A carbon dioxide gas concentration detection system and method based on liquid-based confined interface physical adsorption

Abstract

The application discloses a carbon dioxide gas detection system and method based on liquid-based limited interface physical adsorption, which comprises a gas container and a sealing device in communication with each other, the gas container is provided with a gas to be detected, and the sealing device is provided with a liquid-based porous material, wherein the liquid-based porous material is composed of a functional liquid which can strongly physically adsorb carbon dioxide and does not react with carbon dioxide; and the application further discloses a pressure detection device, which is used for measuring the critical transmembrane pressure of the gas breaking through the liquid film of the liquid-based porous material.

Description

Technical Field

[0001] This invention relates to a gas detection system and method, belonging to the field of chemical analysis system and method design. Background Technology

[0002] Gas detection technology has significant application value in environmental monitoring, industrial production, and safety assurance. Traditional carbon dioxide gas detection methods mainly include optical sensors and electrical sensors, depending on the signal type. However, these methods have some limitations in application. The signals from optical and electrical sensors are prone to saturation in high-concentration gas environments, making them unsuitable for wide-range gas detection. For example, CN202311584147.5 (A self-adjusting zero-range infrared laser carbon dioxide detection device and its usage method) utilizes the absorption of incident light by carbon dioxide to detect carbon dioxide concentration, with a range of only 380-1000 ppm; CN202311267176.9 (A carbon dioxide detection device and method based on optical waveguides) has a detection range of 0-2000 ppm. Commercially available infrared gas detection technology is mature and can be multi-moduleed to achieve carbon dioxide gas detection in the 0-100% range, but it is expensive and limited by device size, making it unsuitable for portable and complex environment detection, such as the carbon dioxide concentration in volcanic emissions (typically between 10-40%). In recent years, with a deeper understanding of liquid-based confined interfaces, their efficient and sensitive molecular responses have led to their increasing use in detecting chemical substances. However, they also face challenges such as insufficient sensitivity to gas molecules, susceptibility to environmental influences, and irreversibility. Therefore, the development of a low-cost gas detection system and method capable of quantitatively detecting carbon dioxide concentration over a wide range and less susceptible to environmental influences is urgently needed. Summary of the Invention

[0003] The purpose of this invention is to overcome the drawback of traditional gas sensors being prone to saturation at high concentrations, and to provide a carbon dioxide gas concentration detection system and method based on the physical adsorption of gas at a liquid-based confined interface.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A carbon dioxide gas detection system based on liquid-based confined interface physical adsorption includes an interconnected gas container and a sealed device. The gas container contains a gas of the concentration to be measured, and the sealed device contains a liquid-based porous material. The liquid-based porous material is composed of a functional liquid-wetted pore material that can strongly physically adsorb carbon dioxide gas without chemically reacting with it. The system also includes a pressure detection device for measuring the critical transmembrane pressure at which the gas breaks through the liquid membrane of the liquid-based porous material.

[0006] Strong physical adsorption refers to the existence of strong van der Waals forces between gas and liquid ions or molecules without any chemical reaction.

[0007] Optionally, a partial pressure environment proportional to the gas concentration is formed within the sealed device.

[0008] Optionally, the pore material includes at least one of nylon porous membrane, aqueous mixed cellulose membrane, polytetrafluoroethylene membrane, polyvinylidene fluoride membrane, porous glass membrane, and metal porous membrane, with a pore size ranging from 0.22 to 10 μm.

[0009] Optionally, the gas includes a first gas, carbon dioxide, and a second gas, and the functional liquid can strongly physically adsorb the first gas.

[0010] Optionally, the second gas is at least one of nitrogen, oxygen, argon, and air.

[0011] Optionally, the first gas, carbon dioxide, can form an adsorption layer at the gas-liquid interface of the functional liquid, and the amount of adsorption is correlated with the partial pressure of the first gas. The adsorption layer formed by the first gas, carbon dioxide, at the gas-liquid interface can change the surface tension of the functional liquid, and the amount of change in surface tension is quantitatively related to the amount of adsorption.

[0012] Optionally, when the functional liquid is a liquid that has a weak interaction with carbon dioxide, such as ionic liquid, silicone oil, or perfluorinated liquid, the presence of the first gas, carbon dioxide, will significantly reduce the critical transmembrane pressure of the liquid-based porous material, and the change in critical transmembrane pressure is quantitatively related to the concentration of carbon dioxide.

[0013] Optionally, the functional liquid has extremely low volatility, allowing the system to be reused repeatedly over a long period of time.

[0014] A method for detecting carbon dioxide gas based on liquid-based confined interface physical adsorption includes the following steps:

[0015] 1) Store the gas of the concentration to be measured in a gas container and connect it to a sealed device through a gas path;

[0016] 2) The pore material is fully immersed in a functional liquid that can strongly physically adsorb carbon dioxide without reacting with it chemically to make a gas detection unit, and the detection unit is placed in a sealed device.

[0017] 3) The gas pressure on the unit is monitored by a pressure detection device. When the gas completely breaks through the liquid film, the gas pressure is at its highest value, which is recorded as the critical transmembrane pressure.

[0018] Optionally, a constant flow rate of gas is introduced into a closed device, and the gas pressure information is monitored by a pressure detection device. The concentration value of the gas to be measured is determined by the critical transmembrane pressure.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The gas detection system designed by the present invention based on the change of saturated physical adsorption amount of different concentrations of gas on the liquid-based confined interface can quantitatively detect carbon dioxide gas in the range of 0-100%, with relatively uniform sensitivity, and overcomes the limitations caused by the physical principles of optical and electrical sensors.

[0021] (2) The present invention can achieve a wide range of gas detection without adjusting the module. The device designed in this way is small in size, portable and low in cost.

[0022] (3) The present invention realizes carbon dioxide gas detection at the liquid-based confined interface. Reasonable selection of functional liquid can enable the system to effectively resist external environmental interference, such as acid corrosion resistance, moisture resistance, stability at high and low temperatures, and ultra-long service life (more than 1 year). Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a carbon dioxide gas detection system based on liquid-based confined interface physical adsorption, according to an embodiment of the present invention. Schematic diagrams a and b show the overall structure of the device and the construction of the liquid-based porous material, respectively.

[0024] Figure 2 This is a schematic diagram of the mechanism of the carbon dioxide gas detection method based on liquid-based confined interface physical adsorption according to an embodiment of the present invention.

[0025] Figure 3 This is a time-pressure signal diagram of different gases passing through a liquid-based porous material in Example 1.

[0026] Figure 4 The graph shows the transmembrane pressure test results for different carbon dioxide concentrations in Example 1.

[0027] Figure 5 The graph shows the test results of the lifespan of the carbon dioxide gas detection system based on liquid-based confined interface physical adsorption in Example 1.

[0028] Figure 6 The figure shows the test results of the acid corrosion resistance of Example 1.

[0029] Figure 7 The graph shows the transmembrane pressure test results for different carbon dioxide concentrations in Example 2.

[0030] Figure 8 The graph shows the transmembrane pressure test results for different carbon dioxide concentrations in Example 3.

[0031] Figure 9The graph shows the transmembrane pressure test results for different carbon dioxide concentrations in Example 4.

[0032] Figure 10 The graph shows the transmembrane pressure test results for different carbon dioxide concentrations in Example 5. Detailed Implementation

[0033] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0034] The accompanying drawings are for illustrative purposes only to facilitate understanding of the invention, and their specific proportions can be adjusted as needed. The positions of the components described herein are relative, and therefore can all be flipped to present the same components, all of which should fall within the scope disclosed in this specification.

[0035] Embodiments of the present invention provide a carbon dioxide gas detection system and method based on liquid-based confined interface physical adsorption. (Reference) Figure 1 A schematic diagram of the system device and the specific construction of the liquid-based porous material are shown.

[0036] A gas detection system based on liquid-based confined interface physical adsorption includes a gas container 1, a pressure sensor 3, and a sealing device 4. The gas container 1 is a variable-volume container, such as a syringe. The outlet of the gas container 1 is divided into two paths: one connects to the sensor 3, and the other connects to the sealing device 4 via a pipeline. A gas path switching valve 2 is installed at the bifurcation point of these two paths.

[0037] In this system, gas container 1 contains the gas of the concentration to be detected, and gas path switching valve 2 is used to switch between detection and non-detection modes. In detection mode, gas path switching valve 2 connects gas container 1, pressure sensor 3, and sealing device 4. Sealing device 4 contains liquid-based porous material 7, which is constructed by impregnating porous material 5 with functional liquid 6. Liquid-based porous material 7 divides sealing device 4 into two parts, one of which is connected to a pipeline. Pressure sensor 3 is used to test the pressure in sealing device 4. As the gas is compressed, the reading of pressure sensor 3 continuously increases until all the pores of the liquid-based porous material are opened. The pressure at this point is recorded as the critical transmembrane pressure (see...). Figure 3 ).

[0038] Specifically, the gas to be tested should be a mixture of the first gas, carbon dioxide, and the second gas. The second gas is at least one of nitrogen, oxygen, argon, and air. The functional liquid can be an ionic liquid that can strongly physically adsorb carbon dioxide without reacting chemically with it, such as methyl 1-butyl-3-methyl-imidazolium sulfate or 1-butyl-3-methyl-imidazolium hexafluorophosphate. When the functional liquid is the aforementioned ionic liquid, the porous material can be a solid porous membrane with a strong affinity for it, such as a polyvinylidene fluoride membrane with a pore size between 0.22 and 10 μm. When the gas to be tested, the functional liquid, and the porous material are the above-mentioned substances, the critical transmembrane pressure of the gas to be tested is linearly related to the concentration of the gas to be tested. By recording the critical transmembrane pressure of the unknown gas passing through the liquid-based porous material, the concentration of the first gas within the unknown gas can be deduced.

[0039] The mechanism of this gas detection method based on liquid-based confined interface physical adsorption is as follows: Figure 2 As shown, when the gas of the desired concentration enters the sealed device 4, it creates a partial pressure environment within the device that is proportional to the concentration of the first gas, carbon dioxide. After the gas enters, the first gas undergoes physical adsorption on the surface of the functional liquid, and the saturated adsorption amount is related to the partial pressure of the first gas. A physical adsorption layer of the first gas is formed at the gas-liquid interface. Based on Gibbs theory, the relationship between surface tension, adsorption excess, and the partial pressure of the first gas is derived. According to the Laplace pressure formula, the critical pressure for the gas to break through the liquid film is related to the surface tension, thus obtaining a quantitative relationship between the critical transmembrane pressure of the gas of the desired concentration and the concentration of the first gas.

[0040] Example 1

[0041] In Example 1 of this application, taking carbon dioxide as the first gas and nitrogen as the second gas as an example, a gas detection system and method based on liquid-based confined interface physical adsorption are described in detail. In Example 1, the functional liquid 6 is an imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium sulfate methyl ester, and the porous material 5 is a polyvinylidene fluoride membrane with a pore size of 1 μm. The porous membrane is immersed in the ionic liquid for at least 5 minutes, drained, and then immersed in approximately 0.05 g of the ionic liquid. The experiment is conducted at room temperature. Gas in gas container 1 is propelled at a certain flow rate (2-4 mL / min). The gas is a mixture containing different concentrations of carbon dioxide and nitrogen. When the gas enters the sealed device 4 and forms a partial pressure environment, carbon dioxide molecules are captured by the functional liquid 6 due to quadrupole-charge interactions and strong interfacial dispersion, forming an adsorption layer at the gas-liquid interface. The adsorption excess is linearly correlated with the partial pressure of carbon dioxide. The adsorption of gas at the interface weakens the interaction between ions or molecules on the liquid surface, thereby reducing the surface tension. Mathematical calculations show that the decrease in surface tension is linearly correlated with the partial pressure of carbon dioxide. As the gas is continuously compressed, the reading of pressure sensor 3 rises until the gas is compressed to the point where it breaks through the liquid layer in the porous material, at which point the pressure sensor reading reaches its maximum value, denoted as the critical transmembrane pressure. According to the Laplace formula, this pressure is linearly related to the surface tension of the liquid. Therefore, theoretically, the critical transmembrane pressure of carbon dioxide of different concentrations passing through a liquid-based porous material should be linearly related to the carbon dioxide concentration.

[0042] refer to Figure 3 The pressure-time graph of carbon dioxide and the second gas (nitrogen, argon, oxygen, air) compressed until passing through the liquid-based porous material was measured. The critical transmembrane pressure was determined as follows: Figure 3 As shown, the critical transmembrane pressure of carbon dioxide passing through the liquid-based porous material is significantly lower than that of the second gas, indicating that the system has good specificity for carbon dioxide.

[0043] refer to Figure 4 The critical transmembrane pressure of carbon dioxide / nitrogen mixtures of different concentrations passing through a liquid-based porous material was experimentally measured, and it showed a good linear relationship with the carbon dioxide concentration (R0). 2 >0.99). In actual measurements, the concentration of carbon dioxide in the unknown gas can be derived from a linear relationship by measuring the critical transmembrane pressure of the unknown gas passing through the liquid-based porous material.

[0044] refer to Figure 5Concentrated hydrochloric acid and concentrated nitric acid were continuously introduced into a liquid-based porous material for 2 hours. After standing for 24 hours, scanning electron microscope (SEM) images of the surface morphology of the porous material after the acid gas was introduced were taken and compared with those before the gas introduction. Observation shows that the surface morphology of the porous material was almost undamaged after the acid gas was introduced, verifying the acid corrosion resistance of the detection system. The system's acid corrosion resistance stems from the fact that the acid gas does not directly contact the porous material, but is protected by the liquid layer.

[0045] refer to Figure 6 The critical transmembrane pressure of nitrogen and carbon dioxide was tested at regular intervals. It was observed that the system’s specific response to carbon dioxide can last for more than a year. The ultra-long time stability is due to the fact that carbon dioxide only has a weak interaction with the functional liquid and does not change the properties of the functional liquid. In addition, the functional liquid itself has extremely low volatility and will not be lost over time.

[0046] Example 2

[0047] In Example 2 of this application, the functional liquid of Example 1 is replaced with an imidazole-based ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate or 1-butyl-3-methylimidazolium tetrafluoroborate. Images of the ionic liquid structure and critical transmembrane pressures corresponding to different carbon dioxide concentrations are shown below. Figure 7 As shown. Because the three functional liquids selected in Examples 1 and 2 are all liquids that can effectively physically adsorb carbon dioxide without reacting with it, and the critical transmembrane pressure of different liquid-based functional materials has a good linear correlation with the carbon dioxide concentration, functional liquids that meet this condition can all be used in this gas detection system.

[0048] Example 3

[0049] In Example 3 of this application, the porous material of Example 1 was replaced with a polyvinylidene fluoride membrane with a pore size of 0.45 μm or 5 μm. The critical transmembrane pressure of the test system for different concentrations of carbon dioxide gas passing through the liquid-based porous material was compared with that when the pore size was 1 μm. The test results are as follows: Figure 8 As shown, the critical transmembrane pressure of confined systems with different pore sizes exhibits a good linear relationship with carbon dioxide concentration. The smaller the pore size, the higher the overall critical transmembrane pressure, and the greater the difference in critical transmembrane pressure between pure nitrogen and pure carbon dioxide, consistent with theoretical predictions. When using small-pore porous materials, the system can withstand higher pressures; when using large-pore porous materials, the required pressure is lower, but the introduced experimental error may be larger. Appropriate porous materials can be selected to design the system based on actual measurement conditions.

[0050] Example 4

[0051] In Embodiment 4 of this application, the measurement temperature in Embodiment 1 is replaced with 5°C or 50°C. The critical transmembrane pressure of the test system for different carbon dioxide concentrations of gas passing through the liquid-based porous material is tested, and the results are as follows: Figure 9 As shown, increasing temperature leads to a decrease in the critical transmembrane pressure, which stems from the decrease in surface tension with increasing temperature. At both high and low temperatures, the critical transmembrane pressure exhibits a linear relationship with carbon dioxide concentration, but the linearity decreases, possibly due to uneven heating of the system. Because the selected functional liquid does not solidify at low temperatures and does not volatilize at high temperatures, the system possesses good thermal stability.

[0052] Example 5

[0053] In Example 5 of this application, the second gas in Example 1 is replaced with humid air, which is generated by a humidifier. The functional liquid is changed to the hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate. The mixed gas is carbon dioxide / humid air. The critical transmembrane pressure of the system for different carbon dioxide concentrations passing through the liquid-based porous material is tested, and the results are as follows. Figure 10 As shown, under high humidity, the system's critical transmembrane pressure still exhibits a good linear relationship with carbon dioxide concentration, attributed to the hydrophobicity of the selected functional liquid and the fact that water molecules do not occupy carbon dioxide adsorption sites. This measurement result demonstrates the system's adaptability to humid environments.

[0054] The gas detection system based on liquid-based confined interface physical adsorption detects gas concentration by altering the critical transmembrane pressure of the gas passing through a liquid-based porous material through the specific physical adsorption of gas on a functional liquid. This system can be applied to a wide range of quantitative detection in various complex environments and has potential application value. Similar to the carbon dioxide detection system described above, as long as a functional liquid with specific physical adsorption for a certain gas is found, gas detection can be performed in a similar manner to the examples. The above embodiments are only used to further illustrate a gas detection system and method based on liquid-based confined interface physical adsorption of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A carbon dioxide gas detection system based on liquid-based confined interface physisorption, characterized in that: The application relates to a gas concentration detection device, which comprises a gas container and a sealing device, wherein the gas container is filled with a gas with a concentration to be detected, the sealing device is internally provided with liquid-based porous material, the liquid-based porous material is composed of a functional liquid which can physically absorb carbon dioxide and does not react with the carbon dioxide, and the sealing device is provided with a pressure detection device for measuring the critical transmembrane pressure when the gas breaks through the liquid film of the liquid-based porous material. The sealing device forms a partial pressure environment which is proportional to the gas concentration. The porous material comprises at least one of nylon porous film, water-based mixed cellulose film, polytetrafluoroethylene film, polyvinylidene fluoride film, porous glass film and metal porous film, and the pore size ranges from 0.22 to 10 mu m. The gas comprises first gas carbon dioxide and second gas. The second gas is at least one of nitrogen, oxygen, argon and air. The first gas carbon dioxide can form an adsorption layer at the gas-liquid interface of the functional liquid, and the adsorption amount is related to the partial pressure of the first gas; the adsorption layer formed by the first gas carbon dioxide at the gas-liquid interface can change the surface tension of the functional liquid, and the change amount of the surface tension is quantitatively related to the adsorption amount. The functional liquid is a liquid which has weak interaction with carbon dioxide, and the first gas carbon dioxide can significantly reduce the critical transmembrane pressure of the liquid-based porous material, and the change of the critical transmembrane pressure is quantitatively related to the concentration of the carbon dioxide.

2. A method for detecting carbon dioxide gas based on liquid-based confined interface physical adsorption, using the carbon dioxide gas detection system of claim 1, characterized in that: The application further discloses a gas concentration detection method, which comprises the following steps: 1) storing the gas with a concentration to be detected in a gas container, and connecting the gas container with the sealing device through a gas channel; 2) placing the porous material in a functional liquid which can strongly physically absorb carbon dioxide and does not react with the carbon dioxide to sufficiently soak the porous material to form a gas detection unit, and placing the detection unit in the sealing device; 3) monitoring the gas pressure on the detection unit through the pressure detection device, and when the gas completely breaks through the liquid film, the gas pressure is at the highest value, which is recorded as the critical transmembrane pressure.

3. The method for detecting carbon dioxide gas based on liquid-based confined interfacial physisorption according to claim 2, characterized in that: The gas with a constant flow rate is introduced into the sealing device, the gas pressure information is monitored through the pressure detection device, and the concentration value of the gas to be detected is reflected through the critical transmembrane pressure.

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