Preparation method and application of low-temperature ammonia-free denitration catalyst

Abstract

The invention provides a preparation method and application of a low-temperature ammonia-free denitration catalyst, and relates to the technical field of catalysts.The preparation method of the low-temperature ammonia-free denitration catalyst comprises the steps that a metal precursor is complexed through tartaric acid, the metal precursor is loaded on a composite carrier through ultrasonic impregnation, and the catalyst is obtained through stepped roasting, the catalyst comprises active components, sulfur-resistant auxiliaries, MgO-coated CNTs, a titanium-germanium composite carrier and a silicon-aluminum composite sol adhesive, the active components comprise MnO, FeO and CeO, and the sulfur-resistant auxiliaries comprise MoO and CoO; the catalyst has efficient denitration performance on industrial flue gas under the low-temperature condition of 80-150 DEG C, the NOx removal rate at 150 DEG C reaches 95.2%, and meanwhile, the sulfur resistance is remarkable.

Description

Technical Field

[0001] The present application relates to the field of catalyst technology, and in particular to a preparation method and application of a low-temperature ammonia-free denitrification catalyst. Background Art

[0002] Driven by clean energy policies, flue gas treatment technologies for steel sintering machines and coke ovens are widely used. However, with increasingly stringent environmental standards, nitrogen oxide (NOx) emissions have become a key bottleneck hindering the industry's development. While the current mainstream ammonia-based denitrification technology can achieve emission standards, it also creates a more problematic secondary pollution chain. Ammonium salt particles formed by ammonia escape not only corrode downstream equipment but also combine with acidic substances in the atmosphere to form difficult-to-monitor secondary pollutants. This superficial approach forces companies into a dilemma: either bear the high safety risks of liquid ammonia storage and the ever-increasing costs of denitrification agents, or face environmental penalties for excessive ammonia escape. The industry has attempted to control NOx generation at the source through combustion optimization, but the frequent load fluctuations of gas-fired boilers make combustion stability difficult to maintain. When the boiler is operating at low load, the imbalanced temperature field in conventional low-NOx burners creates localized high-temperature zones that inversely increase the NOx generation rate. This operating-condition dependency prevents front-end control technologies from fully replacing end-of-pipe treatment. While existing ammonia-free denitrification catalysts avoid the risk of ammonia pollution, their active temperature window is fundamentally misaligned with the actual operating conditions of gas-fired boilers. When the flue gas temperature drops below 300°C, the catalytic activity exhibits a cliff-like decline. The root cause lies in the serious lack of activation capacity of the chemical adsorption sites on the surface of traditional catalysts for reactants in low-temperature environments, and the microporous structure is easily blocked by capillary condensation in water-containing flue gas. Even more problematic is that existing technology systems generally separate the physical structure design of the catalyst from the chemical reaction pathway in research and development. For example, while loading active components through the impregnation method can increase the density of surface acid sites, it does so at the expense of mesopore connectivity; and while the use of templates to prepare hierarchical pore structures optimizes mass transfer efficiency, it also leads to a decrease in the dispersion of active components. This mutual constraint between physical structure and chemical properties forms a technical closed loop that is difficult to break through, resulting in a constant trade-off between low-temperature activity and water and sulfur resistance. The market is in urgent need of a type of catalyst that can penetrate the "low-temperature activity forbidden zone". It must meet three contradictory demands at the same time: maintain structural stability in a low-temperature and high-humidity environment, have accurate molecular recognition capabilities under complex flue gas components, and achieve rapid activation response under frequent start-stop conditions. Existing patented technologies have proposed to improve low-temperature activity through precious metal doping or rare earth modification, but such solutions not only significantly increase material costs, but their improvement effects are often quickly offset in sulfur-containing flue gases. Other studies have attempted to compensate for the lack of activity by increasing the specific surface area of ​​the catalyst, but have ignored the limiting size effect of the microporous structure - when the pore size is close to the kinetic diameter of water molecules, the preferential adsorption of water molecules will completely block the reactant transport channel. This failure mechanism hidden at the microscopic scale is easily overlooked in routine testing, but it directly leads to the collective failure of catalysts that perform well in the laboratory in engineering applications.A deeper analysis of the industry's pain points reveals that the true technological barrier lies in building a "three-in-one" synergistic system: creating a new low-temperature activation pathway to overcome limitations at the reaction principle level; designing biomimetic mass transfer channels that are resistant to moisture and blockage at the physical structure level; and constructing a multi-active site relay catalytic network at the chemical composition level. This requires overturning the traditional catalyst R&D paradigm, integrating the previously isolated optimization of materials parameters, structural mechanical properties, and surface chemical processes into unified design variables. Only through the deep integration of reaction mechanism innovation and material genetic reconstruction can low-temperature ammonia-free denitrification technology with practical engineering value be developed, fundamentally resolving the environmental compliance dilemma faced by gas-fired boilers under variable load conditions.

[0003] In summary, the market is in urgent need of developing a new preparation method and application of low-temperature ammonia-free denitrification catalyst. Summary of the Invention

[0004] The present application provides a preparation method of a low-temperature ammonia-free denitrification catalyst and its application, in order to solve the problems raised in the above background technology.

[0005] To solve the above technical problems, the present application discloses a method for preparing a low-temperature ammonia-free denitrification catalyst, comprising the following steps:

[0006] S1. Preparation of titanium-germanium composite support;

[0007] S2. Preparation of a carrier loaded with an active component and an anti-sulfur additive: complexing the active component and the anti-sulfur additive precursor with tartaric acid to obtain a metal tartaric acid complex solution, immersing the MgO@CNTs, titanium-germanium composite support and a binder in the metal tartaric acid complex solution and ultrasonically dispersing the mixture;

[0008] S3. Drying and calcining to obtain a low-temperature ammonia-free denitrification catalyst.

[0009] Furthermore, the method for preparing the titanium-germanium composite support includes ball-milling titanium dioxide and germanium dioxide for 120 minutes, and then preparing the titanium-germanium composite support through a spray drying tower.

[0010] Furthermore, titanium dioxide and germanium dioxide were added to a ball mill with a ball-to-material ratio of 10:1, and ball milled at a speed of 300 r / min for 120 min. The slurry after ball milling was fed into a spray drying tower with an inlet temperature of 200°C and an outlet temperature of 90°C to obtain a titanium-germanium composite carrier with a particle size of 5-10 μm.

[0011] Furthermore, Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, Ce(NO3)3·6H2O, (NH4)6Mo7O 24·4H2O and Co(NO3)2·6H2O were dissolved in deionized water, tartaric acid (1.5 times the total molar amount of metal ions) was added, and the mixture was stirred at 60°C and 500 r / min for 120 min to prepare a metal tartaric acid complex solution.

[0012] Furthermore, MgO@CNTs, titanium-germanium composite support and silicon-aluminum composite sol were immersed in a metal tartaric acid complex solution, 2 parts of dispersant polyethylene oxide were added and ultrasonically dispersed at 60°C for 60 minutes, and allowed to stand for 12 hours to obtain a support loaded with active components and anti-sulfur additives.

[0013] Furthermore, the carrier loaded with active components and anti-sulfur additives was dried at 80°C for 12 h, heated from 100°C to 300°C at 2°C / min, calcined at 300°C for 1 h, heated from 300°C to 500°C at 5°C / min, and calcined at 500°C for 4 h to obtain a low-temperature ammonia-free denitrification catalyst.

[0014] Furthermore, the preparation method of MgO@CNTs includes: immersing 5 parts of MWCNTs in 80 parts of HNO3 by weight, ultrasonically treating at 80°C for 2 hours, centrifuging and washing, and drying at 110°C for 12 hours to obtain pretreated MWCNTs, dissolving 1 part of Mg(NO3)2·6H2O in 10 parts of deionized water, adding 3 parts of EDTA, stirring at 60°C and adding pretreated MWCNTs, immersing in vacuum oscillation at 40°C for 6 hours, drying at 60°C for 12 hours, and heating to 550°C at 2°C / min in a N2 atmosphere and calcining for 5 hours to obtain MgO@CNTs.

[0015] Furthermore, the low-temperature ammonia-free denitration catalyst prepared by the preparation method comprises, by weight, 25-30 parts of active components, 10-14 parts of anti-sulfur additives, 52-57 parts of composite carriers and 3-8 parts of adhesives.

[0016] Furthermore, the active components include manganese tetraoxide, ferric oxide and cerium dioxide; the anti-sulfur additives include molybdenum trioxide and cobalt tetraoxide; the composite carrier includes MgO@CNTs and titanium germanium composite carrier; and the binder is silicon-aluminum composite sol.

[0017] The present application discloses an application of a low-temperature ammonia-free denitrification catalyst prepared by the preparation method in industrial flue gas denitrification. The low-temperature ammonia-free denitrification catalyst is suitable for a low-temperature environment of 80-150°C, and the NOx concentration in the flue gas is ≤1000mg / m³ and SO2 is ≤200ppm.

[0018] The mechanism of action of the above raw material components is as follows: First, the active component acts as the core driving force for low-temperature ammonia-free denitrification, achieving efficient denitrification through electron transfer and surface acidity regulation of multi-metal oxides. Manganese tetraoxide has abundant surface oxygen vacancies and variable valence (Mn²⁺ / Mn³⁺ / Mn4 ⁺), directly activates nitrogen oxide molecules at low temperatures, causing them to dissociate into active nitrogen oxide intermediates. Iron trioxide enhances the adsorption and activation of ammonia by providing Lewis acid sites, while its interfacial electron transfer with manganese further accelerates the redox cycle. The introduction of cerium dioxide significantly improves oxygen storage capacity, through Ce³⁺ / Ce 4 ⁺ The conversion buffers oxygen concentration fluctuations in the reaction system, maintaining the catalyst's stability in oxygen-deficient environments. The three components form a synergistic network of "manganese as the primary oxidant, iron as the acidifier, and cerium as the oxygen balance regulator," achieving deep reduction of nitrogen oxides. Secondly, the anti-sulfur additive combats sulfur poisoning through both physical isolation and chemical conversion. Molybdenum trioxide preferentially reacts with sulfur dioxide in the flue gas to form thermally stable molybdenum sulfate, blocking the diffusion of sulfur to the active components. Simultaneously, the molybdenum species modify the support surface acidity, reducing low-temperature deposition of ammonium bisulfate. Cobalt trioxide, leveraging its sulfur adsorption selectivity, converts gaseous sulfur dioxide into solid cobalt sulfide, maintaining the cleanliness of active sites through lattice oxygen regeneration. The two components synergistically form a sulfur barrier layer characterized by "molybdenum capture and cobalt fixation," significantly slowing activity decay caused by sulfur species coverage. Thirdly, the composite support improves the catalyst's mass transfer efficiency and active site dispersion through microstructural design and chemical modification. In MgO@CNTs, magnesium oxide nanoparticles are anchored to the carbon nanotube surface. Their alkaline sites neutralize acidic components in flue gas, while the high conductivity of the carbon nanotubes promotes electron migration from the support to the active components, accelerating redox kinetics. The titanium-germanium composite support stabilizes the nanodispersion of the active components through the strong metal-support interaction (SMSI effect) formed by the titanium-germanium heterogeneous lattice. Its mesoporous structure provides gas diffusion channels, shortening the path for reactants to reach the active sites. The combined "conductive skeleton-mesoporous confinement" structure of the two optimizes the reaction microenvironment. Fourthly, the silica-alumina composite sol acts as a binder, forming a three-dimensional silica-alumina network through a polycondensation reaction between the colloidal particles. During calcination, this network transforms into an inorganic ceramic binder phase, which not only mechanically anchors the active components to the support particles but also forms Si-OM (M = Mn, Fe, Ce) covalent bonds with the metal oxides on its surface, enhancing interfacial bonding. Furthermore, the binder's nanofilling effect reduces catalyst pore blockage, maintaining a high specific surface area and gas permeability.

[0019] The mechanism of action of the above preparation method is as follows: Support pretreatment directly determines the loading efficiency of the active component. During the preparation of MgO@CNTs, nitric acid-treated carbon nanotubes generate carboxyl and hydroxyl groups, enhancing surface hydrophilicity and providing anchoring sites for magnesium ions. EDTA chelates magnesium ions, delaying hydrolysis and precipitation, ensuring a monolayer dispersion of magnesium oxide on the carbon nanotube surface. Ball milling of the titanium-germanium support mechanically alloys the grain boundaries between titanium dioxide and germanium dioxide, forming a titanium-germanium solid solution. The resulting lattice strain induces more oxygen vacancies, which serve as nucleation sites for the subsequent active component. Complexation of the metal precursor with tartaric acid is key to achieving uniform dispersion. The dicarboxyl groups of tartaric acid form five-membered ring chelates with metal ions (such as Mn⁺ and Fe⁺), which inhibit particle aggregation during calcination through steric hindrance. In the step-by-step impregnation strategy, the silica-alumina sol first wets the support surface to form a hydroxylated layer. The metal complex then adsorbs to the support surface through hydrogen bonding and electrostatic interactions, achieving molecular-level dispersion. The addition of polyethylene oxide prevents particle settling by entanglement of long-chain polymers, forming a stable suspension. A stepwise calcination procedure drives the directional formation of the active phase. The low-temperature stage (100–300°C) primarily removes physical water and tartaric acid decomposition products, preventing carbon residue. Slow heating in the intermediate temperature stage (300–500°C) promotes the stepwise decomposition of nitrates into oxides. Simultaneously, solid-phase diffusion occurs between the magnesium-titanium-germanium support and the active components, forming a mixed crystal phase of Mn2O3-Fe2O3-CeO2. Cobalt trioxide and molybdenum trioxide complete their crystalline transformation at this temperature, resulting in a spinel structure and the formation of layered cobalt molybdate, further enhancing sulfur resistance. The resulting hierarchical pore structure of the catalyst stems from thermally induced self-organization of the multiple components. The silica-alumina binder phase melts at 500°C to form a glassy network, bonding the MgO@CNTs to the titanium-germanium support. Active component particles grow epitaxially on the support surface, their size limited by the support's mesopore diameter. Cobalt molybdenum oxide segregates at grain boundaries, forming sulfur-resistant isolation zones. This micro-area distribution of "core-shell-isolation zone" maximizes the exposure of active sites and inhibits sintering. In summary, the catalyst achieves denitrification through the "endogenous reduction" pathway under ammonia-free conditions: carbon monoxide in the flue gas is oxidized to carbon dioxide at the iron-manganese active sites, and the reactive oxygen species produced at the same time oxidize nitrogen oxides to nitrate intermediates; cerium dioxide promotes the decomposition of nitrates into nitrogen, forming a closed redox cycle. The anti-sulfur component blocks the contact of sulfur dioxide with the active sites by preferentially adsorbing sulfur dioxide, ensuring smooth reaction channels.

[0020] Compared with the prior art, this application provides a method for preparing a low-temperature ammonia-free denitrification catalyst and its application, which has the following beneficial effects:

[0021] 1. This application uses manganese tetraoxide as the main active component, combined with the oxygen storage capacity of cerium dioxide, significantly broadening the low-temperature reaction window; the titanium-germanium composite carrier is formed into a high specific surface structure through ball milling and spray drying, which enhances the dispersion of the active components. Mn3O4 is responsible for the initial activation of NO, Fe2O3 drives the reduction reaction, and CeO2 maintains the reaction stability. The three form a closed-loop catalytic network, synergistically constructing a low-temperature ammonia-free denitrification system of "manganese as the main oxide - iron provides acidity - cerium regulates oxygen balance" to enhance efficiency;

[0022] 2. The denitrification process of this application does not require the addition of ammonia or other reducing agents, which solves the ammonia escape problem of traditional SCR technology and avoids ammonium salt clogging and equipment corrosion. Ferric oxide and manganese tetraoxide form a redox cycle, directly catalyzing the decomposition of NOx into N2. The tartaric acid complex impregnation process ensures the uniform loading of active components on the carrier surface, thereby improving the catalytic activity.

[0023] 3. The low-temperature ammonia-free denitrification catalyst prepared in this application maintains high stability in sulfur-containing flue gas with SO2 ≤ 200 ppm. The sulfur-resistant additives molybdenum trioxide and cobalt tetroxide can inhibit sulfate formation. Molybdenum trioxide preferentially adsorbs SO2 and forms a reversible intermediate. Cobalt tetroxide inhibits SO3 formation through electron transfer. In addition, the MgO alkaline sites in the MgO@CNTs carrier neutralize acidic sulfides and protect the active centers.

[0024] 4. The carriers involved in this application synergistically enhance the mechanical strength and service life of the catalyst. After calcination, the composite carrier MgO@CNTs and the titanium-germanium composite carrier reduce the wear rate of the prepared low-temperature ammonia-free denitration catalyst while extending its service life. The CNTs network is fully utilized to improve the conductivity and toughness of the carrier. The titanium-germanium composite carrier is used to inhibit the TiO2 phase change by germanium doping. The OX@CMC type silicon-aluminum composite sol binder is used to enhance the physical structural integrity of the low-temperature ammonia-free denitration catalyst.

[0025] 5. This application overcomes to a high degree the industry difficulty of balancing activity, sulfur resistance and life span, which is common in low-temperature ammonia-free denitrification, through the optimization of Mn3O4 / Fe2O3 / CeO2 synergistic active components, the design of MoO3 / Co3O4 electron transfer anti-sulfur structure, the acid-base controlled carrier functionalization of MgO@CNTs, and the preparation process of tartaric acid complexation and step-by-step roasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the low-temperature ammonia-free denitration catalyst prepared in Example 1 of the present application;

[0027] Figure 2 This is the SEM image of the catalyst prepared in Comparative Example 1 of this application. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0029] In addition, in this application, descriptions such as "first" and "second" are only used for descriptive purposes and do not specifically refer to the order or ranking, nor are they used to limit this application. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions and technical features between the various embodiments can be combined with each other, but this must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0030] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component contents, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are analytical reagents (AR) unless otherwise specified, which were purchased from commercial channels.

[0031] DL-tartaric acid was purchased from Sichuan Lvcheng Biotechnology Co., Ltd., CAS No.: 133-37-9, food grade; polyethylene oxide was Dow UCARFLOC 309; multi-walled carbon nanotubes (MWCNTs) were purchased from Zhejiang Yamei Nano, model: AM-C6-068-1, diameter 5-10 nm, purity 99.9%.

[0032] Example 1

[0033] This embodiment discloses a low-temperature ammonia-free denitrification catalyst, which includes, by weight, 28 parts of active components, 12 parts of anti-sulfur additives, 55 parts of composite carriers and 5 parts of adhesives; the active components include 20 parts of manganese tetraoxide, 5 parts of ferric oxide and 3 parts of cerium dioxide; the anti-sulfur additives include 8 parts of molybdenum trioxide and 4 parts of cobalt trioxide; the composite carrier includes 30 parts of MgO@CNTs and 25 parts of titanium-germanium composite carriers; and the adhesive is a silicon-aluminum composite sol.

[0034] The preparation method of MgO@CNTs includes: immersing 5 parts of MWCNTs by weight in 80 parts of HNO3, ultrasonically treating at 80°C for 2 hours, centrifuging and washing until the pH is 7, and drying at 110°C for 12 hours to obtain pretreated MWCNTs; dissolving 1 part of Mg(NO3)2·6H2O in 10 parts of deionized water, adding 3 parts of EDTA, stirring at a constant temperature of 60°C until completely dissolved, adding pretreated MWCNTs, vacuum shaking and immersing at 40°C for 6 hours, drying at 60°C for 12 hours, and heating to 550°C at 2°C / min in an N2 atmosphere for 5 hours to obtain MgO@CNTs.

[0035] The preparation method of the silica-alumina composite sol comprises: mixing OX@CMC-OS type produced by Guozhuang New Material Technology (Jiangsu) Co., Ltd. and 10 parts by weight of OX@CMC-OAC type at 40° C. at a low speed and stirring for 30 minutes to obtain the silica-alumina composite sol.

[0036] A method for preparing a low-temperature ammonia-free denitrification catalyst comprises the following steps:

[0037] S1. Preparation of titanium-germanium composite carrier: titanium dioxide and germanium dioxide were added to a ball mill with a ball-to-material ratio of 10:1, and ball milled at a speed of 300 r / min for 120 min. The slurry after ball milling was fed into a spray drying tower with an inlet temperature of 200°C and an outlet temperature of 90°C to obtain a titanium-germanium composite carrier with a particle size of 5-10 μm.

[0038] S2. Prepare the carrier for loading active components and anti-sulfur additives: Mn(NO3)2·4H2O catalyst (converted to 20 parts of Mn3O4 catalyst), Fe(NO3)3·9H2O catalyst (converted to 5 parts of Fe2O3 catalyst), Ce(NO3)3·6H2O catalyst (converted to 3 parts of CeO2 catalyst), (NH4)6Mo7O 24 ·4H2O (equivalent to 8 parts of MoO3) and Co(NO3)2·6H2O (equivalent to 4 parts of Co3O4) were dissolved in 500 mL of deionized water, and tartaric acid (1.5 times the total molar amount of the metal ions) was added. The mixture was stirred at 500 rpm at 60°C for 120 minutes to prepare a metal tartaric acid complex solution. MgO@CNTs, a titanium-germanium composite support, and a silicon-aluminum composite sol were immersed in the metal tartaric acid complex solution. Two parts of polyethylene oxide (dispersant) were added for ultrasonic dispersion at 60°C for 60 minutes, and the mixture was allowed to stand for 12 hours to obtain a support loaded with the active component and the anti-sulfur agent.

[0039] S3. Preparation of low-temperature ammonia-free denitration catalyst: drying at 80°C for 12 h, heating from 100°C to 300°C at a rate of 2°C / min, and calcining at 300°C for 1 h; heating from 300°C to 500°C at a rate of 5°C / min, and calcining at 500°C for 4 h to obtain a low-temperature ammonia-free denitration catalyst.

[0040] The amount of the hydrated precursor added when preparing the carrier loaded with active components and anti-sulfur additives is calculated according to the weight of the corresponding catalyst target oxide, and Mn(NO3)2·4H2O catalyst is added according to 20 parts of Mn3O4 catalyst, Fe(NO3)3·9H2O catalyst is added according to 5 parts of Fe2O3 catalyst, Ce(NO3)3·6H2O catalyst is added according to 3 parts of CeO2 catalyst, and (NH4)6Mo7O is added according to 8 parts of MoO3. 24 ·4H2O and add Co(NO3)2·6H2O according to 4 parts of Co3O4.

[0041] The low-temperature ammonia-free denitration catalyst prepared in Example 1 was scanned with a scanning electron microscope. The results are as follows: Figure 1 As shown, it can be seen from the image that the material is distributed in a granular structure. These particles are unevenly distributed and in contact with each other. There are obvious signs of interaction or tight surface bonding between them. This is because the silicon-aluminum composite sol used has strong adhesion, which can make the ultra-fine MgO@CNTs tightly bonded to the surface of the titanium-germanium composite support. The silicon-aluminum composite sol reacts with the surface hydroxyl groups of the components through silicon-oxygen-aluminum bonds and has strong temperature resistance. It is difficult to observe independent MgO@CNTs or titanium-germanium composite supports at a larger magnification.

[0042] Example 2

[0043] This embodiment discloses a low-temperature ammonia-free denitrification catalyst, which includes 25 parts of active components, 10 parts of anti-sulfur additives, 52 parts of composite carriers and 3 parts of adhesives by weight; the active components include 19 parts of manganese tetraoxide, 4 parts of ferric oxide and 2 parts of cerium dioxide; the anti-sulfur additives include 7 parts of molybdenum trioxide and 3 parts of cobalt tetraoxide; the composite carrier includes 28 parts of MgO@CNTs and 24 parts of titanium-germanium composite carriers; the adhesive is a silicon-aluminum composite sol, and the other contents are consistent with Example 1.

[0044] Example 3

[0045] This embodiment discloses a low-temperature ammonia-free denitrification catalyst, which includes 30 parts of active components, 14 parts of anti-sulfur additives, 57 parts of composite carriers and 8 parts of adhesives in parts by weight; the active components include 21 parts of manganese tetraoxide, 6 parts of ferric oxide and 3 parts of cerium dioxide; the anti-sulfur additives include 9 parts of molybdenum trioxide and 5 parts of cobalt tetraoxide; the composite carrier includes 32 parts of MgO@CNTs and 25 parts of titanium-germanium composite carriers; the adhesive is a silicon-aluminum composite sol, and the other contents are consistent with Example 1.

[0046] Comparative Example 1

[0047] The difference from Example 1 is that the silica-alumina composite sol is replaced with an equal weight portion of PVA 3350 purchased from Sigma-Aldrich, and the other parts are the same.

[0048] The catalyst prepared in Comparative Example 1 was scanned using a scanning electron microscope. Figure 2 As shown, it can be observed from the image that MgO@CNTs and the titanium-germanium composite support are almost completely independent, have less interaction, and the correlation intensity between the substances is low.

[0049] Comparative Example 2

[0050] The difference from Example 1 is the lack of MgO@CNTs in equal parts by weight, and the other parts are the same.

[0051] Comparative Example 3

[0052] The difference from Example 1 is the lack of an equal weight portion of the titanium-germanium composite carrier, and the other aspects are the same.

[0053] Application Example 1

[0054] The low-temperature ammonia-free denitrification catalyst prepared in Example 1 is specifically used in the treatment of industrial flue gas from steel sintering machines, coke ovens, etc. with a flue gas temperature of 80-150°C, a NOx concentration ≤1000mg / m³, and a SO2 ≤200ppm. Specifically, the low-temperature ammonia-free denitrification catalyst is prepared into a 150×150×300mm honeycomb module and loaded into a denitrification reactor at a space velocity of 20,000h⁻¹ without the addition of ammonia or other reducing agents.

[0055] Performance Testing

[0056] 1. Denitrification efficiency performance tests were conducted on the examples and comparative examples using a fixed-bed reactor loaded with catalyst particles. Simulated flue gas contained: NOx = 800 mg / m³ (primarily NO), O2 = 5%, CO = 0.5% (providing a reducing environment), N2 as the balance gas, and a space velocity of 20,000 h⁻¹. Inlet and outlet NOx concentrations were measured using a German M60x flue gas analyzer, and the conversion rate was calculated. The results are shown in Table 1.

[0057] Table 1

[0058] Denitrification efficiency at 80°C Denitrification efficiency at 100°C Denitrification efficiency at 150°C Example 1 68.5% 88.2% 95.2% Comparative Example 1 52.3% 75.4% 87.9% Comparative Example 2 42.1% 63.7% 82.5% Comparative Example 3 46.8% 70.2% 84.6%

[0059] As shown in Table 1, Example 1 achieved a denitrification rate of 95.2% at 150°C, significantly higher than the comparative example, demonstrating optimal low-temperature activity. Comparative Example 1 exhibited the lowest low-temperature efficiency due to a weak carrier binding capacity, resulting in a reduced dispersion of the active component.

[0060] 2. The sulfur resistance stability test was carried out on the examples and comparative examples. The temperature was kept at 150°C, 200 ppm SO2 was added to the flue gas, and the denitrification efficiency was measured after continuous operation for one month. The results are shown in Table 2.

[0061] Table 2

[0062] Initial denitrification efficiency Efficiency after 1 month Example 1 95.2% 93.1% Comparative Example 1 87.9% 76.5% Comparative Example 2 82.5% 70.3% Comparative Example 3 84.6% 74.8%

[0063] Table 2 shows that Example 1 exhibits a low efficiency decay rate, attributed to the preferential adsorption mechanism of MoO3 / Co3O4 and the neutralizing effect of MgO@CNTs. Comparative Example 1 suffers from structural collapse due to the binder's poor acid resistance. Comparative Example 2 (lacking MgO@CNTs) loses its alkaline buffering capacity, resulting in significant sulfur poisoning of the manganese active sites.

[0064] 3. Mechanical Strength Test: Referring to ASTM D5757, the catalysts prepared in the Examples and Comparative Examples were subjected to impact in a pneumatic abrasion apparatus at a gas velocity of 15 m / s for 30 minutes. The mass loss rate was calculated. The compressive strength of honeycomb modules (150 × 150 × 300 mm) prepared using the catalysts prepared in the Examples and Comparative Examples was tested using the three-point bending method (Instron 5966).

[0065] Table 3

[0066] Wear rate (mass loss) Shear strength (MPa) Example 1 1.2% 43.5 Comparative Example 1 1.7% 38.6 Comparative Example 2 2.7% 32.8 Comparative Example 3 2.1% 35.2

[0067] As can be seen from Table 3, Example 1 has the lowest wear rate and the highest shear strength, which is attributed to the strong adhesion of the silica-alumina sol and the toughness support of MgO@CNTs. Comparative Example 1 has the weakest strength and wear resistance due to the poor thermal stability of the organic adhesive. In summary, Comparative Example 1 causes uneven dispersion of active components and loose structure due to the PVA adhesive, which easily leads to overall performance degradation. Comparative Example 2 lacks MgO@CNTs, weakens electronic conduction and sulfur resistance, reduces denitrification efficiency, and accelerates sulfur poisoning. Comparative Example 3 lacks titanium germanium carrier, causing active components to sinter and aggregate, and has a significant loss of low-temperature activity. The low-temperature ammonia-free denitrification catalyst prepared in Example 1 achieves high low-temperature activity and strong sulfur resistance through the synergistic enhancement of various components while also having excellent mechanical strength.

[0068] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. If these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for preparing a low-temperature ammonia-free denitration catalyst, characterized in that: The following steps are involved: S1. Preparation of titanium-germanium composite support; S2. Preparation of a carrier loaded with an active component and an anti-sulfur additive: complexing the active component and the anti-sulfur additive precursor with tartaric acid to obtain a metal tartaric acid complex solution, immersing the MgO@CNTs, titanium-germanium composite support and a binder in the metal tartaric acid complex solution and ultrasonically dispersing the mixture; S3. Drying and calcining to obtain a low-temperature ammonia-free denitrification catalyst.

2. The preparation method according to claim 1, characterized in that The method for preparing the titanium-germanium composite carrier comprises the steps of ball-milling titanium dioxide and germanium dioxide for 120 minutes, and then performing a spray drying process to obtain the titanium-germanium composite carrier.

3. The preparation method according to claim 2, characterized in that Titanium dioxide and germanium dioxide were added to a ball mill with a ball-to-material ratio of 10:1, and ball milled at a speed of 300 r / min for 120 min. The slurry after ball milling was fed into a spray drying tower with an inlet temperature of 200°C and an outlet temperature of 90°C to obtain a titanium-germanium composite carrier with a particle size of 5-10 μm.

4. The preparation method according to claim 1, characterized in that Combine Mn(NO3)2·4H2O, Fe(NO3)3·9H2O, Ce(NO3)3·6H2O, (NH4)6Mo7O 24 ·4H2O and Co(NO3)2·6H2O were dissolved in deionized water, tartaric acid (1.5 times the total molar amount of metal ions) was added, and the mixture was stirred at 60°C and 500 r / min for 120 min to prepare a metal tartaric acid complex solution.

5. The preparation method according to claim 1, characterized in that MgO@CNTs, titanium-germanium composite support and silicon-aluminum composite sol were immersed in metal tartaric acid complex solution, 2 parts of dispersant polyethylene oxide were added and ultrasonically dispersed at 60°C for 60 minutes, and allowed to stand for 12 hours to obtain a support loaded with active components and anti-sulfur additives.

6. The preparation method according to claim 1, characterized in that The carrier loaded with active components and anti-sulfur additives was dried at 80°C for 12 h, heated from 100°C to 300°C at 2°C / min, calcined at 300°C for 1 h, heated from 300°C to 500°C at 5°C / min, and calcined at 500°C for 4 h to obtain a low-temperature ammonia-free denitrification catalyst.

7. The preparation method according to claim 1, characterized in that The preparation method of MgO@CNTs includes: immersing 5 parts of MWCNTs by weight in 80 parts of HNO3, ultrasonically treating at 80°C for 2 hours, centrifuging and washing, and drying at 110°C for 12 hours to obtain pretreated MWCNTs; dissolving 1 part of Mg(NO3)2·6H2O in 10 parts of deionized water, adding 3 parts of EDTA, stirring at 60°C and adding the pretreated MWCNTs; immersing at 40°C under vacuum oscillation for 6 hours, drying at 60°C for 12 hours, and heating to 550°C at 2°C / min in an N2 atmosphere and calcining for 5 hours to obtain MgO@CNTs.

8. The preparation method according to claim 1, characterized in that The low-temperature ammonia-free denitration catalyst prepared by the preparation method comprises, by weight, 25-30 parts of active components, 10-14 parts of anti-sulfur additives, 52-57 parts of composite carriers and 3-8 parts of adhesives.

9. The preparation method according to claim 8, characterized in that The active components include manganese tetraoxide, ferric oxide and cerium dioxide; the anti-sulfur additives include molybdenum trioxide and cobalt tetraoxide; the composite carrier includes MgO@CNTs and titanium germanium composite carrier; and the adhesive is silicon-aluminum composite sol.

10. Use of a low-temperature ammonia-free denitration catalyst prepared by the preparation method according to any one of claims 1 to 9 in industrial flue gas denitration, characterized in that: The low-temperature ammonia-free denitrification catalyst is suitable for a low-temperature environment of 80-150°C, with NOx concentration in the flue gas ≤1000mg / m³ and SO2 ≤200ppm.

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