JPH0353157Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Field of industrial application The present invention relates to a surface area or specific surface area measuring device, and more specifically to a surface area or specific surface area measuring device that employs a flow method based on the principle of low-temperature gas adsorption method.

(b) Prior art In a specific surface area measuring device using a flow method based on a low-temperature gas adsorption method, a mixed gas obtained by mixing an adsorbed gas and a carrier gas at an accurate mixing ratio is generally used as the measurement gas. . usually,
Nitrogen gas is used as the adsorption gas, and helium gas is used as the carrier gas, with a mixing ratio of 3:7. Therefore, except for those for special purposes such as measurement experiments, this type of apparatus usually uses a mixing cylinder in which nitrogen gas and helium gas are mixed at the above-mentioned mixing ratio. However, in order to calibrate the device, pure adsorbed gas, ie, pure nitrogen gas, is required. Therefore, an injection septum serving as an injection port for calibration gas is usually provided in the measurement channel, and pure adsorbed gas collected from the outside is injected using a syringe or the like.
In this case, it is necessary to prepare a pure gas cylinder and a flow path separately from the measuring device. When nitrogen gas is used as the adsorption gas, it can be collected from liquid nitrogen used as a refrigerant in the cold trap of the measuring device. However, the refrigerant container of the cold trap in the conventional device is an open container.
When collecting nitrogen gas from this container using a syringe several centimeters above the liquid nitrogen level, there is a risk that impurities such as water vapor and air may be mixed in. Furthermore, when collecting samples with the needle tip of the syringe immersed in the liquid level, there is a risk that the syringe will burst during suction, which poses problems in terms of both workability and measurement reliability.

(c) Purpose The present invention was developed in view of the above points, and is particularly suitable for measuring surface area or specific surface area using a mixed gas cylinder containing a mixed gas of adsorbed gas and non-adsorbed gas. A simple configuration is possible without the need to prepare a cylinder for sampling, taking advantage of the fact that liquid nitrogen is generally used as the refrigerant in cold traps, and that nitrogen gas is also commonly used as the adsorption gas. A surface area or specific surface area measuring device that can easily collect pure gas for calibration without any impurities mixed in, and can perform highly accurate measurements with simple operation. The purpose is to provide

(d) Structure In order to achieve the above object, the present invention uses a semi-closed type cold trap container for cooling the passing gas, which prevents gas from flowing in from the outside and allows gas to flow out from the inside. At the same time, this refrigerant container is provided with a sampling port for sampling the gas inside the container from the outside.

In other words, the present invention takes advantage of the fact that liquid nitrogen is extremely commonly used as a refrigerant in cold traps, and makes the refrigerant container of this cold trap semi-hermetic so that only the internal gas can flow out. By doing this, after a predetermined period of time has elapsed after the refrigerant is contained, only pure vaporized gas of the refrigerant, that is, pure nitrogen gas, is present in the refrigerant container, and this pure nitrogen gas is extracted from the sampling port provided in the container. This allows for easy removal without contamination with impurities.

(E) Embodiments Examples of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.

The mixed gas flow path for measurement has a known configuration, and the mixed gas inlet 1 is connected to a mixed gas cylinder in which nitrogen gas and helium gas are mixed at a ratio of 3:7. Downstream from the mixed gas inlet 1, there are a pressure regulator 2, a flow control valve 3, a cold trap section 4, a septum 5 for injecting calibration gas,
Measuring section 6, flow meter 7, degassing section 8, diffusion prevention section 9
are connected to the mixed gas outlet 10.

The measuring section 6 and the degassing section 8 are provided with cell attachment/detachment connectors 6a and 8a, respectively, and the sample cell S containing the sample can be airtightly connected to the mixed gas outlet 10 gas flow path. .

The thermal conductivity detector (TCD) 11 detects the thermal conductivity of the gas in the flow path upstream and downstream of the measuring section 6, thereby detecting the mixed gas introduced into the sample cell S of the measuring section 6, The difference in concentration of adsorbed gas (nitrogen gas) in the mixed gas discharged from the sample cell is determined, thereby obtaining the amount of gas adsorbed by the sample in the sample cell S, and the specific surface area of the sample can be calculated. In order to calibrate the output of the thermal conductivity detector 11, pure adsorbed gas in the gas mixture used for measurement, that is, pure nitrogen gas, is required. Brasion gas is injected from the septum 5 using a syringe.

The sample cell S of the measurement unit 6 is immersed in a coolant such as liquid nitrogen in order to predominantly cause physical adsorption.

A sample cell S attached to the degassing section 8 is filled with a sample before measurement. Then, by passing the mixed gas through the sample cell S while heating it with the heater 8b, impurities such as moisture contained in the sample are removed. The reason why the sample cell S is heated by the heater 8b is to prevent the adsorbed gas from being physically adsorbed to the sample before measurement during the degassing process.

Note that the pressure regulator 2, the flow rate control valve 3, and the flow meter 7 are provided to set the pressure and flow rate of the measurement mixed gas introduced from the mixed gas inlet 1 to desired values. Further, the diffusion prevention section 9 is provided to prevent air from entering the flow path.

The cold trap section 4 is a cold trap 4.
a, a connector 4b for connecting the cold trap 4a to a flow path, and a refrigerant container 12 for storing liquid nitrogen, which is a refrigerant for the cold trap, to cool the mixed gas for measurement. The purpose is to improve the dew point.

A lid 12a is attached to the refrigerant container 12, and the cold trap 4a is connected to the O-
It is inserted airtight into the container via the ring 12b. The lid 12a is also provided with a check valve 12c and a suction septum 12d, and the check valve 12c allows the gas inside the refrigerant container 12 to flow out when the pressure exceeds a predetermined pressure. , is installed in a direction that prohibits gas inflow from the outside.

The air sampling septum 12d is configured, for example, as shown in the cross-sectional view in FIG. 2, and the gas inside can be sampled with a syringe while keeping the refrigerant container 12 airtight to the outside. That is, 2
1 is a guide for guiding the syringe needle, 22 is a gas flow path connected to the upper part of the refrigerant container 12, 23 is a cylindrical rubber stopper, and 24 is a sealing cap.The needle of the syringe is inserted into the rubber stopper 23 and sucked. Thereby, the gas in the refrigerant container 12 can be sampled without mixing outside air. Note that this structure is the same as the above-mentioned septum 5 for injecting calibration gas.

According to the above-described embodiment of the present invention, air is mixed in the space of the refrigerant container 12 at the beginning, but when cooling the cold trap 4a with a large heat capacity, the liquid nitrogen that is the refrigerant boils violently and the check valve is closed. A large amount of nitrogen gas flows out via 12c. From this point on, only pure nitrogen gas will exist in the space within the refrigerant container 12. In this state, if a syringe is inserted into the sampling septum 12d and the internal gas is sucked, pure nitrogen gas can be collected, and this can be injected into the measurement channel from the calibration gas injection septum 5. Therefore, it can be used as a calibration gas for the thermal conductivity detector 11.

In the above embodiment, a check valve 12c was provided to make the refrigerant container 12 semi-closed, and a gas sampling septum 12d was provided to collect the gas inside. 1
If a minute opening is provided in 2a, it can be made into a substantially semi-sealed type as long as the outside air pressure does not become higher than the internal pressure, and it is also possible to draw air from this minute opening.

Further, in order to prevent an accident due to an abnormal increase in the pressure inside the refrigerant container 12 due to unexpected boiling of liquid nitrogen, the refrigerant container 12 may be provided with a rupture disc.

Furthermore, the calibration gas is not drawn and injected using a syringe, but instead of being drawn into the drawing septum 1.
It is also possible to directly connect the portion 2d and the septum 5 portion for injecting calibration gas, and to introduce a certain amount of gas into the measurement flow path only during calibration.

(f) Effects As explained above, according to the present invention, a refrigerant can be The refrigerant container of a cold trap, in which liquid nitrogen is very commonly used, is semi-sealed so that only the internal gas can escape, and this refrigerant container is equipped with a sampling port for collecting the internal gas. As time passes, the gas in the refrigerant container inevitably becomes only the pure vaporized gas of the refrigerant, that is, pure nitrogen gas, and pure nitrogen gas for calibration can be easily collected from the sampling port without contamination with impurities. This makes it possible to perform highly accurate measurements with a simple configuration without the need for a separate gas cylinder for calibration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of the structure of the air intake septum 12d. 1...Mixed gas inlet, 4...Cold trap section, 4a...Cold trap, 4b...Connector, 5...Septum for calibration gas injection, 6...Measurement section, 6a...Cell attachment/detachment connector ,
7... Flow meter, 8... Degassing section, 8a... Cell attachment/detachment connector, 9... Diffusion prevention section preventing air from entering, 10... Mixed gas outlet, 11... Thermal conductivity detector (TCD) , 12... Refrigerant container, 12a...
Lid, 12b... O-ring, 12c... Check valve, 12d... Gas sampling septum, S... Sample cell.

Claims (1)

[Scope of utility model registration request] It is equipped with a sample cell that encloses a sample and a cold trap that cools the passing gas using liquefied gas contained in a container as a refrigerant, and mixes a measurement mixed gas consisting of adsorbed gas and non-adsorbed gas. In an apparatus configured to obtain the surface area or specific surface area of the sample in the sample cell by introducing the sample from a gas cylinder through the cold trap into the sample cell and measuring the change in the gas mixture ratio before and after the introduction, The refrigerant container of the cold trap is formed in a semi-sealed shape that prevents gas from flowing in from the outside and allows gas to flow out from the inside. A surface area or specific surface area measuring device characterized by being provided with a sampling port for sampling from.