Low-medium temperature high-sulfur resistant denitration catalyst, preparation method and application thereof

Abstract

The application discloses a kind of low-temperature resistant high-sulfur denitration catalyst, preparation method and application, and the preparation method of catalyst is as follows: S1: respectively, titanium source and tin source are dispersed in deionized water, then the solution is mixed, and ammonia water is added to stir to form gel;S2: after the gel of S1 is dried, calcined and ground, TiO2-SnO2 carrier is prepared;S3: molybdenum source, oxalic acid and vanadium source are dissolved in deionized water, and the TiO2-SnO2 carrier of S2 is added, after mixing, it is placed, dried, cooled and ground to obtain powder raw material;S4: indium source and S3 powder raw material are mixed uniformly in deionized water, after standing, drying, calcining and crushing, a low-temperature resistant high-sulfur denitration catalyst is obtained.The rutile TiO2 carrier and active component are modified by Sn and In respectively, and the modified V2O5-MoO3 / TiO2 catalyst has improved redox capacity at low temperature through the synergistic effect of the two, and mainly shows excellent denitration efficiency and extremely low SO2 / SO3 conversion rate.

Description

Technical Field

[0001] This invention relates to the field of denitrification catalyst technology, and in particular to medium- and low-temperature high-sulfur denitrification catalysts, their preparation methods, and applications. Background Technology

[0002] In recent years, non-power industries such as cement, steel, and coking have become important areas for nitrogen oxide (NOx) control. On January 19, 2024, the Ministry of Ecology and Environment and other departments issued the "Opinions on Promoting the Implementation of Ultra-Low Emissions in the Cement Industry," which requires promoting ultra-low emission upgrades for cement clinker production enterprises (excluding mines) and independent grinding stations (including cement enterprises producing special cement and co-processing solid waste). x Emission standards have been reduced to as low as 50 mg / m³ 3 By the end of 2025, efforts will be made to complete the transformation of 50% of cement clinker production capacity; by the end of 2028, efforts will be made to complete the transformation of 80% of cement clinker production capacity nationwide.

[0003] Under the dual-carbon development strategy, the conversion of preheaters from 5 stages to 6 stages has become a trend in the cement industry. Furthermore, pure low-temperature waste heat power generation technology is widely used in my country's cement clinker production lines. This technology utilizes the enthalpy of exhaust gases from the kiln head and tail to generate electricity using advanced technology and equipment without affecting cement production or process performance, or adding any heat source. This technology can effectively recover a certain amount of heat energy, and the electricity generated from the waste heat can be recycled for cement production. Under normal design, the theoretical temperature of the C1 outlet of the six-stage preheater is 250℃. The subsequent layout follows a medium-temperature, medium-dust process route, with the waste heat power generation boiler connected to an SCR reactor, to achieve energy conservation and emission reduction goals.

[0004] The flue gas temperature after waste heat power generation is 190-200℃, while the activity window of traditional V2O5-WO3 / TiO2 catalysts is generally 300-400℃. Catalyst activity decreases rapidly at this temperature. Furthermore, the presence of low-grade limestone, coal, and various complex alternative feedstocks leads to high sulfur content (>1000 mg / m³). 3 The generation of flue gas leads to the rapid deactivation of the catalyst.

[0005] To meet the catalytic requirements of low-temperature and high-sulfur environments, the cement industry widely uses low-temperature denitrification catalysts. These catalysts are primarily vanadium-molybdenum-titanium based, using TiO2 as a support, V2O5 as the active component, and MoO3 as a co-catalyst. In practical flue gas purification applications, the vanadium content is typically increased to enhance low-temperature denitrification activity. Unlike the low vanadium content of 1% in SCR catalysts used in the power industry, SCR catalysts applied to low-temperature flue gas denitrification have vanadium contents as high as 4%. High-vanadium SCR catalysts are not only more prone to side reactions, generating large amounts of N2O byproducts, but also lead to increased SO2 oxidation rates and higher biotoxicity. It is also worth noting that SO2 oxidation by the catalyst inevitably produces SO3.

[0006] In summary, the main problems with low- and medium-temperature denitrification reactions in the cement industry currently include:

[0007] Traditional low-vanadium catalysts have poor denitrification efficiency and sulfur resistance under medium-low temperature and high-sulfur flue gas conditions. At the same time, SO3 generated by SO2 oxidation reacts with NH3 and water, and the resulting ammonium sulfate substances cover the surface active sites of the catalyst and are difficult to decompose, affecting the adsorption and diffusion of reactants, ultimately leading to a decrease in the NH3-SCR activity of the catalyst.

[0008] Therefore, research and development of denitrification catalysts with high efficiency at medium and low temperatures, wide activity temperature windows, and excellent sulfur resistance are crucial for addressing NO emissions from industrial flue gas under the trend of ultra-low emissions. x Emissions reduction is of great significance. Summary of the Invention

[0009] Based on the technical problems existing in the background technology, this invention proposes a medium-low temperature high-sulfur denitrification catalyst, its preparation method and application. Through the synergistic effect between Sn-modified rutile TiO2 support and the auxiliary agent Mo-In, a denitrification catalyst with excellent medium-low temperature denitrification efficiency, a wide active temperature window and extremely low SO2 / SO3 conversion rate under high sulfur conditions is prepared.

[0010] The preparation method of the medium-low temperature resistant high-sulfur denitrification catalyst proposed in this invention includes the following steps:

[0011] S1: Disperse the titanium source and tin source separately in deionized water, then mix the solutions, and slowly add ammonia solution to adjust the pH to 8-9 to carry out the reaction until gel is formed;

[0012] S2: The TiO2-SnO2 support was prepared by drying, calcining and grinding the S1 gel;

[0013] S3: Dissolve molybdenum source, oxalic acid and vanadium source in deionized water, then add TiO2-SnO2 support of S2, mix, and then obtain powder raw material after standing, drying, cooling and grinding;

[0014] S4: The indium source and S3 powder raw materials are mixed evenly in deionized water, and after standing, drying, calcining and pulverizing, a medium and low temperature high sulfur denitrification catalyst is obtained.

[0015] Preferably, in S1, the titanium source is tetrabutyl titanate and the tin source is tin tetrachloride pentahydrate; the molar ratio of the titanium source to the tin source is 1:0.05 to 0.2.

[0016] Preferably, the calcination temperature in S2 is 450–550°C, the heating rate is 5–10°C / min, and the calcination time is 2–6 h.

[0017] Preferably, in S3, the molybdenum source is ammonium molybdate, the vanadium source is ammonium metavanadate, the mass ratio of oxalic acid to vanadium source is 1 to 3:1, and the mass ratio of TiO2-SnO2 support, molybdenum source, and vanadium source is 1:0.02 to 0.05:0.01 to 0.03.

[0018] Preferably, the indium source in S4 is indium nitrate; the mass ratio of indium source to powder raw material is 0.02 to 0.08:1.

[0019] Preferably, the calcination temperature in S4 is 450–550°C, the time is 2–6 h, and the heating rate is 2–5°C / min.

[0020] The medium- and low-temperature resistant high-sulfur denitrification catalyst prepared by the method proposed in this invention.

[0021] The application of the above-mentioned medium-low temperature high-sulfur denitrification catalyst proposed in this invention in industrial flue gas denitrification.

[0022] Beneficial technical effects of the present invention:

[0023] This invention first obtains a tin-modified rutile titanium dioxide support via the sol-gel method, and then obtains an indium-modified vanadium-molybdenum-titanium denitration catalyst via an impregnation method. Introducing Sn into the support enhances catalytic activity by increasing the surface acidic sites of the catalyst, while simultaneously inhibiting SO2 adsorption. Modification with the additive In leads to the generation of more oxygen vacancies, further improving the catalyst's low-temperature redox performance. The synergistic effect of these two factors allows the modified denitration catalyst to achieve both high-efficiency denitration and low SO2 oxidation rate. This catalyst achieves a denitration efficiency of 90% at 400 ppm SO2 and 190℃, with an SO2 / SO3 conversion rate as low as 0.2%, and maintains a denitration efficiency above 90% within the temperature range of 190–320℃. This fully meets the new requirements for medium-temperature denitration catalysts in the context of the cement industry's "5-stage to 6-stage" preheater upgrade and ultra-low emission reform, and has positive significance for national environmental governance and reducing enterprise energy consumption. Attached Figure Description

[0024] Figure 1 This is a comparison curve of the denitrification performance of the catalyst proposed in this invention;

[0025] Figure 2 This is a graph showing the sulfur resistance performance of the catalyst in Example 2 of this invention.

[0026] Figure 3 This is a curve showing the SO2 oxidation rate of the catalyst in Example 2 of the present invention. Detailed Implementation

[0027] The present invention will be further explained below with reference to specific embodiments.

[0028] Example 1

[0029] The preparation method of the medium-low temperature resistant high-sulfur denitrification catalyst proposed in this invention includes the following steps:

[0030] S1: Add 17.0150g of tetrabutyl titanate and 5ml of ethanol to 15ml of deionized water, and then stir rapidly to mix to obtain sol A.

[0031] S2: Add 3.5060g of tin tetrachloride pentahydrate to 15ml of deionized water, and disperse by ultrasonication to obtain solution B;

[0032] S3: After adding sol A to solution B, continue to slowly add 1 mol / L ammonia solution while stirring continuously until gel C is formed;

[0033] S4: The gel C was dried in an oven at 110°C, then calcined in a muffle furnace at 500°C for 2 hours with a heating rate of 5°C / min, and then ground to obtain a powdered TiO2-SnO2 support.

[0034] S5: Add 0.1225g of ammonium molybdate, 0.1412g of oxalic acid, and 0.0917g of ammonium metavanadate to 15ml of deionized water and stir continuously until completely dissolved. Then add 2.0000g of TiO2-SnO2 powder and stir at a constant speed on a magnetic stirrer for 2 hours to fully mix and obtain mixed solution D.

[0035] S6: Let the mixed solution D stand for 4 hours, and then dry it in a constant temperature drying oven at 100°C for no less than 10 hours. After drying, the solid is cooled, crushed and ground to obtain powder raw material E.

[0036] S7: Add 0.0524g of indium nitrate to 15ml of deionized water and stir until homogeneous. Then add 2.0000g of powdered raw material E and stir until homogeneous to obtain mixed solution F.

[0037] S8: After the mixed solution F is left to stand for 4 hours, it is transferred to a drying oven at 100°C and dried for at least 10 hours. After drying, the solid is transferred to a muffle furnace for calcination. The calcination conditions are calcination at 500°C for 2 hours and a heating rate of 2°C / min. The calcined solid is crushed and sieved through a 40-60 mesh screen to obtain the medium-low temperature high-sulfur denitrification catalyst.

[0038] Example 2

[0039] In this example S7, the amount of indium nitrate used is 0.1048g, and all other conditions are the same as in Example 1.

[0040] Example 3

[0041] In this example S7, the amount of indium nitrate used is 0.1572g, and all other conditions are the same as in Example 1.

[0042] Comparative Example 1

[0043] In this comparative example S2, tin tetrachloride pentahydrate was not added, and all other conditions were the same as in Example 2.

[0044] Comparative Example 2

[0045] In this comparative example S7, indium nitrate was not added, and all other conditions were the same as in Example 2.

[0046] The prepared catalyst was subjected to denitrification performance and sulfur resistance performance tests.

[0047] Denitrification performance testing method: The catalyst was placed in a quartz tube reactor with an inner diameter of 7 mm, an outer diameter of 10 mm, and a length of 40 cm. This quartz tube reactor was then placed in a constant-temperature zone near the thermocouple in the middle of a vertical tubular furnace. A mixed gas mixture consisting of N2, Air, NH3 / N2, NO / N2, and SO2 / N2 cylinder gases was then introduced into the furnace to simulate the flue gas environment under actual operating conditions. The concentrations of NH3 and NO in this mixed gas were both 500 ppm, and the O2 content was 5%. The total flow rate of the mixed gas was 1000 mL / min, and the gas hourly space velocity was 30000 h⁻¹. -1 The temperature inside the tubular furnace was controlled at 150-350℃, and a Bruker OMEGA5 flue gas analyzer was used to detect NO and SO2 in the exhaust gas emitted after the catalytic reaction.

[0048] Sulfur resistance performance test method: The catalyst was placed in a quartz tube reactor with an inner diameter of 7 mm, an outer diameter of 10 mm, and a length of 40 cm. The quartz tube reactor was placed in a constant temperature zone near the thermocouple in the middle of a vertical tube furnace, and the temperature inside the tube furnace was controlled at 190℃. Then, a mixed gas consisting of 500 ppm NH3, 500 ppm NO, 5% O2, 400 ppm SO2, and N2 was introduced into the reactor. The total flow rate of the mixed gas was 1000 mL / min, and the gas hourly space velocity was 30000 h⁻¹. -1 .

[0049] The denitrification performance test results of Examples 1-3 and Comparative Examples 1-2 are as follows: Figure 1 As shown, compared to Comparative Example 1 (without modified support) and Comparative Example 2 (with modified support), the Sn-modified rutile TiO2 support and the Mo-In promoter exhibit superior catalytic activity. The low-temperature sulfur-resistant denitrification catalyst prepared using the method in Example 2 shows better catalytic activity against NO in a temperature environment of 170-270℃. x The removal rate can consistently remain above 90%, meaning it can efficiently remove NO under medium and low temperature environments. x The removal work.

[0050] The NOx removal rate and SO2 oxidation rate of the catalyst prepared in Example 2 are as follows: Figure 2 and Figure 3 As shown in the figure. The results indicate that the catalyst activity curve shifts slightly towards the high-temperature region after introducing 400 ppm SO2, but it still achieves a denitrification efficiency of 90% at 190°C, demonstrating its excellent sulfur resistance at low temperatures below 200°C. At the same temperature, compared to the 1% SO2 conversion rate of commercial catalysts, the SO2 conversion rate of this catalyst is significantly lower, only 0.2% at 190°C, but it gradually increases with increasing temperature. That is, the catalyst in Example 2 not only maintains high catalytic activity at a low temperature of 190°C, but also avoids the problem of excessive SO2 oxidation rate during the denitrification reaction.

Claims

1. A method for preparing a medium-low temperature high-sulfur denitrification catalyst, characterized in that, The preparation method steps are as follows: S1: Disperse the titanium source and tin source separately in deionized water, then mix the solutions, and add ammonia solution to adjust the pH to 8-9 to carry out the reaction until gel is formed; S2: The TiO2-SnO2 support was prepared by drying, calcining and grinding the S1 gel; S3: Dissolve molybdenum source, oxalic acid and vanadium source in deionized water, then add TiO2-SnO2 support of S2, mix, and then obtain powder raw material after standing, drying, cooling and grinding; S4: The indium source and S3 powder raw materials are mixed evenly in deionized water, and after standing, drying, calcining and pulverizing, a medium and low temperature high sulfur denitrification catalyst is obtained. In S1, the titanium source is tetrabutyl titanate, and the tin source is tin tetrachloride pentahydrate. The molar ratio of the titanium source to the tin source is 1:(0.05~0.2). In S3, the molybdenum source is ammonium molybdate; the vanadium source is ammonium metavanadate; the mass ratio of oxalic acid to vanadium source is (1~3):1; and the mass ratio of TiO2-SnO2 support, molybdenum source, and vanadium source is 1:(0.02~0.05):(0.01~0.03). In S4, the indium source is indium nitrate; the mass ratio of indium source to powdered raw material is (0.02~0.08):1; The calcination temperature of S4 is 450-550℃, the time is 2-6h, and the heating rate is 2-5℃ / min. The term "medium-low temperature resistance to high sulfur" refers to 170-270℃ and 400ppm SO2.

2. The preparation method of the medium-low temperature resistant high-sulfur denitrification catalyst according to claim 1, characterized in that, The calcination temperature in S2 is 450~550℃, the heating rate is 5-10℃ / min, and the time is 2~6h.

3. The medium-low temperature high-sulfur denitrification catalyst prepared by the preparation method according to any one of claims 1 or 2.

4. The application of the low-temperature, high-sulfur-resistant denitrification catalyst as described in claim 3 in low-temperature, high-sulfur-resistant denitrification of industrial flue gas, characterized in that, The term "medium-low temperature resistance to high sulfur" refers to 170-270℃ and 400ppm SO2.

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