Medium and low temperature high-sulfur-resistant denitration catalyst, preparation method and application

Abstract

The invention discloses a medium and low temperature high sulfur resistant denitration catalyst, a preparation method and application, the preparation method of the catalyst comprises the following steps: S1, respectively dispersing a titanium source and a tin source in deionized water, then mixing the solutions, adding ammonia water, and stirring to form gel; s2, the gel in the S1 is dried, calcined and ground, and then a TiO2-SnO2 carrier is prepared; s3, dissolving a molybdenum source, oxalic acid and a vanadium source in deionized water, adding the TiO2-SnO2 carrier in the S2, mixing, standing, drying, cooling and grinding to obtain a powder raw material; and S4, uniformly mixing an indium source and the powder raw material obtained in S3 in deionized water, standing, drying, calcining and crushing to obtain the medium-low temperature high-sulfur-resistant denitration catalyst. According to the invention, the rutile type TiO2 carrier and the active component are respectively modified by Sn and In, the oxidation-reduction capability of the modified V2O5-MoO3 / TiO2 catalyst at low temperature is improved through the synergistic effect of Sn and In, and the modified V2O5-MoO3 / TiO2 catalyst mainly shows the characteristics of excellent denitration efficiency and extremely low SO2 / SO3 conversion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration catalysts, and in particular to a medium-low temperature and high-sulfur resistant denitration catalyst, a preparation method and an application thereof. Background Art

[0002] In recent years, non-electric industries represented by cement, steel, coking, etc. have become important areas for nitrogen oxide governance. The Ministry of Ecology and Environment and other departments issued the "Opinions on Promoting the Implementation of Ultra-low Emissions in the Cement Industry" on January 19, 2024, which requires the promotion of ultra-low emission transformation of cement clinker production enterprises (excluding mines) and independent grinding stations (including cement enterprises that produce special cement and coordinate solid waste disposal), NO x The emission standard has been reduced to 50mg / m 3 By the end of 2025, we will strive to complete the transformation of 50% of cement clinker production capacity; by the end of 2028, we will strive to complete the transformation of 80% of cement clinker production capacity nationwide.

[0003] Under the background of dual carbon, the trend of "changing from 5-stage to 6-stage" preheaters in the cement industry has become a trend, and pure low-temperature waste heat power generation technology has been widely used in my country's cement clinker production lines, that is, the technology of partially utilizing the heat enthalpy discharged from the exhaust gas at the head and tail of the kiln, and using advanced technology and equipment to generate electricity without affecting cement production and process performance and without adding any heat source. This technology can effectively recover a certain amount of heat energy, and use the electricity generated by waste heat to recycle in cement production. According to the normal design, the theoretical temperature value of the C1 outlet of the six-stage preheater is 250℃, and then it is arranged according to the medium-temperature and medium-dust process route of the waste heat power generation boiler followed by the SCR reactor to achieve the goal of energy saving and consumption reduction.

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

[0005] In order to adapt to the catalytic needs in the above-mentioned medium and low temperature and high sulfur environment, the cement industry currently widely uses medium and low temperature denitrification catalysts. This catalyst is mainly vanadium-molybdenum-titanium, with TiO2 as the carrier, V2O5 as the active component and MoO3 as the co-catalyst. In actual flue gas purification applications, the vanadium content is usually increased to achieve the purpose of improving low-temperature denitrification activity. Unlike the low vanadium content of 1% in the SCR catalyst of the power industry, the vanadium content of the SCR catalyst used for medium and low temperature flue gas denitrification is as high as 4%. High-vanadium SCR catalysts are not only more prone to side reactions and generate a large amount of N2O by-products, but also bring about problems such as increased SO2 oxidation rate and high biological toxicity. It is also worth noting that SO2 will inevitably generate SO3 after oxidation by the catalyst.

[0006] In summary, the main problems of medium and low temperature denitrification reaction in the cement industry currently include: 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 the oxidation of SO2 reacts with NH3 and water. The generated ammonium sulfate substances will cover the surface active sites of the catalyst and are difficult to decompose, affecting the adsorption and diffusion of the reactants, and ultimately leading to a decrease in the NH3-SCR activity of the catalyst.

[0007] Therefore, the research and development of denitrification catalysts with high efficiency at medium and low temperatures, wide active temperature window, and excellent sulfur resistance is of great significance for the ultra-low emission trend of industrial flue gas. x Emission reduction is of great significance. Summary of the invention

[0008] Based on the technical problems existing in the background technology, the present invention proposes a medium-low temperature resistant high-sulfur denitrification catalyst, a preparation method and an application. Through the synergistic effect between the Sn-modified rutile TiO2 carrier and the additive Mo-In, a denitrification catalyst with excellent medium-low temperature denitrification efficiency under high-sulfur conditions, a wide active temperature window and extremely low SO2 / SO3 conversion rate is prepared.

[0009] The preparation method of the medium-low temperature high-sulfur resistant denitration catalyst proposed by the present invention comprises the following steps: S1: Disperse the titanium source and the tin source in deionized water respectively, mix the solutions, and slowly add ammonia solution to adjust the pH value to 8-9 for reaction until gel is formed; S2: The S1 gel is dried, calcined and ground to obtain a TiO2-SnO2 carrier; S3: dissolving the molybdenum source, oxalic acid and vanadium source in deionized water, adding the TiO2-SnO2 carrier of S2, mixing, standing, drying, cooling and grinding to obtain a powder raw material; S4: The indium source and the powdered raw material of S3 are mixed evenly in deionized water, and after standing, drying, calcining and crushing, a medium-low temperature and high-sulfur resistant denitrification catalyst is obtained.

[0010] 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 1:0.05-0.2.

[0011] 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.

[0012] Preferably, the molybdenum source in S3 is ammonium molybdate, the vanadium source is ammonium metavanadate, the mass ratio of oxalic acid to the vanadium source is 1~3:1, and the mass ratio of the TiO2-SnO2 carrier, the molybdenum source and the vanadium source is 1:0.02~0.05:0.01~0.03.

[0013] Preferably, the indium source in S4 is indium nitrate; and the mass ratio of the indium source to the powder raw material is 0.02-0.08:1.

[0014] Preferably, the calcination temperature in S4 is 450-550° C., the time is 2-6 hours, and the heating rate is 2-5° C. / min.

[0015] The invention provides a medium-low temperature high-sulfur resistant denitration catalyst prepared by the above method.

[0016] The present invention provides an application of the medium-low temperature and high-sulfur resistant denitrification catalyst in industrial flue gas denitrification.

[0017] Beneficial technical effects of the present invention: The present invention first obtains a tin-modified rutile titanium dioxide carrier by a sol-gel method, and then obtains an indium-modified vanadium-molybdenum-titanium denitration catalyst by an impregnation method. The introduction of Sn into the carrier can improve the catalytic activity by increasing the surface acid sites of the catalyst, while inhibiting the adsorption of SO2. The modification of the auxiliary component In leads to the generation of more oxygen vacancies, further improving the low-temperature redox performance of the catalyst. The synergistic effect of the two enables the modified denitration catalyst to take into account both efficient denitration and low SO2 oxidation rate. The catalyst can achieve a denitration efficiency of 90% under the conditions of 400ppmSO2 and 190℃, the SO2 / SO3 conversion rate is as low as 0.2%, and the denitration efficiency in the temperature range of 190-320℃ can be maintained above 90%. This can fully meet the new requirements for medium-temperature denitration catalysts in the context of the "5-level to 6-level" preheater in the cement industry and the ultra-low emission reform, which has positive significance for national environmental governance and reducing enterprise energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a comparison curve of the denitration performance of the catalyst proposed in the present invention; Figure 2 This is a curve diagram of the sulfur resistance performance of the catalyst of Example 2 proposed by the present invention; Figure 3 This is a curve diagram of the SO2 oxidation rate of the catalyst of Example 2 proposed by the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further explained below in conjunction with specific embodiments.

[0020] Example 1 The preparation method of the medium-low temperature high-sulfur resistant denitration catalyst proposed by the present invention comprises the following steps: S1: 17.0150 g of tetrabutyl titanate and 5 ml of ethanol were added into 15 ml of deionized water, and then the mixture was rapidly stirred to prepare silica sol A; S2: 3.5060 g of tin tetrachloride pentahydrate was added to 15 ml of deionized water, and solution B was prepared after ultrasonic dispersion; S3: After adding solution A to solution B, continue to slowly add 1 mol / L ammonia solution and stir continuously until gel C is formed; S4: drying the gel C in an oven at 110° C., and then calcining the gel C in a muffle furnace at 500° C. for 2 h at a heating rate of 5° C. / min, and grinding the gel C to obtain a powdered TiO2-SnO2 carrier. S5: Add 0.1225 g of ammonium molybdate, 0.1412 g of oxalic acid, and 0.0917 g of ammonium metavanadate into 15 ml of deionized water and stir continuously until completely dissolved, then add 2.0000 g of TiO2-SnO2 powder, stir uniformly on a magnetic stirrer for 2 h to fully mix, to obtain a mixed solution D; S6: the mixed solution D is allowed to stand for 4 hours, and then dried in a constant temperature forced air drying oven at 100° C. for not less than 10 hours. The dried solid is cooled, crushed and then ground to obtain a powdered raw material E; S7: adding 0.0524 g of indium nitrate to 15 ml of deionized water and stirring evenly, then adding 2.0000 g of powdered raw material E and stirring evenly to obtain a mixed solution F; S8: After the mixed solution F is allowed 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 sieve to obtain the medium- and low-temperature resistant high-sulfur denitrification catalyst.

[0021] Example 2 The amount of indium nitrate used in Example S7 is 0.1048 g, and other conditions are the same as those in Example 1.

[0022] Example 3 The amount of indium nitrate used in Example S7 is 0.1572 g, and other conditions are the same as those in Example 1.

[0023] Comparative Example 1 In this comparative example S2, tin tetrachloride pentahydrate was not added, and other conditions were the same as those in Example 2.

[0024] Comparative Example 2 In this comparative example S7, indium nitrate was not added, and other conditions were the same as those in Example 2.

[0025] The prepared catalyst was tested for its denitrification performance and anti-sulfur performance.

[0026] Denitrification performance test method: The catalysts are placed in a quartz tube reactor with an inner diameter of 7mm, an outer diameter of 10mm, and a length of 40cm, and the quartz tube reactor is placed in a constant temperature zone near the thermocouple in the middle of a vertical tube furnace. Then a mixed gas prepared from cylinder gas of N2, Air, NH3 / N2, NO / N2, and SO2 / N2 is introduced into the reactor to simulate the flue gas environment under actual working conditions; the concentrations of NH3 and NO in the mixed gas are both 500ppm, and the O2 content is 5%. The total flow rate of the mixed gas is 1000mL / min, and the gas volume space velocity is 30,000h -1 The temperature in the tube furnace is controlled at 150-350°C, and a Bruker OMEGA5 flue gas analyzer is used to detect NO and SO2 in the exhaust gas emitted after the catalytic reaction.

[0027] Anti-sulfur performance test method: Put the catalyst into a quartz tube reactor with an inner diameter of 7mm, an outer diameter of 10mm, and a length of 40cm, and place the quartz tube reactor in a constant temperature zone near the thermocouple in the middle of a vertical tube furnace. The temperature in the tube furnace is controlled at 190°C. Then, a mixed gas consisting of 500ppmNH3, 500ppmNO, 5%O2, 400ppmSO2 and N2 is introduced into the reactor. The total flow rate of the mixed gas is 1000mL / min, and the gas volume space velocity is 30000h -1 .

[0028] The denitration performance test results of Examples 1-3 and Comparative Examples 1-2 are as follows: Figure 1As shown, compared with the comparative example 1 in which the carrier is not modified and the comparative example 2 in which the carrier is modified, the synergistic effect between the Sn-modified rutile TiO2 carrier and the additive Mo-In shows better catalytic activity. The medium- and low-temperature sulfur-resistant denitrification catalyst prepared by the preparation method of Example 2 has a higher catalytic activity for NO in a temperature environment of 170-270°C. x The removal rate can always be maintained above 90%, that is, it can efficiently complete the removal of NO in medium and low temperature environments. x removal work.

[0029] The test results of NOx removal rate and SO2 oxidation rate of the catalyst prepared in Example 2 are as follows: Figure 2 and Figure 3 As shown. The results show that after the introduction of 400ppm SO2, the catalyst activity curve will shift slightly to the high temperature zone, but it can still achieve a denitration efficiency of 90% at 190°C, reflecting its excellent anti-sulfur performance at low temperatures below 200°C. At the same temperature, compared with the 1% SO2 conversion rate of commercial catalysts, the SO2 conversion rate of this catalyst is greatly reduced, only 0.2% at 190°C, but it will gradually increase with increasing temperature. That is, the catalyst in Example 2 can not only maintain high catalytic activity at a low temperature of 190°C, but also avoid the problem of excessive SO2 oxidation rate during the denitration reaction.

Claims

1. A method for preparing a medium-low temperature high-sulfur resistant denitrification catalyst, characterized in that: The steps are as follows: S1: Disperse the titanium source and the tin source in deionized water respectively, mix the solutions, and add an ammonia solution to adjust the pH value to 8-9 for reaction until a gel is formed; S2: The S1 gel is dried, calcined and ground to obtain a TiO2-SnO2 carrier; S3: dissolving the molybdenum source, oxalic acid and vanadium source in deionized water, adding the TiO2-SnO2 carrier of S2, mixing, standing, drying, cooling and grinding to obtain a powder raw material; S4: The indium source and the powdered raw material of S3 are mixed evenly in deionized water, and after standing, drying, calcining and crushing, a medium-low temperature and high-sulfur resistant denitrification catalyst is obtained.

2. The method for preparing the medium-low temperature and high-sulfur resistant denitration catalyst according to claim 1, characterized in that: In S1, the titanium source is tetrabutyl titanate, the tin source is tin tetrachloride pentahydrate, and the molar ratio of the titanium source to the tin source is 1:0.05-0.

2.

3. The method for preparing the medium-low temperature and high-sulfur resistant denitration catalyst according to claim 1, characterized in that: The calcination temperature in S2 is 450-550°C, the heating rate is 5-10°C / min, and the time is 2-6h.

4. The method for preparing a medium-low temperature and high-sulfur resistant denitration catalyst according to claim 1, characterized in that: The molybdenum source in S3 is ammonium molybdate; the vanadium source is ammonium metavanadate; the mass ratio of oxalic acid and vanadium source is 1~3:1, and the mass ratio of TiO2-SnO2 carrier, molybdenum source and vanadium source is 1:0.02~0.05:0.01~0.

03.

5. The method for preparing a medium-low temperature and high-sulfur resistant denitration catalyst according to claim 1, characterized in that: The indium source in S4 is indium nitrate; the mass ratio of the indium source to the powder raw material is 0.02~0.08:

1.

6. The method for preparing a medium-low temperature and high-sulfur resistant denitration catalyst according to claim 1, characterized in that: The calcination temperature in S4 is 450-550°C, the time is 2-6h, and the heating rate is 2~5°C / min.

7. A medium-low temperature and high-sulfur resistant denitrification catalyst prepared by the method according to any one of claims 1 to 6.

8. Use of the medium-low temperature and high-sulfur resistant denitrification catalyst as claimed in claim 7 in industrial flue gas denitrification.

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