WO2015037536A1

WO2015037536A1 - Oxidation catalyst, exhaust gas treatment device, regenerative combustion burner, method for oxidizing combustible components contained in gas, and method for removing nitrogen oxide contained in gas

Info

Publication number: WO2015037536A1
Application number: PCT/JP2014/073516
Authority: WO
Inventors: 健治平
Original assignee: 新日鐵住金株式会社
Priority date: 2013-09-10
Filing date: 2014-09-05
Publication date: 2015-03-19
Also published as: TWI600467B; CN105531026A; KR20160009603A; CN105531026B; JPWO2015037536A1; JP6103067B2; TW201515701A; KR101814893B1

Abstract

The purpose of the present invention is to provide an oxidation catalyst which can efficiently oxidize, with a reduction in the amount of an active species metal supported, environmental pollutants at a space velocity higher than a conventional space velocity at a low temperature in a gas that is to be treated and that contains a catalyst-poisoning substance such as sulfur oxide or water vapor. This oxidation catalyst comprises at least one transition element which is selected from the group consisting of platinum, palladium and rhodium and which is supported on a carrier, wherein the surface area of micropores of 10nm or more in radius accounts for more than 49% of the total surface area of micropores of 2 to 100nm in radius.

Description

Oxidation catalyst, exhaust gas treatment device, regenerative combustion burner, method for oxidizing combustible components in gas, and method for removing nitrogen oxides in gas

The present invention relates to an oxidation catalyst that oxidizes a combustible component in a gas, an exhaust gas treatment device that uses heat generated when the combustible component in the gas is oxidized, a heat storage combustion burner, a method for oxidizing the combustible component in the gas, and nitrogen oxidation. In particular, an oxidation catalyst, an exhaust gas treatment device, a heat storage combustion burner, a method for oxidizing a combustible component in a gas, and a gas in a gas containing a gas containing water vapor and sulfur oxide that can be poisonous substances of the catalyst. The present invention relates to a method for removing nitrogen oxides.

Developed processes to reduce environmental burden by removing carbon monoxide and methane contained in exhaust gas in response to increasing environmental awareness. The exhaust gas contains carbon monoxide and methane at concentrations lower than the lower combustion limit, and it is difficult to burn and remove carbon monoxide and methane even under conditions containing oxygen. That is, it can be said that carbon monoxide and methane are unburned components contained in the exhaust gas. Therefore, by catalytically burning these unburned components using an oxidation catalyst, carbon monoxide and methane are efficiently converted into carbon dioxide and water vapor and removed from the exhaust gas. In recent years, methods for improving the thermal efficiency of processes by recovering heat generated by catalytic combustion have been studied, and methods for improving the efficiency of burners and exhaust gas treatment processes have also been reported (for example, the following patents) (See Reference 1 and Patent Reference 2.) By applying the catalytic combustion technology to unburned components in the exhaust gas, there is a possibility that not only environmental load reduction but also cost reduction can be achieved.

In the case of decomposing and removing organic substances contained in wastewater, biological treatment methods using microorganisms are often used, but methods for treatment using an oxidation catalyst have also been reported (for example, (See Patent Document 3). However, in the wastewater treatment process using an oxidation catalyst, the maximum temperature reached in the process is at most less than 230 ° C. for the convenience of treating liquid water, and the thermal change of the catalyst support that occurs during the reaction is small. . Furthermore, since liquid water has a large specific heat and density and a small processing space velocity, it is unlikely that the temperature of the catalytic reaction part will be higher than the set temperature. Under such circumstances, different catalysts are used in the wastewater treatment process and the exhaust gas treatment process. For example, wastewater treatment catalysts are often not treated at a high temperature of 500 ° C. or higher during production, and when used for combustion of unburned components in exhaust gas, the properties of the catalyst change during the reaction, There is a risk that strength and catalytic activity may decrease. For this reason, it is difficult to apply the wastewater treatment catalyst as it is to a process for treating unburned components in the exhaust gas. The catalysts that can be used in other processes also differ depending on the target reaction and process conditions, and it is difficult to apply these catalysts to oxidative combustion of unburned components in exhaust gas as they are. is there.

When burning a small amount of a combustible component contained in a gas, it is common to use an oxidation catalyst containing a noble metal as an active species, and the reaction occurs on the surface of the noble metal fine particles supported on various carriers. It is known to progress. Here, a large amount of catalyst poisonous substances typified by sulfur oxides are contained in factory exhaust gas typified by sintering furnace exhaust gas and exhaust gas of automobiles and ships using fuel that is insufficiently desulfurized. . The oxidation catalyst is rapidly deteriorated or its activity is reduced due to the fact that the noble metal particles are covered with the catalyst poisoning substance. In order to cope with such a problem, it is common to take measures such as increasing the reaction temperature or increasing the amount of noble metal to be supported. Similar measures are also taken in the denitration process development using the combustion heat of carbon monoxide with respect to the sintering furnace exhaust gas (see, for example, Patent Document 4 below).

For these reasons, the oxidation catalyst used in the gas to be treated containing sulfur oxide supports a noble metal of 1% by mass or more using a carrier having a surface area of a certain level or more, and the space velocity (unit volume is 1). It is common to cope with this by reducing the volume of the raw material in terms of the standard state passing per hour) to 50000 or less. If the amount of noble metal supported is increased too much, the oxidation of sulfur dioxide to sulfur trioxide increases, but many attempts have been made to suppress the oxidation of sulfur dioxide by adding different elements (for example, the following) (See Patent Documents 5 to 7.)

JP 2001-336733 A Japanese Patent Laid-Open No. 5-115750 JP 2002-79092 A JP 61-161143 A Japanese Patent No. 4508693 JP 2000-300961 A Japanese Patent Publication No.55-35178

In exhaust gas containing a large amount of sulfur oxide, water vapor, etc., it is known that the activity of the oxidation catalyst is greatly reduced, and in order to obtain an oxidation catalyst exhibiting high activity, an active metal species that increases the reaction temperature. In general, a countermeasure such as increasing the amount of the carrier is taken. However, all of these measures cause a significant increase in cost.

The present invention suppresses a decrease in the activity of an oxidation catalyst in a gas to be treated containing a catalyst poisonous substance such as sulfur oxide or water vapor while suppressing the amount of metal active species supported, and has a higher space velocity than the prior art. An object of the present invention is to provide an oxidation catalyst capable of efficiently oxidizing a combustible substance such as carbon monoxide at a low temperature.

Further, the present invention uses such an oxidation catalyst to efficiently oxidize a combustible substance such as carbon monoxide at a low temperature in a gas to be treated containing a catalyst poisonous substance. The object is to provide a method of oxidation.

Furthermore, the present invention is an exhaust gas that is filled with such an oxidation catalyst and that can efficiently oxidize a combustible substance such as carbon monoxide even at a low temperature by using heat generated during oxidation of the combustible component in the gas. It is an object of the present invention to provide a treatment apparatus, a heat storage combustion burner, and an efficient nitrogen oxide removal method using such an oxidation catalyst.

In order to solve the above-mentioned problems, the present inventor has conducted intensive research on a support supporting an active metal and a catalyst supporting an active metal, focusing on specific surface area, pore distribution, constituent elements, and crystal structure. It was.

The present inventor then pays attention to the pore distribution of the support and the catalyst, and creates a catalyst having a high ratio of pores having a large pore radius, thereby containing a catalyst poisoning substance typified by sulfur oxide. In the process gas, a method for suppressing the decrease in the activity of the oxidation catalyst was found, and the present invention was completed.

Specifically, the present invention provides the following.
(1) An oxidation catalyst in which at least one transition element selected from the group consisting of platinum, palladium, and rhodium is supported on a carrier, and the pores having a pore radius in the range of 2 nm to 100 nm in the oxidation catalyst The ratio of the surface area formed by pores having a pore radius of 10 nm or more to the total surface area of pores in the range is more than 49%.
(2) An oxidation catalyst for oxidizing a combustible component in a gas, in which at least one transition element selected from the group consisting of platinum, palladium, and rhodium is supported on a carrier, the pore radius in the oxidation catalyst An oxidation catalyst in which the proportion of the surface area formed by pores having a pore radius of 10 nm or more in the pores in the range of 2 nm to 100 nm is more than 49% in the total surface area of the pores in the range.
(3) The oxidation catalyst according to (1) or (2), wherein a ratio of a surface area formed by pores having a pore radius of 10 nm or more to a total surface area of pores in the above range is 60% or more.
(4) The ratio of the surface area formed by pores having a pore radius of 20 nm or more to the total surface area of the pores in the above range is 20% or more, according to any one of (1) to (3) The oxidation catalyst as described.
(5) The ratio of the surface area formed by pores having a pore radius of 20 nm or more to the total surface area of the pores in the above range is 30% or more, according to any one of (1) to (4) The oxidation catalyst as described.
(6) The ratio of the surface area formed by pores having a pore radius of 80 nm or more to the total surface area of the pores in the above range is 2% or more, according to any one of (1) to (5) The oxidation catalyst as described.
(7) The oxidation catalyst according to any one of (1) to (6), wherein the specific surface area is 20 m ² / g or less.
(8) The oxidation catalyst according to any one of (1) to (7), wherein the transition metal supported on the oxidation catalyst is platinum.
(9) The ratio of the transition element supported on the oxidation catalyst is 0.01% or more and 2.0% or less with respect to the total mass of the oxidation catalyst as the sum of the mass ratio of the transition element in terms of metal. The oxidation catalyst according to any one of (1) to (8), wherein
(10) The oxidation catalyst according to any one of (1) to (9), wherein the support of the oxidation catalyst is an oxide support having a melting point of 1300 ° C. or higher.
(11) The oxidation catalyst according to any one of (1) to (10), wherein the support of the oxidation catalyst is either titanium dioxide or zirconium oxide.
(12) The oxidation catalyst according to (11), wherein the support of the oxidation catalyst is titanium dioxide having an anatase structure.
(13) The oxidation catalyst according to (11) or (12), wherein the titanium dioxide is titanium dioxide produced by a sulfuric acid method.
(14) A combustion catalyst unit for burning unburned components contained in the gas to be treated using a catalyst is provided, and the oxidation catalyst according to any one of (1) to (13) is provided in the combustion catalyst unit An exhaust gas treatment device filled with
(15) A gas heating unit that is provided upstream of the combustion catalyst unit and increases the temperature of the gas to be processed; and a denitration that is provided downstream of the combustion catalyst unit and removes nitrogen oxides in the gas to be processed. The exhaust gas treatment apparatus according to (14), further comprising: a unit.
(16) A denitration unit for removing nitrogen oxides in the gas to be treated and a gas heating unit for raising the temperature of the gas to be treated, which is provided in a previous stage of the denitration unit. When,
The exhaust gas treatment apparatus according to (14), wherein the combustion heat generated in the combustion catalyst unit is used for heating the gas to be treated supplied to the gas heating unit.
(17) An air-fuel mixture injection unit that injects a mixture of fuel and combustion air and a heat storage body are arranged, distribute the gas to be treated to store sensible heat in the heat storage body, and distribute the combustion air after the heat storage And a heat storage section that heats the combustion air with the amount of heat stored, and the combustion catalyst section provided between the heat storage section and the air-fuel mixture injection section or the heat storage section includes (1) A heat storage combustion burner filled with the oxidation catalyst according to any one of (13) to (13).
(18) Using the oxidation catalyst according to any one of (1) to (13), selected from the group consisting of carbon monoxide, nitrogen monoxide, and methane in a gas to be treated containing water vapor and sulfur oxide A method to oxidize combustible components in gas.
(19) The method for oxidizing a combustible component in the gas according to (18), wherein a temperature at which the gas to be treated and the oxidation catalyst are in contact is 250 ° C. or higher and lower than 300 ° C.
(20) Using a gas treatment process having a gas heating part for raising the temperature of the gas to be treated and a denitration part for removing nitrogen oxides in the gas to be treated, and containing nitrogen oxides, steam and sulfur oxidation A method for removing nitrogen oxides in a gas to be treated containing an object and a combustible gas, wherein any one of (1) to (13) is provided between the gas heating unit and the denitration unit. A combustion catalyst part filled with the oxidation catalyst described above is disposed, the gas to be treated heated by the gas heating part is passed through the combustion catalyst part, and the combustible component in the gas to be treated is burned. A method for removing nitrogen oxides in a gas, wherein the temperature of the gas to be treated is further increased by combustion heat.
(21) A heat exchanger and a gas heating burner or an electric heater are used as the gas heating unit, and the gas discharged from the denitration unit is used as a high-temperature gas of the heat exchanger. To remove nitrogen oxides in the gas.
(22) As the gas heating unit, a heat exchanger and a gas heating burner or an electric heater are used, and the position of the combustion catalyst unit is set between the gas heating unit and the denitration unit, and the gas heating unit and the denitration unit. The method for removing nitrogen oxides in a gas according to (20), wherein the gas discharged from the combustion catalyst part is used as a high-temperature gas of the heat exchanger after being rearranged at a stage after the denitration part.
(23) The method for removing nitrogen oxides in a gas according to any one of (20) to (22), wherein the gas to be treated is exhaust gas of a sintering furnace in a steel manufacturing process.

As described above, according to the present invention, it is possible to oxidize carbon monoxide, nitrogen monoxide, and methane contained in the gas to be treated containing sulfur oxide at a lower temperature than in the prior art, and the metal activity It is possible to provide a catalyst that can be oxidized even when the amount of seed supported is small. In addition, using such an oxidation catalyst, exhaust gas treatment equipment that uses heat generated during the oxidation of combustible components in the gas, and efficiently oxidize carbon monoxide, nitrogen monoxide, and methane in the gas to be treated And a method for manufacturing such an oxidation catalyst.

It is explanatory drawing which shows the flow path of the process in exhaust gas denitration method. It is explanatory drawing which shows the flow path of the process in exhaust gas denitration method. It is explanatory drawing which shows the flow path of the process of the thermal storage combustion burner containing an exhaust gas treatment process. It is a graph which shows the pore distribution by the area distribution display of the example of an invention calculated by the Dollimore-Heal method (DH method), and its accumulation value. It is a graph which shows the pore distribution by the area distribution display of the example of an invention calculated by DH method, and its accumulation value. It is a graph which shows the pore distribution by the area distribution display of the example of an invention calculated by DH method, and its accumulation value. It is a graph which shows the pore distribution by the area distribution display of the comparative example calculated by DH method, and its cumulative value. It is a graph which shows the pore distribution by the area distribution display of the comparative example calculated by DH method, and its cumulative value. It is a graph which shows the pore distribution by the area distribution display of the comparative example calculated by DH method, and its cumulative value. It is a figure which shows the result of Test Example 1, Comprising: It is a graph which shows the relationship between reaction time and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 1, Comprising: It is a graph which shows the relationship between reaction time and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 1, Comprising: It is a graph which shows the relationship between reaction time and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 1, Comprising: It is a graph which shows the relationship between reaction time and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 2, Comprising: It is a graph which shows the relationship between reaction temperature and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 4, Comprising: It is a graph which shows the relationship between reaction time and a carbon monoxide conversion rate. It is a figure which shows the result of Test Example 5, Comprising: It is a graph which shows the relationship between reaction time and carbon monoxide conversion. It is a figure which shows the result of Test Example 5, Comprising: It is a graph which shows the relationship between reaction time and carbon monoxide conversion. It is a figure which shows the result of Test Example 5, Comprising: It is a graph which shows the relationship between reaction time and carbon monoxide conversion.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(About examination by the present inventor)
Factory exhaust gas typified by exhaust gas from a sintering furnace and exhaust gas from a burner contains a large amount of water vapor in addition to sulfur oxides typified by sulfur dioxide and sulfur trioxide. When combustible substances contained in these exhaust gases are burned using an oxidation catalyst, sulfur dioxide is oxidized, the amount of sulfur trioxide increases, and concentrated sulfuric acid is generated. It is known that sulfur trioxide and concentrated sulfuric acid easily react with many oxides to form a sulfate, and this reaction is known to greatly impair the activity of the catalyst.

Of many oxide carriers, titanium dioxide and zirconium oxide are known as carriers that are not easily sulfated. It is known that when titanium dioxide is dissolved in concentrated sulfuric acid, a titanium oxide sulfate film is formed on the surface of the titanium dioxide particles, preventing internal sulfation. Moreover, when the ilmenite ore used as the raw material of titanium dioxide is dissolved, it is necessary to raise the temperature of the ilmenite ore to about 1000 ° C. in hot concentrated sulfuric acid.

As described above, titanium dioxide and zirconium oxide show high resistance to sulfur oxides. However, the use of titanium dioxide or zirconium oxide as a carrier can suppress a decrease in activity in the gas to be treated containing sulfur oxides. Absent. This knowledge is as shown in the following experimental example. Moreover, when the temperature dependence of the reaction activity was investigated for the catalyst that showed a rapid decrease in activity, it showed a sharp change in activity near 300 ° C, and this activity change was repeatedly observed reversibly by raising and lowering the temperature. It was done. Assuming that aggregation of precious metal particles and isomerization of the carrier are the main causes of decreased activity, it is unlikely that such a reversible change in activity will occur, and some activity other than the reaction between the carrier and the gas to be treated It was thought that there was a decrease factor.

Therefore, attention was paid to pore clogging by by-product concentrated sulfuric acid as another catalyst deterioration factor. When an oxidation reaction using an oxidation catalyst is performed in a gas to be treated containing sulfur oxides, oxygen, and water vapor, oxidation of sulfur dioxide proceeds as a side reaction, and concentrated sulfuric acid is produced by the reaction between the generated sulfur trioxide and water vapor. Produces. Concentrated sulfuric acid is a liquid having a very low vapor pressure and has a boiling point of 300 ° C. or higher. The concentrated sulfuric acid produced as a by-product can stably exist as a liquid even in a temperature range below the boiling point. In addition, it is known that the ease of condensation of concentrated sulfuric acid is greatly influenced by the shape of the carrier.

As an influence of the shape of the carrier on the condensation of concentrated sulfuric acid, firstly, the liquid vapor pressure changes depending on the pore radius of the carrier. The equilibrium of state change is determined by the change in Gibbs energy and depends on the energy difference before and after the state change. In the state change that occurs inside the fine pores, the influence of the interfacial energy at the gas-liquid interface increases as the curvature inside the pores increases, and as a result, the partial pressure of the atmospheric pressure in equilibrium with the liquid decreases. Such a decrease in partial pressure means that the liquid tends to condense. The equation showing this relationship is known as the Kelvin equation and is shown by the following equation. The equation of such Kelvin, as the pore radius r is reduced, it can be seen that the vapor pressure P is reduced relative to the vapor pressure P _o on a plane. The meanings of the formulas and symbols used in the formulas are shown below.

Kelvin's formula: ln (P / P ₀ ) = − 2γV _m COSθ / (rRT)

P: Vapor pressure P ₀ : Saturated vapor pressure γ: Surface tension [N / m]
V _m : molar volume [m ³ / mol] r: droplet radius [m]
R: Gas constant [J / mol · K] T: Absolute temperature [K] θ: Contact angle [rad]

Secondly, the influence of the shape of the carrier on the condensation of concentrated sulfuric acid is that the gas diffusion rate changes depending on the pore radius. It is known that the surface of both titanium dioxide and zirconium oxide is sulfated. For example, in the case of titanium oxide sulfate (IV) produced by sulfating the surface of titanium dioxide, it is in a hydrated state in the range of 400 ° C. or lower. On such a surface, sulfur trioxide and water vapor are easily adsorbed. For this reason, these molecules diffuse in the pores while repeating adsorption and desorption, and cause the diffusion to be delayed. When the gaseous gas species is nitrogen, the pressure is 1 atm, and the temperature is 523 K, the mean free path of gas molecules is 100 nm or more. Therefore, in the case of pores of 10 nm or less, collisions between gas molecules are almost ignored, and gas molecules travel in the pores while repeating collisions with the pore wall surfaces (free molecular flow region).

● Under the condition that the free molecular flow region is established, the influence of the interaction between the pore wall surface and the gas molecule is likely to appear. In fact, it is known that the reaction activity of a zeolite catalyst containing a portion that easily adsorbs water vapor in the pores is greatly reduced in a gas containing water vapor (see, for example, Non-Patent Document 1 above). . Sulfur dioxide is oxidized to sulfur trioxide in the reaction on the noble metal present in the pores. For the above reason, sulfur trioxide diffuses in the pores and is difficult to escape out of the pores. As a result, sulfur trioxide has a relatively high partial pressure within the pores containing the noble metal. The diffusion rate decreases greatly as the pore radius decreases.

As described above, due to the first factor according to the Kelvin equation and the second factor governed by the interaction with the pore wall surface, condensation of concentrated sulfuric acid easily occurs in the pores, and the pores are blocked. It is thought to occur.

(About the present invention)
Based on the above examination, it was considered that blockage of concentrated sulfuric acid inside the pores could be suppressed by using a carrier having a high pore ratio with a large pore radius. That is, for the first factor, it was considered that the vapor pressure required for condensing the liquid increases due to the increase in the pore radius, which makes it difficult to block the pores. As for the second factor, as the pore radius increases with respect to the mean free process, the influence of collision between molecules moving in the gas phase appears, and the influence due to collision with the wall surface becomes smaller. As a result, diffusion of sulfur trioxide within the pores was likely to occur, and it was considered that the pores were less likely to be clogged with respect to the second factor.

Therefore, in view of the above examination, the present inventor conducted an experiment using a carrier having a high pore ratio with a large pore radius, and the influence of clogging was suppressed, and in a temperature region below the boiling point of concentrated sulfuric acid. Catalytic activity increased, and no steep activity fluctuations near the boiling point of concentrated sulfuric acid were observed. At that time, these phenomena were found to have a strong correlation with the pore distribution. In particular, in addition to a small proportion of pores having a small pore diameter such as a pore radius of less than 10 nm in the whole pore, a relatively large pore radius of 20 nm or more in order to promote diffusion of sulfur trioxide. It was confirmed that a higher effect can be obtained when the ratio of the pores is high.

As a result of intensive studies by the present inventors, among the surface areas formed by pores having a pore radius in the range of 2 nm to 100 nm, an oxidation catalyst in which more than 49% is formed by pores having a pore radius of 10 nm or more is used. Thus, it was confirmed that catalytic activity can be obtained even in a gas containing sulfur oxide. The reason for limiting the range of the pore radius to be considered to 2 nm or more and 100 nm or less will be described later. The ratio of the surface area formed by pores having a pore radius of 10 nm or more out of the surface areas formed by pores having a pore radius of 2 nm or more and 100 nm or less is more preferably 50% or more, % Or more is more preferable, and 80% or more is even more preferable. There is no upper limit to the ratio of the surface area formed by pores having a pore radius of 10 nm or more, and the effect of the present invention is considered to be exhibited even at 100%. However, it is expected to be difficult to make a catalyst that has no gap of a size of 10 nm or less.

Furthermore, of the surface areas formed by pores having a pore radius in the range of 2 nm to 100 nm, not only the ratio of the surface area formed by pores having a pore radius of 10 nm or more, but also pores having a pore radius of 20 nm or more. By setting the ratio of the surface area to be formed to 20% or more, the effect of the present invention can be further exerted, and not only the ratio of the surface area formed by pores having a pore radius of 10 nm or more but also fine pores having a radius of 20 nm or more. By setting the ratio of the surface area formed by the holes to 30% or more, the effect of the present invention is more preferably exhibited. Moreover, it is preferable that the ratio of the surface area formed by pores having a pore radius of 80 nm or more is 2% or more among the surface areas formed by pores having a pore radius of 2 nm or more and 100 nm or less.

In addition, in a carrier having a BET specific surface area of 60 m ² / g or more, which is used as a general carrier for an oxidation catalyst, the peak of pore distribution is less than a pore radius of 10 nm and is formed by pores having a pore radius of 10 nm or more. The ratio of the surface area is small. Such findings are as shown in the following experimental examples.

For the measurement of the pore distribution in the present invention, the Dollimore-Heal method (DH method) was used. The DH method is one of the methods for calculating the pore distribution. The DH method is provided as standard in the analysis software attached to the specific surface area measuring device, and the details are shown in the manual attached to the device. Further, details are shown in many reference books (see, for example, Non-Patent Document 2 above).

In addition, the Barrett-Joyner-Halenda (BJH) method, the Cranston-Inkley (CI) method, etc. are known as methods for obtaining the pore distribution, and the models used for calculation are basically the same in any method. is there. In any case, in the range of the pore radius of 2 nm or more and 100 nm or less, the difference between the models is small, and the influence of the measurement error of the apparatus is also small. Therefore, in the present invention, the range of the pore radius to be taken into consideration is limited to the range of 2 nm to 100 nm.

Within this range, since the difference between the DH method, the BJH method, and the CI method is small, any method can be used. However, in any case, it has been found from experiments conducted by the present inventors that the pore distribution obtained by the analysis using the measurement data in the adsorption process has a stronger correlation with the activity of the catalyst. .

Also, attention should be paid to measurement accuracy. All the pore distribution analysis methods including the DH method perform calculations based on the difference in nitrogen adsorption amount between two measurement points in the adsorption isotherm measurement process. For this reason, if the measurement interval becomes too wide, the obtained distribution is also greatly increased, and evaluation using the pore distribution cannot be performed. Therefore, it is preferable to perform measurement under the condition that the pore distribution is obtained at intervals of less than 2 nm, particularly for measurement points corresponding to the range of pore radius of 5 nm or more and less than 15 nm. In the range where the pore radius is 15 nm or more and less than 30 nm, the measurement is preferably performed under the condition that the pore distribution is obtained at intervals of less than 5 nm. In the range where the pore radius is 30 nm or more and less than 60 nm, the measurement is preferably performed under the condition that the pore distribution is obtained at intervals of less than 10 nm. In the range where the pore radius is 60 nm or more and less than 100 nm, the measurement is preferably performed under the condition that the pore distribution is obtained at intervals of less than 15 nm. In the following experimental examples, all measurements are performed under these conditions. However, there is no problem if it is determined that a sufficient number of measurements are obtained to determine the state of the pore distribution even when the interval of the pore distribution obtained from this is wide.

In general, it is said that a catalyst having higher activity can be produced by using a carrier having a small pore radius and a large specific surface area. This is an idea based on the basics of catalyst development, and has been taken up in many reference books (see, for example, Non-Patent Document 3 above). The main idea is as follows.

When a solid heterogeneous catalyst is used, the catalytic reaction proceeds on an active point showing catalytic activity. In the catalyst poisoning, the poisoning substance is adsorbed on some or all of these active sites, thereby reducing the proportion of the portion contributing to the catalytic reaction or reducing the activity of adjacent active sites. As a countermeasure against this catalyst poisoning, an attempt is made to increase the absolute number of active sites that maintain the activity even in the presence of poisonous substances by increasing the number of active sites. In order to increase the active points, the amount of active metal species supported on the carrier is increased. In order to support a large amount of active metal species in a highly dispersed state, a large specific surface area is required. In order to increase the specific surface area, a structure with more irregularities is required, and a structure with a small pore radius is required.

For the above reasons, in the catalyst development, research with a particular emphasis on the specific surface area of the catalyst support is generally performed. Regardless of the constituent elements of the support, it is common to use a support of 60 m ² / g or more, and it is rare to use a support having a specific surface area of 20 m ² / g or less and a small specific surface area. However, in the oxidation catalyst of the present invention, in order to realize catalyst stability in a gas containing sulfur oxide, a specific surface area is preferably 50 m ² / g or less, more preferably by using a carrier having a small specific surface area. Preferably, an oxidation catalyst having a specific surface area of 20 m ² / g or less is realized.

In the case of a titanium dioxide carrier, an anatase type structure in which a large specific surface area is easily obtained is often used, and a rutile type carrier in which a high specific surface area is difficult to obtain is rarely used. There are studies focusing on pore volume as another structural parameter, but there are many discussions on mechanical strength. Macroscopic pores exceeding 1 micrometer generated when a powdered catalyst is molded and the shape of the honeycomb to which the catalyst is applied have been studied from the viewpoint of the influence of dust and mist. There are no known studies relating micro-pore distribution with pore radius to catalyst stability in gases containing sulfur oxides.

As shown in the following experimental examples, in aluminum oxide, titanium oxide, and zirconium oxide, the same tendency is observed in the behavior of pore radius and activity change, and it is considered that it does not depend on the composition of the support. However, it has been confirmed that aluminum oxide is sulfated during the reaction and the specific surface area gradually decreases. If long-term stability is expected, a support containing titanium oxide and zirconium oxide is preferable. A silica carrier is also known as a highly acid-resistant carrier and is considered to be usable.

As shown in the following experimental examples, when titanium dioxide was used as a carrier, there was a difference in the activity of the catalyst obtained depending on the type of carrier. Compared with carriers prepared by the sulfuric acid method, the rutile type has a high tendency for platinum to be oxidized, and a reduction treatment is necessary to obtain high activity. For this reason, the crystal structure of the titanium dioxide support is more preferably an anatase type structure. Titanium dioxide support is often obtained as a mixture of rutile and anatase types, but a mass ratio calculated from the relative ratio of the strongest diffraction lines of powder X-ray diffraction measurement, that 50% or more has an anatase type structure. preferable. Subsequently, in comparison between anatase type structures, when an anatase type structure carrier prepared by the chlorine method and an anatase type structure carrier prepared by the sulfuric acid method are compared, a carrier prepared by the chlorine method is used. In the case of platinum, the prepared platinum was oxidized, and the activity could not be obtained without reduction treatment. For this reason, it is preferable to prepare a catalyst using a carrier prepared by a sulfuric acid method as the titanium dioxide carrier.

When the pores are blocked by concentrated sulfuric acid, the contact between the gas to be treated and the metal active species as the catalytic active point is hindered. In any catalytic reaction using a metal active species as an active site, any reaction proceeds on the metal surface (see, for example, Non-Patent Document 4 above). When clogging occurs, the reactants do not come into contact with the noble metal in the first place, and the activity is reduced in any reaction under the condition of pore clogging. In the reaction under conditions where sulfur dioxide is oxidized, what can be used in engineering is an oxidation reaction. Examples of such an oxidation reaction include oxidation reactions of carbon monoxide, nitrogen monoxide, and methane. In any of these oxidation reactions, it is known that the reaction proceeds on the surface of the noble metal and the reaction does not easily proceed in the absence of the noble metal.

The active metal species is not particularly limited, but if it reacts easily with sulfur dioxide, the active species itself loses its activity even if pore clogging does not occur, and the activity cannot be obtained. As metal species having high activity as an oxidation catalyst, for example, cobalt, nickel, copper, ruthenium, rhodium, palladium, platinum, gold and the like are known. The standard generation enthalpy of oxide can be used as an index as a substance that hardly reacts with sulfur dioxide to form sulfur oxide, and it can be determined that the smaller the absolute value of the standard generation enthalpy is, the less the substance is oxidized. The standard generation enthalpy value is published not only in books but also in databases on the Internet (for example, see Non-Patent Document 5 above).

From this point of view, gold, platinum, palladium and rhodium are preferable as the active metal species, and platinum and gold are particularly preferable. However, it is known that a catalyst supporting gold alone has a high oxidation activity at the interface between the gold fine particles and the oxide carrier, and the surface of the oxide carrier is sulfated, so that it is highly active. Decreases. Therefore, when using gold, it is more preferable to use in combination with other transition metals or to use platinum. In addition, when using palladium or rhodium, which is likely to be a sulfate compared to platinum or gold, the surface of palladium or rhodium particles is covered with platinum and used as a core-shell structure, so that the formation of sulfate can be suppressed. In addition, the amount of platinum used can be reduced, and the cost can be reduced.

The amount of the active metal species supported is not particularly limited, but is limited from an economical viewpoint. In general, as the loading amount increases, the active point increases and the catalytic activity increases, while the particle size of the supported metal fine particles increases, and the proportion of the portion that does not contribute to the reaction tends to increase. Furthermore, since the noble metal particles themselves cause clogging / stenosis of the pores and the influence of the clogging of the pores due to the concentrated sulfuric acid is likely to occur, the proportion of the portion that does not contribute to the reaction further increases.

It is also known that when platinum is supported, the ratio of sulfur dioxide oxidized to sulfur trioxide increases as the amount of platinum supported increases. It is also known that the rate of this side reaction increases on the active metal particles as the platinum particle diameter increases (for example, see Non-Patent Document 6 above), and by suppressing the amount of noble metal supported, Generation of sulfur trioxide can be suppressed. In fact, in the reaction test in the laboratory, the amount of sulfuric acid mist adhering to the inner wall of the reaction tube after the reaction test was small under the condition where the amount of platinum supported was small. On the other hand, even if the supported amount is reduced beyond a certain level, further refinement of the metal fine particles cannot be expected, and the catalyst active point per unit amount of active metal species does not increase. In a study examining the relationship between the supported amount of platinum and the refinement of platinum particles, if the supported amount is up to about 0.4% by mass per 10 m ² / g, the refinement of platinum particles is achieved. Has been reported (for example, see Non-Patent Document 7 above). Therefore, for example, if the platinum loading is 0.04% by mass, it is considered that a degree of dispersion sufficient to exhibit catalytic activity can be obtained even with a specific surface area of about 1 m ² / g. As a result, if the supported amount is too small, the amount of the necessary carrier increases, and the amount of the catalyst increases as a whole, and the cost increases. It is unlikely to use a carrier having a specific surface area of less than 1 m ² / g as the catalyst carrier, and even when the loading amount is suppressed with the aim of suppressing the platinum fine particle aggregation during the reaction, the loading amount is 0.01 mass. % Or more is preferable. Further, as shown in the following experimental examples, all of the catalysts exhibiting high sulfur resistance according to the present invention have a specific surface area of 50 m ² / g or less, so that the platinum loading is 2.0 mass% or less. It is considered that finer platinum particles can be achieved, which is preferable.

The oxidation catalyst of the present invention exhibits high activity in many gases to be treated, but the effect is exhibited particularly in a gas containing sulfur oxide and water vapor. When the oxidation reaction proceeds in a state where these gases are contained in the gas to be treated, concentrated sulfuric acid is generated as a side reaction regardless of the concentration, and pores are blocked. By suppressing the effect of this pore blockage, it is expected that the decrease in activity is suppressed.

However, it is known that sulfur oxides strongly adsorb to active metal species. When the partial pressure is too high, adsorption of carbon monoxide, nitrogen monoxide and methane to the active metal species occurs almost. There is a possibility that the reaction does not proceed even if the influence of pore blockage is suppressed. Therefore, the volume ratio of the sulfur oxide in the gas to be treated is preferably smaller than at least the sum of the volume ratios of carbon monoxide, nitrogen monoxide, and methane.

On the other hand, when the partial pressure of sulfur oxide is too small, it is expected that pore clogging does not occur regardless of the pore distribution. Therefore, when the volume ratio of the sulfur oxide is 1 ppm or more, the effect of the present invention is exhibited, which is suitable as a gas to be treated.

As for the temperature of the gas to be treated, it is expected that the activity equal to or higher than that of the conventional catalyst can be obtained at any temperature. However, if the reaction temperature is raised to be higher than the boiling point of concentrated sulfuric acid, there is a difference due to the difference in pore radius. Hard to come out. The boiling point of concentrated sulfuric acid varies greatly depending on its concentration and is also influenced by the concentration of water vapor in the gas to be treated, so it is difficult to determine uniquely. However, at 400 ° C. or higher, the sum of the partial pressures of water vapor and hydrosulfuric acid is 1 atm or higher in concentrated sulfuric acid of all concentrations (see, for example, Non-Patent Document 8 above). The reaction temperature is preferably at least 400 ° C. or lower.

On the other hand, if the reaction temperature is too low, the reaction will not proceed in the first place, and it will be necessary to increase the amount of catalyst, leading to an increase in cost. Here, in the presence of sulfur dioxide, even when platinum / gold is used as a metal active species and 1% by mass is supported, high activity cannot be obtained unless the reaction temperature is increased to about 200 ° C. It is known (see, for example, Non-Patent Document 9 above). Therefore, also in the method according to the present invention, it is preferable to increase the reaction temperature to 200 ° C. or higher.

Also, the reaction temperature is more preferably 250 ° C. or higher from the viewpoint of increasing the reaction rate and suppressing the necessary amount of catalyst. Further, as shown in the following experimental examples, the effect of the present invention becomes difficult to obtain at a temperature of 300 ° C. or higher, and therefore the reaction temperature is more preferably 300 ° C. or lower.

As shown later in the examples, there is a strong correlation between the pore distribution of the catalyst carrier and the pore distribution of the catalyst prepared using such a carrier, and a carrier with a high ratio of pores having a large pore radius is used. When a catalyst is prepared by using the catalyst, the ratio of pores having a large pore radius is also high in the obtained catalyst. However, it is important that the catalyst carrier be heated and calcined at a temperature higher than the maximum temperature reached during catalyst preparation so as not to be deformed by heat treatment accompanying catalyst preparation. The pore distribution has a strong correlation with the performance of the catalyst obtained thereafter.

The method for supporting the active metal species is not particularly limited, but it is considered that the precipitation reduction method avoids excessive heat treatment on the support and easily obtains the expected pore distribution. However, since it is difficult to prepare the amount of the active metal species to be supported by the precipitation reduction method, it is most convenient to use the impregnation method when the support is only subjected to heat treatment within a range in which no modification occurs. . When platinum is supported as an active metal species by an impregnation method, a platinum-supported catalyst is often obtained by performing calcination treatment at about 500 ° C. using chloroplatinic acid as a precursor. Therefore, it is preferable to use a carrier having a small structural change when the temperature is raised to 500 ° C.

Specifically, it is preferable to use a carrier having a Tamman temperature of 500 ° C. or more, which is an empirical indicator that atoms on the solid surface start to diffuse. Since the Tamman temperature is an empirical expression that is about ½ of the melting point in absolute temperature notation, it is preferable to use a carrier having a melting point of 1300 ° C. or higher. Examples of such carriers include titanium dioxide, zirconium oxide, aluminum oxide, silicon dioxide and the like.

When titanium dioxide is used as a carrier, titanium dioxide tends to cause a phase transition, so that the pore distribution changes when the firing temperature is not appropriate. Although not shown in the following experimental examples, when baking is performed at 650 ° C. for 5 hours in the air, the ratio of the pores having a small pore radius increases. On the other hand, when firing for 1 hour at 500 ° C. in the atmosphere, the specific surface area decreases, the number of pores having a pore radius of 10 nm or less decreases, and the pore radius of pores having a pore radius of 10 nm or more is reduced. Changes in the direction of decreasing. This changes the relationship between the pore radius and the specific surface area. It is important to use a carrier having pores having a sufficiently large pore radius so that the specific surface area of pores having a pore radius of 10 nm or more is kept large even if the pore distribution changes. Specifically, it is preferable that the heat treatment is performed in advance and the noble metal precursor is devised to avoid heating to 650 ° C. or higher. As such a noble metal precursor, for example, when gold is used, gold chloride (III) acid hydrate is suitable, and when platinum is used, platinum chloride (IV) acid hydrate is suitable, When palladium is used, diammine dinitropalladium (II) or the like is preferable, and when rhodium is used, rhodium (III) chloride hydrate or the like is preferable.

It is also possible to realize an exhaust gas treatment apparatus having a combustion catalyst unit for burning unburned components in exhaust gas containing water vapor using a catalyst having the above properties. That is, the oxidation catalyst according to the present invention is filled in the combustion catalyst portion provided in the exhaust gas treatment apparatus. This exhaust gas treatment device is used as a removal device for unburned components such as carbon monoxide and nitrogen oxides, exhaust heat recovery equipment that recovers and uses the amount of heat generated by combustion of unburned components, or as an energy saving process. Can be applied.

In these exhaust gas treatment apparatuses, the oxidative combustion reaction of the unburned components performed using the oxidation catalyst according to the present embodiment is performed under a pressure of about normal pressure to about 0.2 MPa. Since the reaction is carried out at normal pressure to about 0.2 MPa, it is preferable that the direction of travel of the exhaust gas in the combustion catalyst section is the horizontal direction or the direction from the upper side to the lower side in the vertical direction. Further, in the combustion catalyst part of such an exhaust gas treatment device, the reaction proceeds using the sensible heat of the exhaust gas, and unlike the waste water treatment process, it is not necessary to heat the combustion catalyst part itself.

In addition, the filling method of the oxidation catalyst according to the present invention in the combustion catalyst section is not particularly limited, and various known methods such as filling the oxidation catalyst according to the present invention into a honeycomb shape may be used. Can be used. At this time, the transition element as described above may be supported on the support formed in the honeycomb shape, and after adding various binders to the above oxidation catalyst, the oxidation catalyst itself is added to the honeycomb. You may form in a shape.

As an example of an application destination of such an exhaust gas treatment apparatus, there is a process facility for performing an exhaust gas denitration method including a combustible gas. In this process, it is necessary to heat and raise the temperature of the exhaust gas flowing into the denitration catalyst in order to advance the reaction between ammonia and nitrogen oxides by the denitration catalyst. This heating is usually performed using combustion heat such as natural gas. Here, the cost can be reduced by substituting the heating with the combustion heat of the combustible gas component obtained by the oxidation catalyst according to the present invention. 1 and 2 show an outline of a process for carrying out such an exhaust gas denitration method.

The process shown in FIG. 1 includes a heat exchange unit 1, a gas heating burner 2 that is an example of a gas heating unit provided at the subsequent stage of the heat exchange unit 1, and a combustion catalyst provided at the subsequent stage of the gas heating burner 2. Part 3 and a denitration device part 4 which is an example of a denitration part provided at the rear stage of combustion catalyst part 3. The exhaust gas introduced into the heat exchange unit 1 is heat-exchanged using heat generated in the subsequent denitration device unit 4 and then flows into the gas heating burner 2. The exhaust gas heated by the gas heating burner 2 flows into the combustion catalyst section 3 filled with the oxidation catalyst according to the present invention, and the unburned components contained in the exhaust gas are oxidized and burned by the oxidation catalyst according to the present invention. As a result, the exhaust gas is further heated by the generated combustion heat. The exhaust gas combusted with the unburned components flows into the denitration unit 4 together with ammonia, and the reaction between ammonia and nitrogen oxide proceeds by the denitration catalyst. Further, the exhaust gas after the denitration process is supplied to the heat exchanging unit 1 for heat exchange.

The process shown in FIG. 2 includes a heat exchange unit 11, a gas heating burner 12 that is an example of a gas heating unit provided at the subsequent stage of the heat exchange unit 11, and a denitration process that is provided at the subsequent stage of the gas heating burner 12. The denitration device unit 13, which is an example of the unit, and the combustion catalyst unit 14 provided at the subsequent stage of the denitration device unit 13 are provided. The exhaust gas introduced into the heat exchange unit 11 is heat-exchanged using the combustion heat generated in the combustion catalyst unit 14 at the subsequent stage, and then flows into the gas heating burner 12. The exhaust gas heated by the gas heating burner 12 flows into the denitration unit 13 together with ammonia, and the reaction between ammonia and nitrogen oxide proceeds by the denitration catalyst. The exhaust gas that has undergone the denitration treatment flows into the combustion catalyst section 14 filled with the oxidation catalyst according to the present invention, and the unburned components contained in the exhaust gas that has undergone the denitration treatment are oxidized and combusted by the oxidation catalyst according to the present invention. Is done. The generated combustion heat is supplied to the heat exchange unit 1.

As shown in FIGS. 1 and 2, the installation location of the combustion catalyst unit may be either upstream or downstream of the denitration device. Since the temperature required to advance the reaction in the denitration catalyst unit is constant, in the process of FIG. 1, the reaction temperature at the inlet of the combustion catalyst unit is 200 to 250 ° C. In the process of FIG. The reaction temperature at the entrance of the combustion catalyst section is about 250 to 300 ° C.

Other examples of the application of exhaust gas treatment equipment include regenerative burners and radiant tube heat storage combustion burners. The process in these heat storage combustion burners is a process in which one set of a burner and a heat storage body is used as a pair, and the exhaust heat of exhaust gas when burner injection is performed in one set is stored in the other heat storage body. .

FIG. 3 shows an outline of the process in such a heat storage combustion burner. Such a process injects, as main components, an exhaust air flow path switch 21, a

heat storage section

22a, 22b containing a heat storage body and a combustion catalyst, a fuel

gas supply section

23a, 23b, and a mixture of combustion air and fuel gas. The air-fuel

mixture injection sections

24a and 24b, a space 25 heated by burner injection, an air introduction path 26, and an exhaust gas path 27 are provided. Here, the oxidation catalyst which concerns on this invention is utilized for the combustion catalyst contained in the

thermal storage part

22a, 22b. That is, in the heat storage combustion burner shown in FIG. 3, it can be said that the

heat storage portions

22a and 22b are composed of a heat storage body and a combustion catalyst portion. FIG. 3 shows a process in the case of performing burner injection at the mixture injection section 24a and taking out the exhaust gas from the mixture injection section 24b.

Such a burner controls the exhaust air flow path switch 21 to introduce air into the heat storage section 22a from the air introduction path 26, and the air heated by the heat storage section and the fuel gas supplied from the fuel gas supply section 23a. Are injected from the mixture injection section 24a. Then, the exhaust gas discharged through the air-fuel mixture injection unit 24b is introduced into the heat storage unit 22b, the air introduced from the secondary air introduction unit 28b and the unburned components in the exhaust gas are burned by the combustion catalyst, After the obtained heat is stored in the heat storage unit 22b, the exhaust gas is exhausted from the exhaust gas passage 27.

When the temperature of the heat storage unit 22a decreases and the temperature of the heat storage unit 22b increases, the exhaust air switch 21 is switched to reverse the flow of the

heat storage units

22a and 22b and the

burner injection units

24a and 24b. By repeating such control for each set, combustion heating is performed on the oxidation catalyst using unburned components in the exhaust gas injected from the air-fuel

mixture injection units

24a and 24b, and the amount of sensible heat stored in the heat storage body is increased. Can be improved.

The temperature of the

heat accumulators

22a and 22b in a general burner is higher at a portion closer to the space 25 and reaches about 1200 ° C. at the highest, while the temperature is lower at a portion closer to the exhaust air flow path switching device 21 and at the highest. It reaches only about 250 ° C. From the viewpoint of suppressing catalyst deterioration, the combustion catalyst filled in the

heat storage units

22a and 22b is preferably filled in a portion where the maximum temperature reaches less than 600 ° C, and more preferably a portion where the temperature reaches less than 500 ° C. . In the

heat storage units

22a and 22b, it is considered that the time when the temperature is lower than 300 ° C. becomes longer in a portion having a relatively low temperature range. Therefore, by using the oxidation catalyst according to the present invention as a combustion catalyst, it is possible to obtain the effect of preventing the decrease in activity due to concentrated sulfuric acid.

In addition, the structure of the heat storage combustion burner according to the present invention is not limited to the above structure. For example, in the above structure, the heat storage body and the fuel catalyst part filled with the oxidation catalyst according to the present invention are installed in the same place, but the heat storage body and the combustion catalyst part are divided as separate components, The heat storage unit and the fuel catalyst unit may be independent from each other. In addition, FIG. 3 illustrates a case where the heat storage unit includes two systems. However, the flow path is branched from the exhaust air switching device 21 into three or more systems so as to have three or more heat storage units. A configuration may be adopted in which a plurality of flow paths are switched simultaneously.

Further, the application destination of the exhaust heat recovery equipment using the exhaust gas treatment apparatus of the present invention is not limited to the exhaust gas denitration method and the heat storage combustion burner described above, but also applies to the exhaust heat recovery apparatus in other processes. Can do. In particular, since a large amount of sulfur oxide is contained in the combustion exhaust gas of the process containing sulfur in the fuel, it is suitable as an application destination of the catalyst of the present invention.

Next, the present invention will be specifically described based on Examples, Comparative Examples, and Test Examples, but the present invention is not limited to the Examples, Comparative Examples, and Test Examples.

[Production of catalyst carrier]
(Carriers 1 to 11)
Titanium oxide support TIO-2 (reference catalyst), titanium oxide support TIO-6 (reference catalyst), zirconium oxide support ZRO-4 (reference catalyst), titanium oxide support TIO-4 (reference catalyst) ), Titanium oxide support TIO-8 (catalyst society reference catalyst), titanium oxide support TIO-7 (catalysis society reference catalyst), titanium oxide support ST-01 (Ishihara Sangyo), titanium oxide support FTL-110 (Ishihara Sangyo), Titanium oxide support FTL-200 (Ishihara Sangyo), zirconium oxide support ZRO-3 (catalyst society reference catalyst), and aluminum oxide support ALO-1 (catalysis society reference catalyst) were prepared. Baked for hours. The obtained carriers were designated as carriers 1 to 11, respectively.

In addition, all the carriers after firing were made to have a particle size of 75 μm or more and less than 150 μm using a stainless steel sieve, and were used in the subsequent experiments. The shape of the carrier is powdery. The physical properties of the carriers 1 to 8 are summarized in Table 1 below. The crystal structure of the carrier was determined by powder X-ray diffraction measurement, and when possible, the abundance ratio was calculated using the relative intensity of the strongest diffraction line of each phase. Specific surface area was determined by BET method using nitrogen adsorption isotherm at liquid nitrogen temperature, and pore distribution was determined by DH method using data of adsorption process. The pore volume was calculated using the value of the relative partial pressure 0.99 of the adsorption isotherm. Thereafter, in all Examples and Comparative Examples, physical property values were obtained in the same manner.

[Catalyst preparation]
(Example 1: platinum-supported catalyst)
0.00265 g of hexachloroplatinic acid was dissolved in 0.20 ml, 0.45 ml, 0.20 ml, and 0.35 ml of pure water. The obtained platinum precursor solution was added dropwise to 1.00 g of each of the oxide carriers 1 to 5 while being sufficiently mixed, and impregnated. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalysts were used as Samples 1 and 4-7. The amount of platinum supported was 0.1% by mass in terms of platinum in the metal state.

BET specific surface area was measured for Samples 1 and 4-7, and the pore distribution in area distribution (dV / dr) display calculated by the DH method from the obtained data and the pore radius of 2 nm or more and 100 nm or less FIG. 4A to FIG. 4C show cumulative values of the ratio (A _r / A _{2-100 nm} ) of the surface area formed by the pores having the respective pore radii below the surface area formed by the pores in the range. Table 2 shows values obtained by calculating the ratio of the surface area formed by pores having a pore radius of 10 nm or more out of the surface areas formed by pores having a pore radius of 2 nm or more and 100 nm or less. This value was calculated by subtracting from 100 the value of A _r / A _2-100 nm at a pore radius of 10 nm.

(Example 2: Palladium-supported catalyst)
Dinitrodiammine palladium (Kojima Chemical) 0.00220 g was dissolved in 15 ml of nitric acid, and 1.00 g of oxide carrier 1 of carrier 1 was added. After stirring for 1 hour, the mixture was stirred on a hot stirrer at 80 ° C. and evaporated to dryness. The obtained solid was dried at 120 ° C. for 10 hours in the air, then heated to 400 ° C. and calcined for 30 minutes. The catalyst obtained after cooling was designated as Sample 2. Table 2 shows the physical property values of Sample 2 measured in the same manner as in Example 1.

(Example 3: Rhodium supported catalyst)
Rhodium (III) chloride trihydrate 0.00256 was dissolved in 0.20 ml of pure water. The obtained aqueous rhodium precursor solution was added dropwise to 1.00 g of the oxide carrier of carrier 1 while being sufficiently mixed, and impregnated. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalyst was used as Sample 3. The supported amount of rhodium was 0.1% by mass in terms of rhodium in the metal state. Table 2 shows the physical property values of Sample 3 measured in the same manner as in Example 1.

Example 4: Low supported platinum supported catalyst
0.00265 g of hexachloroplatinic acid was dissolved in 1.0 ml of pure water. 0.30 ml of the obtained platinum precursor solution was added dropwise to 1.00 g of each oxide carrier of carrier 1 while being sufficiently mixed, and impregnated. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalyst was used as Sample 8. The amount of platinum supported was 0.03% by mass in terms of platinum in the metal state. Table 2 shows the physical property values of Sample 8 measured in the same manner as in Example 1.

(Example 5: High supported platinum supported catalyst)
Hexachloroplatinic acid 0.02589 g and 0.05178 were dissolved in 0.45 ml of pure water, respectively. Each of the obtained platinum precursor solutions was dropped and impregnated while being sufficiently mixed with 1.00 g of the oxide carrier of the carrier 2. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalysts were used as Samples 9 and 10, respectively. The supported amounts of platinum were 1% by mass and 2% by mass, respectively, in terms of platinum in the metal state. Table 2 shows physical property values of Samples 9 and 10 measured in the same manner as in Example 1.

(Comparative Example 1: Platinum-supported catalyst)
0.00265 g of hexachloroplatinic acid was dissolved in the same amount of pure water as the pore volume of the carriers 6 to 11 shown in Table 1. The obtained platinum precursor solution was added dropwise to 1.00 g of each of the oxide carriers of the carriers 6 to 11 while being sufficiently mixed, and impregnated in each carrier. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalysts were used as Samples A to F. The amount of platinum supported was 0.1% by mass in terms of platinum in the metal state.

BET specific surface area was measured for samples A to D, and the pore distribution in the area distribution (dV / dr) display calculated by the DH method from the obtained data and the pore radius in the range of 2 nm to 100 nm. FIG. 5A to FIG. 5C show the ratio (A _r / A _{2-100 nm} ) of the surface area formed by the pores having the pore diameters or less among the surface _areas formed by the pores. Table 3 shows the physical property values of Samples A to F measured in the same manner as in Example 1.

(Comparative Example 2: Palladium-supported catalyst)
Dinitrodiammine palladium (Kojima Chemical) 0.00220 g was dissolved in nitric acid 15 ml, and oxide carrier 1.00 g of carrier 6 was added. After stirring for 1 hour, the mixture was stirred on a hot stirrer at 80 ° C. and evaporated to dryness. The obtained solid was dried at 120 ° C. in the atmosphere for 10 hours, then heated to 400 ° C. and calcined for 30 minutes. The catalyst obtained after cooling was designated as Sample G. Table 3 shows the physical property values of sample G measured in the same manner as in Example 1.

(Comparative Example 3: Rhodium supported catalyst)
Rhodium (III) chloride trihydrate 0.00256 was dissolved in 0.20 ml of pure water. The obtained rhodium precursor aqueous solution was added dropwise to 1.00 g of the oxide carrier of the carrier 6 while being sufficiently mixed, and impregnated. The obtained powder was calcined at 100 ° C. for 10 hours and at 500 ° C. for 1 hour, and the obtained catalyst was used as sample H. The supported amount of rhodium is 0.1% by mass in terms of rhodium in the metal state. Table 3 shows the physical property values of Sample H measured in the same manner as in Example 1.

[Catalyst performance evaluation]
(Test Example 1: Acceleration test after reduction pretreatment)

Samples

1, 4 to 10 and Samples A to F were subjected to a carbon monoxide oxidation reaction test.
First, 20 mg of

carrier

1, 2, 3, 4, 5, 2, 2, 6, 7, 8, 9, for 10 mg of each catalyst of

samples

1, 4 to 7, 9, 10, and A to F, 10 and 11 were mixed and diluted, respectively, and filled into quartz glass tubes. For sample 8 with a small amount of noble metal supported, 33 mg was weighed and filled into a quartz glass tube without dilution.
Next, after reducing for 1 hour at 500 ° C. in a hydrogen stream of 60 cm ³ / min, the temperature was lowered to 250 ° C. 100 cm ³ / min at a nitrogen gas stream after the purge for 10 minutes, the reaction temperature 250 ° C., the reaction by flowing a gas having the composition shown in Table 4 at a flow rate of 100 cm ³ / min at atmospheric pressure was carried out.

The space velocity indicating the relative ratio of gas and catalyst amount is approximately 600000 cm ³ · hour ⁻¹ · catalyst mass (g) ⁻¹ . In general, the value of the space velocity used for the reaction is about 1/10 of the space velocity. It was decided to demonstrate the high stability of the catalyst of the present invention by conducting the activity test at a space velocity higher than a general value. The gas flow rate and composition are adjusted using a mass flow controller, and the gas cylinder as a gas source is carbon monoxide 5% + nitrogen 95%, sulfur dioxide 200 ppm + nitrogen monoxide 200 ppm + nitrogen balance, oxygen (purity 99.9999 or more) And four types of nitrogen (purity 99.9999% or more) were prepared. The water vapor was adjusted by introducing a required amount of pure water with a water pump. Thereafter, the gas composition was adjusted in the same manner in all tests.

The results of the reaction test are shown in FIG. 6A to FIG. 6D.
Although Samples 9 and 10 are not shown in FIGS. 6A to 6D, the carbon monoxide conversion rate remained at 100% from the start to the end of the reaction in both cases.

Samples

1 and 4 to 10 of the invention example and Samples A to F of the comparative example have a great difference in time dependency of the conversion rate of carbon monoxide.

Samples

1 and 4 to 10 have a reaction time of 15 hours. However, it can be seen that in Samples A to F, the activity decreased greatly after 15 hours.

Sample 6 has a lower activity at the time point of 15 hours than

Samples

1, 4, and 5 of the invention, and sample 7 has an unstable activity. When the pore distribution shown in Table 2 is observed, the ratio of the surface area formed by pores having a pore radius of 10 nm or more is lower in Sample 6 than in the other invention examples, and the pore radius is 10 nm or more. It is considered that a higher carbon monoxide conversion is obtained as the ratio of the specific surface area formed by the pores is larger.

Further, when the pore distribution shown in Table 2 is observed for sample 7, the ratio of the surface area formed by pores having a pore radius of 20 nm or more is high although the ratio of the surface area formed by pores having a pore radius of 10 nm or more is high. The ratio is significantly lower than that of Samples 1 and 4-6. It can also be seen that the ratio of the surface area formed by pores having a pore radius of 80 nm or more is lower than that of Samples 1 and 4-6. Even when the ratio of the specific surface area formed by pores having a pore radius of 10 nm or more is high, the specific surface area formed by relatively large pores having a pore radius of 20 nm or more and larger pores having a pore radius of 80 nm or more When the ratio is low, it is assumed that the cause is that the desorption rate of by-product concentrated sulfuric acid tends to be insufficient.

Thus, in order to maintain a stable activity of the catalyst, in addition to a large proportion of the surface area formed by pores having a pore radius of 10 nm or more, the surface area formed by pores having a pore radius of 20 nm or more. It can be seen that a higher ratio is more preferable. It can also be seen that a higher proportion of the surface area formed by pores having a pore radius of 80 nm or more is more preferable.

In Sample B, a phenomenon in which the activity increases intermittently even after the carbon monoxide conversion rate once decreases is observed. As a result, the pore distribution of sample B slightly changes, and in the pores in the range of pore radius of 2 nm to 100 nm, the surface area of the pores having a pore radius of 10 nm or more occupying the total surface area of the pores in this range. If the ratio exceeds 40%, a significant decrease in activity may be avoided.

For sample 8 with a small amount of noble metal supported, the amount of catalyst used is increased, and as a result of using an amount of catalyst containing the same amount of noble metal as the other samples, activity comparable to that of sample 1 is obtained. I understand. From this, it is presumed that even when the amount of noble metal supported is decreased, the same level of activity can be obtained per unit noble metal amount.

It can also be seen that in Sample F, the time required for the carbon monoxide conversion rate to drop significantly is longer than in Samples A to E. This is probably due to two factors.

First, it has a large pore volume. Since the average pore diameter is small and the pore volume is large, it can be understood that the total extended distance of the pores as a whole is long. Considering that the specific surface area is large, it can be predicted that the pores have a very complicated network structure, and it is considered that the time required until the pores are completely blocked is increased. It is considered that the difference in behavior between the sample B and the samples C and D can be explained by the same discussion as above. That is, in the case of pores having a pore radius in the range of 2 nm or more and 100 nm or less, when focusing on the ratio of the surface area of the pores having a pore radius of 10 nm or more to the total surface area of the pores in such a range, samples C and D Is expected to be higher in stability than sample B, but samples C and D have a significantly smaller pore volume than sample B, so it is considered that the time required to close the pores is shorter.

Second, the alumina carrier itself reacts with concentrated sulfuric acid to become a sulfate. In other titania and zirconia carriers, only the outermost surface of the carrier reacts with concentrated sulfuric acid, so that concentrated sulfuric acid produced as a by-product remains as concentrated sulfuric acid as it is, and it is considered that the pores are blocked. On the other hand, the alumina carrier reacts with concentrated sulfuric acid to form sulfate, and the amount of sulfate remaining as concentrated sulfuric acid is relatively reduced. It is considered that the time required for the carbon monoxide conversion rate to decrease is increased due to these factors. However, in the case of an alumina carrier, the reaction of the carrier and the concentrated concentrated sulfuric acid reacts, and the activity gradually decreases as the reaction time increases. Furthermore, it has been confirmed by experiments conducted by the inventors that a significant reduction in non-surface area has occurred after the reaction, and it can be understood that it is not suitable for long-term use.

(Test Example 2: Temperature dependence of oxidation reaction)
The temperature dependence of carbon monoxide oxidation activity was examined for

Samples

1 and 4 which are invention examples and Sample B which is a comparative example.

Each 1 mg of each of the three types of catalysts was diluted by mixing 30 mg of

carriers

1, 2, and 7 and filled in quartz glass tubes.

After reducing for 1 hour at 500 ° C. in a hydrogen stream of 60 cm ³ / min, the temperature was lowered to 250 ° C. At 100 cm ³ / min nitrogen gas stream after the purge 10 minutes, the reaction was carried out by passing a flow 100 cm ³ / gas having the composition shown in Table 4 min. In this test, a reaction test was performed under conditions where the amount of catalyst was relatively small compared to other test examples. The space velocity indicating the relative ratio of gas and catalyst amount is approximately 6000000 cm ³ · hour ⁻¹ · catalyst mass (g) ⁻¹ . After performing the reaction at a reaction temperature of 250 ° C. and atmospheric pressure for 20 hours, the reaction temperature was raised and the carbon monoxide conversion was measured.

Results are shown in FIG. In Sample B, the carbon monoxide conversion rate changes sharply around 300 ° C. Concentrated sulfuric acid at a concentration that reaches equilibrium at 300 ° C. with the partial pressure of water vapor under the present experimental conditions has a boiling point of about 300 ° C. (see, for example, Non-Patent Document 8 above). It is thought that the influence of the blockage of the holes has disappeared.

Further, in the temperature range below 300 ° C., the difference between the example and the comparative example is large, and it can be seen that the catalytic activity of the sample B is very low. In the region where the saturated vapor pressure of concentrated sulfuric acid is low, it is considered that the influence of pore clogging has become obvious. Also from these points, it is considered that in the Examples, the influence of pore clogging by concentrated sulfuric acid is small, and high activity is obtained.

In addition, when the supported amount of platinum is 0.03% by mass or less, it is considered that the platinum fine particles are present as fine particles having a critical particle size, and even when the supported amount of noble metal is 0.03% by mass or less, the unit It is expected that the same level of catalytic activity can be obtained in terms of per noble metal. For example, the effect of the present invention is exhibited even with a catalyst having a loading amount of 0.01%, and the activity in the range of 300 ° C. or lower can be achieved by using a catalyst having a high surface area ratio occupied by pores having a pore radius of 10 nm or more. However, it is considered that the ratio of the surface area occupied by pores having a pore radius of 10 nm or more is higher than that of a catalyst having a low surface area.

(Test Example 3: Influence of sulfur dioxide concentration and water vapor concentration)
For Sample B, the same measurement as in Test Example 1 was performed. Thereafter, from the gas composition shown in Table 4, the measurement was performed in each case where the sulfur dioxide was 20 ppm or the water vapor amount was 10%. As a result, the conversion rates of carbon monoxide were 9.4% and 7.4%, respectively, which were values that were not significantly different from 8.4% before the gas composition was changed. From this, it is considered that the clogging of the pores due to the concentrated sulfuric acid observed in the sample B occurs even if the concentrations of sulfur dioxide and water vapor are different.

(Test Example 4: Pt, Rh, Pd supported catalyst)
Samples 1 to 3 and Samples G and H were subjected to a carbon monoxide oxidation reaction test. 20 mg of carrier 1 was mixed and diluted with 10 mg of each catalyst of Samples 1 to 3, respectively, and filled in a quartz glass tube. Further, 20 mg of the carrier 5 was mixed and diluted with 10 mg of each of the catalysts of Samples G and H, and each was filled in a quartz glass tube. The temperature was raised to 250 ° C. in a nitrogen stream at 100 cm ³ / min. After confirming that the temperature was stable, the reaction was performed by flowing a gas having the composition shown in Table 4 at a flow rate of 100 cm ³ / min. The space velocity indicating the relative ratio of gas and catalyst amount is approximately 600000 cm ³ · hour ⁻¹ · catalyst mass (g) ⁻¹ .

The results are shown in FIG. Looking at Samples 1 to 3, it can be seen that the activity varies greatly depending on the supported metal species, and in particular, a high carbon monoxide conversion rate is obtained with platinum. Further, when comparing the

samples

2 and 3 with the samples G and H, even when the supported noble metal species is Pd or Rh, in the carrier having a high surface area ratio formed by pores having a pore radius of 10 nm or more, It can be seen that higher CO conversion is obtained.

(Test Example 5: Influence of titanium dioxide carrier species)

Samples

1, 4, and 6 were subjected to a carbon monoxide oxidation reaction test. For 10 mg of each of the three types of catalysts, 20 mg of

carriers

1, 2, and 4 were mixed and diluted, respectively, and filled into quartz glass tubes. Before starting the reaction, the composition shown in Table 4 at a reaction temperature of 250 ° C. and a flow rate of 100 cm ³ / min was used for both the case where the reduction treatment was performed under a hydrogen stream at 500 ° C. and 60 cm ³ / min. The reaction was performed by flowing gas.

The results are shown in FIGS. 9A to 9C. In Sample 1, the same carbon monoxide conversion rate was obtained regardless of the presence or absence of the reduction treatment, but in

Samples

4 and 6, the activity changed greatly depending on the presence or absence of the reduction treatment, and the reduction treatment was not performed. There is no activity. The titanium dioxide carrier used in Sample 1 is an anatase type structure carrier prepared by the sulfuric acid method, has a smaller amount of oxygen deficiency than the rutile type structure of Sample 5, and is difficult to oxidize the supported platinum. It is known that high activity is likely to occur even when there is no reduction treatment. Further, it is known that the anatase type structure prepared by the sulfuric acid method is less likely to cause a phase transition at a temperature of 500 ° C. or higher than the anatase type structure prepared by the chlorine method of Sample 6. For this reason, it is considered that the conversion rate of carbon monoxide in Sample 1 was the same as that obtained in the case of the reduction treatment even in the case of no reduction treatment.

(Test Example 6: Application to denitration process)
Each of the powders of

Samples

1, 2, and 5 was coated on a cordierite honeycomb material with a pitch of 4.2 mm (wall thickness of 0.5 mm) at 200 g / m ² per surface area of the substrate. 3 was obtained. As the denitration catalyst, a lattice-shaped catalyst in which a 3.3 mm pitch cordierite honeycomb was coated with a titanium dioxide-based denitration catalyst at a base surface area of 200 g / m ² was used.

The denitration process shown in FIG. 1 was examined using each of the honeycomb-shaped

catalysts

1, 2, and 3. In the apparatus configuration of FIG. 1, a throw-in type electric heater was used instead of the gas heating burner 2, and a shell and tube type heat exchanger was used as the heat exchanging unit 1. A denitration reaction test was conducted with the entire apparatus kept warm. As the combustion catalyst filled in the combustion catalyst portion 3, the honeycomb-shaped

catalysts

1, 2, and 3 were used, and the filling amount was 1.2L. The denitration catalyst unit 4 was filled with 5 L of the lattice catalyst. As the composition of the exhaust gas, a gas having the composition shown in Table 5 that simulates the sintering furnace exhaust gas of the steel manufacturing process was used.

The honeycomb-shaped

oxidation catalysts

1, 2, and 3 of the present invention are filled with 1.2 L and denitration catalyst with 1.6 L, and an exhaust gas at 60 ° C. having the composition shown in Table 5 is supplied from the inlet of the heat exchange section to 30 Nm ³ / hour (hour). It was made to flow in. The electric heater is turned on, and when the temperature at the inlet of the combustion catalyst reaches 200 ° C., ammonia is injected from the upstream of the denitration unit 4 so that the flow rate ratio to nitrogen monoxide is 0.9. The heater was turned off. A good denitration rate was maintained in all cases of the

honeycomb catalysts

1, 2, and 3. The results are shown in Table 6.

(Test Example 7: Application to denitration process)
Each of the powders of

Samples

1, 2, and 5 was coated on a cordierite honeycomb material with a pitch of 4.2 mm (wall thickness of 0.5 mm) at 200 g / m ² per surface area of the substrate. 3 was obtained.

The denitration process shown in FIG. 2 was examined using each of the above honeycomb-

like catalysts

1, 2, and 3. In the apparatus configuration of FIG. 2, a throwing type electric heater was used instead of the gas heating burner 12, and a shell and tube type heat exchanger was used for the heat exchanging portion 11. The denitration catalyst section 13 was filled with a 3.3 mm pitch titanium dioxide-based lattice catalyst, and a denitration reaction test was performed in a state where the entire apparatus was sufficiently kept warm. As the combustion catalyst filled in the combustion catalyst section 14, the honeycomb-shaped

catalysts

1, 2, and 3 were used, and the composition of the exhaust gas was a gas having the composition shown in Table 5 as in Test Example 6.

The honeycomb-shaped

catalysts

1, 2, and 3 were filled with 1.2 L and the denitration catalyst was filled with 1.6 L, and an exhaust gas at 60 ° C. having the composition shown in Table 5 was introduced at 30 Nm ³ / hour from the inlet of the heat exchange section. . The electric heater is turned on, and when the temperature at the inlet of the combustion catalyst section reaches 280 ° C., ammonia is injected from the upstream side of the denitration apparatus section 13 so that the flow rate ratio to nitrogen monoxide becomes 0.9. The heater was turned off. A good denitration rate was maintained in all cases of the

honeycomb catalysts

1, 2, and 3. The results are shown in Table 7.

In the denitration unit, NO is reacted with NH ₃ to denitrate, but since the concentration of NO is low and the calorific value is not high, the temperature difference between the inlet and outlet of the denitration unit is slight. is there.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Heat exchange part 2 Gas heating burner 3 Combustion catalyst part 4 Denitration apparatus part 11 Heat exchange part 12 Gas heating burner 13 Denitration part 14 Combustion catalyst part 21 Exhaust air

flow path switcher

22a, 22b

Thermal storage part

23a, 23b Fuel

gas supply Portion

24a, 24b Mixture injection unit 25 Space 26 Air introduction path 27

Exhaust gas path

28a, 28b Secondary air introduction path

Claims

An oxidation catalyst in which at least one transition element selected from the group consisting of platinum, palladium, and rhodium is supported on a carrier;
In the pores having a pore radius in the range of 2 nm to 100 nm in the oxidation catalyst, the ratio of the surface area formed by pores having a pore radius of 10 nm or more to the total surface area of the pores in the range is more than 49%. There is an oxidation catalyst.
An oxidation catalyst for oxidizing a combustible component in a gas, in which at least one transition element selected from the group consisting of platinum, palladium, and rhodium is supported on a carrier,
In the pores having a pore radius in the range of 2 nm to 100 nm in the oxidation catalyst, the ratio of the surface area formed by pores having a pore radius of 10 nm or more to the total surface area of the pores in the range is more than 49%. There is an oxidation catalyst.
The oxidation catalyst according to claim 1 or 2, wherein a ratio of a surface area formed by pores having a pore radius of 10 nm or more to a total surface area of pores in the range is 60% or more.
The oxidation catalyst according to any one of claims 1 to 3, wherein a ratio of a surface area formed by pores having a pore radius of 20 nm or more to a total surface area of pores in the range is 20% or more.
The oxidation catalyst according to any one of claims 1 to 4, wherein a ratio of a surface area formed by pores having a pore radius of 20 nm or more to a total surface area of pores in the range is 30% or more.
The oxidation catalyst according to any one of claims 1 to 5, wherein a ratio of a surface area formed by pores having a pore radius of 80 nm or more to a total surface area of pores in the range is 2% or more.
The oxidation catalyst according to any one of claims 1 to 6, wherein the specific surface area is 20 m 2 / g or less.
The oxidation catalyst according to any one of claims 1 to 7, wherein the transition metal supported on the oxidation catalyst is platinum.
The ratio of the transition element supported on the oxidation catalyst is 0.01% or more and 2.0% or less with respect to the total mass of the oxidation catalyst as the sum of the mass ratio of the transition element in terms of metal, The oxidation catalyst according to any one of claims 1 to 8.
The oxidation catalyst according to any one of claims 1 to 9, wherein the oxidation catalyst support is an oxide support having a melting point of 1300 ° C or higher.
The oxidation catalyst according to any one of claims 1 to 10, wherein a carrier of the oxidation catalyst is either titanium dioxide or zirconium oxide.
The oxidation catalyst according to claim 11, wherein the support of the oxidation catalyst is titanium dioxide having an anatase structure.
The oxidation catalyst according to claim 11 or 12, wherein the titanium dioxide is titanium dioxide produced by a sulfuric acid method.
It has a combustion catalyst part that burns unburned components contained in the gas to be treated using a catalyst,
An exhaust gas treatment apparatus, wherein the combustion catalyst section is filled with the oxidation catalyst according to any one of claims 1 to 13.
A gas heating unit that is provided upstream of the combustion catalyst unit and increases the temperature of the gas to be treated;
A denitration unit that is provided downstream of the combustion catalyst unit and removes nitrogen oxides in the gas to be treated;
The exhaust gas treatment apparatus according to claim 14, further comprising:
A denitration unit that is provided upstream of the combustion catalyst unit and removes nitrogen oxides in the gas to be treated;
A gas heating unit provided upstream of the denitration unit to raise the temperature of the gas to be treated;
Further comprising
The exhaust gas treatment apparatus according to claim 14, wherein combustion heat generated in the combustion catalyst unit is used for heating the gas to be treated supplied to the gas heating unit.
An air-fuel mixture injection unit for injecting an air-fuel mixture of fuel and combustion air;
A heat accumulator is arranged, circulates the gas to be treated, accumulates sensible heat in the heat accumulator, circulates the combustion air after heat accumulation, and heats the combustion air with the amount of heat stored; and
With
A heat storage unit in which the combustion catalyst unit provided between the heat storage unit and the air-fuel mixture injection unit or the heat storage unit is filled with the oxidation catalyst according to any one of claims 1 to 13. Burning burner.
An oxidation catalyst according to any one of claims 1 to 13 is used to oxidize a combustible component selected from the group consisting of carbon monoxide, nitrogen monoxide, and methane in a gas to be treated containing water vapor and sulfur oxide. A method of oxidizing flammable components in a gas.
The method of oxidizing a combustible component in a gas according to claim 18, wherein a temperature at which the gas to be treated and the oxidation catalyst are in contact is 250 ° C or higher and lower than 300 ° C.
Using a gas treatment process having a gas heating part for raising the temperature of the gas to be treated and a denitration part for removing nitrogen oxides in the gas to be treated, and containing nitrogen oxides, water vapor, sulfur oxides and combustible A method for removing nitrogen oxides in a gas to be treated containing a reactive gas,
A combustion catalyst part filled with the oxidation catalyst according to any one of claims 1 to 13 is disposed between the gas heating part and the denitration part,
A gas that causes the gas to be treated heated by the gas heating part to pass through the combustion catalyst part, burns combustible components in the gas to be treated, and further raises the temperature of the gas to be treated by the combustion heat. Of removing nitrogen oxides therein.
As the gas heating unit, using a heat exchanger, a gas heating burner or an electric heater,
21. The method for removing nitrogen oxides in a gas according to claim 20, wherein the gas discharged from the denitration unit is used as a high-temperature gas of the heat exchanger.
As the gas heating unit, using a heat exchanger, a gas heating burner or an electric heater,
The position of the combustion catalyst unit is rearranged between the gas heating unit and the denitration unit to the subsequent stage of the gas heating unit and the denitration unit,
The method for removing nitrogen oxides in a gas according to claim 20, wherein the gas discharged from the combustion catalyst section is used as a high-temperature gas of the heat exchanger.
The method for removing nitrogen oxides in a gas according to any one of claims 20 to 22, wherein the gas to be treated is exhaust gas from a sintering furnace in a steel production process.