obtain a solution A, mixing deionized water, concentrated nitric acid and cerium nitrate to obtain a solution B, adding the solution A into the solution B, and aging, drying and calcining to obtain a carrier; dissolving ammonium molybdate, ammonium metatungstate and cerous nitrate in an oxalic acid solution, immersing the carrier in the oxalic acid solution, taking out the carrier, and carrying out gradient roasting to obtain a catalyst matrix A; stirring citric acid, ammonium metavanadate, manganous nitrate and molten nitrate in a water bath to obtain a coordination solution, dispersing the catalyst matrix A in water, adding the coordination solution into the water, stirring, activating and drying to obtain a catalyst matrix B; and putting the precursor into a tubular furnace containing (NH4) 2HPO4 steam, carrying out high-temperature treatment, introducing hexamethyldisilazane steam, carrying out CVD deposition, and annealing, thereby obtaining the product. The catalyst prepared by the invention has wide-temperature synergistic removal capability, and can efficiently treat various pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, in particular to an SCR denitration catalyst and a preparation method and application thereof. Background Art

[0002] In the field of catalyst preparation technology, the application of SCR denitrification catalysts faces many challenges. Traditional SCR denitrification catalysts have obvious defects. Their carrier uses pure TiO2, which has extremely weak oxygen storage capacity of less than 0.1mmol / g, and the SO2 oxidation rate exceeds 3%, which seriously affects the performance and use of the catalyst. As for the active layer V2O5-WO3 / TiO2, it performs poorly in low temperature environments. When the temperature is below 200°C, the conversion rate is less than 50%. At the same time, the temperature application range is narrow, and it only performs well in the range of 350-400°C. In terms of anti-poison design, traditional catalysts use surface phosphoric acid treatment, but this method can only delay As poisoning and cannot effectively resist the blockage of the catalyst by siloxane. The hydrophobic protection uses a carbon coating, which will fail in a high temperature environment above 300°C, resulting in a decrease in catalyst performance.

[0003] Siloxane poisoning is a key issue facing traditional SCR denitrification catalysts. Siloxane (D4) decomposes on the catalyst surface, generating SiO2. This SiO2 blocks micropores with a pore size of less than 5nm. Micropores account for over 70% of traditional catalysts. This significantly reduces the catalyst's active sites and destroys the pore structure, significantly reducing its catalytic efficiency and shortening its service life.

[0004] In addition, the problem of heavy metal competitive adsorption cannot be ignored. As2O3 and V2O5 will form V-As-O compounds, which are unstable and easily destroy the denitrification active sites, causing the catalyst to reduce the NOx removal efficiency. At the same time, the limitation of the temperature window also restricts the application range of the catalyst. Although the MnOx catalyst has certain low-temperature activity, in the presence of SO2, MnOx is not as effective as the catalyst. 4+ MnSO4 is easily generated, but MnSO4 has poor stability, which makes it difficult for MnOx catalysts to exert stable low-temperature denitrification effects in practical applications. Summary of the Invention

[0005] In light of the above shortcomings in the prior art, the present invention aims to provide an SCR denitration catalyst with significantly improved poison resistance and a significantly higher As poisoning threshold. Furthermore, the catalyst exhibits wide-temperature synergistic removal capabilities, enabling efficient treatment of a variety of pollutants.

[0006] Another object of the present invention is to provide a method for preparing an SCR denitration catalyst, which is simple and suitable for industrial production.

[0007] The third object of the present invention is to provide an application of an SCR denitrification catalyst for treating waste gas generated by waste incineration, biomass gasification waste gas, electronic waste smelting waste gas or polysilicon tail gas.

[0008] The present invention is achieved by adopting the following technical solutions: The preparation method of the SCR denitration catalyst comprises the following steps: (1) Butyl titanate and anhydrous ethanol are mixed to obtain solution A, deionized water, concentrated nitric acid and cerium nitrate are mixed to obtain solution B, solution A is added to solution B, and after aging, drying and calcination, a support (TiO2-CeO2 composite support) is obtained; (2) Dissolve ammonium molybdate, ammonium metatungstate, and cerium nitrate in oxalic acid solution, immerse the support (impregnation of equal volume), remove the support, and then calcine it in a gradient manner to obtain catalyst matrix A (MoO3-WO3-CeO2 solid solution); (3) Stirring citric acid, ammonium metavanadate, manganese nitrate and ferric nitrate in a water bath to obtain a coordination liquid, dispersing the catalyst matrix A in water, adding the coordination liquid thereto, stirring, activating and drying, and obtaining the catalyst matrix B; (4) The catalyst substrate B is placed in a tubular furnace containing (NH4)2HPO4 vapor and treated at high temperature. Then, hexamethyldisilazane vapor (HMDS) is introduced for CVD deposition. After annealing, the SCR denitrification catalyst is obtained.

[0009] In the step (1), the molar ratio of butyl titanate to anhydrous ethanol is 1: (2-2.5), and the molar ratio of H2O to Ce is 1: (2-2.5). 3+ The molar ratio of Ce to Ti is (18-22):1, the molar ratio of Ce to Ti is 0.05-0.10; the pH of solution B is 1.2-1.8; the conditions after adding solution A to solution B are: stirring at 75-85℃ for 3-5h to form a yellow sol, and aging at 40-43℃ for 2-3h. Among them, Ce / Ti = 0.05-0.10 (molar ratio), specific surface area ≥ 110m 2 / g, pore size 10nm.

[0010] The drying and calcining conditions in step (1) are: drying at 80-85°C for 24-28 hours, and then calcining at 500-600°C for 3-5 hours, with a heating rate of 5°C / min.

[0011] In the step (2), ammonium molybdate, ammonium metatungstate and cerium nitrate are all added in the form of solutions, with the concentration of ammonium molybdate being 0.08-0.12 mol / L; the concentration of ammonium metatungstate being 0.18-0.22 mol / L; the concentration of cerium nitrate being 0.45-0.55 mol / L; and the concentration of oxalic acid solution being 0.25-0.35 mol / L.

[0012] In the step (2), the conditions for carrier immersion are: ultrasonic assistance for 30-40 minutes, drying at 115-120°C for 6-8 hours, 250-350W; the conditions for gradient calcination are: calcination at 330-370°C for 1.5-2.5 hours under N2 atmosphere, then switching to air and calcination at 520-580°C for 3-5 hours.

[0013] In the step (3), citric acid, ammonium metavanadate, manganese nitrate and ferric nitrate are added in the form of a solution, the concentration of citric acid is 18-22 wt%; the concentration of ammonium metavanadate is 0.04-0.06 mol / L; the concentration of manganese nitrate is 0.18-0.22 mol / L; the concentration of ferric nitrate is 0.08-0.12 mol / L; and the water bath temperature is 55-60°C.

[0014] In the step (3), when the catalyst matrix A is dispersed in water, the solid content is 40-42%, and ammonia water is added to adjust the pH to 9.8-10.2; the drying and activation conditions are: drying at 115-120°C, air calcining at 480-500°C for 3-3.5h, and a heating rate of 2-4°C / min.

[0015] In the step (4), the concentration of (NH4)2HPO4 vapor is 4-6%, and the high temperature treatment conditions are: 300-310℃ treatment for 1-1.5h; the conditions for introducing hexamethyldisilazane vapor are 0.8-1.2mL / min, N2 carrier gas, CVD deposition at 280-320℃ for 0.8-1.2h; and the annealing conditions are: annealing at 250-255℃ in N2 atmosphere for 1-1.5h.

[0016] The SCR denitration catalyst is prepared by the above-mentioned method for preparing the SCR denitration catalyst.

[0017] The SCR denitration catalyst is used for treating waste gas generated by garbage incineration, biomass gasification waste gas, electronic waste smelting waste gas or polysilicon tail gas.

[0018] Under N2 atmosphere, at 330-370℃, ammonium molybdate exists in the form of (NH4)2MoO4.

[0019] Some of the above raw materials need to be pretreated before use, specifically: Butyl titanate pretreatment: Butyl titanate and acetylacetone were mixed in a molar ratio of 1:0.1, stirred at 40°C for 2 hours to form a chelate; anhydrous ethanol was added in a volume ratio of 1:1, and stored under nitrogen for later use.

[0020] Cerium nitrate pretreatment: Cerium nitrate was dissolved in deionized water with a concentration of 0.5 mol / L and ascorbic acid was added. 3+ : ascorbic acid = 1:0.05; deoxygenate with nitrogen and store in the dark.

[0021] Ammonium molybdate activation: Dissolve ammonium molybdate in ammonia water (25wt%) to prepare a 0.5mol / L solution; add oxalic acid dropwise to pH = 4.5, and stir at 60℃ for 1h to form a soluble ammonium molybdate-oxalic acid complex.

[0022] The SCR denitration catalyst prepared by the present invention adopts a core-shell structure, and the carrier core is TiO2-CeO2, which has a high specific surface area and can effectively anchor the active components. 3+ / Ce 4+ The oxygen storage cycle mechanism can buffer the impact of SO2 and provide a guarantee for the stable operation of the catalyst. The protective layer is P-SiO2, and the formation mechanism is: (NH4)2HPO4→2NH3+H3PO4; H3PO4+SiO2→Si-O-PO(OH)2 (forming a P-doped layer), forming a hydrophobic barrier, in which P fills the vacancies, inhibits the generation of Si-OH, reduces the surface energy, and reduces the siloxane adsorption energy, thereby effectively resisting siloxane poisoning. The anti-poison layer is Mo-W-Ce, Mo can fix heavy metals such as As / Pb, and WO3 can adsorb Hg 0 , Ce helps promote Hg 0 →Hg 2+ The conversion improves the efficiency of mercury removal. The active layer is V-Mn-Fe, V2O5 is responsible for medium-temperature denitrification, MnOx activates low-temperature activity, and Fe2O3 widens the temperature window. The three work synergistically to achieve wide-temperature and high-efficiency denitrification. In terms of resistance to siloxanes, ≡Si-CH3 on the catalyst surface reacts with D4 to form ≡Si-O-Si(CH3)2, which reduces the deposition of siloxanes on the catalyst surface through competitive adsorption. At the same time, the hydrophobic methyl group makes the surface contact angle greater than 120°, reduces the surface energy, and reduces the adsorption energy of siloxane from -1.8eV to -1.1eV, effectively inhibiting the adsorption of siloxanes. When resisting arsenic, 2MoO3 reacts with As2O3 to generate 2MoAsO4, forming a stable arsenomolybdate, which improves the arsenic resistance of the catalyst. During the anti-sulfur process, the oxygen vacancies of CeO2 capture SO2, and CeO2+SO2+1 / 2O2→SO4 occurs. 2- -Ce reaction, and can periodically regenerate to release SO4²⁻, avoiding sulfate deposition and ensuring the stable operation of the catalyst in a sulfur-containing environment. 0 Oxidized to Hg 2+ Afterwards, it is removed by the downstream adsorbent, and the removal rate includes two stages: oxidation and capture.

[0023] Using the sol-gel method, butyl titanate is hydrolyzed and polycondensed to form a Ti-O-Ti network, Ce 3+ Embedded in the lattice, it inhibits the phase transition from anatase to rutile, maintaining the high specific surface area of ​​the catalyst. In the step-by-step impregnation-calcination process, calcination in N2 atmosphere can prevent Mo 6+Premature oxidation leads to agglomeration, and then switching to air promotes the formation of MoO3-WO3-CeO2 solid solution, which enhances the performance of the catalyst. In the coordination precipitation method, citric acid forms [Cit-Metal] with V / Mn / Fe. n- The complex slowly releases metal ions under alkaline conditions, achieving molecular-level dispersion and improving the dispersibility of the active components. During vapor deposition, (NH4)2HPO4 decomposes into 2NH3 and H3PO4. HMDS reacts with H2O to form SiO2 and (CH3)3SiNH2, forming a hydrophobic layer. P atoms replace Si in the Si-O network, forming PO-Si bonds, which enhance the stability of the protective layer.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The SCR denitrification catalyst prepared by the present invention has significantly improved anti-poisoning ability and significantly increased siloxane tolerance life. At the same time, the catalyst has a wide temperature range synergistic removal capability, the denitrification temperature window is expanded, and it can efficiently treat a variety of pollutants.

[0025] (2) The preparation process of the present invention has been optimized. The dispersibility is improved by the coordination precipitation method, the carrier is optimized by the sol-gel method, and the solid solution is formed by step-by-step impregnation and calcination. The vapor deposition protective layer is resistant to siloxane. The process has precise temperature control, low energy consumption, and short drying time.

[0026] (3) The SCR denitrification catalyst prepared by the present invention can be used to treat waste gas generated by waste incineration, biomass gasification waste gas, electronic waste smelting waste gas, or polysilicon tail gas. In the electronic smelting scenario, the As removal rate exceeds 92%, and the siloxane adsorption capacity in polysilicon tail gas treatment is less than 12 mg / g, which can meet the waste gas treatment needs of different industrial fields. DETAILED DESCRIPTION

[0027] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail below.

[0028] The following are some of the raw materials used in the Examples, Comparative Examples, Application Examples, and Application Comparative Examples: Butyl titanate: TBT-99, Panzhihua Iron and Steel Group Titanium Co., Ltd. Hexamethyldisilazane: HMDS-98, Shanghai Aladdin Biochemical Technology Co., Ltd.; VW-Ti catalyst: DNT-25, active components: V2O5: 1.0%, WO3: 8.0%, Chengdu Oriental Kateri Environmental Protection Catalyst Co., Ltd.

[0029] Some of the raw materials in the Examples and Comparative Examples require pretreatment before use, specifically: Butyl titanate pretreatment: Butyl titanate and acetylacetone were mixed in a molar ratio of 1:0.1, stirred at 40°C for 2 hours to form a chelate; anhydrous ethanol was added in a volume ratio of 1:1, and stored under nitrogen for later use.

[0030] Cerium nitrate pretreatment: Cerium nitrate was dissolved in deionized water with a concentration of 0.5 mol / L and ascorbic acid was added. 3+ : ascorbic acid = 1:0.05; deoxygenate with nitrogen and store in the dark.

[0031] Ammonium molybdate activation: Dissolve ammonium molybdate in ammonia water (25wt%) to prepare a 0.5mol / L solution; add oxalic acid dropwise to pH = 4.5, and stir at 60℃ for 1h to form a soluble ammonium molybdate-oxalic acid complex.

[0032] Test method: Specific surface area: GB / T19587-2017; Pore ​​size distribution: GB / T21650.3-2011; Surface hydrophobicity: GB / T30693-2014; NOx conversion rate: GB / T31584-2015, simulated flue gas: NO: 500ppm, NH3: 550ppm, O2: 5%, space velocity 10000h -1 , temperature gradient 160-420℃; SO2 oxidation rate: GB / T31587-2015; Hg 0 Oxidation rate: GB / T31985-2015; Siloxane adsorption: GB / T36392-2018; As poisoning threshold: Q / CPRI147-2017, the As2O3 concentration in the flue gas is gradually increased, and the critical concentration is reached when the NOx conversion rate drops to 90%; Dioxin degradation rate: HJ77.2-2008; Hg removal rate: GB / T31985; As removal rate: HJ1131-2020; HCl corrosion weight loss: GB / T10124.

[0033] Example 1 The preparation method of the SCR denitration catalyst comprises the following steps: (1) Solution A: Mix butyl titanate and anhydrous ethanol in a molar ratio of 1:2 and stir for 30 minutes. Solution B: Mix deionized water, concentrated nitric acid and cerium nitrate in a molar ratio of H2O and Ce. 3+Mix solution A and solution B in a molar ratio of 18:1, adjust the pH to 1.2, and stir for 30 minutes. Solution A was slowly added dropwise to solution B at a rate of 2 mL / min. Stir at 75°C for 3 hours to form a yellow sol, which was then aged at 40°C for 2 hours. Dry at 80°C for 24 hours, then calcined at 500°C for 3 hours at a heating rate of 5°C / min to obtain a support (TiO2-CeO2 composite support) with a Ce / Ti molar ratio of 0.05, a specific surface area of ​​110 m² / g, and a pore size of 10 nm.

[0034] (2) 0.08 mol / L ammonium molybdate, 0.18 mol / L ammonium metatungstate, and 0.48 mol / L cerium nitrate were dissolved in 0.25 mol / L oxalic acid solution. The support was immersed in the solution and ultrasonically assisted for 30 min. The support was dried at 120°C for 6 h at 250 W. The support was calcined at 330°C for 1.5 h in N2 atmosphere, then switched to air and calcined at 520°C for 3 h to obtain catalyst matrix A (MoO3-WO3-CeO2 solid solution). The ratio of Mo:W:Ce was 0.8:1.8:4.8.

[0035] (3) 18 wt% citric acid, 0.04 mol / L ammonium metavanadate, 0.18 mol / L manganese nitrate, and 0.08 mol / L ferric nitrate were stirred in a 60°C water bath to obtain a coordination solution. Catalyst matrix A was dispersed in water (solid content 40%) and ammonia was added to adjust the pH to 9.8. The coordination solution was slowly added to the carrier slurry, maintaining the pH at 9.8, and stirred for 4 h. The slurry was dried at 115°C and then calcined in air at 480°C for 3 h at a heating rate of 2°C / min to obtain catalyst matrix B. The ratio of V:Mn:Fe was 0.4:1.8:0.8.

[0036] (4) Catalyst substrate B was placed in a tube furnace containing (NH4)2HPO4 vapor (concentration 4%) and treated at 300°C for 1 hour. Hexamethyldisilazane vapor was then introduced at 0.8 mL / min with N2 carrier gas and CVD deposition was performed at 280°C for 0.8 hours. Annealing was then performed at 250°C in an N2 atmosphere for 1 hour to obtain an SCR denitration catalyst. The resulting SCR denitration catalyst was placed in an atmosphere containing 10% water vapor at 310°C for 500 hours. The measured contact angle decreased by 4.8° and the siloxane adsorption amount increased by 9%. Example 2 The preparation method of the SCR denitration catalyst comprises the following steps: (1) Solution A: Mix butyl titanate and anhydrous ethanol in a molar ratio of 1:2.2 and stir for 30 minutes. Solution B: Mix deionized water, concentrated nitric acid and cerium nitrate in a molar ratio of H2O and Ce. 3+Mix solution A and solution B in a molar ratio of 20:1, adjust the pH to 1.5, and stir for 30 minutes. Solution A was slowly added dropwise to solution B at a rate of 2 mL / min. Stir at 80°C for 4 hours to form a yellow sol, which was then aged at 42°C for 2 hours. Dry at 82°C for 26 hours, then calcined at 550°C for 4 hours at a heating rate of 5°C / min to obtain a support (TiO2-CeO2 composite support) with a Ce / Ti molar ratio of 0.08, a specific surface area of ​​110 m² / g, and a pore size of 10 nm.

[0037] (2) 0.1 mol / L ammonium molybdate, 0.2 mol / L ammonium metatungstate, and 0.5 mol / L cerium nitrate were dissolved in 0.3 mol / L oxalic acid solution. The support was immersed in the solution and ultrasonically assisted for 30 min. The support was dried at 120°C for 6 h at 300 W. The support was calcined at 350°C for 2 h in N2 atmosphere, then switched to air and calcined at 550°C for 4 h to obtain catalyst matrix A (MoO3-WO3-CeO2 solid solution). The ratio of Mo:W:Ce was 1:2:5.

[0038] (3) 20 wt% citric acid, 0.05 mol / L ammonium metavanadate, 0.2 mol / L manganese nitrate, and 0.1 mol / L ferric nitrate were stirred in a 60°C water bath to obtain a coordination solution. Catalyst matrix A was dispersed in water (solid content 40%) and ammonia water was added to adjust the pH to 10. The coordination solution was slowly added to the carrier slurry, maintaining the pH at 10 and stirring for 4 h. The slurry was dried at 120°C and then air-calcined at 490°C for 3.5 h at a heating rate of 3°C / min to obtain catalyst matrix B. Here, V:Mn:Fe = 1:4:2.

[0039] (4) Catalyst substrate B was placed in a tube furnace containing (NH4)2HPO4 vapor (concentration 5%) and treated at 310°C for 1 hour; then hexamethyldisilazane vapor was introduced at 1 mL / min and N2 carrier gas was used for CVD deposition at 300°C for 1 hour; then annealing was performed at 252°C in N2 atmosphere for 1 hour to obtain an SCR denitrification catalyst.

[0040] Example 3 The preparation method of the SCR denitration catalyst comprises the following steps: (1) Solution A: Mix butyl titanate and anhydrous ethanol in a molar ratio of 1:2.5 and stir for 30 minutes. Solution B: Mix deionized water, concentrated nitric acid and cerium nitrate in a molar ratio of H2O and Ce. 3+Mix solution A and solution B in a molar ratio of 22:1, adjust the pH to 1.8, and stir for 30 minutes. Solution A was slowly added dropwise to solution B at a rate of 2 mL / min. Stir at 85°C for 5 hours to form a yellow sol, which was then aged at 43°C for 3 hours. Dry at 85°C for 28 hours, then calcined at 600°C for 5 hours at a heating rate of 5°C / min to obtain a support (TiO2-CeO2 composite support) with a Ce / Ti molar ratio of 0.1, a specific surface area of ​​110 m² / g, and a pore size of 10 nm.

[0041] (2) 0.12 mol / L ammonium molybdate, 0.22 mol / L ammonium metatungstate, and 0.52 mol / L cerium nitrate were dissolved in 0.35 mol / L oxalic acid solution. The support was immersed in the solution and ultrasonically assisted for 30 min. The support was dried at 120°C for 6 h and calcined at 350W under N2 atmosphere at 370°C for 2.5 h. The catalyst was then switched to air and calcined at 580°C for 5 h to obtain catalyst matrix A (MoO3-WO3-CeO2 solid solution). The ratio of Mo:W:Ce was 1.2:2.2:5.2.

[0042] (3) 22 wt% citric acid, 0.06 mol / L ammonium metavanadate, 0.22 mol / L manganese nitrate, and 0.12 mol / L ferric nitrate were stirred in a 60°C water bath to obtain a coordination solution. Catalyst matrix A was dispersed in water (solid content 40%) and ammonia water was added to adjust the pH to 10.2. The coordination solution was slowly added to the carrier slurry, maintaining the pH at 10.2 and stirring for 4 h. The slurry was dried at 120°C and then air-calcined at 500°C for 3.5 h at a heating rate of 4°C / min to obtain catalyst matrix B. Here, V:Mn:Fe = 0.6:2.2:1.2.

[0043] (4) Catalyst substrate B was placed in a tube furnace containing (NH4)2HPO4 vapor (concentration 6%) and treated at 310°C for 1.5 h. Hexamethyldisilazane vapor was then introduced at 1.2 mL / min with N2 carrier gas and CVD deposition was performed at 320°C for 1.2 h. Annealing was then performed at 255°C in N2 atmosphere for 1.5 h to obtain an SCR denitration catalyst.

[0044] Comparative Example 1 Compared with Example 1, the difference is that no cerium nitrate is added, and a pure TiO2 carrier is used, and its amount is the same as that of the TiO2-CeO2 composite carrier.

[0045] Comparative Example 2 Compared with Example 2, the difference is that ammonium molybdate is not added, and the amount of ammonium metatungstate and cerium nitrate is increased, with W:Ce=2.5:5.5.

[0046] Comparative Example 3 Compared with Example 3, the difference is that no manganese nitrate is added, and the amount of ammonium metavanadate and ferric nitrate is increased, with V:Fe=1.7:2.3.

[0047] Comparative Example 4 Compared with Example 1, the difference is that hexamethyldisilazane vapor is not introduced, and the proportion of micropores is 45%.

[0048] The test data of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0049] Table 1: Test data of Examples 1-3 and Comparative Examples 1-4

[0050] It can be seen from the data in Table 1 that the various performance indicators of Examples 1-3 are better than those of the comparative examples. Compared with Comparative Example 1, after adding the CeO2 carrier in Example 2, the Hg oxidation rate increased by more than 120%, and the SO2 oxidation rate decreased to 1 / 5 of the original, indicating that the CeO2 carrier has a significant effect on improving the demercuration ability and reducing the SO2 oxidation rate. Compared with Comparative Example 2, Example 2 shows that the addition of the MoO3 anti-poison layer increases the As tolerance threshold by 3 times, indicating that the MoO3 anti-poison layer can effectively enhance the arsenic resistance of the catalyst. Compared with Comparative Example 3, Example 2 shows that the addition of the Mn active component significantly enhances the low-temperature activity at 160°C, and the NOx conversion rate increases from 82% to 93%. Compared with Comparative Example 4, Example 2 shows that the presence of the protective layer reduces the amount of siloxane adsorption by 82%, indicating that the protective layer can effectively resist the adsorption of siloxane.

[0051] Application Example 1 The SCR denitration catalyst obtained in Example 2 was used to treat waste incineration tail gas.

[0052] Pollutant concentrations in waste incineration exhaust gas: NOx 400-600ppm, SO2 800-1200ppm, Hg 100-200μg / m 3 It also contains dioxins. The processing temperature is 350℃.

[0053] Application Example 2 The SCR denitration catalyst obtained in Example 2 was used to treat biomass gasification tail gas.

[0054] Pollutant concentrations of biomass gasification tail gas: NOx 200-400ppm, SO2 300-500ppm, tar 10-30g / Nm 3 . Processing temperature 270℃.

[0055] Application Example 3 The SCR denitration catalyst obtained in Example 3 was used to treat tail gas from electronic waste smelting.

[0056] Pollutant concentrations of electronic waste smelting tail gas are: NOx800-1500ppm, As / Pb20-50ppm, Cl2500-1000ppm, and the processing temperature is 360℃.

[0057] Application Example 4 The SCR denitration catalyst obtained in Example 1 was used to treat polysilicon tail gas.

[0058] Pollutant concentrations of polysilicon tail gas: NOx 100-300ppm, siloxane >50ppm, H 25-10%, processing temperature 310℃.

[0059] Comparative Application Example 1 The difference from the comparative example 1 is that the SCR denitration catalyst obtained in the comparative example 2 is used instead.

[0060] Application Comparative Example 2 The difference from Comparative Application Example 1 is that the VW-Ti catalyst DNT-25 was used instead.

[0061] Application Comparative Example 3 The difference from Comparative Example 2 is that the SCR denitration catalyst obtained in Comparative Example 3 is used instead.

[0062] Comparative Application Example 4 The difference from Comparative Example 2 is that the VW-Ti catalyst DNT-25 was used instead.

[0063] Application Comparative Example 5 The difference from Comparative Example 3 is that the SCR denitration catalyst obtained in Comparative Example 2 is used instead.

[0064] Application Comparative Example 6 The difference from Comparative Example 3 is that the VW-Ti catalyst DNT-25 was used instead.

[0065] Application Comparative Example 7 The difference from Comparative Example 4 is that the SCR denitration catalyst obtained in Comparative Example 1 is used instead.

[0066] Comparative Application Example 8 The difference from the comparative example 4 is that the VW-Ti catalyst DNT-25 is used instead, and the micropores account for 72%.

[0067] The test data of Application Example 1 and Application Comparative Examples 1-2 are shown in Table 2.

[0068] The test data of Application Example 2 and Application Comparative Examples 3-4 are shown in Table 3.

[0069] The test data of Application Example 3 and Application Comparative Examples 5-6 are shown in Table 4.

[0070] The test data of Application Example 4 and Application Comparative Examples 7-8 are shown in Table 5.

[0071] Table 2: Test data of application example 1 and application comparative examples 1-2

[0072] Table 3: Test data of application example 2 and application comparative examples 3-4

[0073] Table 4: Test data of application example 3 and application comparative examples 5-6

[0074] Table 5: Test data of Application Example 4 and Application Comparative Examples 7-8

[0075] As can be seen from the data in Tables 2-5, the test data for Application Example 1 and Application Comparative Examples 1-2 show that the lack of a protective layer causes a 6.5-fold surge in the siloxane blockage rate, accelerating activity decay, and significantly reducing the Hg removal rate and dioxin degradation rate. Comparing Application Example 2 with Application Comparative Examples 3-4, the lack of the Mn active component reduces the low-temperature denitrification efficiency by 14.5%, while the pore blockage rate in Application Comparative Example 4 due to alkali metal poisoning exceeds four times that of Application Example 2. Comparing Application Example 3 with Application Comparative Examples 5-6, the lack of MoO3 reduces the As removal rate by 40.7% and increases the Pb retention by 3.4 times. The HCl corrosion rate in Application Comparative Example 6 exceeds 4.3 times that of Application Example 3 due to heavy metal poisoning. Comparing Application Example 4 with Application Comparative Examples 7-8, the lack of the CeO2 carrier increases the H2 reduction deactivation rate by 3.6 times, and the surface Si deposition thickness in Application Comparative Example 8 exceeds 5.4 times that of Application Example 4. These data fully demonstrate the rationality and effectiveness of the components and structural design of the SCR denitrification catalyst. Compared with traditional catalysts and comparative catalysts, it has obvious advantages in anti-poisoning ability, denitrification efficiency, and adaptability to different working conditions.

Claims

1. A method for preparing an SCR denitration catalyst, characterized in that: The following steps are involved: (1) Butyl titanate and anhydrous ethanol are mixed to obtain solution A, deionized water, concentrated nitric acid and cerium nitrate are mixed to obtain solution B, solution A is added to solution B, and after aging, drying and calcination, a carrier is obtained; (2) Dissolve ammonium molybdate, ammonium metatungstate and cerium nitrate in oxalic acid solution, immerse the support in the solution, take it out and calcine it in a gradient manner to obtain catalyst substrate A; (3) Stirring citric acid, ammonium metavanadate, manganese nitrate and ferric nitrate in a water bath to obtain a coordination liquid, dispersing the catalyst matrix A in water, adding the coordination liquid thereto, stirring, activating and drying, and obtaining the catalyst matrix B; (4) The catalyst substrate B is placed in a tubular furnace containing (NH4)2HPO4 vapor and treated at high temperature. Then, hexamethyldisilazane vapor is introduced for CVD deposition. After annealing, the SCR denitrification catalyst is obtained.

2. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (1), the molar ratio of butyl titanate to anhydrous ethanol is 1: (2-2.5), and the molar ratio of H2O to Ce is 1: (2-2.5). 3+ The molar ratio of Ce to Ti is (18-22):1, the molar ratio of Ce to Ti is 0.05-0.10; the pH of solution B is 1.2-1.8; the conditions after solution A is added to solution B are: stirring at 75-85℃ for 3-5h to form a yellow sol, and aging at 40-43℃ for 2-3h.

3. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: The drying and calcining conditions in step (1) are: drying at 80-85°C for 24-28 hours, and then calcining at 500-600°C for 3-5 hours, with a heating rate of 5°C / min.

4. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (2), ammonium molybdate, ammonium metatungstate and cerium nitrate are all added in the form of solutions, with the concentration of ammonium molybdate being 0.08-0.12 mol / L; the concentration of ammonium metatungstate being 0.18-0.22 mol / L; the concentration of cerium nitrate being 0.45-0.55 mol / L; and the concentration of oxalic acid solution being 0.25-0.35 mol / L.

5. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (2), the conditions for carrier immersion are: ultrasonic assistance for 30-40 minutes, drying at 115-120°C for 6-8 hours, 250-350W; the conditions for gradient calcination are: calcination at 330-370°C for 1.5-2.5 hours under N2 atmosphere, then switching to air and calcination at 520-580°C for 3-5 hours.

6. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (3), citric acid, ammonium metavanadate, manganese nitrate and ferric nitrate are added in the form of a solution, the content of citric acid is 18-22wt%; the concentration of ammonium metavanadate is 0.04-0.06mol / L; the concentration of manganese nitrate is 0.18-0.22mol / L; the concentration of ferric nitrate is 0.08-0.12mol / L; and the water bath temperature is 55-60°C.

7. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (3), when the catalyst matrix A is dispersed in water, the solid content is 40-42%, and ammonia water is added to adjust the pH to 9.8-10.2; the activation drying conditions are: drying at 115-120°C, air calcining at 480-500°C for 3-3.5h, and a heating rate of 2-4°C / min.

8. The method for preparing the SCR denitration catalyst according to claim 1, characterized in that: In the step (4), the concentration of (NH4)2HPO4 vapor is 4-6 vol%, and the high-temperature treatment conditions are: 300-310°C for 1-1.5 h; the conditions for introducing hexamethyldisilazane vapor are 0.8-1.2 mL / min, N2 carrier gas, and CVD deposition at 280-320°C for 0.8-1.2 h; the annealing conditions are: 250-255°C, N2 atmosphere annealing for 1-1.5 h.

9. An SCR denitration catalyst, characterized in that: The catalyst is prepared by the method for preparing the SCR denitration catalyst according to any one of claims 1 to 8.

10. An application of the SCR denitration catalyst according to claim 9, characterized in that: Used for the treatment of waste gas generated by garbage incineration, biomass gasification waste gas, electronic waste smelting waste gas or polysilicon tail gas.

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