Fiber ceramic-based catalytic filter element for denitration of industrial flue gas and preparation method of fiber ceramic-based catalytic filter element

Abstract

The invention discloses a fiber ceramic-based catalytic filter element for denitration of industrial flue gas and a preparation method of the fiber ceramic-based catalytic filter element, and belongs to the technical field of catalytic filter elements. According to the preparation method, firstly, a chelating agent is introduced in the preparation process of TiO2 sol to improve the dispersity and particle size uniformity of TiO2 nanoparticles, the chelating agent can effectively adjust the hydrolysis rate of butyl titanate by means of the strong coordination acting force of the chelating agent and titanium ions, and high-dispersity and small-particle-size TiO2 sol is constructed; then, the fiber ceramic base material is immersed in the TiO2 sol, a firm TiO2 coating is formed after calcination, the firm TiO2 coating serves as a carrier with a high specific surface area, and the binding force between the firm TiO2 coating and the base material is enhanced; the preparation method comprises the following steps: firstly, preparing a TiO2 coating, then dipping a solution containing vanadium and tungsten precursors onto the composite carrier, and calcining to form a main active component V2O5 and a cocatalyst WO3 which are highly dispersed on the surface of the TiO2 coating to form selective catalytic reduction active sites, thereby finally obtaining the fiber ceramic-based catalytic filter element which is good in blocking resistance, water-resistant, sulfur-resistant and high-temperature-resistant and can be used for industrial flue gas denitration.

Description

Technical Field

[0001] This invention belongs to the field of catalytic filter technology, and particularly relates to a fiber ceramic-based catalytic filter for industrial flue gas denitrification and its preparation method. Background Technology

[0002] Large amounts of nitrogen oxides (NOx) are emitted during the combustion of fossil fuels and the incineration of solid waste. x Nitrogen oxides (NOx) and particulate matter (PM) are pollutants that not only cause a series of regional environmental problems such as photochemical smog, acid rain, and haze, but also threaten human respiratory and cardiovascular health. Currently, industrial processes commonly employ multi-stage purification units in series to remove NOx and particulate matter. This involves first capturing particulate matter using dust removal equipment, and then using selective catalytic reduction (SCR) devices to remove NOx. x However, this process suffers from problems such as lengthy procedures, complex systems, high initial investment, and high operating and maintenance costs. Against this backdrop, catalytic converter filters (CFEs), which combine physical separation and catalytic conversion functions, show great promise for application.

[0003] Currently, the mainstream technologies for catalytic filter elements include coated catalytic filter elements (such as SCR or oxidation catalysts loaded on DPF or GPF) and integral catalytic filter elements (such as catalytic ceramic fiber filter elements). However, existing technologies still face significant problems: insufficient bonding strength between the catalyst and the filter substrate, leading to easy detachment under high flow rates or thermal shock; the microporous structure is easily clogged by dust, resulting in increased pressure drop and energy consumption; simultaneously, the catalyst is prone to deactivation under complex operating conditions due to high-temperature sintering or chemical poisoning, affecting long-term stability and conversion efficiency. Therefore, how to prepare catalytic filter elements with high bonding strength between the catalyst and the filter substrate, good anti-clogging performance, water and sulfur resistance, and high-temperature resistance has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a fiber ceramic-based catalytic filter element for industrial flue gas denitrification and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, comprising the following steps:

[0007] (1) Add tetrabutyl titanate to anhydrous ethanol to obtain solution A; add chelating agent to anhydrous ethanol to obtain solution B; add solution B to solution A under stirring to obtain TiO2 sol; the chelating agent is selected from acetylacetone or triethanolamine;

[0008] (2) The fiber ceramic substrate is immersed in the TiO2 sol, and then subjected to a first vacuum impregnation, aging, a first drying and a first calcination to obtain a TiO2-loaded fiber ceramic substrate;

[0009] (3) Oxalic acid, ammonium tungstate and ammonium metavanadate are added to water and stirred to obtain an impregnation solution; the TiO2-loaded fiber ceramic substrate is placed in the impregnation solution and subjected to a second vacuum impregnation, a second drying and a second calcination to obtain the fiber ceramic-based catalytic filter element for industrial flue gas denitrification.

[0010] Further, in step (1), the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-3):1.

[0011] Further, in step (1), when the chelating agent is acetylacetone, the molar ratio of the chelating agent to tetrabutyl titanate is (1-3):1; when the chelating agent is triethanolamine, the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-1.2):1.

[0012] Further, in step (2), the mass ratio of the fiber ceramic substrate to the TiO2 sol is 1:(2-4).

[0013] Furthermore, in step (2), the vacuum degree of the first vacuum impregnation is ≥0.095MPa, and the time is 40-60min;

[0014] The aging temperature is 60-70℃, and the time is 10-12 hours;

[0015] The first drying temperature is 105-120℃, and the time is 12-16h;

[0016] The first calcination temperature is 400-450℃ and the time is 3-6h.

[0017] Further, in step (3), the concentration of oxalic acid in the impregnation solution is 0.3-1.0 wt%, the concentration of ammonium tungstate is 0.4-1.4 wt%, and the concentration of ammonium metavanadate is 0.1-1.0 wt%.

[0018] Further, in step (3), the mass ratio of the TiO2-loaded fiber ceramic substrate to the impregnation liquid is 1:(2-4).

[0019] Further, in step (3), the vacuum degree of the second vacuum impregnation is ≥0.095MPa, and the time is 40-60min;

[0020] The second drying temperature is 105℃, and the time is 12 hours;

[0021] The second calcination temperature is 400℃ and the time is 3 hours.

[0022] This invention provides a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, which is prepared according to the preparation method described in the above technical solution.

[0023] The present invention also provides an application of the fiber ceramic-based catalytic filter element for industrial flue gas denitrification as described above in industrial flue gas denitrification.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] This invention first introduces a chelating agent during the preparation of TiO2 sol to improve the dispersibility and particle size uniformity of TiO2 nanoparticles. The chelating agent, with its strong coordination force with titanium ions, can effectively regulate the hydrolysis rate of tetrabutyl titanate, constructing a highly dispersed TiO2 sol with small particle size. Subsequently, a fiber ceramic substrate is immersed in the TiO2 sol, allowing the TiO2 sol to penetrate deep into the substrate pores. After calcination, a robust TiO2 coating is formed. This TiO2 coating serves as both a carrier with a high specific surface area and enhances the bonding force with the fiber ceramic substrate. Next, a solution containing vanadium and tungsten precursors is impregnated onto the composite carrier. After calcination, the surface of the TiO2 coating shows a highly dispersed main active component V2O5 and a co-catalyst WO3, forming selective catalytic reduction active sites. Finally, a fiber ceramic-based catalytic filter element with good anti-clogging performance, water and sulfur resistance, high temperature resistance, and suitable for industrial flue gas denitrification is obtained.

[0026] This invention achieves a deep integration of catalytic function and filtration structure at the microscale. The prepared catalytic filter element has both high-efficiency denitrification and physical filtration functions. Its catalytic active components are evenly distributed and firmly bonded to the carrier, ensuring good NH3-SCR denitrification activity and stability under complex industrial flue gas conditions. At the same time, the inherent three-dimensional network structure of the fiber ceramic substrate is preserved, ensuring low airflow resistance and excellent anti-clogging performance, realizing integrated pollutant removal and system energy efficiency improvement. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 This is a process flow diagram of the preparation method of the fiber ceramic-based catalytic filter element used for industrial flue gas denitrification in Example 1;

[0029] Figure 2FT-IR images of tetrabutyl titanate, acetylacetone and TiO2 sol obtained in step (1) of Example 1 (a), structural formula of the six-membered ring chelate structure in TiO2 sol (b), and average particle size of TiO2 sol with different amounts of acetylacetone added obtained in step (1) of Example 1 (c).

[0030] Figure 3 SEM images of the catalysts supported on the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1, where a1 and a2 are CFE-1, b1 and b2 are CFE-1.5, c1 and c2 are CFE-2, d1 and d2 are CFE-3, a1~d1 are 400 nm, and a2~d2 are 200 nm.

[0031] Figure 4 SEM and EDS images of the fiber ceramic-based catalytic filter CFE-2 prepared in Example 1 are shown, where a1 is the SEM image (4 μm), a2 is the SEM image (1 μm), and b is the EDS image.

[0032] Figure 5 XRD patterns of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1;

[0033] Figure 6 N2 adsorption-desorption isotherms (a) and pore size distribution diagrams (b) of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1;

[0034] Figure 7 The image shows the XPS spectrum of the catalyst supported on the fiber ceramic-based catalytic filter element prepared in Example 1, where a represents Ti 2p, b represents V 2p, and c represents O 1s.

[0035] Figure 8 The NH3-TPD spectrum (a) and H2-TPR spectrum (b) of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1 are shown.

[0036] Figure 9 A schematic diagram of the fixed-bed reactor used for testing catalytic performance;

[0037] Figure 10 The denitrification efficiency of the fiber ceramic-based catalytic filter element prepared in Example 1 is given by: a) NO conversion rate of CFE-1, CFE-1.5, CFE-2, and CFE-3 in the temperature range of 200-450℃; b) NO conversion rate at a space velocity of 100,000 h⁻¹. -1 -250000h -1The NO conversion rate of CFE-2 under the given conditions is given by c, where c represents the NO conversion rate of CFE-2 under different oxygen concentrations, d represents the NO conversion rate of CFE-2 under different NH3 / NO molar ratios, and e represents the NO conversion rate of CFE-2 under different NO concentrations.

[0038] Figure 11 Water and sulfur resistance (a) and denitrification stability (b) of the fiber ceramic-based catalytic filter element CFE-2 prepared in Example 1;

[0039] Figure 12 The NO conversion rates of the fiber ceramic-based catalytic filter elements prepared in Example 2 (0.25TEA-VWTi, 0.5TEA-VWTi, 0.75TEA-VWTi, 1TEA-VWTi, 1.1TEA-VWTi, and 1.2TEA-VWTi) in the temperature range of 200-500℃ are shown. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] This invention provides a method for preparing a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, comprising the following steps:

[0043] (1) Add tetrabutyl titanate to anhydrous ethanol to obtain solution A; add chelating agent to anhydrous ethanol to obtain solution B; add solution B to solution A under stirring to obtain TiO2 sol; the chelating agent is selected from acetylacetone or triethanolamine;

[0044] (2) The fiber ceramic substrate is immersed in the TiO2 sol, and then subjected to a first vacuum impregnation, aging, a first drying and a first calcination to obtain a TiO2-loaded fiber ceramic substrate;

[0045] (3) Oxalic acid, ammonium tungstate and ammonium metavanadate are added to water and stirred to obtain an impregnation solution; the TiO2-loaded fiber ceramic substrate is placed in the impregnation solution and subjected to a second vacuum impregnation, a second drying and a second calcination to obtain the fiber ceramic-based catalytic filter element for industrial flue gas denitrification.

[0046] In a preferred embodiment, in step (1), the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-3):1; when the chelating agent is acetylacetone, the molar ratio of the chelating agent to tetrabutyl titanate is (1-3):1, more preferably (1-2):1; when the chelating agent is triethanolamine, the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-1.2):1. The present invention introduces a chelating agent during the preparation of titanium sol, which can effectively improve the dispersibility and particle size uniformity of TiO2 nanoparticles. The chelating agent, with its strong coordination force with titanium ions, can effectively regulate its hydrolysis rate and construct a highly dispersed TiO2 support layer.

[0047] In a preferred embodiment, in step (2), the mass ratio of the fiber ceramic substrate to the TiO2 sol is 1:(2-4).

[0048] In a preferred embodiment, in step (2), the vacuum degree of the first vacuum impregnation is 0.095 MPa, and the time is 40-60 min. The vacuum impregnation of this invention removes air from the pores of the fiber ceramic substrate, allowing the TiO2 sol to fully penetrate and uniformly adhere to the fiber ceramic substrate.

[0049] In a preferred embodiment, in step (2), the aging temperature is 60-70°C and the time is 10-12 hours. This invention promotes further cross-linking and stabilization of TiO2 sol particles through aging, thereby forming a stable gel network structure.

[0050] In a preferred embodiment, in step (2), the first drying temperature is 105-120°C, and the time is 12-16 hours. This invention removes solvent and moisture from the gel through gentle drying, preventing gel cracking and thus forming a dry gel coating.

[0051] In a preferred embodiment, in step (2), the first calcination temperature is 400-450℃ and the time is 3-6 hours. This invention thoroughly decomposes organic matter through calcination, causing TiO2 to crystallize and solidify, forming a robust carrier layer on the surface of the fiber ceramic substrate.

[0052] In a preferred embodiment, in step (3), the concentration of oxalic acid in the impregnation solution is 0.3-1.0 wt%, the concentration of ammonium tungstate is 0.4-1.4 wt%, and the concentration of ammonium metavanadate is 0.1-1.0 wt%.

[0053] In a preferred embodiment, in step (3), the mass ratio of the TiO2-loaded fiber ceramic substrate to the impregnation liquid is 1:(2-4).

[0054] In a preferred embodiment, in step (3), the vacuum degree of the second vacuum impregnation is ≥0.095MPa, and the time is 40-60min. This invention enables the impregnation solution containing vanadium and tungsten active components to deeply penetrate and uniformly adsorb into the TiO2 support layer through vacuum impregnation, laying the foundation for loading a highly dispersed active phase.

[0055] In a preferred embodiment, in step (3), the second drying temperature is 105°C and the time is 12 hours. This invention removes moisture from the impregnated substrate through gentle drying, allowing the active precursor salt to be initially fixed on the surface of the carrier layer, preventing component migration and aggregation during subsequent high-temperature treatment.

[0056] In a preferred embodiment, in step (3), the second calcination temperature is 400°C and the time is 3 hours. This invention decomposes the precursor salt through calcination to generate catalytically active V2O5 and WO3 crystals, which are then firmly bonded to the TiO2 support, ultimately forming a stable and efficient SCR catalytic active center.

[0057] This invention provides a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, which is prepared according to the preparation method described in the above technical solution.

[0058] The present invention also provides an application of the fiber ceramic-based catalytic filter element for industrial flue gas denitrification as described above in industrial flue gas denitrification.

[0059] In this embodiment of the invention, room temperature refers to "25±2℃".

[0060] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0061] The fiber ceramic substrate was purchased from Deqing Hengnai Crystal Fiber Co., Ltd., and the titanium tetrabutyl ester (C 16 H 36 O4Ti), acetylacetone (ACAC, C5H8O2), and ammonium metavanadate (NH4VO3) were all purchased from Tianjin Kemei Chemical Reagent Co., Ltd., oxalic acid (C2H2O4·2H2O) was purchased from Tianjin Damao Chemical Reagent Factory, and ammonium tungstate ((NH4) 10 W 12 O 41 ·xH2O) was purchased from Sinopharm Chemical Reagent Co., Ltd., along with anhydrous ethanol (CH3CH2OH) and triethanolamine (C6H2O). 15 NO3 was purchased from Tianjin Fuyu Fine Chemical Co., Ltd., and all reagents were of analytical grade.

[0062] Example 1

[0063] A method for preparing a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, the process flow diagram is shown below. Figure 1 The specific steps are as follows:

[0064] (1) Add tetrabutyl titanate slowly to anhydrous ethanol and stir continuously for 1 h to obtain solution A; add ACAC (molar ratio of ACAC to tetrabutyl titanate is 1:1, 1.5:1, 2:1, 3:1) slowly to anhydrous ethanol and stir continuously for 1 h to obtain solution B; while stirring, add solution B slowly dropwise to solution A and stir continuously for 1 h to obtain TiO2 sol with different amounts of ACAC added, which are denoted as 1ACAC, 1.5ACAC, 2ACAC, and 3ACAC respectively.

[0065] (2) The fiber ceramic substrate was immersed in the TiO2 sol obtained in step (1) at a mass ratio of 1:3. It was immersed for 1 hour under a vacuum degree ≥0.095MPa. Then it was transferred to a 60℃ water bath for 11 hours of aging treatment. After taking it out, it was placed in a 120℃ forced-air drying oven for 24 hours and then calcined at 400℃ for 6 hours to obtain the fiber ceramic substrate loaded with TiO2.

[0066] (3) Oxalic acid, ammonium tungstate and ammonium metavanadate are added to deionized water in sequence and stirred in a water bath at 60°C for 15 min to fully dissolve them, so as to obtain an impregnation solution with an oxalic acid concentration of 0.92wt%, an ammonium tungstate concentration of 0.95wt% and an ammonium metavanadate concentration of 0.43wt%. The TiO2-loaded fiber ceramic substrate obtained in step (2) is placed in the above impregnation solution at a mass ratio of 1:3 and impregnated for 1 h under a vacuum degree ≥0.095MPa. Then it is dried at 105°C for 12 h and calcined at 400°C for 3 h to obtain a fiber ceramic-based catalytic filter for industrial flue gas denitrification. According to the amount of ACAC added, the obtained fiber ceramic-based catalytic filter is named CFE-1, CFE-1.5, CFE-2 and CFE-3 respectively.

[0067] Example 2

[0068] A method for preparing a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, comprising the following steps:

[0069] (1) Add tetrabutyl titanate slowly to anhydrous ethanol and stir continuously for 1 h to obtain solution A; add triethanolamine (the molar ratio of triethanolamine to tetrabutyl titanate is 0.25:1, 0.5:1, 0.75:1, 1:1, 1.1:1, 1.2:1 respectively) slowly to anhydrous ethanol and stir continuously for 1 h to obtain solution B; while stirring, add solution B slowly dropwise to solution A and stir continuously for 1 h to obtain TiO2 sols with different amounts of triethanolamine added.

[0070] Steps (2) to (3) are the same as in Example 1. The resulting fiber ceramic-based catalytic filter cartridges are respectively named 0.25TEA-VWTi, 0.5TEA-VWTi, 0.75TEA-VWTi, 1TEA-VWTi, 1.1TEA-VWTi, and 1.2TEA-VWTi.

[0071] As a bidentate ligand, ACAC's enol group is more likely to coordinate with tetrabutyl titanate than the hydroxyl group of water molecules, thus effectively inhibiting the direct formation of Ti(OH)4 and regulating the hydrolysis rate. ACAC-modified tetrabutyl titanate undergoes hydrolysis and condensation to generate colloidal particles, promoting the gradual transformation of the system into TiO2 sol. To further explore the chelation mechanism of ACAC, tetrabutyl titanate, acetylacetone, and the TiO2 sol obtained in step (1) of Example 1 were characterized using a Fourier transform infrared spectroscopy (IRTracer-100, Shimadzu, Japan). The results are shown in [Figure 1]. Figure 2 Part a of the text; The average particle size of the TiO2 sol with different ACAC addition amounts obtained in step (1) of Example 1 was characterized using a Zetasizer nanoparticle size analyzer (Zetasizer Pro, Malvern, UK). The results are shown in [the original text]. Figure 2 Part c in the text.

[0072] Figure 2 FT-IR images of TiO2 sol obtained by adding tetrabutyl titanate, acetylacetone and step (1) of Example 1 (a), structural formula of the six-membered ring chelate structure in TiO2 sol (b), and average particle size of TiO2 sol with different ACAC addition amounts obtained by step (1) of Example 1 (c). Figure 2 Part a of the results shows that, in the infrared spectrum of tetrabutyl titanate, the value is located at 2958 cm⁻¹. -1 and 2870cm -1 The absorption peak is attributed to the vibration of the CH bond in the butoxy group; in the infrared spectrum of ACAC, 1709 cm⁻¹ -1 With 1620cm -1 The absorption peaks at these locations are attributed to the C=O bond stretching vibrations of the keto and enol structures in ACAC, respectively. In the infrared spectrum of TiO2 sol, the disappearance of these two C=O absorption peaks indicates that tetrabutyl titanate has reacted with acetylacetone and formed a structure resembling... Figure 2 The stable chelate with a six-membered ring structure shown in part b. Figure 2The results in section c show that the amount of ACAC added has a significant impact on the average particle size of TiO2 sol. When the molar ratio of ACAC to tetrabutyl titanate is 1:1, the average particle size of TiO2 sol is 197 nm. With the increase of ACAC addition, the particle size of TiO2 sol shows a trend of first decreasing and then increasing, reaching a minimum of 149 nm when the molar ratio of ACAC to tetrabutyl titanate is 2:1. When the amount of ACAC added is insufficient, the hydrolysis and condensation reaction rate of tetrabutyl titanate during the sol-gel process is faster, resulting in a larger particle size of the generated TiO2 sol. However, with the continued increase of ACAC addition, the ACAC-modified tetrabutyl titanate further condenses after hydrolysis, causing the sol particle size to increase again.

[0073] The microstructure of the fiber ceramic-based catalytic filter element prepared in Example 1 was analyzed by scanning electron microscopy (SEM) (GeminiSEM 360, Zeiss, Germany). The results are shown in the figure. Figure 3 .

[0074] Figure 3 SEM images of the catalysts supported on the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1 are shown. In these images, a1 and a2 represent CFE-1, b1 and b2 represent CFE-1.5, c1 and c2 represent CFE-2, and d1 and d2 represent CFE-3. A1~d1 wavelengths are 400 nm, and a2~d2 wavelengths are 200 nm. Figure 3 It can be seen that as the amount of acetylacetone added increases, the degree of agglomeration of the catalytic filter element is significantly reduced; when the molar ratio of ACAC to tetrabutyl titanate is 1:2, the agglomeration phenomenon is effectively alleviated, and the catalytic filter element presents as uniformly dispersed nano-spherical particles. However, after further increasing the amount of chelating agent, a certain degree of agglomeration reappears between the particles of the catalytic filter element.

[0075] The microstructure and elemental distribution of the fiber ceramic-based catalytic filter element CFE-2 prepared in Example 1 were analyzed by scanning electron microscopy (SEM) (GeminiSEM 360, Zeiss, Germany) combined with energy dispersive spectroscopy (EDS). The results are shown in the figure. Figure 4 .

[0076] Figure 4 SEM and EDS images of the fiber ceramic-based catalytic filter CFE-2 prepared in Example 1 are shown, where a1 is a SEM image (4 μm), a2 is a SEM image (1 μm), and b is an EDS image. Figure 4The a1 and a2 sections reveal that a large number of highly dispersed and continuously distributed nanoparticles are attached to the fiber surface, indicating that the V2O5-WO3 / TiO2 catalyst has been successfully constructed on the fiber surface, forming a dense catalytic layer. This structure is beneficial for promoting sufficient contact between gaseous reactants and catalytic active sites in the NH3-SCR process. Figure 4 As can be seen from part b, the four elements V, W, O and Ti are uniformly distributed on the fiber surface without obvious agglomeration, which further confirms that a uniformly distributed and completely covered catalytic layer is formed on the fiber surface, laying a key structural foundation for CFE-2 to achieve excellent NH3-SCR catalytic performance.

[0077] The crystal structure of the fiber ceramic-based catalytic filter element prepared in Example 1 was analyzed by X-ray diffraction (XRD) (SmartLab SE, Rikaku, Japan). The results are shown in [Figure number missing]. Figure 5 .

[0078] Figure 5 XRD patterns of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1. From... Figure 5 As can be seen, typical anatase TiO2 diffraction peaks were observed in all samples (JCPDS PDF# 21-1272), proving that a catalytic layer with anatase TiO2 phase was successfully constructed on the surface of the fiber ceramic. The presence of anatase TiO2 phase contributes to the efficient SCR reaction in the catalytic filter element. No characteristic diffraction peaks of V2O5 and WO3 were observed in the XRD patterns, indicating that V2O5 and WO3 are uniformly dispersed on the TiO2 layer, a conclusion consistent with previous results obtained through EDS elemental distribution analysis. With increasing ACAC addition, the diffraction peaks of anatase TiO2 phase significantly increased, indicating that ACAC promotes TiO2 crystallization.

[0079] N2 adsorption-desorption experiments were conducted using a fully automated specific surface area and porosity analyzer (Nova 2000e, Quantachrome, USA). The results are shown in [Figure number missing]. Figure 6 Part a in the text.

[0080] Figure 6 The N2 adsorption-desorption isotherms (a) and pore size distribution diagrams (b) of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1 are shown. Figure 6 As can be seen from part a, all samples exhibit typical type IV adsorption isotherms, indicating the presence of abundant mesoporous structures in the samples. Figure 6Part b further confirms the presence of abundant mesoporous structures in the sample. The presence of mesoporous structures is beneficial to enhancing the mass transfer efficiency at the gas-solid interface and promoting the adsorption of gaseous reactants, thereby promoting the SCR reaction.

[0081] The grain size of the fiber ceramic-based catalytic filter element prepared in Example 1 was calculated based on the Scherrer equation, and the results are shown in Table 1. The specific area, pore volume, and pore size distribution of the fiber ceramic-based catalytic filter element prepared in Example 1 were calculated based on the Brunauer-Emmett-Teller (BET) multilayer adsorption theory and the Barrett-Joyner-Halenda (BJH) method, and the results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from the grain size data in Table 1, the increase in ACAC addition is accompanied by an increase in grain size, further indicating that ACAC accelerates the growth of anatase TiO2 particles. It is noteworthy that CFE-2 maintains a relatively small grain size (10.8 nm) while retaining high crystallinity, a characteristic that is beneficial to improving catalytic performance.

[0085] Based on the specific surface area, total pore volume, and average pore size data in Table 1, it can be seen that with the increase of ACAC addition, the specific surface area and total pore volume of the samples first increase and then decrease, with CFE-2 exhibiting the largest specific surface area (40.218 m²). 2 / g), maximum total pore volume (0.05795cm³). 3 The CFE-2 catalyst has a relatively small average pore size (5.76347 nm) and a large specific surface area, which is beneficial for the dispersion and exposure of active components, thereby generating more effective active sites. The large total pore volume and small average pore size indicate that the catalyst supported on CFE-2 has a more developed pore structure, which creates superior mass transfer conditions for the SCR catalytic process and thus significantly promotes the SCR catalytic reaction.

[0086] The elemental composition and atomic valence states of the catalyst supported on the fiber ceramic-based catalytic filter element prepared in Example 1 were analyzed using X-ray photoelectron spectroscopy (XPS) (K-Alpha, Thermo Fisher, USA). All obtained spectra were corrected for binding energy using the C1s peak at 284.8 eV as the standard. The results are shown in [Figure number missing]. Figure 7 .

[0087] Figure 7The image shows the XPS spectrum of the catalyst supported on the fiber ceramic-based catalytic filter element prepared in Example 1, where a represents Ti 2p, b represents V 2p, and c represents O 1s. Figure 7 The Ti 2p XPS spectrum in part a was fitted to two peaks, one at 458.7 eV and the other at the Ti 2p peak. 1 / 2 The peak and Ti 2p at 464.4 eV 3 / 2 The peaks and the difference in their binding energies indicate that titanium mainly exists in the tetravalent form. Figure 7 The V 2p XPS spectrum in part b was fitted to two peaks, located at 515.8 eV and 517.1 eV, respectively, corresponding to V 4+ Species and V 5+ Species. Figure 7 The O 1s XPS spectrum of the middle c part was fitted into three peaks: lattice oxygen Oβ at 530 eV, chemisorbed oxygen Oα at 531.6 eV, and hydroxyl oxygen Oγ at 533.1 eV.

[0088] according to Figure 7 The fitted peak area was used to calculate the Oβ / (Oα+Oβ+Oγ) ratio and V of the catalytic filter element. 4+ / (V 4+ +V 5 + The ratio is shown in Table 2.

[0089] Table 2

[0090]

[0091] Table 2 shows that the catalyst supported on the CFE-2 catalytic filter element not only has the highest Vc 4+ / (V 4+ +V 5+ The ratio of Oβ to (Oα+Oβ+Oγ) was 38.7%, and its Oβ / (Oα+Oβ+Oγ) ratio (14%) was also the largest. 4+ It can promote the generation of chemically adsorbed oxygen and improve the oxygen absorption capacity of the catalyst. Compared with lattice oxygen, chemically adsorbed oxygen exhibits stronger oxidation reactivity. Therefore, the greater the amount of chemically adsorbed oxygen, the stronger the oxidation capacity of the catalyst, which in turn promotes the NH3-SCR reaction on the catalytic filter element, indicating that the catalytic filter element CFE-2 has the strongest catalytic performance.

[0092] Temperature-programmed desorption (NH3-TPD) and temperature-programmed reduction (H2-TPR) were performed using a temperature-programmed chemisorption analyzer (TP-5076, Xianquan, China). The consumption of desorbed NH3 and H2 was continuously monitored using a TCD. The results are shown in [Figure number missing]. Figure 8In the NH3-TPD test, the sample was first purged in nitrogen at 350℃ and 30 mL / min for 30 min, then cooled to room temperature. Next, the sample was placed in an NH3 atmosphere for adsorption for 30 min, then purged with nitrogen for 10 min. Finally, the sample was placed under a nitrogen flow and heated to 700℃ at a rate of 10℃ / min. In the H2-TPR test, the sample was exposed to a 7.5% H2 / N2 flow and heated to 800℃ at a rate of 10℃ / min.

[0093] Figure 8 The NH3-TPD (a) and H2-TPR (b) spectra of the fiber ceramic-based catalytic filter cartridges CFE-1, CFE-1.5, CFE-2, and CFE-3 prepared in Example 1 are shown. Figure 8 As shown in section a, the NH3 desorption peaks of all samples are distributed across a wide temperature range from 20℃ to 600℃. Based on the NH3 desorption temperature, acidic sites can be categorized into weakly acidic sites (<200℃), moderately acidic sites (200-350℃), and strongly acidic sites (>350℃). Among all samples, the catalyst supported on CFE-2 exhibits the largest desorption peak area, indicating its strongest NH3 adsorption capacity. This can be attributed to its higher specific surface area, exposing more acidic sites. The number of acidic sites directly affects the adsorption and activation efficiency of NH3; more acidic sites are more conducive to NH3 adsorption and activation, thereby improving catalytic activity. Figure 8 As can be seen from part b, below 750℃, all samples exhibit two distinct reduction peaks: the reduction peak located near 530℃ can be attributed to V. 5+ →V 4+ and W 6+ →W 4+ The synergistic reduction process; the reduction peak near 700℃ corresponds to W 4+ Further restoration to W 0+ Among all samples, the reduction peak intensity of the catalyst supported on CFE-2 was significantly higher than that of the other samples, and the temperature of the first reduction peak was slightly lower than that of the other samples, indicating that it has superior redox properties. This phenomenon may be related to its higher specific surface area, which allows for better dispersion of its active components compared to other samples, making it easier to be reduced by H2.

[0094] Catalytic performance testing: The denitrification performance of the catalytic filter element prepared in Example 1 was investigated using a fixed-bed reactor. A schematic diagram of the fixed-bed reactor is shown below. Figure 9 The test results are shown below. Figure 10-11The simulated flue gas consists of 500 ppm NO, 4 vol% O2, 500 ppm NH3, 100 ppm SO2 (in use), 5 vol% H2O (in use), and a balanced nitrogen atmosphere. The total gas flow rate is 1 L / min, corresponding to a mass hourly space velocity (HHSV) of 100,000 h⁻¹. -1 The NO concentration at the outlet was measured using a flue gas analyzer (Testo 350-Pro). Stability testing was conducted with continuous catalysis at 325°C for 24 hours. NO conversion was calculated using the following formula:

[0095] ;

[0096] in Represents NO x Initial concentration, ppm; NO represents the end of the reaction x Concentration, ppm.

[0097] Figure 10 The denitrification efficiency of the fiber ceramic-based catalytic filter element prepared in Example 1 is given by: a) NO conversion rate of CFE-1, CFE-1.5, CFE-2, and CFE-3 in the temperature range of 200-450℃; b) NO conversion rate at a space velocity of 100,000 h⁻¹. -1 -250000h -1 The NO conversion rate of CFE-2 under the given conditions is given by: c represents the NO conversion rate of CFE-2 under different oxygen concentrations, d represents the NO conversion rate of CFE-2 under different NH3 / NO molar ratios, and e represents the NO conversion rate of CFE-2 under different NO concentrations. Figure 10 As shown in section a, the catalytic filter cartridges prepared with different amounts of acetylacetone exhibit significant differences in catalytic activity. CFE-2, within a temperature range of 275-375℃, shows a NO conversion rate exceeding 90%, demonstrating excellent denitrification activity and a wide activity window. It is well known that the NH3-SCR activity of the catalytic filter cartridge depends on its adsorption capacity and activation rate for gaseous reactants (NO, O2, NH3). NH3-TPD characterization results indicate that the catalyst supported on CFE-2 has a stronger adsorption capacity for NH3, mainly due to its larger specific surface area, providing more active sites. Furthermore, H2-TPR and XPS characterization results show that the catalyst supported on CFE-2 possesses stronger redox properties and more V... 4+ The presence of certain species is beneficial for the activation of O2 and NH3. Simultaneously, the catalytic layer on CFE-2 is well dispersed on the fiber ceramic, facilitating effective contact between the reactant gases and the active sites. These factors work together to give CFE-2 excellent denitrification performance. Figure 10 As can be seen from part b, the NO removal rate increases with space velocity from 250,000 h⁻¹.-1 Reduced to 100,000h -1 It shows a gradual upward trend: at an airspeed of 250,000 h -1 At that time, the highest NO removal rate was 92%; while when the space velocity was reduced to 100,000 h⁻¹, the NO removal rate was 92%. -1 At this point, the removal rate can be further increased to 98%. Under low space velocity conditions, the contact time between the reactant gas and the catalyst is long, which is conducive to the complete occurrence of the reaction. Figure 10 As shown in section c, when the reactant gas contains no O2, the NO conversion rate of CFE-2 is only 14%. After introducing a small amount of O2, the NO conversion rate increases sharply. However, the rate of increase gradually slows down after the O2 concentration exceeds 0.5%, and then stabilizes at approximately 1%. This is because as the O2 concentration increases, the demand for O2 gradually becomes saturated, leading to a gradual weakening of the reaction rate-promoting effect. Figure 10 As shown in section d, the NO conversion rate exhibits a linear upward trend as the NH3 / NO molar ratio gradually increases from 0.4 to 1. Under low NH3 / NO molar ratio conditions, insufficient NH3 supply results in a limited amount of reducing agent participating in the reaction, leading to a large amount of NO remaining unreduced. With increasing NH3 / NO ratio, more NO is reduced, thus driving a rapid increase in NO conversion rate. When the NH3 / NO molar ratio reaches 1, the NO conversion rate reaches saturation and does not change with further increases in the NH3 / NO molar ratio. This is because excess NH3 gas cannot continue to participate in the NO reduction reaction. Figure 10 As can be seen from part e, when the NO concentration increases from 200 ppm to 1200 ppm, the NO conversion rate only decreases slightly by about 2%, remaining at a high level overall. This indicates that the CFE-2 catalytic filter element exhibits good reaction adaptability over a wide range of NO concentrations, demonstrating good potential for industrial applications.

[0098] Figure 11 The water and sulfur resistance (a) and denitrification stability (b) of the fiber ceramic-based catalytic filter element CFE-2 prepared in Example 1 are shown. Figure 11As shown in section a, when 100 ppm of SO2 was introduced into the reaction system, the NO conversion rate of CFE-2 did not decrease and remained stable at a high level of 98%. After stopping the SO2 injection, the NO conversion rate of CFE-2 remained at 98% without change. When 5% H2O was injected into the reaction system, the NO conversion rate of CFE-2 immediately showed a downward trend and eventually stabilized at 94%. After stopping the H2O injection, the NO conversion rate quickly recovered to the initial level. Similarly, when both 5% H2O and 100 ppm SO2 were injected simultaneously, the NO conversion rate of CFE-2 also showed a downward trend, eventually stabilizing at 94%. After stopping the H2O and SO2 injections, the NO conversion rate of CFE-2 also returned to its initial level. These results indicate that SO2 has virtually no adverse effect on the denitrification performance of CFE-2, while H2O caused a reversible decrease in denitrification performance. SO2 did not inhibit the denitrification performance of CFE-2, which can be attributed to the absence of sulfate formation on its catalyst surface, preventing blockage of active sites and thus maintaining the denitrification performance of CFE-2. H2O molecules and gaseous reactants compete for adsorption at the active sites on the catalytic filter element surface, temporarily reducing the NH3-SCR reaction efficiency, which in turn leads to a reversible decrease in NO conversion. In summary, the fiber ceramic-based catalytic filter element CFE-2 prepared in Example 1 exhibits good sulfur resistance and water resistance. Figure 11 As shown in section b, the NO conversion rate remained consistently at a high level of 99% throughout the entire 24-hour test period. This phenomenon strongly demonstrates that the CFE-2 catalytic filter element possesses exceptional stability and can continuously and efficiently exert its catalytic effect under prolonged reaction conditions.

[0099] The denitrification performance of the catalytic filter element prepared in Example 1 was tested, and the denitrification efficiency of the fiber ceramic-based catalytic filter element prepared in Example 2 was tested at a reaction space velocity of 300,000 h⁻¹. -1 Other test conditions were the same as in Example 1, and the results are shown in [link to example]. Figure 12 .

[0100] Figure 12 The NO conversion rates of the fiber ceramic-based catalytic filter cartridges prepared in Example 2 (0.25TEA-VWTi, 0.5TEA-VWTi, 0.75TEA-VWTi, 1TEA-VWTi, 1.1TEA-VWTi, and 1.2TEA-VWTi) within the temperature range of 200-500℃ are shown. Figure 12 It can be seen that at 300,000h -1At extremely high space velocities, with the increase of triethanolamine addition, the catalytic activity of the fiber ceramic-based catalytic filter element first increases and then decreases throughout the temperature range. The catalytic activity is optimal when the molar ratio of triethanolamine to tetrabutyl titanate is 1:1. In the temperature range of 300~450℃, the NO conversion rate of 1TEA-VWTi reaches over 75%.

[0101] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a fiber ceramic-based catalytic filter element for industrial flue gas denitrification, characterized in that, Includes the following steps: (1) Add tetrabutyl titanate to anhydrous ethanol to obtain solution A; add chelating agent to anhydrous ethanol to obtain solution B; Under stirring, solution B is added to solution A to obtain TiO2 sol; the chelating agent is selected from acetylacetone or triethanolamine; (2) The fiber ceramic substrate is immersed in the TiO2 sol, and then subjected to a first vacuum impregnation, aging, a first drying and a first calcination to obtain a TiO2-loaded fiber ceramic substrate; (3) Add oxalic acid, ammonium tungstate and ammonium metavanadate to water and stir to obtain an impregnation solution; The TiO2-loaded fiber ceramic substrate is placed in the impregnation solution, and then subjected to a second vacuum impregnation, a second drying, and a second calcination to obtain the fiber ceramic-based catalytic filter element for industrial flue gas denitrification.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-3):

1.

3. The preparation method according to claim 2, characterized in that, In step (1), when the chelating agent is acetylacetone, the molar ratio of the chelating agent to tetrabutyl titanate is (1-3):1; when the chelating agent is triethanolamine, the molar ratio of the chelating agent to tetrabutyl titanate is (0.25-1.2):

1.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the fiber ceramic substrate to the TiO2 sol is 1:(2-4).

5. The preparation method according to claim 1, characterized in that, In step (2), the vacuum degree of the first vacuum impregnation is ≥0.095MPa, and the time is 40-60min; The aging temperature is 60-70℃, and the time is 10-12 hours; The first drying temperature is 105-120℃, and the time is 12-16h; The first calcination temperature is 400-450℃ and the time is 3-6h.

6. The preparation method according to claim 1, characterized in that, In step (3), the concentration of oxalic acid in the impregnation solution is 0.3-1.0 wt%, the concentration of ammonium tungstate is 0.4-1.4 wt%, and the concentration of ammonium metavanadate is 0.1-1.0 wt%.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of the TiO2-loaded fiber ceramic substrate to the impregnation liquid is 1:(2-4).

8. The preparation method according to claim 1, characterized in that, In step (3), the vacuum degree of the second vacuum impregnation is ≥0.095MPa, and the time is 40-60min; The second drying temperature is 105℃, and the time is 12 hours; The second calcination temperature is 400℃ and the time is 3 hours.

9. A fiber-ceramic-based catalytic filter element for industrial flue gas denitrification, characterized in that, It is prepared according to any one of claims 1-8.

10. The application of the fiber ceramic-based catalytic filter element for industrial flue gas denitrification as described in claim 9 in industrial flue gas denitrification.

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