Ethylene gas sensitive material and preparation method thereof, and gas sensor

Abstract

The application discloses a gas-sensitive material and a preparation method thereof, and a gas sensor. The gas-sensitive material comprises a gas-sensitive film and a catalytic film which are stacked. The material of the gas-sensitive film comprises La 1‑x Sr x CoO3, and 0.2<=x<=0.6. The material of the catalytic film comprises a molecular sieve and a supported metal oxide supported on the molecular sieve. The supported metal oxide comprises an oxide of a noble metal and an oxide of a rare earth metal. The La 1‑x Sr x CoO3 is used as the material of the gas-sensitive film to efficiently and stably detect ethylene gas. The catalytic film is attached to the gas-sensitive film. The molecular sieve in the catalytic film has a molecular sieve separation effect, thereby reducing the interference of other gases. The oxide of the noble metal can induce local reconstruction, thereby selectively epoxidizing ethylene. In the synergistic effect of the oxide of the noble metal and the oxide of the rare earth metal, more oxygen defects are generated, and the catalytic oxidation of ethylene to ethylene oxide is more easily induced. The activation energy required for the next reaction of ethylene oxide is reduced, and the selectivity to ethylene gas is improved.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials, and in particular to an ethylene gas-sensitive material, its preparation method, and a gas sensor. Background Technology

[0002] Ethylene (C2H4) is a representative gaseous hormone that promotes plant growth and development during seed germination, flowering, leaf abscission, fruit ripening, and senescence. However, ethylene concentrations below 1 ppm or at high concentrations can cause spoilage of agricultural products during transportation or storage. Therefore, highly selective, highly sensitive, and low-cost ethylene detection devices have considerable potential in numerous agricultural applications and are also of great significance for food storage.

[0003] Traditional methods for detecting ethylene include gas chromatography, photoacoustic spectroscopy, and fluorescent probes. However, these methods all require sample pretreatment before detection and analysis using analytical instruments. Furthermore, these methods require specialized operation and are complex, cumbersome, and time-consuming, significantly limiting their application outside the laboratory. Therefore, portable, real-time detection, and cost-effective metal-oxide-semiconductor (MOS) sensors have attracted widespread attention.

[0004] Although single-component semiconductor gas sensors can currently measure ethylene gas at low temperatures, ethylene lacks polar chemical functions and does not interact with semiconductor materials. Traditional metal oxide semiconductor materials have a certain degree of response to all gases, and still suffer from poor selectivity, low sensitivity, and high detection limits, which greatly limits the widespread application of this type of sensor in daily life. Summary of the Invention

[0005] Therefore, it is necessary to provide an ethylene gas-sensitive material with good selectivity and high sensitivity, as well as its preparation method and gas sensor.

[0006] This application provides an ethylene gas-sensitive material, including a stacked gas-sensitive membrane and a catalytic membrane;

[0007] The material of the gas-sensitive membrane includes La. 1-x Sr x CoO3, 0.2≤x≤0.6;

[0008] The catalytic membrane is made of a molecular sieve and a supported metal oxide on the molecular sieve, wherein the supported metal oxide includes oxides of noble metals and oxides of rare earth metals.

[0009] In one embodiment, the material of the gas-sensitive membrane further includes oxides of transition metals;

[0010] Optionally, the transition metal includes one or more of iron, cobalt, and nickel.

[0011] In one embodiment, the oxide of the transition metal and La 1-x Sr x The molar ratio of CoO3 is (0.5~1):1.

[0012] In one embodiment, the pore size of the molecular sieve is

[0013] In one embodiment, the mass ratio of the noble metal, the oxide of the rare earth metal, and the molecular sieve in the material of the catalytic membrane is (0.5-2):(1-3):200.

[0014] In one embodiment, one or more of the following conditions are met:

[0015] (1) The thickness of the gas-sensitive membrane is 2μm to 4μm;

[0016] (2) The thickness of the catalyst film is 5 μm to 10 μm.

[0017] In one embodiment, one or more of the following conditions are met:

[0018] (1) The precious metals include one or more of platinum, silver and gold;

[0019] (2) The rare earth metals include one or more of lanthanum, samarium and cerium.

[0020] This application further provides a method for preparing the above-mentioned ethylene gas-sensitive material, including the following steps:

[0021] Using La 1-x Sr x CoO3, 0.2≤x≤0.6, for preparing gas-sensitive slurry;

[0022] Preparation of catalytic slurry;

[0023] A gas-sensitive slurry membrane was prepared using the aforementioned gas-sensitive slurry, and then subjected to a first drying and a first sintering process to prepare the gas-sensitive membrane.

[0024] Using the catalytic slurry, a catalytic slurry film is prepared on the surface of the gas-sensitive membrane, followed by a second drying and a second sintering.

[0025] In one embodiment, the gas-sensitive slurry and the catalytic slurry each independently comprise an organic slurry, which includes one or more of terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil.

[0026] Furthermore, this application provides a gas sensor, including the ethylene gas-sensitive material as described above.

[0027] La, a metal oxide semiconductor material with a perovskite structure 1-x Sr x CoO3, as an ethylene gas-sensitive membrane material, can efficiently and stably detect ethylene gas. By attaching a catalytic membrane to the gas-sensitive membrane, the molecular sieve in the catalytic membrane has a molecular sieving effect, which can play a role in gas separation, thereby effectively improving the selectivity for the target gas. On the other hand, the selection of noble metal oxides can induce local reconstruction of the interaction of ethylene, thereby enabling selective epoxidation of ethylene. Moreover, under the synergistic effect with rare earth metals, more oxygen vacancies are generated, making it easier to induce the catalytic oxidation of ethylene to ethylene oxide, thereby reducing the activation energy required for the next reaction on the gas-sensitive membrane and improving the selectivity for ethylene gas. Attached Figure Description

[0028] Figure 1 The gas sensors prepared in Examples 1-2 and Comparative Examples 1-3 of this application are shown to respond to 10 ppm ethylene gas at different temperatures.

[0029] Figure 2 The responses of Example 1 and Comparative Example 1 of this application to ethylene, ethanol, acetone, methane and ammonia at 350°C. Detailed Implementation

[0030] This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application. Of course, they are merely examples and are not intended to limit this application. Furthermore, reference numerals and / or letters may be repeated in different instances. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0032] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the compositions of this application. Unless otherwise specified, all masses of the listed ingredients are given as the content of the active substance and therefore do not include solvents or byproducts that may be present in commercially available materials. The term "percentage by mass" may be expressed by the symbol "%".

[0033] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means additional steps and components that may be added without affecting the final result. The term “comprising” also includes the terms “composed of” and “substantially composed of.” The compositions and methods / processes of this application comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0034] The terms "preferred," "more preferably," etc., used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application.

[0035] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0036] This application provides an ethylene gas-sensitive material, including a stacked gas-sensitive membrane and a catalytic membrane;

[0037] Among them, the materials of the gas-sensitive membrane include La 1-x Sr x CoO3, 0.2≤x≤0.6;

[0038] The materials of the catalytic membrane include molecular sieves and supported metal oxides on the molecular sieves. The supported metal oxides include oxides of noble metals and oxides of rare earth metals.

[0039] La, a metal oxide semiconductor material with a perovskite structure 1-x Sr xCoO3, as a gas-sensitive membrane material, can efficiently and stably detect ethylene gas. By attaching a catalytic membrane to the gas-sensitive membrane, the molecular sieve in the catalytic membrane has a molecular sieving effect, which can play a role in gas separation, thereby effectively improving the selectivity for the target gas. On the other hand, choosing noble metal oxides can induce local reconstruction of the interaction of ethylene, thereby enabling selective epoxidation of ethylene. Moreover, under the synergistic effect with rare earth metals, more oxygen vacancies will be generated, making it easier to induce the catalytic oxidation of ethylene to ethylene oxide, thereby reducing the activation energy required for the next reaction on the gas-sensitive membrane and improving the selectivity for ethylene gas.

[0040] In a specific example, La 1-x Sr x In CoO3, x can be, but is not limited to, 0.2, 0.3, 0.4, 0.5, or 0.6.

[0041] In one specific example, the material of the gas-sensitive membrane also includes oxides of transition metals. Further, the material of the gas-sensitive membrane includes oxides of transition metals and La... 1-x Sr x CoO3 composite materials.

[0042] In a specific example, the oxide of a transition metal and La 1-x Sr x The molar ratio of CoO3 is (0.5–1):1, specifically, the oxides of transition metals and La... 1-x Sr x The amount of CoO3 can be, but is not limited to, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.

[0043] Furthermore, the transition metal includes one or more of iron, cobalt, and nickel; specifically, the transition metal includes cobalt. Understandably, the material of the gas-sensitive membrane includes Co3O4-La. 0.5 Sr 0.5 CoO3 composite materials, 0.2≤x≤0.6

[0044] Cobalt oxides typically contain Co. 2+ and Co 3+ When cobalt changes from a +3 oxidation state to a +2 oxidation state, the vacated electron pair attracts free water molecules from the air, forming hydroxyl groups and increasing oxygen vacancies. Furthermore, when cobalt oxide reacts with La... 1-x Sr x After CoO3 is combined, a heterojunction, namely La, will be formed between the two. 1-x Sr x New materials composed of CoO3 and cobalt oxides expand the La... 1-x Sr xThe hydroxide ions on the surface of CoO3 not only enhance the oxygen storage and release capacity of cobalt oxide but also raise the Schottky barrier, thereby hindering the reaction of gases with low electron affinity at the gas-sensitive membrane. This improves the sensitivity and selectivity to olefin gases such as ethylene. Furthermore, the aforementioned cobalt oxide reacts with La... 1-x Sr x The CoO3 composite exhibits exceptional sensitivity to ethylene oxide, with significant changes in resistance before and after the reaction. The synergistic effect of the catalyst layer and the gas-sensitive layer enables rapid identification of ethylene gas concentration.

[0045] In a specific example, the pore size of the molecular sieve is

[0046] Preferably, the pore size of the molecular sieve is [missing information]. Specifically, the pore size of the molecular sieve can be, but is not limited to, [specific pore size]. or The molecular sieve can be understood as a MER molecular sieve, and the pore size of a MER molecular sieve is... It can filter out substances such as ethanol. ) and acetone ( Gases with relatively large sizes, such as ) and the pore size of MER molecular sieves being similar to the molecular dynamic diameter of ethylene ( Similar to ethylene, it can achieve selective adsorption of ethylene.

[0047] In a specific example, the mass ratio of noble metal oxides, rare earth metal oxides, and molecular sieves in the catalytic membrane material is (0.5–2):(1–3):200.

[0048] Furthermore, the mass ratio of noble metal oxides, rare earth metal oxides, and molecular sieves in the catalytic membrane material is (0.5–1.5):(1.5–2.5):200.

[0049] Preferably, the precious metal includes one or more of platinum, silver, and gold, and specifically, the precious metal includes silver.

[0050] In one specific example, the rare earth metal includes one or more of lanthanum, samarium, and cerium, preferably, the rare earth metal includes cerium.

[0051] The interaction between ethylene and the silver oxide surface can induce local reconstruction, leading to the selective epoxidation of ethylene. Furthermore, the synergistic effect with the rare earth metal cerium (Ce) generates more oxygen vacancies, making it easier to induce the catalytic oxidation of ethylene to ethylene oxide. This lowers the activation energy required for the next reaction on the gas-sensitive membrane and results in higher activity than other uncatalyzed gases. Through molecular sieving and catalytic effects, the synergistic effect of both can filter out most interfering gases, thus significantly improving the selectivity for ethylene.

[0052] In one specific example, the thickness of the gas-sensitive membrane is 2 μm to 4 μm. Preferably, the thickness of the gas-sensitive membrane can be, but is not limited to, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm or 4 μm.

[0053] In one specific example, the thickness of the catalytic membrane is 5 μm to 10 μm. Preferably, the thickness of the catalytic membrane can be, but is not limited to, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0054] Attaching a catalytic membrane to a gas-sensitive membrane has two advantages: firstly, the catalytic membrane can reduce interference from large-sized gases, enabling selective adsorption of ethylene; secondly, during the passage of ethylene through the catalytic membrane, it is preferentially decomposed into ethylene oxide, lowering the activation energy required for its next reaction on the gas-sensitive membrane and exhibiting higher reactivity than other uncatalyzed gases. Simultaneously, La... 1-x Sr x The combination of CoO3 and Co3O4 exhibits exceptional sensitivity to ethylene oxide, with significant changes in resistance before and after the reaction. The synergistic effect of the catalyst layer and the gas-sensitive layer enables rapid identification of ethylene gas concentration.

[0055] This application further provides a method for preparing the above-mentioned ethylene gas-sensitive material, including the following steps:

[0056] Using La 1-x Sr x CoO3, 0.2≤x≤0.6, for preparing gas-sensitive slurry;

[0057] Preparation of catalytic slurry;

[0058] A gas-sensitive slurry membrane was prepared using a gas-sensitive slurry, followed by a first drying and a first sintering process to prepare the gas-sensitive membrane.

[0059] A catalytic slurry membrane is prepared on the surface of a gas-sensitive membrane using a catalytic slurry, followed by a second drying and a second sintering.

[0060] Furthermore, the gas-sensitive slurry includes Co3O4-La 1-x Sr x CoO3 composite materials and organic slurries, understandably, Co3O4-La 1-x Sr x The CoO3 composite material and organic slurry mixture can meet the application viscosity requirements of 10 mPa·S to 20 mPa·S.

[0061] Furthermore, Co3O4-La 1-x Sr x The preparation method of CoO3 composite material includes the following steps:

[0062] Mix La at a ratio of (1–8) mmol: (1–8) mmol: (20–80) ml 1-x Sr x CoO3, Co(NO3)2·6H2O, and deionized water were stirred for 10-15 minutes to prepare a mixed solution. The pH of the mixed solution was adjusted to 8.5-9.5 using a 1-3 mol / L monobasic strong base aqueous solution. The solution was heated at 130-170℃ for 6-10 hours. The precipitate from the heated product was collected, washed, and dried at 70-90℃ for 8-12 hours. The dried precipitate was then calcined in air at a temperature of 450-600℃ for 1-3 hours, with the temperature increased from room temperature at a rate of 4-6℃ / min.

[0063] Understandably, a monobasic strong base may be, but is not limited to, sodium hydroxide or potassium hydroxide, and preferably, sodium hydroxide.

[0064] In a specific example, Co3O4-La 1-x Sr x The preparation method of CoO3 composite material includes the following steps:

[0065] Mix La at a ratio of (1–8) mmol: (1–8) mmol: (20–80) ml 1-x Sr x A mixed solution was prepared by stirring CoO3, Co(NO3)2·6H2O, and deionized water for 10-15 minutes. The pH of the mixed solution was adjusted to 9-9.4 using a 1.5 mol / L-2.5 mol / L monobasic strong base aqueous solution. The solution was heated at 140-160℃ for 7-9 hours. The precipitate from the heated product was collected, washed, and dried at 75-85℃ for 9-11 hours. The dried precipitate was then calcined in air at a temperature of 4-6℃ / min from room temperature to 480-520℃ for 1-3 hours.

[0066] Furthermore, the pH value of the mixed solution can be adjusted using a monobasic strong base aqueous solution with a concentration of 1 mol / L to 3 mol / L, but is not limited to 9, 9.1, 9.2, 9.3, or 9.4.

[0067] In a specific example, La 1-x Sr x The preparation method of CoO3, 0.2≤x≤0.6 includes the following steps:

[0068] A primary mixed solution was prepared by mixing La(Cl)3·6H2O, Sr(Cl)3, CoCl2·6H2O, and deionized water in a ratio of (10-10x) mmol:(10x) mmol:10 mmol:(20-80) ml and stirring for 20-30 min. For every 10 mmol of CoCl2·6H2O contained in the primary mixed solution, 0.4 g-0.6 g of urea was added and stirred for 1-2 h to prepare a secondary mixed solution. The secondary mixed solution was then heated at 230-270°C for 46-50 h. h, take the first precipitate, add 20ml-40ml of ethanol and 30ml-50ml of dichloromethane to the first precipitate, centrifuge at 4500r / min-6000r / min for 1min-8min, remove the supernatant after centrifugation, wash until the supernatant is colorless, dry the second precipitate at 70℃-90℃ for 8h-12h, precalcine the dried second precipitate at 550℃-650℃ for 2h-5h, and then calcine at 800℃-1000℃ for 2h-5h.

[0069] Understandably, the particle size of the gas-sensitive slurry is less than 70 μm, and preferably the particle size of the gas-sensitive slurry is less than or equal to 60 μm.

[0070] A gas-sensitive slurry membrane is prepared using a gas-sensitive slurry. The membrane is prepared by a first drying and a first sintering. The conditions for the first drying include drying at a temperature of 70℃ to 90℃ for 18h to 22h. The conditions for the first sintering include sintering at a temperature of 300℃ to 500℃ for 1h to 5h to remove organic slurry from the gas-sensitive slurry to prepare the gas-sensitive membrane.

[0071] The catalytic slurry includes Ag₂O-CeO₂ bimetallic supported MER-type molecular sieves and an organic slurry. Understandably, the Ag₂O-CeO₂ bimetallic supported MER-type molecular sieves are mixed with the organic slurry to meet the application viscosity requirements of 10 mPa·s to 20 mPa·s.

[0072] Further, the preparation method of Ag2O-CeO2 bimetallic supported MER-type molecular sieve includes the following steps: Ce(NO3)3·6H2O, MER-type molecular sieve, and deionized water are mixed in a ratio of (0.08–0.3) g:(2–6) g:(20–80) ml to prepare a first slurry. The slurry is stirred for 20–40 min, centrifuged, and the precipitate is washed with deionized water and dried at 70–90°C for 1–4 h. The precipitate is then calcined at 200–400°C for 6–10 h to prepare CeO2 / MER powder. CeO2 / MER powder, silver nitrate, and ethylene glycol are mixed in a ratio of (1–4) g:(0.01–0.04) g:(20–60) ml and stirred for 10–14 h to prepare a suspension. The suspension is then filtered, washed, and dried at 50–70°C.

[0073] Furthermore, the preparation method of Ag2O-CeO2 bimetallic supported MER-type molecular sieve includes the following steps: Ce(NO3)3·6H2O, MER-type molecular sieve, and deionized water are mixed in a ratio of (0.1–0.15) g:(3–5) g:(30–70) ml to prepare a first slurry. The slurry is stirred for 25–35 min, centrifuged, and the precipitate is washed with deionized water and dried at 75–85°C for 1.5–3.5 h. The precipitate is then calcined at 250–350°C for 7–9 h to prepare CeO2 / MER powder. CeO2 / MER powder, silver nitrate, and ethylene glycol are mixed in a ratio of (1–3) g:(0.012–0.02) g:(20–60) ml and stirred for 11–13 h to prepare a suspension. The suspension is then filtered, washed, and dried at 55–65°C.

[0074] Furthermore, the preparation method of MER-type molecular sieve includes the following steps: mixing potassium oxide, silicon dioxide, aluminum oxide and water in a molar ratio of (2.5~4):(9~11):(1~3):(70~78) to prepare a calcined material, and calcining the calcined material at a temperature of 140℃~160℃ for 10h~13h.

[0075] Preferably, the preparation method of MER type molecular sieve includes the following steps: mixing potassium oxide, silicon dioxide, aluminum oxide and water in a molar ratio of (2.5~3.9):(9~11):(1~3):(68~78) to prepare a calcined material, and calcining the calcined material at a temperature of 140℃~160℃ for 10h~13h.

[0076] The particle size of the catalytic slurry is less than 120 μm, preferably less than or equal to 100 μm.

[0077] A catalytic slurry is used to prepare a catalytic slurry membrane on the surface of a gas-sensitive membrane. After a second drying and a second sintering, the conditions for the second drying include drying at a temperature of 70℃~90℃ for 12h~18h, and the conditions for the second sintering include sintering at a temperature of 250℃~350℃ for 1h~3h and then sintering at a temperature of 450℃~650℃ for 1h~3h to remove the organic slurry in the catalytic slurry, thus preparing a catalytic membrane on the gas-sensitive membrane.

[0078] In one specific example, the gas-sensitive slurry and the catalyst slurry each independently comprise an organic slurry, which includes one or more of terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil.

[0079] Specifically, the organic pulp comprises terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil in a mass ratio of (50–70):(20–40):(5–15):(4–8):(2–6):(0.5–4):(0.1–1).

[0080] Furthermore, this application provides a gas sensor, including the ethylene gas-sensitive material as described above.

[0081] Understandably, a gas-sensitive slurry is sequentially sprayed onto a substrate, followed by a first drying and a first sintering process to prepare a gas-sensitive membrane. A catalytic membrane is then prepared on the surface of the gas-sensitive membrane by a second drying and a second sintering process, and finally encapsulated to prepare a gas sensor.

[0082] Specifically, the matrix is ​​a ceramic matrix, which may be, but is not limited to, a zirconia matrix.

[0083] The following detailed description, in conjunction with specific embodiments, illustrates the gas-sensitive material and its preparation method, as well as the gas sensor of this application. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0084] Example 1

[0085] (1) Preparation of gas-sensitive membrane: Dissolve 5 mmol La(Cl)3·6H2O, 5 mmol Sr(Cl)3, and 10 mmol CoCl2·6H2O in 50 ml of deionized water and stir magnetically for 20–30 min to obtain solution A. Add 0.54 g urea to solution A and stir magnetically for 1–2 h to obtain solution B. Transfer the solution to a 100 ml reaction vessel and incubate at 250 °C for 48 h. After incubation, discard the supernatant and remove the bottom precipitate. Add 30 ml ethanol to the precipitate, stir well, add 40 ml dichloromethane, and then transfer to two 50 ml centrifuge tubes. Centrifuge at 5500 r / min for 5 min. After centrifugation, discard the supernatant and wash 3–6 times until the supernatant is colorless. Place the washed precipitate in a constant temperature incubator and dry at 80 °C for 10 h. The powder was pre-calcined at 600℃ for 4 hours, and then calcined again at 900℃ for 4 hours to obtain La. 0.5 Sr 0.5 CoO3 powder.

[0086] 1.1g La 0.5 Sr 0.5 CoO3 and 1.455 g of Co(NO3)2·6H2O were added to 50 ml of deionized water and magnetically stirred for 10–15 min to obtain a mixed solution. 2 mol / L NaOH was added dropwise to the above solution until the pH reached 9.2. The mixed solution was then transferred to a 100 ml reactor and heated at 150 °C for 8 h. After holding at this temperature, the supernatant was discarded, and the bottom precipitate was removed. The precipitate was washed using the same method, and the dried powder was placed in a muffle furnace at 500 °C. The temperature was increased from room temperature to 500 °C at a rate of 5 °C / min and calcined for 2 h in air atmosphere to obtain Co3O4-La. 0.5 Sr 0.5 CoO3 composite material.

[0087] Finally, the Co3O4-La 0.5 Sr 0.5 CoO3 composite material is mixed and ground with organic slurry. The organic slurry is prepared by mixing terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone and hydrogenated castor oil in a mass ratio of 60:30:10:6:4:1:0.5. The mixture is prepared to meet the application viscosity requirement of 10 mPa·s to 20 mPa·s. This is used to prepare the gas-sensitive film spraying slurry.

[0088] (2) Preparation of catalytic membrane: Using silica-alumina dry gel as the silica-alumina source and potassium hydroxide as the alkali source, a small amount of water was added. The colloidal composition was n(K2O):n(SiO2):n(Al2O3):n(H2O) = 3.75:10:2:74. The reaction was carried out at 150℃ for 12 h to obtain a highly crystalline MER-type molecular sieve. 0.11 g of cerium nitrate hexahydrate was dissolved in 50 ml of deionized water, and then 4.0 g of MER-type molecular sieve was added to the solution. The mixture was magnetically stirred for 30 min to obtain a uniform slurry. The solid precipitate was separated by centrifugation, washed twice with deionized water, and then dried in a drying oven at 80℃ for 2 h. The obtained powder was placed in a muffle furnace and calcined at 300℃ for 8 h to obtain CeO2 / MER powder. 2 g of CeO2 / MER powder was added to 40 ml of ethylene glycol, stirred evenly, and then 0.0145 g of silver nitrate was added. The mixture was then magnetically stirred for 12 h to form a uniform suspension. The suspension was filtered, washed, and dried at 60°C to obtain a highly crystalline Ag₂O-CeO₂-loaded MER-type molecular sieve, with a final CeO₂:Ag₂O:MER ratio of 2:1:200. This was then mixed with an organic slurry, ensuring the final viscosity met the application requirements of 10 mPa·s to 20 mPa·s, to prepare a spraying slurry for the catalytic membrane. The organic slurry was formulated by mixing terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil in a mass ratio of 60:30:10:6:4:1:0.5.

[0089] (3) Fabrication of the stacked gas sensor structure: A gas-sensitive slurry was sprayed onto a zirconia substrate using a needle with a 60-micron aperture. The substrate was then dried at 80°C for 20 hours in a constant-temperature drying oven, followed by sintering at 400°C for 3 hours to remove the organic slurry and obtain a gas-sensitive membrane. A slurry for a catalytic membrane was then sprayed onto the surface of the gas-sensitive membrane using a needle with a 100-micron aperture. The membrane was dried at 80°C for 15 hours in a constant-temperature drying oven, followed by sintering at 300°C for 2 hours in a muffle furnace, and then sintering at 550°C for 2 hours to obtain an ethylene gas-sensitive material. This ethylene gas-sensitive material was then encapsulated into a device to obtain an ethylene gas sensor.

[0090] Example 2

[0091] The difference between Example 2 and Example 1 is that the gas-sensitive membrane preparation process does not incorporate Co3O4, and the prepared powder sample is only La. 0.5 Sr 0.5 CoO3.

[0092] Comparative Example 1

[0093] The difference between Comparative Example 1 and Example 1 is that the ethylene gas sensor does not have a catalyst layer.

[0094] Comparative Example 2

[0095] The difference between Comparative Example 2 and Example 1 is that no Ag2O-CeO2 loading was introduced during the preparation of the catalytic membrane.

[0096] Comparative Example 3

[0097] The difference between Comparative Example 3 and Example 1 is that La is not composited during the preparation of the gas-sensitive membrane. 0.5 Sr 0.5 CoO3 was used to prepare powder samples, but the resulting samples were only Co3O4.

[0098] Test methods and test results

[0099] Gas-sensitive test: The concentration of the test gas (ethylene) is fixed at 10 ppm, the humidity is generally 40-60%, the working mode is constant temperature, the working temperature range is set to 150-400℃, the temperature step is 50℃, and the test is carried out sequentially from high to low. The response value of each material combination at the corresponding working temperature is recorded. The gas-sensitive response specifically refers to: gas-sensitive response S = Rg / Ra, where Rg is the resistance at the corresponding working temperature of the target gas, and Ra is the resistance in the air.

[0100] like Figure 1 The images show the responses of the gas sensors prepared in Examples 1-2 and Comparative Examples 1-3 of this application to 10 ppm ethylene gas at different temperatures.

[0101] like Figure 2 The figures show the responses of Example 1 and Comparative Example 1 of this application to 10 ppm ethylene, 10 ppm ethanol, 10 ppm acetone, 10 ppm methane and 10 ppm ammonia at 350°C.

[0102] The gas-sensitive membrane in Example 2 uses only La as its material. 0.5 Sr 0.5 Although the gas-sensing response decreased somewhat due to the absence of a CoO3-Co3O4 composite, it remained at a high level. In Comparative Example 1, the gas-sensing material without a catalyst layer showed the largest decrease in gas-sensing response compared to Example 1, highlighting the importance of the composite between the gas-sensing layer and the catalyst layer in the gas-sensing material. In Comparative Example 2, the lack of a catalyst membrane and the absence of metal loading on the molecular sieve resulted in a significant decrease in gas-sensing response, further demonstrating that a metal-loaded molecular sieve catalyst membrane significantly improves the catalytic performance of the gas-sensing material. In Comparative Example 3, the gas-sensing membrane used only Co3O4 without any La... 0.5 Sr 0.5 Although the CoO3 composite significantly reduced the gas sensitivity, it reflects the presence of La in the gas-sensitive membrane. 0.5 Sr 0.5 The importance of the CoO3-Co3O4 complex.

[0103] also, Figure 2 It can be seen that the gas-sensitive material of Example 1 has a high selectivity for ethylene gas compared to other gases such as ethanol, methane and ammonia.

[0104] 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An ethylene gas sensitive material, characterized by, This includes stacked gas-sensitive membranes and catalytic membranes; The material of the gas sensitive film comprises La 1-x Sr x CoO3 and an oxide of a transition metal, 0.2≤x≤0.6, the transition metal being cobalt. The catalytic membrane material includes a molecular sieve and a supported metal oxide on the molecular sieve, wherein the supported metal oxide includes oxides of noble metals and oxides of rare earth metals. The molecular sieve in the catalytic membrane has a molecular sieving effect, which can play a role in gas separation; the oxide of the noble metal enables selective epoxidation of ethylene; and the oxide of the rare earth metal improves the selectivity for ethylene gas. The precious metal is silver, and the oxide of the rare earth metal is cerium dioxide.

2. The ethylene gas sensing material of claim 1, wherein the oxide of the transition metal and La 1- x Sr x the ratio of the amount of substance of the CoO3and SrO is (0.5-1) :

1.

3. The ethylene gas sensing material of claim 1, wherein The molecular sieve has a pore size of 4.18 Å to 4.4 Å.

4. The ethylene gas sensing material of claim 1, wherein The mass ratio of the noble metal oxide, the rare earth metal oxide, and the molecular sieve in the catalytic membrane material is (0.5~2): (1~3):

200.

5. The ethylene gas sensing material according to any one of claims 1 to 4, wherein The thickness of the gas-sensitive membrane is 2μm~4μm.

6. The ethylene gas sensing material according to any one of claims 1 to 4, wherein The thickness of the catalytic film is 5 μm to 10 μm.

7. The method of producing an ethylene gas sensing material according to any one of claims 1 to 6, wherein Includes the following steps: La 1-x Sr x CoO3, 0.2≤x≤0.6, to prepare a gas sensitive slurry; Preparation of catalytic slurry; A gas-sensitive slurry membrane was prepared using the aforementioned gas-sensitive slurry, and then subjected to a first drying and a first sintering process to prepare the gas-sensitive membrane. Using the catalytic slurry, a catalytic slurry film is prepared on the surface of the gas-sensitive membrane, followed by a second drying and a second sintering.

8. The method for preparing the ethylene gas-sensitive material as described in claim 7, characterized in that, The gas-sensitive slurry and the catalytic slurry each independently comprise an organic slurry, which includes one or more of terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil.

9. A gas sensor, characterized by Includes the ethylene gas-sensitive material as described in any one of claims 1 to 6.

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