JP2009220101A - Method for producing gas adsorbing material and carbon dioxide, and method for recovering carbon dioxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the sorptive property of carbon dioxide and to recover carbon dioxide efficiently. <P>SOLUTION: A gas adsorbing material 10 is composed of a stacked unit wherein a plurality of monomers 20 provided with four complex nuclear metals 22 (for example, Zn) combined in a tetrahedron shape by oxygen, and a plurality of monocarboxylic acids 24 that are coordinated in the complex nuclear metals 22 so as to have interaction parts 25 (e.g., benzene ring) stacked with other structures by uncombined interaction and to surround the complex nuclear metals 22. When an adsorption gas (carbon dioxide) is present, the gas adsorbing material 10 undergoes phase transition to a structure having spaces each of which is larger in molecular size than the gas, so as to incorporate the adsorbed gas. When the pressure of adsorbed gas is further increased, it undergoes even greater structural phase transition to a structure capable of incorporating a larger amount of the adsorbed gas. The gas adsorbing material 10 undergoes such structural phase transition reversibly, so that it can achieve adsorption and desorption of carbon dioxide while exerting a high adsorption amount compared with methane, nitrogen, steam, or the like. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas adsorbing material, a carbon dioxide production method, and a carbon dioxide recovery method.

  In recent years, as a countermeasure against global warming, removal and storage of carbon dioxide in exhaust gas discharged from thermal power plants and petrochemical industries have attracted attention. As this gas adsorbing material, the dried raw material gas is introduced into a plurality of PSA (Pressure Swing Adsorption) apparatuses to perform an adsorption process, and a part of the recovered carbon dioxide is used as a purge gas and in the opposite direction to the adsorption process. An apparatus that adsorbs carbon dioxide has been proposed that is disposed in a PSA apparatus that repeatedly performs a PSA process of compressing carbon dioxide obtained in a desorption process by circulating dry air (see, for example, Patent Document 1). As this gas adsorbing material, activated carbon or zeolite can be used.

  From the viewpoint of effective use of energy, so-called methane refining, in which carbon dioxide is removed from anaerobic digestion gas or landfill gas of sewage sludge, has also attracted attention. It is considered that this carbon dioxide removal is also suitable for a small-scale plant by a PSA process using an adsorbent material. As this gas adsorbing material, activated carbon or zeolite is mainly used.

JP 2003-93836 A

  However, in the gas adsorbing material described in Patent Document 1, water vapor may be strongly adsorbed in addition to carbon dioxide, and a dry raw material gas obtained by removing water vapor from the raw material gas is used or is not in a dry state. A process of removing the moisture adsorbed on the gas adsorbing material after the PSA process using the raw material gas is necessary, and the recovery of carbon dioxide was not efficient. In addition, for example, a gas adsorbing material having high carbon dioxide adsorption characteristics that selectively adsorbs carbon dioxide has been desired.

  The present invention has been made in view of such problems, and an object thereof is to provide a gas adsorbing material having high carbon dioxide adsorption characteristics. Another object of the present invention is to provide a gas adsorbing material, a carbon dioxide production method, and a carbon dioxide recovery method that can efficiently recover carbon dioxide.

  As a result of diligent research in order to achieve the above-described object, the present inventors have found that a plurality of structures are integrated such that a plurality of structures move and spaces are provided between the plurality of structures. Assuming that a gas adsorbing material constituted by a body is used, a material having high carbon dioxide gas adsorption characteristics is obtained, and it has been found that carbon dioxide can be efficiently recovered, and the present invention has been completed.

That is, the gas adsorption material of the present invention is
A gas adsorbing material composed of an integrated body in which a plurality of structures are integrated,
The structure has four complex nucleus metals bonded in a tetrahedral form by oxygen and an interaction part that accumulates with other structures by non-binding interaction so as to surround the complex nucleus metal. A plurality of monocarboxylic acids coordinated to the metal,
The integrated body is configured such that the plurality of structures move through the space provided between the plurality of structures and / or the interaction unit, and the carbon dioxide enters the space provided between the plurality of structures. It adsorbs gas.

The method for producing carbon dioxide of the present invention comprises:
A method for producing carbon dioxide by refining a raw material gas,
A gas adsorption step of adsorbing carbon dioxide gas contained in the raw material gas at a predetermined adsorption temperature to the gas adsorbing material described above.

The method for recovering carbon dioxide of the present invention comprises:
A gas adsorption step of adsorbing carbon dioxide gas contained in the raw material gas at a predetermined adsorption temperature to the gas adsorbing material described above.

  With this gas adsorbing material, high carbon dioxide adsorption characteristics can be obtained. Further, by adsorbing carbon dioxide, carbon dioxide can be recovered more easily and carbon dioxide can be produced efficiently. The reason why such an effect is obtained is presumed as follows. For example, it has four complex nuclear metals bonded in a tetrahedral form by oxygen and an interaction part that accumulates with other structures by non-bonding interaction and coordinates to the complex nuclear metal so as to surround this complex nuclear metal In a gas adsorbing material composed of an integrated body in which a plurality of structures including a plurality of monocarboxylic acids are integrated, a space is created by moving the plurality of structures, or a space having a shape suitable for gas adsorption is formed. The gas may be adsorbed in this space, for example, because it originally exists. In this gas adsorbing material, since these spaces are suitable for carbon dioxide, it is presumed that the adsorptivity of carbon dioxide is high.

It is explanatory drawing which shows an example of the monomer 20 which comprises a gas adsorption material. 3 is an explanatory diagram of a carbon dioxide adsorption mechanism of the gas adsorption material 10. FIG. 2 is a configuration diagram illustrating an example of a carbon dioxide production apparatus 30. FIG. 2 is a configuration diagram showing an example of a methane purification apparatus 40. FIG. It is a figure of the adsorption isotherm measurement result of the carbon dioxide of an Example, nitrogen, and methane. It is a figure of the adsorption isotherm measurement result of the water vapor | steam of an Example.

The gas adsorbing material of the present invention is composed of an integrated body in which a plurality of structures are integrated. This structure is composed of a plurality of complex nucleus metals and a plurality of monocarboxylic acids coordinated to the complex nucleus metal so as to surround the complex nucleus metal having an interaction part that accumulates with other structures by non-bonding interaction. And. Here, the “non-bonding interaction” means a weak bond or an intermolecular interaction having an individual bond energy of 10 kcal / mol or less, such as π-π stacking, CH-π interaction, and hydrogen bond. For example, this gas adsorbing material includes four complex core metals M bonded tetrahedrally by tetracoordinate oxygen (μ ₄ -O), six monocarboxylic acids having a functional group R 1 as an interaction part, and The monomer represented by the following formula (1) including the structure may be a structure, and the aggregate may be configured by accumulating monomers so as to have a three-dimensional structure by the functional group R1. The functional group R1 is a monocarboxylic acid substituent. This monomer constitutes a gas adsorbing material by being three-dimensionally integrated by non-bonding interaction generated between substituents R1 of adjacent monomers. The gas adsorbing material configured in this way is adsorbed by moving the plurality of monomers so that a space is provided between the plurality of monomers by the interaction unit with respect to a predetermined gas species (also referred to as adsorption gas) to be adsorbed. Gas is absorbed and desorbed (see FIG. 2 described later). Alternatively, the adsorbed gas is adsorbed and desorbed in a space having a shape suitable for gas adsorption. Here, for convenience of explanation, the movement of the plurality of monomers is referred to as a structural phase transition. This structural phase transition occurs due to the flexibility of the non-bonding interaction between the monomers, and occurs when the adsorbed gas approaches and changes to a more stable structure that incorporates the adsorbed gas. The non-bonding interaction is preferably at least one of π-π stacking, CH-π interaction, and hydrogen bonding from the viewpoint of easily causing a structural phase transition.

  The gas adsorbing material is preferably obtained by heat-treating an aggregate composed of monomers and organic molecules to remove the organic molecules. The reason for this is presumed that the organic molecules are once taken in and then removed, whereby a large number of pores and cracks are formed in the crystal of the gas adsorbing material, and the adsorbed gas is easily taken in. The formed pores are preferably closed pores or pores whose inlet diameter is smaller than the gas molecules to be adsorbed. In this way, it is considered that it is difficult to adsorb other than the adsorbed gas. The organic molecule to be removed is preferably acetonitrile, acetone, methanol, dimethylformamide, or diethylformamide. Of these, acetone is preferred because it is highly volatile and easy to remove and easy to handle. The heat treatment for removing the organic molecules is preferably performed under vacuum conditions. When this gas adsorbing material is subjected to a process for removing organic molecules (activation process), the structure is changed to cause a phase transition to a stable structure, and the gas adsorbing material has a characteristic that it is difficult to adsorb gases other than the intended one. On the other hand, when the adsorbed gas approaches, the adsorbed gas is taken into the structure by changing the structure (with structural phase transition). Therefore, the gas adsorbing material of the present invention is less likely to adsorb gases other than the target even when the activation treatment is performed, and the structure is less likely to collapse because the structural distortion is relaxed and stabilized by the structural phase transition.

  In this gas adsorbing material, the integrated body includes at least one of a space provided between the plurality of structures and a space provided between the plurality of structures by moving the plurality of structures through the interaction portion. One side adsorbs carbon dioxide gas. In this gas adsorbing material, carbon dioxide is probably adsorbed mainly in the latter space. Further, the gas adsorbing material is preferably one having higher carbon dioxide adsorbability among nitrogen gas, water vapor, hydrocarbon gas, and carbon dioxide. That is, if carbon dioxide is selectively adsorbed, it is easy to selectively recover carbon dioxide from a raw material gas such as an exhaust gas containing carbon dioxide or a hydrocarbon gas containing carbon dioxide. Here, examples of the hydrocarbon gas include saturated hydrocarbons such as methane and ethane, and unsaturated hydrocarbons such as ethylene. Of these, methane may be used. Note that when the raw material gas containing carbon dioxide contains a gas having a higher adsorptivity than carbon dioxide, a gas obtained by removing this highly adsorbable gas by some method may be used as the raw material gas. Alternatively, the gas may be separated from the carbon dioxide after the gas is adsorbed by the gas adsorbing material in a state in which the gas having higher adsorptivity than the carbon dioxide is contained.

  The complex core metal contained in the structure is preferably any one of Zn, Cu, Mg, Al, Mn, Fe, Co and Ni from the viewpoint that a desired gas adsorbing material can be easily obtained. Zn is more preferable. In addition, the interaction part included in the structure is a functional group bonded to a monocarboxylic acid, from the viewpoint of causing a non-binding interaction, an aromatic ring, an alkyl group, a hydroxyl group, an amino acid, a nitrile group, a halogen group Of these, an aromatic ring is more preferable. Moreover, the structure of the functional group may include only one functional group, or may include a plurality of the same or different functional groups. In addition, the aromatic ring may be monocyclic, polycyclic, or heterocyclic. Furthermore, substitution positions such as ortho-position, meta-position and para-position may be substituted by the substituents as described above, and the substitution position may be one place or plural places.

  FIG. 1 is an explanatory view showing an example of the monomer 20 constituting the gas adsorbing material, and FIG. 2 is an explanatory view of the carbon dioxide adsorption mechanism of the gas adsorbing material 10 constituted by the monomer 20. Here, as shown in FIG. 1, in the monomer 20 constituting the gas adsorbing material 10, the complex nucleus metal 22 is Zn, and the interaction part 25 of the monocarboxylic acid 24 is constituted by a benzene ring. The monocarboxylic acid 24 is bonded to the two complex nucleus metals 22 through a coordinate bond between the carboxyl group (—COO) of the monocarboxylic acid 24 and the complex nucleus metal 22, and the monocarboxylic acid 24 is a single molecule as shown in FIG. Form monomers.

  Although the adsorption mechanism of the gas adsorbing material 10 is not clear, it is presumed that the gas adsorbing material 10 adsorbs while changing the structure as shown in FIG. As shown in the first stage of FIG. 2, the gas adsorbing material 10 has a structure in which a plurality of monomers 20 are accumulated by non-bonding interactions by the interaction portions 25. When the adsorbed gas (carbon dioxide in this case) exists, the phase transitions to a structure in which the adsorbed gas is taken in by opening larger than the molecular size of the adsorbed gas (second stage in FIG. 2). When the pressure of the adsorbed gas is further increased, a larger structural phase transition occurs, and more adsorbed gas is taken in (third and fourth stages in FIG. 2). In the gas adsorbing material 10, it is considered that adsorption / desorption of the adsorbed gas is performed by reversibly performing these structural phase transitions. The gas adsorbing material 10 exhibits higher carbon dioxide adsorption characteristics than methane, nitrogen, water vapor, and the like. In addition, in water vapor | steam, it is preferable to use the gas adsorption material 10 in the range whose water vapor pressure P / P0 is 0.9 or less, and it is more preferable to use it in the range whose P / P0 is 0.8 or less. If it carries out like this, adsorption | suction of water vapor | steam can be suppressed and the gas adsorption material 10 will adsorb | suck carbon dioxide more selectively.

  Next, the manufacturing method of the carbon dioxide using the gas adsorption material of this invention is demonstrated. FIG. 3 is an explanatory diagram illustrating an example of the carbon dioxide production apparatus 30. The carbon dioxide production apparatus 30 includes a plurality of PSA towers 32 that are provided with the gas adsorbing material 10 and collect carbon dioxide gas contained in the raw material gas, a raw material valve 33 that supplies the raw material gas to the PSA tower 32, and a PSA tower. A purifying valve 34 that recovers carbon dioxide gas from 32, a discharge valve 35 that discharges gas other than carbon dioxide, and a purge valve 36 that supplies purge gas to the PSA tower 32 are configured. Each valve is provided in each PSA tower 32. Here, the exhaust gas containing nitrogen, water vapor, and carbon dioxide will be described as a raw material gas. Note that nitrogen was used as the purge gas for regenerating the gas adsorbing material 10. First, a gas adsorption process is performed in which the raw material valve 33 is opened and the raw material gas is pressurized and supplied to the PSA tower 32 to adsorb carbon dioxide to the gas adsorbing material 10. This adsorption temperature can be set to a temperature of 273K to 333K. The adsorption pressure can be in the range of 0.1 MPa to 10 MPa. At this time, since the adsorption of nitrogen or water vapor is inactive, the gas adsorbing material 10 adsorbs carbon dioxide with high selectivity. Next, the discharge valve 35 is opened to perform a discharge process for discharging non-adsorbed nitrogen and water vapor. Subsequently, the recovery step of recovering carbon dioxide adsorbed on the gas adsorbing material 10 is performed by opening only the purification valve 34 and reducing the pressure on the purification port side. In addition, at a predetermined timing for repeating these steps, the purge valve 36 and the discharge valve 35 are opened, and a regeneration step for regenerating the gas adsorbing material 10 provided in any PSA tower 32 is performed. Here, since the adsorption of nitrogen or water vapor is inactive, the gas adsorbing material 10 requires fewer regenerating treatments than those that strongly adsorb water vapor such as activated carbon and zeolite. Note that the recovery rate can be increased by further recovering carbon dioxide contained in the exhaust gas by supplying the exhaust gas to the raw material gas side. Thus, carbon dioxide can be produced by refining from the raw material gas.

  Next, a method for purifying methane using the gas adsorbing material of the present invention will be described. FIG. 4 is an explanatory diagram showing an example of the methane purification device 40. The methane refining device 40 includes a plurality of PSA towers 42 for disposing the gas adsorbing material 10 and collecting carbon dioxide gas contained in the raw material gas, a raw material valve 43 for supplying the raw material gas to the PSA tower 42, and the PSA tower 42. A purifying valve 44 for recovering methane gas from the exhaust gas, a discharge valve 45 for discharging carbon dioxide contained in methane from the PSA tower 42, and a purge valve 46 for supplying purge gas to the PSA tower 42. Each valve is provided in each PSA tower 42. Here, an anaerobic gas containing methane and carbon dioxide will be described as a raw material gas. Note that nitrogen was used as the purge gas for regenerating the gas adsorbing material 10. First, a gas adsorption process is performed in which the raw material valve 43 is opened and the raw material gas is pressurized and supplied to the PSA tower 42 to cause the gas adsorbing material 10 to adsorb carbon dioxide. This adsorption temperature can be set to a temperature of 273K to 333K. The adsorption pressure can be in the range of 0.1 MPa to 10 MPa. At this time, since the adsorption of methane is inactive, the gas adsorbing material 10 adsorbs carbon dioxide with high selectivity. Next, a purification step is performed in which the purification valve 44 is opened and the purification port side is depressurized so that non-adsorbed methane is extracted as a purified gas. Subsequently, at a predetermined timing, the purge valve 46 and the discharge valve 45 are opened, and the discharge port side is decompressed to recover the carbon dioxide adsorbed on the gas adsorbing material 10, which is provided in any PSA tower 42. Then, a recovery / regeneration step for regenerating the gas adsorbing material 10 is performed. Here, since the adsorption of methane is inactive, the gas adsorbing material 10 can efficiently recover carbon dioxide and increase the concentration of methane. Thus, methane can be manufactured by refine | purifying from source gas.

  According to the gas adsorbing material 10 of the present embodiment described in detail above, the carbon dioxide adsorption property is high, and the carbon dioxide can be recovered more easily by more selectively adsorbing the carbon dioxide. Manufacture and purification of methane gas can be performed.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

    For example, in the above-described embodiment, the gas adsorbing material 10 of the present invention is used in the PSA process. However, any process can be used as long as it is a process for adsorbing carbon dioxide gas. For example, carbon dioxide gas may be adsorbed and separated in a TSA (Temperature Swing Adsorption) process, and the gas adsorbing material 10 may be used in this process. In the above-described embodiment, the gas adsorbing material 10 is used to separate carbon dioxide and methane, or carbon dioxide, nitrogen, and water vapor. However, a gas is used to separate carbon dioxide gas and one or more other gases. The adsorbing material 10 may be used.

  In the above-described embodiment, the gas adsorbing material 10 is used for the production of carbon dioxide and the production of methane gas. However, the present invention is not particularly limited to this, and if it is used for the adsorption of carbon dioxide, it can be used for any purpose. It may be used.

Below, the example which manufactured the gas adsorption material concretely is demonstrated. After dissolving 1.0 g of commercially available zinc benzoate (Zn (C ₆ H ₅ COO) ₂ ) (manufactured by Kanto Chemical) in 70 mL of acetone dried over anhydrous magnesium sulfate (MgSO ₄ ), this solution was cooled to 50 ° C. When heated for 30 minutes, a white precipitate precipitated. The white precipitate was filtered off by suction filtration, and the filtered precipitate was vacuum dried at room temperature. The yield of the precipitate was 0.71 g. The obtained precipitate was measured by chemical analysis, infrared absorption spectrum, X-ray diffraction and the like, and [Zn ₄ O (C ₆ H ₅ COO) ₆ ] (hereinafter referred to as Zbz) containing acetone shown in FIG. It was confirmed that Next, acetone was removed by heat-treating the obtained acetone-containing Zbz under vacuum at 150 ° C. for 4 hours to obtain a gas adsorbing material of the example. Note that the weight of Zbz after the removal of acetone was reduced by 5.6% by weight, and the yield was 0.67 g. This weight reduction was approximately in agreement with the value of loss of one molecule of acetone per monomer Zbz (5.5% by weight).

[X-ray diffraction measurement]
The powder X-ray diffraction patterns of the examples were measured using a qualitative X-ray diffraction apparatus (RAD-1B manufactured by Rigaku Corporation). When X-ray diffraction was measured before and after the measurement of the gas adsorption isotherm, there was no significant change in the measurement result of the X-ray diffraction before carbon dioxide was captured and after carbon dioxide was captured and released. Moreover, when the nitrogen adsorption characteristic of the Example after taking in and releasing carbon dioxide was measured, the nitrogen adsorption amount did not change. From the above, it was considered that the structure of this gas adsorbing material did not change before capturing and releasing carbon dioxide.

[Specific surface area measurement and gas adsorption characteristics measurement]
The adsorption isotherm of nitrogen at 77K was measured using the specific surface area / pore distribution measuring device ASAP2020 (manufactured by Micromeritics) for the gas adsorption material of the example. Helium was used to measure the dead volume. When the BET specific surface area was calculated using the result, the specific surface area was 1 m ² / g. Next, using the same apparatus, adsorption isotherm measurements of carbon dioxide, nitrogen, and methane at 303K were performed. Helium was used to measure the dead volume. FIG. 5 shows the measurement results of adsorption isotherms for carbon dioxide, nitrogen and methane in the examples. In the gas adsorption isotherm measurement, the adsorption temperature is set to 303K, 0.1 g of the gas adsorbing material is used, and it is determined that the adsorption equilibrium is obtained when the measurement pressure does not change by 0.01% or more over 30 seconds. The measurement was performed under the measurement conditions for performing adsorption at the next measurement point where the differential pressure target was 38 mmHg. As a result, the gas adsorbing materials of the examples were found to have a larger amount of carbon dioxide adsorption than other gases. Next, with respect to the gas adsorbing material of the example, water vapor adsorption measurement was performed using a gravimetric gas adsorption measuring device using a quartz spring (manufactured by Makuhari Chemical Glass Manufacturing Co., Ltd.). FIG. 6 is a measurement result of the adsorption isotherm of water vapor in the example. Regarding the adsorption of water vapor, the gas adsorbing materials of the examples showed slight adsorption in the range where the water vapor pressure P / P0 was 0.8 or less, but almost in the range where the water vapor pressure P / P0 was 0.7 or less. It was found that water vapor is not adsorbed. Further, after the water vapor was adsorbed, a vacuum heat treatment was performed at 200 ° C. for 12 hours. As a result, the weight of the gas adsorbing material returned to the value before the water vapor adsorption. Thus, in the gas adsorbing materials of the examples, among carbon dioxide gas, helium gas, nitrogen gas, methane gas, and water vapor, it is clear that the amount of carbon dioxide adsorption is the largest, and the adsorption of other gases hardly occurs. became. Therefore, it has been clarified that when these mixed gases are used, carbon dioxide can be adsorbed more selectively and is an effective material for collecting carbon dioxide.

  The present invention can be used in the field related to gas adsorbents.

  DESCRIPTION OF SYMBOLS 10 Gas adsorption material, 20 Monomer, 22 Complex nucleus metal, 24 Monocarboxylic acid, 25 Interaction part, 30 Carbon dioxide production apparatus, 32,42 PSA tower, 33,43 Raw material valve, 34,44 Purification valve, 35,45 Drain valve, 36, 46 Purge valve, 40 Methane purifier.

Claims (9)

A gas adsorbing material composed of an integrated body in which a plurality of structures are integrated,
The structure has four complex nucleus metals bonded in a tetrahedral form by oxygen and an interaction part that accumulates with other structures by non-binding interaction so as to surround the complex nucleus metal. A plurality of monocarboxylic acids coordinated to the metal,
The integrated body is configured such that the plurality of structures move through the space provided between the plurality of structures and / or the interaction unit, and the carbon dioxide enters the space provided between the plurality of structures. Adsorb gas,
Gas adsorption material.   The gas adsorption material according to claim 1, wherein the complex core metal is any one of Zn, Cu, Mg, Al, Mn, Fe, Co, and Ni.   3. The gas adsorption according to claim 1, wherein the interaction unit is any one of an aromatic ring, an alkyl group, a hydroxyl group, an amino acid, a nitrile group, and a halogen group, which is a functional group bonded to the monocarboxylic acid. material. The structure is a monomer represented by the following formula (1):
The gas adsorption material according to any one of claims 1 to 3, wherein the aggregate is configured by accumulating the structures so as to have a three-dimensional structure with the functional group R1 as the interaction part.

  The gas adsorbing material according to any one of claims 1 to 4, wherein the gas adsorbing material has a characteristic of not adsorbing water vapor until the water vapor pressure P / P0 is 0.8. A method for producing carbon dioxide by refining a raw material gas,
A method for producing carbon dioxide, comprising: a gas adsorption step for adsorbing carbon dioxide gas contained in the raw material gas at a predetermined adsorption temperature to the gas adsorbing material according to any one of claims 1 to 5.   The method for producing carbon dioxide according to claim 6, wherein in the gas adsorption step, carbon dioxide gas is adsorbed by a pressure fluctuation type adsorption method. A method for recovering carbon dioxide,
A method for recovering carbon dioxide, comprising: a gas adsorption step of adsorbing carbon dioxide gas contained in the raw material gas at a predetermined adsorption temperature to the gas adsorbing material according to any one of claims 1 to 5.   The carbon dioxide recovery method according to claim 8, wherein in the gas adsorption step, carbon dioxide gas is adsorbed by a pressure fluctuation type adsorption method.

Images