Treatment method for improving NH3-SCR catalytic performance of iron-containing molecular sieve

Abstract

The invention discloses a treatment method for improving NH3-SCR (selective catalytic reduction) catalytic performance of an iron-containing molecular sieve, which is characterized in that the catalytic activity of the molecular sieve is further improved after the iron-containing molecular sieve is subjected to high-temperature steam treatment. The obtained molecular sieve has excellent NH3-SCR performance, the catalytic activity of the iron-containing molecular sieve is improved, the operation is simple, and the application value of the iron-containing molecular sieve in the field of NH3-SCR is greatly improved.

Description

Technical Field

[0001] The invention relates to a treatment method for improving the NH3-SCR catalytic performance of an iron-containing molecular sieve, and in particular to a method for improving the NH3-SCR catalytic performance of an iron-containing molecular sieve by using high-temperature steam treatment, and belongs to the technical field of molecular sieve preparation. Background Art

[0002] Nitrogen oxides are a common air pollutant, and its composition mainly includes NO, NO2 and N2O. The presence of nitrogen oxides not only seriously endangers human health, but also causes acid rain, photochemical smog, etc. The main sources of nitrogen oxides include mobile sources and fixed sources. Nitrogen oxides produced by fixed sources mainly come from emissions from power stations, industrial heaters, etc. Nitrogen oxides produced by mobile sources mainly come from the exhaust gas of gasoline and diesel engines. With my country's increasing attention to nitrogen oxide pollution and the increasing improvement of emission standards, reducing nitrogen oxide emissions has become an urgent matter.

[0003] Ammonia selective catalytic reduction technology is widely used as a mature denitrification technology. NH3-SCR technology refers to the use of a reducing agent to selectively reduce nitrogen oxides in flue gas under the action of a catalyst to obtain nitrogen and water.

[0004] Molecular sieves have become a hot topic in the research of NH3-SCR catalysts due to their unique pore structure and abundant acid sites. Metal-modified molecular sieves not only have good denitrification performance, but also have a wide activity window and better thermal stability. Iron-containing molecular sieves are one of the most studied metal-modified molecular sieves in recent years. Compared with vanadium-titanium-based catalysts, iron-containing molecular sieves have no biological toxicity and are safer.

[0005] FER is a layered medium-pore molecular sieve with two vertically intersecting pores of eight-membered rings and ten-membered rings. FER zeolite has a unique pore structure and excellent catalytic performance, and is one of the best catalysts for high-temperature N2O decomposition reactions.

[0006] Patent CN 114345402A introduces a method for preparing iron-containing molecular sieves. It uses MWW molecular sieves as seed crystals and prepares Fe / FER through a one-pot hydrothermal method. The Fe / FER prepared by this method has good catalytic activity in the NH3-SCR catalytic reaction, but the crystallization of the molecular sieve in the one-pot hydrothermal preparation process takes seven days, and the preparation cycle is too long.

[0007] In addition to the one-pot method, the method for preparing iron-containing molecular sieves also includes post-treatment methods (equal volume impregnation, mechanical mixing, and solid-state ion exchange). The post-treatment method refers to first synthesizing the parent molecular sieve by a hydrothermal method, and then loading the metal on it by other methods. The crystallization time of the parent molecular sieve is relatively short, about 2-3 days. Therefore, the cycle of preparing molecular sieves by the post-treatment method is shorter than that of the one-pot method. However, there is literature evidence (2017, 9(10): 1754-1757) that the catalytic performance of the iron-containing molecular sieve Fe-SSZ-39 prepared by the post-treatment method in the NH3-SCR field is not as good as that of the one-pot method.

[0008] Therefore, it is very necessary to develop a simple and easy-to-operate method to improve the NH3-SCR catalytic performance of iron-containing molecular sieves. Summary of the invention

[0009] In view of the fact that the catalytic performance of existing iron-containing molecular sieves needs to be improved, the present invention provides a method for improving the catalytic performance of iron-containing molecular sieves. The method subjects the prepared iron-containing molecular sieve to high-temperature water vapor treatment, thereby effectively improving the catalytic activity of the iron-containing molecular sieve and giving it a better application prospect.

[0010] In order to solve the above technical problems, the present invention provides a treatment method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR, comprising the following steps:

[0011] (1) using a hydrothermal method, an aluminum source, an iron source, a silicon source, a template agent ethylene glycol, water, and an alkali source are mixed in a ratio (molar ratio) of SiO2:Na2O:Al2O3:EG:H2O=0.7-1.5:0.10-0.20:0.025-0.033:5-10:10-20, preferably, a ratio (molar ratio) of SiO2:Na2O:Al2O3:EG:H2O=1:0.12:0.033:7:15; after aging, the mixture is placed in a homogeneous reactor and crystallized at 180°C for 48 hours to obtain a precursor, which is then washed, calcined, exchanged with ammonium nitrate, and deammonized to obtain a parent molecular sieve, which is denoted as Hy;

[0012] (2) After grinding ferric nitrate nonahydrate, the parent molecular sieve Hy is added and then ground again, the iron content is 2 to 6 wt %, preferably 5 wt %, and the iron-containing molecular sieve is obtained after calcination, which is recorded as MM-Fe / y;

[0013] (3) Mixing a parent molecular sieve Hy, ferric nitrate nonahydrate and n-hexane, wherein the iron content of the mixture is 2 to 6 wt %, preferably 5 wt %, and the ratio of the parent molecular sieve Hy to n-hexane is 0.01:0.02, stirring and then rotary evaporating to dryness, and calcining to obtain an iron-containing molecular sieve, which is recorded as SSIE-Fe / y;

[0014] (4) adding the parent molecular sieve Hy to a ferric nitrate solution with an iron content of 2 to 6 wt %, preferably 5 wt %, ultrasonically and stirred, dried, and calcined at high temperature to obtain an iron-containing molecular sieve, which is recorded as IM-Fe / y;

[0015] (5) Treat the iron-containing molecular sieve with high-temperature steam. Place it in a tubular furnace, introduce flowing N2 into the tubular furnace, and heat it to a certain temperature in the N2 atmosphere. After keeping the temperature in the water-containing N2 atmosphere for a certain period of time, a molecular sieve treated with high-temperature steam is obtained.

[0016] As a preferred embodiment of the above technical solution, a treatment method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR provided by the present invention further includes some or all of the following technical features:

[0017] As an improvement of the above technical solution, the ratio of the aluminum source, iron source, silicon source, template agent ethylene glycol, water, and alkali source in step (1) is SiO2:Na2O:Al2O3:EG:H2O=1:0.12:0.025-0.033:7:15; wherein the molar ratio z of Si / Al is 15-20.

[0018] As an improvement of the above technical solution, the molecular sieve type y in the molecular sieve described in step (1) is FER or MWW, preferably FER.

[0019] As an improvement of the above technical solution, the number of high-temperature treatment times m in step (5) is 1-3; the high-temperature treatment is high-temperature steam treatment, specifically, heating to a certain temperature under N2 atmosphere, and keeping warm for a certain time under N2 atmosphere containing water; after the high-temperature treatment in step (5), passing through a 40-60 mesh molecular sieve.

[0020] As an improvement of the above technical solution, the molecular sieve treated with high-temperature steam in step (5) needs to be fixed in the middle of a quartz tube, separated on both sides by quartz wool and quartz sand, respectively, and heated to 750°C in a tubular furnace at a heating rate of 10°C / min, the nitrogen atmosphere is selected with a nitrogen flow rate of 100ml / min, and the method of introducing water vapor is bubbling.

[0021] As an improvement of the above technical solution, the volume content of water obtained by the bubbling method is 10%, and the water vapor content is controlled by water bath heating. The water bath heating temperature is 48° C. and the water vapor content is about 10%.

[0022] A kind of iron-containing molecular sieve NH3-SCR, the general formula of the iron-containing molecular sieve NH3-SCR is x-Fe / yz-mA, abbreviated as x-Fe / yz-mA; wherein x is the iron introduction method, y is the molecular sieve type, z is the Si / Al molar ratio of the molecular sieve, A represents high-temperature steam treatment, and m represents the number of high-temperature steam treatments. The iron-containing molecular sieve NH3-SCR is prepared by any of the above methods.

[0023] The iron introduction method x includes mechanical mixing, solid-state ion exchange method, and equal volume impregnation, preferably mechanical mixing; the parent molecular sieve type y in the molecular sieve is FER, MWW, preferably FER; the high temperature treatment times m is 1-3.

[0024] An application of any of the above iron-containing molecular sieve NH3-SCR catalysts, wherein the catalyst is used for selective catalytic reduction of nitrogen oxides by ammonia. The NH3-SCR performance of the catalyst is improved within the range of 100-550°C.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: the high-temperature steam treatment method of the present invention is simple and easy to operate, and the treated iron-containing molecular sieve has improved NH3-SCR catalytic activity compared with the untreated molecular sieve, and at the same time, the activity window is wider, and the overall activity is improved in the range of 100-550°C.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in combination with the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0028] Figure 1 The catalytic activity comparison diagram of the iron-containing FER molecular sieve catalysts with different silicon-aluminum molar ratios prepared by the equal volume impregnation method before and after high-temperature steam treatment in the NH3-SCR reaction of the present invention is shown; wherein: IM-Fe / FER-15 and IM-Fe / FER-20 represent catalyst samples with silicon-aluminum molar ratios of 15 and 20, respectively, and a molecular sieve structure of FER;

[0029] Figure 2 The catalytic activity comparison diagram of catalysts of different molecular sieves prepared by equal volume impregnation before and after high-temperature steam treatment in the present invention in the NH3-SCR reaction; wherein IM-Fe / FER-20 and IM-Fe / MWW-20 represent catalyst samples with a silicon-aluminum molar ratio of 20 and molecular sieve structures of FER and MWW, respectively;

[0030] Figure 3 The catalytic activity comparison diagram of the iron-containing FER molecular sieve catalyst in the NH3-SCR reaction after IM-Fe / FER-15 was treated with high-temperature steam for multiple times, wherein: IM-Fe / FER-15-A, IM-Fe / FER-15-2A, IM-Fe / FER-15-3A represent the catalyst samples obtained after IM-Fe / FER-15 was treated with high-temperature steam for one, two, and three times, respectively (15 represents the silicon-aluminum molar ratio in the molecular sieve is 15);

[0031] Figure 4 The catalytic activity diagram of the iron-containing FER molecular sieve prepared by mechanical mixing in the present invention before and after high-temperature steam treatment in the NH3-SCR reaction. Among them: MM-Fe / FER-15 represents the iron-containing FER molecular sieve of the present invention prepared by mechanical mixing, with a silicon-aluminum molar ratio of 15; MM-Fe / FER-15-A represents the iron-containing FER molecular sieve prepared by mechanical mixing and treated with high-temperature steam, with a silicon-aluminum molar ratio of 15;

[0032] Figure 5 The catalytic activity diagram of the iron-containing FER molecular sieve in the NH3-SCR reaction before and after high-temperature steam treatment by the solid-state ion exchange method of the present invention. Among them: SSIE-Fe / FER-15 represents the iron-containing FER molecular sieve of the present invention using the solid-state ion exchange method, and the silicon-aluminum molar ratio is 15; SSIE-Fe / FER-15-A represents the iron-containing FER molecular sieve prepared by the solid-state ion exchange method after high-temperature steam treatment, and the silicon-aluminum molar ratio is 15;

[0033] Figure 6 The figure is a comparison of the catalytic activities in the NH3-SCR reaction of different Fe / FER-15 catalysts treated with high-temperature steam, wherein MM-Fe / FER-15-A, IM-Fe / FER-15-A, and SSIE-Fe / FER-15-A represent the iron-containing FER molecular sieves treated with high-temperature steam prepared by mechanical mixing, equal volume impregnation, and solid-state ion exchange, respectively; OP-Fe / FER-15 represents the iron-containing FER molecular sieve prepared by the one-pot method described in the present invention (15 represents the silicon-aluminum molar ratio of the molecular sieve is 15). DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are described in detail below. As a part of this specification, the principles of the present invention are explained by examples, and other aspects, features and advantages of the present invention will become clear through this detailed description. The following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present application belongs.

[0035] Unless otherwise specified, the units of water vapor content in the following examples are all volume percentages.

[0036] Example 1

[0037] 1.84 g of ferric nitrate nonahydrate and 5 g of an H-FER molecular sieve carrier with Si / Al=15 were weighed, and according to the measured water absorption rate of the molecular sieve (the measured water absorption rate of the H-FER molecular sieve was 3.56 g / g molecular sieve), a certain amount of pure water and ferric nitrate nonahydrate were taken to prepare a ferric nitrate solution, and then the two were mixed, ultrasonically shaken for 20 minutes, and then magnetically stirred at room temperature for 24 hours, and then dried at 110° C. in a forced air drying oven overnight, and then calcined at 550° C. in a muffle furnace for 6 hours to obtain an iron-containing FER catalyst with a silicon-aluminum molar ratio of 15. The sample was marked as IM-Fe / FER-15.

[0038] Example 2

[0039] Weigh 2.37 g of ferric nitrate nonahydrate and 6.58 g of H-FER molecular sieve with Si / AI=20, and according to the measured water absorption (the water absorption of H-FER is 2.80 g / g molecular sieve), take a certain amount of pure water and ferric nitrate nonahydrate to prepare a ferric nitrate solution, then mix the two, ultrasonically vibrate for 20 minutes, and then magnetically stir at room temperature for 24 hours, then transfer to a drying oven to dry at 100°C overnight, and finally calcine in a muffle furnace at 550°C for 6 hours to obtain an iron-containing FER catalyst with a silicon-aluminum molar ratio of 20. The sample is marked as IM-Fe / FER-20 molecular sieve.

[0040] Example 3

[0041] Weigh 1.73 g of ferric nitrate nonahydrate and 4.79 g of H-MWW molecular sieve with Si / AI=20. According to the measured water absorption (the water absorption of H-MWW is 3.62 g / g molecular sieve), take a certain amount of pure water and ferric nitrate nonahydrate to prepare a ferric nitrate solution, then mix the two, ultrasonically vibrate for 20 minutes, and then magnetically stir at room temperature for 24 hours. Then transfer it to a drying oven and dry it at 100°C overnight. Finally, calcine it in a muffle furnace at 550°C for 6 hours to obtain an iron-containing MWW catalyst with a silicon-aluminum molar ratio of 20. The sample is marked as IM-Fe / MWW-20.

[0042] Example 4

[0043] 1.84 g of ferric nitrate nonahydrate was taken into a mortar and ground for 10 min. Then, 5 g of H-FER molecular sieve with Si / A1=15 was added and grinding was continued for about 15 min until the mixture was evenly mixed without any granular feeling. The evenly mixed catalyst was calcined at 550° C. in a muffle furnace for 6 hours to obtain an iron-containing FER catalyst with a silicon-aluminum molar ratio of 15. The sample was labeled MM-Fe / FER-15.

[0044] Example 5

[0045] 1.84 g of ferric nitrate nonahydrate and 5 g of H-FER molecular sieve with Si / AI=15 were placed in a 500 ml round-bottom flask, 300 ml of n-hexane was added, and the mixture was vigorously stirred for 3 h with a mechanical stirrer to mix evenly. The suspension was then rotary evaporated to dryness at 60°C on a vacuum rotary evaporator, and then taken out and ground. The mixture was calcined at 550°C in a muffle furnace for 6 hours to obtain an iron-containing FER catalyst with a silicon-aluminum molar ratio of 15. The sample was labeled SSIE-Fe / FER-15.

[0046] High temperature steam treatment (1)

[0047] Take a certain amount of 40-60 mesh iron-containing molecular sieve IM-Fe / FER-15 prepared in Example 1 for high-temperature steam treatment, fix it in the middle of a quartz tube, separate it on both sides with quartz wool and quartz sand, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750℃ at a rate of 10℃ / min in N2 atmosphere. Then, let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, keep it warm for 16h in a water-containing N2 atmosphere, and obtain IM-Fe / FER-15-A catalyst treated with high-temperature steam.

[0048] High temperature steam treatment (2)

[0049] Take a certain amount of 40-60 mesh iron-containing molecular sieve IM-Fe / FER-20 prepared in Example 2 for high-temperature steam treatment, fix it in the middle of a quartz tube, separate it on both sides with quartz wool and quartz sand, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750℃ at a rate of 10℃ / min in N2 atmosphere. Then, let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, keep it warm for 16h in a water-containing N2 atmosphere, and obtain IM-Fe / FER-20-A catalyst treated with high-temperature steam.

[0050] High temperature steam treatment (3)

[0051] Take a certain amount of 40-60 mesh iron-containing molecular sieve IM-Fe / MWW-20 prepared in Example 3 for high-temperature steam treatment, fix it in the middle of a quartz tube, separate it with quartz wool and quartz sand on both sides, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750°C at a rate of 10°C / min under N2 atmosphere. Then, let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, and keep it warm for 16h under the water-containing N2 atmosphere to obtain the IM-Fe / MWW-20-A catalyst treated with high-temperature steam.

[0052] High temperature steam treatment (4)

[0053] Take a certain amount of 40-60 mesh iron-containing molecular sieve MM-Fe / FER-15 prepared in Example 4 for high-temperature steam treatment, fix it in the middle of a quartz tube, separate it on both sides with quartz wool and quartz sand, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750℃ at a rate of 10℃ / min in N2 atmosphere. Then, let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, keep it warm for 16h in a water-containing N2 atmosphere, and obtain a high-temperature steam-treated MM-Fe / FER-15-A catalyst.

[0054] High temperature steam treatment (5)

[0055] Take a certain amount of 40-60 mesh iron-containing molecular sieve SSIE-Fe / FER-15 prepared in Example 5 for high-temperature steam treatment, fix it in the middle of a quartz tube, separate it on both sides with quartz wool and quartz sand, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750℃ at a rate of 10℃ / min in N2 atmosphere. Then, let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, keep it warm for 16h in a water-containing N2 atmosphere, and obtain a SSIE-Fe / FER-15-A catalyst treated with high-temperature steam.

[0056] High temperature steam treatment (6)

[0057] Take a certain amount of 40-60 mesh iron-containing molecular sieve IM-Fe / FER-15 prepared in Example 1 and treat it with high-temperature steam for multiple times. Fix it in the middle of a quartz tube, separate it with quartz wool and quartz sand on both sides, and put it into a tubular furnace. Put it in a tubular furnace, introduce flowing N2 into the tubular furnace, the N2 flow rate is 100ml / min, and heat the tubular furnace to 750℃ at a rate of 10℃ / min in a N2 atmosphere. Then let N2 pass through an iron tank with water before passing into the tubular furnace, and make N2 contain water by bubbling method, the volume content of water is 10%, keep it warm for 16h in a water-containing N2 atmosphere, and obtain a high-temperature steam-treated IM-Fe / FER-A catalyst. Repeat the above steps to obtain a high-temperature steam-treated IM-Fe / FER-2A catalyst. Repeat the high-temperature steam treatment three times to obtain an IM-Fe / FER-3A catalyst.

[0058] Comparative Example 1

[0059] An iron-containing FER molecular sieve with a silicon-aluminum molar ratio of 20 was prepared by a one-pot hydrothermal method. Take 71g of distilled water, add 1.3g of NaOH, 0.6g of sodium aluminate, 14.8g of silica sol, and 2.0g of ferric nitrate, mix them together, stir them magnetically for 1h, add HMI, add 3wt% MWW seeds to the synthetic gel, and continue stirring and aging for 4h. The obtained gel was added to a reactor with a polytetrafluoroethylene liner and rotated and crystallized at 170°C in a homogeneous reactor for 6 days. The crystallized product was filtered, washed, and dried to obtain an iron-doped Na-type molecular sieve sample. The synthesized sample was calcined at 550°C in air for 10 hours to remove the template. Then, ammonium nitrate (NH4NO3) exchange was carried out, and after filtration, washing, drying, and calcination (calcination at 550°C for 6h), an iron-containing FER catalyst with a silicon-aluminum molar ratio of 20 was prepared. The sample was labeled as OP-Fe / FER-20.

[0060] Application Examples

[0061] Take a certain amount of 40-60 mesh catalyst for NH3-SCR activity evaluation, fix the catalyst in the middle of the quartz tube, separate the two sides with quartz wool and quartz sand, and put it into a tubular furnace. Before evaluating the NH3-SCR activity, the catalyst must be activated. The activation conditions are: in a 5% O2 / N2 atmosphere of 75mL / min, heat to 120℃ at a heating rate of 10℃ / min and keep warm for 30min, then heat to 550℃ at a heating rate of 10℃ / min, keep warm for 60min, and then cool naturally to 100℃. After the activation is completed, 500ppm NO, 500ppm NH3, 5vol.% O2, N2 are introduced as the balance carrier gas, the total flow rate is 300ml / min, after being evenly mixed in the mixing tank, enter the fixed bed reactor for reaction, the reaction temperature is 100-550℃, the air velocity is 36000h-1 The flue gas components before and after the reaction were detected and analyzed using an ultraviolet flue gas analyzer to investigate its NH3-SCR catalytic performance.

[0062] Figure 1 The catalytic activity comparison of the iron-containing FER molecular sieve catalysts with different silicon-aluminum molar ratios prepared by the equal volume impregnation method before and after high-temperature steam treatment in the NH3-SCR reaction is shown in Figure 1. Among them, IM-Fe / FER-15 and IM-Fe / FER-20 represent catalyst samples with silicon-aluminum molar ratios of 15 and 20, respectively, and a molecular sieve structure of FER. Figure 1 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitrification test, Example 1 and Example 2 have different denitrification activities before and after high-temperature steam treatment. Among them, the catalytic activity of IM-Fe / FER-15 (IM-Fe / FER-15-A) after high-temperature treatment is more significantly improved, and the low-temperature catalytic effect is also better.

[0063] Figure 2 The catalytic activity comparison diagram of different molecular sieve catalysts prepared by equal volume impregnation before and after high-temperature steam treatment in the present invention in the NH3-SCR reaction. Among them, IM-Fe / FER-20 and IM-Fe / MWW-20 represent catalyst samples with a silicon-aluminum molar ratio of 20 and molecular sieve structures of FER and MWW, respectively. Figure 2 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitration test, Example 2 and Example 3 have different denitration activities before and after high-temperature steam treatment. Among them, the catalytic activity of IM-Fe / FER-20 is improved in the whole temperature range (100-550℃) after high-temperature steam treatment.

[0064] Figure 3 The catalytic activity comparison chart of the iron-containing FER molecular sieve catalyst in the NH3-SCR reaction after multiple high-temperature steam treatment of IM-Fe / FER-15, where: IM-Fe / FER-15-A, IM-Fe / FER-15-2A, IM-Fe / FER-15-3A represent the catalyst samples obtained after IM-Fe / FER-15 was treated with high-temperature steam once, twice, and three times, respectively (15 represents the silicon-aluminum molar ratio in the molecular sieve is 15). Figure 3 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitrification test, Example 1 had different denitrification activities after multiple high-temperature steam treatments, among which the IM-Fe / FER-15-A catalyst had the best low-temperature activity after one high-temperature steam treatment.

[0065] Figure 4The catalytic activity diagram of the iron-containing FER molecular sieve prepared by mechanical mixing in the present invention before and after high-temperature steam treatment in the NH3-SCR reaction. Among them: MM-Fe / FER-15 represents the iron-containing FER molecular sieve of the present invention prepared by mechanical mixing, with a silicon-aluminum molar ratio of 15. MM-Fe / FER-15-A represents the iron-containing FER molecular sieve prepared by mechanical mixing and treated with high-temperature steam, with a silicon-aluminum molar ratio of 15. Figure 4 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitrification test, Example 4 has different denitrification activities before and after high-temperature steam treatment, among which MM-Fe / FER-15-A has better catalytic activity.

[0066] Figure 5 The catalytic activity diagram of the iron-containing FER molecular sieve in the NH3-SCR reaction before and after high-temperature steam treatment by the solid-state ion exchange method of the present invention. Among them: SSIE-Fe / FER-15 represents the iron-containing FER molecular sieve of the present invention using the solid-state ion exchange method, and the silicon-aluminum molar ratio is 15. SSIE-Fe / FER-15-A represents the iron-containing FER molecular sieve after high-temperature steam treatment prepared by the solid-state ion exchange method, and the silicon-aluminum molar ratio is 15. Figure 5 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitrification test, Example 5 has different denitrification activities before and after high-temperature steam treatment, among which SSIE-Fe / FER-15-A has better catalytic activity.

[0067] Figure 6 The figure is a comparison of the catalytic activities in the NH3-SCR reaction after different Fe / FER-15 catalysts were treated with high-temperature steam, wherein MM-Fe / FER-15-A, IM-Fe / FER-15-A, and SSIE-Fe / FER-15-A respectively represent the iron-containing FER molecular sieves treated with high-temperature steam prepared by mechanical mixing, equal volume impregnation, and solid-state ion exchange. OP-Fe / FER-15 represents the iron-containing FER molecular sieve prepared by the one-pot method described in the present invention (15 represents the silicon-aluminum molar ratio in the molecular sieve is 15). Figure 6 It can be seen that at an airspeed of 36000h -1 In the standard NH3-SCR denitration test, the denitration activity of MM-Fe / FER-15 was improved most significantly by comparing the denitration activity of the catalysts before and after high-temperature steam treatment. Moreover, after high-temperature steam treatment, IM-Fe / FER-15-A, MM-Fe / FER-15-A, and SSIE-Fe / FER-15-A all showed catalytic activity similar to that of OP-Fe / FER-15.

[0068] The raw materials listed in the present invention, as well as the upper and lower limits and interval values ​​of the raw materials of the present invention, and the upper and lower limits and interval values ​​of the process parameters (such as temperature, time, etc.) can all realize the present invention, and the embodiments are not listed one by one here.

[0069] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR, characterized in that: The following steps are included: (1) using a hydrothermal method, an aluminum source, an iron source, a silicon source, a template agent ethylene glycol, water, and an alkali source are prepared according to a molar ratio of SiO2:Na2O:Al2O3:EG:H2O=0.7-1.5:0.10-0.20:0.025-0.033:5-10:10-20, and after aging, they are placed in a homogeneous reactor and crystallized at 180°C for 48 hours to obtain a precursor, which is then washed, calcined, exchanged with ammonium nitrate, and deammonized to obtain a parent molecular sieve, which is denoted as Hy; (2) After grinding ferric nitrate nonahydrate, the parent molecular sieve Hy is added and then ground again, the iron content is 2-6 wt %, and the iron-containing molecular sieve is obtained after calcination, which is recorded as MM-Fe / y; (3) Mixing a parent molecular sieve Hy, ferric nitrate nonahydrate, and n-hexane, wherein the iron content of the mixture is 2 to 6 wt %, and the ratio of the parent molecular sieve Hy to n-hexane is 0.01:0.02, stirring, and then rotary evaporating to dryness, and calcining to obtain an iron-containing molecular sieve, which is recorded as SSIE-Fe / y; (4) adding the parent molecular sieve Hy to a ferric nitrate solution with an iron content of 2 to 6 wt %, performing ultrasonication and stirring, drying, and calcining at high temperature to obtain an iron-containing molecular sieve, which is recorded as IM-Fe / y; (5) treating the iron-containing molecular sieve with high-temperature steam to obtain a molecular sieve treated with high-temperature steam.

2. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR according to claim 1, characterized in that: In the step (1), the aluminum source is sodium aluminate, the iron source is ferric nitrate nonahydrate, the silicon source is silicon dioxide, the template agent is ethylene glycol, and the alkali source is sodium hydroxide: wherein the molar ratio z of Si / Al is 15-20.

3. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR according to claim 1, characterized in that: The parent molecular sieve type y in the molecular sieve described in step (1) is FER or MWW, preferably FER.

4. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR according to claim 1, characterized in that: The number of high-temperature treatment times m in step (5) is 1-3; the high-temperature treatment is high-temperature steam treatment, specifically, heating to a certain temperature under N2 atmosphere, and keeping the temperature under water-containing N2 atmosphere for a certain time; after the high-temperature treatment in step (5), passing through a 40-60 mesh molecular sieve.

5. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR according to claim 5, characterized in that: The molecular sieve treated with high-temperature steam in step (5) needs to be fixed in the middle of a quartz tube, separated on both sides by quartz wool and quartz sand, and heated to 750°C at a heating rate of 10°C / min in a tubular furnace. The nitrogen gas flow rate of the N2 atmosphere is selected to be 100ml / min, and the method of introducing water vapor is the bubbling method.

6. A method for improving the catalytic performance of iron-containing molecular sieve NH3-SCR according to claim 5, characterized in that: The volume content of water obtained by the bubbling method is 10%, and the water vapor content is controlled by heating in a water bath. The water bath heating temperature is 48° C., and the water vapor content is about 10%.

7. An iron-containing molecular sieve NH3-SCR, characterized in that: The general formula of the iron-containing molecular sieve NH3-SCR is x-Fe / yz-mA, abbreviated as x-Fe / yz-mA; wherein x is the iron introduction method, y is the molecular sieve type, z is the Si / Al molar ratio of the molecular sieve, A represents high-temperature steam treatment, and m represents the number of high-temperature steam treatments. The iron-containing molecular sieve NH3-SCR is prepared by any method of claims 1-7.

8. The iron-containing molecular sieve NH3-SCR according to claim 7, characterized in that: The iron introduction method x includes mechanical mixing, solid-state ion exchange method, and equal volume impregnation, preferably mechanical mixing; the parent molecular sieve type y in the molecular sieve is FER, MWW, preferably FER; the high temperature treatment times m is 1-3.

9. An application of the iron-containing molecular sieve NH3-SCR according to any one of claims 1 to 8, characterized in that: The catalyst is used for the selective catalytic reduction of nitrogen oxides by ammonia.

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