A sulfur-resistant denitration catalyst and a method for preparing the same

Abstract

The application discloses a kind of anti-sulfur denitration catalyst and preparation method thereof, the preparation method is: after mixing cerium nitrate and zirconium nitrate, ammonia solution is added to carry out reaction, after reaction, the precipitation containing pore-forming agent is taken in solvent, after centrifugation, drying, ball milling, obtain cerium zirconium solid solution powder;Manganese is impregnated on cerium zirconium solid solution powder using impregnation method, the product after impregnation is vacuum dried and calcined, obtain MnOx-CeO2-ZrO2 Powder;Titanium chloride and pore-forming agent are added to the ethanol solution dissolved with stannic chloride pentahydrate, then MnOx-CeO2-ZrO2 Powder, ammonia water is added and stirred, after standing and removing supernatant, spray drying, calcination, obtain the anti-sulfur denitration catalyst.The catalyst prepared by the preparation method has excellent low-temperature sulfur denitration performance, and good wear resistance, which can prolong the service life of the catalyst.

Description

TECHNICAL FIELD

[0001] The application relates to a sulfur-resistant denitration catalyst and a preparation method thereof, and belongs to the technical field of catalysts and preparation thereof. BACKGROUND

[0002] In industrial kiln flue gas treatment, the commonly used medium-low temperature denitration catalyst is a vanadium-tungsten-titanium catalyst, but the vanadium-based catalyst has biological toxicity and will harm the ecological environment and cause secondary pollution after being discarded. In addition, SO2 in the flue gas will react with NH3 in the reducing agent to generate ammonium bisulfate under medium-low temperature conditions, which will adhere to the vanadium-based catalyst and cause catalyst poisoning or blockage; secondly, the catalyst has poor wear resistance, which will affect the service life. SUMMARY

[0003] The application aims to provide a sulfur-resistant denitration catalyst and a preparation method thereof, which has excellent low-temperature sulfur-resistant denitration performance and good wear resistance, and can prolong the service life of the catalyst.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0005] A preparation method of a sulfur-resistant denitration catalyst, comprising the following steps:

[0006] S1, mixing cerium nitrate and zirconium nitrate, then adding an ammonia water solution to react, taking the precipitate after the reaction and dispersing it in a solvent containing a pore-forming agent, centrifuging, drying, and ball milling to obtain cerium-zirconium solid solution powder;

[0007] S2, impregnating manganese on the cerium-zirconium solid solution powder by using an impregnation method, vacuum drying the impregnated product, and calcining to obtain MnOx-CeO2-ZrO2 powder;

[0008] S3, adding titanium chloride and a pore-forming agent to an ethanol solution containing tin chloride pentahydrate, then adding MnOx-CeO2-ZrO2 powder, ammonia water, and stirring, removing the supernatant after standing, and spray drying and calcining to obtain the sulfur-resistant denitration catalyst.

[0009] Preferably, in the step S1, the molar ratio of cerium to zirconium in the cerium nitrate and the zirconium nitrate is 1:(2-7).

[0010] Preferably, in the step S1, the drying temperature is 70-100 DEG C, and the drying time is 5-24 h.

[0011] Preferably, in the step S1, the particle size of the cerium-zirconium solid solution powder obtained after ball milling is 100-500 meshes.

[0012] Preferably, in the step S2, the specific method of impregnating manganese on the cerium-zirconium solid solution powder by using an equal-volume impregnation method is as follows:

[0013] The manganese precursor is dissolved in deionized water and added dropwise to the cerium-zirconium solid solution powder, and impregnated for 2-12h;

[0014] The number of moles of manganese ions in the manganese precursor is 10-15% of the total number of moles of cerium and zirconium in the cerium-zirconium solid solution powder.

[0015] Preferably, the manganese precursor is any one of manganese nitrate or manganese acetate.

[0016] Preferably, in the step S2, the temperature of vacuum drying is 80-110℃, and the time is 5-15h.

[0017] The temperature of calcination is 350-450℃, and the time is 5-10h.

[0018] Preferably, in the step S3, the mass ratio of titanium chloride, tin chloride pentahydrate, and MnOx-CeO2-ZrO2 powder is (78-86):(2-8):(8-15).

[0019] Preferably, in the step S3,

[0020] The temperature of spray drying is 300-380℃, and the time is 2-7h.

[0021] The temperature of calcination is 400-750℃, and the time is 2-8h.

[0022] An anti-sulfur denitration catalyst is prepared by any one of the above methods.

[0023] The present application has the following advantages:

[0024] 1. The cerium-zirconium solid solution is beneficial to improve the water-sulfur resistance of the catalyst, and the catalyst still has high denitration reactivity under the condition of water and sulfur at low and medium temperatures, which shows high desulfurization efficiency and water-sulfur resistance in the temperature range of 150-250℃, and the catalyst is an environmentally friendly catalyst and can be applied to low-temperature denitration of industrial kiln flue gas.

[0025] 2. The titanium dioxide composite carrier doped with tin oxide is prepared by the reaction of ammonia water with titanium chloride and tin chloride pentahydrate, the doping of tin oxide can promote the formation and stability of the crystal structure of cerium-zirconium oxide, increase the specific surface area and the number of available active sites of the catalyst, and promote the catalytic degradation of flue gas; on the other hand, tin oxide can also form a more stable structure with cerium-zirconium oxide, which can improve its chemical stability, and also improve the hardness and wear resistance of the catalyst, effectively reducing the wear and shedding of the catalyst surface, and prolonging the service life of the catalyst.

[0026] 3. The increase of the specific surface area of the catalyst indirectly improves the interaction between manganese and cerium, generates more acid sites and active oxygen vacancies, and further improves the denitration efficiency of the catalyst. DETAILED DESCRIPTION

[0027] The application will be described in detail below with reference to examples.

[0028] Example 1

[0029] A preparation method of a sulfur-tolerant denitration catalyst is as follows:

[0030] 2.8 g of cerium nitrate and 32.6 g of zirconium nitrate were mixed with water to obtain a 200 ml solution, and the solution was slowly added to ammonia water. After the addition was completed, the suspension was stirred at 45°C under air until it turned yellow. The suspension was filtered and washed to obtain a cerium-zirconium composite oxide precipitate. The precipitate was added to water again, and 10 g of PEG 1500 was added as a pore-forming agent. The precipitate was stirred to disperse uniformly. The dispersed cerium-zirconium composite oxide was centrifuged and placed in a drying oven. The drying temperature was 85°C, and the drying time was 15 h. A cerium-zirconium solid solution was obtained. The dried cerium-zirconium solid solution was ball milled to obtain a powder with a particle size of 200-300 mesh.

[0031] 2.7 g of manganese nitrate was dissolved in 80 ml of deionized water and added to 20 g of cerium-zirconium solid solution powder for 3 h of impregnation. The impregnated sample was left to stand at room temperature for 3 h and then dried in a vacuum drying oven at 100°C for 8 h. The dried sample was placed in a muffle furnace and calcined at 400°C for 6 h under air. A MnOx-CeO2-ZrO2 powder was obtained after natural cooling.

[0032] 40 g of titanium chloride and 6 g of PEG 2000 were added to a flask containing a 100 ml ethanol solution of 3 g of tin chloride pentahydrate. 7 g of MnOx-CeO2-ZrO2 powder, 150 ml of 30% ammonia water, and 3 h of stirring were added. The mixed solution was left to stand to remove the supernatant, and then spray dried at 350°C. The dried sample was calcined in a muffle furnace at 500°C for 5 h, and then naturally cooled to obtain a sulfur-tolerant denitration catalyst, which was labeled as MnOx-CeO2-ZrO2 / TiO2@SnO2.

[0033] Comparative Example 1

[0034] A preparation method of a sulfur-tolerant denitration catalyst is as follows:

[0035] A solution of 2.8 g cerium nitrate and 32.6 g zirconium nitrate in 200 ml water was prepared and slowly added to ammonia water. After the addition was completed, the solution was stirred at 45°C under air until the suspension became yellow. The cerium-zirconium composite oxide precipitate was obtained by filtration and washing. The precipitate was re-dissolved in water and 10 g PEG 1500 was added as a pore-forming agent. The precipitate was dispersed uniformly by stirring. The dispersed cerium-zirconium composite oxide was centrifuged and placed in a drying oven at 85°C for 15 h to obtain a cerium-zirconium solid solution. The cerium-zirconium solid solution was ground by a ball mill to obtain a powder having a particle size of 200-300 mesh.

[0036] A solution of 2.7 g manganese nitrate in 80 ml deionized water was prepared and impregnated into 20 g of the cerium-zirconium solid solution powder for 3 h. The impregnated sample was left at room temperature for 3 h and then dried in a vacuum drying oven at 100°C for 8 h. The dried sample was calcined in a muffle furnace at 400°C for 6 h under air to obtain a MnOx-CeO2-ZrO2 powder.

[0037] A solution of 40 g titanium chloride and 6 g PEG 2000 in 100 ml ethanol was prepared and then 7 g of the MnOx-CeO2-ZrO2 powder, 150 ml of 30% ammonia water were added and stirred for 3 h. The mixed solution was left to stand to remove the supernatant and then spray dried at 350°C. The dried sample was calcined in a muffle furnace at 500°C for 5 h to obtain a sulfur-tolerant denitration catalyst, which was designated as MnOx-CeO2-ZrO2 / TiO2.

[0038] Comparative Example 2

[0039] A sulfur-tolerant denitration catalyst was prepared by the following method:

[0040] A solution of 2.8 g cerium nitrate in 200 ml water was prepared and slowly added to ammonia water. After the addition was completed, the solution was stirred at 45°C under air. The cerium oxide precipitate was obtained by filtration and washing. The precipitate was re-dissolved in water and 10 g PEG 1500 was added as a pore-forming agent. The precipitate was dispersed uniformly by stirring. The dispersed cerium oxide was centrifuged and placed in a drying oven at 85°C for 15 h. The cerium oxide was ground by a ball mill to obtain a powder having a particle size of 200-300 mesh.

[0041] A solution of 2.7 g manganese nitrate in 80 ml deionized water was prepared and impregnated into 20 g of the cerium oxide powder for 3 h. The impregnated sample was left at room temperature for 3 h and then dried in a vacuum drying oven at 100°C for 8 h. The dried sample was calcined in a muffle furnace at 400°C for 6 h under air to obtain a MnOx-CeO2 powder.

[0042] Add 40g of titanium chloride and 6g of PEG 2000 to a flask containing 100ml of ethanol solution, then add 7g of MnOx-CeO2 powder and 150ml of 30% ammonia water and stir for 3h. After the mixed solution is allowed to stand and the supernatant is removed, it is spray-dried at 350℃. The dried sample is then placed in a muffle furnace and calcined at 500℃ for 5h. After natural cooling, the anti-sulfur denitrification catalyst is obtained, denoted as MnOx-CeO2 / TiO2.

[0043] The physical adsorption of the above three samples was characterized. Nitrogen was used as the adsorbent gas, and helium was used as the carrier gas. Before the measurement, the samples were evacuated at 350℃ for 4 hours, and then the adsorption experiment was carried out at liquid nitrogen temperature. The results of the physical adsorption characterization are shown in Table 1.

[0044] Table 1. Physical adsorption characterization results of denitrification catalysts

[0045] Sample Name Specific surface area (m 2 / g) Example 1 MnOx-CeO2-ZrO2 / TiO2@SnO2 141 Comparative Example 1 MnOx-CeO2-ZrO2 / TiO2 128 Comparative Example 2 Comparative Example 3 MnOx-CeO2 / TiO2 125

[0046] The data from Example 1 and Comparative Example 1 show that SnO2 doping can increase the specific surface area of ​​the sample, and the specific surface area of ​​the SnO2-doped catalyst (Example 1) is also increased compared with Comparative Example 2.

[0047] The denitrification reactivity of the samples was tested. The reaction conditions were: 500 ppm NO, 500 ppm NH3, 10% O2, with N2 as the equilibrium gas, and a space velocity of 30,000 h⁻¹. -1 The concentration of NO before and after the reaction was detected using an infrared analyzer, and the denitrification efficiency was calculated. Under the original reaction conditions, 3% H2O and 100ppm SO2 were added, and the concentration of NO before the reaction and after 10 hours of reaction was detected using an infrared analyzer. The denitrification efficiency was calculated, and the results are shown in Table 2.

[0048] The water-sulfur resistance of the samples was tested. The reaction conditions were: 500 ppm NO, 500 ppm NH3, 10% O2, 3% H2O, 100 ppm SO2, with N2 as the equilibrium gas, and a space velocity of 30,000 h⁻¹. -1 The concentration of NO before and 10 hours after the reaction was detected using an infrared analyzer. The denitrification efficiency was calculated, and the water-sulfur resistance stability was obtained. The results are shown in Table 2. Simultaneously, under the same conditions, the hourly wear rate of the above three samples was tested, and the results are shown in Table 3.

[0049] Table 2. Results of denitrification activity and water and sulfur resistance of the denitrification catalyst.

[0050]

[0051] From the denitration efficiency of example 1, comparative example 1-2, it can be seen that the higher the specific surface area of the sample, the better the denitration reactivity. On the one hand, the higher the specific surface area, the more conducive to the physical adsorption of gas, increasing the contact area and mass transfer efficiency between the reaction gases. On the other hand, the increase in specific surface area improves the interaction between manganese and cerium, generating more acid sites and active oxygen vacancies, thereby improving the denitration efficiency of the catalyst. From the denitration efficiency after passing water and sulfur, it can be seen that the catalyst containing zirconia (comparative example 1) exhibits more excellent water and sulfur resistance than the catalyst not containing zirconia (comparative example 2), which is because cerium nitrate and zirconium nitrate form a cerium-zirconium solid solution by coprecipitation, and compared with pure cerium oxide, the cerium-zirconium solid solution has higher stability, which can enable the catalyst to maintain high denitration efficiency for a long time under the condition of passing water and sulfur. The catalyst doped with tin oxide (example 1) also exhibits better denitration efficiency and water and sulfur resistance than the catalyst not doped with tin oxide (comparative example 1), which is because tin oxide can promote the formation of cerium-zirconium oxide lattice structure, increase the number of available active sites, and promote the catalytic degradation of flue gas.

[0052] Table 3: Results of denitration catalyst wear rate per hour

[0053]

[0054]

[0055] As can be seen from table 3, the wear rate per hour of the catalyst doped with tin oxide in the carrier is significantly lower than that of the catalyst doped with tin oxide, which is because tin oxide can form a more stable structure with cerium-zirconium oxide, improve its chemical stability and the wear resistance of the catalyst, effectively reduce the wear and fall of the catalyst surface, and prolong the service life of the catalyst.

[0056] The above only describes the preferred embodiments of the present patent, and it should be noted that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present patent, and these improvements and refinements should also be considered as the protection scope of the present patent.

Claims

1. A method for preparing an anti-sulfurization and denitrification catalyst, characterized in that, Includes the following steps: S1. Cerium nitrate and zirconium nitrate are mixed and added to an ammonia solution for reaction. After the reaction, the precipitate is dispersed in a solvent containing a pore-forming agent, centrifuged, dried, and ball-milled to obtain cerium-zirconium solid solution powder. S2. Manganese was impregnated onto cerium-zirconium solid solution powder by impregnation method. The impregnated product was dried under vacuum and then calcined to obtain MnOx-CeO2-ZrO2 powder. S3. Add titanium chloride and pore-forming agent to an ethanol solution containing tin chloride pentahydrate, then add MnOx-CeO2-ZrO2 powder and ammonia water and stir. After standing and removing the supernatant, spray dry and calcine to obtain the anti-sulfurization and denitrification catalyst. The mass ratio of titanium chloride, tin chloride pentahydrate and MnOx-CeO2-ZrO2 powder is (78-86):(2-8):(8-15).

2. The preparation method of the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S1, the molar ratio of cerium to zirconium in cerium nitrate and zirconium nitrate is 1:(2-7).

3. The preparation method of the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S1, the drying temperature is 70-100℃, and the drying time is 5-24 hours.

4. The preparation method of the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S1, the particle size of the cerium-zirconium solid solution powder obtained after ball milling is 100-500 mesh.

5. The method for preparing the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S2, the specific method for impregnating manganese onto the cerium-zirconium solid solution powder using the equal-volume impregnation method is as follows: Dissolve the manganese precursor in deionized water and add it dropwise to the cerium-zirconium solid solution powder, then impregnate for 2-12 hours. The number of moles of manganese ions in the manganese precursor is 10-15% of the total number of moles of cerium and zirconium in the cerium-zirconium solid solution powder.

6. The method for preparing the anti-sulfurization and denitrification catalyst according to claim 5, characterized in that, The manganese precursor is either manganese nitrate or manganese acetate.

7. The method for preparing the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S2, the vacuum drying temperature is 80-110℃, and the drying time is 5-15 hours. The roasting temperature is 350-450℃, and the roasting time is 5-10 hours.

8. The method for preparing the anti-sulfurization and denitrification catalyst according to claim 1, characterized in that, In step S3 The spray drying temperature is 300-380℃, and the drying time is 2-7 hours. The calcination temperature is 400-750℃, and the time is 2-8 hours.

9. A sulfur-resistant denitrification catalyst, characterized in that, It is prepared by the method described in any one of claims 1-8.

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