Low-silicon Cu-ERI type molecular sieve based monolithic foam catalyst as well as preparation method and application thereof

Abstract

The invention discloses a low-silicon Cu-ERI type molecular sieve based monolithic foam catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. According to the catalyst, an organic template-free method is adopted, and a low-silicon ERI type molecular sieve membrane layer (Si / Allt, Si / Allt) is directly constructed on the surface of foamed Al2O3 through fluorine-containing or fluorine-free super-dilute sol (n (H2O) / n (SiO2) > = 120); and 5) carrying out copper ion exchange to form the 3D through monolithic catalyst. Particularly, the addition of fluorine ions enhances the stability of a catalyst film layer, and the activity retention rate gt under the working condition of 100 ppm SO2 + 5% H2O; and the conversion rate at the high-temperature section (350-500 DEG C) is reversely increased by 5-10%. According to the technology, the thickness of the low-silicon molecular sieve membrane layer is controllable (15-40 microns), the use amount of raw materials is small, the cost is reduced by 60% compared with that of a traditional molecular sieve based denitration catalyst, and the catalyst is suitable for complex flue gas denitration scenes such as steel sintering machines and waste incineration.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NO) x Photochemical smog is the primary pollutant emitted by both stationary and mobile sources, and is also known as photochemical smog, acid rain, and PM2.5. 2.5 The key precursors formed pose a significant threat to human health and the ecological environment. Ammonia selective catalytic reduction (NH3-SCR) is widely recognized as the most mature and efficient NO reduction method under oxygen-rich conditions. x End-of-pipe treatment technologies. However, commercial V2O5–WO3 / TiO2 catalysts have a narrow operating temperature window (300–400℃), high vanadium toxicity, and poor hydrothermal stability. Developing green, efficient, and wide-temperature-window alternative materials is urgently needed.

[0003] Copper-based small-pore molecular sieves have become the benchmark material for NH3-SCR due to their wide-temperature activity, high N2 selectivity, excellent low-temperature performance, and outstanding hydrothermal stability. Currently, the only commercially available Cu-SSZ-13 requires the use of expensive and environmentally unfriendly N,N,N-trimethyl-1-adamantane ammonium hydroxide (TMAdaOH), significantly increasing costs and environmental impact. Therefore, constructing a new generation of molecular sieve catalysts that do not require organic templates and possess both high denitrification activity and hydrothermal stability has significant scientific and industrial value.

[0004] ERI (Erythritolite) possesses a three-dimensional eight-membered ring channel (3.6 × 5.1 Å), and its unique "cage-channel" structure can effectively suppress low-activity CuO. x Clustering enhances N2 selectivity, achieving SCR comparable to CHA. However, the synthetic window for pure-phase ERI is extremely narrow, and existing studies mostly rely on organic templates: Wang et al. from Tianjin University ( Micropor. Mesopor. Mater. (2019, 279, 407-415) Using N,N-dimethylpiperidinium hydroxide (DMPOH) as a template and FAU molecular sieve as a silica-alumina source for hydrothermal conversion; Zhu et al., University of Tokyo ( Adv. Sci. 2024, 11, 2307674; J. Catal. (2020, 391, 346-356) uses tetrapropylammonium hydroxide (TPAOH) and hexamethylammonium bromide (C 12 H 30 High-silicon ERI (Si / Al = 9.1) was prepared using a dual organic template (Br2N2). However, the above process has high template costs and a significant environmental impact, and the resulting Cu-ERI is mostly in the form of particles / powders, resulting in high bed pressure drop, making it difficult to scale up directly to industrial applications.

[0005] Monolithic catalysts can grow zeolite layers on the surface of the support in situ, with the advantages of low pressure drop, high mechanical strength and easy modularization. However, ERI zeolites face a "silicon-aluminum ratio-stability-cost" triangle contradiction: high-silicon systems (Si / Al>8) have good hydrothermal stability, but require expensive templates and long crystallization periods; low-silicon systems (Si / Al<5) have abundant acid sites and ion exchange sites, high low-temperature activity, and wide temperature windows, but have insufficient hydrothermal stability. More troublesome is that under the conditions of no organic template and low silicon, OFF / ERI coexisting phases or dense mixed crystal layers are easily generated, blocking the channels, and so far the controllable construction of low-silicon pure-phase ERI on Al2O3 foam carriers has not been achieved. SUMMARY

[0006] Therefore, the present application proposes a new strategy for growing low-silicon Cu-ERI monolithic catalysts on the surface of Al2O3 foam with the aid of ultrasonic-assisted rapid aging without organic templates, aiming to solve the four problems of "low-cost synthesis-high activity-high stability-low bed resistance" at the same time, and provide a new generation of technical route for the deep purification of mobile and fixed sources of NOx. x

[0007] The technical solution of the present application is as follows: A low-silicon Cu-ERI type zeolite-based monolithic foam catalyst, which comprises foam Al2O3 having a supporting effect and an ERI zeolite membrane layer located on the foam Al2O3, and the ERI zeolite membrane layer contains Cu.

[0008] Preferably, the ERI zeolite membrane layer further contains F, the Cu:Al molar ratio is 0.18-0.28, the F:Si molar ratio is 0-0.06, and the Si:Al molar ratio is 2.9-3.7.

[0009] More preferably, the Cu:Al molar ratio is 0.18-0.28, the F:Si molar ratio is 0-0.06, and the Si:Al molar ratio is 2.9-3.7.

[0010] Preferably, the morphology of the ERI zeolite is rod crystal bundle, the diameter is about 0.5 μm, and the length is 15-18 μm; and the thickness of the ERI zeolite membrane layer is 15-19 μm.

[0011] The present application also provides a preparation method of the low-silicon Cu-ERI type zeolite-based monolithic foam catalyst. S1, an impregnation solution containing ERI zeolite seeds is prepared, Al2O3 foam is immersed in the impregnation solution, and then dried to obtain seed-treated foam Al2O3; ​S2, mixing potassium hydroxide, sodium hydroxide, aluminum hydroxide, sodium fluoride, potassium fluoride, colloidal silicon oxide and water to form a mixed solution; placing the mixed solution into an ultrasonic instrument for aging treatment at room temperature to obtain a synthesis sol; crystallizing the synthesis sol with the seed-impregnated foam Al2O3 in S1, and washing with deionized water to obtain a 3D structure ERI@Al2O3 molecular sieve membrane; S3, placing the above molecular sieve membrane into a copper nitrate solution to obtain a whole type Cu-ERI molecular sieve catalyst.

[0012] The application adopts a secondary hydrothermal synthesis method, constructs a Cu-ERI film layer on an Al2O3 foam support through an organic template-free method containing a fluorine-containing dilute sol, and introduces a metal active component through a simple ion exchange method. The catalyst applied to an NH3-SCR reaction shows a wide temperature conversion window, and especially shows excellent NO x conversion rate in a complex system containing SO2 and H2O.

[0013] Preferably, the molar ratio of each component in the preparation of the ERI molecular sieve seed is SiO2:Al2O3:K2O:TEAOH:C 12 H 30 Br2N2:H2O=1:0.03:0.09:0.8:0.13:25.

[0014] Preferably, the specific steps for preparing the ERI molecular sieve seed are as follows: dissolving aluminum sec-butoxide in tetraethylammonium hydroxide TEAOH to prepare an aluminum source solution; then, adding colloidal silicon oxide dropwise into the aluminum source solution, and placing the solution in an oil bath at 90 DEG C for aging and stirring for 20 hours; after the aging is completed, sequentially adding potassium hydroxide and C 12 H 30 Br2N2 solution into the solution, and finally, pouring the mixed solution into a reaction kettle for reaction at 150 DEG C for 120 hours; after the reaction is completed, sequentially performing centrifugation, drying and grinding operations on the product, and calcining at 550 DEG C for 10 hours to remove the template to obtain the final product.

[0015] Preferably, in S1, the concentration of the seed-containing impregnating solution is 6-10 wt%, and the impregnation times are 1-3 times, and drying is performed at 60-100 DEG C.

[0016] Preferably, in S2, the molar ratio of each component in the synthesis sol in the form of oxides is SiO2:Al2O3:K2O:Na2O:H2O:(NaF+KF)=1:0.015:0.11:0.34:(80-200):(0-1), n (NaF) / n (KF)=3.

[0017] More preferably, the molar ratio of the oxides of the components in the synthesis sol is SiO2:Al2O3:K2O:Na2O:H2O:(NaF+KF)=1:0.015:0.11:0.34:(120-160):(0.8-1.0).

[0018] Preferably, in S2, the ultrasonic aging treatment power is 20 kHz, the temperature is room temperature, and the treatment time is 1.0 h; the temperature of the crystallization reaction is 175℃, and the time of the crystallization reaction is 24 h.

[0019] Preferably, in S3, the concentration of the copper nitrate solution is 0.1-2 mol / L, the immersion treatment temperature is 60-80℃, the immersion treatment time is 6-12 h, and the immersion treatment times is 1.

[0020] More preferably, the concentration of the copper nitrate solution is 0.5-1.0 mol / L.

[0021] The third aspect of the present application provides the use of the catalyst in an NH3-SCR reaction.

[0022] The present application has at least one of the following beneficial effects: (1) The present application uses an organic template-free fluorine-containing ultra-dilute sol method to grow a dense ERI crystal film layer on a monolithic Al2O3 foam, which saves the step of calcining to remove the template and reduces the raw material cost by more than 60%, without the need for external equipment (such as a 3D printer), and has the advantages of simple operation and low cost.

[0023] (2) The present application realizes the growth of low-silicon ERI on Al2O3 foam for the first time, solving the problem of easy formation of OFF / ERI symbiotic phase or dense mixed crystal layer in low-silicon gel.

[0024] (3) The fluorine-containing and non-fluorine-containing synthesis sols of the present application can both produce ERI type monolithic catalysts, especially the innovative introduction of fluorine ions in the synthesis sol effectively improves the stability of ERI crystals, making them exhibit excellent water resistance and sulfur resistance.

[0025] (4) The catalyst prepared by the present application is different from the traditional impregnation and smearing method, has abundant catalytic active sites, and exhibits extremely high catalytic activity and stability, and is a new type of catalyst with great development prospects. In the NH3 selective catalytic reduction NO x (NH3-SCR) reaction, according to the experimental data of the present embodiment, the catalyst realizes more than 90% of NO xThe conversion rate is high, and the N2 selectivity is close to 100%. In addition, the catalyst still exhibits excellent catalytic performance in a complex environment containing water and SO2, and exhibits excellent water resistance and sulfur resistance. The ERI type molecular sieve has become the next generation of small-pore molecular sieve-based catalysts with the highest industrialization potential in the NH3-SCR field after CHA, because of the advantages of template-free synthesis, high activity at low temperature, and excellent sulfur and water resistance. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0027] Figure 1 X-ray diffraction (XRD) patterns of (a) seeds in Example 1 (the small figure inserted therein is an SEM image thereof) and (b) the catalyst obtained in Comparative Example 1 are shown.

[0028] Figure 2 XRD patterns of the Al2O3 foam support, the catalysts obtained in Examples 1-4, and the catalyst obtained in Comparative Example 2 are shown.

[0029] Figure 3 Scanning electron microscope (SEM) images of the catalysts obtained in Examples 1-4 and Comparative Example 2 are shown; (a) and (b) are Comparative Example 2, (c) and (d) are Example 2, (e) and (f) are Example 3, (g) and (h) are Example 1, and (i) and (j) are Example 4.

[0030] EDX results of the catalysts obtained in Examples 1-4 and Comparative Example 2 are shown in Table 1.

[0031] Figure 4 DeNOx performance of the catalysts obtained in Examples 1-4 and Comparative Example 2 in NH3-SCR is shown, (a) is the conversion rate of NO x ; and (b) is the selectivity of N2.

[0032] Figure 5 DeNOx performance of the catalysts obtained in Examples 5-7 and Comparative Example 2 in NH3-SCR is shown, (a) is the conversion rate of NO x ; and (b) is the selectivity of N2.

[0033] Figure 6 DeNOx performance of the catalysts obtained in Examples 8-10 and Comparative Example 2 in NH3-SCR is shown.

[0034] Figure 7Figure showing the performance of the catalysts obtained in Examples 11-13 and Example 1 in NH3-SCR.

[0035] Figure 8 Figure showing the sulfur resistance performance of the catalysts obtained in Examples 1-4 and Comparative Example 2 in NH3-SCR.

[0036] Figure 9 Figure showing the water resistance performance of the catalysts obtained in Examples 1-4 and Comparative Example 2 in NH3-SCR.

[0037] Figure 10 Figure showing the water and sulfur resistance performance of the catalyst obtained in Example 1 in NH3-SCR.

[0038] Figure 11 Figure showing the water and sulfur resistance performance of the catalyst obtained in Comparative Example 2 in NH3-SCR. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0040] Example 1 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which specifically comprises the following steps: Step 1: 0.5 g of ERI molecular sieve seeds were dissolved in 4.5 g of deionized water, and after being stirred uniformly, ultrasonic dispersion was performed for 10 minutes to prepare a uniform impregnation solution containing ERI molecular sieve seeds. Subsequently, the Al2O3 foam (height: 10 mm, diameter: 10 mm, Chengjunda New Material Technology Co., Ltd.) was slowly and vertically immersed in the impregnation solution, so that the seeds were uniformly loaded thereon. After being dried, the impregnation was repeated once again. Finally, the seed-coated Al2O3 foam was dried at 80°C for standby, thereby obtaining the seed-coated Al2O3 foam.

[0041] The process of the ERI molecular sieve seeds in Step 1 is as follows: Aluminum sec-butoxide was dissolved in tetraethylammonium hydroxide (TEAOH) to prepare an aluminum source solution. Subsequently, colloidal silicon oxide (containing 30% of SiO2 by mass fraction, Sigma-Aldrich Co.) was added dropwise into the aluminum source solution, which was transferred into a PP bottle and stirred uniformly. The PP bottle was placed in an oil bath at 90°C, and stirring aging was performed for 20 hours. After aging was completed, potassium hydroxide and hexamethonium bromide (C 12 H 30Br2N2) solution, and mixed well. Finally, the mixed solution was poured into a reactor and reacted at 150 °C for 120 hours. After the reaction, the product was sequentially subjected to centrifugation, drying and grinding operations, and calcined at 550 °C for 10 hours to remove the template agent, to obtain the final product; the molar ratio of the components in the form of oxides in the synthesis sol was n (SiO2) : n (Al2O3) : n (K2O) : n (TEAOH) : n (C 12 H 30 Br2N2) : n (H2O) = 1 : 0.03 : 0.09 : 0.8 : 0.13 : 25.

[0042] Step 2: First, potassium hydroxide (KOH), sodium hydroxide (NaOH), sodium fluoride (NaF), potassium fluoride (KF) and aluminum hydroxide were sequentially dissolved in deionized water, and after stirring until the solution was clear, colloidal silicon oxide (containing 30% SiO2 by mass, Sigma-Aldrich) was slowly added dropwise to form a synthesis sol, and the ratio (molar ratio) of the components in the form of oxides was n (SiO2) : n (Al2O3) : n (K2O) : n (Na2O) : n (H2O) : n (NaF + KF) = 1 : 0.015 : 0.11 : 0.34 : 120 : 0.8, n (NaF) / n (KF) = 3; subsequently, the mixed solution was placed in an ultrasonic instrument for ultrasonic aging at room temperature, with an ultrasonic aging treatment power of 20 kHz and a temperature of room temperature, for 1 h.

[0043] The above-mentioned aged synthesis sol was placed in a reactor together with the seed crystalized Al2O3 foam support in Step 1, and crystallization was carried out at 175 °C for 24 hours. After the reaction, the obtained sample was washed to neutral with deionized water, and dried to obtain the product ERI@Al2O3 molecular sieve membrane; Step 3: The above-mentioned ERI@Al2O3 molecular sieve membrane was placed in a 100 mL copper nitrate solution with a concentration of 1.0 mol / L, and continuously stirred at 80 °C for 6 hours. After the reaction, the sample was washed to neutral with deionized water, and then dried to obtain the monolithic Cu-ERI foam catalyst.

[0044] Example 2 A method for preparing a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the ratio of the synthetic sol in step 2 of Example 1 is changed to n (NaF + KF) / (SiO2) is changed to 0.1, and the catalyst is finally obtained. n (NaF + KF) / (SiO2) is changed to 0.1, and the catalyst is finally obtained.

[0045] Example 3 A method for preparing a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the ratio of the synthetic sol in step 2 of Example 1 is changed to n (NaF + KF) / (SiO2) is changed to 0.3, and the catalyst is finally obtained. n (NaF + KF) / (SiO2) is changed to 0.3, and the catalyst is finally obtained.

[0046] Example 4 A method for preparing a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the ratio of the synthetic sol in step 2 of Example 1 is changed to n (NaF + KF) / (SiO2) is changed to 1.0, and the catalyst is finally obtained. n (NaF + KF) / (SiO2) is changed to 1.0, and the catalyst is finally obtained.

[0047] The molar ratio of each element in the catalysts prepared in Examples 1-4 and Comparative Example 2 is shown in Table 1.

[0048] Table 1

[0049] Example 5 A method for preparing a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the ratio of the synthetic sol in step 2 of Example 1 is changed to n (SiO2) : n (Al2O3) : n (K2O) : n (Na2O) : n (H2O) = 1 : 0.015 : 0.11 : 0.34 : 80, and the catalyst is finally obtained.

[0050] Example 6 A method for preparing a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the ratio of the synthetic sol in step 2 of Example 1 is changed to n (SiO2) : n (Al2O3) : n (K2O) : n (Na2O) : n(H2O) = 1 : 0.015 : 0.11 : 0.34 : 160, to obtain the catalyst finally.

[0051] Example 7 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the synthetic sol ratio in step 2 of Example 1 is changed to n (SiO2) = 80, to obtain the catalyst finally. n (Al2O3) = 0.015, to obtain the catalyst finally. n (K2O) = 0.11, to obtain the catalyst finally. n (Na2O) = 0.34, to obtain the catalyst finally. n (H2O) = 1 : 0.015 : 0.11 : 0.34 : 200, to obtain the catalyst finally.

[0052] Example 8 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 5, except that the copper nitrate concentration in step 3 of Example 5 is changed to 0.1 mol / L, to obtain the catalyst finally.

[0053] Example 9 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 5, except that the copper nitrate concentration in step 3 of Example 5 is changed to 0.5 mol / L, to obtain the catalyst finally.

[0054] Example 10 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 5, except that the copper nitrate concentration in step 3 of Example 5 is changed to 2.0 mol / L, to obtain the catalyst finally.

[0055] Example 11 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the synthetic sol ratio in step 2 of Example 1 is changed to n (H2O) = 1 : 0.015 : 0.11 : 0.34 : 160, to obtain the catalyst finally. n (SiO2) = 80, to obtain the catalyst finally.

[0056] Example 12 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as Example 1, except that the synthetic sol ratio in step 2 of Example 1 is changed to n (H2O) = 1 : 0.015 : 0.11 : 0.34 : 160, to obtain the catalyst finally. n (SiO2) = 160, to obtain the catalyst finally.

[0057] Example 13 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as those of Example 1, except that the ratio of the synthesis sol in step 2 in Example 1 is changed to n (H2O): n (SiO2)=200, to obtain the catalyst finally.

[0058] Comparative Example 1 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as those of Example 1, except that the seed coating in step 1 is not performed, that is, the Al2O3 foam is not immersed in the seed immersion solution, but is directly used in step 2.

[0059] The results are shown in Figure 1 b. From the corresponding XRD patterns, only the diffraction peaks of the Al2O3 foam support body appear, and no obvious molecular sieve diffraction peaks are observed, indicating that the product is amorphous, and indicating that a crystalline film layer cannot be formed without adding ERI seeds.

[0060] In addition, from the XRD and SEM patterns of the ERI seeds in Figure 1 a, it can be seen that the ERI seeds are elliptical in shape, with a size of about 200 nm x 500 nm.

[0061] Comparative Example 2 A preparation method of a low-silicon Cu-ERI type molecular sieve-based monolithic foam catalyst, which has the same steps as those of Example 1, except that the ratio of n (NaF+KF) / n (SiO2) in step 2 in Example 1 is changed to 0, to obtain a catalyst without fluorine finally.

[0062] Example 14 In this embodiment, the catalysts prepared in Examples 1-4 are analyzed for relevant characterization data, and the specific results are as follows: Figure 2 The X-ray diffraction patterns of the catalysts obtained in Examples 1-4 and Comparative Example 2 of the present application are shown in Figure 2 It can be seen from that the XRD diffraction peaks of all samples are consistent with the standard characteristic diffraction peaks of the Al2O3 support body and the ERI type molecular sieve, and no other impurity crystal phase is present. This indicates that we have successfully synthesized an ERI type molecular sieve film layer on the Al2O3 support body. At the same time, no diffraction peaks of Cu species appear in the XRD patterns. This also indicates that the Cu species may be uniformly dispersed in the crystal framework in the form of oxide clusters or ions, without changing its crystal structure.

[0063] Figure 3The images shown are scanning electron microscope (SEM) images of the catalysts obtained in Examples 1-4 and Comparative Example 2. Figure 1 As shown in a and 1b, the surface of the fluorine-free film is completely covered by many rod-shaped crystals, each with a diameter of about 0.2 μm and a length of about 5 μm. These rod-shaped crystals form a continuous and relatively dense film with a thickness of about 18 μm; when a small amount of fluoride ions are introduced into the synthetic sol ( n (F - ) / n (SiO2)=0.1)( Figure 1 In cases c and 1d), the film surface still consists of rod-shaped crystals, but the number of crystals is reduced, and the film is not as continuous and dense, with noticeable pores visible. This is consistent with... Figure 2 The observed decrease in crystallinity in the corresponding XRD results is consistent with the phenomenon observed in the film, which is approximately 15 μm thick. As more fluoride ions are introduced into the synthetic sol, the rod-shaped crystals gradually aggregate and become longer. n (F - ) / n When the SiO2 concentration increases to 0.8, the crystals form relatively distinct rod-shaped bundles with a diameter of approximately 0.5 μm and a length reaching 15 μm. Figure 1 g and 1h); further increase in fluoride ions (g and 1h); n (F - ) / n (SiO2)=1.0), the rod-shaped crystal bundles continue to grow, still 0.5 μm in diameter, but with a length of 18 μm. The film thickness remains basically between 17 and 19 μm (e.g., SiO2=1.0). Figure 3 (as shown in f, 3h, and 3j).

[0064] Example 15 The catalysts prepared in Examples 1-7 and Comparative Example 2 of this invention were applied to the NH3-SCR reaction. The specific process is as follows: The catalyst was placed directly into a quartz tube (5 mm inner diameter, 500 mm length) for testing. To ensure accuracy, the catalyst was placed in the middle of the quartz tube, above the thermocouple, and the furnace temperature was controlled by a temperature control system, with a test temperature range of 100–600 °C. The simulated flue gas was [NO] = [NH3] = 500 ppm, 5% O2 (volume fraction), with N2 as the balance gas. The total gas flow rate was set to 100 mL / min, and the calculated GHSV was 60,000 h⁻¹. -1 Before testing, the simulated flue gas was thoroughly mixed in a mixer, and after stabilization, it was bypassed and introduced into the flue gas analyzer to record NO. xThe total intake value of (NO and NO2) was then transferred to the reaction path. After stabilization, the temperature was increased, and data was recorded every 50°C. To ensure the reaction reached a stable state, NO was recorded after holding at each target temperature for 20-30 minutes. x The outgassing values ​​of NH3 and N2O are shown in the figure. Figure 4 and Figure 5 .

[0065] Figure 4 The catalytic performance of all catalysts in Examples 1-4 in the NH3-SCR reaction is compared. When comparing the Cu-ERI membrane without fluorine on the Al2O3 foam support in Comparative Example 2, NO2 content is significantly higher in the temperature range of 200-500 °C. x The conversion rate is nearly 100%, especially at a low temperature of 150℃ for NO. x The conversion rate was as high as 85%, and the N2 selectivity was close to 100%; while in Examples 2 and 3 n (F - ) / n When Cu-ERI films were synthesized with SiO2 at concentrations of 0.1 and 0.3, NO was also detected in the medium-high temperature region (200~450 ℃). x The conversion rate is close to 100%. Meanwhile, NO... x The conversion rate was higher than that of Comparative Example 2. As more fluoride ions were introduced into the synthetic sol, the Cu-ERI membranes obtained in Examples 1 and 4 remained unchanged except for a slight decrease in the low temperature region, and the N2 selectivity of all catalysts was close to 100, showing the best denitrification performance.

[0066] Figure 5 The catalytic performance of all catalysts in Examples 6-7 and Comparative Example 2 in the NH3-SCR reaction is shown. Compared with the catalyst in Comparative Example 2, when... n (H2O) / n When (SiO2) = 80 and 160, the prepared catalysts exhibit NO activity in the low-temperature region. x The conversion rates are basically similar, while NO in the high-temperature zone x However, the conversion rate decreased by approximately 18%; further improvement n (H2O) / n When (SiO2)=200, the obtained catalyst only produces NO within a narrow temperature range of 250~350 ℃. x The conversion rate exceeds 90%, which does not affect the selectivity of N2.

[0067] Figure 6 The catalytic performance of all catalysts in Examples 8-10 and Comparative Example 2 in the NH3-SCR reaction is shown. Compared with the catalyst in Comparative Example 2, the prepared catalysts showed better performance in the low-temperature region (≤150℃) and the high-temperature region (≥450℃) at lower initial copper ion concentrations.x The conversion rates of NOxof all the catalysts prepared in Examples 11-13 and Example 1 were all decreased by 10-20%, while the conversion rates of NOxof the catalysts prepared by further increasing the initial copper ion concentration to 2 mol / L were basically maintained in the high-temperature region, but the conversion rates of NOxof the catalysts prepared by further increasing the initial copper ion concentration to 2 mol / L were decreased by about 30% in the low-temperature region. x

[0068] Figure 7 The catalytic performances of all the catalysts in the NH3-SCR reaction were tested. The conversion rates of NOxof all the catalysts were all greater than 90% in a wide temperature window (200-500 ℃), especially for the catalysts prepared from the dilute sols (Examples 12 and 13), the conversion rates of NOxof the catalysts were all increased by about 10% in the low-temperature region (≤ 150 ℃) and the high-temperature region (≥ 500 ℃), which showed that the dilute sols could promote the de-NOxperformance of the catalysts. x x

[0069] Example 16 The catalysts prepared in Examples 1-4 and Comparative Example 2 were applied to the anti-water and anti-sulfur tests in the NH3-SCR reaction, and the specific process was as follows: To test the anti-water and anti-sulfur performances of the de-NOx catalysts, 100 ppm SO2 and 5 vol% H2O (water vapor) were respectively introduced into the simulated flue gas, and the values of the flue gas analyzer at different times were recorded. The H2O in the simulated flue gas was carried out from the heated steam generator via N2, and the actual heating temperature of the steam generator could be calculated by the saturated vapor pressure and water content table at different temperatures and the Clapeyron equation; when the anti-water test was not performed, N2 did not pass through the pipeline equipped with the steam generator, and the flow rate was controlled by switching the three-way valve. If 100 ppm SO2 and 5 vol% H2O were introduced at the same time, NH4HSO4 and NH4HSO3 were easily generated to cover the catalyst and block the pipeline, which could be decomposed at above 150 ℃. Therefore, to ensure the de-NOx efficiency and prevent the pipeline from being blocked, the upper, lower and standby pipeline temperatures were set to 120 ℃, 160 ℃ and 160 ℃ respectively to decompose the nitrate and nitrite, and the results were shown in Table 2. Figure 8~Figure 10

[0070] Figure 8 and Figure 9 The Cu-ERI@Al2O3 catalysts in Examples 1-4 in Table 1 exhibited excellent anti-water and anti-sulfur performances under the simulated flue gas conditions. In the atmosphere containing only 100 ppm SO2 or 5 vol% H2O, the conversion rates of NOxof all the catalysts were all stable in the whole temperature range, and the conversion rates of NOxof all the catalysts were obviously increased in the high-temperature region (> 500 ℃). Especially in the test containing 5 vol% H2O, the conversion rates of NOxof all the catalysts were obviously increased in the high-temperature region (> 500 ℃). x x ​​​​​Conversion rates of up to 100% are possible.

[0071] Figure 10 Further, the performance of Example 1 was tested at 150°C with 100 ppm SO2 and 5 vol% H2O simultaneously. When only 100 ppm SO2 was introduced, NO x Conversion rate was not affected; when only 5% H2O was introduced, conversion rate decreased by about 30%, but the performance could quickly recover to the initial level after stopping the introduction of H2O. When SO2 and H2O coexisted, NO x conversion rate decreased by about 35%, and also quickly recovered after stopping the introduction.

[0072] In contrast, the Comparative Example 2 catalyst without fluorine had NO x conversion rate was stable, but in a 5 vol% H2O atmosphere, NO x conversion rate remained stable, and at other temperature points, decreased by about 10-30%. When SO2 and H2O were introduced simultaneously (as shown in Figure 11 NO x conversion rate also decreased by 10-15%. Thus, the low-silicon Cu-ERI monolithic foam catalyst synthesized according to the present application has a significant advantage in terms of water and sulfur resistance, and can maintain high deNOx performance under complex working conditions.

[0073] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, can make equivalent replacements or changes within the technical range disclosed by the present application, which should be encompassed within the protection scope of the present application.

Claims

1. A low-silica Cu-ERI type molecular sieve-based monolithic foam catalyst, characterized in that, The structure comprises a foam Al2O3 with a supporting effect and an ERI molecular sieve membrane layer on the foam Al2O3, wherein the ERI molecular sieve membrane layer contains Cu.

2. The low-silica Cu-ERI type molecular sieve-based monolithic foam catalyst according to claim 1, characterized in that, The ERI molecular sieve membrane layer further contains F; the molar ratio of Cu:Al is 0.18-0.28; the molar ratio of F:Si is 0-0.06; and the molar ratio of Si:Al is 2.9-3.

7.

3. The low-silica Cu-ERI type molecular sieve-based monolithic foam catalyst according to claim 1, characterized in that, The morphology of the ERI molecular sieve is a rod crystal bundle, with a diameter of about 0.5 μm and a length of 15-18 μm; and the thickness of the ERI molecular sieve membrane layer is 15-19 μm.

4. A process for the preparation of a catalyst as claimed in any one of claims 1 to 3, characterized in that The method comprises the following steps: S1. Preparing an impregnation solution containing ERI molecular sieve seeds, immersing Al2O3 foam in the impregnation solution, drying, and obtaining seed-treated foam Al2O3; S2. Mixing potassium hydroxide, sodium hydroxide, aluminum hydroxide, sodium fluoride, potassium fluoride, and colloidal silicon dioxide with water to form a mixed solution; placing the mixed solution in an ultrasonic instrument for aging treatment at room temperature to obtain a synthesis sol; and crystallizing the synthesis sol with the seed-treated foam Al2O3 in S1, and washing with deionized water to obtain a 3D structure ERI@Al2O3 molecular sieve membrane; S3. Immersing the above molecular sieve membrane in a copper nitrate solution to obtain a monolithic Cu-ERI type molecular sieve catalyst.

5. The production method according to claim 4, characterized by, The molar ratio of each component in the preparation of ERI molecular sieve seed crystal is SiO2:Al2O3:K2O:TEAOH:C 12 H 30 Br2N2:H2O = 1 : 0.03 : 0.09 : 0.8 : 0.13 : 25; The specific steps for preparing ERI molecular sieve seeds are as follows: dissolving aluminum sec-butoxide in tetraethylammonium hydroxide (TEAOH) to prepare an aluminum source solution; then, adding colloidal silicon dioxide dropwise to the aluminum source solution, and placing in an oil bath at 90℃ for stirring and aging for 20 hours. After aging is completed, potassium hydroxide and C 12 H 30 Br2N2solution, and finally, the mixed solution is poured into a reaction kettle and reacted at 150°C for 120 hours; after the reaction is completed, the product is subjected to centrifugation, drying and grinding operations in sequence, and calcination at 550°C for 10 hours to remove the template agent to obtain the final product.

6. The preparation method according to claim 4, characterized in that, In S1, the concentration of the seed-containing impregnation solution is 6-10 wt%, the impregnation times are 1-3 times, and the drying is performed at 60-100℃.

7. The preparation method according to claim 4, characterized in that, In S2, the molar ratio of each component in the form of oxide in the synthesis sol is Si02: Al203: K20: Na20: H20: (NaF + KF) = 1 : 0.015 : 0.11 : 0.34 : (80 ~ 200) : (0 ~ 1), n (NaF) / n (KF) = 3.

8. The preparation method according to claim 4, characterized in that, In S2, the ultrasonic aging treatment power is 20 kHz, the temperature is room temperature, the treatment time is 1.0 h, the crystallization reaction temperature is 175℃, and the crystallization reaction time is 24 h.

9. The preparation method according to claim 4, characterized in that, In S3, the concentration of the copper nitrate solution is 0.1-2.0 mol / L, the impregnation treatment temperature is 60-80℃, the impregnation treatment time is 6-12 h, and the impregnation treatment times are 1 time.

10. Application of the catalyst of any one of claims 1-3 or the catalyst prepared by any one of claims 4-9 in an NH3-SCR reaction.

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