WO2020013005A1

WO2020013005A1 - Gas detection material

Info

Publication number: WO2020013005A1
Application number: PCT/JP2019/026072
Authority: WO
Inventors: 雅人辻口; 丸尾　容子
Original assignee: 日本電気硝子株式会社; 学校法人東北工業大学
Priority date: 2018-07-13
Filing date: 2019-07-01
Publication date: 2020-01-16

Abstract

Provided is a gas detection material which is small-sized and inexpensive, and which can detect an aldehyde-based gas. A gas detection material characterized by having a porous body having pores, an alkaline compound carried in the pores, and a gas sensing agent.

Description

Gas detection material

The present invention relates to a gas detection material.

Lung cancer is one of the highest mortality cancers. This is because it is difficult to detect lung cancer early with chest x-ray, which is the current main examination method. Therefore, a method of diagnosing lung cancer at an early stage by analyzing a component that specifically increases in lung cancer patients from exhaled breath is being studied.

For example, the result of analyzing the breath of a lung cancer patient using a gas chromatography mass spectrometer (GC-MS) and disclosing the result that an aldehyde-based gas such as nonanal is contained at a higher concentration than a healthy person is disclosed. (For example, see Non-Patent Document 1).

However, GC-MS is problematic in that it is large-scale and very expensive, and it takes a long time for analysis.

The present invention has been made in view of such circumstances, and has as its object to provide a gas detection material which is small and inexpensive and can detect an aldehyde-based gas.

ガス The gas detection material of the present invention is characterized by having a porous body having pores, an alkaline compound supported in the pores, and a gas detection agent. When the gas detector carried in the pores of the porous body reacts with the aldehyde-based gas under an alkaline compound as a catalyst, the absorbance of the gas detector at a specific wavelength changes. By measuring the change in the absorbance, an aldehyde-based gas can be detected.

The gas detection material of the present invention is preferably a porous glass in which the porous body contains 85 to 100% of SiO _{2 by} mass%.

ガス In the gas detection material of the present invention, the alkaline compound preferably contains sodium hydroxide.

は In the gas detection material of the present invention, the gas detection agent preferably contains vanillin and / or a derivative of vanillin.

ガス The gas detection material of the present invention is preferably for detecting aldehyde gas.

According to the present invention, a small and inexpensive gas detection material capable of detecting an aldehyde-based gas can be provided.

ガス The gas detection material of the present invention will be described.

ガス The gas detection material of the present invention has a porous body having pores, an alkaline compound, and a gas detection agent. Both the alkaline compound and the gas detector are supported in the pores of the porous body.

する Each component will be described below.

(Porous body)
As described above, since the aldehyde-based gas is detected by measuring the change in the absorbance of the gas detector at a specific wavelength, the porous body is required to have a high light transmittance. Therefore, the porous body is preferably a porous glass having high light transmittance. Although porous glass is inferior to light in terms of light transmittance, a porous polymer material, porous ceramic, silica gel, or the like may be used as the porous body.

(4) A method for producing a porous glass will be described below.

First, a glass base material for porous glass is prepared as follows. In mass%, SiO ₂ 40 to 80%, B ₂ O ₃ 0 to 40%, Na ₂ O 0 to 20%, ZrO ₂ 0 to 10%, Al ₂ O ₃ 0 to 5%, RO (R is (At least one selected from Mg, Ca, Sr and Ba) so that the glass composition contains 0 to 20% and Na ₂ O / B ₂ O ₃ in a mass ratio of 0.25 to 0.5. Mix glass raw materials. The reason why the content of each component is specified as described above will be described below. Unless otherwise specified, "%" means "% by mass" in the following description of the component content.

SiO ₂ is a component that forms a glass network. The content of SiO ₂ is preferably 40 to 80%, 45 to 75%, 50 to 70%, and particularly preferably 52 to 65%. If the content of SiO ₂ is too small, the weather resistance and mechanical strength tend to decrease. On the other hand, if the content of SiO ₂ is too large, phase separation becomes difficult.

B ₂ O ₃ is a component that forms a glass network and promotes phase separation. The content of B ₂ O ₃ is preferably more than 0 to 40%, 10 to 30%, particularly preferably 20 to 25%. If B ₂ O ₃ is not contained, the above effect is difficult to obtain. On the other hand, if the content of B ₂ O ₃ is too large, the weather resistance tends to decrease.

B ₂ O ₃ / SiO ₂ is preferably from 0.3 to 0.5, 0.35 to 0.48, 0.38 to 0.46, particularly preferably 0.4 to 0.45. If B ₂ O ₃ / SiO ₂ is too small, internal stress is likely to be generated in the step of removing the SiO ₂ colloid with an alkaline aqueous solution described later, so that the porous glass is likely to be cracked. On the other hand, if B ₂ O ₃ / SiO ₂ is too large, the mechanical strength tends to decrease in the step of removing the SiO ₂ colloid with an alkaline aqueous solution described later, so that the porous glass is likely to crack. “B ₂ O ₃ / SiO ₂ ” indicates a value obtained by dividing the content of B ₂ O _{3 by} the content of SiO ₂ .

Na ₂ O is a component that lowers the melting temperature to improve the meltability and promotes phase separation. The content of Na ₂ O is preferably more than 0 to 20%, 3 to 10%, particularly preferably 4 to 8%. If Na ₂ O is not contained, the above effect is difficult to obtain. On the other hand, if the content of Na ₂ O is too large, phase separation will be difficult.

Na ₂ O / B ₂ O ₃ is preferably 0.25 to 0.5, 0.28 to 0.4, and more preferably 0.3 to 0.35. If Na ₂ O / B ₂ O ₃ is too small, it becomes difficult to remove the boron oxide-rich phase in the step of removing the boron oxide-rich phase with an acid described later. On the other hand, if Na ₂ O / B ₂ O ₃ is too large, the amount of expansion due to hydration of the silica gel tends to be smaller than the amount of contraction due to elution of Na ₂ O from the silica-rich phase, and the porous glass may be cracked. More likely to occur.

ZrO ₂ is a component that improves weather resistance. When the porous glass reacts with the alkaline compound, the alkaline compound is consumed in the reaction, and the amount of the alkaline compound carried in the porous glass is reduced. As a result, the function of the gas detection material may be reduced. There is. On the other hand, when ZrO ₂ is contained in the porous glass, the alkali resistance of the porous glass is improved, so that the above-described problems are less likely to occur. The content of ZrO ₂ is preferably 0 to 10%, 1 to 10%, more than 3 to 10%, 4 to 8%, particularly preferably 5 to 7%. If the content of ZrO ₂ is too large, devitrification tends to occur and phase separation becomes difficult.

Al ₂ O ₃ is a component that improves weather resistance and mechanical strength. The content of Al ₂ O ₃ is preferably 0 to 5%, 2 to 5%, particularly preferably 3 to 4%. If the content of Al ₂ O ₃ is too large, phase separation becomes difficult.

RO (R is at least one selected from Mg, Ca, Sr and Ba) is a component that increases the ZrO ₂ content of the silica-rich phase and improves weather resistance. The content of RO (the total amount of MgO, CaO, SrO, and BaO) is 0 to 20%, 0.5 to 20%, 1 to 17%, 3 to 15%, 4 to 13%, particularly 5 to 10%. Preferably, there is. If the content of RO is too large, phase separation becomes difficult. The contents of MgO, CaO, SrO and BaO are each preferably 0 to 20%, 1 to 17%, 3 to 15%, 4 to 13%, and particularly preferably 5 to 10%. Among them, CaO is preferably used because the effect of improving weather resistance is particularly large.

ガラス The glass base material for porous glass of the present invention may contain the following components in addition to the above components.

K ₂ O is a component that lowers the melting temperature to improve the meltability and promotes phase separation. The content of K ₂ O is preferably 0 to 20%, 3 to 10%, particularly preferably 4 to 8%. If the content of K ₂ O is too large, it is difficult to separate phases.

ZnO is a component that increases the ZrO ₂ content in the silica-rich phase and improves weather resistance. The content of ZnO is preferably 0 to 20%, 0 to 10%, particularly preferably 0 to less than 3%. If the content of ZnO is too large, phase separation becomes difficult.

In addition to the above components, various components can be contained within a range that does not impair the effects of the present invention. For example, TiO ₂ , La ₂ O ₃ , Ta ₂ O ₅ , TeO ₂ , Nb ₂ O ₅ , Gd ₂ O ₃ , Y ₂ O ₃ , Eu ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , P ₂ O ₅ And Bi ₂ O ₃ or the like may be contained in a range of 15% or less, further 10% or less, particularly 5% or less, and a total amount of 30% or less.

Next, the prepared glass batch is melted at 1300-1500 ° C. for 4-12 hours. Next, the molten glass is formed into a plate shape, and then gradually cooled at 400 to 600 ° C. for 10 minutes to 10 hours to obtain a glass base material. The shape of the obtained glass base material is not particularly limited, but the surface shape is preferably a rectangular or circular plate. In addition, in order to make the obtained glass base material into a desired shape, processing such as cutting and polishing may be performed. Also, continuous production using a refractory furnace may be used. The method of melting and shaping the glass is not limited to the above method.

アスペクト The obtained glass base material preferably has an aspect ratio of 2 to 1000, particularly preferably 5 to 500. If the aspect ratio is too small, in the step of removing the boron oxide-rich phase with an acid to be described later, a large difference appears in the speed of removing the boron oxide-rich phase between the surface and the inside of the glass base material. The porous glass is easily broken. On the other hand, if the aspect ratio is too large, handling becomes difficult. The aspect ratio is calculated by the following equation.

Aspect ratio = (bottom area of glass base material) ^1/2 / thickness of glass base material

Note that the bottom area and the thickness of the obtained glass base material may be appropriately adjusted so as to have the above aspect ratio. For example, the bottom area is preferably 1 to 1000 mm ² , particularly preferably 5 to 500 mm ² , and the thickness is preferably 0.1 to 1 mm, particularly preferably 0.2 to 0.5 mm.

Next, the obtained glass base material is subjected to a heat treatment to separate into two phases, a silica-rich phase and a boron oxide-rich phase. The heat treatment temperature is preferably from 500 to 800 ° C, particularly preferably from 600 to 700 ° C. If the heat treatment temperature is too high, the glass base material softens, and it becomes difficult to obtain a desired shape. On the other hand, if the heat treatment temperature is too low, it becomes difficult to phase separate the glass base material. The heat treatment time is preferably at least 10 minutes, at least 1 hour, especially at least 3 hours. If the heat treatment time is too short, it becomes difficult to phase separate the glass base material. Although the upper limit of the heat treatment time is not particularly limited, the phase separation does not advance beyond a certain level even if the heat treatment is performed for a long time.

(4) Next, the glass base material separated into two phases is immersed in an acid to remove the boron oxide-rich phase to obtain a porous glass. Hydrochloric acid and nitric acid can be used as the acid. Note that these acids may be used as a mixture. The concentration of the acid is preferably 0.1 to 5N, more preferably 0.5 to 3N. The acid immersion time is preferably 1 hour or more, 10 hours or more, particularly preferably 20 hours or more. If the immersion time is too short, it becomes difficult to obtain a porous glass. The upper limit of the immersion time is not particularly limited, but is practically 100 hours or less. The immersion temperature is preferably 20 ° C. or higher, 25 ° C. or higher, particularly preferably 30 ° C. or higher. If the immersion temperature is too low, it becomes difficult to obtain a porous glass. The upper limit of the immersion temperature is not particularly limited, but is actually 95 ° C. or less.

In the step of heat-treating the glass base material to separate into two phases, a silica-rich phase and a boron oxide-rich phase, a silica-containing layer (a layer containing about 80% by mass or more of silica) is formed on the outermost surface of the glass base material. Tends to form. Since the silica-containing layer is difficult to remove with an acid, when the silica-containing layer is formed, the phase-separated glass base material is cut and polished. It is easier to remove the phase.

Further, it is preferable to remove the ZrO ₂ colloid and SiO ₂ colloid remaining in the pores of the obtained porous glass. Hereinafter, a method for removing the ZrO ₂ colloid and the SiO ₂ colloid will be described, but the method is not limited to these methods.

The ZrO ₂ colloid can be removed with, for example, sulfuric acid. The concentration of sulfuric acid is preferably 0.1 to 5N, particularly preferably 1 to 5N. The immersion time of sulfuric acid is preferably 1 hour or more, particularly preferably 10 hours or more. If the immersion time is too short, it will be difficult to remove the ZrO ₂ colloid. The upper limit of the immersion time is not particularly limited, but is practically 100 hours or less. The immersion temperature is preferably 20 ° C. or higher, 25 ° C. or higher, particularly preferably 30 ° C. or higher. If the immersion temperature is too low, it becomes difficult to remove the ZrO ₂ colloid. The upper limit of the immersion temperature is not particularly limited, but is actually 95 ° C. or less.

The SiO ₂ colloid can be removed with, for example, an alkaline aqueous solution. As the alkali, sodium hydroxide, potassium hydroxide and the like can be used. Note that these alkalis may be mixed and used. The immersion time of the alkaline aqueous solution is preferably 10 minutes or more, particularly preferably 30 minutes or more. If the immersion time is too short, it becomes difficult to remove the SiO ₂ colloid. The upper limit of the immersion time is not particularly limited, but is practically 100 hours or less. The immersion temperature is preferably 15 ° C. or higher, particularly preferably 20 ° C. or higher. If the immersion temperature is too low, it becomes difficult to remove the SiO ₂ colloid. The upper limit of the immersion temperature is not particularly limited, but is actually 95 ° C. or less.

The obtained porous glass preferably contains 85 to 100% of SiO _{2 by} mass%. As other components, Al ₂ O ₃ , ZrO _{2 and the} like may be contained.

中央 The central diameter of the pore distribution of the porous glass is preferably 1 to 100 nm, 4 to 90 nm, and particularly preferably 7 to 80 nm. If the median diameter of the pore distribution is too small, diffusion of gas into the pores becomes extremely difficult. On the other hand, if the central diameter of the pore distribution is too large, the light transmittance tends to decrease. The pores have various shapes such as a true sphere, a substantially ellipsoid, and a tube. The thickness and aspect ratio of the porous glass are the same as those of the glass base material.

光 The porous glass preferably has a light transmittance of 0.02% or more, 0.05% or more, particularly 0.1% or more at a wavelength of 400 nm and a thickness of 0.5 mm. If the light transmittance is too low, it tends to be difficult to use the gas detection material as a porous material.

(Alkaline compound)
Examples of the alkaline compound include an alkali metal hydroxide, an alkali metal carbonate, an alkali metal bicarbonate, an alkaline earth metal hydroxide, and an alkaline earth metal carbonate. Among them, it is preferable to use sodium hydroxide having a high catalytic ability.

(Gas detector)
The gas detector is not particularly limited as long as it has an absorption wavelength of 350 to 750 nm, reacts with an aldehyde-based gas under an alkaline compound, and changes the absorbance. Vanillin and / or a vanillin derivative may be used. Is preferred. Vanillin and / or a vanillin derivative have the advantage of being easy to handle because they do not volatilize at room temperature. It should be noted that other gas detecting agents can be used.

Next, an example of the method for producing a gas detection material of the present invention will be described.

{Circle around (1)} First, an alkaline compound and a gas detector are mixed with a solvent such as water to obtain a mixed solution containing the alkaline compound and the gas detector. The concentration of the alkaline compound in the mixture is preferably 0.1 to 10N, more preferably 0.25 to 5N. If the concentration of the alkaline compound is too low, the reaction between the gas and the gas detector may not proceed sufficiently. On the other hand, if the concentration of the alkaline compound is too high, it tends to react with the porous body, and the mechanical strength of the porous body may be reduced.

添加 The addition amount of the gas detector (content in the mixed solution) is preferably gas detector / porous material = 0.01 to 100, particularly preferably 0.1 to 10, by mass ratio to the porous material. If the added amount of the gas detecting agent is too small, the function of the gas detecting material tends to be insufficient. On the other hand, if the amount of the gas detecting agent is too large, the pores of the porous body may be blocked, and also in this case, the function of the gas detecting material tends to be insufficient.

Next, the porous body is immersed in the obtained mixed solution to obtain a gas detection material in which the pores of the porous body carry the alkaline compound and the gas detection agent. It is preferable that 0.01 g to 10 kg (preferably 10 g to 10 kg) of the porous body is dipped in 0.01 to 100 L (preferably 0.1 to 10 L) of the mixed solution, and the dipping time is 1 hour. It is preferably from minutes to 50 hours. After the porous body is immersed, moisture may be volatilized by natural drying or the like.

担持 The support of the alkaline compound and the gas detecting agent may be carried out by immersing the porous body in the mixed solution a plurality of times. In this case, it is preferable that the concentration of the alkaline compound in the mixed solution is increased as the stage after the immersion step. Thereby, it is possible to more reliably suppress the reaction product (for example, silicic acid hydrate) of the alkaline compound and the porous body from hindering the loading of the gas detecting agent in the previous stage of the immersion step. For example, a porous body is first immersed in a mixture of an alkaline compound and a gas detector at a concentration of 0.01 to 0.5N, and then a mixture of an alkaline compound and a gas detector at a concentration of 0.1 to 10N. It is preferable to immerse in the water.

Also, the alkaline compound and the gas detector may be separately loaded. Specifically, a gas detector is mixed with a dispersion medium such as water to obtain a gas detector dispersion. By immersing the porous body in the obtained dispersion, a porous body carrying the gas detection agent is obtained. Subsequently, the alkaline compound is mixed with a solvent such as water to obtain an alkaline compound solution. By immersing the porous body supporting the gas detecting agent in the obtained solution, a gas detecting material supporting the gas detecting agent and the alkaline compound is obtained. Thus, an effect is obtained that the reaction product of the porous body and the alkaline compound can more reliably prevent the gas detection agent from being carried.

Next, a method for detecting an aldehyde-based gas will be described.

First, the absorbance of the gas detection material at a specific wavelength is measured by a spectrophotometer or the like.

Next, the gas detection material is placed in a tetra bag or the like in which the measurement gas is sealed, and left for 1 minute to 5 hours to expose the measurement gas to the gas detection material. In order to promote the reaction between the gas detection material and the measurement gas, the gas detection material after exposure may be heated at 50 to 200 ° C. for 5 minutes to 1 hour.

Next, the absorbance at a specific wavelength of the gas detection material after the exposure is measured by a spectrophotometer or the like.If the absorbance of the gas detection material is different from the absorbance of the gas detection material previously measured, the measurement gas contains an aldehyde-based gas. Become. If a calibration curve is prepared using a standard gas having a known amount of the aldehyde-based gas in advance, the amount of the aldehyde-based gas can be determined from the difference in absorbance of the gas detection material before and after exposure.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

(Example 1)
(Preparation of porous glass)
First, raw materials prepared so as to have a glass composition of 53% by mass of SiO ₂ , 23% of B ₂ O ₃ , 7% of Na ₂ O, 6% of ZrO ₂ , 3% of Al ₂ O ₃ , and 8% of CaO by mass%. After putting in a platinum crucible, it was melted at 1400 ° C. for 6 hours. In melting the glass batch, the mixture was stirred using a platinum stirrer to homogenize. Next, the molten glass was poured out onto a carbon plate, formed into a plate shape, and then gradually cooled at 500 ° C. for 30 minutes to obtain a glass base material.

(4) The obtained glass base material was heat-treated at 675 ° C. for 72 hours in an electric furnace to separate phases. The glass base material after the phase separation was cut and polished to 5 mm × 5 mm × 0.5 mm (thickness). Next, the film was immersed in 1 N nitric acid (90 ° C.) for 48 hours, and then immersed in 3 N sulfuric acid (90 ° C.) for 48 hours. Then, it was washed with ion-exchanged water to obtain a porous glass.

Observation of the surface of the obtained porous glass by FE-SEM (SU-8220 manufactured by Hitachi, Ltd.) revealed that each of the glasses had a skeleton structure based on spinodal phase separation. The composition of the obtained porous glass was 93% of SiO ₂ , 4% of ZrO ₂ , and 3% of Al ₂ O ₃ by mass%, and the median diameter of the pore distribution was 80 nm. The light transmittance at a wavelength of 400 nm and a thickness of 0.5 mm was 0.1%.

The composition was measured with an energy dispersive X-ray analyzer (EX-250 manufactured by Horiba, Ltd.).

中央 The median of the pore distribution was measured by a pore distribution measuring device (QUADRASORB SI by Kantachrome).

Light transmittance was measured by a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation).

(Preparation of gas detection material)
First, 0.35 g of vanillin, 1 g, 4 g, 10 g or 20 g of sodium hydroxide are mixed with 100 ml of pure water, and the sodium hydroxide concentration is 0.25 normal, 1 normal, 2.5 normal, and 4 normal, respectively. Was obtained.

Next, 10 g of porous glass was immersed in 100 ml of each of the obtained mixed liquids for 2 hours, and then left in the air for 24 hours to evaporate water, thereby obtaining a gas detection material.

(Detection of nonanal)
First, the absorbance at a wavelength of 420 nm of a gas detection material prepared using a mixed solution having a sodium hydroxide concentration of 5 N was measured with a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation). .) Was 4.2.

(4) Next, the gas detection material was placed in a tetrabag filled with a gas containing 2.5 ppm of nonanal and left for 4 hours to expose the gas to the gas detection material. Next, the exposed gas detection material was heated at 100 ° C. for 20 minutes.

The absorbance of the heated gas detection material at a wavelength of 420 nm was measured with a spectrophotometer. The absorbance was 4.5, which was 0.3 larger than the absorbance before exposure. When a similar test was performed on a gas detection material prepared using a mixed solution having a sodium hydroxide concentration of 0.25N, 1N, and 2.5N, the absorbance after gas exposure was higher than that before exposure. The value was increased by about 0.1 in comparison. From this, it was found that nonanal can be detected on the order of ppm.

(Example 2)
(Preparation of porous glass)
The glass base material produced in the same manner as in Example 1 was heat-treated at 675 ° C. for 36 hours in an electric furnace to separate phases. The glass base material after the phase separation was subjected to cutting, polishing, acid treatment, and washing with ion-exchanged water in the same manner as in Example 1 to obtain a porous glass. The obtained porous glass had a skeleton structure based on spinodal phase separation, and the median diameter of the pore distribution was 50 nm. The light transmittance at a wavelength of 400 nm and a thickness of 0.5 mm was 1%.

(Preparation of gas detection material)
0.35 g of vanillin and 2 g of sodium hydroxide were mixed with 100 ml of pure water to obtain a mixed solution having a sodium hydroxide concentration of 0.5 N. Separately, 20 g of sodium hydroxide was mixed with 100 ml of pure water to obtain a 5N sodium hydroxide solution.

First, 1 g of the porous glass is immersed in 100 ml of a mixed solution having a sodium hydroxide concentration of 0.5 N for 2 hours, and then left in the air for 24 hours to evaporate water. Soaked in sodium solution for 2 hours. Thereafter, the porous glass was allowed to stand in the air for 24 hours to evaporate water, thereby obtaining a gas detection material.

(Detection of nonanal)
First, the absorbance of the gas detection material at a wavelength of 420 nm was measured with a spectrophotometer (UV-3100, manufactured by Shimadzu Corporation), and the absorbance was 3.1.

(4) The absorbance of the heated gas detection material at a wavelength of 420 nm was measured with a spectrophotometer. The absorbance was 3.6, which was 0.5 larger than the absorbance before exposure. From this, it was found that nonanal can be detected on the order of ppm.

ガス The gas detection material of the present invention is suitable for a wide range of applications such as breath diagnosis, skin gas measurement, bad breath checker, environmental monitoring, and work environment management.

Claims

ガス A gas detection material comprising a porous body having pores, an alkaline compound supported in the pores, and a gas detection agent.
2. The gas detection material according to claim 1, wherein the porous body is a porous glass containing 85 to 100% of SiO 2 by mass%.
(3) The gas detection material according to (1) or (2), wherein the alkaline compound is sodium hydroxide.
(4) The gas detection material according to any one of (1) to (3), wherein the gas detection agent is vanillin and / or a derivative of vanillin.
The gas detection material according to any one of claims 1 to 4, which is used for detecting an aldehyde-based gas.