Method for improving the water and sulfur resistance of catalysts, catalyst supports and methods for their preparation

Abstract

The application provides a method for improving water and sulfur resistance of a catalyst, a catalyst carrier and a preparation method of the catalyst carrier, which comprises three steps of preparing a wide temperature window catalyst carrier, preparing nano-MnO2 and preparing a manganese-based catalyst. The method for improving water and sulfur resistance of the catalyst adopts a denitration catalyst carrier with a wide temperature window (212.9-579.7 DEG C) to prepare the manganese-based catalyst, the NO conversion rate of the manganese-based catalyst can be kept above 80% after a 6h test in an atmosphere of 5% H2O and 50ppm SO2, and the deactivation is reversible; and the method improves the water and sulfur resistance and denitration efficiency of the manganese-based catalyst.

Description

Technical Field

[0001] This invention belongs to the field of nitrogen oxide treatment technology, and relates to denitrification catalysts, specifically to a method for improving the water and sulfur resistance of catalysts, a catalyst support and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) in the atmosphere x Nitrogen oxides (NOx) mainly originate from two sources: natural generation and human activities. Human-induced emissions primarily come from mobile sources (gasoline vehicles, diesel vehicles, ships, engineering machinery, etc.) and stationary sources (cement, coking, steel, glass, ceramics, waste incineration, industrial boilers, etc.) of industrial combustion. In recent years, with rapid economic development and continuous technological progress, large-scale thermal power plants have emerged, and the proportion of natural gas vehicles in medium and heavy-duty road vehicles has increased year by year, leading to a continuous increase in NOx emissions. Excessive NOx emissions have exacerbated environmental problems. Therefore, the development of excellent denitrification catalysts is crucial for NH3-SCR technology.

[0003] Manganese-based catalysts are commonly used, high-performance low-temperature denitrification catalysts, typically placed after wet desulfurization units. Although the SO2 concentration can be reduced to approximately 10 ppm after desulfurization, manganese-based catalysts are more susceptible to SO2 poisoning compared to commercial vanadium-based catalysts. Therefore, the development of superior denitrification catalyst supports to address the sulfur resistance issue of manganese-based catalysts is urgently needed. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, the purpose of this invention is to provide a method for improving the water and sulfur resistance of catalysts, a catalyst support and its preparation method, and to solve the technical problem that the sulfur resistance of manganese-based denitrification catalysts in the prior art needs to be further improved.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for improving the water and sulfur resistance of a catalyst, the method specifically includes the following steps:

[0007] Step 1, Preparation of catalyst support:

[0008] Cerium salt and citric acid were added to water and stirred to dissolve, thus obtaining solution A. The molar ratio of cerium salt to citric acid was 0.021:(0.0065~0.013). Phosphoric acid was added to water to obtain solution B. Then, solution B was slowly added dropwise to solution A. After stirring, the pH of the system was adjusted to 5 and allowed to stand for aging. The product obtained after aging was filtered, washed with water, and dried. Then, it was heated at a rate of 2~5℃ / min and calcined at 300~500℃ for 3~5h. After calcination, it was ground to obtain the catalyst support.

[0009] Step 2, Preparation of nano-MnO2:

[0010] An aqueous solution containing MnSO4·H2O and KMnO4 was transferred to a reaction vessel and kept at a constant temperature. The obtained product was then filtered, washed with water, dried, and calcined to obtain nano-MnO2.

[0011] Step 3, Preparation of manganese-based catalyst:

[0012] The catalyst support obtained in step one was dispersed in an ethanol solution and stirred; then the nano-MnO2 obtained in step two was added and stirred continuously; after filtration, washing with water, drying, grinding and calcination, the manganese-based catalyst was obtained.

[0013] The present invention also has the following technical features:

[0014] In step one, the mass ratio of citric acid to phosphoric acid is (1.1350~2.5000):1.275.

[0015] In step one, the cerium salt is Ce(NO3)3·6H2O.

[0016] In step one, the drying conditions are: drying in an oven at 110°C for 12 hours.

[0017] In step one, the pH of the system is adjusted to 5 using ammonia.

[0018] In step two, the insulation conditions are: maintaining the temperature at 160°C for 24 hours in a sealed environment.

[0019] In steps two and three, the calcination conditions are as follows: heating at a rate of 2℃ / min and calcining at 400℃ for 4 hours.

[0020] In step three, the mass ratio of the catalyst support to nano-MnO2 is 10:1.

[0021] The present invention also protects the method for preparing the catalyst support as described above.

[0022] The present invention also protects catalyst supports prepared by the method described above.

[0023] The beneficial technical effects of this invention compared to the prior art are as follows:

[0024] (I) The method of the present invention for improving the water and sulfur resistance of catalysts uses a denitrification catalyst support with a wide temperature window (212.9~579.7℃) to prepare a manganese-based catalyst. After a 6-hour test in an atmosphere of 5% H2O and SO2, the NO conversion rate of the manganese-based catalyst can still be maintained above 80%, and this deactivation is reversible. The method improves the water and sulfur resistance and denitrification efficiency of the manganese-based catalyst.

[0025] (I) This invention, by improving the preparation method of the catalyst support, yields a highly efficient denitrification catalyst support. This catalyst support exhibits a denitrification rate >80% within the temperature range of 212.9-579.7℃, and possesses wide temperature window activity and resistance to water and sulfur. The preparation method is simple and has broad application prospects in the field of nitrogen oxide treatment. Attached Figure Description

[0026] Figure 1 The graph shows the relationship between NO conversion and temperature for CeO2-CePO4-CA-C, CeO2-CePO4-CA-Cp, and CeO2-CePO4-CA-CpG catalyst supports.

[0027] Figure 2 CeO2-CePO4-CA x The relationship between NO conversion rate and temperature for -CpG (x=0~6) catalyst support.

[0028] Figure 3 CeO2-CePO4-CA x Water and sulfur resistance test results of -CpG (x=0, 6) catalyst support (test conditions: 300℃, 50ppm SO2+5% H2O, GSHV=75000mL·g) -1 ·h -1 ).

[0029] Figure 4 CeO2-CePO4-CA4-pH x The relationship between NO conversion rate and temperature for -CpG (x=1, 3, 5, 7) catalyst supports.

[0030] Figure 5 Water and sulfur resistance test results for CeO2-CePO4-CA4-pH5-CpG catalyst support (test conditions: 300℃, 50ppm SO2 + 5% H2O, GSHV = 75000 mL·g) -1 ·h-1 ).

[0031] Figure 6 CeO2-CePO4-CA4-pH x TEM images of the -CpG (x = 1, 3, 5, 7) catalyst support.

[0032] Figure 7 The graph shows the relationship between NO conversion rate and temperature for catalyst supports Mn / TiO2-A, Mn / CeO2-CePO4-CA2-pH5-CpG, Mn / TiO2-P25, Mn / TiO2-R930, and Mn / Al2O3.

[0033] Figure 8 Water and sulfur resistance test results for Mn / TiO2-A, Mn / CeO2-CePO4-CA2-pH5-CpG, and Mn / TiO2-P25 catalyst supports (test conditions: 300℃, 50ppm SO2 + 5% H2O, GSHV = 75000 mL·g) -1 ·h -1 ).

[0034] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the art.

[0036] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0037] Example 1:

[0038] This embodiment provides a method for preparing a wide-temperature-window denitration catalyst support. The specific process of this method is as follows:

[0039] At room temperature, 9.2362 g (0.021 mol) of Ce(NO3)3·6H2O and 2.5000 g (0.013 mol) of citric acid were added to 70 mL of deionized water and stirred until dissolved to obtain solution A. 1.5 mL of 85 wt% phosphoric acid was added to 20 mL of deionized water to obtain solution B. Solution B was then slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 30 min. The pH of the system was then adjusted using ammonia. The pH value was adjusted to 5, and the mixture was allowed to stand for 24 hours for aging. After filtration and washing with deionized water, the mixture was dried in an oven at 110℃ for 12 hours, heated in a muffle furnace at a heating rate of 2℃ / min, and then calcined at 400℃ for 4 hours. After calcination, the mixture was ground to obtain catalyst supports CeO2-CePO4-CA-CpG, CeO2-CePO4-CA4-CpG, and CeO2-CePO4-CA4-pH5-CpG.

[0040] Example 2:

[0041] This embodiment presents a method for preparing a wide-temperature-window denitration catalyst support. The method is essentially the same as others, differing only in the amount of citric acid added. The specific process of this method is as follows:

[0042] At room temperature, 9.2362 g (0.021 mol) of Ce(NO3)3·6H2O and 1.1350 g (0.0065 mol) of citric acid were added to 70 mL of deionized water and stirred to dissolve, thus preparing solution A. 1.5 mL of 85 wt% phosphoric acid was added to 20 mL of deionized water to prepare solution B. Solution B was then slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 30 min. The pH of the system was adjusted to 5 with ammonia water and allowed to stand for 24 h. After filtration, washing with deionized water, and drying in an oven at 110 °C for 12 h, the mixture was heated in a muffle furnace at a heating rate of 2 °C / min and then calcined at 400 °C for 4 h. After calcination, the mixture was ground to obtain the catalyst support CeO2-CePO4-CA2-CpG.

[0043] Comparative Example 1:

[0044] This comparative example provides a method for preparing a catalyst support, which is basically the same as that in Example 1, except that: after calcination, grinding is not performed to obtain the catalyst support CeO2-CePO4-CA-Cp.

[0045] Comparative Example 2:

[0046] This comparative example presents a method for preparing a catalyst support (combustion method), the specific process of which is as follows:

[0047] At room temperature, 9.2362 g of Ce(NO3)3·6H2O and 1.5 mL of 85% phosphoric acid were added to 100 mL of deionized water and sonicated for 5 min to obtain aqueous solution A. 2.5000 g of citric acid was added to 20 mL of deionized water and sonicated for 5 min to obtain aqueous solution B. Subsequently, solution B was slowly added dropwise to solution A, and the mixture was magnetically stirred in an 80℃ water bath for 1 h and then dried in an oven at 110℃. Finally, the dried solid was placed in a muffle furnace and heated at a rate of 5℃ / min, and then calcined at 400℃ for 4 h to obtain the catalyst support CeO2-CePO4-CA-C.

[0048] Comparative Example 3:

[0049] This comparative example provides a method for preparing a catalyst support, which is basically the same as that in Example 1, except that the amount of citric acid added is different. The specific process of this method is as follows:

[0050] At room temperature, 9.2362 g (0.021 mol) of Ce(NO3)3·6H2O and 0 g, 0.4540 g, 1.8000 g, 3.2000 g, and 3.8600 g of citric acid were added to 70 mL of deionized water and stirred until dissolved to obtain solution A. 1.5 mL of 85 wt% phosphoric acid was added to 20 mL of deionized water to obtain solution B. Solution B was then slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 30 min. The pH of the system was then adjusted to 5 with ammonia and allowed to stand for 24 h. After filtration, washing with deionized water, and drying in an oven at 110℃ for 12 hours, the catalyst supports CeO2-CePO4-CA0-CpG, CeO2-CePO4-CA1-CpG, CeO2-CePO4-CA3-CpG, CeO2-CePO4-CA5-CpG, and CeO2-CePO4-CA6-CpG were obtained.

[0051] Comparative Example 4:

[0052] This comparative example provides a method for preparing a catalyst support, which is basically the same as that in Example 1, except that the pH value of the system is different. The specific process of this method is as follows:

[0053] At room temperature, 9.2362 g (0.021 mol) of Ce(NO3)3·6H2O and 2.5000 g (0.013 mol) of citric acid were added to 70 mL of deionized water and stirred until dissolved to obtain solution A. 1.5 mL of 85 wt% phosphoric acid was added to 20 mL of deionized water to obtain solution B. Solution B was then slowly added dropwise to solution A, and the mixture was magnetically stirred at room temperature for 30 min. The pH of the system was then adjusted to 1 using ammonia. 3 and 7 were allowed to stand for 24 hours for aging; after filtration and washing with deionized water, they were dried in an oven at 110℃ for 12 hours, then heated in a muffle furnace at a heating rate of 2℃ / min, and calcined at 400℃ for 4 hours. After calcination, they were ground to obtain catalyst supports CeO2-CePO4-CA4-pH1-CpG, CeO2-CePO4-CA4-pH3-CpG, and CeO2-CePO4-CA4-pH7-CpG.

[0054] Example 3:

[0055] This embodiment provides a method for improving the water and sulfur resistance of a catalyst, which specifically includes the following steps:

[0056] Step 1: Preparation of a wide-temperature-window denitration catalyst support:

[0057] In this embodiment, the specific process of step one is exactly the same as that in embodiment 2.

[0058] Step 2, Preparation of nano-MnO2:

[0059] A 75 mL aqueous solution containing 2.4800 g of MnSO4·H2O and 1.6600 g of KMnO4 was transferred to a 100 mL Teflon-lined stainless steel autoclave, sealed, and kept at 160 °C for 24 h. The resulting black slurry was filtered, washed 4–5 times with deionized water, dried at 110 °C for 24 h, and then calcined in a muffle furnace at 500 °C with a heating rate of 2 °C / min for 6 h to obtain nano-MnO2.

[0060] Step 3, Preparation of manganese-based catalyst:

[0061] 5.0000 g of CeO2-CePO4-CA2-pH5-CpG was dispersed in 50 mL of ethanol solution and stirred at room temperature for 30 min. Then, 0.5000 g of nano MnO2 powder was added and stirred at room temperature for 20 h. After filtration and washing with deionized water 4-5 times, the product was dried in an oven at 110 ℃ for 12 h and then ground. The ground product was then calcined at 400 ℃ for 4 h at a heating rate of 2 ℃ / min to obtain the sample Mn / CeO2-CePO4-CA2-pH5-CpG.

[0062] Comparative Example 5:

[0063] This comparative example presents a method for improving the water and sulfur resistance of catalysts, which specifically includes the following steps:

[0064] Step 1: Prepare TiO2-A, TiO2-P25, TiO2-R930, and Al2O3 as catalyst supports.

[0065] Step 2, Preparation of nano-MnO2:

[0066] In this comparative example, step two is exactly the same as step two in Example 3.

[0067] Step 3, Preparation of manganese-based catalyst:

[0068] 5.0000 g of TiO2-A, TiO2-P25, TiO2-R930, and Al2O3 were dispersed in 50 mL of ethanol solution and stirred at room temperature for 30 min. Then, 0.5000 g of nano MnO2 powder was added and stirred at room temperature for 20 h. After filtration and washing with deionized water 4-5 times, the product was dried in an oven at 110 °C for 12 h and then ground. The ground product was then calcined at 400 °C for 4 h at a heating rate of 2 °C / min to obtain samples Mn / TiO2-A, Mn / TiO2-P25, Mn / TiO2-R930, and Mn / Al2O3.

[0069] Effect verification:

[0070] This invention, through the above examples and comparative examples, investigated the effects of different preparation methods on the temperature window activity of CeO2-CePO4 catalyst supports, the effects of different pH values ​​on the temperature window activity and morphology of CeO2-CePO4 catalyst supports, the effects of different citric acid contents on the temperature window activity and water and sulfur resistance of the prepared CeO2-CePO4 catalyst supports, the effects of different pH values ​​on the temperature window activity and morphology of CeO2-CePO4 catalyst supports, and manganese-based catalyst supports prepared from anatase (TiO2-A), rutile (TiO2-R930), anatase-rutile mixed phase (TiO2-P25), CeO2-CePO4-CA2-pH5-CpG, and Al2O3 support materials. Specific results are as follows: Figures 1 to 8 As shown.

[0071] (A) The following conclusions can be drawn from Example 1, Comparative Example 1, and Comparative Example 2:

[0072] Depend on Figure 1It can be seen that, compared with the combustion method and the method of calcination without grinding, the CeO2-CePO4-CA-CpG prepared in Example 1 has excellent wide temperature window activity, with NO conversion rate exceeding 80% in the range of 212.9 to 579.7 °C.

[0073] (B) The following conclusions can be drawn from Examples 1, 2 and 3:

[0074] Depend on Figure 2 It can be seen that the CeO2-CePO4-CA-CpG prepared in Example 1 exhibits excellent wide temperature window activity, and compared with the traditional commercial vanadium-tungsten-titanium catalyst support anatase (TiO2-A), the CeO2-CePO4 catalyst support has a wider overall temperature window and a higher NO conversion rate. Meanwhile, from Figure 3 It can be seen that CeO2-CePO4-CA4-CpG has significantly better resistance to water and sulfur than the catalyst support without CA. After 6 hours of experiment in an atmosphere of 5% H2O and SO2, the NO conversion rate of CeO2-CePO4-CA4-CpG can still be maintained above 80%, while the NO conversion rate of CeO2-CePO4-CA0-CpG decreases to 60%. Moreover, this deactivation is reversible.

[0075] (C) The following conclusions can be drawn from Example 1 and Comparative Example 4:

[0076] Depend on Figure 4 and Figure 5 It is known that CeO2-CePO4-CA4-PH5-CpG has excellent wide temperature window activity and water and sulfur resistance. Moreover, after 6 hours of testing in an atmosphere of 5% H2O and SO2, the NO conversion rate can still be maintained above 80%, and this deactivation is reversible.

[0077] like Figure 6 As shown, pH has a significant impact on the morphology of the CeO2-CePO4 catalyst support. Figure 6

[0078] As shown in (c) and (d), when pH = 1, hexagonal nanorods with lengths of approximately 100 nm to 1 μm and diameters of 10 to 100 nm were obtained; Figure 6 As shown in (g) and (h), when pH = 3, the length of the nanorods shortens, forming some hemispherical aggregates with a diameter of less than 20 nm; as Figure 6 As shown in (k) and (1), when pH = 5, the morphology begins to change and transforms into agglomerates of hemispherical nanoparticles. Under these conditions, two morphologies coexist: nanorods and agglomerated particles; as Figure 6 As shown in (o) and (p), when the pH increases to 7, the number of spherical particles increases, growing together with fine and thin nanorods.

[0079] (D) The following conclusions can be drawn from Example 3 and Comparative Example 5:

[0080] like Figure 7 As shown, the catalytic activities of Mn / TiO2-R930 and Mn / Al2O3 prepared in Comparative Example 5 are both less than 80%. The T80 temperature window of Mn / CeO2-CePO4-CA2-pH5-CpG is 201.8-445.5℃, which is the widest compared to the catalyst supports Mn / TiO2-A and Mn / TiO2-P25, and it has the best low-temperature activity.

[0081] like Figure 8 As shown, after introducing 50 ppm H2O and 5% SO2 at 300℃, the NO conversion rate of all three catalyst supports gradually decreased. However, after 6 hours of reaction, the NO conversion rate of the Mn / CeO2-CePO4-CA2-pH5-CpG catalyst support still exceeded 80%, while the NO conversion rates of the Mn / TiO2-A and Mn / TiO2-P25 catalyst supports rapidly decreased to below 30% within 30 minutes after the introduction of water and sulfur. After shutting off the water and sulfur for 30 minutes, the NO conversion rate of the Mn / CeO2-CePO4-CA2-pH5-Cp catalyst support rapidly recovered to over 90%, while the NO conversion rates of the Mn / TiO2-A and Mn / TiO2-P25 catalyst supports showed no significant change within 30 minutes. Clearly, the Mn / CeO2-CePO4-CA2-pH5-Cp catalyst support exhibits better water and sulfur resistance than the Mn / TiO2-A and Mn / TiO2-P25 catalyst supports.

[0082] Based on the above analysis, compared with commonly used anatase (TiO2-A), rutile (TiO2-R930), anatase-rutile mixed phase (TiO2-P25), and Al2O3 catalyst support materials, the manganese-based catalyst supported on CeO2-CePO4-CA2-pH5-CpG exhibits superior wide-temperature-window denitrification activity and resistance to water and sulfur. Furthermore, after 6 hours of testing in an atmosphere of 5% H2O and SO2, the NO conversion rate can still be maintained above 80%, indicating that this deactivation is reversible.

Claims

1. A method for improving the water and sulfur resistance of a catalyst, characterized in that, The method specifically includes the following steps: Step 1, Preparation of catalyst support: Cerium salt and citric acid were added to water and stirred to dissolve, thus obtaining solution A, wherein the molar ratio of cerium salt to citric acid was 0.021:(0.0065 or 0.013); phosphoric acid was added to water to obtain solution B; then, solution B was slowly added dropwise to solution A, and the pH of the system was adjusted to 5 after stirring and allowed to stand for aging; the product obtained after aging was filtered, washed with water, dried, and then calcined at a temperature of 300-500℃ for 3-5 hours at a heating rate of 2-5℃ / min; after calcination, it was ground to obtain the catalyst support; Step 2, Preparation of nano-MnO2: An aqueous solution containing MnSO4•H2O and KMnO4 was transferred to a reaction vessel and kept at a certain temperature. The obtained product was then filtered, washed with water, dried, and calcined to obtain nano-MnO2. Step 3, Preparation of manganese-based catalyst: The catalyst support obtained in step one was dispersed in an ethanol solution and stirred; then the nano-MnO2 obtained in step two was added and stirring continued; after filtration, washing with water, drying, grinding and calcination, the manganese-based catalyst was obtained.

2. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In step one, the cerium salt is Ce(NO3)3•6H2O.

3. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In step one, the drying conditions are: drying in an oven at 110°C for 12 hours.

4. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In step one, the pH of the system is adjusted to 5 using ammonia.

5. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In step two, the insulation conditions are: maintaining the temperature at 160°C for 24 hours in a sealed environment.

6. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In steps two and three, the calcination conditions are as follows: heating at a rate of 2℃ / min and calcining at 400℃ for 4 hours.

7. The method for improving the water and sulfur resistance of a catalyst as described in claim 1, characterized in that, In step three, the mass ratio of the catalyst support to nano-MnO2 is 10:

1.

8. A method for preparing a catalyst support, characterized in that, This method specifically includes the following steps: Cerium salt and citric acid were added to water and stirred to dissolve, thus obtaining solution A, wherein the molar ratio of cerium salt to citric acid was 0.021:(0.0065 or 0.013). Phosphoric acid was added to water to obtain solution B. Subsequently, solution B was slowly added dropwise to solution A, and the pH of the system was adjusted to 5 after stirring and allowed to stand for aging. The product obtained after aging was filtered, washed with water, and dried. Then, it was heated at a rate of 2-5℃ / min and calcined at 300-500℃ for 3-5 hours. After calcination, it was ground to obtain the catalyst support.

9. A catalyst support prepared by the method of preparing the catalyst support as described in claim 8.

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