Nano-coated modified ceramic membrane for oxygen-enriched combustion and preparation method thereof

Abstract

The application discloses a kind of nanometer coating modified ceramic membranes for oxygen-enriched combustion and a preparation method thereof, and belongs to the technical field of ceramic oxygen-permeable membrane.The ceramic membrane grows in situ a zinc-tin composite oxide nanostructure layer with specific stoichiometric ratio and micro-morphology on the surface of mixed conductor ceramic oxygen-permeable membrane matrix, significantly improving the oxygen permeability and high temperature stability.The three-dimensional "nanoflower" porous covering layer structure can effectively increase the oxygen permeation active sites, promote the surface exchange and bulk diffusion of oxygen ions.The perovskite oxide selected as the matrix has excellent oxygen ion and electron mixed conduction characteristics, providing a basis for high oxygen permeation flux.The preparation method precisely controls the steps of matrix membrane preparation, pretreatment, precursor preparation, in-situ hydrothermal growth and programmed temperature calcination, and cooperatively improves the high temperature oxygen permeation flux, CO2 corrosion resistance and long-term stability of the membrane, solving the problem that flux and stability are difficult to balance in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of ceramic oxygen-permeable membrane technology, specifically relating to a nano-coated modified ceramic membrane for oxygen-enriched combustion and its preparation method. Background Technology

[0002] Oxygen-enriched combustion is one of the key technologies for carbon capture and storage, and its core lies in the efficient and stable supply of high-purity oxygen. However, the high cost of oxygen supply has always been a major factor restricting the commercialization of oxygen-enriched combustion technology.

[0003] Currently, the industrial production of oxygen mainly focuses on the following processes:

[0004] (1) Oxygen production by cryogenic condensation fractionation: Pure oxygen is produced by condensing air at low temperature and then separating it according to the different boiling points of components such as oxygen and nitrogen in the air through fractionation. This method produces oxygen with high purity and high efficiency, and can also produce gases and liquids such as nitrogen; however, this method consumes a lot of energy and has high cost, and is only suitable for large-scale production.

[0005] (2) Pressure Swing Adsorption (PSA) for Oxygen Production: This method utilizes the property that molecular sieves have a greater adsorption capacity for nitrogen than for oxygen. Nitrogen is adsorbed under pressure and desorbed under depressurization, thereby enriching oxygen. This method has simple equipment and low energy consumption, but the oxygen purity and recovery rate are relatively low, and the molecular sieves are easily contaminated and become ineffective.

[0006] (3) Membrane separation oxygen production: This method separates oxygen and nitrogen in the air by utilizing the different diffusion rates of oxygen and nitrogen molecules in a polymer membrane. It has attracted attention because it can be applied under atmospheric conditions and has a very fast start-up speed. However, the oxygen produced by this method is not very pure and is generally only used to produce oxygen-enriched air (oxygen content of 25-50%).

[0007] In recent years, hybrid conductor ceramic oxygen-permeable membranes have demonstrated significant advantages. Because ceramic membranes achieve oxygen separation through oxygen ion conduction at temperatures above 700°C, they exhibit 100% oxygen permeability selectivity, a rapid permeation rate (2-3 orders of magnitude faster than organic membranes), low oxygen production costs (30-50% lower than traditional cryogenic distillation or pressure swing adsorption methods), high mechanical strength, and good corrosion resistance, allowing operation in harsh environments. The process and operation are simple, making them suitable for oxygen-consuming environments of various scales and possessing a very broad market prospect.

[0008] However, directly applying ceramic oxygen-permeable membranes to processes such as oxy-fuel combustion or integrated gasification combined cycle (IGCC) faces extremely harsh operating environments: high temperatures (850-950℃) and high concentrations of carbon dioxide (CO2) in flue gas or process gas. Under these conditions, ceramic oxygen-permeable membranes mainly exhibit the following failure mechanisms: First, at high temperatures, oxygen ions diffuse rapidly in the bulk phase, and the membrane performance is often limited by the adsorption, dissociation, and exchange kinetics of oxygen on the membrane surface (surface exchange process), restricting flux improvement. Second, under long-term high-temperature operation, the membrane material is prone to segregation of alkaline earth metals or rare earth metals, phase structure evolution, and grain coarsening, leading to loss of active sites and decreased oxygen permeability. Most seriously, CO2 reacts with alkaline oxides segregated on the membrane material surface or the material itself to form thermodynamically stable carbonates. This not only physically blocks surface active sites, severely hindering the oxygen exchange process, but may also cause membrane peeling and cracking, resulting in irreversible mechanical damage.

[0009] Currently, research on the modification of ceramic oxygen-permeable membranes mainly focuses on bulk doping or surface coating to improve stability. For example, CN101302121B discloses a surface nano-coating modification technology, which involves coating the surface of membrane material particles with a continuous and dense layer of inert oxides such as Al2O3 and ZrO2 to suppress bulk ion migration and phase transition. Although this method can improve mechanical and phase stability, the continuous and dense coating inevitably hinders the surface exchange process of oxygen, resulting in a significant decrease in the initial oxygen permeability. Furthermore, its protective effect against CO2 corrosion is limited because it cannot prevent CO2 from diffusing through grain boundaries or defects to react with the membrane substrate.

[0010] Therefore, developing a ceramic oxygen-permeable membrane modification technology that can actively enhance surface oxygen exchange kinetics to increase flux, effectively resist corrosion in high-temperature and high-carbon dioxide environments from a physical and chemical perspective, and maintain long-term structural stability has become a core issue in promoting the commercial application of this technology in carbon capture and storage related fields. Summary of the Invention

[0011] This invention addresses the problems of existing technologies by providing a nano-coated modified ceramic membrane for oxygen-enriched combustion and its preparation method. It aims to solve the problems of limited oxygen flux, sluggish surface exchange kinetics, susceptibility to CO2 corrosion, and insufficient long-term stability of existing hybrid conductor ceramic oxygen-permeable membranes under high-temperature and high-CO2 environments. This invention achieves synergistic modification of the ceramic oxygen-permeable membrane by in-situ growing a zinc-tin composite oxide nanostructure layer with a specific stoichiometric ratio and a unique three-dimensional "nanoflower" morphology on the surface of the hybrid conductor ceramic oxygen-permeable membrane substrate. This zinc-tin composite oxide nanostructure layer not only serves as a highly efficient surface oxygen exchange active site, significantly accelerating the adsorption, dissociation, and exchange of oxygen on the membrane surface, thereby increasing oxygen permeability; its unique three-dimensional "nanoflower" porous covering structure, assembled from extremely thin nanosheets, effectively blocks direct contact between CO2 gas and the membrane substrate, slowing down CO2 diffusion and permeation, while also utilizing the stability of its chemical composition to prevent reaction with CO2 to form harmful carbonates; simultaneously, this in-situ grown nanostructure layer has good interfacial bonding strength with the substrate, which can inhibit grain coarsening and elemental segregation of the substrate at high temperatures, thus comprehensively improving the long-term operational stability and reliability of the ceramic oxygen-permeable membrane under harsh environments such as oxygen-enriched combustion.

[0012] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0013] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a mixed conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 1-3:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0014] Furthermore, in the zinc-tin composite oxide, the molar ratio of zinc to tin is 1:1.

[0015] Furthermore, the hybrid conductor ceramic oxygen-permeable membrane substrate is a perovskite oxide with the general chemical formula A. 1- x M x B 1-y N y O 3-δ Where A is selected from one or more of La, Ba, and Pr, M is selected from one or more of Sr, Ca, and Gd, B is selected from one or more of Co and Mn, N is selected from one or more of Fe, Cu, Zr, Nb, Ga, and Al, 0 < x ≤ 0.5, 0 < y ≤ 0.8, and δ is the oxygen vacancy concentration, with a value range of 0.1-0.5.

[0016] Furthermore, the hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3-δ Or La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0017] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0018] (1) Preparation of substrate membrane: The metal source raw materials were weighed according to the stoichiometric ratio of perovskite oxide, and after mixing, molding and sintering, a mixed conductor ceramic oxygen-permeable membrane substrate was obtained;

[0019] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0020] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 1-3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0021] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) (immersion is sufficient) and hydrothermal reaction is carried out. After the reaction is completed, the substrate is removed, cleaned and dried.

[0022] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0023] Furthermore, in step (1), the metal source is an oxide or a carbonate, the mixing process is wet ball milling, the ball-to-material ratio is 10:1, the ball milling speed is 300 r / min, and the ball milling time is 24 h; the forming adopts a combination of dry pressing preforming and isostatic pressing forming process, the dry pressing preforming pressure is 20 MPa, the holding time is 5 min, the isostatic pressing forming pressure is 100 MPa, and the holding time is 10 min; the sintering adopts programmed temperature rise, the maximum sintering temperature is 1150-1300℃, and the holding time is 4-6 h.

[0024] Furthermore, in step (2), the ultrasonic cleaning power is 300W, the cleaning time is 15-30min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature, the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum, the vacuum degree is -0.09MPa, and the drying time is 2h.

[0025] Further, in step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the ratio of the mixture of zinc and tin sources to the mixed solution is 1g:20mL. The structure-directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1. The total amount of the two structure-directing agents added is 1-1.5 times the total molar amount of zinc and tin sources; the stirring speed is 500r / min, and the stirring time is 60min.

[0026] Furthermore, in step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 6-12h, and the heating rate is 5℃ / min.

[0027] Furthermore, in step (5), the programmed heating and calcination regime is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2 hours; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is increased to 800℃ at a rate of 3℃ / min and held for 4-6 hours, and then cooled to room temperature in the furnace after calcination.

[0028] Through the above technical solution, the present invention achieves the following significant beneficial effects:

[0029] 1. Precise and synergistic control of morphology and composition was achieved, resulting in an ideal three-dimensional "nanoflower" structure: This invention creatively employs a dual-structure directing agent combination of triethanolamine and urea, which is key to obtaining a uniform and stable "nanoflower" morphology. Its mechanism of action lies in the slow decomposition of urea under hydrothermal conditions, uniformly releasing CO3. 2- and OH -This provides a stable and mild alkaline environment for the homogeneous nucleation of zinc-tin composite hydroxides and the growth of two-dimensional nanosheets. Triethanolamine, as a complexing agent and alkali source, can regulate the release rate and form of metal ions in the solution, and works synergistically with urea to induce anisotropic growth and bending assembly of two-dimensional nanosheets. The two work together to first guide the formation of a large number of ultrathin primary nanosheets (5-30 nm thick), which are then orderly constructed into uniformly sized and structurally stable three-dimensional "nanoflowers" through Ostwald ripening and self-assembly processes. This unique morphology possesses an extremely high specific surface area and abundant mesoporous structure, laying an ideal physical foundation for subsequent functional realization.

[0030] 2. Significantly improved surface oxygen exchange kinetics and oxygen flux of ceramic oxygen-permeable membranes: The in-situ grown Zn-Sn composite oxide "nanoflower" layer, with its open porous structure composed of ultrathin nanosheets, greatly increases the effective reaction area on the membrane surface, significantly reducing the mass transfer resistance of oxygen molecules during adsorption and dissociation. More importantly, the combination of Zn and Sn produces a synergistic effect: the SnO2 component provides excellent surface oxygen exchange active sites, while the introduction of ZnO optimizes the surface electronic structure and enhances the migration kinetics of oxygen ions on the surface layer, fundamentally alleviating the limitation of the surface exchange process on the overall oxygen permeability rate.

[0031] 3. This invention endows the membrane with excellent resistance to high-temperature carbon dioxide corrosion, solving a core bottleneck in oxygen-enriched combustion applications: this is one of the most outstanding effects of the invention. The three-dimensional "nanoflower" structure itself acts as a porous physical barrier, effectively dispersing and delaying the direct impact and penetration of high-concentration CO2 gas flow onto the membrane substrate surface. More importantly, the ZnO component possesses extremely high chemical stability and extremely low cation mobility. This Zn-Sn-O composite surface layer can act as a "stabilizing anchor," strongly inhibiting the growth of Sr in the perovskite matrix. 2+ Ba 2+ The segregation of alkaline cations to the surface at high temperatures effectively cuts off the pathway for the reaction with CO2 to form dense carbonate layers such as SrCO3 and BaCO3. Experiments show that, in a harsh atmosphere of 850°C and 20% CO2, after several hundred hours of operation, the oxygen permeability degradation rate of the membrane of this invention is much lower than that of the unmodified membrane and the single metal oxide modified membrane.

[0032] 4. Significantly enhanced overall long-term operational stability and mechanical reliability of the membrane: The nanoflower layer, grown in situ via hydrothermal method, forms a strong chemical bond and mechanical interlock with the ceramic substrate, resulting in high bonding strength and resistance to peeling during thermal cycling. This functional layer, acting as a "sacrificial layer" and "stabilizing layer," effectively blocks direct erosion of the substrate by harsh external environments. Simultaneously, its stable structure pins the surface grains of the substrate, inhibiting abnormal grain growth and harmful phase transitions at high temperatures. Therefore, the membrane of this invention not only exhibits stability in a CO2 atmosphere but also demonstrates extremely low performance degradation during long-term high-temperature operation in an inert atmosphere, fundamentally improving durability.

[0033] 5. The preparation process is controllable and highly reproducible, with potential for industrial application: The preparation method of this invention, especially the hydrothermal process using triethanolamine and urea as dual guiding agents, operates under mild conditions and easily controllable parameters, enabling uniform and reproducible growth of nanoflower layers on the substrate surface. The entire process requires no complex equipment and is highly compatible with traditional ceramic membrane preparation processes, providing a reliable technical route for the large-scale preparation of high-performance, long-life oxygen-enriched combustion ceramic oxygen-permeable membranes.

[0034] In summary, this invention, through ingenious compositional design (Zn-Sn synergy), innovative morphology control (dual-directing agent-induced three-dimensional nanoflowers), and optimized preparation process, successfully prepared a composite ceramic oxygen-permeable membrane that combines high oxygen permeability, excellent CO2 corrosion resistance, and ultra-strong long-term stability. Its comprehensive performance far exceeds that of existing technologies, and it has extremely high application value and market prospects in fields such as oxygen-enriched combustion carbon capture. Attached Figure Description

[0035] Figure 1 This is a diagram of the oxygen permeability testing device of the present invention;

[0036] Figure 2 This is an electron microscope image of the surface morphology of the nano-coated modified ceramic film obtained in Example 1 of the present invention;

[0037] Figure 3 Electron micrographs of the surface morphology of the ceramic films obtained in Comparative Examples 1-3.

[0038] Figure 4 This is a graph showing the long-term oxygen permeability of the nano-coated modified ceramic membrane obtained in Example 1 of the present invention under a 20% carbon dioxide atmosphere. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0040] Example 1

[0041] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 1:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0042] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ .

[0043] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0044] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0045] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0046] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 1:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0047] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0048] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0049] In step (1), the mixing process adopts wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h; the molding adopts a combination of dry pressing pre-forming and isostatic pressing forming process, with a dry pressing pre-forming pressure of 20 MPa and a holding time of 5 min, and an isostatic pressing forming pressure of 100 MPa and a holding time of 10 min; the sintering adopts programmed temperature rise with a maximum sintering temperature of 1150℃ and a holding time of 6 h.

[0050] In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 15min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

[0051] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1; the total amount of the two structure directing agents added is 1 times the total molar amount of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0052] In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 12h, and the heating rate is 5℃ / min.

[0053] In step (5), the programmed heating and calcination regime is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2 hours; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is increased to 800℃ at a rate of 3℃ / min and held for 4 hours. After calcination, the temperature is cooled to room temperature in the furnace.

[0054] Example 2

[0055] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 2:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0056] The hybrid conductor ceramic oxygen-permeable membrane substrate is Ba. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ .

[0057] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0058] (1) Preparation of substrate membrane: According to the stoichiometric ratio of perovskite oxides, 99.5% BaCO3 (purity 99.5%), SrCO3 (purity 99.5%), Co3O4 (purity 99.0%), and Fe2O3 (purity 99.0%) were weighed as metal source raw materials, and after mixing, molding, and sintering, a mixed conductor ceramic oxygen-permeable membrane substrate was obtained;

[0059] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0060] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 2:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0061] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0062] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0063] In step (1), the mixing process adopts wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h; the molding adopts a combination of dry pressing pre-forming and isostatic pressing forming process, with a dry pressing pre-forming pressure of 20 MPa and a holding time of 5 min, and an isostatic pressing forming pressure of 100 MPa and a holding time of 10 min; the sintering adopts programmed temperature rise, with a maximum sintering temperature of 1200℃ and a holding time of 5 h.

[0064] In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 20min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

[0065] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1; the total amount of the two structure directing agents added is 1.2 times the total molar amount of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0066] In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 8h, and the heating rate is 5℃ / min.

[0067] In step (5), the programmed heating and calcination regime is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2 hours; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is increased to 800℃ at a rate of 3℃ / min and held for 4 hours. After calcination, the temperature is cooled to room temperature in the furnace.

[0068] Example 3

[0069] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 3:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0070] The hybrid conductor ceramic oxygen-permeable membrane substrate is Ba. 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3-δ .

[0071] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0072] (1) Preparation of substrate membrane: BaCO3 (purity 99.5%), SrCO3 (purity 99.5%), Co3O4 (purity 99.0%) and Fe2O3 (purity 99.0%) of metal source raw materials were weighed according to the stoichiometric ratio of perovskite oxides, mixed, shaped and sintered to obtain a mixed conductor ceramic oxygen-permeable membrane substrate;

[0073] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0074] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0075] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0076] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0077] In step (1), the mixing process adopts wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h; the molding adopts a combination of dry pressing pre-forming and isostatic pressing forming process, with a dry pressing pre-forming pressure of 20 MPa and a holding time of 5 min, and an isostatic pressing forming pressure of 100 MPa and a holding time of 10 min; the sintering adopts programmed temperature rise, with a maximum sintering temperature of 1250℃ and a holding time of 5 h.

[0078] In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 30min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

[0079] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1; the total amount of the two structure directing agents added is 1 times the total molar amount of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0080] In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 10h, and the heating rate is 5℃ / min.

[0081] In step (5), the temperature-increasing calcination process is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2 hours; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is increased to 800℃ at a rate of 3℃ / min and held for 5 hours. After calcination, the temperature is cooled to room temperature in the furnace.

[0082] Example 4

[0083] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 3:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0084] The hybrid conductor ceramic oxygen-permeable membrane substrate is La.0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0085] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0086] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0087] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0088] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0089] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0090] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0091] In step (1), the mixing process adopts wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h; the molding adopts a combination of dry pressing pre-forming and isostatic pressing forming process, with a dry pressing pre-forming pressure of 20 MPa and a holding time of 5 min, and an isostatic pressing forming pressure of 100 MPa and a holding time of 10 min; the sintering adopts programmed temperature rise with a maximum sintering temperature of 1300℃ and a holding time of 4 h.

[0092] In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 20min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

[0093] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1; the total amount of the two structure directing agents added is 1.5 times the total molar amount of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0094] In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 12h, and the heating rate is 5℃ / min.

[0095] In step (5), the programmed heating and calcination regime is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2 hours; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is increased to 800℃ at a rate of 3℃ / min and held for 6 hours. After calcination, the temperature is cooled to room temperature in the furnace.

[0096] Comparative Example 1

[0097] In this comparative example, all conditions were the same as in Example 4, except that no structure-directing agent was used.

[0098] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 3:1.

[0099] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0100] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0101] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0102] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0103] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 3:1, adjust the pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0104] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0105] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0106] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water with a volume ratio of 1:1; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0107] Comparative Example 2

[0108] In this comparative example, except that only triethanolamine was used in the structure-directing agent, all other conditions were the same as in Example 4, namely:

[0109] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 3:1.

[0110] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0111] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0112] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0113] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0114] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0115] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0116] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0117] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is triethanolamine, and the amount of the structure directing agent added is 1.5 times the total molar number of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0118] Comparative Example 3

[0119] In this comparative example, except that only urea was used in the structure-directing agent, all other conditions were the same as in Example 4, namely:

[0120] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 3:1.

[0121] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0122] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0123] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0124] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0125] (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly, and obtain zinc-tin composite oxide precursor solution;

[0126] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0127] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0128] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is urea, and the amount of the structure directing agent added is 1.5 times the total molar number of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

[0129] Comparative Example 4

[0130] In this comparative example, except that zinc was not used in the nanocoating layer, all other conditions were the same as in Example 4, namely:

[0131] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a tin oxide nanostructure layer grown in situ on the surface of the substrate. The nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers. The nanoflowers form a porous covering layer on the surface of the substrate.

[0132] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0133] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0134] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0135] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0136] (3) Preparation of precursor solution: Dissolve the tin source in a mixed solvent, add the structure directing agent, adjust the pH value to 8.0-8.5, stir evenly, and obtain the tin oxide precursor solution;

[0137] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0138] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0139] In step (3), the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1. The total amount of the two structure directing agents added is 1.5 times the total number of moles of the tin source; the stirring speed is 500 r / min and the stirring time is 60 min.

[0140] Comparative Example 5

[0141] In this comparative example, except that tin is not used in the nano-coating layer, all other conditions are the same as in Example 4, namely:

[0142] A nano-coated modified ceramic membrane for oxygen-enriched combustion includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc oxide nanostructure layer grown in situ on the surface of the substrate; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

[0143] The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0144] A method for preparing a nano-coated modified ceramic membrane for oxygen-enriched combustion includes the following steps:

[0145] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0146] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0147] (3) Preparation of precursor solution: Dissolve the zinc source in a mixed solvent, add the structure directing agent, adjust the pH value to 8.0-8.5, stir evenly, and obtain zinc oxide precursor solution;

[0148] (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried.

[0149] (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

[0150] In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the structure directing agent is a combination of triethanolamine and urea, and the molar ratio of triethanolamine and urea is 1:1. The total amount of the two structure directing agents added is 1.5 times the total number of moles of the zinc source; the stirring speed is 500 r / min and the stirring time is 60 min.

[0151] In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 12h, and the heating rate is 5℃ / min.

[0152] In step (5), the programmed heating and roasting regime is as follows: heat up to 300℃ at a rate of 2℃ / min and hold for 2h; then heat up to 600℃ at a rate of 5℃ / min and hold for 3h; finally heat up to 800℃ at a rate of 3℃ / min and hold for 4-6h, and then cool to room temperature with the furnace after roasting.

[0153] Comparative Example 6

[0154] In this comparative example, except for the absence of nano-coating, all other steps are the same as in Example 4, namely:

[0155] A ceramic membrane for oxygen-enriched combustion, wherein the substrate of the hybrid conductor ceramic oxygen-permeable membrane is La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

[0156] A method for preparing a ceramic membrane for oxygen-enriched combustion includes the following steps:

[0157] (1) Preparation of substrate membrane: The metal source raw materials La2O3 (purity 99.9%), SrCO3 (purity 99.5%), Co2O3 (purity 99.0%) and Fe2O3 (purity 99.0%) were weighed according to the stoichiometric ratio of perovskite oxides, and mixed, shaped and sintered to obtain the mixed conductor ceramic oxygen permeable membrane substrate;

[0158] (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use.

[0159] (3) Calcination and curing: The substrate dried in step (2) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a ceramic film for oxygen-enriched combustion.

[0160] In step (1), the mixing process adopts wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h; the molding adopts a combination of dry pressing pre-forming and isostatic pressing forming process, with a dry pressing pre-forming pressure of 20 MPa and a holding time of 5 min, and an isostatic pressing forming pressure of 100 MPa and a holding time of 10 min; the sintering adopts programmed temperature rise with a maximum sintering temperature of 1300℃ and a holding time of 4 h.

[0161] In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 20min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

[0162] In step (3), the programmed heating and roasting regime is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 2h; then the temperature is increased to 600℃ at a rate of 5℃ / min and held for 3h; finally the temperature is increased to 800℃ at a rate of 3℃ / min and held for 4-6h. After roasting, the temperature is cooled to room temperature in the furnace.

[0163] Performance testing:

[0164] Membranes were prepared according to the methods of the examples and comparative examples. Five samples were repeated for each group of experiments, and the average value of the results was taken.

[0165] Scanning electron microscopy (SEM) analysis

[0166] The surface morphology of the membrane can be observed using a JSM-6700F cold field emission scanning electron microscope with an accelerating voltage of 15kV and a current of 10μA. The sample is sheet-like and needs to be sputtered with gold to improve conductivity before testing.

[0167] Oxygen permeability test

[0168] All oxygen permeability experiments on the membrane material were characterized using a self-made high-temperature oxygen permeability testing system, such as... Figure 1 As shown. The formula for calculating oxygen permeability is as follows: , where J o2 This indicates the oxygen permeability of the oxygen-permeable membrane, measured in ml·min. -1 ·cm -2 C O2 This indicates the oxygen concentration in the exhaust gas detected by a gas chromatograph; F sweep This indicates the total purge gas flow rate, expressed in ml·min. -1 S represents the effective area of ​​the diaphragm, in cm². -2 .

[0169] The oxygen permeability of the membrane material was tested under helium and carbon dioxide atmospheres, respectively.

[0170] Oxygen permeability test: The membrane was sealed in a high-temperature permeation device. Air (oxygen partial pressure 0.21 atm) was introduced into one side of the membrane, while the other side was purged with high-purity helium (oxygen partial pressure ~0 atm). At 900℃, the gas composition on the permeate side was analyzed online using a gas chromatograph, and the flow rate was measured using a soap membrane flow meter to calculate the oxygen permeation flux (J). O2 The initial flux and flux stability over 400 hours were tested, and the results are shown in Table 1.

[0171] CO2 corrosion resistance test: The test conditions were changed to include 20% CO2 (the remainder being He) in the purge gas to simulate an oxygen-rich combustion flue gas environment. The system was continuously operated at 850℃ for 400 hours, and the initial flux (J0) and the flux after 400 hours (J0) were recorded. 400 ), calculate flux retention rate (J 400 ( / J0×100%), the results are shown in Table 1.

[0172] Table 1 Test results for each experimental group

[0173]

[0174] The data in the table show that the nano-coated modified ceramic membranes for oxygen-enriched combustion prepared in Examples 1-4 are significantly superior to those in Comparative Examples 1-6 in all performance indicators. The initial oxygen permeation flux (J) at 900℃ is significantly higher. O2Regarding the aspect, Example 4 uses 2.45 mL·cm -2 ·min -1 Ranked among the top, Example 2 (2.35 mL·cm -2 ·min -1 Example 3 (2.18 mL·cm) -2 ·min -1 ) and Example 1 (2.12 mL·cm -2 ·min -1 All of them also exhibited high oxygen permeability, while the initial J of the control group without nano-coating showed better performance. O2 Only 1.60 mL·cm -2 ·min -1 The initial J of Comparative Examples 1-5 using a single structure directing agent or only coating a single zinc / tin oxide O2 The flux retention rates were also generally lower than those of the examples. This indicates that the in-situ growth of the specific zinc-tin composite oxide nanostructure layer of this invention can effectively improve the oxygen permeability of the membrane. In the CO2 corrosion resistance test, the examples also exhibited excellent stability. After continuous operation for 400 hours at 850°C in an atmosphere containing 20% ​​CO2, the flux retention rates of Example 1 were 90.3%, Example 4 90.0%, Example 3 88.8%, and Example 2 88.4%. In contrast, the flux retention rate of Comparative Example 6 was only 50.1%, Comparative Example 1 56.0%, and the flux retention rates of the other comparative examples were all below 70%. This fully demonstrates that the zinc-tin composite oxide nanocoating layer prepared by this invention can significantly enhance the CO2 corrosion resistance of the ceramic membrane in an oxygen-rich combustion flue gas environment, effectively inhibiting the possible chemical reaction between CO2 and the membrane substrate, thereby maintaining high oxygen permeability stability during long-term operation. In summary, Example 4 showed the best performance in both oxygen permeability and CO2 corrosion resistance. This is closely related to the synergistic effect of its optimized zinc-tin nanolayer, composite structure directing agent, and precise preparation process parameters, which verifies the advanced nature of the preparation method of this invention and the excellent performance of the obtained product.

[0175] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A nano-coated modified ceramic membrane for oxygen-enriched combustion, characterized in that, The invention includes a hybrid conductor ceramic oxygen-permeable membrane substrate and a zinc-tin composite oxide nanostructure layer grown in situ on the surface of the substrate, wherein the molar ratio of zinc to tin in the zinc-tin composite oxide is 1-3:1; the nanostructure layer exhibits a three-dimensional "nanoflower" morphology and is assembled from nanosheets with a thickness of 5-30 nanometers, and the nanoflowers form a porous covering layer on the surface of the substrate.

2. The nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 1, characterized in that, In the zinc-tin composite oxide, the molar ratio of zinc to tin is 1:

1.

3. The nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 1, characterized in that, The hybrid conductor ceramic oxygen-permeable membrane substrate is a perovskite oxide with the general chemical formula A. 1-x M x B 1-y N y O 3-δ Where A is selected from one or more of La, Ba, and Pr, M is selected from one or more of Sr, Ca, and Gd, B is selected from one or more of Co and Mn, N is selected from one or more of Fe, Cu, Zr, Nb, Ga, and Al, 0 < x ≤ 0.5, 0 < y ≤ 0.8, and δ is the oxygen vacancy concentration, with a value range of 0.1-0.

5.

4. The nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 3, characterized in that, The hybrid conductor ceramic oxygen-permeable membrane substrate is La. 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3-δ Or La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ .

5. A method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of substrate membrane: The metal source raw materials were weighed according to the stoichiometric ratio of perovskite oxide, and after mixing, molding and sintering, a mixed conductor ceramic oxygen-permeable membrane substrate was obtained; (2) Substrate pretreatment: The substrate obtained in step (1) is ultrasonically cleaned with deionized water and anhydrous ethanol, then acid etched with dilute acid solution, and dried for later use. (3) Preparation of precursor solution: Dissolve zinc source and tin source in a mixed solvent at a molar ratio of 1-3:1, add structure directing agent, adjust pH value to 8.0-8.5, stir evenly to obtain zinc-tin composite oxide precursor solution; the structure directing agent is a combination of triethanolamine and urea; (4) In-situ growth: The substrate after pretreatment in step (2) is placed in the precursor solution prepared in step (3) and subjected to hydrothermal reaction. After the reaction is completed, the substrate is removed, cleaned and dried. (5) Calcination and curing: The substrate dried in step (4) is subjected to programmed heating and calcination to complete degreasing, crystallization and densification in sequence, so as to obtain a nano-coated modified ceramic film for oxygen-enriched combustion.

6. The method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 5, characterized in that, In step (1), the metal source is an oxide or carbonate. The mixing process is wet ball milling with a ball-to-material ratio of 10:1, a ball milling speed of 300 r / min, and a ball milling time of 24 h. The forming process is a combination of dry pressing pre-forming and isostatic pressing. The dry pressing pre-forming pressure is 20 MPa and the holding time is 5 min. The isostatic pressing pressure is 100 MPa and the holding time is 10 min. The sintering process is programmed temperature rise with a maximum sintering temperature of 1150-1300℃ and a holding time of 4-6 h.

7. The method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 5, characterized in that, In step (2), the ultrasonic cleaning power is 300W and the cleaning time is 15-30min; the dilute acid solution is a 5% dilute nitric acid solution, the acid etching temperature is room temperature and the acid etching time is 10min; the drying temperature is 60℃, the drying environment is vacuum with a vacuum degree of -0.09MPa and the drying time is 2h.

8. The method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 5, characterized in that, In step (3), the zinc source is zinc nitrate Zn(NO3)2·6H2O, and the tin source is tin chloride SnCl4·5H2O; the mixed solvent is a mixture of ethylene glycol and deionized water in a volume ratio of 1:1; the molar ratio of the structure-directing agent triethanolamine to urea is 1:1, and the total amount of the two structure-directing agents added is 1-1.5 times the total molar amount of the zinc source and the tin source; the stirring speed is 500 r / min, and the stirring time is 60 min.

9. The method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 5, characterized in that, In step (4), the hydrothermal reaction temperature is 120-160℃, the reaction time is 6-12h, and the heating rate is 5℃ / min.

10. The method for preparing the nano-coated modified ceramic membrane for oxygen-enriched combustion according to claim 5, characterized in that, In step (5), the programmed heating and roasting method is as follows: heat up to 300℃ at a rate of 2℃ / min and hold for 2 hours; then heat up to 600℃ at a rate of 5℃ / min and hold for 3 hours; finally heat up to 800℃ at a rate of 3℃ / min and hold for 4-6 hours, and then cool to room temperature with the furnace after roasting.

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