Preparation and application of Fe-Mn / NbOPO4 catalyst for improving water resistance and sulfur resistance of NH3-SCR reaction

Abstract

The invention relates to the field of nitrogen oxide treatment, and particularly provides preparation and application of a Fe-Mn / NbOPO4 catalyst for improving water resistance and sulfur resistance of NH3-SCR (selective catalytic reduction) reaction. The preparation method comprises the following steps: 1, preparation of an NbOPO4 carrier: mixing and stirring a niobium source and a phosphorus source, dropwise adding ammonia water, filtering and washing to obtain a precipitate, further adding a CTAB / H2O solution, adjusting the pH value with H3PO4, carrying out hydrothermal aging in a reaction kettle, and finally filtering, washing, drying and calcining; and 2, loading Fe and Mn active components, dissolving an iron source and a manganese source in water by adopting a wet impregnation method, adding the NbOPO4 carrier, stirring, carrying out rotary evaporation, drying and calcining. When the air speed is 60000mL. G <-1 >. H <-1 >, the NOx conversion rate in the temperature range of 75-297 DEG C reaches 90% or above, and in a water-resistant and sulfur-resistant performance test of 5vol.% H2O and 100ppm SO2, the reaction activity is almost not obviously reduced. The SCR reaction temperature window of the manganese-based catalyst is widened, the water resistance and sulfur resistance of the manganese-based catalyst are effectively improved, and the manganese-based catalyst has wide application prospects.

Description

Technical Field

[0001] This invention, which belongs to the field of nitrogen oxide treatment, relates to the preparation and application of an Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of the NH3-SCR reaction. Compared to other traditional manganese-based catalysts, the Fe-Mn / NbOPO4 catalyst has a lower reaction temperature and a wider reaction temperature window, and exhibits excellent water and sulfur resistance and cyclic stability, showing broad application prospects. Background Art

[0002] As a common air pollutant, nitrogen oxides (NO x ) will not only cause environmental problems such as acid rain, photochemical smog, and ozone layer depletion, but will also cause serious harm to the human body and cause various lung diseases. Therefore, countries around the world have issued strict pollutant emission standards to control NO x Among them, for NO emissions from stationary pollution sources x NH3-SCR technology is the most effective degradation method. It has been widely used around the world and has become one of the most promising denitrification technologies in the range of 200-600℃.

[0003] A wide range of solid catalysts are used for NH3-SCR reactions, including vanadium-, cerium-, iron-, and manganese-based metal oxide catalysts and molecular sieve catalysts primarily composed of Cu-zeolite. Mn-based catalysts, among others, exhibit excellent low-temperature SCR activity due to their numerous surface Lewis acid sites, abundant surface active oxygen species, strong redox properties, and diverse valence states. However, in actual operation, denitrification often occurs after desulfurization and dust removal. SO2 contained in the flue gas readily interacts with Mn species, producing difficult-to-remove metal sulfates, which can poison the catalyst. The poor sulfur tolerance of Mn-based catalysts severely hinders their practical application.

[0004] Studies have shown that by doping other transition metals, more acid sites are constructed and the surface acidity of the catalyst is increased, which can effectively inhibit the adsorption of SO2. For example, the doping of Gd species in MnGdO-2 ​​catalyst effectively increases the surface Mn 4+ The Sm-modified MnTiSnO y The composite oxide catalyst can increase a large number of weak acid sites, which is beneficial to the adsorption and activation of NH3, and the addition of Sm transfers electrons from Sm species to Mn species, thereby inhibiting the formation of manganese sulfate.

[0005] NbOPO4 is a new type of inorganic material with high specific surface area, high thermal stability and strong acidity, making it a promising carrier in NH3-SCR reaction. Iron oxide is a well-known active ingredient or promoter in NH3-SCR reaction, which can neutralize the redox performance of the catalyst and make MnO x Free from sulfation.

[0006] Based on this, we used a new NbOPO4 carrier to load the Mn active species and introduced Fe as a second active species for doping modification to improve the low-temperature activity and water and sulfur resistance of the manganese-based catalyst. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation and application of an Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of the NH3-SCR reaction, so as to improve the low-temperature activity of the catalyst and broaden the reaction temperature window. After cyclic stability testing, testing under different space velocity conditions and water and sulfur resistance testing, the SCR activity of the catalyst did not decrease significantly, and it has excellent stability and anti-poisoning ability.

[0008] Here, the preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction described in the present invention, the catalyst includes an active component and a carrier, and the components and contents thereof are respectively:

[0009] Fe-Mn active component: molar ratio Fe / Mn = 0.1-1.0, total mass percentage 20%-30%;

[0010] NbOPO4 carrier: mass percentage is 70% to 80%.

[0011] The present invention discloses the preparation and application of an Fe-Mn / NbOPO4 catalyst for improving water and sulfur resistance in NH3-SCR reactions. The NbOPO4 carrier is prepared using the following method: 2.5-3.0 g of NbCl5 is dissolved in 40-50 mL of deionized water (Solution A), and 2.0-2.5 g of H3PO4 (85%) is dissolved in 40-50 mL of deionized water (Solution B). Solution B is added dropwise to Solution A and stirred for 30-60 minutes. A sufficient amount of NH4OH (pH = 12.9, 27 wt.%) is then added, stirred for 5-10 minutes, and filtered for washing. The resulting solid mixture is then added to CTAB / H2O and stirred for 30-60 minutes. The pH is adjusted to 3.7-4.5 with phosphoric acid and stirred for a further 30-60 minutes. The mixed solution is then added to a polytetrafluoroethylene liner, placed in an autoclave, and hydroheated at 140-180°C for 40-60 hours. The product was taken out, washed with deionized water, dried for 8 to 12 hours, and finally calcined at 500 to 650° C. for 4 to 8 hours with a heating rate of 1 to 2° C. / min.

[0012] The present invention discloses the preparation and application of an Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reactions. The Fe-Mn / NbOPO4 catalyst is prepared using an excess impregnation method. Specifically, Fe(NO3)3·9H2O and a 50wt.% Mn(NO3)2 solution are mixed, diluted with an appropriate amount of deionized water, and a prepared NbOPO4 carrier is added. The mixture is stirred at room temperature for 8 to 15 hours, then rotary evaporated at 60 to 80°C, dried for 8 to 12 hours, and finally calcined in an air atmosphere at 400 to 600°C for 4 to 8 hours at a heating rate of 1 to 2°C / min.

[0013] The preparation and application of the Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of the NH3-SCR reaction described in the present invention include using 100 mg of the catalyst with a mesh size of 40 to 60 to carry out the NH3-SCR reaction. The specific reaction conditions are: 300 to 500 ppm NO, 300 to 500 ppm NH3, 5 to 8 vol.% O2, argon as a balance gas, a gas flow rate of 100 to 300 mL / min, and a reaction space velocity of 60,000 to 180,000 mL·g -1 ·h -1 .

[0014] The preparation and application of the Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of the NH3-SCR reaction described in the present invention is characterized in that, on the basis of the NH3-SCR reaction atmosphere, 5-10 vol.% H2O and 50-200 ppm SO2 are additionally introduced for testing the water and sulfur resistance of the Fe-Mn / NbOPO4 catalyst.

[0015] The dual Fe-Mn active centers in the Fe-Mn / NbOPO4 catalyst described herein effectively enhance the catalyst's redox performance, promoting O2 activation and NO2 generation, thereby facilitating the fast-SCR reaction. Furthermore, the abundant acidic sites on the NbOPO4 support surface facilitate activation of NH3 species and significantly inhibit SO2 adsorption, effectively preventing the deposition of metal sulfates.

[0016] One of the significant advantages of the present invention is that the most preferred Fe3-Mn7 / NbOPO4 catalyst has excellent SCR activity, T 90 It is only 75℃ and can still maintain 90% NO at 297℃ x Conversion rate.

[0017] The second significant advantage of the present invention is that the most preferred Fe3-Mn7 / NbOPO4 catalyst has excellent cyclic stability and water and sulfur resistance, and its activity does not decrease significantly after 5 cycles and water and sulfur resistance tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Effect of different Fe / Mn molar ratios on the NH3-SCR activity of Fe-Mn / NbOPO4 catalysts;

[0019] Figure 2 The effect of Fe3-Mn7 loaded on different carriers on NH3-SCR activity;

[0020] Figure 3 The effect of reaction times on the NH3-SCR activity of Fe3-Mn7 / NbOPO4 catalyst;

[0021] Figure 4 The effect of different volumetric space velocities on the NH3-SCR activity of Fe3-Mn7 / NbOPO4 catalyst;

[0022] Figure 5 The figure shows the comparison of water and sulfur resistance of Fe3-Mn7 / NbOPO4, Fe3-Mn7 / Al2O3 and Fe3-Mn7 / TiO2 catalysts. Specific implementation plan

[0023] The present invention will be described in detail below with reference to specific embodiments, but this does not limit the scope of protection of the present invention.

[0024] Example 1:

[0025] Preparation of NbOPO4 carrier: Dissolve 2.73g NbCl5 in 50mL deionized water as solution A, and dissolve 2.3g H3PO4 (85%) in 50mL deionized water as solution B. Add solution B dropwise to solution A and stir for 30min. Then, add sufficient NH4OH (pH=12.9, 27wt.%) and stir for 5min, filter and wash. Then add the obtained solid mixture to 2.90g CTAB / 20mL H2O and stir for 30min. Adjust the pH to 4 with phosphoric acid and stir for another 30min. Add the mixed solution to a polytetrafluoroethylene liner, place it in a high-pressure reactor, and hydroheat it at 160℃ for 48h. Take it out, wash it with deionized water, dry it for 12h, and finally calcine it at 550℃ for 6h with a heating rate of 1℃ / min.

[0026] Example 2:

[0027] Fe 0.5 -Mn 9.5 Preparation of / NbOPO4 catalyst: 0.20g Fe(NO3)3·9H2O and 3.40g 50wt.% Mn(NO3)2 solution were mixed, diluted with 30mL deionized water, and 2.20g NbOPO4 carrier in Example 1 was added. The mixture was stirred at room temperature for 10h, then the mixture was rotary evaporated at 60℃, dried for 12h, and finally calcined in air atmosphere at 400℃ for 4h with a heating rate of 1℃ / min.

[0028] Example 3:

[0029] Preparation of Fe1-Mn9 / NbOPO4 catalyst: Mix 0.40g Fe(NO3)3·9H2O and 3.22g 50wt.% Mn(NO3)2 solution, add 30mL deionized water to dilute, and add 2.20g NbOPO4 carrier in Example 1. Stir at room temperature for 10h, then rotary evaporate the mixture at 60℃, dry for 12h, and finally calcine at 400℃ in air atmosphere for 4h, with a heating rate of 1℃ / min.

[0030] Example 4:

[0031] Preparation of Fe3-Mn7 / NbOPO4 catalyst: 1.21 g of Fe(NO3)3·9H2O and 2.51 g of 50 wt.% Mn(NO3)2 solution were mixed, diluted with 30 mL of deionized water, and 2.21 g of the NbOPO4 carrier in Example 1 were added. The mixture was stirred at room temperature for 10 h, then the mixture was rotary evaporated at 60°C, dried for 12 h, and finally calcined in an air atmosphere at 400°C for 4 h with a heating rate of 1°C / min.

[0032] Example 5:

[0033] Preparation of Fe5-Mn5 / NbOPO4 catalyst: Mix 2.02g of Fe(NO3)3·9H2O and 1.79g of 50wt.% Mn(NO3)2 solution, add 30mL of deionized water to dilute, and add 2.22g of the NbOPO4 carrier in Example 1. Stir at room temperature for 10h, then rotary evaporate the mixture at 60℃, dry for 12h, and finally calcine at 400℃ in air atmosphere for 4h with a heating rate of 1℃ / min.

[0034] Example 6:

[0035] Preparation of Fe7-Mn3 / NbOPO4 catalyst: Mix 2.83g of Fe(NO3)3·9H2O and 1.07g of 50wt.% Mn(NO3)2 solution, add 30mL of deionized water to dilute, and add 2.23g of the NbOPO4 carrier in Example 1. Stir at room temperature for 10h, then rotary evaporate the mixture at 60℃, dry for 12h, and finally calcine at 400℃ in air atmosphere for 4h with a heating rate of 1℃ / min.

[0036] Example 7:

[0037] Preparation of Fe9-Mn1 / NbOPO4 catalyst: 3.64g Fe(NO3)3·9H2O and 0.36g 50wt.% Mn(NO3)2 solution were mixed, diluted with 30mL deionized water, and 2.24g NbOPO4 carrier in Example 1 was added. The mixture was stirred at room temperature for 10h, then rotary evaporated at 60°C, dried for 12h, and finally calcined in air atmosphere at 400°C for 4h with a heating rate of 1°C / min.

[0038] Example 8:

[0039] Fe 9.5 -Mn 0.5 Preparation of / NbOPO4 catalyst: 3.84g Fe(NO3)3·9H2O and 0.18g 50wt.% Mn(NO3)2 solution were mixed, diluted with 30mL deionized water, and 2.24g NbOPO4 carrier in Example 1 was added. The mixture was stirred at room temperature for 10h, then rotary evaporated at 60℃, dried for 12h, and finally calcined in air atmosphere at 400℃ for 4h with a heating rate of 1℃ / min.

[0040] Example 9:

[0041] Preparation of Fe3-Mn7 / Al2O3 catalyst: Mix 1.21g Fe(NO3)3·9H2O and 2.51g 50wt.% Mn(NO3)2 solution, add 30mL deionized water to dilute, and add 2.21g Al2O3 carrier. Stir at room temperature for 10h, then rotary evaporate the mixture at 60℃, dry for 12h, and finally calcine at 400℃ in air atmosphere for 4h, with a heating rate of 1℃ / min.

[0042] Example 10:

[0043] Preparation of Fe3-Mn7 / TiO2 catalyst: Mix 1.21g Fe(NO3)3·9H2O and 2.51g 50wt.% Mn(NO3)2 solution, add 30mL deionized water to dilute, and add 2.21g TiO2 carrier, stir at room temperature for 10h, then rotary evaporate the mixture at 60℃, dry for 12h, and finally calcine at 400℃ in air atmosphere for 4h, with a heating rate of 1℃ / min.

[0044] Application Example 1:

[0045] The catalysts in Examples 2 to 10 were tested for NH3-SCR activity. The test conditions were as follows: 100 mg (40-60 mesh) of catalyst was weighed and placed in a fixed-bed quartz reactor. The reaction gas composition was 500 ppm NO, 500 ppm NH3, and 5 vol.% O2. Argon was used as the balance gas. The flow rates of the gases were controlled by mass flow controllers. The total gas flow rate was 100 mL / min, and the reaction volume space velocity was 60,000 mL·g -1 ·h -1 The gas is passed into the mixing tank for mixing, and the excess NH3 and water vapor are removed by concentrated phosphoric acid and anhydrous calcium chloride. The temperature is controlled by a temperature controller with a K-type thermocouple. The tail gas after the reaction is tested by a nitrogen oxide analyzer for NO x concentration.

[0046] NO of the catalyst x The conversion rate calculation formula is as follows:

[0047]

[0048] Among them, C(NO x ) in and C(NO x ) out NO x The inlet and outlet concentrations.

[0049] Effect of different Fe / Mn molar ratios on the NH3-SCR activity of Fe-Mn / NbOPO4 catalysts Figure 1As shown in Figure 2, with the increase of Fe / Mn molar ratio, T 90 The conversion temperature window gradually widens and then narrows, with an inflection point at Fe:Mn=3:7, indicating that the Fe3-Mn7 / NbOPO4 catalyst is the optimal ratio.

[0050] After that, the Fe3-Mn7 ratio was kept constant and the effects of different supports on the NH3-SCR activity were compared. Figure 2 Compared with the traditional metal oxides Al2O3 and TiO2, Fe3-Mn7 / NbOPO4 catalyst has better low temperature activity and wider reaction temperature window, with NO x The conversion rate is over 90%.

[0051] Application Example 2:

[0052] The number of reactions of the Fe3-Mn7 / NbOPO4 catalyst was changed to 1, 2, 3, 4, and 5 reactions respectively. The performance evaluation conditions of the Fe3-Mn7 / NbOPO4 catalyst were the same as those in Application Example 1.

[0053] Effect of reaction times on NH3-SCR activity of Fe3-Mn7 / NbOPO4 catalyst Figure 3 As shown. Figure 3 It can be seen that as the number of reactions increases, the activity curves of the Fe3-Mn7 / NbOPO4 catalyst almost overlap, indicating that the Fe3-Mn7 / NbOPO4 catalyst has excellent cyclic stability.

[0054] Application Example 3

[0055] Only the total gas flow rate in Application Example 1 was changed to 50, 200 and 300 mL / min to explore the Fe3-Mn7 / NbOPO4 catalyst at volume space velocities of 30000, 120000 and 180000 mL·g -1 ·h -1 NH3-SCR reaction performance under NH3-SCR reaction conditions.

[0056] Effects of different volumetric space velocities on the NH3-SCR activity of Fe3-Mn7 / NbOPO4 catalysts Figure 4 As shown. Figure 4 It can be seen that with the increase of volume space velocity, the activity curve of Fe3-Mn7 / NbOPO4 catalyst only has a slight decrease in the low temperature zone, indicating that the increase of space velocity has little effect on the activity of Fe3-Mn7 / NbOPO4 catalyst.

[0057] Application Example 4

[0058] The reaction conditions of the Fe3-Mn7 / NbOPO4 catalyst were changed to additionally introduce 5 vol.% H2O and / or 100 ppm SO2 into the reaction atmosphere, and the reaction temperature was kept constant at 180°C. Other conditions were the same as those in Application Example 1 to compare the water and sulfur resistance of the catalysts in Examples 4, 9, and 10.

[0059] Comparison of water and sulfur resistance of Fe3-Mn7 / NbOPO4, Fe3-Mn7 / Al2O3 and Fe3-Mn7 / TiO2 catalysts Figure 5 The activity of Fe3-Mn7 / Al2O3 and Fe3-Mn7 / TiO2 catalysts decreased rapidly, while Fe3-Mn7 / NbOPO4 catalyst showed excellent anti-sulfur stability, NO x The conversion rate was maintained at 90% for up to 10 hours. Once the H2O was stopped, the activity of the three catalysts was partially restored, but the presence of SO2 still caused the activity of Fe3-Mn7 / Al2O3 and Fe3-Mn7 / TiO2 catalysts to gradually decrease. In contrast, the NO conversion of Fe3-Mn7 / NbOPO4 catalyst was x The conversion rate remained stable at 92% for 10 hours without any downward trend. Subsequently, when the addition of SO₂ and H₂O was stopped, the activity of the Fe₃-Mnₐ / NbOPO₄ catalyst was largely restored, while the activity of the Fe₃-Mnₐ / Al₂O₃ and Fe₃-Mnₐ / TiO₂ catalysts decreased significantly, indicating that the Fe₃-Mnₐ / NbOPO₄ catalyst has excellent water and sulfur resistance.

[0060] In summary, the present invention provides a preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction. -1 ·h -1 When Fe3-Mn7 / NbOPO4 catalyst is in the temperature range of 75~297℃, NO x The conversion rate is over 90%, and in the water and sulfur resistance test of 5 vol.% H2O and 100 ppm SO2, the reaction activity has almost no significant decrease, showing excellent water and sulfur resistance stability.

[0061] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. Preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction, characterized in that: The catalyst includes an active component and a carrier, and its components and contents are as follows: Fe-Mn active component: molar ratio Fe / Mn = 0.1-1.0, total mass percentage 20%-30%; NbOPO4 carrier: mass percentage is 70% to 80%.

2. The preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction according to claim 1, characterized in that: The NbOPO4 carrier is prepared by the following method. 2.5-3.0 g NbCl5 is dissolved in 40-50 mL deionized water and recorded as liquid A. 2.0-2.5 g H3PO4 (85%) is dissolved in 40-50 mL deionized water and recorded as liquid B. Liquid B is added dropwise to liquid A and stirred for 30-60 min. Afterwards, sufficient NH4OH (pH=12.9, 27 wt.%) is added and stirred for 5-10 min, filtered and washed. The obtained solid mixture is then added to CTAB / H2O and stirred for 30-60 min. Adjust the pH to 3.7-4.5 with phosphoric acid and further stir for 30-60 min. The mixed solution is added to a polytetrafluoroethylene liner, placed in a high-pressure reactor, and hydroheated at 140-180°C for 40-60 h. The product was taken out, washed with deionized water, dried for 8 to 12 hours, and finally calcined at 500 to 650° C. for 4 to 8 hours with a heating rate of 1 to 2° C. / min.

3. The preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction according to claims 1-2, characterized in that: The Fe-Mn / NbOPO4 catalyst is prepared using an excess impregnation method. Specifically, Fe(NO3)3·9H2O and a 50wt.% Mn(NO3)2 solution are mixed, diluted with an appropriate amount of deionized water, and the prepared NbOPO4 carrier is added. The mixture is stirred at room temperature for 8 to 15 hours, then rotary evaporated at 60 to 80°C, dried for 8 to 12 hours, and finally calcined in an air atmosphere at 400 to 600°C for 4 to 8 hours, with a heating rate of 1 to 2°C / min.

4. The preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction according to claim 1, characterized in that: The NH3-SCR reaction was carried out using 100 mg of 40-60 mesh catalyst. The specific reaction conditions were: 300-500 ppm NO, 300-500 ppm NH3, 5-8 vol.% O2, argon as the balance gas, a gas flow rate of 100-300 mL / min, and a reaction space velocity of 60,000-180,000 mL·g -1 ·h -1 .

5. The preparation and application of a Fe-Mn / NbOPO4 catalyst for improving the water and sulfur resistance of NH3-SCR reaction according to claims 1 and 4, characterized in that: On the basis of claim 4, 5-10 vol.% H2O and 50-200 ppm SO2 are additionally introduced to test the water and sulfur resistance of the Fe-Mn / NbOPO4 catalyst.

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