JP2008203154A - Gas adsorption characteristic measuring device for pore particulate, and measuring method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device with more improved reliability, capable of measuring gas absorption characteristics of pore particulates. <P>SOLUTION: The gas adsorption characteristic measuring device 1 comprises: an NMR magnet 5 for generating a fixed magnetic field; an NMR probe 7 in which a sample tube 3 containing pore particulates 6 of a measuring sample can be arranged, for transmitting a signal to the measuring sample and receiving a signal from the measuring sample; a nuclear magnetic resonance device 2 containing an NMR spectroscope 8 for measuring the signal received by the NMR probe; the sample tube 3 connected to a tube 10 with a high vacuum-proof cock 9 capable of controlling airtight; and a pressure-adjusting section 4 arranged in the NMR probe 7 for controlling a pressure in the sample tube 3. The pressure-adjusting section 4 includes, for example a pressure gauge 11, a probe molecule gas supply source 12, a dryer 13, and an evacuation system 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for measuring gas adsorption characteristics of fine pore particles and a measuring method thereof.

As a method for evaluating the surface characteristics such as the adsorption surface area and pore distribution of the fine pore particles, for example, the amount of adsorption of N ₂ gas is quantified by the volumetric method, and the adsorption isotherm obtained thereby is analyzed to obtain the surface characteristics. There is a way. In contrast to such a method, a method of evaluating surface characteristics by attracting a probe molecule to the surface of fine pore particles and measuring nuclear magnetic resonance (NMR) of the probe molecule has attracted attention. In particular, a method of observing ¹²⁹ Xe NMR by adsorbing Xe (xenon) is a method that has been expected since the 1980s as an evaluation method that can provide more information on the microenvironment. This is because the ¹²⁹ Xe chemical shift changes greatly reflecting the decrease in adsorption sharply. In addition, the recent hyperpolarization technology has made it possible to increase the sensitivity of ¹²⁹ XeNMR, and the expectations for its technological development are further expanding. Although there are not many examples of its application, several patents have been disclosed (for example, patents). Reference 1 and 2).
JP 2004-93187 A Japanese Patent Laying-Open No. 2005-30808

  Conventionally, in order to determine the adsorption surface area of fine pore particles, a method using a BET adsorption device has been widely used. However, this method can only provide data on the adsorption surface area, and in order to obtain adsorption energy (adsorption heat), Another method such as a calorimeter method must be used, and the handling of the sample is complicated, and it takes a long time for measurement as a whole, which is problematic in terms of efficiency.

On the other hand, it is difficult to say that a technique for analyzing the surface characteristics of fine pore particles using the signal intensity and chemical shift of ¹²⁹ XeNMR has been well established. For example, handling of a sample for measuring surface characteristics may not provide accurate data with conventional methods. This is because the conventional method is insufficient to ensure the airtightness of the sample and often sensitively reflects subtle changes in the pore surface due to the incorporation of moisture in the air. That is, in the observation of adsorbed probe molecules by spectroscopic methods, modification of the adsorbed surface due to contamination with moisture or the like may cause a much larger change in spectroscopic data such as the chemical shift of adsorbed molecules than the amount of adsorption. . Therefore, when measuring surface characteristics using NMR for probe molecule detection such as ¹²⁹ XeNMR, there is a problem that the airtightness of the measurement sample must be made more reliable.

In addition, for example, when the adsorption surface area is obtained by NMR for probe molecule detection of ¹²⁹ XeNMR, it is necessary to obtain calibration data. Conventionally, however, it is necessary to replace the sample tube in order to measure the calibration sample. There is a problem that there is no way to accurately calibrate the intensity.

As methods for obtaining the adsorption energy (heat of adsorption) by NMR for probe molecule detection such as ¹²⁹ XeNMR, two methods using the following formula [1] or [2] have been proposed. The following equation [1] is an equation relating the chemical shift δ _obs of the probe molecules adsorbed on the pore surface of the measurement sample and the adsorption heat ΔH (VT Terskikh et al, J. Chem. Soc., Faraday Trans., 89, 4239-4243, 1993). In the following formula [1], δ _a is an adsorption intrinsic chemical shift, which is a chemical shift of the probe molecule when the probe molecule is on the pore surface, and V and S are the cavity volumes in the pore, respectively. And K ₀ is a Henry equation constant, R is a gas constant, and T is an absolute temperature.

The following formula [2] shows that the energy difference ΔE between the gas state and the adsorption state in the pore is expressed by the intrinsic chemical shift δ _f of the gaseous probe molecule in the pore and the probe molecule adsorbed on the surface. It is _a formula relating to the intrinsic chemical shift δ _a (QJ Chen and J. Fraisard, J. Phys. Chem., 96, 1809-1414, 1992).

However, there are few reports of the heat of adsorption ΔH obtained using the above equation [1], and reliability has not been established. Further, the above formula [2] have been reported value of applied ΔE = 5.5kJ / mol in the ¹²⁹ Xe NMR, this value is considerably smaller than the heat of evaporation 12.6kJ / mol of Xe itself, After all it cannot be said that the reliability is high. In these methods, _a constant value independent of temperature is used as the adsorption intrinsic chemical shift δ _a . For example, the value of 243 ppm reported for zeolites with low alumina content (J. Demarquay and J. Fraisard, Chem. Phys. Lett., 136, 314-318, 1987) is often used. In addition, there is a report that a value of 115 ppm or a value (107-160 ppm) that is the lowest value among the values measured for individual samples was used. That is, since the value of the adsorption intrinsic chemical shift δ _a of probe molecules such as ¹²⁹ Xe is a chemical shift of the interaction system, the temperature dependence should not be taken into consideration. There is a problem that the value of δ _a is constant regardless of the temperature.

In addition, a method for evaluating the chemical shift δ _obs of adsorbed ¹²⁹ Xe and the following formula [3] has been proposed (J. Demarquay and J. Fraisard, Chem. Phys. Lett., 136, 314- 318, 1987), the general applicability of this method is said to be problematic. Also in this method, an adsorption intrinsic chemical shift δ _a = 243 ppm is used. In the following formula [3], L is an average free process of collision with the wall, L = D _C −D _Xe in the infinite length cylindrical cavity, and L = (D _S − in the spherical cavity. D _Xe ) / 2 (D _C and D _S are the cavity diameters, and D _Xe is the diameter of the Xe atoms).

  Accordingly, an object of the present invention is to provide an apparatus capable of measuring gas adsorption characteristics of fine pore particles with improved reliability.

In order to achieve the above object, the gas adsorption property measuring apparatus for fine pore particles of the present invention comprises:
An NMR magnet that generates a constant magnetic field, an NMR probe that can arrange a sample tube containing pore microparticles as a measurement sample, and transmit a signal to the sample and receive a signal from the sample, And a nuclear magnetic resonance apparatus including an NMR spectrometer for measuring a signal received by the NMR probe, the sample tube connected to a tube having a high vacuum resistant cock and capable of airtight control, and disposed in the NMR probe. A pressure adjusting unit that controls the pressure in the sample tube, and the NMR probe includes a temperature adjusting unit that controls the temperature in the sample tube disposed therein, and the pressure adjusting unit includes a pressure gauge, The sample tube disposed in the NMR probe includes a probe molecular gas supply source and an evacuation system, and can be connected to the pressure adjusting unit via the high vacuum resistant cock. And this and features.

^In the observation of surface property measurement using a spectroscopic method such as NMR for probe molecule detection such as ¹²⁹ XeNMR, the necessity of pretreatment for high temperature heating has been known. However, the present inventors have noted that, for example, modification of the adsorption surface due to contamination with moisture or the like can cause a much larger change to spectroscopic data such as the chemical shift of the adsorbed molecule than to change the amount of adsorption. . In addition, in order to obtain more reliable measurement data, it has been found that it is important to perform a pretreatment for high-temperature heating, which has been conventionally performed, under a high vacuum. Then, the present inventors can strictly ensure the airtightness of the measurement sample from pretreatment to measurement, and if it is a measurement device that can use a sample tube that can withstand high vacuum, The inventors have found that the reliability of measurement data can be improved, and have reached the present invention.

  In the gas adsorption property measuring apparatus of the present invention, since the sample tube is connected to a tube having a high vacuum resistant cock and can be hermetically controlled, pretreatment can be performed under high vacuum, and after the pretreatment. The NMR for probe molecule detection can be measured without mixing outside air. Therefore, according to the present invention, the reliability of the measurement of the surface characteristics of the fine pore particles can be preferably improved.

In the gas adsorption property measuring apparatus of the present invention, the sample tube is connected to the pressure adjusting unit in a state of being arranged in the NMR probe of the nuclear magnetic resonance apparatus, and the NMR probe further connects the temperature adjusting unit. Since it is provided, for example, one sample can be measured under various temperature and pressure conditions without moving the sample tube. This makes it possible to evaluate the temperature dependence of the adsorption intrinsic chemical shift δ _a of the probe molecule, as will be described later. Therefore, according to the present invention, the reliability and simplicity of the measurement of the surface characteristics of the fine pore particles can be preferably improved.

In addition to ¹²⁹ Xe, the gas adsorption property measuring apparatus of the present invention includes a fluorine-based gas (tetrafluoromethane CF ₄ or the like) containing ³ He and ¹⁹ F, and a carbon-based gas (carbon dioxide gas) containing ¹³ C. such as ¹³ CO _2), and, the probe molecule selected from the nitrogen-based gas containing ¹⁵ N (such as ammonia gas ¹⁵ NH _3), preferably, be used. In general, the change in chemical shift due to adsorption is less than ¹²⁹ Xe for ³ He, but it is applicable if the adsorption peak is observed separated from the gaseous peak. Like ¹²⁹ Xe, these probe molecules can achieve high sensitivity by using hyperpolarization technology, and can be reduced in volume and speeded up.

  The present invention can be preferably used for the analysis and evaluation of the pore surface characteristics of a product including, for example, the development and production of a product containing fine pore particles. For example, when improving characteristics such as the touch, whiteness, and brightness of powder cosmetics, an improvement guideline may be obtained by analyzing and comparing pore surface characteristics. In addition, for example, in the zeolite industry, it can be applied to the characteristic analysis of a product newly developed as a catalyst or reaction medium, and further development can be promoted. Furthermore, it can also be used, for example, for product quality confirmation at the manufacturing stage.

  The gas adsorption characteristic measuring device of the present invention further includes a pretreatment device for the sample, and the pretreatment device includes the heater capable of arranging the sample tube therein, and the high vacuum resistant cock through the heater. It is preferable that the high vacuum exhaust part connectable with a sample tube is included. According to such a pretreatment apparatus, for example, the sample can be pretreated by heating at a high temperature under high vacuum.

  In the gas adsorption property measuring apparatus of the present invention, it is preferable that the sample tube includes a standard sample holding portion in which a calibration standard sample can be arranged at a position spatially separated from the measurement sample inside. By providing such a standard sample holder, for example, the measurement sample and the standard sample can be sealed in the sample tube from the pretreatment stage, and destruction of the standard sample due to high heat can be avoided.

  The gas adsorption characteristic measuring apparatus of the present invention further includes a control unit for controlling the temperature and pressure in the sample tube in a state of being arranged in the NMR probe by controlling the temperature adjusting unit and the pressure adjusting unit. Is preferred.

  It is preferable that the gas adsorption property measuring apparatus of the present invention further includes a data processing unit that processes the signal data measured by the NMR spectrometer.

The data processing unit calculates at a temperature T ₁ by a least square method based on chemical shift versus pressure data δ _obs (P) measured under a plurality of pressure conditions and a constant temperature T ₁ and the following equation [10]. The step of obtaining the adsorption intrinsic chemical shift δ _a (T ₁ ), in the same manner as in the previous step, δ _a (T ₂ ) to δ _a (T ₅ ) at at least four temperatures T _{2 to} T ₅ different from T ₁ obtaining a), and the _{δ a (T 1) ~δ a} (T 5) of at least 5 points including adsorption specific chemical shifts based on [delta] _a suction specific chemical shifts [delta] _a linear function of the temperature of the; [delta] _a ( T) = aT + b (where a and b are constants) may be performed. By using the following formula [10], for example, the adsorption intrinsic chemical shift δ _a can be evaluated from the chemical shift data of the pressure-dependent probe molecule, and further, for example, the temperature dependence of the adsorption intrinsic chemical shift δ _a is considered. The surface adsorption characteristics can be analyzed.

（上記式［１０］中、ｃｏｎｓｔは、積分のときの定数を表す。）

(In the above equation [10], const represents a constant at the time of integration.)

In addition, the data processing unit calculates based on the chemical shift versus pressure data δ _obs (P) measured under an arbitrary temperature and a plurality of pressure conditions and the following equations [13] and [14] to obtain the adsorption energy. A process including a step of obtaining the corresponding βE ₀ may be performed. With such a process, for example, the adsorption energy can be evaluated from chemical shift data at an arbitrary temperature and pressure.

（上記式［１３］、［１４］中、ｗ_aは圧力Ｐのときの吸着量を表し、ｗ₀は飽和吸着量を表し、Ｐ_eqはその時の相当圧力を表す。）

(In the above formulas [13] and [14], w _a represents the adsorption amount at the pressure P, w ₀ represents the saturated adsorption amount, and P _eq represents the equivalent pressure at that time.)

In addition, the data processing unit calculates by the least square method based on the signal intensity data versus pressure S (P) measured under a plurality of pressure conditions at a constant temperature and the following equation [12], and completes the coverage. obtaining a signal strength S _∞ steps, and the S _∞ and the a calibration data measured from the standard sample S (P _CA) / S _std and the following formula [19 '] and per unit mass calculated by based on The process including the step of obtaining the adsorption surface area A may be performed. With such processing, for example, the adsorption surface area can be evaluated only from signal intensity data without using chemical shift data.

（上記式［１９’］中、Ｃ_stdは前記標準試料中のプローブ分子濃度を表し、Ｖ_stdは前記標準試料の容積を表し、Ｓ_Prは１モルのプローブ分子相当の表面積を表し、Ｗ_sampleは測定試料の質量を表す。）

(In the above formula [19 ′], C _std represents the concentration of the probe molecule in the standard sample, V _std represents the volume of the standard sample, S _Pr represents the surface area equivalent to 1 mol of the probe molecule, and W _sample Represents the mass of the measurement sample.)

In addition, the data processing unit calculates signal intensity versus pressure data S (P) measured under an arbitrary temperature and a plurality of pressure conditions, and sets w _a / w ₀ to S (P) / S in the following formula [13]. obtaining a signal strength S _∞ of calculated by the least squares method on the basis of the replaced and expressions _∞ when the corresponding beta E ₀ and completely covered in adsorption energy, and calibration the measured from S _∞ and the standard sample A process including a step of obtaining an adsorption surface area A per unit mass by calculation based on data S (P _CA ) / S _std and the following equation [19 ′] may be performed. With such processing, for example, adsorption energy and adsorption surface area can be evaluated from signal intensity data at an arbitrary temperature and pressure.

（上記式［１３］中、ｗ_aは圧力Ｐのときの吸着量を表し、ｗ₀は飽和吸着量を表し、Ｐ_eqはその時の相当圧力を表す。また、上記式［１９’］中、Ｃ_stdは前記標準試料中のプローブ分子濃度を表し、Ｖ_stdは前記標準試料の容積を表し、Ｓ_Prは１モルのプローブ分子相当の表面積を表し、Ｗ_sampleは測定試料の質量を表す。）

(In the above formula [13], w _a represents the adsorption amount at the pressure P, w ₀ represents the saturated adsorption amount, and P _eq represents the equivalent pressure at that time. Also, in the above formula [19 ′], C _std represents the probe molecule concentration in the standard sample, V _std represents the volume of the standard sample, S _Pr represents the surface area equivalent to 1 mol of probe molecules, and W _sample represents the mass of the measurement sample.)

  In another aspect, the present invention is a method for measuring gas adsorption characteristics of fine pore particles, wherein the fine pore particles, which are measurement samples, are pretreated by heating in a sample tube capable of airtight control under high vacuum. A step of placing the sample tube in an NMR probe of a nuclear magnetic resonance apparatus while maintaining the airtight state of the sample tube, and introducing a probe molecular gas into the sample tube disposed in the NMR probe. Adjusting the pressure; adjusting the pressure of the probe molecular gas while the sample tube is set on the NMR probe; and measuring nuclear magnetic resonance at at least two pressures; and the nuclear magnetic resonance apparatus And a process for processing the signal data measured in step (b).

  The gas adsorption property measuring method of the present invention includes a step of placing a calibration standard sample in a portion in the sample tube that is not directly heated in the pretreatment step before the pretreatment step, and after the pretreatment step, Before the step of placing the sample tube in the NMR probe, the method may include a step of moving the standard sample to the same site as the measurement sample while maintaining the airtight state of the sample tube. By including such steps, the standard sample can coexist with the measurement sample in the sealed sample tube from the pretreatment stage. The calibration standard sample may be an ampoule of a solution containing a probe molecule and a known concentration of an inclusion compound.

  In the gas adsorption property measuring method of the present invention, the signal data processing step may be a data processing step in the data processing unit of the gas adsorption property measuring apparatus of the present invention.

  In another aspect, the present invention provides a method for producing a product containing fine pore particles, the gas adsorption characteristic measuring device of the invention or the gas of the fine pores using the gas adsorption characteristic measuring method of the invention. Provided is a production method including a step of measuring adsorption characteristics.

  In the present invention, the “pore fine particles” are selected from the group consisting of, for example, a polymer material, a carbon material system, a metal system, a metal oxide system, and a porous material of a mixture thereof. For example, examples of the fine pore particles include zeolite, silica gel, mesoporous material, alumina, activated carbon and the like. The particle diameter of the fine pore particles is not particularly limited as long as it falls within the range of the sample tube, and is, for example, 5 μm to 8 mm. The pore diameter of the fine pore particles is not particularly limited, and is, for example, 0.3 nm to 500 nm.

In the present invention, the “probe molecule” is a molecule that is adsorbed on the surface of a pore and contains a nuclide that can be detected by NMR in a part of the molecule, for example, ¹²⁹ Xe, ³ He, Examples include molecules containing nuclides such as ¹⁹ F, ¹³ C, and ¹⁵ N. In the present invention, the “probe molecular gas” is a gas used for the purpose of adsorption among the molecules of the probe. For example, Xe (xenon) gas, He (helium) gas, CF ₄ , Examples thereof include fluorine-based gases such as SF ₆ , carbon-based gases such as CO ₂ , nitrogen-based gases such as NH ₃ , and hyperpolarized gases thereof. It is preferable to use a hyperpolarized gas because higher sensitivity and speed can be achieved. Furthermore, in the present invention, “NMR for detecting a probe molecule” is a nuclear magnetic resonance spectroscopy that detects a signal of the probe molecule, and includes, for example, a ¹²⁹ Xe signal, a ³ He signal, a ¹⁹ F signal, a ¹³ C signal, This refers to observing signals, ¹⁵ N signals, etc. with a nuclear magnetic resonance apparatus.

In the present invention, “gas adsorption property” means a spectrum obtained by NMR for probe molecule detection and / or FID (free induction decay) or echo signal, and chemical shift, adsorption surface area, Includes adsorption energy, pore distribution, etc. In the present invention, “chemical shift δ _obs of adsorbed probe molecule” refers to a chemical shift of a peak other than a peak in a pure gas state of 0 ppm among peaks observed in an NMR spectrum. adsorption specific chemical shifts [delta] _a "is of an inherent chemical shift in the state where the probe molecule is completely adsorbed bound to pore surfaces, the coverage is equivalent to [delta] _obs when the 1, if indicated by the coverage It means the value.

In the present invention, “high vacuum” is 10 ⁻² Pa or less, preferably 10 ⁻³ Pa to 10 ⁻² Pa, and more preferably 10 ⁻⁵ Pa to 10 ⁻⁴ Pa. . In the present invention, "vacuum", for example, there is 10 ^-1 Pa or less, ^{preferably, 0.5 × 10 -1 Pa~10 -1 Pa} .

  Hereinafter, a device for measuring gas adsorption characteristics of fine pore particles according to the present invention will be described based on an embodiment shown in FIGS.

  The gas adsorption characteristic measuring apparatus 1 shown in FIG. 1 can arrange an NMR magnet 5 that generates a constant magnetic field and a sample tube 3 containing fine pores 6 that are measurement samples in the measurement sample 6. A nuclear magnetic resonance apparatus 2 that includes an NMR probe 7 that transmits the signal and receives a signal from the measurement sample 6, a NMR spectrometer 8 that measures the signal received by the NMR probe 7, and a high vacuum resistance The sample tube 3 is connected to a tube 10 having a cock 9 and capable of airtight control, and a pressure adjusting unit 4 that controls the pressure in the sample tube 3 disposed in the NMR probe 7. The NMR probe 7 includes a temperature adjusting unit (not shown) that controls the temperature in the sample tube 3 disposed therein, and the pressure adjusting unit 4 includes a pressure gauge 11 and a probe molecular gas supply. The sample tube 3, which includes a source 12, a dryer 13, and an evacuation system (indicated by an arrow 14) and is disposed in the NMR probe 7, is connected to the pressure adjusting unit 4 via the high vacuum resistant cock 9. Connected.

  1 includes a data processing unit 15 for processing signal data measured by the NMR spectrometer 8 and a control unit 16. The control unit 16 controls at least one of the nuclear magnetic resonance apparatus 2, the temperature adjustment unit, and the pressure adjustment unit 4. One end of the tube 10 is detachably connected to the sample tube 3 by a high vacuum resistant joint 17 and the other end is detachably connected to the pressure adjusting unit 4 by a high vacuum resistant joint 18. . The pressure adjusting unit 4 includes cocks 19 to 23 for purging with a probe molecular gas under vacuum.

  As the NMR magnet 5 and the NMR spectrometer 8 in the nuclear magnetic resonance apparatus 2 of the gas adsorption property measuring apparatus 1 of the present invention, those included in a known nuclear magnetic resonance apparatus can be used. Also, the NMR probe 7 can be a known one as long as it includes an NMR probe having a temperature adjustment unit, and those skilled in the art can attach a temperature adjustment unit to a conventional NMR probe. Is easy. The adjustable temperature range of the temperature adjusting unit is, for example, −70 ° C. to + 70 ° C., and preferably −150 ° C. to + 100 ° C. As the data processing unit 15 and the control unit 16, the same or separate computers can be used.

  FIG. 2 shows an embodiment of the pretreatment apparatus of the present invention. In the figure, the same parts as those in FIG. 2 includes a heater 31 capable of disposing the sample tube 3 therein, and a high vacuum evacuation unit 32 connectable to the sample tube 3 via the high vacuum resistant cock 9.

  The high vacuum exhaust unit 32 is for heating the measurement sample 6 at a high temperature under high vacuum. For example, as shown in FIG. 2, the cooling unit 33, the liquid reservoir 34, the high vacuum resistant cocks 35, 36, And the thing containing the high vacuum exhaust system 37 is mention | raise | lifted. The water evaporated from the sample 6 by the high-temperature heating of the heater 31 can be cooled by the cooling unit 33 to be liquid or solid. The liquid reservoir 34 can be used, for example, for measuring the amount of water obtained from the sample 6. The sample tube 3 including the pre-processed sample 6 can be kept airtight by the high vacuum resistant cock 9, separated by the high vacuum resistant joint 18, and directly transferred to the gas adsorption characteristic measuring apparatus 1 shown in FIG. 1.

Surface characteristics obtained by NMR for probe molecule detection such as ¹²⁹ Xe NMR due to adsorption of moisture in the air for fine pore particles, especially materials with small pore diameters such as zeolite and mesoporous silica (mesoporous material) The present inventors have found that changes or deteriorates significantly (for example, see Example 1). Therefore, the gas adsorption property measuring device 1 and the pretreatment device 2 of the present invention have a structure that prevents the measurement sample 6 from being exposed to the outside air from the pretreatment to the subsequent NMR measurement for probe molecule detection. .

  Examples of the pretreatment for measuring the pore material generally include firing at 300 ° C. for 2 hours or more under a vacuum or inert gas flow, which is a condition recommended by the Catalytic Society of Japan. However, in order to improve the reliability of NMR measurement data for probe molecule detection, it is important to carry out under high vacuum. Therefore, the sample tube 3, the tube 10, the joints 17 and 18, the cocks 9, 35, and 36, and other tubes and devices used in the pretreatment apparatus of the present invention shown in FIG. 2 must be able to withstand high vacuum conditions. The high vacuum exhaust system 37 preferably includes a vacuum pump capable of high vacuum or higher. On the other hand, the evacuation system 14 in the pressure adjusting unit 4 of FIG. 1 only needs to be able to be vacuumed or higher, and the member of the pressure adjusting unit 4 that can withstand the degree of vacuum can be used. The tube including the tube 10 shown in FIGS. 1 and 2 may be made of glass (for example, Pyrex (registered trademark) tube).

  One embodiment of the sample tube 3 is shown in FIG. The sample tube 3 in FIG. 3 includes a distal end portion 43 and a connection portion 42. In the figure, the same parts as those in FIGS. The tip portion 43 may have the same composition and form as a glass tube used as a normal NMR sample tube. For example, a glass tube having an outer diameter of about 3 to 15 mm and a wall thickness of 0.2 to 0.6 mm can be used. The connecting portion 42 is preferably thicker for connection with the joint 17, and preferably has a thickness of 1.0 to 2.0 mm, for example. Further, the sample tube 3 of FIG. 3 preferably includes a standard sample holder 41. Thus, the measurement sample 6 can be pretreated while the ampule 40 of the calibration standard sample that cannot withstand the high temperature heat treatment of the pretreatment is present at a position that does not enter the heater 31 in the sample tube 3. It becomes possible. After pre-processing, the standard sample ampoule 40 is moved so as to be buried in the measurement sample 6, and the sample tube 3 is placed in the NMR probe 7 for measurement, thereby enabling signal calibration as will be described later. . The shape of the standard sample holder 41 is not particularly limited as long as the standard sample ampoule 40 can be temporarily held in the vertical or inclined sample tube 3.

  After the pretreatment, the probe molecular gas is introduced from the gas supply source 12 through the dryer 13 into the sample tube 3 disposed in the NMR probe 7 in a vacuum state. By passing the dryer 13, it is possible to prevent the sample molecular gas from being mixed even when moisture is contained in the probe molecular gas. Therefore, it is preferable that the pressure adjusting unit 4 includes a dryer 13. However, when carbon dioxide is used as the probe molecular gas, it reacts with a desiccant as described later, and therefore it is preferable to supply the gas without passing through the dryer 13. The probe molecule gas supply source 12 is not particularly limited as long as it can supply a probe molecule gas or a hyperpolarized probe molecule gas. As the dryer 13, for example, an alloy of K and Na liquefied or a commercially available strong gas drying set (trade name: Mini Fine Purer, manufactured by Liquid Gas Co., Ltd.) can be used. The pressure gauge 11 is not particularly limited, and for example, a digital pressure gauge or other pressure gauge can be used. The bypass of the dryer 13 in FIG. 1 also directly uses the gas of the gas supply source 12 for purging (removing) trace moisture adhering to the inner surface of the pipe by filling the probe molecular gas before the measurement into the pipe, for example. It is possible to do.

  Therefore, in another aspect, the present invention provides a step of pre-treating the fine pores 6 as a measurement sample by heating them under high vacuum in a sample tube 3 capable of airtight control, While maintaining the state, the step of arranging the sample tube 3 in the NMR probe 7 of the nuclear magnetic resonance apparatus 2, and introducing the probe molecular gas into the sample tube 3 arranged in the NMR probe 7 to adjust the pressure. A step of adjusting the pressure of the probe molecular gas while the sample tube 3 is set on the NMR probe 7 and measuring nuclear magnetic resonance at at least two pressures; and the nuclear magnetic resonance apparatus 2 A method for measuring gas adsorption characteristics, including a step of processing measured signal data. The gas adsorption characteristic measuring method of the present invention can be performed using the gas adsorption characteristic measuring apparatus of the present invention. In the step of adjusting the pressure by introducing the probe molecular gas, the probe molecular gas is preferably introduced through the dryer 13 when the probe molecular gas other than carbon dioxide is used as described above. .

Next, a preprocessing method in the present invention will be described. As described above, the preprocessing can be performed using, for example, the preprocessing apparatus of FIG. The pressure in the sample tube in the pretreatment is, for example, 10 ⁻² Pa or less, preferably 10 ⁻⁴ Pa to 10 ⁻² Pa, more preferably 10 ⁻⁵ Pa to 10 ⁻⁴ Pa. As temperature which heats a measurement sample, it is 300 degreeC, for example, Preferably, it is 300 to 400 degreeC, More preferably, it is 400 degreeC. Moreover, as time to heat the said temperature, it is 5 hours or more, for example, Preferably, it is 5 to 8 hours, More preferably, it is 8 hours. The amount of the measurement sample placed in the sample tube is 10 mg to 200 mg, preferably 30 mg to 150 mg, more preferably 100 mg to 150 mg. However, it is preferable that the amount of the sample does not exceed the range of the transmission / reception coil. When the hyperpolarized noble gas is used, the amount of the sample can be reduced to 1/10 or less.

  Hereinafter, a calibration standard sample and a method for calibrating NMR signal intensity using the same in the present invention will be described using an embodiment using Xe gas as a probe molecule gas.

The NMR signal intensity, whether spectral intensity, FID or echo signal, is proportional to the number of target spins in the receiving coil when measured under ideal conditions without the influence of saturation. If so, the absolute number of spins can be measured. In the measurement of the adsorption surface area using Xe, the adsorption surface area can be obtained by calculating the number of Xe adsorbed on a certain amount of sample from the signal intensity and multiplying it by the cross-sectional area corresponding to one Xe atom. . However, it is necessary to obtain the signal intensity from the experimental results when the surface is completely covered by single-layer adsorption, that is, when the coverage ratio θ = 1. The following conditions 1) to 4) are listed as conditions to be satisfied by the signal intensity calibration standard sample.
1) Instead of exchanging the sample tube and measuring the measurement sample and the calibration standard sample separately, the calibration standard sample and the measurement sample are put together in the sample tube. This is because it is preferable to measure at the same time because the calibration accuracy becomes higher.
2) The calibration standard sample is put together in the NMR sample tube at the stage of the pretreatment of the measurement sample, and after the pretreatment, the measurement sample is directly subjected to NMR measurement without being exposed to air. This is because loss of the effect of the pretreatment can be prevented.
3) The calibration standard sample should not give a signal to the gas signal (0 ppm). Moreover, the thing which does not overlap with the adsorption | suction signal of a measurement sample is good. At the time of ¹²⁹ Xe NMR observation of the measurement sample, since Xe gas is filled, gas signals are usually observed in addition to the adsorption signal. Therefore, if the gas signal is a standard sample for calibration, it overlaps with the filled gas signal. This is because calibration becomes difficult. However, as will be described later, when both signals can be clearly separated using waveform processing (for example, deconvolution), even if the signals overlap, they can be effectively used as a calibration standard sample.
4) The Xe concentration of the calibration standard sample can be accurately predicted.

  An example of the calibration standard sample that satisfies the above conditions is an Xe solution encapsulated. If the gas is simply blown into the solvent and dissolved, the concentration cannot be determined, and it is necessary to calibrate by a special method separately as described later. The guest molecule which is an inclusion partner is not particularly limited, and examples thereof include α-cyclodextrin, cryptophan A, and calixarene. Calixallene is preferable in that the inclusion phenomenon with Xe in an aqueous solution has been examined in detail by NMR (J. Fukutomi et al., J. Inc1. Phen. Macrocyc. Chem., Published online, 2006). Cryptophan A is preferable in that the equilibrium constant is 3000 l / mol or more. Therefore, the standard sample for calibration in the present invention is one in which Xe gas is blown into a guest molecule solution (α-cyclodextrin is water and cryptophan A is an organic solvent) whose concentration is measured, and a certain amount is enclosed in a glass ampule. can give.

An example of determining the total Xe concentration in a glass ampoule of calixarene clathrated with Xe is shown below. Since Xe and calixarene (abbreviated as CD in the following formula) form a 1: 1 inclusion complex, Xe + CD = Xe · CD. When this equilibrium constant is K, the following formula [4] is obtained, and the observed chemical shift δ _obs of ¹²⁹ XeNMR is given by the following formula [5], so the following formula [6] is obtained from both formulas.

Here, in the above formulas [5] and [6], δ _Xe and δ _{Xe · CD} are chemical shifts in the solution of free Xe and clathrate Xe, respectively. In an aqueous solution at 25 ° C., δ _Xe = 182 ppm, δ _{Xe · CD} = 135 ppm, and [Xe] = 4.37 mM. Therefore, [Xe] is calculated from δ _{obs of the} calibration standard sample using the above equation [6]. CD] is obtained, and as a result, the total concentration of Xe can be obtained from [Xe] + [Xe · CD].

As another embodiment of the calibration standard sample, a solution in which a probe molecule is simply dissolved in a solvent is sealed in a glass ampule. When using such a calibration standard sample, for example, put it in an NMR sample tube together with a certain amount of the above clathrate solution, and obtain the concentration of the probe molecule dissolved in the solvent from the signal intensity ratio, etc. Then, the probe molecule concentration in the ampoule is measured. Or you may use the glass ampule by which the probe molecule concentration was measured in this way as a calibration standard sample of this invention. A calibration standard sample in which an appropriate probe molecule is dissolved can be selected and used corresponding to the nuclide contained in the probe molecule such as ¹²⁹ Xe, ³ He, ¹⁹ F, ¹³ C, and ¹⁵ N.

The calibration standard sample ampoule of the present invention preferably further includes a relaxation reagent such as a radical. Consideration of relaxation time (T ₁ ) is necessary for accurate measurement of signal strength. If the waiting time for repeated measurement is not made about 10 times longer than T ₁ , the strength is distorted due to saturation. Here, there is a problem that T ₁ of Xe of the clathrate used for calibration is as long as about 20 seconds. Therefore, the relaxation time can be shortened by adding a relaxation reagent such as a radical. In the case of a calibration standard sample using an inclusion body, the relaxation reagent is not particularly limited, and examples thereof include a nitroxide radical (TEMPO or 3-carbamoyl-PROXYL) having a relatively large molecular diameter. . Those incorporated into the clathrate, such as paramagnetic metal ions such as Mn ^2+, may be inconvenient. When a probe molecule such as Xe or He dissolved in a specific solvent is used as a calibration standard sample, examples of the relaxation reagent include Cr (acac) ₂ , Fe (acac) ₃ , Cr (dpm) _3. And paramagnetic relaxation reagents.

  It is difficult to add a calibration standard sample in the form of a glass ampoule to a measurement sample in the pretreatment stage. This is because the pretreatment is performed at a very high temperature as described above. Therefore, in the pretreatment stage, for example, it is preferable that the ampoule is placed in the standard sample holder or the like so that the ampoule does not enter the high temperature heating unit. After the pretreatment, it is preferable to move the ampoule into the measurement sample while keeping the airtight state of the sample tube.

In the present invention, when the calibration standard sample is used, the resolution of NMR for probe molecule detection may be adjusted. That is, at the stage where the sample tube was introduced probe molecule gas is disposed in the NMR probe, to adjust the resolution by ¹ H-NMR with water (solvent) signal of the calibration standard samples. For example, the resolution adjustment parameter is adjusted so that the water (solvent) signal of ¹ H-NMR is sharp and strong. A person skilled in the art can easily improve the resolution of NMR by this step.

An example of the flow of steps up to data collection in the gas adsorption characteristic measuring method of the present invention is shown in FIG. Incidentally, in the case of not using the calibration standard sample may not perform the ST2,4,7,11 in the diagram marked with the ^*. ST10 is preferably repeated until the measurement pressure point is, for example, 5 to 50 points, preferably 10 to 40 points, and more preferably 15 to 30 points.

  In order to measure the chemical shift of NMR for probe molecule detection, it is necessary to obtain a spectrum by taking FID (free induction decay) or echo signal data and then performing Fourier transform. When only the signal intensity is measured, the Fourier transform can be omitted, and the signal intensity can be quantified from the FID or the echo signal. Therefore, even if the NMR spectrometer does not have a Fourier transform function, the adsorption enthalpy and entropy can be evaluated using only the signal intensity data. For example, the signal intensity is obtained from the FID or echo signal, and as will be described later, the adsorption equilibrium constant is evaluated from the measurement of the signal intensity, and the enthalpy and entropy of the adsorption can be evaluated from the temperature dependence.

On the other hand, in the present invention, the adsorption energy can be evaluated from the observed chemical shift of the probe molecule. In that case, it is preferable to consider the temperature dependence of the adsorption intrinsic chemical shift δ _a in the data processing section of the gas adsorption property measuring apparatus of the present invention and the data processing step of the gas adsorption property measuring method of the present invention. Specifically, paying attention to the pressure dependence of the chemical shift of the probe molecule in the adsorption system, the chemical shift of the probe molecule at a plurality of pressures is measured under a constant temperature condition, and the following equation [10], which will be described later, at that temperature The adsorption intrinsic chemical shift δ _a is obtained (ST1 in FIG. 5). As mentioned above, the measurement pressure point is, for example, 5 to 50 points, preferably 10 to 40 points, and more preferably 15 to 30 points. Next, the adsorption intrinsic chemical shift δ _a is similarly determined at _a plurality of temperatures (ST2 in FIG. 5). The measurement temperature point is, for example, 5 to 50 points, preferably 10 to 40 points, and more preferably 15 to 30 points. Then, the temperature dependence of [delta] _a, for _{example, δ a (T) = aT} + b (T is the temperature, a, b are constants) expressed by the formula, such as (ST3 in FIG. 5). Thus, for example, it is possible to evaluate the adsorption energy in consideration of the temperature dependency of adsorption specific chemical shifts [delta] _a. Note that the equation for the temperature dependence of δ _a is not limited to a linear equation.

Induction of formula from the analysis of the pressure dependence of the chemical shifts of the probe molecule is a basic formula in a method for determining the adsorption specific chemical shifts [delta] _a [10] are as follows. In the following description, ¹²⁹ Xe is used as the probe molecule.

Xe atoms in the pores, as shown in FIG. 6, if earlier equilibrium relationship between the adsorption state of gaseous (V) and pore surfaces (a), observed chemical shifts [delta] _obs is the following formula As in [7], it is given as a weighted average of the intrinsic chemical shifts of both states. In the equation, n represents the number of spins (Xe) in the both states, [delta] _f represents a unique chemical shifts of gaseous Xe. The following formula [8] is derived from the following formula [7]. In the following formula [8], ρ represents the concentration of Xe, V represents the volume of the gas phase, A represents the adsorption surface area, and D _Xe represents the diameter of the Xe atom. The last equal sign on the right side of the following formula [8] is obtained by placing ρ _v / ρ _a = K and (V−AD _Xe ) / AD _Xe = C, where C is the pore size. Represents the geometric factor of. K is a concentration ratio of Xe between the gas phase and the adsorption phase, and corresponds to a distribution coefficient (Henry constant). Taking the logarithm of the following formula [8] and differentiating with the pressure P, the following formula [9] is obtained. At this time, the fact that the adsorption energy is ΔE = −RTlnK and the differential pressure is the volume change ΔV (dΔE / dP = ΔV) was used. The following formula [10] is obtained by integrating the following formula [9] and taking an index. At this time, δ _f = 0 was set as a reference for the chemical shift of the gas phase. Const represents a constant at the time of integration.

For reference, the above formula [2] is obtained by taking the logarithm of the above formula [8] and differentiating it at the temperature 1 / T. When the above formula [2] is integrated to take an index and transformed by setting δ _f = 0, the following formula [11] is obtained, and ΔE = −ΔH (ΔH is heat of adsorption and the sign is positive), the above formula [ 1] is obtained. However, in equation [1], T ^-1/2 is added before the denominator index. This is because the temperature dependence of the Henry constant is expressed in the form of K = K ₀ e ^{ΔH / RT} / T ^1/2 in the derivation of the equation [1]. In a simpler form, K = T ^-1/2 is omitted when expressed as K ₀ e ^{ΔH / RT} .

An example of a step of obtaining an adsorption energy in consideration of the temperature dependency of adsorption specific chemical shifts [delta] _a shown in FIG. After obtaining temperature-dependent chemical shift data δ _obs and δ _a (T) = aT + b as described above (ST1 to ST3 in FIG. 5), ΔE is derived by applying the above equation [2] (FIG. 5). ST4) and / or ΔH can be derived by applying the above equation [1] (ST5 in FIG. 5). Specifically, when the above formula [2] is applied, the formula [2] is integrated and the chemical shift δ _f = 0 of the gas state is used. ΔE can be determined from the slope plotted against T. Further, when the above formula [1] is applied, ΔH can be obtained from the slope obtained by plotting the value of the left side against 1 / T using the following formula [1 ′] obtained by modifying the formula [1].

  In addition to the above-described Henry type adsorption formula (the above formula [2]), DR analysis or a Langmuir type adsorption formula can be used as the basic formula for obtaining the adsorption energy. The DR analysis is a model in which adsorption occurs in a pore-embedded type, the Langmuir type is a model in which adsorption proceeds in a saturated form on a planar adsorption surface, and the Henry type is represented by Henry's law. This is a model in which adsorption proportional to the gas concentration occurs. In addition, there is a BET type adsorption model in which multilayer adsorption occurs in a plane. When these models are applied to NMR, the relative change in the amount of adsorption can be replaced by a change in the signal intensity of the adsorption peak, but measurement under conditions that avoid the distortion of intensity data such as saturation is essential. is there. On the other hand, the chemical shift of the adsorption peak can be measured with higher accuracy than the peak area. Therefore, if a method of applying chemical shift data to these adsorption models is established, the merit is very large. By using a hyperpolarized noble gas, the chemical shift can be measured quickly with high sensitivity, and in this respect as well, the establishment of an analysis method from the chemical shift is significant. In an embodiment described later, an example applied to the above three models other than the BET type is shown. A method for evaluating the data adsorption surface area using calibration data obtained from a calibration standard sample will also be described in the examples described later. However, in the data processing unit of the gas adsorption characteristic measuring apparatus of the present invention and the data processing step of the gas adsorption characteristic measuring method of the present invention, the processing methods of chemical shift data, signal intensity data, and calibration data are limited to these. However, those skilled in the art can apply known processing methods other than these, and the program for the data processing unit can be used as necessary.

  The present invention can be used for analysis and evaluation of pore surface characteristics of a product including, for example, a product containing pore fine particles at the stage of development and production. For example, when improving characteristics such as the touch, whiteness, and brightness of powder cosmetics, an improvement guideline may be obtained by analyzing and comparing pore surface characteristics. In addition, for example, in the zeolite industry, it can be applied to the characteristic analysis of a product newly developed as a catalyst or reaction medium, and further development can be promoted. Furthermore, it can also be used, for example, for product quality confirmation at the manufacturing stage. Accordingly, the present invention, in yet another aspect, includes a step of measuring the gas adsorption characteristics of the fine pore particles using the gas adsorption characteristic measurement device of the present invention and / or the gas adsorption characteristic measurement method of the present invention. It is a manufacturing method of a product containing pore fine particles. The product containing the fine pore particles is not particularly limited, and examples thereof include cosmetics, catalysts, chemical adsorbents such as deodorizers and chemical sensors.

  The present invention will be further described below using examples. In the following examples, Xe gas is used. However, in the present invention, the probe molecule gas is not limited to Xe gas.

(Confirmation of the effect of exposing the sample to air after pretreatment-1)
About 100 mg of zeolite sample (trade name: ZEOLUM F9, manufactured by Tosoh Corporation) is weighed into a sample tube with an outer diameter of 10 mm, connected to a vacuum, and it takes 2-3 hours under a high vacuum from 10 ⁻³ Pa. The temperature was slowly raised to 300 ° C., and pretreatment was performed at 300 ° C. for 8 hours. As a result of ¹²⁹ XeNMR measurement of this sample, a chemical shift as shown in FIG. 7A was obtained. Next, the zeolite sample pretreated under the above conditions was transferred to another sample tube containing a calibration standard sample, kept at a high vacuum of 10 ⁻³ Pa at room temperature for 3 hours, and then measured for ¹²⁹ XeNMR. The result is shown in FIG. 7B. As shown in FIG. 7B, when the sample was refilled after pretreatment under high vacuum and high temperature, peak splitting and peak deviation of 15 ppm or more were observed even after pretreatment at room temperature. . Note that the sharp signal of 145.2 ppm in FIG. 7B is an Xe signal included for calibration.

(Confirmation of the effect of exposing the sample to air after pretreatment-2)
About 100 mg of ZSM-5 sample (Reference sample of the Japan Society for Catalysts; JRC-Z5-70Na) is weighed into a sample tube with an outer diameter of 10 mm, connected to a vacuum, and heated to 300 ° C. under a high vacuum of 10 ⁻³ Pa. Pre-treatment was held for 8 hours. As a result of measuring ¹²⁹ XeNMR of this sample, a chemical shift as shown in FIG. 8A was obtained. Next, the ZSM-5 sample pretreated under the above conditions was transferred to another sample tube containing a calibration standard sample, held at a high vacuum of 10 ⁻³ Pa for 3 hours at room temperature, and then ¹²⁹ XeNMR measurement did. The result is shown in FIG. 8B. As shown in FIG. 8B, when the sample was refilled after pretreatment under high vacuum and high temperature, no peak splitting was observed even after pretreatment at room temperature, but a peak of about 18 ppm. Was observed. Note that the sharp signal of 145.2 ppm in FIG. 8B is an Xe signal included for calibration.

⁽¹²⁹ Measurement of adsorption surface area by Xe NMR)
A sample to be measured (trade name: CBV5524G, manufactured by Zeolist) is measured in a sample tube 3 (see FIG. 3) having an outer diameter of 10 mm, and 12 mg of the standard sample ampoule 40 for calibration is attached to the standard sample holder 41 of the sample tube 3. After the arrangement, in the pretreatment apparatus 30 of FIG. 2, the pretreatment was performed by connecting to the high vacuum exhaust section 32 and maintaining at 300 ° C. for 8 hours under a high vacuum from 10 ⁻³ Pa. As the standard sample ampule for calibration, an ampule containing 0.11M calixarene aqueous solution containing Xe, and TEMPO (2, 2, 6, 6- 6), which is a more typical stable nitroxy hydroradical in the aqueous solution, are used. An ampule added with tetramethylpiperidine 1-oxyl) to 2.4 μM was used. By the pretreatment, usually about 2-3% of water is recovered in the liquid nitrogen trap. After the cock 9 was operated to ensure airtightness, the joint 18 was removed, the sample tube 3 was tilted, and the upper calibration standard sample 40 was guided and buried in the bottom sample 6. Next, as shown in FIG. 1, the sample tube 3 was connected to the pressure adjusting unit 4 of the gas adsorption characteristic measuring apparatus 1 of the present invention via a joint 18 and set in the NMR probe 7. The pressure adjusting unit 4 was evacuated to the cock 9 and purged with Xe gas to sufficiently remove moisture adhering to the glass tube surface in the piping. Xe gas was introduced into the sample tube 3 by cock operation to adjust the pressure. Further, the temperature of the sample tube 3 was adjusted by the temperature adjustment unit of the NMR probe 7. Furthermore, ¹ H-NMR measurement was performed using the water signal in the calibration standard sample, and the NMR resolution was adjusted. Specifically, the resolution adjustment parameter was adjusted so that the water signal of ¹ H-NMR was sharp and strong. This operation improved the resolution easily.

An example of the result of the signal intensity versus pressure data S (P) of the measurement sample at a measurement temperature of 25 ° C. is shown in the graph of FIG. In the graph, the horizontal axis represents pressure (atm), and the vertical axis represents signal intensity (adsorption peak area) (arbitrary unit). Furthermore, FIG. 10 shows an example of the ¹²⁹ XeNMR spectrum of the measurement sample and the calibration standard sample at a temperature of 25 ° C. and a pressure of 0.62 atm. The NMR measurement conditions at this time were SW = 25 kHz, at = 0.4 sec, d1 = 50 sec, 1296 fids, np = 20 k point, fn = 64 k point. In addition, the data obtained from the measurement of the calibration standard sample; S (P _CA ) / S _std , that is, S (0.62 atm) / S _std is the adsorption peak (135.3 ppm) in FIG. Calculated from the area ratio of the calibration peak (145.2 ppm), it was 7.05. Further, S (0.62 atm) was 2.7 × 10 ⁻⁵ as shown in FIG.

  When a curve that reaches saturation on the high pressure side as shown in FIG. 9 (so-called Langmuir type adsorption characteristics) is obtained, the evaluation of the adsorption surface area from these data should be performed by the method shown in FIG. Can do.

First, the signal intensity when the single-layer adsorption has completely occurred (when the coverage ratio θ = 1) is obtained (ST1 in FIG. 11). When a saturated constant value is observed on the high pressure side, the value may be used instead of ST1 in FIG. In general, a curve on the way to saturation as shown in FIG. 9 is obtained. This type of curve can be analyzed as Langmuir type adsorption characteristics. That is, if S is the NMR signal intensity (area) when the pressure is P and S _∞ is the signal intensity when the coating is complete, θ = S _∞ / S, and the following equation [12] is obtained. That is, when P / S is plotted against P, the adsorption equilibrium constant K and the signal intensity S _{∞ of the} complete coating are obtained.

Next, determine the adsorption surface area from S _∞, performed by using the signal strength S _std of the calibration sample (ST2 in Fig. 11). S _∞ / S _std = n _∞ / n _std (n is the number of moles of Xe), n _std = C _std V _std (C _std is the Xe concentration of the calibration solution, V _std is the volume of the calibration solution in the ampoule) Since C _std = [Xe] + [Xe · CD] from the above equation [6], n _∞ can be obtained. The adsorption surface area is calculated as n _∞ S _Xe per sample volume. Here, S _Xe is an occupied area per mole of _Xe and takes a value of 0.25 nm ² × Avocado number. That is, the adsorption surface area A per unit mass can be obtained from the following formula [19], where W _sample is the mass of the measurement sample.
_{A = (S ∞ / S std} ) C std V std S Xe / W sample [19]

Results of the evaluation of the adsorption surface area of the measurement sample as described above, S (0.62atm) / S ( CA) = 7.05, S (0.62atm) / S ∞ = 0.79, from the sample weight = 12 mg, The adsorption surface area was 317 m ² / g. This result was close to the specification value of 420 m ² / g.

The T ₁ of the clathrate Xe in the calibration standard sample ampoule was 15.6 ± 2.4 seconds before the radical addition, but 4.3 ± 0 after the addition of 2.4 μM TEMPO. It was 9 seconds. Accordingly, signal integration every 50 seconds was realized with 10 times T ₁ as a guideline, and the effectiveness of relaxation agent addition was confirmed.

Here, when the hyperpolarized ¹²⁹ Xe gas is used, since the signal intensity greatly depends on the polarization rate, it is difficult to quantitatively consider the signal intensity. However, even when hyperpolarized Xe gas is used, S _∞ can be obtained by measuring the signal intensity under one pressure and thermal equilibrium condition with the calibration standard sample included. That is, the adsorption equilibrium constant K obtained from the measurement of chemical shift using hyperpolarized Xe gas may be used. In this case, if the signal intensity measurement is performed on the thermal equilibrium noble gas at the same pressure and in the presence of the calibration standard sample, S _∞ is obtained and the adsorption surface area is obtained.

(Determination of adsorption intrinsic chemical shift δ _a from pressure dependence of ¹²⁹ Xe chemical shift, and evaluation of adsorption energy considering temperature dependence of adsorption intrinsic chemical shift δ _a )
Based on the chemical shift versus pressure data δ _obs (P) obtained from ¹²⁹ XeNMR, the adsorption intrinsic shift δ _a was obtained by the method shown in FIG. 5, the temperature dependence was evaluated, and the adsorption energy was evaluated based on the information. .

Chemical shift versus pressure data δ _obs (P) was obtained at various temperatures in the same manner as in Example 2 except that no calibration standard sample ampoule was used. An example of the result is shown in FIG. In the graph of the figure, the horizontal axis is pressure (atm), and the vertical axis is chemical shift (ppm). As for the measurement temperature, * is −50 ° C., x is −25 ° C., Δ is 0 ° C., ■ is 25 ° C., and ◆ is 50 ° C. In each temperature was determined [delta] _a and analyzed by least square method using the above formula [10]. For the analysis, commercially available software was used (trade name; ORIGIN, manufactured by Lightstone). The results are shown in Table 1 below.

Δ _a at room temperature is 146 ppm, and the literature [I. L. Moudrakovski et al. , J .; Phys. Chem. , B, 106, 5938-5946, 2002], close to the value reported at 180 K for mesoporous silica PNNL. However, this document does not consider the temperature dependence of δ _a , so detailed comparison is difficult. The fact that the adsorption intrinsic shift observed here shifts to a low magnetic field as the temperature decreases is the same tendency as the temperature dependence of ¹ H chemical shift in a system that interacts with hydrogen bonds and charge transfer, which is a reasonable result. .

FIG. 13 shows an example in which chemical shifts δ _obs of adsorption peaks obtained at 8 points from 273K to 343K are plotted. In the graph of the figure, the horizontal axis is temperature (K), and the vertical axis is the chemical shift δ _obs (ppm) of the adsorption peak. In Table 1 above, a temperature-dependent linear expression such as δa = −0.36T + 253.3 was obtained from the high temperature side range of 0 ° C. (273 K) or higher. Using this equation, ST4 and ST5 in FIG. 5 are performed, and the results of obtaining ΔE and ΔH are shown in Table 2 and FIGS. 14A and 14B, respectively. Table 2 also shows the results obtained by the conventional method with δ _a = 243 ppm. As shown in Table 2 and FIGS. 14A and B, confirmed 0 ° C. (273K) In the above, by considering the temperature dependence of [delta] _a, that reasonable values of about 30 kJ / mol is obtained as adsorption energy did.

(Derivation of adsorption energy by DR analysis)
The Dubinin-Radushkevich analysis (DR analysis) is a model assuming that adsorption occurs in a so-called embedded type, and it is considered that the energy is stabilized by βE _{0 in the} pores in the adsorption state. β takes a value specific to the adsorbent and is 0.5 for Xe. adsorption amount when the w _a pressure P, and the w ₀ saturated adsorption amount considerable pressure at that time and P _eq. At this time, the following formula [13] becomes the DR formula.

When using the signal strength versus pressure data S (P) obtained from ¹²⁹ Xe NMR, the above expression, by fitting a _{S / S ∞ = w a /} w 0, can be obtained beta E ₀ of adsorption energy equivalent ( ST1 in FIG. At this time, since S _∞ can be obtained simultaneously, the adsorption surface area can be obtained based on the above equation [19] (ST2 in FIG. 15).

On the other hand, when using DR analysis using chemical shift versus pressure data δ _obs (P) obtained from ¹²⁹ Xe NMR, it is necessary to set a basic equation. Therefore, obtained w _a / w _0, noted that represents the ratio of the actual adsorption amount with respect to the saturated amount of adsorption sites, represents the [delta] _obs in virial expansion type w _a / w _0, the following formula [14] Thus, βE ₀ corresponding to the adsorption energy can be obtained from this and the above equation [13] (ST1 in FIG. 16).

In the DR analysis, the constant temperature condition is not necessary. The temperature and pressure are mutually variable, and βE ₀ corresponding to the adsorption energy can be obtained without changing the temperature. Further, an equivalent heat of adsorption q _st is obtained from βE ₀ and the following equation [15] (ST3 in FIG. 15 and ST2 in FIG. 16). In the following formula [15], [Delta] H _V is the heat of vaporization Xe (12.6 kJ / mol).

Table 3 below shows an example of the results analyzed by the methods of FIGS. 15 and 16 using the signal intensity vs. pressure data S (P) and chemical shift vs. pressure data δ _obs (P) obtained in Example 2, respectively. Shown in

(Application of Langmuir type analysis)
The Langmuir type adsorption equation is a formula derived in consideration of the case where adsorption occurs on the surface close to a flat plate from the gas phase. However, even when adsorbed by thin cylindrical pores such as zeolite, if an equilibrium relationship is established between the bulk gas phase and the spins in the cylindrical pores, that is, between the bulk phase and the pores. However, the exchange rate is slow compared to the NMR chemical shift difference, and both signals can be separated and observed. However, when the chemical equilibrium is considered to be in a dynamic equilibrium state, the Langmuir type adsorption isotherm can be applied. This can be said to belong to type I in the classification of adsorption isotherms.

^When the signal intensity versus pressure data S (P) obtained from ¹²⁹ XeNMR is used, the adsorption equilibrium constant K is obtained from the analysis by the above equation [12] (ST1 and ST2 in FIG. 17). (Adsorption enthalpy) and ΔS (adsorption entropy) can be obtained (ST3 in FIG. 17).

On the other hand, when using chemical shift versus pressure data δ _obs (P) obtained from ¹²⁹ XeNMR, it is necessary to select a special relational expression. Therefore, the adsorption equilibrium constant K can be obtained by expressing the chemical shift of adsorption as in the following formulas [16] to [18] using θ (coverage) (ST1 in FIG. 18). Thereafter, (ΔH (adsorption enthalpy) and ΔS (adsorption entropy) can be obtained in the same manner as in the case of using the signal intensity versus pressure data S (P) (ST2 and ST3 in FIG. 18).

θ = KP / (1 + KP) [16]
θ = S / S _∞ [17]
δ _obs = δ _a0 + F ₁ θ + F ₂ θ ² + F ₃ θ ³ +... [18]

Table 4 below shows an example of the results analyzed by the method of FIGS. 17 and 18 using the signal intensity vs. pressure data S (P) and chemical shift vs. pressure data δ _obs (P) obtained in Example 2, respectively. Shown in In the above equation [18], up to F ₁ was obtained, and 0 after F ₂ .

In addition, if it analyzes using the [17] Formula from the said signal strength, K / atm < ^-1 > = 3.72 (323K), 7.04 (298K), 15.8 (273K), 106.6 (248K). 210.6 (223 K), and ΔH = −25.9 kJ / mol and ΔS = −70 J / (K · mol) were obtained.

  As described above, the present invention is useful, for example, in the field of nuclear magnetic resonance apparatus, the research field of fine pore particles, and the field of development and production of industrial products using fine pore particles.

FIG. 1 is a schematic view showing an example of a device for measuring gas adsorption characteristics of fine pore particles according to the present invention. FIG. 2 is a schematic view showing an example of the pretreatment apparatus of the present invention. FIG. 3 is a schematic diagram showing an example of a sample tube used in the present invention. FIG. 4 shows an example of an NMR measurement process for probe molecule detection in the gas adsorption property measurement method of the present invention. Figure 5 shows an example of a data processing method for evaluating the adsorption energy in consideration of the temperature dependency of adsorption specific chemical shifts [delta] _a. FIG. 6 is a schematic diagram illustrating an adsorption equilibrium state of Xe gas. FIG. 7 is an example showing the influence of contact between the sample and air on the chemical shift. FIG. 8 is another example showing the influence of contact between the sample and air on the chemical shift. FIG. 9 is an example of a graph showing the pressure dependence of the adsorption peak area (signal intensity) obtained by ¹²⁹ XeNMR measurement. FIG. 10 is an example of a ¹²⁹ Xe NMR spectrum of a measurement sample and a calibration standard sample. FIG. 11 shows an example of a data processing method for evaluating the adsorption surface area from the signal intensity versus pressure data S (P). FIG. 12 is an example of a graph showing the dependence of ¹²⁹ Xe adsorption chemical shift on pressure and temperature. FIG. 13 is an example of a graph showing the temperature dependence of the chemical shift δ _obs of the adsorption peak. Figure 14 is an example of a result of obtaining an adsorption energy in consideration of the temperature dependency of adsorption specific chemical shifts [delta] _a. FIG. 15 shows an example of a data processing method for evaluating the adsorption surface area and adsorption energy from the signal intensity versus pressure data S (P) by DR analysis. FIG. 16 shows an example of a data processing method for evaluating adsorption energy from chemical shift versus pressure data δ _obs (P) by DR analysis. FIG. 17 shows an example of a data processing method for evaluating adsorption energy from signal intensity versus pressure data S (P) by Langmuir type analysis. FIG. 18 shows an example of a data processing method for evaluating adsorption energy from chemical shift versus pressure data δ _obs (P) by Langmuir type analysis.

Explanation of symbols

1. Gas adsorption characteristic measuring device 2. Nuclear magnetic resonance device 3. Sample tube 4. Pressure adjusting unit 5. NMR magnet 6. Measurement sample 7. NMR probe 8. NMR spectrometer 9. High vacuum cock 10 ·· Tube 11 · Pressure gauge 12 · Probe molecular gas supply source 13 · Dryer 14 · Vacuum exhaust system 15 · Data processing unit 16 · Control units 17 and 18 · High resistance Vacuum joints 19 to 23 ··· Cock 30 · · Pretreatment device 31 · Heater 32 · · High vacuum evacuation unit 33 · Cooling unit 34 · Reservoir 35 and 36 · · High vacuum cock 37 · · High vacuum exhaust System 40 ··· Standard sample ampule 41 for calibration · · Standard sample holder 42 · · Connection 43 · · Tip

Claims (13)

An apparatus for measuring gas adsorption characteristics of fine pore particles,
An NMR magnet that generates a constant magnetic field, and a sample tube containing fine pores, which are measurement samples, can be placed therein, and it transmits signals to the measurement sample and receives signals from the measurement sample A nuclear magnetic resonance apparatus including a probe and an NMR spectrometer that measures a signal received by the NMR probe;
The sample tube connected to a tube having a high vacuum resistant cock and capable of airtight control;
A pressure adjusting unit for controlling the pressure in the sample tube disposed in the NMR probe,
The NMR probe includes a temperature adjusting unit that controls the temperature in the sample tube disposed therein,
The pressure adjusting unit includes a pressure gauge, a probe molecular gas supply source, and an evacuation system,
The gas adsorption property measuring apparatus according to claim 1, wherein the sample tube disposed in the NMR probe is connectable to the pressure adjusting unit through the high vacuum resistant cock. Further, the apparatus includes a pretreatment device for the measurement sample, and the pretreatment device includes a heater capable of arranging the sample tube therein, and a high vacuum exhaust capable of being connected to the sample tube via the high vacuum resistant cock. The gas adsorption property measuring apparatus according to claim 1, comprising a unit. The gas adsorption property measuring apparatus according to claim 1 or 2, wherein the sample tube includes a standard sample holding portion in which a calibration standard sample can be arranged at a position spatially separated from the measurement sample therein. Furthermore, a control part is included, The said control part controls the temperature and the pressure in the said sample tube of the state arrange | positioned in the said NMR probe by controlling the said temperature adjustment part and the said pressure adjustment part. The gas adsorption property measuring apparatus according to any one of the above. Furthermore, it includes a data processing unit that processes the signal data measured by the NMR spectrometer, the data processing unit,
Based on the chemical shift versus pressure data δ _obs (P) measured under a plurality of pressure conditions at a constant temperature T ₁ and the following equation [10], the adsorption inherent chemical shift δ _a at the temperature T ₁ is calculated. Obtaining (T ₁ ),
Similar to the above step, obtaining δ _a (T ₂ ) to δ _a (T ₅ ) at at least four temperatures T _{2 to} T ₅ different from T ₁ , and
Wherein _{δ a (T 1) ~δ a} (T 5) on the basis of adsorption specific chemical shifts [delta] _a of at least 5 points including adsorption specific chemical shifts linear function of [delta] _{a temperature; δ a (T) = aT} + b (a, The gas adsorption property measuring apparatus according to claim 1, wherein a process including a step of obtaining b is a constant is performed.

(In the above equation [10], const represents a constant at the time of integration.) Furthermore, it includes a data processing unit that processes the signal data measured by the NMR spectrometer, the data processing unit,
A step of calculating βE ₀ corresponding to the adsorption energy by calculating based on chemical shift versus pressure data δ _obs (P) measured under an arbitrary temperature and a plurality of pressure conditions and the following equations [13] and [14] The gas adsorption characteristic measuring device according to any one of claims 1 to 5 which performs processing including.

(In the above formulas [13] and [14], w _a represents the adsorption amount at the pressure P, w ₀ represents the saturated adsorption amount, and P _eq represents the equivalent pressure at that time.) Furthermore, it includes a data processing unit that processes the signal data measured by the NMR spectrometer, the data processing unit,
A step of obtaining a signal intensity S _∞ at the time of complete covering by calculating by the least square method based on the signal intensity versus pressure data S (P) measured under a plurality of pressure conditions at a constant temperature and the following equation [12]: And a step of obtaining an adsorption surface area A per unit mass by calculating based on S (P _CA ) / S _std which is calibration data measured from the S _∞ and the standard sample and the following equation [19 ′]. The gas adsorption characteristic measuring device according to any one of claims 3 to 6 which performs processing.

(In the above formula [19 ′], C _std represents the concentration of the probe molecule in the standard sample, V _std represents the volume of the standard sample, S _Pr represents the surface area equivalent to 1 mol of the probe molecule, and W _sample Represents the mass of the measurement sample.) Furthermore, it includes a data processing unit that processes the signal data measured by the NMR spectrometer, the data processing unit,
Based on signal intensity vs. pressure data S (P) measured under arbitrary temperature and multiple pressure conditions, and an equation in which w _a / w ₀ is replaced with S (P) / S _∞ in the following equation [13] A step of obtaining βE ₀ corresponding to the adsorption energy and signal intensity S _∞ at the time of complete coating by calculation by the least square method, and S (P _CA ) which is calibration data measured from the S _∞ and the standard sample The gas adsorption property measuring apparatus according to any one of claims 3 to 7, wherein a process including a step of obtaining an adsorption surface area A per unit mass by performing a calculation based on / S _std and the following equation [19 '] is performed.

(In the above formula [13], w _a represents the adsorption amount at the pressure P, w ₀ represents the saturated adsorption amount, and P _eq represents the equivalent pressure at that time. Also, in the above formula [19 ′], C _std represents the probe molecule concentration in the standard sample, V _std represents the volume of the standard sample, S _Pr represents the surface area equivalent to 1 mol of probe molecules, and W _sample represents the mass of the measurement sample.) A method for measuring gas adsorption characteristics of fine pore particles,
A process of pre-treating the fine pore particles as a measurement sample by heating them in a high vacuum under a sample tube capable of airtight control;
Placing the sample tube in an NMR probe of a nuclear magnetic resonance apparatus while maintaining the airtight state of the sample tube;
Introducing a probe molecular gas into the sample tube disposed in the NMR probe and adjusting the pressure;
Adjusting the pressure of the probe molecular gas while setting the sample tube on the NMR probe, and measuring nuclear magnetic resonance at at least two pressures;
And a step of processing signal data measured by the nuclear magnetic resonance apparatus. Prior to the pretreatment step, placing a calibration standard sample at a site in the sample tube that is not directly heated in the pretreatment step;
After the pretreatment step, before the step of placing the sample tube in the NMR probe, the step of moving the standard sample to the same site as the measurement sample while maintaining the airtight state of the sample tube The gas adsorption property measuring method according to claim 9. The gas adsorption property measuring method according to claim 9 or 10, wherein the calibration standard sample is an ampoule of a solution containing a probe molecule and a clathrate compound having a known concentration. The process of processing the signal data is a process of performing a data processing step in a data processing unit of the gas adsorption characteristic measuring device according to any one of claims 5 to 8. The gas adsorption property measuring method described. It is a manufacturing method of the product containing pore fine particles, Comprising: The gas adsorption property measuring apparatus as described in any one of Claim 1 to 8, or the gas adsorption property as described in any one of Claims 9 to 12. A production method comprising a step of measuring gas adsorption characteristics of the fine pore particles using a measurement method.

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