JP3485148B2 - Contact combustion type gas sensor for low boiling point fuel gas leak detection - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic combustion type gas sensor which is insensitive to alcohol which causes noise when detecting gas.

[0002]

2. Description of the Related Art Catalytic combustion type sensors detect flammable gas in air and are widely used in gas leak alarms and the like. However, when used as a gas leak detector for low boiling point fuel gas such as hydrogen or methane / ethane, the conventional sensor has sensitivity to alcohols in the atmosphere, and therefore, for example, for cleaning or wiping. When alcohols are used or alcohol vapors generated by heating alcoholic beverages during cooking are detected, problems such as misreporting occur.

Here, as a technique for desensitizing alcohol, xCuO.yA in Japanese Utility Model Publication No. 7-14875.
l ₂ O · zSiO ₂ · mH ₂ 0 (x = 0.9 to 1.1, y
= 1, z = 1 to 2, m: 9 or less), a technique of desensitizing to alcohol by using a zeolite catalyst represented by a temperature compensating element has been proposed. Also fair 1-278
No. 64 proposes a technique for attaching an adsorbent having an adsorbing property to a miscellaneous gas other than the flammability detecting target gas to a gas detecting element. However, in the former case, the long-term durability of the temperature compensation element and the influence of ambient temperature change are large,
There was a flaw. On the other hand, the latter method using an adsorbent increases the cost because a filter is attached outside the sensor,
There is also a problem that the size of the sensor section becomes large.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, that is, it does not require a separate component that causes a cost increase and an increase in size, and a measurement error is less likely to occur. An object of the present invention is to provide a catalytic combustion type gas sensor capable of accurately measuring gas concentration.

[0005]

That is, the low boiling point of the present invention
A contact combustion type gas sensor for detecting a point fuel gas leak is claim 1.
As described, it possesses a temperature compensation element detecting element, a low
In a catalytic combustion gas sensor for detecting leakage of boiling point fuel gas , a temperature compensation element has an alumina layer supporting manganese oxide, and the amount of manganese in the alumina layer is 10% by weight or more based on the weight of alumina. It has a certain configuration.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The temperature compensating element used in the gas sensor according to the present invention can be manufactured, for example, as follows. That is, it can be obtained by adding a compound containing manganese to alumina or an alumina-forming material, arranging it around a metal wire, and further heat treating it in the presence of oxygen. Examples of the compound containing manganese in the present invention include manganese nitrate and manganese dioxide. Any other material that forms dimanganese trioxide by heating can be preferably used.

The above manganese-containing compound, alumina or an alumina-forming material, a small amount of water and, if necessary, an alumina binder (aluminum hydroxide) are added and kneaded to form a paste, and the metal as shown in FIG. The coil portion of the wire is coated in a granular form and heat-treated in the presence of oxygen. Here, the material of the metal wire is determined in consideration of oxidation resistance, durability, heat resistance, and price, but it is usually desirable to use platinum. Further, in the heat treatment in the presence of oxygen, firing is performed at 600 ° C. or higher in an environment where oxygen is present such as in air. It is known that dimanganese trioxide is formed by heat treatment in air at 530 to 940 ° C. In the present invention, the compound containing manganese is appropriately determined according to the required performance, but usually the amount of manganese is 1 with respect to the weight of alumina.
It is preferably 0% by weight or more. If the amount of manganese is too large, the strength of the coating layer of the temperature compensating element tends to decrease, so it is usually desirable to be 30% by weight or less. In addition, in the present invention, the material used for the normal catalytic combustion type gas sensor can be directly used as a raw material for the detection element.

[0008]

EXAMPLES Next, examples of the present invention will be specifically described. (Production of Temperature Compensation Element) Manganese nitrate was added to γ-alumina obtained by heat treatment of boehmite-type aluminum hydroxide at 850 ° C., and the mixture was heated to 650 ° C. to obtain α-alumina carrying manganese trioxide. Was crushed to a particle size of about 1 to 2 μm. A small amount of alumina-based binder (aluminum hydroxide) and water are added to this, and the mixture is kneaded to form a paste, and the coil portion of a platinum wire (coil portion outer diameter: 0.6 mm) whose appearance is shown in FIG. 1 is shown. Was adhered in the form of granules so as to cover and was air dried. Then, the platinum wire was energized to generate heat and baked at around 700 ° C. to obtain a temperature compensation element.

(Production of Sensing Element) An aqueous chloroplatinate solution containing 5% by weight of platinum and 5% by weight of palladium were used.
An equal amount of a palladium chloride aqueous solution of palladium chloride prepared to have a weight percentage was mixed in equal amounts to prepare a catalyst supporting aqueous solution. 850 boehmite type aluminum hydroxide was added to this catalyst supporting aqueous solution.
The γ-alumina obtained by heat treatment at ℃ was immersed, filtered, taken out, dried, added with a little water and a binder, and kneaded. Attach it in a granular manner so as to cover the coil part,
After air drying, electricity was applied and baking was performed at around 700 ° C. to obtain a detection element.

(Assembly of Catalytic Combustion Gas Sensor and Its Evaluation) A bridge circuit was formed using the temperature compensating element and the sensing element obtained as described above to obtain a catalytic combustion gas sensor. Then, both elements of this catalytic combustion type gas sensor are
The sensitivity to hydrogen, methane, isobutane and ethyl alcohol was examined by keeping the temperature at 00 ° C. The results are shown in Figure 2. The horizontal axis of FIG. 2 is the weight% of manganese in the coating layer. From FIG. 2, it is understood that the catalytic combustion gas sensor according to the present invention can significantly reduce the sensitivity to ethyl alcohol without affecting the sensitivity to methane gas and hydrogen gas. Note that FIG. 3 shows an X-ray diffraction spectrum measured for confirming the production of dimanganese trioxide in the coating layer of the temperature compensation element.

[0011]

The catalytic combustion type gas sensor of the present invention is inexpensive and compact because it does not require a housing, can be easily inspected even after the sensor is attached, and measurement errors are less likely to occur, and the gas concentration of the target gas can be measured. Is an excellent one that can be accurately measured over a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram showing a metal wire as a conductor used in a catalytic combustion type gas sensor.

FIG. 2 is a diagram showing the sensitivity of the catalytic combustion type gas sensor according to the present invention to various gases.

FIG. 3 is an X-ray diffraction spectrum measured to confirm the production of dimanganese trioxide in the coating layer of the temperature compensation element manufactured in the example.

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Claims (2)

(57) [Claims] [Claim 1] possess a temperature compensation element detecting element, a low-boiling
In a catalytic combustion gas sensor for detecting leakage of point fuel gas , a temperature compensation element has an alumina layer supporting manganese oxide, and the amount of manganese in the alumina layer is 10% by weight or more based on the weight of alumina. Characterized by being
Contact combustion type gas sensor for low-boiling fuel gas leak detection. 2. The catalytic combustion gas sensor for detecting low-boiling fuel gas leakage according to claim 1, wherein the manganese oxide is dimanganese trioxide.