Low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst and preparation method thereof

Abstract

The invention discloses a low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst and a preparation method thereof, and belongs to the field of air pollution control. The catalyst is prepared by taking NH-Ce-BDC as a precursor, loading manganous nitrate and tin acetate and then calcining, and the chemical general formula of the catalyst is Ce10Mn3Sn0. 3Ox, Ce10Mn (f) 3Sn0. 3Ox or Ce10Mn3Sn (f) 0. 3Ox. The preparation method comprises three steps of precursor synthesis, impregnation loading and calcination at 400 DEG C, and the process is simple. The NOx conversion rate of the catalyst at the temperature of 100-225 DEG C is greater than 80%, the Nselectivity of the catalyst at the temperature of less than 175 DEG C is greater than 80%, the sulfur resistance is strong, and NOx in low-temperature flue gas can be efficiently removed.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, specifically relating to a cerium-manganese-tin (Ce-Mn-Sn) ternary composite denitrification catalyst derived from a cerium-based metal-organic framework (NH2-Ce-BDC), particularly suitable for the removal of nitrogen oxides (NOx) from low-temperature flue gas (50-225℃) in ammonia selective catalytic reduction (NH3-SCR) reactions. x It removes nitrogen and has excellent N2 selectivity and sulfur resistance. Background Technology

[0002] Nitrogen oxides (NO) x NOx is a major pollutant produced during coal combustion, seriously endangering the ecological environment and human health. Ammonia selective catalytic reduction (NH3-SCR) technology is currently the most effective method for controlling NOx. x The mainstream approach involves catalysts, which are the core of this technology.

[0003] Vanadium-based catalysts (V₂O₅-WO₃ / TiO₂) widely used in industry have significant drawbacks: a narrow activity temperature window (300-400℃), making them unsuitable for low-temperature flue gas environments; and V₂O₅ is toxic, easily causing secondary pollution. To address these issues, researchers have turned to the development of non-vanadium-based catalysts.

[0004] Among cerium-based catalysts, CeSn catalysts exhibit excellent N2 selectivity and structural stability, but their low-temperature denitrification activity is insufficient, limiting their application in low-temperature flue gas treatment. On the other hand, manganese (Mn)-based catalysts, with their strong oxidizing properties, can enhance the low-temperature NO oxidation capacity and effectively compensate for the low-temperature activity deficiency, but they are prone to N2 selectivity decrease due to excessive oxidation, increasing the generation of by-products.

[0005] Therefore, achieving a balance between "low-temperature activity" and "high N2 selectivity" while improving the catalyst's sulfur resistance has become a key technical challenge in the current research and development of low-temperature denitrification catalysts. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst and its preparation method, which can effectively solve the problems of high toxicity and narrow temperature window of existing vanadium-based catalysts, insufficient low-temperature activity of CeSn catalysts, and low N2 selectivity of Mn-based catalysts, and achieve NO under low-temperature conditions. x Highly efficient removal.

[0007] To achieve the above or other objectives, the present invention is implemented through the following technical solutions.

[0008] The catalyst was prepared by calcination using a cerium-based metal-organic framework (NH2-Ce-BDC) as a precursor, supported with manganese and tin sources. The general chemical formula of the catalyst is Ce. 10 Mn3Sn 0.3 O x Ce 10 Mn(f)3Sn 0.3 O x and Ce 10 Mn3Sn(f) 0.3 O x .

[0009] Furthermore, the precursor NH2-Ce-BDC is prepared by reacting 2-aminoterephthalic acid (NH2-BDC) with cerium chloride (CeCl3・7H2O);

[0010] Furthermore, the manganese source is selected from manganese nitrate (Mn(NO3)2・4H2O);

[0011] Furthermore, the tin source is selected from tin acetate (Sn(CH3COO)2).

[0012] This invention provides a method for preparing a low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst, comprising the following steps:

[0013] (1) Synthesis of NH2-Ce-BDC precursor: 2-aminoterephthalic acid (NH2-BDC) was dispersed in deionized water, the pH was adjusted to 5-6 with 1M NaOH solution, CeCl3・7H2O was added, the mixture was stirred and allowed to stand for reaction, the product was washed by centrifugation with deionized water and ethanol alternately, and dried to obtain NH2-Ce-BDC precursor;

[0014] (2) Metal species loading: The NH2-Ce-BDC precursor prepared in step (1) is dispersed in anhydrous ethanol, and manganese source and tin source are added in different order. The mixture is then magnetically stirred at a certain temperature until the solvent evaporates.

[0015] (3) Calcination treatment: The sample obtained in step (2) is placed in a muffle furnace and heated to a set temperature at a specific heating rate. The sample is then calcined in air for a certain time to obtain the target catalyst.

[0016] Preferably, in step (1), the amount of 2-aminoterephthalic acid used is 1.65 g, the amount of deionized water used is 330 mL, and the amount of CeCl3・7H2O used is 1.452 g;

[0017] Preferably, in step (1), the stirring time is 1 min, the standing reaction time is 40 min, the number of centrifugal washing cycles is 6, the drying temperature is 80℃, and the drying time is 12 h;

[0018] Preferably, in step (2), the amount of NH2-Ce-BDC precursor used is 1.6g, the amount of anhydrous ethanol used is 20mL, and the stirring temperature is 70℃;

[0019] Preferably, in step (2), the loading method of the metal species is co-impregnation or step-by-step impregnation; the step-by-step impregnation includes two sequences: loading manganese source first and then loading tin source, and loading tin source first and then loading manganese source.

[0020] Preferably, in step (3), the heating rate is 5℃ / min, the calcination temperature is 400℃, and the calcination time is 2h;

[0021] More preferably, the catalyst prepared by the co-impregnation method is named Ce. 10 Mn3Sn 0.3 O x ;

[0022] More preferably, the catalyst prepared by the stepwise impregnation method of first loading a manganese source and then loading a tin source is named Ce. 10 Mn(f)3Sn 0.3 O x ;

[0023] More preferably, the catalyst prepared by the stepwise impregnation method of first loading a tin source and then loading a manganese source is named Ce. 10 Mn3Sn(f) 0.3 O x .

[0024] The low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst provided by this invention introduces Mn to form a "Ce-Sn-Mn" ternary synergistic effect. This retains the high N2 selectivity advantage of CeSn catalysts while leveraging the redox properties of Mn to compensate for the low-temperature activity deficiency. Simultaneously, by controlling the impregnation sequence of the metal components, the redox performance and acidic site distribution of the catalyst are optimized, effectively improving the low-temperature activity, selectivity, and sulfur resistance of the catalyst, and increasing the NO concentration in low-temperature flue gas. x Removal efficiency.

[0025] Experimental results show that the composite denitrification catalyst prepared in this invention has significantly improved denitrification performance, N2 selectivity, and sulfur resistance under low temperature (100-225℃) conditions.

[0026] Compared with existing technologies, the present invention has the following advantages:

[0027] (1) The low-temperature activity, N2 selectivity and sulfur resistance of the catalyst were significantly improved.

[0028] (2) The preparation method of the present invention is simple and easy to industrialize. Attached Figure Description

[0029] Figure 1: XRD pattern of the catalyst;

[0030] Figure 2: Activity curve of the NH3-SCR catalyst;

[0031] Figure 3: N2 selectivity of the catalyst;

[0032] Figure 4: Sulfur resistance performance of the catalyst. Detailed Implementation

[0033] Example 1: Preparation of CeSn catalyst

[0034] (1) Disperse 1.65g of 2-aminoterephthalic acid (NH2-BDC) in 330mL of deionized water and adjust the pH to 5-6 with 1M NaOH;

[0035] (2) Add 1.452g CeCl3・7H2O to the above solution, stir for 1 min and let stand for 40 min to carry out the reaction;

[0036] (3) The product after the reaction was washed 6 times by alternating centrifugation with deionized water and ethanol, and then dried at 80°C for 12 h to obtain the NH2-Ce-BDC precursor;

[0037] (4) Take 1.6g of NH2-Ce-BDC and disperse it in 20mL of anhydrous ethanol. At the same time, add an appropriate amount of Sn (CH3COO)2 and stir magnetically at 70℃ until the solvent evaporates.

[0038] (5) The above-mentioned Sn species-supported sample was placed in a muffle furnace and heated to 400°C at a rate of 5°C / min. It was then calcined in air for 2 hours to obtain the CeSn catalyst.

[0039] X-ray diffraction tests were performed on the samples prepared in this embodiment, and the results are shown in the figure. Figure 1 No diffraction peaks related to Sn species were observed in the XRD diffraction patterns of CeSn catalyst. According to the magnified 27-30° local image, the diffraction peaks of CeSn on the CeO2(111) crystal plane are all shifted to a larger angle, indicating that Sn is doped into the CeO2 lattice.

[0040] Example 2: Preparation of Ce by co-impregnation method 10 Mn3Sn 0.3 O x catalyst

[0041] (1) Disperse 1.65g of 2-aminoterephthalic acid (NH2-BDC) in 330mL of deionized water and adjust the pH to 5-6 with 1M NaOH;

[0042] (2) Add 1.452g CeCl3・7H2O to the above solution, stir for 1 min and let stand for 40 min to carry out the reaction;

[0043] (3) The product after the reaction was washed 6 times by alternating centrifugation with deionized water and ethanol, and then dried at 80°C for 12 h to obtain the NH2-Ce-BDC precursor;

[0044] (4) Take 1.6g of NH2-Ce-BDC and disperse it in 20mL of anhydrous ethanol. At the same time, add appropriate amounts of Mn(NO3)2・4H2O and Sn(CH3COO)2 and stir magnetically at 70℃ until the solvent evaporates.

[0045] (5) The above-mentioned Sn and Mn species-loaded samples were placed in a muffle furnace and heated to 400°C at a rate of 5°C / min, and calcined in air for 2 hours to obtain Ce. 10 Mn3Sn 0.3 O x catalyst.

[0046] X-ray diffraction tests were performed on the samples prepared in this embodiment, and the results are shown in the figure. Figure 1 Ce 10 Mn3Sn 0.3 O x No other diffraction peaks were observed in the catalyst besides the relevant CeO2 diffraction peaks, and the typical 27-30° diffraction peaks shifted to higher 2θ values, indicating that Sn or Mn was doped into the CeO2 lattice.

[0047] Example 3: Preparation of Ce by stepwise impregnation method (Mn first, then Sn) 10 Mn(f)3Sn 0.3 O x catalyst

[0048] (1) Disperse 1.65g of 2-aminoterephthalic acid (NH2-BDC) in 330mL of deionized water and adjust the pH to 5-6 with 1M NaOH;

[0049] (2) Add 1.452g CeCl3・7H2O to the above solution, stir for 1 min and let stand for 40 min to carry out the reaction;

[0050] (3) The product after the reaction was washed 6 times by alternating centrifugation with deionized water and ethanol, and then dried at 80°C for 12 h to obtain the NH2-Ce-BDC precursor;

[0051] (4) Take 1.6g of NH2-Ce-BDC and disperse it in 20mL of anhydrous ethanol. At the same time, add an appropriate amount of Mn(NO3)2・4H2O and stir magnetically at 70℃ until the solvent evaporates.

[0052] (5) Disperse the sample obtained in step (4) into 20 mL of anhydrous ethanol, and add an appropriate amount of Sn (CH3COO)2. Stir magnetically at 70 °C until the solvent evaporates.

[0053] (6) The above-mentioned Sn and Mn species-loaded samples were placed in a muffle furnace and heated to 400°C at a rate of 5°C / min, and calcined in air for 2 hours to obtain Ce. 10 Mn(f)3Sn 0.3 O x catalyst.

[0054] X-ray diffraction tests were performed on the samples prepared in this embodiment, and the results are shown in the figure. Figure 1 Ce 10 Mn(f)3Sn 0.3 O x No other diffraction peaks were observed in the catalyst besides the relevant CeO2 diffraction peaks, and the typical 27-30° diffraction peaks shifted to higher 2θ values, indicating that Sn or Mn was doped into the CeO2 lattice.

[0055] Example 4: Preparation of Ce by stepwise impregnation method (Sn first, then Mn) 10 Mn3Sn(f) 0.3 O x catalyst

[0056] (1) Disperse 1.65g of 2-aminoterephthalic acid (NH2-BDC) in 330mL of deionized water and adjust the pH to 5-6 with 1M NaOH;

[0057] (2) Add 1.452g CeCl3・7H2O to the above solution, stir for 1 min and let stand for 40 min to carry out the reaction;

[0058] (3) The product after the reaction was washed 6 times by alternating centrifugation with deionized water and ethanol, and then dried at 80°C for 12 h to obtain the NH2-Ce-BDC precursor;

[0059] (4) Take 1.6g of NH2-Ce-BDC and disperse it in 20mL of anhydrous ethanol. At the same time, add an appropriate amount of Sn (CH3COO)2 and stir magnetically at 70℃ until the solvent evaporates.

[0060] (5) Disperse the sample obtained in step (4) into 20 mL of anhydrous ethanol, and add an appropriate amount of Mn(NO3)2・4H2O. Stir magnetically at 70 °C until the solvent evaporates.

[0061] (6) The above-mentioned Sn and Mn species-loaded samples were placed in a muffle furnace and heated to 400°C at a rate of 5°C / min, and calcined in air for 2 hours to obtain Ce. 10 Mn3Sn(f) 0.3 O x catalyst.

[0062] X-ray diffraction tests were performed on the samples prepared in this embodiment, and the results are shown in the figure. Figure 1 Ce 10 Mn3Sn(f) 0.3 O x No other diffraction peaks were observed in the catalyst besides the relevant CeO2 diffraction peaks, and the typical 27-30° diffraction peaks shifted to higher 2θ values, indicating that Sn or Mn was doped into the CeO2 lattice.

[0063] Example 5: Catalyst Denitrification Performance Test

[0064] The catalysts prepared in Examples 1-4 were used to simulate industrial exhaust gas atmospheres, and their denitrification performance was measured in an NH3-SCR activity evaluation device.

[0065] Test conditions: The reactor uses a fixed-bed quartz reaction tube under atmospheric pressure with an inner diameter of 5 mm; before gas mixing, the gas path is purged with high-purity N2, and then the reaction gas is delivered through a multi-path automatic gas mixing system; the reaction gas is simulated flue gas with a space velocity of 60000 h⁻¹, and the gas composition is N2, O2 (5.00%, volume fraction), NO (500 ppm), and NH3 (500 ppm), with a mixed gas flow rate of 100 mL / min; 0.1 mL of catalyst is packed in the quartz tube, and the average catalyst particle size is 40-60 mesh; the test temperature range is 50~225℃, with 25℃ as one test interval.

[0066] Test results are as follows Figure 2 As shown: Ce 10 Mn(f)3Sn 0.3 O x The low-temperature denitrification activity of the catalyst is slightly lower than that of Ce. 10 Mn(f)3Sn 0.3 O x However, it exhibits superior overall denitrification performance, with the widest temperature window, covering NO levels within the 100-200℃ range. x The conversion rate reached over 80%.

[0067] Example 6: Catalyst N2 Selectivity Test

[0068] The catalysts prepared in Examples 1-4 were used in the same reaction apparatus and gas composition as in Example 5 to determine the N2 selectivity of the catalysts at different temperatures.

[0069] Test results are as follows Figure 3 As shown: within the test temperature range, the N2 selectivity of CeSn catalysts remained at a high level close to 100%; the N2 selectivity curves of all CeMnSn catalysts generally decreased with increasing temperature, which may be due to the over-oxidation of NH3 caused by the increase in temperature; under low temperature conditions (<175℃), the N2 selectivity of the three CeMnSn catalysts all exceeded 80%.

[0070] Example 7: Catalyst Sulfur Resistance Test

[0071] Ce obtained in Example 3 10 Mn(f)3Sn 0.3 O x The catalyst was used to simulate the exhaust atmosphere of industrial waste gas. SO2 was introduced into the NH3-SCR activity evaluation device to determine the denitrification stability of the catalyst in the presence of SO2.

[0072] Test conditions: Except for the addition of 50ppm SO2 to the reaction gas, the other conditions were the same as in Example 5. The test temperature was 200℃ and the test was conducted continuously for 8 hours.

[0073] Test results are as follows Figure 4 As shown: After SO2 is introduced for 8 hours, the NO content of the catalyst... x The conversion rate decreased from 84% to 68%, a drop of only 16%, indicating that SO2 had a certain poisoning effect on the catalyst, but the catalyst still has excellent sulfur resistance.

Claims

1. A low-temperature sulfur-resistant MOF-derived cerium-manganese-tin composite denitration catalyst, characterized in that, It is prepared by calcination of NH2-Ce-BDC as a precursor, loaded with manganese and tin sources, and has the general chemical formula Ce. 10 Mn3Sn 0.3 O x Ce 10 Mn(f)3Sn 0.3 O x or Ce 10 Mn3Sn(f) 0.3 O x The molar ratio of Ce:Mn:Sn is 10:3:0.

3.

2. The catalyst according to claim 1, characterized in that, The manganese source is manganese nitrate, and the tin source is tin acetate.

3. The catalyst according to claim 1, characterized in that, Suitable for NH3-SCR denitrification of low-temperature flue gas at 50-225℃.

4. A method for preparing the catalyst according to any one of claims 1-3, characterized in that, include: (1) Synthesis of NH2-Ce-BDC precursor; (2) Co-impregnation or step-impregnation with loaded manganese and tin sources; (3) Heat to 400℃ at 5℃ / min and calcine for 2 hours.

5. The method as described in claim 4, characterized in that, In step (1), the pH was adjusted to 5-6 with 1M NaOH, and the product was washed and dried at 80℃ for 12h.

6. The method as described in claim 4, characterized in that, In step (2), the mixture is magnetically stirred at 70°C until the solvent evaporates.

Images