Catalyst for methane ultrahigh-temperature catalytic combustion as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for methane ultrahigh-temperature catalytic combustion as well as a preparation method and application of the catalyst. The catalyst is a composite oxide comprising a cobalt element, an iron element, a cerium element, an aluminum element, a lanthanum element and a magnesium element, wherein based on the total mass of the catalyst, the mass percentage of each element is as follows: 10-20% of cobalt, 15-20% of iron, 10-18% of cerium, 5-15% of aluminum, 6-12% of lanthanum and 1.0-3.0% of magnesium, and the mass ratio of the lanthanum element to the magnesium element is (4-8): 1; the catalyst is prepared by the following steps: carrying out parallel flow co-precipitation reaction on a mixed salt solution containing a cobalt salt, an iron salt, a cerium salt, a lanthanum salt, a magnesium salt and an aluminum salt and a precipitant solution, and then aging, drying and roasting. The catalyst is a full non-noble metal Co-Fe-Ce-Al-La-Mg six-membered composite oxide, a stable skeleton structure is formed through the La-Mg synergistic effect, the efficient effect of a Co-Fe-Ce core catalytic unit is combined, and the catalyst has excellent low-temperature light-off activity and 1300 DEG C ultrahigh-temperature long-acting stability.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysis and clean energy technology, specifically relating to a catalyst for ultra-high temperature catalytic combustion of methane, its preparation method, and its application. Background Technology

[0002] Natural gas catalytic combustion technology is used to improve the energy efficiency of industrial furnaces and kilns and reduce nitrogen oxides (NOx). X The key to clean combustion technology for pollutants such as carbon monoxide (CO) and unburned hydrocarbons (HC) lies in developing catalysts that have both good low-temperature ignition activity and extreme high-temperature thermal stability to meet the stringent operating requirements of ultra-high temperature industrial scenarios such as aluminum rod furnaces and metal smelting furnaces at 1300°C.

[0003] Currently, the design stable operating temperature of non-precious metal methane combustion catalysts widely used in industry is generally limited to between 800-1150℃. When the catalyst bed temperature exceeds 1200℃ and is operated for a long period, it faces two major failure mechanisms: first, the catalyst support alumina undergoes an irreversible phase transition from the high specific surface area and high activity γ phase to the low specific surface area and non-catalytically active α-Al2O3; second, the active metal components of the catalyst undergo severe high-temperature sintering and agglomeration. These failures directly lead to a sharp drop in the catalyst's specific surface area, collapse of the pore structure, degradation of mechanical strength, and rapid decline in catalytic activity. Their service life is far from meeting the actual requirements of industrial furnaces for long-cycle (≥3600 hours) and maintenance-free stable operation.

[0004] Existing high-temperature methane combustion catalysts are mainly divided into two categories: noble metal catalysts (such as Pt and Pd-based catalysts) exhibit excellent low-temperature activity, but their raw material costs are high, and the noble metal components are prone to sintering and deactivation above 1000℃; non-noble metal catalysts (such as perovskite and hexaaluminate catalysts) have lower costs, but they generally cannot effectively suppress the alumina α-phase transformation and sintering of active components during long-term operation at ultra-high temperatures above 1200℃. For example, the catalyst disclosed in Chinese patent CN103372447A showed a decrease in specific surface area to 8.2 m² / g after 500 hours of operation at 1200℃, and a significant α-Al₂O₃ phase was detected; the catalyst disclosed in Chinese patent CN104084210A showed a 20% decrease in methane catalytic activity after 1000 hours of operation at 1150℃. Recent literature (Appl. Catal. B: Environ., 2021, 298,120581; Chem.Eng.J.,2022,428,132011) also confirms that existing non-precious metal catalysts exhibit significant activity degradation and α-Al2O3 phase formation after operating at 1100-1200℃ for several hundred to one thousand hours.

[0005] In summary, existing technologies have failed to address the stability issue of methane combustion catalysts under ultra-high temperature and long-term operation at 1300℃. Typically, after operating at 1100-1200℃ for hundreds to thousands of hours, the specific surface area generally decreases to below 10 m² / g, with a large amount of α-Al₂O₃ phase generated, leading to a catalytic activity decay rate exceeding 20%. Furthermore, existing catalyst preparation methods often fail to simultaneously achieve high mechanical strength and regular morphology, making them unsuitable for industrial spraying and loading processes, thus limiting their industrial application. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art, and to provide a catalyst for ultra-high catalytic combustion of methane, its preparation method and application, and to design an industrial combustion system and combustion method adapted to the catalyst. This invention solves the technical problems of existing non-precious metal catalysts in long-term operation at ultra-high temperature of 1300℃, such as a sharp drop in specific surface area, rapid activity decay and short service life caused by the α phase change of alumina support and sintering of active components. It also achieves a low cost, high mechanical strength and perfect compatibility with industrial spraying processes for the catalyst.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, this application provides a catalyst for the catalytic combustion of methane. The catalyst is a composite oxide comprising cobalt, iron, cerium, aluminum, lanthanum, and magnesium. The mass percentage of each element, based on the total mass of the catalyst, is as follows: cobalt 10-20%, iron 15-20%, cerium 10-18%, aluminum 5-15%, lanthanum 6-12%, and magnesium 1.0-3.0%. The mass ratio of lanthanum to magnesium is (4-8):1. The catalyst is prepared by a method comprising co-precipitating a mixed salt solution containing cobalt salt, iron salt, cerium salt, lanthanum salt, magnesium salt, and aluminum salt with a precipitant solution in a co-current flow, followed by aging, drying, and calcination.

[0008] In some embodiments of this application, the catalyst contains a La-Mg-Al-O composite spinel phase.

[0009] In some embodiments of this application, the catalyst contains 0.1-2.0% strontium by mass percentage, based on the total mass of the catalyst; and / or, The catalyst contains 0.5-4.0% zirconium by mass; and / or, The molar ratio of cobalt, iron and cerium in the catalyst is (0.9-1.5):1:(0.2-0.5).

[0010] In some embodiments of this application, the specific surface area of ​​the catalyst is ≥40 m² / g, and the average particle size D of the catalyst is...50 The particle size is 40-80μm, and the crushing strength of a single particle is ≥55N.

[0011] Secondly, this application provides a method for preparing a catalyst for the catalytic combustion of methane, characterized by comprising the following steps: (1) A mixed salt solution containing cobalt, iron, cerium, aluminum, lanthanum and magnesium is prepared and then co-precipitated with a precipitant solution in a co-current flow to obtain a coprecipitated slurry. (2) The coprecipitated slurry obtained in step (1) is subjected to an aging reaction, and then filtered and washed to obtain a filter cake; (2) The filter cake obtained in step (2) is redispersed and spray-dried to obtain the catalyst precursor; (4) The catalyst precursor obtained in step (3) is calcined in an air atmosphere to obtain the catalyst.

[0012] In some embodiments of this application, in step (1), the soluble salt is a nitrate or a chloride; the precipitant is one or more of ammonium carbonate, ammonia, or ammonium bicarbonate; and / or, The process of redispersing the filter cake in step (3) includes re-pulping the filter cake and adjusting the solid content of the slurry to 15-25 wt% and the viscosity to 500-1500 mPa·s.

[0013] In some embodiments of this application, in step (1), the concentration of metal ions in the mixed salt solution is 0.3-1.0 mol / L, the pH of the coprecipitation reaction is 8.5-10.0, and the temperature of the coprecipitation reaction is 50-90℃; and / or, In step (2), the aging reaction temperature is 50-90℃, and the aging time is 2-6 hours; and / or, In step (3), the inlet temperature of the spray dryer is 250-350℃, and the outlet temperature is 100-150℃; and / or, The roasting temperature in step (4) is 550-700℃, the roasting time is 3-6 hours, and the roasting heating rate is 1-5℃ / min.

[0014] Thirdly, this application provides the application of the above-mentioned catalyst or the catalyst prepared by the above-mentioned method in a combustion device, wherein the combustion device is selected from an aluminum rod furnace, a metal smelting furnace or a ceramic sintering furnace.

[0015] Fourthly, this application provides an industrial combustion system, including a burner and a catalytic combustion module, wherein the catalytic combustion module is filled with the above-mentioned catalyst or a catalyst prepared by the above-mentioned preparation method.

[0016] Preferably, the catalytic combustion module is a fixed bed structure, and the catalyst is loaded onto the FeCrAl high-temperature resistant alloy substrate by spraying, with a dry film loading of 6000-6500 g / m²; the binder used for spraying includes silica sol and alumina sol, wherein the mass ratio of silica sol to alumina sol is 1:1-3.

[0017] More preferably, the FeCrAl high-temperature alloy substrate is roughened by sandblasting and degreased with acetone before spraying, and the surface roughness of the substrate after roughening is Ra5-Ra10; the curing process of the adhesive is: first pre-drying at 80-100℃ for 2-4 hours, and then calcining at 500-600℃ for 1-2 hours.

[0018] Fifthly, this application also provides a combustion method applied to the aforementioned industrial combustion system, comprising the following steps: preheating natural gas with a methane content ≥95% (v / v) to 180-190°C and then introducing it into a burner for combustion; the furnace operating temperature is 1280-1350°C; the catalyst bed temperature in the catalytic combustion module is 1290-1310°C; and the apparent space velocity of the reactant gas at the catalyst bed is 10000-50000 h⁻¹. -1 The natural gas supply pressure is 0.1-0.3 MPa, and the system volumetric air-fuel ratio is 1:(9.0-10.0). Beneficial effects

[0019] The catalyst in this application combines a specific six-element formulation with a co-precipitation process. The synergistic effect of La-Mg is used to construct a stable catalyst framework. Combined with the high efficiency of the Co-Fe-Ce core catalytic unit, the catalyst achieves both low-temperature ignition activity and ultra-high temperature stability at 1300℃.

[0020] Furthermore, this invention achieves atomically uniform mixing, regular spherical morphology, and high mechanical strength of the catalyst through an integrated preparation process of "co-current co-precipitation - spray drying - calcination," making the catalyst perfectly suited for industrial spray loading processes.

[0021] Furthermore, the industrial combustion system and method designed in conjunction with this invention optimize the loading method and operating parameters based on the performance characteristics of the catalyst, fully transforming the advantages of the catalyst's formulation and process into advantages for industrial applications. In long-term operation verification in an ultra-high temperature industrial combustion scenario at 1300℃, the catalyst exhibited excellent structural stability and catalytic performance, with an efficiency decay rate of <5% after 3600 hours of continuous operation, and also possessed good renewability. In industrial applications, it achieved a gas saving rate of 25.3%, reducing CO and NO emissions significantly. X Emissions are far below national standards, achieving near-zero emissions.

[0022] In addition, compared with the prior art, the catalyst of the present invention is a completely non-precious metal system, with low raw material costs, easy preparation process, and a single service life that is more than 3 times longer than existing non-precious metal catalysts. The overall operation and maintenance cost is reduced by 60%, and it has broad commercial application prospects in ultra-high temperature industrial combustion scenarios of 1300℃ such as aluminum rod furnaces, metal smelting furnaces, and ceramic sintering furnaces. Attached Figure Description

[0023] Figure 1 The images show the scanning electron microscope (SEM) image and particle size distribution curve of catalyst CAT-1 prepared in Example 1, where a is a 5000x SEM image, b is a 20000x SEM image, and c is the particle size distribution curve.

[0024] Figure 2 The image shows a high-resolution transmission electron microscope (HR-TEM) image of a fresh sample of catalyst CAT-1 prepared in Example 1.

[0025] Figure 3 The elemental distribution mapping (EDS) of the fresh sample of catalyst CAT-1 prepared in Example 1 is shown.

[0026] Figure 4 The X-ray photoelectron spectroscopy spectrum of the fresh sample of catalyst CAT-1 prepared in Example 1 is shown.

[0027] Figure 5 The image is a high-resolution transmission electron microscope (HR-TEM) image of catalyst CAT-1 prepared in Example 1 after running at 1300°C for 3600 hours.

[0028] Figure 6 Fast Fourier Transform (FFT) analysis and elemental distribution map of HR-TEM image of catalyst CAT-1 prepared in Example 1 after running at 1300℃ for 3600 hours; a is HR-TEM image; b is FFT analysis of region A; c is FFT analysis of region B; d is elemental distribution map.

[0029] Figure 7 The elemental distribution mapping (EDS) of catalyst CAT-1 prepared in Example 1 after running at 1300°C for 3600 hours is shown. Detailed Implementation

[0030] The present invention will now be described in detail with reference to embodiments. The principles and features of the present invention are described below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0033] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0034] The terms “combinations thereof,” “any combination thereof,” and “any combination thereof” as used in this application include all suitable combinations of any two or more of the listed items.

[0035] In this application, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0036] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are merely used to describe implementation methods or embodiments that achieve better results, and should be understood not to limit the scope of protection of this application.

[0037] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0038] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0039] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0040] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0041] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0042] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0043] In this application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0044] In this application, the methane catalytic combustion efficiency decay rate refers to the percentage decrease in methane conversion rate relative to the initial (fresh) methane conversion rate after the catalyst has been running continuously for a certain period of time (t, such as 3600 hours) under specific and stable operating conditions, i.e., [(X0-X...] t [) / X0] × 100%, where X0 is the initial methane conversion rate, X t The methane conversion rate is t hours after operation.

[0045] In this application, the average catalytic combustion efficiency of methane refers to the time average of the methane conversion rate during continuous operation of the catalyst under specific and stable operating conditions.

[0046] In this application, the volumetric air-fuel ratio refers to the volume ratio of fuel (methane or natural gas) to air, denoted as (fuel: air).

[0047] In this application, T 90The lowest reaction temperature at which the catalytic combustion conversion rate of methane reaches 90% is a key indicator for evaluating the low-temperature ignition activity of a catalyst.

[0048] In this application, T 50 The lowest reaction temperature at which the catalytic combustion conversion rate of methane reaches 50% is determined to aid in the evaluation of the catalyst's low-temperature ignition activity.

[0049] In this application, apparent space velocity (GHSV) refers to the volume of reactant gas passing through a unit volume catalyst bed per unit time, and the unit is h. -1 This characterizes the contact time between the reactant gas and the catalyst.

[0050] In this application, crushing strength refers to the minimum force required to crush a single catalyst microsphere, measured in N, and is a core indicator for evaluating the mechanical strength of catalysts in industrial applications.

[0051] In this application, D 50 It refers to the particle size corresponding to a sample when the cumulative volumetric particle size distribution percentage reaches 50%, which characterizes the average particle size of the catalyst.

[0052] In this application, mass percentage (wt%) refers to the percentage of the mass of a certain component relative to the total mass of the catalyst.

[0053] In this application, the nano-reinforced phase refers to the LaAlO3 and MgAl2O4 spinel phases generated in situ from the reaction of La, Mg, and Al in the catalyst. These phases have a grain size of 5-20 nm, exhibit extremely high thermal stability, and can form a stable framework for the catalyst.

[0054] In this application, the hot and cold start-stop cycle is defined as follows: under an air atmosphere, the temperature is programmed to rise from room temperature to 1300°C at a rate of 10°C / min, held at the temperature for 2 hours, then the heat source is cut off and the temperature is programmed to drop to below 100°C at a rate of 20-30°C / min, thus completing one cycle.

[0055] In a specific embodiment of this application, a catalyst for the catalytic combustion of methane is provided, which is a composite oxide comprising cobalt, iron, cerium, lanthanum, magnesium, and aluminum. The mass percentages of each element, based on the total mass of the catalyst, are: cobalt 10-20%, iron 15-20%, cerium 10-18%, lanthanum 6-12%, magnesium 1.0-3.0%, and aluminum 5-15%, wherein the mass ratio of lanthanum to magnesium is (5-8):1. The catalyst is prepared by a method comprising co-precipitating a mixed salt solution containing cobalt salt, iron salt, cerium salt, lanthanum salt, magnesium salt, and aluminum salt with a precipitant solution, followed by aging, drying, and calcination.

[0056] The catalyst of this invention is a system of six-membered composite oxides containing Co-Fe-Ce-La-Mg-Al designed at the atomic scale. Lanthanum and magnesium are synergistically combined in a specific mass ratio of 4-8:1, and the ratio of six elements is limited to 10-20% cobalt, 15-20% iron, 10-18% cerium, and 5-15% aluminum. It is obtained through a co-current co-precipitation calcination process, achieving a balance between low-temperature ignition activity and ultra-high temperature stability at 1300℃. The initial catalyst T... 90 With a temperature of ≤442℃, it exhibits good low-temperature ignition activity; after 100 hours of harsh aging at 1300℃, the specific surface area retention rate exceeds 90%, and the methane conversion rate decreases by <5% after 100 hours of aging at 1300℃, demonstrating excellent ultra-high temperature stability.

[0057] In some embodiments of this application, the catalyst contains a La-Mg-Al-O composite spinel phase. This composite spinel phase structure exhibits high thermal stability, which is beneficial for forming a stable framework for the catalyst. In this structure, La... 3+ With Mg 2+ Co-doping into the alumina lattice introduces significant lattice distortion and stress, greatly increasing the onset temperature of the γ-Al2O3 to α-phase transformation to above 1350℃. At the same time, the La and Mg oxides segregated at the grain boundaries produce a strong "pinning" effect, which complements the oxygen storage synergy of CeO2, ultimately constructing a LaAlO2 / MgAl2O4 nano-reinforced framework to achieve a firm anchoring of Co / Fe / Ce active nanoclusters.

[0058] Furthermore, Co, Fe, and Ce constitute the core catalytic and oxygen storage units of the catalyst: CeO2 and its strong interaction with Co / Fe construct an efficient dynamic cycle of "active site-oxygen reservoir," ensuring the rapid adsorption and conversion of methane reactants. The composite oxide surface formed by the doping of La and Mg helps to inhibit carbon deposition from methane cracking, promotes the deep oxidation of intermediate products, and improves catalytic combustion efficiency. The synergistic effect of these elements ultimately enables the catalyst to form a unique microstructure of "LaAlO3 / MgAl2O4 stable framework encapsulating and anchoring Co / Fe / Ce active nanoclusters." TEM characterization confirms that the size of the active clusters is stable at 5-15 nm, structurally solving the technical challenges of high-temperature phase transformation and sintering of active components.

[0059] It is understood that the theoretical explanations provided in this paper are only the most likely correct explanations based on the inventor's current understanding and existing technological level, and their purpose is to aid in understanding the invention. As technology advances, these theoretical explanations may be proven not to be entirely correct. Therefore, the invention is not limited by these theoretical explanations.

[0060] In some embodiments of this application, the cobalt content in the catalyst, based on the total mass of the catalyst, can be 11-20 wt%, 12-20 wt%, 15-20 wt%, 17-20 wt%, or 19-20 wt%.

[0061] In some embodiments of this application, the iron content in the catalyst, based on the total mass of the catalyst, can be 15-19 wt%, 15-18 wt%, 15-17 wt%, or 15.5-16.5 wt%.

[0062] In some embodiments of this application, the content of cerium in the catalyst, based on the total mass of the catalyst, can be 10-17 wt%, 10-16 wt%, 10-15 wt%, 11-18 wt%, 12-18 wt%, 11-15 wt%, or 11-13 wt%.

[0063] In some embodiments of this application, the lanthanum content may be 7-12 wt%, 8-12 wt%, 9-12 wt%, 10-12 wt%, or 11-12 wt% based on the total mass of the catalyst.

[0064] In some embodiments of this application, the magnesium content, based on the total mass of the catalyst, may be 1.2-3 wt%, 1.5-3 wt%, 2-3 wt%, 2-2.5 wt%, or 2-2.2 wt%.

[0065] In some embodiments of this application, the aluminum content, based on the total mass of the catalyst, can be 4-14 t%, 4-13 wt%, 4-12 wt%, 4-10 wt%, 5-15 wt%, 7-15 wt%, 7-13 wt%, 7-11 wt%, or 7-9 wt%.

[0066] In some embodiments of this application, the molar ratio of cobalt, iron and cerium, based on the total mass of the catalyst, is preferably (0.9-1.5):1:(0.2-0.5).

[0067] The catalyst can also be selectively doped with strontium (Sr) and / or zirconium (Zr) to optimize overall performance. In some embodiments, the mass percentage of strontium is 0.1-2.0% and the mass percentage of zirconium is 0.5-4.0% by total mass of the catalyst, preferably 0.3-0.8% strontium and 1.0-1.5% zirconium; wherein Sr 2+ Zr helps to increase the alkalinity of the catalyst surface and promote methane adsorption and activation. 4+ It helps to refine the catalyst grains and further enhance structural stability.

[0068] In some embodiments of this application, the average particle size (D) of the catalyst is...50 The particle size is 40-80μm, the single particle crushing strength is ≥55N, and it presents a regular spherical morphology. It is not only perfectly adapted to industrial spraying processes, but also has excellent thermal shock stability and can withstand the frequent start-up and shutdown of industrial furnaces.

[0069] Secondly, this application provides a method for preparing a catalyst, which is obtained by a co-current co-precipitation reaction of a mixed salt solution containing cobalt salt, iron salt, cerium salt, lanthanum salt, magnesium salt and aluminum salt with a precipitant solution, followed by aging, drying and calcination.

[0070] In some embodiments of this application, the preparation method includes the following steps: (1) Prepare a mixed salt solution containing soluble salts of cobalt, iron, cerium, aluminum, lanthanum and magnesium, and carry out a co-precipitation reaction with a precipitant to obtain a coprecipitated slurry; (2) The coprecipitated slurry obtained in step (1) is subjected to an aging reaction, and then filtered and washed to obtain a filter cake; (3) The filter cake obtained in step (2) is redispersed and spray-dried to obtain the catalyst precursor; (4) The catalyst precursor obtained in step (3) is calcined in an air atmosphere to obtain the catalyst.

[0071] Step (1) allows all metal ions to precipitate simultaneously, achieving uniform mixing of six elements at the atomic / molecular scale, laying the foundation for the formation of a uniform composite crystalline phase, which cannot be achieved by traditional impregnation or physical mixing methods. Step (2) aging ensures complete crystallization, and washing removes impurity ions, avoiding the influence of impurities on the formation and performance of the catalyst crystalline phase. Step (3) forces the nano-precursor to be tightly "compressed" and rapidly solidified within the droplet, forming dense microspheres composed of nanoparticles bonded by strong chemical bonds. This is key to obtaining high mechanical strength (≥55N), regular spherical morphology, and rich mesoporous structure, overcoming the shortcomings of irregular morphology and low mechanical strength in catalyst preparation by traditional drying-crushing methods, and ensuring the industrial spraying applicability of the catalyst. Step (4) fully transforms the precursor into a target composite oxide with complete crystal form and stable structure.

[0072] In some embodiments of this application, in step (1), the soluble salt is a nitrate or a chloride; the precipitant is one or more of ammonium carbonate, ammonia, or ammonium bicarbonate.

[0073] In some embodiments of this application, the process of redispersing the filter cake in step (3) includes re-pulping the filter cake and adjusting the solid content of the slurry to 15-25 wt%, preferably controlling the viscosity to 500-1500 mPa·s.

[0074] In some embodiments of this application, in step (1), the concentration of metal ions in the mixed salt solution is 0.3-1.0 mol / L, preferably the pH of the coprecipitation reaction is 8.5-10.0, and more preferably the temperature of the coprecipitation reaction is 50-90℃.

[0075] In some embodiments of this application, in step (2), the temperature of the aging reaction is 50-90°C, and the aging time is preferably 2-6 hours.

[0076] In some embodiments of this application, in step (3), the inlet temperature of the spray dryer is 250-350°C and the outlet temperature is 100-150°C.

[0077] In some embodiments of this application, the calcination temperature in step (4) is 550-700°C, the calcination time is preferably 3-6 hours, and the calcination heating rate is more preferably 1-5°C / min.

[0078] In some embodiments of this application, the molar ratio of cobalt, iron, cerium, lanthanides, alkaline earth metals, and aluminum in the mixed salt solution is 1-3:1-3:0.3-1.1:0.2-0.8:0.2-1.1:1-5. In some embodiments, the molar ratio of cobalt, iron, cerium, lanthanides, alkaline earth metals, and aluminum in the mixed salt solution is 1-1.5:1-2:0.3-0.5:0.25-0.35:0.25-0.35:1-2.

[0079] Thirdly, this application also provides a catalyst prepared by the above preparation method, which is a composite oxide containing cobalt, iron, cerium, lanthanum, magnesium and aluminum. The mass percentage of each element, based on the total mass of the catalyst, is as follows: cobalt 10-20%, iron 15-20%, cerium 10-18%, lanthanum 6-12%, magnesium 1.0-3.0%, and aluminum 5-15%. The mass ratio of lanthanum to magnesium is (4-8):1.

[0080] In some embodiments of this application, the catalyst contains a La-Mg-Al-O composite spinel phase.

[0081] Fourthly, this application also provides the application of the above-mentioned catalyst or the catalyst prepared by the above-mentioned method in a combustion device; wherein the combustion device is selected from aluminum rod furnaces, metal smelting furnaces, or ceramic sintering furnaces. The catalyst of this invention can be applied to methane catalytic combustion systems in various industrial combustion devices, especially suitable for ultra-high temperature industrial combustion scenarios at 1300℃ such as aluminum rod furnaces, metal smelting furnaces, and ceramic sintering furnaces, enabling efficient and clean combustion of natural gas while significantly reducing natural gas consumption and pollutant emissions from furnaces and kilns.

[0082] Fifthly, this application also provides an industrial combustion system integrating the above-mentioned catalyst, including a burner body and a catalytic combustion module (usually made in the form of a catalytic plate or catalytic chip) disposed in the combustion chamber or channel of the burner; the catalytic combustion module is filled or loaded with the above-mentioned catalyst.

[0083] In some embodiments of this application, the system is optimized for the physical properties and catalytic characteristics of the catalyst of the present invention. The core includes a burner and a catalytic combustion module. The catalytic combustion module is a fixed bed structure, which is filled / loaded with the catalyst described in the first aspect of the present invention or the catalyst prepared by the preparation method described in the second aspect. The catalyst is loaded onto a pretreated FeCrAl high-temperature resistant alloy substrate by spraying, with a loading of 6000-6500 g / m². The binder used for spraying is a silica sol-alumina sol composite system (silica sol to alumina sol mass ratio of 1:1-3), ensuring the firmness and durability of the catalyst coating at an ultra-high temperature of 1300℃.

[0084] Before spraying, the FeCrAl high-temperature alloy substrate needs to be roughened by sandblasting and degreased with acetone. After roughening, the surface roughness of the substrate is Ra5-Ra10, which improves the adhesion between the substrate and the catalyst coating. The curing process of the adhesive is as follows: first, pre-dry at 80-100℃ for 2-4 hours, and then calcine at 500-600℃ for 1-2 hours to ensure the high temperature resistance and bonding strength of the adhesive after curing.

[0085] Sixthly, this application also provides a combustion method, which optimizes various operating parameters based on the performance characteristics of the catalyst of this invention and the structural design of the industrial combustion system, aiming to achieve efficient and stable catalytic combustion of natural gas, while maximizing the protection of the catalyst structure and extending its service life. The method specifically includes the following steps: Natural gas with a methane content ≥95% (v / v) is preheated to 180-190℃ (using waste heat from the exhaust gas to heat the air-natural gas mixture via a heat exchanger) and then introduced into the burner for combustion. The furnace operating temperature is controlled at 1280-1350℃, the catalyst bed temperature in the catalytic combustion module is 1290-1310℃, and the apparent space velocity of the reactant gas at the catalyst bed is 10000-50000 h⁻¹. -1 The natural gas supply pressure is controlled at 0.1-0.3 MPa, and the system volumetric air-fuel ratio is strictly controlled at 1:(9.0-10.0).

[0086] The coordinated control of the above parameters not only ensures the efficient catalytic combustion of methane, but also avoids problems such as catalyst bed overheating and active component sintering caused by parameter imbalance, while achieving long-term stable operation of the catalyst.

[0087] All raw materials and reagents used in this invention were purchased from mainstream manufacturers on the market. Those without specified manufacturers or concentrations are all analytical grade raw materials or reagents that are routinely available. There are no particular restrictions as long as they achieve the intended effect. The instruments and equipment used in this embodiment were all purchased from major manufacturers on the market. There are no particular limitations as long as they achieve the intended effect. Where specific techniques or conditions are not specified in this embodiment, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions.

[0088] In the following examples, the content of each metal element in the catalyst was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Example 1

[0089] Preparation of catalysts for the catalytic combustion of methane (1) Raw material preparation The raw materials were weighed and prepared according to the elemental molar ratio Co:Fe:Ce:La:Mg:Al = 1.2:1.0:0.3:0.3:0.25:1.0. The specific steps are as follows: Weigh 350gCo(NO3)2·6H2O, 404.0gFe(NO3)3·9H2O: 130.3gCe(NO3)3·6H2O, 129.8gLa(NO3)3·6H2O, 64.0gMg(NO3)2·6H2O, 375.1gAl(NO3)3·9H2O.

[0090] Dissolve the weighed raw materials together in an appropriate amount of deionized water, stir until completely dissolved, and then make up to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L.

[0091] Prepare a 1.0 mol / L ammonium carbonate solution as precipitant B.

[0092] (2) Coprecipitation and aging Mixed salt solution A and precipitant B were added dropwise in a parallel flow under stirring at 65℃ and 200 rpm, with the pH controlled at 9.0 ± 0.1. After the addition was complete, the mixture was aged at 65℃ for 4 hours.

[0093] (3) Washing Filter the aged reaction solution and wash the filter cake with 70℃ hot water until the conductivity of the filtrate is <50μS / cm.

[0094] (4) Spray drying The washed filter cake was redispersed in deionized water to form a homogeneous slurry with a solid content of approximately 20 wt%, and the viscosity was adjusted to 800 mPa·s. The slurry was then dried using a spray dryer with the inlet temperature controlled at 300°C and the outlet temperature at 120°C to obtain spherical catalyst precursor microspheres.

[0095] (5) Roasting The microsphere precursor obtained in step (4) was placed in a muffle furnace and heated to 600°C at a rate of 2°C / min in air atmosphere, and then calcined at this temperature for 4 hours. After natural cooling in the furnace, the methane catalytic combustion catalyst of the present invention was obtained, denoted as CAT-1. The contents of each metal element in catalyst CAT-1 were determined by ICP-OES as follows: Co: 19.7 wt%, Fe: 16.0 wt%, Ce: 12.1 wt%, La: 11.6 wt%, Mg: 2.1 wt%, Al: 7.8 wt%.

[0096] Scanning electron microscope image and particle size distribution curve of catalyst CAT-1 are shown below. Figure 1 As shown, a is a 5000x SEM image, b is a 20000x SEM image, and c is the particle size distribution curve. Figure 1 The catalyst is clearly shown to have a microsphere morphology and a mesoporous surface structure; the microsphere particle size D50 is about 55 μm, and the particle size distribution range is 40-80 μm.

[0097] HR-TEM image of catalyst CAT-1 as follows Figure 2 As shown, by Figure 2 It is known that the catalyst is composed of tightly packed nanocrystals with a size of 5-15 nm, and clear lattice fringes can be observed. The nanocrystal structure provides abundant active sites for the catalytic reaction.

[0098] The elemental distribution mapping of catalyst CAT-1 is shown in the figure below. Figure 3 As shown, by Figure 3 It can be seen that the six elements Co, Fe, Ce, Al, La and Mg are all highly uniformly distributed within the microspheres, with an element distribution uniformity error of ≤5%, and no obvious element segregation or phase separation, which confirms that the co-current coprecipitation process has successfully achieved uniform mixing at the atomic / molecular level.

[0099] The X-ray photoelectron spectroscopy (XPS) spectrum of catalyst CAT-1 is shown below. Figure 4 As shown, where, Figure 4 For catalyst CAT-1, Al 2p, La 3d s / 2 XPS peak fitting results for the three characteristic spectral bands of Mg1s, Mg2+, and Mg2+. Figure 4It can be seen that in the Al 2p spectral band (70-80 eV), the measured binding energy is 74.8 eV, which differs from that of pure Al2O3 (approximately 74.5 eV) or pure LaAlO3 (approximately 75.2 eV), indicating that the Al element is in the lattice environment of the La-Mg-Al-O composite spinel; La 3d s / 2 Spectral range (830-840 eV): The measured binding energy was 835.2 eV, a positive shift compared to pure La₂O₃ (approximately 834.0 eV), confirming that La₂O₃... 3+ With Al 3+ Mg 2+ A strongly interacting composite oxide lattice was formed. In the Mg 1s spectrum (1300-1306 eV): the measured binding energy was 1303.5 eV, a positive shift compared to pure MgO (approximately 1303.0 eV), indicating that Mg2+... + The inclusion of the La-Mg-Al-O4 composite spinel structure within the Al-O lattice leads to the formation of a MgAl2O4-type spinel structure. Therefore, the synergistic shift in binding energies across the three spectral bands, combined with Raman spectroscopy characterization, confirms the presence of the La-Mg-Al-O composite spinel phase in the catalyst.

[0100] Example 2 Preparation of catalysts for the catalytic combustion of methane (1) Raw material preparation and calculation Weigh 350gCo(NO3)2·6H2O, 404.0 gFe(NO3)3·9H2O: 130.3 gCe(NO3)3·6H2O, 129.8 g La(NO3)3·6H2O, 64.0 g Mg(NO3)2·6H2O, 375.1 g Al(NO3)3·9H2O, 4.2 g Sr(NO3)2, and 23.2 g ZrO(NO3)2·2H2O. Dissolve the above-weighed raw materials together in an appropriate amount of deionized water, stirring until completely dissolved. Then, dilute to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L.

[0101] Prepare a 1.0 mol / L ammonium carbonate solution as precipitant B.

[0102] (2) Coprecipitation and aging At 65℃ and a stirring rate of 300 r / min, mixed salt solution A and precipitant B were added dropwise to the reactor in a parallel flow. The pH of the reaction system was strictly controlled to be 9.0 ± 0.1 by adjusting the dropping rate. After the addition was complete, the mixture was aged for 4 hours at 65℃ and 300 r / min with stirring.

[0103] (3) Washing The aged slurry was filtered, and the filter cake was thoroughly washed with deionized hot water at a temperature above 70°C until the conductivity of the filtrate was <50 μS / cm, thus obtaining a pure metal hydroxide / carbonate coprecipitated filter cake.

[0104] (4) Spray drying The washed filter cake was re-slurried with deionized water, and the solid content of the slurry was adjusted to 20 wt%, with a viscosity of approximately 800 mPa·s. The slurry was then dried using a centrifugal spray dryer (atomizing disc speed 20000 r / min), with the inlet temperature controlled at 300℃ and the outlet temperature at 120℃, to obtain spherical catalyst precursor microspheres.

[0105] (5) Roasting The precursor microspheres obtained by spray drying were placed in a muffle furnace and heated to 600°C at a programmed heating rate of 2°C / min under air atmosphere, and then calcined at this temperature for 4 hours. After natural cooling to room temperature, the Sr / Zr co-doped methane catalytic combustion catalyst of the present invention was obtained, denoted as CAT-2.

[0106] Catalyst composition analysis The mass percentages of each element in catalyst CAT-2, as determined by inductively coupled plasma optical emission spectrometry (ICP-OES), are as follows: Co: 19.1%, Fe: 15.5%, Ce: 11.7%, Al: 7.5%, La: 11.2%, Mg: 2.0%, Sr: 0.5%, Zr: 1.2%.

[0107] Example 3 Preparation of catalysts for the catalytic combustion of methane (1) Raw material preparation Weigh out 366.8 g Co(NO3)2·6H2O, 808.0 g Fe(NO3)3·9H2O, 234.5 g Ce(NO3)3·6H2O, 138.5 g La(NO3)3·6H2O, 76.9 g Mg(NO3)2·6H2O, and 517.7 g Al(NO3)3·9H2O. Dissolve all the above raw materials together in an appropriate amount of deionized water, stir until completely dissolved, and then dilute to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L.

[0108] Prepare an ammonia solution with a concentration of 1.0 mol / L as precipitant B.

[0109] (2) Coprecipitation and aging Mixed salt solution A and precipitant B were added dropwise in a parallel flow under stirring at 50℃ and 200 r / min, with the pH controlled at 9.0±0.1. After the addition was complete, the mixture was aged at 50℃ for 6 hours.

[0110] (3) Washing Filter the aged reaction solution and wash the filter cake with 70℃ hot water until the conductivity of the filtrate is <50 μS / cm.

[0111] (4) Spray drying The washed filter cake was redispersed in deionized water to form a homogeneous slurry with a solid content of approximately 20 wt%. The viscosity was adjusted to approximately 800 mPa·s. The slurry was then dried using a spray dryer with the inlet temperature controlled at 300°C and the outlet temperature at 120°C to obtain spherical catalyst precursor microspheres.

[0112] (5) Roasting The microsphere precursor obtained in step (4) was placed in a muffle furnace and heated to 700°C at a rate of 5°C / min in air atmosphere, and then calcined at this temperature for 3 hours. After natural cooling in the furnace, the methane catalytic combustion catalyst of the present invention was obtained, denoted as CAT-B1. The content of each metal element in catalyst CAT-B1 was determined by ICP-OES as follows: Co: 10wt%, Fe: 15wt%, Ce: 10wt%, La: 6wt%, Mg: 1wt%, Al: 5wt%.

[0113] Example 4 Preparation of catalysts for the catalytic combustion of methane (1) Raw material preparation Weigh out 1095.0 g Co(NO3)2·6H2O, 1010.0 g Fe(NO3)3·9H2O, 586.3 g Ce(NO3)3·6H2O, 1245.6 g La(NO3)3·6H2O, 276.5 g Mg(NO3)2·6H2O, and 1751.3 g Al(NO3)3·9H2O. Dissolve all the above raw materials together in an appropriate amount of deionized water, stir until completely dissolved, and then dilute to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L.

[0114] Prepare an aqueous solution of ammonia with a concentration of 1.0 mol / L as precipitant B.

[0115] (2) Coprecipitation and aging Mixed salt solution A and precipitant B were added dropwise in a parallel flow under stirring at 90℃ and 200 r / min, with the pH controlled at 9.0±0.1. After the addition was complete, the mixture was aged at 90℃ for 2 hours.

[0116] (3) Washing Filter the aged reaction solution and wash the filter cake with 70℃ hot water until the conductivity of the filtrate is <50 μS / cm.

[0117] (4) Spray drying The washed filter cake was redispersed in deionized water to form a homogeneous slurry with a solid content of approximately 20 wt%. The viscosity was adjusted to approximately 800 mPa·s. The slurry was then dried using a spray dryer with the inlet temperature controlled at 300°C and the outlet temperature at 120°C to obtain spherical catalyst precursor microspheres.

[0118] (5) Roasting The microsphere precursor obtained in step (4) was placed in a muffle furnace and heated to 550°C at a rate of 1°C / min in air atmosphere, and then calcined at this temperature for 6 hours. After natural cooling in the furnace, the methane catalytic combustion catalyst of the present invention was obtained, denoted as CAT-B2. The content of each metal element in catalyst CAT-B2 was determined by ICP-OES as follows: Co: 20wt%, Fe: 20wt%, Ce: 18wt%, La: 12wt%, Mg: 3wt%, Al: 15wt%.

[0119] Comparative Example 1 The difference from Example 1 is that the mixed salt solution A does not contain La(NO3)3·6H2O and Mg(NO3)2·6H2O. Specifically, 350g of Co(NO3)2·6H2O, 404.0g of Fe(NO3)3·9H2O, 130.3g of Ce(NO3)3·6H2O, and 375.1g of Al(NO3)3·9H2O were weighed. The weighed raw materials were dissolved together in an appropriate amount of deionized water and stirred until completely dissolved. Then, the solution was diluted to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L. The other steps were the same as in Example 1, and the resulting catalyst was designated CAT-D1. ICP-OES analysis showed that the metal element content in catalyst CAT-D1 was: Co: 22.5 wt%, Fe: 18.5 wt%, Ce: 13.8 wt%, and Al: 9.0 wt%.

[0120] Comparative Example 2 Preparation of catalysts for the catalytic combustion of methane (1) Raw material preparation Weigh out 640.0g Co(NO3)2·6H2O, 404.0g Fe(NO3)3·9H2O, 39g Ce(NO3)3·6H2O, 210g La(NO3)3·6H2O, 25.6g Mg(NO3)2·6H2O, and 1875g Al(NO3)3·9H2O (Co : Fe : Ce : La : Mg : Al = 2.2 : 1 : 0.086 : 0.51 : 0.1 : 4.97). Dissolve the above raw materials together in an appropriate amount of deionized water, stir until completely dissolved, and then dilute to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L.

[0121] Prepare a 1.0 mol / L ammonium carbonate solution as precipitant B.

[0122] (2) Coprecipitation and aging Mixed salt solution A and precipitant B were added dropwise in a parallel flow under stirring at 65℃ and 200 r / min, with the pH controlled at 9.0±0.1. After the addition was complete, the mixture was aged at 65℃ for 4 hours.

[0123] (3) Washing Filter the aged reaction solution and wash the filter cake with 70℃ hot water until the conductivity of the filtrate is <50 μS / cm.

[0124] (4) Spray drying The washed filter cake was redispersed in deionized water to form a homogeneous slurry with a solid content of approximately 20 wt%. The viscosity was adjusted to 800 mPa·s. The slurry was then dried using a spray dryer, with the inlet temperature controlled at 300°C and the outlet temperature at 120°C, to obtain spherical catalyst precursor microspheres.

[0125] (5) Roasting The microsphere precursor obtained in step (4) was placed in a muffle furnace and heated to 600°C at a rate of 2°C / min in air atmosphere, and then calcined at this temperature for 4 hours. After natural cooling in the furnace, the methane catalytic combustion catalyst of the present invention was obtained, denoted as CAT-D2. The contents of each metal element in the catalyst CAT-D2 were determined by ICP-OES as follows: Co: 22.5 wt%, Fe: 9.8 wt%, Ce: 2.1 wt%, Al: 23.5 wt%, La: 11.6 wt%, Mg: 0.42 wt%.

[0126] Comparative Example 3 The difference from Example 1 is that the mixed salt solution A does not contain Mg(NO3)2·6H2O. Specifically, 350g Co(NO3)2·6H2O, 404.0g Fe(NO3)3·9H2O, 130.3g Ce(NO3)3·6H2O, 129.8g La(NO3)3·6H2O, and 375.1g Al(NO3)3·9H2O were weighed out. The weighed raw materials were dissolved together in an appropriate amount of deionized water and stirred until completely dissolved. The solution was then diluted to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L. Other steps were the same as in Example 1, and the resulting catalyst was designated CAT-D3. ICP-OES analysis revealed the following metal element contents in catalyst CAT-D3: Co: 21.5 wt%, Fe: 17.0 wt%, Ce: 12.8 wt%, La: 12.7 wt%, Al: 8.2 wt%.

[0127] Comparative Example 4 The difference from Example 1 is that the mixed salt solution A does not contain Mg(NO3)2·6H2O. Specifically, 350g of Co(NO3)2·6H2O, 404.0g of Fe(NO3)3·9H2O, and 130.3g of Ce(NO3)3·6H2O were weighed out. 129.8 g La(NO3)3·6H2O and 375.1 g Al(NO3)3·9H2O were weighed and dissolved together in an appropriate amount of deionized water. The solution was stirred until completely dissolved, and then diluted to volume in a volumetric flask to prepare a mixed salt solution A with a total metal ion concentration of 0.5 mol / L. Other steps were the same as in Example 1, and the resulting catalyst was designated CAT-D4. ICP-OES analysis showed that the metal element content in catalyst CAT-D4 was: Co: 23.8 wt%, Fe: 18.8 wt%, Ce: 14.2 wt%, Mg: 2.1 wt%, and Al: 9.5 wt%.

[0128] Comparative Example 5 Following the citric acid complexation method disclosed in the journal article (Appl. Catal. B: Environ., 2019, 244, 827-834. Title: Three-dimensionally ordered macroporous LaCoO3 perovskites for catalytic oxidation of soot. Authors: Y. Wang, H. Arandiyan, J. Scott, A. Bagheri, H. Dai, R. Amal), a typical perovskite catalyst, LaCoO3, was prepared, denoted as catalyst Ref-1. The specific preparation method is as follows: (1) Solution preparation: Weigh La(NO3)3·6H2O and Co(NO3)2·6H2O according to the stoichiometric ratio of La:Co = 1:1, dissolve them in deionized water, and prepare a mixed solution with a total metal ion concentration of 0.5 mol / L. Weigh citric acid according to the ratio of total metal ion moles to citric acid moles of 1:1.5, add it to the above mixed solution, and stir until completely dissolved.

[0129] (2) Gelification and drying: The above solution was placed in an 80°C water bath and stirred continuously to evaporate the water until a viscous sol was formed. Then it was transferred to a 120°C oven and dried for 12 hours to obtain a fluffy dry gel.

[0130] (3) Calcination: The dry gel was placed in a muffle furnace and heated to 750°C at a heating rate of 5°C / min in air atmosphere, and calcined at this temperature for 5 hours to obtain LaCoO3 perovskite powder, denoted as Ref-1.

[0131] (4) Characterization of catalyst composition and physical morphology: ICP-OES analysis revealed that the metal content in catalyst Ref-1 was: La: 43.2 wt%, Co: 38.5 wt%, with the remainder being oxygen.

[0132] XRD analysis showed that its main crystalline phase is perovskite-type LaCoO3.

[0133] The catalyst is an irregularly shaped block powder, making it impossible to determine a meaningful average particle size (D). 50 The physical morphology of the particles is completely unsuitable for industrial spraying processes, as evidenced by the single-particle crushing strength test.

[0134] Comparative Example 6 Catalyst Ref-2 was prepared according to the method in Example 1 of Chinese Patent CN10408421A. Specifically: 2.0178 g of tin powder, 7.7944 g of La(NO3)3·6H2O, 0.5128 g of Mg(NO3)2·6H2O, 0.8731 g of Co(NO3)2·6H2O, and 8.4056 g of citric acid were weighed and placed in a three-necked flask. 80 mL of 32.5 wt% nitric acid was then added to prepare a nitric acid-containing metal original solution. Under co-occurrence conditions, the several metal original solutions were refluxed at 80–90 °C for 6–8 hours. The solution was then transferred to a beaker and reacted in a water bath at 70 °C for 6–8 hours. Afterward, it was dried overnight in a 100 °C infrared oven to form a semi-dry gel. The gel was then calcined in a muffle furnace at 500 °C for 3 hours, followed by calcination at 900 °C for 3 hours to obtain a 0.01 mol La-Mg-Sn-Co-O dual-doped composite metal oxide catalyst, denoted as catalyst Ref-2.

[0135] Experimental Example 1 The catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were tested according to the following test methods. The test results are shown in Table 1. 1. Specific surface area test The nitrogen adsorption-desorption method (BET method) was used for determination. The testing instrument was a Micro ASAP2460. Before the test, the sample was degassed in vacuum at 200℃ for 4 hours to remove adsorbed water and impurities on the surface. The nitrogen adsorption-desorption isotherm test was carried out at -196℃. The specific surface area was calculated using the BET model and the mesopore size distribution was analyzed using the BJH model.

[0136] 2. High-resolution transmission electron microscopy test The catalyst samples were observed using a high-resolution transmission electron microscope (HR-TEM, model: JEOL JEM-2100F). The test conditions were as follows: accelerating voltage 200 kV; the sample was ultrasonically dispersed in ethanol and then dropped onto a copper mesh support film, observed under a 5% H₂ / Ar atmosphere.

[0137] 3. X-ray diffraction (XRD) analysis Testing instrument: Bruker D8 Advance X-ray diffractometer Test conditions: Cu Kα ray source (λ=1.5406 Å), tube voltage 40 kV, tube current 40 mA; scanning range 2θ=10°-80°, scanning speed 2° / min, step size 0.02°.

[0138] 4. X-ray photoelectric energy dispersive spectroscopy analysis Testing instrument: Thermo Fisher Scientific ESCALAB 250Xi X-ray photoelectron spectrometer Excitation source: monochromatic Al Kα rays (hν = 1486.6 eV), beam size approximately 500 μm Test conditions: Vacuum degree < 1×10 -9 mbar, with the contaminated carbon C 1s (binding energy 284.8 eV) as the internal standard for binding energy calibration.

[0139] Analysis steps: 1) First, perform a full spectrum scan of the sample (binding energy 0-1350 eV) to determine the types of elements present on the surface; 2) Perform high-resolution narrow-spectrum scanning on the target elements (Al 2p, La 3d, Mg 1s, Co 2p, Fe 2p, Ce 3d) with a scan step size of 0.05 eV and ≥3 scans per spectral band to improve the signal-to-noise ratio; 3) XPS Peak 4.1 software was used to perform peak fitting on the high-resolution spectrum to determine the chemical state and binding energy of each element, with the full width at half maximum (FWHM) controlled within the range of 1.0-2.0 eV.

[0140] 5. Catalytic activity test: Test setup: Fixed-bed micro-quartz reactor (8 mm inner diameter) Test conditions: Catalyst loading 0.5 g (40-60 mesh sieve); Reactant gas composition: 1% CH4, 10% O2, N2 equilibrium; Total space velocity (GHSV) = 30000 h⁻¹ -1 The programmed heating rate is 2℃ / min, and the temperature range is 200-600℃.

[0141] Analytical methods: The concentrations of CH4 and CO2 in the exhaust gas were analyzed online using a gas chromatograph (Shimadzu GC-2014, equipped with an FID detector), and the methane conversion rate was calculated.

[0142] Evaluation indicators: based on T 90 (Lowest temperature at which methane conversion reaches 90%) Evaluation of low-temperature ignition activity 6. High-temperature aging test: Test apparatus: Tubular muffle furnace Aging conditions: The catalyst was treated at a constant temperature of 1300℃ in a static air atmosphere for 100 hours to simulate industrial ultra-high temperature conditions.

[0143] Subsequent testing: After aging, the samples were repeatedly tested for specific surface area, XRD, catalytic activity, etc., and the performance changes were compared.

[0144] 7. Physical performance testing: The average particle size (D50) was determined using a laser particle size analyzer (Malvin Mastersizer 3000), with a test range of 0.01-3500 μm. The crushing strength of at least 30 intact microspheres was randomly tested using a smart particle strength tester (Ruike FT-3000) and the average value was taken.

[0145] Raman spectroscopy: A Raman spectrometer (Thermo Fisher Scientific DXR2xi micro Raman spectrometer) was used, with the following test conditions: 532 nm laser excitation, 5 mW power, and a scanning range of 100-1200 cm⁻¹. -1 The characteristic Raman peaks (~490 cm-1, 670 cm-1) of the La-Mg-Al-O composite spinel phase were detected.

[0146] 9. Methane catalytic combustion efficiency decay rate test: Test setup: Fixed-bed micro-quartz reactor (8 mm inner diameter) Test conditions: Catalyst loading 0.5 g (40-60 mesh sieve); Reactant gas composition: 1% CH4, 20% O2, N2 equilibrium; Total space velocity (GHSV) = 50000 h⁻¹ -1 The samples were pretreated in air at 500℃ for 2 hours before testing. Analytical methods: The concentrations of CH4, CO, and CO2 in the exhaust gas were analyzed online using gas chromatography, and the methane conversion rate at different temperatures was calculated; Calculation of methane catalytic combustion efficiency decay rate: Methane catalytic combustion efficiency decay rate = [(Initial methane conversion rate - Methane conversion rate after aging) / Initial methane conversion rate] × 100% Table 1 Catalyst characterization results

[0147]

[0148] Based on the above test methods and the data in Table 1, the following conclusions can be drawn, which fully demonstrate the superiority and innovation of the catalyst of this invention: Excellent structural stability at ultra-high temperatures: After harsh aging at 1300℃ for 100 hours, the specific surface area retention rate of all catalysts in this invention (CAT-1 to CAT-4) exceeded 90%. XRD tests confirmed that no α-Al2O3 phase was formed, and Raman spectroscopy detected the characteristic peaks of the La-Mg-Al-O composite spinel phase, indicating that the LaAlO3 / MgAl2O4 composite crystal phase structure is stable. The element retention rate is high, with no obvious loss or segregation, which completely solves the technical problem of alumina α-phase transformation at high temperatures in existing catalysts.

[0149] Excellent catalytic activity and stability: The catalyst in the example has an initial T90 ≤ 442℃, exhibiting good low-temperature ignition activity, meeting the industrial low-temperature start-up requirements; after aging at 1300℃, the methane catalytic combustion efficiency decay rate is < 5%, with extremely high activity retention, far superior to the comparative catalysts (decay rate 22.2%-65.0%), demonstrating the synergistic advantage of the active component and the stable framework.

[0150] Excellent mechanical strength and industrial compatibility: The catalysts in the examples are all regular spherical microspheres with an average particle size of 40-80μm and a single particle crushing strength of ≥55N. After high-temperature aging, the mechanical strength retention rate is ≥85%, which fully meets the load requirements of industrial spraying process. The coating is firm and does not peel off after spraying. In contrast, the control catalysts (Ref-1, Ref-2) have irregular morphology and are prone to agglomeration, making it impossible to test their mechanical strength and thus lacking industrial application value.

[0151] Compared with this application, the comparative catalysts (CAT-D1 to CAT-D4) that lack the La-Mg 5-8:1 mass ratio limitation of this application, have a six-element ratio that exceeds the scope of this application, or do not use a co-precipitation process, although they partially contain Al, La, and Mg elements, cannot form a stable LaAlO3 / MgAl2O4 nano-reinforced framework, nor do they have a La-Mg-Al-O composite spinel phase. Their performance deteriorates sharply after high-temperature aging, which fully proves that the ultra-high temperature stability effect of the catalyst in this application is the synergistic result of specific element ratios, exclusive preparation processes, and composite crystal phase structures, and cannot be achieved by simple element coexistence.

[0152] Furthermore, comparing Example 1 and Example 2, it can be seen that after co-doping with Sr and Zr, the catalyst maintains a high specific surface area while its low-temperature ignition activity (T90) and mechanical strength are further optimized, verifying the effect of Sr / Zr doping on improving the overall performance of the catalyst.

[0153] Application Experiment Example To verify the industrial application performance of the catalyst of this invention, a long-term industrial side-line operation verification of more than 3,600 hours was carried out on the B4 aluminum rod melting furnace (furnace volume 22m³, designed aluminum rod processing capacity 1t / h) of Foshan Guangcheng Aluminum Industry.

[0154] 1. Experimental System Setup The CAT-1 catalyst prepared in Example 1 was sprayed onto a FeCrAl high-temperature resistant alloy substrate with a loading of 6250 g / m². The binder used for spraying was a silica sol-alumina sol composite system (silica sol to alumina sol mass ratio of 1:2). Before spraying, the FeCrAl substrate was roughened by sandblasting (roughness Ra8) and degreased with acetone. The binder was pre-dried at 90°C for 3 hours and calcined at 550°C for 1.5 hours to cure. The catalyst-loaded substrate was integrated into the catalytic combustion module of an aluminum rod furnace to construct a complete industrial catalytic combustion system.

[0155] 2. Industrial operating conditions The fuel used in the industrialization experiment was industrial natural gas (CH4 ≥ 97% (v / v), with the remainder being small amounts of ethane and nitrogen). The system's volumetric air-fuel ratio was controlled at 1:9.8. After exchanging heat with the waste heat from the exhaust gas, the natural gas and air reached approximately 180°C before entering the burner. The temperature in the upper combustion zone of the furnace was 1280-1350°C, and the catalyst bed temperature in the catalytic combustion module was 1300±10°C. The apparent space velocity of the reactant gas at the catalyst bed was approximately 30,000 h⁻¹. -1 The natural gas supply pressure is 0.3 MPa.

[0156] 3. Detection Method The gas chromatograph (Shimadzu GC-2014) and nitrogen oxide analyzer (Xuedilong NOA-7000) were used for online detection of CH4, CO, and NO in the exhaust gas. X The concentration of the catalyst was measured in accordance with the "Emission Standard of Air Pollutants for Industrial Furnaces and Kilns" (GB9078-1996). After 3600 hours of operation, samples were taken to analyze the structure and performance of the catalyst. The detection methods included ICP-OES (Shimadzu ICPE-9820), BET (Mike ASAP2460), XRD (Brook D8 Advance), and HR-TEM (Thermo Fisher Talos F200X).

[0157] 4. Industrial Operation Results (1) Stability of catalyst structure

[0158] After 3600 hours of operation, the structural performance test results of the catalyst are shown in Table 2. The HR-TEM image and EDS elemental distribution mapping diagram of the catalyst are shown in the figure below. Figure 5-7 As shown.

[0159] Table 2. Results of structural stability test of catalyst after 3600 hours of industrial operation. Test Project Test Results Test methods / standards Performance requirements Compliance status Specific surface area after operation 23.6 m² / g BET Law ≥20 m² / g Meets standards <![CDATA[Diffraction peaks of α-Al2O3 after running]]> none XRD detection none Meets standards La element retention rate 99.6% ICP-OES testing ≥99.5% Meets standards Mg element retention rate 99.9% ICP-OES testing ≥99.8% Meets standards Crushing strength after operation 52 N Particle strength tester ≥45 N Meets standards Mechanical strength retention rate 89.7% After running / Initial × 100% ≥85% Meets standards Average grain size 8-12 nm HR-TEM analysis No obvious growth Meets standards Uniformity of element distribution Unbiased analysis EDS Mapping Uniform distribution Meets standards (2) Catalytic performance of catalyst

[0160] The methane catalytic combustion efficiency of the catalyst was monitored online throughout the entire process. The results showed that during 3600 hours of continuous operation, the average methane catalytic combustion efficiency was ≥96%, and the methane catalytic combustion efficiency decay rate was <5%, which fully met the requirements for long-term industrial operation. After the catalyst underwent 12 cycles of cold and hot start-up and shutdown from room temperature to 1300℃, the methane catalytic combustion efficiency recovered to more than 95% within 12 hours, demonstrating excellent thermal shock stability. (3) Energy saving and environmental protection benefits

[0161] Table 3 shows the natural gas consumption and pollutant emissions data of the aluminum rod furnace during industrial operation. Compared with the original combustion system of the furnace, it has achieved significant gas-saving and environmental protection benefits.

[0162] Table 3. Test Results of Energy Conservation and Environmental Protection Benefits in Industrial Operations Test Project Test Results National standard limits (GB 9078-1996) Improved compared to the original system CO emission concentration 6 mg / m³ (standard dry) ≤150 mg / m³ Reduced by 96% <![CDATA[NO X Emission concentration 10 mg / m³ (standard dry) ≤400 mg / m³ Reduced by 97.5% Natural gas consumption per ton of aluminum 22.4 Nm³ / t-Al - Reduced by 25.3% Solar term rate 25.3% - - <![CDATA[Unburned CH4 emission concentration]]> <50 ppm (standard dry) - Near-zero emissions (4) Catalyst regeneration performance

[0163] The catalyst was sampled after 3600 hours of operation and regenerated by calcining at 800℃ for 4 hours in air. After regeneration, its catalytic and structural properties were tested: the methane catalytic combustion efficiency was restored to 98%, the specific surface area was restored to 38.2 m² / g, and the crushing strength was restored to 55 N. The activity and structural properties of the catalyst were effectively restored, and it can continue to be put into industrial operation, which verifies the good regenerability of the catalyst.

[0164] 5. Analysis of Industrial Operation Results Figure 5 These are high-resolution transmission electron microscopy (HR-TEM) images of catalyst CAT-1 prepared in Example 1 before and after operation at 1300°C for 3600 hours. Figure 5 It can be seen that after long-term operation, the catalyst particles still maintain an intact nanocrystalline structure, with no significant growth in grain size and no obvious sintering or agglomeration. Figure 6 The following is a Fast Fourier Transform (FFT) analysis and elemental distribution map of the HR-TEM image of catalyst CAT-1 prepared in Example 1 after operation at 1300℃ for 3600 hours. Figure 6 In the diagram, b and c represent the FFT analysis of regions A and B, respectively. Figure 6 It can be seen that the diffraction patterns in regions b and c perfectly match the

[011] zone axis of MgAl2O4 and the

[001] zone axis of LaAlO3, respectively, directly visualizing the stable existence of the LaAlO3 / MgAl2O4 nano-reinforced phase; Figure 7The EDS elemental distribution map shows that the elements are still evenly distributed. Al, La, and Mg form a dense framework network, while Co, Fe, and Ce are uniformly anchored by the network in the form of nanoclusters. The unique microstructure of "stable framework-active clusters" is the fundamental reason why the catalyst achieves long-term stability at ultra-high temperature of 1300℃.

[0165] Therefore, industrial operation data confirms that the catalyst of this invention has excellent catalytic performance, structural stability and industrial adaptability in real 1300℃ ultra-high temperature industrial combustion scenarios, while achieving significant gas saving and near-zero emission effects, fully meeting the actual application needs of industrial furnaces and kilns.

[0166] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0167] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0168] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A catalyst for the catalytic combustion of methane, characterized in that, It is a composite oxide comprising cobalt, iron, cerium, aluminum, lanthanum, and magnesium. The mass percentage of each element, based on the total mass of the catalyst, is as follows: cobalt 10-20%, iron 15-20%, cerium 10-18%, aluminum 5-15%, lanthanum 6-12%, and magnesium 1-3%, wherein the mass ratio of lanthanum to magnesium is (4-8):

1. The catalyst is prepared by a method comprising co-precipitating a mixed salt solution containing cobalt salt, iron salt, cerium salt, lanthanum salt, magnesium salt, and aluminum salt with a precipitant solution in a co-current flow, followed by aging, drying, and calcination.

2. The catalyst according to claim 1, characterized in that, The catalyst contains a La-Mg-Al-O composite spinel phase.

3. The catalyst according to claim 1 or 2, characterized in that, The catalyst contains 0.1-2.0% strontium by mass percentage, based on the total mass of the catalyst; and / or, The catalyst contains 0.5-4.0% zirconium by mass; and / or, The molar ratio of cobalt, iron and cerium in the catalyst is (0.9-1.5):1:(0.2-0.5).

4. The catalyst according to any one of claims 1-3, characterized in that, The catalyst has a specific surface area ≥ 40 m² / g and an average particle size D. 50 The particle size is 40-80μm, and the crushing strength of a single particle is greater than or equal to 55N.

5. A method for preparing a catalyst for the catalytic combustion of methane, characterized in that, Includes the following steps: (1) A mixed salt solution containing cobalt, iron, cerium, aluminum, lanthanum and magnesium is prepared and then co-precipitated with a precipitant solution in a co-current flow to obtain a coprecipitated slurry. (2) The coprecipitated slurry obtained in step (1) is subjected to an aging reaction, and then filtered and washed to obtain a filter cake; (3) The filter cake obtained in step (2) is redispersed and spray-dried to obtain the catalyst precursor; (4) The catalyst precursor obtained in step (3) is calcined in an air atmosphere to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that, In step (1), the soluble salt is a nitrate or chloride; the precipitant is one or more of ammonium carbonate, ammonia, or ammonium bicarbonate; and / or, The process of redispersing the filter cake in step (3) includes re-pulping the filter cake and adjusting the solid content of the slurry to 15-25 wt% and the viscosity to 500-1500 mPa·s.

7. The preparation method according to claim 5 or 6, characterized in that, In step (1), the concentration of metal ions in the mixed salt solution is 0.3-1.0 mol / L, the pH of the coprecipitation reaction is 8.5-10.0, and the temperature of the coprecipitation reaction is 50-90℃; and / or, In step (2), the aging reaction temperature is 50-90℃, and the aging time is 2-6 hours; and / or, In step (3), the inlet temperature of the spray dryer is 250-350℃, and the outlet temperature is 100-150℃; and / or, The roasting temperature in step (4) is 550-700℃, the roasting time is 3-6 hours, and the roasting heating rate is 1-5℃ / min.

8. The use of the catalyst according to any one of claims 1-4 or the catalyst prepared by any one of claims 5-7 in a combustion device, wherein, The combustion device is selected from aluminum rod furnace, metal smelting furnace or ceramic sintering furnace.

9. An industrial combustion system, comprising a burner and a catalytic combustion module, characterized in that, The catalytic combustion module is filled with a catalyst according to any one of claims 1-4 or any one of claims 5-7; Preferably, the catalytic combustion module is a fixed bed structure, and the catalyst is loaded onto the FeCrAl high-temperature resistant alloy substrate by spraying, with a catalyst dry film loading of 6000-6500 g / m²; the binder used for spraying includes silica sol and alumina sol, wherein the mass ratio of silica sol to alumina sol is 1:1-3. More preferably, the FeCrAl high-temperature alloy substrate is roughened by sandblasting and degreased with acetone before spraying, and the surface roughness of the substrate after roughening is Ra5-Ra10; the curing process of the adhesive is: first pre-drying at 80-100℃ for 2-4 hours, and then calcining at 500-600℃ for 1-2 hours.

10. A combustion method, characterized in that, The industrial combustion system described in claim 9 comprises the following steps: preheating natural gas with a methane content ≥95% (v / v) to 180-190°C and then introducing it into a burner for combustion; the temperature of the upper combustion zone in the furnace is 1280-1350°C; the temperature of the catalyst bed in the catalytic combustion module is 1290-1310°C; and the apparent space velocity of the reactant gas at the catalyst bed is 10000-50000 h⁻¹. -1 The natural gas supply pressure is 0.1-0.3 MPa, and the system volumetric air-fuel ratio is 1:(9.0-10.0).

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