JPH0758255B2 - Adsorption amount measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an adsorption amount measuring device based on a so-called constant volume method among devices for measuring an adsorption amount of a gas by a sample, for example, a powder using the gas adsorption method. The present invention relates to a device that can be used for highly accurate measurement of the surface area and pore distribution of a body or a porous body.

<Prior Art> By physically adsorbing gas molecules on the surface of a sample and measuring the adsorption amount, the surface area and pore distribution of the sample can be obtained. The flow method and the constant volume method are known.

The flow method is basically a method in which a mixed gas of an adsorbed gas and a non-adsorbed gas is caused to flow in a container containing a sample, and the amount of gas adsorbed by the sample is obtained from the change in gas mixing in the upstream and downstream of the container. Thus, it is a measuring method for the purpose of simply measuring a part of the adsorption / desorption isotherm in a short time, and is suitable for use in the field of quality control of powders and porous bodies.

On the other hand, the constant volume method is a partition between the known volume of the manifold and the sample container is separated by an on-off valve, and after the on-off valve is closed, adsorbed gas is introduced into the manifold under a predetermined pressure,
Open the on-off valve to introduce the adsorbed gas into the sample container, adsorb it to the sample, and measure the pressure at the time when adsorption equilibrium is reached. Basically, the adsorption isotherm of the sample is obtained by repeating the process while changing the pressure.
It is a measurement method mainly intended to accurately measure adsorption / desorption isotherms over a long period of time, and is used in the field of research / development, etc. when strict measurement of the surface area and pore distribution of a sample is desired.

By the way, when measuring such an adsorption amount, a degassing process for removing impurities adhering to the sample surface is required as a pretreatment of the sample to be measured.

Therefore, in the adsorption amount measuring device based on the flow method,
Prior to the actual measurement, the sample in the container is degassed by heating the sample container while it is attached to the conduit for flowing the mixed gas and flowing a non-adsorbed gas such as helium gas into the sample container. There is.

On the other hand, in the adsorption amount measuring device based on the constant volume method, conventionally, in addition to the measurement stage for actually measuring the adsorption amount, a degassing stage consisting of a pipe system separate from this is provided.

FIG. 3 shows a configuration example of a conventional degassing stage. In this example, the sample is mounted in the cell mounting parts 31a and 31b of the degassing stage while being housed in the sample cells 30a and 30b. In this mounted state, the sample is heated by the heaters 32a and 32b, and the insides of the sample cells 30a and 30b are evacuated by the vacuum pump 33 to remove impurities on the sample surface.

Such pretreatment operation is automatically performed by controlling the valves 36a, 36b to 39 via the valve driver 35 based on the control signal from the degassing control computer 34.

In the figure, 40 is a vacuum gauge for monitoring the degree of vacuum, and 41 is A
The -D converter, 42 is a temperature controller for the heater.

When such pretreatment is completed, an inert gas such as helium is filled in the sample cells 30a and 30b, and the sample is transferred to the measurement stage so as not to come into contact with the outside air.

In the measurement stage, an adsorption gas such as nitrogen is introduced into the sample cell while the sample cell is cooled by liquid nitrogen or the like to make physical adsorption dominant, and the amount of gas adsorbed by the sample is measured.

<Problems to be Solved by the Invention> As described above, in the conventional adsorption amount measuring device based on the constant volume method, a degassing stage constituted by a pipe system and a control device, etc., which is completely different from the measuring stage, is provided. However, after the degassing process was completed, it was necessary to bring the cell containing the sample to the measurement stage and reattach it. Therefore, even if the degassing process or the measurement operation is automated, it is substantially impossible to automate the entire process from the degassing process to the end of the measurement.

<Means for Solving the Problems> The adsorption amount measuring device of the present invention is a cooling means for cooling a container containing a sample in a state where the container is mounted in the container mounting part, and an adsorbed gas is introduced into the container in the cooled state. An apparatus having an adsorbed gas introduction means for measuring an adsorption amount of a gas in a container by a sample in a cooled state, a heating means for heating the container mounted in the container mounting part, and a container mounted in the container mounting part Evacuation means for evacuating the inside, and control means for selectively operating the heating means, the exhaust means, the cooling means, and the adsorbed gas introduction means according to a preset procedure are provided. It is characterized in that it is configured such that the container attached to the container is heated and evacuated while being evacuated, and then the adsorbed gas is introduced into the container while cooling the container.

<Operation> While the sample container is mounted on the container mounting part for measuring the adsorption amount, prior to the actual measurement of cooling the container and introducing the adsorbed gas into the inside, the container is heated by the heating means and exhausted. By evacuating the inside of the container by means of the means, the sample can be degassed with high accuracy, and it is not necessary to move the container of the sample between each process of degassing process to adsorption amount measurement. .

<Embodiment> FIG. 1 is an overall configuration diagram showing a block diagram of a piping system and a control circuit of an embodiment of the present invention.

The sample cell 1 containing the sample is connected to the piping system at the cell mounting portion 2.

The piping system is provided with valves 3 to 10 at appropriate locations, a nitrogen gas source as an adsorbing gas and a helium gas source as an inert gas are connected, and a vacuum pump for evacuating the system. 11 is connected.

The pressure in this piping system is measured by a vacuum gauge 12 and a pressure gauge 13, digitized by an AD converter 14, and then taken into a computer 15.

In the piping system, 16 and 17 are throttles, 18 is a saturated vapor pressure measuring tube, and 19 is a calibration volume.

Below the piping system, a Dewar bottle 20 containing a refrigerant such as liquid nitrogen for cooling the sample cell 1 is provided.
The Dewar bottle 20 is moved up and down by the elevator mechanism 21 based on a command from the computer 15. Further, the valves 3 to 10 described above are controlled to be opened / closed by a control signal from the valve driver 22 based on the same command from the computer 15.

The above configuration is equivalent to the measurement stage in the conventional device.

Now, the feature of this embodiment is that a heater 23 for heating the sample cell 1 and a drive mechanism 24 for changing its position are provided below the piping system.
The temperature controller 25 which controls the temperature and ON / OFF and the movement of the drive mechanism 24 are configured to be controlled by a command signal from the computer 15.

The drive mechanism 24 can fix the heater 23 and move the heater 23 vertically. That is, the sample cell 1 can be heated by moving the heater 23 upward from the state shown in the drawing, and the heater 23 can be rotated from the state shown in the drawing so as not to prevent the Dewar bottle 20 from rising. Can be evacuated to.

FIG. 2 is a flow chart showing the contents of the program written in the computer 15. The operation of the embodiment of the present invention will be described below with reference to this figure.

The sample is inserted into the sample cell 1 and mounted on the cell mounting part 2 as it is, and a start command is given to the apparatus.

When a start command is given, first a command is given to the drive mechanism 24 and the temperature controller 25 to turn on the heater 23 and raise it. At the same time, by opening only the valves 3 and 6, the inside of the sample cell 1 is evacuated. Further, the sample inside is heated, and the sample is degassed. After the degree of vacuum in the system has risen to some extent, the valve 5 is opened and the vacuum is drawn through this.

Then, it is determined whether a preset degassing completion condition is satisfied, and if it is satisfied, the heater is
Turn OFF 23 and lower it, then rotate it to retract sideways.

In that state, this time, the Dewar 20 is raised and the sample cell 1
Is immersed in the refrigerant, cooling of the sample is started, and the measurement operation is automatically performed.

The degassing completion conditions described above include, for example, that a certain time has elapsed after the start of heating, or when a certain degree of vacuum is reached, the valves 5 or 6 are closed to stop the exhaust and the vacuum gauge 12 The data can be monitored, and it can be adopted that the degree of vacuum change is within a certain range.

It should be noted that in the above embodiment, the one having one measuring stage has been described, but it goes without saying that the present invention can be applied to the one having two or more measuring stages in the same manner.

In addition to the measurement stage having such a degassing function, if a degassing stage dedicated to pretreatment as shown in FIG. Processing becomes possible and the measurement efficiency can be improved.

Further, by utilizing the function of the present invention, not only physical adsorption but also chemical adsorption can be measured.

That is, a gas such as oxygen or hydrogen is used for the measurement of chemisorption, and it is usually measured in a temperature range above normal temperature.
Therefore, the temperature control of the heater 23 is set to be programmable so that it can be adapted to chemisorption, and after the degassing at the measurement stage is completed, the temperature of the heater 23 is controlled as it is without cooling the sample cell 1 to perform chemisorption. Can be configured to perform measurements of

<Effects of the Invention> As described above, according to the present invention, a heating means for heating the container in a state where the container is mounted on the container mounting part for measurement in the adsorption amount measuring device based on the constant volume method, and An evacuation means for evacuating the inside of the container is provided, and these heating means and evacuation means, as well as the container cooling means for measurement and the adsorbed gas introducing means are selectively operated based on a preset procedure. A control means is provided to heat the container and evacuate the inside of the container prior to the actual adsorption amount measurement operation, so the sample container is attached to the container mounting part for adsorption amount measurement based on the constant volume method. As it is, it is possible to automatically degas the sample inside, and transfer the sample container between the degassing stage and the measuring stage like the adsorption amount measuring device based on the conventional constant volume method. Dress Not only does it not have to be reattached, it is possible to automate all the processes from degassing as a pretreatment of the sample to the measurement of the adsorption amount, while maintaining a high degree of vacuum after degassing. With this, it becomes possible to shift to the measurement operation, and the measurement accuracy can be improved.

Moreover, since the degassing is performed by evacuating the inside of the sample container while heating it, the amount of change in the degree of vacuum due to the gas released from the sample can be adopted as the degassing determination condition. Degassing treatment with high reliability can be performed.

In addition, if the present invention is configured to be applicable to the measurement of chemisorption, even if a highly reactive gas or a highly toxic gas is used as the pretreatment gas, the pretreatment can be changed to the measurement without touching the outside air. Since automatic transfer is possible, there is also an effect that safety and reliability are improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is a flow chart showing the contents of a program written in the computer 15, and FIG. 3 is a configuration diagram of a conventional degassing stage. 1 …… Sample cell 2 …… Cell mounting part 3 ～ 10 …… Valve 11 …… Vacuum pump 15 …… Computer 20 …… Dewar bottle 21 …… Elevator mechanism 23 …… Heater 24 …… Drive mechanism 25 …… Temperature control vessel

Claims (1)

[Claims] 1. A cooling means for cooling a container containing a sample in a state where the container is mounted in a container mounting portion, and an adsorption gas introducing means for introducing an adsorption gas into the inside of the container in the cooling state. In a device for measuring the amount of gas adsorbed in a container by a sample, heating means for heating the container mounted in the container mounting part, exhaust means for evacuating the container mounted in the container mounting part, and The heating means, the exhausting means, the cooling means, and the adsorbed gas introducing means are provided with a control means for selectively operating them according to a preset procedure, and the control means heats the container mounted in the container mounting part. The apparatus for measuring an adsorption amount is characterized in that the adsorption gas is introduced into the interior of the container while the container is cooled while being evacuated.