JP2000325790A - Sulfide oxidizing catalyst and sulfide concentration measuring device using this catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sequence of technical procedures for simply and correctly measuring the concentration of a sulfide content of gas and a catalyst to be used for such procedures and also a sulfide concentration measuring device which is of a small size and shows superb response characteristics using the procedures. SOLUTION: This sulfide oxidizing catalyst 1 comprises a metal honeycomb carrier and a catalytic layer consisting of one or more than one kind of fine particles of a precious metal oxide as a catalyst and a wash coat with a capability of oxidizing a sulfide contained in gas to be measured including a specified amount of oxygen and at the same time. making the partial pressure ratio of SO2/SO3 contained in the oxidized gas to be measured an equilibrium value corresponding to the partial pressure of the included oxygen and consequently, stabilizing the reference partial pressure of the SO2 or SO3. In addition, the sulfide concentration measuring device is constituted of the sulfide oxidizing catalyst 1 and a measuring means (a sensor element) 10 which is provided in the downstream of the catalyst 1 and capable of detecting the SO2 or SO3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfide oxidation catalyst used for measuring a sulfide concentration in a gas and a sulfide concentration measuring device using the catalyst.

[0002]

2. Description of the Related Art Petroleum, coal, natural gas, and other fossil fuels
Is a small amount of sulfur, hydrogen sulfide, mercaptan, etc.
Hazardous to these sulfides
Is well known. Also flue
In combustion gas of fossil fuel such as gas and exhaust gas,
Oxidation of the sulfide indicated causes sulfurous acid gas (SO
₂) And its oxide sulfuric anhydride (SO₃)
Yellow oxide (SO_x)It is included. And these fuels
SO in burning gas_xThe impact on animals and plants has become severe
In recent years, discussions on emission concentration regulations have become active.
ing.

Here, in order to prevent pollution by sulfide,
Techniques for measuring the sulfide concentration in fossil fuels or their combustion gases are important. However, the technology for measuring the sulfide concentration in gas is not always established,
There are few things that can be performed easily and that can obtain accurate values. For example, although As the measurement method in the conventional gas SO _x concentration are various, as measured using a gas detector tube Each concentration after separation and determination of the SO ₂ and SO _3,
And infrared absorption analysis. In the former, however, it is difficult to separate and quantify SO ₂ —SO _3,
O _x total difficult to measure, and also, the latter also SO ₂
There is a problem that only measurements can be made.

Many conventional sulfide concentration measuring devices in gas are large and have a complicated structure. However, in order to properly investigate the influence of sulfide on the environment, it is necessary to use a chimney or a vehicle exhaust. It is desired to develop a device that can be directly attached to a discharge source of a system or the like and that can measure a sulfide concentration in real time.

[0005]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and a series of techniques for simply and accurately determining the sulfide concentration in a gas, and a catalyst used therein, An object of the present invention is to provide a compact sulfide concentration measuring device having excellent response characteristics by applying the technique.

[0006]

Means for Solving the Problems Among the above-mentioned problems, the present inventors first attempted to accurately and simply measure the concentration of sulfide in a gas by mixing oxygen into the gas to be measured and measuring the sulfide concentration in the gas. Is oxidized to SO ₂ and SO ₃ , and the partial pressure ratio between the two is assumed to approximate a theoretical equilibrium value corresponding to the oxygen partial pressure to be injected, and the concentration of either SO ₂ or SO ₃ is measured. I came up with that. According to this method, by measuring either SO ₂ or SO ₃ in an equilibrium state after oxidation, the total SO _x concentration can be accurately measured from the equilibrium value, and the sulfide concentration in the measurement gas is calculated. can do.

However, it is difficult to reliably oxidize the sulfide in the gas and to bring it into an equilibrium state even if oxygen is simply mixed into the measurement gas. Thus, the present inventors
It has been concluded that the presence of a catalyst is indispensable in order to promptly and reliably generate sulfide oxidation and the above-mentioned equilibrium state. At the same time, they faced the problem of catalyst poisoning. That is, in the sulfide oxidation catalyst, SO ₂ generated by oxidation of the sulfide easily adsorbs to the active site on the catalyst, and repeats adsorption and desorption at the active site.
As a result, they found that there was a problem that the active site was apparently blocked, and the active site lost its oxidizing function. The number of active sites affected by the adsorption / desorption equilibrium of SO ₂ (ratio to all active sites)
Is determined by the equilibrium value of SO ₂ —SO ₃ in the oxidized gas. If the number increases and all the active sites are closed, the function of the entire catalyst body is reduced.

From the above process, the present inventors have developed a sulfide oxidation catalyst which has excellent oxidation activity and does not cause catalyst poisoning in order to quickly measure the sulfide concentration by the above-mentioned method. Came to the view that it was necessary. Further, as a result of further research, the invention according to claims 1 and 2 has been completed.

The invention according to claim 1 of the present application oxidizes sulfide in a measurement gas mixed with a predetermined amount of oxygen,
By setting the SO ₂ / SO ₃ partial pressure ratio in the oxidized measurement gas to an equilibrium value corresponding to the mixed oxygen partial pressure, sulfide used to stabilize the reference SO ₂ or SO ₃ partial pressure is used. A catalyst for oxidation of a substance, a metal honeycomb carrier,
And a catalyst layer composed of one or more noble metal oxide fine particles as a catalyst and a wash coat. The invention according to claim 2 is the sulfide oxidation catalyst according to claim 1, wherein the catalyst layer does not include a washcoat and is composed of only one or two or more kinds of noble metal oxide fine particles.

The sulfide oxidation catalyst of the present invention is used as a carrier.
Using metal honeycomb, has a catalytic action on this carrier
A so-called carrier-type touch that disperses noble metal oxide fine particles
It is a medium. This supported catalyst is the catalyst
Act as a catalyst for reasons not affected by poisoning
Precious metal oxides are dispersed and adhered on the carrier as fine particles.
The surface area of the active substance increases significantly
it is conceivable that. That is, as described above,₂Absorption and desorption
The number of active sites where equilibrium occurs is determined by the SOx of the measured gas after oxidation.
₂-SO₃Since it is constant according to the equilibrium value,
Significantly increase the active material surface area (the number of active sites)
Therefore, some active sites have SO ₂The adsorption and desorption of raw
All active sites are SO₂Affected by
Therefore, the oxidation activity of the catalyst body as a whole can be maintained.
It is due to the idea that it will come.

[0011] In the sulfide oxidation catalyst according to the first aspect, the catalyst layer on the carrier is composed of noble metal oxide fine particles and a wash coat. This is to maximize the surface area of the active substance by increasing the amount of catalyst particles and the degree of dispersion by using a washcoat. According to the catalyst of this first aspect, it is possible to sulfide oxidation catalyst having excellent several durability increase of active sites which escape adsorption SO _2. As for the type of the wash coat, a general wash coat such as aluminum oxide, zirconium oxide, or silicon-zirconium oxide can be used.

On the other hand, in the sulfide oxidation catalyst according to the second aspect, the catalyst layer is made of only noble metal oxide fine particles without using a washcoat. Sulfide oxidation catalyst body according to the second _aspect, promotion of SO 2 -SO ₃ equilibrium reaction, in other words, it takes into account the response of the catalyst. That is, in the first aspect of the present invention, although the active surface area of the catalyst body is increased to the durability increased by using a washcoat, by SO ₂ is adsorbed on the base material of the washcoat, SO ₂ -SO ₃ equilibrium May slow the reaction rate until reaching. Therefore,
It is an excellent catalyst in response by excluding washcoat may affect SO ₂ -SO ₃ equilibrium reaction as claimed in claim 2, wherein. The sulfide oxidation catalyst according to claim 2 gives priority to the response, but has a good overall balance because the sulfide oxidation characteristics and the catalyst poisoning resistance are maintained. be able to.

As described above, the two sulfide oxidation catalysts according to the present invention are common in that the catalyst poisoning resistance is improved by dispersing and supporting noble metal oxide fine particles on a metal honeycomb carrier. Response characteristics differ depending on whether a washcoat is used or not. These catalysts may be properly used depending on the characteristics of the measurement gas and the purpose of use. For example, when the sulfide concentration in the measurement gas fluctuates drastically, it can be dealt with by using the catalyst according to claim 2 which has excellent response.

In the present invention, the catalyst component to be supported is precious metal oxide particles. This is based on the idea that it is appropriate to apply a noble metal oxide in consideration of both the catalytic activity and the anti-sulfuration property because it is easy to adsorb and easily form a stable sulfide. Here, claim 1 and claim 2
In the above, “one kind of noble metal oxide” refers to one in which one kind of noble metal oxide is dispersed on a carrier, and “two kinds of noble metal oxides” means that two or more kinds of noble metal oxides This includes not only the case where they are separately dispersed but also the case where two kinds of noble metal oxides are dispersed as one substance in a composite state.

The noble metal oxide to be supported is palladium oxide (Pd
O), rhodium oxide (Rh ₂ O ₃ ), ruthenium oxide (RuO ₂ ), and iridium oxide (IrO ₂ ) are preferable. The reason for optimizing these noble metal oxides is not necessarily clear, but according to the present inventors' consideration, it is considered that these noble metals have a particularly low adsorption strength to SO ₂ . In addition, as described above, in the present invention, not only one in which the above-described noble metal oxide is supported, but also one in which a composite oxide of two types of noble metal oxides is supported, For example, Rh
It is considered that a catalyst supporting a composite oxide such as ₂ O ₃ .PdO is particularly effective.

According to sulfide oxidation catalyst body more of claims 1 to 3, wherein, to rapidly oxidize the sulfides measurement gas, the corresponding SO 2 _/ SO ₃ min pressure ratio of oxygen partial pressure equilibrium By setting the value, the reference partial pressure of SO ₂ or SO ₃ can be stabilized. Then, a sulfide concentration measuring device can be manufactured by using the catalyst. That is, a fourth aspect of the present invention provides a sulfide oxidation catalyst according to any one of the first to third aspects, and a measurement provided downstream of the sulfide oxidation catalyst and capable of detecting SO ₂ or SO _3. And a sulfide concentration measuring device.

Here, "SO ₂ or SO ₂ "
Applicable examples of "measurement means capable of detecting ₃ " include sulfide concentration measurement means such as a gas detection tube and an infrared absorption analyzer, which have already been described as a conventional technique. In other words, since the catalyst body according to the present invention effectively functions also with respect to the conventional measurement means, by installing it in the gas introduction part of these devices, SO ₂ or SO ₃ is measured, and the value is measured. S below
The total amount of O ₂ and SO ₃ is obtained, and the concentration of sulfide contained in the measurement gas can be estimated.

[0018] However, as a particularly preferable measuring means, the measuring means according to claim 5 includes a substrate made of an oxygen ion conductive ceramic and a noble metal such as platinum formed on one surface side of the substrate. A standard electrode, a sub-electrode formed on the other side of the substrate and made of a crystalline inorganic salt containing a sulfate, and a sub-electrode formed on the surface of the sub-electrode and reacting with SO ₃ to constitute the sub-electrode. A sensor element comprising a sulfate and a metal electrode made of a metal that changes to the same substance.

This sensor element has an SO₃To
SO in the measurement gas which is sensitive to
₃The metal in the metal electrode becomes the secondary electrode due to the reaction between
Reaction to the same substance as the sulfate in₃And vice
The reaction with the sulfate in the electrode is in equilibrium
In this case, the electromotive force generated between the standard electrode and the metal electrode ₃
It is intended to measure the concentration.

The material of the metal electrode and the sub-electrode in the sensor element of the present invention is, as described in claim 6, the metal electrode is a metal containing silver, and the sulfate constituting the sub-electrode is silver sulfate. It is preferable to configure as a sulfate containing. By using such a material, an equilibrium state between the reaction at the metal electrode and the reaction at the sub-electrode can be easily realized. here,
The operation principle of the sensor element according to the sixth aspect and the method of calculating the SO ₃ concentration in the measurement gas will be described in more detail as follows.

The following reaction occurs in the silver phase in the metal electrode.

Embedded image On the other hand, in the silver sulfate phase in the sub-electrode, SO
₂ / SO ₃ and the reaction SO ₃ of gas, such as the following reactions occur.

Embedded image Further, the following reaction occurs in the standard electrode.

Embedded image Then, the following reaction occurs in the entire sensor element.

Embedded image

The above reaction causes a potential difference between the metal electrode and the standard electrode. By measuring the electromotive force based on this potential difference, the partial pressure of SO ₃ can be obtained. Specifically, the SO ₃ partial pressure can be determined by the following so-called Nernst equation.

E = E ₀ −RT · ln (P _SO3 ) / 2F (where E is a potential difference between a metal electrode and a platinum electrode, E ₀ is a standard electromotive force, and T is a temperature ( P _SO3 indicates the partial pressure of SO ₃ , R is the gas constant, F
Is the Faraday constant. )

The sulfide concentration in the measurement gas can be obtained from an SO ₂ —SO ₃ equilibrium constant that is thermodynamically calculated corresponding to the oxygen partial pressure mixed in the measurement gas.

This sensor element is obtained by laminating a plurality of thin films on a ceramic substrate, and can operate even if the thickness of each layer is about several mm. This makes it possible to reduce the size of the apparatus in each stage as compared with the case where the detection means such as the infrared absorption analyzer described above is applied. In addition, this sensor element is capable of continuous measurement, and unlike other detection means, even when the sulfide concentration in the measurement gas fluctuates, the potential difference based on the reaction equilibrium at that moment should be measured immediately. , Real-time measurement becomes possible.

Here, the substrate made of oxide ion conductive ceramic is preferably made of yttria-stable zirconia (YSZ). In the sensor according to the present invention, it is necessary to set the operating temperature to about 600 ° C. in consideration of ionic conductivity, but by using YSZ, it is possible to ensure the heat resistance of the device at high temperatures. .

As for the sulfate constituting the sub-electrode,
It is not necessary to constitute all of the sub-electrodes with silver sulfate, and it may be composed of a mixture of another sulfate, for example, lithium sulfate, sodium sulfate, barium sulfate or the like, and silver sulfate. In particular, since barium sulfate has a higher melting point than silver sulfate, when the sub-electrode is made of a mixture of barium sulfate and silver sulfate as described in claim 8, silver sulfate is used when used at a high temperature. This has the advantage of preventing the flow of water.

[0027]

Preferred embodiments of the present invention will be described below with reference to the drawings. In this embodiment, after manufacturing a sulfide oxidation catalyst in which rhodium oxide (Rh ₂ O ₃ ) is supported on a metal honeycomb as a catalyst component as a noble metal oxide, a sensor element is manufactured, and these are combined. Manufactures sulfide concentration measurement equipment. Hereinafter, each content will be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view of a sulfide oxidation catalyst 1 according to the present embodiment. The catalyst body 1 has a honeycomb structure in which a catalyst foil 2 as a carrier is wound into a cylindrical shape, and a catalyst layer composed of a wash coat and catalyst particles is laminated on the surface of the carrier. The catalyst foil 2 is made of a heat-resistant alloy and uses a band-shaped corrugated metal foil and a flat spacer foil. The metal foil is made of a stainless steel heat-resistant alloy containing aluminum (Fe-20% Cr-5% Al-0.0
8% La) was used. Then, the catalyst foil 2 is coated with a wash coat on the entire surface of the corrugated metal foil,
Noble metal oxide was carried as a catalyst component. Specifically, a metal foil with a thickness of about 50 μm
A heat treatment of heating at 900 ° C. for 5 hours was performed to form aluminum oxide whiskers on the metal surface.
This whisker is provided to improve the adhesion strength of a wash coat or the like applied to the surface. Then, the wash coat was applied by dipping in a zirconium oxide colloid solution.

FIG. 2 is a diagram schematically showing an enlarged view of the vicinity of the catalyst layer 3 of the sulfide oxidation catalyst 1. In FIG. 2, a catalyst layer 3 is formed on a catalyst foil 2, a washcoat 4 is laminated, and rhodium oxide particles 5 as a catalyst component are adhered to this. By dispersing the innumerable rhodium oxide particles 5 in this manner, the contact area with the sulfide-containing gas 6 passing through the catalyst layer 3 is increased.

Next, the sensor element will be described. FIG. 3 shows the structure of the sensor element 10 in the present embodiment. In the sensor element 10 shown in FIG. 3, a sub-electrode 12 made of a mixture of silver sulfate and barium sulfate is provided on the surface of a concave ceramic substrate 11 made of YSZ as an oxygen-ion conductive ceramic. Is provided with a metal electrode 13 made of platinum plated with silver. The sub electrode 12 and the metal electrode 13 come into contact with the measurement gas. A standard electrode 14 made of platinum is provided on the back surface of the ceramic substrate 11. The metal electrode 13 and the standard electrode 14 are connected to platinum wires 15, 1
6 is connected to a voltmeter 17 so that the potential difference between both electrodes can be measured.

As a method of manufacturing this sensor element, a mixed powder obtained by mixing silver sulfate powder and barium sulfate powder in a proportion of 50 mol% is filled in the concave portion 18 of the ceramic substrate 11 and then fired at a temperature of about 790 ° C. An electrode 12 was formed. Further, regarding the metal electrode 13, the recess 1 of the substrate 12 is used.
8 is filled with the mixed powder, and then subjected to the above-mentioned sintering process in a state where the metal electrode made of silver-plated platinum is placed on the powder, so as to be integrated with the sub-electrode 12. I have. The platinum wire 15 is joined to the metal electrode 13 by spot welding. The standard electrode 14
Is formed by depositing platinum by a sputtering method and bonding a platinum mesh to which a platinum wire 16 is welded with a platinum paste.

The sulfide concentration measuring device according to the present invention is composed of a combination of the sulfide oxidation catalyst 1 and the sensor element 10. FIG. 4 is a schematic structural diagram of the sulfide concentration measurement 20 according to the present embodiment. In FIG. 4, the sulfide concentration measuring device 20 includes a sulfide oxidation catalyst 1 in a cylinder 21.
And the sensor element 10 are arranged in series. The end of the ceramic base 11 is partially in contact with the cylindrical body 21 and is further glass-bonded. This sulfide concentration measurement 2
0, the sulfide-containing gas 6 introduced into the cylinder 21
Passes through the sulfide oxidation catalyst 1, whereby the sulfide in the gas is oxidized and contacts the sub-electrode 12 of the sensor element while maintaining the equilibrium between SO ₂ and SO ₃ generated. It is discharged after generating electromotive force. This electromotive force and SO
_Since there is a certain relationship between the gaseous matter and the gaseous catalyst No. _{3, the} concentration of SO _{3 in} the gas after passing through the catalyst can be determined by measuring the electromotive force using a voltmeter (not shown).

Experimental Example 1 First, the sulfide oxidation characteristics and the catalyst poisoning resistance of the catalyst of the present invention were examined using the catalyst evaluation device 30 shown in FIG. In the catalyst evaluation device 30 shown in FIG. 5, the sulfide oxidation catalyst 1 is loaded in a quartz tube 31 and further inserted into an electric furnace 32. Then, a flow meter 3 is supplied from a gas cylinder 33 in which a test gas composed of SO ₂ and O ₂ having a predetermined concentration and N ₂ as a balance gas is sealed.
The test gas is introduced into the quartz tube 31 through the
The concentration of SO _{2 in} the test gas after passing through the sulfide oxidation catalyst 1 heated and energized by the flowmeter ₂ is analyzed by an analyzer (ND)
The oxidizing ability of the sulfide oxidation catalyst 1 is examined by measuring with an IR analyzer. The reaction temperature can be monitored by inserting a thermocouple 37. Regarding the measured concentration of SO ₂ in the oxidized gas, the oxidation performance of the catalyst is examined by comparing with the equilibrium value between SO _{2 and} SO ₃ obtained by thermodynamic calculation.
In the measurement, after the air is sent from the compressor 34 to purge the inside of the quartz tube 31, the test gas is sent by switching the valve 36.

FIG. 6 shows that the SO ₂ concentration of the test gas is set to ₂₀₀ p.
₂ shows the time change of the SO ₂ concentration in the exhaust gas when the O ₂ concentration is set to 21.8% and the O ₂ concentration is set to 21.8%. As shown in FIG. 6, the SO ₂ concentration in the exhaust gas after passing through the catalyst is stable at around 30 ppm, and is almost close even when comparing this value with the theoretical equilibrium value (35.9 ppm) under the experimental conditions. It was possible to confirm the oxidation activity of the sulfide oxidation catalyst according to the present embodiment.

Experimental Example 2 : Next, the oxidation resistance of the catalyst body after exposing the catalyst body according to the present embodiment to a gas containing a high concentration of SO ₂ was measured to examine its sulfuration resistance. did. In the experiment, first, the catalyst body was exposed to an exposure gas (SO ₂ 100
0 ppm, O ₂ 0.5%, N ₂ balance) for up to 200 hours, appropriately take out the S, and pass the same test gas as in Experimental Example 1 using the evaluation apparatus shown in FIG.
The O ₂ concentration was determined by measuring. Other measurement conditions are the same as those in Experimental Example 1.

FIG. 7 shows the result. From this figure, it can be seen that the SO ₂ concentration in the exhaust gas after passing through the catalyst body according to the present embodiment is stable even after being exposed to a gas containing a high concentration of SO ₂ for 200 hours or more, and has high sulfuration resistance. Was confirmed.

Comparative Example : In order to confirm the performance of the sulfide oxidation catalyst according to this embodiment, the noble metal (platinum) shown in FIG.
The oxidation activity and sulfuration resistance of the mesh catalyst composed of the mesh were examined. The mesh catalyst body 40 shown in FIG.
A mesh 41 made of a 6 μm platinum wire plain-woven with a roughness of 80 mesh is formed into a cylindrical frame 42 made of stainless steel.
It is a thing attached to three.

FIG. 9 shows the change over time of the SO ₂ concentration in the gas after the mesh catalyst body 40 is mounted on the catalyst evaluation device of FIG. 5 and a test gas containing 20 ppm of SO ₂ is passed. As is clear from FIG. 9, the SO ₂ concentration in the gas when the mesh catalyst body 40 is used tends to increase. That is,
It can be seen that the oxidizing activity decreases continuously as the gas passage time increases. The difference between the test result according to this comparative example and the result in the present embodiment is because almost all of the active sites are blocked by sulfur because the active surface area of the mesh catalyst body is considerably lower than that of the supported catalyst. it is conceivable that.

Experimental Example 3 : After confirming the performance of the above catalyst, the sulfide concentration measuring device 20 incorporating this catalyst was used.
About, various characteristics when the test gas was passed were confirmed.

FIG. 10 shows changes in the electromotive force E when test gases having various SO ₂ concentrations are passed. In FIG. 10, the horizontal axis shows the SO ₂ concentration in the test gas, and the vertical axis shows the value of the electromotive force E. As shown in FIG. 10, it can be seen that the sulfide concentration measuring device 20 according to the present embodiment shows a good linear relationship with the SO ₂ concentration in the gas.

FIGS. 11 and 12 show a response curve and a return curve of the sulfide concentration measuring apparatus according to this embodiment. In this experiment, the concentration of SO _{2 in} the test gas was increased from 0 ppm to 10 ppm.
When switching to 0 ppm, and 100 ppm
This is done by reading the change in electromotive force when switching from 5 to 5 ppm.

First, it can be seen from the response curve of FIG. 11 that the response time (90% response time) at the time of switching the test gas is 90 seconds or less, indicating a good response characteristic. FIG.
Also for the return curve of No. 2, the sensor according to the present embodiment:
Since the sensor and the sulfide concentration measuring device according to the present embodiment can perform continuous measurement even when the measurement gas changes, since the sensor and the sulfide concentration measurement device according to the present embodiment show a favorable response to the switching of the gas having different SO ₂ concentrations. It was confirmed that there was.

Further, the influence on the sensor electromotive force when other gas species (NO ₂ , O ₂ ) other than the sulfide in the measurement gas were examined. 13, 10 to the NO ₂
Each N when applying a test gas containing 50 ppm
The relationship between the SO ₂ concentration and the electromotive force in the O ₂ -containing gas is shown. As is clear from this figure, it can be said that the influence of NO ₂ on the sensor according to the present embodiment is extremely small.

As shown in FIG. 14, when the oxygen concentration in the gas changes, the effect of the oxygen concentration in the measurement gas on the electromotive force of the sensor varies between the sulfide concentration in the gas and the electromotive force. , The linear relationship is almost maintained, but the intercept with respect to the vertical axis, ie,

It has been found that it mainly affects the value of E ₀ in Eq. Therefore, in actual use, it is necessary to perform correction according to the oxygen concentration in the gas to be measured.

[0045]

As described above, according to the present invention, the sulfide concentration in the gas can be easily and accurately determined. This is achieved by the sulfide oxidation catalyst according to claims 1 to 3, and according to this catalyst, sulfide in the gas to be measured is SO ₂ and SO _3.
And the partial pressure ratio between the two can be approximated to a theoretical equilibrium value corresponding to the oxygen partial pressure to be injected.

In addition, the sulfide concentration measuring apparatus according to the present invention using this catalyst is compact and excellent in response characteristics.
It can be measured continuously. Thus, according to the present invention,
It can be directly attached to the source of sulfide-containing gas, such as flue gas and automobile exhaust systems, to monitor the sulfide concentration in the gas in real time.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a sulfide oxidation catalyst.

FIG. 2 is an enlarged view of the catalyst layer of FIG.

FIG. 3 is a structural diagram of a sensor element according to the embodiment.

FIG. 4 is a structural diagram of a sulfide concentration measuring device according to the embodiment.

FIG. 5 is a schematic diagram of a catalyst evaluation device.

FIG. 6 is a time-dependent change in the concentration of SO ₂ in gas after passing through a sulfide oxidation catalyst.

FIG. 7 shows a test result of a high concentration SO ₂ gas exposure test.

FIG. 8 is a perspective view of a mesh catalyst body used as a comparative example.

FIG. 9: Time change of SO ₂ concentration in gas after passing through a mesh catalyst body

FIG. 10 is a graph showing a relationship between sensor electromotive force and sulfide (SO ₂ ) concentration in gas.

FIG. 11 is a response curve of the sulfide measurement device according to the embodiment.

FIG. 12 is a return curve in the sulfide measurement device according to the present embodiment.

FIG. 13 is a diagram showing the effect of NO ₂ gas on sensor electromotive force.

FIG. 14 is a diagram showing the effect of O ₂ gas on sensor electromotive force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sulfide oxidation catalyst 2 Catalyst foil 3 Catalyst layer 4 Wash coat 5 Rhodium oxide 6 Sulfide-containing gas 10 Sensor element 11 Ceramic substrate 12 Sub electrode 13 Metal electrode 14 Standard electrode 15, 16 Platinum wire 17 Voltmeter 18 Concave 20 Sulfurization Material concentration measuring device 21 Cylindrical body 30 Catalyst evaluation device 31 Quartz tube 32 Electric furnace 33 Test gas 34 Compressor 35 Flow meter 36 Valve 37 Thermocouple

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 31/00 G01N 27/46 371G 31/10 27/58 B (72) Inventor Misa Watanabe Nagano City, Nagano Prefecture 711, Rita, Kurita-sha, Shinko Electric Industry Co., Ltd. (72) Inventor Shigeaki Suganuma, 711, Rita-sha, Rita, Nagano-shi, Nagano F-term in Shinko Electric Co., Ltd. 2G004 BB04 BE04 BE22 BE23 BE28 BE29 BF02 BF05 BF07 BM04 BM07 2G042 AA01 BB14 BB20 CA01 CB01 DA03 DA10 FA08 FB05 HA07 4D048 AA02 AB01 BA31X BA32X BA33X BA41X BA41Y BB02 DA05 4G069 AA03 BB09A BB09B BC70A BC70B BC71A BC71B BC BC BC

Claims (8)

[Claims] 1. A method for oxidizing a sulfide in a measurement gas into which a predetermined amount of oxygen is mixed, and a method for oxidizing SO in the oxidized measurement gas.
_A sulfide oxidation catalyst used to stabilize the reference partial pressure of SO ₂ or SO ₃ by setting the ₂ / SO ₃ partial pressure ratio to an equilibrium value corresponding to the mixed oxygen partial pressure, A sulfide oxidation catalyst comprising a metal honeycomb carrier, and a catalyst layer comprising one or more noble metal oxide fine particles as a catalyst and a wash coat. 2. The sulfide oxidation catalyst according to claim 1, wherein the catalyst layer does not include a washcoat and is composed of only one or two or more kinds of noble metal oxide fine particles. 3. The sulfide oxidation catalyst according to claim 1, wherein the noble metal oxide forming the catalyst layer is an oxide of palladium, rhodium, ruthenium, and iridium. 4. A sulfide oxidation catalyst according to claim 1, further comprising a sulfide oxidation catalyst provided downstream of the sulfide oxidation catalyst,
_A sulfide concentration measuring device comprising measuring means capable of detecting ₂ or SO ₃ . 5. A measuring means comprising: a substrate made of oxygen ion conductive ceramic; a standard electrode formed on one surface of the substrate, made of a noble metal such as platinum; and a standard electrode formed on the other surface of the substrate;
A sub-electrode made of a crystalline inorganic salt containing a sulfate, and a metal electrode made of a metal formed on the surface of the sub-electrode and reacting with SO ₃ to change into the same substance as the sulfate constituting the sub-electrode. Wherein a reaction between SO ₃ and the sub-electrode and a reaction between SO ₃ and the metal electrode generate an electromotive force between the standard electrode and the metal electrode. Item 5. A sulfide concentration measuring device according to item 4. 6. The sulfide concentration measuring device according to claim 5, wherein the metal constituting the metal electrode is a metal containing silver, and the sulfate constituting the sub-electrode is a sulfate containing silver sulfate. 7. The sulfide concentration measuring device according to claim 5, wherein the oxygen ion conductive ceramic constituting the substrate is yttria-stable zirconia (YSZ). 8. The sulfide concentration measuring device according to claim 5, wherein the sulfate constituting the sub-electrode comprises a mixture of silver sulfate and barium sulfate.