JPH0353158Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a specific surface area measuring device, and more specifically, to a specific surface area measuring device that employs a flow method based on the principle of the BET one-point method.

(B) Prior Art In a specific surface area measuring device using a flow method based on the BET one-point method, a mixed gas obtained by mixing an adsorbed gas and a carrier gas at a precise mixing ratio is generally used as the measuring gas. In such devices, therefore, the mixing cylinder is connected to the measuring channel. However, in order to calibrate the device, pure adsorbed gas is required. The accuracy of this calibration is determined by how much molecular weight of the adsorbed gas can be accurately measured.
The most reliable method is to use a microsyringe to inject a fixed volume of adsorbed gas defined by its capacity into the measurement channel. Furthermore, the method of injecting adsorbed gas into the measurement channel using such a syringe has the advantage that calibration can be performed over a wide range simply by changing the syringe capacity.
Therefore, an injection septum serving as a calibration gas injection port is usually provided in the measurement flow path, 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 in the cold trap section of the measuring device. However, when collecting with 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. Further, when collecting the sample with the needle tip of the syringe submerged in the liquid surface, there is a risk that the syringe may burst during suction. Furthermore, even if nitrogen gas is sucked into the syringe using either method, there are problems such as the need to leave the gas until it reaches room temperature, which poses difficulties in terms of workability and measurement reliability. It was hot.

Furthermore, there are problems with conventional measuring devices of this type.
There is a problem with degassing. Degassing treatment is an essential pretreatment process prior to measurement in order to remove impurities such as moisture adhering to the sample. In order to perform this process, in conventional devices, a degassing stage is provided downstream of the measurement stage, and the mixed gas that has passed through the measurement stage is passed through the sample awaiting the next measurement while being heated. However, the time required to perform complete degassing treatment often exceeds the measurement time; for example, while the actual measurement time is less than 10 minutes, the degassing time is several tens of minutes or more. The reality is that it usually takes several hours, which impairs the rapidity that characterizes the flow specific surface area measurement method.

(C) Purpose The present invention has a simple structure and was developed to solve all of the above-mentioned problems with conventional devices at once. It is an object of the present invention to provide a specific surface area measuring device that allows easy collection and shortens the degassing treatment time in the measurement channel.

(D) Structure The feature of the present invention is that at least one gas flow path for flowing the adsorbed gas is provided independently from the measurement flow path, and the gas flow path has a By installing a septum for collecting gas in the channel and a preliminary degassing stage that can connect a sample cell on the downstream side, it is possible to collect pure gas for calibration at any time, and at the same time,
The advantage is that a preliminary gas stage is used to perform preliminary degassing prior to degassing within the measurement channel.

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

FIG. 1 is a schematic piping diagram showing the configuration of an embodiment of the present invention.

The piping consists of two systems: a measurement flow path Wm and a calibration gas flow path Wc.

The measurement flow path Wm has a known configuration, and allows a mixed gas for measurement, such as a mixture of nitrogen gas as an adsorption gas and helium gas as a carrier gas at a ratio of 3:7, to flow in from the mixed gas inlet 1. Going downstream from the mixed gas inlet 1, there are a flow control valve 2, a cold trap 3, a septum 4 for calibration gas injection, a measurement stage 5, a filter 6, a selector valve 7, a flow meter 8, and a degassing stage 9. It is connected to the mixed gas outlet 10.

In order to introduce the mixed gas accurately mixed at the above-mentioned mixing ratio into the measurement flow path Wm, the mixed gas inlet 1 is
is connected to the mixing cylinder. The measurement stage 5 and the degassing stage 9 are provided with cell attachment/detachment connectors 5a and 9a, respectively, so that the sample cell S containing the sample can be airtightly connected to the measurement channel Wm.

The thermal conductivity detector (TCD) 11 detects the thermal conductivity of the gas in the measurement flow path Wm upstream and downstream of the measurement stage 5.
The adsorbed gas concentration difference between the mixed gas introduced into the sample cell S and the mixed gas discharged from the sample cell S is determined, and the amount of gas adsorbed by the sample in the sample cell S is obtained. The specific surface area is calculated. The sample cell S of the measurement stage 5 and the cold trap 3 are immersed in a coolant such as liquid nitrogen during the measurement. In order to calibrate the output of the thermal conductivity detector 11, pure gas of the adsorbed gas in the mixed gas used for measurement is required, and this pure gas is injected into the syringe from the septum 4 for injecting the calibration gas. is injected using
The structure of the septum 4 for injecting calibration gas is shown, for example, in a sectional view in FIG. That is, 41 is a guide for guiding the syringe needle, 42 is a flow path connected to the measurement flow path Wm, and 4
3 is a cylindrical rubber stopper, and 44 is a sealing cap. By inserting the needle of a syringe that has sucked calibration gas into the rubber stopper 43 and injecting it, the measuring flow path Wm is kept airtight with the outside. Calibration gas can be introduced into the chamber.

A sample cell S attached to the degassing stage 9 is filled with a sample before measurement. By passing the mixed gas through the sample cell S while heating it with the mantle heater 9b, impurities such as moisture contained in the sample are removed. Here, the sample is heated to prevent the adsorbed gas in the mixed gas from being physically adsorbed onto the sample before measurement.

The calibration gas flow path Wc is the measurement flow path
It is completely independent from Wm, and consists of a flow path leading to a calibration gas outlet 24 via a calibration gas inlet 21, a septum 22 for sampling calibration gas, and a preliminary degassing stage 23. Calibration gas inlet 21
is connected to a cylinder of the same pure gas as the adsorbed gas in the gas mixture used for measurement.

The preliminary degassing stage 23 is provided with a cell attachment/detachment connector 23a, and the sample cell S containing the sample can be airtightly connected to the calibration gas flow path Wc. A sample before being degassed by the degassing stage 9 is sealed in the sample cell S attached to the preliminary degassing stage 23, and the sample is heated by the mantle heater 23b while passing the calibration gas. It is possible to preliminarily remove impurities contained in the

Calibration gas sampling septum 22
has the same structure as the above-mentioned septum 4 for injecting calibration gas, and the gas in the calibration gas flow path Wc can be sampled with a syringe.

When using the above-described embodiment of the present invention, a small amount of calibration gas is always allowed to flow through the calibration gas flow path Wc. Thereby, preliminary degassing treatment of the sample can be performed in the preliminary degassing stage 23. Furthermore, calibration gas can be sampled from the calibration gas sampling septum 22 at any time and introduced into the measurement channel Wm from the calibration gas injection septum 4. If the layout of each piping system is considered so that the septum 4 for injecting the calibration gas and the septum 22 for sampling the calibration gas are arranged close to each other, the series of operations from sampling the calibration gas with a syringe to injection can be simplified. It is convenient to be

In the above embodiment, the case where only one calibration gas flow path Wc was provided was explained, but similar flow paths may be provided independently and in parallel, and each flow path may be filled with nitrogen gas or argon gas, for example. By creating a unique flow path for pure gas such as, it is effective for measurement work that requires frequent changes in the type of calibration gas.

Furthermore, as shown in FIG. 3, which shows the calibration gas flow path of another embodiment of the present invention, if a plurality of preliminary degassing stages 23 are provided in series downstream of the septum 22 for sampling calibration gas, efficiency can be improved. Preliminary degassing treatment can be performed.

The same thing can be said even if a plurality of preliminary degassing stages are provided in parallel as shown in FIG.

(f) Effects As explained above, according to the present invention, a sample can be measured by introducing a mixed gas in which adsorbed gas and non-adsorbed gas are mixed at a fixed ratio into the measurement channel from a mixed gas cylinder. In an apparatus for measuring the specific surface area of Since a detachable spare gas stage is provided, adsorbed gas for calibration can be collected into a syringe at any time, easily, and without fear of contamination with impurities. High-precision calibration can be performed, and preliminary degassing of the sample can also be performed at the same time, greatly shortening the degassing time in the measurement channel.

As a result of the above, the present invention not only improves the reliability of measurement based on a simple configuration, but also simultaneously achieves the rapidity of measurement, which is a characteristic of the flow type non-surface area measurement method.

[Brief explanation of the drawing]

Fig. 1 is a schematic piping diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a sectional view showing the structure of the septum for injecting calibration gas, and Figs.
Each figure is a piping schematic diagram showing the configuration of a calibration gas flow path in other embodiments of the present invention. 1... Mixed gas inlet, 4... Calibration injection septum, 5... Measurement stage, 9...
Degassing stage, 10...Mixed gas outlet, 21...
... Calibration gas inlet, 22... Calibration gas collection septum, 23... Preliminary degassing stage, 24... Calibration gas outlet, 5a, 9a, 23a... Cell attachment/detachment connector, 9b, 23b ...Mantle heater, S...
Sample cell, Wm...Measurement channel, Wc...Calibration gas channel.

Claims (1)

[Scope of utility model registration request] A mixed gas consisting of an adsorbed gas and a non-adsorbed gas is caused to flow from a mixed gas cylinder into a measurement channel equipped with a measurement stage and a degassing stage downstream thereof, and connected to the measurement channel at the measurement stage. By detecting changes in the mixing ratio of the above-mentioned mixed gas in the upper and downstream parts of the sample cell and measuring the amount of adsorbed gas adsorbed by the sample in the sample cell, the specific surface area of the sample can be measured. , in an apparatus configured to degas a sample in a sample cell connected to the measurement channel in the degassing stage, at least one gas channel for flowing the adsorbed gas therein; is provided independently of the measurement flow path, and on this gas flow path, there is a septum for sampling the gas in the flow path, and a spare to which a sample cell can be connected downstream. A specific surface area measuring device characterized by being equipped with a degassing stage.