Low-temperature denitration catalyst and preparation method thereof

Abstract

The application discloses a low-temperature denitration catalyst and a preparation method thereof, and belongs to the technical field of flue gas denitration catalysts. 60 The catalyst is prepared by doping fullerene C 60 The pi electron system of C 60 is highly delocalized on the three-dimensional curved surface thereof, so that C 60 has excellent electron transfer capacity; and the doping proportion of C 60 can effectively promote the rapid progress of the catalytic reaction. Therefore, the catalyst prepared by the application can be applied to low-temperature flue gas denitration, can significantly improve the denitration efficiency, can widen the active temperature range of the catalyst, and can solve the problems of poor low-temperature activity, insufficient sulfur resistance and easy poisoning of traditional catalysts.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification catalyst technology, specifically relating to a low-temperature denitrification catalyst for NH3-SCR flue gas denitrification and its preparation method. Background Technology

[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants, mainly originating from the combustion of fossil fuels, such as exhaust gas from coal-fired power plants, flue gas from industrial boilers, and vehicle exhaust. x Excessive emissions of NO can cause environmental problems such as photochemical smog, acid rain, the greenhouse effect, and ozone layer depletion. The "Emission Standard of Air Pollutants for Thermal Power Plants (GB 13223-2011)" and the "Technical Specification for Ultra-Low Emission Flue Gas Treatment Engineering of Coal-fired Power Plants" clearly stipulate the limits for NO in flue gas. x Emission concentration ≤50mg / m³ 3 Therefore, effectively removing NO x It is an important issue in environmental protection.

[0003] Selective catalytic reduction of ammonia (NH3-SCR) is currently the most widely used, mature, and effective flue gas denitrification technology. It utilizes a denitrification catalyst to reduce NO3- in a suitable temperature range. x When combined with NH3, it is reduced to harmless N2 and H2O, achieving a denitrification efficiency generally exceeding 85%. The core of NH3-SCR technology lies in the catalyst. Currently, vanadium-tungsten-titanium series catalysts are the most widely used NH3-SCR catalysts, exhibiting good denitrification activity at 300-400℃ and widely applied in medium-temperature flue gas denitrification in coal-fired power plants. However, existing commercial catalysts operate at high temperatures, making it difficult to meet the denitrification requirements of low-temperature flue gas (<200℃) in non-power industries. Therefore, developing SCR catalysts with high activity at low temperatures is of significant importance and practical value.

[0004] Manganese-based denitrification catalysts exhibit good catalytic activity in a relatively low temperature range (120-180℃), but their sulfur resistance is poor, making them susceptible to poisoning and permanent deactivation. Therefore, improving the sulfur resistance of manganese-based catalysts is a key research focus, and the active temperature window of manganese-based catalysts needs further expansion. Patent CN 108772057A discloses a MnO2 catalyst with a highest denitrification efficiency of approximately 90% at 200℃, but below 150℃, the denitrification efficiency is less than 80%, and the catalyst's sulfur resistance was not investigated. Patent CN 105289586B discloses a spherical cerium-manganese composite oxide low-temperature denitrification catalyst prepared by a hydrothermal method, achieving a NOx removal efficiency of 90-98% in the 100-200℃ range; however, this preparation method is costly and cannot be industrialized.

[0005] Based on the problems existing in current manganese-based catalysts, this invention utilizes C 60 Its reversible electron gain and loss properties allow it to be incorporated as an additive into iron-manganese-based composite catalysts, thereby regulating C 60 By adjusting the doping ratio, a low-temperature, high-efficiency, and easily prepared sulfur-resistant denitrification catalyst was developed. Applying the catalyst prepared in this invention to low-temperature flue gas denitrification significantly improves denitrification efficiency, broadens the catalyst's activity temperature range, and solves the problems of poor low-temperature activity, insufficient sulfur resistance, and susceptibility to poisoning found in traditional catalysts. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature denitrification catalyst and its preparation method. The preparation process is simple, the resulting catalyst has good stability, and it has good catalytic activity and sulfur resistance. This can solve the problems of narrow activity temperature window and poor sulfur resistance of existing denitrification catalysts.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A low-temperature denitration catalyst, which is made by incorporating C into a composite oxide of Fe and Mn. 60 And it was made.

[0009] Furthermore, the molar ratio of Fe to Mn in the catalyst is 2:1.

[0010] Furthermore, the catalyst contains C 60 The percentage of mass is 0.3-1.2%.

[0011] The preparation method of the low-temperature denitration catalyst includes the following steps:

[0012] (1) C 60 After mixing with benzene, a strong oxidizing agent is added. The mixture is heated and reacted, then the liquid is evaporated to dryness. The residue is washed three times with anhydrous ethanol and then dried to obtain the treated C. 60 ;

[0013] (2) Add citric acid as a complexing agent to a mixed solution containing iron and manganese salts and stir to dissolve, thus obtaining a mixed metal salt solution;

[0014] (3) Take the processed C obtained in step (1) 60 Add to the mixed metal salt solution obtained in step (2), and sonicate to C. 60 After uniform dispersion, continue stirring at room temperature for 30-60 minutes, and then react to obtain a foam-like solid;

[0015] (4) The foam-like solid obtained in step (3) is calcined under heat and then naturally cooled, and then ground to obtain C. 60 Doped Fe-Mn-based low-temperature denitration catalyst.

[0016] Furthermore, the C used in step (1) 60 The purity is 99.9%.

[0017] Furthermore, the strong oxidant mentioned in step (1) is any one of m-chloroperoxybenzoic acid, concentrated sulfuric acid, or concentrated nitric acid.

[0018] Furthermore, the C used in step (1) 60 The mass ratio of the strong oxidant to the strong oxidant is 1:12-15.

[0019] Furthermore, the heating reaction in step (1) is carried out at a temperature of 60-100°C for 6-10 hours.

[0020] Furthermore, the drying temperature in step (1) is 50°C and the drying time is 8 hours.

[0021] Furthermore, the iron salt mentioned in step (2) is one or both of ferric nitrate and ferric chloride.

[0022] Furthermore, the manganese salt mentioned in step (2) is one or two of manganese chloride, manganese sulfate, and manganese acetate.

[0023] Furthermore, in step (2), the ratio of the amount of citric acid used to the total molar amount of metal elements in the iron and manganese salts is 1-2:1.

[0024] Furthermore, the temperature of the ultrasound in step (3) is 30-40℃, the power is 450-550W, the frequency is 30-50kHz, and the time is 30-60min.

[0025] Furthermore, the reaction in step (3) is carried out at a temperature of 100-140°C for 12-16 hours.

[0026] Furthermore, the heat preservation calcination described in step (4) is carried out in an air atmosphere, with the temperature increased to 300-400℃ at a rate of 5℃ / min, and calcined for 4 hours.

[0027] Further, after grinding in step (4), the material is sieved through a 100-200 mesh sieve.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) C 60 The π-electron system is highly delocalized on its three-dimensional surface, giving it excellent electron transfer capabilities and the ability to reversibly gain or lose electrons. This allows it to adjust the chemical valence and oxidizing properties of the metals in the components, thereby increasing the surface acidity and dispersibility of the catalyst, significantly improving the low-temperature activity and stability of the catalyst, and giving it excellent denitrification performance.

[0030] (2) The low-temperature denitrification catalyst provided by the present invention has a wide active temperature window and good activity and sulfur resistance in the range of 90-210℃, demonstrating excellent low-temperature denitrification performance and solving the problems of easy poisoning and deactivation and poor sulfur resistance of existing commercial catalysts.

[0031] (2) The low-temperature denitrification catalyst provided by the present invention has a simple synthesis process, low production cost, and is easy to industrialize, and has broad application prospects in the field of low-temperature flue gas denitrification. Attached Figure Description

[0032] Figure 1 C 60 Raw materials and Example 1 after pretreatment C 60 XRD pattern.

[0033] Figure 2 The image shows the NH3-TPD diagrams of the catalysts prepared in Example 1 and Comparative Example 1.

[0034] Figure 3 SEM images of the catalysts prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0035] A low-temperature denitration catalyst, the preparation of which includes the following steps:

[0036] (1) C 60 Place benzene and phenol in a three-necked flask, add C 60 A strong oxidizing agent at 12-15 times its mass was added, and the mixture was heated at 60-100℃ for 6-10 hours. The remaining liquid was transferred to a beaker and evaporated to dryness in a water bath. The residue was washed three times with anhydrous ethanol and then dried in a vacuum oven at 50℃ for 8 hours to obtain the treated C. 60 ;

[0037] (2) Prepare a mixed solution of iron salt and manganese salt, add citric acid as a complexing agent, stir and dissolve to obtain a mixed metal salt solution; wherein the molar ratio of Fe to Mn is 2:1, and the ratio of the amount of citric acid to the total molar amount of Fe and Mn is 1-2:1.

[0038] (3) Take the processed C obtained in step (1) 60 Add to the mixed metal salt solution obtained in step (2), and sonicate at 30-40℃ (power 450-550W, frequency 30-50kHz) for 30-60 minutes until C 60 After uniform dispersion, continue stirring at room temperature for 30-60 minutes, then react in an electric thermostatic drying oven at 100-140℃ for 12-16 hours to obtain a foam-like solid.

[0039] (4) Transfer the foam-like solid obtained in step (3) to a crucible, heat it to 300-400℃ at a rate of 5℃ / min in a tube furnace under air atmosphere, hold it at that temperature for 4 hours, and then let it cool naturally. After grinding, sieve it through a 100-200 mesh sieve to obtain C. 60 Doped Fe-Mn-based low-temperature denitration catalyst; the resulting catalyst contains C 60 The percentage of mass is 0.3-1.2%.

[0040] Among them, C used in step (1) 60 The purity is 99.9%, and the strong oxidant is any one of m-chloroperoxybenzoic acid, concentrated sulfuric acid, or concentrated nitric acid.

[0041] The iron salt mentioned in step (2) is one or two of ferric nitrate and ferric chloride. The manganese salt is one or two of manganese chloride, manganese sulfate, and manganese acetate.

[0042] The present invention and its embodiments are described below. This description is not restrictive, and actual embodiments are not limited thereto. In short, if those skilled in the art are inspired by this description and, without departing from the spirit of the invention, design similar structures and embodiments to this technical solution, such designs should fall within the protection scope of the present invention.

[0043] Example 1

[0044] A method for preparing a low-temperature denitration catalyst specifically includes the following steps:

[0045] (1) Take 80mg of C 60 50 mL of benzene was placed in a three-necked flask, and 1 g of m-chloroperoxybenzoic acid was added. After reacting at 80 °C for 6 h, the remaining liquid was transferred to a beaker and evaporated to dryness in a water bath. The residue was washed three times with anhydrous ethanol and then placed in a vacuum oven and dried at 50 °C for 8 h to obtain the treated C. 60 ;

[0046] (2) Weigh out appropriate amounts of ferric nitrate nonahydrate and manganese acetate tetrahydrate, dissolve them separately in 50 mL of deionized water to prepare solutions of a certain concentration, then mix the two metal salt solutions and add citric acid, and stir magnetically at room temperature until the solid dissolves to obtain a mixed metal salt solution; the molar ratio of ferric nitrate nonahydrate, manganese acetate tetrahydrate and citric acid used is 2:1:3;

[0047] (3) Weigh the C obtained from step (1). 60 Add the mixture to the mixed metal salt solution obtained in step (2), and sonicate at room temperature in an ultrasonic machine with a power of 100W for 30 minutes until C 60After being evenly dispersed in the solution, the mixture was stirred for 30 minutes at room temperature, and then placed in an electric thermostatic drying oven at 100°C for 12 hours to obtain a foam-like solid.

[0048] (4) Transfer the foam-like solid obtained in step (3) to a crucible, heat it to 300°C in a tube furnace at a rate of 5°C / min, hold it at that temperature for 3 hours, and after natural cooling, grind it and sieve it through a 100-mesh sieve to obtain 0.6wt.%C. 60 Doped Fe-Mn-based denitration catalyst.

[0049] Example 2

[0050] (1) Take 80mg of C 60 50 mL of benzene was placed in a three-necked flask, and 1 g of m-chloroperoxybenzoic acid was added. After reacting at 80 °C for 6 h, the remaining liquid was transferred to a beaker and evaporated to dryness in a water bath. The residue was washed three times with anhydrous ethanol and then placed in a vacuum oven and dried at 50 °C for 8 h to obtain the treated C. 60 ;

[0051] (2) Weigh out appropriate amounts of ferric nitrate nonahydrate and manganese acetate tetrahydrate, dissolve them separately in 50 mL of deionized water to prepare solutions of a certain concentration, then mix the two metal salt solutions and add citric acid, and stir magnetically at room temperature until the solid dissolves to obtain a mixed metal salt solution; the molar ratio of ferric nitrate nonahydrate, manganese acetate tetrahydrate and citric acid used is 2:1:3;

[0052] (3) Weigh the C obtained from step (1). 60 Add the mixture to the mixed metal salt solution obtained in step (2), and sonicate at room temperature in an ultrasonic machine with a power of 100W for 30 minutes until C 60 After being evenly dispersed in the solution, the mixture was stirred for 30 minutes at room temperature, and then placed in an electric thermostatic drying oven at 100°C for 12 hours to obtain a foam-like solid.

[0053] (4) Transfer the foam-like solid obtained in step (3) to a crucible, heat it to 300°C in a tube furnace at a rate of 5°C / min, hold it at that temperature for 3 hours, and after natural cooling, grind it and sieve it through a 100-mesh sieve to obtain 0.3wt.%C. 60 Doped Fe-Mn-based denitration catalyst.

[0054] Example 3

[0055] (1) Take 80mg of C 6050 mL of benzene was placed in a three-necked flask, and 1 g of m-chloroperoxybenzoic acid was added. After reacting at 80 °C for 6 h, the remaining liquid was transferred to a beaker and evaporated to dryness in a water bath. The residue was washed three times with anhydrous ethanol and then placed in a vacuum oven and dried at 50 °C for 8 h to obtain the treated C. 60 ;

[0056] (2) Weigh out appropriate amounts of ferric nitrate nonahydrate and manganese acetate tetrahydrate, dissolve them separately in 50 mL of deionized water to prepare solutions of a certain concentration, then mix the two metal salt solutions and add citric acid, and stir magnetically at room temperature until the solid dissolves to obtain a mixed metal salt solution; the molar ratio of ferric nitrate nonahydrate, manganese acetate tetrahydrate and citric acid used is 2:1:3;

[0057] (3) Weigh the C obtained from step (1). 60 Add the mixture to the mixed metal salt solution obtained in step (2), and sonicate at room temperature in an ultrasonic machine with a power of 100W for 30 minutes until C 60 After being evenly dispersed in the solution, the mixture was stirred for 30 minutes at room temperature, and then placed in an electric thermostatic drying oven at 100°C for 12 hours to obtain a foam-like solid.

[0058] (4) Transfer the foam-like solid obtained in step (3) to a crucible, heat it to 300°C in a tube furnace at a rate of 5°C / min, hold it at that temperature for 3 hours, and after natural cooling, grind it and sieve it through a 100-mesh sieve to obtain 1.2wt.%C. 60 Doped Fe-Mn-based denitration catalyst.

[0059] Comparative Example 1

[0060] Prepare C-free according to the procedure in Example 1 60 Doped Fe-Mn-based denitration catalyst.

[0061] Comparative Example 2

[0062] Commercial MnO2 catalyst was ground and sieved using a 100-mesh sieve.

[0063] Comparative Example 3

[0064] (1) Take 80mg of C 60 50 mL of benzene was placed in a three-necked flask, and 1 g of m-chloroperoxybenzoic acid was added. After reacting at 80 °C for 6 h, the remaining liquid was transferred to a beaker and evaporated to dryness in a water bath. The residue was washed three times with anhydrous ethanol and then placed in a vacuum oven and dried at 50 °C for 8 h to obtain the treated C. 60 ;

[0065] (2) Weigh out appropriate amounts of ferric nitrate nonahydrate and manganese acetate tetrahydrate, dissolve them separately in 50 mL of deionized water to prepare solutions of a certain concentration, then mix the two metal salt solutions and add citric acid, and stir magnetically at room temperature until the solid dissolves to obtain a mixed metal salt solution; the molar ratio of ferric nitrate nonahydrate, manganese acetate tetrahydrate and citric acid used is 2:1:3;

[0066] (3) Weigh the C obtained from step (1). 60 Add the mixture to the mixed metal salt solution obtained in step (2), and sonicate at room temperature in an ultrasonic machine with a power of 100W for 30 minutes until C 60 After being evenly dispersed in the solution, the mixture was stirred for 30 minutes at room temperature, and then placed in an electric thermostatic drying oven at 100°C for 12 hours to obtain a foam-like solid.

[0067] (4) Transfer the foam-like solid obtained in step (3) to a crucible, heat it to 300°C in a tube furnace at a rate of 5°C / min, hold it at that temperature for 3 hours, and after natural cooling, grind it and sieve it through a 100-mesh sieve to obtain 2.0 wt.% C. 60 Doped Fe-Mn-based denitration catalyst.

[0068] For the C used in Example 1 60 and C after pretreatment 60 XRD testing was performed, and the results are as follows: Figure 1 As shown in the figure. It can be seen from the figure that after preprocessing, C... 60 All diffraction peaks are related to C 60 The diffraction peaks of the raw material powder match, indicating high crystallinity and the absence of impurities.

[0069] 0.6 wt.% C prepared in Example 1 60 The NH3-TPD of the MnFe2O4 catalyst and the MnFe2O4 catalyst prepared in Comparative Example 1 are as follows: Figure 2 As shown. By Figure 2 It can be seen that 0.6wt.%C 60 The desorption peak of -MnFe2O4 is significantly broader and has a higher intensity, indicating that C 60 Doping can give the catalyst surface a greater number of acid sites with stronger acidity.

[0070] 0.6 wt.% C prepared in Example 1 60 SEM images of the MnFe2O4 catalyst and the MnFe2O4 catalyst prepared in Comparative Example 1 are shown below. Figure 3 As shown. By Figure 3 It can be seen that, compared with the undoped MnFe2O4 catalyst, 0.6wt.%C 60 The doped MnFe2O4 catalyst exhibits better dispersion.

[0071] Catalyst activity evaluation:

[0072] 1. Take 0.5g of the Fe-Mn-based catalyst prepared in the examples or comparative examples for SCR reaction. The reactor program is raised to the required temperature and kept stable. The change in NO concentration at the outlet is recorded, and the NO conversion rate is calculated. Specifically, the catalytic performance of the catalyst is evaluated using a fixed reaction bed with a diameter of 15 mm. The simulated gas composition is as follows: NO flow rate is set to 40 mL / min, NH3 flow rate is set to 40 mL / min, O2 volume ratio is 3%, and N2 is used as the balance gas; the total gas flow rate is 1000 mL / min. At 90℃, 110℃, 130℃, 150℃, 170℃, 190℃, and 210℃, a Testo flue gas analyzer is used to analyze the NO concentration at the inlet and outlet. x The concentration of NO was tested, and the effect of the catalyst on NO at different temperatures was obtained through the denitrification efficiency calculation formula. x The denitrification efficiency is shown in Table 1.

[0073] Denitrification efficiency calculation formula:

[0074] Table 1. Comparison of denitrification performance of catalysts obtained in the examples and comparative examples.

[0075]

[0076] As can be seen from Table 1, the NO content of commercial MnO2 catalysts in this temperature range... x The removal effect was very poor. When C... 60 When the doping concentration reached 2.0 wt.%, the doping failed to improve the catalytic performance of the Fe-Mn based catalyst. Only C... 60 Fe-Mn based catalysts with doping amounts of 0.3-1.2 wt.% show a significant improvement in denitrification efficiency.

[0077] 2. The sulfur resistance performance was tested at 150℃ and SO2 flow rate of 10 mL / min. The results are shown in Table 2.

[0078] Table 2 Comparison of the sulfur resistance performance of the catalysts obtained in the examples and comparative examples

[0079]

[0080] Table 2 shows that the commercial MnO2 catalyst exhibits poor sulfur resistance at 150℃. However, when C... 60 When the doping concentration reached 2.0 wt.%, the doping did not improve the sulfur resistance of the Fe-Mn based catalyst. Only C 60Fe-Mn based catalysts with doping amounts of 0.3-1.2 wt.% all showed significantly improved sulfur resistance.

[0081] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A low-temperature denitrification catalyst, characterized in that, The catalyst is a composite oxide of Fe and Mn incorporating C. 60 It is made by means of the following steps: (1) C 60 After mixing with benzene, a strong oxidizing agent is added. The mixture is heated and reacted, then the liquid is evaporated to dryness. The residue is washed three times with anhydrous ethanol and then dried to obtain the treated C. 60 ; (2) Add citric acid as a complexing agent to a mixed solution containing iron and manganese salts and stir to dissolve, thus obtaining a mixed metal salt solution; (3) Take the processed C obtained in step (1) 60 Add to the mixed metal salt solution obtained in step (2), and sonicate to C. 60 After uniform dispersion, continue stirring at room temperature for 30-60 minutes, and then react to obtain a foam-like solid; (4) The foam-like solid obtained in step (3) is calcined under heat and then naturally cooled, and then ground to obtain C. 60 Doped Fe-Mn-based low-temperature denitration catalyst.

2. The low-temperature denitrification catalyst according to claim 1, characterized in that, The catalyst has a Fe to Mn molar ratio of 2:1 and C 60 The percentage of mass is 0.3-1.2%.

3. The low-temperature denitrification catalyst according to claim 1, characterized in that, C used in step (1) 60 The purity is 99.9%.

4. The low-temperature denitrification catalyst according to claim 1, characterized in that, C used in step (1) 60 The mass ratio of the strong oxidant to the strong oxidant is 1:12-15; the strong oxidant is any one of m-chloroperoxybenzoic acid, concentrated sulfuric acid, or concentrated nitric acid.

5. The low-temperature denitrification catalyst according to claim 1, characterized in that, The heating reaction in step (1) is carried out at a temperature of 60-100℃ for 6-10 hours.

6. The low-temperature denitrification catalyst according to claim 1, characterized in that, In step (2), the ratio of the amount of citric acid used to the total molar amount of metal elements in the iron and manganese salts is 1-2:1; The iron salt is one or two of ferric nitrate and ferric chloride, and the manganese salt is one or two of manganese chloride, manganese sulfate, and manganese acetate.

7. The low-temperature denitrification catalyst according to claim 1, characterized in that, The reaction in step (3) is carried out at a temperature of 100-140℃ for 12-16 hours.

8. The low-temperature denitrification catalyst according to claim 1, characterized in that, The heat preservation calcination mentioned in step (4) is to heat to 300-400℃ at a rate of 5℃ / min in an air atmosphere and calcine for 4 hours.

9. The low-temperature denitrification catalyst according to claim 1, characterized in that, After grinding, the material is sieved through a 100-200 mesh sieve.

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