Sensor for refrigerant detection and preparation method and application of catalytic part

Abstract

The invention relates to the technical field of sensors, and discloses a sensor for refrigerant detection and a preparation method and application of a catalytic part. The sensor comprises a detection part, an electrode part and the catalytic part; the detection part is used for detecting whether a refrigerant leaks or not, the electrode part is connected with the detection part and used for detecting the resistance of the detection part, and the catalysis part is used for activating refrigerant molecules so as to split the refrigerant molecules into active free radicals which can be detected by the detection part. According to the sensor, multiple different types of refrigerants can be detected after the refrigerants leak, and the application range of the sensor is widened.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a sensor for refrigerant detection, a preparation method of a catalytic part and an application thereof. Background Art

[0002] Refrigerant is a working medium used in refrigeration systems or heat engines. It achieves cooling or heating by absorbing heat in the evaporator and releasing heat in the condenser. Freon gas is the most common refrigerant.

[0003] Refrigerant leakage will cause serious environmental or safety risks. At the same time, refrigerant leakage will also lead to a decrease in the efficiency of the refrigeration system or heat engine and an increase in energy consumption. Therefore, how to detect refrigerants is a technical problem that needs to be solved today. Summary of the invention

[0004] A sensor for detecting refrigerant, a preparation method of a catalytic part and an application thereof can detect a variety of different types of refrigerants after a refrigerant leaks.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include: In a first aspect, an embodiment of the present application provides a sensor for refrigerant detection, comprising a detection part, an electrode part and a catalytic part; the detection part is used to detect whether there is a refrigerant leakage, the electrode part is connected to the detection part, and the electrode part is used to detect the resistance of the detection part, wherein the catalytic part is used to activate refrigerant molecules to crack the refrigerant molecules into active free radicals that can be detected by the detection part.

[0006] A sensor for refrigerant detection proposed in an embodiment of the present application has a detection unit that can directly detect the refrigerant, and the detection unit can detect the active free radicals after the catalytic unit decomposes and activates the refrigerant molecules into active free radicals, thereby judging the degree of refrigerant leakage based on the amount of free radicals detected; it can be understood that the catalytic unit decomposes and activates the refrigerant that cannot be directly detected by the detection unit, and produces active free radicals that can be detected by the detection unit, thereby expanding the number of refrigerant types that can be detected.

[0007] Optionally, the catalytic part, the detection part and the electrode part are layered structures, and the catalytic part, the detection part and the electrode part are stacked; along the thickness direction of the catalytic part, the detection part or the electrode part, the detection part is located between the catalytic part and the electrode part.

[0008] In the above scheme, the catalytic part has a layered structure, which increases its contact area with the refrigerant gas, making the contact between the refrigerant molecules and the catalyst more complete, thereby improving the catalytic efficiency; the detection part has a layered structure, which increases its contact area with the refrigerant gas or active free radicals, thereby improving the sensor's response ability to different types of refrigerants.

[0009] In addition, along the thickness direction of the catalyst part, the detection part or the electrode part, the catalyst part, the detection part and the electrode part are arranged in sequence, so that the active free radicals generated by the catalyst part are detected by the detection part, thereby improving the sensor's response to different types of refrigerants. At the same time, the catalyst part, the detection part or the electrode part of the layered structure are stacked together, which can also reduce the volume of the sensor, so that the sensor can be used in a variety of different working conditions, thereby improving the applicability of the sensor. Optionally, along the thickness direction of the catalyst part, the projected area of ​​the catalyst part is larger than the projected area of ​​the detection part, and the projected area of ​​the detection part is larger than the projected area of ​​the electrode part.

[0010] It can be understood that along the thickness direction of the catalytic part, the catalytic part, the detection part and the electrode part form a pagoda-shaped structure, which further improves the response capability of the sensor.

[0011] Optionally, the detection portion is constructed as a metal oxide semiconductor material piece, and the detection portion includes at least one of tin oxide, zinc oxide and tungsten oxide.

[0012] In the above scheme, the metal oxide semiconductor material piece can detect the presence of gas and the gas concentration, thereby improving the sensor's response capability to different refrigerants.

[0013] Optionally, the catalytic portion comprises gamma-phase alumina.

[0014] In the above scheme, γ-phase alumina decomposes and activates the Freon refrigerant molecules to produce active free radicals that can be detected by the detection unit. It can be understood that γ-phase alumina is configured into a porous structure with a high specific surface area and excellent chemical stability, which provides abundant active sites and a stable reaction environment for the catalytic reaction.

[0015] Optionally, the specific surface area of ​​the catalytic part is not less than 340m 2 / g.

[0016] In the above scheme, because the specific surface area of ​​the catalytic part meets the above range, it helps to provide more reactive sites, making the catalytic reaction more efficient and improving the catalytic efficiency.

[0017] Optionally, the catalyst portion further includes a metal dopant, and the metal dopant is at least one of Pt, Pd, Au, and Ag.

[0018] In the above scheme, adding the above metal dopants to the catalyst part can not only improve the catalytic activity, but also introduce new catalytic sites, thereby improving the catalytic efficiency.

[0019] Optionally, the ratio of the metal dopant to the catalyst portion is no more than 3 wt %.

[0020] In the above scheme, since the content of metal dopants in the catalyst part meets the above range, on the one hand, the catalytic performance of the catalyst part is improved, and on the other hand, the anti-interference ability of the catalyst part is guaranteed.

[0021] In a second aspect, an embodiment of the present application provides a method for preparing a catalyst portion, comprising: catalytically coating a glycerol-dispersed porous γ-phase alumina or a metal-doped porous γ-phase alumina on a preparation plate; The coated catalytic raw material layer is dried and sintered.

[0022] In the above scheme, the surface activity of porous γ-phase alumina is improved by glycerol dispersion or metal doping to improve the catalytic efficiency, and the stability of the catalyst part is improved by drying and sintering to ensure that the catalyst part can be formed and layered, thereby achieving stable catalysis of the refrigerant and reducing the chance of reduced catalytic performance during cracking and activation.

[0023] In a third aspect, the embodiments of the present application provide a sensor as described in any of the above embodiments or a catalytic part prepared by the above method for activating and detecting fourth-generation HFOs Freon refrigerant molecules.

[0024] In the above scheme, after the fourth-generation HFOs-type Freon refrigerant molecules are activated by the catalytic unit, active free radicals are generated and detected by the detection unit, so that the sensor of the present application can detect the fourth-generation HFOs-type Freon refrigerant after the fourth-generation HFOs-type Freon refrigerant leaks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 is a schematic diagram of the structure of a sensor in some embodiments; Figure 2 It is a schematic diagram of the structure of sensors in other embodiments; Figure 3 It is a schematic diagram of the structure of sensors in other embodiments; Figure 4 It is a schematic diagram of the structure of sensors in other embodiments; Figure 5 This is a schematic diagram of the detection performance test results of the Pd-doped sensor; Figure 6 Schematic diagram of the steps of the preparation method of the catalyst in some embodiments; Figure 7 It is a schematic diagram of the responsiveness test results of the fourth generation Freon refrigerant R1234yf in some specific embodiments; Figure 8 Schematic diagram of the test results of interference and universality of the fourth generation Freon refrigerant R1234yf in some specific embodiments; Fig. 9 It is a schematic diagram of the structure of sensors in other specific embodiments; Fig.10 Schematic diagram of the structure of sensors in other embodiments.

[0027] 1: catalytic part; 101: γ-phase alumina; 102: metal dopant; 103: Pd-doped porous γ-phase alumina; 2: detection unit; 201: metal oxide semiconductor material piece; 202: tin oxide; 3: Electrode part; 301: Interdigital electrode; 302- gold interdigital electrode. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0030] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0031] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0033] The term "multiple" as used in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0034] Refrigerant is a working medium used in refrigeration systems or heat engines, which achieves cooling or heating by absorbing heat in the evaporator and releasing heat in the condenser. The refrigerant can evaporate and absorb heat at low temperature and low pressure, and condense and release heat at high temperature and high pressure, thereby completing the heat transfer.

[0035] Freon gas is the most common refrigerant. The first generation of Freon refrigerant is chlorofluorocarbons (CFCs) gas, which was once widely used in air conditioners and refrigerators. However, due to its strong destructiveness to the atmospheric ozone layer, it has been completely banned.

[0036] The second generation of Freon refrigerants are hydrochlorofluorocarbons (HCFCs, such as R22). As transitional products, these refrigerants still have a certain degree of ozone depletion and pose environmental risks. The third generation of Freon refrigerants are hydrofluorocarbons (HFCs, such as R134a). These refrigerants do not contain chlorine and have an ODP (ozone depletion potential) value of 0. They are friendly to the ozone layer and are currently the mainstream type of refrigerants.

[0037] However, the global warming potential (GWP) of HFCs refrigerants is still high, and there are still environmental problems. Currently, Freon refrigerants are developing towards the fourth generation of hydrofluoroolefins (HFOs, such as R1234yf). This type of refrigerant is both ozone-friendly (ODP value is 0) and low GWP value, which is more ideal; however, HFOs still have safety risks in a closed environment, such as causing suffocation and explosion.

[0038] It can be seen that Freon refrigerant will cause serious environmental or safety risks after leakage. At the same time, the leakage of refrigerant will also lead to a decrease in the working efficiency of the refrigeration system or heat engine and an increase in energy consumption. Moreover, due to problems with pipe connections, wear or aging of components over time, and mechanical structure failures, Freon refrigerant is very easy to leak. Therefore, for Freon refrigerant, leakage detection is very important.

[0039] At present, the main Freon refrigerant leakage detection technologies are: (1) Infrared spectrum detection technology, which uses the refrigerant's absorption characteristics of infrared light of a specific wavelength. When the refrigerant leaks into the air, the infrared light passes through the detection area, and the refrigerant absorbs part of the infrared light, causing the light intensity to weaken. The detection instrument determines the refrigerant leakage by analyzing the changes in the absorption spectrum. Its advantages are that it is applicable to a variety of refrigerant types and has high detection accuracy; its disadvantages are that the equipment cost is high and it is greatly affected by environmental interference.

[0040] (2) Halogen leak detector detection. Halogen leak detectors are specially used to detect refrigerants containing fluorine, chlorine and other halogens. Platinum wire coated with alkali metals will produce positive ion emission at a high temperature of about 900 degrees. When encountering halogen gas, the positive ion emission will increase sharply. Halogen leak detectors are made based on this principle. This detection method is simple, rapid and widely used. The disadvantage is that Freon is easily adsorbed on the surface of the workpiece being tested, which is difficult to remove, easily causing false detection and sensor poisoning.

[0041] (3) Ultrasonic detection. When the refrigerant gas leaks, it will generate high-frequency ultrasonic signals. The ultrasonic leak detector identifies the leak point by detecting these ultrasonic waves. This method is generally used in high-voltage systems because high-voltage leaks will generate more obvious ultrasonic signals. The disadvantage is that the detection sensitivity is greatly affected by environmental noise and is not sensitive to small leaks.

[0042] (4) Electrochemical gas sensor detection: Electrochemical sensor detection is based on the chemical reaction of the refrigerant under specific conditions to generate a detectable electrical signal. The sensor contains electrolytes and electrodes. When the refrigerant gas reacts chemically with the electrodes in the sensor, a change in current or voltage will occur, thereby achieving detection. The advantage of this method is that it can detect a variety of refrigerant gases with high sensitivity. The disadvantage is that existing electrochemical gas sensors cannot detect the fourth-generation HFOs-type Freon refrigerants because HFOs are inert and cannot react on the surface of semiconductor oxides.

[0043] In view of this, in order to detect more types of Freon, an embodiment of the present application provides a sensor for refrigerant detection, and the sensor includes a detection part 2 and an electrode part 3.

[0044] The detection part 2 is used to detect whether there is a refrigerant leak; it is understandable that after the refrigerant leaks, the refrigerant molecules will come into contact with the detection part 2 and will be adsorbed by the detection part 2, causing the conductive properties of the detection part 2 to be changed. As the refrigerant gas concentration changes, the conductivity of the detection part 2 changes.

[0045] The electrode part 3 is connected to the detection part 2 , and the electrode part 3 is used to detect the resistance of the detection part 2 ; it can be understood that when the detection part 2 detects the refrigerant, the resistance of the detection part 2 changes, and the electrode part 3 detects the resistance of the detection part 2 .

[0046] Please refer to Figure 1 The sensor is further provided with a catalytic unit 1, which is used to activate the refrigerant molecules so as to crack the refrigerant molecules into active free radicals that can be detected by the detection unit 2.

[0047] It can be understood that the sensor of the present application can detect a single type of Freon refrigerant gas, which can be a first-generation refrigerant, a second-generation refrigerant, a third-generation refrigerant, a fourth-generation refrigerant, or other types of single refrigerants; of course, the sensor of the present application can detect a mixed refrigerant formed by mixing multiple different types of Freon gases in proportion.

[0048] The sensor in the embodiment of the present application is provided with the above-mentioned catalytic part 1. The catalytic part 1 activates the refrigerant molecules and decomposes them into more active free radicals, so that the sensor can detect more types of Freon gases or their decomposition products. It has a universal response capability to different refrigerant gases and is suitable for detecting different types of refrigerants. It can also be used in leakage detection of mixed refrigerants, thereby expanding its scope of application.

[0049] It can be understood that in a complex environment where multiple gases coexist, the catalytic unit 1 can specifically activate and crack the refrigerant molecules, reduce the interference of other gases, have good detection stability, and have a good linear relationship between the signal intensity at different refrigerant gas concentrations.

[0050] It can be understood that the catalytic unit 1 activates the refrigerant molecules and breaks them into more active free radicals, which causes a greater change in the conductivity of the detection unit 2, enhances the signal strength of the detection unit 2, and enables the sensor to detect lower concentrations of refrigerant gas.

[0051] In other embodiments, the catalyst unit 1 is configured to activate fourth generation HFOs type Freon refrigerant molecules.

[0052] In the above scheme, the catalyst part 1 in the embodiment of the present application can crack and activate HFOs with a certain degree of inertness, so that the sensor with the above catalyst part 1 can detect HFOs refrigerant molecules, which helps to reduce the probability of leakage, suffocation and explosion during the use of HFOs refrigerant molecules.

[0053] It is understandable that the fourth generation HFOs type Freon refrigerant molecules include one or more of a variety of tetrafluoropropenes including HFO-1234yf, HFO-1234ze, and HFO-1233zd.

[0054] In other embodiments, the catalytic part 1, the detection part 2 and the electrode part 3 are all layered structures, and the catalytic part 1, the detection part 2 and the electrode part 3 are stacked in sequence.

[0055] The layered catalyst part 1 increases the contact area with the refrigerant gas, making the refrigerant molecules more fully in contact with the catalyst part 1, thereby improving the catalytic efficiency. The layered electrode part 3 can more effectively carry out charge transfer and ion transfer during the electrochemical reaction, thereby improving the reaction efficiency.

[0056] The layered structure of the detection part 2 increases the contact area with the refrigerant gas or its cracked products, so that the contact between the detection part 2 and the refrigerant gas or its cracked products is more complete, thereby improving the sensor's response capability to different types of refrigerants.

[0057] In other embodiments, along the thickness direction of the catalyst part 1, the detection part 2 or the electrode part 3, the detection part 2 is located between the catalyst part 1 and the electrode part 3. The refrigerant gas first passes through the catalyst part 1, where some or all of the refrigerant molecules are cracked and catalyzed, and then reaches the detection part 2 to be detected by the detection part 2, so that more types of Freon refrigerants can be detected.

[0058] At the same time, the layered structure of the catalytic part 1, the detection part 2 or the electrode part 3 stacked together can also reduce the volume of the sensor, so that the sensor can be used in a variety of different working conditions, thereby improving the applicability of the sensor.

[0059] In some embodiments of the present application, the catalytic part 1, the detection part 2 and the electrode part 3 are all constructed as a layered structure, and along the thickness direction of the catalytic part 1, the projected area of ​​the catalytic part 1 is larger than the projected area of ​​the detection part 2 and the projected area of ​​the electrode part 3.

[0060] Thus, the catalytic unit 1 can activate more refrigerants per unit time, so that the detection unit 2 can quickly detect the refrigerant leakage, and after the refrigerant leakage occurs, the sensor can quickly respond to the leaked refrigerant.

[0061] Furthermore, along the thickness direction of the catalytic part 1, the projected area of ​​the catalytic part 1 is larger than the projected area of ​​the detection part 2, and the projected area of ​​the detection part 2 is larger than the projected area of ​​the electrode part 3. In other words, the three-layer structure is in an inverted pagoda shape.

[0062] The larger catalytic part can provide a larger contact area with the refrigerant gas, so that the detection part 2 can better detect the refrigerant or the active molecules after the refrigerant is cracked, thereby improving the response speed of the sensor to the leaked refrigerant.

[0063] In some embodiments of the present application, the sensor further includes a flow guiding device for quickly guiding the gas to the catalyst section 1. The flow guiding device may be an active flow guiding device or a passive flow guiding device. The active flow guiding device may be a structure such as a fan. The passive flow guiding device may include a guide pipe, and along the gas flow direction, the guide pipe includes a first section, a second section, and a third section, and the cross-sectional area of ​​the second section is smaller than the cross-sectional area of ​​the first section and the cross-sectional area of ​​the third section, thereby passively increasing the speed of the gas flowing to the catalyst section 1.

[0064] In other embodiments, please refer to Figure 2 , the detection part 2 is configured as a metal oxide semiconductor material piece 201. It is understandable that when the refrigerant gas molecules contact the metal oxide surface, adsorption occurs, thereby changing the conductive properties of the metal oxide semiconductor material.

[0065] Among them, as the concentration of the refrigerant gas increases, the conductivity of the metal oxide semiconductor material piece 201 will change, which is manifested as a decrease in resistance or an increase in current. At this time, the detection unit 2 detects the change in the conductivity of the metal oxide semiconductor material piece 201 and converts it into a measurable electrical signal, thereby improving the sensitivity of refrigerant detection.

[0066] In other embodiments, the detection part 2 includes at least one of tin oxide 202, zinc oxide and tungsten oxide. For example, the detection part 2 may include one of tin oxide 202, zinc oxide and tungsten oxide, or the detection part 2 may include two or three of tin oxide 202, zinc oxide and tungsten oxide.

[0067] In other embodiments, please refer to Figure 3 The catalyst part 1 includes γ-phase alumina 101, and the γ-phase alumina 101 can be pure γ-phase alumina 101 or metal-doped γ-phase alumina 101. It can be understood that the γ-phase alumina 101 is configured as a porous structure with extremely high specific surface area and pore volume, which can provide more reactive sites, and has good adsorption performance and catalytic activity, thereby improving the efficiency of the catalytic reaction.

[0068] Furthermore, the porous γ-phase alumina 101 can adsorb reactants, increase the concentration of reactants on the catalyst surface, and thus accelerate the catalytic reaction.

[0069] When conducting refrigerant detection, γ-phase alumina 101 can activate the fourth-generation refrigerant HFOs gas molecules, cracking them into active free radicals that can be detected by the detection layer, thereby expanding the applicability of the sensor to different types of Freon refrigerants.

[0070] In other embodiments, the specific surface area of ​​the catalyst portion 1 is not less than 340 m 2 For example, the specific surface area of ​​the catalyst part 1 can be 340m 2 / g, 380m 2 / g, 420m 2 / g, 460m 2 / g or 480m 2 / g.

[0071] In the above scheme, since the specific surface area of ​​the catalyst part 1 meets the above range, it helps to provide more reaction active sites. After increasing the number of active sites in the catalyst part 1, the chance of the Freon refrigerant molecules in the refrigerant gas contacting the surface of the active sites in the catalyst part 1 increases, making the catalytic reaction more efficient and improving the catalytic efficiency.

[0072] In other embodiments, please refer to Figure 4 The catalyst portion 1 further includes a metal dopant 102, and the metal dopant 102 includes at least one of Pt, Pd, Au, and Ag.

[0073] As an example, the Ra value refers to the resistance value of the component in clean air at room temperature, and the Rg value refers to the resistance value of the component in a measured gas of a specified concentration. Ra / Rg represents the sensitivity of the component to the detected gas, that is, the responsiveness. The larger the Ra / Rg, the higher the sensitivity of the component.

[0074] Among them, Figure 5As shown, the sensitivity of the catalyst portion 1 having the metal dopant 102 is generally higher than the sensitivity of the catalyst portion 1 without the metal dopant 102 . Among them, when the catalytic part of the sensor is Pt-doped porous γ-phase alumina, the detected Ra / Rg value reaches 3.3 in 500ppm R1234yf gas; when the catalytic part of the sensor is porous γ-phase alumina without metal doping, the detected Ra / Rg value reaches 8.3 in 500ppm R1234yf gas; when the catalytic part of the sensor is Au-doped porous γ-phase alumina, the detected Ra / Rg value reaches 10.5 in 500ppm R1234yf gas; when the catalytic part of the sensor is Pt-doped porous γ-phase alumina, the detected Ra / Rg value reaches 40.5 in 500ppm R1234yf gas; that is to say, the Pd-doped sensor with Pd metal dopant has the best detection performance and the highest sensitivity. The Ra / Rg value of the Pd-doped sensor is 4.9 times that of the sensor without metal dopant.

[0075] It is understandable that the metal dopant 102 can form new active sites on the surface of the γ-phase alumina 101, or improve the activity of nearby γ-phase alumina sites, thereby improving the catalytic efficiency.

[0076] Furthermore, the metal dopant 102 can affect the adsorption and reaction path of the Freon refrigerant molecules on the surface of the catalyst part 1, which is beneficial to the generation of specific active free radicals and improves the selectivity.

[0077] In other embodiments, the ratio of the metal dopant 102 to the catalyst portion 1 is not greater than 3wt%, and the ratio of the metal dopant 102 to the catalyst portion 1 is at least 1wt%, for example, the ratio of the metal dopant 102 to the catalyst portion 1 may be 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%.

[0078] In the above scheme, since the content of the metal dopant 102 in the catalyst part 1 satisfies the above range, on the one hand, it can not only improve the catalytic activity, but also introduce new catalytic sites, thereby improving the catalytic efficiency; on the other hand, the lower doping ratio helps to achieve uniform dispersion of metal atoms and prevent metal atoms from aggregating on the surface of the catalyst part 1, thereby maintaining the long-term stability and activity of the catalyst part 1.

[0079] In other embodiments, please refer to Figure 6 An embodiment of the present application provides a method for preparing a catalytic part 1, comprising: S1: catalytically coating a glycerol-dispersed porous γ-phase alumina 101 or a metal-doped porous γ-phase alumina 101 on a preparation plate; wherein the porous γ-phase alumina 101 is glycerol-dispersed or metal-doped to increase its surface activity and improve the catalytic efficiency.

[0080] S2: Drying and sintering the coated catalytic raw material layer; the catalytic raw material layer is dried and sintered to form a stable structure, ensuring that the catalytic part can be formed and present a layered shape, so as to achieve stable catalysis of the refrigerant and reduce the probability of reduced catalytic performance during cracking and activation.

[0081] In other embodiments, the glycerol dispersed porous γ-phase alumina 101 or the metal-doped porous γ-phase alumina 101 is coated on the prepared plate in a manner including but not limited to drop coating, spin coating or sputtering deposition.

[0082] The drop coating method refers to uniformly dropping a solution onto the surface of a substrate by dropping a liquid, and then using a spin coater to spread the solution into a thin film.

[0083] As an example, the catalyst layer is drip-coated and then sintered at high temperature. The drip-coating raw material is glycerol-dispersed porous γ-phase alumina 101 or metal-doped porous γ-phase alumina 101. The sintering temperature after drip-coating is between 400°C and 600°C, and the sintering time is within 3 hours.

[0084] Spin coating refers to a method of uniformly coating a liquid material by rotating a substrate, where the liquid coating material is dropped onto the rotating substrate; then, the substrate is rotated at a certain speed, and the centrifugal force and the surface tension of the solution act together to cause the liquid material to spread rapidly and form a uniform film.

[0085] As an example, the catalyst layer is spin-coated and then sintered at high temperature. The spin-coating raw material is prepared by a sol-gel method. The spin-coating speed is between 1000-3000 rpm and the spin-coating time does not exceed 60 s. The high-temperature sintering temperature is between 400°C and 600°C and the sintering time is 2h-6h.

[0086] Sputtering deposition refers to a method in which a target material is bombarded with high-energy particles, causing atoms in the target material to sputter out and deposit on the surface of the substrate to form a thin film.

[0087] As an example, the aforementioned porous γ-phase alumina 101 or metal-doped porous γ-phase alumina 101 is prepared by high-temperature sintering, the raw material is a pseudo-boehmite aqueous solution, or a metal-doped pseudo-boehmite aqueous solution, the sintering temperature is between 400°C and 600°C, and the sintering time is 2h-6h.

[0088] Wherein, pure porous γ-phase alumina 101 is produced after high-temperature sintering of pseudo-boehmite aqueous solution, and metal-doped porous γ-phase alumina 101 is produced after high-temperature sintering of metal-doped pseudo-boehmite aqueous solution.

[0089] In other embodiments, when detecting the refrigerant gas, the operating temperature of the sensor is in the range of 250° C.-350° C., preferably 300° C. The detectable refrigerant gas concentration range is between 1 ppm and 1000 ppm.

[0090] In another embodiment, drying and sintering the coated catalytic raw material layer includes: a sintering temperature of 400° C.-600° C., and a sintering time of 2 h-6 h.

[0091] In the above scheme, since the above conditions are adopted during the drying and sintering of the catalytic raw material layer, the pore structure of the catalytic raw material layer is further optimized. Furthermore, under the above conditions, the pore size distribution in the porous structure formed by the catalytic raw material layer is mainly within the mesopore range, thereby improving the catalytic efficiency and mass transfer efficiency of the Freon refrigerant molecules.

[0092] In another embodiment, the electrode layer includes two disconnected positive and negative electrodes, and the positive and negative electrodes can be of any shape or structure. Figure 7 , including but not limited to the micro-pitch electrode structure including the interdigitated electrodes 301.

[0093] The interdigitated electrode 301 refers to an electrode with a periodic pattern, which is used to generate capacitance associated with the electric field that can penetrate material samples and sensitive coatings; it can be divided into alumina ceramic substrate interdigitated electrodes, PET / PI flexible interdigitated electrodes, porous gold modified interdigitated electrodes, silica interdigitated electrodes, etc. according to different substrate materials, and this application does not impose any restrictions on this.

[0094] Among them, the porous gold-modified interdigitated electrode can increase the loading amount of electrode active materials and improve the sensitivity of the sensor due to its large specific surface area.

[0095] In a specific embodiment, the Freon refrigerant molecule is the fourth generation Freon refrigerant R1234yf. Figure 8 The embodiment of the present application discloses a novel electrochemical gas sensor for detecting fourth-generation Freon refrigerants, having the following structure: Pd-doped porous γ-phase alumina 103, tin oxide 202 and gold interdigital electrodes 302; Pd-doped porous γ-phase alumina 103, tin oxide 202 and gold interdigital electrodes 302 are stacked in sequence.

[0096] The present application discloses a method for preparing a detection layer, comprising: preparing SnCl by a sol-gel method 2 -Ethanol hydrosol was used as the raw material for spin coating and sintering, the spin coating parameters were 2500 rpm, the spin coating time was 20 s, the sintering temperature was 550 °C, and the sintering time was 2 h.

[0097] The embodiment of the present application discloses a method for preparing a catalytic layer, comprising: using a glycerol-dispersed Pd-doped porous γ-phase alumina 103 dispersion as a raw material for drop coating and sintering, the sintering temperature after drop coating is 500° C., and the sintering time is 1 hour.

[0098] The embodiment of the present application discloses a method for preparing a Pd-doped porous γ-phase alumina 103 layer powder, comprising: high-temperature sintering using a 1wt% Pd-doped pseudo-boehmite aqueous solution as a raw material, the sintering temperature being 550° C. and the sintering time being 4 hours.

[0099] The fourth generation Freon refrigerant R1234yf was tested, and the sensor operating temperature was set to 300℃. The test results are as follows: Fig. 9 As shown in the figure, at a concentration of 500 ppm, the sensor's responsiveness to R1234yf is as high as 40.5 (Ra / Rg value). The same method is used to prepare a conventional electrochemical gas sensor of metal semiconductor oxide without a catalytic activation layer. 2 For comparison, the SnO 2 The sensor does not respond to R1234yf.

[0100] In the interference and universality tests, the test results are as follows Fig.10 As shown, the sensor of the embodiment of the present application has basically no response to common interfering gases acetone and ethanol, and therefore has very good selectivity; it has good responsiveness to third-generation Freon refrigerants such as R134a and R32.

[0101] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0102] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0103] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0104] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A sensor for refrigerant detection, characterized in that: include: Detection unit, used to detect whether there is refrigerant leakage; an electrode portion, connected to the detection portion, and used to detect the resistance of the detection portion; The catalytic part is used to activate the refrigerant molecules so as to crack the refrigerant molecules into active free radicals that can be detected by the detection part.

2. The sensor according to claim 1, characterized in that The catalytic part, the detection part and the electrode part are layered structures, and the catalytic part, the detection part and the electrode part are stacked; Along the thickness direction of the catalytic portion, the detection portion or the electrode portion, the detection portion is located between the catalytic portion and the electrode portion. 3 . The sensor according to claim 2 , wherein along the thickness direction of the catalytic portion, the projected area of ​​the catalytic portion is larger than the projected area of ​​the detection portion, and the projected area of ​​the detection portion is larger than the projected area of ​​the electrode portion.

4. The sensor according to claim 1, characterized in that The detection portion is constructed as a metal oxide semiconductor material, and the detection portion includes at least one of tin oxide, zinc oxide, and tungsten oxide.

5. The sensor according to claim 1, characterized in that The catalytic portion includes gamma-phase alumina.

6. The sensor according to claim 5, characterized in that The specific surface area of ​​the catalyst part is not less than 340m 2 / g.

7. The sensor according to claim 5, characterized in that The catalyst part also includes a metal dopant, and the metal dopant is at least one of Pt, Pd, Au, and Ag.

8. The sensor according to claim 7, characterized in that The metal dopant is Pd.

9. The sensor according to claim 7 or 8, characterized in that The ratio of the metal dopant to the catalyst portion is no more than 3 wt %.

10. A method for preparing a catalyst part, characterized in that: include: Catalytically coating the prepared plate with glycerol-dispersed porous γ-phase alumina or metal-doped porous γ-phase alumina; The coated catalytic raw material layer is dried and sintered.

11. Use of the sensor according to any one of claims 1 to 9 or the catalytic part prepared by the method according to claim 10 in activating and detecting fourth-generation HFOs Freon refrigerant molecules.

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