Gas Adsorption Amount Measuring Device and Gas Adsorption Amount Measuring Method

Abstract

The gas adsorption amount measuring device as an example of an embodiment of the present invention includes at least one sample tube, a reference tube, and a control unit. The control unit measures the reference volume Vd of the available space of the sample tube without a sample and the reference volume Vd of the available space of the reference tube using the adsorption gas st，ads and calculates the gas adsorption amount of the sample using the reference volumes Vd ref，ads , Vd st，ads , and Vd ref，ads .

Description

Technical Field

[0001] The present invention relates to a gas adsorption amount measuring device and a gas adsorption amount measuring method, and more particularly, to a measuring device and a measuring method for the constant volume method. Background Art

[0002] Conventionally, there is known a gas adsorption amount measuring device that measures the adsorption isotherm of a material using the constant volume method. The adsorption isotherm is one of the important basic physical properties that can obtain information such as the specific surface area and micropore distribution of a material, and is measured using an adsorption gas such as nitrogen or argon at a temperature such as liquid nitrogen (LN2: 77K) or liquid argon (LAr: 87K). For example, Patent Document 1 discloses an adsorption characteristic measuring device as follows: a glass sample tube containing a powder material is immersed in a Dewar flask filled with liquid nitrogen, nitrogen is supplied to the sample tube, and the pressure change of the sample tube is measured to calculate the gas adsorption amount of the powder material.

[0003] Generally, when measuring the gas adsorption amount using the constant volume method, before the adsorption measurement, the sample tube containing the sample is immersed in a refrigerant container such as a Dewar flask filled with a refrigerant such as liquid nitrogen, and helium gas that is difficult to be adsorbed by the sample is used to measure the reference volume of the available space. In addition, when the sample is a microporous material such as zeolite or activated carbon, the reference volume of the available space is measured after measuring the gas adsorption amount. Helium gas is also used in this case.

[0004] However, if the liquid nitrogen in the Dewar flask vaporizes during the measurement of the adsorption characteristics, resulting in a gradual decrease in the liquid level, the reference volume of the available space changes, and it is difficult to accurately measure the gas adsorption amount. Therefore, it is necessary to use a liquid level gauge to gradually raise the Dewar flask or other methods to suppress the volume change.

[0005] On the other hand, a method that directly utilizes the characteristic that the reference volume of the available space also changes at any time when the liquid level of liquid nitrogen gradually decreases has also been proposed (for example, refer to Patent Document 2 and Non-Patent Document 1). In this method, a reference tube and a sample tube are immersed side by side in liquid nitrogen. Before the adsorption measurement, the reference volume of the available space of each tube is measured first, and then the change rate of the internal pressure and volume of the reference tube that changes with time is calculated, and this change rate is used to calculate the volume of the available space of the sample tube.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: JP Patent No. 6037760 Gazette;

[0009] Patent Document 2: JP Patent No. 3756919 Gazette.

[0010] Non-Patent Documents

[0011] Non-Patent Document 1: Masayuki Yoshida, Kazuyuki Nakai, "Development of a New Method for Measuring the Dead Volume of a Constant-Volume Adsorption Device", Adsorption News, The Adsorption Society of Japan, December 25, 2007, Vol.21, No.4 (December 2007), Total Volume No.83, p.5-9. Summary of the Invention

[0012] (Technical Problem to be Solved by the Invention)

[0013] As described above, in conventional gas adsorption measurement (including the technologies disclosed in Patent Document 2 and Non-Patent Document 1), helium is used to measure the reference volume of the available space in the sample tube. However, with the increasing demand for helium and the decreasing resource volume, it can be anticipated that it will become increasingly difficult to obtain helium. Therefore, in the near future, it is necessary to develop a method for measuring the reference volume of the available space required for gas adsorption amount calculation without using helium.

[0014] An object of the present invention is to provide an unprecedented gas adsorption amount measurement device and gas adsorption amount measurement method that can measure the reference volume of the available space in the sample tube without using helium and use this volume to accurately measure the gas adsorption amount.

[0015] (Technical Solution for Solving the Problem)

[0016] The inventor of the present invention conducted repeated in-depth research to solve the above problems and found that by using a reference tube, the reference volume of the available space in the sample tube measured using an adsorption gas such as nitrogen can be applied to high-precision gas adsorption amount measurement. The gas adsorption amount measurement device of the present invention uses the adsorption gas to separately measure the reference volume Vd of the available space in the sample tube without the sample st，ads and the reference volume Vd of the available space in the reference tube ref，ads , and uses this reference volume Vd st，ads , Vd ref，ads to calculate the gas adsorption amount of the sample. The gas adsorption amount measurement device of the present invention is an unprecedented device that can perform high-precision gas adsorption amount measurement without using helium.

[0017] A gas adsorption amount measuring device according to an aspect of the present invention includes at least one sample tube that supplies an adsorption gas to the sample tube to measure the gas adsorption amount of a sample accommodated in the sample tube; a reference tube for determining the volume of the available space of the sample tube; a piping section for connecting the sample tube, the reference tube, and the supply tube of the adsorption gas; a pressure gauge for measuring the pressure of the piping section, the sample tube, and the reference tube; a device for maintaining the temperatures of the sample tube and the reference tube at a specified temperature; and a control section; the control section measures, under calibration conditions, the reference volume Vd of the available space of the sample tube without a sample loaded therein using the adsorption gas st，ads and the reference volume Vd of the available space of the reference tube ref，ads , and calculates a volume change amount ΔVd based on the reference volume Vd ref，ads and the volume Vd of the available space of the reference tube under the actual measurement conditions of the gas adsorption amount ref，ads(i) , calculates the volume Vd of the available space of the sample tube under the actual measurement conditions based on the volume change amount ΔVd ref(i) and the reference volume Vd ref(i) , and calculates the gas adsorption amount of the sample under the actual measurement conditions based on the volume Vd st，ads and the volume Vd of the available space of the sample tube with the sample loaded therein under the actual measurement conditions st，ads(i) . st，ads(i) sam，ads(i) sam，ads(i) sam，ads(i)

[0018] A gas adsorption amount measuring method according to an aspect of the present invention uses at least one sample tube and a reference tube for determining the volume of the available space of the sample tube. Under calibration conditions, the method measures the reference volume Vd of the available space of the sample tube without a sample loaded therein using an adsorption gas st，ads and the reference volume Vd of the available space of the reference tube ref，ads , calculates a volume change amount ΔVd based on the reference volume Vd ref，ads and the volume Vd of the available space of the reference tube under the actual measurement conditions of the gas adsorption amount ref，ads(i) , calculates the volume Vd of the available space of the sample tube under the actual measurement conditions based on the volume change amount ΔVd ref(i) and the reference volume Vd ref(i) , calculates the volume Vd of the available space of the sample tube with the sample loaded therein under the actual measurement conditions based on the volume Vd st，ads and the volume Vd of the available space of the sample tube with the sample loaded therein under the actual measurement conditions st，ads(i) , and calculates the gas adsorption amount of the sample under the actual measurement conditions based on the volume Vd st，ads(i) and the volume Vd of the available space of the sample tube with the sample loaded therein under the actual measurement conditions sam，ads(i) .

[0019] (Advantages of the Invention)

[0020] The gas adsorption amount measuring device and the gas adsorption amount measuring method according to the present invention can measure the reference volume of the available space of the sample tube without using helium gas, and use this volume to measure the gas adsorption amount with high precision. In the device and method of the present invention, an adsorption gas such as nitrogen is used instead of helium to measure the reference volume of the available space of the sample tube. In addition, according to the device and method of the present invention, it is not necessary to measure the reference volume of the available space of the sample tube every time the gas adsorption amount is measured as in the past, so the measurement time can be shortened.

[0021] In addition, in the conventional method, when the sample is a microporous material such as zeolite or activated carbon, helium is captured by the micropores, resulting in a decrease in measurement accuracy. However, according to the device and method of the present invention, since helium is not used, the measurement accuracy will not decrease. The conventional method overcomes this problem by measuring the available space using helium after measuring the adsorption amount, but there are problems such as the adsorption isotherm cannot be evaluated during the measurement process, and it takes time to discharge the adsorption gas and measure the available space after the measurement to prevent residual adsorption gas. According to the device and method of the present invention, even for microporous samples, the measurement time can be shortened and the measurement accuracy can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a structural diagram of a gas adsorption amount measuring device as an embodiment of the present invention.

[0023] Figure 2 is an explanatory diagram of a gas adsorption amount measuring method as an embodiment of the present invention.

[0024] Figure 3 is a flowchart showing an example of the measurement steps of the reference volume of the available space of the sample tube and the reference tube.

[0025] Figure 4 is a flowchart showing an example of the measurement steps of the gas adsorption amount (net adsorption amount) of the sample. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, a gas adsorption amount measuring device 10 as an embodiment of the present invention will be described in detail with reference to the drawings. The gas adsorption amount measuring device 10 is merely an example of the embodiment, and the present invention is not limited thereto. In addition, in this specification, when the description "substantially ~" is used as an example of being substantially the same, it includes the cases of being exactly the same and being substantially the same.

[0027] Figure 1 is a structural diagram of the gas adsorption amount measuring device 10. As Figure 1As shown, the gas adsorption amount measuring device 10 includes a plurality of sample tubes 11, 12, and 13, and can simultaneously measure the gas adsorption amounts of samples 1, 2, and 3 respectively accommodated in each tube. In Figure 1 , three sample tubes 11, 12, and 13 are illustrated. The number of sample tubes is not particularly limited, and may be one or two, or four or more. The three sample tubes 11, 12, and 13 are the same as each other and have substantially the same inner diameter. Samples 1, 2, and 3 are objects to be measured for gas adsorption amount, and are, for example, powder materials.

[0028] The gas adsorption amount measuring device 10 includes a reference tube 14, and the reference tube 14 is used to determine the volume of the available space of the sample tubes 11, 12, and 13. A plurality of reference tubes 14 may be provided, but regardless of the number of sample tubes, preferably one reference tube is provided. The reference tube 14 is the same as the sample tubes 11, 12, and 13, and has substantially the same inner diameter as each sample tube. In particular, the inner diameter of the part immersed in the refrigerant 19 described later must be substantially the same. In addition, in the gas adsorption amount measuring device 10, a saturated vapor pressure tube 15 for actually measuring the saturated vapor pressure (P0) of the adsorbed gas is also provided. Alternatively, the gas adsorption amount measuring device 10 may not be provided with the saturated vapor pressure tube 15, but instead calculate the saturated vapor pressure (P0) by measuring the temperature of the refrigerant 19 using a thermometer.

[0029] The gas adsorption amount measuring device 10 includes a piping section 16 and a pressure gauge. The piping section 16 is used to connect the sample tubes 11, 12, and 13, the reference tube 14, and the supply tube 101 of the adsorbed gas, and the pressure gauge is used to measure the pressures of the piping section 16, the sample tubes 11, 12, and 13, and the reference tube 14. One pressure gauge may be provided, but preferably a plurality of pressure gauges are provided in the piping section 16. The pressure gauges include a pressure gauge 20 for measuring the pressure of a reference volume section S described later in the piping section 16, and pressure gauges 21, 22, 23, and 24 for measuring the internal pressures of the sample tubes 11, 12, and 13 and the reference tube 14 respectively. A pressure gauge 25 is also provided in the piping section 16, and the pressure gauge 25 is used to measure the internal pressure of the saturated vapor pressure tube 15.

[0030] In addition, the gas adsorption amount measuring device 10 includes a device for maintaining the temperatures of the sample tubes 11, 12, and 13 and the reference tube 14 at a specified temperature, and a control section 40 for controlling the operation of the device to perform the gas adsorption amount measurement. The device includes, for example, a refrigerant container 18 filled with a refrigerant 19, and a lifting mechanism (not shown) for lifting the refrigerant container 18. The refrigerant 19 is not particularly limited, and usually liquid nitrogen or liquid argon is used. Hereinafter, unless otherwise specified, the refrigerant 19 is liquid nitrogen.

[0031] The gas adsorption amount measuring device 10 generally has a housing incorporating a built-in piping section 16, a control section 40, etc. In addition, a sample tube 11, 12, 13, a reference tube 14, a saturated vapor pressure tube 15, a refrigerant container 18, etc. are mounted on the housing. On the gas adsorption amount measuring device 10 (housing), a first connection section 50 for connecting a supply pipe 101 extending from an adsorption gas supply source 100 and a second connection section 53 for connecting an exhaust pipe 103 extending from an exhaust pump 102 are provided. An example of the adsorption gas supply source 100 is a nitrogen gas cylinder, and an example of the exhaust pump 103 is a vacuum pump.

[0032] The piping section 16 is composed of the sample tubes 11, 12, 13, the reference tube 14, the saturated vapor pressure tube 15, and a plurality of pipes respectively for connecting the first connection section 50 and the second connection section 53. On the piping section 16, a manifold for aggregating the plurality of pipes and a plurality of switching valves are provided. A second device for maintaining the temperature of the manifold 17 at a prescribed temperature may also be provided on the piping section 16, and the temperature of the internal space of the manifold 17, i.e., the reference volume section S, can be maintained at a constant temperature by the second device. The volume of the reference volume section S is a reference when measuring the volume of the available space of the sample tube 11, etc.

[0033] In Figure 1 In the example shown, corresponding to the sample tubes 11, 12, 13, the reference tube 14, the saturated vapor pressure tube 15, the first connection section 50, and the second connection section 53, switching valves 31, 32, 33, 34, 35, 51, 54 are respectively provided. When the switching valve 51 is opened, an adsorption gas is introduced into the reference volume section S surrounded by the respective switching valves of the piping section 16. For example, when the switching valve 31 is opened, an adsorption gas is introduced into the sample tube 11. Each switching valve operates under the control of the control section 40.

[0034] In the gas adsorption amount measuring device 10, helium is not used when measuring the available space volume, so a helium supply source is not connected. In other words, the gas adsorption amount measuring device 10 does not have a connection section with a helium supply source. In addition, the gas adsorption amount measuring device 10 may also include a plurality of first connection sections 50 and can connect supply sources of various adsorption gases. Furthermore, the gas adsorption amount measuring device 10 may also have a communication function, and part of the functions of the control section 40 may be provided in an external server or in the cloud, etc.

[0035] Hereinafter, each component of the gas adsorption amount measuring device 10 will be described in further detail. In the gas adsorption amount measuring device 10, since the sample tubes 11, 12, 13 have the same configuration, regarding the common content of the sample tubes 11, 12, 13, the sample tube 11 will be taken as an example for description.

[0036] The sample tube 11 is a tubular container made of glass with one end open and the other end closed. An example of a dimension of the sample tube 11 is an inner diameter of 1 cm and a length of 20 cm. Additionally, a quartz container or a metal container (the same applies to the reference tube 14) can also be used as the sample tube 11. Furthermore, the shape of the sample tube 11 is not particularly limited and can be a cylindrical shape with a fixed tube diameter in the longitudinal direction, or a shape where the bottom side for accommodating the sample 1 is thicker than the opening side.

[0037] The sample tube 11 is connected to the port 56 of the piping section 16. A port 56, which is the connection port for the sample tube 11, is provided on the gas adsorption amount measuring device 10 (housing), and the open end of the sample tube 11 is connected to the port 56. After the sample tube 11 is connected to the port 56, the sample tube 11 can be connected to the adsorption gas supply source 100 and the exhaust pump 102 through the piping section 16. Additionally, the gas adsorption amount measuring device 10 has ports 57 and 58, which are the connection ports for the sample tubes 12 and 13. In the usage state of the gas adsorption amount measuring device 10, the ports 56, 57, and 58 are arranged side by side in the horizontal direction, and the installation heights of the sample tubes 11, 12, and 13 are the same.

[0038] As described above, the reference tube 14 is the same as the sample tube 11 and has a substantially the same inner diameter. The volume of the reference tube 14 is the reference for calculating the available space volume of the sample tube 11. Details will be described later. By using the reference tube 14, the reference volume of the available space of the adsorption gas measurement sample tube 11 can be measured without using helium. The gas adsorption amount measuring device 10 has a port 59, which is the connection port for the reference tube 14. In the usage state of the gas adsorption amount measuring device 10, the port 59 is arranged side by side at the same height in the horizontal direction with the ports 56, 57, and 58.

[0039] The reference tube 14 is arranged so that it can be immersed in the liquid nitrogen filled in the refrigerant container 18 together with the sample tubes 11, 12, and 13. Since the installation heights of the sample tubes 11, 12, and 13 and the reference tube 14 are the same, the bottoms of the respective tubes are immersed in the liquid nitrogen at the same height. Additionally, the same applies to the saturated vapor pressure tube 15, which is connected to the port 60 of the piping section 16 and is immersed in the refrigerant 19 filled in the refrigerant container 18 together with the sample tube 11, etc.

[0040] The refrigerant container 18 is a container filled with a refrigerant 19 such as liquid nitrogen and has an internal space capable of accommodating the sample tubes 11, 12, 13, the reference tube 14, and the saturated vapor pressure tube 15. Preferably, the refrigerant container 18 is a Dewar flask with a heat insulation function. When using nitrogen as the adsorption gas, the refrigerant 19 is usually liquid nitrogen (LN2: 77K). Additionally, a device for maintaining the sample tubes 11, 12, 13, the reference tube 14, and the saturated vapor pressure tube 15 at a specified temperature can also have a constant temperature water bath (adsorption temperature close to room temperature) or a heater (high temperature adsorption temperature).

[0041] As described above, in the gas adsorption amount measuring apparatus 10, pressure gauges 21, 22, 23, 24, and 25 are provided for measuring the internal pressures of the sample tubes 11, 12, 13, the reference tube 14, and the saturated vapor pressure tube 15, respectively. In Figure 1 the example shown, a pressure gauge 21 is provided on the pipe 56a for connecting the sample tube 11 to the manifold 17. Further, on the pipe 56a, a switching valve 31 is also provided on the side closer to the manifold 17 than the pressure gauge 21. That is, the pressure gauge 21 is provided on the pipe 56a between the port 56 and the switching valve 31 for measuring the internal pressure of the sample tube 11 (including a part of the pipe 56a).

[0042] Similar to the pressure gauge 21 and the switching valve 31, pressure gauges 22, 23, 24, 25 and switching valves 32, 33, 34, 35 are respectively provided on the pipes 57a, 58a, 59a, 60a for connecting the sample tubes 12, 13, the reference tube 14, and the saturated vapor pressure tube 15 to the manifold 17. Further, a switching valve 51 and a flow rate adjusting valve 52 are provided on the pipe for connecting the first connection portion 50 to the manifold 17, and a switching valve 54 and a flow rate adjusting valve 55 are provided on the pipe for connecting the second connection portion 53 to the manifold 17. A pressure gauge 20 is provided on the manifold 17 for measuring the internal pressure of the manifold 17 (reference volume portion S).

[0043] As described above, the internal space of the manifold 17 surrounded by the switching valves 31, 32, 33, 34, 35, 51, 54 is referred to as the reference volume portion S, and its volume is the reference when measuring the available space volume of the sample tubes 11, etc. On the other hand, the internal spaces of the sample tubes 11, 12, 13 and the reference tube 14 are referred to as the available space. In addition, the volume of the available space of the sample tube 11 is accurately the volume obtained by adding the internal space of a part of the pipe 56a (from the switching valve 31 to the port 56) and the internal space of the sample tube 11.

[0044] The control unit 40 controls the operation of the gas adsorption amount measuring apparatus 10 to perform the measurement of the gas adsorption amount. Specifically, it controls the switching valves and the flow rate adjusting valves of the pipe portion 16, supplies an adsorption gas at a specified relative pressure (P / P0) to the sample tube 11, and calculates the gas adsorption amount of the sample 1 accommodated in the sample tube 11 based on the measured values of the pressure gauges. A needle valve can be used as the flow rate adjusting valve, or a dummy column can be used instead of the flow rate adjusting valve to adjust the flow rate of the adsorption gas. Further, before measuring the gas adsorption amount, the control unit 40 first measures the reference volume of the available space of the sample tube 11 without loading the sample 1. In addition, in the gas adsorption amount measuring apparatus 10, the reference volumes of the available spaces of the sample tubes 12, 13 can be measured while measuring the sample tube 11.

[0045] The control unit 40 is composed of a computer including a processor 46, a memory 47, an input / output interface, etc. The processor 46 is constituted by, for example, a CPU or a GPU, and reads and executes a processing program to implement the functions of the respective processing units described later. The memory 47 includes non-volatile memories such as ROM, HDD, and SSD, and volatile memories such as RAM. The processing program is stored in the non-volatile memory.

[0046] In addition, the gas adsorption amount measuring device 10 may further include an input device for inputting information required for measuring the gas adsorption amount such as the sample mass, and a display device for displaying the measurement results of the gas adsorption amount, etc. Alternatively, a general keyboard, a monitor, etc. may be connected to the gas adsorption amount measuring device 10.

[0047] As Figure 1 shown, the control unit 40 includes a reference volume measurement processing unit 41 for measuring the reference volume of the available spaces of the sample tube 11 and the reference tube 14. In addition, the control unit 40 includes processing units (volume change amount calculation processing unit 42, sample tube volume calculation processing unit 43, and adsorption amount calculation processing unit 44) for performing the gas adsorption amount measurement of the sample using the reference volume measured by the function of the reference volume measurement processing unit 41. Furthermore, the control unit 40 may further include a surface excess amount calculation processing unit 45 for calculating the surface excess adsorption amount of the sample. Hereinafter, the case of using nitrogen as the adsorption gas is exemplified.

[0048] The control unit 40 measures the reference volume Vd of the available space of the sample tube 11 without the sample 1 and the reference volume Vd of the available space of the reference tube 14 using nitrogen under calibration conditions st，ads and the reference volume Vd of the available space of the reference tube 14 ref，ads . The reference volume Vd st，ads , Vd ref，ads is measured by the function of the reference volume measurement processing unit 41. In the conventional measurement system, helium, which is difficult to adsorb by the sample, is used to measure the reference volume of the sample tube containing the sample, but in the gas adsorption amount measuring device 10, nitrogen is used to measure the reference volume Vd of the available space of the sample tube 11 without the sample 1 st，ads .

[0049] Here, the so-called calibration conditions refer to the conditions when measuring the reference volumes Vd st，ads , Vd ref，ads , for example, it refers to that the liquid level of the liquid nitrogen filled in the refrigerant container 18 for cooling the sample tube 11 and the reference tube 14 is in the first state (liquid level A). The detailed content will be described later. The reference volumes Vd st，RT , Vd ref，RT at room temperature are measured, and the measured values are used to measure the reference volume Vd at the adsorption temperature.st，ads and Vd ref，ads . The difference between the reference volume at room temperature and the adsorption temperature can be used for thermal conversion correction (pressure correction). Additionally, it is also possible to calculate the gas adsorption amount using only the reference volume Vd st，ads and Vd ref，ads (i.e., without using the reference volume Vd st，RT and Vd ref，RT ).

[0050] Furthermore, the so-called measured conditions described later refer to the conditions when measuring the gas adsorption amount of the sample. For example, it refers to the liquid level of the liquid nitrogen filled in the refrigerant container 18 for cooling the sample tube 11 and the reference tube 14 being in the second state (liquid level B). Generally, the relative pressure (P / P0) of the nitrogen gas supplied to the sample tube 11 is changed to perform multiple measurements of the gas adsorption amount. Therefore, there are multiple measured conditions (liquid levels of liquid nitrogen), such as liquid levels B, C, D, ···. Additionally, when measuring the reference volume Vd st，ads and Vd ref，ads and the gas adsorption amount of the sample, the liquid levels of liquid nitrogen can be at a similar level, but it is difficult to maintain them exactly the same.

[0051] After the reference volume measurement processing unit 41 measures the reference volume Vd of the available space of the sample tube 11 at room temperature (temperature T RT ), it immerses the sample tube 11 and the reference tube 14 together in the liquid nitrogen filled in the refrigerant container 18 and cools them to the temperature T st，RT , and then calculates the reference volume Vd based on the pressure change before and after cooling ads . Similarly, the reference volume measurement processing unit 41 measures the reference volume Vd of the available space of the reference tube 14 at room temperature (temperature T st，ads RT ), and uses the reference volume Vd ref，RT to measure the reference volume Vd ref，RT . The reference volume measurement processing unit 41 saves, for example, the reference volume Vd ref，ads of the sample tube 11, such as Vd ref，RT , Vd ref，ads , Vd st，RT , Vd st，ads , the temperature T ads , T RT in the memory 47.

[0052] The reference volume measurement processing unit 41 can also immerse the sample tube 11 and the reference tube 14 in the liquid nitrogen and cool them to the temperature T ads , introduce nitrogen gas into the manifold 17 and measure the internal pressure using the pressure gauge 20, then introduce nitrogen gas into the sample tube 11 to measure the internal pressures of the manifold 17 and the sample tube 11, and calculate the reference volume Vd based on each measured value st，ads ​Similarly, the reference volume measurement processing unit 41 can also introduce nitrogen gas from the manifold 17 into the reference tube 14 cooled to the temperature T ads and measure the internal pressures of the manifold 17 and the reference tube 14 to calculate the reference volume Vd ref，ads .

[0053] When measuring the gas adsorption amount by the functions of the volume change amount calculation processing unit 42, the sample tube volume calculation processing unit 43, and the adsorption amount calculation processing unit 44, the sample tube 11 for which the reference volume Vd st，ads has been obtained and the reference tube 14 for which the reference volume Vd ref，ads has been obtained are used. Further, the volume change amount ΔVd ref(i) described later required for measuring the gas adsorption amount and the volume Vd st，ads(i) of the sample tube 11 are obtained under the actual measurement conditions in which the sample tube 11 containing the sample 1 and the empty reference tube 14 are respectively installed on the ports 56 and 59 and immersed in liquid nitrogen for cooling.

[0054] The control unit 40 calculates the volume change amount ΔVd ref，ads of the available space of the reference tube 14 based on the reference volume Vd ref，ads(i) of the available space of the reference tube 14 and the volume Vd ref(i) of the available space of the reference tube 14 under the actual measurement conditions of the gas adsorption amount. The calculation of the volume change amount ΔVd ref(i) is executed by the function of the volume change amount calculation processing unit 42. By measuring the volume change amount ΔVd ref(i) using the reference tube 14, the volume of the available space of the sample tube 11 can be accurately obtained under the actual measurement conditions where the liquid level of the liquid nitrogen is different from the calibration conditions.

[0055] The volume change amount calculation processing unit 42 measures the volume Vd ref，ads(i) of the available space of the reference tube 14 at each measurement point where the relative pressure (P / P0) of nitrogen gas is changed to measure the gas adsorption amount, and calculates the volume change amount ΔVd ref(i) . Further, since the liquid level of the liquid nitrogen in the refrigerant container 18 changes at each measurement point, the calculation of the volume change amount ΔVd ref(i) is also executed multiple times at different liquid levels. The volume change amount calculation processing unit 42 reads, for example, the reference volume Vd ref，ads from the memory 47 and calculates the volume change amount ΔVd ref(i) based on the internal pressures of the manifold 17 and the reference tube 14. The volume change amount ΔVd ref(i) is stored in the memory 47.

[0056] The control unit 40 calculates based on the volume change amount ΔVd ref(i) and the reference volume Vd st，ads, to calculate the volume Vd of the available space of the sample tube 11 under the actual measurement conditions st，ads(i) . The volume Vd st，ads(i) is calculated by the function of the sample tube volume calculation processing unit 43. The volume Vd st，ads(i) and the reference volume Vd st，ads The difference can be equivalently regarded as the volume change amount ΔVd of the reference tube 14 ref(i) , and the volume Vd can be calculated by the following formula 1 st，ads(i) .

[0057]

Equation 1

[0058] (Formula 1)

[0059] Vd st,ads(i) = Vd st,ads - ΔV ref(i)

[0060] The sample tube volume calculation processing unit 43 calculates the volume Vd at each measurement point for measuring the gas adsorption amount st，ads(i) . That is, similar to the volume change amount ΔVd ref(i) , the calculation of the volume Vd st，ads(i) is also performed multiple times in multiple states with different liquid nitrogen levels. The sample tube volume calculation processing unit 43 reads the volume change amount ΔVd ref(i) from the memory 47 and calculates the volume Vd st，ads(i) according to the above formula 1. The volume Vd st，ads(i) is stored in the memory 47 and can be used to calculate the gas adsorption amount of the sample 1. The volume Vd st，ads(i) can be said to be the reference volume of the sample tube 11 corrected by actual measurement at each measurement point.

[0061] The control unit 40 calculates the gas adsorption amount of the sample 1 based on the volume Vd st，ads(i) of the available space of the sample tube 11 under the actual measurement conditions and the volume Vd sam，ads(i) of the available space of the sample tube 11 containing the sample 1 under the actual measurement conditions. The calculation of the gas adsorption amount is performed by the function of the adsorption amount calculation processing unit 44. When measuring and calculating the gas adsorption amount of the sample 1, in addition to using the volume Vd st，ads(i) , the same method as before can be applied. The adsorption amount calculation processing unit 44 obtains the volume Vd st，ads(i) at each measurement point where the relative pressure (P / P0) of the nitrogen gas supplied to the sample tube 11 etc. is different, thereby calculating the adsorption isotherm of the sample 1.

[0062] The control unit 40 calculates the surface excess adsorption amount by excluding the volume of the sample 1 previously obtained from the volume of the available space of the sample tube 11 obtained during the calculation process of the gas adsorption amount. The calculation of the surface excess adsorption amount is performed through the function of the surface excess amount calculation processing unit 45. In the gas adsorption amount measuring device 10, the reference volume Vd of the available space of the sample tube 11 without the sample 1 loaded is used st，ads to measure the gas adsorption amount of the sample 1. Therefore, this adsorption amount is the net adsorption amount considering the volume of the sample 1. According to the gas adsorption amount measuring device 10, for example, the surface excess adsorption amount measured by a general measuring device can be easily calculated by subtracting the volume of the sample 1 from the volume Vd sam，ads(i) .

[0063] The surface excess amount calculation processing unit 45 calculates the volume Vd' of the available space of the sample tube 11 after excluding the volume of the sample 1 according to the following formula 2 sam，ads(i) .

[0064]

Equation 2

[0065] (Formula 2)

[0066]

[0067] In the formula, SW is the mass (g) of the sample 1, and ρ is the true density (g / cm 3 ). The true density of the sample 1 can be, for example, a literature value or a measured value of a true density measuring device. The mass and true density of the sample 1 can be input into the system in advance using an input device and stored in the memory 47. The surface excess amount calculation processing unit 45 reads the mass and true density of the sample 1 from the memory 47 and calculates the surface excess adsorption amount according to Formula 2.

[0068] Hereinafter, with reference to Figures 2 to 4 the measurement method of the gas adsorption amount using the gas adsorption amount measuring device 10 will be described in detail. Figure 2 is a simplified diagram of the structure diagram of Figure 1 for explaining the measurement method of the gas adsorption amount. Figure 3 is a flowchart showing an example of the measurement steps of the reference volume Vd st，ads of the available space of the sample tube 11 and the reference volume Vd ref，ads of the available space of the reference tube 14.

[0069] As Figure 2 shown, when measuring the gas adsorption amount of the sample 1 using the gas adsorption amount measuring device 10, the sample 1 ( Figure 2The sample tube 11 (not shown in the figure), the reference tube 14, and the saturated vapor pressure tube 15 are respectively installed on the piping section 16. The temperature of the manifold 17 serving as the reference volume section S (volume Vs) can be maintained at the temperature T by the above-described second device m , or it can be the room temperature T RT . Hereinafter, the case where the temperature of the manifold 17 is T m will be described as an example.

[0070] In the gas adsorption amount measuring device 10, before measuring the gas adsorption amount of the sample 1, the reference volume Vd of the available space of the sample tube 11 is first measured using nitrogen st，ads . The measurement of the reference volume Vd st，ads is performed using the empty sample tube 11 that does not contain the sample 1. In addition, while measuring the reference volume Vd st，ads , the reference volume Vd of the reference tube 14 is measured ref，ads . The reference volumes Vd st，ads , Vd ref，ads are measured in a state where the sample tube 11 and the reference tube 14 are immersed in liquid nitrogen, that is, at the adsorption temperature. The reference conditions for measuring the reference volumes Vd st，ads , Vd ref，ads are, for example, a state where the liquid level of the liquid nitrogen is at the liquid level A.

[0071] It is not necessary to perform the measurement of the reference volumes Vd st，ads , Vd ref，ads every time the gas adsorption amount is measured. It can be performed only once on the sample tube 11. Or it can be performed regularly. For example, it can be performed once within a specified period (for example, 1 year), or once every specified number of measurements (for example, every 100 measurements). In the past, it was necessary to measure the reference volume using helium every time the gas adsorption amount was measured, but according to the measurement method of the present invention, the number of measurements of the reference volume Vd st，ads can be greatly reduced, and the measurement time can be shortened.

[0072] In Figure 3 the example shown, the reference volumes Vd st，RT , Vd ref，RT of the sample tube 11 and the reference tube 14 measured at room temperature are used to calculate the reference volumes Vd st，ads , Vd ref，ads at the adsorption temperature (for example, the state of the liquid level A). In this case, thermal conversion correction can be performed to further improve the measurement accuracy.

[0073] In Figure 3 the example shown, first, the reference volume Vd of the available space of the reference tube 14 at room temperature (temperature T RT ) is measured ref，RT(S10 - S12). Additionally, the reference volume Vd of the sample tube 11 can also be measured first. st，RT .

[0074] First, use the exhaust pump 102 to evacuate the system including the internal space of the manifold 17, the sample tube 11, and the reference tube 14, and confirm that the vacuum degree reaches below the measurement lower limit of each pressure gauge. Then, close all the switching valves and zero all the pressure gauges. Next, open the switching valve 51 to introduce nitrogen into the manifold 17 as the reference volume part S (volume Vs). When the internal pressure of the manifold 17 reaches the specified value, close the switching valve 51. After that, when the pressure is stable, measure the internal pressure P of the manifold 17 using the pressure gauge 20. s，i (S10).

[0075] Next, open the switching valve 34 corresponding to the reference tube 14 to introduce the nitrogen in the manifold 17 into the reference tube 14. After allowing the nitrogen to diffuse in the reference tube 14 for a sufficient time (e.g., 5 seconds), close the switching valve 34. When the pressure is stable, measure the internal pressure P of the manifold 17 using the pressure gauge 20. s，e , and measure the internal pressure P of the reference tube 14 using the pressure gauge 24. ref，e (S11).

[0076] Based on the pressures measured in S10 and S11, the volume Vs of the manifold 17, and the temperature T m , calculate the reference volume Vd of the available space of the reference tube 14 at room temperature through the following formula. ref，RT (S12). The mass balance before and after introducing nitrogen into the reference tube 14 is represented by Equation 3, and the reference volume Vd at room temperature is calculated according to Equation 4. ref，RT .

[0077]

Equation 3

[0078] (Equation 3)

[0079]

[0080]

Equation 4

[0081] (Equation 4)

[0082]

[0083] The reference volume Vd ref，RT is the reference value of the available space of the reference tube 14 and is used to calculate the volume of the available space of the sample tube 11.

[0084] Next, for the sample tube 11, open the switching valve 31 corresponding to the sample tube 11 to introduce the nitrogen in the manifold 17 into the sample tube 11, close the switching valve 31, and when the pressure is stable, measure the internal pressure P of the sample tube 11 using the pressure gauge 21. st，e(S13). Then, using the same formula as Equation 4, calculate the reference volume Vd of the available space of the sample tube 11 at room temperature st，RT (S14).

[0085] Next, immerse the reference tube 14 and the sample tube 11 together in the liquid nitrogen filled in the refrigerant container 18 and cool them to the temperature T dads (S15). At this time, the pressures of the sample tube 11 and the reference tube 14 will change. When the pressure is stable, measure the internal pressure P of the reference tube 14 using the pressure gauge 24 ref，e(ads) (S16), and calculate the reference volume Vd of the available space of the reference tube 14 at the adsorption temperature (for example, the state of the liquid level A) according to the following formula ref，ads (S17). The mass balance caused by the pressure change before and after cooling the reference tube 14 is represented by Equation 5, and the reference volume Vd at the adsorption temperature is calculated by Equation 6 ref，ads .

[0086]

Equation 5

[0087] (Equation 5)

[0088] P ref,e Vd ref,RT =P ref,e(ads) Vd ref,ads

[0089]

Equation 6

[0090] (Equation 6)

[0091]

[0092] Then, for the sample tube 11, when the pressure is stable, measure the internal pressure P of the sample tube 11 using the pressure gauge 21 st，e(ads) (S18), and calculate the reference volume Vd of the available space of the sample tube 11 at the adsorption temperature through the same formula as Equation 6 st，ads (S19). In addition, while measuring the sample tube 11, the reference volumes of the sample tubes 12 and 13 can also be measured.

[0093] The steps of S10 to S19 are executed through the functions of the reference volume measurement processing unit 41. The reference volume measurement processing unit 41, for example, stores the reference volume Vd ref，ads , Vd st，ads , and the temperature T ads in the memory 47. In addition, the reference volume measurement processing unit 41 can also store the reference volume Vd ref，RT , Vd st，RT , and the temperature T RT in the memory 47.

[0094] When using other refrigerants 19 such as liquid argon to measure the gas adsorption amount, argon is required to measure the reference volume Vd ref，ads and Vd st，ads . In this case, for the sample tube 11, the reference volume measurement processing unit 41, in addition to referring to the library of liquid nitrogen (e.g., Vd ref，RT and Vd ref，ads (N2), Vd st，RT and Vd st，ads (N2), temperature T ads (N2)), also needs to refer to the library of liquid argon (e.g., Vd ref，RT and Vd ref，ads (Ar), Vd st，RT and Vd st，ads (Ar), temperature T ads (Ar)).

[0095] In addition, when the reference tube 14 is damaged or lost, the reference volume Vd ref，RT and Vd ref，ads can be measured for the new reference tube 14, and the difference between the measured value and the measured value of the previous reference tube 14 is applied to the reference volume of the measured sample tube. That is, there is no need to measure the reference volume of the sample tube again.

[0096] Figure 4 is a flowchart showing an example of the measurement steps of the gas adsorption amount of sample 1. The measurement of the gas adsorption amount of sample 1 is performed through the function of the adsorption amount calculation processing unit 44. In Figure 4 , the measurement steps of the net adsorption amount considering the volume of sample 1 are shown. However, for example, by subtracting the volume of sample 1 from the volume Vd sam，ads(i) , the surface excess adsorption amount can be easily calculated. The calculation of the surface excess adsorption amount is performed through the function of the surface excess amount calculation processing unit 45.

[0097] Generally, when measuring the gas adsorption amount of sample 1, pretreatment of sample 1 is required. The pretreatment is as follows: Load sample 1 into the sample tube 11 and heat it to a temperature at which the physical properties do not change under vacuum or in an inert gas stream. Connect the sample tube 11 containing the pretreated sample 1 to the port 56 and start the following measurement steps.

[0098] First, evacuate the system including the internal space of the manifold 17, the sample tube 11, the reference tube 14, and the saturated vapor pressure tube 15 using the exhaust pump 102, and confirm that the vacuum degree reaches below the measurement lower limit of each pressure gauge. Then, close all the switching valves and zero all the pressure gauges. Next, open the switching valve 51 to introduce nitrogen into the manifold 17, and close the switching valve 51 when the internal pressure of the manifold 17 reaches the specified value. After that, when the pressure is stable, measure the internal pressure P of the manifold 17 using the pressure gauge 20 s，i(1)(S20).

[0099] Next, introduce the nitrogen gas in the manifold 17 into the reference tube 14. After a specified time, close the switching valve 34. When the pressure stabilizes, measure the internal pressure P of the manifold 17 using the pressure gauge 20 s，e(1) , and measure the internal pressure P of the reference tube 14 using the pressure gauge 24 ref，e(1) (S21). Calculate the volume Vd of the available space of the reference tube 14 at room temperature using the following formula 7 ref，RT(1) (S22). Confirm Vd ref，RT(1) = Vd ref，RT . After that, it can be known that this reference tube 14 is the same as the reference tube 14 used to measure the reference volume of the sample tube 11.

[0100]

Equation 7

[0101] (Equation 7)

[0102]

[0103] When Vd ref，RT(1) is inconsistent with Vd ref，RT , the error is caused by, for example, the difference in the room temperature T RT during measurement and is usually negligible. Store the room temperature T RT during the measurement of the reference volume, and compare it with the room temperature T ref，RT(1) during the measurement of the volume Vd RT to correct the error caused by the change in the room temperature T RT .

[0104] Next, immerse the reference tube 14 and the sample tube 11 together in the liquid nitrogen filled in the refrigerant container 18 and cool them to the temperature T dads (S23). When the pressure stabilizes, measure the internal pressure P of the reference tube 14 using the pressure gauge 24 ref，e(ads1) (S24), and calculate the volume Vd of the available space of the reference tube 14 at the adsorption temperature using the following formula 8 ref，ads(1) (S25). The first measured condition when measuring the volume Vd ref，ads(1) is, for example, the state where the liquid level of the liquid nitrogen is at the liquid level B.

[0105]

Equation 8

[0106] (Equation 8)

[0107]

[0108] At this time, Vd ref，ads (1) ≠ Vd ref，ads, this difference is caused by the liquid level difference of liquid nitrogen (for example, the difference between liquid levels A and B). Then, the volume change rate ΔV of the available space of the reference tube 14 is calculated by the following formula 9 ref(1) (S26). The step of S26 is executed by the function of the volume change calculation processing unit 42.

[0109]

Equation 9

[0110] (Equation 9)

[0111] ΔV ref(1) =Vd ref,ads -Vd ref,ads(1)

[0112] Next, based on the volume change amount ΔVd ref(1) and the reference volume Vd of the sample tube 11 st，ads , the volume Vd of the available space of the sample tube 11 at the adsorption temperature (for example, the state of liquid level B) is calculated st，ads(1) (S27). The calculation of the volume Vd st，ads (1) is executed by the function of the sample tube volume calculation processing unit 43. The volume Vd st，ads(1) and the reference volume Vd st，ads(1) The difference can be equivalently regarded as the volume change amount ΔVd of the reference tube 14 ref(1) , so the volume Vd can be calculated by the following formula 10 st，ads(1 ).

[0113]

Equation 10

[0114] (Equation 10)

[0115] Vd st,ads(1) =Vd st,ads -ΔV ref(1)

[0116] Next, nitrogen is introduced into the sample tube 11 containing the sample 1 and the switch valve 31 is closed, so that nitrogen is adsorbed on the sample 1. When the sample 1 inhales nitrogen, it takes a specified time for the internal pressure of the sample tube 11 to reach the equilibrium state. Whether the equilibrium state is reached can be judged by continuous pressure change monitoring. In the equilibrium state, the internal pressure P of the sample tube 11 is measured by the pressure gauge 21 sam,e(ads1) (S28), the volume Vd of the available space of the sample tube 11 is calculated sam，ads(1) , and the gas adsorption amount of the sample 1 under the first measured conditions is calculated (S29).

[0117] The adsorption amount calculation processing unit 44 changes the relative pressure (P / P0) of the nitrogen supplied to the sample tube 11 and the like, thereby calculating the adsorption isotherm of the sample 1. That is, under multiple measured conditions with different relative pressures (P / P0) of nitrogen, the steps of S20 to S29 are executed multiple times.

[0118] In Figure 3 and Figure 4 In the example shown, the reference volume Vd at room temperature is measured st，RT 、Vd ref，RT , but it is also possible not to measure this reference volume, but only to use the reference volume Vd at the adsorption temperature st，ads 、Vd ref，ads to calculate the gas adsorption amount. Specifically, after immersing the sample tube 11 and the reference tube 14 in liquid nitrogen and cooling them to the temperature T ads , nitrogen is introduced into the manifold 17 and the internal pressure is measured. Then, nitrogen is introduced into the reference tube 14 and the internal pressures of the manifold 17 and the reference tube 14 are measured, and the reference volume Vd ref，ads (the same applies to the sample tube 11) is calculated based on each measured value.

[0119] As described above, according to the gas adsorption amount measuring device 10 and the above measuring method, it is possible to measure the reference volume Vd of the available space of the sample tube 11 using other adsorption gases instead of helium st，ads , and use this volume to perform high-precision gas adsorption amount measurement. It has been confirmed that the gas adsorption amount calculated based on the reference volume Vd st，ads measured using the adsorption gas is the same as the value of the gas adsorption amount calculated based on the reference volume measured using helium. That is, the above measuring method can measure the gas adsorption amount with the same degree of accuracy as the conventional measuring method using helium. Furthermore, according to the above measuring method, it is not necessary to measure the reference volume Vd every time the gas adsorption amount is measured as in the past st，ads , thereby shortening the measurement time.

[0120]

Symbol Explanation

[0121] 1, 2, 3 Samples; 10 Gas adsorption amount measuring device; 11, 12, 13 Sample tubes; 14 Reference tube; 15 Saturated vapor pressure tube; 16 Pipe section; 17 Manifold; 18 Refrigerant container; 19 Refrigerant; 20, 21, 22, 23, 24, 25 Pressure gauges; 31, 32, 33, 34, 35, 51, 54 On-off valves; 40 Control unit; 41 Reference volume measurement processing unit; 42 Volume change amount calculation processing unit; 43 Sample tube volume calculation processing unit; 44 Adsorption amount calculation processing unit; 45 Surface excess amount calculation processing unit; 46 Processor; 47 Memory; 50 First connection part; 52, 55 Flow rate adjustment valves; 53 Second connection part; 56, 57, 58, 59, 60 Ports; 56a, 57a, 58a, 59a, 60a Pipes; 100 Adsorption gas supply source; 101 Supply pipe; 102 Exhaust pump; 103 Exhaust pipe.

Claims

1. A gas adsorption amount measuring device, at least including a sample tube, supplying an adsorption gas to the sample tube, measuring the gas adsorption amount of a sample accommodated in the sample tube, and including: A reference tube for determining the volume of the available space of the sample tube; A piping section for connecting the sample tube, the reference tube, and the supply tube for the adsorbed gas; A pressure gauge for measuring the pressures of the piping section, the sample tube, and the reference tube; A device for maintaining the temperatures of the sample tube and the reference tube at a specified temperature; And, A control unit; Under calibration conditions, introducing the adsorbed gas into the sample tube and the reference tube without adding a sample to measure the pressures inside each of these tubes; Under calibration conditions, the control unit calculates, based on the pressure in each tube, the temperature of each tube, and the volume of the piping section, the reference volume Vd of the available space of the sample tube in which no sample is loaded st，ads and the reference volume Vd of the available space of the reference tube ref，ads ; Based on the reference volume Vd ref，ads and the volume Vd of the available space of the reference tube under the actual measurement conditions of the gas adsorption amount ref，ads（i） , calculate the volume change amount ΔVd ref（i） ; According to the volume change amount ΔVd ref（i） and the reference volume Vd st，ads , calculate the volume Vd of the available space of the sample tube under the measured conditions st，ads（i） ; Under the measured conditions, introduce the adsorbed gas into the sample tube containing the sample to measure the pressure therein, and calculate the volume Vd of the available space of the sample tube sam，ads（i） ; and based on the volume Vd st，ads（i） and the volume Vd of the available space of the sample tube containing the sample under the measured conditions sam，ads（i） , to calculate the gas adsorption amount of the sample under the measured conditions.

2. The gas adsorption amount measuring device according to claim 1, wherein, A plurality of the sample tubes are provided, The control unit calculates the reference volume Vd of a plurality of the sample tubes respectively using one of the reference tubes st，ads .

3. The gas adsorption amount measuring device according to claim 1 or 2, wherein, The control unit calculates the surface excess adsorption amount by excluding the volume of the sample obtained in advance from the volume of the available space of the sample tube obtained from the calculation process of the gas adsorption amount.

4. A gas adsorption amount measuring method for the gas adsorption amount measuring device according to claim 1, using at least one sample tube and a reference tube, the reference tube being used to determine the volume of the available space of the sample tube, the method, Under calibration conditions, introducing the adsorption gas into the sample tube and the reference tube without adding a sample to measure the pressure in each tube; Based on the pressure in each tube, the temperature of each tube, and the volume of the piping section, calculate the reference volume Vd of the available space of the sample tube without the sample loaded respectively st，ads and the reference volume Vd of the available space of the reference tube ref，ads ; Based on the reference volume Vd ref，ads and the volume Vd of the available space of the reference tube under the actual measurement conditions of the gas adsorption amount ref，ads（i） , calculate the volume change amount ΔVd ref（i） ; According to the volume change amount ΔVd ref（i） and the reference volume Vd st，ads , calculate the volume Vd of the available space of the sample tube under the measured conditions st，ads（i） ; Under the actual measurement conditions, introduce the adsorbed gas into the sample tube containing the sample to measure the pressure therein, and calculate the volume Vd of the available space of the sample tube sam，ads（i） ; and based on the volume Vd st，ads（i） and the volume Vd of the available space of the sample tube filled with the sample under the measured conditions sam，ads（i） , to calculate the gas adsorption amount of the sample under the measured conditions.

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