An auxiliary device and system for constant free space for physisorption

Abstract

The application relates to an auxiliary device and system for constant free space of physical adsorption in the technical field of analysis instruments; the auxiliary device comprises a sealing cover, an adsorption test cavity, a pressure regulating pipeline, an adjusting valve and a liquid level detection device; wherein the sealing cover is provided with a through hole, the pressure regulating pipeline is arranged on the annular surface of the sealing cover, and the adjusting valve is arranged on the pressure regulating pipeline. In the application, the auxiliary device is sealingly connected with a low-temperature liquid storage device, the bottom of the adsorption test cavity is immersed into the low-temperature liquid, and the outer wall of the adsorption test cavity and the inner wall of the low-temperature storage device form an annular sealing cavity. The technical scheme of the application adopts the liquid level detection device to detect the liquid level height of the adsorption test cavity in real time, adjusts the pressure of the sealing cavity through the adjusting valve and the pressure regulating pipeline, and then adjusts the liquid level height of the adsorption test cavity to keep it unchanged, so that the constant of the second free space value is ensured.

Description

Technical Field

[0001] This invention relates to the field of analytical instrument technology, and in particular to an auxiliary device and system for a constant free space for physical adsorption. Background Technology

[0002] With the rapid development of materials science, including nanomaterials, energy storage materials, and catalytic materials, physical adsorption technology has been widely applied to the analysis of specific surface area, pore size distribution, adsorption performance, and separation effect of solid materials. Nitrogen and argon are commonly used analytical gases. To control the adsorption process step by step, the sample needs to be maintained at the phase transition temperature of the corresponding analytical gas. For example, when nitrogen is used as the analytical gas, the sample needs to be immersed in liquid nitrogen; when argon is used, the sample needs to be immersed in liquid argon. Throughout the analysis process, the pressure needs to be continuously increased or decreased until adsorption equilibrium is reached. Then, the adsorption amount of the sample at constant temperature and different partial pressures is calculated using the gas equation, obtaining isotherms. Finally, different analytical models are used to analyze the isotherms to obtain information such as the specific surface area, pore size distribution, and pore volume of the sample.

[0003] Unlike chemisorption, physical adsorption is a weak, non-selective adsorption process. Reaching adsorption equilibrium at each partial pressure requires a considerable amount of time, and isotherms often require data collection at multiple partial pressures. The more data collected, the more accurate the subsequent analysis results, but the longer the analysis time. The volume of the test tube containing the sample, measured at room temperature, is the first free space; the volume measured at the test temperature (usually low temperature), is the second free space. At this temperature, the test tube is partially submerged in the cryogenic liquid (such as liquid nitrogen or liquid argon) and partially above it. Calculating the adsorption capacity of the sample requires knowing the effective free space of the test tube, which is calculated from the first and second free spaces. Due to the lengthy analysis process and the gradual evaporation of the cryogenic liquid in the cryogenic storage device, the liquid level continuously decreases, causing the second free space to change, which in turn affects the effective free space. This introduces considerable uncertainty into the calculation of the adsorption capacity. In addition, during the first and second free space tests, the instrument host and the upper part of the test tube are at room temperature. However, the room temperature will change constantly with various factors such as day and night, seasonal changes, and instrument placement. These factors, along with the changes in the low temperature liquid level, will cause the first and second free spaces to change slightly at all times, thus affecting the repeatability and accuracy of the test.

[0004] To address the impact of liquid level changes on free space, existing main technologies include porous material methods and constant liquid level methods, both of which require elevators and Dewar flasks.

[0005] The porous material method involves encasing a porous material around a test tube. An elevator raises a Dewar flask to a fixed position, where a cryogenic liquid cools the test tube and the porous material. Because the cryogenic liquid evaporates, the liquid level drops. The porous material, using capillary action, draws the cryogenic liquid to its highest point, thus maintaining a constant second free space and consequently, a constant effective free space. However, in reality, during prolonged analysis, the liquid level drops, and the porous material inevitably becomes increasingly exposed above the cryogenic liquid, creating a temperature difference from top to bottom. This results in a shrinking second free space, leading to a lower calculated adsorption capacity. Furthermore, the volume of the test tube immersed in and unimmersed in the cryogenic liquid constantly changes throughout the process, causing variations in the gas density distribution within the test tube, even with the same molar amount of gas. This, in turn, affects the pressure readings and the sample adsorption test results.

[0006] The constant-level method uses a liquid level sensor system to control the elevator's vertical movement, thus ensuring a constant volume of the test tube immersed in the cryogenic liquid. During analysis, when the liquid level drops, the liquid level sensor loses contact with the liquid surface, and the elevator slowly rises the Dewar flask until the liquid level sensor contacts the cryogenic liquid surface. This process is repeated to assume the second free space is fixed. However, in reality, although the volume of the test tube immersed in the cryogenic liquid remains constant as the Dewar flask rises, the portion of the test tube extending into the Dewar flask but not submerged gradually increases. The temperature inside the Dewar flask is inevitably lower than room temperature, causing the second free space to actually increase, resulting in an overestimation of the adsorption capacity. Throughout the constant-level method, although the volume of the test tube immersed in the cryogenic liquid remains unchanged, the gas density in the portion of the test tube not submerged in the cryogenic liquid continuously increases, inevitably affecting the pressure value and the sample adsorption test results.

[0007] In both of these methods, the second free space is constantly changing, which introduces test errors, especially the influence of environmental factors on the test results (such as temperature changes). Currently, there is no mature method on the market that can solve this problem. Summary of the Invention

[0008] To address the issue of free space being susceptible to environmental factors such as liquid level and room temperature variations, and to achieve accurate free space measurement while maintaining a constant second free space throughout the entire process, thereby improving the accuracy and repeatability of the test, this invention discloses an auxiliary device and system for maintaining a constant free space for physical adsorption. The technical solution of this invention is implemented as follows:

[0009] An auxiliary device for a constant free space for physical adsorption includes a sealing cover, an adsorption test chamber, a pressure regulating pipe, a regulating valve, and a liquid level detection device.

[0010] The sealing cap has a through hole, the pressure regulating pipe is disposed on the annular surface of the sealing cap, the regulating valve is disposed on the pressure regulating pipe, and the liquid level detection device is disposed in the adsorption test chamber or the through hole.

[0011] Preferably, the liquid level detection device is selected from one of radar, liquid level gauge, and thermometer.

[0012] Preferably, the liquid level detection device includes a blank tube and a pressure gauge;

[0013] The blank tube is placed inside the adsorption test chamber, and the pressure gauge is connected to and measures the pressure of the blank tube.

[0014] Preferably, it also includes a sleeve;

[0015] The sleeve is disposed on the inner or outer wall of the adsorption test chamber; the sleeve is made of a porous material.

[0016] Preferably, a pressure sensor is also provided on the pressure regulating pipe.

[0017] A system for a constant free space for physical adsorption includes a test tube, a standard tube, an insulation shell, a cryogenic liquid storage device, auxiliary devices, and a control host. The standard tube is disposed inside the insulation shell and is connected to the test tube via a pipe.

[0018] The auxiliary device is sealed and connected to the cryogenic liquid storage device;

[0019] The control host controls the liquid level detection device and regulating valve via a communication line or wireless connection.

[0020] Preferably, it also includes a sealing door, which provides a sealed connection between the cryogenic liquid storage device and the insulation shell.

[0021] In this invention, the auxiliary device is sealed to the cryogenic liquid storage device. The bottom of the adsorption test chamber is submerged in the cryogenic liquid. The outer wall of the adsorption test chamber and the inner wall of the cryogenic storage device form an annular sealed cavity, and the pressure inside this sealed cavity is the same as the pressure on the liquid surface of the adsorption test chamber. When the cryogenic liquid evaporates, the liquid level in the adsorption test chamber drops, breaking the pressure balance. At this time, the pressure in the sealed cavity is greater than the liquid surface pressure in the adsorption test chamber, causing the liquid level in the adsorption test chamber to rise until pressure balance is restored. To maintain the second free space volume constant, the liquid level in the adsorption test chamber must remain constant. Therefore, the technical solution of this invention uses a liquid level detection device to detect the liquid level height in the adsorption test chamber in real time, and adjusts the pressure of the sealed cavity through a regulating valve and a pressure regulating pipe, thereby adjusting the liquid level height in the adsorption test chamber to keep it constant, thus ensuring the constancy of the second free space value. This method is not only suitable for low pressure but can also be applied to high pressure testing, greatly improving the accuracy of the test results. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A top-view structural schematic diagram of an embodiment of an auxiliary device for a constant free space used in physical adsorption (liquid level detection device not shown);

[0024] Figure 2 A schematic diagram of the structure from an elevation view of an embodiment of an auxiliary device for a constant free space used in physical adsorption (liquid level detection device not shown);

[0025] Figure 3 A schematic diagram of a longitudinal section of an embodiment of an auxiliary device for a constant free space used for physical adsorption (liquid level detection device not shown);

[0026] Figure 4 This is a schematic diagram of an embodiment of an auxiliary device for a constant free space used in physical adsorption.

[0027] Figure 5 A top-view structural schematic diagram of an embodiment of an auxiliary device for a constant free space used in physical adsorption;

[0028] Figure 6 A schematic diagram of a longitudinal section of an embodiment of an auxiliary device for a constant free space used in physical adsorption;

[0029] Figure 7This is a schematic diagram of an embodiment of an auxiliary device for a constant free space used in physical adsorption.

[0030] Figure 8 A schematic diagram of a system embodiment for a constant free space used for physical adsorption;

[0031] Figure 9 This is a schematic diagram of a system embodiment for another physical adsorption system with constant free space.

[0032] In the above figures, the figure numbers indicate the following:

[0033] 1. Sealing cap;

[0034] 2. Adsorption test chamber;

[0035] 3. Pressure regulating pipeline;

[0036] 4. Control valve;

[0037] 5. Blank tube;

[0038] 6. Cryogenic liquid storage device;

[0039] 7. Level gauge;

[0040] 8. Sleeve;

[0041] 9. Pressure sensor;

[0042] 10. Test tube;

[0043] 11. Standard pipe;

[0044] 12. Insulation shell;

[0045] 13. Semiconductor Peltier;

[0046] 14. Heat sink;

[0047] 15. Fan;

[0048] 16. Sealed door;

[0049] Pb, pressure sensor. Detailed Implementation

[0050] The technical solutions of the present invention will now be clearly and completely described with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] In a specific embodiment 1, such as Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, an auxiliary device for a constant free space for physical adsorption includes a sealing cover 1, an adsorption test chamber 2, a pressure regulating pipe 3, a regulating valve 4, and a liquid level detection device.

[0053] The sealing cover 1 is provided with a through hole, the pressure regulating pipe 3 is provided on the annular surface of the sealing cover 1, and the regulating valve 4 is provided on the pressure regulating pipe 3.

[0054] In this embodiment, the liquid level detection device includes a blank tube 5 and a pressure gauge Pb. The blank tube 5 is disposed in the adsorption test chamber 2, and the pressure gauge Pb is connected to and measures the pressure of the blank tube 5.

[0055] This embodiment is applied to a cryogenic liquid storage device 6, such as a Dewar flask.

[0056] The application process of this embodiment is as follows:

[0057] The sealing cap 1 is sealed to the cryogenic liquid storage device 6. The bottom of the adsorption test chamber 2 is submerged in the cryogenic liquid. The outer wall of the adsorption test chamber 2 and the inner wall of the cryogenic liquid storage device 6 form an annular sealed cavity. The pressure inside this sealed cavity is the same as the pressure on the liquid surface of the adsorption test chamber 2. When the cryogenic liquid evaporates, the liquid level in the adsorption test chamber 2 drops, breaking the pressure balance. At this time, the pressure in the sealed cavity is greater than the liquid surface pressure in the adsorption test chamber 2, causing the liquid level in the adsorption test chamber 2 to rise until pressure balance is restored. To maintain the second free space volume constant, the liquid level in the adsorption test chamber 2 must remain constant. In this embodiment, the pressure at this liquid level in the adsorption test chamber 2 is detected in real time using a blank tube 5 and a pressure gauge Pb. The pressure in the sealed cavity is adjusted by a regulating valve 4 and a pressure regulating pipe 3, thereby adjusting the pressure in the blank tube 5 to maintain a constant pressure, thus maintaining the liquid level in the adsorption test chamber 2 and ensuring the constant value of the second free space. In this embodiment, the method for detecting the liquid level in the adsorption test chamber 2 is as follows:

[0058] During the physical adsorption test, blank tube 5 is filled with a non-condensable gas (such as helium) at a certain pressure and the bottom is immersed in a cryogenic liquid. The pressure gauge Pb measures the pressure inside blank tube 5 in real time. When the cryogenic liquid evaporates and the liquid level drops, the length of the part of blank tube 5 that is immersed in the cryogenic liquid changes, which in turn causes a change in the internal temperature, and ultimately leads to a change in pressure.

[0059] When the liquid level rises back to its original height, the reading of pressure gauge Pb will also return to its initial state, at which point regulating valve 4 can be closed.

[0060] In this embodiment, the pressure adjustment methods for the sealed cavity are divided into pressurization and depressurization.

[0061] During pressurization, the pressure regulating pipe 3 is connected to an external air source. After the regulating valve 4 and the external air source are opened, the external gas slowly enters the sealed cavity, increasing its pressure and thus raising the liquid level in the adsorption test chamber 2.

[0062] When the pressure is reduced, the regulating valve 4 is opened, and the gas in the sealed cavity flows out slowly through the pressure regulating pipe 3, and the pressure is reduced at any time, thereby reducing the liquid level in the adsorption test chamber 2.

[0063] Example 2

[0064] In a preferred embodiment 2, such as Figure 5 and Figure 6 As shown, an auxiliary device for a constant free space for physical adsorption includes a sealing cover 1, an adsorption test chamber 2, a pressure regulating pipe 3, a regulating valve 4, and a liquid level detection device.

[0065] The sealing cover 1 has a through hole, the liquid level detection device is installed in the through hole, the pressure regulating pipe 3 is installed on the annular surface of the sealing cover 1, and the regulating valve 4 is installed on the pressure regulating pipe 3.

[0066] In this embodiment, the liquid level detection device is a liquid level gauge 7.

[0067] This embodiment is applied to a cryogenic liquid storage device 6, such as a Dewar flask.

[0068] In this embodiment, the level gauge 7 is positioned above the cryogenic liquid in the adsorption test chamber 2 to detect the liquid level in the adsorption test chamber 2 in real time.

[0069] The application process of this embodiment is as follows:

[0070] The sealing cap 1 is sealed to the cryogenic liquid storage device 6. The bottom of the adsorption test chamber 2 is submerged in the cryogenic liquid. The outer wall of the adsorption test chamber 2 and the inner wall of the cryogenic liquid storage device 6 form an annular sealed cavity. The pressure inside this sealed cavity is the same as the pressure on the liquid surface of the adsorption test chamber 2. When the cryogenic liquid evaporates, the liquid level in the adsorption test chamber 2 drops, breaking the pressure balance. At this time, the pressure inside the sealed cavity is greater than the pressure on the liquid surface of the adsorption test chamber 2, causing the liquid level in the adsorption test chamber 2 to rise until pressure balance is restored. To maintain a constant volume of the second free space, the liquid level in the adsorption test chamber 2 must remain constant. In this embodiment, the liquid level height inside the adsorption test chamber 2 is detected in real time by the level gauge 7, and the pressure of the sealed cavity is adjusted by the regulating valve 4 and the pressure regulating pipe 3. This adjusts the liquid level height in the adsorption test chamber 2 to keep it constant, thereby ensuring the constant value of the second free space.

[0071] In this embodiment, the pressure adjustment methods for the sealed cavity are divided into pressurization and depressurization.

[0072] During pressurization, the pressure regulating pipe 3 is connected to an external air source. After the regulating valve 4 and the external air source are opened, the external gas slowly enters the sealed cavity, increasing its pressure and thus raising the liquid level in the adsorption test chamber 2.

[0073] When the pressure is reduced, the regulating valve 4 is opened, and the gas in the sealed cavity flows out slowly through the pressure regulating pipe 3, and the pressure is reduced at any time, thereby reducing the liquid level in the adsorption test chamber 2.

[0074] Example 3

[0075] In a preferred embodiment 3, such as Figure 7 As shown, an auxiliary device for a constant free space for physical adsorption includes a sealing cover 1, an adsorption test chamber 2, a pressure regulating pipe 3, a regulating valve 4, and a liquid level detection device.

[0076] The sealing cover 1 has a through hole, the liquid level detection device is installed in the through hole, the pressure regulating pipe 3 is installed on the annular surface of the sealing cover 1, and the regulating valve 4 is installed on the pressure regulating pipe 3.

[0077] In this embodiment, the liquid level detection device is a liquid level gauge 7.

[0078] This embodiment is applied to a cryogenic liquid storage device 6, such as a Dewar flask.

[0079] In this embodiment, the level gauge 7 is positioned above the cryogenic liquid in the adsorption test chamber 2 to detect the liquid level in the adsorption test chamber 2 in real time.

[0080] In this embodiment, a sleeve 8 is also included; the sleeve 8 encloses the adsorption test chamber 2; the sleeve 8 is made of porous material.

[0081] This embodiment relies on the structural implementation of Embodiment 2 and is an optimization of Embodiment 2.

[0082] To improve the accuracy of the test, this embodiment wraps the adsorption test chamber 2 with a sleeve 8 made of porous material. The porous material reacts with the cryogenic liquid, creating capillary action. The capillary force generated by the sleeve 8 adsorbs a portion of the cryogenic liquid. When the cryogenic liquid evaporates and the liquid level drops, the presence of adsorbed cryogenic liquid inside the sleeve 8 mitigates the adverse effects of temperature changes caused by the evaporation of the cryogenic liquid within the adsorption test chamber 2, effectively creating a temperature buffer zone. This embodiment effectively improves the accuracy of the test process.

[0083] The application process of this embodiment is the same as that of Embodiment 2, and the principle is also the same.

[0084] In a preferred embodiment, a pressure sensor 9 is also provided on the pressure regulating pipe 3.

[0085] The function of pressure sensor 9 is to detect the pressure in the sealed cavity in real time. Based on the pressure difference with atmospheric pressure, it is used to calculate the liquid level and thus determine whether it is necessary to add cryogenic liquid automatically or manually.

[0086] Example 4

[0087] In a specific embodiment 4, such as Figure 8 As shown, a system for a constant free space for physical adsorption includes a test tube 10, a standard tube 11, an insulation shell 12, a cryogenic liquid storage device 6, and a control host. The standard tube 11 is disposed inside the insulation shell 12 and is connected to the test tube 10 through a pipe. It also includes auxiliary devices.

[0088] The auxiliary device is sealed and connected to the cryogenic liquid storage device 6;

[0089] The control host controls the liquid level detection device and regulating valve 4 via a communication line or wireless connection.

[0090] This embodiment relies on the technical solution of Embodiment 3.

[0091] The calculation of the first free space volume is common knowledge in the art. The core of this embodiment lies in the addition of an auxiliary device to maintain the second free space volume constant. The method for maintaining this constant volume is the same as that in Embodiment 3.

[0092] In this embodiment, the control host is the control center built into the adsorption testing instrument, which is not shown in the figure.

[0093] The testing process in this embodiment is as follows:

[0094] 1. First, start the adsorption equipment and keep the temperature of the standard tube 11 constant at the target temperature, for example, 45℃;

[0095] 2. Vacuum the test tube 10 containing the sample (at this time, the test tube 10 is not placed in the cryogenic liquid storage device 6), and heat or cool the heat sink 14 through the semiconductor Peltier 13, and then diffuse the heat or cold air into the sealing door 16 through the fan 15, thereby adjusting the temperature of the test tube 10 to be the same as that of the standard tube 11.

[0096] 3. At the target temperature, perform the first free space test on test tube 10, denoted as Vfs_ST;

[0097] 4. Raise the cryogenic liquid storage device 6 until the sample in the test tube 10 is immersed in the cryogenic liquid, and then fix the position of the cryogenic liquid storage device 6.

[0098] 5. Based on the liquid level measured by the level gauge 7, the pressure of the annular sealed cavity formed by the outer wall of the adsorption test chamber 2 and the inner wall of the cryogenic liquid storage device 6 is adjusted by the regulating valve 4, thereby maintaining the liquid level stable.

[0099] 6. After the pressure stabilizes, test the second free space, denoted as Vfs_AT;

[0100] The effective free space Vfs of test tube 10 can be calculated based on the values ​​of Vfs_ST and Vfs_AT.

[0101] In step 6, the control unit adjusts the liquid level in real time according to the changes in the liquid level (by controlling the opening or closing of the regulating valve 4 to change the pressure in the sealed cavity, thereby adjusting the liquid level in the adsorption test chamber 2).

[0102] The calculation of the effective free space Vfs of the test tube 10 is a conventional technique in the art and is not elaborated in this embodiment.

[0103] Example 5

[0104] In a preferred embodiment 5, such as Figure 9 As shown, a system for a constant free space for physical adsorption includes a test tube 10, a standard tube 11, an insulation shell 12, a cryogenic liquid storage device 6, an auxiliary device, a sealing door 16, and a control host. The standard tube 11 is disposed inside the insulation shell 12 and is connected to the test tube 10 through a pipe.

[0105] The auxiliary device is sealed and connected to the cryogenic liquid storage device 6;

[0106] The sealed door 16 is provided with a sealed connection between the cryogenic liquid storage device 6 and the insulation shell 12.

[0107] The control host controls the liquid level detection device and regulating valve 4 via a communication line or wireless connection.

[0108] This embodiment relies on the technical solution of Embodiment 3. It is an optimization of Embodiment 4.

[0109] The function of the sealing door 16 is to prevent external moisture from entering the test area and condensing into ice, thus preventing it from affecting the test results.

Claims

1. A system for a constant free space for physical adsorption, comprising a test tube, a standard tube, an insulating shell, a cryogenic liquid storage device, and a control host, wherein the standard tube is disposed within the insulating shell and connected to the test tube via a pipe, characterized in that, It also includes auxiliary devices; The auxiliary device includes a sealing cover, an adsorption test chamber, a pressure regulating pipe, a regulating valve, and a liquid level detection device; The sealing cap is provided with a through hole, the pressure regulating pipe is provided on the annular surface of the sealing cap, the regulating valve is provided on the pressure regulating pipe, and the liquid level detection device is provided in the adsorption test chamber or the through hole. The liquid level detection device includes a blank tube and a pressure gauge; The blank tube is placed inside the adsorption test chamber, and the pressure gauge is connected to and measures the pressure of the blank tube. The auxiliary device is sealed and connected to the cryogenic liquid storage device; The control host controls the liquid level detection device and regulating valve via a communication line or wireless connection. A pressure sensor is also installed on the pressure regulating pipeline.

2. The system according to claim 1, characterized in that, The liquid level detection device is selected from one of the following: radar, liquid level gauge, and thermometer.

3. The system according to claim 1, characterized in that, It also includes sleeves; The sleeve is disposed on the outer or inner wall of the adsorption test chamber; the sleeve is made of a porous material.

4. The system according to claim 1, characterized in that, It also includes a sealing door, which provides a sealed connection between the cryogenic liquid storage device and the insulation shell.

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